project te chemical

8/8/2019 Project Te Chemical.

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A PROJECT REPORT ON

PHOTOCATALYTIC DEGRADATION OF

PESTICIDES BY TiO2

Submitted to the

Department of Chemical Engineering

BHARATI VIDYAPEETH UNIVERSITY

COLLEGE OF ENGINEERING

under the guidance of

Mrs. S.J.RAUT

Submitted By:-

Vinit rungta (436372)

Pratik kumar (436368)Khushbu kumari (436360)

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DEPARTMENT OF CHEMICAL ENGINEERING

BHARATI VIDYAPEETH UNIVERSITY

COLLEGE OF ENGINEERING

CERTIFICATE

This is to certify that the project entitledPHOTOCATALYTIC DEGRADATION OF PESTICIDES BY

TiO2 PARTICLES carried out by Vinit Rungta, Pratik

kumar and Khushbu Kumari of 3rd year Chemical

Engineering, during academic year 2008-09, is a bonafide

work submitted to the Department of Chemical

Engineering of B.V.U.C.O.E.

Mrs. S.J.Raut Mr. S.J.Attar

Project Guide Head of the department

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Department of Chemical Engg.

Department of Chemical Engg.

INDEX

Topic PageNumber

INTRODUCTION

04

CHAPTER 1 - USES OF PESTICIDES

05-06

CHAPTER 2 - PHOTOCATALYTIC DEGRADATION

OF VARIOUS PESTICIDES07-11

CHAPTER 3 - SOLAR PHOTOCATALYSIS

12-14

CHAPTER4 - DEGRADATION BY TIO2

NANO-PARTICLES

15-24

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CHAPTER5 - HEALTH IMPACTS

25-27

CONCLUSION28

REFERENCES

29

INTRODUCTION:-

A pesticide is a substance or mixture of substances used tokill a pest. A pesticide may be a chemical substance,biological agent (such as a virus or bacteria), antimicrobial,disinfectant or device used against any pest. Pests include

insects, plant pathogens, weeds, molluscs, birds, mammals,fish, nematodes (roundworms) and microbes that competewith humans for food, destroy property, spread or are avector for disease or cause a nuisance. Although there arebenefits to the use of pesticides, there are also drawbacks,such as potential toxicity to humans and other animals. FAOhas defined the term ofpesticide as:

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http://en.wikipedia.org/wiki/Pest_(organism)http://en.wikipedia.org/wiki/Chemicalhttp://en.wikipedia.org/wiki/Pest_(animal)http://en.wikipedia.org/wiki/Insecthttp://en.wikipedia.org/wiki/Pathogenhttp://en.wikipedia.org/wiki/Molluscahttp://en.wikipedia.org/wiki/Birdhttp://en.wikipedia.org/wiki/Fishhttp://en.wikipedia.org/wiki/Roundwormhttp://en.wikipedia.org/wiki/Microbehttp://en.wikipedia.org/wiki/Vector_(biology)http://en.wikipedia.org/wiki/Food_and_Agriculture_Organizationhttp://en.wikipedia.org/wiki/Chemicalhttp://en.wikipedia.org/wiki/Pest_(animal)http://en.wikipedia.org/wiki/Insecthttp://en.wikipedia.org/wiki/Pathogenhttp://en.wikipedia.org/wiki/Molluscahttp://en.wikipedia.org/wiki/Birdhttp://en.wikipedia.org/wiki/Fishhttp://en.wikipedia.org/wiki/Roundwormhttp://en.wikipedia.org/wiki/Microbehttp://en.wikipedia.org/wiki/Vector_(biology)http://en.wikipedia.org/wiki/Food_and_Agriculture_Organizationhttp://en.wikipedia.org/wiki/Pest_(organism)


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any substance or mixture of substances intended forpreventing, destroying or controlling any pest, includingvectors of human or animal disease, unwanted species ofplants or animals causing harm during or otherwise

interfering with the production, processing, storage,transport or marketing of food, agricultural commodities,wood and wood products or animal feedstuffs, or substanceswhich may be administered to animals for the control ofinsects, arachnids or other pests in or on their bodies.

DIFFERENT TYPES OF PESTICIDES:-

A. OP insecticides

B. Organochlorine insecticides

C. Carbamate insecticides

D. Herbicides

E. Fungicides

CHAPTER 1

1.1 USES OF PESTICIDES:-

Pesticides are used to control organisms which areconsidered harmful.For example, they are used to killmosquitoes that can transmit potentially deadly diseases likewest nile virus, yellow fever, and malaria. They can also killbees, wasps or ants that can cause allergic reactions.Insecticides can protect animals from illnesses that can becaused by parasites such as fleas.Pesticides can preventsickness in humans that could be caused by mouldy food or

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http://en.wikipedia.org/wiki/Foodhttp://en.wikipedia.org/w/index.php?title=Agricultural_commodities&action=edit&redlink=1http://en.wikipedia.org/wiki/Arachnidhttp://en.wikipedia.org/wiki/Mosquitoeshttp://en.wikipedia.org/wiki/West_nile_virushttp://en.wikipedia.org/wiki/Yellow_feverhttp://en.wikipedia.org/wiki/Malariahttp://en.wikipedia.org/wiki/Beehttp://en.wikipedia.org/wiki/Wasphttp://en.wikipedia.org/wiki/Anthttp://en.wikipedia.org/wiki/Parasiteshttp://en.wikipedia.org/wiki/Fleahttp://en.wikipedia.org/wiki/Mouldhttp://en.wikipedia.org/wiki/Foodhttp://en.wikipedia.org/w/index.php?title=Agricultural_commodities&action=edit&redlink=1http://en.wikipedia.org/wiki/Arachnidhttp://en.wikipedia.org/wiki/Mosquitoeshttp://en.wikipedia.org/wiki/West_nile_virushttp://en.wikipedia.org/wiki/Yellow_feverhttp://en.wikipedia.org/wiki/Malariahttp://en.wikipedia.org/wiki/Beehttp://en.wikipedia.org/wiki/Wasphttp://en.wikipedia.org/wiki/Anthttp://en.wikipedia.org/wiki/Parasiteshttp://en.wikipedia.org/wiki/Fleahttp://en.wikipedia.org/wiki/Mould


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diseased produce. Herbicides can be used to clear roadsideweeds, trees and brush. They can also kill invasive weeds inparks and wilderness areas which may cause environmentaldamage. Herbicides are commonly applied in ponds and

lakes to control algae and plants such as water grasses thatcan interfere with activities like swimming and fishing andcause the water to look or smell unpleasant.Uncontrolledpests such as termites and mould can damage structuressuch as houses. Pesticides are used in grocery stores andfood storage facilities to manage rodents and insects thatinfest food such as grain. Each use of a pesticide carriessome associated risk.

1.2 PESTICIDES BANNED FOR

MANUFACTURE, IMPORT AND USE (IN

INDIA)

1. Aldrin

2. Benzene Hexachloride

3. Calcium Cyanide

4. Chlordane

5. Copper Acetoarsenit

6. CIbromochloropropane

7. Endrin

8. Ethyl Mercury Chloride

9. Ethyl Parathion

10. Heptachlor

11. Menazone

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http://en.wikipedia.org/wiki/Weedhttp://en.wikipedia.org/wiki/Natural_environmenthttp://en.wikipedia.org/wiki/Algaehttp://en.wikipedia.org/wiki/Rodentshttp://en.wikipedia.org/wiki/Weedhttp://en.wikipedia.org/wiki/Natural_environmenthttp://en.wikipedia.org/wiki/Algaehttp://en.wikipedia.org/wiki/Rodents


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12. Nitrofen

13. Paraquat Dimethyl Sulphate

14. Pentachloro Nitrobenzene

15. Pentachlorophenol

16. Phenyl Mercury Acetate

17. Sodium Methane Arsonate

18. Tetradifon

19. Toxafen

20. Aldicarb

21. Chlorobenzilate

CHAPTER -2

2.1 PHOTOCATALYTIC DEGRADATION OF

VARIOUS PESTICIDES:-

Photocatalysis has been proved to be an effective andinexpensive tool for the removal of organic and inorganic

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pollutants from water. Of particular interest in this context,in recent years, has been the complete photocatalyticmineralisation of a variety of pesticides into harmlessproducts. The technique is now reaching the pre-industrial

level, with several pilot plants and prototypes beingoperational in various countries. This paper reviews themajor developments in the area, with special reference tothe mechanism of the process involved, nature of thereactive intermediates and final products.

Photocatalytic degradation hasbeen proved to be a promising method for the treatment ofwastewater contaminated with organic and inorganicpollutants. The process, as a means of removal of persistentwater contaminants such as pesticides, which exhibit

chemical stability and resistance to biodegradation, hasattracted the attention of many researchers in recent years[1-19]. Many of these investigation have utilised aqueoussuspension of semiconductors illuminated by UV light tophotodegrade the pollutants. The method offers manyadvantages over traditional wastewater treatmenttechniques such as activated carbon adsorption, chemicaloxidation, biological treatment, etc. For example, activatedcarbon adsorption involves phase transfer of pollutants

without decomposition and thus induces another pollutionproblem. Chemical oxidation is unable to mineralise allorganic substances and is only economically suitable for theremoval of pollutants at high concentrations. For biologicaltreatment, the main drawbacks are: slow reaction rates,disposal of sludge and the need for strict control ofproper pHand temperature. In this context, photocatalytic processesoffer many advantages for the removal ofpollutants of lowconcentration from water. These include:

1. Complete oxidation of organic pollutants within few

hours.

2. No formation of polycyclised products.

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3. Availability of highly active and cheap catalysts capable of

adapting to specially designed reactor systems.

4. Oxidation of pollutants in the ppb range, etc.

2.2 DIFFERENT PHOTOCATALYSTS

AVAILABLE:-

Several catalysts have been studied as potential

photocatalysts for this purpose. These include: CdS, ZnS, a-

Fe2O3, y-Fe2O3, TiO2, ZrO2, SnO2 and WO3, CN~,

Cr2O7,AgCl/Al2O3, niobium oxides, lanthanide tantallates,ZnO/TiO2, TiO2/SiO2 and TiO2/Al2O3. Among the

semiconductors used, TiO2 is one of the most popular and

promising materials, because of its stability under harsh

conditions, commercial availability, different allotropic forms

with high photoactivity, possibility of coating as a thin film

on solid support, ease of preparation in the laboratory, etc.

Its absorption spectrum overlaps with the solar spectrum

and hence opens up the possibility of using solar energy as

the source of irradiation. Another advantage is that the

photocatalytic activity of TiO2 can be studied in the fixed bed

form as well as in the form of a suspension. Further, TiO2-

based mixed oxide catalysts such as TiO2/In2O3, TiO2/SiO2 and

TiO2/ZrO2 supported catalysts such as Pt/TiO2, Rh/TiO2 and

Ru/TiO2 and titania-based thin films have also been proved

to be very good photocatalysts.

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2.3 PRIMARY EVENTS AND REACTIVE

SPECIES IN PHOTOCATALYTIC PROCESSES

Pelizzetti et al has summarised the primary events takingplace in a photocatalysed reaction as follows:

TiO2 + hv > e~ + h+, (1)

(O2)ads + e~ > (O^ )ads, (2)

Ti(IV)OH~+h+-Ti(IV) *OH, (3)

Ti(IV)OH2+h+Ti(IV) * OH + H+. (4)

2.4 PHOTOCATALYTIC DEGRADATION OF

CONTAMINENTS IN WATER

The presence of pesticide contaminants in surface and

ground water has increased many fold in recent years due totheir large-scale use in intensive agriculture. The sources

ofthis contamination may be summarised as follows:

(i) pesticide treatment as routine agricultural practice;

(ii) rinse water polluted with pesticides from containers and

spray equipment

(iii) wastewater from agricultural industry (cleaning or post-harvest treatment of fruits and vegetables) and

(iv) plant residues contaminated with pesticides.

All these end up ultimately in polluting water bodies with

pesticides. The inherent disadvantages of conventional

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paper) have prompted scientists to examine the possibility

of using the advance oxidation process (AOP) based on

photocatalysis. Both heterogeneous photocatalysis by

semiconductors such as TiO2 and homogeneous catalysis by

photofenton have been tested in this context. Most of thephotocatalytic studies, reported so far in this field, are briefly

reviewed here. For convenience of reference, the pesticides

are classified according to their chemistry (OP,

organochlorine, etc.) as well as the chief mode of action

(insecticides, herbicides, etc.).

2.5 ROLE OF ADDITIVES

The effect of H2O2 on the photocatalytic degradation

oforganic pollutants has been a subject of many

investigations, with the view of exploiting the same for

enhanced degradation rates. The formation of H2O2 in the

photocatalytic degradation of organic compounds has been

reported earlier by many workers. H2O2, formed as an

intermediate in many photocatalysed reactions was found to

undergo simultaneous decomposition resulting in the

generation of d OH radicals, which enhance the

photodecomposition of many pollutants in water, The

autocatalysis observed in the ZnO-catalysed photooxidation

ofbenzyl alcohol was attributed to the formation of H2O2 and

its subsequent participation in the process.

The presence ofions such as CO3H~, CO3, Cl-, etc., normally

present in surface and ground water has been reported to

retard the oxidation of organic carbon over illuminated TiO2.In the case of EPTC and lindane, this retarding effect was

very small. The effect of Cl-, PO4- and NO^ on the

photocatalytic degradation ofphosphamidon on TiO2 also was

found to be negligible at lower concentration of the ions.

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Sulphate and hydrogen phosphate anions also inhibit the

photocatalytic degradation rate oforganic pollutants.

Presumably, these anions penetrate the inner co-ordination

sphere ofTiO2, thereby inhibiting its catalytic efficiency.

2.6 CHARACTERISTICS OF TIO2

PARTICLES:-

By far, the most investigated photocatalyst for the removal

of organic pollutants from water is TiO2 in various

physicochemical forms. These studies suggest that thephotocatalytic activity of suspended TiO2 in the solution

depends on physical properties of the catalyst (e.g. crystal

structure, surface area, surface hydroxyls, particle size) and

operating conditions (e.g. light intensity, oxygen, initial

concentration of chemicals, amount ofTiO2 and pH value).

Ohtani et al. investigated the effects of crystal structures of

TiO2 on its photocatalytic activity and reported that the

activity of amorphous TiO2 is negligible, whereas anatase

having the same particle size has appreciable photoactivity.

Tanaka et al. studied the effect of crystallinity of TiO2 on its

photocatalytic action for the degradation of trichlorethylene,

dichloracetic acid and phenol, and reported that pure

anatase has the best catalytic efficiency while pure rutile has

the least. However, Lee et al. report that the rutileanatase

ratio of TiO2 is not very important in determining its

photocatalytic efficiency to degrade organic pollutants. They

observed that irradiation ofTiO2 with laser light resulted in

the development of a more rutile form of the oxide. The

treatment results in the formation of more spherical-shaped

particles, though the average particle size remains mostly

unchanged. The band gap or surface area also does not

undergo much change by this irradiation. While studying the

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effect of particle size on the photocatalytic hydrogenation of

propyne (CH3CCH), using TiO2 suspensions, Anpo et al. noted

that the activity increases with decrease in particle size,

especially with particles ofsize less than 10 nm. According to

them, reduction in particle size might result in someelectronic modification ofTiO2 and produce an enhancement

ofthe activities ofelectrons and holes and/or suppression

often radiationless transfer ofabsorbed photon energies.

Similar results were reported by Xu et al. from the study on

the photocatalytic degradation ofmethylene blue in aqueous

suspensions.

CHAPTER-3

3.1 SOLAR PHOTOCATALYSIS IN THE

DEGRADATION OF PESTICIDES

Heterogeneous photocatalysis is now approaching the pre-industrial level. Several pilots and prototypes have been built

in various countries. Different types of photoreactors have

been built, with the catalysts used in various forms/shapes:

fixed bed, magnetically or mechanically agitated slurries,

catalyst particles anchored on the walls ofthe photoreactor

or on membranes or on glass beads or on glass wool sleeves,

small spherical pellets etc.. The main criterion is to have

easy separation ofthe catalyst from the fluid medium and

this is achieved using supported TiO2.

Various devices have been developed and tested. These

include TiO2-coated tubular reactors, annular and spiral

photoreactors, falling-film photoreactors, etc. Of these, two

systems are in commercial use at present for the treatment

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Fig 3.1.1 Isometric drawing of solar

detoxification demonstration plant

The use of additional oxidants is recommended when the

organic content of the water is relatively high and/or the

mineralization rate is low. These additives should be capable

of dissociating into harmless by-products and leading to the

formation of d OH or other oxidizing agents.

Peroxydisulphate is one such additive which has beensuccessfully used to enhance the photocatalytic degradation

of oxamyl in water. The effect is being explained both in

terms of the scavenging action of S2O8~ and often

participation of SO4~ in the oxidation reactions, directly or

through the formation of d OH radicals .

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3.2 REMARKS

A large volume of literature has been published in the last

1015 years on the photocatalytic degradation of pesticide

pollutants. In most cases, the degradation products havebeen identified. However, mechanistic studies leading to the

formation of such products are relatively few. This may be,

in part, due to the very short lifetime of most intermediates

and the absence of ultrafast kinetic techniques such as laser

flash photolysis or pulse radiolysis in the nano- or picosecond

regime in many laboratories. The effect of many parameters

such as the presence of salts and other natural organic

matter in the water also is not clearly understood. Studies onthe use of sunlight as the source of energy for the

degradation process have yielded encouraging results and

the solar photocatalytic treatment pesticides is already at

the pilot.

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CHAPTER-4

DEGRADATION OF DIFFERENTTYPES OF PESTICIDES BY TiO2NANO-PARTICLES.

4.1Photocatalytic Degradation of a WaterSoluble Herbicide by Pure and Noble

Metal Deposited TiO2 Nanocrystalline Films.

We present the photocatalytic degradation of a water soluble

sulfonylurea herbicide: azimsulfuron in the presence of

titania nanocrystalline films. Efficient photodegradation of

herbicide was achieved by using low-intensity black light

tubes emitting in the Near-UV. The degradation of the

herbicide follows first-order kinetics according to the

Langmuir-Hinshelwood model. Intermediate products wereidentified by the LC-MS-MS technique during photocatalytic

degradation. In order to increase photodegradation rate of

the herbicide, we examined the effect of titania modification

by depositing noble metals at various quantities and valence

states. The presence of platinum at neutral valence state

and optimum concentration induced higher

photodegradation rates while silver-modified titania

exhibited similar photocatalytic rates with those obtained

with pure nanocrystalline TiO2 films. Finally, the effect of

initial pH value was also examined. Acidic or alkaline media

were unfavorable for azimsulfuron photodegradation.

Photodegradation of

various organic pollutants by pho-tocatalysis, using wide

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bandgap semiconductors, has been extensively studied [1

3]. Among them, TiO2 a relatively inexpensive

semiconductor exhibits high photocatalytic activity, stability

in aqueous solution, nontoxicity and so forth. However, TiO2

usage has a few drawbacks; for example, it absorbs only inthe UVA part of the light spectrum where solar radiation is

only 2-3% of the total reaching the surface of the Earth.

Moreover, the application of TiO2 for photocatalytic

oxidation of organic molecules is limited by high charge

carrier recombination rates that results in low quantum

efficiency. In recent years, surface metallization of TiO2 has

received considerable attention as an option to overcome

the high degree of charge carrier recombination. Platinum,and some other noble metals, may be used for this purpose

thus providing an electron sink. In addition, they may extent

TiO2 absorbance in the Visible. The presence of a metal at

the surface of TiO2 results in the formation of a Schottky

barrier at the metal-semiconductor interface, which

facilitates the interfacial electron transfer and subsequently

encourages the charge carrier separation.

Among the various organic substances, which are known aswater pollutants, herbicides are a major pollution source for

both underground and surface waters. Advanced oxidation

processes are used, among others, also for the degradation

of herbicides. Azimsulfuron (AZS, see Scheme 1 for chemical

structure) belongs to the class of sulfonylurea herbicides,

which have a broad spectrum of weed control, low

application rate, and low animal toxicity. Sulfonylurea

herbicides, in addition to playing an important role inmodern agriculture, are also degradable by heterogeneous

photocatalysis, as it has been proven in the past. In the

present work, sol-gel prepared TiO2 films, which were further

modified with noble metal ions, were examined for the

photodegradation of AZS in water. The effect of various

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parameters, such as the amount of metal deposits and pH

value of herbicide aqueous solution, were studied in order to

evaluate the optimum conditions for the photocatalytic

oxidation of AZS.

4.1.1 DESCRIPTION OF THE PHOTOCATALYTIC REACTOR

The cylindrical reactor schematically shown in Figure 1 was

used in all experiments [19]. Air was pumped through the

gas inlet using a small pump to ensure continuous oxygen

supply to the reaction solution while simultaneously agitating

it. In cases where experiments were carried out in the

absence of oxygen, the solution was deoxygenated by

nitrogen flow and the openings were sealed. Four black light

fluorescent tubes of 4 W nominal power were placed around

the reactor. The whole construction was covered with a

cylindrical aluminum reflector. Cooling was achieved by air

flow from below the reactor using a ventilator. The catalyst

was in the form of four-glass rings, covered on both sides

with nanocrystalline TiO2 film. Film deposition is described

below. The glass rings were of 38 mm of diameter and 15 mm

height, stacked and coaxially placed inside the reactor. Thus,

the total surface of the photocatalyst film was approximately

2x71.6= 143 cm2. The intensity of radiation reaching the

surface of the film on the side facing lamps was measured

with an Oriel radiant power meter and found equal to

0.79mW/cm2.

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Fig no.4.1.1 Nanocrystalline Titania films and metal deposition

Titania films were deposited by following the previously

reported procedure [20, 21]. Briefly, for 25 mL solution, 3.6 g

of the nonionic surfactant Triton X-100 (polyoxyethylene-10-

isooctylphenyl ether) was mixed with 20 mL of ethanol,

followed by addition of 1.6 mL of glacial acetic acid and 1.8

mL of titanium isopropoxide under vigorous stirring. Self

organization of the surfactant in this original sol creates

organized assemblies that act as templates definingnanoparticle size. The surfactant is burned out during

calcination. After a few minutes stirring, the glass rings

described above, which were previously thoroughly washed,

sonicated in ethanol and dried in a N2 stream, were dipped

in the above sol and withdrawn slowly by hand. After the film

was dried in air for a few minutes, it was calcined in an oven.

The temperature was increased in a ramp rate of 20C/ min

up to 550C and left at that temperature for about 10minutes. When the titania-covered rings were taken out of

the oven, they were transparent and optically uniform. The

above procedure was repeated several times in order to

reach the quantity of catalyst necessary for the purposes of

the present work. The final mass of titania on the four glass

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rings was 80 mg (20 mg on each glass ring). Noble metal

ions were deposited on titania films by adsorption from

aqueous solutions containing one of the following metal

salts: Na2PtCl4-xH2O or AgNO3 at various concentrations

(from 10-4 to 10-3 M for the platinum salt and from 5 X 10-4 to10-2M for the silver salt). After the last layer of TiO2 was

deposited and immediately after the film was taken out from

the oven, the rings were submerged in the salt aqueous

solution and were left for half an hour in the dark. Then, the

rings were washed, dried, and subjected to UV radiation for

30 minutes; or they were additionally heated at 500 C for 15

minutes. UV and heat treatment were performed to reduce

cationic species to neutral metallic particles.

4.1.2 REMARKS

The herbicide azimsulfuron can be effectively photode-

graded by employing pure or noble metal-modified titania

nanocrystalline films as photocatalysts with black light tubes

as low-intensity UV illumination source. The catalyst was

deposited by the sol-gel method on glass rings; it could be

thus easily recuperated and repeatedly used in subsequent

photodegradation procedures. The best photocatalytic rates

were achieved in the case of platinum modified nanocrys-

talline TiO2 films. The pH of AZS aqueous solution affected

photodegradation rates. The fastest rate was obtained in the

case of natural pH of the solution.

4.2 Photocatalytic degradation of 3,4-xylyl N-methylcarbamate and other

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carbamate pesticides in aqueousTiO2suspensions

Five carbamate pesticides were degraded photocatalytically

on TiO2. The comparison of their disappearance ratesshowed that the degradation rate is governed predominantly

by their adsorbability to TiO2, and followed Hammetts law in

a different manner from ordinary electrophilic reaction. As a

degradation pathway of 3,4-xylyl N-methylcarbamate

MPMC. successive hydroxylation of aromatic ring was

suggested, and polyhydroxylation is considered to lead to

the opening of the aromatic ring to form oxygenated

aliphatic intermediates. It was indicated in this process thatthe formation of acetic acid, one of the major aliphatic

intermediates, mainly originates from methyl substituents on

the aromatic ring.

Photocatalysis provides a

new method for water decontamination. Recent intensive

study showed that it can be applied to the degradation of

many pollutants w1x. Among them, pesticides have been

considered to be one of the major pollutants to which it ispromising to apply photocatalysis w2,3x. Many pesticides

cannot be degraded by conventional biological methods

w4,5x, whereas complete mineralization can be achieved by

photocatalysis w6,7x. In this work the photocatalytic

degradation of several carba-mate pesticides were studied in

regard to degradation rate, degradation process and

intermediate compounds, and the degradation rate was

correlated to the chemical structure of the pesticides toinvestigate the factors influencing the photocatalytic

reaction.

Carbamates are an important group of insecticides which are

widely used throughout the world. Contamination of surface

and underground waters by these pesticides have been

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reported in different parts of the world w811x. Because of

their toxicity and that of their degradation intermediates

w12x, their complete degradation is of great environmental

concern.

Carbamate pesticides used in this study are of analytical

grade and their chemical structures are shown in Fig. 4.2

Fig.4.2 Chemical structures of five carbamate pesticides.

4.2. 1 EXPERIMENTAL

The TiO2 used throughout the experiment is TP-2 anatase.

supplied by Fujititan. Its specific surface area is 17.3 m2rg

w13x.

Carbamate pesticides used in this study are of analytical

grade and their chemical structures are shown in Fig. 1.

For degradation experiment 75 mg of TiO2 powder was

suspended in 25 ml of 10y4 mol ly1 solution of pesticide in aPyrex glass bottle by stirring magnetically. The bottle was

illuminated by a 500 W super-high-pressure mercury lamp

through a water filter. After illumination for a given time, the

sample was filtered through a Millipore membrane filter of

0.2-mm pore size and the filtrate was subjected to analyses.

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Degradation was monitored by a JASCO 880-PU with a

multiwavelength UVVIS detector JASCO MD-90. The

aromatic intermediate was identified by the same

instrument. Organic acid intermediate was analyzed by an

ionchro-matograph Yokogawa IC 7000.

NOy3 , NOy2 and NHq4 were detected by an ionchromatograph

consisting of a JASCO 880-PU pump and Shodex CD-4

conductometer. Total organic carbon TOC. was measured

by a Shimadzu TOC-500. Aldehyde and ketone were

determined following the method described in the literature

w14,15x. Solubilities of pesticides were measured as follows

w16x. An adequate amount of pesticide was dissolved in

water at room temperature by stirring for 1 week, and then

left standing for 1 day at 258C. After filtration the filtrate

was analyzed.

4.2.2 REMARKS

Disappearance of the five carbamate pesticides were quick

and the rates increased with pH. Their photocatalyticdegradations are governed by their adsorbability to TiO2more than electron density on the aromatic ring and fol-

lowed Hammetts law, but in a different manner from

ordinary electrophilic reaction. The formation of acetic acid

as major intermediate was attributed partly to methyl

substituents on the aromatic ring. In the mineralization

process nitrogen was converted predominantly to NHq4.

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4.2Photocatalytic degradation of

agricultural N-heterocyclic organic

pollutants using immobilized

nanoparticles of titania.

Degradation and mineralization of two agricultural organic

pollutants (Diazinon and Imidacloprid as N-heterocyclic

aromatics) in aqueous solution by nanophotocatalysis using

immobilized titania nanoparticles were investigated.

Insecticides, Diazinon and Imidacloprid, are persistent

pollutants in agricultural soil and watercourses. A simple andeffective method was developed to immobilization of titania

nanoparticles. UVvis, ion chromatography (IC) and chemical

oxygen demand (COD) analyses were employed. The effects

of operational parameters such as H2O2 and inorganic anions

(NO3-, Cl- and SO42-) were investigated. The mineralization of

Diazinon and Imidacloprid was evaluated by monitoring of

the formed inorganic anions. The selected pollutants are

effectively degraded following first order kinetics model.Results show that the nanophotocatalysis using immobilized

titania nanoparticle is an effective method for treatment

Diazinon and Imidacloprid from contaminated water.

The presence of highly

biorecalcitrant organic contaminants such as pesticides in

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the hydrosphere due to industrial and intensive agricultural

activities is of particular concern for the freshwater (surface

and groundwater), coastal and marine environments . In

general, pesticides applied directly to soils, turf, or plants can

be washed into waterways during storm events or throughirrigation. As a result, pesticide presence in storm water runoff

can directly impact the health of aquatic organisms and

present a threat to humans through contamination of

drinking water supplies. Pesticides such as Diazinon and

Imidaclo-prid have been associated with toxicity in ambient

waters, point source discharges, and agricultural discharges.

4.3.1 DEGRADATION METHOD OF INSECTICIDES

Photocatalytic degradation processes were performed

using a 5 L solution containing specified concentration of

pollutants (0.13 mM Diazinon, 0.22 mM Imidacloprid, pH:

neutral (5.5) and room temperature). The solutions were

first agitated under gentle air in the dark for 30 min to

reach equilibrated condition. Samples were withdrawn

from sample point at certain time intervals and analyzed

for degradation.

4.3.2 IMMOBILIZATION OF TITANIUM DIOXIDE

NANOPARTICLES AND PHOTOCATALYTIC REACTOR

A simple and effective method was used to immobilization of

TiO2 nanoparticles as follows: inner surfaces of reactor wallswere cleaned with acetone and distilled water to remove any

organic or inorganic material attached to or adsorbed on the

surface and was dried in the air. A pre-measured mass of

TiO2 nanoparticle (16g) were attached on the inner surfaces

of reactor walls using a thin layer of a UV resistant polymer

(silicon polymer). Immediately after preparation, the inner26 | P a g e


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surface reactor wallpolymerTiO2 system was placed in the

laboratory for at least 60 h for complete drying of the

polymer .

Experiments were carried out in a batch mode immersionrectangular immobilized photocatalytic reactor made of

Pyrex glass, which is shown in Fig.4.3.2.The radiation source

was two UV-C lamps (15W, Philips). A water pump and air

pump were utilized for the transferring and aeration of

polluted solution, respectively.

Fig.4.3.2. Scheme of immobilized titania nanopartcles

photocatalytic reactor.

Two insecticides, Diazinon and Imidacloprid, could be suc-

cessfully degraded and mineralized by nanophotocatalysis in

an immobilized titania nanoparticles photocatalytic reactor.

The degradation rate for insecticides goes through a

maximum when the concentration of the hydrogen peroxideincreases from 0 to optimal concentration (3.53 mM) and

then it does not appreciable change. Chloride exhibited the

strongest inhibition effect on the selected insecticide followed

by nitrate. The photocatalytic degradation kinetics follows a

first order model. The formation of carboxylic acids

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intermediates (acetic, formic and oxalic) initially increased

with the illumination time, and then dropped due to directly

reaction with holes and generation of CO2 according to the

photo-Kolbe reaction. MineralizationofDiazinon and Imi-

dacloprid is identified by production of inorganic anions(nitrate, sulfate, phosphate and chloride). Thin-film coating of

photocat-alyst may resolve the problem of suspension system

of selected insecticides degradation. Nanophotocatalysis by

immobilized titanium dioxide nanoparticle in the presence of

hydrogen peroxide is able to treatment of selected

insecticides from polluted waters without using high pressure

of oxygen or heating. Hence, this technique may be a viable

one for treatment of large volume of water polluted byinsecticides.

CHAPTER 5

HEALTH IMPACTS

Application and health effects of pesticides

commonly used in India

S.No. PesticideName

What it is used for Health impacts

1. ddt effective againstwide variety ofinsects, includingdomestic insectsand mosquitoes

chronic liverdamage cirrhosisand chronichepatitis,endocrine andreproductive

disorders, immunosuppression,cytogenic effects,breast cancer, nonhodkinslymphoma,polyneuritis.

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2. endosulfan it is used as abroad spectrumnon systemic,contact and

stomachinsecticide, andacaricide againstinsect pests onvarious crops

effects kidneys,developing foetus,and liver immuno-suppression,

decrease in thequality of semen,increase intesticular andprostate cancer,increase in defectsin male sexorgans, andincreasedincidence ofbreast cancer. it isalso mutatagenic

3. aldrin effective againstwireworms and tocontrol termites

lung cancer, liverdiseases

4. dieldrin used againstectoparasites suchas blowflies, ticks,lice and widelyemployed in cattleand sheep dips.also used toprotect fabricsfrom moths,beetles andagainst carrot andcabbage root flies/also used as seed

dressing againstwheat and bulbfly

liver diseases,parkinson's &alzheimer'sdiseases

5. heptachlor it controls soilinhibiting pests.

reproductivedisorders, blooddyscariasis

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6. chlordane it is a contact,stomach andrespiratory poisonsuitable for the

control of soilpests, white grubsand termites.

reproductivedisorders, blooddyscariasis, braincancer, non

hodkins lymphoma

7. lindane it is used againstsucking and bitingpest and as smokefor control of pestsin grain sores. it isused as dust to

control various soilpests.such as fleabeetles andmushroom flies. itis effective as soildressing againstthe attack of soilinsects

chronic liverdamage-cirrhosisand chronichepatitis,endocrine andreproductive

disorders, allergicdermatitis, breastcancer, nonhodkinslymphoma,polyneuritis.

8. fenitrothion it is a broadspectrum contactinsecticideeffective for thecontrol of chewingand sucking pests-locusts aphids,caterpillars andleaf hoppers. it isalso used againstdomestic insects

and mosquitoes

humanepidemiologicalevidence indicatesfenitrothioncauses eye effectssuch as retinaldegeneration andmyopia. chronicexposure tofenitrothion cancause frontal lobe

impairment.organo-phosphates aresuspected ofcausing neurologicdeficits.

9. fenthion it is a persistent fenthion may be

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contact insecticidevaluable againstfruitflies, leafhoppers, cereal

bugs, andweaverbirds in thetropics

mutagenic:causing geneticaberrations. it maybe a carcinogen

10. parathion a contactinsecticide andacaricide withsome fumigantaction. veryeffective against

soil insects withhigh mammaliantoxicity

parathion is apossiblecarcinogen

CONCLUSION:-

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Pesticides can save farmers' money by preventing crop

losses to insects and other pests but the illeffects cant be

ignored. many side effects,as we mentioned above are very

dangerous.study has linked breast cancer from exposure to

DDT prior to puberty.Poisoning may also occur due to use ofchlorinated hydrocarbons by entering the human food chain

when animal tissues are affected. Symptoms include

nervous excitement, tremors, convulsions or death.

Scientists estimate that DDT and other chemicals in the

organophosphate class of pesticides are cause of many

human deaths in 1977. One study found that use of

pesticides may be behind the finding that the rate of birth

defects such as missing or very small eyes is twice as high inrural areas as in urban areas.Another study found no

connection between eye abnormalities and pesticides.In the

USA, increase in birth defects is associated with conceiving

in the same period of the year when agrichemicals are in

elevated concentrations in surface water

So its essential to degrade the pesticides,by the methods

mentioned above.tio2 particles are accepted world

wide,nowdays.

SO, USE IT AND MAKE THE WORLD FREE FROM

PESTICIDE POLLUTION.

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REFERENCES:-

[1] D. Bahnemann, Photocatalytic detoxification of polluted waters, in TheHandbook of Environmental Chemistry. Vol. II. Part L, O. Hutzinger, Ed.,pp. 285351, Springer, Berlin, Germany, 1999.

[2] M. R. Hoffmann, S. T. Martin, W. Choi, and D. W. Bahnemann,Environmental applications of semiconductor photocatalysis, ChemicalReviews, vol. 95, no. 1, pp. 6996, 1995.

[3] E. Evgenidou, I. Konstantinou, K. Fytianos, I. Poulios, and T. Albanis,Photocatalytic oxidation of methyl parathion over TiO2 and ZnOsuspensions, Catalysis Today, vol. 124, no. 3-4, pp. 156162, 2007.

[4] O. Zahraa, H. Y. Chen, and M. Bouchy, Photocatalytic degradation of 1,2-dichloroethane on supported TiO2, Journal of Advanced OxidationTechnologies, vol. 4, pp. 11691176, 1999.

[5] S. Malato, J. Blanco, J. Caceres, A. R. Fernandez-Alba, A. Aguera, and A.Rodrguez, Photocatalytic treatment of water-soluble pesticides by photo-Fenton and TiO2 using solar energy, Catalysis Today, vol. 76, no. 24, pp.209220, 2002.

[6] Z. Zou, J. Ye, K. Sayama, and H. Arakawa, Direct splitting of water undervisible light irradiation with an oxide semiconductor photocatalyst,Nature, vol. 414, no. 6864, pp. 625627, 2001.

[7] L. Sun and J. R. Bolton, Determination of the quantum yield for thephotochemical generation of hydroxyl radicals in TiO2 suspensions,Journalof Physical Chemistry, vol. 100, no. 10, pp. 41274134, 1996.

[8] D. Ollis and H. Al-Ekabi, Eds., Photocatalytic Purification and Treatment ofWater and Air, Elsevier Science, Amsterdam, The Netherlands, 1993.

[10] S. Malato, J. Blanco, A. Vidal, D. Alarcon, M.I. Maldonado, J. Caceres, W.Gernjak, Applied studies in solar photocatalytic detoxification: anoverview, Solar Energy 75 (2003) 329336.

[11] I. Arsalan-Alaton, A review of the effects of dye-assisting chemicals onadvanced oxidation of reactive dyes in wastewater, Color. Technol. 119(2003) 345353.

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