Upload
pratik
View
224
Download
0
Embed Size (px)
Citation preview
8/8/2019 Project Te Chemical.
1/34
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)
1 | P a g e
8/8/2019 Project Te Chemical.
2/34
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
2 | P a g e
8/8/2019 Project Te Chemical.
3/34
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
3 | P a g e
8/8/2019 Project Te Chemical.
4/34
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:
4 | P a g e
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)8/8/2019 Project Te Chemical.
5/34
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
5 | P a g e
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/Mould8/8/2019 Project Te Chemical.
6/34
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
6 | P a g e
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/Rodents8/8/2019 Project Te Chemical.
7/34
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
7 | P a g e
8/8/2019 Project Te Chemical.
8/34
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.
8 | P a g e
8/8/2019 Project Te Chemical.
9/34
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.
9 | P a g e
8/8/2019 Project Te Chemical.
10/34
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
decontamination techniques (as discussed earlier in this10 | P a g e
8/8/2019 Project Te Chemical.
11/34
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.
11 | P a g e
8/8/2019 Project Te Chemical.
12/34
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
12 | P a g e
8/8/2019 Project Te Chemical.
13/34
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
13 | P a g e
8/8/2019 Project Te Chemical.
14/34
8/8/2019 Project Te Chemical.
15/34
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 .
15 | P a g e
8/8/2019 Project Te Chemical.
16/34
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.
16 | P a g e
8/8/2019 Project Te Chemical.
17/34
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
17 | P a g e
8/8/2019 Project Te Chemical.
18/34
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
18 | P a g e
8/8/2019 Project Te Chemical.
19/34
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.
19 | P a g e
8/8/2019 Project Te Chemical.
20/34
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
20 | P a g e
8/8/2019 Project Te Chemical.
21/34
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
21 | P a g e
8/8/2019 Project Te Chemical.
22/34
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
22 | P a g e
8/8/2019 Project Te Chemical.
23/34
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.
23 | P a g e
8/8/2019 Project Te Chemical.
24/34
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.
24 | P a g e
8/8/2019 Project Te Chemical.
25/34
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
25 | P a g e
8/8/2019 Project Te Chemical.
26/34
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
8/8/2019 Project Te Chemical.
27/34
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
27 | P a g e
8/8/2019 Project Te Chemical.
28/34
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.
28 | P a g e
8/8/2019 Project Te Chemical.
29/34
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
29 | P a g e
8/8/2019 Project Te Chemical.
30/34
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
30 | P a g e
8/8/2019 Project Te Chemical.
31/34
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:-
31 | P a g e
8/8/2019 Project Te Chemical.
32/34
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.
32 | P a g e
http://en.wikipedia.org/wiki/Anophthalmiahttp://en.wikipedia.org/wiki/Microphthalmiahttp://en.wikipedia.org/wiki/Anophthalmiahttp://en.wikipedia.org/wiki/Microphthalmia8/8/2019 Project Te Chemical.
33/34
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.
33 | P a g e
8/8/2019 Project Te Chemical.
34/34