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Review ArticleInfluencing Parameters in the Photocatalytic Degradation ofOrganic Effluent via Nanometal Oxide Catalyst A Review

A Gnanaprakasam V M Sivakumar and M Thirumarimurugan

Department of Chemical Engineering Coimbatore Institute of Technology Coimbatore 641 014 India

Correspondence should be addressed to V M Sivakumar vmsivakumargmailcom

Received 26 May 2015 Accepted 2 September 2015

Academic Editor Kourosh Kalantar-Zadeh

Copyright copy 2015 A Gnanaprakasam et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

This paper aims to review the recent works on the photocatalytic degradation of organic pollutants in the presence ofnanophotocatalyst In this regard the effects of operation parameters which could influence the photocatalytic degradation oforganic pollutants (such as catalyst preparation method initial concentration of organic pollutants presence of doping catalystloading calcinations temperature pH presence of oxidants UV intensity temperature and presence of supports) are discussedRecent research suggests that the parameters mentioned above have great influence on the photocatalytic activity of preparednanocatalyst Also the general mechanism of photocatalytic degradation and some recent synthesis methods are discussed here

1 Introduction

In recent years development of industries like textile leatherpaint food plastics and cosmetics is enlarged and theseindustries are connected with the discarding of a vast numberof organic pollutants which are harmful to microbes aquaticsystem and human health by influencing the followingparameters [1ndash4] In addition to that the effect of theseorganic effluents in the wastewater can be sensed by changein the vital parameters of the discharged water such as chem-ical oxygen demand biochemical oxygen demand toxicityunpleasant odour and colour [5] Even the presence of a traceamount of colored organic compounds in the aquatic systemcan result in coloration of wastewater The consequence ofcolored water is detrimental to environment since the colorobstructs the sunlight access to aquatic organisms and plantsand it diminishes the photo synthesis and affects the ecosys-tem [6 7] Therefore the removal of color and sanitizationhave become an ecological concern and they are vital forthe environmental sustainability Industrial development andits association with discharge of organic matter into theaquatic systems demands the technological development tosolve the environmental problems related to organic effluents[8]Many practices have been widely applied in the treatment

of organic effluent such as biological treatment reverseosmosis ozonation filtration adsorption on solid phasesincineration and coagulation [9] However each of themethodologies has its own advantages and limitations assuch incineration can result in deadly toxic volatiles products[10] biological treatment needs prolonged treatment timeand results in ghastly smell ozonation can be effective wayfor the treatment of organic effluent but the stability of ozoneis the biggest concern which was well influenced by theexistence of salts pH and temperature [9 11]The traditionalphysical methods (adsorption filtration reverse osmosis andcoagulation) are quite expensive and also these techniques donot eliminate the organicmolecules utterly but just transformone phase to another [12 13] In recent era advanced oxida-tion processes (AOPs) have been found as an effective andalternative way for the treatment of organic effluent in aque-ous system [14ndash16] The recent research demonstrates thatAOPs based on photocatalysts are valuable and this methodbenefits complete mineralization of organic molecules intonontoxic CO

2and H

2O at the atmospheric conditions [17ndash

20] Further AOPs result in the generation of hydroxylradicals (∙OH) as main oxidizing agents which can removeeven nonbiodegradable organic compounds fromwastewaterstream [21 22] Photocatalytic degradation of organic effluent

Hindawi Publishing CorporationIndian Journal of Materials ScienceVolume 2015 Article ID 601827 16 pageshttpdxdoiorg1011552015601827

2 Indian Journal of Materials Science

LightConduction band

Band gap

Valence band

Photocatalyst

O2

minus+ HO2

OH VOC

O2

Photocatalyticmineralization


Organicpollutants

H2O

CO2 + H2O

Figure 1 Schematic diagram of photocatalytic degradation of organic effluent

emerged as one of the bestmethodologies for the treatment oftoxic organic effluents which uses the semiconductor as cata-lyst such TiO

2 ZnO ZnS WO

3 CdS and Fe

2O3 and SrTiO

3

[23 24 24ndash27] Among themTiO2andZnOhave beenwidely

applied as photocatalyst due to their high activity nontox-icity chemical stability lower costs optical and electricalproperties and environment friendly characteristics [28ndash32]Since the first revolutionary papers in the 1970s the attentionof researchers in heterogeneous photocatalyst has developedgreatly [33 34] and showed the advantages of photocatalyticpractices over the conventional techniques such as rapidoxidation no formation of polycyclic compounds completeoxidation of pollutants and high efficiency [35ndash37] In thismanner the heterogeneous photocatalyst turns out to bean elegant alternative for organic effluent treatment and thecatalyst reduced to the nanoscale can demonstrate differentproperties compared to properties at macroscale size facil-itating unique applications in photocatalyst degradation oforganic waste [38] Nanophotocatalysts have been intensivelyexamined because of their increased surface area which stur-dily influences their physiochemical properties [39 40] Effi-ciency of the prepared photocatalyst for the degradation oforganic effluent is greatly influenced by various parametersstarting from synthesis of nanocatalyst to operation conditionof degradation of effluent In recent year nanocatalyst synthe-sis and its application in the degradation of organicmoleculeswere studied extensively [41]This paper discusses the variousfactors which could affect the photocatalytic activity of thenanocatalyst staring from synthesis of operating condition

2 Reaction Mechanism

In general the photocatalytic degradation involves severalsteps such as adsorption-desorption electron-hole pair pro-duction recombination of electron pair and chemical reac-tion [42 43]The generalmechanism of photocatalytic degra-dation of organic molecules is explained as follows (Figure 1)[39 44ndash46] When the photocatalyst (PC) is irradiated withphotons of energy equal to or more than band gap energy ofPC the electrons (eminus) are excited from the valence band (VB)

to the conduction band (CB) with the simultaneous creationof holes (h+) in the VB

PC + hv 997888rarr eCBminus+ hVB

+ (1)

where hV is the energy essential to transfer the electron fromvalence band to conduction band The electrons generatedthrough irradiation could be readily trapped by O

2absorbed

on the photocatalyst surface or the dissolved O2to give

superoxide radicals (O2

∙minus)

eCBminus+O2997888rarr O

2

∙minus (2)

Consequently O2

∙minus could react with H2O to produce

hydroperoxy radical (HO2

∙) and hydroxyl radical (OH∙)which are strong oxidizing agents to decompose the organicmolecule

O2

∙minus+H2O 997888rarr HO

2

∙+OH (3)

Simultaneously the photoinduced holes could be trappedby surface hydroxyl groups (or H

2O) on the photocatalyst

surface to give hydroxyl radicals (OH∙)

hVB++OHminus 997888rarr ∙OHad

hVB++H2O 997888rarr ∙OH +H+

(4)

Finally the organic molecules will be oxidized to yieldcarbon dioxide and water as follows

∙OH + organic molecules +O2

997888rarr products (CO2and H

2O)

(5)

Meanwhile recombination of positive hole and electroncould take place which could reduce the photocatalyticactivity of prepared nanocatalyst

eCBminus+ hVB

+997888rarr PC (6)

3 Nanocatalyst Preparation Methods

Here some of the recently used methods for the preparationof nanocatalyst in the photocatalytic application are discussedbriefly

Indian Journal of Materials Science 3

Catalyst startingmaterial Solvent

Sol formation

Gel

Precipitatingagent

Drying of gelPulverization Calcination at

Nanocatalystproduct

200ndash600∘C

formation

Figure 2 Synthesis of photo nanocatalyst by sol-gel method

Hydrothermalcrystallization Cooling to room

temperature

WashingDrying

Nanocatalystproduct

at 100ndash200∘Cfor 1ndash12h

Precursor + solventcatalyst starting

precipitant agent

Figure 3 Synthesis of photo nanocatalyst by hydrothermal treatment method

31 Sol-Gel Method Synthesis of photo nanocatalyst by sol-gel method is shown in Figure 2

Catalyst starting material is dissolved in the suitable sol-vent and then precipitating agent is added dropwise with vig-orous stirring and solvent and precipitate (gel) are separatedTo eliminate even the trace amount of the solvents in theobtained gel the gel has to be dried at temperature betweenslightly near and above the boiling point of solvent thenproduct is pulverized and calcined to get the desired nanocat-alyst [63 64]

32 Hydrothermal Method Synthesis of photo nanocatalystby hydrothermal treatment method is shown in Figure 3

In hydrothermal treatment method precursor is dis-solved in the solvent Then the precipitating agent is addeddropwise followed by hydrothermal treatment of preparedsolution at 100ndash200∘C for 1ndash12 hours in autoclave under auto-genous pressure The solid particles are cooled and washed

with washing agent and then dried for 24 h at 80∘C to givenanoparticles [65 66]

33 Coprecipitation Method Synthesis of photo nanocatalystby coprecipitation method is shown in Figure 4

Precursor of catalyst and doping agent are dissolvedseparately in deionized water and mixed under vigorousstirring to get the uniform distribution of dissolvedmaterialsThen precipitating agent (NaOH) was added dropwise intoprecursor solution with the continuous stirring of the partic-ular period of timeTheprecipitate is filtered andwashedwithdeionisedwater until thewashed solution reaches neutral pHThe obtained precipitate is dried at 80ndash100∘C in an oven for24 h and calcined at 400ndash500∘C for 5 h to get the nanocatalyst[65 67]

34 Reverse Microemulsion Method Synthesis of photo-nanocatalyst particle by reverse microemulsion method isshown in Figure 5


Precursor of catalyst and dopingagent

solvent

Stirring Dropwise addition of precipitating agent

Washing with water+

Drying at 80∘C for 24h Calcination at 500∘Cfor 5h

Figure 4 Synthesis of photo nanocatalyst by coprecipitation method

calcining atCentrifugation filtrating and

500ndash1000∘C for 2hcalcining at

Aqueous solution of precursor salt

Stirring

Stirring

Adequate ammonia

Oil phase mixture A Oil phase mixture B

DropwiseDropwise

Stirring anddropwise addition


Centrifugation filtrating and

Forward-titrationproduct

Reverse titrationproduct

Transparentmicroemulsion

A


B

Surfactant + cosurfactant + solvent

Stirring

500ndash1000∘C for 2h

Figure 5 Synthesis of photo nanocatalyst particle by reverse microemulsion method

Desired mole ratios of precursor salts are dissolved in thedeionized water The surfactant and cosurfactant are mixedin solvent with vigorous stirring As shown in Figure 5 twotypes of microemulsions are prepared In part A mixture ofaqueous solution of precursor salts is added into one of themixtures of surfactant and cosurfactant to result in trans-parent microemulsion A In the same manner the adequateammonia is added into the other microemulsion mixture toyield a transparent microemulsion B (part B) Then parts Aand B are mixed continuously until clear solution appeared

and solution was allowed 1-2-day aging Subsequently aftercentrifugation washing drying and calcinations of sepa-rated particles could be done to yield the effective photocata-lyst [68]

4 Factor Affecting the Photodegradation

41 Nanocatalyst Preparation MethodCondition In generalchanges in process conditions or preparation methods resultin catalyst with different catalytic activity In recent decades


Table 1 Comparison of photocatalytic activity of nanocatalyst at different initial pollutant concentration

Light source Catalyst preparationmethod Catalyst used Organic pollutant Initial pollutant

concentrationIrradiationtime (min)

Degradationefficiency () Reference

Solar radiation Sol-gel method TiO2

2-Chlorophenol50mglit 90 100

[47]100mglit 120 100150mglit 120 100


24-Dichlorophenol50mglit 100 100

[47]100mglit 120 100150mglit 120 100


246-Trichlorophenol50mglit 120 100

[47]100mglit 120 100150mglit 120 100

100Wmercurylamp Sol-gel method Codoped TiO

22-Chlorophenol

125 ppm

180

100

[48]25 ppm 9550 ppm 9075 ppm 80

UV radiation P25 TiO2

Victoria blue R05 gL

720100

[49]15 gL 5025 gL 30

there are many researchers who has been involved in themodification of catalyst preparation method to improve thephotocatalytic activity of prepared nanocatalyst [69 70] Forexample in the case of TiO

2catalyst it was found that lab-

made rutile exhibited a good photocatalytic activity due topresence of vast number of hydroxyl groups (Table 4) Butcontradictory to that the rutile obtained at a higher tem-perature is inactive due to limited surface hydroxyl content[66] Further many researchers have observed that size of theprepared catalyst is very well influenced by condition ofcatalyst preparation [71] It is desired to have photocatalystwith smaller size to result in a higher photocatalytic activityBut reduction in the size of photocatalyst leads to increase insurface energy of the photocatalystThis causes the agglomer-ation of particles which could reduce the porosity of the cata-lyst Thereby access of organic molecules could be preventedinto interparticle porous surface and reduce the surface areaavailable It obliterates photocatalytic activity of preparedphotocatalyst [72] But the above could be eliminated bydoing slight change in sol-gel method by using stearic acidas capping agent to prevent agglomeration of small sizenanoparticles due to surface repulsion [73 74] By usingsurfactant as electrostatic stabilization agent calcinationtemperature required for the formation of anatase phase TiO

2

could be reduced [75] And it was found that deposition ofdopant ions on the surface of photocatalyst is well affected bythe pH of precursor solution [76]

42 Initial Concentration of Organic Compound Increasinginitial organic compound concentration reduces the pho-tocatalyst degradation efficiency It might be due to theincrease of the initial concentration of organic compound inwhich more molecules were adsorbed on the surface of thephotocatalystThis results in unavailability of catalyst surface

for the building of hydroxyl radicals which reduces the pho-tocatalytic activity of the catalyst [49] Also escalating initialconcentration of organic compound decreases the number ofphotons or path length of photon that is arrived on the surfaceof photocatalysis (the Beer-Lambert law) which reduces theexcitation of electron from valance band to conduction bandIt results in the decrease in the photocatalytic activity of pre-pared nanocatalyst [18 30 50 77] Comparison of removalpercentage of organic pollutants at different initial pollutantconcentration is presented in Table 1

43 Doping Doping of photocatalyst could improve thephotocatalyst efficiency in the following way (1) band gapnarrowing [67] (2) formation impurity energy levels [78] (3)oxygen vacancies (4) unique surface area for the adsorptionof organic molecules [79] and (5) electron trapping [39] Ingeneral catalyst with a smaller band gap energy is preferredto be an effective photocatalyst to generate more electron-hole pairs [72] Band gap narrowing introduction of impurityenergy level and oxygen-deficient sites can result in a catalystwith higher photocatalytic activity even under visible light[63 78 80ndash83] The photocatalytic activity of prepared cata-lyst depend well on how the recombination of photoinducedhole-electron pairs is preventedDoping prevents recombina-tion of electrons and holes and gets better the photocatalyticactivity by trapping the photoinduced electrons [28 30 4684 85] Incorporation of dopant ions in the catalyst is eitherinterstitial or substitutional In the case of interstitial modethe radius of doped ionswill be lesser than the radius of latticeions and the lattice spaceThis allows the doped ions to piercethe crystal cell of themetal oxide In the case of substitutionalmode doping ions replace the lattice oxide or lattice ions [78]Further it has been found that the dopant ions incorporatedinto catalyst crystal lattice can alter the electronic property


Table 2 Comparison of photocatalytic activity of TiO2with different noble metal doping

Doping and optimumdoping concentration(wt )

Light source Catalystpreparation method Catalyst used Organic pollutant Irradiation

time (min)Degradationefficiency () Reference

15 UV radiation Photochemicalreduction Pt doped TiO

2Methyl orange 90 98 [14]

3 UV radiation Photo reduction Ag doped TiO2

Direct red 23 120 97 [50]08 UV radiation Impregnation Au doped TiO

2Acid green 16 60 98 [51]

Table 3 Comparison of photocatalytic activity of different metal doped photocatalyst

Doping and optimumdoping concentration(mol )

Light source Catalyst preparationmethod Catalyst used Organic

pollutantIrradiation

timeDegradationefficiency () Reference

050 UV radiation FSP technique Nb-loaded ZnO Phenol 1840min 100 [52]

01 UV radiation Combustiontechnique Codoped TiO

2 Phenol 45min 100 [53]

002 500W halogen lamp Coprecipitationmethod Ni-doped ZnS Methylene blue 120min 50 [54]

0036 100Wmercury lamp Sol-gel method Codoped TiO2

2-Chlorophenol 180min 90 [48]

of prepared nanocatalyst and improve its light absorptionability in the visible light region [1 18 78] It has been foundthat the red-shift of absorption edge with respect to purematerial is resulted from d electron transfer But beyond opti-mum level of doping concentration decrease in photocatalyticactivity results from (i) decreasing surface area of catalyst and(ii) narrowing space charge region and the penetration depthof radiation into photocatalyst may exceed the space chargelayer so that the recombination of the photogenerated hole-electron pairs turns to be easier [86] and some case dopingparticles can act as electron-hole recombination centres [2850 87] because the average distance between trap sites isreduced with increasing the dopant concentration [74] Thusthe photocatalytic activity of nanocatalyst is decreased Tianet al found that in the case of TiO

2 the composition of

rutile is increased to some extent with increasing dopingconcentration by reducing the thermal stability of anataseand favours the phase transformation from anatase to rutile[1] In addition to that the increase in the doping contentresults in clusters of doping molecule to form overlyingagglomerates which can shadow the photocatalytic activityby surface plasmon absorption phenomenon [46] In thecase of mesoporous nanoparticles doping material might beascribed to lower photocatalytic activities due to the fact thatsurface site might be blocked by doping material [88 89] Incontrast to that Tong et al reported that doping increasesthe surface area by increasing mesoporous structure in thenanocatalyst [90]

431 Noble Metal Doping Noble metal may enhance pho-tocatalytic activity through the following route (i) enhancedadsorption of organic molecules on the photocatalyst surface[40] (ii) the surface plasmon resonance of noble nanoparti-cles on photocatalyst which is excited by visible light increas-ing electron excitation and electron-hole separation [91]

(iii) noble nanoparticles acting as electron traps to hin-der electronhole recombination [54] and (iv) Fermi levelequilibration between noble nanoparticles and photocatalyst(semiconductors) which may lessen the band gap of thephotocatalyst and in turn weaken the fast electron-hole pairsrecombination [40] and also it is reported that the photo cor-rosion of ZnO catalyst is prevented by adding pt doping to thephotocatalyst Thereby life time of catalyst is increased [85]

Comparison of the photocatalytic degradation rate ofdifferent organic pollutants for different noble metal dopingis given in Table 2

432 Metal Doping Metal doping could alter the morphol-ogy particle size [89] crystal structure [27] and specificsurface area of nanocatalyst which are significant factors thatdecide the photocatalytic activity of prepared photocatalyst

Comparison of photocatalytic activity of different metaldoped catalyst is presented in Table 3

433 Nonmetallic Anionic dopants are reported to be supe-rior than metal dopants regarding stability of the dopedphotocatalyst photocatalytic activity and simplicity of dop-ing process [92] The quantum yield of doped photocatalystunder visible light irradiation is far lower than that of pho-tocatalyst under UV irradiation Photocatalyst with anion-doping to obtain the visible light-activated photocatalyst hasbeen reported in last decades [42 62 79 93 94] Variousanionic species such as nitrogen carbon [95] phosphorusfluorine [96] and sulphur were recognized to potentiallyform a new impurity energy level neighboring to the valenceband while maintaining the largest band gap for maximumefficiency Nitrogen can be incorporated into the nanopho-tocatalyst structure as substitutional and as interstitials [42]In the case of activated carbon hybridized nanophotocatalystthe surface area of photocatalyst increases with the increase


Table 4 Photocatalytic activity of nonmetallic doped TiO2catalyst

Optimum dopingconcentration ( wt) Light source Catalyst preparation

method Catalyst used Organic pollutant Irradiationtime (min)


0012 UV radiation Hydrothermal S doped TiO2

Methyl orange 42 96 [55]

Table 5 Photocatalytic activity of earth metal doped photocatalyst

Doping and optimumdoping concentration Light source Catalyst preparation

method Catalyst used Organicpollutant

Irradiationtime (min)


15 Er3+ UV radiation Sol-gel method Er3+ doped TiO2 Orange I 60 100 [56]

in activated carbon content but activity decreases dueto increase of ZnOTiO

2concentration because the pore

entrances of the activated carbon could be blocked by excessZnOTiO

2composition [62 96] Also Yu et al found that the

crystalline nature of prepared catalyst was suppressed by theincrease in the amount of doping with cerium and nitrogenand this trend was strengthened with the increase in dopingamount Meanwhile the growth of crystal size of catalyst wassuppressed to different extent of doping [87]

434 Earth Metals Doping In case of TiO2nanocatalyst

preparation phase transition from anatase to rutile wasinhibited by earth ions during the thermal treatment Similarresult is observed in nonmetal dopant and combination ofnonearth and nonmetal dopants [79 89] In the case ofTiO2 the inhibition of the phase transition was ascribed

to the stabilization of the anatase phase by rare earth ionsthrough the formation of TiO

2rare earth element bonds [64]

Rare earth metal doping significantly inhibits the growthof nanocrystalline size [64 97] due to earth metal-O-Tibonds formation on the surface of nanocatalyst and in thecalcinations [56 64 98] Shi et al [64] observed that unit cellvolumes and lattice distortion of doped nanocatalyst particlesare larger than that of undoped photocatalyst because smallpart of Ti ions are replaced by earth metal ions in the TiO

2

lattice and this causes the distortion and expansion of latticecrystal structure Similar result has been reported for Fe3+doping [90] It results in easy absorption of oxygenmoleculesas electron trap on the defects which originated from thelattice distortion and expansionTherefore the recombinationrate of electron-hole pairs could be decreased and increasedphotocatalytic activity of the nanocatalyst is observed Photo-catalytic activity of earth metal doped photocatalyst is givenin Table 5

44 Catalyst Loading In general due to increasing in activesites the rate of photocatalytic degradation organic pollutantsincreases with photocatalyst dosage [6 32 60]This is mainlydue to increase of hydroxyl radical produced from irradiatedphotocatalyst [46 99] At lower catalyst loading degradationof organic molecule is low because more light is transmittedthrough the reactor and lesser transmitted radiation only willbe utilised in the photocatalytic reaction [49 61] But beyondthe optimum amount of catalyst loading the degradationrate might be reduced due to increase in the opacity of thesuspension and thus increasing the light scattering and also

the infiltration depth of the photons is diminished and lessphotocatalysts could be activated [18 84 100] Additional towhat is mentioned above agglomeration of nanoparticles athigh concentrations reasoning a decline in the number of sur-face active sites available for the photocatalytic degradation[77 99] and deactivation of activated molecules could resultfrom the collision of activated molecules with ground statemolecules [61 101] Dependence of photocatalytic activity oncatalyst loading is given in Table 6

45 Calcination Temperature Calcination temperature has avital influence on the optical property crystal size and crystalstructure of the prepared photocatalyst [56] Moreover thecommon synthesis of nanophotocatalyst usually involveshigh-temperature calcinations to translate amorphous intocrystal structure which usually results in particle growth andleads to decrease in surface area and decrease in photocat-alytic degradation efficiency [64 75 101] Shi et al reported[64] that the absorption profile shifted slightly to longerwave-lengths (red-shift) with the increase of calcined temperatureIn the case of TiO

2 anatase phase has higher thermal stability

than rutile phase which results in higher concentration ofanatase phase at higher temperature [1] and it has beenreported that anatase possesses higher photocatalytic activitythan rutile [64 102] Because the adsorptive affinity ofanatase for organic molecules is higher than that of rutileanatase structure also displays low rate of recombination ofhole-electron pair in contrast to rutile [64] and also highercalcination temperature helps the formation of larger crystalsand the rutile phase by agglomeration [74] Sun et al foundthat doping of nitrogen with TiO

2would drop increasingly

with rise in temperature and the crystal particle sizes of dopedphotocatalyst became bigger with increasing calcinationstemperature [103] Comparison of photocatalytic degradationof different organic pollutants for different calcinations tem-perature is shown in Table 7

46 pH pH of aqueous dye solution plays a vital role inthe photocatalytic activity of prepared catalyst pH influencesthe adsorption and dissociation of the organic molecule[41 104] surface charge of photocatalyst and oxidationpotential of the valence band [101] Photocatalyst surface ispredominantly negatively charged when the pH is increasedbeyond isoelectric point of nanophotocatalyst As the pHreduced the functional groups are protonated thus raisingthe positive charge of photocatalyst surface The surface of


Table6Dependenceo

fpho

tocatalytic

activ

ityon

catalystloading

Source

ofcatalyst

Lightsou

rce

Catalystpreparationmetho

dCa

talystused

Organicpo

llutant

Catalystconcentration

Irradiationtim

eDegradatio

neffi

ciency

()

Reference

TiCl4andcobalt(III)

24-pentanedionate

UVradiation

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

10mgL

3h964

[57]

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

Nocatalyst

180m

in

10

[48]

550

1090

3090


Table7Com

paris

onof

photocatalyticdegradationof

different

organicp

ollutantsfor

different

calcinations

temperature

Lightsou

rce


dCa

talystused

Catalystdo

sage

Organicpo

llutant

Calcinations

temperature

(∘ C)

Irradiationtim

eDegradatio

neffi

ciency

()

Reference

UVradiation

Sol-g

eltechniqu

eTiO2

25m

glit

Phthalicacid

673

475m

in99

[58]

723

45

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

10mglit

2-Ch

loroph

enol

100

180m

in

30

[48]

400

5060

090

800

60


Table8Optim

umpH

forthe

different

photocatalyticsyste

m

Lightsou

rce

Catalystpreparation

metho

dInitialconcentration

Catalystused

Organicpo

llutant

Optim

umpH

Irradiation

time(min)

Degradatio

neffi

ciency

Reference

UVlight

Hydrothermal

process

2000

mglit

(COD)

TiO2

Cok

ingwater

760

30

[59]

100W

mercury

lamp

Sol-g

elmetho

d50

ppm

Cod

oped

TiO2

2-Ch

loroph

enol

12180

95

[48]

UVlight

Degussa

P25

12times10minus4M

TiO2andcement

Reactiv

eyellowdye17

5ndash7

480

85[60]

40W

fluorescent

lamp

Aqueou

sreaction

metho

d6times10minus6M

MnW

O4

Methylorange

9480

50[41]


Table 9 Dependence of photocatalytic activity on light intensity

Light source Catalyst preparationmethod Catalyst used Organic pollutant Initial concentration Irradiation

time (min) Degradation efficiency Reference

UV radiation Hydrothermalmethod TiO

2Coke water 2000mglit (COD) 60min 15 (400mWcmminus2) [47]

30 (1300mWcmminus2)UV radiation Degussa P25 TiO

2Reactive yellow 17 1 times 10minus4M 360 100 [61]

Sun light 720UV radiation Simple mixing 9ACndashZnO 4-Acetylphenol 3 times 10minus4molLminus1 150 100 [62]Sun light 120

photocatalyst will be charged negatively and results in theincreased adsorption cationic molecules at higher pH valuewhile in the reverse situation it would adsorb anionicmolecules very easily [27 49 50 99] In the meantimethe increased pH value increases the hydroxyl radicals gen-eration [105] But the degradation of organic molecules isrepressed when the pH of solution is too high (pH gt 12)because hydroxyl ions compete with organic molecules forthe adsorption on the surface of the catalysts [27]On the con-trary at low pH the adsorption of cationic organic moleculeon the photocatalyst surface is reduced because the surfaceof photocatalyst is positively charged which results in thedecrease in adsorption of cationic organic molecules Thusthe degradation efficiency is declined in lower pH or acidicsolution [18 77 106]That is the optimum pH of solution hasto be fixed for the different organic solution

On the other hand Prado andCosta [107] noticed that thedegradation of malachite green was lesser in basic medium(higher pH) the degradation efficiency of photocatalystincreases with the decrease in pH value Similar effects wereobserved by other researchers [32 52] Optimum pH for thedifferent photocatalytic system is presented in Table 8

47 Effect of Oxidants The electron-hole recombination inphotocatalyst can be diminished by adding some irreversibleelectron acceptors (H

2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)

to the reactionmixture [14 50] Inmost casesH2O2is used to

increase the photocatalytic activity of prepared photocatalystThe mechanism in which H

2O2alters the photocatalytic

degradation is given as follows

H2O2+O2

∙minus997888rarr∙OH +OHminus +O

2

H2O2+ hv 997888rarr 2∙OH

H2O2+ eCBminus997888rarr∙OH+∙OHminus

(7)

The increase of H2O2concentration resulted in a quicker

degradation of the organic molecules [108] Because pho-tolysis of H

2O2is to generate OH radicals and H

2O2helps

for trapping electrons and thus prevents the recombinationof hole-electron pairs in consequence the chance of theformation of OH radical and O

2on the surface of the photo-

catalyst is increased Beyond the optimum concentration ofH2O2 increase in H

2O2level decreases the degradation rate

of dye due to quenching of OH radical by H2O2[60] Sobana

and Swaminathan reported that addition of H2O2beyond

the optimum level results in generation of peroxide radicalwhich acts as a hole scavenger and thus results in the decreaseof photocatalytic degradation efficiency [30]

48 Light Intensity Semiconductor catalyst absorbs the lightwith an energy equal to or more than band gap energy [83]which causes the movement of electrons from valence bandto conduction band by leaving holes in the valance band[36 77] The photocatalytic degradation rate increased withincreasing intensity of radiation [59]The chance of excitationof catalyst can be improved by raising the intensity of incidentradiation [109] But recombination of hole-electron pair is anormally encountered difficulty in photocatalysis At lowerlight intensity hole-electron pair separation struggles withrecombination which reduces the formation of free radicalsand thus causes reduction in the degradation of the organicmolecules [61] which could be eliminated by using light withhigher intensity Therefore enhancement of the photodegra-dation rate could be achieved with increase in the intensityof incident radiation [28 101] Dependence of photocatalyticactivity on light intensity is presented in Table 9

49 Effect of Temperature The photocatalytic degradationefficiency of organic molecules steadily increased as thetemperature is raised When the temperature is increased itcauses the bubbles formation in the solution which resultsin the generation of free radicals Additionally the increasein temperature helps the degradation reaction to overcomeelectron-hole recombination Besides that the increasingtemperature may enhance the oxidation rate of organicmolecules at the interface [32] Influence of reaction temper-ature on photocatalytic degradation is presented in Table 10

410 Effect of the Support Application of support for thenanophotocatalystmaintains the dispersion of the nanoparti-cle and prevents agglomeration and sintering [104 110] Alsosupports increase the photocatalytic activity by enhancingcharge separation (high electric conductivity supports) orthe adsorption of organic molecules [19] Generally sup-portmagnetic coating is used to immobilize the nanocatalystso that the reusability of nanocatalyst can be achieved[111 112] and also supports help the adsorption of organicmolecules to increase the efficiency of photocatalytic degra-dation The organic pollutants which are adsorbed on themesoporous (support) materials have an opportunity to be


Table 10 Comparison of the photocatalytic degradation rate of organic pollutants at different temperature

Light source Catalyst preparationmethod Catalyst used Organic pollutant Temperature Irradiation time Degradation

efficiency () Reference

UV radiation Sol-gel method Ag doped TiO3

Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63

degraded due to the appearance of hydroxyl radical on thesupport surface [77 113]

5 Conclusion

The technology of nanocatalyst as a photocatalyst has under-gone an explosive growth during the past decade for envi-ronmental remediation by using both artificial and naturalUV-visible irradiation Hence it is possible to obtain visiblelight-active photocatalyst achieved by altering the synthesisand operating condition so that industrial implementationof photocatalytic degradation of organic effluent can beachieved over conventional treatment methods

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] B Tian C Li F Gu H Jiang Y Hu and J Zhang ldquoFlamesprayed V-doped TiO

2nanoparticles with enhanced photocat-

alytic activity under visible light irradiationrdquo Chemical Engi-neering Journal vol 151 no 1ndash3 pp 220ndash227 2009

[2] L M S Colpini and H J Alves ldquoOnelia aparecida andreo dossantrdquo Dyes and Pigments vol 76 pp 525ndash529 2008

[3] T Robinson G McMullan R Marchant and P Nigam ldquoReme-diation of dyes in textile effluent a critical review on currenttreatment technologieswith a proposed alternativerdquoBioresourceTechnology vol 77 no 3 pp 247ndash255 2001

[4] R Vinu and Giridhar ldquoCatalysis at interfacerdquo Journal of theIndian Institute of Science vol 90 no 2 pp 118ndash230 2010

[5] A B Dos Santos F J Cervantes and J B van Lier ldquoReviewpaper on current technologies for decolourisation of textilewastewaters perspectives for anaerobic biotechnologyrdquo Biore-source Technology vol 98 no 12 pp 2369ndash2385 2007

[6] S Senthilvelan V L Chandraboss B Karthikeyan L Natana-patham and M Murugavelu ldquoTiO

2 ZnO and nanobimetallic

silica catalyzed photodegradation of methyl greenrdquo MaterialsScience in Semiconductor Processing vol 16 no 1 pp 185ndash1922013

[7] M-S Chiou and H-Y Li ldquoEquilibrium and kinetic modelingof adsorption of reactive dye on cross-linked chitosan beadsrdquoJournal of HazardousMaterials vol 93 no 2 pp 233ndash248 2002

[8] W Zhou M Cao S Su et al ldquoA newly-designed polyox-ometalate-based plasmonic visible-light catalyst for the pho-todegradation of methyl bluerdquo Journal of Molecular Catalysis AChemical vol 371 pp 70ndash76 2013

[9] J Garcıa-Montano X Domenech J A Garcıa-Hortal FTorrades and J Peral ldquoThe testing of several biological andchemical coupled treatments for Cibacron Red FN-R azo dyeremovalrdquo Journal of Hazardous Materials vol 154 no 1ndash3 pp484ndash490 2008

[10] M Vinita R P J Dorathi and K Palanivelu ldquoDegradation of246-trichlorophenol by photo Fentonrsquos likemethod using nanoheterogeneous catalytic ferric ionrdquo Solar Energy vol 84 no 9pp 1613ndash1618 2010

[11] C C Chen C S Lu Y C Chung and J L Jan ldquoUV lightinduced photodegradation of malachite green on TiO

2nano-

particlesrdquo Journal of Hazardous Materials vol 141 no 3 pp520ndash528 2007

[12] G Zelmanov and R Semiat ldquoPhenol oxidation kinetics inwater solution using iron(3)-oxide-based nano-catalystsrdquoWaterResearch vol 42 no 14 pp 3848ndash3856 2008

[13] S Kaur and V Singh ldquoTiO2mediated photocatalytic degrada-

tion studies of Reactive Red 198 by UV irradiationrdquo Journal ofHazardous Materials vol 141 no 1 pp 230ndash236 2007

[14] M Huang C Xu Z Wu Y Huang J Lin and J WuldquoPhotocatalytic discolorization of methyl orange solution by Ptmodified TiO

2loaded on natural zeoliterdquo Dyes and Pigments

vol 77 no 2 pp 327ndash334 2008[15] B Zhao G Mele I Pio J Li L Palmisano and G Vasapollo

ldquoDegradation of 4-nitrophenol (4-NP) using Fe-TiO2as a

heterogeneous photo-Fenton catalystrdquo Journal of HazardousMaterials vol 176 no 1ndash3 pp 569ndash574 2010

[16] J Jing J Li J Feng W Li and W W Yu ldquoPhotodegradationof quinoline in water over magnetically separable Fe

3O4TiO2

composite photocatalystsrdquo Chemical Engineering Journal vol219 pp 355ndash360 2013

[17] R Vinu S U Akki and G Madras ldquoInvestigation of dyefunctional group on the photocatalytic degradation of dyes bynano-TiO

2rdquo Journal ofHazardousMaterials vol 176 no 1ndash3 pp

765ndash773 2010[18] H R Pouretedal A Norozi M H Keshavarz and A Semnani

ldquoNanoparticles of zinc sulfide doped with manganese nickeland copper as nanophotocatalyst in the degradation of organicdyesrdquo Journal of Hazardous Materials vol 162 no 2-3 pp 674ndash681 2009

[19] T T Vu L del Rıo T Valdes-Solıs and G Marban ldquoStainlesssteel wire mesh-supported ZnO for the catalytic photodegrada-tion of methylene blue under ultraviolet irradiationrdquo Journal ofHazardous Materials vol 246-247 pp 126ndash134 2013


[20] R Ullah and J Dutta ldquoPhotocatalytic degradation of organicdyes with manganese-doped ZnO nanoparticlesrdquo Journal ofHazardous Materials vol 156 no 1ndash3 pp 194ndash200 2008

[21] Y Ju J Qiao X Peng et al ldquoPhotodegradation of malachitegreen using UV-vis light from two microwave-powered elec-trodeless discharge lamps (MPEDL

minus2) further investigation on

products dominant routes and mechanismrdquo Chemical Engi-neering Journal vol 221 pp 353ndash362 2013

[22] L Shang B Li W Dong et al ldquoHeteronanostructure of Agparticle on titanate nanowire membrane with enhanced pho-tocatalytic properties and bactericidal activitiesrdquo Journal ofHazardous Materials vol 178 no 1ndash3 pp 1109ndash1114 2010

[23] R Wahab I H Hwang Y-S Kim et al ldquoNon-hydrolyticsynthesis and photo-catalytic studies of ZnO nanoparticlesrdquoChemical Engineering Journa vol 175 pp 450ndash457 2011

[24] K Byrappa A K Subramani S Ananda K M L Rai RDinesh andM Yoshimura ldquoPhotocatalytic degradation of rho-damine B dye using hydrothermally synthesized ZnOrdquo Bulletinof Materials Science vol 29 no 5 pp 433ndash438 2006

[25] M Soltaninezhad and A Aminifar ldquoStudy nanostructures ofsemiconductor zinc oxide (ZnO) as a photocatalyst for thedegradation of organic pollutantsrdquo International Journal ofNano Dimension vol 2 no 2 pp 137ndash145 2011

[26] P Sathishkumar N Pugazhenthiran R V Mangalaraja A MAsiri and S Anandan ldquoZnO supported CoFe

2O4nanophoto-

catalysts for the mineralization of Direct Blue 71 in aqueousenvironmentsrdquo Journal ofHazardousMaterials vol 252-253 pp171ndash179 2013

[27] H R Rajabi O KhaniM Shamsipur andV Vatanpour ldquoHigh-performance pure and Fe3+-ion doped ZnS quantum dots asgreen nanophotocatalysts for the removal of malachite greenunder UV-light irradiationrdquo Journal of Hazardous Materialsvol 250-251 pp 370ndash378 2013

[28] C Shifu ZWei LWei ZHuaye andY Xiaoling ldquoPreparationcharacterization and activity evaluation of p-n junction photo-catalyst p-CaFe

2O4n-ZnOrdquo Chemical Engineering Journal vol

155 no 1-2 pp 466ndash473 2009

[29] X Qiu L Li J Zheng J Liu X Sun and G Li ldquoOriginof the enhanced photocatalytic activities of semiconductors acase study of ZnO doped with Mg2+rdquo The Journal of PhysicalChemistry C vol 112 no 32 pp 12242ndash12248 2008

[30] N Sobana and M Swaminathan ldquoThe effect of operationalparameters on the photocatalytic degradation of acid red 18 byZnOrdquo Separation and Purification Technology vol 56 no 1 pp101ndash107 2007

[31] H Y He ldquoComparison study of photocatalytic properties ofSrTiO

3and TiO

2powders in decomposition of methyl orangerdquo

International Journal of Environmental Research vol 3 no 1 pp57ndash60 2009

[32] L Karimi S Zohoori and M E Yazdanshenas ldquoPhotocatalyticdegradation of azo dyes in aqueous solutions under UV irradi-ation using nano-strontium titanate as the nanophotocatalystrdquoJournal of Saudi Chemical Society vol 18 no 5 pp 581ndash5882014

[33] H Zhao L Liang and H wen Liu ldquoFast photo-catalyticdegradation of pyridine in nano aluminum oxide suspensionsystemsrdquo Journal of Environmental Sciences vol 23 supplementpp S156ndashS158 2011

[34] A Di Paola E Garcıa-Lopez G Marcı and L Palmisano ldquoAsurvey of photocatalytic materials for environmental remedi-ationrdquo Journal of Hazardous Materials vol 211-212 pp 3ndash292012

[35] J Saien Z Ojaghloo A R Soleymani and M H RasoulifardldquoHomogeneous and heterogeneous AOPs for rapid degradationof Triton X-100 in aqueous media via UV light nano titaniahydrogen peroxide and potassium persulfaterdquo Chemical Engi-neering Journal vol 167 no 1 pp 172ndash182 2011

[36] T Chen Y Zheng J-M Lin and G Chen ldquoStudy on thephotocatalytic degradation of methyl orange in water usingAgZnO as catalyst by liquid chromatography electrosprayionization ion-trapmass spectrometryrdquo Journal of the AmericanSociety for Mass Spectrometry vol 19 no 7 pp 997ndash1003 2008

[37] H R PouretedalMH KeshavarzMH Yosefi A Shokrollahiand A Zali ldquoPhotodegradation of HMX and RDX in the pres-ence of nanocatalyst of zinc sulfide doped with copperrdquo IranianJournal of Chemistry and Chemical Engineering vol 28 no4 pp 13ndash19 2009

[38] S Chaturvedi P N Dave and N K Shah ldquoApplications ofnano-catalyst in new erardquo Journal of Saudi Chemical Society vol16 no 3 pp 307ndash325 2012

[39] N AM BarakatM A Kanjwal I S Chronakis andH Y KimldquoInfluence of temperature on the photodegradation processusing Ag-doped TiO

2nanostructures negative impact with the

nanofibersrdquo Journal ofMolecular Catalysis A Chemical vol 366pp 333ndash340 2013

[40] P S S Kumar M R Raj and S Anandan ldquoNanoporous AundashTiMCM-41mdashan inorganic hybrid photocatalyst toward visiblephotooxidation of methyl orangerdquo Solar Energy Materials andSolar Cells vol 94 no 10 pp 1783ndash1789 2010

[41] H Y He J F Huang L Y Cao and J PWu ldquoPhotodegradationof methyl orange aqueous on MnWO

4powder under different

light resources and initial pHrdquo Desalination vol 252 no 1ndash3pp 66ndash70 2010

[42] J Ananpattarachai P Kajitvichyanukul and S Seraphin ldquoVisi-ble light absorption ability and photocatalytic oxidation activityof various interstitial N-doped TiO

2prepared from different

nitrogen dopantsrdquo Journal of Hazardous Materials vol 168 no1 pp 253ndash261 2009

[43] M A Fox and M T Dulay ldquoHeterogeneous photocatalysisrdquoChemical Reviews vol 93 no 1 pp 341ndash357 1993

[44] Y N Tan C LWong andA RMohamed ldquoAn overview on thephotocatalytic activity of nano-doped-TiO

2in the degradation

of organic pollutantsrdquo ISRN Materials Science vol 2011 ArticleID 261219 18 pages 2011

[45] S Ma R Li C Lv W Xu and X Gou ldquoFacile synthesis ofZnO nanorod arrays and hierarchical nanostructures for pho-tocatalysis and gas sensor applicationsrdquo Journal of HazardousMaterials vol 192 no 2 pp 730ndash740 2011

[46] Y Liu Y Ohko R Zhang Y Yang and Z Zhang ldquoDegradationof malachite green on PdWO

3photocatalysts under simulated

solar lightrdquo Journal of Hazardous Materials vol 184 no 1ndash3 pp386ndash391 2010

[47] M M Ba-Abbad A A H Kadhum A B Mohamad M STakriff and K Sopian ldquoSynthesis and catalytic activity of TiO

2

nanoparticles for photochemical oxidation of concentratedchlorophenols under direct solar radiationrdquo International Jour-nal of Electrochemical Science vol 7 pp 4871ndash4888 2012


[48] M A Barakat H Schaeffera G Hayes and S Ismat-ShahldquoPhotocatalytic degradation of 2-chlorophenol by Co-dopedTiO2nanoparticlesrdquoApplied Catalysis B Environmental vol 57

no 1 pp 23ndash30 2005[49] F D Mai C S Lu C W Wu C H Huang J Y Chen

and C C Chen ldquoMechanisms of photocatalytic degradation ofVictoria Blue R using nano-TiO

2rdquo Separation and Purification

Technology vol 62 no 2 pp 423ndash436 2008[50] N Sobana K Selvam and M Swaminathan ldquoOptimization of

photocatalytic degradation conditions of Direct Red 23 usingnano-Ag doped TiO

2rdquo Separation and Purification Technology

vol 62 no 3 pp 648ndash653 2008[51] S Sakthivel M V Shankar M Palanichamy B Arabindoo

D W Bahnemann and V Murugesan ldquoEnhancement of pho-tocatalytic activity by metal deposition characterisation andphotonic efficiency of Pt Au and Pd deposited onTiO

2catalystrdquo

Water Research vol 38 no 13 pp 3001ndash3008 2004[52] V Kruefu H Ninsonti N Wetchakun B Inceesungvorn P

Pookmanee and S Phanichphant ldquoPhotocatalytic degradationof phenol using Nb-loaded ZnO nanoparticlesrdquo EngineeringJournal vol 16 no 3 pp 91ndash99 2012

[53] M J Pawar and V B Nimbalkar ldquoSynthesis and phenoldegradation activity of Zn and Cr doped TiO

2nanoparticlesrdquo

Research Journal of Chemical Sciences vol 2 no 1 pp 32ndash372012

[54] V Subramanian E E Wolf and P V Kamat ldquoCatalysis withTiO2gold nanocomposites Effect of metal particle size on the

fermi level equilibrationrdquo Journal of the American ChemicalSociety vol 126 no 15 pp 4943ndash4950 2004

[55] C L Yu J C Yu and M Chan ldquoSonochemical fabricationof fluorinated mesoporous titanium dioxide microspheresrdquoJournal of Solid State Chemistry vol 182 no 5 pp 1061ndash10692009

[56] C-H Liang M-F Hou S-G Zhou et al ldquoThe effect of erbiumon the adsorption and photodegradation of orange I in aqueousEr3+-TiO

2suspensionrdquo Journal of HazardousMaterials vol 138

no 3 pp 471ndash478 2006[57] M A Barakata H Schaeffera G Hayesa and S Ismat-Shaha

ldquoPhotocatalytic degradation of 2-chlorophenol by Co-dopedTiO2nanoparticlesrdquoApplied Catalysis B Environmental vol 57

no 1 pp 23ndash30 2005[58] V G Gandhi M K Mishra M S Rao A Kumar P A Joshi

and D O Shah ldquoComparative study on nano-crystalline tita-nium dioxide catalyzed photocatalytic degradation of aromaticcarboxylic acids in aqueous mediumrdquo Journal of Industrial andEngineering Chemistry vol 17 no 2 pp 331ndash339 2011

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2-TiO2nanorod arraysrdquo Catalysis Today vol 174

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bindoo andVMurugesan ldquoPhotocatalytic degradation of reac-tive yellow 17 dye in aqueous solution in the presence of TiO2with cement binderrdquo International Journal of Photoenergy vol5 no 2 pp 45ndash49 2003

[61] B Neppolian H C Choi S Sakthivel B Arabindoo and VMurugesan ldquoSolarUV-induced photocatalytic degradation ofthree commercial textile dyesrdquo Journal of Hazardous Materialsvol 89 no 2-3 pp 303ndash317 2002

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ing vol 2 no 3 pp 157ndash164 2008[64] J-W Shi J-T Zheng and P Wu ldquoPreparation characterization

and photocatalytic activities of holmium-doped titanium diox-ide nanoparticlesrdquo Journal of Hazardous Materials vol 161 no1 pp 416ndash422 2009

[65] M Kang S-J Choung and J Y Park ldquoPhotocatalytic perfor-mance of nanometer-sized Fe

119909O119910TiO2particle synthesized by

hydrothermal methodrdquo Catalysis Today vol 87 no 1ndash4 pp 87ndash97 2003

[66] J Yu H Yu B Cheng M Zhou and X Zhao ldquoEnhancedphotocatalytic activity of TiO

2powder (P25) by hydrothermal

treatmentrdquo Journal of Molecular Catalysis A Chemical vol 253no 1-2 pp 112ndash118 2006

[67] P Sathishkumar R V Mangalaraja S Anandan and MAshokkumar ldquoCoFe

2O4TiO2nanocatalysts for the photocat-

alytic degradation of Reactive Red 120 in aqueous solutionsin the presence and absence of electron acceptorsrdquo ChemicalEngineering Journal vol 220 pp 302ndash310 2013

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2O4nanoparti-

cles synthesized by reverse microemulsion methodrdquo MaterialsResearch vol 16 no 4 pp 844ndash849 2013

[69] J Fu Y Tian B Chang F Xi and X Dong ldquoSoft-chemicalsynthesis of mesoporous nitrogen-modified titania with supe-rior photocatalytic performance under visible light irradiationrdquoChemical Engineering Journal vol 219 pp 155ndash161 2013

[70] T Soltani andMH Entezari ldquoSono-synthesis of bismuth ferritenanoparticles with high photocatalytic activity in degradationof Rhodamine B under solar light irradiationrdquo Chemical Engi-neering Journal vol 223 pp 145ndash154 2013

[71] F Dong W Zhao Z Wu and S Guo ldquoBand structure andvisible light photocatalytic activity ofmulti-type nitrogen dopedTiO2nanoparticles prepared by thermal decompositionrdquo Jour-

nal of Hazardous Materials vol 162 no 2-3 pp 763ndash770 2009[72] A Yousefi A Allahverdi and P Hejazi ldquoEffective dispersion of

nano-TiO2powder for enhancement of photocatalytic proper-

ties in cement mixesrdquo Construction and Building Materials vol41 pp 224ndash230 2013

[73] R K Upadhyay M Sharma D K Singh S S Amritphaleand N Chandra ldquoPhoto degradation of synthetic dyes usingcadmium sulfide nanoparticles synthesized in the presence ofdifferent capping agentsrdquo Separation and Purification Technol-ogy vol 88 pp 39ndash45 2012

[74] C Chen Z Wang S Ruan B Zou M Zhao and F WuldquoPhotocatalytic degradation of CI Acid Orange 52 in thepresence of Zn-doped TiO

2prepared by a stearic acid gel

methodrdquo Dyes and Pigments vol 77 no 1 pp 204ndash209 2008[75] J Jing J FengW Li andWW Yu ldquoLow-temperature synthesis

of water-dispersible anatase titanium dioxide nanoparticles forphotocatalysisrdquo Journal of Colloid and Interface Science vol 396pp 90ndash94 2013

[76] S Song Z Sheng Y LiuHWang andZWu ldquoInfluences of pHvalue in deposition-precipitation synthesis process on Pt-doped


TiO2catalysts for photocatalytic oxidation of NOrdquo Journal of

Environmental Sciences vol 24 no 8 pp 1519ndash1524 2012[77] S Sohrabnezhad A Pourahmad and E Radaee ldquoPhoto-

catalytic degradation of basic blue 9 by CoS nanoparticlessupported on AlMCM-41 material as a catalystrdquo Journal ofHazardous Materials vol 170 no 1 pp 184ndash190 2009

[78] Y Cao Y Cao Y Yu P Zhang L Zhang and T He ldquoAnenhanced visible-light photocatalytic activity of TiO

2by nitro-

gen and nickel-chlorine modificationrdquo Separation and Purifica-tion Technology vol 104 pp 256ndash262 2013

[79] Y Wu M Xing B Tian J Zhang and F Chen ldquoPreparation ofnitrogen and fluorine co-doped mesoporous TiO

2microsphere

and photodegradation of acid orange 7 under visible lightrdquoChemical Engineering Journal vol 162 no 2 pp 710ndash717 2010

[80] A FuerteMDHernandez-Alonso A JMaira et al ldquoNanosizeTi-W mixed oxides effect of doping level in the photocatalyticdegradation of toluene using sunlight-type excitationrdquo Journalof Catalysis vol 212 no 1 pp 1ndash9 2002

[81] R Asahi T Morikawa T Ohwaki K Aoki and Y Taga ldquoVisi-ble-light photocatalysis in nitrogen-doped titanium oxidesrdquoScience vol 293 no 5528 pp 269ndash271 2001

[82] V Rodguez-Gonzalez R Zanella G del Angel and R GomezaldquoMTBE visible-light photocatalytic decomposition over AuTiO2and AuTiO

2ndashAl2O3sol-gel prepared catalystsrdquo Journal

of Molecular Catalysis A Chemical vol 281 no 1-2 pp 93ndash982008

[83] J-L Shie C-H Lee C-S Chiou C-T Chang C-C Changand C-Y Chang ldquoPhotodegradation kinetics of formaldehydeusing light sources of UVA UVC and UVLED in the presenceof composed silver titanium oxide photocatalystrdquo Journal ofHazardous Materials vol 155 no 1-2 pp 164ndash172 2008

[84] H-Y Lin Y-F Chen and Y-W Chen ldquoWater splitting reactionon NiOInVO

4under visible light irradiationrdquo International

Journal of Hydrogen Energy vol 32 no 1 pp 86ndash92 2007[85] Q Zhang Q Zhang H Wang and Y Li ldquoA high efficiency

microreactor with PtZnO nanorod arrays on the inner wall forphotodegradation of phenolrdquo Journal of Hazardous Materialsvol 254-255 no 1 pp 318ndash324 2013

[86] A-W Xu Y Gao and H-Q Liu ldquoThe preparation character-ization and their photocatalytic activities of rare-earth-dopedTiO2nanoparticlesrdquo Journal of Catalysis vol 207 no 2 pp 151ndash

157 2002[87] T Yu X Tan L Zhao Y Yin P Chen and JWei ldquoCharacteriza-

tion activity and kinetics of a visible light driven photocatalystcerium and nitrogen co-doped TiO

2nanoparticlesrdquo Chemical

Engineering Journal vol 157 no 1 pp 86ndash92 2010[88] J Xiao T Peng R Li Z Peng and C Yan ldquoPreparation

phase transformation and photocatalytic activities of cerium-doped mesoporous titania nanoparticlesrdquo Journal of Solid StateChemistry vol 179 no 4 pp 1161ndash1170 2006

[89] Y Ma J Zhang B Tian F Chen and L Wang ldquoSynthesis andcharacterization of thermally stable SmN co-doped TiO

2with

highly visible light activityrdquo Journal of HazardousMaterials vol182 no 1ndash3 pp 386ndash393 2010

[90] T Tong J Zhang B Tian F Chen and D He ldquoPreparation ofFe3+-doped TiO

2catalysts by controlled hydrolysis of titanium

alkoxide and study on their photocatalytic activity for methylorange degradationrdquo Journal of Hazardous Materials vol 155no 3 pp 572ndash579 2008

[91] H Widiyandari A Purwanto R Balgis T Ogi and KOkuyama ldquoCuOWO

3and PtWO

3nanocatalysts for efficient

pollutant degradation using visible light irradiationrdquo ChemicalEngineering Journal vol 180 pp 323ndash329 2012

[92] M Ghaffari H Huang P Y Tan and O K Tan ldquoSynthesisand visible light photocatalytic properties of SrTi

(1minus119909)Fe119909O(3minus120590)

powder for indoor decontaminationrdquo Powder Technology vol225 pp 221ndash226 2012

[93] T Morikawa R Asahi T Ohwaki K Aoki K Suzuki andY Taga ldquoVisible-light photocatalystmdashnitrogen doped titaniumdioxiderdquo RampDReview of Toyota CRDL vol 40 no 3 pp 45ndash502005

[94] S Sakthivel and H Kisch ldquoDaylight photocatalysis by carbon-modified titanium dioxiderdquo Angewandte Chemie InternationalEdition vol 42 no 40 pp 4908ndash4911 2003

[95] H Wang and J P Lewis ldquoEffects of dopant states on pho-toactivity in carbon-doped TiO

2rdquo Journal of Physics Condensed

Matter vol 17 no 21 2005[96] J C Yu J Yu W Ho Z Jiang and L Zhang ldquoEffects of Fminus

doping on the photocatalytic activity and microstructures ofnanocrystalline TiO

2powdersrdquo Chemistry of Materials vol 14

no 9 pp 3808ndash3816 2002[97] T Tong J Zhang B Tian F Chen D He andM Anpo ldquoPrepa-

ration of CendashTiO2catalysts by controlled hydrolysis of titanium

alkoxide based on esterification reaction and study on its pho-tocatalytic activityrdquo Journal of Colloid and Interface Science vol315 no 1 pp 382ndash388 2007

[98] Z Xu Q Yang C Xie et al ldquoStructure luminescence propertiesand photocatalytic activity of europium doped-TiO

2nanopar-

ticlesrdquo Journal of Materials Science vol 40 no 6 pp 1539ndash15412005

[99] X Zhang F Wu XWu P Chen and N Deng ldquoPhotodegrada-tion of acetaminophen in TiO

2suspended solutionrdquo Journal of

Hazardous Materials vol 157 no 2-3 pp 300ndash307 2008[100] H Seshadri S Chitra K Paramasivan and P K Sinha

ldquoPhotocatalytic degradation of liquid waste containing EDTArdquoDesalination vol 232 no 1ndash3 pp 139ndash144 2008

[101] N Venkatachalam M Palanichamy B Arabindoo and VMurugesan ldquoEnhanced photocatalytic degradation of 4-chloro-phenol byZr4+ dopednanoTiO

2rdquo Journal ofMolecular Catalysis

A Chemical vol 266 no 1-2 pp 158ndash165 2007[102] J Zhang T Ayusawa M Minagawa et al ldquoInvestigations of

TiO2photocatalysts for the decomposition of NO in the flow

system the role of pretreatment and reaction conditions in thephotocatalytic efficiencyrdquo Journal of Catalysis vol 198 no 1 pp1ndash8 2001

[103] H Sun Y Bai W Jin and N Xu ldquoVisible-light-driven TiO2

catalysts doped with low-concentration nitrogen speciesrdquo SolarEnergy Materials and Solar Cells vol 92 no 1 pp 76ndash83 2008

[104] F Li S Sun Y Jiang M Xia M Sun and B Xue ldquoPhotodegra-dation of an azo dye using immobilized nanoparticles of TiO

2

supported by natural porous mineralrdquo Journal of HazardousMaterials vol 152 no 3 pp 1037ndash1044 2008

[105] Y-J Chiang and C-C Lin ldquoPhotocatalytic decolorization ofmethylene blue in aqueous solutions using coupled ZnOSnO

2

photocatalystsrdquo Powder Technology vol 246 pp 137ndash143 2013[106] C Karunakaran and R Dhanalakshmi ldquoSemiconductor-cat-

alyzed degradation of phenols with sunlightrdquo Solar EnergyMaterials and Solar Cells vol 92 no 11 pp 1315ndash1321 2008


[107] A G S Prado and L L Costa ldquoPhotocatalytic decouloration ofmalachite green dye by application of TiO

2nanotubesrdquo Journal

of Hazardous Materials vol 169 no 1ndash3 pp 297ndash301 2009[108] N Sapawe A A Jalil and S Triwahyono ldquoPhotodecoloriza-

tion of methylene blue over EGZrO2EGZnOEGFe

2O3HY

photocatalyst effect of radical scavengerrdquoMalaysian Journal ofFundamental and Applied Sciences vol 9 no 2 pp 67ndash73 2013

[109] T A Saleh M A Gondal Q A Drmosh Z H Yamaniand A AL-yamani ldquoEnhancement in photocatalytic activityfor acetaldehyde removal by embedding ZnO nano particleson multiwall carbon nanotubesrdquo Chemical Engineering Journalvol 166 no 1 pp 407ndash412 2011

[110] X Qiu Z Fang B Liang F Gu and Z Xu ldquoDegradation ofdecabromodiphenyl ether by nano zero-valent iron immobi-lized in mesoporous silica microspheresrdquo Journal of HazardousMaterials vol 193 pp 70ndash81 2011

[111] M S Lucas P B Tavares J A Peres et al ldquoPhotocatalyticdegradation of Reactive Black 5 with TiO

2-coated magnetic

nanoparticlesrdquo Catalysis Today vol 209 pp 116ndash121 2013[112] R Shao L Sun L Tang and Z Chen ldquoPreparation and charac-

terization of magnetic core-shell ZnFe2O4ZnO nanoparticles

and their application for the photodegradation of methylenebluerdquo Chemical Engineering Journal vol 217 pp 185ndash191 2013

[113] S Liu H Sun S Liu and S Wang ldquoGraphene facilitated visiblelight photodegradation ofmethylene blue over titaniumdioxidephotocatalystsrdquoChemical Engineering Journal vol 214 pp 298ndash303 2013

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


LightConduction band

Band gap

Valence band

Photocatalyst

O2

minus+ HO2

OH VOC

O2



Organicpollutants

H2O

CO2 + H2O

Figure 1 Schematic diagram of photocatalytic degradation of organic effluent

emerged as one of the bestmethodologies for the treatment oftoxic organic effluents which uses the semiconductor as cata-lyst such TiO

2 ZnO ZnS WO

3 CdS and Fe

2O3 and SrTiO

3

[23 24 24ndash27] Among themTiO2andZnOhave beenwidely

applied as photocatalyst due to their high activity nontox-icity chemical stability lower costs optical and electricalproperties and environment friendly characteristics [28ndash32]Since the first revolutionary papers in the 1970s the attentionof researchers in heterogeneous photocatalyst has developedgreatly [33 34] and showed the advantages of photocatalyticpractices over the conventional techniques such as rapidoxidation no formation of polycyclic compounds completeoxidation of pollutants and high efficiency [35ndash37] In thismanner the heterogeneous photocatalyst turns out to bean elegant alternative for organic effluent treatment and thecatalyst reduced to the nanoscale can demonstrate differentproperties compared to properties at macroscale size facil-itating unique applications in photocatalyst degradation oforganic waste [38] Nanophotocatalysts have been intensivelyexamined because of their increased surface area which stur-dily influences their physiochemical properties [39 40] Effi-ciency of the prepared photocatalyst for the degradation oforganic effluent is greatly influenced by various parametersstarting from synthesis of nanocatalyst to operation conditionof degradation of effluent In recent year nanocatalyst synthe-sis and its application in the degradation of organicmoleculeswere studied extensively [41]This paper discusses the variousfactors which could affect the photocatalytic activity of thenanocatalyst staring from synthesis of operating condition

2 Reaction Mechanism

In general the photocatalytic degradation involves severalsteps such as adsorption-desorption electron-hole pair pro-duction recombination of electron pair and chemical reac-tion [42 43]The generalmechanism of photocatalytic degra-dation of organic molecules is explained as follows (Figure 1)[39 44ndash46] When the photocatalyst (PC) is irradiated withphotons of energy equal to or more than band gap energy ofPC the electrons (eminus) are excited from the valence band (VB)

to the conduction band (CB) with the simultaneous creationof holes (h+) in the VB

PC + hv 997888rarr eCBminus+ hVB

+ (1)

where hV is the energy essential to transfer the electron fromvalence band to conduction band The electrons generatedthrough irradiation could be readily trapped by O

2absorbed

on the photocatalyst surface or the dissolved O2to give

superoxide radicals (O2

∙minus)

eCBminus+O2997888rarr O

2

∙minus (2)

Consequently O2

∙minus could react with H2O to produce

hydroperoxy radical (HO2

∙) and hydroxyl radical (OH∙)which are strong oxidizing agents to decompose the organicmolecule

O2

∙minus+H2O 997888rarr HO

2

∙+OH (3)

Simultaneously the photoinduced holes could be trappedby surface hydroxyl groups (or H

2O) on the photocatalyst

surface to give hydroxyl radicals (OH∙)

hVB++OHminus 997888rarr ∙OHad

hVB++H2O 997888rarr ∙OH +H+

(4)

Finally the organic molecules will be oxidized to yieldcarbon dioxide and water as follows

∙OH + organic molecules +O2

997888rarr products (CO2and H

2O)

(5)

Meanwhile recombination of positive hole and electroncould take place which could reduce the photocatalyticactivity of prepared nanocatalyst

eCBminus+ hVB

+997888rarr PC (6)

3 Nanocatalyst Preparation Methods

Here some of the recently used methods for the preparationof nanocatalyst in the photocatalytic application are discussedbriefly



Sol formation

Gel

Precipitatingagent


Nanocatalystproduct

200ndash600∘C

formation



temperature

WashingDrying

Nanocatalystproduct



precipitant agent












solvent


Washing with water+






Stirring

Stirring

Adequate ammonia


DropwiseDropwise







A


B


Stirring














[47]100mglit 120 100150mglit 120 100



[47]100mglit 120 100150mglit 120 100



[47]100mglit 120 100150mglit 120 100


22-Chlorophenol

125 ppm

180

100

[48]25 ppm 9550 ppm 9075 ppm 80



720100

[49]15 gL 5025 gL 30




2














2Acid green 16 60 98 [51]








2 Phenol 45min 100 [53]




































2











Table6Dependenceo

fpho

tocatalytic

activ

ityon

catalystloading

Source

ofcatalyst

Lightsou

rce


dCa

talystused

Organicpo

llutant


Irradiationtim

eDegradatio

neffi

ciency

()

Reference

TiCl4andcobalt(III)

24-pentanedionate

UVradiation

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

10mgL

3h964

[57]

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

Nocatalyst

180m

in

10

[48]

550

1090

3090


Table7Com

paris

onof


different

organicp

ollutantsfor

different

calcinations

temperature

Lightsou

rce


dCa

talystused

Catalystdo

sage

Organicpo

llutant

Calcinations

temperature

(∘ C)

Irradiationtim

eDegradatio

neffi

ciency

()

Reference

UVradiation

Sol-g

eltechniqu

eTiO2

25m

glit

Phthalicacid

673

475m

in99

[58]

723

45

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

10mglit

2-Ch

loroph

enol

100

180m

in

30

[48]

400

5060

090

800

60


Table8Optim

umpH

forthe

different

photocatalyticsyste

m

Lightsou

rce

Catalystpreparation

metho


Catalystused

Organicpo

llutant

Optim

umpH

Irradiation

time(min)

Degradatio

neffi

ciency

Reference

UVlight

Hydrothermal

process

2000

mglit

(COD)

TiO2

Cok

ingwater

760

30

[59]

100W

mercury

lamp

Sol-g

elmetho

d50

ppm

Cod

oped

TiO2

2-Ch

loroph

enol

12180

95

[48]

UVlight

Degussa

P25

12times10minus4M

TiO2andcement

Reactiv

eyellowdye17

5ndash7

480

85[60]

40W

fluorescent

lamp

Aqueou

sreaction

metho

d6times10minus6M

MnW

O4

Methylorange

9480

50[41]













2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)





H2O2+O2


2



(7)




2O2helps
















Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Sol formation

Gel

Precipitatingagent


Nanocatalystproduct

200ndash600∘C

formation



temperature

WashingDrying

Nanocatalystproduct



precipitant agent












solvent


Washing with water+






Stirring

Stirring

Adequate ammonia


DropwiseDropwise







A


B


Stirring














[47]100mglit 120 100150mglit 120 100



[47]100mglit 120 100150mglit 120 100



[47]100mglit 120 100150mglit 120 100


22-Chlorophenol

125 ppm

180

100

[48]25 ppm 9550 ppm 9075 ppm 80



720100

[49]15 gL 5025 gL 30




2














2Acid green 16 60 98 [51]








2 Phenol 45min 100 [53]




































2











Table6Dependenceo

fpho

tocatalytic

activ

ityon

catalystloading

Source

ofcatalyst

Lightsou

rce


dCa

talystused

Organicpo

llutant


Irradiationtim

eDegradatio

neffi

ciency

()

Reference

TiCl4andcobalt(III)

24-pentanedionate

UVradiation

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

10mgL

3h964

[57]

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

Nocatalyst

180m

in

10

[48]

550

1090

3090


Table7Com

paris

onof


different

organicp

ollutantsfor

different

calcinations

temperature

Lightsou

rce


dCa

talystused

Catalystdo

sage

Organicpo

llutant

Calcinations

temperature

(∘ C)

Irradiationtim

eDegradatio

neffi

ciency

()

Reference

UVradiation

Sol-g

eltechniqu

eTiO2

25m

glit

Phthalicacid

673

475m

in99

[58]

723

45

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

10mglit

2-Ch

loroph

enol

100

180m

in

30

[48]

400

5060

090

800

60


Table8Optim

umpH

forthe

different

photocatalyticsyste

m

Lightsou

rce

Catalystpreparation

metho


Catalystused

Organicpo

llutant

Optim

umpH

Irradiation

time(min)

Degradatio

neffi

ciency

Reference

UVlight

Hydrothermal

process

2000

mglit

(COD)

TiO2

Cok

ingwater

760

30

[59]

100W

mercury

lamp

Sol-g

elmetho

d50

ppm

Cod

oped

TiO2

2-Ch

loroph

enol

12180

95

[48]

UVlight

Degussa

P25

12times10minus4M

TiO2andcement

Reactiv

eyellowdye17

5ndash7

480

85[60]

40W

fluorescent

lamp

Aqueou

sreaction

metho

d6times10minus6M

MnW

O4

Methylorange

9480

50[41]













2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)





H2O2+O2


2



(7)




2O2helps
















Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





solvent


Washing with water+






Stirring

Stirring

Adequate ammonia


DropwiseDropwise







A


B


Stirring














[47]100mglit 120 100150mglit 120 100



[47]100mglit 120 100150mglit 120 100



[47]100mglit 120 100150mglit 120 100


22-Chlorophenol

125 ppm

180

100

[48]25 ppm 9550 ppm 9075 ppm 80



720100

[49]15 gL 5025 gL 30




2














2Acid green 16 60 98 [51]








2 Phenol 45min 100 [53]




































2











Table6Dependenceo

fpho

tocatalytic

activ

ityon

catalystloading

Source

ofcatalyst

Lightsou

rce


dCa

talystused

Organicpo

llutant


Irradiationtim

eDegradatio

neffi

ciency

()

Reference

TiCl4andcobalt(III)

24-pentanedionate

UVradiation

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

10mgL

3h964

[57]

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

Nocatalyst

180m

in

10

[48]

550

1090

3090


Table7Com

paris

onof


different

organicp

ollutantsfor

different

calcinations

temperature

Lightsou

rce


dCa

talystused

Catalystdo

sage

Organicpo

llutant

Calcinations

temperature

(∘ C)

Irradiationtim

eDegradatio

neffi

ciency

()

Reference

UVradiation

Sol-g

eltechniqu

eTiO2

25m

glit

Phthalicacid

673

475m

in99

[58]

723

45

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

10mglit

2-Ch

loroph

enol

100

180m

in

30

[48]

400

5060

090

800

60


Table8Optim

umpH

forthe

different

photocatalyticsyste

m

Lightsou

rce

Catalystpreparation

metho


Catalystused

Organicpo

llutant

Optim

umpH

Irradiation

time(min)

Degradatio

neffi

ciency

Reference

UVlight

Hydrothermal

process

2000

mglit

(COD)

TiO2

Cok

ingwater

760

30

[59]

100W

mercury

lamp

Sol-g

elmetho

d50

ppm

Cod

oped

TiO2

2-Ch

loroph

enol

12180

95

[48]

UVlight

Degussa

P25

12times10minus4M

TiO2andcement

Reactiv

eyellowdye17

5ndash7

480

85[60]

40W

fluorescent

lamp

Aqueou

sreaction

metho

d6times10minus6M

MnW

O4

Methylorange

9480

50[41]













2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)





H2O2+O2


2



(7)




2O2helps
















Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










[47]100mglit 120 100150mglit 120 100



[47]100mglit 120 100150mglit 120 100



[47]100mglit 120 100150mglit 120 100


22-Chlorophenol

125 ppm

180

100

[48]25 ppm 9550 ppm 9075 ppm 80



720100

[49]15 gL 5025 gL 30




2














2Acid green 16 60 98 [51]








2 Phenol 45min 100 [53]




































2











Table6Dependenceo

fpho

tocatalytic

activ

ityon

catalystloading

Source

ofcatalyst

Lightsou

rce


dCa

talystused

Organicpo

llutant


Irradiationtim

eDegradatio

neffi

ciency

()

Reference

TiCl4andcobalt(III)

24-pentanedionate

UVradiation

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

10mgL

3h964

[57]

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

Nocatalyst

180m

in

10

[48]

550

1090

3090


Table7Com

paris

onof


different

organicp

ollutantsfor

different

calcinations

temperature

Lightsou

rce


dCa

talystused

Catalystdo

sage

Organicpo

llutant

Calcinations

temperature

(∘ C)

Irradiationtim

eDegradatio

neffi

ciency

()

Reference

UVradiation

Sol-g

eltechniqu

eTiO2

25m

glit

Phthalicacid

673

475m

in99

[58]

723

45

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

10mglit

2-Ch

loroph

enol

100

180m

in

30

[48]

400

5060

090

800

60


Table8Optim

umpH

forthe

different

photocatalyticsyste

m

Lightsou

rce

Catalystpreparation

metho


Catalystused

Organicpo

llutant

Optim

umpH

Irradiation

time(min)

Degradatio

neffi

ciency

Reference

UVlight

Hydrothermal

process

2000

mglit

(COD)

TiO2

Cok

ingwater

760

30

[59]

100W

mercury

lamp

Sol-g

elmetho

d50

ppm

Cod

oped

TiO2

2-Ch

loroph

enol

12180

95

[48]

UVlight

Degussa

P25

12times10minus4M

TiO2andcement

Reactiv

eyellowdye17

5ndash7

480

85[60]

40W

fluorescent

lamp

Aqueou

sreaction

metho

d6times10minus6M

MnW

O4

Methylorange

9480

50[41]













2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)





H2O2+O2


2



(7)




2O2helps
















Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials












2Acid green 16 60 98 [51]








2 Phenol 45min 100 [53]




































2











Table6Dependenceo

fpho

tocatalytic

activ

ityon

catalystloading

Source

ofcatalyst

Lightsou

rce


dCa

talystused

Organicpo

llutant


Irradiationtim

eDegradatio

neffi

ciency

()

Reference

TiCl4andcobalt(III)

24-pentanedionate

UVradiation

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

10mgL

3h964

[57]

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

Nocatalyst

180m

in

10

[48]

550

1090

3090


Table7Com

paris

onof


different

organicp

ollutantsfor

different

calcinations

temperature

Lightsou

rce


dCa

talystused

Catalystdo

sage

Organicpo

llutant

Calcinations

temperature

(∘ C)

Irradiationtim

eDegradatio

neffi

ciency

()

Reference

UVradiation

Sol-g

eltechniqu

eTiO2

25m

glit

Phthalicacid

673

475m

in99

[58]

723

45

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

10mglit

2-Ch

loroph

enol

100

180m

in

30

[48]

400

5060

090

800

60


Table8Optim

umpH

forthe

different

photocatalyticsyste

m

Lightsou

rce

Catalystpreparation

metho


Catalystused

Organicpo

llutant

Optim

umpH

Irradiation

time(min)

Degradatio

neffi

ciency

Reference

UVlight

Hydrothermal

process

2000

mglit

(COD)

TiO2

Cok

ingwater

760

30

[59]

100W

mercury

lamp

Sol-g

elmetho

d50

ppm

Cod

oped

TiO2

2-Ch

loroph

enol

12180

95

[48]

UVlight

Degussa

P25

12times10minus4M

TiO2andcement

Reactiv

eyellowdye17

5ndash7

480

85[60]

40W

fluorescent

lamp

Aqueou

sreaction

metho

d6times10minus6M

MnW

O4

Methylorange

9480

50[41]













2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)





H2O2+O2


2



(7)




2O2helps
















Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials


























2











Table6Dependenceo

fpho

tocatalytic

activ

ityon

catalystloading

Source

ofcatalyst

Lightsou

rce


dCa

talystused

Organicpo

llutant


Irradiationtim

eDegradatio

neffi

ciency

()

Reference

TiCl4andcobalt(III)

24-pentanedionate

UVradiation

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

10mgL

3h964

[57]

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

Nocatalyst

180m

in

10

[48]

550

1090

3090


Table7Com

paris

onof


different

organicp

ollutantsfor

different

calcinations

temperature

Lightsou

rce


dCa

talystused

Catalystdo

sage

Organicpo

llutant

Calcinations

temperature

(∘ C)

Irradiationtim

eDegradatio

neffi

ciency

()

Reference

UVradiation

Sol-g

eltechniqu

eTiO2

25m

glit

Phthalicacid

673

475m

in99

[58]

723

45

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

10mglit

2-Ch

loroph

enol

100

180m

in

30

[48]

400

5060

090

800

60


Table8Optim

umpH

forthe

different

photocatalyticsyste

m

Lightsou

rce

Catalystpreparation

metho


Catalystused

Organicpo

llutant

Optim

umpH

Irradiation

time(min)

Degradatio

neffi

ciency

Reference

UVlight

Hydrothermal

process

2000

mglit

(COD)

TiO2

Cok

ingwater

760

30

[59]

100W

mercury

lamp

Sol-g

elmetho

d50

ppm

Cod

oped

TiO2

2-Ch

loroph

enol

12180

95

[48]

UVlight

Degussa

P25

12times10minus4M

TiO2andcement

Reactiv

eyellowdye17

5ndash7

480

85[60]

40W

fluorescent

lamp

Aqueou

sreaction

metho

d6times10minus6M

MnW

O4

Methylorange

9480

50[41]













2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)





H2O2+O2


2



(7)




2O2helps
















Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Table6Dependenceo

fpho

tocatalytic

activ

ityon

catalystloading

Source

ofcatalyst

Lightsou

rce


dCa

talystused

Organicpo

llutant


Irradiationtim

eDegradatio

neffi

ciency

()

Reference

TiCl4andcobalt(III)

24-pentanedionate

UVradiation

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

10mgL

3h964

[57]

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

2-Ch

loroph

enol

Nocatalyst

180m

in

10

[48]

550

1090

3090


Table7Com

paris

onof


different

organicp

ollutantsfor

different

calcinations

temperature

Lightsou

rce


dCa

talystused

Catalystdo

sage

Organicpo

llutant

Calcinations

temperature

(∘ C)

Irradiationtim

eDegradatio

neffi

ciency

()

Reference

UVradiation

Sol-g

eltechniqu

eTiO2

25m

glit

Phthalicacid

673

475m

in99

[58]

723

45

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

10mglit

2-Ch

loroph

enol

100

180m

in

30

[48]

400

5060

090

800

60


Table8Optim

umpH

forthe

different

photocatalyticsyste

m

Lightsou

rce

Catalystpreparation

metho


Catalystused

Organicpo

llutant

Optim

umpH

Irradiation

time(min)

Degradatio

neffi

ciency

Reference

UVlight

Hydrothermal

process

2000

mglit

(COD)

TiO2

Cok

ingwater

760

30

[59]

100W

mercury

lamp

Sol-g

elmetho

d50

ppm

Cod

oped

TiO2

2-Ch

loroph

enol

12180

95

[48]

UVlight

Degussa

P25

12times10minus4M

TiO2andcement

Reactiv

eyellowdye17

5ndash7

480

85[60]

40W

fluorescent

lamp

Aqueou

sreaction

metho

d6times10minus6M

MnW

O4

Methylorange

9480

50[41]













2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)





H2O2+O2


2



(7)




2O2helps
















Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Table7Com

paris

onof


different

organicp

ollutantsfor

different

calcinations

temperature

Lightsou

rce


dCa

talystused

Catalystdo

sage

Organicpo

llutant

Calcinations

temperature

(∘ C)

Irradiationtim

eDegradatio

neffi

ciency

()

Reference

UVradiation

Sol-g

eltechniqu

eTiO2

25m

glit

Phthalicacid

673

475m

in99

[58]

723

45

100W

mercury

lamp

Sol-g

elmetho

dCod

oped

TiO2

10mglit

2-Ch

loroph

enol

100

180m

in

30

[48]

400

5060

090

800

60


Table8Optim

umpH

forthe

different

photocatalyticsyste

m

Lightsou

rce

Catalystpreparation

metho


Catalystused

Organicpo

llutant

Optim

umpH

Irradiation

time(min)

Degradatio

neffi

ciency

Reference

UVlight

Hydrothermal

process

2000

mglit

(COD)

TiO2

Cok

ingwater

760

30

[59]

100W

mercury

lamp

Sol-g

elmetho

d50

ppm

Cod

oped

TiO2

2-Ch

loroph

enol

12180

95

[48]

UVlight

Degussa

P25

12times10minus4M

TiO2andcement

Reactiv

eyellowdye17

5ndash7

480

85[60]

40W

fluorescent

lamp

Aqueou

sreaction

metho

d6times10minus6M

MnW

O4

Methylorange

9480

50[41]













2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)





H2O2+O2


2



(7)




2O2helps
















Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Table8Optim

umpH

forthe

different

photocatalyticsyste

m

Lightsou

rce

Catalystpreparation

metho


Catalystused

Organicpo

llutant

Optim

umpH

Irradiation

time(min)

Degradatio

neffi

ciency

Reference

UVlight

Hydrothermal

process

2000

mglit

(COD)

TiO2

Cok

ingwater

760

30

[59]

100W

mercury

lamp

Sol-g

elmetho

d50

ppm

Cod

oped

TiO2

2-Ch

loroph

enol

12180

95

[48]

UVlight

Degussa

P25

12times10minus4M

TiO2andcement

Reactiv

eyellowdye17

5ndash7

480

85[60]

40W

fluorescent

lamp

Aqueou

sreaction

metho

d6times10minus6M

MnW

O4

Methylorange

9480

50[41]













2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)





H2O2+O2


2



(7)




2O2helps
















Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials















2O2 (NH

4)2S2O8 KBrO

3 and K

2S208)





H2O2+O2


2



(7)




2O2helps
















Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








Rhodamine B dye

5∘C

180min

35

[39]15∘C 4025∘C 5545∘C 6055∘C 63


5 Conclusion




References
















2nano-











3O4TiO2

















2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials













2O4nanophoto-





155 no 1-2 pp 466ndash473 2009




3and TiO






















2in the degradation







2












2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials













2catalystrdquo




2nanoparticlesrdquo






























2O4nanoparti-



















2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








2by nitro-



2microsphere



















2with






3and PtWO




(1minus119909)Fe119909O(3minus120590)













2nanopar-














2



2








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








2O3HY





2-coated magnetic












CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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