SYNTHESIS OF METAL OXIDES
NANOPHOTOCATALYST FOR WASTE
WATER TREATMENT
By
INAM ULLAH M. Phil (UAF)
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
IN
CHEMISTRY
DEPARTMENT OF CHEMISTRY
FACULTY OF SCIENCES
UNIVERSITY OF AGRICULTURE, FAISALABAD
PAKISTAN
2017
Declaration
I hereby declare that the contents of the thesis “Synthesis of Metal Oxides
Nanophotocatalyst for Waste Water Treatment” are the product of my own research
and no part has been occupied from any published sources (except the references,
standard mathematical or genetic model/equations/formula/ protocol etc). I further
declare that this work has not been submitted for the award of any other
diploma/degree. The university may take action if the information provided is found
inaccurate at any stage. In case of any default, the scholar will be proceeded against as
per HEC plagiarism policy.
––––––––––––––––
INAM ULLAH
2006-ag-362
M.Phil. Chemistry, UAF
T o ,
The Controller of Examinations,
University of Agriculture,
Faisalabad.
“We, the Supervisory Committee, certify that the contents and form of thesis
submitted by Mr. INAM ULLAH, Reg. No. 2006-ag-362, have been found satisfactory
and recommend that it be processed for evaluation, by the External Examiner(s) for
the award of degree”.
Supervisory Committee
1. Chairman __________________________
(Dr. Shaukat Ali)
2. Member __________________________
(Dr. Muhammad Asif Hanif)
3. Member __________________________
(Dr. Muhammad Anjum Zia)
I want to consecrate this humble effort to the gleaming tower of knowledge
Hazrat Muhammad
(May Peace and Blessings of Allah be upon Him)
&
My Affectionate Parents
Whose esteemed love enabled me to get the success and whose hearts are
always beating to wish for me maximum felicity in life.
ACKNOWLEDGEMENT
All praises to Almighty ALLAH, the creator, dominant, self-existing and sustainer, who enabled me
to accomplish this project and all respect is for his last Prophet MUHAMMAD (Peace and Blessing
of Allah Be upon Him) who is forever a torch of guidance and knowledge in our life.
I pay my humble gratitude to my worthy supervisor Dr. Shaukat Ali, Assistant Professor, Dept. of
Chemistry, University of Agriculture Faisalabad for his absorbing attitude, constant guidance, timely
suggestions, inspiration and encouragement throughout my studies.
I am greatly indebted to Dr. Muhammah Asif Hanif and Dr. Muhammad Anjum Zia for their co-
operation, valuable suggestions and guidance during my research and compilation of my thesis. I am
thankful to Dr. Lizbeth Grondahl, School of Chemistry and Molecular Biosciences, University Of
Queensland, Australia for her kind guidance and research assistance towards completing a part of my
Ph. D. research work in Australia.
I offer my cordial and profound thanks to Prof. Dr. Haq Nawaz Bhatti, Chairman, Dept. of
Chemistry, University of Agriculture Faisalabad.
Special thanks are extended to Muhammad Idrees Jilani, Asif Javid Bhatti, Waqar Azeem, Mirza
Ikram and Rana Shamshad Sahib for their prayers, moral support and sincere suggestions. Special
thanks are due to my all lab fellows for their friendly behavior and co-operation during research work.
Words always seem to shallow whenever it comes to my dear and loving Father. I am absolutely
nothing without his encouragement and especially his prayers. My appreciation and great thanks are
extended to my beloved wife Dr. Sana Sadaf, brothers and sisters for their moral support and prayers.
I want to pay thanks for School of Chemistry and Molecular Biosciences, University Of Queensland,
Australia and Centre for Microscopy and Microanalysis, The University of Queensland node of the
Australian Microscopy and Microanalysis Research Facility (AMMRF) for providing me valuable
facilities. Last but not the least thanks are extended to Higher Education Commission of Pakistan for
their financial support during this project.
INAM ULLAH
.
vii
CONTENTS
Chapter No. TITLE Page No.
1 INTRODUCTION 1
2 REVIEW OF LITERATURE 9
3 MATERIALS AND METHODS 28
4 RESULTS AND DISCUSSION 44
5 SUMMARY 139
LITERATURE CITED 141
viii
Table of contents
Chapter
No.
Title Page No.
Chapter 1 Introduction 1
Chapter 2 Review of literature 9
Chapter 3 Materials And Methods 28
3.1 Apparatus and Chemicals 28
3.1.1 Apparatus 28
3.1.2 Chemicals 28
3.2 Instruments 29
3.3 Chemical co-precipitation 30
3.3.1 Co-precipitation by mechanical stirring 30
3.3.2 Co-precipitation by ultra-sonic assisted mechanical stirring 30
3.4 Synthesis of (Al2O3)1-x(ZnO)xFe2O3 31
3.5 Synthesis of (ZrO2)1-x(ZnO)xFe2O3 32
3.6 X-Ray Diffraction Analysis 33
3.7 Scanning Electron Microscopy (SEM) 34
3.8 Energy Dispersive X-ray Spectroscopy (EDX) 34
3.9 Particles Size Analysis 35
3.10 Surface area Pore Size Analysis 36
3.11 Photocatalytic activity 36
3.11.1 Photocatalytic activity test 38
3.11.2 Optimization of pH 38
3.11.3 Optimization of photocatalyst dose 38
3.11.4 Optimization of dye concentration 39
3.13 Reusability test 39
3.12 Evaluation of Quality Assurance Parameters 39
3.12.1 Chemical Oxygen Demand (COD) 39
3.12.2 Total organic carbons (TOC) 40
ix
3.12.5 Mineralization test 41
3.12.3 Total suspended solids (TSS) 42
3.12.4 Hemolytic Activity (Toxicity) 42
3.13 Data analysis 43
Chapter 4 Results And Discussions 44
4.1 X-Ray Diffraction Analysis 44
4.1.1 X-Ray Diffraction Analysis of (Al2O3)1-x(ZnO)x(Fe2O3) 44
4.1.1.1 X-Ray Diffraction Analysis of Al2O3.Fe2O3 synthesized by
mechanically stirred co-precipitation 44
4.1.1.2 XRD Analysis of Al2O3.Fe2O3 by synthesized by ultra-sonic
assisted mechanically stirred co-precipitation. 46
4.1.1.3 X-Ray Diffraction Analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 -
synthesized by mechanically stirred co-precipitation 46
4.1.1.4 X-Ray Diffraction Analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 -
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation
46
4.1.1.5 X-Ray Diffraction Analysis of (Al2O3)0.50(ZnO)0.50Fe2O3 -
synthesized by mechanically stirred co-precipitation 48
4.1.1.6 X-Ray Diffraction Analysis of (Al2O3)0.50(ZnO)0.50Fe2O3 -
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation
49
.1.1.7 X-Ray Diffraction Analysis of (Al2O3)0.25(ZnO)0.75Fe2O3 -
synthesized by mechanically stirred co-precipitation 50
4.1.1.8 X-Ray Diffraction Analysis of (Al2O3)0.25(ZnO)0.75Fe2O3 -
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation
51
4.1.1.9 X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by
mechanically stirred co-precipitation 51
4.1.1.10 X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation 52
x
4.1.2 X-Ray Diffraction Analysis of (ZrO2)1-x(ZnO)x(Fe2O3) 53
4.1.2.1 X-Ray Diffraction Analysis of ZrO2.Fe2O3 synthesized by
mechanically stirred co-precipitation 53
4.1.2.2 X-Ray Diffraction Analysis of ZrO2 .Fe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation 54
4.1.2.3 X-Ray Diffraction Analysis of (ZrO2)0.75(ZnO)0.25 Fe2O3 -
synthesized by mechanically stirred co-precipitation 54
4.1.2.4 Diffraction Analysis of (ZrO2)0.75(ZnO)0.25 Fe2O3 -
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation
56
4.1.2.5 X-Ray Diffraction Analysis of (ZrO2)0.50(ZnO)0.50 Fe2O3 -
synthesized by mechanically stirred co-precipitation 56
4.1.2.6 X-Ray Diffraction Analysis of (ZrO2)0.50(ZnO)0.50 Fe2O3 -
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation
57
4.1.2.7 X-Ray Diffraction Analysis of (ZrO2)0.25(ZnO)0.75 Fe2O3 -
synthesized by mechanically stirred co-precipitation
58
4.1.2.8
Diffraction Analysis of (ZrO2)0.25(ZnO)0.75 Fe2O3 -
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation
58
4.1.2.9
X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by
mechanically stirred and ultra-sonic assisted mechanically
stirred co-precipitation
60
4.2 Scanning Electron Microscopy 60
4.2.1 Scanning Electron Microscopy of (Al2O3)1-x(ZnO)xFe2O3 60
4.2.2 Scanning Electron Microscopy for (ZrO2)1-x(ZnO)xFe2O3 62
4.3 Energy Dispersive X-Ray (EDX) Analysis 65
4.3.1 Energy Dispersive X-Ray (EDX) Analysis of
(Al2O3)1-x(ZnO)xFe2O3
65
4.3.1.1 Energy Dispersive X-Ray Analysis of Al2O3 .Fe2O3 65
4.3.1.2 Energy Dispersive X-Ray Analysis of 66
xi
(Al2O3)0.75(ZnO)0.25Fe2O3
4.3.1.3 Energy Dispersive X-Ray Analysis of
(Al2O3)0.50(ZnO)0.50Fe2O3 68
4.3.1.4 Energy Dispersive X-Ray Analysis of (Al2O3)0.25(ZnO)0.75
Fe2O3
69
4.3.1.5 Energy Dispersive X-Ray Analysis of ZnO.Fe2O3 71
4.3.2 Energy Dispersive X-Ray (EDX) Analysis of (ZrO2)1-
x(ZnO)xFe2O3
72
4.3.2.1 Energy Dispersive X-Ray Analysis of ZrO2.Fe2O3 72
4.3.2.2 Energy Dispersive X-Ray Analysis of (ZrO2)0.75(ZnO)0.25
Fe2O3
73
4.3.2.3 Energy Dispersive X-Ray Analysis of
(ZrO2)0.50(ZnO)0.50Fe2O3
75
4.3.2.4 Energy Dispersive X-Ray Analysis of (ZrO2)0.25(ZnO)0.75
Fe2O3
76
4.4 Particle Size, Surface area and porosity analysis 78
4.4.1 Particle Size analysis of (Al2O3)1─x(ZnO)xFe2O3 78
4.4.2 Particle Size analysis of (ZrO2)1-x(ZnO)xFe2O3 84
4.4.3 Surface area and porosity analysis of
(Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3
90
4.5 Photocatalytic Activity 91
4.5.1 Optimization of pH for the degradation of Methyl Orange 91
4.5.2 Optimization of catalyst dose for the degradation of Methyl
Orange
94
4.5.3 Optimization of dye concentration for the degradation of
Methyl Orange
96
4.5.4
Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 and
(ZrO2)1-x(ZnO)xFe2O3 synthesized by mechanically stirred
co-precipitation for the degradation of Methyl Orange
99
4.5.5
Optimization of x value (Al2O3)1-x(ZnO)xFe2O3 synthesized
by ultra-sonic assisted mechanically stirred co-precipitation
for the degradation of Methyl Orange
101
xii
4.5.6 Optimization of pH for the degradation of CI Reactive
Black 5
104
4.5.7 Optimization of photocatalyst dose for the degradation of CI
Reactive Black 5
107
4.5.8 Optimization of initial dye concentration for the degradation
of CI Reactive Black 5
110
4.5.9
Optimization of x values for (Al2O3)1-x(ZnO)xFe2O3 &
(ZrO2)1-x(ZnO)xFe2O3 synthesized by mechanically stirred
co-precipitation for the degradation of CI Reactive Black 5
112
4.5.10
Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 &
(ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation for the degradation of
CI Reactive Black 5
115
4.5.11 Optimization of pH for the degradation of Methylene Blue 117
4.5.12 Optimization of catalyst dose for the degradation of
Methylene Blue
120
4.5.13 Optimization of initial dye concentration for the degradation
of Methylene Blue
122
4.5.14
Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 and
(ZrO2)1-x(ZnO)xFe2O3 and synthesized by mechanically
stirred co-precipitation for the degradation of Methylene
Blue
125
4.5.15
Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 and
(ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation for the degradation of
Methylene Blue
127
4.6 Reusability Test for (Al2O3)0.75(ZnO)0.25Fe2O3 and
ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation
130
4.7 Evaluation of Quality Assurance Parameters 132
4.7.1 Chemical Oxygen Demand (COD), Total Organic Carbon
(TOC) analysis.
132
4.7.2 Mineralization of dyes 135
xiii
4.7.3 Total Suspended Solids (TSS) 136
4.7.4 Haemolytic activity (Toxicity) 137
Chapter 5 Summary 139
Literature Cited 141
xiv
List of Tables
Table
No.
Title
Page
No.
3.1 Normal amounts of AlCl3, ZnCl2 and FeCl3 used for the synthesis of
(Al2O3)1-x(ZnO)xFe2O3
31
3.2 Normal amounts of ZrCl4, ZnCl2 and FeCl3 used for the synthesis of
(ZrO2)1-x(ZnO)xFe2O3
32
4.1 Table No. 4.1 Estimated weight and molar percent of Al2O3.Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation and calcined at 600ᴼC from EDX spectra
66
4.2 Estimated weight and molar percent of (Al2O3)0.75(ZnO)0.25Fe2O3
from EDX spectra. Synthesized by ultra-sonic assisted mechanically
stirred co-precipitation and Calcined at 600ᴼC from EDX spectra.
68
4.3 Estimated weight and molar percent of (Al2O3)0.50(ZnO)0.50Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation and calcined at 600ᴼC from EDX spectra
69
4.4 Estimated weight and molar percent of (Al2O3)0.25(ZnO)0.75 Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation and calcined at 600ᴼC from EDX spectra
70
4.5 Estimated weight and molar percent of ZnO.Fe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation and
calcined at 600ᴼC from EDX spectra
72
4.6 Estimated weight and molar percent of ZrO2.Fe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation and
calcined at 600ᴼC from EDX spectra
73
4.7 Estimated weight and molar percent of (ZrO2)0.75(ZnO)0.25Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation and calcined at 600ᴼC from EDX spectra
75
xv
4.8 Estimated weight and molar percent of (ZrO2)0.50(ZnO)0.50Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation and calcined at 600ᴼC from EDX spectra
76
4.9 Estimated weight and molar percent of (ZrO2)0.25(ZnO)0.75Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-
precipitation and calcined at 600ᴼC from EDX spectra
77
4.10 particle sizes of (Al2O3)1-x(ZnO)xFe2O3 synthesized with
mechanically stirred co-precipitation technique at different values of
x
78
4.11 particle sizes of (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation technique at different
values of x
79
4.12 particle sizes of (ZrO2)1-x(ZnO)xFe2O3 synthesized with mechanically
stirred co-precipitation technique at different values of x
85
4.13 Particle sizes of (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation technique at different
values of x
85
4.12.1 Surface area and porosity analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 90
4.13.1 Surface area and porosity analysis of ZrO2.Fe2O3 91
4.14 Optimization of pH for the degradation of Methyl Orange With
(Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-
precipitation with 50mg/100ml catalyst loading, 50ppm initial dye
concentration at room temperature
92
4.15 Optimization of pH for the degradation of Methyl Orange With
(ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-
precipitation at 50mg/100ml catalyst loading, 50ppm initial dye
concentration at room temperature
93
4.16 Optimization of catalyst dose for the degradation of Methyl Orange
With (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred
co-precipitation at pH = 3, and 50ppm initial dye concentration at
room temperature
94
xvi
4.17 Optimization of catalyst dose for the degradation of Methyl Orange
With (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred
co-precipitation at pH = 3, and 50ppm initial dye concentration at
room temperature
95
4.18 Optimization of initial dye concentration for the degradation of
Methyl Orange With (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by
mechanically stirred co-precipitation at pH = 3, and 60mg/100ml
catalyst dose at room temperature
97
4.19 Optimization of initial dye concentration for the degradation of
Methyl Orange With (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by
mechanically stirred co-precipitation at pH = 3, and 60mg/100ml
catalyst dose at room temperature
98
4.20 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of methyl
orange at pH=3, catalyst dose 60mg/100ml and initial dye
concentration 50ppm at room temperature
99
4.21 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of methyl
orange at pH=3, catalyst dose 60mg/100ml and initial dye
concentration 50ppm at room temperature
100
4.22 value of x and their respective photocatalysts for (Al2O3)1-
x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3
101
4.23 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation for the
degradation of methyl orange at pH=3, catalyst dose 60mg/100ml
and initial dye concentration 50ppm at room temperature.
102
4.24 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation for the
degradation of methyl orange at pH=3, catalyst dose 60mg/100ml
and initial dye concentration 50ppm at room temperature.
103
xvii
4.25 Optimization of pH for the degradation of CI Reactive Black 5 With
(Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-
precipitation with 60mg/100ml catalyst loading, 50ppm initial dye
concentration at room temperature
105
4.26 Optimization of pH for the degradation of CI Reactive Black 5 With
ZrO2 Fe2O3) synthesized by mechanically stirred co-precipitation
with 60mg/100ml catalyst loading, 50ppm initial dye concentration
at room temperature
106
4.27 Optimization of pH for the degradation of CI Reactive Black 5 With
ZrO2 Fe2O3) synthesized by mechanically stirred co-precipitation
with 60mg/100ml catalyst loading, 50ppm initial dye concentration
at room temperature
108
4.28 Table No. 4.28 Optimization of catalysts dose for the degradation of
CI Reactive Black 5 With ZrO2.Fe2O3 synthesized by mechanically
stirred co-precipitation at pH = 3 and 50ppm initial dye concentration
at room temperature
109
4.29 Optimization of initial dye concentration for the degradation of CI
Reactive Black 5 With (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by
mechanically stirred co-precipitation at pH = 3 and 60mg/100ml
catalyst dose at room temperature
110
4.30 Optimization of initial dye concentration for the degradation of CI
Reactive Black 5 With ZrO2.Fe2O3 synthesized by mechanically
stirred co-precipitation at pH = 3 and 60mg/100ml catalyst dose at
room temperature
111
4.31 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of CI
Reactive Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye
concentration 50ppm at room temperature
113
4.32 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of CI
114
xviii
Reactive Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye
concentration 50ppm at room temperature
4.33 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation for the
degradation of CI Reactive Black 5 at pH=3, catalyst dose
60mg/100ml and initial dye concentration 50ppm at room
temperature
115
4.34 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation for the
degradation of CI Reactive Black 5 at pH=3, catalyst dose
60mg/100ml and initial dye concentration 50ppm at room
temperature
116
4.35 Optimization of pH for the degradation of methylene blue with
(Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-
precipitation at 60mg/100ml catalyst dose and 50ppm initial dye
concentration at room temperature
118
4.36 Optimization of pH for the degradation of methylene blue with
ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at
60mg/100ml catalyst dose and 50ppm initial dye concentration at
room temperature
119
4.37 Optimization of catalyst dose for the degradation of methylene blue
with (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred
co-precipitation at pH = 9 and 50ppm initial dye concentration at
room temperature
120
4.38 Optimization of catalyst dose for the degradation of methylene blue
with ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation
at pH = 9 and 50ppm initial dye concentration at room temperature
121
4.39 Optimization of initial dye concentration for the degradation of
methylene blue with (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by
mechanically stirred co-precipitation at pH = 9 and 60mg/100ml
catalyst dose at room temperature
123
xix
4.40 Optimization of initial dye concentration for the degradation of
methylene blue with ZrO2.Fe2O3 synthesized by mechanically stirred
co-precipitation at pH = 9 and 60mg/100ml catalyst dose at room
temperature
124
4.41 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of
methylene blue at pH = 9, 60mg/100ml catalyst dose and 50ppm
initial dye concentration at room temperature
125
4.42 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of
methylene blue at pH = 9, 60mg/100ml catalyst dose and 50ppm
initial dye concentration at room temperature
126
4.43 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation for the
degradation of methylene blue at pH = 9, 60mg/100ml catalyst dose
and 50ppm initial dye concentration at room temperature
128
4.44 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation for the
degradation of methylene blue at pH = 9, 60mg/100ml catalyst dose
and 50ppm initial dye concentration at room temperature
129
4.45 Reusability of (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 in six cycles
for MO, RB5 and MB at optimum operational conditions
130
4.46 Degradation, decrease in COD and decrease in TOC with
(Al2O3)0.75(ZnO)0.25Fe2O3 & ZrO2.Fe2O3
132
xx
List of Figures
Fig.
No.
Title
Page
No. 4.1 XRD patterns of Al2O3.Fe2O3 synthesized by mechanically stirred co-
precipitation
45
4.2 XRD patterns of Al2O3.Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
45
4.3 XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically
stirred co-precipitation
47
4.4 XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation
47
4.5 XRD patterns of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by mechanically
stirred co-precipitation
48
4.6 XRD patterns of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation
49
4.7 XRD patterns of (Al2O3)0.25(ZnO)0.75Fe2O3 synthesized by mechanically
stirred co-precipitation
50
4.8 XRD patterns of (Al2O3)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation
51
4.9 XRD patterns of ZnO.Fe2O3 synthesized by mechanically stirred co-
precipitation
52
4.10 XRD patterns of ZnO.Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
53
4.11 XRD patterns of ZrO2.Fe2O3 synthesized by mechanically stirred co-
precipitation
54
4.12 XRD patterns of ZrO2.Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
55
4.13 XRD patterns of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by mechanically
stirred co-precipitation
55
4.14 XRD patterns of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation
56
xxi
4.15 XRD patterns of (ZrO2)0.50(ZnO)0.50 Fe2O3 synthesized by mechanically
stirred co-precipitation
57
4.16 XRD patterns of (ZrO2)0.50(ZnO)0.50 Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation
58
4.17 XRD patterns of (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by mechanically
stirred co-precipitation
59
4.18 XRD patterns of (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation
59
4.19 SEM image of Al2O3.Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
60
4.20 SEM Image of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
61
4.21 SEM Image of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
61
4.22 SEM Image of (Al2O3)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
62
4.23 SEM Image of ZnO.Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
62
4.24 SEM Image of ZrO2.Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
63
4.25 SEM Image of (ZrO2)0.75(ZnO)0.75Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
63
4.26 SEM Image of (ZrO2)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
64
4.27 SEM Image of (ZrO2)0.25(ZnO)0.750Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
64
4.28 SEM (back scatter) image for EDX spectra of Al2O3.Fe2O3 synthesized
by ultra-sonic assisted mechanically stirred co-precipitation and calcined
at 600ᴼC
65
4.29 EDX spectra of Al2O3.Fe2O3 synthesized by ultra-sonic assisted 66
xxii
mechanically stirred co-precipitation and calcined at 600ᴼC
4.30 SEM (back scatter) image for EDX spectra of (Al2O3)0.75(ZnO)0.25Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
and calcined at 600ᴼC
67
4.31 EDX spectra of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
67
4.32 SEM (back scatter) image for EDX spectra of (Al2O3)0.50(ZnO)0.50Fe2O3
synthesized by ultra-sonic assisted mechanically stirred and calcined at
600ᴼC
68
4.33 EDX spectra of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
69
4.34 SEM (back scatter) image for EDX spectra of (Al2O3)0.25(ZnO)0.75 Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
and calcined at 600ᴼC
70
4.35 EDX spectra of (Al2O3)0.25(ZnO)0.75 Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
70
4.36 SEM (back scatter) image for EDX spectra of ZnO.Fe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC
71
4.37 EDX spectra of ZnO.Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
71
4.38 SEM (back scatter) image for EDX spectra of ZrO2.Fe2O3 synthesized
by ultra-sonic assisted mechanically stirred co-precipitation and calcined
at 600ᴼC
72
4.39 EDX spectra of ZrO2.Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
73
4.40 SEM (back scatter) image for EDX spectra of (ZrO2)0.75(ZnO)0.25Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
and calcined at 600ᴼC
74
xxiii
4.41 EDX spectra of (ZrO2)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
74
4.42 SEM (back scatter) image for EDX spectra of (ZrO2)0.50(ZnO)0.50Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
and calcined at 600ᴼC.
75
4.43 EDX spectra of (ZrO2)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
76
4.44 SEM (back scatter) image for EDX spectra of (ZrO2)0.25(ZnO)0.75Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
and calcined at 600ᴼC
77
4.45 EDX spectra of (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC
77
4.46 Particle size distribution by intensity for Al2O3.Fe2O3 synthesized by
mechanically stirred co-precipitation
79
4.47 Particle size distribution by intensity for (Al2O3)0.75(ZnO)0.25Fe2O3
synthesized by mechanically stirred co-precipitation
80
4.48 Particle size distribution by intensity for (Al2O3)0.50(ZnO)0.50Fe2O3
synthesized by mechanically stirred co-precipitation
80
4.49 Particle size distribution by intensity for (Al2O3)0.25(ZnO)0.75Fe2O3
synthesized by mechanically stirred co-precipitation
81
4.50 Particle size distribution by intensity for ZnO.Fe2O3 synthesized by
mechanically stirred co-precipitation
81
4.51 Particle size distribution by intensity for Al2O3.Fe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation
82
4.52 Particle size distribution by intensity for (Al2O3)0.75(ZnO)0.25Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
82
4.53 Particle size distribution by intensity for (Al2O3)0.50(ZnO)0.50Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
83
4.54 Particle size distribution by intensity for (Al2O3)0.25(ZnO)0.75Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
83
xxiv
4.55 Particle size distribution by intensity for ZnO.Fe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation
84
4.56 Particle size distribution by intensity for ZrO2.Fe2O3 synthesized by
mechanically stirred co-precipitation
86
4.57 Particle size distribution by intensity for (ZrO2)0.75(ZnO)0.25Fe2O3
synthesized by mechanically stirred co-precipitation
86
4.58 Particle size distribution by intensity for (ZrO2)0.50(ZnO)0.50Fe2O3
synthesized by mechanically stirred co-precipitation
87
4.59 Particle size distribution by intensity for (ZrO2)0.25(ZnO)0.75Fe2O3
synthesized by mechanically stirred co-precipitation
87
4.60 Particle size distribution by intensity for ZrO2.Fe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation
88
4.61 Particle size distribution by intensity for (ZrO2)0.75(ZnO)0.25Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
88
4.62 Particle size distribution by intensity for (ZrO2)0.50(ZnO)0.50Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
89
4.63 Particle size distribution by intensity for (ZrO2)0.25(ZnO)0.75Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
89
4.64 Optimization of pH for the degradation of methyl orange with
(Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-
precipitation at 50mg/100ml catalyst loading, 50ppm initial dye
concentration at room temperature
92
4.65 Optimization of pH for the degradation of methyl orange with
(ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-
precipitation at 50mg/100ml catalyst loading, 50ppm initial dye
concentration at room temperature.
93
4.66 Optimization of catalyst dose for the degradation of methyl orange with
(Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-
precipitation at pH = 3, and 50ppm initial dye concentration at room
temperature
95
xxv
4.67 Optimization of catalyst dose for the degradation of methyl orange with
(ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-
precipitation at pH = 3, and 50ppm initial dye concentration at room
temperature
96
4.68 Optimization of initial dye concentration for the degradation of methyl
orange with (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically
stirred co-precipitation at pH = 3, and 60mg/100ml catalyst dose at room
temperature.
97
4.69 Optimization of initial dye concentration for the degradation of methyl
orange with (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically
stirred co-precipitation at pH = 3, and 60mg/100ml catalyst dose at room
temperature.
98
4.70 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of methyl
orange at pH=3, catalyst dose 60mg/100ml and initial dye concentration
50ppm at room temperature
100
4.71 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of methyl
orange at pH=3, catalyst dose 60mg/100ml and initial dye concentration
50ppm at room temperature
101
4.72 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation
of methyl orange at pH=3, catalyst dose 60mg/100ml and initial dye
concentration 50ppm at room temperature
103
4.73 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation
of methyl orange at pH=3, catalyst dose 60mg/100ml and initial dye
concentration 50ppm at room temperature
104
4.74 Optimization of pH for the degradation of CI Reactive Black 5 With
(Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-
precipitation with 60mg/100ml catalyst loading, 50ppm initial dye
106
xxvi
concentration at room temperature
4.75 Optimization of pH for the degradation of CI Reactive Black 5 With
(ZrO2)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-
precipitation with 60mg/100ml catalyst loading, 50ppm initial dye
concentration at room temperature
107
4.76 Optimization of catalysts dose for the degradation of CI Reactive Black
5 With (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred
co-precipitation at pH = 3 and 50ppm initial dye concentration at room
temperature
108
4.77 Optimization of catalysts dose for the degradation of CI Reactive Black
5 With ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation
at pH = 3 and 50ppm initial dye concentration at room temperature
109
4.78 Optimization of initial dye concentration for the degradation of CI
Reactive Black 5 With (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by
mechanically stirred co-precipitation at pH = 3 and 60mg/100ml catalyst
dose at room temperature
111
4.79 Optimization of initial dye concentration for the degradation of CI
Reactive Black 5 With ZrO2.Fe2O3 synthesized by mechanically stirred
co-precipitation at pH = 3 and 60mg/100ml catalyst dose at room
temperature
112
4.80 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of CI Reactive
Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye
concentration 50ppm at room temperature
113
4.81 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of CI Reactive
Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye
concentration 50ppm at room temperature
114
4.82 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation
of CI Reactive Black 5 at pH=3, catalyst dose 60mg/100ml and initial
116
xxvii
dye concentration 50ppm at room temperature
4.83 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation
of CI Reactive Black 5 at pH=3, catalyst dose 60mg/100ml and initial
dye concentration 50ppm at room temperature
117
4.84 Optimization of pH for the degradation of methylene blue with
(Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-
precipitation at 60mg/100ml catalyst dose and 50ppm initial dye
concentration at room temperature
118
4.85 Optimization of pH for the degradation of methylene blue with
ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at
60mg/100ml catalyst dose and 50ppm initial dye concentration at room
temperature
119
4.86 Optimization of catalyst dose for the degradation of methylene blue with
(Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred co-
precipitation at pH = 9 and 50ppm initial dye concentration at room
temperature
121
4.87 Optimization of catalyst dose for the degradation of methylene blue with
ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH =
9 and 50ppm initial dye concentration at room temperature
122
4.88 Optimization of initial dye concentration for the degradation of
methylene blue with (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by
mechanically stirred co-precipitation at pH = 3 and 60mg/100ml catalyst
dose at room temperature
123
4.89 Optimization of initial dye concentration for the degradation of
methylene blue with ZrO2.Fe2O3 synthesized by mechanically stirred co-
precipitation at pH = 9 and 60mg/100ml catalyst dose at room
temperature
124
4.90 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of methylene
blue at pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye
126
xxviii
concentration at room temperature
4.91 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of methylene
blue at pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye
concentration at room temperature
127
4.92 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation
of methylene blue at pH = 9, 60mg/100ml catalyst dose and 50ppm
initial dye concentration at room temperature
128
4.93 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation
of methylene blue at pH = 9, 60mg/100ml catalyst dose and 50ppm
initial dye concentration at room temperature
129
4.94 Reusability of (Al2O3)0.75(ZnO)0.25Fe2O3 in six cycles for the degradation
of MO, RB5 and MB at optimum operational conditions
131
4.95 Reusability of ZrO2.Fe2O3 in six cycles for the degradation of MO, RB5
and MB at optimum operational conditions
131
4.96 Decrease in COD of MO, RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3 133
4.97 Decrease in COD of MO, RB5 and MB with ZrO2.Fe2O3 133
4.98 Decrease in TOC of MO, RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3 134
4.99 Decrease in TOC of MO, RB5 and MB with ZrO2.Fe2O3 134
4.100 Mineralization of MO,RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3 in 8
hours
135
4.101 Mineralization of MO, RB5 and MB with ZrO2.Fe2O3 25Fe2O3 in 8 hours 136
4.102 Toxicity assay of samples treated with (Al2O3)0.75(ZnO)0.25Fe2O3 and
un-treated samples
137
4.103 Toxicity assay of samples treated with (Al2O3)0.75(ZnO)0.25Fe2O3 and
un-treated samples
138
xxix
ABSTRACT
Water pollution is a major problem around the world especially the countries having
large textile industries as these industries use huge amount of water in textile processing.
Dyes make our world beautiful but dyes industries have major part of water pollution. 10 -15
percent of dye goes to the water stream during the dying process in a textile dyeing
industries. Many of these dyes are carcinogenic and have very harmful effects on human
being as well as aquatic life. Many physical and chemical techniques are used for the
treatment of waste water. One of currently investigating technique is photocatalytic
degradation of organic pollutants from waste water.
In this study two types of novel metal oxides nanophotocatalysts were synthesized
with general formulas (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 where x = 0, 0.25,
0.50, 0.75 and 1. Co-precipitation via simple mechanical stirring and a newly developed
method co-precipitation via ultra-sonic assisted mechanical stirring were used for the
synthesis of both nanophotocatalysts.
Characterization of synthesized photocatalyst was done with X-Ray Diffraction,
Scanning Electron Microscopy, Energy Dispersive X-Ray, Particle size analysis and Surface
analysis like Single Point surface area, BET surface area and pore volume BJH adsorption
and desorption pore volume,
Photocatalytic activity test was performed with three different dyes Methyl Orange
(MO), CI Reactive Black 5 (RB5) and Methylene Blue (MB) by optimizing the pH,
photocatalyst dose and initial dye concentration for both photocatalysts at room temprature.
(Al2O3)1-x(ZnO)xFe2O3 with x=0.25 has maximum degradation efficiency as it degraded MO
93.52%, RB5 91.08% and MB 83.74% with photocatalyst synthesized by ultra-sonic assisted
mechanically stirred co-precipitation while the photocatalyst (ZrO2)1-x(ZnO)xFe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation with x= 0 degraded
the MO 78.38%, RB5 83.21% and MB 73.97% in 140 min.
1
CHAPTER 1
INTRODUCTION
Life on earth depends on water. We cannot think about any sort of life without water.
Relationship between the atmosphere, lithosphere and hydrosphere is through water cycle
and major driving force on our planet is this water cycle. Water on earth and oceans is
constantly evaporating into atmosphere. Rain and snow fall is the result of that evaporated
water when atmosphere is saturated. Some part of water is present in solid form as glaciers or
polar ice. Rain water or melted snow percolates through earth as ground water or go back to
the sea. Human beings are neglecting the importance of water as it is unnecessarily flowed to
sink and polluted with different pollutants and they never thought about the danger which
they are purchasing.
The metropolitan growth and fast industrialization has resulted in continuous
deterioration of the Global environment since many years. These environmental changes are
not in favor of living organisms present on earth. These activities are creating problems like
Global warming and environmental pollution (Hill, 2010). Besides other environmental
issues, water pollution is of major concern. Water is extensively used in many industries
because it is universal solvent. The extensive use of water in many industries and the
pollution of natural water resources have worsened the problem of water scarcity. The
disease free clear drinking water is an important pre-requisite for existence of life on earth
but the quality of drinking water is declining day by day. The pollution of water reservoirs is
also dangerous for aquatic life. Fish are vulnerable to polluted water. To prevent the water
from contamination has become an issue of prime importance for the modern World.
Textile industry is one of the most important and rapidly developing industrial
sectors. It has high importance in terms of its environmental impact, since it consumes
considerably high amounts of water for processing (Tüfekci et al., 2007). Hence the textile
effluents are playing a key role in enhancing the water pollution problem. Theses effluents
usually contain acids, alkalies, salts, surfactants, oxidizing or reducing agents, enzymes, fatty
2
mater and scouring agents along with synthetic dyes. These synthetic colors are major source
or water pollution due to their visibility and recalcitrant nature (Crini, 2006).
Currently more than 8000 types of dyes are being manufactured having different
chemical natures. Major portion of these dyes is consumed by textile processing industries
(Anjaneyulu et al., 2005). These synthetic dyes possess complex aromatic structures so are
mostly non-degradable (Daneshvar et al., 2008). Once these dyes get enter into water
streams, these consume the dissolved oxygen which results in the destruction of aquatic life.
These colored effluents changes the water quality parameters like pH, dissolved oxygen
(DO), biological oxygen demand (BOD) and chemical oxygen demand (COD) etc. (Özer et
al., 2006; Mahmoud et al., 2007). Water becomes unsuitable for aquatic life and human
consumption. Hence, this polluted water requires treatment before its discharge into
environment (Papić et al., 2004).
Different methods for water treatment like chemical, physical, physico-chemical,
mechanical and biological are commercially employed to textile colored waste water
(Ferrero, 2000). Classical techniques which are still in use to decontaminate polluted water
include adsorption (Rauf et al., 2009; Nasuha et al., 2010), chlorination (Ge et al., 2008;
Sharma et al., 2009), coagulation (Ahmad and Puasa, 2007; Riera-Torres et al., 2010), ion
flotation (Shakir et al., 2010)b, membrane process (Lee et al., 2008; Jirankova et al., 2010),
sedimentation (Zodi et al., 2010) and solvent extraction (Egorov et al., 2008; Juang et al.,
2009). All these methods have advantages and drawbacks as well. The end products of these
techniques need to be processed further for complete purification. There are newer advanced
oxidation processes which can be used to degrade harmful products into carbon dioxide and
water (Ullah et al., 2012).
Advanced oxidation processes (AOPs) are alternative methods for decolorizing
and reducing recalcitrant wastewater loads that are generated by textile effluents.
Considerable progress has been made in the development of AOPs for textile effluent in
recent years, especially in ozone-related processes. Conventional oxidation treatment
has found difficulty to oxidize dyestuffs and complex structured organic compounds at
low concentrations or if they are especially resistant to the oxidants. To ease the stated
problems advanced oxidation processes have been developed to generate hydroxyl free
3
radicals by different techniques (Hill, 2010). These processes are combination of ozone
(O3) and hydrogen peroxide (H2O2) and UV irradiation which showed the greatest
promise to treat textile waste water. These oxidants effectively decolorize dyes,
however do not remove COD completely (Al-Kdasi et al., 2004). AOPs also include
biodegradation, fenton, photofenton, photocatalytic, sonolysis, ozonation and UV
photocatalytic processes. These advanced oxidation processes are better than chemical
ones however these are much costly (Ullah et al., 2012).
The development of civilization has been intimately linked with the ability of
human being to work with materials beginning with stone age and ranging through the
era of copper and bronze then iron age and now is the age of advanced materi als i.e.
nano sized particles. Advanced materials or nanoparticles possess a new set of
magnetic, optical, transport, mechanical, electrochemical and photochemical properties
(Nalwa, 1999). First photo electrochemical cell was designed by Fujishima and Honda
for splitting water using Pt coated TiO2 (Fujishima and Honda, 1972). Since then
nanophotocatalysts have been used to decompose organics, in solar cells for the
production of electricity and H2, in electronic devices and in optical coatings
(Hashimoto et al., 2005).
A number of semiconductors having photocatalytic properties have been
investigated for the remediation of water and air pollution. Examples of some
semiconductors along with their band gap energies are Fe2O3 (2.2 eV) (Duret and
Grätzel, 2005), NFeTiO2 (2.8 eV) (Kuvarega et al., 2014), CdS (2.5 eV) (Mews et al.,
1996), SnO2 (3.5 eV) (Leite et al., 1999), SrTiO3 (3.4 eV) (Lee et al., 2013), TiO2 (3.2
eV) (Wold, 1993), WO3 (2.8 eV) (Morales et al., 2008), , ZnFe2O4 (1.9 eV) etc.
(Kondawar et al., 2011)
Then there are attempts to synthesize binary and ternary visible light driven
nanophotocatalysts with enhanced activity e.g. ZrO2/TiO2 (Wang et al., 2006; Hidalgo
et al., 2007; Neppolian et al., 2007; Wu et al., 2009; McManamon et al., 2011; Song et
al., 2011; Sun et al., 2011; Swetha and Balakrishna, 2011; Shao et al., 2014; Pirzada et
al., 2015), Mn/ZrO2 (Alvarez et al., 2007), ZrO2 (Stojadinović et al., 2015), ZnO.ZrO2
(Sultana et al., 2015), Nb2Zr6 O17-x Nx (Kanade et al., 2007), ZrO2 TaON ((Maeda et
al., 2009), Zr TiO4/Bi2O3 (Neppolian et al., 2010), CdS/Zr-McM-41 (Liu et al., 2012)a,
4
ZrO2/SnO2 (Pouretedal et al., 2012), ZrBi2WO6 (Zhang et al., 2011)c, Fe2O3-
ZrO2/Al2O3 (Liu et al., 2012)b and N-Zr-TiO2 (Liu et al., 2015).
Visible light can be defined as portion of electromagnetic spectrum having
wavelength between 380-780 nm. Sunlight contain only about 4% UV-light (λ=300-380
nm). Visible light activation of photocatalyst is being pursued all over the world. Even
though such photocatalysts could not be gained in full success. It has been highly
demanded for immediate and future applications.
Photocatalyst induced by visible light should have a band gap between 2-3 eV
and ionic character of bond below 30 % (Shakir et al., 2010)a. So that photons of visible
light can excite electrons from valence band to conduction band producing electron and
hole (e-/h+) pair (Liu et al., 2012)a. Success of photoreaction depends upon transfer
efficiency of e- or h+ to oxidizing and reducing radicals. But recombination rate of e-
and h+ is very fast (nanoseconds) than the transfer rate (micro seconds to milli seconds).
A large number of charge carriers recombine resulting in heat energy e - + h+ → heat
(Hoffmann et al., 1995). Conduction band e- act as a reducing agent and valence band
h+ act as oxidizing agent at the surface of a semiconductor (Chen et al., 2010).
Photocatalytic activity can be enhanced by controlling recombination rate of photo
generated e- and h+. Suitable scavenger can trap e- or h+ leading to redox reaction and
retarding recombination rate of charge carriers (Wang et al., 2009)b.
Semiconductor should have the following properties so that it can work as a
good photocatalyst.
i. Its chemical nature should be such that it can change its oxidation states to
accommodate positive hole (h+) instead of decomposition (Hoffmann et al.,
1995).
ii. It should have more than one stable oxidation states (Wold, 1993).
iii. It should have suitable band gap energy (Khan and Rao, 1991). Band gap
energy should be up to 3.0 eV (Shakir et al., 2010)a.
iv. It should be inert against chemical and photo corrosion (Nair et al., 1993).
v. It should be non-toxic (Mills et al., 1993).
vi. It should have low cost (Dong et al., 2012).
5
The position of zirconium in periodic table is in IVth B group under titanium.
Structural parameters of Zr indicate that ZrO2 should be a very good semiconductor for
photocatalysis in heterogeneous photocatalysis with band gap energy 5.0 eV and
conductance & valence potential +4 to -1 verses normal hydrogen electrode (NHE)
(Wang et al., 2004; Pouretedal et al., 2012). ZrO2 has thermal stability, resistant to
chemical & photo corrosion and strong mechanical stability (Plaza et al., 1997; Zhang
and Gao, 2001; Yu et al., 2003). ZrO2 can be applied in a number of technological
fields for example high performance ceramics (Garvie et al., 1975), oxygen sensors
(León et al., 1997), high temperature fuel cells (Badwal, 1990; Li et al., 2004; Wang et
al., 2004), catalysts (Haw et al., 2000; Wu et al., 2009), optical coatings (Mansour et
al., 1990), orthopedic and dental implants (Li and Hastings, 1998), white pigment and
opacifier (Siddiquey et al., 2011), photocatalyst composite materials (Zhang and Gao,
2001), chromatographic support materials (Acosta et al., 1995), highly efficient
photocatalysis (Ashkarran et al., 2010; Du et al., 2014) and Ionic conductor (Wei and
Li, 2008; Matsui et al., 2009).
ZrO2 is dominating in photocatalysis field because of its high band gap, nontoxic
nature, high surface area, high photocatalytic activity, wide range of processing
procedure, low cost, reusability and very good chemical and photo chemical stability.
ZrO2 prepared by arc-discharge method showed two times more photocatalytic activity
as compare with Degussa P-25 TiO2 standard photocatalyst under similar experimental
conditions for Rhodamine B degradation (Ashkarran et al., 2010).
A number of research workers and engineers are being involved in the basic
studies, manufacturing, improvements, measurements and application of ferrites.
Ferrites may be defined as magnetic materials composed of oxides containing ferric ion
as the main constituent. Hilpert in 1909 published the first systematic study of the
relationship between the chemical and magnetic preparations: Ferrites are used in the
area of information storage, audio tapes, disk storage media and credit cards. They are
very important due to their optical, electronic, magnetic properties and for their
stability against physical and chemical changes. At the same time these are very good
photocatalysts. e. g. ZnFe2O4 is a n-type semiconductor with band gap of 1.9 eV, can be
activated by the visible light irradiation λ=652 nm or shorter wave lengths, A new
6
magnetic and visible light responsive photocatalyst TiO2-ZnFe2O4 was prepared by
alloying TiO2 and ZnFe2O4 semiconductors. (Srinivasan et al., 2006)a. Magnetic
nanoparticles have got much importance in nano-structured materials (Curtis and
Wilkinson, 2001). These materials have unique paramagnetic property which mean that
they are attracted by a magnet and retain no residual magnetic character when magnetic
field is removed (Yang et al., 2004). Magnetic nanoparticles are applied in various
fields e.g. magnetically assisted drug delivery (Patil, 2003), magnetic separation of
biomolecules (Lee et al., 2006), magnetic resonance imaging (Yallapu et al., 2011),
gene manipulation (Green et al., 2008) and photocatalysis (Rana et al., 2005; Green et
al., 2008; Harraz et al., 2014).
Light induced chemical reaction occurring at the sur face of nano sized catalyst is
termed as photocatalysis. It can be further subdivided in catalyzed and sensitized
whether the excitation take place at catalyst surface or absorbate molecule (Linsebigler
et al., 1995). The absorbed energy is consumed to excite electrons of valence band to
conduction band. Difference of the energy between conduction band and valence band
is known as band gap energy of the semiconductor. If photon has energy equal to or
greater then band gap energy electron of valence band is transferred to conduction band
leaving positive hole in valence band. The pair of this negative (e -) and positive charge
(h+) is known as electron-hole pair (EHP). Band gap energy (Eg) of semiconductor and
wavelength of light (λ) which can produce EHP can be related by the equation
Eg = 1240/ λ (nm) (Shakir et al., 2010)a
This absorption of energy also depends upon the size and surface area of
photocatalyst. The recombination of EHP produces heat energy which is biggest
hindrance in the successful photocatalytic reaction. The life time of EHP is about 30
nano seconds (Colombo and Bowman, 1996).
The photo excited electrons transferred to surface of photocatalyst and parti cipate in
reduction of O2 to O2∙ or singlet oxygen to O∙ in aqueous solution.
O2 + e- O2∙
7
O + e─ O ∙
O∙ + H2O H2O2∙
O∙ + O2 O3
∙ (Goswami, 1995; Cavicchioli and
Gutz, 2002)
These reactions prevent EHP recombination and causes the photocatalysis to start
(Diebold, 2003). Photo generated positive hole (h+) also transferred to the surface of
photocatalyst and oxidizes easily oxidizable organics or react with OH- and produce
OH∙ which is short lived and highly reactive radical
h+ + OH─ OH∙
This OH. radical combine with organic pollutant and degrade into CO2 and H2O
(Shapovalov et al., 2002). The pollutants which can be decomposed photocatalytically
are alcohols, phenols, halo phenols, alkanes, halo alkanes, aromatics, pesticides,
herbicides, surfactants, polymers, dyes, bacteria, molds, fungi, viruses and cancer cells
(Mills and Le Hunte, 1997).
Three parameters which affect the photocatalytic reaction of a photocatalyst are as
under (Martin et al., 1995)
I. Ability to absorb photon of light
II. Rate of oxidation reduction reaction occurring at its surface.
III. Rate of e-/h+ EHP recombination
These three parameters can be controlled by the properties of photocatalyst which are
crystal structure, crystalline phase, porosity, surface area, surface acidity, surface OH -
groups, band gap energy, e─ and h+ separation/recombination and particle size. All of
these properties can be changed by using a number of chemical and physical methods
(Blake, 1994; Boldyrev and Tkáčová, 2000) .
Scientists round the world are working to improve the nanophotocatalysts for the
response of UV activation to visible light activation (Mohamed et al., 2012). This goal
can be achieved by different methods i.e. by doping of photocatalysts with other
8
elements, by sensitizing photocatalysts with colored compounds, by coupling of
different semiconductors. There is an urgent need in the field of photocatalysis to
develop new photocatalysts which can be activated by sun light with enhanced
functions.
This project was designed to treat the colored textile effluents efficiently with low -cost
photocatalysis. To achieve this aim we have developed two novel photocatalyst which
are visible light driven with enhanced photocatalytic activity
I. (Al2O3)1-x(ZnO)xFe2O3.
II. (ZrO2)1-x(ZnO)xFe2O3.
9
CHAPTER 2
REVIEW OF LITERATURE
Visible light driven photocatalysts (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-
x(ZnO)xFe2O3 were synthesized for the treatment of colored effluents. The
photocatalytic activity of these photocatalysts was evaluated by degrading three
different dyes in aqueous solution. These were also characterized for their physical
parameters. Exact literature about these photocatalysts is not available for review.
However some review of literature about different types of nanophotocatalysts is given
below for comparison.
Nanocomposite material WOx-TiO2 was synthesized by sol-gel technique and
characterized by XPS, XRD, SPS, PL, EFISPS and UV-Vis spectroscopy. Particle size
of this catalyst was 23.4 nm and surface area was 85.1 m²g-1. Photocatalytic activity was
determined by degrading methylene blue (MB) dye under visible light irradiation. 83.5
% TOC was removed in 100 min this catalyst was best for M.B. degradation..(Li et al.,
2001).
ZrO2.TiO2 binary oxides nanocomposites were synthesized by sol-gel technique
and calcined at 600ᴼC and 800ᴼC. Nanocomposites were subjected to XPS, XRD, TEM,
SEM, BET, UV-Vis spectroscopy for characterization. Photocatalytic activity was
assessed by salicylic and Cr(VI) degradation. Band gap energy of the sample calcined at
600°C was 3.54 eV and that at 800 °C was 3.36 eV.(Colón et al., 2002)
Degussa P-25 TiO2 was sensitized with average diameter of 30 nm. Acid Red 44
was used as a sensitizer visible light sensitized dye which was pH dependent. The
sensitized dye then activates TiO2. Which then degrade organic pollutant i.e. phenol. At
the same time sensitized dye was also decomposed. In this TiO 2 can degrade phenol and
Acid Red 44 under visible light [λ =420 nm] irradiation (Moon et al., 2003).
Nano crystals of Zr4+ doped TiO2 was synthesized by sol-gel technique. And
characterized by TEM, IR, XRD and BET analysis. The photo catalytic activity was
tested by degrading methyl orange in aqueous solutions Zr 0.06Ti0.94O2 showed best
10
decolorizing efficiency i.e. 87.7 % which is 1.5 time greater as compared with TiO2 and
P25 TiO2. Introduction of Zr24+ in TiO2 resulted in smaller particle size, larger surface
area and lattice deformation (Wang et al., 2004).
A visible light driven nanophotocatalyst TiO2-ZnFe2O4 was synthesized by a co-
precipitation/hydrolysis method and characterization was done by SEM, XRD and UV-
Vis. Spectroscopy. Photocatalytic activity was determined by phenol degradation under
visible (λ> 400 nm), UV and solar light. TiO2-ZnFe2O4 degraded 52 % phenol under
indoor solar light irradiation (Srinivasan et al., 2006)a.
Nanocomposites of CdS/TiO2 were synthesized by a reverse micelle route and
calcined at 500 oC. Photo catalyst was characterized by XRD and SEM-EDS analysis.
Photocatalytic activity was assessed by phenol degradation in aqueous solution. CdS
50% TiO2 degraded 40 % phenol in 3.5 h under visible light (λ> 400 nm) through a cut
off glass filter. The particle size of CdS-TiO2 nanocomposite was [CdS ~ 18.1 nm and
TiO2 ~ 59.9 nm] and surface area was 24 m²g-1 (Srinivasan et al., 2006)b.
ZnS/TiO2 nanocomposite was prepared by solvothermal technique. Visible light
induced photocatalyst was characterized by TEM, XRD, UV/DRS and PL spectroscopy.
Particle size varies between 10-15 nm. Photocatalytic activity was determined by
degrading the parathion-methyl under visible light irradiation. Photo catalyst degraded
100 % parathion methyl in 30 min. The enhanced activity was due to association of
nanophotocatalyst and pollutant molecules (Xiaodan et al., 2006).
ZrO2 was doped with Mn, Fe, Co and Cu using sol-gel technique. Synthesized
photocatalysts were subjected to BET surface area, XPS, XRD, and UV/Vis
Spectroscopy. 2,4 Dichlorophenoxy acetic acid (2,4 D) was degraded as a test pollutant
under UV light (254nm) irradiation. 70 % 2,4, D was decomposed by Mn-ZrO2
calcined at 400○C. Tetragonal phase of ZrO2 was dominant in all the samples. Band gap
energy ranged between 3.6 – 5.5 eV. BET surface area was found to be 55 and 80 m2/g
doped metals could not be detected by XRD being in small concentrations (Alvarez et
al., 2007).
Nanophotocatalyst Fe/ZrO2-TiO2 was synthesized by sol-gel impregnation
technique. It was characterized by EXAFS spectroscopy. Only tetragonal zirconium
dioxide was present with TiO2. Fe-O-Fe and Fe-O-Zr bonds were formed in
11
nanocomposite. Photocatalytic oxidation of salicylic acid was reduced from 15.8 to <1
% due to iron dropping and photocatalytic reduction of Cr IV was reduced from 7 % to
<1 %. Doping of Fe on ZrO2-TiO2 system depressed the photocatalytic activity of ZrO2-
TiO2 (Hidalgo et al., 2007).
Synthesis of binary oxides photocatalyst ZrO2-TiO2 was done by sol-gel
technique with different weight ratios of ZrO2 and TiO2. The photocatalyst was
characterized by FTIR, DRS, XRD, Nitrogen Adsorption, Raman Spectroscopy, Photo
luminescence and TEM analysis. Photocatalytic activity was determined by degrading
4-chloro phenol as a test pollutant. Binary oxides catalyst showed better activity as
compared with ZrO2 or TiO2 or Degussa P25 TiO2. Molar ratio 1:1 ZrO2-TiO2 catalyst
calcined at 500 ○C showed 94 % degradation of 4-chloro phenol under UV light
irradiation in 60 min. Reaction mechanism considering band gap energies was proposed
(Neppolian et al., 2007).
Ag-TiO2 photocatalyst was prepared by sol-gel and photo deposition technique
and characterized by TEM, XRD and UV-Vis spectrometry. Photo catalytic activity was
determined by degrading Reactive Yellow 17 (RY 17) using UV and Visible light.
About 95 % RY-17 was degraded in 120 min under visible light irradiation. 100 % TOC
was removed after 5 hour under visible light irradiation. RY -17 degradation obeyed 1st
order kinetics (Rupa et al., 2007).
TiO2-ZnO binary oxide nano powder synthesized by ultrasonic precipitation
technique was subjected to XRD analysis. Photocatalytic activity was determined by
degrading C.I. Basic Blue-41 in aqueous solution. Optimum pH was 6.2 and dye
concentration was 20 mg/L. 1:1 [TiO2:ZnO] degraded 100 % dye in 1 hour. Dye
degradation reaction showed pseudo Ist order kinetics (Jiang et al., 2008).
K0.3 Ti4 O7.3 OH1.7 was prepared by calcination method and TiO2 anatase
nanoparticles were prepared by hydrothermal technique. Both these materials were
combined by refluxing in HNO3 to prepare K0.3 Ti4 O7.3 OH1.7-TiO2 nanocomposite.
Photocatalyst was characterized by XRD, SEM TEM techniques. Photo catalytic
activity was determined by degrading methylene blue under black light irradiation.
photocatalyst K0.3 Ti4 O7.3 OH1.7 – TiO2 calcined at 600 oC for two hours gave the
highest photocatalytic activity (Tawkaew et al., 2008).
12
Highly activated Fe2O3/SnO2 nanophotocatalyst was synthesized and calcined at
300 oC, 400 oC and 500 oC for 3 hour. Photocatalyst was characterized by TEM, XRD,
BET, and UV-Vis spectroscopy. Sample calcined at 400 oC resulted in smallest particle
sized of 15 nm, largest surface area 28.75 m²g-1 and highest photo catalytic activity i.e.
98 % degradation of acid Blue 60 in 60 min under visible light (λ> 400 nm) irradiation.
This activity was 3.6 times greater as compare with P-25 TiO2 (Xia et al., 2008).
Phosphate Zr doped TiO2 was prepared via non-hydrolytic sol-gel technique.
Samples calcined at 550 °C to 950 °C gave 2.88-5.28 times higher degradation of Bis-
phenol than P-25. TiO2 under UV light (λ= 305 nm) irradiation. Samples were analyzed
by thermal treatment, FTIR, XPS, TEM, XRD techniques. Largest particle size of
TOPO-Zr-TiO2 was 16.1 nm at 950°C and below 750 °C band gap was 3.4 eV. Zr4+ and
p5+ ions did not reduced the band gap energy of T iO2 as they lie in valence and
conduction band regions (Chang et al., 2009).
Polyoxometalate-ZrO2 nanocomposite was synthesized by sol-gel method and
characterized by using SEM, TEM, XRD, FTIR analysis techniques. Photocatalyst was
used for oxidation of primary and secondary benzyl alcohols and was reused for several
times without appreciable loss of activity. Physical characterization was done by FTIR,
XRD, TEM, EET and UV-Vis. Spectroscopy. The average particle size was 15 nm and
surface area was 292 m²g-1 (Farhadi and Zaidi, 2009).
NiO-Bi2O3 nanocomposite was prepared by sol gel technique. It was
characterized by XRD and UV/Vis spectroscopy. The results showed the complete
alloying of two oxides. Photocatalytic activity test was performed by degrading
methylene blue and methyl orange dyes. 100 % methyl orange and 85 % methylene blue
were decomposed in 120 min. (Hameed et al., 2009).
By the modification of TiO2 two photocatalysts Porphyrin/TiO2 and Fe3+-
Porphyrin/TiO2 were prepared through chemisorption technique. Photocatalytic activity
of porphyrin and Fe3+-porphyrin Titanium dioxide was assessed by degrading
Rhodamine B (RhB) in aqueous solution under UV and visible light irradiation.
Porphyrin /TiO2 degraded about 50 % RhB under visible light irradiation. Porphyrin
and Fe3+ Porphyrin enhanced the activity under UV light. But under visible light only
Pr enhanced the activity (Huang et al., 2009).
13
ZnO nano particles were introduced into titanate nano tubes. ZnO/titanate
photocatalyst was characterized by TEM, BET, XRD and UV/Visible spectroscopy.
Hexagonal wartzite phase of ZnO was attached to titanate nano tubes in the nano
composite structure. Photocatalytic activity was determined by degrading Rhodamine B
under visible light (λ=420 nm) irradiation. About 97 % RhB was degraded in 12 hours
by ZnO/titanate 20 % and ZnO/titanate 40 % (Liu et al., 2009).
Re-TiO2 (Re = La, Pr, Nd, Sm, Eµ, Dy and Gd) nanocomposites were
synthesized by hydrolysis in aqueous solution by a low cost method. Photocatalysts
were characterized by SEM, BET, XRD, HRTEM, and UV-Vis Spectroscopy.
Photocatalytic activity was evaluated by degrading Orange II dye dissolved in water
under UV and Visible light (λ-254, 365 and 400 nm). Best activity was shown under
visible light. Nd doped TiO2 is commercially produced to use in self-cleaning paints.
(Štengl et al., 2009).
Visible light photocatalyst S-TiO2-ZrO2 was synthesized by one-step method.
The nanocomposite was characterized by XRD, TEM, XPS, DRS, FTIR, ESR and N2
adsorption desorption measurements. Addition of ZrO 2 inhibited the phase
transformation, enhanced visible light absorption and increased activity. MB
degradation was about 90 % by S-TiO2-ZrO2 calcined at 500 °C (Tian et al., 2009).
TiO2/P3HT photocatalyst was prepared by mixing poly (3-hexylthiophene) with
TiO2 nanoparticles in high speed blender using CHCl3 as solvent. Photocatalyst was
characterized by XRD, XPS, TEM, FTIR and UV-Vis-spectroscopy. It showed good
textural properties similar to that of individual oxides containing two isoelectronic ions.
TiO2/P3HT degraded 88.5% methyl orange in 10 h under visible light irradiation.
Photocatalyst was stable after 10 cycles of reuse. (Wang et al., 2009)a.
Bimetals co-doped Bi/Co-TiO2 and Fe/Co-TiO2 nanocomposites were
synthesized by stearic acid gel technique. Photocatalyst was characterized by XRD,
SEM and UV-Vis spectroscopy. Photocatalytic activity was evaluated by degrading
Rhodamine B in aqueous solution under visible light (λ> 400 nm). Fe (0.1 % - 0.4 %)-
TiO2 showed 100 % efficiency of degrading Rhodamine B in 240 min where Fe alone
had negative effect on activity. Fe/Co co-doped TiO2 was reused three times with a 15
% loss of activity in each reuse (Wang et al., 2009)c.
14
Nanocomposite of TiO2/ZrO2 by facile route containing 10-90 mole% TiO2 was
prepared and characterized by XRD and TEM analysis. Photocatalytic activity was
evaluated by degrading Rhodamine B under UV-light (λ= 365 nm) irradiation. 60:40
TiO2/ZrO2 calcined at 600 °C degraded 90 % RB in 60 min (Yuan et al., 2009).
Bio-mineralization technique was used to produce Cs/CdS nanocomposite.
Chitosan crosslinked nano CdS photocatalyst was characterized by XRD, TEM, SEM,
TGA and FTIR analysis techniques. Photocatalytic activity was assessed by degrading
congo red dye in aqueous solution under visible light through a UV cut off light filter
85.9 % congo red was degraded in 180 min (Zhu et al., 2009).
A magnetic nanophotocatalyst TiO2/SiO2/Ni Fe2O4 by was prepared by hydro
thermal, sol-gel and solvothermal techniques. It was characterized by SEM, TEM,
XRD, HRTEM, VSM and UV-Vis spectroscopy. Nanoparticles were spherical with 30
nm dia. Photocatalytic activity was assessed by basic violet -5 (BV-5) degradation in
aqueous solution under UV light irradiation. 97 % of BV-5 was degraded in 360 min.
Being magnetic photocatalyst was separated very easily by applying external magnetic
field and reused 5 times without appreciable loss of activity (Yuan et al., 2010).
Nanophotocatalyst ZrOx-ZnO with enhanced activity was prepared via cetyl
trimethyl ammonium assisted hydrothermal technique. Binary oxide photocatalyst was
characterized by XRD, XPS, SEM, BET and UV/Vis spectroscopy. ZrO x/ZnO
decomposed 88 % of Dimethyl phthalate within 30 min under microwave irradiations.
Photocatalytic activity of prepared catalyst was 15 % higher than Degussa P25 TiO2.
Half-life of DMP degradation was shortened 45 % as compare with P25 TiO2. Binary
photocatalyst was recycled 6 times with the same efficiency (Liao et al., 2010).
Magnetic photocatalysts MxBi1-xFeO3, (M=Mg, Al or Y) were prepared by citric
acid sol-gel technique and calcined at 600 °C for 3 hours. Nano sized ceramic alloys
were characterized by XRD, SEM, EDX, DR and SQUID measurements. Photocatalytic
activity was evaluated by degrading Rhodamine B (Rh.B) as standard test pollutant.
Under visible light (λ>400 nm) through a cut off filter YBiFeO3 degraded 18 % Rh.B
where BiFeO3 degraded 14 % RhB and P-25 TiO2 degraded 7 % Rh.B. being magnetic
in nature photocatalyst can be easily separated from reaction mixture by applying
external magnet. (Madhu et al., 2010).
15
A visible light responsive photocatalyst ZrTiO4/Bi2O3 was prepared by
hydrothermal technique. The synthesized catalyst was characterized by XRD, XPS,
DRS, PL and TEM analysis. Particle size of 7 nm was obtained when calcined at 450
○C. Photocatalytic activity was determined by degrading 4 -cholorophenol as a test
pollutant. 40 % degradation was achieved in 60 min of visible light irradiation by the
photocatalyst calcined at 450 ○C which is higher than the sample calcined at 400, 500
and 550○C and also from Degussa P25 TiO2. That was due to small particle size, higher
surface area and stronger absorption of visible light. Due to these properties
ZrTiO4/Bi2O3 is a candidate for alternative commercial photocatalyst (Neppolian et al.,
2010).
Nanoparticles of ZnCuS and ZnNiS were synthesized by co-precipitation
method. Appropriate stoichiometric solutions of ZnCl2 and NiCl2.6H2O were co-
precipitated with Na2S.9H2O solution. The precipitated nanoparticles were filtered,
washed, dried in an autoclave at 100 ○C for 2 hours. The nanocomposite photocatalyst
was characterized by XRD, TEM, AAS and UV-Vis spectroscopy. Photocatalytic
activity was determined by degrading congo red under UV-Vis irradiation. Zn0.94Ni0.06S
shoed about 95 % degradation of congo red in 120 min and Zn0.9Cu0.1S about 98% in
120 min. the catalyst was reused 4 times in the degradation process at the cost of 0.5 %
Zn loss (Pouretedal and Keshavarz, 2010).
N-Zr/TiO2 prepared by sol-gel method was studied for the effect of N and NZr
dropping. Phase structure, morphology, mean crystalline size, texture, thermal and
crystallization properties were studied by XRD, SEM, TEM, XPS, BET analysis. The
photocatalytic activity was evaluated by methylene blue (MB) degradation. The MB
degradation rate was 0.717/m as compare with P25 TiO 2 0.116/m. The rate of N-
Zr/TiO2 is 6.18 times greater than P-25 TiO2. Zr doped TiO2 nanomaterial have smaller
particle size, larger surface area higher thermal stability (Lucky and Charpentier, 2010).
Photocatalytic degradation of Methyl Orange and Acid Orange 7 was performed
with WOx/TiO2 under visible light (λ>420 nm). 4.2 % WOx/TiO2 photocatalyst showed
best activity by decolorizing 100% Methyl Orange and Acid Orange 7 in 300 min a nd
240 min respectively. Decolorization of the dyes was investigated with changes in
absorption spectra. Effect of photocatalyst concentration, pH and initial concentration
16
of dye was noted. Photocatalyst was reused for degrading dyes. The nanocomposite was
subjected to XRD, DRS, TEM and EDX analysis (Sajjad et al., 2010).
Fe-TiO2 photocatalyst was synthesized by using hydrothermal technique.
Nanocomposite was characterized by XRD for detection of Fe 2O3 and TiO2.
Photocatalytic activity was assessed by degrading phenol in water solution under
different wavelengths of light irradiation. (λ = 190 -250, 390, 405 nm and sunlight).
About 8 % phenol was degraded under sunlight in 24 hours. Effect of solution
temperature and pH was also observed. The degradation reaction obeyed I st order
kinetics (Shawabkeh et al., 2010).
Ag/V-TiO2 nanophotocatalyst synthesized by sol-gel-solvothermal technique
was characterized by XRD and TEM analysis techniques. Particle size and band gap
energy were 12 nm and 2.25 eV. Photocatalytic activity was determined by degrading
Rhodamine B (RhB) and Coomassie Brilliant Blue G-250 (CBB) in water solution
under UV and visible light (λ = 313 nm and 420 nm respectively) irradiation. Ag/V
TiO2 (1.8 Ag, 4.9 V) was the best catalyst which degraded 62 % RhB and 100 % CBB
in 240m under visible light irradiation (Yang et al., 2010)a.
Hydroxyapatite (Fe3O4/HAP) was prepared via homogeneous precipitation
technique nanophotocatalyst was characterized for its physical parameters by TEM,
FTIR and XRD analysis. Diameter of spherical particles was 25 nm. Photocatalytic test
was performed by degrading diazinon under UV light irradiation. About 75 % of
diazinon was degraded in 60 min. Magnetic nature of nanoparticles helped in the
separation of catalyst from reaction mixture by an external magnet. The photocatalyst
could be reused 7 times with 7 % loss of activity (Yang et al., 2010)b.
Sol-gel technique was used to synthesize TiO2/ZrO2 nanocomposite and
subjected to XRD, TEM, UV-Vis spectroscopy and fluorescence emission spectra
techniques. Nanocomposite contained anatase TiO2 and tetragonal ZrO2. Photocatalytic
activity was determined by the degradation of methyl orange under UV light irradiation.
The catalyst with Ti/Zr ratio 15.2 % showed best activity of 60 % in 105 min. The same
catalyst was reused 5 times with no less of activity (Zhang and Zeng, 2010).
Mn-ZnO nanoparticles were prepared using co-precipitation technique. 75 mmol
solution of (CH3COO)2 Zn in ethanol was mixed with ethanolic solutions of
17
(CH3COO)2 Mn. Mixture solution was heated at 75 °C for 45 min and cooled to room
temperature. NaOH solution was added with stirring (150 rpm) till 8.3 pH was reached.
Resulting precipitates were separated by centrifuging at 4000 rpm for 20 min. washed
with C2H5OH and dried at 110 °C for 12 h. The sample was ground and calcined at 650
°C for 3h. Photocatalyst was characterized by XRD, SEM, TEM, EDX, BET and UV-
Vis reflectance for band gap measurements. Band gap of 1 % Mn-ZnO was 2.2 eV. 1 %
Mn-ZnO4 degraded 88 % O-cresol in 360 min under visible light irradiation (Abdollahi
et al., 2011).
Vanadium-doped TiO2–montmorillonite (MMT) nanophotocatalyst was prepared
by sol-gel method and characterized by XPS, TEM, XRD, DRS, FTIR and N2
adsorption isotherms. V-TiO2 MMT has smaller particle size than TiO2 and V-TiO2.
The photocatalytic activity was estimated by degrading sulpho rhodamine B (SRB)
under visible light λ=450 nm through a cutoff filter. About 65 % SRB was degraded in
18 h by V-TiO2 MMT where the ratio of Ti/MMT was 120 mmol/g (Chen et al., 2011).
Mixed metal oxide (MMO) of Zn-Al-In nanocomposites was synthesized by
chemical co-precipitation method. The solutions of Zn(NO3)2.6H2O, Al(NO3)3.9H2O
and In(NO3)3.4H2O with the molar ratio Zn/Al-In = 3.0 and In/Al-In = 0.3, 0.5 and 0.7
were co-precipitated with 0.24 M NaOH and 0.1 M Na2CO3 solutions. Alkali solutions
were added drop wise up to pH 10. Suspension was kept at 60 ○C for 6 hr. the
precipitate were filtered, washed, dried and calcined at 500 ○C for 4 hr. The prepared
photocatalyst was characterized by XRD, NMR. TEM, N2 adsorption and UV/Vis
defused reflectance spectroscopy. Photocatalytic activity was determined by degrading
Methylene Blue dye in H2O solution. MMO with molar ration 0.5 degraded MB up to
73 % in 240 min under visible light (λ>420 nm) irradiation. Band gap energy of the
sample was 2.50 eV (Fan et al., 2011).
A thin film of W-TiO2 synthesized by liquid phase deposition method was
characterized by XRD, XPS, EDX, SEM techniques. 1 -7 % W doping transferred
absorption wavelength into visible light range which was confirmed by UV-Vis
spectroscopy. Photocatalytic activity was determined by degrading dodecyl benzene
sulfonate (DBS). 5 % W-TiO2 film degraded 84.8 % DBS in 4 hour which was
18
improved up to 92 % in 90 min under +1.0 anodic bias potential under visible light (λ
>540 nm) irradiation (Gong et al., 2011).
Synthesis of C-doped Zn(OH)2V2O7 nanorods was done by hydrothermal
technique. Photocatalyst was characterized by XPS, DRS, SEM and XRD analysis
photocatalytic activity was estimated by methylene Blue (MB) degradation. Visible
light activated catalyst degraded about 90 % MB in 30 m. Dye decoloration obeyed
kinetics of first order reaction. The doped carbon was in free and carbide form on the
surface of nanorods (Guo et al., 2011).
Nanorods and nanotubes of N-TiO2 was prepared by solvothermal method
and characterized by XRD, TEM and UV-Vis spectroscopy. The N2 doping shifted the
band gap from 3.2 eV to 2.05 eV of nanorods and 2.40 eV of nanotubes which shifted
absorbance edge 605 to 504 nm. N-TiO2 nanotube degraded 70 % of methyl orange in
10 hours of visible light irradiation. BET surface area was 247 m²g -1 (He and He, 2011).
Er3+-TiO2 photocatalyst was synthesized by sol-gel method. Fibrous film was
made by electro spinning. Particle size was reduced from 18 nm to 8 nm when doped Er
was changed from 0-1.5 mol %. Photocatalyst was characterized by XRD, SEM, TEM
and UV-Vis spectroscopy. The absorption edge shifted towards red light. Acid
synergetic combination of e- with Er3+ resulted in higher activity under visible light.
Photocatalytic activity was estimated by degrading di fferent dyes i.e. orange-I and
methylene blue dyes by visible light activation (Lee et al., 2011).
Sol-gel technique was used to synthesize P-TiO2 nanophotocatalyst and the
photocatalyst was characterized by XRD, SEM, TEM, BET and UV-vis
spectrophotometry. Photocatalytic activity was determined by degrading rhodamine
B(RhB) under solar light irradiation. Degradation %age of RhB could be attained up to
70 % in 10 h of irradiation (Lv et al., 2011).
ZrO2-TiO2 was prepared by sol-gel method. ZrO2 percentage ranged from 0.5 –
4.0 percent of metal contents. The catalyst was calcined at 700 ○C. the ZrO2-TiO2 was
subjected to XRD, and TEM analysis. Particle size was below 10 nm. Photocatalytic
activity was measured by degrading phenol under UV light (λ ≤ 365 nm). Degradation
was measured by UV/Vis spectrophotometer. 1 % Zr-TiO2 calcined at 700 ○C gave
highest degradation rate of phenol. The catalyst was reused 5 times without any loss of
19
activity. Percentage degradation of phenol was calculated by the formula % DE = (C o –
Ct)/Co x 100. Where Co is initial concentration of phenol and C t concentration of phenol
at time T (McManamon et al., 2011).
Bovine serum albumin capped CdS nanocrystals were prepared by precipitation
method and characterized by XRD, TEM and UV-Vis spectroscopy. Particle size was in
between 3.1-3.8 nm. Photocatalytic activity up to 86 % was obtained from degradation
of methylene blue under visible light (λ -653 nm) irradiation in 7 hour. This bovine
serum albumin (BSA) capped CdS have great potential application in industry (Pathania
et al., 2011).
W/TiO2 nanocomposite was prepared by sol-gel technique. Sample was
subjected to XRD analysis. Photocatalytic activity was determi ned by degrading 2-
chlorophenol (2-Cp) 0.4 % W-TiO2 completely removed 2-Cp in 120 min under blue
light irradiation. The degradation was 75 % of the degradation of P-25 TiO2 under UV-
irradiation. Photocatalytic activity was independent of crystalline structure and showed
Ist order reaction kinetics (Putta et al., 2011).
Nanocomposite of CuO-ZnO was synthesized by wet impregnation process and
calcined at 550 °C for 5 hours which changed the sample from purple to grey color.
Photocatalyst was characterized by XRD, TEM, XPS, DRS techniques. Photocatalytic
activity was determined by degrading Acid Red-88 (AR-88). Activity of CuO/ZnO was
2 times greater as compare with bare CuO and ZnO. Total organic carbon (TOC) was
also removed after decolorization of AR-88 (Sathishkumar et al., 2011).
Magnetic nanocomposite CoFe2O4–Cr2O3–SiO photocatalyst was synthesized by
co-precipitation technique. Band gap energy of nanocomposite was 3-4 eV,
Photocatalytic activity was evaluated by Methylene Blue (MB) degradation under UV
light irradiation. About 90 % MB was degraded in 120 min in the first cycle, 88 % in
the second cycle and 86 % in third cycle. Photocatalyst being magnetic can be easily
separated by applying external magnetic field (Senapati et al., 2011).
WO3/BiOCl was prepared by wet impregnation process. Nanocomposite was
characterized by XRD, SEM, TEM, RS, EDX, N2 absorption and thermo gravimetric
analysis. WO3/BiOCl heterojuction nanocomposite shifted the absorption edge to
visible region photocatalytic efficiency was determined by degradation of rhodamine B
20
(RhB). 10 % WO3/BiOCl degraded RhB completely in 180 min under visible light (λ
<420 nm) through a cutoff glass filter. Degradation reaction showed 1st order kinetic
(Shamaila et al., 2011).
Zr–I–TiO2 was synthesized by hydrolysis technique and calcined at 400-600 ○C.
Nanophotocatalyst was characterized by XRD, TEM, XPS and UV/Vis spectroscopy.
Photocatalytic activity was measured by decolourizing the Methyl orange (MO) in
visible light (λ > 400 nm). Particle size was nearly 10nm and band gap energy of 5 %
Zr-I-TiO2 was 2.52 eV. It degraded 94 % MO in 240 min. Zr on the surface of TiO2
increased the active sites resulting in enhancement of Photocatalytic activity (Song et
al., 2011).
Highly efficient, visible light induced TiO2 photocatalyst was prepared by sol-
gel technique at temperature ≤300 °C nanophotocatalyst was characterized by XPS,
TEM, FTIR, XRD, UV-Vis, DRS and DSC-TGA techniques. Photocatalytic activity
was determined by degrading methyl orange using visible light (λ ≥ 400 nm) TiO 2
nanoparticles have anatase phase with carbon self-doping. Photocatalytic activity of
prepared TiO2 particles is much higher than P25-TiO2, PPY/TiO2, P3HT/TiO2,
PANI/TiO2 N-TiO2 and Fe3+-TiO2. TiO2 (270 °C, 0.5 h) showed the best activity of 80
%. MO degradation in 120 min under visible light irradiation (Wang et al., 2011)b.
Visible light induced CdS/La2Ti2O7 nanophotocatalyst was synthesized by sono-
chemical technique. Photocatalyst was characterized by TEM, SEM, XRD, UV-Vis
diffuse reflectance spectroscopy. Photocatalytic activity was estimated by methyl
orange degradation. Photo catalytic activity of 99 % was achieved with (La/Cd= 1:3) in
140 min. Low band gap energy of the photocatalyst make it responsive in longer
wavelength i.e. visible range (Wang et al., 2011)c.
Fe3+-TiO2 was supported at natural zeolite to make the photocatalyst easily
separateable and to enhance its activity. Photocatalyst was characterized by XRD,
FTIR, UV-Vis spectroscopy, DRS, SEM and EDX analysis. Photocatalytic activity was
evaluated by degrading methyl orange as a test pollutant. Photocatalytic activity was
optimum at 6 % Fe/TiO2/Zeolite. Fe+3 concentration affects the photocatalytic activity
of the sample forming Fe-O-Ti bond 5 % Fe enhanced the activity and there was
decrease in activity from 7 % Fe. (Wang et al., 2011)a.
21
CNTs/P-TiO2 nanocomposite prepared by hydrothermal technique was
characterized by XRD, XPS, TEM, BET, FTIR, TG-DSC, UV-Vis and DRS analytical
techniques. Methyl orange (MO) dye in solution was degraded to determine the
photocatalytic activity of nanocomposite. 95 % MO was decomposed with CNTs/P-
TiO2 photocatalyst in 240 min of visible light irradiation (λ > 410 nm) through a cut off
UV filter (Wang and Zhou, 2011).
Magnetic and optical nanophotocatalyst Fe3O4/ZnO with different composition
was prepared by facile route. The morphology and physicochemical properties were
studied by applying FTIR, TEM, XRD, VSM and UV-Vis spectroscopy. Photocatalytic
activity was estimated by degrading methyl orange (MO) dye in aqueous solution. 93.6
% degradation of MO was achieved in 60m of irradiation under visible light, pH = 7,
concentration of catalyst 0.51 mgL -1 and concentration of MO = 6x10-5 molL-1. Being
magnetic photocatalyst can be recycled easily. There is a 30 % decrease in activity after
5 times use of catalyst 10 % Fe3O4/ZnO molar ratio was optimal for Fe3O4/ZnO4 bi-
functional nanophotocatalyst (Xia et al., 2011).
Ag/MWCNTs nanophotocatalyst was developed by photo reduction and thermal
decomposition techniques. Ag/MWNTs catalyst was characterized by FE -TEM, XPS,
and UV-Vis spectroscopy. Photocatalytic activity of prepared photo catalyst was
determined by degrading Rhodamine B (RhB) as test pollutant under visible light
irradiation. About 55 % degradation of RhB was achieved by 3 % Ag/MW CNTs in 6
hours of visible light irradiation. Photocatalyst prepared by thermal decomposition
showed better results as compared with photo reduction (Yan et al., 2011).
MgFe2O4/TiO2 nanophotocatalyst was prepared by mixing of nano TiO2 & nano
MgFe2O4 and then calcined at 500 °C for 2 hour. The optimal composition was 3 weight
percent MgFe2O4 and optimal annealing temperature was 500 °C. Nanocomposite was
characterized by SEM, TEM, XRD, UV-Vis spectroscopy and N2 sorption. Crystal size
of 2 % MgFe2O4/TiO2 calcined at 500 °C was 24.56 nm and surface area 43 m²g-1. This
catalyst degraded about 90 % Rhodamine B under visible light irradiation in 180 min
(Zhang et al., 2011)a.
An efficient visible light induced photocatalyst ZrO2-Bi2WO6 was
prepared by hydrothermal technique. The photocatalyst was characterized by XRD,
22
TEM, DRS, XPS, PL spectra. Photocatalytic activity test was carried out by degrading
Rhodamine B (RhB) and phenol under visible light (λ >420 nm) irradiation. RhB was
completely removed in 20 min in 3 mol percent Zr and 60% phenol was degraded in
120 min. Photo catalyst was reused five times without appreciable loss of activity
(Zhang et al., 2011)c.
Visible light photocatalyst AgBr/Ag3PO4 hybrid was synthesized by ion
exchange method. Photocatalyst was characterized by XRD, FE -SEM, EDS and DRS
analysis. AgBr/Ag3PO4 6:4 hybrid degraded 95.1 % methyl orange (MO) in 50 min with
visible light irradiation (λ > 420 nm) which is higher than AgBr or Ag3PO4 alone. In the case
of MO dye there is possibility of dye sensitization. To remove this ambiguity a colorless
pollutant was also degraded efficiently. TOC removal of MO was 51.8 % after irradiation in
50 min and that of phenol was 22.5 % in 100 min. MO was first degraded to colour less
products and then into CO2 and H2O. photocatalytic efficiency was decreased upto 5 % in 4
cycles and upto 19 % after 5 cycles of reuse (Cao et al., 2012).
Sulfanilic acid modified TiO2 nanoparticles were prepared by hydrothermal
method and characterized by XRD, SEM, XPS, FTIR and UV-Vis spectroscopy. The
photocatalytic activity of catalyst was determined by congo red decoloration under
visible light irradiation through a cutoff filter (λ >400 nm). TiO2/SA degraded about 90
% Congo red dye in 210 m. The used photocatalyst was separated and dried at 80 °C for
5 hour and recycled 7 times with 15 % total loss of activity (Guo et al., 2012).
Nanocomposites of Fe2O3-ZrO2/Al2O3 were supported at Al2O3 by sol-gel
technique. Nanophotocatalyst was characterized by SEM, TEM, XRD, XPS, ICP-AES
and N2 sorption. Nanocomposite contains iron as λ-Fe2O3 monoclinic, zirconium as
tetragonal ZrO2 and aluminum as Al2O3. Photocatalytic activity was estimated by
degrading phenol in aqueous media. 93 % of phenol was degraded in 120 min under
UV-light irradiation in the presence of H2O2. Band gap energy of Fe2O3-ZrO2 2.68 ev
and Al2O3 = 3.92 eV (Liu et al., 2012)b.
N doped GaZn mixed oxide was synthesized by solid state reaction. Catalyst was
characterized for its structural, electronic and optical properties by XRD, SEM, TEM, SAED,
XPS and UV/Vis-DRS techniques. N-GaZn calcined at 500 °C degraded 54 % of 100 ppm 4-
Chloro-2-Nitrophenol solution in 4 h under direct sunlight irradiation. The band gap energy
23
of photocatalyst was 2.6 eV. Nitrogen contents, surface area, PL intensity and band gap
energy enhanced the photocatalytic activity of nanophotocatalyst (Martha et al., 2012).
Nanoparticles of CdS synthesized by precipitation method and Cd++ were
exchanged into zeolite. Photocatalyst was characterized by XRD, SEM and FTIR
analysis. Photo catalytic activity of the catalyst was determined by the degradation of
86 % crystal violet dye (CV) in 60 min under sunlight. 92 % decrease in COD and
change of TOC was also determined. Sunlight assisted catalyst was reused 4 time with
20 % loss of activity. Photocatalyst was recommended the complete mineralization of
pollutants in waste water (Nezamzadeh-Ejhieh and Banan, 2012).
Three types of photocatalysts ZrO2/SnO2, ZrO2/CeO2 and SnO2/CeO2 were
prepared using sol-gel method and calcined at 550 ○C. Characterization of synthesized
catalysts was done by applying XRD, TEM and IR Spectroscopy XRD patterns
confirmed the monoclinic and tetragonal phases of ZrO 2. Photocatalytic activity
experiments were performed by degrading 2 -nitro-phenol. ZrO2/SnO2 1:4 at pH 5
showed best activity by degrading 90 % 2-nitro phenol in 240 min. Photocatalyst was
reused 5 times with loss of 50 % activity. Used catalyst was removed from the reaction
mixture washed and dried at 80 ○C for 2 h at the end of each cycle (Pouretedal et al.,
2012).
Ag/AgCl nanophotocatalyst was synthesized. The composite material was highly
activated with visible light. The absorption ability was increased by increasing etching time,
the samples were characterized by X-ray Diffractrometery, X-ray Photoelectro Spectroscopy,
SEM and X-ray Energy Dispersive Spectroscopy. Photocatalytic activity was determined by
methyl orange which was decomposed 96 % in 40 min of visible light irradiation. The
catalyst was remained stable during degradation process. The reaction mechanism was also
proposed (Xu et al., 2013).
Nanoparticles of Zn0.5Co0.5Al0.5Fe1.46La0.04 O4 were synthesized by flash auto
combination method and blend them with PVP, PVA, PVAc and PEG polymers as capping
agents. The coating strategy controls the agglomeration of ferrites nanoparticles and
produced a well-designed core-shell nano-assembly with enhanced physical properties. XRD
and HRTEM confirmed the formation of ferrite as a core surrounded by polymeric
properties. All prepared samples were effective in removing dyes from waste water which
24
was cleared from color index analysis, 90 % efficiency was given by
Zn0.5Co0.5Al0.5Fe1.46La0.04O4 /PVP nanocomposite as compared with 76 % with pure ferrite
sample. Polymer blended ferrite in the form of core-shell were better in all respects (Ahmed
et al., 2013).
ZnFe2O4 magnetic nanoparticles were prepared by microwave assisted hydrothermal
method for the degradation of Acid Red 88 dye, Nanoparticles were characterized by XRD,
TEM, SEM, BET, ICP-AES and FTIR analysis. While degrading acid dye concentration (10-
56 mg/L), pH (3.2-10.7) and temperature of bath (20-60 ᴼC) were optimized. Decolorization
of the dye followed the pseudo 2nd order kinetics, Dye was adsorbed by nanoparticles
spontaneously and exothermally (Konicki et al., 2013).
ZnFe2O4 magnetic nanoparticles were prepared for the photocatalytic decolorization
and mineralization of dyes reactive red 198 and reactive red 120. The particles were prepared
by hydrothermal method and calcined at 600 ○C for 1 hour. Nanoparticles were characterized
by XRD, SEM and FTIR analysis. Decolorization of dyes was studied by UV/Vis
spectrophotometer. Initial concentration of dye, salt concentration and concentration of
catalyst were studied under UV radiations (200-280 nm). It was conducted that ZnFe2O4
nanoparticles could be used to degrade and mineralize the colored waste water (Mahmoodi,
2013).
Porous ZnFe2O4 film was fabricated through a template-assisted route and the sample
was calcined at 900 ○C for 3 h. The sample was analyzed by XRD, SEM, EDS, AFM and
ICP-EAS techniques. Photocatalytic activity was measured by degrading rhodamine B dye in
aqueous solution under visible light (> 420 nm) at 25 ○C. Porous ZnFe2O4 film degraded 80
% rhodamine B while ZnFe2O4 powder prepared by solid state method degraded 60 % of dye
in 8 hours. ZnFe2O4 film was recycled five times without any appreciable loss of activity. So
the photo degradation of organic pollutants in industrial waste water can be done successfully
(Nan et al., 2013).
Bismuth ferrite nanoparticles synthesized by sonication for 15 min at 35 ○C were
characterized by XRD and TEM analysis. Nanoparticles exhibited the band gap energy of 2.2
eV with excellent chemical stability. Small sized crystalline nanoparticles degraded 100 %
25
methylene blue in 30 min at pH 12 under sunlight irradiation. COD reduction was 83 %.
Initial concentration of dye had significant effect on rate of reaction. Degradation reaction
obeyed pseudo first order kinetics. Bismuth ferrite nanoparticles can be used to degrade the
organic pollutants in colored waste water (Soltani and Entezari, 2013).
Lanthanum ferrite nanoparticles were prepared by emulsion technique at room
temperature. Nanophotocatalyst was characterized by XRD, SEM, TEM, FT-IR, XRF and
UV/Vis spectroscopy. Nanoparticles were sharply crystalline and well dispersed provskite
phase. The band gap energy was 2.43 eV and particle size 32.68 nm. Photocatalytic activity
of the photocatalyst was estimated by degrading Toluidine Blue O (TBO) under visible light
irradiation. TBO was completely degraded after 90 min. Author proposed that
nanophotocatalyst has potential for industrial applications (Abazari et al., 2014).
Co0.6Zn0.4Cu0.2 Cdx Fe1.8 – xO4 (x= 0.2, 0.4, 0.6, 0.8) was synthesized by sol-gel auto-
combustion technique. Cd+2 substitution changed significantly magnetic, electrical and
structural properties of the ferrite. Nano crystalline ferrite was characterized by XRD, VSM
and UV/Vis spectroscopy. The particle size of nanocrystal was between 33–37 nm (calcined
at 1000 ᴼC). Pore size was increased with increasing Cd+2 concentrations. Photocatalytic
activity was evaluated by methyl orange dye degradation in water solution under visible light
irradiation. Photocatalytic activity of the sample containing Cd+2 (x=0.8) calcined at 1000 ○C
was 100 % after 1 hour of reaction. The catalyst could be easily separated by external magnet
for reuse (Bhukal et al., 2014).
Magnetic CoxNi1-xFe2O4 nanoparticles were prepared by hydrothermal method.
Physical characterization was performed by XRD, SEM, BET and VSM techniques. Congo
red in aqueous solution was used to determined adsorption capacity of cobalt nickel ferrite.
Sample with x= 0.3 gave largest adsorption capacity while the sample with x= 0.5 showed
the quickest adsorption. Adsorption reaction showed the pseudo 2 nd order kinetics. Best
magnetic properties were showed by the sample prepared at 140 ○C for 2 hours. The cobalt
nickel ferrite were good adsorbent to treat waste water containing congo red dye (Chen et al.,
2014).
26
Core-shell TiO2-SiO2/CoFe2O4 photocatalyst was developed such that CoFe2O4 was
synthesized by organic acid precursor technique. TiO2-SiO2 was prepared and coated onto
CoFe2O4 by sol-gel method. In this core-shell CoFe2O4 acts as core and TiO2-SiO2 as shell.
Characterization of photocatalyst was done by XRD, SEM, TEM, XPS, FTIR techniques.
Photocatalytic activity was determined by degrading methylene blue in aqueous solution
under UV light. 98.3 % methylene blue was degraded in 40 min. Efficiency of photocatalyst
was dependent on initial concentration of the dye, pH of the reaction solution and catalyst
dosage. The photocatalyst was separated from the reaction mixture by external magnet and
recycled six times with 4 % loss of activity. The loss of activity was due to the occupation of
active sites of photocatalyst by reaction intermediates (Harraz et al., 2014).
A magnetically ordered mesoporous copper ferrite was developed by nano-casting
with 122 m2/g surface area and 9.2 nm pour size. Meso-CuFe2O4 was characterized by XRD,
SEM, TEM, FT-IR, XPS and Raman Spectra technique. Catalytic activity was determined by
degrading imidaclopride, 100 % removal of imidaclopride took place in 5 hours. The reaction
followed pseudo first order kinetics. Hydroxyl radicles were responsible for the degradation
reaction and their generation was proportional to the degradation efficiency. Iron leaching
from Meso-CuFe2O4 was very low even in acidic solution. The catalyst did not loss activity
in 5 cycles of reuse. The magnetic nanophotocatalyst is a potential candidate for the removal
of organic pollutants (Wang et al., 2014)b.
N-doped TiO2/ZnFe2O4 photocatalyst was synthesized via vapor thermal technique.
Photocatalyst was characterized for is physico-chemical properties using spectroscopic and
microscopic analysis. N-doped TiO2/ZnFe2O4 showed improved photodegradation of dyes as
compared with TiO2/ZnFe2O4 and ZnFe2O4. Being magnetic photocatalyst it could be easily
isolated from reaction mixture using external magnetic field. The synthesized photocatalyst
could be used effective and conveniently for the treatment of waste water (Yao et al., 2015).
N, Zr co-doped mesoporous TiO2 photocatalyst was prepared by solution combustion
synthesis technique. Photocatalyst was characterized by XRD, TEM, BET, XPS and UV-Vis
diffuse spectroscopy. Z-Zr co-doping increased the BET surface area as well as
photocatalytic efficiency. Band gap of N-Zr-TiO2 was between 2.17 to 2.76. Doping of 10 %
27
Zr showed highest photocatalytic efficiency. It was also found that synthesized photocatalyst
was highly dispersable (Liu et al., 2015).
TiO2/ZrO2 was prepared using sol-gel technique. TiO2/ZrO2 photocatalyst was
characterized by XRD, TEM, SEM and TDA/TGA analysis techniques. Tetrahedral ZrO2 and
anatase TiO2 phases were present. The particles were spherical with 10.5 nm diameter. Result
showed increased in band gap energy and decreased in recombination rate of charge carriers
6.0 % ZrO2 addition showed maximum degradation of an azo dye Ponceau BS under UV
light irradiation (Pirzada et al., 2015).
28
CHAPTER 3
MATERIALS AND METHODS
This project was designed regarding current environmental issues to treat the textile
wastewater and achieve maximum mineralization of dyes and other textile auxiliaries that are
frequently present in wastewater. Two nanophotocatalysts were synthesized and
characterized. Colored waste water was treated with theses photocatalysts. Water quality
parameters like chemical oxygen demand (COD), total organic carbons (TOC), total
suspended solids (TSS), Toxicity and mineralization test had been performed. All sort of
research work has been performed in chemistry laboratory, Department of Chemistry
University of Agriculture Faisalabad and School of Chemistry and Molecular Biosciences,
University of Queensland, Australia.
3.1. Apparatus and Chemicals
3.1.1. Apparatus:
Following apparatus was used in research work:
Volumetric flasks (Pyrex)
Pipettes (Pyrex)
Measuring cylinders (Pyrex)
Beakers (Pyrex)
Funnels (Pyrex)
Screw-cap vials (Pyrex)
Three neck flask (Pyrex)
3.1.2. Chemicals:
Following chemicals were used in this research work. All chemical were purchased
from Sigma-Aldrich and used without any further purification.
29
Remazol Black B (CI Reactive Black 5)
Methyl Orange (C.I. 13025)
Methylene Blue (C.I. 52015)
Silver Sulphate
Potassium hydrogen phthalate
Potassium dichromate
Mercury sulphate
Sulphuric acid (98%)
Sodium hydroxide
Glucose
Sodium sulphate
Sodium hydrogen phosphate
Aluminum Chloride
Zirconium Chloride
Zinc Chloride
Ferric Chloride
3.2. Instruments
Mechanical Stirrer (IKA RW 20 Digital)
Heating Mantle (SGS 98-I-B)
Hot plates (IKA RCT Basic)
Digital thermometer (Thermoprobe TL1W)
100 watt Ultra sonic bath with operating frequency 40 kHz (Unisonics FXP12MH)
Scanning Electron Microscope (Philips XL 30)
UV-Visible spectrophotometer (Agilent Cary 60 UV-Vis)
Turbo-Pumped Sputter Coater (Quorum Q150T)
Zeta Sizer (Malvern Nano ZS)
X-ray Diffractometer (Bruker D8 Advance)
Nitrogen Adsorption Surface-Area Pore Size Analyzer (Micromeritics Tristar 3000)
30
3.3 Chemical co-precipitation
Co-precipitation is a simple method for the synthesis of nanoparticles. In this method
low temperature and less time is required as compare with hydrothermal, solvo thermal and
thermal decomposition. Water is used as solvent which is cheap and environmental friendly,
product yield is high and scalable but size and shape of particles is a little inferior. It is a
facile easy and simple method to prepare nanoparticles from metallic salt solutions. Mixture
of salt solutions is co-precipitated by adding a base with vigorous stirring at room
temperature or at elevated temperature in the absence of reactive oxygen (Faraji et al., 2010).
A pH range 8 to 14 is required for complete precipitation of stoichiometric ratio Fe+++: = 2:1
in an inert atmosphere (Iida et al., 2007).
In this project two types of nanophotocatalysts (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-
x(ZnO)xFe2O3 (x = 0, 0.25, 0.50,0.75 and 1) were synthesized by two different methods of co-
precipitation.
i) Co-precipitation by mechanical stirring
ii) Co-precipitation by ultra-sonic assisted mechanical stirring
3.3.1 Co-precipitation by mechanical stirring
In this method co-precipitation was done in three necks round bottom flask of 500 ml
fitted with mechanical stirrer and heating mantle to provide heat to the reaction mixture. One
neck of the flask was used to introduce the ammonia solution through a variable speed
dispenser, one for stirrer and one for the thermometer to note the temperature of the reaction
mixture during the reaction. Reaction conditions used are, temperature 65○C , stirring speed
500 rpm, ammonia solution 30-40 drops/min and the end point was pH = 10.
3.3.2 Co-precipitation by ultra-sonic assisted mechanical stirring
This method was newly developed. In this method co-precipitation was done under
the influence of ultra-sonic radiations during mechanical stirring. The reaction was
performed in a 500 ml three neck flask placed in temperature controlled ultra-sonic bath, an
overhead mechanical stirrer and variable speed dispenser was used for the drop wise
31
introduction of ammonia solution. Reaction conditions used are, temperature 65○C, stirring
speed 500 rpm, ammonia solution 30-40 drops/min and the end point was pH = 10.
3.4 Synthesis of (Al2O3)1-x(ZnO)xFe2O3
Stock solutions of normality 1 were prepared for AlCl3, ZnCl2 and FeCl3.6H2O in
deionized water. 100ml of solutions of both ZnCl2 and AlCl3 were prepared from stock
solutions against the different values of x and labeled as solution A and B respectively.
100ml of 1 normal FeCl3.6H2O solution was used for each value of x and labeled as solution
C. Solution A, B and solution C were mixed slowly with continuous stirring, heated up to
65○C (Behrens et al., 2011), stirred for 30 min at the same temperature. To precipitate
chloride precursors the pH of solution was raised by adding 30% ammonia solution drop
wise with constant stirring to gain pH = 10 (Hessien et al., 2008), this process took 2 hours.
The resulting mixture was kept stirring for another 60 min. The resulting precipitates of
(Al2O3)1-x(ZnO)xFe2O3 were centrifuged and washed with deionized water till chloride free
and a final washing with absolute alcohol (Ren et al., 2012).
Table No. 3.1 Normal amounts of AlCl3, ZnCl2 and FeCl3 used for the synthesis of
(Al2O3)1-x(ZnO)xFe2O3
Value
of x
Normality of 100 ml solutions (Al2O3)1-x(ZnO)xFe2O3
AlCl3
Solution A
ZnCl2
Solution B
FeCl3
Solution C
0 1.00 0.00 1.00 Al2O3.Fe2O3
0.25 0.75 0.25 1.00 (Al2O3)0.75(ZnO)0.25Fe2O3
0.50 0.50 0.50 1.00 (Al2O3)0.5(ZnO)0.5Fe2O3
0.75 0.25 0.75 1.00 (Al2O3)0.25(ZnO)0.75Fe2O3
1 0.00 1.00 1.00 ZnO.Fe2O3
Washed precipitates were dried at 80○C for 24 h in an electric oven and cooled to
room temperature. These were ground in agate pestle and mortar to fine powder and divided
into 3 portions a, b and c. sample a was calcined at 400○C and sample b was calcined at
600○C for four hours and sample c was left uncalcined these samples of nanophotocatalysts
32
were stored in glass bottles kept at a dry place for further use (Bo et al., 2007; Shao et al.,
2014).
The above same process was used for the synthesis of nanophotocatalysts (Al2O3)1-
x(ZnO)xFe2O3 by ultrasonic assisted mechanically stirred co-precipitation only the difference
was in arrangement of apparatus as given in section 3.3.
3.5 Synthesis of (ZrO2)1-x(ZnO)xFe2O3
Stock solutions of normality 1 were prepared for ZrCl4, ZnCl2 and FeCl3.6H2O in
deionized water. 100ml of solutions of both ZnCl2 and ZrCl4 were prepared from stock
solutions against the different values of x and labeled as solution A and B respectively.
100ml of 1 normal FeCl3.6H2O solution was used for each value of x and labeled as solution
C.
Table No. 3.2 Normal amounts of ZrCl4, ZnCl2 and FeCl3 used for the synthesis of
(ZrO2)1-x(ZnO)xFe2O3
Value
of x
Normailty of 100 ml solutions (ZrO2)1-x(ZnO)xFe2O3
AlCl3
(Solution A)
ZnCl2
(Solution B)
FeCl3
(Solution C)
0 1.00 0.00 1.00 ZrO2.Fe2O3
0.25 0.75 0.25 1.00 (ZrO2)0.75(ZnO)0.25Fe2O3
0.50 0.50 0.50 1.00 (ZrO2)0.5(ZnO)0.5Fe2O3
0.75 0.25 0.75 1.00 (ZrO2)0.25(ZnO)0.75Fe2O3
1 0.00 1.00 1.00 ZnO.Fe2O3
Solution A, B and solution C were mixed slowly with continuous stirring, heated up
to 65○C (Behrens et al., 2011), stirred for 30 min at the same temperature. To precipitate
chloride precursors the pH of solution was raised by adding 30% ammonia solution drop
wise with constant stirring to gain pH = 10 (Hessien et al., 2008), this process took 2 hours.
The resulting mixture was kept stirring for another 60 min. The resulting precipitates of
(ZrO2)1-x(ZnO)xFe2O3 were centrifuged, filtered under vacuum and washed with deionized
33
water till chloride free and a final washing with absolute alcohol (Ren et al., 2012). Washed
precipitates were dried at 80○C for 24 h in an electric oven and cooled to room temperature.
These were ground in agate pestle and mortar to fine powder and divided in to 3 portions a, b
and c. Sample a was calcined at 400○C for four hours and sample b was calcined at 600○C for
four hours and sample c was left uncalcined, these samples of nanophotocatalysts were
stored in glass bottles and kept at a dry place for further use (Bo et al., 2007; Shao et al.,
2014).
The above same process was used for the synthesis of nanophotocatalysts (ZrO2)1-
x(ZnO)xFe2O3 by ultrasonic assisted mechanically stirred co-precipitation only the difference
was in arrangement of apparatus as given in section 3.3.
3.6 X-Ray Diffraction Analysis
XRD is an important technique which gives information about the crystalline
structure of solids i.e. lattice constants, geometry of crystals, unknown materials, defects and
stresses on crystalline structure (Azaroff, 1968; Cullity, 1956). Diffraction can occur in an
electromagnetic wave interact with one another having path difference of the order of wave
length. Visible light can be diffracted by grating which have dark lines a few thousand A○
apart of the order of wavelength of visible light. X-ray diffraction takes place at the crystal
two layers of which are separated by the order of wavelength of X-ray. X-rays have wave
length in A○ which is in the range of inter atomic layers in crystalline solids. It can be
diffracted from the atomic layers of atoms which is the characteristic property of crystalline
solid (Ohring, 1992). Bragg’s law states that constructive interference take place between
two waves reflected from successive lattice planes which are d distance apart of the order of
the integral multiple of x-ray wave length λ so that,
n λ = 2d sinθ
θ is an angle which x-ray make with the lattice plane and d is the distance between two
reflecting planes. (Birkholz, 2006). Diffraction lines broadens inversely to crystal size.
Crystal size can be calculated using Scherrer’s formula (Rahman et al., 2013).
Δ2θ = 0.9λ/L Cos θ
34
L is the size of crystal in A○ and Δ2θ is the FWHM of the diffraction line at θ (Daou et al.,
2009).
X-Ray diffraction analysis was performed to calculate the size of crystal and
determining the crystalline phase of photocatalysts, using Bruker’s D8 Advanced with Cu Kα
radiation (λ = 1.5418 A○) with a glass slide having cavity 10x10x1 mm3 as sample holder
(Ismail et al., 2014). Nanocomposite powder was fixed in sample holder and put in the
diffractometer which was controlled by a data scan software with the scan parameters, step
size = 0.05○, scan rate = 1.2○ per min. and 2 θ = 10-100○ (Bai et al., 2014)
3.7 Scanning Electron Microscopy (SEM)
Surface details of the material can be studied by SEM analysis. This analysis gives
information in between a high magnifying microscope and transmission electron microscope.
In this process an electron beam is generated by electron source gun and this beam of
electrons is scanned over the specimen. The image is formed by the secondary or back
scattered electrons through a detector. The secondary electron gives topographic information
of the target material. The back scattered electron produced the e- + h+ pair in semiconductor
detector and give information about the chemical composition of the sample (Zhou and
Wang, 2007; Alyamani and Lemine, 2012).
In this project SEM (Philips XL 30) with LaB6 electron source was used to study the
topography of nanocomposites (Wong et al., 2012; Habibi and Sheibani, 2013). The
powdered photocatalyst was mixed with C2H5OH and dispersed on silicon substrate. It was
dried at 60 ᴼC in an oven for 24 h and placed on a sample stub with the help of magnetic
tape. Sample was coated with 10 nm of platinum layer with help of sputter coater (Quorum
Q150T) (Dewan et al., 2012). Electron microscope was operated at accelerated voltage of 5-
20 Kv, working distance 8-15 mm and spot size 3-5.
3.8 Energy Dispersive X-ray Spectroscopy (EDX)
Energy dispersive X-ray spectroscopy is an elemental analysis technique.
Electromagnetic radiations and sample interact in this technique, charged particles hit the
target metal, X-rays are emitted which are used as analyzing radiations (Toyoda et al., 2004;
35
Corbari et al., 2008). Characterization ability of this method depends upon the fact that X-
rays emitted from each element are of characteristic nature of the element which is unique for
that element. A high energy beam of electrons is focused on the sample to be analyzed for the
emission characteristic X-rays of the atom. The incident beam ejects an electron of the inner
shell leaving there an electron hole which is filled by an electron of high energy shell. The
difference of these two shells is released in the form of characteristic X-rays of the element
which can be measured by an energy dispersive spectrometer peaks with appropriate energies
which provide information about the elemental composition of the sample. Peak height is
proportional to elemental concentration. Position and height of peak with appropriate energy
and net count rate of variables give the composition of the element (Goldstein et al., 2012).
In this project Energy Dispersive X-ray analysis was performed with Philips XL 30
equipped with EDX detector to get EDX spectra and elemental composition of the samples
(Sohrabi et al., 2014; Vanaja et al., 2014). Sample powder was dispersed on magnetic tape
fixed on sample holder. Sample was placed in electron microscope and EDX spectra was
produced from back scattered electron image.
3.9 Particles Size Analysis
Dynamic Light Scattering is used to measure particle and molecular size. The
principle of dynamic light scattering is that fine particles and molecules that are in constant
random thermal motion, called Brownian motion, diffuse at a speed related to their size,
smaller particles diffusing faster than larger particles. The speed of Brownian motion is also
determined by the temperature, therefore precision temperature control is essential for
accurate size measurement. To measure the diffusion speed, the speckle pattern produced by
illuminating the particles with a laser is observed. The scattering intensity at a specific angle
will fluctuate with time, and this is detected using a sensitive avalanche photodiode detector
(APD). The intensity changes are analyzed with a digital auto correlator which generates a
correlation function. This curve can be analyzed to give the size and the size distribution
(Pecora, 2013).
In this project particle size was measured using the dynamic light scattering (DLS)
method with Malvern Zetasizer (Nano ZS) (Omar et al., 2014). Sample was dispersed in
36
deionized water and placed in ultrasonic bath to make good suspension. This suspension was
taken in sample cell and analyzed.
3.10 Surface area Pore Size Analysis
Surface area and porosity are two important physical properties that impact the
quality and utility of solid phase chemicals. Gas Adsorption analysis is commonly used for
surface area and porosity measurements. This involves exposing solid materials to gases or
vapors at a variety of conditions which evaluate either the weight uptake or the sample
volume. Analysis of these data provides information regarding the physical characteristics of
the solid including porosity, total pore volume (TOPV), and pore size distribution. The
Brunauer, Emmett and Teller (BET) technique is the most common method for determining
the surface area of powders and porous materials. Nitrogen gas is generally employed as the
probe molecule and is exposed to a solid under investigation at liquid nitrogen conditions
(i.e. 77ᴼ K). The surface area of the solid is evaluated from the measured monolayer capacity
and knowledge of the cross-sectional area of the molecule being used as a probe (Sing, 2001;
Lowell et al., 2012).
The surface area and adsorption–desorption measurements were carried out on
a Micromeritics Tristar 3000 porosimeter at 77ᴼ K using liquid nitrogen. 0.2g of each sample
was taken in sample tubes and degassed at 150 °C for 12 h (Zhu et al., 2013). Loss of weight
was calculated by measuring the weight of empty tubes, weight of sample + tube before and
after degassing. Then theses sample tubes were fixed in Tristar 3000 calculations was made
by software automatically.
3.11 Photocatalytic activity
There are different terms used for photocatalytic reactions (Lu and Pichat, 2013)
(i) Photoxidation (taking place at hole h+)
(ii) Photoreduction (taking place at surface e─)
(iii) Photosensitization (when electron is absorbed by substrate molecule)
37
All photocatalysts should have filled valence band and empty conduction band. A photon
(hv) of light having equal or greater energy than band gap energy of photocatalyst excite
electron from valence band to conduction band a charge separation take place at the surface
of photocatalyst transferring an electron to conduction band and a positive charge hole (h+) at
valence band. When this electron/hole (e─/h+) recombine producing heat energy. This
situation is the failure of photocatalysis and takes place in nano seconds. A successful
photocatalyst should possess the following characteristics (Gaya, 2013).
i) Photocatalyst can reverse its oxidation state so that it can accommodate a hole
without decomposition i.e. semiconductor should have more than one stable
oxidation states.
ii) Photocatalyst should have suitable band gap energy equal to or less than visible
light photon’s energy.
iii) It should be non-photo-corrosive.
iv) It should be non-toxic.
v) It should be cheap and abundantly available.
Different methods have been employed for the testing of photocatalytic activity of
nanophotocatalyst e.g.
i) Decomposition of water for hydrogen production (Teets and Nocera, 2011;
Preethi and Kanmani, 2013).
ii) Degradation of organic waste for electricity production (Lianos, 2011).
iii) Decomposition of insecticides (Kitsiou et al., 2009).
iv) Decomposition of toxic gasses (Barea et al., 2014).
v) Degradation of organic pollutants like Phenols, dyes etc. (Zhang et al., 2014; Ma
et al., 2015).
As this work is for the treatment of synthetic textile waste water therefore three dyes have
been chosen to degrade
i) Methyl Orange
ii) C I Reactive Black 5
iii) Methylene Blue
I
C I Reactive Black 5
Methyl Orange
Methylene Blue
38
These dyes have been chosen due to the reason that the use of dyes in industry are at the top
as compare with other organic pollutants. The focal aim of this work is the testing of the dye
degradation ability of synthesized nanophotocatalysts under visible light irradiation
3.11.1 Photocatalytic activity test
Photocatalytic activity test was performed by the degradation of dyes. An aqueous
100ml solution of dye with different initial concentrations and initial pH of all three dyes was
used. It was taken in a 250 ml glass reactor. Photocatalyst with different doses was added to
the dye solution and stirred in dark for 30 min to develop adsorption desorption equilibrium
(Abdelaal and Mohamed, 2014). The reactor was exposed to visible light using 150 W
halogen lump (Ananpattarachai et al., 2009) with a constant stirring at 200 rpm with
mechanical stirrer in open atmosphere at room temperature. 3ml aliquots were taken from the
system after each 20 min interval (Gupta et al., 2015). These were centrifuged at 4000 rpm
for 10 min to separate catalyst particles and to obtain the clear solution (Ju et al., 2011). The
absorption values were taken to calculate degradation for each sample using Agilent Cary 60
UV-Vis spectrophotometer (Yang et al., 2013). Spectrophotometer was equipped with
software to record data. Base line correction was performed using deionized water.
Degradation percentage was calculated by using following formula (Gupta et al., 2015).
% Degradation = Co −Ct
Co × 100
Where Co absorbance at zero and Ct absorbance at time t.
3.11.2 Optimization of pH
The initial pH value of the reaction mixture affects the photocatalytic activity of the
photocatalyst low pH produces positive charge while high pH produces negative charge to
the surface of photocatalyst. Experiment 3.11.1 was repeated at pH 1,3,5,7 and 9 to optimize
the pH for the degradation of each dye (Siddique et al., 2011).
3.11.3 Optimization of photocatalyst dose
Degradation rate changes with the change of dose of the photocatalyst. At a certain
concentration maximum light can pass through reaction mixture and activate the
39
photocatalytic particles after that concentration photocatalytic particles itself start to hinder
the passage of light resulting in low degradation (Sapawe et al., 2013)b. Photocatalytic
experiment 3.11.1 was repeated at 20, 30, 40, 50, 60 and 70 mg/100ml for all the three dyes.
3.11.4 Optimization of dye concentration:
Initial concentration of the dye solution affects the photocatalytic efficiency of
photocatalyst. By increasing dye concentration more molecules are available for the
adsorption on surface of photocatalyst. But very higher concentration decreases the passage
of light through the dye solution due to dark color (Sobana et al., 2013). To optimize the
initial dye concentration in photocatalytic experiments 20, 30, 40, 50, 60 and 70 ppm solution
were used for each dye.
3.12 Reusability test
Catalyst lifetime is an important parameter of the photocatalytic process because its
use for a longer period of time leads to a significant cost reduction of the treatment (Subash
et al., 2013)a. Reusability test was performed to check the stability and photocatalytic
efficiency of used photocatalyst. In this experiment 100 ml of 50 ppm dye solution was taken
at optimized pH in reactor and 60 mg of photocatalyst was added to the solution and stirred
for 30 min in dark and then exposed to visible light for 140 min and centrifuged to separate
the catalyst. It was washed with deionized water, dried at 100ᴼC for 2 hours and used again in
next experiment. This experiment was repeated 6 times with both photocatalysts for all three
dyes (Jiang et al., 2014).
3.13 Evaluation of Quality Assurance Parameters
3.13.1 Chemical oxygen demand (COD)
Reagent preparations
Digestion solution
Digestion solution was prepared by adding 2.6g K2Cr2O7, 8.33g HgSO4 in 42ml
concentrated H2SO4 (98%) and then diluting it to 250ml with deionized water.
40
Catalyst solution
5.06 g Ag2SO4 was dissolve in 500 ml concentrated H2SO4 and placed it for 48 h to
ensure complete dissolution of Ag2SO4.
Standard Solution of Potassium hydrogen phthalate (KHP)
A standard solution of Potassium hydrogen phthalate was prepared by dissolving
425mg KHP in 1L of deionized water. 425 ppm solution of KHP gives 500 mg/L COD.
Procedure
For COD analysis according to standard methods 3.5 ml of catalyst solution was
added to1.5 ml of digestion solution in clean screw-cap vials and allowed to stand to ambient
temperature. Then 2.5 ml of sample solution was added and vials were incubated at 150°C
for 2 hours in a dry incubator. After allowing the vials to cool to room temperature COD
values were determined by measuring the absorbance of digested assay solution at λ=600nm
on UV-Visible recording spectrophotometer (Rice et al., 2012).
Calculations:
Standard factor =COD of standard KHP
absorbance of digested solution
COD of sample = standard factor × absorbance of digested solution
Percent decrease in chemical oxygen demand was calculated by using following formula.
Decrease in COD % = (COD)initial − (COD)final
(COD)final × 100
3.13.2 Total organic carbon (TOC)
Reagent preparations
2N potassium dichromate (K2Cr2O7) solution was prepared by dissolving 98.06 gram
per litter.
41
250 ppm solution of glucose was prepared by dilution method from a stock solution
of 1000ppm. 25ml of stock solution was taken and diluted to 100ml in volumetric
flask.
Analytical grade sulphuric acid (98%) was used.
Procedure
1.6ml of sulphuric acid was taken in clean screw-cap vials and then 1ml of 2N
potassium dichromate (K2Cr2O7) was added and mixed. Then 4ml of sample solution or
glucose solution was added and incubated at 110°C for 1.5 hours. After incubation
absorbance were taken at λ= 590nm using UV-Visible recording spectrophotometer. (Rice et
al., 2012)
Calculations
Standard factor = concentration of glucose (mg/L)/ absorbance after incubation
TOC of sample (mg/L) = standard factor × absorbance of sample after incubation.
Removal of TOC in percentage was calculated by using formula.
Removal TOC % = (TOC)initial − (TOC)final
(TOC)final × 100
3.12.2 Mineralization test
In this experiment 100 ml of 50 ppm dye solution was taken at optimized pH in
photocatalytic reactor and 60 mg of photocatalyst was added to the solution and stirred for 30
min in dark and then exposed to visible light for 140 min to test mineralization of the dye. 5
ml aliquots were taken from the system after each 20 min and TOC values were obtained
(Hernández-Uresti et al., 2013).
42
3.13.4 Total suspended solids (TSS)
Procedure:
a. Selection of filter paper and sample volume:
Sample volume should be selected to give yield between 2.5 and 200mg dried residues.
And if volume filtered fail to meet minimum yield, increase sample volume up to 1 L. If
complete filtration takes more than 10 minutes, increase filter pore diameter or decrease
sample volume.
b. Sample analysis:
Wattman # 42 filter paper was used for this analysis and volume chosen was 50ml.
First filter paper was made moisture free by placing it in electric oven at 105°C till constant
weight and then 50ml of sample was taken and allowed to filter. After the completion of
filtration, filter paper once again was dried in electric oven at 105°C for 1 hour or till
constant weight and then weighing of that filter paper containing residues was done. (Rice et
al., 2012)
Calculations:
Total suspended solids (mg
L) =
A − B
Sample volume used in ml× 1000
Where:
A = weight of filter paper + dried residue in mg
B = weight of filter paper in mg
3.12.5 Hemolytic Activity (Toxicity)
Hemolytic activity of the compound was studied by the method used by Powell and
coworkers (Powell et al., 2000). Three mL freshly obtained heparinized human blood was
collected from volunteers after consent and counseling. It was gently mixed, poured into a
sterile 15 mL falcon tube and centrifuged for 5 min at 1000 rpm. The supernatant was poured
off and viscous pellet washed three times with 5 mL of chilled (4oC) sterile isotonic
43
Phosphate-buffer saline (PBS) solution. The pH was adjusted at 7.4 and stabilized by mixing
for almost half an hour at room temperature. The washed cells were suspended in the 29 mL
chilled PBS solution. Erythrocytes were counted and found to be 7.068 X 108 cells per mL
for each assay. Then 20μL of solution of the compound was taken in six apendoff tubes, each
of 2mL size. 20μL Triton X-100 (0.1% v/v) was taken as positive control which caused
100% cell lysis and phosphate buffer saline (PBS) was taken as negative control which
caused 0% cell lysis. Then in each apendoff tube (containing 20 μL sample solution) 180 μL
diluted cell suspension was added and mixed well. Tubes were then incubated for 35 min at
37oC agitated for10 min immediately after incubation and the tubes were placed on ice for 5
min. Then tubes were centrifuged for 5 min at 1000 rpm. After centrifugation 100 μL of the
supernatant was taken from each tube and diluted with 900 μL chilled (4oC) PBS. Then all
the tubes were maintained on ice. Then 200 μL of each of the sample concentration was
added into 96 well micro plate. Positive control (100% lysis) and negative control (0% lysis)
were also taken on the same 96 well micro plate. After sampling the absorbance was noted at
576 nm on μQuant (Bioteck, USA). The % RBCs lysis for each concentration was calculated
by using following formula:
Hb Abs.
% Hemolysis = ————— × 100
Hb100% Abs.
Data observed was expressed Hb hemolysis of the sample and Hb100% of 100% hemolysis of
the blood.
3.13 Data analysis
All experiments were performed in triplicates and the experimental data was analyzed by
applying standard deviation.
44
CHAPTER 4
RESULTS AND DISCUSSIONS
4.1 X-Ray Diffraction Analysis
XRD is an important technique which gives information about the crystalline
structure of solids i.e. lattice constants, geometry of crystals, unknown materials, defects and
stresses on crystalline structure (Park et al., 2010). X-ray diffraction analysis was performed
to check the crystallinity of the samples calcined at different temperature and the first
selection of the photocatalyst was made on the basis of XRD results. Sample with calcination
at 600ᴼC were good crystalline in each mixture of metals oxides.
XRD patterns of the samples were analyzed with the help of Match! 3.0.0 (Phase
Identification software from Powder Diffraction) by Crystal Impact Bonn, Germany.
Database used for the analysis was Crystallography Open Database (COD) REV129424
2015.01.07.
4.1.1 X-Ray Diffraction Analysis of (Al2O3)1-x(ZnO)x(Fe2O3)
4.1.1.1 X-Ray Diffraction Analysis of Al2O3.Fe2O3 synthesized by mechanically stirred
co-precipitation
Al2O3.Fe2O3 synthesized by mechanically stirred co-precipitation was calcined at
400ᴼC and 600 ᴼC and the XRD patterns of un-calcined and calcined sample are given in Fig.
4.1. Un-calcined sample did not show any crystallinity as there is no peak. Sample calcined
at 400ᴼC has peaks for crystalline structures but these peaks are broad which show some
crystalline and some amorphous phase in the sample. But the sample calcined at 600ᴼC has
very sharp peaks which confirm its crystallinity. This sample has two type of crystal system.
Peaks at 2θ is equal to 32.95ᴼ, 35.57ᴼ, 40.94ᴼ, 49.28ᴼ, 62.56ᴼ and 63.87ᴼ are peaks for α-Fe2O3
(hematite) with rhombohedral crystal system according to entry number 96-900-9783.
Hercynite phase was also detected with peaks at 18.78ᴼ, 63.61ᴼ and small peaks at 72.06ᴼ and
45
75.06ᴼ which represents the reported formula AlFe2O4 with cubic crystal system according to
entry number 96-901-2447.
Fig. 4.1 XRD patterns of Al2O3.Fe2O3 synthesized by mechanically stirred co-
precipitation
Fig. 4.2 XRD patterns of Al2O3.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
46
4.1.1.2 XRD Analysis of Al2O3.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation.
XRD pattern of Al2O3.Fe2O3 synthesized by ultra-sonic assisted mechanically stirred and
calcined at 600ᴼC are shown in Fig. 4.2. Two types of crystal system were detected basic
sharp peaks at 2θ = 24.26ᴼ, 33.31ᴼ, 35.76ᴼ, 43.72ᴼ, 54.87ᴼ, 62.75ᴼ, 64.94ᴼ, 72.36ᴼ, 81.83ᴼ,
83.41ᴼ and 89.04ᴼ represents the α-Fe2O3 (Hematite) with trigonal crystal system according to
entry number 96-901-4881. Gahnite phase was also detected at 2θ = 39.41ᴼ, 49.71ᴼ, 56.31ᴼ,
69.93ᴼ, 75.44ᴼ and 94.29ᴼ which represents cubic crystal system according to the entry
number 96-900-7028.
4.1.1.3 X-Ray Diffraction Analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by
mechanically stirred co-precipitation
XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred co-
precipitation are shown in Fig. 4.3. Peaks at 2θ equal to 24.21ᴼ, 33.25ᴼ, 40.96ᴼ, 54.23ᴼ, 57.76ᴼ,
and 69.84ᴼ matching with α-Fe2O3 (hematite) with trigonal crystal system according to entry
number 96-901-4881. Two peaks at 49.60ᴼ and 83.28ᴼ confirm the gahnite phase Al2O4Zn
(entry number 96-900-7025) and a peak at 62.39ᴼ represents ZnO (Zincite) with hexagonal
crystal system according to entry number 96-901-1663. So the sample has more than 1 phase
and crystal systems.
4.1.1.4 X-Ray Diffraction Analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation
XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation are shown in Fig. 4.4. XRD Pattern for the sample
calcined at 600ᴼC showed the peaks at 2θ is equal to 24.21ᴼ, 33.25ᴼ, 40.96ᴼ, 54.23ᴼ, 57.76ᴼ,
and 69.84ᴼ matching with α-Fe2O3 (hematite) with trigonal crystal system according to entry
number 96-901-4881. It is the basic constituent of the (Al2O3)0.75(ZnO)0.25Fe2O3
photocatalyst. Peaks matching with the formula Al2Fe0.4O4Zn0.6 at 64.94ᴼ and 85.23ᴼ which
confirm the presence of gahnite phase in the sample (entry number 96-900-6314).Two more
peaks at 49.60ᴼ and 83.28ᴼ also confirm the gahnite phase matching with Al2O4Zn according
to entry number 96-900-7025.
47
Fig. 4.3 XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred
co-precipitation
Fig. 4.4 XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
48
4.1.1.5 X-Ray Diffraction Analysis of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by
mechanically stirred co-precipitation
XRD patterns of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by mechanically stirred co-
precipitation and calcined at 600ᴼC matched with three different phases Hematite, Hercynite
and Franklinite. α-Fe2O3 (hematite) with trigonal crystals belongs to the peaks at 24.16ᴼ,
33.20ᴼ, 39.75ᴼ, 40.82ᴼ, 64.03ᴼ, 75.65ᴼ and 85.93ᴼ according to the entry number 96-591-0083.
Cubic Fe2O4Zn (Franklinite) has peaks at 2θ is equal to 29.99ᴼ, 35.65ᴼ, 62.52ᴼ and 65.86ᴼ
(entry no. 96-900-6896). A small amount of cubic AlFe2O4 (hercynite) was detected with
peaks at 35.65ᴼ, 54.14ᴼ, 57.70ᴼ and 80.38ᴼ according to entry number 96-901-2447. Patterns
are shown in Fig. 4.5.
Fig. 4.5 XRD patterns of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by mechanically stirred
co-precipitation
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
49
4.1.1.6 X-Ray Diffraction Analysis of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation
Un-calcined (Al2O3)0.50(ZnO)0.50Fe2O3 did not show any crystallinity and calcined at
400ᴼC showed some peaks appeared in both samples synthesized by mechanically stirred and
ultra-sonic assisted mechanically stirred co-precipitation. Only the sample calcined at 600ᴼC
has sharp peaks so phase analysis was performed for it. Patterns are shown in Fig. 4.6. Peaks
at 2θ = 33.21ᴼ, 37.01ᴼ, 49.47ᴼ, 62.46ᴼ, 72.06ᴼ, 75.51ᴼ, 80.86ᴼ, 83.08ᴼ, 88.56ᴼ and 93.84ᴼ are the
characteristics peaks for Al2O3 with orthorhombic crystal system according to entry number
96-100-0443. AlFe2O4 with Hercynite phase is also detected according to entry number 96-
901-2447 and peaks at 2θ equal to 30.55ᴼ, 35.64ᴼ, 54.17ᴼ, 57.69ᴼ, 72.06ᴼ, 75.51ᴼ, 83.08ᴼ and
88.56ᴼ. Peaks at 2θ = 33.21ᴼ, 35.64ᴼ, 40.93ᴼ, 49.47ᴼ, 85.10ᴼ and some common peaks with
other confirmed the presence of α-Fe2O3 (Hematite).
Fig. 4.6 XRD patterns of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
50
4.1.1.7 X-Ray Diffraction Analysis of (Al2O3)0.25(ZnO)0.75Fe2O3 synthesized by
mechanically stirred co-precipitation
X-Ray diffraction analysis of (Al2O3)0.25(ZnO)0.75Fe2O3 also showed the same
behavior for un-calcined and calcined at 400ᴼC. So phase analysis from XRD patterns of
(Al2O3)0.25(ZnO)0.75Fe2O3 calcined at 600ᴼC was done with Match! 3.0.0. XRD patterns are
shown in Fig. 4.7 and 4.8.
(Al2O3)0.25(ZnO)0.75Fe2O3 synthesized by mechanically stirred co-precipitation and
calcined at 600ᴼC showed about 62.6% franklinite phase as the peaks at 2θ = 30.08ᴼ, 62.66ᴼ,
71.42ᴼ and 7.43ᴼ matched with cubic Fe2O4Zn according to the entry 96-900-6896. AlFe2O4
(hercynite) with cubic crystal system was detected by matching with peaks at 30.70ᴼ, 54.32ᴼ,
57.60ᴼ, 63.95ᴼ, 75.43ᴼ and 88.30ᴼ (entry number 96-901-2447). Peaks at 3.70ᴼ, 35.41ᴼ and
80.65ᴼ matched with hexagonal ZnO (entry number 96-101-1260). Some specific peaks for
trigonal hematite were also observed at 24.05ᴼ, 33.36ᴼ, 41.07ᴼ, 49.07ᴼ, 84.96ᴼ and 95.59ᴼ
according to entry number 69-901-4881.
Fig. 4.7 XRD patterns of (Al2O3)0.25(ZnO)0.75Fe2O3 synthesized by mechanically stirred
co-precipitation
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
51
4.1.1.8 X-Ray Diffraction Analysis of (Al2O3)0.25(ZnO)0.75Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation
Another method used for the synthesis of (Al2O3)0.25(ZnO)0.75Fe2O3 was ultra-sonic
assisted mechanically stirred co-precipitation almost the same peaks with some additional
peaks were observed for this sample but there was a change in crystal system. XRD patterns
are shown in Fig. 4.8. It can be observed from peaks for rhombohedral hematite (α-Fe2O3) at
2θ = 24.16ᴼ, 33.16ᴼ, 40.86ᴼ, 49.47ᴼ, 75.51ᴼ, 83.08ᴼ and 88.62ᴼ according to entry number 96-
900-9783. Peaks matched with cubic franklinite (Fe2O4Zn) at 30.18ᴼ, 43.34ᴼ, 62.52ᴼ, 74.66ᴼ,
78.90ᴼ and 89.53ᴼ (entry number 96-9006-895). Some common peaks for hexagonal ZnO
were observed at 54.11ᴼ, 64.02ᴼ, 72.11ᴼ and 80.73ᴼ (entry number 96-101-1260).
Fig. 4.8 XRD patterns of (Al2O3)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
4.1.1.9 X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by mechanically stirred
co-precipitation
Phase identification for ZnO.Fe2O3 synthesized by mechanically stirred co-
precipitation calcined at 600ᴼC was done and two types of phases hematite (α-Fe2O3) and
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
52
franklinite (Fe2O4Zn) were detected. Hematite with rohmbohedral crystal system was
identified at 2θ is equal to 24.09ᴼ, 33.09ᴼ, 49.40ᴼ, 54.04ᴼ, 57.56ᴼ, 62.39ᴼ, 63.95ᴼ, 69.50ᴼ,
71.91ᴼ, 75.37ᴼ, 77.65ᴼ, 80.59ᴼ,8.89ᴼ and 88.48ᴼ according to entry number 96-101-1241.
Franklinite with cubic crystals was identified at 2θ = 18.15ᴼ, 29.90ᴼ, 35.62ᴼ, 42.82ᴼ, 53.12ᴼ,
56.58ᴼ, 62.15ᴼ, 70.54ᴼ, 73.48ᴼ, 88.94ᴼ and 93.64ᴼ according to entry number 96-900-5108.
XRD patterns are shown in Fig. 4.9.
Fig. 4.9 XRD patterns of ZnO.Fe2O3 synthesized by mechanically stirred co-
precipitation
4.1.1.10 X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
XRD patterns of ZnO.Fe2O3 synthesized by ultra-sonic assisted co-precipitation and
calcined at 600ᴼC is shown in Fig. 4.10. It has matched with three phases rhombohedral
hematite (α-Fe2O3), cubic franklinite (Fe2O4Zn) and small amount of hexagonal zincite
(ZnO). Characteristic peaks for hematite are at 2θ = 24.33ᴼ, 33.14ᴼ, 41.04ᴼ, 49.65, ᴼ 54.28ᴼ,
57.74ᴼ, 69.81ᴼ, and all the peaks from 75.62ᴼ to 93.88ᴼ (entry number 96-900-9783). Peaks
identified for franklinite are at 2θ = 18.33, ᴼ 30.14ᴼ, 35.50ᴼ, 43.06ᴼ, 56.89ᴼ and 62.75ᴼ (entry
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
53
number 96-900-6896). Zincite has peaks at 35.25ᴼ, 62.34ᴼ, 64.20ᴼ and 72.09ᴼ(entry No. 96-
101-1260).
Fig. 4.10 XRD patterns of ZnO.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation
4.1.2 X-Ray Diffraction Analysis of (ZrO2)1-x(ZnO)x(Fe2O3)
4.1.2.1 X-Ray Diffraction Analysis of ZrO2.Fe2O3 synthesized by mechanically stirred
co-precipitation
ZrO2.Fe2O3 synthesiszed by mechanically co-precipitation with calcination
temperature 600ᴼC was analyzed for phase identification. ZrO2 with cubic crystal system and
α-Fe2O3 with trigonal crystal system were detected. Peaks at 2 = 24.12ᴼ, 33.12ᴼ, 40.81ᴼ,
49.41ᴼ, 53.98ᴼ and 62.33ᴼ represent α-Fe2O3 according to entry number 96-900-0140 and
peaks at 30.43ᴼ, 50.90ᴼ, 60.54ᴼ and 63.90ᴼ are the characteristics peaks for ZrO2 according to
entry number 96-900-9052. XRD patterns are shown in Fig. 4.11.
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
54
Fig. 4.11 XRD patterns of ZrO2.Fe2O3 synthesized by mechanically stirred co-
precipitation
4.1.2.2 X-Ray Diffraction Analysis of ZrO2 .Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically stirred co-precipitation
and calcined at 600ᴼC showed sharp peaks. Baddeleyite (ZrO2) with monoclinic crystal
system and trigonal hematite (α-Fe2O3) was detected. Baddeleyite has characteristic peaks at
2θ is equal 33.43ᴼ, 36.04ᴼ, 72.89ᴼ, 76.29ᴼ and 89.45ᴼ according to entry number 96-900-7449
and hematite detected at 24.49ᴼ, 33.43ᴼ, 49.80ᴼ, 58.35ᴼ, 72.89ᴼ, 62.59ᴼ and 89.28ᴼ according
to entry number 96-901-6458. Patterns are shown in Fig. 4.12.
4.1.2.3 X-Ray Diffraction Analysis of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by
mechanically stirred co-precipitation
XRD patterns of (ZrO2)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred co-
precipitation technique are shown in Fig.4.13. Sample calcined at 600ᴼC has two broad peaks
from 27ᴼ to 36ᴼ and 60ᴼ to 63ᴼ. Peaks detected under this rang of 2θ are 30.78ᴼ, 34.36ᴼ, 62.02ᴼ
for hexagonal ZnO, 28.25ᴼ, 32.01ᴼ, 36.22ᴼ, 61.49ᴼ and 62.47ᴼ for monoclinic ZrO2, 35.99,
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
55
60.54 for cubic wuestite (FeO) and 31.00ᴼ, 60.54ᴼ for cubic franklinite according to entry
number 96-101-1260, 96-230-0204, 96-900-8637 and 96-900-6908 respectively.
Fig. 4.12 XRD patterns of ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation
Fig. 4.13 XRD patterns of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by mechanically stirred
co-precipitation
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
56
4.1.2.4 X-Ray Diffraction Analysis of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation
Baddeleyite ZrO2 with orthorhombic crystals, cubic Franklinite Fe2O4Zn, ZnO with
hexagonal crystal system and trigonal hematite (α-Fe2O3) were the detected phases in
(ZrO2)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted mechanically stirred co-
precipitation technique. XRD pattern has no very sharp peaks but the specific and some
common peaks which can be observed at 2θ are 30.46ᴼ, 35.62ᴼ, 51.08ᴼ, 60.08ᴼ and 35.92ᴼ for
ZrO2, 30.46ᴼ, 63.61ᴼ and 35.92ᴼ for Fe2O4Zn, 56.64ᴼ, 62.89ᴼ for ZnO and 35.62ᴼ, 56.30ᴼ,
62.56ᴼ for Fe2O3 according to entry number 96-9005836, 96-900-6901, 96-230-0113 and 96-
901-5066 respectively. XRD patterns are shown in Fig. 4.14.
Fig. 4.14 XRD patterns of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
4.1.2.5 X-Ray Diffraction Analysis of (ZrO2)0.50(ZnO)0.50 Fe2O3 synthesized by
mechanically stirred co-precipitation
XRD patterns of (ZrO2)0.50(ZnO)0.50Fe2O3 synthesized by mechanically stirred co-
precipitation are shown in Fig. 4.15. Sample calcined at 600ᴼC has peaks for following
phases. a) Cubic franklinite (Fe2O4Zn) at 2θ = 18.25ᴼ, 30.02ᴼ, 42.88ᴼ and 62.42ᴼ (Entry No.
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
57
96-900-6895). b) Cubic maghemite (Fe2O3) at 2θ = 18.25ᴼ, 30.02ᴼ, 35.75ᴼ and 62.83ᴼ (Entry
no. 96-9006317). c) monoclinic baddeleyite (ZrO2) at 35.75ᴼ, 50.71ᴼ, 59.65ᴼ and 62.45ᴼ
according to entry number 96-900-7449.
Fig. 4.15 XRD patterns of (ZrO2)0.50(ZnO)0.50 Fe2O3 synthesized by mechanically stirred
co-precipitation
4.1.2.6 X-Ray Diffraction Analysis of (ZrO2)0.50(ZnO)0.50 Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation
Phases detected in XRD patterns (ZrO2)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation and calcined at 600ᴼC are. a) Cubic franklinite
(Fe2O4Zn) at 2θ = 18.25ᴼ, 30.02ᴼ, 42.88ᴼ and 62.42ᴼ (Entry No. 96-900-6895). b) Cubic
maghemite (Fe2O3) at 2θ = 24.02ᴼ, 32.25ᴼ, 40.71ᴼ, and 49.25ᴼ (Entry no. 96-901-2693). c)
Cubic ZrO2 at 2θ = 30.54ᴼ, 35.34ᴼ and 63.66ᴼ (Entry No. 96-900-9052). d) Hexagonal ZnO at
2θ = 32.01ᴼ and 63.66ᴼ according to entry number 96-230-0114. Patterns are shown in Fig.
4.16.
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
58
Fig. 4.16 XRD patterns of (ZrO2)0.50(ZnO)0.50 Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
4.1.2.7 X-Ray Diffraction Analysis of (ZrO2)0.25(ZnO)0.75 Fe2O3 synthesized by
mechanically stirred co-precipitation
XRD pattern of (ZrO2)0.25(ZnO)0.75 Fe2O3 synthesized by mechanically stirred co-
precipitation are shown in Fig. 4.17. Sample calcined at 600ᴼC showed four broad peaks
ranging at 2θ = 25ᴼ to 37ᴼ, 47ᴼ to 50ᴼ, 54ᴼ to 60ᴼ and 61ᴼ to 65ᴼ. Maghemite (tetragonal Fe2O3)
was detected at 2θ is equal to 26.14ᴼ, 34.02ᴼ, 55.07ᴼ and 63.07ᴼ (Entry No. 96-901-2693).
Zincite (hexagonal ZnO) was detected at 34.31ᴼ, 35.42ᴼ, 61.95ᴼ and 64.08ᴼ (Entry No. 96-
101-1260). Monoclinic ZrO2 was detected at 35.21ᴼ, 55.25ᴼ, 55.56ᴼ, 55.81ᴼ and 62.85ᴼ (Entry
No. 96-230-0297).
4.1.2.8 X-Ray Diffraction Analysis of (ZrO2)0.25(ZnO)0.75 Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation
Franklinite, baddeleyite and hematite were detected in XRD patterns of
(ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic assisted mechanically stirred co-
precipitation technique which are shown in Fig. 4.18. (ZrO2)0.25(ZnO)0.75Fe2O3 calcined at
600ᴼC has identified peaks at 2θ = 18.30ᴼ, 29.98ᴼ, 53.27ᴼ, 56.73ᴼ, 62.27ᴼ, 73.69 and 89.15 are
the characteristics peaks for franklinite (Fe2O4Zn) with cubic crystals (Entry No. 96-900-
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
59
6895). Orthorhombic baddeleyite (ZrO2) was detected at 2θ = 35.57ᴼ, 43.00ᴼ and 86.41ᴼ
(Entry No. 6-900-5836). Trigonal hematite (Fe2O3) identified with the characteristic peaks at
2θ is equal to 24.10ᴼ, 33.24ᴼ, and 35.57ᴼ according to entry number 96-901-4881.
Fig. 4.17 XRD patterns of (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by mechanically stirred
co-precipitation
Fig. 4.18 XRD patterns of (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
Calcined at 400ᴼC
Calcined at 600ᴼC
Uncalcined
60
4.1.2.9 X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by mechanically stirred
and ultra-sonic assisted mechanically stirred co-precipitation
XRD analysis of ZnO.Fe2O3 synthesized by mechanically stirred is given in section
4.1.1.9 and XRD analysis of ZnO.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred is given in section 4.1.1.10
4.2 Scanning Electron Microscopy
4.2.1 Scanning Electron Microscopy of (Al2O3)1-x(ZnO)xFe2O3
Scanning Electron Microscopy (SEM) was done for the samples with best
photocatalytic activity from (Al2O3)1-x(ZnO)xFe2O3 synthesized by both simple stirred and
ultra-sonic assisted stirred co-precipitation. The samples synthesized by ultra-sonic assisted
mechanically stirred co-precipitation showed good photocatalytic efficiency. All three dyes
have maximum photocatalytic degradation with these samples. SEM images of the samples
synthesized by ultra-sonic assisted mechanically stirred co-precipitation are shown in Fig
4.19 to 4.23 for Al2O3.Fe2O3, (Al2O3)0.75(ZnO)0.25Fe2O3, (Al2O3)0.50(ZnO)0.50 Fe2O3,
(Al2O3)0.25(ZnO)0.75Fe2O3 and ZnO.Fe2O3 (Calcined at 600ᴼC) respectively it is clear from
the images that all the photocatalysts have no specific shape. But the SEM image of
(Al2O3)0.75(ZnO)0.25Fe2O3 has round shape particles with large surface area that is why it was
most active sample for photocatalysis and it degraded all three dyes above 80 percent.
ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ1 µm
Fig. 4.19 SEM image of Al2O3.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation and calcined at 600ᴼC
61
Fig. 4.20 SEM Image of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
Fig. 4.21 SEM Image of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
62
Fig. 4.22 SEM Image of (Al2O3)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
Fig. 4.23 SEM Image of ZnO.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation and calcined at 600ᴼC
4.2.2 Scanning Electron Microscopy for (ZrO2)1-x(ZnO)xFe2O3
Samples with high photocatalytic efficiency were analyzed by Scanning Electron
Microscopic analysis for (ZrO2)1-x(ZnO)xFe2O3.The samples synthesized by ultra-sonic
63
assisted mechanically stirred co-precipitation calcined at 600ᴼC have higher photocatalytic
activity than the samples synthesized by simple mechanically stirred. SEM results are shown
in Fig 4.24 to 4.27 for ZrO2.Fe2O3, (ZrO2)0.75(ZnO)0.25Fe2O3, (ZrO2)0.5(ZnO)0.5Fe2O3 and
(ZrO2)0.25(ZnO)0.75Fe2O3 respectively. ZnO.Fe2O3 is shown in Fig. 4.23. There was no
specific shape observed in all samples.
Fig. 4.24 SEM Image of ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation and calcined at 600ᴼC
Fig. 4.25 SEM Image of (ZrO2)0.75(ZnO)0.75Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
64
Fig. 4.26 SEM Image of (ZrO2)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
Fig. 4.27 SEM Image of (ZrO2)0.25(ZnO)0.750Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
65
4.3 Energy Dispersive X-Ray (EDX) Analysis
4.3.1 Energy Dispersive X-Ray (EDX) Analysis of (Al2O3)1-x(ZnO)xFe2O3
EDX analysis was done for for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic
assisted stirred during co-precipitation. The samples synthesized by ultra-sonic assisted co-
precipitation have best results for the removal of dyes from waste water. . Homogeneity of
the material can be observed form back scatter electron images all samples are homogeneous
but Al2O3.Fe2O3 is non-homogeneous material as its surface has different shades and it looks
like a pours material at the same time it is least efficient for photocatalysis.
4.3.1.1 Energy Dispersive X-Ray Analysis of Al2O3 .Fe2O3
EDX analysis of Al2O3.Fe2O3 was performed with help of Philips XL 30 equipped
with EDX detector and back scatter electron images of the samples were taken to analyze the
chemical composition of the samples for qualitative and some estimation of molar and
weight percentage of elements present in sample. It is clear from the SEM image shown in
Fig. 4.28 that the sample was non-homogeneous metals oxide. The area underlined in Fig.
4.28 was pointed out for EDX spectra which are shown in Fig. 4.29. Spectra have very clear
peaks for Fe, Al and O a small peak of C also observed which is due the magnetic tape used
for the support of sample on stub this peak was eliminated for the weight and molar percent
analysis. Estimated weight and molar percent for Fe, Al and O from the EDX spectra is
shown in Table 4.1.
Fig. 4.28 SEM (back scatter) image for EDX spectra of Al2O3.Fe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation and calcined at 600ᴼC
66
Fig. 4.29 EDX spectra of Al2O3.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation and calcined at 600ᴼC
Table No. 4.1 Estimated weight and molar percent of Al2O3.Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation and calcined at 600ᴼC from EDX
spectra
Component Wt % Mol %
Al2O3 22.74 31.55
Fe2O3 77.26 68.45
Total 100.00 100.00
4.3.1.2 Energy Dispersive X-Ray Analysis of (Al2O3)0.75(ZnO)0.25Fe2O3
Sample with formula (Al2O3)0.75(ZnO)0.25Fe2O3 was analyzed with EDX and back
scatter electron image of the sample was taken to analyze the surface and chemical
composition of the sample for qualitative and quantitative analysis. Fig. 4.30 shows that the
sample was homogeneous metals oxide. EDX spectra shown in Fig. 4.31 have very clear
peaks for Fe, Al, Zn and O. Estimated weight and molar percent was performed from the
EDX spectra which is shown in Table 4.2 which confirm the percent composition used for
the synthesis of photocatalyst.
67
Fig. 4.30 SEM (back scatter) image for EDX spectra of (Al2O3)0.75(ZnO)0.25Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC
Fig. 4.31 EDX spectra of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
68
Table No. 4.2 Estimated weight and molar percent of (Al2O3)0.75(ZnO)0.25Fe2O3 from
EDX spectra. Synthesized by ultra-sonic assisted mechanically stirred co-precipitation
and Calcined at 600ᴼC from EDX spectra.
Component Wt % Mol %
Al2O3 14.24 19.49
Fe2O3 79.20 69.25
ZnO 6.56 11.26
Total 100.00 100.00
4.3.1.3 Energy Dispersive X-Ray Analysis of (Al2O3)0.50(ZnO)0.50Fe2O3
It is clear from back scatter electron SEM image (Fig. 4.32) that sample was
homogeneous metals oxide. EDX spectra shown in Fig. 4.33 have very clear peaks for Fe,
Al, Zn and O a small peak of C was also observed which is due the magnetic tape used for
the support of sample on stub. All other elements were eliminated from Peak list to estimate
the weight and molar percent from the EDX spectra which is shown in table 4.3.
Fig. 4.32 SEM (back scatter) image for EDX spectra of (Al2O3)0.50(ZnO)0.50Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC
69
Fig. 4.33 EDX spectra of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
Table No. 4.3 Estimated weight and molar percent of (Al2O3)0.50(ZnO)0.50Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC from EDX spectra
Component Wt % Mol %
Al2O3 17.34 22.98
Fe2O3 74.01 62.64
ZnO 8.65 14.38
Total 100.00 100.00
4.3.1.4 Energy Dispersive X-Ray Analysis of (Al2O3)0.25(ZnO)0.75 Fe2O3
EDX analysis of homogeneous metals oxide (Al2O3)0.25(ZnO)0.75 Fe2O3 from SEM
back scatter electron image is shown in Fig. 4.34 and EDX spectra in Fig. 4.35. Peaks for Fe,
Al and O are very clear in Fig. 4.24 some other peaks of C and Si due to support used for the
sample. Weight and molar percent estimated from EDX spectra are shown in table 4.4.
70
Fig. 4.34 SEM (back scatter) image for EDX spectra of (Al2O3)0.25(ZnO)0.75 Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC
Fig. 4.35 EDX spectra of (Al2O3)0.25(ZnO)0.75 Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
Table No. 4.4 Estimated weight and molar percent of (Al2O3)0.25(ZnO)0.75 Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC from EDX spectra
Component Wt % Mol %
Al2O3 5.91 8.14
Fe2O3 83.24 73.16
ZnO 10.84 18.70
Total 100.00 100.00
71
4.3.1.5 Energy Dispersive X-Ray Analysis of ZnO.Fe2O3
Sample with formula ZnO.Fe2O3 was analyzed energy dispersive X-rays with help of
Philips XL 30. Image produced by back scatter electrons is given in Fig. 4.36 and EDX
spectra shown in Fig. 4.37. Clear peaks were observed for Fe, Zn and O a small peak of Si
also observed which is due the silicon wafers used for the support of sample on stub.
Estimated weight and molar percent was performed from the EDX spectrum which is shown
in Table 4.5 in this estimation Si peak was eliminated from the observed peaks. Estimated
quantities are near to the percent composition used for the synthesis of photocatalyst.
Fig. 4.36 SEM (back scatter) image for EDX spectra of ZnO.Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation and calcined at 600ᴼC
Fig. 4.37 EDX spectra of ZnO.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation and calcined at 600ᴼC
72
Table No. 4.5 Estimated weight and molar percent of ZnO.Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation and calcined at 600ᴼC from EDX
spectra
Component Wt % Mol %
Fe2O3 87.62 78.29
ZnO 12.38 21.71
Total 100.00 100.00
4.3.2. Energy Dispersive X-Ray (EDX) Analysis of (ZrO2)1-x(ZnO)xFe2O3
4.3.2.1 Energy Dispersive X-Ray Analysis of ZrO2.Fe2O3
Back scatter electron image of the sample was taken to analyze the surface of the
photocatalyst and its chemical composition. Results are shown in Fig. 4.76. SEM image
showed that the sample was homogeneous mixture of metals oxide. An EDX spectrum of the
sample is shown in Fig. 4.77. Peaks for Fe, Zr and O are very clear and peaks for C and Al
also observed which is due the magnetic tape used for the support of sample on aluminum
stub these peaks were not included in elemental estimation. Estimated weight and molar
percent of Zr and Fe oxides are shown in Table 4.45
Fig. 4.38 SEM (back scatter) image for EDX spectra of ZrO2.Fe2O3 synthesized by
ultra-sonic assisted mechanically stirred co-precipitation and calcined at 600ᴼC
73
Fig. 4.39 EDX spectra of ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation and calcined at 600ᴼC
Table No. 4.6 Estimated weight and molar percent of ZrO2.Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation and calcined at 600ᴼC from EDX
spectra
Component Wt % Mol %
Fe2O3 56.26 49.81
ZrO2 43.74 50.19
Total 100.00 100.00
4.3.2.2 Energy Dispersive X-Ray Analysis of (ZrO2)0.75(ZnO)0.25 Fe2O3
(ZrO2)0.75(ZnO)0.25Fe2O3 was analyzed for the surface and chemical composition of
the sample. It is clear from the Fig. 4.40 the sample was homogeneous metals oxide the area
underlined was used for EDX spectra which shown in Fig. 4.41. Spectra have very clear
peaks for Fe, Zr, Zn and O a small peak for Al also observed which is due the Al support
used for sample. Estimated weight and molar percent was performed from the EDX spectra
74
which is shown in Table 4.46 which is almost same to the percent composition used for the
synthesis of photocatalyst.
Fig. 4.40 SEM (back scatter) image for EDX spectra of (ZrO2)0.75(ZnO)0.25Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC
Fig. 4.41 EDX spectra of (ZrO2)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
75
Table No. 4.7 Estimated weight and molar percent of (ZrO2)0.75(ZnO)0.25Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC from EDX spectra
Component Wt % Mol %
Fe2O3 65.76 57.81
ZrO2 28.83 32.85
ZnO 5.41 9.34
Total 100.00 100.00
4.3.2.3 Energy Dispersive X-Ray Analysis of (ZrO2)0.50(ZnO)0.50Fe2O3
EDX analysis of (ZrO2)0.50(ZnO)0.50Fe2O3 was performed for qualitative and
estimation of quantitative analysis. It is clear from the Fig. 4.42 the sample was
homogeneous metals oxide the area underlined was used for EDX spectra shown in Fig. 4.43.
Spectra have very clear peaks for Fe, Zr, Zn and O a small peak of Al also observed which is
due the Al support of sample stub. Estimated elemental weight and molar percent is shown in
Table 4.8 which is almost same as the composition used for the synthesis of photocatalyst.
Fig. 4.42 SEM (back scatter) image for EDX spectra of (ZrO2)0.50(ZnO)0.50Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC.
76
Fig. 4.43 EDX spectra of (ZrO2)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
Table No. 4.8 Estimated weight and molar percent of (ZrO2)0.50(ZnO)0.50Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC from EDX spectra
Component Wt % Mol %
Fe2O3 65.76 57.81
ZrO2 28.83 32.85
ZnO 5.41 9.34
Total 100.00 100.00
4.3.2.4 Energy Dispersive X-Ray Analysis of (ZrO2)0.25(ZnO)0.75 Fe2O3
EDX analysis of (ZrO2)0.25(ZnO)0.75 Fe2O3 was performed from the back scatter
electron image of the sample to analyze the surface and chemical composition of the sample.
Fig. 4.44 showed the homogeneous mixture of metals oxides. EDX spectra are shown in Fig.
4.45. The spectrum has very clear peaks for Fe, Zr and O peaks of C, Al and Si also observed
which is due the magnetic tape used for the support of sample on Al stub and silicon support.
Estimated weight and molar percent was performed from the EDX spectra which is shown in
Table 4.9.
77
Fig. 4.44 SEM (back scatter) image for EDX spectra of (ZrO2)0.25(ZnO)0.75Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC
Fig. 4.45 EDX spectra of (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation and calcined at 600ᴼC
Table No. 4.9 Estimated weight and molar percent of (ZrO2)0.25(ZnO)0.75Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at
600ᴼC from EDX spectra
Component Wt % Mol %
Fe2O3 76.71 66.90
ZrO2 11.62 13.13
ZnO 11.67 19.97
Total 100.00 100.00
78
4.4 Particle Size, Surface area and porosity analysis
4.4.1 Particle Size analysis of (Al2O3)1─x(ZnO)xFe2O3
Particle size was analyzed by Malvern Zetasizer (Nano ZS). Average particle
sizes are given in table No. 4.10 and 4.11 for (Al2O3)1-x(ZnO)xFe2O3 synthesized by co-
precipitation by mechanically stirred co-precipitation and (Al2O3)1-x(ZnO)xFe2O3 synthesized
by co-precipitation by ultra-sonic assisted mechanically stirred co-precipitation with different
values of x. It was observed from SEM images that particles were not of a specific shape so
the Zetasizer calculates the diameter of particles from different directions and give average
particle size as distribution of particle size by intensity. Particle sizes were also calculated
from X-Ray diffraction patterns by using Scherer’s formula. Both results have values close to
each other whith the confirmation of actual particle sizes. Effect of ultra-sonic assisted
stirring during the co-precipitation is the decrease in particle sizes. Photocatalytic activity
was improved due to small particle size and large surface area.
Table No. 4.10 particle sizes of (Al2O3)1-x(ZnO)xFe2O3 synthesized with mechanically
stirred co-precipitation technique at different values of x
X
(Al2O3)1-x(ZnO)xFe2O3
Average particle
Size with Zetasizer
(nm)
Particle size Calculated by
Scherer’s formula from XRD
(nm)
0 Al2O3.Fe2O3 28.21 27.91
0.25 (Al2O3)0.75(ZnO)0.25Fe2O3 53.15 52.40
0.50 (Al2O3)0.5(ZnO)0.5Fe2O3 39.56 38.33
0.75 (Al2O3)0.25(ZnO)0.75Fe2O3 53.64 53.01
1 ZnO.Fe2O3 29.22 28.31
79
Table No. 4.11 particle sizes of (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation technique at different values of x
X
(Al2O3)1-x(ZnO)xFe2O3
Average particle
Size with Zetasizer
(nm)
Particle size Calculated by
Sherer’s formula from XRD
(nm)
0 Al2O3.Fe2O3 12.51 11.09
0.25 (Al2O3)0.75(ZnO)0.25Fe2O3 28.29 23.06
0.50 (Al2O3)0.5(ZnO)0.5Fe2O3 25.21 24.95
0.75 (Al2O3)0.25(ZnO)0.75Fe2O3 36.11 35.37
1 ZnO.Fe2O3 22.15 21.35
Fig. 4.46 Particle size distribution by intensity for Al2O3.Fe2O3 synthesized by
mechanically stirred co-precipitation
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
80
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.47 Particle size distribution by intensity for (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized
by mechanically stirred co-precipitation
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.48 Particle size distribution by intensity for (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized
by mechanically stirred co-precipitation
81
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.49 Particle size distribution by intensity for (Al2O3)0.25(ZnO)0.75Fe2O3 synthesized
by mechanically stirred co-precipitation
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.50 Particle size distribution by intensity for ZnO.Fe2O3 synthesized by
mechanically stirred co-precipitation
82
0 5 10 15 20 25 30 35 400
1
2
3
4
5
6
7
8
Inte
nsity (
%)
Size (d.nm)
Fig. 4.51 Particle size distribution by intensity for Al2O3.Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.52 Particle size distribution by intensity for (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized
by ultra-sonic assisted mechanically stirred co-precipitation
83
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.53 Particle size distribution by intensity for (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized
by ultra-sonic assisted mechanically stirred co-precipitation
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.54 Particle size distribution by intensity for (Al2O3)0.25(ZnO)0.75Fe2O3 synthesized
by ultra-sonic assisted mechanically stirred co-precipitation
84
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.55 Particle size distribution by intensity for ZnO.Fe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation
4.4.2 Particle Size analysis of (ZrO2)1-x(ZnO)xFe2O3
(ZrO2)1-x(ZnO)xFe2O3 synthesized by co-precipitation via mechanical stirring and
ultra-sonic assisted mechanical stirring was analyzed by Zetasizer for the particle size
measurements. Particle sizes were also calculated by Scherer’s formula using XRD patterns.
Results are given in table No. 4.12 and 4.13 with different values of x. SEM images showed
that there was no specific shape of particles. XRD results confirmed more than one crystal
system in samples so the calculations made by Zetasizer are the average particle sizes of the
samples. Particle size distribution by intensity for the samples synthesized by both methods
are given in Fig. 4.56 to 4.63. Particle sizes calculated from both methods have near values
which confirm the actual sizes. Particle sizes were decreased by ultra-sonic assisted
mechanically stirred co-precipitation which showed large surface area and improvement in
photocatalytic activity.
85
Table No. 4.12 particle sizes of (ZrO2)1-x(ZnO)xFe2O3 synthesized with mechanically
stirred co-precipitation technique at different values of x
X
(ZrO2)1-x(ZnO)xFe2O3
Average particle
Size with Zetasizer
(nm)
Particle size Calculated by
Sherer’s formula from XRD
(nm)
0 ZrO2.Fe2O3 23.52 22.41
0.25 (ZrO2)0.75(ZnO)0.25Fe2O3 54.15 53.79
0.50 (ZrO2)0.5(ZnO)0.5Fe2O3 49.83 33.93
0.75 (ZrO2)0.25(ZnO)0.75Fe2O3 54.92 54.16
1 ZnO.Fe2O3 29.22 28.31
Table No. 4.13 Particle sizes of (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation technique at different values of x
X
(ZrO2)1-x(ZnO)xFe2O3
Average particle
Size with Zetasizer
(nm)
Particle size Calculated by
Sherer’s formula from XRD
(nm)
0 ZrO2.Fe2O3 13.89 12.96
0.25 (ZrO2)0.75(ZnO)0.25Fe2O3 19.15 18.07
0.50 (ZrO2)0.5(ZnO)0.5Fe2O3 26.21 25.83
0.75 (ZrO2)0.25(ZnO)0.75Fe2O3 24.15 23.25
1 ZnO.Fe2O3 22.15 21.35
86
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.56 Particle size distribution by intensity for ZrO2.Fe2O3 synthesized by
mechanically stirred co-precipitation
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
35
Inte
nsity (
%)
Size (d.nm)
Fig. 4.57 Particle size distribution by intensity for (ZrO2)0.75(ZnO)0.25Fe2O3 synthesized
by mechanically stirred co-precipitation
87
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.58 Particle size distribution by intensity for (ZrO2)0.50(ZnO)0.50Fe2O3 synthesized
by mechanically stirred co-precipitation
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
Inte
nsity (
%)
Size (d.nm)
Fig. 4.59 Particle size distribution by intensity for (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized
by mechanically stirred co-precipitation
88
0 5 10 15 20 25 30 35 400
1
2
3
4
5
6
7
8
Inte
nsity (
%)
Size (d.nm)
Fig. 4.60 Particle size distribution by intensity for ZrO2.Fe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.61 Particle size distribution by intensity for (ZrO2)0.75(ZnO)0.25Fe2O3 synthesized
by ultra-sonic assisted mechanically stirred co-precipitation
89
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Inte
nsity (
%)
Size (d.nm)
Fig. 4.62 Particle size distribution by intensity for (ZrO2)0.50(ZnO)0.50Fe2O3 synthesized
by ultra-sonic assisted mechanically stirred co-precipitation
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
20
25
Inte
nsity (
%)
Size (d.nm)
Fig. 4.63 Particle size distribution by intensity for (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized
by ultra-sonic assisted mechanically stirred co-precipitation
90
4.4.3 Surface area and porosity analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3
Surface area and porosity analysis was performed by nitrogen adsorption-desorption
using Tristar 3000. Single point, Brunauer-Emmett-Teller (BET) and Langmuir surface area,
BET adsorption, Barret-Joyner-Halenda (BJH) adsorption and desorption pore diameter was
calculated for most active sample which were (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3.
Results are shown in table 4.12.1 & 4.13.1. It is clear from the results that ultra-sonic assisted
stirred co-precipitation improved the surface area and particle size. Pore diameter was
decreased in case of BET and BJH adsorption but BJH desorption diameter was almost same
for both samples. Increase in surface area enhanced the adsorption capacity and
photocatalytic activity of photocatalyst because adsorption processes are depends on the
surface reactions with materials (Hassan et al., 2014).
Table No. 4.12.1 Surface area and porosity analysis of (Al2O3)0.75(ZnO)0.25Fe2O3
Surface area and porosity (Al2O3)0.75(ZnO)0.25Fe2O3 Synthesized by stirring
Synthesized by ultra-sonic
assisted stirring
Single Point Surface Area
(m2/g)
184.37 313.98
BET Surface Area (m2/g) 193.62 332.30
Langmuir Surface Area
(m2/g)
268.86 462.37
BET Adsorption Average
Pore Diameter (nm) 5.28 3.38
BJH Adsorption Average
Pore Diameter (nm) 4.21 3.13
BJH Desorption Average
Pore Diameter (nm) 3.96 3.46
91
Table No. 4.13.1 Surface area and porosity analysis of ZrO2.Fe2O3
Surface area and porosity ZrO2.Fe2O3 Synthesized by stirring
Synthesized by ultra-sonic
assisted stirring
Single Point Surface Area
(m2/g)
153.85 254.16
BET Surface Area (m2/g) 171.51 217.75
Langmuir Surface Area
(m2/g)
193.77 381.28
BET Adsorption Average
Pore Diameter (nm)
4.30 2.84
BJH Adsorption Average
Pore Diameter (nm)
3.85 2.97
BJH Desorption Average
Pore Diameter (nm)
3.62 3.39
4.5 Photocatalytic Activity
4.5.1 Optimization of pH for the degradation of Methyl Orange
Catalysts used for the optimization of pH were (Al2O3)0.50(ZnO)0.50(Fe2O3) and
(ZrO2)0.50(ZnO)0.50Fe2O3) with an initial pH from 1 to 9 using odd numbers. Degradation
was calculated with 20min interval of time up to 140 min on each pH value by taking
absorbance at 507 nm with the help of UV/Vis spectrophotometer and percentage
degradation was calculated from the absorbance. Degradation was increased with increase in
time up to 120 min and almost remained constant after 120 to 140 min. Degradation
efficiency was increased from 1 to 3 pH and then decreased from 3 to 9 pH so the maximum
degradation was 78.12% with (Al2O3)0.50(ZnO)0.50(Fe2O3) and 65.24% with and
(ZrO2)0.50(ZnO)0.50Fe2O3) at pH = 3 with catalyst dose 50mg/100ml, dye concentration 50
ppm at room temperature. Experiments were performed in triplicate. The results are shown in
table No. 4.14 and 4.15 and graphical representation is given in Fig. 4.64 and 4.65.
Photocatalytic activity should be increased with the increase in pH as at higher pH values
more OH ions are available which increase the formation of OH radicals (Kaur et al., 2013).
In this case degradation was decreased by increasing pH of the solution because at lower pH
92
values formation of HO2 radicals takes place which compensate the deficiency of hydroxide
ions (Ku and Hsieh, 1992). Methyl orange is anionic in nature and oxidative attack of the
hole on dye molecule is rate determining step so at low pH this attack will be supported and
more dye molecules will be degraded (Al-Qaradawi and Salman, 2002).
Table No. 4.14 Optimization of pH for the degradation of Methyl Orange With
(Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation with
50mg/100ml catalyst loading, 50ppm initial dye concentration at room temperature
Time (min)
Degradation (%)
pH 1 ± SD pH 3 ± SD pH 5 ± SD pH 7 ± SD pH 9 ± SD
20 12.32 1.01823 15.32 0.89096 9.75 1.06137 5.14 0.91075 2.87 0.96025
40 26.98 1.04652 32.76 1.00381 23.51 1.05217 16.65 0.99278 5.96 1.04794
60 39.19 1.13137 49.46 0.75052 36.46 0.82307 25.15 0.76282 9.18 0.74642
80 55.32 1.04652 65.18 0.9256 48.65 0.85984 33.25 0.88106 12.15 0.95035
100 67.52 1.03238 75.95 1.01221 59.18 1.00381 39.65 0.98316 16.14 1.0502
120 72.78 0.77782 78.21 0.69032 68.81 0.80101 45.44 0.68207 19.32 0.69706
140 72.68 1.04653 78.12 0.69118 69.21 0.94723 45.67 0.61993 20.13 0.67693
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
Degra
dation (
%)
Time (Min)
pH 1
pH 3
pH 5
pH 7
pH 9
Fig. 4.64 Optimization of pH for the degradation of methyl orange with
(Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at
50mg/100ml catalyst loading, 50ppm initial dye concentration at room temperature
93
Table No. 4.15 Optimization of pH for the degradation of Methyl Orange With
(ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at
50mg/100ml catalyst loading, 50ppm initial dye concentration at room temperature
Time
(Min) Degradation (%)
pH 1 ± SD pH 3 ± SD pH 5 ± SD pH 7 ± SD pH 9 ± SD
20 7.42 0.9832 10.15 0.88488 6.12 0.86522 3.52 0.97337 2.21 0.96354
40 20.92 1.0324 24.14 0.92916 17.85 0.89819 11.41 1.00143 5.74 0.9911
60 31.32 1.2987 37.65 1.16883 23.17 1.1039 20.21 1.23377 9.95 1.22078
80 42.13 0.8756 46.22 0.78804 38.32 0.77928 29.18 0.81431 11.15 0.80555
100 50.95 1.1896 56.12 1.07064 46.41 1.07064 35.32 1.08254 15.51 1.07064
120 60.46 0.9632 65.51 0.86688 57.18 0.87651 43.14 0.90541 17.23 0.84762
140 61.47 1.1569 65.75 1.04121 58.90 0.99493 44.85 1.06435 18.15 0.99493
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
Degra
dation (
%)
Time (Min)
pH 1
pH 3
pH 5
pH 7
pH 9
Fig. 4.65 Optimization of pH for the degradation of methyl orange with
(ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at
50mg/100ml catalyst loading, 50ppm initial dye concentration at room temperature.
94
4.5.2 Optimization of catalyst dose for the degradation of Methyl Orange
(Al2O3)0.50(ZnO)0.50(Fe2O3) and (ZrO2)0.50(ZnO)0.50(Fe2O3) were used for the
optimization of catalyst concentration starting from 20mg/100ml to 70mg/100ml degradation
was increased from 20mg to 60mg/100ml. Degradation was increased 40.18 to 80.87 % with
(Al2O3)0.50(ZnO)0.50(Fe2O3) and 13.39 to 69.95 with (ZrO2)0.50(ZnO)0.50(Fe2O3) in 140 min
time of reaction. By increasing photocatalyst amount more particles will be available which
leads to more active sites availability (Wang et al., 2013; Rashid et al., 2014). After
60mg/100ml there was decrease in degradation efficiency because more increase in
concentration can decrease the light passing through dye solution which decreased the
photocatalytic efficiency (Sherly et al., 2014). Results are shown in table No. 4.16, 4.17 and
Fig. 4.66 and 4.67. Optimized dose for the degradation of methyl orange was 60mg/100ml at
optimum pH and 50 ppm dye solution at room temperature.
Table No. 4.16 Optimization of catalyst dose for the degradation of Methyl Orange
With (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at
pH = 3, and 50ppm initial dye concentration at room temperature
Time
(Min)
Degradation (%)
20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD 70mg ± SD
20 5.14 0.6524 8.34 0.63935 11.81 0.71978 15.31 0.58064 16.42 0.64653 13.31 0.53497
40 13.25 0.5247 19.27 0.50371 26.07 0.47223 32.43 0.45649 34.19 0.52103 29.11 0.47223
60 21.06 0.8326 30.12 0.78264 41.28 0.75767 49.57 0.70771 56.38 0.82844 48.29 0.81595
80 28.37 0.9356 39.23 0.86075 55.37 0.86075 65.08 0.77655 71.05 0.93279 61.19 0.83268
100 34.51 0.7145 50.01 0.64305 61.55 0.67163 75.21 0.57874 78.37 0.71379 73.22 0.60018
120 39.31 0.4235 57.19 0.37268 66.1 0.4108 78.09 0.33457 80.28 0.42214 76.05 0.35151
140 40.18 0.9245 58.05 0.79507 66.89 0.88752 78.59 0.71186 80.87 0.91858 76.39 0.74884
95
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
20mg
30mg
40mg
50mg
60mg
70mg
Fig. 4.66 Optimization of catalyst dose for the degradation of methyl orange with
(Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at pH =
3, and 50ppm initial dye concentration at room temperature.
.
Table No. 4.17 Optimization of catalyst dose for the degradation of Methyl Orange
With (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at
pH = 3, and 50ppm initial dye concentration at room temperature.
Time
(Min) Degradation (%)
20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD 70mg ± SD
20 3.52 0.25931 7.09 0.25672 9.95 0.25801 10.35 0.23079 14.31 0.23597 9.83 0.20485
40 4.31 0.12966 9.35 0.12447 14.85 0.12875 24.13 0.1141 32.84 0.12058 22.89 0.09984
60 7.24 0.19448 14.85 0.18281 25.05 0.1939 37.21 0.1692 49.25 0.18476 35.54 0.14586
80 9.28 0.25931 21.67 0.23857 34.87 0.25698 46.25 0.22301 57.65 0.25153 43.59 0.1893
100 11.05 0.32414 26.31 0.31766 45.28 0.32252 56.01 0.27552 63.29 0.3209 53.75 0.25283
120 13.28 0.32414 32.81 0.31117 54.33 0.32284 65.37 0.27228 69.51 0.31766 60.37 0.23986
140 13.45 0.26548 33.05 0.24159 55.1 0.26521 65.58 0.23893 69.95 0.24955 60.57 0.20176
96
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
20mg
30mg
40mg
50mg
60mg
70mg
Fig. 4.67 Optimization of catalyst dose for the degradation of methyl orange with
(ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at pH =
3, and 50ppm initial dye concentration at room temperature.
4.5.3 Optimization of dye concentration for the degradation of Methyl Orange
To optimize the concentration of dye for the degradation of Methyl Orange 20 to 70
ppm of dye solution was used at optimum values of pH = 3 and catalyst dose (60mg/100ml).
The degradation efficiency was increased with the increase in dye concentration up to 50
ppm and after this value of concentration the degradation efficiency was decreased. So
(Al2O3)0.50(ZnO)0.50(Fe2O3) and (ZrO2)0.50(ZnO)0.50(Fe2O3) showed maximum degradation
efficiency at 50ppm. Results are shown in table No. 4.18 & 4.19 with graphical
representation in Fig. 4.68 & 4.69. (Al2O3)0.50(ZnO)0.50(Fe2O3) degraded 80.87% while
ZrO2)0.50(ZnO)0.50(Fe2O3) degraded 69.95% methyl orange in 140 min at optimum
conditions. Degradation rate was directly proportional to the concentration of dye molecules
because by increasing dye concentration more molecules are available so the adsorption of
molecules on the surface of photocatalyst increased (Ahmed et al., 2011). Concentration
above the optimized value decreased the degradation efficiency due to opacity of the reaction
mixture which may decrease the penetration of visible light in the reaction mixture (Swetha
and Balakrishna, 2011).
97
Table No. 4.18 Optimization of initial dye concentration for the degradation of Methyl
Orange With (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-
precipitation at pH = 3, and 60mg/100ml catalyst dose at room temperature.
Time
(Min)
Degradation
(%)
20pp
m ± SD
30ppm
± SD 40pp
m ± SD
50ppm
± SD 60pp
m ± SD
20 7.24 0.78454 9.85 0.70609 12.05 0.76104 16.42 0.70609 14.78 0.62763
40 11.87 0.82412 20.76 0.73347 27.32 0.78291 34.19 0.73347 30.42 0.65105
60 23.18 0.62348 32.54 0.54243 42.85 0.57984 56.38 0.54243 49.06 0.48631
80 29.81 0.27554 40.35 0.25074 56.13 0.27003 71.05 0.24248 64.55 0.21217
100 35.79 0.63857 51.24 0.58748 63.51 0.61303 78.37 0.54917 72.14 0.48531
120 40.17 0.58796 58.11 0.5174 66.13 0.55856 80.28 0.52328 73.21 0.44097
140 40.29 0.45698 58.64 0.42042 66.89 0.42956 80.87 0.39529 74.13 0.33817
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
20ppm
30ppm
40ppm
50ppm
60ppm
Fig. 4.68 Optimization of initial dye concentration for the degradation of methyl orange
with (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at
pH = 3, and 60mg/100ml catalyst dose at room temperature.
98
Table No. 4.19 Optimization of initial dye concentration for the degradation of Methyl
Orange With (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-
precipitation at pH = 3, and 60mg/100ml catalyst dose at room temperature.
Time
(Min) Degradation (%)
20ppm ± SD 30ppm ± SD 40ppm ± SD 50ppm ± SD 60ppm ± SD
20 5.98 0.78454 8.56 0.70609 10.5 0.76104 14.31 0.70609 12.73 0.62763
40 10.95 0.82412 18.12 0.73347 24.86 0.78291 32.84 0.73347 28.57 0.65105
60 20.62 0.62348 28.38 0.54243 38.99 0.57984 49.25 0.54243 43.15 0.48631
80 24.61 0.27554 35.45 0.25074 51.03 0.27003 57.65 0.24248 52.85 0.21217
100 29.57 0.63857 44.58 0.58748 57.41 0.61303 63.29 0.54917 58.94 0.48531
120 34.79 0.58796 50.57 0.5174 60.83 0.55856 69.51 0.52328 61.86 0.44097
140 35.03 0.45698 51.01 0.42042 60.99 0.42956 69.95 0.39529 62.65 0.33817
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
20ppm
30ppm
40ppm
50ppm
60ppm
Fig. 4.69 Optimization of initial dye concentration for the degradation of methyl orange
with (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at
pH = 3, and 60mg/100ml catalyst dose at room temperature.
99
4.5.4 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3
synthesized by mechanically stirred co-precipitation for the degradation of Methyl
Orange
To optimize value of x value for (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3
was done to get maximum degradation efficiency of methyl orange at optimum conditions of
pH, photocatalyst dose and dye concentration (pH = 3, 60mg/100ml catalyst dose and 50ppm
dye concentration) at room temperature. The results are shown in table No. 4.20 & 4.21 and
Fig. 4.70 & 4.71. Values of x and their respective formulas are shown in table No. 4.22. It
can be seen from the results X=0.25 with formula (Al2O3)0.75(ZnO)0.25Fe2O3 form (Al2O3)1-
x(ZnO)xFe2O3 has maximum degradation of methyl orange. By increasing the ZnO and
decreasing Al2O3 degradation efficiency was decreased but the absence of Al2O3 and ZnO
have very low degradation percentage therefore (Al2O3)0.75(ZnO)0.25Fe2O3 has best results for
the removal of methyl orange. In case of (ZrO2)1-x(ZnO)xFe2O3 X = 0 with formula
ZrO2.Fe2O3 showed maximum degradation efficiency. ZnO has negative effect in this
photocatalyst because by increasing Zn there was decrease in photocatalytic efficiency.
Table No. 4.20 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of methyl orange at pH=3,
catalyst dose 60mg/100ml and initial dye concentration 50ppm at room temperature.
Time
(Min) Degradation (%)
X= 0 ± SD X=
0.25 ± SD
X=
0.50 ± SD
X=
0.75 ± SD X= 1 ± SD
20 3.11 0.75632 20.85 0.83256 15.85 0.63985 10.75 0.73363 5.18 0.64287
40 10.24 0.82154 37.94 1.20014 31.72 0.58764 23.18 0.7476 12.97 0.71474
60 17.32 0.97852 61.05 0.96544 52.91 0.86354 39.82 0.92959 21.88 0.87088
80 28.34 1.23547 76.91 0.53214 69.95 0.95485 51.37 1.14899 30.17 1.05015
100 34.21 1.02314 81.07 0.96324 77.28 0.23658 62.74 0.91059 37.06 0.89013
120 39.14 0.96871 83.19 0.62548 80.09 0.48652 76.86 0.93965 51.67 0.86215
140 40.02 0.53214 83.67 0.45981 80.53 0.29364 77.15 0.52682 52.15 0.45232
100
20 40 60 80 100 120 1400
10
20
30
40
50
60
70
80
90
100
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.70 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by mechanically
stirred co-precipitation for the degradation of methyl orange at pH=3, catalyst dose
60mg/100ml and initial dye concentration 50ppm at room temperature.
Table No. 4.21 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of methyl orange at pH=3,
catalyst dose 60mg/100ml and initial dye concentration 50ppm at room temperature.
Time
(Min) Degradation (%)
X= 0 ± SD X=0.25 ± SD X=0.50 ± SD X=0.75 ± SD X= 1 ± SD
20 17.85 0.45682 15.87 0.53691 14.31 0.63985 12.73 0.54387 10.85 0.84532
40 35.64 0.26597 33.76 0.53219 32.84 0.58764 28.57 0.48774 23.71 0.23154
60 55.12 0.56987 53.47 0.49633 49.25 0.86354 41.85 0.7081 34.37 0.74521
80 66.15 0.15698 63.15 0.35972 57.65 0.95485 47.84 0.77343 38.75 0.63214
100 69.89 0.39852 66.94 0.25465 63.29 0.23658 51.29 0.18926 41.32 0.51235
120 75.43 0.49521 70.85 0.65123 69.51 0.48652 54.91 0.39895 45.02 0.78951
140 75.81 0.53246 71.05 0.59864 69.95 0.29364 55.65 0.24078 45.63 0.71326
101
20 40 60 80 100 120 140
10
20
30
40
50
60
70
80
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.71 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by mechanically
stirred co-precipitation for the degradation of methyl orange at pH=3, catalyst dose
60mg/100ml and initial dye concentration 50ppm at room temperature.
Table 4.22 value of x and their respective photocatalysts for (Al2O3)1-x(ZnO)xFe2O3 and
(ZrO2)1-x(ZnO)xFe2O3
X (Al2O3)1-x(ZnO)xFe2O3 (ZrO2)1-x(ZnO)xFe2O3
0 Al2O3.Fe2O3 ZrO2.Fe2O3
0.25 (Al2O3)0.75(ZnO)0.25Fe2O3 (ZrO2)0.75(ZnO)0.25Fe2O3
0.50 (Al2O3)0.5(ZnO)0.5Fe2O3 (ZrO2)0.5(ZnO)0.5Fe2O3
0.75 (Al2O3)0.25(ZnO)0.75Fe2O3 (ZrO2)0.25(ZnO)0.75Fe2O3
1 ZnO.Fe2O3 ZnO.Fe2O3
4.5.5 Optimization of x value (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation for the degradation of Methyl Orange
Selection of best photocatalyst with respect to their x values for the degradation of
methyl orange with (Al2O3)1-x(ZnO)xFe2O3 & (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-
102
sonic assisted mechanically stirred co-precipitation was done on optimum conditions of pH,
photocatalyst dose and initial dye concentration (pH = 3, 60mg/100ml catalyst dose and
50ppm dye concentration). The results are shown in table No. 4.20 and 4.21. Valu of x and
their respective formulas are shown in table 4.22. It can be observed from the results that
x=0.25 with formulas (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 have maximum degradation
of methyl orange. Trend in photocatalytic activity was the same as mechanically stirred co-
precipitation but photocatalytic efficiency was increased from 87.67% to 93.52% with
(Al2O3)0.75(ZnO)0.25Fe2O3 and 75.81 to 78.07 % with ZrO2.Fe2O3 at same reaction conditions.
It is due the decrease in particle size and increase in surface area of the photocatalyst so that
more dye particles can adsorbed on photocatalyst surface which leads to the availability of
more active sites for dye molecules (Peng et al., 2005; Zhang et al., 2014).
Table No. 4.23 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation of methyl
orange at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room
temperature.
Time
(Min) Degradation (%)
X= 0 ± SD X= 0.25 ± SD X= 0.50 ± SD X=
0.75 ± SD X= 1 ± SD
20 6.12 0.85253 21.34 0.86547 18.57 0.97027 13.73 0.85768 7.33 0.86114
40 11.51 1.04749 43.17 1.14857 34.08 0.99926 31.28 1.14053 13.28 1.09114
60 18.26 0.87029 62.24 0.96544 54.19 0.85924 42.19 0.96061 21.49 0.95636
80 23.41 0.65677 78.41 0.73645 65.47 0.63335 50.04 0.73056 27.54 0.67017
100 33.17 0.94981 89.45 1.02654 74.25 0.92389 61.08 1.01935 35.85 1.0213
120 41.23 0.63161 93.04 0.68541 89.13 0.59631 71.18 0.65114 47.15 0.65114
140 42.15 0.20208 93.52 0.21485 89.72 0.39122 72.01 0.4084 49.12 0.51272
103
20 40 60 80 100 120 1400
10
20
30
40
50
60
70
80
90
100
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.72 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation for the degradation of methyl orange at
pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room
temperature.
Table No. 4.24 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation of methyl
orange at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room
temperature.
Time
(Min) Degradation (%)
X= 0 ± SD X=
0.25 ± SD
X=
0.50 ± SD
X=
0.75 ± SD X= 1 ± SD
20 19.85 0.71852 16.97 0.54387 15.01 0.45637 11.67 0.54387 10.47 0.3883
40 38.24 0.19218 35.02 0.48774 34.27 0.44172 29.88 0.48774 22.78 0.22076
60 57.85 0.61107 55.89 0.7081 50.95 0.40699 43.02 0.7081 35.12 0.46729
80 69.15 0.51203 65.72 0.77343 59.12 0.29137 49.24 0.77343 39.88 0.12715
100 74.19 0.40988 69.08 0.18926 64.83 0.20372 52.98 0.18926 42.79 0.31882
120 78.38 0.6474 73.52 0.39895 70.11 0.53401 55.88 0.39895 47.98 0.40607
140 78.07 0.58487 73.87 0.24078 70.57 0.49088 56.05 0.24078 48.01 0.43662
104
20 40 60 80 100 120 140
10
20
30
40
50
60
70
80
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.73 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation for the degradation of methyl orange at
pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room
temperature.
4.5.6 Optimization of pH for the degradation of CI Reactive Black 5
For the optimization of pH the catalysts used were (Al2O3)0.75(ZnO)0.25(Fe2O3) &
ZrO2.Fe2O3 because they showed maximum degradation of methyl orange dye. Initial pH was
taken from 1 to 9 using odd numbers. Degradation efficiency was calculated with 20min
interval of time up to 140 min on each pH value by taking absorbance at 597 nm with the
help of UV/Vis spectrophotometer and percentage degradation was calculated from the
absorbance.
Degradation was increased with increase in time up to 120 min and almost remained
constant after 120 to 140 min. Degradation efficiency was increased up to pH=3 and then
decreased from pH 3 to 7 for both catalysts. At pH 9 degradation was increased again but it
was less than pH 3 so the maximum degradation was achieved at pH = 3 with catalyst dose
60mg/100ml, dye concentration 50 ppm at room temperature. The results are shown in table
105
no. 4.25 & 4.26. Graphical representation of the results is given in Fig. 4.73 & 4.74.
(Al2O3)0.75(ZnO)0.25(Fe2O3) degraded 83.15 % and 72.01 % RB5 at pH 3 & 9 respectively.
Table No. 4.25 Optimization of pH for the degradation of CI Reactive Black 5 With
(Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-precipitation with
60mg/100ml catalyst loading, 50ppm initial dye concentration at room temperature.
Time
(Min) Degradation (%)
pH 1 ± SD pH 3 ± SD pH 5 ± SD pH 7 ± SD pH 9 ± SD
20 19.32 0.24681 21.33 0.68815 11.47 1.01026 8.54 0.6991 18.37 0.88164
40 33.44 0.75432 38.07 0.27318 21.81 0.61665 15.38 0.26596 31.87 0.87144
60 55.51 0.84732 61.71 0.57417 32.29 0.21428 21.58 0.4572 52.08 0.63158
80 69.31 0.54864 77.54 0.23669 45.57 0.46028 28.03 0.21659 65.31 0.74246
100 72.09 1.03238 81.35 0.78206 51.71 0.37072 37.02 0.96082 69.34 0.81558
120 75.53 0.35478 82.77 0.6371 57.07 0.21758 42.54 0.60712 71.85 0.56215
140 76.36 0.15476 83.15 0.15676 57.45 0.22285 42.94 0.60568 72.01 0.54155
This behavior can be explained by mechanism of dye degradation at acidic and basic
conditions. CI Reactive Black 5 dye has sulfonic (-SO3─) and [2(sulfoxy)ethyl]sulfonyl (-
SO2CH2CH2OSO3─) groups which help in solubilizing of dye in water and reactive group for
dye fixation (Muruganandham et al., 2006). At acidic pH surface of photocatalyst charged
positively so the electrostatic attraction takes place which increase the adsorption of dye
molecules on the surface of photocatalyst another reason for this attraction is positively
charged holes so due these reasons acidic pH increased degradation (Kritikos et al., 2007;
Soltani and Entezari, 2013). Photocatalytic activity again increased at pH 9 due to change in
mechanism of reaction at basic pH there are more hydroxide ion available which help in
oxidation of dye molecule and degradation again increased (Zielińska et al., 2001; Soltani
and Entezari, 2013).
106
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
pH 1
pH 3
pH 5
pH 7
pH 9
Fig. 4.74 Optimization of pH for the degradation of CI Reactive Black 5 With
(Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-precipitation with
60mg/100ml catalyst loading, 50ppm initial dye concentration at room temperature
Table No. 4.26 Optimization of pH for the degradation of CI Reactive Black 5 With
ZrO2 Fe2O3) synthesized by mechanically stirred co-precipitation with 60mg/100ml
catalyst loading, 50ppm initial dye concentration at room temperature.
Time
(Min) Degradation (%)
pH 1 ± SD pH 3 ± SD pH 5 ± SD pH 7 ± SD pH 9 ± SD
20 16.27 0.53071 18.71 0.34897 10.84 0.53316 7.046 0.35554 13.22 0.82023
40 30.87 0.94137 34.23 0.33752 19.35 0.84082 13.158 0.44533 27.56 0.92419
60 39.54 0.81452 47.38 0.8345 26.92 0.92188 18.5748 0.35871 33.69 0.59162
80 47.58 0.83206 61.26 0.44719 35.42 0.78319 22.6688 0.54139 42.74 0.97016
100 58.52 1.01648 69.75 0.32323 40.72 0.33722 25.2464 0.49388 50.32 0.26269
120 64.08 0.17357 72.76 0.90682 45.72 0.95158 32.004 0.63379 55.76 0.43662
140 64.88 0.24198 72.35 0.45836 46.22 0.25187 32.354 0.22508 56.46 0.57235
107
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
Degra
dation (
%)
Time (Min)
pH 1
pH 3
pH 5
pH 7
pH 9
Fig.4.75 Optimization of pH for the degradation of CI Reactive Black 5 With
ZrO2.Fe2O3) synthesized by mechanically stirred co-precipitation with 60mg/100ml
catalyst loading, 50ppm initial dye concentration at room temperature.
4.5.7 Optimization of photocatalyst dose for the degradation of CI Reactive Black 5
(RB5)
Optimization of catalyst dose for the degradation of CI Reactive Black 5 with
(Al2O3)0.75(ZnO)0.25(Fe2O3) and ZrO2.Fe2O3 was done from 20mg/100ml to 70mg/100ml.
Reaction conditions were pH=3 and 50ppm initial dye concentration at room temperature.
Degradation was increased from 20mg to 60mg/100ml in 140 min.
(Al2O3)0.75(ZnO)0.25(Fe2O3) degraded RB5 83.15% while ZrO2.Fe2O3 degraded RB5 72.35%.
At photocatalyst concentration 70mg/100ml there was decrease in photocatalytic activity. By
the increase of photocatalyst concentration more active sites are available for the dye
molecule to be adsorbed so that degradation was increased up to 60mg/100ml but at
70mg/100 ml suspension becomes opaque due to large amount of suspended particles of
catalyst which may decrease the intensity of light passing through the reaction mixture by
108
scattering it (Daneshvar et al., 2003; Ahmed et al., 2011; Shirsath et al., 2013). Results are
shown in table no. 4.27 & 4.28, Fig. 4.75 & 4.76.
Table No. 4.27 Optimization of pH for the degradation of CI Reactive Black 5 With
ZrO2 Fe2O3) synthesized by mechanically stirred co-precipitation with 60mg/100ml
catalyst loading, 50ppm initial dye concentration at room temperature.
Time
(Min) Degradation (%)
20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD 70mg ± SD
20 7.88 0.43931 9.97 0.49768 12.74 0.23546 15.02 0.54124 21.33 0.30035 18.77 0.25208
40 12.58 0.34404 15.24 0.33533 18.52 0.12564 22.14 0.22889 38.07 0.19893 35.84 0.1803
60 18.93 0.5257 21.69 0.40281 28.54 0.32657 33.78 0.80322 61.71 0.22418 49.47 0.2208
80 25.99 0.56838 29.66 0.37892 37.41 0.87416 45.28 0.29006 77.54 0.26445 60.11 0.23606
100 31.85 0.41727 38.45 0.25722 46.85 0.29654 57.44 0.42992 81.35 0.74234 67.12 0.62418
120 36.78 0.26045 43.87 0.24309 57.44 0.32155 65.07 0.33215 82.77 0.20769 71.28 0.17294
140 37.08 0.57615 44.13 0.22743 57.97 0.12777 65.42 0.15478 83.15 0.37662 71.88 0.30702
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
20mg
30mg
40mg
50mg
60mg
70mg
Fig. 4.76 Optimization of catalysts dose for the degradation of CI Reactive Black 5 With
(Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-precipitation at pH =
3 and 50ppm initial dye concentration at room temperature.
109
Table No. 4.28 Optimization of catalysts dose for the degradation of CI Reactive Black
5 With ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 3 and
50ppm initial dye concentration at room temperature.
Time
(Min) Degradation (%)
20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD 70mg ± SD
20 6.81 0.71523 9.47 0.94388 12.68 1.02657 14.32 0.81465 18.71 0.99692 15.75 0.72679
40 11.36 0.90502 15.31 0.51949 22.56 0.76496 25.55 0.98858 34.23 0.54895 28.56 0.67858
60 16.84 0.85947 21.85 0.87184 31.58 0.94992 36.87 0.80597 47.38 1.02023 39.85 0.81734
80 22.45 0.90745 30.94 1.0171 39.32 0.73585 47.32 0.94194 61.26 0.75258 51.24 0.92599
100 29.33 0.49588 39.12 0.92247 48.55 0.87963 54.71 0.89804 69.75 0.94041 60.35 0.71778
120 34.55 0.56071 44.25 0.68939 53.25 0.8062 59.55 0.58008 72.76 0.86316 64.85 0.43662
140 35.08 0.91238 44.86 0.36758 53.84 0.9417 59.89 0.94129 72.35 0.94375 65.18 0.9142
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
Degra
dation (
%)
Time (Min)
20mg
30mg
40mg
50mg
60mg
70mg
110
Fig. 4.77 Optimization of catalysts dose for the degradation of CI Reactive Black 5 With
ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 3 and 50ppm
initial dye concentration at room temperature.
4.5.8 Optimization of initial dye concentration for the degradation of CI Reactive Black
5
Concentration of dye is an important factor for photocatalytic activity. CI Reactive
Black 5 was degraded with initial concentration from 20 ppm to 60 ppm. Degradation
efficiency was increased with the increased in dye concentration up to 50 ppm after that it
was decreased at 60 ppm so the optimum value was 50 ppm. Table 4.29 & 4.30 contain the
mean values for % degradation with time and graphically represented in Fig. 4.77 & 4.78.
Maximum degradation was 83.15% with (Al2O3)0.75(ZnO)0.25(Fe2O3) and 72.35% with
ZrO2.Fe2O3. This factor can be explained as the concentration was increased there was
increase in degradation efficiency because more dye molecules were available to adsorb on
the active sites of photocatalyst so the effective collisions were increased. After a specific
concentration (50ppm) degradation efficiency was decreased due to decrease in intensity of
light passing through reaction mixture as more light will be absorbed by dye molecules than
the photocatalyst (Muruganandham et al., 2006; Yao et al., 2010; Konicki et al., 2013).
Table No. 4.29 Optimization of initial dye concentration for the degradation of CI
Reactive Black 5 With (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred
co-precipitation at pH = 3 and 60mg/100ml catalyst dose at room temperature.
Time
(Min) Degradation (%)
20ppm ± SD 30ppm ± SD 40ppm ± SD 50ppm ± SD 60ppm ± SD
20 9.55 0.26208 12.85 0.25931 15.2 0.25931 21.33 0.44826 18.41 0.47845
40 16.74 0.95246 20.89 0.94483 23.33 0.29655 38.07 0.29655 30.25 0.3625
60 27.12 0.49866 35.76 0.25931 42.15 0.94483 61.71 0.94483 55.34 0.26533
80 35.45 0.23035 44.85 0.29655 53.21 0.25931 77.54 0.25931 66.23 0.12985
100 42.34 0.38887 55.79 0.94483 59.38 0.32414 81.35 0.25931 73.85 0.28706
120 53.88 0.23872 62.7 0.32414 68.56 0.32414 82.77 0.32414 76.24 0.36918
140 54.12 0.36156 62.95 0.14781 68.97 0.29561 83.15 0.27553 76.61 0.15725
111
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
20ppm
30ppm
40ppm
50ppm
60ppm
Fig. 4.78 Optimization of initial dye concentration for the degradation of CI Reactive
Black 5 With (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-
precipitation at pH = 3 and 60mg/100ml catalyst dose at room temperature.
Table No. 4.30 Optimization of initial dye concentration for the degradation of CI
Reactive Black 5 With ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation
at pH = 3 and 60mg/100ml catalyst dose at room temperature.
Time
(Min) Degradation (%)
20ppm ± SD 30ppm ± SD 40ppm ± SD 50ppm ± SD 60ppm ± SD
20 12.07 0.93654 13.27 0.94431 15.21 0.95642 18.71 0.5327 16.69 0.79654
40 21.34 0.83568 23.76 0.35078 26.52 0.84562 34.23 0.97546 30.14 0.94968
60 29.38 0.72657 31.94 0.85683 35.46 0.32154 47.38 0.8457 41.26 0.23458
80 37.56 0.89658 41.28 0.95833 45.82 0.76542 61.26 0.75468 52.66 0.73256
100 41.78 0.66547 46.42 0.67292 52.75 0.98745 69.75 0.91258 59.25 0.82578
120 45.63 0.96597 51.27 0.95875 57.63 0.84125 72.76 0.99462 61.84 0.52565
140 45.86 0.32365 51.53 0.62206 57.97 0.62145 72.35 0.24853 61.77 0.89654
112
20 40 60 80 100 120 1400
10
20
30
40
50
60
70
80
De
gra
datio
n (
%)
Time (Min)
20ppm
30ppm
40ppm
50ppm
60ppm
Fig. 4.79 Optimization of initial dye concentration for the degradation of CI Reactive
Black 5 With ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 3
and 60mg/100ml catalyst dose at room temperature.
4.5.9 Optimization of x values for (Al2O3)1-x(ZnO)xFe2O3 & (ZrO2)1-x(ZnO)xFe2O3
synthesized by mechanically stirred co-precipitation for the degradation of CI Reactive
Black 5
Degradation of reactive black B was done on optimum conditions of pH 3,
photocatalyst dose 60mg/100ml and initial dye concentration 50ppm at room temperature to
optimize the value of x for (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation. The results are shown in table No. 4.31 & 4.32 and
Fig. 4.79 and 4.80. Value of x and their respective formulas are shown in table 4.22. It can be
observed from the results x=0.25 for (Al2O3)1-x(ZnO)xFe2O3 and x = 0 for (ZrO2)1-
x(ZnO)xFe2O3. (Al2O3)1-x(ZnO)xFe2O3 showed maximum degradation 83.15% with
(Al2O3)0.75(ZnO)0.25(Fe2O3) and minimum degradation with 35.84% with Al2O3.Fe2O3.
(ZrO2)1-x(ZnO)xFe2O3 showed maximum degradation 72.35% with ZrO2.Fe2O3 and minimum
degradation 40.78 with ZnO.Fe2O3.
113
Table No. 4.31 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of CI Reactive Black 5 at
pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room
temperature.
Time (Min)
Degradation (%)
X= 0 ± SD X= 0.25 ± SD X= 0.50 ± SD X= 0.75 ± SD X= 1 ± SD
20 3.14 0.21043 21.33 0.3073 14.41 0.5468 10.85 0.49212 9.11 0.74902
40 9.44 0.09901 38.07 0.35987 24.52 0.3214 22.74 0.28926 11.27 0.91186
60 16.33 0.22097 61.71 0.20237 38.45 0.2154 33.84 0.59386 17.35 0.50616
80 21.41 0.33667 77.54 0.4722 51.28 0.1254 44.25 0.21286 25.74 0.63214
100 29.5 0.53521 81.35 0.20897 65.58 0.5647 55.12 0.50823 33.24 0.86807
120 35.47 0.38538 82.77 0.38538 69.81 0.6547 61.35 0.8923 40.51 0.81879
140 35.84 0.15705 83.15 0.35562 69.92 0.4658 61.87 0.21456 40.78 0.35683
20 40 60 80 100 120 1400
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.80 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by mechanically
stirred co-precipitation for the degradation of CI Reactive Black 5 at pH=3, catalyst
dose 60mg/100ml and initial dye concentration 50ppm at room temperature.
114
Table No. 4.32 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of CI Reactive Black 5 at
pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room
temperature.
Time (Min)
Degradation (%)
X= 0 ± SD X=
0.25 ± SD
X=
0.50 ± SD
X=
0.75 ± SD X= 1 ± SD
20 18.71 0.44312 15.32 0.53691 12.98 0.63985 10.01 0.54387 9.11 0.74902
40 34.23 0.8187 26.31 0.65236 21.36 0.99494 17.82 0.81461 11.27 0.91186
60 47.38 0.87675 39.72 0.97225 26.84 0.51812 21.75 0.8974 17.35 0.50616
80 61.26 0.66312 48.52 0.78778 34.21 0.8194 28.51 0.60273 25.74 0.63214
100 69.75 0.8918 58.65 0.81136 41.74 0.31848 37.21 0.96655 33.24 0.86807
120 72.76 0.69266 63.12 0.68886 49.35 0.75029 43.51 0.86982 40.51 0.81879
140 72.35 0.35408 63.74 0.21905 49.87 0.20555 43.83 0.38372 40.78 0.35683
20 40 60 80 100 120 140
10
20
30
40
50
60
70
80
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.81 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by mechanically
stirred co-precipitation for the degradation of CI Reactive Black 5 at pH=3, catalyst
dose 60mg/100ml and initial dye concentration 50ppm at room temperature.
115
4.5.10 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 & (ZrO2)1-x(ZnO)xFe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation for the
degradation of CI Reactive Black 5
(Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted
mechanically stirred co-precipitation were used to optimize the x value as well as to compare
the photocatalytic activity of samples synthesized by mechanically stirred co-precipitation
method. The results are shown in table no. 4.33 & 4.34 and Fig. 4.81 & 4.82. Value of x and
their respective formulas are shown in table 4.22. It was found that (Al2O3)0.75(ZnO)0.25Fe2O3
and ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically stirred co-precipitation are
most active photocatalysts similar to the photocatalysts synthesized by mechanically stirred
co-precipitation. But photocatalytic activity of photocatalysts synthesized by ultra-sonic
assisted mechanically stirred co-precipitation was high as compared to photocatalysts
synthesized by mechanically stirred co-precipitation. Degradation was increased from
83.15% to 91.08% with (Al2O3)0.75(ZnO)0.25(Fe2O3) and 72.5% to 83.21% with Al2O3.Fe2O3.
The basic reason for the increase in photocatalytic activity was particle size and surface area
of the sample. Particles size was decreased by ultra-sonic assisted mechanically stirred co-
precipitation which caused the increase in surface area and decreased in pore volume this
change on surface of photocatalyst increased adsorption of dye molecules which lead to
increase in photocatalytic activity. (Tratnyek and Johnson, 2006; Shah et al., 2013).
Table No. 4.33 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation of CI Reactive
Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at
room temperature.
Time
(Min) Degradation (%)
X= 0 ± SD X=
0.25 ± SD
X=
0.50 ± SD
X=
0.75 ± SD X= 1 ± SD
20 6.45 0.52185 16.08 0.36208 12.58 0.42257 10.84 0.35613 8.45 0.78431
40 9.56 0.93169 29.64 0.67766 28.74 0.52164 22.54 0.21123 15.74 0.98367
60 13.25 0.89274 48.25 0.56463 44.84 0.28052 34.88 0.60806 22.58 0.60606
80 22.85 0.31981 67.33 0.70015 54.36 0.90212 49.51 0.56545 33.54 0.39392
100 30.54 0.27779 80.47 0.47315 67.85 0.73172 64.45 0.80733 49.65 0.91561
120 41.77 0.32297 90.75 0.26752 71.85 0.59375 68.05 0.53914 51.87 0.75426
140 41.98 0.76726 91.08 0.18548 72.31 0.33774 68.51 0.25257 52.25 0.60889
116
20 40 60 80 100 120 1400
10
20
30
40
50
60
70
80
90
100
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.82 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation for the degradation of CI Reactive Black
5 at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room
temperature.
Table No. 4.34 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation of CI Reactive
Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at
room temperature.
Time
(Min) Degradation (%)
X= 0 ± SD X= 0.25 ± SD X= 0.50 ± SD X= 0.75 ± SD X= 1 ± SD
20 20.77 0.78259 16.33 0.80036 13.55 0.85637 11.15 0.84153 8.45 0.8431
40 42.35 0.97296 31.54 0.93897 25.46 0.54172 22.25 0.6608 15.74 0.83668
60 56.84 0.51941 43.55 0.72313 36.78 0.60699 33.89 0.88664 22.58 0.96061
80 67.35 1.09624 50.44 0.96515 48.54 0.91373 44.52 0.28263 33.54 0.99392
100 75.29 0.8443 59.87 0.95898 56.84 0.80372 53.28 0.90168 49.65 0.61561
120 83.07 0.76324 71.35 0.82714 63.76 0.93401 59.14 0.46459 51.87 0.85426
140 83.21 0.70299 71.67 0.92624 63.96 0.89088 59.77 0.91725 52.25 0.80889
117
20 40 60 80 100 120 140
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.83 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation for the degradation of CI Reactive Black
5 at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room
temperature.
4.5.11 Optimization of pH for the degradation of Methylene Blue
Initial pH of the reaction mixture plays an important role in photocatalytic
degradation of dyes (Yao and Wang, 2010). Initial pH of solution for degradation of
methylene blue was optimized at pH 1 to 9 with odd numbers with 60mg/100ml catalyst
loading and 50ppm initial dye concentration. Photocatalysts used for the degradation of
methylene blue were (Al2O3)0.75(ZnO)0.25(Fe2O3) and ZrO2.Fe2O3. The degradation
efficiency was increased by increasing pH and the maximum degradation was achieved at
pH=9. (Al2O3)0.75(ZnO)0.25(Fe2O3) degraded MB 76.52% while ZrO2.Fe2O3 degraded MB
64.57% Results with mean values for degradation and their ± SD are given in Table No.
4.35& 4.36 and graphically represented in Fig. 4.83 & 4.84. Methylene blue is a cationic dye
it was attracted towards negatively charged photocatalyst at high pH value due to this
attraction more dye molecules were adsorbed on catalyst surface and photocatalytic activity
was increased (Guillard et al., 2003). Another factor which plays important role is the
118
availability of hydroxide ions at high pH value more hydroxide ions were produced and leads
to increase in the production OH radicals which increased oxidative degradation of
methylene blue at pH = 9 (Chakrabarti and Dutta, 2004; Talebian and Nilforoushan, 2010;
Sultana et al., 2015).
Table No. 4.35 Optimization of pH for the degradation of methylene blue with
(Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-precipitation at
60mg/100ml catalyst dose and 50ppm initial dye concentration at room temperature.
Time
(Min)
Degradation (%)
pH 1 ± SD pH 3 ± SD pH 5 ± SD pH 7 ± SD pH 9 ± SD
20 10.31 1.01823 9.34 0.98995 8.35 1.11723 4.51 0.98995 15.24 0.98995
40 21.34 1.04652 16.37 1.10309 15.25 1.13137 8.33 1.10309 29.91 1.10309
60 36.03 1.13137 27.19 0.82024 24.91 0.84853 11.71 0.82024 43.18 0.82024
80 45.91 1.04652 38.45 0.98995 32.52 0.9051 14.63 0.98995 52.08 0.98995
100 56.43 1.03238 49.05 1.11723 38.41 1.10309 16.24 1.11723 62.94 1.11723
120 67.55 0.77782 61.25 0.74953 43.71 0.83439 17.64 0.74953 76.03 0.74953
140 67.83 1.04653 61.98 0.71256 44.09 0.9568 17.87 0.71256 76.52 0.71256
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
Degra
dation (
%)
Time (Min)
pH 1
pH 3
pH 5
pH 7
pH 9
Fig. 4.84 Optimization of pH for the degradation of methylene blue with
(Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-precipitation at
60mg/100ml catalyst dose and 50ppm initial dye concentration at room temperature.
119
Table No. 4.36 Optimization of pH for the degradation of methylene blue with
ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at 60mg/100ml
catalyst dose and 50ppm initial dye concentration at room temperature.
Time
(Min) Degradation (%)
pH 1 ± SD pH 3 ± SD pH 5 ± SD pH 7 ± SD pH 9 ± SD
20 7.24 0.2354 6.54 0.53687 4.25 0.23587 2.18 0.54699 8.13 0.89542
40 17.85 0.35496 14.58 0.49635 11.89 0.12365 9.88 0.65489 20.27 0.62381
60 29.84 0.16597 25.87 0.26587 20.18 0.32156 12.55 0.51987 33.15 0.85742
80 41.35 0.59876 38.22 0.69874 28.34 0.59874 16.48 0.84592 45.38 0.26587
100 51.37 0.64782 49.94 0.52134 35.28 0.21568 20.78 0.79658 56.54 0.4237
120 59.68 0.24796 58.44 0.86688 43.25 0.21654 24.92 0.90541 64.18 0.62374
140 60.14 0.34569 58.73 0.6548 43.89 0.35982 25.05 0.32154 64.57 0.24621
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
Degra
dation (
%)
Time (Min)
pH 1
pH 3
pH 5
pH 7
pH 9
Fig. 4.85 Optimization of pH for the degradation of methylene blue with ZrO2.Fe2O3
synthesized by mechanically stirred co-precipitation at 60mg/100ml catalyst dose and
50ppm initial dye concentration at room temperature.
120
4.5.12 Optimization of catalyst dose for the degradation of Methylene Blue
Optimization of catalyst does was done at 20mg/100ml to 70mg/100ml at optimized
pH and 50ppm of dye solution. Degradation was increased from 20mg to 60mg/100ml and
76.23% and 64.57 % of methylene blue was degraded with (Al2O3)0.75(ZnO)0.25Fe2O3 and
ZrO2.Fe2O3 in 140 min time of reaction. Further increase in photocatalyst loading there was
decrease in photocatalytic efficiency. Mean values with ±SD are shown in table No. 4.37 and
4.38 by graphical representation in Fig. 4.85 and 4.86. Increase in photocatalytic efficiency is
due the increase in amount of nanophotocatalyst particles in the reaction mixture so
adsorption of methylene blue was increased. Decrease in efficiency is due to light scattering
by access amount of solid particles present in reaction mixture(Sarasidis et al., 2014; Wang
et al., 2014).
Table No. 4.37 Optimization of catalyst dose for the degradation of methylene blue with
(Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 9
and 50ppm initial dye concentration at room temperature.
Time
(Min) Degradation (%)
20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD 70mg ± SD
20 5.15 0.55454 7.18 0.54345 10.24 0.61181 12.78 0.49354 15.35 0.54955 13.37 0.45472
40 11.26 0.43551 18.56 0.41808 23.52 0.39195 26.14 0.37889 30.85 0.43245 27.43 0.39195
60 19.45 0.68273 28.84 0.64176 35.34 0.62129 38.47 0.58032 43.25 0.67932 40.54 0.66908
80 24.35 0.75784 30.56 0.69721 38.72 0.69721 46.34 0.62901 52.46 0.75556 49.34 0.67447
100 28.15 0.57161 33.45 0.51444 41.28 0.53713 52.24 0.46299 63.54 0.57103 57.48 0.48014
120 37.08 0.34727 42.28 0.3056 53.08 0.33686 65.25 0.27435 76.04 0.34615 68.12 0.28824
140 37.81 0.75809 42.47 0.65196 53.54 0.72777 66.12 0.58373 76.23 0.75324 68.72 0.61405
121
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
20mg
30mg
40mg
50mg
60mg
70mg
Fig. 4.86 Optimization of catalyst dose for the degradation of methylene blue with
(Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 9
and 50ppm initial dye concentration at room temperature.
Table No. 4.38 Optimization of catalyst dose for the degradation of methylene blue with
ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 9 and 50ppm
initial dye concentration at room temperature.
Time
(Min) Degradation (%)
20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD 70mg ± SD
20 3.46 0.2152 4.65 0.2438 6.25 0.5103 7.08 0.85065 8.13 0.7969 8.74 0.6267
40 5.17 0.1050 8.23 0.1194 13.98 0.4765 18.59 0.5988 20.27 0.5489 19.91 0.4678
60 8.33 0.1594 15.82 0.1718 23.56 0.2499 29.18 0.8059 33.15 0.7202 30.29 0.6173
80 10.75 0.2074 19.03 0.2171 30.85 0.6358 34.72 0.2419 45.38 0.2528 38.32 0.2259
100 12.17 0.2495 24.23 0.2922 37.74 0.4796 41.38 0.3898 56.54 0.3940 46.25 0.3177
120 15.56 0.2560 30.55 0.2893 44.15 0.8062 47.69 0.5800 64.18 0.5863 50.78 0.4366
140 16.14 0.2123 31.08 0.2367 44.83 0.6417 48.46 0.2412 64.57 0.2437 51.45 0.3142
122
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
Degra
dation (
%)
Time (Min)
20mg
30mg
40mg
50mg
60mg
70mg
Fig. 4.87 Optimization of catalyst dose for the degradation of methylene blue with
ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 9 and 50ppm
initial dye concentration at room temperature.
4.5.13 Optimization of dye initial concentration for the degradation of Methylene Blue
Photocatalytic degradation of methylene blue was carried out with different initial
concentrations ranging from 20 ppm to 60 ppm for the optimization of initial concentration
of methylene blue solution to get maximum degradation. (Al2O3)0.75(ZnO)0.25(Fe2O3)
degraded 76.23% and ZrO2.Fe2O3 degraded 64.57% of methylene blue at 50ppm initial dye
concentration. Results with mean degradation percent and their ± SD are shown in Table No.
4.39 & 4.40 and Fig. 4.87 & 4.88. It can be observed from the results that degradation of
methylene blue was increased by increasing initial concentration of dye and got maximum
degradation at 50 ppm of dye solution due to increase in dye molecule in solution which may
increase adsorption rate at the surface of photocatalyst. Further increase in initial
concentration decrease the degradation efficiency due decrease in intensity of light needed to
active photocatalyst (Shirsath et al., 2013).
123
Table 4.39 Optimization of initial dye concentration for the degradation of methylene
blue with (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-
precipitation at pH = 9 and 60mg/100ml catalyst dose at room temperature.
Time
(Min) Degradation (%)
20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD
20 6.36 0.69824 9.35 0.62136 11.58 0.76104 15.35 0.62136 14.18 0.53349
40 10.63 0.74995 19.38 0.67479 25.68 0.78291 30.85 0.67479 27.15 0.56641
60 20.34 0.57984 28.96 0.49361 37.54 0.57984 43.25 0.49361 39.84 0.42795
80 27.71 0.26176 35.15 0.23319 46.28 0.27003 52.46 0.22551 48.84 0.19095
100 31.13 0.61941 43.54 0.55811 55.88 0.61303 63.54 0.52171 58.78 0.44163
120 35.13 0.58208 48.84 0.48636 61.52 0.55856 76.04 0.49188 68.74 0.40569
140 35.52 0.42042 49.26 0.40781 61.98 0.42956 76.23 0.37553 68.16 0.3145
20 40 60 80 100 120 140 1600
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
20ppm
30ppm
40ppm
50ppm
60ppm
Fig 4.88 Optimization of initial dye concentration for the degradation of methylene blue
with (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-precipitation at
pH = 3 and 60mg/100ml catalyst dose at room temperature.
124
Table 4.40 Optimization of initial dye concentration for the degradation of methylene
blue with ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 9
and 60mg/100ml catalyst dose at room temperature.
Time
(Min) Degradation (%)
20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD
20 6.07 0.23654 6.58 0.49636 7.85 0.45968 8.13 0.13268 7.05 0.79654
40 12.68 0.3568 14.95 0.13654 16.75 0.23657 20.27 0.32587 18.56 0.34968
60 22.54 0.2657 25.85 0.36548 27.54 0.16548 33.15 0.31549 30.54 0.23458
80 30.54 0.49658 34.51 0.28797 39.41 0.02315 45.38 0.32155 41.36 0.13256
100 39.84 0.36547 46.85 0.31587 50.36 0.31256 56.54 0.42366 53.25 0.02578
120 45.38 0.26597 52.34 0.46987 56.87 0.12366 64.18 0.32156 59.56 0.25648
140 45.81 0.12365 52.96 0.36548 58.08 0.13287 64.57 0.18975 59.94 0.48965
20 40 60 80 100 120 1400
10
20
30
40
50
60
70
De
gra
datio
n (
%)
Time (Min)
20ppm
30ppm
40ppm
50ppm
60ppm
Fig. 4.89 Optimization of initial dye concentration for the degradation of methylene
blue with ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 9
and 60mg/100ml catalyst dose at room temperature.
125
4.5.14 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 and
synthesized by mechanically stirred co-precipitation for the degradation of Methylene
Blue
The general formulas (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 has different
composition between oxides with different values of x to optimize value of x for the best
photocatalyst composition for the degradation of methylene blue was done on optimum
conditions pH = 9, catalyst dose 60mg/100ml and initial dye concentration 50 ppm. The
results with mean degradation values are shown in Table No. 4.41 & 4.42 and Fig. 4.89 &
4.90. Value of x and their respective formulas are shown in Table No. 4.22.
(Al2O3)0.75(ZnO)0.25(Fe2O3) with x= 0.25 degraded 76.72% which was the maximum
degradation and minimum degradation of MB was 44.83% with Al2O3.Fe2O3 (x= 0). Other
photocatalyst (ZrO2)1-x(ZnO)xFe2O3 showed maximum degradation 64.57% with ZrO2.Fe2O3
(x= 0) and minimum degradation was 45.63% with ZnO.Fe2O3 (x=1).
Table No. 4.41 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of methylene blue at pH = 9,
60mg/100ml catalyst dose and 50ppm initial dye concentration at room temperature
Time
(Min) Degradation (%)
X= 0 ± SD X= 0.25 ± SD X= 0.50 ± SD X= 0.75 ± SD X= 1 ± SD
20 2.98 0.2654 15.24 0.7854 9.11 0.5468 7.31 0.1246 4.95 0.3878
40 8.12 0.1547 30.57 0.5623 23.54 0.3214 16.53 0.2351 14.05 0.2354
60 15.68 0.3564 43.65 0.3264 31.34 0.2154 22.15 0.6857 19.38 0.5624
80 23.47 0.4951 52.42 0.2165 41.63 0.1254 30.38 0.3257 26.15 0.3571
100 32.58 0.8234 63.25 0.3215 54.12 0.5647 42.38 0.6146 37.35 0.7563
120 44.25 0.4235 76.21 0.4235 62.13 0.6547 59.43 0.7265 54.95 0.2431
140 44.83 0.3141 76.72 0.3124 62.54 0.4658 59.88 0.4598 55.16 0.3547
126
20 40 60 80 100 120 1400
10
20
30
40
50
60
70
80
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.90 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by mechanically
stirred co-precipitation for the degradation of methylene blue at pH = 9, 60mg/100ml
catalyst dose and 50ppm initial dye concentration at room temperature.
Table No. 4.42 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by
mechanically stirred co-precipitation for the degradation of methylene blue at pH = 9,
60mg/100ml catalyst dose and 50ppm initial dye concentration at room temperature.
Time
(Min) Degradation (%)
X= 0 ± SD X=
0.25 ± SD
X=
0.50 ± SD
X=
0.75 ± SD X= 1 ± SD
20 8.13 0.45682 6.34 0.53691 5.75 0.63985 5.93 0.54387 4.65 0.84532
40 20.2
7 0.18618 15.24 0.45236 13.8 0.49949 12.86 0.21461 9.78 0.33154
60 33.1
5 0.4274 26.96 0.37225 22.12 0.51812 19.34 0.2974 15.23 0.24521
80 45.3
8 0.11303 38.56 0.28778 33.15 0.38194 26.57 0.50273 24.35 0.53214
100 56.5
4 0.33874 47.12 0.21136 41.98 0.23185 35.21 0.16655 33.05 0.41235
120 64.1
8 0.27141 56.87 0.46889 50.63 0.35029 46.78 0.38698 44.81 0.18951
140 64.5
7 0.37272 57.41 0.21905 50.91 0.20555 46.81 0.23837 45.63 0.21326
127
20 40 60 80 100 120 140
10
20
30
40
50
60
70
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.91 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by mechanically
stirred co-precipitation for the degradation of methylene blue at pH = 9, 60mg/100ml
catalyst dose and 50ppm initial dye concentration at room temperature.
4.5.15 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation for the
degradation of Methylene Blue
Optimum conditions for the degradation of methylene blue were used for the
selection of best photocatalyst from (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 with
respect to x value. The results are show in Table No. 4.13 and Fig. 4.21 and value of x and
their respective formulas are shown in Table No. 4.22. Table No. 4.43 and 4.44 contains the
mean values for percent degradation of MB with their ± SD. Best metals oxide composition
from (Al2O3)1-x(ZnO)xFe2O3 was x = 0.25 with formula (Al2O3)0.75(ZnO)0.25(Fe2O3) which
degraded methylene blue 83.74% and x=0 with formula ZrO2.Fe2O3 from (ZrO2)1-
x(ZnO)xFe2O3 degraded 73.97% of MB. Minimum degradation was 45.82% with
Al2O3.Fe2O3 and 47.18% with ZnO.Fe2O3. Photocatalysts synthesized by ultra-sonic assisted
mechanically stirred co-precipitation showed increase in photocatalytic efficiency as
compared to photocatalysts synthesized by mechanically stirred co-precipitation due to small
particle size and large surface area which increase the adsorption of dye molecules on surface
of photocatalyst. (Huang et al., 2013).
128
Table No. 4.43 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation of methylene
blue at pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye concentration at room
temperature
Time
(Min) Degradation (%)
X= 0 ± SD X= 0.25
± SD X= 0.50
± SD X= 0.75
± SD X= 1 ± SD
20 4.12 0.72465 16.11 0.73565 11.34 0.82473 8.15 0.72903 6.88 0.53159
40 7.98 0.36854 32.93 0.75296 26.89 0.5796 19.97 0.2347 13.06 0.64852
60 14.25 0.76586 46.88 0.84959 41.18 0.75613 31.28 0.84534 20.43 0.6734
80 24.34 0.59109 64.34 0.63335 56.91 0.54468 47.36 0.62828 31.54 0.77102
100 33.91 0.86433 74.75 0.52572 69.31 0.81302 60.85 0.89703 45.37 0.79512
120 45.28 0.58108 83.05 0.63058 75.29 0.54861 67.73 0.59905 54.11 0.50473
140 45.82 0.18793 83.74 0.2084 75.82 0.37948 68.08 0.39615 54.32 0.34707
20 40 60 80 100 120 1400
10
20
30
40
50
60
70
80
90
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.92 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation for the degradation of methylene blue at
pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye concentration at room
temperature.
129
Table No. 4.44 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-
sonic assisted mechanically stirred co-precipitation for the degradation of methylene
blue at pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye concentration at room
temperature.
Time
(Min) Degradation (%)
X= 0 ± SD X= 0.25 ± SD X= 0.50 ± SD X= 0.75 ± SD X= 1 ± SD
20 15.36 0.68259 13.1047 0.50036 12.29 0.45637 11.6794 0.4153 9.51 0.35335
40 28.06 0.17296 22.952 0.43897 21.5 0.44172 19.99723 0.4108 16.99 0.20531
60 41.97 0.51941 35.856 0.62313 32.49 0.40699 28.92011 0.38664 25.34 0.44393
80 58.85 0.40962 49.6155 0.66515 43.45 0.29137 39.56453 0.28263 36.41 0.12334
100 67.84 0.3443 57.2352 0.15898 51.89 0.20372 43.5703 0.20168 39.12 0.31563
120 73.54 0.56324 64.9318 0.32714 55.52 0.53401 51.11538 0.46459 46.82 0.35328
140 73.97 0.50299 65.3489 0.19262 55.91 0.49088 51.44373 0.41725 47.18 0.37113
20 40 60 80 100 120 140
10
20
30
40
50
60
70
80
Degra
dation (
%)
Time (Min)
x = 0
x = 0.25
x = 0.50
x = 0.75
x = 1
Fig. 4.93 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic
assisted mechanically stirred co-precipitation for the degradation of methylene blue at
pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye concentration at room
temperature.
130
4.6 Reusability Test for (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3
synthesized by ultra-sonic assisted mechanically stirred co-precipitation
Stability of photocatalysts is an important aspect in application of photocatalysts for
the removal of dyes or any other organic matter from waste water. Photocatalyst used for
longer time can reduce the cost of water treatment (Subash et al., 2013b; Tonda et al., 2014).
The most efficient photocatalysts (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 were reused in
six cycles to check stability of these photocatalysts against all three dyes Methyl Orange
(MO), CI Reactive Black 5 (RB5) and Methylene Blue (MB) 3 mg photocatalyst was added
in each cycle to recover the loss of catalyst during separation and washing process (Shahid et
al., 2013). Photocatalyst was active efficiently in 6 cycles (Jiang et al., 2014). 5 – 7 % loss
of activity was observed. The results are shown in Table No. 4.45 and Fig. 4.93 & 4.94. It
can be concluded from the results that both catalysts can be reuse successfully for the
removal of dyes from waste water which can reduce the cost of waste water treatment.
Table No. 4.45 Reusability of (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 in six cycles for
MO, RB5 and MB at optimum operational conditions.
Catalyst
Dye
% Degradation in 6 cycles
1 ±SD 2 ±SD 3 ±SD 4 ±SD 5 ±SD 6 ±SD
A MO 93.52 0.5684
92.78 0.4659
91.06 0.3125
90.25 0.2354
89.71 0.5236
88.96 0.3258
RB5 91.08 0.4556
90.26 0.6354
89.71 0.6624
87.05 0.4236
86.16 0.4965
84.87 0.5286
MB 83.74 0.5234
82.90 0.5648
82.14 0.5321
81.33 0.4587
80.24 0.4756
78.86 0.4523
B MO 78.38 0.4831
77.65 0.4287
76.63 0.2875
75.51 0.3166
75.02 0.4817
74.37 0.5997
RB5 83.21 0.4156 82.41 0.5337 81.85 0.4983 80.84 0.5165 80.24 0.4121 79.38 0.3878
MB 73.97 0.4397 73.15 0.4800 72.27 0.5234 71.69 0.4899 71.04 0.4042 70.54 0.4845
A = (Al2O3)0.75(ZnO)0.25Fe2O3
B = ZrO2.Fe2O3
MO = Methyl Orange
RB5 = CI Reactive Black 5
MB = Methylene Blue
131
MO RB5 MB0
20
40
60
80
100
120
Degra
da
tion (
%)
Cycle 1
Cycle 2
Cycle 3
Cycle 4
Cycle 5
Cycle 6
Fig. 4.93 Reusability of (Al2O3)0.75(ZnO)0.25Fe2O3 in six cycles for the degradation of
MO, RB5 and MB at optimum operational conditions.
MO RB5 MB0
20
40
60
80
100
120
De
gra
da
tio
n (
%)
Cycle 1
Cycle 2
Cycle 3
Cycle 4
Cycle 5
Cycle 6
Fig. 4.95 Reusability of ZrO2.Fe2O3 in six cycles for the degradation of MO, RB5 and
MB at optimum operational conditions.
132
4.7 Evaluation of Quality Assurance Parameters
4.7.1 Chemical Oxygen Demand (COD), Total Organic Carbon (TOC) analysis.
COD is the measurement of oxygen required for the oxidation of organic matter
present in a sample by strong chemical oxidant (Dan et al., 2000). TOC is the measure of
total organic matter present in sample (Thurman, 2012). To check the degradation efficiency
COD and TOC test was performed because TOC and COD values can show that during
photocatalytic process only chromophoric groups are break down to decolorize the dye
solution or other organic groups are break down into CO2 and H2O. The photocatalysts
(Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 synthesized by ultra-sonic assisted co-precipitation
were used for this purpose because these catalysts showed maximum degradation efficiency.
This test was performed for all three dyes Methyl Orange (MO), CI Reactive Black 5 (RB5)
and Methylene Blue (MB). Values for degradation, decrease in COD and decrease in TOC
are given in table 4.46.
Table No. 4.46 Degradation, decrease in COD and decrease in TOC with
(Al2O3)0.75(ZnO)0.25Fe2O3 & ZrO2.Fe2O3
(Al2O3)0.75(ZnO)0.25Fe2O3
Dye Degradation
(%)
Decrease in COD
(%)
Decrease in TOC
(%)
MO 93.52 51.82 43.56
RB5 91.08 44.58 38.77
MB 83.74 54.92 47.88
ZrO2.Fe2O3
MO 78.38 42.78 35.87
RB5 83.21 37.25 32.55
MB 73.97 46.23 39.84
It can be observed from the results that percent decrease of COD and TOC was less
than degradation of dye in case of both photocatalysts and all three dyes. Reason for this
difference is that only chromophoric groups of dye molecules are break down which are
133
responsible for colors removal. Dye molecules converted into other color less organic
products like phenolic or other benzene ring containing compounds (Paul et al., 2011;
Sapawe et al., 2013)b.
20 40 60 80 100 1200
10
20
30
40
50
60
Decre
ase in C
OD
(%
)
Time (Min)
MO
RB5
MB
Fig 4.96 Decrease in COD of MO, RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3
20 40 60 80 100 1200
10
20
30
40
50
Decre
ase in C
OD
(%
)
Time (Min)
MO
RB5
MB
Fig 4.97 Decrease in COD of MO, RB5 and MB with ZrO2.Fe2O3
134
20 40 60 80 100 1200
10
20
30
40
50
Decre
ase in T
OC
(%
)
Time (Min)
MO
RB5
MB
Fig 4.98 Decrease in TOC of MO, RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3
20 40 60 80 100 1200
10
20
30
40
Decre
ase in T
OC
(%
)
Time (Min)
MO
RB5
MB
Fig 4.99 Decrease in TOC of MO, RB5 and MB with ZrO2.Fe2O3
135
4.7.2 Mineralization of dyes
Concentration of organic pollutant in any sample is indexed by TOC values. Degree
of mineralization of compound under study is indicated by TOC (Reddy et al., 2013). Long
time treatment upto 8 h was performed to get the maximum mineralization (Ullah et al.,
2013). It was done for all three dyes with (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3.
Mineralization was increased with increasing time which indicated that organic carbon
present in sample was converted into carbon dioxide and water (Chen et al., 2004).
(Al2O3)0.75(ZnO)0.25Fe2O3 mineralize MO 80.45%, RB5 72.05% and MB 85.12% in 8 h time
of reaction at pH = 3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room
temperature. While ZrO2.Fe2O3 mineralize MO 69.42%, RB5 = 64.82 % and MB 74.28% in
8 at optimum conditions.
1 2 3 4 5 6 7 8 9
10
20
30
40
50
60
70
80
90
Decre
ase in T
OC
(%
)
Time (hour)
MO
RB5
MB
Fig. 4.100 Mineralization of MO,RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3 in 8 hours
136
1 2 3 4 5 6 7 8 9
10
20
30
40
50
60
70
80
Decre
ase
in
TO
C (
%)
Time (hour)
MO
RB5
MB
Fig. 4.101 Mineralization of MO, RB5 and MB with ZrO2.Fe2O3 25Fe2O3 in 8 hours
4.7.3 Total Suspended Solids (TSS)
Total suspended solids (TSS) is an important parameter to find the insoluble
quantities of pollutants in waste water specially disposed by the textile industries. Solid
particles in water can block the sun light which can affect the vegetation and cause rise in
temperature on surface (Mulligan et al., 2009). High TSS amounts can decrease the dissolved
oxygen level from normal level required for aquatic life and good quality of water. TSS
values are very high in waste water coming from textile industries as they use variety of
textile auxiliaries during processes. In this project we used dye solutions as synthetic
effluents, therefore TSS values were negligible or near to zero before treatment. But after
photocatalyst loading there was very small increase in TSS as 0.95mg/L, 1.13 mg/L and 1.10
mg/L for (Al2O3)0.75(ZnO)0.25Fe2O3 and 1.21mg/L, 1.26mg/L and 1.22mg/L for ZrO2.Fe2O3
with methyl orange, CI Reactive Black 5 and methylene blue respectively.
137
4.7.3 Haemolytic activity (Toxicity)
Toxicity of the sample can be estimated from the rate of haemolysis by applying different
concentrations of synthetic compounds on human erythrocytes (Sharma and Sharma, 2001).
Human red blood cell lysis was compared with samples after treatment containing Triton-
X100 1% as positive control it showed 100% lysis while Phosphate Buffer Saline (PBS) as
negative control showed 0% lysis. Results of treated samples were compared with these
controls. Haemolytic activity was performed for Methyl Orange (MO), CI Reactive Black 5
(RB5) and Methylene Blue (MB) solutions before and after treatment.
(Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically
stirred co-precipitation were used for treatment. Results are shown in Fig. 4.102 for
(Al2O3)0.75(ZnO)0.25Fe2O3 and in Fig. 4.103 for ZrO2.Fe2O3. It can be observed from the
results that toxicity of treated samples was decreased by both catalysts. Decrease in toxicity
by (Al2O3)0.75(ZnO)0.25Fe2O3 was more than ZrO2.Fe2O3 for all three dyes.
PBS MO RB5 MB Triton X 100
0
20
40
60
80
100
RC
Bs L
ysis
(%
)
Before Treatment
After Treatment
Fig. 102 Toxicity assay of samples treated with (Al2O3)0.75(ZnO)0.25Fe2O3 and un-treated
samples.
138
PBS MO RB5 MB Triton X 100
0
20
40
60
80
100
RC
Bs L
ysis
(%
)
Before Treatment
After Treatment
Fig. 102 Toxicity assay of samples treated with (Al2O3)0.75(ZnO)0.25Fe2O3 and un-treated
samples.
139
CHAPTER-5
SUMMARY
Textile industrial effluents are playing a significant role in enhancing water pollution.
These effluents contain different chemicals especially synthetic dyes which are very difficult
to degrade by using the classical techniques. Evolution of a new branch of science known as
nano science has completely replaced the previously used classical technologies because
Nanomaterials completely mineralize most of organics and remove completely organic
matter from polluted water. Nanophotocatalyst are non-toxic, non-corrosive and stable
chemically and thermally.
In this study two types of novel metal oxides nanophotocatalysts were synthesized
with general formulas (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 where x = 0, 0.25,
0.50, 0.75 and 1. Co-precipitation via simple mechanical stirring and a newly developed
method co-precipitation via ultra-sonic assisted mechanical stirring were used for the
synthesis of both nanophotocatalyst. Samples were calcined at 400ᴼC and 600ᴼC to get
crystalline structures. Characterization of synthesized photocatalyst was done with X-Ray
Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray
analysis (EDX), Particle size analysis and Surface analysis like Single Point surface area,
BET surface area and pore volume BJH adsorption and desorption pore volume.
Photocatalytic activity test was performed with three different dyes Methyl Orange (MO), CI
Reactive Black 5 (RB5) and Methylene Blue (MB) by optimizing the pH, photocatalyst dose
and initial dye concentration for both photocatalysts at room temperature.
X-Ray diffraction patterns showed that samples calcined at 600ᴼC are good
crystalline. In phase analysis more than one phase were detected in all samples. No specific
shape was seen in SEM images of most photo-catalytically active samples. EDX analysis was
also performed for highly efficient photocatalysts all components were detected in EDX
spectra of all samples at their relative energies. Particle sizes were calculated from XRD data
with help of Scherer’s formula and Zetasizer both results were matched with each other.
140
Particles with different sizes were detected in different samples ranging from 12 nm to 55
nm. Surface area was increased with decrease in particle size by ultra-sonic assisted
mechanically stirred co-precipitation.
Optimum pH was 3 for MO and RB5 while maximum degradation of MB was
occurred at pH 9. Catalyst dose was 60mg/100ml and optimum Initial dye concentration
was 50ppm for all three dyes with both catalysts. Co-precipitation via ultra-sonic assisted
mechanical stirring enhanced the photocatalytic activity of both photocatalysts by decreasing
particle size and increasing surface area of photocatalysts. (Al2O3)1-x(ZnO)xFe2O3 synthesized
by ultra-sonic assisted mechanically stirred co-precipitation with x=0.25 has maximum
degradation efficiency as it degraded MO 93.52%, RB5 91.08% and MB 83.74% while the
photocatalyst (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted mechanically stirred
co-precipitation with x= 0 degraded the MO 78.38%, RB5 83.21% and MB 73.97% in 140
min. Therefore both are potential nanophotocatalysts for wastewater treatment.
141
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