WASTE TO VALUABLE BY PRODUCT: UTILIZATION OF CARBONISED DECANTER CAKE

FROM PALM OIL MILLING PLANT AS AN EFFECTIVE ADSORBENT

FOR HEAVY METAL IONS IN AQUEOUS SOLUTION

NUGROHO DEWAYANTO

Thesis submitted in fulfillment of the requirements for the award of the degree of

Master of Engineering in Chemical Engineering

Faculty of Chemical and Natural Resources Engineering UNIVERSITI MALAYSIA PAHANG

JULY 2010

vii

ABSTRACT

Palm oil milling plant generates large amount of waste that was proven to cause environmental problems. About 40 kg decanter cake was generated from each ton of fresh fruit bunch processed. Previous studies suggested agricultural waste could be employed as heavy metal ion adsorbent. Due to the similarity of decanter cake with other agricultural waste we proposed to explore the use of decanter cake as an adsorbent for heavy metal ion removal.

Utilization of decanter cake as an effective adsorbent for Cd 2 , Cu2 and Pb2 ion removal from aqueous solution has been studied. The decanter cake was first dried at 105 °C and then carbonized at various temperatures. The resulting carbonized decanter cake were tested for removing Cd2 , Cu 7+ and Pb2 ions. Proximate analysis using thermogravimetry analysis of decanter cake carbonized at 500 °C indicated that the adsorbent contained 4% moisture, 21% volatile,23% fixed carbon, and 52% ash. Adsorption test were normally carried out by mixing 1.0 g of the decanter cake in 100 mL aqueous solution of the various ions. The concentration of metal ions in the solutions used is in the range of 100 - 1000 mg/t.

The results of adsorption studies indicated that the removal of metal ions was highest in the case of Pb2 when the carbonization temperature was 500 °C and 600 °C in the case of Cd2 and Cu2 . Maximum removal of the Cd2 , Cu2 and Pb2 were also observed to take place when the pH of the solution is in the range of 4 - 5. Langmuir and Freundlich isotherm models were used to fit the isotherm experimental data. The maximum uptakes of Cd2 , Cu2 and Pb2 onto the carbonized decanter cake in this study were estimated to be 24, 23, and 97 mg/g respectively. Adsorbed metal ions can be desorbed from adsorbent using dilute HC1 solution. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. Thermodynamic parameters such as standard enthalpy (MI"), standard entropy (AS-) and Gibbs free energy (AG-) were determined. Adsorption process was endothermic and had negative value of Gibbs free energy changes. The competitive adsorption characteristics of binary and ternary heavy metal ions Cd2 , Cu2 and Pb2 on PDC500 were investigated in batch systems. Equilibrium adsorption data showed that PDC500 displays a high selectivity toward one metal in two-component or a three-component system with an affinity order of Pb2> Cu2 > Cd2 Chemical activation of decanter cake using ZnC12 increased the maximum adsorption capacity for Cd2 , Cu2 and Pb2 significantly to 52, 44, and 159 mg/g respectively. Kinetic and thermodynamic properties of adsorption were affected by chemical activation.

Scale up of the batch process into industrial scale was explored using the Langmuir parameter from experimental data. A three-stage continuous counter current adsorption unit gave the best adsorption performance for Pb2 ion removal in term of minimum adsorbent consumption.

viii

ABSTRAK

Kilang ke1apa sawit menghasilkan sejumlah besar bahan buangan di mana ia menjadi punca terhadap pencemaran alam sekitar. Setiap satu tan tandan buah segar kelapa sawit yang diproses menghasilkan 40 kg decanter cake. Kajian terdahulu mencadangkan bahawa bahan buangan pertanian dapat digunakan sebagai penjerap ion logam berat. Memandangkan decanter cake mempunyai persamaan dengan bahan buangan pertanian yang lain, ia dicadangkan sebagai bahan penjerap untuk menyingkirkan ion logam berat.

Penyingkiran ion-ion Cd2 , Cu2 dan Pb2 daripada decanter cake minyak kelapa sawit telah dikaji. Decanter cake dikeringkan terlebih dahulu pada 105 °C dan path pelbagai suhu. Hasil pirolisis mendakan itu diuji untuk menyingkir ion-ion Cd2 , Cu2

dan Pb2t Analisa pirolisis mendakan pada 500 °C dengan menggunakan 'thermogravimetry' mendapati bahawa penjerab mengandungi 4% kelembapan, 21% bahan ruap, 23% karbon mampat dan 52 % abu. Ujian penjerapan dijalankan dengan mencampurkan 1.0 g mendakan ke dalam 100 mL larutan pelbagai ion. Kepekatan ion-ion logam yang digunakan di dalam larutan adalah dalam lingkungan 100-1000 mg/L.

Hasil ujikaji penjerapan menunjukan penyingkiran ion-ion Pb 2 adalah tinggi pada suhu 500 o o C dan 600 C bagi ion Cd2+ dan Cu2+ Penym i gkiran on-ion Cd2+ , Cu2+ and Pb2 adalah maksimajuga diperhatikan apabila pH larutan di datam lingkungan 4-5. Model isoterma Langmuir dan Freundlich telah digunakan untuk mengukuhkan lagi data eksperiment. Maksimum ion- ion Cd2 , Cu2 dan Pb2 terhadap pirolisis mendakan adalah dianggarkan 24, 23 dan 97 mg/g masing-masing. Ion-ion logam yang terjerap botch dinyahkan dan penyerap dengan menggunakan tarutan HCL cair. Kinetik penjerapan didapati mengikut model kinetik order kedua pseudo. Parameter termodinamik seperti enthalpy piawai (Mb), entropi piawai (AS-) dan tenaga bebas piawai (AG-) telah ditentukan. Pengaktifan kimia bagi hasil mendakan dengan menggunakan ZnC12 meningkatkan keupayaan penjerapan maksimum bagi Cd 2 , Cu2

dan Pb2 sebingga 52, 44 dan 159 mg/g. Ciri-ciri kinetic dan termadinamik penjerapan telah dipengaruhi oteh pengaktifan secara kimia. Ciri-ciri perbezaan penjerapan binari dan ketiga bagi ion-ion logam berat Cd2 , Cu2 dan Pb2 terhadap PDC500 telah dikaji dalam sistem kelompok. Data keseimbangan penjerapan menunjukan bahawa PDC500 memberikan kupayaan memitih yang tinggi terhadap togam dalam system dua komponen atau tiga komponen dengan turutan Pb 2 > Cu2 > Cd2t

Berdasarkan data-data yang diperolehi, sistem berskala makmat dinaikskata kepada skala industri menggunakan parameter Langmuir. Didapati, proses penyingkiran optimum ion Pb2 berdasarkan penggunaan minimum bahan penj crap diperotehi apabita proses penjerapan tiga peringkat arus melawan berterusan digunakan.

Ix

TABLE OF CONTENTS

Contents

SUPERVISOR'S DECLARATION

111

STUDENT'S DECLARATION

iv

ACKNOWLEDGEMENT vi

ABSTRACT vii

ABSTRAK viii

LIST OF TABLES xli

LIST OF FIGURES xiv

LIST OF SYMBOLS xvii

LIST OF ABBREVIATIONS xviii

CHAPTER 1 INTRODUCTION

1

1.1 Waste 1

1.2 Waste Reduction 4

1.3 Adsorption Process 7

1.4 Problem Statement

8

1.5 Objectives 8

1.6 Scope Of Work

9

1.7 Thesis Structure 9

CHAPTER 2 LITERATURE REVIEW

11

2.1 Decanter Cake Of Palm Oil Milling Plant

11

2.2 Cadmium, Copper And Lead Ions In Environment

13

2.2.1 Cadmium in Environment

13 2.2.2 Copper in Environment

15

2.2.3 Lead in Environment

17 2.2.4 Heavy metal removal from environment

18

2.3 Adsorbent

21

x

2.3.1 Types of adsorbent 21 2.3.2 Agricultural waste as adsorbent 23 2.3.3 Carbonized agricultural waste as adsorbent 26

2.4 Adsorption Of Heavy Metal Ion 28

2.4.1 Adsorption mechanism 28 2.4.2 Effect of pH in metal ion adsorption 30 2.4.3 Adsorption isotherm 31 2.4.4 Adsorption kinetic 39 2.4.5 Adsorption thermodynamic 41 2.4.6 Desorption 47 2.4.7 Adsorption selectivity 47 2.4.8 Effect of activation of carbonized decanter cake on adsorption parameter48

2.5 Scale Up Of The Adsorption Process 49

2.5.1 Single stage batch 51 2.5.2 Multiple stages batch 52 2.5.3 Single stage continuous 54 2.5.4 Multistage countercurrent 54 2.5.5 Column contact 56

2.6 Utilization Of Atomic Absorption Spectrometry In Heavy Metal Analysis 57

2.6.1 Basic Principles of Atomic Absorption Spectrometry 57 2.6.2 Quantitative analysis 58 2.6.3 Analytical condition for Cd 2 , Cu2 and Pb2 ion analysis 59

CHAPTER 3 MATERIALS AND METHODS 61

3.1 Material Preparation 61

3. 1.1 Adsorbent and reagents preparation 61 3.1.2 Characterization 62

3.2 Heavy Metal Ion Analysis Using Atomic Absorption Spectrometry 62

3.2.1 Calibration curve 62 3.2.2 Preparation of sample 63

3.3 Experiments 63

3.3.1 Equilibrium time 63 3.3.2 Effect of carbonization temperature 64 3.3.3 Effect of pH 64 3.3.4 Adsorption isotherm 64 3.3.5 Desorption studies 65

3.3.6 Kinetic studies 65

3.3.7 Thermodynamic studies 65 3.3.8 Competitive adsorption of metal ions in binary and ternary ion mixture 66 3.3.9 Effect of chemical activation on adsorption parameters 66

xi

CHAPTER 4 RESULTS AND DISCUSSIONS

67

4.1 Introduction 67

4.2 Characterization 68

4.2.1 Thermogravimetry analysis

68 4.2.2 Scanning Electron Microscope and EDX Spectrometry

71

4.2.3. Surface area and porosity of adsorbent

75

4.3 Adsorption Studies 77

4.3.1 Equilibrium time 78

4.3.2 Effect of carbonization temperature

79 4.3.3 Effect of pH

80 4.3.4 Adsorption isotherm

81 4.3.5 Desorption 86

4.4 Kinetic And Thermodynamic Studies

89

4.4.1 Kinetic studies 90

4.4.2 Thermodynamic studies

95

4.5 Competitive Adsorption 98

4.6 Effect Of Decanter Cake Activation 101

4.6.1 Effect of activation on adsorption isotherm

102 4.6.2 Effect of activation on adsorption kinetic

105

4.6.3 Effect of activation on adsorption thermodynamic

110

4.7 Scale Up Of The Adsorption Process

112

4.7.1 Single stage batch

113 4.7.2 Multiple stages batch

114

4.7.3 Single stage continuous 114

4.7.4 Multistage countercurrent

115

CHAPTER 5 CONCLUSION AND RECOMMENDATION FOR FUTURE

RESEARCH 117

5.1 Conclusion 117

5.2 Recommendation For Future Research

118

REFERENCES 120

xli

LIST OF TABLES

Table Title Page

2.1 Physical and chemical properties of cadmium 13

2.2 Physical and chemical properties of copper 15

2.3 Physicochemical properties of common copper compounds 16

2.4 Physical and chemical properties of lead 17

2.5 Different precipitant used for heavy metal recovery 19

2.6 Typical application of commercial adsorbents 24

2.7 Summary of modified plant wastes as adsorbents for the removal of 25 heavy metal ions from aqueous solution

2.8 Summary of carbonaceous adsorbents derived from agricultural 27 waste or agricultural by-product

2.9 Langmuir parameters and conditions for adsorption of heavy metals 36 by various kinds of biosorbents

2.10 Freundlich parameters and conditions for adsorption of heavy metals 38 by various kinds of biosorbents

2.11 Kinetic studies on heavy metal biosorption 42

2.12 Thermodynamic studies on heavy metal biosorption 45

2.13 Analytical conditions for Cd2 , Cu2 and Pb2 analysis. 57

3.1 Concentration variation of standard solution for each metal ion 60

4.1 Proximate analysis of adsorbent from decanter cake at various 68 carbonization temperatures

4.2 Quantitative result of EDX spectrometry on carbonized decanter 72 cake

4.3 BET surface area and porosity of adsorbents 74

4.4 Correlation between carbonization temperature, its properties and 77 metal ion uptake

4.5 Langmuir and Freundlich parameters for adsorption of metal ions 83 onto pyrolized decanter cake

4.6 Comparison of Langmuir parameters between decanter cake and 84 other selected agricultural waste based carbonaceous adsorbents

4.7 Pseudo-first-order and pseudo-second-order kinetic model 88. parameters for Cd2 , Cu2 and Pb2 adsorption onto PDC500

xlii

Table Title Page

4.8 Comparison of pseudo second order kinetic parameter of decanter 91 cake with other selecting waste based adsorbents

4.9 Thermodynamic parameters for adsorption of Cd2+, Cu2+ and Pb2+ 93 onto pyrolized decanter cake

4.10 Selectivity of particular metal ion in multi ion mixture system 96

4.11 Electronegativities, hydrated ionic radius and hydration energies of 98 Cd2 , Cu2 , and Pb2 ion

4.12 Langrnuir and Freundlich parameters for adsorption of Cd2 , Cu2 , 101 and Pb2 onto activated decanter cake

4.13 Pseudo first order and seudo second order kinetic parameters for 104 adsorption of Cd2 , Cu , and Pb2 onto activated decanter cake

4.14 Thermodynamic parameters of andsorption of Pb 2 , Pb2 , and Pb2 109 onto inactivated and activated decanter cake

4.15 Design parameter of single stage batch adsorption for Pb2 removal 110

4.16 Design parameter of multiple-stage batch adsorption for Pb2 111 removal

4.17 Design parameter of single stage continuous adsorption for Pb 2 112 removal

4.18 Design parameter of three stages continuous counter current 113 adsorption system for lead removal

LIST OF FIGURES

Figure Title Page

2.1 Average value of waste generation rate (per ton FFB) 12

2.2 Diagram of biosorption mechanism 29

2.3 Typical plot of initial solution Ph vs adsorption capacity of metal ion 31

2.4 Isotherm showing concentration variables for a transition from 33 (c'1, n') to (c" , n"1 )

2.5 Plot of laboratory data for Langmuir isotherm (a) C. VS qe, 34 and (b) Ce vs Ce/qe

2.6 Log-log plot of Freundlich isotherm model 35

2.7 Linear plot of pseudo first (a) and second order (b) models for 41 adsorption kinetic

2.8 Linear plot of In KdVS 1/T 44

2.9 Single stage batch adsorption 51

2.10 Determination of adsorption capacity of adsorbent for single stage 52 batch mode using Langmuir plot

2.11 Double stages batch adsorption 53

2.12 Single stage continuous adsorption 54

2.13 Multistage countercurrent adsorption 55

2.14 Schematic design of an atomic absorption spectrometry 56

2.15 Typical calibration curve of AAS analysis 57

4.1 Plot of TGA (a), derivative (b) 77

4.2 SEM micrographs of PDC 300 (a), PDC 500 (b), PDC 700 (c), and ash (d) 79

4.3 EDX spectrum for PDC300 (a), PDC500 (b), PDC700 (c) and ash (d) 81

4.4 BET plot 84

4.5 Equilibrium time for Cd2 , Cu2 and Pb2t 86

4.6 Effect of carbonization temperature in adsorption of Cd2 , Cu2 and Pb2 onto carbonized decanter cake 87

xiv

xv

Figure Title Page

4.7 Effect of initial Ph in the adsorption of Cd2+ and Cu2+ onto PDC600 and Pb2+ onto PDC500 88

4.8 Adsorption isotherm for Cd2+ onto PDC 600 (a), plot of linearized Langmuir model (b), and plot of linearized-Freundlich model (c) 90

4.9 Adsorption isotherm for Cu2 onto PDC 600 (a), plot of linearized Langmuir model (b), and plot of linearized-Freundlich model (c) 91

4.10 Adsorption isotherm for Pb2 onto PDC 500 (a), plot of linearized Langmuir model (b), and plot of linearized-Freundlich model (c) 92

4.11 Desorption of Cd2 , Cu2 and Pb2 ions from decanter in different concentrations of HC1 solution 94

4.12 Plot of desorption efficiency (%) vs. time 95

4.13 Plot of data experiment, q vs. t 98

4.14 Plot of pseudo-first-order (a) and pseudo-second-order (b) kinetic models for adsorption of Cd2 , Cu2 and Pb2 onto PDC500 99

4.15 Correlation of temperature and metal ion uptake for adsorption of Cd2 , Cu2 and Pb2 onto PDC500 101

4.16 Plot of In Kd vs. lIT for Cd2 , Cu2 and Pb2 adsorption onto decanter cake 101

4.17 Adsorption uptake of Cd onto PDC 500 in single, binary and ternary system vs. adsorption time 103

4.18 Adsorption uptake of Cu onto PDC 500 in single, binary and ternary system vs. adsorption time 104 104

4.19 Adsorption uptake of Pb onto PDC 500 in single, binary and ternary system vs. adsorption time. 104

4.20 Langmuir and Freundlich adsorption isotherm models for Cd2 adsorption onto H3PO4 (A-prefix) and ZnC12 activated (Z-prefix) decanter cake 107

4.21 Langmuir and Freundlich adsorption isotherm models for Cu2 adsorption onto H3PO4 (A-prefix) and ZnC12 activated (Z-prefix) decanter cake 107

4.22 Langmuir and Freundlich adsorption isotherm models for Pb2 adsorption onto H3PO4 (A-prefix) and ZnC12 activated (Z-prefix) decanter cake 108

4.23 Plot of kinetic data for Cd2 (a), Cu2 (b), and Pb2 (c) adsorption onto PDC500, ADC and ZDC 109

Figure Title

4.24 Linearized plot of pseudo first order kinetic model for Cd 2 (a), Cu2 (b), and Pb2 (c) adsorption onto PDC500, ADC and ZDC 112

4.25 Linearized plot of pseudo second order kinetic model for Cd 2 (a), Cu2 (b), and Pb2 (c) adsorption onto PDC500, ADC and ZDC 113

4.26 Plot of In Kd vs. l/T for Cd2 adsorption onto PDC500, ADC and ZDC 114

4.27 Plot of in Kd vs. lIT for Cu2 adsorption onto PDC500, ADC and ZDC 115

4.28 Plot of in Kd vs. l/T for Pb2 adsorption onto PDC500, ADC and ZDC 115

4.29 Mass balance of three stages continuous counter current adsorption 119

xvi

Page

LIST OF SYMBOLS

Ce equilibrium concentration of metal ions in solution

c1 concentration of adsorbate in solution (linear isotherm)

F fluid flow rate

ki first order rate constant

k2 second order rate constant

Kd equilibrium constant

KF Freundlich constant

K1 adsorption constant (linear isotherm)

KL affinity constant of Langmuir isotherm

n intensity of adsorption constant (Freundlich isotherm)

n1 concentration of adsorbate in adsorbent (linear isotherm)

q amount of metal ion adsorbed per unit weight adsorbent

qe amount of metal ion adsorbed per unit weight adsorbent at equilibrium

qm maximum adsorption capacity of the adsorbent

R ideal gas constant

R2 correlation coefficient

S selectivity

T temperature

t adsorption time

V fluid volume

W adsorbent weight/flow rate

AG Gibbs free energy change

till enthalpy change

AS entropy change

xvii

LIST OF ABBREVIATIONS

AAS Atomic Absorption Spectrometry

BET Brunauer-Emmer-Teller

BOD Biological oxygen demand;

CFC Chiorofluorocarbon

CPO Crude palm oil

CST Continuous settling tank

DOE Department of Environment

EDX Energy dispersive X-ray fluorescence

EEA European Environmental Agency

EFB Empty fruit bunch

EPA Environmental Protection Agency

ESCAP Economic and Social Commission for Asia and the Pacific

FAAS Flame Atomic Absorption Spectrometry

FELDA Federal Land Development Authority

FFB Fresh fruit bunch

GFAAS Graphite Furnace Atomic Absorption Spectrometry

ICP-MS Inductively Coupled Plasma-Mass Spectrometry

ICP-OES Inductively Coupled Plasma-Optical Emission Spectrometry

MSW Municipal solid waste

NOS Non oil solid

NRC National Research Council

SEM Scanning electron microscope

TGA Thermogravimetry analysis

TKN Total Kjeldahl Nitrogen

VOC Volatile organic compound

WHO World Health Organization

WW Wastewater

xviii

CHAPTER 1

INTRODUCTION

1.1 WASTE

Waste is an unavoidable by-product of most human activity. Economic

development and rising living standards have led to increases in the quantity and

complexity of generated waste; whilst industrial diversification and the provision of

higher quality of processed agricultural products have added substantial quantities of

industrial and agricultural waste into the waste stream with potentially severe

environmental and human health consequences. The rising of waste generation as the

consequences of economic development become serious challenge to develop robust

and cost effective waste management strategies. It is important to have a clear

appreciation of the quantities and characteristic of the waste being generated to do that.

There are three major waste sources: municipal waste, industrial waste and

agricultural waste. Municipal waste is generated from households, offices, hotels, shops,

schools and other institutions. The major components are food waste, paper, plastic,

rags, metal and glass, although demolition and construction debris is often included in

collected waste, such as electric light bulbs, batteries, automotive parts and discarded

medicines and chemicals. The composition of municipal solid waste varies significantly

across the region. As an example, Kuala Lumpur has generated waste containing

approximately 60 per cent organic waste, while Bangkok has generated it by 50 per cent

of organic waste, according to Economic and Social Commission for Asia and the

Pacific (ESCAP, 2000).

I

2

Industrial solid waste encompasses a wide range of materials of varying

environmental toxicity. Typically this range would include paper, packaging materials,

waste from food processing, oils, solvents, resins, paints and sludge, glass, ceramics,

stones, metals, plastics, rubber, leather, wood, cloth, straw, abrasives, etc. Based on an

average ratio of the region, the industrial solid waste generation in Asia Pacific region is

equivalent to 1,900 million tones per annum. This amount is expected to increase

substantially and at the current growth rates, it is estimated that it will double in less

than 20 years (ESCAP, 2000). As the existing industrial solid waste collection,

processing and disposal systems of many countries are grossly inadequate; such

incremental growth will pose very serious challenges to the environment.

Expanding agricultural production has naturally resulted in increased quantities

of livestock waste, agricultural crop residues and agro-industrial by-products. The

approximate annual production of agricultural waste and residues in Malaysia is 42

million tones (ESCAP, 2000). From this 54.5 per cent was generated from oil palm

industries, while other portions of it were mainly generated from rubber, coconut, rice

and wood industries.

For two last decades, palm oil significantly showed increase of world's

consumption and became important edible oil among the other, e.g. soybean oil,

sunflower oil, rapeseed oil and others. This amazing increaseof consumption is enabled

by the spectacular growth of production sector of palm oil in the last decade. Many new

plantations and palm oil milling plants are installed in South East Asia to meet demands

of world's consumption. In Malaysia and Indonesia,, palm oil becomes a major

commodity to lead the economic growth in the area. Malaysia became the most

important palm oil producer with 44% share equals by 14.962 million metric tons,

leading from Indonesia (42% share) in 2005 (Basiron 2007).

The commercial variety of oil palm planted in Malaysia is Elaeis guineensis

which originates from Africa. The species was first introduced into Malaya as

ornamental plant in 1875, and started to be commercialized commodities in 1917. Since

1960, planted area for oil palm in Malaysia has been increasing rapidly, covering 4.05

3

million hectares in 2005 with annual growth of 10.06% (Basiron, 2007). With these

areas, oil palm became largest agricultural commodities in Malaysia leaving rubber in

second.

Palm oil industries contribute enormous waste and effluent to the environment.

More than 70% of fresh fruit bunches processed are released as effluent and waste

during the milling process. There are three major types of waste and effluent generated

by palm oil milling plant. Air emission of palm oil plant consist vapor, steam blow

down and particulate matters. Waste water effluent covers oil contaminated and high

organic contaminated waste water. Solid waste was generated by palm oil industries in

the forms of empty fruit bunch, fiber, shell, decanter cake and ashes.

The major solid wastes that result from the milling operations are empty fruit

bunches, palm fiber, and palm kernel shell. The wastes that are mentioned above usually

are not considered as waste, but refer as by-product since they could be used for

economic purposes. Traditionally, the biomass can be treated easily as fuel source after

drying under the sun. The fuel can be used for boiler to produce steam for oil palm

extraction process or to move steam turbine and generate electricity (Yusoff, 2006).

Empty fruit bunches or palm fiber can also be sent back to plantation as fertilizer.

Pyrolysis of palm oil biomass converts it into a volatile fraction consisting of gases,

vapors and tar components and a carbon rich solid residue (char) fraction. The volatile

fraction can be used as a fuel or as a chemical feedstock. For the remaining solid

fraction, it can be used in several applications, for example, in the production of

activated carbon or used directly as a solid fuel (Luangkiattikhun et al., 2008). Palm

kernel shell can be used as granular filter for water treatment, as a suitable aggregate in

plain, light and dense concretes and as a road building material road (Olanipekun et al.,

2006). Tangchirapat et al. (2006) utilized the palm oil fuel ash as constituents in

concrete.

Decanter cake is a solid waste produced from the three phase separation step of

crude palm oil process. The production rate of decanter cake amount to about 4 - 5

weight % of fresh fruit bunch processed. Fresh decanter cake contains about 70 weight

4

% moisture, while the dry matter contains oils, fiber and inorganic components. The

most common utilization of decanter cake is as fertilizer and animal nutrition sources

due to the presence of C, N, P, K and Mg (Chavalparit et al.; 2006).

1.2 WASTE REDUCTION

Many methods have been developed to reduce the solid waste generation and its

impact to environment. The concept of waste management include the options of

prevention of waste generation, minimizing waste source, reuse, recycle, energy

recovery of waste, and waste disposal. Transforming the waste into a valuable by

product can be another option to reduce it and give more benefits rather than other

options.

Recent studies have indicated the potential utilization of agricultural waste and

solid waste as effective adsorbent. Pulp and paper mill has been investigated as a

prospective adsorbent. Khalili et al. (2002) reported that conversion of paper mill sludge

to useful activated carbons and biocatalysts was a significant process since it reduced

environmental problems associated with disposal of waste sludge, enhanced wastewater

treatment using carbons produced from industrial waste itself, and promoted

conservation of the naturally available primary resources currently used to make

activated carbons. Paper mill sludge was also reported capable for increasing the

capability of soil to retain heavy metal, particularly cadmium and lead (Battaglia et al.,

2003). Dried paper mill sludge has been successfully employed to remove lead, copper,

silver and cadmium ion from aqueous solution in acid condition (Calace et al., 2003).

Tha et al. (2006) also reported that pulp and paper mill sludge has been investigated to

absorp nickel.

A number of studies on adsorption by sewage sludge have been reported.

Sewage sludge could be transformed into activated carbon adsorbent by heat treatment

(Fan and Zhang, 2008), chemical activation (Rozada et al., 2002; Martin et al., 2003;

Zhang et al., 2005), or steam activation (Rio et al., 2006). Other materials like

discarded tyres (Rozada et al., 2005), coconut husks (Tay et al., 2001) and rice straw

(Shuang-quan, 2009) were mixed with sewage sludge to obtain higher adsorption

properties. Applications of sewage sludge, modified, sewage sludge and its derivates

have been investigated for dyes adsorption (Rozada et al. 2003; Martin et al., 2003),

mercury removal (Zhang et al., 2005), alkaline black adsorption (Fan and Zhang, 2008),

lead and chromium (III) ion removal (Rozada et al., 2008). Dried sewage sludge

demonstrated ability for use as a low-cost biosorbent for phenol from wastewater

(Thaworchaisit and Pakulanon, 2001). Seredych and Bandosz (2006) also reported that

sewage sludge can be employed as an adsorbent to remove copper from aqueous

solution.

Agricultural waste or by-products in their original form and in some cases

appropriately modified have been established to have high capacity for heavy metal

adsorption (Demirbas, 2008a). Agricultural by-products usually are composed of lignin

and cellulose as major constituents and may also include other polar functional groups

of lignin, which includes alcohols, aldehydes, ketones, carboxylic, phenolic and ether

groups. These groups have the ability to some extent to bind heavy metals by donation

of an electron pair from these groups to form complexes with the metal ions in solution

(Pagnanelli et al., 2003). Activated carbon was developed from agricultural waste or by-

products were also used for the removal of dyes from wastewater successfully

(Demirbas, 2008b). Since agricultural solid wastes are freely, abundantly and locally

available, its use for adsorption is expected to be economically viable for wastewater

treatment.

Some of agricultural by-products that has been investigated as adsorbent for

metal ion; are brown rot fungus Lentinus edodes (Chen et al., 2008), olive pomace

(Martin-Lara et al., 2008), palm shell (Issabayeva et al., 2008), sugar cane bagasse

(Gurgel et al., 2008), sugar beet pulp (Reddad et al., 2002; Peh!ivan et al., 2008) , pinus

bark (Vazquez et al., 2002), kenaf bark (Othman et al., 2008), peanut hull (Johnson et

al., 2002), sawdust (Ajmal et al., 1998), peanut shell (Tao and Xiaoqin, 2008), hazelnut

shell (Cimino et al., 2000), hazelnut husk (Imamoglu and Tekir, 2008), corncobs

(Vaughan et al., 2001), and rice hull (Low et al., 1999).

With rapid development in agriculture, industry, commerce, hospital and health-

care facilities, many activities are consuming significant quantities of toxic chemicals

and generating a large amount of hazardous waste. Currently, there are about 110 000

types of toxic chemicals commercially available. Each year, another 1 000 new

chemicals are added to the market for industrial and other uses. One of the most

hazardous pollutants in environment is heavy metals. Heavy metals generally refers to

the elements such as Cd (cadmium), Cr (chromium), Cu (copper), Hg (mercury), Ni

(nickel), Pb (lead), and Zn (zinc) which are commonly associated with pollution and

toxicity problems. Heavy metals occur naturally in rock formation and ore minerals and

so a range of normal background concentration is associated with each of these

elements in soils, sediments, waters and living organisms. Industrial uses of metals and

other domestic processes have introduced substantial amounts of potentially toxic heavy

metals into the atmosphere and into the aquatic and terrestrial environments.

In small quantities, certain heavy metals are nutritionally essential for healthy

life. Some of these are referred to as the trace elements (e.g., iron, copper, manganese,

and zinc). These elements, or some form of them, are commonly found naturally in

foodstuffs, in fruits and vegetables, and in commercially available multivitamin

products. Heavy metals are also common in industrial applications such as in the

manufacture of pesticides, batteries, alloys, electroplated metal parts, textile dyes, steel,

and so forth). Many of these products are in our homes and actually add to our quality

of life when properly used. However, high concentrations of heavy metals are known to

produce a range of toxic effect. Lead can cause encephalopathy, cognitive impairment,

behavioral disturbances, kidney damage, anemia, and toxicity to the reproductive

system (Pagliuca and Mufti, 1990). At high exposure level, cadmium can cause

nephrotoxic effect, while after long term exposure it can cause bone damage (Friberg,

1985). Other study reported that copper can cause weakness, lethargy, anorexia, and

gastrointestinal tract (Theopanides and Anastassopoulou, 2002).

Concerning the health hazard, heavy metals are among the most detrimental

Pollutants in source and treated water, and are becoming a severe health problem. Since

the damaging effects of heavy metals in environment are known, many methods have

WA

been developed for removal of heavy metals from waste discharges. Various chemical

treatment methods have been developed for the removal and recovery of heavy metals

from wastewater. There are four major classes of chemical separation technologies:

chemical precipitation, electrolytic recovery, adsorption/ion exchange, and solvent

extraction/liquid membrane separation (Lewinsky, 2007). These major classes involves

various methods including chemical treatment with lime, caustic oxidation and

reduction, ion exchange, adsorption, reverse osmosis, solvent extraction, membrane

filtration, electrochemical treatment and evaporative recovery. Some of chemical

methods are often not economically viable especially when the effluents contain a large

concentration of heavy metals. Most metal rich wastewater is treated by precipitation

process. In this process, soluble metal ions are removed as insoluble hydroxide

precipitates. But this process has several disadvantages. The major disadvantage with

this treatment technique is the production of sludge. As a result, an aquatic problem is

changed into solid waste problem. Electrolytic recovery technique uses lesser chemical

consumption and recover pure metal as an added economic value, but requires high

capital cost and less efficient at dilute concentrations. Solvent extraction and membrane

separation provide selective heavy metal removal. Major disadvantage of these methods

is high capital cost. For low concentration of heavy metal, adsorption is highly effective

method to be applied. Usage of low cost adsorbent will reduce the operating cost of the

process (Lewinsky, 2007).

1.3 ADSORPTION PROCESS

In general, adsorption can be defined as accumulation or depletion of solute

molecules at an interface. Adsorption process can be a physical adsorption which

involve only relatively weak intermolecular forces, and chemisorptions which involve

the formation of a chemical bond between the sorbate molecule and the surface of the

adsorbent. Chemical adsorption results in the formation of a monomolecular layer of the

adsorbate on the surface through forces of residual valence of the surface molecules.

Physical adsorption results from molecular condensation in the capillaries of the solid.

Adsorption of heavy metals onto adsorbent is a pH dependent phenomenon. In general,

the cationic species removal will increase with increasing solution pH, while in the case

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of inorganic ion present as anionic species; removal generally increases with decreasing

pH (Lewinsky, 2007).

Heavy metal ion adsorption onto adsorbent can be characterized by some

parameters. Adsorption capacity and heavy metal affinity by adsorbent can be illustrated

by Langmuir and Freundlich adsorption isotherm model. Some other adsorption models

can be used to explain the adsorption mechanism for specific case like Temkin

isotherm, Dubinin-Radushkevich equation, Flory-Huggins isotherm, Halsey isotherm,

Brunauer-Emmer-Teller (BET) model, Sips isotherm, Toth equation and Redlich-

Paterson isotherm (Febrianto et al., 2008). Other important parameters of adsorption

process are kinetic and thermodynamic properties. Selectivity of particular metal ion is

becoming important parameter due to the complexity of wastewater composition.

1.4 PROBLEM STATEMENT

Palm oil milling plant generate large amount of decanter cake that can cause

serious environmental impact. Currently, the decanter cake from palm oil milling plant

are discharge as landfill, or is utilized in small quantities as fertilizer or ruminant feed

ingredient. There are no further developments to transform decanter cake into more

valuable by-product. In the other hand, heavy metal pollution especially in aquatic

environment becomes the most detrimental pollution since heavy metal ion exposure to

human can cause adverse health effects are well known. This research is aiming to solve

the two of problems in one simultaneous process by utilize decanter cake from palm oil

milling plant as an effective adsorbent to remove heavy metal ion from aqueous

solution.

1.5 OBJECTIVES

Objectives of this research are to:

1. Investigate the nature of heavy metal adsorption onto carbonized decanter cake

include equilibrium time, effect of pH, adsorption isotherm and desorption.

2. Evaluate the kinetic and thermodynamic properties of heavy metal adsorption

onto carbonized decanter cake.

3. Investigate the effect of chemical activation of decanter cake on adsorption

parameters.

4. Evaluate industrial application of adsorption unit base on batch experimental

data in laboratory scale.

1.6 SCOPE OF WORK

This research is limited to the following scope of work:

1. The study use decanter cake from LKPP Corporation Sdn. Bhd. palm oil mill in

Lepar, Pahang as sample.

2. Cadmium (II), copper (II) and lead (II) ion are employed in investigation of

metal ion adsorption parameter like equilibrium time, pH effect, adsorption

isotherm, kinetic and thermodynamic properties.

3. Batch experiments in laboratory scale are carried out to obtain all data in this

study.

1.7 THESIS STRUCTURE

Chapter one of this thesis provides the general information and background of

the research, while chapter two provides the detail information about the current status

of palm oil industries, the heavy metals adsorption and their mechanisms. This chapter

also presents the adsorption equilibria, kinetic and thermodynamics of adsorption.

Chapter three discusses experimental techniques used in this work. This chapter

gives detail information on how decanter cake of palm oil milling plant was prepared

for the experiments, and how the whole experiments are carried out. This chapter also

provides the information about chemical, reagents used and characterization procedures.

In chapter four, results of the present work are presented and discussed. It also

discussed the effect of parameters and various factors towards the adsorption process.

lEO]

Effects of adsorbent carbonization temperature, equilibrium time, pH, initial

concentration of metal ions, were varied systematically to ascertain their effects towards

the adsorption process.

Conclusions of present work and recommendations for future work are discussed

in chapter five.

CHAPTER 2

LITERATURE REVIEW

2.1 DECANTER CAKE OF PALM OIL MILLING PLANT

Almost in every step of palm oil extraction produce waste. The waste can be

divided into two groups: liquid effluent and solid waste. In a well run palm oil mill, it is

expected that each 100 tons of FFB processed yields 20 to 24 tons of crude palm oil and

about 4 tons of palm kernels. Thus 72 to 76 wt percent of the FFB comes out at various

stages of the process as waste (P01w, 2002). Wastes from palm oil milling plant are

generated in the form of air emission, wastewater and solid waste. Solid wastes are

released as empty fruit bunch, fiber, shell, decanter cake and ash. Figure 2.1 shows per

ton FFB generate 530 kg of solid waste, 0.64 m3 of wastewater flow and 12.7 m3 gas

emissions. The natural resources consumption per ton of FFB processed is 1.26 in 3 of

water, 0.12 L of fuel, 14.5 kWh of electricity (Chavalparit et al., 2006).

Palm oil decanter cake is a by-product from palm oil milling decantation

process. In the last stage of clarification process of crude palm oil, extracted palm oil is

introduced to decanter unit. Extracted palm oil is separated into three phases in the

decanter: oil phase, aqueous phase, and solid phase. Oil phase in the top of decanter

cake are collected as product and sent to refined-bleached-deodorized palm oil plant.

Aqueous phase is discharged as palm oil milling effluent. Fine solid particles which are

suspended in extracted palm oil will be completely decanted after certain residence

time. A screw conveyor in the bottom of the decanter discharges the decanter cake from

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