Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2013 Article ID 578191 11 pageshttpdxdoiorg1011552013578191

Research ArticleThe Comparison of Photocatalytic Degradation andDecolorization Processes of Dyeing Effluents

Ewa Adamek1 Wojciech Baran1 Justyna ZiemiaNska2 and Andrzej Sobczak12

1 Department of General and Analytical Chemistry Medical University of Silesia Jagiellonska 4 41-200 Sosnowiec Poland2 Institute of Occupational Medicine and Environmental Health Koscielna 13 41-200 Sosnowiec Poland

Correspondence should be addressed to Ewa Adamek ewaadamek11wppl

Received 18 September 2012 Revised 13 December 2012 Accepted 19 December 2012

Academic Editor Leonardo Palmisano

Copyright copy 2013 Ewa Adamek et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Treatment of dye effluents resulting from the industrial scale dyeing of cotton polyacrylic fibres leather and flax fabrics byphotocatalytic methods was investigated Photocatalytic processes were initiated by UV-a light (120582max 366 nm) and were conductedin the presence of TiO

2 TiO2FeCl

3 or FeCl

3as photocatalysts It was found that the photocatalytic process carried out with TiO

2

and TiO2FeCl

3was the most effective method for decolorization of textile dyeing effluents and degradation of dyes except for

effluents containing very high concentrations of stable azo dyes During the photocatalytic degradation of anionic dyes a mixtureof TiO

2FeCl

3was more effective while in the case of cationic dyes more suitable seems to be TiO

2alone

1 Introduction

The textile industry is recognized as one of a major pollutingindustry which generates large quantities of wastewater [1]It is estimated that the annual market for dyes is more than7 times 10

5 tonnes per year and about 10ndash15 of the world dyeproduction is lost during the dyeing process and released intothe environment [2 3]The conventional biological methodswidely used in recent years for the treatment of textile effluentcontaining synthetic stable dyes can often be ineffective [4]As a result colored textile effluents containing mixturesof heavy metals auxiliaries and recalcitrant materials canbe released into the environment This and the presenceof suspended solids and sediments can negatively affectthe aquatic life due to the toxicity of these compounds adepletion of transparency and dissolved oxygen in water [5]High level of decolorization of dyeing wastewater is achievedusing various physicochemical methods for example micro-filtration precipitation coagulation flocculation or differentsorption techniques commonly with activated carbon [6]Unfortunately these methods only lead to the separation ofdyes and to their physical transfer in the environment forexample from water or wastewater to another storage place(eg to sludge dumps) but not to their degradation [2 7]Therefore in recent years special attention has been focused

on the studies concerning the use of advanced oxidation pro-cesses (AOPs) that base on the production of highly reactiveoxygen species including hydroxyl radicals (HO∙) AOPs canbe an alternative for the treatment of wastewater or effluentcontaining hardly biodegradable organic compounds becausethey may lead to the formation of low-molecular-weightcarboxylic acids or to complete degradation of pollutants toCO2and H

2O [8ndash10]

The photocatalytic process can be carried out underheterogeneous for example TiO

2[11 12] conditions as

follows

TiO2(aq) + ℎ120584 997888rarr TiO

2(hVB+ eCBminus) (aq) (1)

TiO2(hVB+ eCBminus) (aq) +O

2997888rarr HO∙ +O

2

∙minus+H+ (2)

andor homogeneous conditions for example Fe3+ salts [1314] as follows

Fe3+ (aq) + ℎ120584 997888rarr Fe2+ (aq) +HO∙ +H+ (3)

The properties of TiO2as a photocatalyst are commonly

known and well described in the literature [11 15]There havebeen numerous studies on the removal of organic pollutantsincluding dyes from wastewater on the photoirradiated TiO

2

2 International Journal of Photoenergy

surface [16ndash19] The photocatalytic degradation of pollutantsin the presence of Fe(III) salts has been also presented in theliterature [20ndash22] but there are only few papers describingphotocatalytic properties of TiO

2FeCl3mixture [23ndash25] It

was found that a combination of Fe3+ ions and TiO2in

suspension showed a positive synergistic effect acceleratingthe photodegradation of organic pollutants [24 25]Howevernone of these papers related to the degradation of azo dyes inreal wastewaters

Most of the experiments were conducted in artificial sys-tems with the use of aqueous solutions (often distilled water)that do not mimic the conditions like in real wastewaterMeanwhile real dyes effluents commonly contain unuseddyes inorganic ions and other organic substances thatcan significantly slow down the photocatalytic degradationefficiency of contaminants So far there are some papersand reports concerning treatment of real dye wastewaterusing photocatalytic processes [26ndash29] but they demandmore profound investigations The main objective of thestudy was to compare the efficiency of photodegradation anddecolorization processes carried out in the presence of TiO

2

and FeCl3as well as in the mixture of TiO

2FeCl3during

the treatment of raw real effluents including azodyes Weintended to test four types of wastewaters from large textilefactory industrial tannery and two from small manufac-turies

2 Experimental

21 Characteristics of the Used Effluents The used raw efflu-ents (without dilution and pretreatment) were obtained fromthe industrial scale dyeing of cotton (WCot) polyacrylicfibers (WPac) leathers (WLeat) and flax fabrics (WFlax)They contained auxiliary substances used during the dyeingprocess and also in the case of WLeat municipal wastes andtannins Physical and chemical characteristics of effluents arepresented in Table 1 A criterion for choice of wastewater wasthe presence of azo dyes resistant to biological degradationThe analyzed wastes differed due to the type of used tech-nology and the type of dyed materials Dyes contained inwastewaters were stable and did not undergo biodegradationduring the storage by a period of 28 days in room tempera-ture To remove sulfides wastes were intensively aerated for30min before commencement of the experiments

22 Characteristics of Photocatalysts Titanium (IV) dioxidepowder (TiO

2) used as the photocatalyst was obtained from

Riedel de Haen (anatase 100 a mean BET surface area of 9ndash11m2 gminus1 residues on filter gt40120583m after dispersion in waterlt002 pHpzc = 300 plusmn 005) [30] During preliminarystudies it was found that during decolorization of cationicdyes solutions this catalyst wasmore effective than TiO

2-P25

Moreover its mixture with FeCl3was more effective during

decolorization of anionic dyes in distilledwater than thatwithTiO2-P25 [23]

The iron (III) chloride (FeCl3sdot6H2O) and all other

chemicals used for analysis were purchased from POCH(Poland) and were of analytical grade Freshly prepared

UV lamps

Cold airStirrer

Glasscrystallizer

Sample

Figure 1 The scheme of test stand

FeCl3stock solution in distilled water (10mol Lminus1) or solid

TiO2(25 g Lminus1) or a mixture of TiO

2(25 g Lminus1) and FeCl

3

(10mol Lminus1) was added to 100mL of effluents The concen-trations of TiO

2and FeCl

3were established as optimal based

on preliminary published experiments [23] and according tothe unpublished data The used amount of FeCl

3solution

was determined experimentally in such manner that after itsaddition to effluent the pH of sample was about 3 (Table 2)

23 Irradiation Before irradiation the samples with TiO2

were stirred magnetically for 20min in the dark to ensurethe complete equilibrium between adsorptiondesorptionprocesses of organic compounds on the photocatalyst surface

In all experiments five open glass crystallizers (volume500mL the exposed surface 102 cm2) containing 100mL ofeffluent with catalysts were irradiated by four UV-a lamps(Philips TL-40 W05 at 120582max 366 nm) in order to ensure thesteady-state illumination of the entire surface of crystallizersThe intensity of UV-a and VIS radiation measured by theQuantum-foto radiometer DO9721 (Delta OHM) was 535and 120Wmminus2 respectively The scheme of the test stand isshown in Figure 1

During the whole experiment all samples were inten-sively stirred at a constant speed and had a free contact withatmospheric air but were not aerated additionally Duringirradiation the concentration of dissolved oxygen in thesamples was gt80 The initial temperature of samples was20 plusmn 2

∘C The pH and concentration of oxygen dissolved inirradiated samples were measured by multimeter HD225692(Delta OHM)

24 The Analysis After the appropriate irradiation time (0ndash300min) samples were centrifuged for 30min at 4000 rpmat room temperature (MPW-360 centrifuge Poland) TheUV-VIS spectra of the irradiated effluents in the rangefrom 200 to 800 nm were recorded by spectrophotometer(Secoman S-750) in 1 cm quartz cuvettes The concentrationsof dyes in samples were determined using HPLC method(HPLC D-7000 Merck detector UV VIS Hitachi-L 7400column Supelcosil LC-185 120583m 250mmtimes 46mm mobile

International Journal of Photoenergy 3

Table1Th

echaracteristicso

fthe

investigated

dyee

ffluents

Effluent

from

dyeing

processo

f

Dyeing

techno

logy

Abbreviatio

nin

text

Azo

dyes

ineffl

uents

Other

substances

ineffl

uents

pHCO

D(m

gO2

1)

Max

ofabsorbance

(120582max)inraweffl

uents

Com

ments

CIname

Chem

ical

character

Polyacrylic

fibres

Con

tinuo

usprocess

WPac

Basic

Yello

w28

Basic

Red22

Basic

Blue

41Ba

sicBlack

Catio

nic

Catio

nic

Catio

nic

Catio

nic

Thickener(Prisu

lon)

Auxiliary

agents

(RoksolPAN3K

)Glutaric

acids

44plusmn01

1440

0262(340

nm)

0159(430

nm)

0166(540

nm)

0199(610nm

)

Biologically

stablea

Acid

Red88

Anion

ic

Leather

Batch

process

WLeat

Acid

Blue

193

Anion

iclt10of

tann

erywastes

70plusmn01

460

0365(510nm

)0075(620

nm)

Biologically

unstable

c

Other

dyes

bAnion

ic

Flax

fabric

Batch

process

WFlax

Unk

nown

Anion

icUnk

nown

69plusmn01

910

0965(350

nm)d

Biologically

stablea

Cottonfabric

Batch

process

WCot

Dire

ctBlack22

Anion

icUnk

nown

82plusmn02

8930

4005(480

nm)

Biologically

stablea

a Theb

iologicalstabilityo

fdyeingeffl

uent

was

estim

ated

basedon

changesintheira

ppearance(changesinUV-VIS

spectrum

precipitatio

nof

sediments)and

theird

igestio

ndu

ringthes

torage

perio

dof

28days

(at

20∘Cun

dera

naerob

iccond

ition

s)

b Onlyin

tracea

mou

nts

c Effluentsw

ered

igesteddu

ringshort-tim

estorage

(abo

utfewho

urs)bu

ttheirabsorbance

at120582510nm

didno

tund

ergo

significantchanges

d Absorptionband

with

outany

clearm

axim

um

4 International Journal of Photoenergy

Table 2 The concentrations of reagents used and experimentalconditions

Effluent FeCl3(mmol Lminus1)

TiO2(g Lminus1) pHa

Concentration of Fe(III)in irradiated effluenta

(mmol Lminus1)10 mdash 33 ndb

WPac mdash 25 44 mdash10 25 36 ndb

mdash mdash 31 002WLeat mdash 25 70 mdash

15 25 34 00415 mdash 32 030

WFlax mdash 25 63 mdash15 25 32 03013 mdash 30 280

WCot mdash 25 88 mdash13 25 28 182

aAt the beginning of UV-a irradiation bno data

phase 10mM K2HPO4at pH 90CH

3CN in the ratio 95 5

for WLeat WFlax and WCot and 20mM acetic buffer atpH 48CH

3CN in the ratio 6 4 for WPac resp) Before

HPLC analysis water-insoluble sediments containing Fe(III)compounds with components of effluents were dissolvedafter adding the concentrated HCl (to pH lt 1) or NaOH(to pH asymp 13) The chemical oxygen demand (COD)was estimated by titration method (US EPA 4101-3) [31]Additionally dyes degradation in effluents was determinedspectrophotometrically based on the decrease of peaks oncharacteristic wavelengths at 120582max (Table 3) The analysis ofthe intermediate products was not performed because it wasnot the main aim of this study

25 Results Elaboration The degree of degradation for par-ticular dyes (119883

119894) was calculated based on the results obtained

from HPLC method according to the following equation

119883119894= 100 sdot (1 minus

119878119894

119878119900

) (4)

where 119878119894is the peak area corresponding to the undecomposed

dye after the irradiation of wastewater and 119878119900is the peak area

corresponding to the dye before the irradiationIts means that any transformation of dye occurring as a

result of the irradiation in the presence of a photocatalystwas considered as its degradation In this sense the dyedegradation does not mean its mineralization In the case ofazo dyes their degradation will mean their decompositionto lower and simpler organic compounds by breaking of azobonds

The reaction rate constant for dyes photodegradation(119896119883119894) was determined as for the pseudo first-order reaction

that is as the slope of the following linear dependency

ln119878119900

119878119894

= 119891 (119905) (5)

Reduction of color in the physical process only (119884)was calculated based on the absorbance of raw centrifugedeffluents (119860

119900) and the absorbance of the same effluents but

after addition of the catalyst (TiO2andor FeCl

3) and after

centrifugation (119860119884) as follows

119884 = 100 sdot (1 minus119860119884

119860119900

) (6)

In these cases the photocatalyst-containing samples were notexposed to irradiation that is the photocatalytic processesdid not proceed in them but only adsorption coagulationflocculation and precipitation In some samples the additionof FeCl

3resulted in an increased intensity of color in effluents

so the 119884 value was negativeReduction of color in the photocatalytic process only

(119885) was determined based on the absorbance of centrifugedeffluents with catalysts (TiO

2andor FeCl

3) (119860119884) and the

absorbance of the same effluents but after their irradiationwith these catalysts (119860

119911) as follows

119885 = 100 sdot (1 minus119860119885

119860119884

) (7)

In these cases the reason of effluents decolorationmay be thephotocatalytic process only

The rate constant for dyes photodecolorization (119896119885119894) was

determined as the slope of the following linear function

ln 119860119884119860119885

= 119891 (119905) (8)

Total decolorization of effluents (Total) was calculatedusing the following formula

Total = 100 sdot (1 minus119860119911

119860119900

) (9)

COD removal (119877COD) was determined based on thefollowing equation

119877COD = 100 sdot (1 minusCOD300

CODo) (10)

where CODo was determined in raw effluents and COD300

was determined in the same effluents but after 300min ofUV-a irradiation in the presence of TiO

2andor FeCl

3

3 Results and Discussion

31 Effect of FeCl3 The high photocatalytic activity of Fe(III)salts in model solutions is related to their partial hydrolysisproducts namely Fe(OH)2+ ions that show the maximumphotocatalytic activity in the pH asymp 3 [13] The additionof FeCl

3to effluent samples caused precipitation of water-

insoluble matter (with the exception of WPac) and almosttotal their decolorization (Table 3) However the UV-a irra-diation for 60min did not cause significant changes inUV-Visspectra and in HPLC chromatograms for any of the analyzedsamples Additionally after a prolonged irradiation time to

International Journal of Photoenergy 5

Table3Th

eresultsof

thetreatmento

fdye

effluents

Dyesd

egradatio

naft

erRe

ductionof

color

Effluent120582max(nm)

Photocatalytic

syste

m60

min

ofirr

adiatio

nIn

thep

hotocatalytic

process

Inthep

hysic

alprocesses

Y(

)

Totald

ecolorizationof

effluentsa

t120582max

CODremovalaft

er300m

inaft

er60

min

ofirr

adiatio

nTo

tal()

ofirr

adiatio

n119877COD(

)

X(

)119896119883(m

inminus1)

Z(

)119896119885(m

inminus1)

FeCl

3sim0

sim0

2sim0

minus60

6minus593

340

TiO

237

0008plusmn0002

26000

6plusmn0002

328

TiO

2FeCl

310

0002plusmn0001

780024plusmn0003

minus347

1

FeCl

3sim0

sim0

sim0

sim0

minus147

minus155

430

TiO

258

0014plusmn0003

360008plusmn0002

440

WPac

TiO

2FeCl

317

0003plusmn0002

490010plusmn0002

minus76

11sim0149

a

FeCl

3sim0

sim0

sim0

sim0

minus17

minus20

540

TiO

286

0030plusmn0005

570014plusmn0002

358

TiO

2FeCl

340

0008plusmn0002

22000

4plusmn0001

minus7

17

FeCl

3nd

bnd

3sim0

47

610

TiO

2nd

nd

830030plusmn000

44

84TiO

2FeCl

3nd

nd

35000

6plusmn0002

1142

FeCl

3sim0

sim0

sim0

sim0

9595

510

TiO

224

(63)

c000

4plusmn0002

110002plusmn000

014

24

WLeat

TiO

2FeCl

3sim30

(100)c

0005plusmn0001

110002plusmn0001

9595

sim040

15a

FeCl

3nd

nd

sim0

sim0

100

100

620

TiO

2nd

nd

210003plusmn0001

1836

TiO

2FeCl

3nd

nd

100

mdash96

100

FeCl

3sim0e

sim0

10lt0001

5053

sim0

WFlax

350d

TiO

210

e0001plusmn

0001

220003plusmn0002

sim0

22minus40

TiO

2FeCl

335divide42

e0008plusmn0002

500011plusmn

0003

3366

minus33

FeCl

3sim0(0)c

sim0

sim0c

sim0

9696

csim0

WCot

480

TiO

2sim0(5)c

sim0

5csim0

sim0

5c11

TiO

2FeCl

3sim0(5)c

sim0

5csim0

9796

c7

a Inthep

resenceo

fFeC

l 3TiO2andTiO2FeCl

3respectiv

elybno

datacaft

er300m

inof

UV-airadiation

d absorptionband

with

outclear

maxim

umebasedon

thep

eakarea

measurementat4

80nm

usingHPL

Cmetho

d

6 International Journal of Photoenergy

300min no significant changes in chromatograms and inCOD values were observed

After the dissolution of water insoluble Fe-organic com-plexes chromatograms of samples (before and after UVirradiation) remained practically unchanged This observa-tion indicates that during UV-a irradiation of effluents withFe(III) salt only dyes did not undergo the photocatalyticdegradationThe use of FeCl

3and probably also other Fe(III)

salts as a catalyst in the photocatalytic treatment processof dye effluents is completely ineffective (after 60min ofirradiation the photodegradation efficiency was in the rangeof 0) Therefore under model conditions model Fe(OH)2+ions can have photocatalytic activity at pH 3 but in realwastewater samples for example in dye effluents they mayact as a coagulant only

32 Effect of TiO2 After centrifugation of nonirradiatedsamples with TiO

2 no significant changes in UV-VIS spec-

tra (Figure 2) and HPLC chromatograms were observedSimultaneously in all effluent samples the photocatalyst wascoagulated only in a negligible level

As can be seen from the UV-VIS spectra shown inFigure 2(a) after UV-a irradiation of samples containingcationic dyes (WPac) with TiO

2for 60min the effluent

underwent high decolorization resulting in a completelycolorless effluent The disappearance of the absorption bands(120582max at 340 430 520 and 610 nm) suggests that the chro-mophore groups responsible for color progressively breakdown during UV-a irradiation Therefore in the case ofcationic dyes the effluent decolorization was almost exclu-sively the result of the photocatalytic process and only ina small degree due to physical processes such as precipita-tion coagulation or sorption The degradation efficiency ofcationic dyes was in the range of 37ndash86 but the CODremoval was low even after 300min of irradiation and wasonly 14 (Table 3)

The decolorization (a decrease in absorbance) was alsoobserved in WLeat and WFlax effluents containing anionicdyes (Figures 2(b) and 2(c)) After irradiation of samplesin the presence of TiO

2 a decrease of absorbance at 510

and 620 nm for WLeat and a decrease of a continuous band(without any distinctmaximum) forWFlaxwere observed Inthe case of effluent resulting from dyeing of leather (WLeat)decolorization was the result of both the photodegrada-tion and the physical processes The maximum degradationdegree of one of the dyes namely Acid Red 88 was 63 after300min of UV-a irradiation (Table 3)

On the other hand WFlax effluents irradiated for 60minwith TiO

2exhibited lower dyes degradation in the range

of 10 The UV-a irradiation for 300min caused a decreasein COD value about 40 in WLeat effluents and on thecontrary an increase in COD value of 40 in WFlax(Table 3)

As shown in Figure 2(d) in effluents from cotton dyeingprocesses (WCot) decolorization and changes inHPLCchro-matograms practically were not observed The degradationdegree of dye was lt5 even after 300min UV-a irradiationIn these samples the degradation efficiency was very low

probably because of less transmission of UV-a light throughthe black effluents Additionally WCot samples containinghigh concentration of dye (Direct Black 22) had the highestCOD over 8900mg O

2Lminus1 Therefore after 300min of

irradiation the COD removal was about 11 (Table 3)The photodegradation of compounds duringin hetero-

geneous photocatalysis depends among other factors on thechemical properties of substrates and their adsorption abilityonto the photocatalyst surface [11] In accordance to hetero-geneous catalysis theory (Langmuir- Himselwood model)the increase in adsorption of dyes causes the increase in thephotocatalytic degradation rate Additionally TiO

2shows an

amphoteric character and its photocatalytic activity dependsalso on the pH of samples In the case of the investigated TiO

2

(pure anatase) the determined pH value of the point of zerocharge (pHpzc) was 300 In the used dyes effluents the pHswere always higher than pHpzc and therefore TiO

2surface

should be negatively charged as follows

Ti ndashOH2

+pHltpHpzclArrrArr TindashOH

pHgtpHpzclArrrArr TiOminus (11)

This fact may explain the higher adsorption and higher pho-todegradation ability of cationic dyes (inWPac effluents) andlower adsorption of anionic dyes (WCot andWFlax) onto theTiO2surface under the studied conditions However it does

not simply explain high degradation of anionic dyes inWLeateffluents The adsorption process onto TiO

2surface under

UV-irradiation conditions is complex and some differencesin an adsorption capacity of particles may occur Probablya higher removal of COD in WLeat can be attributed to theadsorption of increased amounts of undissociated particles(eg anionic dyeswith organic or inorganic ions) on the TiO

2

surface Additionally the organic compounds in WLeat thatis dyes surfactant agents and auxiliaries were rather photolabile and they were easily transformed to less stable organics(byproducts)

33 Effect of TiO2FeCl3 As shown in Figure 3 the additionof TiO

2FeCl3mixture to nonirradiated effluents caused a

significant coagulation and decolorization of all samplesTherefore in these processes Fe salts could play a roleof coagulant However UV-a irradiation of such samplesresulted in their decolorization (Figure 3 Table 3) and thismay indicate its role as a photosensitizer

It was found that the photocatalytic degradation in efflu-ent containing cationic dyes (WPac) was less effective in themixture of TiO

2FeCl3than in the presence of TiO

2alone

(Table 3) After 60min of UV-a irradiation the degradationefficiency of dyes was in the range 10ndash40 SimultaneouslyWPac underwent the effective decolorization which can beexplained only as the dyes photodegradation (Figure 3(a))This process was not inhibited by strong coagulation ofphotocatalysts and by auxiliary substances contained in thesesamples After the addition of TiO

2FeCl3but before UV-

a irradiation absorbance in WPac effluent at 120582 lt 500 nmwas significantly higher due to the presence of dissolvedFe(III) compounds (dashed line) The data concerning CODremoval indicate that the efficiency of WPac mineralizationafter 300min of UV-a irradiation reached only 9

International Journal of Photoenergy 7

0

005

01

015

02

025

03

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(b)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriz

atio

n (

)

(c)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(d)

Figure 2 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent 119860

119900 dotted line (blue) effluent with TiO

2 without UV-a irradiation 119860

119884 solid line (blue) effluent with TiO

2 after UV-a irradiation

119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and after UV-a irradiation ( ⃝) decolorization of effluent as a result of the

photocatalytic process in the presence of TiO2(25 g Lminus1) and after UV-a irradiation

On the contrary effluents containing anionic dyes(WLeat and WFlax) underwent the photocatalytic degra-dation more effectively in the presence of TiO

2FeCl3than

in TiO2alone (Table 3) Upon UV-a irradiation there were

continuous decreases in absorbance all along the spectrameaning the fragmentation of organic structures and thephotocatalytic degradation of dyes (Figures 3(b) and 3(c))As shown in Table 2 the complete removal of Acid Red 88fromWLeat was the result of both direct precipitation andoradsorption on the photocatalyst surface and photodegrada-tion process The degradation efficiency of this dye was highand reached even 100 after 300min of UV-a irradiation(Table 3)Thedecolorization ofWFlaxwas caused to a greaterextent by the photocatalytic process than coagulation andor

precipitation (Figure 3(c)) The dyes degradation was in therange 35ndash42 after 60min of UV-a irradiation Removal ofCOD in WLeat in the presence of TiO

2FeCl3was 15 and

was lower than in the presence of TiO2alone On the other

hand similarly as during irradiation of WFlax with TiO2

alone after 300min of UV-a irradiation with TiO2FeCl3

there was not a decrease of COD value but its increaseIn our opinion an increase in COD removal upon UV-

a irradiation of WFlax with TiO2and TiO

2FeCl3is only

provisional This effect can be explained by an increase in theconcentration of smaller organics molecules formed duringthe photocatalytic oxidation of dyes and suspended solidsMost of the decomposable compounds are removed in theinitial time of this process and the remained part of organic

8 International Journal of Photoenergy

0

01

02

03

04

05

06

07

08

09

1

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

Abs

orba

nce

Dec

olor

izat

ion

()

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(b)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriza

tion

()

(c)

Abs

orba

nce

Dec

olor

izatio

n (

)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(d)

Figure 3 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent119860

119900 dotted line (blue) effluent with TiO

2and FeCl

3but without UV-a irradiation119860

119884 solid line (blue) effluent with TiO

2 FeCl

3and

after UV-a irradiation 119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and FeCl

3(10 mmol Lminus1) and after UV-a irradiation ( ⃝)

decolorization of effluent as a result of the photocatalytic process in the presence of TiO2(25 g Lminus1) FeCl

3(10mmol Lminus1) and after UV-a

irradiation

pollutants for example lower molecular weight carboxylicacids aldehydes and ketones can be less removable Thesebyproducts may not be completely mineralized by K

2Cr2O7

because they are quite resistant and their chemical oxida-tion can be the rate-limiting step in oxidation processesTherefore they require more severe oxidation conditions ora longer time for their conversion On the other hand theCOD values enable only qualitative rather than quantitativeassessment of the mineralization process [32]

After the addition of TiO2FeCl3toWCot the decoloriza-

tion was found to be almost 100 resulting in a completelycolorless effluent (Figure 3(d)) However the removal ofDirect Black 22 was the result of its precipitation only and not

the photocatalytic process The efficiency of photocatalyticdegradation of this dye after 300min of UV-a irradiation waslt5 (Table 3)

Furthermore the organic load ofWCot effluent irradiatedwith TiO

2FeCl3did not change significantly the COD

removal remained low at a value of about 7 Taking intoaccount the high chemical stability of dye (Direct Black 22)in WCot as well as its high concentration in effluent thephotocatalytic degradation of WCot in the presence of TiO

2

and TiO2FeCl3is not an effective method

An estimation of the efficiency of the studied photo-catalytic systems (TiO

2and TiO

2FeCl3) used during the

photocatalytic degradation of real effluents also depends on

International Journal of Photoenergy 9

the chemical properties of dyes and on the possibility offormation of coordination compounds with Fe3+ ions

In the case of effluents containing cationic dyes (WPac)the addition of Fe(III) salt was unfavorable because the effi-ciency of photodegradation of these dyes and COD removalwere lower than that in the presence of TiO

2only The

explanation of this result can be the change of charge ofTiO2particles (in the presence of Fe3+ ions) that limits the

possibility of sorption of the positively charged particles ofcationic dyes

In the case of effluents containing anionic dyes (WLeatand WFlax) the presence of Fe3+ ions had a beneficialeffect on the efficiency of photocatalytic degradation of thesecompoundsThe possible explanations may be a formation ofphotoactive complexes between dyes particles and Fe3+ ionsthat absorb UV-a irradiation much better than individualmolecules of dyes or an adsorption of complexes of dyes withFe3+ ions on the photocatalyst surface

The investigated dyes effluents containing also otherpollutants such as fatty acids sugars and amino acids whichmay also be substrates for the photodegradation and cantherefore compete with the dyes Additionally they maycontain inorganic mobile anions such as Clminus CO

3

2minusSO4

minus2 PO4

3minus and NO3

minus which may significantly affect thedistribution of hydroxyl radicals in the following process

XO119899minus +HO∙ 997888rarr XO∙(119899minus1)minus

+OHminus (12)

As a result these anions at high concentrations candecrease the photodegradation that simultaneously occursbetween HO∙ radicals and dyes molecules

From the viewpoint of COD removal TiO2alone was

a much more effective photocatalyst than TiO2FeCl3 The

increase in COD value in WFlax effluent probably wasconnected with the presence of a very persistent substance(s)that did not undergo the oxidation during the COD deter-mination On the other hand the photocatalytic processleads to degradation of these substances and the obtainedproducts are much less chemically resistant In this aspectthe observed phenomenon is not negative In our publication[33] we have reported similar to other authors [34] that thecomplete photocatalytic degradation of contaminants duringthe treatment of effluents is still not economically feasible dueto high operating costs Therefore the reduction of time ofphotocatalytic process only to the time necessary to initialdegradation of nonbiodegradable substances (eg azo dyes)towards the most readily biodegradable intermediates is themost reasonable It is obvious that one single treatment stepcannot remove all pollutants contained in dyes effluents Theoptimal solution is the combination of different treatmentprocesses for example the photocatalytic degradation usingsunlight as the source of UV light with a biological processIt may significantly decrease the overall cost of the dyeeffluents treatment Additionally the photocatalytic pre-treatment of dyeing effluents can lead to improvement oftheir biodegradability for example initial toxicity inducedby photodegradation of textile antraquinone dye to Vibriafisheri progressively decreased during the course of pro-cess [35] In this way a significant decrease in the overall

cost of the treatment of dyes effluents is expected mainlythrough the combination of several AOPs for example thephotocatalytic degradation as a pretreatment method withbiological processes [36] An increase of biodegradability ofthese effluents would facilitate their subsequent biologicaltreatment and an effective removal of undesirable andorrecalcitrant pollutants making the complete mineralizationunnecessary

4 The Mechanism of WastewaterDecolorization Processes

The experiments confirmed that TiO2caused decolorization

of wastewatermainly due to photocatalytic process Howeverthe decolorization ofWLeat could be a result of dyes sorptiononto TiO

2surface (Table 3)

As previously described FeCl3alone could not be the

cause of decolorization of wastewater during the photocat-alytic process On the other hand the addition of FeCl

3

accelerated undoubtedly the photocatalytic degradation ofanionic dyes According to Mestankova et al this effectwas mainly the result of the synergism of photochemicalactivity between TiO

2and FeCl

3[24] However the results

of experiments showing that FeCl3alone did not exhibit the

photochemical activity in wastewater and it decreased thephotodegradation rate of cationic dyes may indicate otherpossible mechanism It should be noted that even moreimportant is the above described process of intensification ofsorption of dyes coordinated with FeCl

3onto TiO

2surface

[23] The other reason could be the fact that the additionof FeCl

3and simultaneously decrease of pH cause agglom-

eration of suspensions in wastewaters and also increase instability and photoavailability of the TiO

2used [30]

5 Conclusions

Dyeing effluents irradiated in the presence of FeCl3alone

were decolorized but azo dyes almost completely did notundergo degradation On the country the photocatalyticprocess carried out with TiO

2and TiO

2FeCl3as photo-

catalysts was the effective method of decolorization anddyes photodegradation in the investigated effluents (exceptsamples containing high concentration of very stable azodye) During the photocatalytic degradation of anionic dyesa mixture of TiO

2FeCl3was more effective while in the case

of cationic dyes more suitable seems to be TiO2alone

Acknowledgment

This work was supported by the Medical University of Silesia(Grant no KNW-1-043P20)

References

[1] R G Saratale G D Saratale J S Chang and S P GovindwarldquoDecolorization and biodegradation of reactive dyes and dyewastewater by a developed bacterial consortiumrdquo Biodegrada-tion vol 21 no 6 pp 999ndash1015 2010

10 International Journal of Photoenergy

[2] 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

[3] J C Garcia J L Oliveira A E C Silva C C OliveiraJ Nozaki and N E de Souza ldquoComparative study of thedegradation of real textile effluents by photocatalytic reactionsinvolvingUVTiO

2H2O2andUVFe2+H

2O2systemsrdquo Journal

of Hazardous Materials vol 147 no 1-2 pp 105ndash110 2007[4] I M C Goncalves A Gomes R Bras M I A Ferra M T

P Amorim and R S Porter ldquoBiological treatment of effluentcontaining textile dyesrdquoColoration Technology vol 116 pp 393ndash397 2000

[5] M Asgher H N Bhatti S A H Shah M J Asad and R LLegge ldquoDecolorization potential of mixed microbial consortiafor reactive and disperse textile dyestuffsrdquo Biodegradation vol18 no 3 pp 311ndash316 2007

[6] B H Hameed A L Ahmad and K N A Latiff ldquoAdsorptionof basic dye (methylene blue) onto activated carbon preparedfrom rattan sawdustrdquo Dyes and Pigments vol 75 no 1 pp 143ndash149 2007

[7] H Selcuk ldquoDecolorization and detoxification of textile wastew-ater by ozonation and coagulation processesrdquo Dyes and Pig-ments vol 64 no 3 pp 217ndash222 2005

[8] A S Stasinakis ldquoUse of selected advanced oxidation processes(AOPs) for wastewater treatmentmdashamini reviewrdquoGlobal NESTJournal vol 10 pp 376ndash385 2008

[9] R Aplin and T D Waite ldquoComparison of three advancedoxidation processes for degradation of textile dyesrdquo WaterScience and Technology vol 42 no 5-6 pp 345ndash354 2000

[10] I Arslan-Alaton G Tureli and T Olmez-Hanci ldquoTreatmentof azo dye production wastewaters using Photo-Fenton-likeadvanced oxidation processes optimization by response surfacemethodologyrdquo Journal of Photochemistry and Photobiology Avol 202 no 2-3 pp 142ndash153 2009

[11] J M Herrmann ldquoHeterogeneous photocatalysis state of the artand present applicationsrdquoTopics in Catalysis vol 34 no 1ndash4 pp49ndash65 2005

[12] I K Konstantinou and T A Albanis ldquoTiO2-assisted photocat-

alytic degradation of azo dyes in aqueous solution kinetic andmechanistic investigations a reviewrdquo Applied Catalysis B vol49 no 1 pp 1ndash14 2004

[13] W Feng and D Nansheng ldquoPhotochemistry of hydrolyticiron (III) species and photoinduced degradation of organiccompounds A minireviewrdquo Chemosphere vol 41 no 8 pp1137ndash1147 2000

[14] I P Pozdnyakov Y A Sosedova V F Plyusnin et al ldquoPho-todegradation of organic pollutants in aqueous solutions causedby (OH)2+aq photolysis evidence of OH radical formationrdquoInternational Journal of Photoenergy vol 6 no 2 pp 89ndash932004

[15] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalyticdegradation of organic contaminants over titanium dioxidea review of fundamentals progress and problemsrdquo Journal ofPhotochemistry and Photobiology C vol 9 no 1 pp 1ndash12 2008

[16] O K Dalrymple D H Yeh and M A Trotz ldquoRemovingpharmaceuticals and endocrine-disrupting compounds fromwastewater by photocatalysisrdquo Journal of Chemical Technologyand Biotechnology vol 82 no 2 pp 121ndash134 2007

[17] R Rajeswari and S Kanmani ldquoA study on degradation of pes-ticide wastewater by TiO

2photocatalysisrdquo Journal of Scientific

and Industrial Research vol 68 no 12 pp 1063ndash1067 2009

[18] Z F Guo R X Ma and G J Li ldquoDegradation of phenolby nanomaterial TiO

2in wastewaterrdquo Chemical Engineering

Journal vol 119 pp 55ndash59 2006[19] C Jia YWang C Zhang and Q Qin ldquoUV-TiO

2photocatalytic

degradation of landfill leachaterdquo Water Air and Soil Pollutionvol 217 no 1ndash4 pp 375ndash385 2011

[20] V Sarria M Deront P Peringer and C Pulgarin ldquoDegradationof a biorecalcitrant dye precursor present in industrial wastew-aters by a new integrated iron(III) photoassisted-biologicaltreatmentrdquoApplied Catalysis B vol 40 no 3 pp 231ndash246 2003

[21] L Poulain G Mailhot P Wong-Wah-Chung and M BolteldquoPhotodegradation of chlortoluron sensitised by iron(III) aqua-complexesrdquo Journal of Photochemistry and Photobiology A vol159 no 1 pp 81ndash88 2003

[22] C Catastini S Rafqah G Mailhot and M Sarakha ldquoDegra-dation of amitrole by excitation of iron(III) aquacomplexes inaqueous solutionsrdquo Journal of Photochemistry and PhotobiologyA vol 162 no 1 pp 97ndash103 2004

[23] W Baran A Makowski and W Wardas ldquoThe influence ofFeCl3on the photocatalytic degradation of dissolved azo dyes

in aqueous TiO2suspensionsrdquo Chemosphere vol 53 no 1 pp

87ndash95 2003[24] H Mestankova J Krysa J Jirkovsky G Mailhot and M

Bolte ldquoThe influence of Fe(III) speciation on supported TiO2

efficiency example of monuron photocatalytic degradationrdquoApplied Catalysis B vol 58 pp 185ndash191 2005

[25] J Zhang D Fu Q Peng L Deng and X Yang ldquoFe3+-assistedphotocatalytic oxidation of sulfamethazine in TiO

2suspended

solutionrdquo Fresenius Environmental Bulletin vol 20 no 4 pp1051ndash1056 2011

[26] I A Alaton I A Balcioglu and D W Bahnemann ldquoAdvancedoxidation of a reactive dyebath effluent Comparison of O

3

H2O2UV-C and TiO

2UV-A processesrdquo Water Research vol

36 no 5 pp 1143ndash1154 2002[27] P A Pekakis N P Xekoukoulotakis and D Mantzavinos

ldquoTreatment of textile dyehouse wastewater by TiO2photocatal-

ysisrdquoWater Research vol 40 no 6 pp 1276ndash1286 2006[28] C C Liu Y H Hsieh P F Lai C H Li and C L Kao ldquoPho-

todegradation treatment of azo dye wastewater by UVTiO2

processrdquo Dyes and Pigments vol 68 no 2-3 pp 191ndash195 2006[29] J C Garcia J I Simionato A E C Silva J Nozaki and N E de

Souza ldquoSolar photocatalytic degradation of real textile effluentsby associated titanium dioxide and hydrogen peroxiderdquo SolarEnergy vol 83 no 3 pp 316ndash322 2009

[30] W Baran E Adamek and A Makowski ldquoThe influence ofselected parameters on the photocatalytic degradation of azo-dyes in the presence of TiO

2aqueous suspensionrdquo Chemical

Engineering Journal vol 145 no 2 pp 242ndash248 2008[31] ldquoMethods for Chemical Analysis of Water and Wastes Chem-

ical Oxygen Demand Titrimetric Methods 4101-3rdquo US EPAUnited States Environmental Protection Agency Office ofResearch and Development Washington DC USA EPA6004-79020 pp 443ndash451 March 1983 httpnepisepagov

[32] W Baran A Makowski and W Wardas ldquoChanges in CODvalues in aqueous solutions of the selected azo dyes duringthe photocatalytic degradation processrdquo in Micropollution inthe Human Environment vol 51 pp 215ndash221 CzestochowaUniversity of Technology Publishing House CzestochowaPoland 2003

[33] W Baran J Sochacka andWWardas ldquoToxicity and biodegrad-ability of sulfonamides and products of their photocatalytic

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

2 International Journal of Photoenergy

surface [16ndash19] The photocatalytic degradation of pollutantsin the presence of Fe(III) salts has been also presented in theliterature [20ndash22] but there are only few papers describingphotocatalytic properties of TiO

2FeCl3mixture [23ndash25] It

was found that a combination of Fe3+ ions and TiO2in

suspension showed a positive synergistic effect acceleratingthe photodegradation of organic pollutants [24 25]Howevernone of these papers related to the degradation of azo dyes inreal wastewaters

Most of the experiments were conducted in artificial sys-tems with the use of aqueous solutions (often distilled water)that do not mimic the conditions like in real wastewaterMeanwhile real dyes effluents commonly contain unuseddyes inorganic ions and other organic substances thatcan significantly slow down the photocatalytic degradationefficiency of contaminants So far there are some papersand reports concerning treatment of real dye wastewaterusing photocatalytic processes [26ndash29] but they demandmore profound investigations The main objective of thestudy was to compare the efficiency of photodegradation anddecolorization processes carried out in the presence of TiO

2

and FeCl3as well as in the mixture of TiO

2FeCl3during

the treatment of raw real effluents including azodyes Weintended to test four types of wastewaters from large textilefactory industrial tannery and two from small manufac-turies

2 Experimental

21 Characteristics of the Used Effluents The used raw efflu-ents (without dilution and pretreatment) were obtained fromthe industrial scale dyeing of cotton (WCot) polyacrylicfibers (WPac) leathers (WLeat) and flax fabrics (WFlax)They contained auxiliary substances used during the dyeingprocess and also in the case of WLeat municipal wastes andtannins Physical and chemical characteristics of effluents arepresented in Table 1 A criterion for choice of wastewater wasthe presence of azo dyes resistant to biological degradationThe analyzed wastes differed due to the type of used tech-nology and the type of dyed materials Dyes contained inwastewaters were stable and did not undergo biodegradationduring the storage by a period of 28 days in room tempera-ture To remove sulfides wastes were intensively aerated for30min before commencement of the experiments

22 Characteristics of Photocatalysts Titanium (IV) dioxidepowder (TiO

2) used as the photocatalyst was obtained from

Riedel de Haen (anatase 100 a mean BET surface area of 9ndash11m2 gminus1 residues on filter gt40120583m after dispersion in waterlt002 pHpzc = 300 plusmn 005) [30] During preliminarystudies it was found that during decolorization of cationicdyes solutions this catalyst wasmore effective than TiO

2-P25

Moreover its mixture with FeCl3was more effective during

decolorization of anionic dyes in distilledwater than thatwithTiO2-P25 [23]

The iron (III) chloride (FeCl3sdot6H2O) and all other

chemicals used for analysis were purchased from POCH(Poland) and were of analytical grade Freshly prepared

UV lamps

Cold airStirrer

Glasscrystallizer

Sample

Figure 1 The scheme of test stand

FeCl3stock solution in distilled water (10mol Lminus1) or solid

TiO2(25 g Lminus1) or a mixture of TiO

2(25 g Lminus1) and FeCl

3

(10mol Lminus1) was added to 100mL of effluents The concen-trations of TiO

2and FeCl

3were established as optimal based

on preliminary published experiments [23] and according tothe unpublished data The used amount of FeCl

3solution

was determined experimentally in such manner that after itsaddition to effluent the pH of sample was about 3 (Table 2)

23 Irradiation Before irradiation the samples with TiO2

were stirred magnetically for 20min in the dark to ensurethe complete equilibrium between adsorptiondesorptionprocesses of organic compounds on the photocatalyst surface

In all experiments five open glass crystallizers (volume500mL the exposed surface 102 cm2) containing 100mL ofeffluent with catalysts were irradiated by four UV-a lamps(Philips TL-40 W05 at 120582max 366 nm) in order to ensure thesteady-state illumination of the entire surface of crystallizersThe intensity of UV-a and VIS radiation measured by theQuantum-foto radiometer DO9721 (Delta OHM) was 535and 120Wmminus2 respectively The scheme of the test stand isshown in Figure 1

During the whole experiment all samples were inten-sively stirred at a constant speed and had a free contact withatmospheric air but were not aerated additionally Duringirradiation the concentration of dissolved oxygen in thesamples was gt80 The initial temperature of samples was20 plusmn 2

∘C The pH and concentration of oxygen dissolved inirradiated samples were measured by multimeter HD225692(Delta OHM)

24 The Analysis After the appropriate irradiation time (0ndash300min) samples were centrifuged for 30min at 4000 rpmat room temperature (MPW-360 centrifuge Poland) TheUV-VIS spectra of the irradiated effluents in the rangefrom 200 to 800 nm were recorded by spectrophotometer(Secoman S-750) in 1 cm quartz cuvettes The concentrationsof dyes in samples were determined using HPLC method(HPLC D-7000 Merck detector UV VIS Hitachi-L 7400column Supelcosil LC-185 120583m 250mmtimes 46mm mobile

International Journal of Photoenergy 3

Table1Th

echaracteristicso

fthe

investigated

dyee

ffluents

Effluent

from

dyeing

processo

f

Dyeing

techno

logy

Abbreviatio

nin

text

Azo

dyes

ineffl

uents

Other

substances

ineffl

uents

pHCO

D(m

gO2

1)

Max

ofabsorbance

(120582max)inraweffl

uents

Com

ments

CIname

Chem

ical

character

Polyacrylic

fibres

Con

tinuo

usprocess

WPac

Basic

Yello

w28

Basic

Red22

Basic

Blue

41Ba

sicBlack

Catio

nic

Catio

nic

Catio

nic

Catio

nic

Thickener(Prisu

lon)

Auxiliary

agents

(RoksolPAN3K

)Glutaric

acids

44plusmn01

1440

0262(340

nm)

0159(430

nm)

0166(540

nm)

0199(610nm

)

Biologically

stablea

Acid

Red88

Anion

ic

Leather

Batch

process

WLeat

Acid

Blue

193

Anion

iclt10of

tann

erywastes

70plusmn01

460

0365(510nm

)0075(620

nm)

Biologically

unstable

c

Other

dyes

bAnion

ic

Flax

fabric

Batch

process

WFlax

Unk

nown

Anion

icUnk

nown

69plusmn01

910

0965(350

nm)d

Biologically

stablea

Cottonfabric

Batch

process

WCot

Dire

ctBlack22

Anion

icUnk

nown

82plusmn02

8930

4005(480

nm)

Biologically

stablea

a Theb

iologicalstabilityo

fdyeingeffl

uent

was

estim

ated

basedon

changesintheira

ppearance(changesinUV-VIS

spectrum

precipitatio

nof

sediments)and

theird

igestio

ndu

ringthes

torage

perio

dof

28days

(at

20∘Cun

dera

naerob

iccond

ition

s)

b Onlyin

tracea

mou

nts

c Effluentsw

ered

igesteddu

ringshort-tim

estorage

(abo

utfewho

urs)bu

ttheirabsorbance

at120582510nm

didno

tund

ergo

significantchanges

d Absorptionband

with

outany

clearm

axim

um

4 International Journal of Photoenergy

Table 2 The concentrations of reagents used and experimentalconditions

Effluent FeCl3(mmol Lminus1)

TiO2(g Lminus1) pHa

Concentration of Fe(III)in irradiated effluenta

(mmol Lminus1)10 mdash 33 ndb

WPac mdash 25 44 mdash10 25 36 ndb

mdash mdash 31 002WLeat mdash 25 70 mdash

15 25 34 00415 mdash 32 030

WFlax mdash 25 63 mdash15 25 32 03013 mdash 30 280

WCot mdash 25 88 mdash13 25 28 182

aAt the beginning of UV-a irradiation bno data

phase 10mM K2HPO4at pH 90CH

3CN in the ratio 95 5

for WLeat WFlax and WCot and 20mM acetic buffer atpH 48CH

3CN in the ratio 6 4 for WPac resp) Before

HPLC analysis water-insoluble sediments containing Fe(III)compounds with components of effluents were dissolvedafter adding the concentrated HCl (to pH lt 1) or NaOH(to pH asymp 13) The chemical oxygen demand (COD)was estimated by titration method (US EPA 4101-3) [31]Additionally dyes degradation in effluents was determinedspectrophotometrically based on the decrease of peaks oncharacteristic wavelengths at 120582max (Table 3) The analysis ofthe intermediate products was not performed because it wasnot the main aim of this study

25 Results Elaboration The degree of degradation for par-ticular dyes (119883

119894) was calculated based on the results obtained

from HPLC method according to the following equation

119883119894= 100 sdot (1 minus

119878119894

119878119900

) (4)

where 119878119894is the peak area corresponding to the undecomposed

dye after the irradiation of wastewater and 119878119900is the peak area

corresponding to the dye before the irradiationIts means that any transformation of dye occurring as a

result of the irradiation in the presence of a photocatalystwas considered as its degradation In this sense the dyedegradation does not mean its mineralization In the case ofazo dyes their degradation will mean their decompositionto lower and simpler organic compounds by breaking of azobonds

The reaction rate constant for dyes photodegradation(119896119883119894) was determined as for the pseudo first-order reaction

that is as the slope of the following linear dependency

ln119878119900

119878119894

= 119891 (119905) (5)

Reduction of color in the physical process only (119884)was calculated based on the absorbance of raw centrifugedeffluents (119860

119900) and the absorbance of the same effluents but

after addition of the catalyst (TiO2andor FeCl

3) and after

centrifugation (119860119884) as follows

119884 = 100 sdot (1 minus119860119884

119860119900

) (6)

In these cases the photocatalyst-containing samples were notexposed to irradiation that is the photocatalytic processesdid not proceed in them but only adsorption coagulationflocculation and precipitation In some samples the additionof FeCl

3resulted in an increased intensity of color in effluents

so the 119884 value was negativeReduction of color in the photocatalytic process only

(119885) was determined based on the absorbance of centrifugedeffluents with catalysts (TiO

2andor FeCl

3) (119860119884) and the

absorbance of the same effluents but after their irradiationwith these catalysts (119860

119911) as follows

119885 = 100 sdot (1 minus119860119885

119860119884

) (7)

In these cases the reason of effluents decolorationmay be thephotocatalytic process only

The rate constant for dyes photodecolorization (119896119885119894) was

determined as the slope of the following linear function

ln 119860119884119860119885

= 119891 (119905) (8)

Total decolorization of effluents (Total) was calculatedusing the following formula

Total = 100 sdot (1 minus119860119911

119860119900

) (9)

COD removal (119877COD) was determined based on thefollowing equation

119877COD = 100 sdot (1 minusCOD300

CODo) (10)

where CODo was determined in raw effluents and COD300

was determined in the same effluents but after 300min ofUV-a irradiation in the presence of TiO

2andor FeCl

3

3 Results and Discussion

31 Effect of FeCl3 The high photocatalytic activity of Fe(III)salts in model solutions is related to their partial hydrolysisproducts namely Fe(OH)2+ ions that show the maximumphotocatalytic activity in the pH asymp 3 [13] The additionof FeCl

3to effluent samples caused precipitation of water-

insoluble matter (with the exception of WPac) and almosttotal their decolorization (Table 3) However the UV-a irra-diation for 60min did not cause significant changes inUV-Visspectra and in HPLC chromatograms for any of the analyzedsamples Additionally after a prolonged irradiation time to

International Journal of Photoenergy 5

Table3Th

eresultsof

thetreatmento

fdye

effluents

Dyesd

egradatio

naft

erRe

ductionof

color

Effluent120582max(nm)

Photocatalytic

syste

m60

min

ofirr

adiatio

nIn

thep

hotocatalytic

process

Inthep

hysic

alprocesses

Y(

)

Totald

ecolorizationof

effluentsa

t120582max

CODremovalaft

er300m

inaft

er60

min

ofirr

adiatio

nTo

tal()

ofirr

adiatio

n119877COD(

)

X(

)119896119883(m

inminus1)

Z(

)119896119885(m

inminus1)

FeCl

3sim0

sim0

2sim0

minus60

6minus593

340

TiO

237

0008plusmn0002

26000

6plusmn0002

328

TiO

2FeCl

310

0002plusmn0001

780024plusmn0003

minus347

1

FeCl

3sim0

sim0

sim0

sim0

minus147

minus155

430

TiO

258

0014plusmn0003

360008plusmn0002

440

WPac

TiO

2FeCl

317

0003plusmn0002

490010plusmn0002

minus76

11sim0149

a

FeCl

3sim0

sim0

sim0

sim0

minus17

minus20

540

TiO

286

0030plusmn0005

570014plusmn0002

358

TiO

2FeCl

340

0008plusmn0002

22000

4plusmn0001

minus7

17

FeCl

3nd

bnd

3sim0

47

610

TiO

2nd

nd

830030plusmn000

44

84TiO

2FeCl

3nd

nd

35000

6plusmn0002

1142

FeCl

3sim0

sim0

sim0

sim0

9595

510

TiO

224

(63)

c000

4plusmn0002

110002plusmn000

014

24

WLeat

TiO

2FeCl

3sim30

(100)c

0005plusmn0001

110002plusmn0001

9595

sim040

15a

FeCl

3nd

nd

sim0

sim0

100

100

620

TiO

2nd

nd

210003plusmn0001

1836

TiO

2FeCl

3nd

nd

100

mdash96

100

FeCl

3sim0e

sim0

10lt0001

5053

sim0

WFlax

350d

TiO

210

e0001plusmn

0001

220003plusmn0002

sim0

22minus40

TiO

2FeCl

335divide42

e0008plusmn0002

500011plusmn

0003

3366

minus33

FeCl

3sim0(0)c

sim0

sim0c

sim0

9696

csim0

WCot

480

TiO

2sim0(5)c

sim0

5csim0

sim0

5c11

TiO

2FeCl

3sim0(5)c

sim0

5csim0

9796

c7

a Inthep

resenceo

fFeC

l 3TiO2andTiO2FeCl

3respectiv

elybno

datacaft

er300m

inof

UV-airadiation

d absorptionband

with

outclear

maxim

umebasedon

thep

eakarea

measurementat4

80nm

usingHPL

Cmetho

d

6 International Journal of Photoenergy

300min no significant changes in chromatograms and inCOD values were observed

After the dissolution of water insoluble Fe-organic com-plexes chromatograms of samples (before and after UVirradiation) remained practically unchanged This observa-tion indicates that during UV-a irradiation of effluents withFe(III) salt only dyes did not undergo the photocatalyticdegradationThe use of FeCl

3and probably also other Fe(III)

salts as a catalyst in the photocatalytic treatment processof dye effluents is completely ineffective (after 60min ofirradiation the photodegradation efficiency was in the rangeof 0) Therefore under model conditions model Fe(OH)2+ions can have photocatalytic activity at pH 3 but in realwastewater samples for example in dye effluents they mayact as a coagulant only

32 Effect of TiO2 After centrifugation of nonirradiatedsamples with TiO

2 no significant changes in UV-VIS spec-

tra (Figure 2) and HPLC chromatograms were observedSimultaneously in all effluent samples the photocatalyst wascoagulated only in a negligible level

As can be seen from the UV-VIS spectra shown inFigure 2(a) after UV-a irradiation of samples containingcationic dyes (WPac) with TiO

2for 60min the effluent

underwent high decolorization resulting in a completelycolorless effluent The disappearance of the absorption bands(120582max at 340 430 520 and 610 nm) suggests that the chro-mophore groups responsible for color progressively breakdown during UV-a irradiation Therefore in the case ofcationic dyes the effluent decolorization was almost exclu-sively the result of the photocatalytic process and only ina small degree due to physical processes such as precipita-tion coagulation or sorption The degradation efficiency ofcationic dyes was in the range of 37ndash86 but the CODremoval was low even after 300min of irradiation and wasonly 14 (Table 3)

The decolorization (a decrease in absorbance) was alsoobserved in WLeat and WFlax effluents containing anionicdyes (Figures 2(b) and 2(c)) After irradiation of samplesin the presence of TiO

2 a decrease of absorbance at 510

and 620 nm for WLeat and a decrease of a continuous band(without any distinctmaximum) forWFlaxwere observed Inthe case of effluent resulting from dyeing of leather (WLeat)decolorization was the result of both the photodegrada-tion and the physical processes The maximum degradationdegree of one of the dyes namely Acid Red 88 was 63 after300min of UV-a irradiation (Table 3)

On the other hand WFlax effluents irradiated for 60minwith TiO

2exhibited lower dyes degradation in the range

of 10 The UV-a irradiation for 300min caused a decreasein COD value about 40 in WLeat effluents and on thecontrary an increase in COD value of 40 in WFlax(Table 3)

As shown in Figure 2(d) in effluents from cotton dyeingprocesses (WCot) decolorization and changes inHPLCchro-matograms practically were not observed The degradationdegree of dye was lt5 even after 300min UV-a irradiationIn these samples the degradation efficiency was very low

probably because of less transmission of UV-a light throughthe black effluents Additionally WCot samples containinghigh concentration of dye (Direct Black 22) had the highestCOD over 8900mg O

2Lminus1 Therefore after 300min of

irradiation the COD removal was about 11 (Table 3)The photodegradation of compounds duringin hetero-

geneous photocatalysis depends among other factors on thechemical properties of substrates and their adsorption abilityonto the photocatalyst surface [11] In accordance to hetero-geneous catalysis theory (Langmuir- Himselwood model)the increase in adsorption of dyes causes the increase in thephotocatalytic degradation rate Additionally TiO

2shows an

amphoteric character and its photocatalytic activity dependsalso on the pH of samples In the case of the investigated TiO

2

(pure anatase) the determined pH value of the point of zerocharge (pHpzc) was 300 In the used dyes effluents the pHswere always higher than pHpzc and therefore TiO

2surface

should be negatively charged as follows

Ti ndashOH2

+pHltpHpzclArrrArr TindashOH

pHgtpHpzclArrrArr TiOminus (11)

This fact may explain the higher adsorption and higher pho-todegradation ability of cationic dyes (inWPac effluents) andlower adsorption of anionic dyes (WCot andWFlax) onto theTiO2surface under the studied conditions However it does

not simply explain high degradation of anionic dyes inWLeateffluents The adsorption process onto TiO

2surface under

UV-irradiation conditions is complex and some differencesin an adsorption capacity of particles may occur Probablya higher removal of COD in WLeat can be attributed to theadsorption of increased amounts of undissociated particles(eg anionic dyeswith organic or inorganic ions) on the TiO

2

surface Additionally the organic compounds in WLeat thatis dyes surfactant agents and auxiliaries were rather photolabile and they were easily transformed to less stable organics(byproducts)

33 Effect of TiO2FeCl3 As shown in Figure 3 the additionof TiO

2FeCl3mixture to nonirradiated effluents caused a

significant coagulation and decolorization of all samplesTherefore in these processes Fe salts could play a roleof coagulant However UV-a irradiation of such samplesresulted in their decolorization (Figure 3 Table 3) and thismay indicate its role as a photosensitizer

It was found that the photocatalytic degradation in efflu-ent containing cationic dyes (WPac) was less effective in themixture of TiO

2FeCl3than in the presence of TiO

2alone

(Table 3) After 60min of UV-a irradiation the degradationefficiency of dyes was in the range 10ndash40 SimultaneouslyWPac underwent the effective decolorization which can beexplained only as the dyes photodegradation (Figure 3(a))This process was not inhibited by strong coagulation ofphotocatalysts and by auxiliary substances contained in thesesamples After the addition of TiO

2FeCl3but before UV-

a irradiation absorbance in WPac effluent at 120582 lt 500 nmwas significantly higher due to the presence of dissolvedFe(III) compounds (dashed line) The data concerning CODremoval indicate that the efficiency of WPac mineralizationafter 300min of UV-a irradiation reached only 9

International Journal of Photoenergy 7

0

005

01

015

02

025

03

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(b)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriz

atio

n (

)

(c)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(d)

Figure 2 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent 119860

119900 dotted line (blue) effluent with TiO

2 without UV-a irradiation 119860

119884 solid line (blue) effluent with TiO

2 after UV-a irradiation

119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and after UV-a irradiation ( ⃝) decolorization of effluent as a result of the

photocatalytic process in the presence of TiO2(25 g Lminus1) and after UV-a irradiation

On the contrary effluents containing anionic dyes(WLeat and WFlax) underwent the photocatalytic degra-dation more effectively in the presence of TiO

2FeCl3than

in TiO2alone (Table 3) Upon UV-a irradiation there were

continuous decreases in absorbance all along the spectrameaning the fragmentation of organic structures and thephotocatalytic degradation of dyes (Figures 3(b) and 3(c))As shown in Table 2 the complete removal of Acid Red 88fromWLeat was the result of both direct precipitation andoradsorption on the photocatalyst surface and photodegrada-tion process The degradation efficiency of this dye was highand reached even 100 after 300min of UV-a irradiation(Table 3)Thedecolorization ofWFlaxwas caused to a greaterextent by the photocatalytic process than coagulation andor

precipitation (Figure 3(c)) The dyes degradation was in therange 35ndash42 after 60min of UV-a irradiation Removal ofCOD in WLeat in the presence of TiO

2FeCl3was 15 and

was lower than in the presence of TiO2alone On the other

hand similarly as during irradiation of WFlax with TiO2

alone after 300min of UV-a irradiation with TiO2FeCl3

there was not a decrease of COD value but its increaseIn our opinion an increase in COD removal upon UV-

a irradiation of WFlax with TiO2and TiO

2FeCl3is only

provisional This effect can be explained by an increase in theconcentration of smaller organics molecules formed duringthe photocatalytic oxidation of dyes and suspended solidsMost of the decomposable compounds are removed in theinitial time of this process and the remained part of organic

8 International Journal of Photoenergy

0

01

02

03

04

05

06

07

08

09

1

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

Abs

orba

nce

Dec

olor

izat

ion

()

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(b)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriza

tion

()

(c)

Abs

orba

nce

Dec

olor

izatio

n (

)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(d)

Figure 3 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent119860

119900 dotted line (blue) effluent with TiO

2and FeCl

3but without UV-a irradiation119860

119884 solid line (blue) effluent with TiO

2 FeCl

3and

after UV-a irradiation 119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and FeCl

3(10 mmol Lminus1) and after UV-a irradiation ( ⃝)

decolorization of effluent as a result of the photocatalytic process in the presence of TiO2(25 g Lminus1) FeCl

3(10mmol Lminus1) and after UV-a

irradiation

pollutants for example lower molecular weight carboxylicacids aldehydes and ketones can be less removable Thesebyproducts may not be completely mineralized by K

2Cr2O7

because they are quite resistant and their chemical oxida-tion can be the rate-limiting step in oxidation processesTherefore they require more severe oxidation conditions ora longer time for their conversion On the other hand theCOD values enable only qualitative rather than quantitativeassessment of the mineralization process [32]

After the addition of TiO2FeCl3toWCot the decoloriza-

tion was found to be almost 100 resulting in a completelycolorless effluent (Figure 3(d)) However the removal ofDirect Black 22 was the result of its precipitation only and not

the photocatalytic process The efficiency of photocatalyticdegradation of this dye after 300min of UV-a irradiation waslt5 (Table 3)

Furthermore the organic load ofWCot effluent irradiatedwith TiO

2FeCl3did not change significantly the COD

removal remained low at a value of about 7 Taking intoaccount the high chemical stability of dye (Direct Black 22)in WCot as well as its high concentration in effluent thephotocatalytic degradation of WCot in the presence of TiO

2

and TiO2FeCl3is not an effective method

An estimation of the efficiency of the studied photo-catalytic systems (TiO

2and TiO

2FeCl3) used during the

photocatalytic degradation of real effluents also depends on

International Journal of Photoenergy 9

the chemical properties of dyes and on the possibility offormation of coordination compounds with Fe3+ ions

In the case of effluents containing cationic dyes (WPac)the addition of Fe(III) salt was unfavorable because the effi-ciency of photodegradation of these dyes and COD removalwere lower than that in the presence of TiO

2only The

explanation of this result can be the change of charge ofTiO2particles (in the presence of Fe3+ ions) that limits the

possibility of sorption of the positively charged particles ofcationic dyes

In the case of effluents containing anionic dyes (WLeatand WFlax) the presence of Fe3+ ions had a beneficialeffect on the efficiency of photocatalytic degradation of thesecompoundsThe possible explanations may be a formation ofphotoactive complexes between dyes particles and Fe3+ ionsthat absorb UV-a irradiation much better than individualmolecules of dyes or an adsorption of complexes of dyes withFe3+ ions on the photocatalyst surface

The investigated dyes effluents containing also otherpollutants such as fatty acids sugars and amino acids whichmay also be substrates for the photodegradation and cantherefore compete with the dyes Additionally they maycontain inorganic mobile anions such as Clminus CO

3

2minusSO4

minus2 PO4

3minus and NO3

minus which may significantly affect thedistribution of hydroxyl radicals in the following process

XO119899minus +HO∙ 997888rarr XO∙(119899minus1)minus

+OHminus (12)

As a result these anions at high concentrations candecrease the photodegradation that simultaneously occursbetween HO∙ radicals and dyes molecules

From the viewpoint of COD removal TiO2alone was

a much more effective photocatalyst than TiO2FeCl3 The

increase in COD value in WFlax effluent probably wasconnected with the presence of a very persistent substance(s)that did not undergo the oxidation during the COD deter-mination On the other hand the photocatalytic processleads to degradation of these substances and the obtainedproducts are much less chemically resistant In this aspectthe observed phenomenon is not negative In our publication[33] we have reported similar to other authors [34] that thecomplete photocatalytic degradation of contaminants duringthe treatment of effluents is still not economically feasible dueto high operating costs Therefore the reduction of time ofphotocatalytic process only to the time necessary to initialdegradation of nonbiodegradable substances (eg azo dyes)towards the most readily biodegradable intermediates is themost reasonable It is obvious that one single treatment stepcannot remove all pollutants contained in dyes effluents Theoptimal solution is the combination of different treatmentprocesses for example the photocatalytic degradation usingsunlight as the source of UV light with a biological processIt may significantly decrease the overall cost of the dyeeffluents treatment Additionally the photocatalytic pre-treatment of dyeing effluents can lead to improvement oftheir biodegradability for example initial toxicity inducedby photodegradation of textile antraquinone dye to Vibriafisheri progressively decreased during the course of pro-cess [35] In this way a significant decrease in the overall

cost of the treatment of dyes effluents is expected mainlythrough the combination of several AOPs for example thephotocatalytic degradation as a pretreatment method withbiological processes [36] An increase of biodegradability ofthese effluents would facilitate their subsequent biologicaltreatment and an effective removal of undesirable andorrecalcitrant pollutants making the complete mineralizationunnecessary

4 The Mechanism of WastewaterDecolorization Processes

The experiments confirmed that TiO2caused decolorization

of wastewatermainly due to photocatalytic process Howeverthe decolorization ofWLeat could be a result of dyes sorptiononto TiO

2surface (Table 3)

As previously described FeCl3alone could not be the

cause of decolorization of wastewater during the photocat-alytic process On the other hand the addition of FeCl

3

accelerated undoubtedly the photocatalytic degradation ofanionic dyes According to Mestankova et al this effectwas mainly the result of the synergism of photochemicalactivity between TiO

2and FeCl

3[24] However the results

of experiments showing that FeCl3alone did not exhibit the

photochemical activity in wastewater and it decreased thephotodegradation rate of cationic dyes may indicate otherpossible mechanism It should be noted that even moreimportant is the above described process of intensification ofsorption of dyes coordinated with FeCl

3onto TiO

2surface

[23] The other reason could be the fact that the additionof FeCl

3and simultaneously decrease of pH cause agglom-

eration of suspensions in wastewaters and also increase instability and photoavailability of the TiO

2used [30]

5 Conclusions

Dyeing effluents irradiated in the presence of FeCl3alone

were decolorized but azo dyes almost completely did notundergo degradation On the country the photocatalyticprocess carried out with TiO

2and TiO

2FeCl3as photo-

catalysts was the effective method of decolorization anddyes photodegradation in the investigated effluents (exceptsamples containing high concentration of very stable azodye) During the photocatalytic degradation of anionic dyesa mixture of TiO

2FeCl3was more effective while in the case

of cationic dyes more suitable seems to be TiO2alone

Acknowledgment

This work was supported by the Medical University of Silesia(Grant no KNW-1-043P20)

References

[1] R G Saratale G D Saratale J S Chang and S P GovindwarldquoDecolorization and biodegradation of reactive dyes and dyewastewater by a developed bacterial consortiumrdquo Biodegrada-tion vol 21 no 6 pp 999ndash1015 2010

10 International Journal of Photoenergy

[2] 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

[3] J C Garcia J L Oliveira A E C Silva C C OliveiraJ Nozaki and N E de Souza ldquoComparative study of thedegradation of real textile effluents by photocatalytic reactionsinvolvingUVTiO

2H2O2andUVFe2+H

2O2systemsrdquo Journal

of Hazardous Materials vol 147 no 1-2 pp 105ndash110 2007[4] I M C Goncalves A Gomes R Bras M I A Ferra M T

P Amorim and R S Porter ldquoBiological treatment of effluentcontaining textile dyesrdquoColoration Technology vol 116 pp 393ndash397 2000

[5] M Asgher H N Bhatti S A H Shah M J Asad and R LLegge ldquoDecolorization potential of mixed microbial consortiafor reactive and disperse textile dyestuffsrdquo Biodegradation vol18 no 3 pp 311ndash316 2007

[6] B H Hameed A L Ahmad and K N A Latiff ldquoAdsorptionof basic dye (methylene blue) onto activated carbon preparedfrom rattan sawdustrdquo Dyes and Pigments vol 75 no 1 pp 143ndash149 2007

[7] H Selcuk ldquoDecolorization and detoxification of textile wastew-ater by ozonation and coagulation processesrdquo Dyes and Pig-ments vol 64 no 3 pp 217ndash222 2005

[8] A S Stasinakis ldquoUse of selected advanced oxidation processes(AOPs) for wastewater treatmentmdashamini reviewrdquoGlobal NESTJournal vol 10 pp 376ndash385 2008

[9] R Aplin and T D Waite ldquoComparison of three advancedoxidation processes for degradation of textile dyesrdquo WaterScience and Technology vol 42 no 5-6 pp 345ndash354 2000

[10] I Arslan-Alaton G Tureli and T Olmez-Hanci ldquoTreatmentof azo dye production wastewaters using Photo-Fenton-likeadvanced oxidation processes optimization by response surfacemethodologyrdquo Journal of Photochemistry and Photobiology Avol 202 no 2-3 pp 142ndash153 2009

[11] J M Herrmann ldquoHeterogeneous photocatalysis state of the artand present applicationsrdquoTopics in Catalysis vol 34 no 1ndash4 pp49ndash65 2005

[12] I K Konstantinou and T A Albanis ldquoTiO2-assisted photocat-

alytic degradation of azo dyes in aqueous solution kinetic andmechanistic investigations a reviewrdquo Applied Catalysis B vol49 no 1 pp 1ndash14 2004

[13] W Feng and D Nansheng ldquoPhotochemistry of hydrolyticiron (III) species and photoinduced degradation of organiccompounds A minireviewrdquo Chemosphere vol 41 no 8 pp1137ndash1147 2000

[14] I P Pozdnyakov Y A Sosedova V F Plyusnin et al ldquoPho-todegradation of organic pollutants in aqueous solutions causedby (OH)2+aq photolysis evidence of OH radical formationrdquoInternational Journal of Photoenergy vol 6 no 2 pp 89ndash932004

[15] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalyticdegradation of organic contaminants over titanium dioxidea review of fundamentals progress and problemsrdquo Journal ofPhotochemistry and Photobiology C vol 9 no 1 pp 1ndash12 2008

[16] O K Dalrymple D H Yeh and M A Trotz ldquoRemovingpharmaceuticals and endocrine-disrupting compounds fromwastewater by photocatalysisrdquo Journal of Chemical Technologyand Biotechnology vol 82 no 2 pp 121ndash134 2007

[17] R Rajeswari and S Kanmani ldquoA study on degradation of pes-ticide wastewater by TiO

2photocatalysisrdquo Journal of Scientific

and Industrial Research vol 68 no 12 pp 1063ndash1067 2009

[18] Z F Guo R X Ma and G J Li ldquoDegradation of phenolby nanomaterial TiO

2in wastewaterrdquo Chemical Engineering

Journal vol 119 pp 55ndash59 2006[19] C Jia YWang C Zhang and Q Qin ldquoUV-TiO

2photocatalytic

degradation of landfill leachaterdquo Water Air and Soil Pollutionvol 217 no 1ndash4 pp 375ndash385 2011

[20] V Sarria M Deront P Peringer and C Pulgarin ldquoDegradationof a biorecalcitrant dye precursor present in industrial wastew-aters by a new integrated iron(III) photoassisted-biologicaltreatmentrdquoApplied Catalysis B vol 40 no 3 pp 231ndash246 2003

[21] L Poulain G Mailhot P Wong-Wah-Chung and M BolteldquoPhotodegradation of chlortoluron sensitised by iron(III) aqua-complexesrdquo Journal of Photochemistry and Photobiology A vol159 no 1 pp 81ndash88 2003

[22] C Catastini S Rafqah G Mailhot and M Sarakha ldquoDegra-dation of amitrole by excitation of iron(III) aquacomplexes inaqueous solutionsrdquo Journal of Photochemistry and PhotobiologyA vol 162 no 1 pp 97ndash103 2004

[23] W Baran A Makowski and W Wardas ldquoThe influence ofFeCl3on the photocatalytic degradation of dissolved azo dyes

in aqueous TiO2suspensionsrdquo Chemosphere vol 53 no 1 pp

87ndash95 2003[24] H Mestankova J Krysa J Jirkovsky G Mailhot and M

Bolte ldquoThe influence of Fe(III) speciation on supported TiO2

efficiency example of monuron photocatalytic degradationrdquoApplied Catalysis B vol 58 pp 185ndash191 2005

[25] J Zhang D Fu Q Peng L Deng and X Yang ldquoFe3+-assistedphotocatalytic oxidation of sulfamethazine in TiO

2suspended

solutionrdquo Fresenius Environmental Bulletin vol 20 no 4 pp1051ndash1056 2011

[26] I A Alaton I A Balcioglu and D W Bahnemann ldquoAdvancedoxidation of a reactive dyebath effluent Comparison of O

3

H2O2UV-C and TiO

2UV-A processesrdquo Water Research vol

36 no 5 pp 1143ndash1154 2002[27] P A Pekakis N P Xekoukoulotakis and D Mantzavinos

ldquoTreatment of textile dyehouse wastewater by TiO2photocatal-

ysisrdquoWater Research vol 40 no 6 pp 1276ndash1286 2006[28] C C Liu Y H Hsieh P F Lai C H Li and C L Kao ldquoPho-

todegradation treatment of azo dye wastewater by UVTiO2

processrdquo Dyes and Pigments vol 68 no 2-3 pp 191ndash195 2006[29] J C Garcia J I Simionato A E C Silva J Nozaki and N E de

Souza ldquoSolar photocatalytic degradation of real textile effluentsby associated titanium dioxide and hydrogen peroxiderdquo SolarEnergy vol 83 no 3 pp 316ndash322 2009

[30] W Baran E Adamek and A Makowski ldquoThe influence ofselected parameters on the photocatalytic degradation of azo-dyes in the presence of TiO

2aqueous suspensionrdquo Chemical

Engineering Journal vol 145 no 2 pp 242ndash248 2008[31] ldquoMethods for Chemical Analysis of Water and Wastes Chem-

ical Oxygen Demand Titrimetric Methods 4101-3rdquo US EPAUnited States Environmental Protection Agency Office ofResearch and Development Washington DC USA EPA6004-79020 pp 443ndash451 March 1983 httpnepisepagov

[32] W Baran A Makowski and W Wardas ldquoChanges in CODvalues in aqueous solutions of the selected azo dyes duringthe photocatalytic degradation processrdquo in Micropollution inthe Human Environment vol 51 pp 215ndash221 CzestochowaUniversity of Technology Publishing House CzestochowaPoland 2003

[33] W Baran J Sochacka andWWardas ldquoToxicity and biodegrad-ability of sulfonamides and products of their photocatalytic

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

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CatalystsJournal of

International Journal of Photoenergy 3

Table1Th

echaracteristicso

fthe

investigated

dyee

ffluents

Effluent

from

dyeing

processo

f

Dyeing

techno

logy

Abbreviatio

nin

text

Azo

dyes

ineffl

uents

Other

substances

ineffl

uents

pHCO

D(m

gO2

1)

Max

ofabsorbance

(120582max)inraweffl

uents

Com

ments

CIname

Chem

ical

character

Polyacrylic

fibres

Con

tinuo

usprocess

WPac

Basic

Yello

w28

Basic

Red22

Basic

Blue

41Ba

sicBlack

Catio

nic

Catio

nic

Catio

nic

Catio

nic

Thickener(Prisu

lon)

Auxiliary

agents

(RoksolPAN3K

)Glutaric

acids

44plusmn01

1440

0262(340

nm)

0159(430

nm)

0166(540

nm)

0199(610nm

)

Biologically

stablea

Acid

Red88

Anion

ic

Leather

Batch

process

WLeat

Acid

Blue

193

Anion

iclt10of

tann

erywastes

70plusmn01

460

0365(510nm

)0075(620

nm)

Biologically

unstable

c

Other

dyes

bAnion

ic

Flax

fabric

Batch

process

WFlax

Unk

nown

Anion

icUnk

nown

69plusmn01

910

0965(350

nm)d

Biologically

stablea

Cottonfabric

Batch

process

WCot

Dire

ctBlack22

Anion

icUnk

nown

82plusmn02

8930

4005(480

nm)

Biologically

stablea

a Theb

iologicalstabilityo

fdyeingeffl

uent

was

estim

ated

basedon

changesintheira

ppearance(changesinUV-VIS

spectrum

precipitatio

nof

sediments)and

theird

igestio

ndu

ringthes

torage

perio

dof

28days

(at

20∘Cun

dera

naerob

iccond

ition

s)

b Onlyin

tracea

mou

nts

c Effluentsw

ered

igesteddu

ringshort-tim

estorage

(abo

utfewho

urs)bu

ttheirabsorbance

at120582510nm

didno

tund

ergo

significantchanges

d Absorptionband

with

outany

clearm

axim

um

4 International Journal of Photoenergy

Table 2 The concentrations of reagents used and experimentalconditions

Effluent FeCl3(mmol Lminus1)

TiO2(g Lminus1) pHa

Concentration of Fe(III)in irradiated effluenta

(mmol Lminus1)10 mdash 33 ndb

WPac mdash 25 44 mdash10 25 36 ndb

mdash mdash 31 002WLeat mdash 25 70 mdash

15 25 34 00415 mdash 32 030

WFlax mdash 25 63 mdash15 25 32 03013 mdash 30 280

WCot mdash 25 88 mdash13 25 28 182

aAt the beginning of UV-a irradiation bno data

phase 10mM K2HPO4at pH 90CH

3CN in the ratio 95 5

for WLeat WFlax and WCot and 20mM acetic buffer atpH 48CH

3CN in the ratio 6 4 for WPac resp) Before

HPLC analysis water-insoluble sediments containing Fe(III)compounds with components of effluents were dissolvedafter adding the concentrated HCl (to pH lt 1) or NaOH(to pH asymp 13) The chemical oxygen demand (COD)was estimated by titration method (US EPA 4101-3) [31]Additionally dyes degradation in effluents was determinedspectrophotometrically based on the decrease of peaks oncharacteristic wavelengths at 120582max (Table 3) The analysis ofthe intermediate products was not performed because it wasnot the main aim of this study

25 Results Elaboration The degree of degradation for par-ticular dyes (119883

119894) was calculated based on the results obtained

from HPLC method according to the following equation

119883119894= 100 sdot (1 minus

119878119894

119878119900

) (4)

where 119878119894is the peak area corresponding to the undecomposed

dye after the irradiation of wastewater and 119878119900is the peak area

corresponding to the dye before the irradiationIts means that any transformation of dye occurring as a

result of the irradiation in the presence of a photocatalystwas considered as its degradation In this sense the dyedegradation does not mean its mineralization In the case ofazo dyes their degradation will mean their decompositionto lower and simpler organic compounds by breaking of azobonds

The reaction rate constant for dyes photodegradation(119896119883119894) was determined as for the pseudo first-order reaction

that is as the slope of the following linear dependency

ln119878119900

119878119894

= 119891 (119905) (5)

Reduction of color in the physical process only (119884)was calculated based on the absorbance of raw centrifugedeffluents (119860

119900) and the absorbance of the same effluents but

after addition of the catalyst (TiO2andor FeCl

3) and after

centrifugation (119860119884) as follows

119884 = 100 sdot (1 minus119860119884

119860119900

) (6)

In these cases the photocatalyst-containing samples were notexposed to irradiation that is the photocatalytic processesdid not proceed in them but only adsorption coagulationflocculation and precipitation In some samples the additionof FeCl

3resulted in an increased intensity of color in effluents

so the 119884 value was negativeReduction of color in the photocatalytic process only

(119885) was determined based on the absorbance of centrifugedeffluents with catalysts (TiO

2andor FeCl

3) (119860119884) and the

absorbance of the same effluents but after their irradiationwith these catalysts (119860

119911) as follows

119885 = 100 sdot (1 minus119860119885

119860119884

) (7)

In these cases the reason of effluents decolorationmay be thephotocatalytic process only

The rate constant for dyes photodecolorization (119896119885119894) was

determined as the slope of the following linear function

ln 119860119884119860119885

= 119891 (119905) (8)

Total decolorization of effluents (Total) was calculatedusing the following formula

Total = 100 sdot (1 minus119860119911

119860119900

) (9)

COD removal (119877COD) was determined based on thefollowing equation

119877COD = 100 sdot (1 minusCOD300

CODo) (10)

where CODo was determined in raw effluents and COD300

was determined in the same effluents but after 300min ofUV-a irradiation in the presence of TiO

2andor FeCl

3

3 Results and Discussion

31 Effect of FeCl3 The high photocatalytic activity of Fe(III)salts in model solutions is related to their partial hydrolysisproducts namely Fe(OH)2+ ions that show the maximumphotocatalytic activity in the pH asymp 3 [13] The additionof FeCl

3to effluent samples caused precipitation of water-

insoluble matter (with the exception of WPac) and almosttotal their decolorization (Table 3) However the UV-a irra-diation for 60min did not cause significant changes inUV-Visspectra and in HPLC chromatograms for any of the analyzedsamples Additionally after a prolonged irradiation time to

International Journal of Photoenergy 5

Table3Th

eresultsof

thetreatmento

fdye

effluents

Dyesd

egradatio

naft

erRe

ductionof

color

Effluent120582max(nm)

Photocatalytic

syste

m60

min

ofirr

adiatio

nIn

thep

hotocatalytic

process

Inthep

hysic

alprocesses

Y(

)

Totald

ecolorizationof

effluentsa

t120582max

CODremovalaft

er300m

inaft

er60

min

ofirr

adiatio

nTo

tal()

ofirr

adiatio

n119877COD(

)

X(

)119896119883(m

inminus1)

Z(

)119896119885(m

inminus1)

FeCl

3sim0

sim0

2sim0

minus60

6minus593

340

TiO

237

0008plusmn0002

26000

6plusmn0002

328

TiO

2FeCl

310

0002plusmn0001

780024plusmn0003

minus347

1

FeCl

3sim0

sim0

sim0

sim0

minus147

minus155

430

TiO

258

0014plusmn0003

360008plusmn0002

440

WPac

TiO

2FeCl

317

0003plusmn0002

490010plusmn0002

minus76

11sim0149

a

FeCl

3sim0

sim0

sim0

sim0

minus17

minus20

540

TiO

286

0030plusmn0005

570014plusmn0002

358

TiO

2FeCl

340

0008plusmn0002

22000

4plusmn0001

minus7

17

FeCl

3nd

bnd

3sim0

47

610

TiO

2nd

nd

830030plusmn000

44

84TiO

2FeCl

3nd

nd

35000

6plusmn0002

1142

FeCl

3sim0

sim0

sim0

sim0

9595

510

TiO

224

(63)

c000

4plusmn0002

110002plusmn000

014

24

WLeat

TiO

2FeCl

3sim30

(100)c

0005plusmn0001

110002plusmn0001

9595

sim040

15a

FeCl

3nd

nd

sim0

sim0

100

100

620

TiO

2nd

nd

210003plusmn0001

1836

TiO

2FeCl

3nd

nd

100

mdash96

100

FeCl

3sim0e

sim0

10lt0001

5053

sim0

WFlax

350d

TiO

210

e0001plusmn

0001

220003plusmn0002

sim0

22minus40

TiO

2FeCl

335divide42

e0008plusmn0002

500011plusmn

0003

3366

minus33

FeCl

3sim0(0)c

sim0

sim0c

sim0

9696

csim0

WCot

480

TiO

2sim0(5)c

sim0

5csim0

sim0

5c11

TiO

2FeCl

3sim0(5)c

sim0

5csim0

9796

c7

a Inthep

resenceo

fFeC

l 3TiO2andTiO2FeCl

3respectiv

elybno

datacaft

er300m

inof

UV-airadiation

d absorptionband

with

outclear

maxim

umebasedon

thep

eakarea

measurementat4

80nm

usingHPL

Cmetho

d

6 International Journal of Photoenergy

300min no significant changes in chromatograms and inCOD values were observed

After the dissolution of water insoluble Fe-organic com-plexes chromatograms of samples (before and after UVirradiation) remained practically unchanged This observa-tion indicates that during UV-a irradiation of effluents withFe(III) salt only dyes did not undergo the photocatalyticdegradationThe use of FeCl

3and probably also other Fe(III)

salts as a catalyst in the photocatalytic treatment processof dye effluents is completely ineffective (after 60min ofirradiation the photodegradation efficiency was in the rangeof 0) Therefore under model conditions model Fe(OH)2+ions can have photocatalytic activity at pH 3 but in realwastewater samples for example in dye effluents they mayact as a coagulant only

32 Effect of TiO2 After centrifugation of nonirradiatedsamples with TiO

2 no significant changes in UV-VIS spec-

tra (Figure 2) and HPLC chromatograms were observedSimultaneously in all effluent samples the photocatalyst wascoagulated only in a negligible level

As can be seen from the UV-VIS spectra shown inFigure 2(a) after UV-a irradiation of samples containingcationic dyes (WPac) with TiO

2for 60min the effluent

underwent high decolorization resulting in a completelycolorless effluent The disappearance of the absorption bands(120582max at 340 430 520 and 610 nm) suggests that the chro-mophore groups responsible for color progressively breakdown during UV-a irradiation Therefore in the case ofcationic dyes the effluent decolorization was almost exclu-sively the result of the photocatalytic process and only ina small degree due to physical processes such as precipita-tion coagulation or sorption The degradation efficiency ofcationic dyes was in the range of 37ndash86 but the CODremoval was low even after 300min of irradiation and wasonly 14 (Table 3)

The decolorization (a decrease in absorbance) was alsoobserved in WLeat and WFlax effluents containing anionicdyes (Figures 2(b) and 2(c)) After irradiation of samplesin the presence of TiO

2 a decrease of absorbance at 510

and 620 nm for WLeat and a decrease of a continuous band(without any distinctmaximum) forWFlaxwere observed Inthe case of effluent resulting from dyeing of leather (WLeat)decolorization was the result of both the photodegrada-tion and the physical processes The maximum degradationdegree of one of the dyes namely Acid Red 88 was 63 after300min of UV-a irradiation (Table 3)

On the other hand WFlax effluents irradiated for 60minwith TiO

2exhibited lower dyes degradation in the range

of 10 The UV-a irradiation for 300min caused a decreasein COD value about 40 in WLeat effluents and on thecontrary an increase in COD value of 40 in WFlax(Table 3)

As shown in Figure 2(d) in effluents from cotton dyeingprocesses (WCot) decolorization and changes inHPLCchro-matograms practically were not observed The degradationdegree of dye was lt5 even after 300min UV-a irradiationIn these samples the degradation efficiency was very low

probably because of less transmission of UV-a light throughthe black effluents Additionally WCot samples containinghigh concentration of dye (Direct Black 22) had the highestCOD over 8900mg O

2Lminus1 Therefore after 300min of

irradiation the COD removal was about 11 (Table 3)The photodegradation of compounds duringin hetero-

geneous photocatalysis depends among other factors on thechemical properties of substrates and their adsorption abilityonto the photocatalyst surface [11] In accordance to hetero-geneous catalysis theory (Langmuir- Himselwood model)the increase in adsorption of dyes causes the increase in thephotocatalytic degradation rate Additionally TiO

2shows an

amphoteric character and its photocatalytic activity dependsalso on the pH of samples In the case of the investigated TiO

2

(pure anatase) the determined pH value of the point of zerocharge (pHpzc) was 300 In the used dyes effluents the pHswere always higher than pHpzc and therefore TiO

2surface

should be negatively charged as follows

Ti ndashOH2

+pHltpHpzclArrrArr TindashOH

pHgtpHpzclArrrArr TiOminus (11)

This fact may explain the higher adsorption and higher pho-todegradation ability of cationic dyes (inWPac effluents) andlower adsorption of anionic dyes (WCot andWFlax) onto theTiO2surface under the studied conditions However it does

not simply explain high degradation of anionic dyes inWLeateffluents The adsorption process onto TiO

2surface under

UV-irradiation conditions is complex and some differencesin an adsorption capacity of particles may occur Probablya higher removal of COD in WLeat can be attributed to theadsorption of increased amounts of undissociated particles(eg anionic dyeswith organic or inorganic ions) on the TiO

2

surface Additionally the organic compounds in WLeat thatis dyes surfactant agents and auxiliaries were rather photolabile and they were easily transformed to less stable organics(byproducts)

33 Effect of TiO2FeCl3 As shown in Figure 3 the additionof TiO

2FeCl3mixture to nonirradiated effluents caused a

significant coagulation and decolorization of all samplesTherefore in these processes Fe salts could play a roleof coagulant However UV-a irradiation of such samplesresulted in their decolorization (Figure 3 Table 3) and thismay indicate its role as a photosensitizer

It was found that the photocatalytic degradation in efflu-ent containing cationic dyes (WPac) was less effective in themixture of TiO

2FeCl3than in the presence of TiO

2alone

(Table 3) After 60min of UV-a irradiation the degradationefficiency of dyes was in the range 10ndash40 SimultaneouslyWPac underwent the effective decolorization which can beexplained only as the dyes photodegradation (Figure 3(a))This process was not inhibited by strong coagulation ofphotocatalysts and by auxiliary substances contained in thesesamples After the addition of TiO

2FeCl3but before UV-

a irradiation absorbance in WPac effluent at 120582 lt 500 nmwas significantly higher due to the presence of dissolvedFe(III) compounds (dashed line) The data concerning CODremoval indicate that the efficiency of WPac mineralizationafter 300min of UV-a irradiation reached only 9

International Journal of Photoenergy 7

0

005

01

015

02

025

03

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(b)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriz

atio

n (

)

(c)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(d)

Figure 2 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent 119860

119900 dotted line (blue) effluent with TiO

2 without UV-a irradiation 119860

119884 solid line (blue) effluent with TiO

2 after UV-a irradiation

119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and after UV-a irradiation ( ⃝) decolorization of effluent as a result of the

photocatalytic process in the presence of TiO2(25 g Lminus1) and after UV-a irradiation

On the contrary effluents containing anionic dyes(WLeat and WFlax) underwent the photocatalytic degra-dation more effectively in the presence of TiO

2FeCl3than

in TiO2alone (Table 3) Upon UV-a irradiation there were

continuous decreases in absorbance all along the spectrameaning the fragmentation of organic structures and thephotocatalytic degradation of dyes (Figures 3(b) and 3(c))As shown in Table 2 the complete removal of Acid Red 88fromWLeat was the result of both direct precipitation andoradsorption on the photocatalyst surface and photodegrada-tion process The degradation efficiency of this dye was highand reached even 100 after 300min of UV-a irradiation(Table 3)Thedecolorization ofWFlaxwas caused to a greaterextent by the photocatalytic process than coagulation andor

precipitation (Figure 3(c)) The dyes degradation was in therange 35ndash42 after 60min of UV-a irradiation Removal ofCOD in WLeat in the presence of TiO

2FeCl3was 15 and

was lower than in the presence of TiO2alone On the other

hand similarly as during irradiation of WFlax with TiO2

alone after 300min of UV-a irradiation with TiO2FeCl3

there was not a decrease of COD value but its increaseIn our opinion an increase in COD removal upon UV-

a irradiation of WFlax with TiO2and TiO

2FeCl3is only

provisional This effect can be explained by an increase in theconcentration of smaller organics molecules formed duringthe photocatalytic oxidation of dyes and suspended solidsMost of the decomposable compounds are removed in theinitial time of this process and the remained part of organic

8 International Journal of Photoenergy

0

01

02

03

04

05

06

07

08

09

1

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

Abs

orba

nce

Dec

olor

izat

ion

()

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(b)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriza

tion

()

(c)

Abs

orba

nce

Dec

olor

izatio

n (

)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(d)

Figure 3 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent119860

119900 dotted line (blue) effluent with TiO

2and FeCl

3but without UV-a irradiation119860

119884 solid line (blue) effluent with TiO

2 FeCl

3and

after UV-a irradiation 119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and FeCl

3(10 mmol Lminus1) and after UV-a irradiation ( ⃝)

decolorization of effluent as a result of the photocatalytic process in the presence of TiO2(25 g Lminus1) FeCl

3(10mmol Lminus1) and after UV-a

irradiation

pollutants for example lower molecular weight carboxylicacids aldehydes and ketones can be less removable Thesebyproducts may not be completely mineralized by K

2Cr2O7

because they are quite resistant and their chemical oxida-tion can be the rate-limiting step in oxidation processesTherefore they require more severe oxidation conditions ora longer time for their conversion On the other hand theCOD values enable only qualitative rather than quantitativeassessment of the mineralization process [32]

After the addition of TiO2FeCl3toWCot the decoloriza-

tion was found to be almost 100 resulting in a completelycolorless effluent (Figure 3(d)) However the removal ofDirect Black 22 was the result of its precipitation only and not

the photocatalytic process The efficiency of photocatalyticdegradation of this dye after 300min of UV-a irradiation waslt5 (Table 3)

Furthermore the organic load ofWCot effluent irradiatedwith TiO

2FeCl3did not change significantly the COD

removal remained low at a value of about 7 Taking intoaccount the high chemical stability of dye (Direct Black 22)in WCot as well as its high concentration in effluent thephotocatalytic degradation of WCot in the presence of TiO

2

and TiO2FeCl3is not an effective method

An estimation of the efficiency of the studied photo-catalytic systems (TiO

2and TiO

2FeCl3) used during the

photocatalytic degradation of real effluents also depends on

International Journal of Photoenergy 9

the chemical properties of dyes and on the possibility offormation of coordination compounds with Fe3+ ions

In the case of effluents containing cationic dyes (WPac)the addition of Fe(III) salt was unfavorable because the effi-ciency of photodegradation of these dyes and COD removalwere lower than that in the presence of TiO

2only The

explanation of this result can be the change of charge ofTiO2particles (in the presence of Fe3+ ions) that limits the

possibility of sorption of the positively charged particles ofcationic dyes

In the case of effluents containing anionic dyes (WLeatand WFlax) the presence of Fe3+ ions had a beneficialeffect on the efficiency of photocatalytic degradation of thesecompoundsThe possible explanations may be a formation ofphotoactive complexes between dyes particles and Fe3+ ionsthat absorb UV-a irradiation much better than individualmolecules of dyes or an adsorption of complexes of dyes withFe3+ ions on the photocatalyst surface

The investigated dyes effluents containing also otherpollutants such as fatty acids sugars and amino acids whichmay also be substrates for the photodegradation and cantherefore compete with the dyes Additionally they maycontain inorganic mobile anions such as Clminus CO

3

2minusSO4

minus2 PO4

3minus and NO3

minus which may significantly affect thedistribution of hydroxyl radicals in the following process

XO119899minus +HO∙ 997888rarr XO∙(119899minus1)minus

+OHminus (12)

As a result these anions at high concentrations candecrease the photodegradation that simultaneously occursbetween HO∙ radicals and dyes molecules

From the viewpoint of COD removal TiO2alone was

a much more effective photocatalyst than TiO2FeCl3 The

increase in COD value in WFlax effluent probably wasconnected with the presence of a very persistent substance(s)that did not undergo the oxidation during the COD deter-mination On the other hand the photocatalytic processleads to degradation of these substances and the obtainedproducts are much less chemically resistant In this aspectthe observed phenomenon is not negative In our publication[33] we have reported similar to other authors [34] that thecomplete photocatalytic degradation of contaminants duringthe treatment of effluents is still not economically feasible dueto high operating costs Therefore the reduction of time ofphotocatalytic process only to the time necessary to initialdegradation of nonbiodegradable substances (eg azo dyes)towards the most readily biodegradable intermediates is themost reasonable It is obvious that one single treatment stepcannot remove all pollutants contained in dyes effluents Theoptimal solution is the combination of different treatmentprocesses for example the photocatalytic degradation usingsunlight as the source of UV light with a biological processIt may significantly decrease the overall cost of the dyeeffluents treatment Additionally the photocatalytic pre-treatment of dyeing effluents can lead to improvement oftheir biodegradability for example initial toxicity inducedby photodegradation of textile antraquinone dye to Vibriafisheri progressively decreased during the course of pro-cess [35] In this way a significant decrease in the overall

cost of the treatment of dyes effluents is expected mainlythrough the combination of several AOPs for example thephotocatalytic degradation as a pretreatment method withbiological processes [36] An increase of biodegradability ofthese effluents would facilitate their subsequent biologicaltreatment and an effective removal of undesirable andorrecalcitrant pollutants making the complete mineralizationunnecessary

4 The Mechanism of WastewaterDecolorization Processes

The experiments confirmed that TiO2caused decolorization

of wastewatermainly due to photocatalytic process Howeverthe decolorization ofWLeat could be a result of dyes sorptiononto TiO

2surface (Table 3)

As previously described FeCl3alone could not be the

cause of decolorization of wastewater during the photocat-alytic process On the other hand the addition of FeCl

3

accelerated undoubtedly the photocatalytic degradation ofanionic dyes According to Mestankova et al this effectwas mainly the result of the synergism of photochemicalactivity between TiO

2and FeCl

3[24] However the results

of experiments showing that FeCl3alone did not exhibit the

photochemical activity in wastewater and it decreased thephotodegradation rate of cationic dyes may indicate otherpossible mechanism It should be noted that even moreimportant is the above described process of intensification ofsorption of dyes coordinated with FeCl

3onto TiO

2surface

[23] The other reason could be the fact that the additionof FeCl

3and simultaneously decrease of pH cause agglom-

eration of suspensions in wastewaters and also increase instability and photoavailability of the TiO

2used [30]

5 Conclusions

Dyeing effluents irradiated in the presence of FeCl3alone

were decolorized but azo dyes almost completely did notundergo degradation On the country the photocatalyticprocess carried out with TiO

2and TiO

2FeCl3as photo-

catalysts was the effective method of decolorization anddyes photodegradation in the investigated effluents (exceptsamples containing high concentration of very stable azodye) During the photocatalytic degradation of anionic dyesa mixture of TiO

2FeCl3was more effective while in the case

of cationic dyes more suitable seems to be TiO2alone

Acknowledgment

This work was supported by the Medical University of Silesia(Grant no KNW-1-043P20)

References

[1] R G Saratale G D Saratale J S Chang and S P GovindwarldquoDecolorization and biodegradation of reactive dyes and dyewastewater by a developed bacterial consortiumrdquo Biodegrada-tion vol 21 no 6 pp 999ndash1015 2010

10 International Journal of Photoenergy

[2] 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

[3] J C Garcia J L Oliveira A E C Silva C C OliveiraJ Nozaki and N E de Souza ldquoComparative study of thedegradation of real textile effluents by photocatalytic reactionsinvolvingUVTiO

2H2O2andUVFe2+H

2O2systemsrdquo Journal

of Hazardous Materials vol 147 no 1-2 pp 105ndash110 2007[4] I M C Goncalves A Gomes R Bras M I A Ferra M T

P Amorim and R S Porter ldquoBiological treatment of effluentcontaining textile dyesrdquoColoration Technology vol 116 pp 393ndash397 2000

[5] M Asgher H N Bhatti S A H Shah M J Asad and R LLegge ldquoDecolorization potential of mixed microbial consortiafor reactive and disperse textile dyestuffsrdquo Biodegradation vol18 no 3 pp 311ndash316 2007

[6] B H Hameed A L Ahmad and K N A Latiff ldquoAdsorptionof basic dye (methylene blue) onto activated carbon preparedfrom rattan sawdustrdquo Dyes and Pigments vol 75 no 1 pp 143ndash149 2007

[7] H Selcuk ldquoDecolorization and detoxification of textile wastew-ater by ozonation and coagulation processesrdquo Dyes and Pig-ments vol 64 no 3 pp 217ndash222 2005

[8] A S Stasinakis ldquoUse of selected advanced oxidation processes(AOPs) for wastewater treatmentmdashamini reviewrdquoGlobal NESTJournal vol 10 pp 376ndash385 2008

[9] R Aplin and T D Waite ldquoComparison of three advancedoxidation processes for degradation of textile dyesrdquo WaterScience and Technology vol 42 no 5-6 pp 345ndash354 2000

[10] I Arslan-Alaton G Tureli and T Olmez-Hanci ldquoTreatmentof azo dye production wastewaters using Photo-Fenton-likeadvanced oxidation processes optimization by response surfacemethodologyrdquo Journal of Photochemistry and Photobiology Avol 202 no 2-3 pp 142ndash153 2009

[11] J M Herrmann ldquoHeterogeneous photocatalysis state of the artand present applicationsrdquoTopics in Catalysis vol 34 no 1ndash4 pp49ndash65 2005

[12] I K Konstantinou and T A Albanis ldquoTiO2-assisted photocat-

alytic degradation of azo dyes in aqueous solution kinetic andmechanistic investigations a reviewrdquo Applied Catalysis B vol49 no 1 pp 1ndash14 2004

[13] W Feng and D Nansheng ldquoPhotochemistry of hydrolyticiron (III) species and photoinduced degradation of organiccompounds A minireviewrdquo Chemosphere vol 41 no 8 pp1137ndash1147 2000

[14] I P Pozdnyakov Y A Sosedova V F Plyusnin et al ldquoPho-todegradation of organic pollutants in aqueous solutions causedby (OH)2+aq photolysis evidence of OH radical formationrdquoInternational Journal of Photoenergy vol 6 no 2 pp 89ndash932004

[15] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalyticdegradation of organic contaminants over titanium dioxidea review of fundamentals progress and problemsrdquo Journal ofPhotochemistry and Photobiology C vol 9 no 1 pp 1ndash12 2008

[16] O K Dalrymple D H Yeh and M A Trotz ldquoRemovingpharmaceuticals and endocrine-disrupting compounds fromwastewater by photocatalysisrdquo Journal of Chemical Technologyand Biotechnology vol 82 no 2 pp 121ndash134 2007

[17] R Rajeswari and S Kanmani ldquoA study on degradation of pes-ticide wastewater by TiO

2photocatalysisrdquo Journal of Scientific

and Industrial Research vol 68 no 12 pp 1063ndash1067 2009

[18] Z F Guo R X Ma and G J Li ldquoDegradation of phenolby nanomaterial TiO

2in wastewaterrdquo Chemical Engineering

Journal vol 119 pp 55ndash59 2006[19] C Jia YWang C Zhang and Q Qin ldquoUV-TiO

2photocatalytic

degradation of landfill leachaterdquo Water Air and Soil Pollutionvol 217 no 1ndash4 pp 375ndash385 2011

[20] V Sarria M Deront P Peringer and C Pulgarin ldquoDegradationof a biorecalcitrant dye precursor present in industrial wastew-aters by a new integrated iron(III) photoassisted-biologicaltreatmentrdquoApplied Catalysis B vol 40 no 3 pp 231ndash246 2003

[21] L Poulain G Mailhot P Wong-Wah-Chung and M BolteldquoPhotodegradation of chlortoluron sensitised by iron(III) aqua-complexesrdquo Journal of Photochemistry and Photobiology A vol159 no 1 pp 81ndash88 2003

[22] C Catastini S Rafqah G Mailhot and M Sarakha ldquoDegra-dation of amitrole by excitation of iron(III) aquacomplexes inaqueous solutionsrdquo Journal of Photochemistry and PhotobiologyA vol 162 no 1 pp 97ndash103 2004

[23] W Baran A Makowski and W Wardas ldquoThe influence ofFeCl3on the photocatalytic degradation of dissolved azo dyes

in aqueous TiO2suspensionsrdquo Chemosphere vol 53 no 1 pp

87ndash95 2003[24] H Mestankova J Krysa J Jirkovsky G Mailhot and M

Bolte ldquoThe influence of Fe(III) speciation on supported TiO2

efficiency example of monuron photocatalytic degradationrdquoApplied Catalysis B vol 58 pp 185ndash191 2005

[25] J Zhang D Fu Q Peng L Deng and X Yang ldquoFe3+-assistedphotocatalytic oxidation of sulfamethazine in TiO

2suspended

solutionrdquo Fresenius Environmental Bulletin vol 20 no 4 pp1051ndash1056 2011

[26] I A Alaton I A Balcioglu and D W Bahnemann ldquoAdvancedoxidation of a reactive dyebath effluent Comparison of O

3

H2O2UV-C and TiO

2UV-A processesrdquo Water Research vol

36 no 5 pp 1143ndash1154 2002[27] P A Pekakis N P Xekoukoulotakis and D Mantzavinos

ldquoTreatment of textile dyehouse wastewater by TiO2photocatal-

ysisrdquoWater Research vol 40 no 6 pp 1276ndash1286 2006[28] C C Liu Y H Hsieh P F Lai C H Li and C L Kao ldquoPho-

todegradation treatment of azo dye wastewater by UVTiO2

processrdquo Dyes and Pigments vol 68 no 2-3 pp 191ndash195 2006[29] J C Garcia J I Simionato A E C Silva J Nozaki and N E de

Souza ldquoSolar photocatalytic degradation of real textile effluentsby associated titanium dioxide and hydrogen peroxiderdquo SolarEnergy vol 83 no 3 pp 316ndash322 2009

[30] W Baran E Adamek and A Makowski ldquoThe influence ofselected parameters on the photocatalytic degradation of azo-dyes in the presence of TiO

2aqueous suspensionrdquo Chemical

Engineering Journal vol 145 no 2 pp 242ndash248 2008[31] ldquoMethods for Chemical Analysis of Water and Wastes Chem-

ical Oxygen Demand Titrimetric Methods 4101-3rdquo US EPAUnited States Environmental Protection Agency Office ofResearch and Development Washington DC USA EPA6004-79020 pp 443ndash451 March 1983 httpnepisepagov

[32] W Baran A Makowski and W Wardas ldquoChanges in CODvalues in aqueous solutions of the selected azo dyes duringthe photocatalytic degradation processrdquo in Micropollution inthe Human Environment vol 51 pp 215ndash221 CzestochowaUniversity of Technology Publishing House CzestochowaPoland 2003

[33] W Baran J Sochacka andWWardas ldquoToxicity and biodegrad-ability of sulfonamides and products of their photocatalytic

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

4 International Journal of Photoenergy

Table 2 The concentrations of reagents used and experimentalconditions

Effluent FeCl3(mmol Lminus1)

TiO2(g Lminus1) pHa

Concentration of Fe(III)in irradiated effluenta

(mmol Lminus1)10 mdash 33 ndb

WPac mdash 25 44 mdash10 25 36 ndb

mdash mdash 31 002WLeat mdash 25 70 mdash

15 25 34 00415 mdash 32 030

WFlax mdash 25 63 mdash15 25 32 03013 mdash 30 280

WCot mdash 25 88 mdash13 25 28 182

aAt the beginning of UV-a irradiation bno data

phase 10mM K2HPO4at pH 90CH

3CN in the ratio 95 5

for WLeat WFlax and WCot and 20mM acetic buffer atpH 48CH

3CN in the ratio 6 4 for WPac resp) Before

HPLC analysis water-insoluble sediments containing Fe(III)compounds with components of effluents were dissolvedafter adding the concentrated HCl (to pH lt 1) or NaOH(to pH asymp 13) The chemical oxygen demand (COD)was estimated by titration method (US EPA 4101-3) [31]Additionally dyes degradation in effluents was determinedspectrophotometrically based on the decrease of peaks oncharacteristic wavelengths at 120582max (Table 3) The analysis ofthe intermediate products was not performed because it wasnot the main aim of this study

25 Results Elaboration The degree of degradation for par-ticular dyes (119883

119894) was calculated based on the results obtained

from HPLC method according to the following equation

119883119894= 100 sdot (1 minus

119878119894

119878119900

) (4)

where 119878119894is the peak area corresponding to the undecomposed

dye after the irradiation of wastewater and 119878119900is the peak area

corresponding to the dye before the irradiationIts means that any transformation of dye occurring as a

result of the irradiation in the presence of a photocatalystwas considered as its degradation In this sense the dyedegradation does not mean its mineralization In the case ofazo dyes their degradation will mean their decompositionto lower and simpler organic compounds by breaking of azobonds

The reaction rate constant for dyes photodegradation(119896119883119894) was determined as for the pseudo first-order reaction

that is as the slope of the following linear dependency

ln119878119900

119878119894

= 119891 (119905) (5)

Reduction of color in the physical process only (119884)was calculated based on the absorbance of raw centrifugedeffluents (119860

119900) and the absorbance of the same effluents but

after addition of the catalyst (TiO2andor FeCl

3) and after

centrifugation (119860119884) as follows

119884 = 100 sdot (1 minus119860119884

119860119900

) (6)

In these cases the photocatalyst-containing samples were notexposed to irradiation that is the photocatalytic processesdid not proceed in them but only adsorption coagulationflocculation and precipitation In some samples the additionof FeCl

3resulted in an increased intensity of color in effluents

so the 119884 value was negativeReduction of color in the photocatalytic process only

(119885) was determined based on the absorbance of centrifugedeffluents with catalysts (TiO

2andor FeCl

3) (119860119884) and the

absorbance of the same effluents but after their irradiationwith these catalysts (119860

119911) as follows

119885 = 100 sdot (1 minus119860119885

119860119884

) (7)

In these cases the reason of effluents decolorationmay be thephotocatalytic process only

The rate constant for dyes photodecolorization (119896119885119894) was

determined as the slope of the following linear function

ln 119860119884119860119885

= 119891 (119905) (8)

Total decolorization of effluents (Total) was calculatedusing the following formula

Total = 100 sdot (1 minus119860119911

119860119900

) (9)

COD removal (119877COD) was determined based on thefollowing equation

119877COD = 100 sdot (1 minusCOD300

CODo) (10)

where CODo was determined in raw effluents and COD300

was determined in the same effluents but after 300min ofUV-a irradiation in the presence of TiO

2andor FeCl

3

3 Results and Discussion

31 Effect of FeCl3 The high photocatalytic activity of Fe(III)salts in model solutions is related to their partial hydrolysisproducts namely Fe(OH)2+ ions that show the maximumphotocatalytic activity in the pH asymp 3 [13] The additionof FeCl

3to effluent samples caused precipitation of water-

insoluble matter (with the exception of WPac) and almosttotal their decolorization (Table 3) However the UV-a irra-diation for 60min did not cause significant changes inUV-Visspectra and in HPLC chromatograms for any of the analyzedsamples Additionally after a prolonged irradiation time to

International Journal of Photoenergy 5

Table3Th

eresultsof

thetreatmento

fdye

effluents

Dyesd

egradatio

naft

erRe

ductionof

color

Effluent120582max(nm)

Photocatalytic

syste

m60

min

ofirr

adiatio

nIn

thep

hotocatalytic

process

Inthep

hysic

alprocesses

Y(

)

Totald

ecolorizationof

effluentsa

t120582max

CODremovalaft

er300m

inaft

er60

min

ofirr

adiatio

nTo

tal()

ofirr

adiatio

n119877COD(

)

X(

)119896119883(m

inminus1)

Z(

)119896119885(m

inminus1)

FeCl

3sim0

sim0

2sim0

minus60

6minus593

340

TiO

237

0008plusmn0002

26000

6plusmn0002

328

TiO

2FeCl

310

0002plusmn0001

780024plusmn0003

minus347

1

FeCl

3sim0

sim0

sim0

sim0

minus147

minus155

430

TiO

258

0014plusmn0003

360008plusmn0002

440

WPac

TiO

2FeCl

317

0003plusmn0002

490010plusmn0002

minus76

11sim0149

a

FeCl

3sim0

sim0

sim0

sim0

minus17

minus20

540

TiO

286

0030plusmn0005

570014plusmn0002

358

TiO

2FeCl

340

0008plusmn0002

22000

4plusmn0001

minus7

17

FeCl

3nd

bnd

3sim0

47

610

TiO

2nd

nd

830030plusmn000

44

84TiO

2FeCl

3nd

nd

35000

6plusmn0002

1142

FeCl

3sim0

sim0

sim0

sim0

9595

510

TiO

224

(63)

c000

4plusmn0002

110002plusmn000

014

24

WLeat

TiO

2FeCl

3sim30

(100)c

0005plusmn0001

110002plusmn0001

9595

sim040

15a

FeCl

3nd

nd

sim0

sim0

100

100

620

TiO

2nd

nd

210003plusmn0001

1836

TiO

2FeCl

3nd

nd

100

mdash96

100

FeCl

3sim0e

sim0

10lt0001

5053

sim0

WFlax

350d

TiO

210

e0001plusmn

0001

220003plusmn0002

sim0

22minus40

TiO

2FeCl

335divide42

e0008plusmn0002

500011plusmn

0003

3366

minus33

FeCl

3sim0(0)c

sim0

sim0c

sim0

9696

csim0

WCot

480

TiO

2sim0(5)c

sim0

5csim0

sim0

5c11

TiO

2FeCl

3sim0(5)c

sim0

5csim0

9796

c7

a Inthep

resenceo

fFeC

l 3TiO2andTiO2FeCl

3respectiv

elybno

datacaft

er300m

inof

UV-airadiation

d absorptionband

with

outclear

maxim

umebasedon

thep

eakarea

measurementat4

80nm

usingHPL

Cmetho

d

6 International Journal of Photoenergy

300min no significant changes in chromatograms and inCOD values were observed

After the dissolution of water insoluble Fe-organic com-plexes chromatograms of samples (before and after UVirradiation) remained practically unchanged This observa-tion indicates that during UV-a irradiation of effluents withFe(III) salt only dyes did not undergo the photocatalyticdegradationThe use of FeCl

3and probably also other Fe(III)

salts as a catalyst in the photocatalytic treatment processof dye effluents is completely ineffective (after 60min ofirradiation the photodegradation efficiency was in the rangeof 0) Therefore under model conditions model Fe(OH)2+ions can have photocatalytic activity at pH 3 but in realwastewater samples for example in dye effluents they mayact as a coagulant only

32 Effect of TiO2 After centrifugation of nonirradiatedsamples with TiO

2 no significant changes in UV-VIS spec-

tra (Figure 2) and HPLC chromatograms were observedSimultaneously in all effluent samples the photocatalyst wascoagulated only in a negligible level

As can be seen from the UV-VIS spectra shown inFigure 2(a) after UV-a irradiation of samples containingcationic dyes (WPac) with TiO

2for 60min the effluent

underwent high decolorization resulting in a completelycolorless effluent The disappearance of the absorption bands(120582max at 340 430 520 and 610 nm) suggests that the chro-mophore groups responsible for color progressively breakdown during UV-a irradiation Therefore in the case ofcationic dyes the effluent decolorization was almost exclu-sively the result of the photocatalytic process and only ina small degree due to physical processes such as precipita-tion coagulation or sorption The degradation efficiency ofcationic dyes was in the range of 37ndash86 but the CODremoval was low even after 300min of irradiation and wasonly 14 (Table 3)

The decolorization (a decrease in absorbance) was alsoobserved in WLeat and WFlax effluents containing anionicdyes (Figures 2(b) and 2(c)) After irradiation of samplesin the presence of TiO

2 a decrease of absorbance at 510

and 620 nm for WLeat and a decrease of a continuous band(without any distinctmaximum) forWFlaxwere observed Inthe case of effluent resulting from dyeing of leather (WLeat)decolorization was the result of both the photodegrada-tion and the physical processes The maximum degradationdegree of one of the dyes namely Acid Red 88 was 63 after300min of UV-a irradiation (Table 3)

On the other hand WFlax effluents irradiated for 60minwith TiO

2exhibited lower dyes degradation in the range

of 10 The UV-a irradiation for 300min caused a decreasein COD value about 40 in WLeat effluents and on thecontrary an increase in COD value of 40 in WFlax(Table 3)

As shown in Figure 2(d) in effluents from cotton dyeingprocesses (WCot) decolorization and changes inHPLCchro-matograms practically were not observed The degradationdegree of dye was lt5 even after 300min UV-a irradiationIn these samples the degradation efficiency was very low

probably because of less transmission of UV-a light throughthe black effluents Additionally WCot samples containinghigh concentration of dye (Direct Black 22) had the highestCOD over 8900mg O

2Lminus1 Therefore after 300min of

irradiation the COD removal was about 11 (Table 3)The photodegradation of compounds duringin hetero-

geneous photocatalysis depends among other factors on thechemical properties of substrates and their adsorption abilityonto the photocatalyst surface [11] In accordance to hetero-geneous catalysis theory (Langmuir- Himselwood model)the increase in adsorption of dyes causes the increase in thephotocatalytic degradation rate Additionally TiO

2shows an

amphoteric character and its photocatalytic activity dependsalso on the pH of samples In the case of the investigated TiO

2

(pure anatase) the determined pH value of the point of zerocharge (pHpzc) was 300 In the used dyes effluents the pHswere always higher than pHpzc and therefore TiO

2surface

should be negatively charged as follows

Ti ndashOH2

+pHltpHpzclArrrArr TindashOH

pHgtpHpzclArrrArr TiOminus (11)

This fact may explain the higher adsorption and higher pho-todegradation ability of cationic dyes (inWPac effluents) andlower adsorption of anionic dyes (WCot andWFlax) onto theTiO2surface under the studied conditions However it does

not simply explain high degradation of anionic dyes inWLeateffluents The adsorption process onto TiO

2surface under

UV-irradiation conditions is complex and some differencesin an adsorption capacity of particles may occur Probablya higher removal of COD in WLeat can be attributed to theadsorption of increased amounts of undissociated particles(eg anionic dyeswith organic or inorganic ions) on the TiO

2

surface Additionally the organic compounds in WLeat thatis dyes surfactant agents and auxiliaries were rather photolabile and they were easily transformed to less stable organics(byproducts)

33 Effect of TiO2FeCl3 As shown in Figure 3 the additionof TiO

2FeCl3mixture to nonirradiated effluents caused a

significant coagulation and decolorization of all samplesTherefore in these processes Fe salts could play a roleof coagulant However UV-a irradiation of such samplesresulted in their decolorization (Figure 3 Table 3) and thismay indicate its role as a photosensitizer

It was found that the photocatalytic degradation in efflu-ent containing cationic dyes (WPac) was less effective in themixture of TiO

2FeCl3than in the presence of TiO

2alone

(Table 3) After 60min of UV-a irradiation the degradationefficiency of dyes was in the range 10ndash40 SimultaneouslyWPac underwent the effective decolorization which can beexplained only as the dyes photodegradation (Figure 3(a))This process was not inhibited by strong coagulation ofphotocatalysts and by auxiliary substances contained in thesesamples After the addition of TiO

2FeCl3but before UV-

a irradiation absorbance in WPac effluent at 120582 lt 500 nmwas significantly higher due to the presence of dissolvedFe(III) compounds (dashed line) The data concerning CODremoval indicate that the efficiency of WPac mineralizationafter 300min of UV-a irradiation reached only 9

International Journal of Photoenergy 7

0

005

01

015

02

025

03

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(b)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriz

atio

n (

)

(c)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(d)

Figure 2 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent 119860

119900 dotted line (blue) effluent with TiO

2 without UV-a irradiation 119860

119884 solid line (blue) effluent with TiO

2 after UV-a irradiation

119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and after UV-a irradiation ( ⃝) decolorization of effluent as a result of the

photocatalytic process in the presence of TiO2(25 g Lminus1) and after UV-a irradiation

On the contrary effluents containing anionic dyes(WLeat and WFlax) underwent the photocatalytic degra-dation more effectively in the presence of TiO

2FeCl3than

in TiO2alone (Table 3) Upon UV-a irradiation there were

continuous decreases in absorbance all along the spectrameaning the fragmentation of organic structures and thephotocatalytic degradation of dyes (Figures 3(b) and 3(c))As shown in Table 2 the complete removal of Acid Red 88fromWLeat was the result of both direct precipitation andoradsorption on the photocatalyst surface and photodegrada-tion process The degradation efficiency of this dye was highand reached even 100 after 300min of UV-a irradiation(Table 3)Thedecolorization ofWFlaxwas caused to a greaterextent by the photocatalytic process than coagulation andor

precipitation (Figure 3(c)) The dyes degradation was in therange 35ndash42 after 60min of UV-a irradiation Removal ofCOD in WLeat in the presence of TiO

2FeCl3was 15 and

was lower than in the presence of TiO2alone On the other

hand similarly as during irradiation of WFlax with TiO2

alone after 300min of UV-a irradiation with TiO2FeCl3

there was not a decrease of COD value but its increaseIn our opinion an increase in COD removal upon UV-

a irradiation of WFlax with TiO2and TiO

2FeCl3is only

provisional This effect can be explained by an increase in theconcentration of smaller organics molecules formed duringthe photocatalytic oxidation of dyes and suspended solidsMost of the decomposable compounds are removed in theinitial time of this process and the remained part of organic

8 International Journal of Photoenergy

0

01

02

03

04

05

06

07

08

09

1

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

Abs

orba

nce

Dec

olor

izat

ion

()

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(b)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriza

tion

()

(c)

Abs

orba

nce

Dec

olor

izatio

n (

)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(d)

Figure 3 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent119860

119900 dotted line (blue) effluent with TiO

2and FeCl

3but without UV-a irradiation119860

119884 solid line (blue) effluent with TiO

2 FeCl

3and

after UV-a irradiation 119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and FeCl

3(10 mmol Lminus1) and after UV-a irradiation ( ⃝)

decolorization of effluent as a result of the photocatalytic process in the presence of TiO2(25 g Lminus1) FeCl

3(10mmol Lminus1) and after UV-a

irradiation

pollutants for example lower molecular weight carboxylicacids aldehydes and ketones can be less removable Thesebyproducts may not be completely mineralized by K

2Cr2O7

because they are quite resistant and their chemical oxida-tion can be the rate-limiting step in oxidation processesTherefore they require more severe oxidation conditions ora longer time for their conversion On the other hand theCOD values enable only qualitative rather than quantitativeassessment of the mineralization process [32]

After the addition of TiO2FeCl3toWCot the decoloriza-

tion was found to be almost 100 resulting in a completelycolorless effluent (Figure 3(d)) However the removal ofDirect Black 22 was the result of its precipitation only and not

the photocatalytic process The efficiency of photocatalyticdegradation of this dye after 300min of UV-a irradiation waslt5 (Table 3)

Furthermore the organic load ofWCot effluent irradiatedwith TiO

2FeCl3did not change significantly the COD

removal remained low at a value of about 7 Taking intoaccount the high chemical stability of dye (Direct Black 22)in WCot as well as its high concentration in effluent thephotocatalytic degradation of WCot in the presence of TiO

2

and TiO2FeCl3is not an effective method

An estimation of the efficiency of the studied photo-catalytic systems (TiO

2and TiO

2FeCl3) used during the

photocatalytic degradation of real effluents also depends on

International Journal of Photoenergy 9

the chemical properties of dyes and on the possibility offormation of coordination compounds with Fe3+ ions

In the case of effluents containing cationic dyes (WPac)the addition of Fe(III) salt was unfavorable because the effi-ciency of photodegradation of these dyes and COD removalwere lower than that in the presence of TiO

2only The

explanation of this result can be the change of charge ofTiO2particles (in the presence of Fe3+ ions) that limits the

possibility of sorption of the positively charged particles ofcationic dyes

In the case of effluents containing anionic dyes (WLeatand WFlax) the presence of Fe3+ ions had a beneficialeffect on the efficiency of photocatalytic degradation of thesecompoundsThe possible explanations may be a formation ofphotoactive complexes between dyes particles and Fe3+ ionsthat absorb UV-a irradiation much better than individualmolecules of dyes or an adsorption of complexes of dyes withFe3+ ions on the photocatalyst surface

The investigated dyes effluents containing also otherpollutants such as fatty acids sugars and amino acids whichmay also be substrates for the photodegradation and cantherefore compete with the dyes Additionally they maycontain inorganic mobile anions such as Clminus CO

3

2minusSO4

minus2 PO4

3minus and NO3

minus which may significantly affect thedistribution of hydroxyl radicals in the following process

XO119899minus +HO∙ 997888rarr XO∙(119899minus1)minus

+OHminus (12)

As a result these anions at high concentrations candecrease the photodegradation that simultaneously occursbetween HO∙ radicals and dyes molecules

From the viewpoint of COD removal TiO2alone was

a much more effective photocatalyst than TiO2FeCl3 The

increase in COD value in WFlax effluent probably wasconnected with the presence of a very persistent substance(s)that did not undergo the oxidation during the COD deter-mination On the other hand the photocatalytic processleads to degradation of these substances and the obtainedproducts are much less chemically resistant In this aspectthe observed phenomenon is not negative In our publication[33] we have reported similar to other authors [34] that thecomplete photocatalytic degradation of contaminants duringthe treatment of effluents is still not economically feasible dueto high operating costs Therefore the reduction of time ofphotocatalytic process only to the time necessary to initialdegradation of nonbiodegradable substances (eg azo dyes)towards the most readily biodegradable intermediates is themost reasonable It is obvious that one single treatment stepcannot remove all pollutants contained in dyes effluents Theoptimal solution is the combination of different treatmentprocesses for example the photocatalytic degradation usingsunlight as the source of UV light with a biological processIt may significantly decrease the overall cost of the dyeeffluents treatment Additionally the photocatalytic pre-treatment of dyeing effluents can lead to improvement oftheir biodegradability for example initial toxicity inducedby photodegradation of textile antraquinone dye to Vibriafisheri progressively decreased during the course of pro-cess [35] In this way a significant decrease in the overall

cost of the treatment of dyes effluents is expected mainlythrough the combination of several AOPs for example thephotocatalytic degradation as a pretreatment method withbiological processes [36] An increase of biodegradability ofthese effluents would facilitate their subsequent biologicaltreatment and an effective removal of undesirable andorrecalcitrant pollutants making the complete mineralizationunnecessary

4 The Mechanism of WastewaterDecolorization Processes

The experiments confirmed that TiO2caused decolorization

of wastewatermainly due to photocatalytic process Howeverthe decolorization ofWLeat could be a result of dyes sorptiononto TiO

2surface (Table 3)

As previously described FeCl3alone could not be the

cause of decolorization of wastewater during the photocat-alytic process On the other hand the addition of FeCl

3

accelerated undoubtedly the photocatalytic degradation ofanionic dyes According to Mestankova et al this effectwas mainly the result of the synergism of photochemicalactivity between TiO

2and FeCl

3[24] However the results

of experiments showing that FeCl3alone did not exhibit the

photochemical activity in wastewater and it decreased thephotodegradation rate of cationic dyes may indicate otherpossible mechanism It should be noted that even moreimportant is the above described process of intensification ofsorption of dyes coordinated with FeCl

3onto TiO

2surface

[23] The other reason could be the fact that the additionof FeCl

3and simultaneously decrease of pH cause agglom-

eration of suspensions in wastewaters and also increase instability and photoavailability of the TiO

2used [30]

5 Conclusions

Dyeing effluents irradiated in the presence of FeCl3alone

were decolorized but azo dyes almost completely did notundergo degradation On the country the photocatalyticprocess carried out with TiO

2and TiO

2FeCl3as photo-

catalysts was the effective method of decolorization anddyes photodegradation in the investigated effluents (exceptsamples containing high concentration of very stable azodye) During the photocatalytic degradation of anionic dyesa mixture of TiO

2FeCl3was more effective while in the case

of cationic dyes more suitable seems to be TiO2alone

Acknowledgment

This work was supported by the Medical University of Silesia(Grant no KNW-1-043P20)

References

[1] R G Saratale G D Saratale J S Chang and S P GovindwarldquoDecolorization and biodegradation of reactive dyes and dyewastewater by a developed bacterial consortiumrdquo Biodegrada-tion vol 21 no 6 pp 999ndash1015 2010

10 International Journal of Photoenergy

[2] 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

[3] J C Garcia J L Oliveira A E C Silva C C OliveiraJ Nozaki and N E de Souza ldquoComparative study of thedegradation of real textile effluents by photocatalytic reactionsinvolvingUVTiO

2H2O2andUVFe2+H

2O2systemsrdquo Journal

of Hazardous Materials vol 147 no 1-2 pp 105ndash110 2007[4] I M C Goncalves A Gomes R Bras M I A Ferra M T

P Amorim and R S Porter ldquoBiological treatment of effluentcontaining textile dyesrdquoColoration Technology vol 116 pp 393ndash397 2000

[5] M Asgher H N Bhatti S A H Shah M J Asad and R LLegge ldquoDecolorization potential of mixed microbial consortiafor reactive and disperse textile dyestuffsrdquo Biodegradation vol18 no 3 pp 311ndash316 2007

[6] B H Hameed A L Ahmad and K N A Latiff ldquoAdsorptionof basic dye (methylene blue) onto activated carbon preparedfrom rattan sawdustrdquo Dyes and Pigments vol 75 no 1 pp 143ndash149 2007

[7] H Selcuk ldquoDecolorization and detoxification of textile wastew-ater by ozonation and coagulation processesrdquo Dyes and Pig-ments vol 64 no 3 pp 217ndash222 2005

[8] A S Stasinakis ldquoUse of selected advanced oxidation processes(AOPs) for wastewater treatmentmdashamini reviewrdquoGlobal NESTJournal vol 10 pp 376ndash385 2008

[9] R Aplin and T D Waite ldquoComparison of three advancedoxidation processes for degradation of textile dyesrdquo WaterScience and Technology vol 42 no 5-6 pp 345ndash354 2000

[10] I Arslan-Alaton G Tureli and T Olmez-Hanci ldquoTreatmentof azo dye production wastewaters using Photo-Fenton-likeadvanced oxidation processes optimization by response surfacemethodologyrdquo Journal of Photochemistry and Photobiology Avol 202 no 2-3 pp 142ndash153 2009

[11] J M Herrmann ldquoHeterogeneous photocatalysis state of the artand present applicationsrdquoTopics in Catalysis vol 34 no 1ndash4 pp49ndash65 2005

[12] I K Konstantinou and T A Albanis ldquoTiO2-assisted photocat-

alytic degradation of azo dyes in aqueous solution kinetic andmechanistic investigations a reviewrdquo Applied Catalysis B vol49 no 1 pp 1ndash14 2004

[13] W Feng and D Nansheng ldquoPhotochemistry of hydrolyticiron (III) species and photoinduced degradation of organiccompounds A minireviewrdquo Chemosphere vol 41 no 8 pp1137ndash1147 2000

[14] I P Pozdnyakov Y A Sosedova V F Plyusnin et al ldquoPho-todegradation of organic pollutants in aqueous solutions causedby (OH)2+aq photolysis evidence of OH radical formationrdquoInternational Journal of Photoenergy vol 6 no 2 pp 89ndash932004

[15] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalyticdegradation of organic contaminants over titanium dioxidea review of fundamentals progress and problemsrdquo Journal ofPhotochemistry and Photobiology C vol 9 no 1 pp 1ndash12 2008

[16] O K Dalrymple D H Yeh and M A Trotz ldquoRemovingpharmaceuticals and endocrine-disrupting compounds fromwastewater by photocatalysisrdquo Journal of Chemical Technologyand Biotechnology vol 82 no 2 pp 121ndash134 2007

[17] R Rajeswari and S Kanmani ldquoA study on degradation of pes-ticide wastewater by TiO

2photocatalysisrdquo Journal of Scientific

and Industrial Research vol 68 no 12 pp 1063ndash1067 2009

[18] Z F Guo R X Ma and G J Li ldquoDegradation of phenolby nanomaterial TiO

2in wastewaterrdquo Chemical Engineering

Journal vol 119 pp 55ndash59 2006[19] C Jia YWang C Zhang and Q Qin ldquoUV-TiO

2photocatalytic

degradation of landfill leachaterdquo Water Air and Soil Pollutionvol 217 no 1ndash4 pp 375ndash385 2011

[20] V Sarria M Deront P Peringer and C Pulgarin ldquoDegradationof a biorecalcitrant dye precursor present in industrial wastew-aters by a new integrated iron(III) photoassisted-biologicaltreatmentrdquoApplied Catalysis B vol 40 no 3 pp 231ndash246 2003

[21] L Poulain G Mailhot P Wong-Wah-Chung and M BolteldquoPhotodegradation of chlortoluron sensitised by iron(III) aqua-complexesrdquo Journal of Photochemistry and Photobiology A vol159 no 1 pp 81ndash88 2003

[22] C Catastini S Rafqah G Mailhot and M Sarakha ldquoDegra-dation of amitrole by excitation of iron(III) aquacomplexes inaqueous solutionsrdquo Journal of Photochemistry and PhotobiologyA vol 162 no 1 pp 97ndash103 2004

[23] W Baran A Makowski and W Wardas ldquoThe influence ofFeCl3on the photocatalytic degradation of dissolved azo dyes

in aqueous TiO2suspensionsrdquo Chemosphere vol 53 no 1 pp

87ndash95 2003[24] H Mestankova J Krysa J Jirkovsky G Mailhot and M

Bolte ldquoThe influence of Fe(III) speciation on supported TiO2

efficiency example of monuron photocatalytic degradationrdquoApplied Catalysis B vol 58 pp 185ndash191 2005

[25] J Zhang D Fu Q Peng L Deng and X Yang ldquoFe3+-assistedphotocatalytic oxidation of sulfamethazine in TiO

2suspended

solutionrdquo Fresenius Environmental Bulletin vol 20 no 4 pp1051ndash1056 2011

[26] I A Alaton I A Balcioglu and D W Bahnemann ldquoAdvancedoxidation of a reactive dyebath effluent Comparison of O

3

H2O2UV-C and TiO

2UV-A processesrdquo Water Research vol

36 no 5 pp 1143ndash1154 2002[27] P A Pekakis N P Xekoukoulotakis and D Mantzavinos

ldquoTreatment of textile dyehouse wastewater by TiO2photocatal-

ysisrdquoWater Research vol 40 no 6 pp 1276ndash1286 2006[28] C C Liu Y H Hsieh P F Lai C H Li and C L Kao ldquoPho-

todegradation treatment of azo dye wastewater by UVTiO2

processrdquo Dyes and Pigments vol 68 no 2-3 pp 191ndash195 2006[29] J C Garcia J I Simionato A E C Silva J Nozaki and N E de

Souza ldquoSolar photocatalytic degradation of real textile effluentsby associated titanium dioxide and hydrogen peroxiderdquo SolarEnergy vol 83 no 3 pp 316ndash322 2009

[30] W Baran E Adamek and A Makowski ldquoThe influence ofselected parameters on the photocatalytic degradation of azo-dyes in the presence of TiO

2aqueous suspensionrdquo Chemical

Engineering Journal vol 145 no 2 pp 242ndash248 2008[31] ldquoMethods for Chemical Analysis of Water and Wastes Chem-

ical Oxygen Demand Titrimetric Methods 4101-3rdquo US EPAUnited States Environmental Protection Agency Office ofResearch and Development Washington DC USA EPA6004-79020 pp 443ndash451 March 1983 httpnepisepagov

[32] W Baran A Makowski and W Wardas ldquoChanges in CODvalues in aqueous solutions of the selected azo dyes duringthe photocatalytic degradation processrdquo in Micropollution inthe Human Environment vol 51 pp 215ndash221 CzestochowaUniversity of Technology Publishing House CzestochowaPoland 2003

[33] W Baran J Sochacka andWWardas ldquoToxicity and biodegrad-ability of sulfonamides and products of their photocatalytic

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

International Journal of Photoenergy 5

Table3Th

eresultsof

thetreatmento

fdye

effluents

Dyesd

egradatio

naft

erRe

ductionof

color

Effluent120582max(nm)

Photocatalytic

syste

m60

min

ofirr

adiatio

nIn

thep

hotocatalytic

process

Inthep

hysic

alprocesses

Y(

)

Totald

ecolorizationof

effluentsa

t120582max

CODremovalaft

er300m

inaft

er60

min

ofirr

adiatio

nTo

tal()

ofirr

adiatio

n119877COD(

)

X(

)119896119883(m

inminus1)

Z(

)119896119885(m

inminus1)

FeCl

3sim0

sim0

2sim0

minus60

6minus593

340

TiO

237

0008plusmn0002

26000

6plusmn0002

328

TiO

2FeCl

310

0002plusmn0001

780024plusmn0003

minus347

1

FeCl

3sim0

sim0

sim0

sim0

minus147

minus155

430

TiO

258

0014plusmn0003

360008plusmn0002

440

WPac

TiO

2FeCl

317

0003plusmn0002

490010plusmn0002

minus76

11sim0149

a

FeCl

3sim0

sim0

sim0

sim0

minus17

minus20

540

TiO

286

0030plusmn0005

570014plusmn0002

358

TiO

2FeCl

340

0008plusmn0002

22000

4plusmn0001

minus7

17

FeCl

3nd

bnd

3sim0

47

610

TiO

2nd

nd

830030plusmn000

44

84TiO

2FeCl

3nd

nd

35000

6plusmn0002

1142

FeCl

3sim0

sim0

sim0

sim0

9595

510

TiO

224

(63)

c000

4plusmn0002

110002plusmn000

014

24

WLeat

TiO

2FeCl

3sim30

(100)c

0005plusmn0001

110002plusmn0001

9595

sim040

15a

FeCl

3nd

nd

sim0

sim0

100

100

620

TiO

2nd

nd

210003plusmn0001

1836

TiO

2FeCl

3nd

nd

100

mdash96

100

FeCl

3sim0e

sim0

10lt0001

5053

sim0

WFlax

350d

TiO

210

e0001plusmn

0001

220003plusmn0002

sim0

22minus40

TiO

2FeCl

335divide42

e0008plusmn0002

500011plusmn

0003

3366

minus33

FeCl

3sim0(0)c

sim0

sim0c

sim0

9696

csim0

WCot

480

TiO

2sim0(5)c

sim0

5csim0

sim0

5c11

TiO

2FeCl

3sim0(5)c

sim0

5csim0

9796

c7

a Inthep

resenceo

fFeC

l 3TiO2andTiO2FeCl

3respectiv

elybno

datacaft

er300m

inof

UV-airadiation

d absorptionband

with

outclear

maxim

umebasedon

thep

eakarea

measurementat4

80nm

usingHPL

Cmetho

d

6 International Journal of Photoenergy

300min no significant changes in chromatograms and inCOD values were observed

After the dissolution of water insoluble Fe-organic com-plexes chromatograms of samples (before and after UVirradiation) remained practically unchanged This observa-tion indicates that during UV-a irradiation of effluents withFe(III) salt only dyes did not undergo the photocatalyticdegradationThe use of FeCl

3and probably also other Fe(III)

salts as a catalyst in the photocatalytic treatment processof dye effluents is completely ineffective (after 60min ofirradiation the photodegradation efficiency was in the rangeof 0) Therefore under model conditions model Fe(OH)2+ions can have photocatalytic activity at pH 3 but in realwastewater samples for example in dye effluents they mayact as a coagulant only

32 Effect of TiO2 After centrifugation of nonirradiatedsamples with TiO

2 no significant changes in UV-VIS spec-

tra (Figure 2) and HPLC chromatograms were observedSimultaneously in all effluent samples the photocatalyst wascoagulated only in a negligible level

As can be seen from the UV-VIS spectra shown inFigure 2(a) after UV-a irradiation of samples containingcationic dyes (WPac) with TiO

2for 60min the effluent

underwent high decolorization resulting in a completelycolorless effluent The disappearance of the absorption bands(120582max at 340 430 520 and 610 nm) suggests that the chro-mophore groups responsible for color progressively breakdown during UV-a irradiation Therefore in the case ofcationic dyes the effluent decolorization was almost exclu-sively the result of the photocatalytic process and only ina small degree due to physical processes such as precipita-tion coagulation or sorption The degradation efficiency ofcationic dyes was in the range of 37ndash86 but the CODremoval was low even after 300min of irradiation and wasonly 14 (Table 3)

The decolorization (a decrease in absorbance) was alsoobserved in WLeat and WFlax effluents containing anionicdyes (Figures 2(b) and 2(c)) After irradiation of samplesin the presence of TiO

2 a decrease of absorbance at 510

and 620 nm for WLeat and a decrease of a continuous band(without any distinctmaximum) forWFlaxwere observed Inthe case of effluent resulting from dyeing of leather (WLeat)decolorization was the result of both the photodegrada-tion and the physical processes The maximum degradationdegree of one of the dyes namely Acid Red 88 was 63 after300min of UV-a irradiation (Table 3)

On the other hand WFlax effluents irradiated for 60minwith TiO

2exhibited lower dyes degradation in the range

of 10 The UV-a irradiation for 300min caused a decreasein COD value about 40 in WLeat effluents and on thecontrary an increase in COD value of 40 in WFlax(Table 3)

As shown in Figure 2(d) in effluents from cotton dyeingprocesses (WCot) decolorization and changes inHPLCchro-matograms practically were not observed The degradationdegree of dye was lt5 even after 300min UV-a irradiationIn these samples the degradation efficiency was very low

probably because of less transmission of UV-a light throughthe black effluents Additionally WCot samples containinghigh concentration of dye (Direct Black 22) had the highestCOD over 8900mg O

2Lminus1 Therefore after 300min of

irradiation the COD removal was about 11 (Table 3)The photodegradation of compounds duringin hetero-

geneous photocatalysis depends among other factors on thechemical properties of substrates and their adsorption abilityonto the photocatalyst surface [11] In accordance to hetero-geneous catalysis theory (Langmuir- Himselwood model)the increase in adsorption of dyes causes the increase in thephotocatalytic degradation rate Additionally TiO

2shows an

amphoteric character and its photocatalytic activity dependsalso on the pH of samples In the case of the investigated TiO

2

(pure anatase) the determined pH value of the point of zerocharge (pHpzc) was 300 In the used dyes effluents the pHswere always higher than pHpzc and therefore TiO

2surface

should be negatively charged as follows

Ti ndashOH2

+pHltpHpzclArrrArr TindashOH

pHgtpHpzclArrrArr TiOminus (11)

This fact may explain the higher adsorption and higher pho-todegradation ability of cationic dyes (inWPac effluents) andlower adsorption of anionic dyes (WCot andWFlax) onto theTiO2surface under the studied conditions However it does

not simply explain high degradation of anionic dyes inWLeateffluents The adsorption process onto TiO

2surface under

UV-irradiation conditions is complex and some differencesin an adsorption capacity of particles may occur Probablya higher removal of COD in WLeat can be attributed to theadsorption of increased amounts of undissociated particles(eg anionic dyeswith organic or inorganic ions) on the TiO

2

surface Additionally the organic compounds in WLeat thatis dyes surfactant agents and auxiliaries were rather photolabile and they were easily transformed to less stable organics(byproducts)

33 Effect of TiO2FeCl3 As shown in Figure 3 the additionof TiO

2FeCl3mixture to nonirradiated effluents caused a

significant coagulation and decolorization of all samplesTherefore in these processes Fe salts could play a roleof coagulant However UV-a irradiation of such samplesresulted in their decolorization (Figure 3 Table 3) and thismay indicate its role as a photosensitizer

It was found that the photocatalytic degradation in efflu-ent containing cationic dyes (WPac) was less effective in themixture of TiO

2FeCl3than in the presence of TiO

2alone

(Table 3) After 60min of UV-a irradiation the degradationefficiency of dyes was in the range 10ndash40 SimultaneouslyWPac underwent the effective decolorization which can beexplained only as the dyes photodegradation (Figure 3(a))This process was not inhibited by strong coagulation ofphotocatalysts and by auxiliary substances contained in thesesamples After the addition of TiO

2FeCl3but before UV-

a irradiation absorbance in WPac effluent at 120582 lt 500 nmwas significantly higher due to the presence of dissolvedFe(III) compounds (dashed line) The data concerning CODremoval indicate that the efficiency of WPac mineralizationafter 300min of UV-a irradiation reached only 9

International Journal of Photoenergy 7

0

005

01

015

02

025

03

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(b)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriz

atio

n (

)

(c)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(d)

Figure 2 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent 119860

119900 dotted line (blue) effluent with TiO

2 without UV-a irradiation 119860

119884 solid line (blue) effluent with TiO

2 after UV-a irradiation

119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and after UV-a irradiation ( ⃝) decolorization of effluent as a result of the

photocatalytic process in the presence of TiO2(25 g Lminus1) and after UV-a irradiation

On the contrary effluents containing anionic dyes(WLeat and WFlax) underwent the photocatalytic degra-dation more effectively in the presence of TiO

2FeCl3than

in TiO2alone (Table 3) Upon UV-a irradiation there were

continuous decreases in absorbance all along the spectrameaning the fragmentation of organic structures and thephotocatalytic degradation of dyes (Figures 3(b) and 3(c))As shown in Table 2 the complete removal of Acid Red 88fromWLeat was the result of both direct precipitation andoradsorption on the photocatalyst surface and photodegrada-tion process The degradation efficiency of this dye was highand reached even 100 after 300min of UV-a irradiation(Table 3)Thedecolorization ofWFlaxwas caused to a greaterextent by the photocatalytic process than coagulation andor

precipitation (Figure 3(c)) The dyes degradation was in therange 35ndash42 after 60min of UV-a irradiation Removal ofCOD in WLeat in the presence of TiO

2FeCl3was 15 and

was lower than in the presence of TiO2alone On the other

hand similarly as during irradiation of WFlax with TiO2

alone after 300min of UV-a irradiation with TiO2FeCl3

there was not a decrease of COD value but its increaseIn our opinion an increase in COD removal upon UV-

a irradiation of WFlax with TiO2and TiO

2FeCl3is only

provisional This effect can be explained by an increase in theconcentration of smaller organics molecules formed duringthe photocatalytic oxidation of dyes and suspended solidsMost of the decomposable compounds are removed in theinitial time of this process and the remained part of organic

8 International Journal of Photoenergy

0

01

02

03

04

05

06

07

08

09

1

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

Abs

orba

nce

Dec

olor

izat

ion

()

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(b)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriza

tion

()

(c)

Abs

orba

nce

Dec

olor

izatio

n (

)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(d)

Figure 3 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent119860

119900 dotted line (blue) effluent with TiO

2and FeCl

3but without UV-a irradiation119860

119884 solid line (blue) effluent with TiO

2 FeCl

3and

after UV-a irradiation 119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and FeCl

3(10 mmol Lminus1) and after UV-a irradiation ( ⃝)

decolorization of effluent as a result of the photocatalytic process in the presence of TiO2(25 g Lminus1) FeCl

3(10mmol Lminus1) and after UV-a

irradiation

pollutants for example lower molecular weight carboxylicacids aldehydes and ketones can be less removable Thesebyproducts may not be completely mineralized by K

2Cr2O7

because they are quite resistant and their chemical oxida-tion can be the rate-limiting step in oxidation processesTherefore they require more severe oxidation conditions ora longer time for their conversion On the other hand theCOD values enable only qualitative rather than quantitativeassessment of the mineralization process [32]

After the addition of TiO2FeCl3toWCot the decoloriza-

tion was found to be almost 100 resulting in a completelycolorless effluent (Figure 3(d)) However the removal ofDirect Black 22 was the result of its precipitation only and not

the photocatalytic process The efficiency of photocatalyticdegradation of this dye after 300min of UV-a irradiation waslt5 (Table 3)

Furthermore the organic load ofWCot effluent irradiatedwith TiO

2FeCl3did not change significantly the COD

removal remained low at a value of about 7 Taking intoaccount the high chemical stability of dye (Direct Black 22)in WCot as well as its high concentration in effluent thephotocatalytic degradation of WCot in the presence of TiO

2

and TiO2FeCl3is not an effective method

An estimation of the efficiency of the studied photo-catalytic systems (TiO

2and TiO

2FeCl3) used during the

photocatalytic degradation of real effluents also depends on

International Journal of Photoenergy 9

the chemical properties of dyes and on the possibility offormation of coordination compounds with Fe3+ ions

In the case of effluents containing cationic dyes (WPac)the addition of Fe(III) salt was unfavorable because the effi-ciency of photodegradation of these dyes and COD removalwere lower than that in the presence of TiO

2only The

explanation of this result can be the change of charge ofTiO2particles (in the presence of Fe3+ ions) that limits the

possibility of sorption of the positively charged particles ofcationic dyes

In the case of effluents containing anionic dyes (WLeatand WFlax) the presence of Fe3+ ions had a beneficialeffect on the efficiency of photocatalytic degradation of thesecompoundsThe possible explanations may be a formation ofphotoactive complexes between dyes particles and Fe3+ ionsthat absorb UV-a irradiation much better than individualmolecules of dyes or an adsorption of complexes of dyes withFe3+ ions on the photocatalyst surface

The investigated dyes effluents containing also otherpollutants such as fatty acids sugars and amino acids whichmay also be substrates for the photodegradation and cantherefore compete with the dyes Additionally they maycontain inorganic mobile anions such as Clminus CO

3

2minusSO4

minus2 PO4

3minus and NO3

minus which may significantly affect thedistribution of hydroxyl radicals in the following process

XO119899minus +HO∙ 997888rarr XO∙(119899minus1)minus

+OHminus (12)

As a result these anions at high concentrations candecrease the photodegradation that simultaneously occursbetween HO∙ radicals and dyes molecules

From the viewpoint of COD removal TiO2alone was

a much more effective photocatalyst than TiO2FeCl3 The

increase in COD value in WFlax effluent probably wasconnected with the presence of a very persistent substance(s)that did not undergo the oxidation during the COD deter-mination On the other hand the photocatalytic processleads to degradation of these substances and the obtainedproducts are much less chemically resistant In this aspectthe observed phenomenon is not negative In our publication[33] we have reported similar to other authors [34] that thecomplete photocatalytic degradation of contaminants duringthe treatment of effluents is still not economically feasible dueto high operating costs Therefore the reduction of time ofphotocatalytic process only to the time necessary to initialdegradation of nonbiodegradable substances (eg azo dyes)towards the most readily biodegradable intermediates is themost reasonable It is obvious that one single treatment stepcannot remove all pollutants contained in dyes effluents Theoptimal solution is the combination of different treatmentprocesses for example the photocatalytic degradation usingsunlight as the source of UV light with a biological processIt may significantly decrease the overall cost of the dyeeffluents treatment Additionally the photocatalytic pre-treatment of dyeing effluents can lead to improvement oftheir biodegradability for example initial toxicity inducedby photodegradation of textile antraquinone dye to Vibriafisheri progressively decreased during the course of pro-cess [35] In this way a significant decrease in the overall

cost of the treatment of dyes effluents is expected mainlythrough the combination of several AOPs for example thephotocatalytic degradation as a pretreatment method withbiological processes [36] An increase of biodegradability ofthese effluents would facilitate their subsequent biologicaltreatment and an effective removal of undesirable andorrecalcitrant pollutants making the complete mineralizationunnecessary

4 The Mechanism of WastewaterDecolorization Processes

The experiments confirmed that TiO2caused decolorization

of wastewatermainly due to photocatalytic process Howeverthe decolorization ofWLeat could be a result of dyes sorptiononto TiO

2surface (Table 3)

As previously described FeCl3alone could not be the

cause of decolorization of wastewater during the photocat-alytic process On the other hand the addition of FeCl

3

accelerated undoubtedly the photocatalytic degradation ofanionic dyes According to Mestankova et al this effectwas mainly the result of the synergism of photochemicalactivity between TiO

2and FeCl

3[24] However the results

of experiments showing that FeCl3alone did not exhibit the

photochemical activity in wastewater and it decreased thephotodegradation rate of cationic dyes may indicate otherpossible mechanism It should be noted that even moreimportant is the above described process of intensification ofsorption of dyes coordinated with FeCl

3onto TiO

2surface

[23] The other reason could be the fact that the additionof FeCl

3and simultaneously decrease of pH cause agglom-

eration of suspensions in wastewaters and also increase instability and photoavailability of the TiO

2used [30]

5 Conclusions

Dyeing effluents irradiated in the presence of FeCl3alone

were decolorized but azo dyes almost completely did notundergo degradation On the country the photocatalyticprocess carried out with TiO

2and TiO

2FeCl3as photo-

catalysts was the effective method of decolorization anddyes photodegradation in the investigated effluents (exceptsamples containing high concentration of very stable azodye) During the photocatalytic degradation of anionic dyesa mixture of TiO

2FeCl3was more effective while in the case

of cationic dyes more suitable seems to be TiO2alone

Acknowledgment

This work was supported by the Medical University of Silesia(Grant no KNW-1-043P20)

References

[1] R G Saratale G D Saratale J S Chang and S P GovindwarldquoDecolorization and biodegradation of reactive dyes and dyewastewater by a developed bacterial consortiumrdquo Biodegrada-tion vol 21 no 6 pp 999ndash1015 2010

10 International Journal of Photoenergy

[2] 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

[3] J C Garcia J L Oliveira A E C Silva C C OliveiraJ Nozaki and N E de Souza ldquoComparative study of thedegradation of real textile effluents by photocatalytic reactionsinvolvingUVTiO

2H2O2andUVFe2+H

2O2systemsrdquo Journal

of Hazardous Materials vol 147 no 1-2 pp 105ndash110 2007[4] I M C Goncalves A Gomes R Bras M I A Ferra M T

P Amorim and R S Porter ldquoBiological treatment of effluentcontaining textile dyesrdquoColoration Technology vol 116 pp 393ndash397 2000

[5] M Asgher H N Bhatti S A H Shah M J Asad and R LLegge ldquoDecolorization potential of mixed microbial consortiafor reactive and disperse textile dyestuffsrdquo Biodegradation vol18 no 3 pp 311ndash316 2007

[6] B H Hameed A L Ahmad and K N A Latiff ldquoAdsorptionof basic dye (methylene blue) onto activated carbon preparedfrom rattan sawdustrdquo Dyes and Pigments vol 75 no 1 pp 143ndash149 2007

[7] H Selcuk ldquoDecolorization and detoxification of textile wastew-ater by ozonation and coagulation processesrdquo Dyes and Pig-ments vol 64 no 3 pp 217ndash222 2005

[8] A S Stasinakis ldquoUse of selected advanced oxidation processes(AOPs) for wastewater treatmentmdashamini reviewrdquoGlobal NESTJournal vol 10 pp 376ndash385 2008

[9] R Aplin and T D Waite ldquoComparison of three advancedoxidation processes for degradation of textile dyesrdquo WaterScience and Technology vol 42 no 5-6 pp 345ndash354 2000

[10] I Arslan-Alaton G Tureli and T Olmez-Hanci ldquoTreatmentof azo dye production wastewaters using Photo-Fenton-likeadvanced oxidation processes optimization by response surfacemethodologyrdquo Journal of Photochemistry and Photobiology Avol 202 no 2-3 pp 142ndash153 2009

[11] J M Herrmann ldquoHeterogeneous photocatalysis state of the artand present applicationsrdquoTopics in Catalysis vol 34 no 1ndash4 pp49ndash65 2005

[12] I K Konstantinou and T A Albanis ldquoTiO2-assisted photocat-

alytic degradation of azo dyes in aqueous solution kinetic andmechanistic investigations a reviewrdquo Applied Catalysis B vol49 no 1 pp 1ndash14 2004

[13] W Feng and D Nansheng ldquoPhotochemistry of hydrolyticiron (III) species and photoinduced degradation of organiccompounds A minireviewrdquo Chemosphere vol 41 no 8 pp1137ndash1147 2000

[14] I P Pozdnyakov Y A Sosedova V F Plyusnin et al ldquoPho-todegradation of organic pollutants in aqueous solutions causedby (OH)2+aq photolysis evidence of OH radical formationrdquoInternational Journal of Photoenergy vol 6 no 2 pp 89ndash932004

[15] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalyticdegradation of organic contaminants over titanium dioxidea review of fundamentals progress and problemsrdquo Journal ofPhotochemistry and Photobiology C vol 9 no 1 pp 1ndash12 2008

[16] O K Dalrymple D H Yeh and M A Trotz ldquoRemovingpharmaceuticals and endocrine-disrupting compounds fromwastewater by photocatalysisrdquo Journal of Chemical Technologyand Biotechnology vol 82 no 2 pp 121ndash134 2007

[17] R Rajeswari and S Kanmani ldquoA study on degradation of pes-ticide wastewater by TiO

2photocatalysisrdquo Journal of Scientific

and Industrial Research vol 68 no 12 pp 1063ndash1067 2009

[18] Z F Guo R X Ma and G J Li ldquoDegradation of phenolby nanomaterial TiO

2in wastewaterrdquo Chemical Engineering

Journal vol 119 pp 55ndash59 2006[19] C Jia YWang C Zhang and Q Qin ldquoUV-TiO

2photocatalytic

degradation of landfill leachaterdquo Water Air and Soil Pollutionvol 217 no 1ndash4 pp 375ndash385 2011

[20] V Sarria M Deront P Peringer and C Pulgarin ldquoDegradationof a biorecalcitrant dye precursor present in industrial wastew-aters by a new integrated iron(III) photoassisted-biologicaltreatmentrdquoApplied Catalysis B vol 40 no 3 pp 231ndash246 2003

[21] L Poulain G Mailhot P Wong-Wah-Chung and M BolteldquoPhotodegradation of chlortoluron sensitised by iron(III) aqua-complexesrdquo Journal of Photochemistry and Photobiology A vol159 no 1 pp 81ndash88 2003

[22] C Catastini S Rafqah G Mailhot and M Sarakha ldquoDegra-dation of amitrole by excitation of iron(III) aquacomplexes inaqueous solutionsrdquo Journal of Photochemistry and PhotobiologyA vol 162 no 1 pp 97ndash103 2004

[23] W Baran A Makowski and W Wardas ldquoThe influence ofFeCl3on the photocatalytic degradation of dissolved azo dyes

in aqueous TiO2suspensionsrdquo Chemosphere vol 53 no 1 pp

87ndash95 2003[24] H Mestankova J Krysa J Jirkovsky G Mailhot and M

Bolte ldquoThe influence of Fe(III) speciation on supported TiO2

efficiency example of monuron photocatalytic degradationrdquoApplied Catalysis B vol 58 pp 185ndash191 2005

[25] J Zhang D Fu Q Peng L Deng and X Yang ldquoFe3+-assistedphotocatalytic oxidation of sulfamethazine in TiO

2suspended

solutionrdquo Fresenius Environmental Bulletin vol 20 no 4 pp1051ndash1056 2011

[26] I A Alaton I A Balcioglu and D W Bahnemann ldquoAdvancedoxidation of a reactive dyebath effluent Comparison of O

3

H2O2UV-C and TiO

2UV-A processesrdquo Water Research vol

36 no 5 pp 1143ndash1154 2002[27] P A Pekakis N P Xekoukoulotakis and D Mantzavinos

ldquoTreatment of textile dyehouse wastewater by TiO2photocatal-

ysisrdquoWater Research vol 40 no 6 pp 1276ndash1286 2006[28] C C Liu Y H Hsieh P F Lai C H Li and C L Kao ldquoPho-

todegradation treatment of azo dye wastewater by UVTiO2

processrdquo Dyes and Pigments vol 68 no 2-3 pp 191ndash195 2006[29] J C Garcia J I Simionato A E C Silva J Nozaki and N E de

Souza ldquoSolar photocatalytic degradation of real textile effluentsby associated titanium dioxide and hydrogen peroxiderdquo SolarEnergy vol 83 no 3 pp 316ndash322 2009

[30] W Baran E Adamek and A Makowski ldquoThe influence ofselected parameters on the photocatalytic degradation of azo-dyes in the presence of TiO

2aqueous suspensionrdquo Chemical

Engineering Journal vol 145 no 2 pp 242ndash248 2008[31] ldquoMethods for Chemical Analysis of Water and Wastes Chem-

ical Oxygen Demand Titrimetric Methods 4101-3rdquo US EPAUnited States Environmental Protection Agency Office ofResearch and Development Washington DC USA EPA6004-79020 pp 443ndash451 March 1983 httpnepisepagov

[32] W Baran A Makowski and W Wardas ldquoChanges in CODvalues in aqueous solutions of the selected azo dyes duringthe photocatalytic degradation processrdquo in Micropollution inthe Human Environment vol 51 pp 215ndash221 CzestochowaUniversity of Technology Publishing House CzestochowaPoland 2003

[33] W Baran J Sochacka andWWardas ldquoToxicity and biodegrad-ability of sulfonamides and products of their photocatalytic

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

6 International Journal of Photoenergy

300min no significant changes in chromatograms and inCOD values were observed

After the dissolution of water insoluble Fe-organic com-plexes chromatograms of samples (before and after UVirradiation) remained practically unchanged This observa-tion indicates that during UV-a irradiation of effluents withFe(III) salt only dyes did not undergo the photocatalyticdegradationThe use of FeCl

3and probably also other Fe(III)

salts as a catalyst in the photocatalytic treatment processof dye effluents is completely ineffective (after 60min ofirradiation the photodegradation efficiency was in the rangeof 0) Therefore under model conditions model Fe(OH)2+ions can have photocatalytic activity at pH 3 but in realwastewater samples for example in dye effluents they mayact as a coagulant only

32 Effect of TiO2 After centrifugation of nonirradiatedsamples with TiO

2 no significant changes in UV-VIS spec-

tra (Figure 2) and HPLC chromatograms were observedSimultaneously in all effluent samples the photocatalyst wascoagulated only in a negligible level

As can be seen from the UV-VIS spectra shown inFigure 2(a) after UV-a irradiation of samples containingcationic dyes (WPac) with TiO

2for 60min the effluent

underwent high decolorization resulting in a completelycolorless effluent The disappearance of the absorption bands(120582max at 340 430 520 and 610 nm) suggests that the chro-mophore groups responsible for color progressively breakdown during UV-a irradiation Therefore in the case ofcationic dyes the effluent decolorization was almost exclu-sively the result of the photocatalytic process and only ina small degree due to physical processes such as precipita-tion coagulation or sorption The degradation efficiency ofcationic dyes was in the range of 37ndash86 but the CODremoval was low even after 300min of irradiation and wasonly 14 (Table 3)

The decolorization (a decrease in absorbance) was alsoobserved in WLeat and WFlax effluents containing anionicdyes (Figures 2(b) and 2(c)) After irradiation of samplesin the presence of TiO

2 a decrease of absorbance at 510

and 620 nm for WLeat and a decrease of a continuous band(without any distinctmaximum) forWFlaxwere observed Inthe case of effluent resulting from dyeing of leather (WLeat)decolorization was the result of both the photodegrada-tion and the physical processes The maximum degradationdegree of one of the dyes namely Acid Red 88 was 63 after300min of UV-a irradiation (Table 3)

On the other hand WFlax effluents irradiated for 60minwith TiO

2exhibited lower dyes degradation in the range

of 10 The UV-a irradiation for 300min caused a decreasein COD value about 40 in WLeat effluents and on thecontrary an increase in COD value of 40 in WFlax(Table 3)

As shown in Figure 2(d) in effluents from cotton dyeingprocesses (WCot) decolorization and changes inHPLCchro-matograms practically were not observed The degradationdegree of dye was lt5 even after 300min UV-a irradiationIn these samples the degradation efficiency was very low

probably because of less transmission of UV-a light throughthe black effluents Additionally WCot samples containinghigh concentration of dye (Direct Black 22) had the highestCOD over 8900mg O

2Lminus1 Therefore after 300min of

irradiation the COD removal was about 11 (Table 3)The photodegradation of compounds duringin hetero-

geneous photocatalysis depends among other factors on thechemical properties of substrates and their adsorption abilityonto the photocatalyst surface [11] In accordance to hetero-geneous catalysis theory (Langmuir- Himselwood model)the increase in adsorption of dyes causes the increase in thephotocatalytic degradation rate Additionally TiO

2shows an

amphoteric character and its photocatalytic activity dependsalso on the pH of samples In the case of the investigated TiO

2

(pure anatase) the determined pH value of the point of zerocharge (pHpzc) was 300 In the used dyes effluents the pHswere always higher than pHpzc and therefore TiO

2surface

should be negatively charged as follows

Ti ndashOH2

+pHltpHpzclArrrArr TindashOH

pHgtpHpzclArrrArr TiOminus (11)

This fact may explain the higher adsorption and higher pho-todegradation ability of cationic dyes (inWPac effluents) andlower adsorption of anionic dyes (WCot andWFlax) onto theTiO2surface under the studied conditions However it does

not simply explain high degradation of anionic dyes inWLeateffluents The adsorption process onto TiO

2surface under

UV-irradiation conditions is complex and some differencesin an adsorption capacity of particles may occur Probablya higher removal of COD in WLeat can be attributed to theadsorption of increased amounts of undissociated particles(eg anionic dyeswith organic or inorganic ions) on the TiO

2

surface Additionally the organic compounds in WLeat thatis dyes surfactant agents and auxiliaries were rather photolabile and they were easily transformed to less stable organics(byproducts)

33 Effect of TiO2FeCl3 As shown in Figure 3 the additionof TiO

2FeCl3mixture to nonirradiated effluents caused a

significant coagulation and decolorization of all samplesTherefore in these processes Fe salts could play a roleof coagulant However UV-a irradiation of such samplesresulted in their decolorization (Figure 3 Table 3) and thismay indicate its role as a photosensitizer

It was found that the photocatalytic degradation in efflu-ent containing cationic dyes (WPac) was less effective in themixture of TiO

2FeCl3than in the presence of TiO

2alone

(Table 3) After 60min of UV-a irradiation the degradationefficiency of dyes was in the range 10ndash40 SimultaneouslyWPac underwent the effective decolorization which can beexplained only as the dyes photodegradation (Figure 3(a))This process was not inhibited by strong coagulation ofphotocatalysts and by auxiliary substances contained in thesesamples After the addition of TiO

2FeCl3but before UV-

a irradiation absorbance in WPac effluent at 120582 lt 500 nmwas significantly higher due to the presence of dissolvedFe(III) compounds (dashed line) The data concerning CODremoval indicate that the efficiency of WPac mineralizationafter 300min of UV-a irradiation reached only 9

International Journal of Photoenergy 7

0

005

01

015

02

025

03

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(b)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriz

atio

n (

)

(c)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(d)

Figure 2 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent 119860

119900 dotted line (blue) effluent with TiO

2 without UV-a irradiation 119860

119884 solid line (blue) effluent with TiO

2 after UV-a irradiation

119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and after UV-a irradiation ( ⃝) decolorization of effluent as a result of the

photocatalytic process in the presence of TiO2(25 g Lminus1) and after UV-a irradiation

On the contrary effluents containing anionic dyes(WLeat and WFlax) underwent the photocatalytic degra-dation more effectively in the presence of TiO

2FeCl3than

in TiO2alone (Table 3) Upon UV-a irradiation there were

continuous decreases in absorbance all along the spectrameaning the fragmentation of organic structures and thephotocatalytic degradation of dyes (Figures 3(b) and 3(c))As shown in Table 2 the complete removal of Acid Red 88fromWLeat was the result of both direct precipitation andoradsorption on the photocatalyst surface and photodegrada-tion process The degradation efficiency of this dye was highand reached even 100 after 300min of UV-a irradiation(Table 3)Thedecolorization ofWFlaxwas caused to a greaterextent by the photocatalytic process than coagulation andor

precipitation (Figure 3(c)) The dyes degradation was in therange 35ndash42 after 60min of UV-a irradiation Removal ofCOD in WLeat in the presence of TiO

2FeCl3was 15 and

was lower than in the presence of TiO2alone On the other

hand similarly as during irradiation of WFlax with TiO2

alone after 300min of UV-a irradiation with TiO2FeCl3

there was not a decrease of COD value but its increaseIn our opinion an increase in COD removal upon UV-

a irradiation of WFlax with TiO2and TiO

2FeCl3is only

provisional This effect can be explained by an increase in theconcentration of smaller organics molecules formed duringthe photocatalytic oxidation of dyes and suspended solidsMost of the decomposable compounds are removed in theinitial time of this process and the remained part of organic

8 International Journal of Photoenergy

0

01

02

03

04

05

06

07

08

09

1

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

Abs

orba

nce

Dec

olor

izat

ion

()

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(b)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriza

tion

()

(c)

Abs

orba

nce

Dec

olor

izatio

n (

)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(d)

Figure 3 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent119860

119900 dotted line (blue) effluent with TiO

2and FeCl

3but without UV-a irradiation119860

119884 solid line (blue) effluent with TiO

2 FeCl

3and

after UV-a irradiation 119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and FeCl

3(10 mmol Lminus1) and after UV-a irradiation ( ⃝)

decolorization of effluent as a result of the photocatalytic process in the presence of TiO2(25 g Lminus1) FeCl

3(10mmol Lminus1) and after UV-a

irradiation

pollutants for example lower molecular weight carboxylicacids aldehydes and ketones can be less removable Thesebyproducts may not be completely mineralized by K

2Cr2O7

because they are quite resistant and their chemical oxida-tion can be the rate-limiting step in oxidation processesTherefore they require more severe oxidation conditions ora longer time for their conversion On the other hand theCOD values enable only qualitative rather than quantitativeassessment of the mineralization process [32]

After the addition of TiO2FeCl3toWCot the decoloriza-

tion was found to be almost 100 resulting in a completelycolorless effluent (Figure 3(d)) However the removal ofDirect Black 22 was the result of its precipitation only and not

the photocatalytic process The efficiency of photocatalyticdegradation of this dye after 300min of UV-a irradiation waslt5 (Table 3)

Furthermore the organic load ofWCot effluent irradiatedwith TiO

2FeCl3did not change significantly the COD

removal remained low at a value of about 7 Taking intoaccount the high chemical stability of dye (Direct Black 22)in WCot as well as its high concentration in effluent thephotocatalytic degradation of WCot in the presence of TiO

2

and TiO2FeCl3is not an effective method

An estimation of the efficiency of the studied photo-catalytic systems (TiO

2and TiO

2FeCl3) used during the

photocatalytic degradation of real effluents also depends on

International Journal of Photoenergy 9

the chemical properties of dyes and on the possibility offormation of coordination compounds with Fe3+ ions

In the case of effluents containing cationic dyes (WPac)the addition of Fe(III) salt was unfavorable because the effi-ciency of photodegradation of these dyes and COD removalwere lower than that in the presence of TiO

2only The

explanation of this result can be the change of charge ofTiO2particles (in the presence of Fe3+ ions) that limits the

possibility of sorption of the positively charged particles ofcationic dyes

In the case of effluents containing anionic dyes (WLeatand WFlax) the presence of Fe3+ ions had a beneficialeffect on the efficiency of photocatalytic degradation of thesecompoundsThe possible explanations may be a formation ofphotoactive complexes between dyes particles and Fe3+ ionsthat absorb UV-a irradiation much better than individualmolecules of dyes or an adsorption of complexes of dyes withFe3+ ions on the photocatalyst surface

The investigated dyes effluents containing also otherpollutants such as fatty acids sugars and amino acids whichmay also be substrates for the photodegradation and cantherefore compete with the dyes Additionally they maycontain inorganic mobile anions such as Clminus CO

3

2minusSO4

minus2 PO4

3minus and NO3

minus which may significantly affect thedistribution of hydroxyl radicals in the following process

XO119899minus +HO∙ 997888rarr XO∙(119899minus1)minus

+OHminus (12)

As a result these anions at high concentrations candecrease the photodegradation that simultaneously occursbetween HO∙ radicals and dyes molecules

From the viewpoint of COD removal TiO2alone was

a much more effective photocatalyst than TiO2FeCl3 The

increase in COD value in WFlax effluent probably wasconnected with the presence of a very persistent substance(s)that did not undergo the oxidation during the COD deter-mination On the other hand the photocatalytic processleads to degradation of these substances and the obtainedproducts are much less chemically resistant In this aspectthe observed phenomenon is not negative In our publication[33] we have reported similar to other authors [34] that thecomplete photocatalytic degradation of contaminants duringthe treatment of effluents is still not economically feasible dueto high operating costs Therefore the reduction of time ofphotocatalytic process only to the time necessary to initialdegradation of nonbiodegradable substances (eg azo dyes)towards the most readily biodegradable intermediates is themost reasonable It is obvious that one single treatment stepcannot remove all pollutants contained in dyes effluents Theoptimal solution is the combination of different treatmentprocesses for example the photocatalytic degradation usingsunlight as the source of UV light with a biological processIt may significantly decrease the overall cost of the dyeeffluents treatment Additionally the photocatalytic pre-treatment of dyeing effluents can lead to improvement oftheir biodegradability for example initial toxicity inducedby photodegradation of textile antraquinone dye to Vibriafisheri progressively decreased during the course of pro-cess [35] In this way a significant decrease in the overall

cost of the treatment of dyes effluents is expected mainlythrough the combination of several AOPs for example thephotocatalytic degradation as a pretreatment method withbiological processes [36] An increase of biodegradability ofthese effluents would facilitate their subsequent biologicaltreatment and an effective removal of undesirable andorrecalcitrant pollutants making the complete mineralizationunnecessary

4 The Mechanism of WastewaterDecolorization Processes

The experiments confirmed that TiO2caused decolorization

of wastewatermainly due to photocatalytic process Howeverthe decolorization ofWLeat could be a result of dyes sorptiononto TiO

2surface (Table 3)

As previously described FeCl3alone could not be the

cause of decolorization of wastewater during the photocat-alytic process On the other hand the addition of FeCl

3

accelerated undoubtedly the photocatalytic degradation ofanionic dyes According to Mestankova et al this effectwas mainly the result of the synergism of photochemicalactivity between TiO

2and FeCl

3[24] However the results

of experiments showing that FeCl3alone did not exhibit the

photochemical activity in wastewater and it decreased thephotodegradation rate of cationic dyes may indicate otherpossible mechanism It should be noted that even moreimportant is the above described process of intensification ofsorption of dyes coordinated with FeCl

3onto TiO

2surface

[23] The other reason could be the fact that the additionof FeCl

3and simultaneously decrease of pH cause agglom-

eration of suspensions in wastewaters and also increase instability and photoavailability of the TiO

2used [30]

5 Conclusions

Dyeing effluents irradiated in the presence of FeCl3alone

were decolorized but azo dyes almost completely did notundergo degradation On the country the photocatalyticprocess carried out with TiO

2and TiO

2FeCl3as photo-

catalysts was the effective method of decolorization anddyes photodegradation in the investigated effluents (exceptsamples containing high concentration of very stable azodye) During the photocatalytic degradation of anionic dyesa mixture of TiO

2FeCl3was more effective while in the case

of cationic dyes more suitable seems to be TiO2alone

Acknowledgment

This work was supported by the Medical University of Silesia(Grant no KNW-1-043P20)

References

[1] R G Saratale G D Saratale J S Chang and S P GovindwarldquoDecolorization and biodegradation of reactive dyes and dyewastewater by a developed bacterial consortiumrdquo Biodegrada-tion vol 21 no 6 pp 999ndash1015 2010

10 International Journal of Photoenergy

[2] 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

[3] J C Garcia J L Oliveira A E C Silva C C OliveiraJ Nozaki and N E de Souza ldquoComparative study of thedegradation of real textile effluents by photocatalytic reactionsinvolvingUVTiO

2H2O2andUVFe2+H

2O2systemsrdquo Journal

of Hazardous Materials vol 147 no 1-2 pp 105ndash110 2007[4] I M C Goncalves A Gomes R Bras M I A Ferra M T

P Amorim and R S Porter ldquoBiological treatment of effluentcontaining textile dyesrdquoColoration Technology vol 116 pp 393ndash397 2000

[5] M Asgher H N Bhatti S A H Shah M J Asad and R LLegge ldquoDecolorization potential of mixed microbial consortiafor reactive and disperse textile dyestuffsrdquo Biodegradation vol18 no 3 pp 311ndash316 2007

[6] B H Hameed A L Ahmad and K N A Latiff ldquoAdsorptionof basic dye (methylene blue) onto activated carbon preparedfrom rattan sawdustrdquo Dyes and Pigments vol 75 no 1 pp 143ndash149 2007

[7] H Selcuk ldquoDecolorization and detoxification of textile wastew-ater by ozonation and coagulation processesrdquo Dyes and Pig-ments vol 64 no 3 pp 217ndash222 2005

[8] A S Stasinakis ldquoUse of selected advanced oxidation processes(AOPs) for wastewater treatmentmdashamini reviewrdquoGlobal NESTJournal vol 10 pp 376ndash385 2008

[9] R Aplin and T D Waite ldquoComparison of three advancedoxidation processes for degradation of textile dyesrdquo WaterScience and Technology vol 42 no 5-6 pp 345ndash354 2000

[10] I Arslan-Alaton G Tureli and T Olmez-Hanci ldquoTreatmentof azo dye production wastewaters using Photo-Fenton-likeadvanced oxidation processes optimization by response surfacemethodologyrdquo Journal of Photochemistry and Photobiology Avol 202 no 2-3 pp 142ndash153 2009

[11] J M Herrmann ldquoHeterogeneous photocatalysis state of the artand present applicationsrdquoTopics in Catalysis vol 34 no 1ndash4 pp49ndash65 2005

[12] I K Konstantinou and T A Albanis ldquoTiO2-assisted photocat-

alytic degradation of azo dyes in aqueous solution kinetic andmechanistic investigations a reviewrdquo Applied Catalysis B vol49 no 1 pp 1ndash14 2004

[13] W Feng and D Nansheng ldquoPhotochemistry of hydrolyticiron (III) species and photoinduced degradation of organiccompounds A minireviewrdquo Chemosphere vol 41 no 8 pp1137ndash1147 2000

[14] I P Pozdnyakov Y A Sosedova V F Plyusnin et al ldquoPho-todegradation of organic pollutants in aqueous solutions causedby (OH)2+aq photolysis evidence of OH radical formationrdquoInternational Journal of Photoenergy vol 6 no 2 pp 89ndash932004

[15] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalyticdegradation of organic contaminants over titanium dioxidea review of fundamentals progress and problemsrdquo Journal ofPhotochemistry and Photobiology C vol 9 no 1 pp 1ndash12 2008

[16] O K Dalrymple D H Yeh and M A Trotz ldquoRemovingpharmaceuticals and endocrine-disrupting compounds fromwastewater by photocatalysisrdquo Journal of Chemical Technologyand Biotechnology vol 82 no 2 pp 121ndash134 2007

[17] R Rajeswari and S Kanmani ldquoA study on degradation of pes-ticide wastewater by TiO

2photocatalysisrdquo Journal of Scientific

and Industrial Research vol 68 no 12 pp 1063ndash1067 2009

[18] Z F Guo R X Ma and G J Li ldquoDegradation of phenolby nanomaterial TiO

2in wastewaterrdquo Chemical Engineering

Journal vol 119 pp 55ndash59 2006[19] C Jia YWang C Zhang and Q Qin ldquoUV-TiO

2photocatalytic

degradation of landfill leachaterdquo Water Air and Soil Pollutionvol 217 no 1ndash4 pp 375ndash385 2011

[20] V Sarria M Deront P Peringer and C Pulgarin ldquoDegradationof a biorecalcitrant dye precursor present in industrial wastew-aters by a new integrated iron(III) photoassisted-biologicaltreatmentrdquoApplied Catalysis B vol 40 no 3 pp 231ndash246 2003

[21] L Poulain G Mailhot P Wong-Wah-Chung and M BolteldquoPhotodegradation of chlortoluron sensitised by iron(III) aqua-complexesrdquo Journal of Photochemistry and Photobiology A vol159 no 1 pp 81ndash88 2003

[22] C Catastini S Rafqah G Mailhot and M Sarakha ldquoDegra-dation of amitrole by excitation of iron(III) aquacomplexes inaqueous solutionsrdquo Journal of Photochemistry and PhotobiologyA vol 162 no 1 pp 97ndash103 2004

[23] W Baran A Makowski and W Wardas ldquoThe influence ofFeCl3on the photocatalytic degradation of dissolved azo dyes

in aqueous TiO2suspensionsrdquo Chemosphere vol 53 no 1 pp

87ndash95 2003[24] H Mestankova J Krysa J Jirkovsky G Mailhot and M

Bolte ldquoThe influence of Fe(III) speciation on supported TiO2

efficiency example of monuron photocatalytic degradationrdquoApplied Catalysis B vol 58 pp 185ndash191 2005

[25] J Zhang D Fu Q Peng L Deng and X Yang ldquoFe3+-assistedphotocatalytic oxidation of sulfamethazine in TiO

2suspended

solutionrdquo Fresenius Environmental Bulletin vol 20 no 4 pp1051ndash1056 2011

[26] I A Alaton I A Balcioglu and D W Bahnemann ldquoAdvancedoxidation of a reactive dyebath effluent Comparison of O

3

H2O2UV-C and TiO

2UV-A processesrdquo Water Research vol

36 no 5 pp 1143ndash1154 2002[27] P A Pekakis N P Xekoukoulotakis and D Mantzavinos

ldquoTreatment of textile dyehouse wastewater by TiO2photocatal-

ysisrdquoWater Research vol 40 no 6 pp 1276ndash1286 2006[28] C C Liu Y H Hsieh P F Lai C H Li and C L Kao ldquoPho-

todegradation treatment of azo dye wastewater by UVTiO2

processrdquo Dyes and Pigments vol 68 no 2-3 pp 191ndash195 2006[29] J C Garcia J I Simionato A E C Silva J Nozaki and N E de

Souza ldquoSolar photocatalytic degradation of real textile effluentsby associated titanium dioxide and hydrogen peroxiderdquo SolarEnergy vol 83 no 3 pp 316ndash322 2009

[30] W Baran E Adamek and A Makowski ldquoThe influence ofselected parameters on the photocatalytic degradation of azo-dyes in the presence of TiO

2aqueous suspensionrdquo Chemical

Engineering Journal vol 145 no 2 pp 242ndash248 2008[31] ldquoMethods for Chemical Analysis of Water and Wastes Chem-

ical Oxygen Demand Titrimetric Methods 4101-3rdquo US EPAUnited States Environmental Protection Agency Office ofResearch and Development Washington DC USA EPA6004-79020 pp 443ndash451 March 1983 httpnepisepagov

[32] W Baran A Makowski and W Wardas ldquoChanges in CODvalues in aqueous solutions of the selected azo dyes duringthe photocatalytic degradation processrdquo in Micropollution inthe Human Environment vol 51 pp 215ndash221 CzestochowaUniversity of Technology Publishing House CzestochowaPoland 2003

[33] W Baran J Sochacka andWWardas ldquoToxicity and biodegrad-ability of sulfonamides and products of their photocatalytic

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

International Journal of Photoenergy 7

0

005

01

015

02

025

03

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(b)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriz

atio

n (

)

(c)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)

(d)

Figure 2 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent 119860

119900 dotted line (blue) effluent with TiO

2 without UV-a irradiation 119860

119884 solid line (blue) effluent with TiO

2 after UV-a irradiation

119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and after UV-a irradiation ( ⃝) decolorization of effluent as a result of the

photocatalytic process in the presence of TiO2(25 g Lminus1) and after UV-a irradiation

On the contrary effluents containing anionic dyes(WLeat and WFlax) underwent the photocatalytic degra-dation more effectively in the presence of TiO

2FeCl3than

in TiO2alone (Table 3) Upon UV-a irradiation there were

continuous decreases in absorbance all along the spectrameaning the fragmentation of organic structures and thephotocatalytic degradation of dyes (Figures 3(b) and 3(c))As shown in Table 2 the complete removal of Acid Red 88fromWLeat was the result of both direct precipitation andoradsorption on the photocatalyst surface and photodegrada-tion process The degradation efficiency of this dye was highand reached even 100 after 300min of UV-a irradiation(Table 3)Thedecolorization ofWFlaxwas caused to a greaterextent by the photocatalytic process than coagulation andor

precipitation (Figure 3(c)) The dyes degradation was in therange 35ndash42 after 60min of UV-a irradiation Removal ofCOD in WLeat in the presence of TiO

2FeCl3was 15 and

was lower than in the presence of TiO2alone On the other

hand similarly as during irradiation of WFlax with TiO2

alone after 300min of UV-a irradiation with TiO2FeCl3

there was not a decrease of COD value but its increaseIn our opinion an increase in COD removal upon UV-

a irradiation of WFlax with TiO2and TiO

2FeCl3is only

provisional This effect can be explained by an increase in theconcentration of smaller organics molecules formed duringthe photocatalytic oxidation of dyes and suspended solidsMost of the decomposable compounds are removed in theinitial time of this process and the remained part of organic

8 International Journal of Photoenergy

0

01

02

03

04

05

06

07

08

09

1

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

Abs

orba

nce

Dec

olor

izat

ion

()

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(b)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriza

tion

()

(c)

Abs

orba

nce

Dec

olor

izatio

n (

)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(d)

Figure 3 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent119860

119900 dotted line (blue) effluent with TiO

2and FeCl

3but without UV-a irradiation119860

119884 solid line (blue) effluent with TiO

2 FeCl

3and

after UV-a irradiation 119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and FeCl

3(10 mmol Lminus1) and after UV-a irradiation ( ⃝)

decolorization of effluent as a result of the photocatalytic process in the presence of TiO2(25 g Lminus1) FeCl

3(10mmol Lminus1) and after UV-a

irradiation

pollutants for example lower molecular weight carboxylicacids aldehydes and ketones can be less removable Thesebyproducts may not be completely mineralized by K

2Cr2O7

because they are quite resistant and their chemical oxida-tion can be the rate-limiting step in oxidation processesTherefore they require more severe oxidation conditions ora longer time for their conversion On the other hand theCOD values enable only qualitative rather than quantitativeassessment of the mineralization process [32]

After the addition of TiO2FeCl3toWCot the decoloriza-

tion was found to be almost 100 resulting in a completelycolorless effluent (Figure 3(d)) However the removal ofDirect Black 22 was the result of its precipitation only and not

the photocatalytic process The efficiency of photocatalyticdegradation of this dye after 300min of UV-a irradiation waslt5 (Table 3)

Furthermore the organic load ofWCot effluent irradiatedwith TiO

2FeCl3did not change significantly the COD

removal remained low at a value of about 7 Taking intoaccount the high chemical stability of dye (Direct Black 22)in WCot as well as its high concentration in effluent thephotocatalytic degradation of WCot in the presence of TiO

2

and TiO2FeCl3is not an effective method

An estimation of the efficiency of the studied photo-catalytic systems (TiO

2and TiO

2FeCl3) used during the

photocatalytic degradation of real effluents also depends on

International Journal of Photoenergy 9

the chemical properties of dyes and on the possibility offormation of coordination compounds with Fe3+ ions

In the case of effluents containing cationic dyes (WPac)the addition of Fe(III) salt was unfavorable because the effi-ciency of photodegradation of these dyes and COD removalwere lower than that in the presence of TiO

2only The

explanation of this result can be the change of charge ofTiO2particles (in the presence of Fe3+ ions) that limits the

possibility of sorption of the positively charged particles ofcationic dyes

In the case of effluents containing anionic dyes (WLeatand WFlax) the presence of Fe3+ ions had a beneficialeffect on the efficiency of photocatalytic degradation of thesecompoundsThe possible explanations may be a formation ofphotoactive complexes between dyes particles and Fe3+ ionsthat absorb UV-a irradiation much better than individualmolecules of dyes or an adsorption of complexes of dyes withFe3+ ions on the photocatalyst surface

The investigated dyes effluents containing also otherpollutants such as fatty acids sugars and amino acids whichmay also be substrates for the photodegradation and cantherefore compete with the dyes Additionally they maycontain inorganic mobile anions such as Clminus CO

3

2minusSO4

minus2 PO4

3minus and NO3

minus which may significantly affect thedistribution of hydroxyl radicals in the following process

XO119899minus +HO∙ 997888rarr XO∙(119899minus1)minus

+OHminus (12)

As a result these anions at high concentrations candecrease the photodegradation that simultaneously occursbetween HO∙ radicals and dyes molecules

From the viewpoint of COD removal TiO2alone was

a much more effective photocatalyst than TiO2FeCl3 The

increase in COD value in WFlax effluent probably wasconnected with the presence of a very persistent substance(s)that did not undergo the oxidation during the COD deter-mination On the other hand the photocatalytic processleads to degradation of these substances and the obtainedproducts are much less chemically resistant In this aspectthe observed phenomenon is not negative In our publication[33] we have reported similar to other authors [34] that thecomplete photocatalytic degradation of contaminants duringthe treatment of effluents is still not economically feasible dueto high operating costs Therefore the reduction of time ofphotocatalytic process only to the time necessary to initialdegradation of nonbiodegradable substances (eg azo dyes)towards the most readily biodegradable intermediates is themost reasonable It is obvious that one single treatment stepcannot remove all pollutants contained in dyes effluents Theoptimal solution is the combination of different treatmentprocesses for example the photocatalytic degradation usingsunlight as the source of UV light with a biological processIt may significantly decrease the overall cost of the dyeeffluents treatment Additionally the photocatalytic pre-treatment of dyeing effluents can lead to improvement oftheir biodegradability for example initial toxicity inducedby photodegradation of textile antraquinone dye to Vibriafisheri progressively decreased during the course of pro-cess [35] In this way a significant decrease in the overall

cost of the treatment of dyes effluents is expected mainlythrough the combination of several AOPs for example thephotocatalytic degradation as a pretreatment method withbiological processes [36] An increase of biodegradability ofthese effluents would facilitate their subsequent biologicaltreatment and an effective removal of undesirable andorrecalcitrant pollutants making the complete mineralizationunnecessary

4 The Mechanism of WastewaterDecolorization Processes

The experiments confirmed that TiO2caused decolorization

of wastewatermainly due to photocatalytic process Howeverthe decolorization ofWLeat could be a result of dyes sorptiononto TiO

2surface (Table 3)

As previously described FeCl3alone could not be the

cause of decolorization of wastewater during the photocat-alytic process On the other hand the addition of FeCl

3

accelerated undoubtedly the photocatalytic degradation ofanionic dyes According to Mestankova et al this effectwas mainly the result of the synergism of photochemicalactivity between TiO

2and FeCl

3[24] However the results

of experiments showing that FeCl3alone did not exhibit the

photochemical activity in wastewater and it decreased thephotodegradation rate of cationic dyes may indicate otherpossible mechanism It should be noted that even moreimportant is the above described process of intensification ofsorption of dyes coordinated with FeCl

3onto TiO

2surface

[23] The other reason could be the fact that the additionof FeCl

3and simultaneously decrease of pH cause agglom-

eration of suspensions in wastewaters and also increase instability and photoavailability of the TiO

2used [30]

5 Conclusions

Dyeing effluents irradiated in the presence of FeCl3alone

were decolorized but azo dyes almost completely did notundergo degradation On the country the photocatalyticprocess carried out with TiO

2and TiO

2FeCl3as photo-

catalysts was the effective method of decolorization anddyes photodegradation in the investigated effluents (exceptsamples containing high concentration of very stable azodye) During the photocatalytic degradation of anionic dyesa mixture of TiO

2FeCl3was more effective while in the case

of cationic dyes more suitable seems to be TiO2alone

Acknowledgment

This work was supported by the Medical University of Silesia(Grant no KNW-1-043P20)

References

[1] R G Saratale G D Saratale J S Chang and S P GovindwarldquoDecolorization and biodegradation of reactive dyes and dyewastewater by a developed bacterial consortiumrdquo Biodegrada-tion vol 21 no 6 pp 999ndash1015 2010

10 International Journal of Photoenergy

[2] 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

[3] J C Garcia J L Oliveira A E C Silva C C OliveiraJ Nozaki and N E de Souza ldquoComparative study of thedegradation of real textile effluents by photocatalytic reactionsinvolvingUVTiO

2H2O2andUVFe2+H

2O2systemsrdquo Journal

of Hazardous Materials vol 147 no 1-2 pp 105ndash110 2007[4] I M C Goncalves A Gomes R Bras M I A Ferra M T

P Amorim and R S Porter ldquoBiological treatment of effluentcontaining textile dyesrdquoColoration Technology vol 116 pp 393ndash397 2000

[5] M Asgher H N Bhatti S A H Shah M J Asad and R LLegge ldquoDecolorization potential of mixed microbial consortiafor reactive and disperse textile dyestuffsrdquo Biodegradation vol18 no 3 pp 311ndash316 2007

[6] B H Hameed A L Ahmad and K N A Latiff ldquoAdsorptionof basic dye (methylene blue) onto activated carbon preparedfrom rattan sawdustrdquo Dyes and Pigments vol 75 no 1 pp 143ndash149 2007

[7] H Selcuk ldquoDecolorization and detoxification of textile wastew-ater by ozonation and coagulation processesrdquo Dyes and Pig-ments vol 64 no 3 pp 217ndash222 2005

[8] A S Stasinakis ldquoUse of selected advanced oxidation processes(AOPs) for wastewater treatmentmdashamini reviewrdquoGlobal NESTJournal vol 10 pp 376ndash385 2008

[9] R Aplin and T D Waite ldquoComparison of three advancedoxidation processes for degradation of textile dyesrdquo WaterScience and Technology vol 42 no 5-6 pp 345ndash354 2000

[10] I Arslan-Alaton G Tureli and T Olmez-Hanci ldquoTreatmentof azo dye production wastewaters using Photo-Fenton-likeadvanced oxidation processes optimization by response surfacemethodologyrdquo Journal of Photochemistry and Photobiology Avol 202 no 2-3 pp 142ndash153 2009

[11] J M Herrmann ldquoHeterogeneous photocatalysis state of the artand present applicationsrdquoTopics in Catalysis vol 34 no 1ndash4 pp49ndash65 2005

[12] I K Konstantinou and T A Albanis ldquoTiO2-assisted photocat-

alytic degradation of azo dyes in aqueous solution kinetic andmechanistic investigations a reviewrdquo Applied Catalysis B vol49 no 1 pp 1ndash14 2004

[13] W Feng and D Nansheng ldquoPhotochemistry of hydrolyticiron (III) species and photoinduced degradation of organiccompounds A minireviewrdquo Chemosphere vol 41 no 8 pp1137ndash1147 2000

[14] I P Pozdnyakov Y A Sosedova V F Plyusnin et al ldquoPho-todegradation of organic pollutants in aqueous solutions causedby (OH)2+aq photolysis evidence of OH radical formationrdquoInternational Journal of Photoenergy vol 6 no 2 pp 89ndash932004

[15] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalyticdegradation of organic contaminants over titanium dioxidea review of fundamentals progress and problemsrdquo Journal ofPhotochemistry and Photobiology C vol 9 no 1 pp 1ndash12 2008

[16] O K Dalrymple D H Yeh and M A Trotz ldquoRemovingpharmaceuticals and endocrine-disrupting compounds fromwastewater by photocatalysisrdquo Journal of Chemical Technologyand Biotechnology vol 82 no 2 pp 121ndash134 2007

[17] R Rajeswari and S Kanmani ldquoA study on degradation of pes-ticide wastewater by TiO

2photocatalysisrdquo Journal of Scientific

and Industrial Research vol 68 no 12 pp 1063ndash1067 2009

[18] Z F Guo R X Ma and G J Li ldquoDegradation of phenolby nanomaterial TiO

2in wastewaterrdquo Chemical Engineering

Journal vol 119 pp 55ndash59 2006[19] C Jia YWang C Zhang and Q Qin ldquoUV-TiO

2photocatalytic

degradation of landfill leachaterdquo Water Air and Soil Pollutionvol 217 no 1ndash4 pp 375ndash385 2011

[20] V Sarria M Deront P Peringer and C Pulgarin ldquoDegradationof a biorecalcitrant dye precursor present in industrial wastew-aters by a new integrated iron(III) photoassisted-biologicaltreatmentrdquoApplied Catalysis B vol 40 no 3 pp 231ndash246 2003

[21] L Poulain G Mailhot P Wong-Wah-Chung and M BolteldquoPhotodegradation of chlortoluron sensitised by iron(III) aqua-complexesrdquo Journal of Photochemistry and Photobiology A vol159 no 1 pp 81ndash88 2003

[22] C Catastini S Rafqah G Mailhot and M Sarakha ldquoDegra-dation of amitrole by excitation of iron(III) aquacomplexes inaqueous solutionsrdquo Journal of Photochemistry and PhotobiologyA vol 162 no 1 pp 97ndash103 2004

[23] W Baran A Makowski and W Wardas ldquoThe influence ofFeCl3on the photocatalytic degradation of dissolved azo dyes

in aqueous TiO2suspensionsrdquo Chemosphere vol 53 no 1 pp

87ndash95 2003[24] H Mestankova J Krysa J Jirkovsky G Mailhot and M

Bolte ldquoThe influence of Fe(III) speciation on supported TiO2

efficiency example of monuron photocatalytic degradationrdquoApplied Catalysis B vol 58 pp 185ndash191 2005

[25] J Zhang D Fu Q Peng L Deng and X Yang ldquoFe3+-assistedphotocatalytic oxidation of sulfamethazine in TiO

2suspended

solutionrdquo Fresenius Environmental Bulletin vol 20 no 4 pp1051ndash1056 2011

[26] I A Alaton I A Balcioglu and D W Bahnemann ldquoAdvancedoxidation of a reactive dyebath effluent Comparison of O

3

H2O2UV-C and TiO

2UV-A processesrdquo Water Research vol

36 no 5 pp 1143ndash1154 2002[27] P A Pekakis N P Xekoukoulotakis and D Mantzavinos

ldquoTreatment of textile dyehouse wastewater by TiO2photocatal-

ysisrdquoWater Research vol 40 no 6 pp 1276ndash1286 2006[28] C C Liu Y H Hsieh P F Lai C H Li and C L Kao ldquoPho-

todegradation treatment of azo dye wastewater by UVTiO2

processrdquo Dyes and Pigments vol 68 no 2-3 pp 191ndash195 2006[29] J C Garcia J I Simionato A E C Silva J Nozaki and N E de

Souza ldquoSolar photocatalytic degradation of real textile effluentsby associated titanium dioxide and hydrogen peroxiderdquo SolarEnergy vol 83 no 3 pp 316ndash322 2009

[30] W Baran E Adamek and A Makowski ldquoThe influence ofselected parameters on the photocatalytic degradation of azo-dyes in the presence of TiO

2aqueous suspensionrdquo Chemical

Engineering Journal vol 145 no 2 pp 242ndash248 2008[31] ldquoMethods for Chemical Analysis of Water and Wastes Chem-

ical Oxygen Demand Titrimetric Methods 4101-3rdquo US EPAUnited States Environmental Protection Agency Office ofResearch and Development Washington DC USA EPA6004-79020 pp 443ndash451 March 1983 httpnepisepagov

[32] W Baran A Makowski and W Wardas ldquoChanges in CODvalues in aqueous solutions of the selected azo dyes duringthe photocatalytic degradation processrdquo in Micropollution inthe Human Environment vol 51 pp 215ndash221 CzestochowaUniversity of Technology Publishing House CzestochowaPoland 2003

[33] W Baran J Sochacka andWWardas ldquoToxicity and biodegrad-ability of sulfonamides and products of their photocatalytic

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

8 International Journal of Photoenergy

0

01

02

03

04

05

06

07

08

09

1

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100

Dec

olor

izatio

n (

)(a)

Abs

orba

nce

Dec

olor

izat

ion

()

0

005

01

015

02

025

03

035

04

045

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(b)

0

02

04

06

08

1

12

14

16

300 400 500 600 700 800Wavelength (nm)

Abs

orba

nce

0

20

40

60

80

100D

ecol

oriza

tion

()

(c)

Abs

orba

nce

Dec

olor

izatio

n (

)

0

5

10

15

20

25

30

35

40

45

300 400 500 600 700 800Wavelength (nm)

0

20

40

60

80

100

(d)

Figure 3 Absorption and decolorization spectra of WPac (a) WLeat (b) WFlax (c) and WCot (d) Solid line (red) initial spectrum ofeffluent119860

119900 dotted line (blue) effluent with TiO

2and FeCl

3but without UV-a irradiation119860

119884 solid line (blue) effluent with TiO

2 FeCl

3and

after UV-a irradiation 119860119885 (∙) total decolorization of effluent with TiO

2(25 g Lminus1) and FeCl

3(10 mmol Lminus1) and after UV-a irradiation ( ⃝)

decolorization of effluent as a result of the photocatalytic process in the presence of TiO2(25 g Lminus1) FeCl

3(10mmol Lminus1) and after UV-a

irradiation

pollutants for example lower molecular weight carboxylicacids aldehydes and ketones can be less removable Thesebyproducts may not be completely mineralized by K

2Cr2O7

because they are quite resistant and their chemical oxida-tion can be the rate-limiting step in oxidation processesTherefore they require more severe oxidation conditions ora longer time for their conversion On the other hand theCOD values enable only qualitative rather than quantitativeassessment of the mineralization process [32]

After the addition of TiO2FeCl3toWCot the decoloriza-

tion was found to be almost 100 resulting in a completelycolorless effluent (Figure 3(d)) However the removal ofDirect Black 22 was the result of its precipitation only and not

the photocatalytic process The efficiency of photocatalyticdegradation of this dye after 300min of UV-a irradiation waslt5 (Table 3)

Furthermore the organic load ofWCot effluent irradiatedwith TiO

2FeCl3did not change significantly the COD

removal remained low at a value of about 7 Taking intoaccount the high chemical stability of dye (Direct Black 22)in WCot as well as its high concentration in effluent thephotocatalytic degradation of WCot in the presence of TiO

2

and TiO2FeCl3is not an effective method

An estimation of the efficiency of the studied photo-catalytic systems (TiO

2and TiO

2FeCl3) used during the

photocatalytic degradation of real effluents also depends on

International Journal of Photoenergy 9

the chemical properties of dyes and on the possibility offormation of coordination compounds with Fe3+ ions

In the case of effluents containing cationic dyes (WPac)the addition of Fe(III) salt was unfavorable because the effi-ciency of photodegradation of these dyes and COD removalwere lower than that in the presence of TiO

2only The

explanation of this result can be the change of charge ofTiO2particles (in the presence of Fe3+ ions) that limits the

possibility of sorption of the positively charged particles ofcationic dyes

In the case of effluents containing anionic dyes (WLeatand WFlax) the presence of Fe3+ ions had a beneficialeffect on the efficiency of photocatalytic degradation of thesecompoundsThe possible explanations may be a formation ofphotoactive complexes between dyes particles and Fe3+ ionsthat absorb UV-a irradiation much better than individualmolecules of dyes or an adsorption of complexes of dyes withFe3+ ions on the photocatalyst surface

The investigated dyes effluents containing also otherpollutants such as fatty acids sugars and amino acids whichmay also be substrates for the photodegradation and cantherefore compete with the dyes Additionally they maycontain inorganic mobile anions such as Clminus CO

3

2minusSO4

minus2 PO4

3minus and NO3

minus which may significantly affect thedistribution of hydroxyl radicals in the following process

XO119899minus +HO∙ 997888rarr XO∙(119899minus1)minus

+OHminus (12)

As a result these anions at high concentrations candecrease the photodegradation that simultaneously occursbetween HO∙ radicals and dyes molecules

From the viewpoint of COD removal TiO2alone was

a much more effective photocatalyst than TiO2FeCl3 The

increase in COD value in WFlax effluent probably wasconnected with the presence of a very persistent substance(s)that did not undergo the oxidation during the COD deter-mination On the other hand the photocatalytic processleads to degradation of these substances and the obtainedproducts are much less chemically resistant In this aspectthe observed phenomenon is not negative In our publication[33] we have reported similar to other authors [34] that thecomplete photocatalytic degradation of contaminants duringthe treatment of effluents is still not economically feasible dueto high operating costs Therefore the reduction of time ofphotocatalytic process only to the time necessary to initialdegradation of nonbiodegradable substances (eg azo dyes)towards the most readily biodegradable intermediates is themost reasonable It is obvious that one single treatment stepcannot remove all pollutants contained in dyes effluents Theoptimal solution is the combination of different treatmentprocesses for example the photocatalytic degradation usingsunlight as the source of UV light with a biological processIt may significantly decrease the overall cost of the dyeeffluents treatment Additionally the photocatalytic pre-treatment of dyeing effluents can lead to improvement oftheir biodegradability for example initial toxicity inducedby photodegradation of textile antraquinone dye to Vibriafisheri progressively decreased during the course of pro-cess [35] In this way a significant decrease in the overall

cost of the treatment of dyes effluents is expected mainlythrough the combination of several AOPs for example thephotocatalytic degradation as a pretreatment method withbiological processes [36] An increase of biodegradability ofthese effluents would facilitate their subsequent biologicaltreatment and an effective removal of undesirable andorrecalcitrant pollutants making the complete mineralizationunnecessary

4 The Mechanism of WastewaterDecolorization Processes

The experiments confirmed that TiO2caused decolorization

of wastewatermainly due to photocatalytic process Howeverthe decolorization ofWLeat could be a result of dyes sorptiononto TiO

2surface (Table 3)

As previously described FeCl3alone could not be the

cause of decolorization of wastewater during the photocat-alytic process On the other hand the addition of FeCl

3

accelerated undoubtedly the photocatalytic degradation ofanionic dyes According to Mestankova et al this effectwas mainly the result of the synergism of photochemicalactivity between TiO

2and FeCl

3[24] However the results

of experiments showing that FeCl3alone did not exhibit the

photochemical activity in wastewater and it decreased thephotodegradation rate of cationic dyes may indicate otherpossible mechanism It should be noted that even moreimportant is the above described process of intensification ofsorption of dyes coordinated with FeCl

3onto TiO

2surface

[23] The other reason could be the fact that the additionof FeCl

3and simultaneously decrease of pH cause agglom-

eration of suspensions in wastewaters and also increase instability and photoavailability of the TiO

2used [30]

5 Conclusions

Dyeing effluents irradiated in the presence of FeCl3alone

were decolorized but azo dyes almost completely did notundergo degradation On the country the photocatalyticprocess carried out with TiO

2and TiO

2FeCl3as photo-

catalysts was the effective method of decolorization anddyes photodegradation in the investigated effluents (exceptsamples containing high concentration of very stable azodye) During the photocatalytic degradation of anionic dyesa mixture of TiO

2FeCl3was more effective while in the case

of cationic dyes more suitable seems to be TiO2alone

Acknowledgment

This work was supported by the Medical University of Silesia(Grant no KNW-1-043P20)

References

[1] R G Saratale G D Saratale J S Chang and S P GovindwarldquoDecolorization and biodegradation of reactive dyes and dyewastewater by a developed bacterial consortiumrdquo Biodegrada-tion vol 21 no 6 pp 999ndash1015 2010

10 International Journal of Photoenergy

[2] 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

[3] J C Garcia J L Oliveira A E C Silva C C OliveiraJ Nozaki and N E de Souza ldquoComparative study of thedegradation of real textile effluents by photocatalytic reactionsinvolvingUVTiO

2H2O2andUVFe2+H

2O2systemsrdquo Journal

of Hazardous Materials vol 147 no 1-2 pp 105ndash110 2007[4] I M C Goncalves A Gomes R Bras M I A Ferra M T

P Amorim and R S Porter ldquoBiological treatment of effluentcontaining textile dyesrdquoColoration Technology vol 116 pp 393ndash397 2000

[5] M Asgher H N Bhatti S A H Shah M J Asad and R LLegge ldquoDecolorization potential of mixed microbial consortiafor reactive and disperse textile dyestuffsrdquo Biodegradation vol18 no 3 pp 311ndash316 2007

[6] B H Hameed A L Ahmad and K N A Latiff ldquoAdsorptionof basic dye (methylene blue) onto activated carbon preparedfrom rattan sawdustrdquo Dyes and Pigments vol 75 no 1 pp 143ndash149 2007

[7] H Selcuk ldquoDecolorization and detoxification of textile wastew-ater by ozonation and coagulation processesrdquo Dyes and Pig-ments vol 64 no 3 pp 217ndash222 2005

[8] A S Stasinakis ldquoUse of selected advanced oxidation processes(AOPs) for wastewater treatmentmdashamini reviewrdquoGlobal NESTJournal vol 10 pp 376ndash385 2008

[9] R Aplin and T D Waite ldquoComparison of three advancedoxidation processes for degradation of textile dyesrdquo WaterScience and Technology vol 42 no 5-6 pp 345ndash354 2000

[10] I Arslan-Alaton G Tureli and T Olmez-Hanci ldquoTreatmentof azo dye production wastewaters using Photo-Fenton-likeadvanced oxidation processes optimization by response surfacemethodologyrdquo Journal of Photochemistry and Photobiology Avol 202 no 2-3 pp 142ndash153 2009

[11] J M Herrmann ldquoHeterogeneous photocatalysis state of the artand present applicationsrdquoTopics in Catalysis vol 34 no 1ndash4 pp49ndash65 2005

[12] I K Konstantinou and T A Albanis ldquoTiO2-assisted photocat-

alytic degradation of azo dyes in aqueous solution kinetic andmechanistic investigations a reviewrdquo Applied Catalysis B vol49 no 1 pp 1ndash14 2004

[13] W Feng and D Nansheng ldquoPhotochemistry of hydrolyticiron (III) species and photoinduced degradation of organiccompounds A minireviewrdquo Chemosphere vol 41 no 8 pp1137ndash1147 2000

[14] I P Pozdnyakov Y A Sosedova V F Plyusnin et al ldquoPho-todegradation of organic pollutants in aqueous solutions causedby (OH)2+aq photolysis evidence of OH radical formationrdquoInternational Journal of Photoenergy vol 6 no 2 pp 89ndash932004

[15] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalyticdegradation of organic contaminants over titanium dioxidea review of fundamentals progress and problemsrdquo Journal ofPhotochemistry and Photobiology C vol 9 no 1 pp 1ndash12 2008

[16] O K Dalrymple D H Yeh and M A Trotz ldquoRemovingpharmaceuticals and endocrine-disrupting compounds fromwastewater by photocatalysisrdquo Journal of Chemical Technologyand Biotechnology vol 82 no 2 pp 121ndash134 2007

[17] R Rajeswari and S Kanmani ldquoA study on degradation of pes-ticide wastewater by TiO

2photocatalysisrdquo Journal of Scientific

and Industrial Research vol 68 no 12 pp 1063ndash1067 2009

[18] Z F Guo R X Ma and G J Li ldquoDegradation of phenolby nanomaterial TiO

2in wastewaterrdquo Chemical Engineering

Journal vol 119 pp 55ndash59 2006[19] C Jia YWang C Zhang and Q Qin ldquoUV-TiO

2photocatalytic

degradation of landfill leachaterdquo Water Air and Soil Pollutionvol 217 no 1ndash4 pp 375ndash385 2011

[20] V Sarria M Deront P Peringer and C Pulgarin ldquoDegradationof a biorecalcitrant dye precursor present in industrial wastew-aters by a new integrated iron(III) photoassisted-biologicaltreatmentrdquoApplied Catalysis B vol 40 no 3 pp 231ndash246 2003

[21] L Poulain G Mailhot P Wong-Wah-Chung and M BolteldquoPhotodegradation of chlortoluron sensitised by iron(III) aqua-complexesrdquo Journal of Photochemistry and Photobiology A vol159 no 1 pp 81ndash88 2003

[22] C Catastini S Rafqah G Mailhot and M Sarakha ldquoDegra-dation of amitrole by excitation of iron(III) aquacomplexes inaqueous solutionsrdquo Journal of Photochemistry and PhotobiologyA vol 162 no 1 pp 97ndash103 2004

[23] W Baran A Makowski and W Wardas ldquoThe influence ofFeCl3on the photocatalytic degradation of dissolved azo dyes

in aqueous TiO2suspensionsrdquo Chemosphere vol 53 no 1 pp

87ndash95 2003[24] H Mestankova J Krysa J Jirkovsky G Mailhot and M

Bolte ldquoThe influence of Fe(III) speciation on supported TiO2

efficiency example of monuron photocatalytic degradationrdquoApplied Catalysis B vol 58 pp 185ndash191 2005

[25] J Zhang D Fu Q Peng L Deng and X Yang ldquoFe3+-assistedphotocatalytic oxidation of sulfamethazine in TiO

2suspended

solutionrdquo Fresenius Environmental Bulletin vol 20 no 4 pp1051ndash1056 2011

[26] I A Alaton I A Balcioglu and D W Bahnemann ldquoAdvancedoxidation of a reactive dyebath effluent Comparison of O

3

H2O2UV-C and TiO

2UV-A processesrdquo Water Research vol

36 no 5 pp 1143ndash1154 2002[27] P A Pekakis N P Xekoukoulotakis and D Mantzavinos

ldquoTreatment of textile dyehouse wastewater by TiO2photocatal-

ysisrdquoWater Research vol 40 no 6 pp 1276ndash1286 2006[28] C C Liu Y H Hsieh P F Lai C H Li and C L Kao ldquoPho-

todegradation treatment of azo dye wastewater by UVTiO2

processrdquo Dyes and Pigments vol 68 no 2-3 pp 191ndash195 2006[29] J C Garcia J I Simionato A E C Silva J Nozaki and N E de

Souza ldquoSolar photocatalytic degradation of real textile effluentsby associated titanium dioxide and hydrogen peroxiderdquo SolarEnergy vol 83 no 3 pp 316ndash322 2009

[30] W Baran E Adamek and A Makowski ldquoThe influence ofselected parameters on the photocatalytic degradation of azo-dyes in the presence of TiO

2aqueous suspensionrdquo Chemical

Engineering Journal vol 145 no 2 pp 242ndash248 2008[31] ldquoMethods for Chemical Analysis of Water and Wastes Chem-

ical Oxygen Demand Titrimetric Methods 4101-3rdquo US EPAUnited States Environmental Protection Agency Office ofResearch and Development Washington DC USA EPA6004-79020 pp 443ndash451 March 1983 httpnepisepagov

[32] W Baran A Makowski and W Wardas ldquoChanges in CODvalues in aqueous solutions of the selected azo dyes duringthe photocatalytic degradation processrdquo in Micropollution inthe Human Environment vol 51 pp 215ndash221 CzestochowaUniversity of Technology Publishing House CzestochowaPoland 2003

[33] W Baran J Sochacka andWWardas ldquoToxicity and biodegrad-ability of sulfonamides and products of their photocatalytic

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

International Journal of Photoenergy 9

the chemical properties of dyes and on the possibility offormation of coordination compounds with Fe3+ ions

In the case of effluents containing cationic dyes (WPac)the addition of Fe(III) salt was unfavorable because the effi-ciency of photodegradation of these dyes and COD removalwere lower than that in the presence of TiO

2only The

explanation of this result can be the change of charge ofTiO2particles (in the presence of Fe3+ ions) that limits the

possibility of sorption of the positively charged particles ofcationic dyes

In the case of effluents containing anionic dyes (WLeatand WFlax) the presence of Fe3+ ions had a beneficialeffect on the efficiency of photocatalytic degradation of thesecompoundsThe possible explanations may be a formation ofphotoactive complexes between dyes particles and Fe3+ ionsthat absorb UV-a irradiation much better than individualmolecules of dyes or an adsorption of complexes of dyes withFe3+ ions on the photocatalyst surface

The investigated dyes effluents containing also otherpollutants such as fatty acids sugars and amino acids whichmay also be substrates for the photodegradation and cantherefore compete with the dyes Additionally they maycontain inorganic mobile anions such as Clminus CO

3

2minusSO4

minus2 PO4

3minus and NO3

minus which may significantly affect thedistribution of hydroxyl radicals in the following process

XO119899minus +HO∙ 997888rarr XO∙(119899minus1)minus

+OHminus (12)

As a result these anions at high concentrations candecrease the photodegradation that simultaneously occursbetween HO∙ radicals and dyes molecules

From the viewpoint of COD removal TiO2alone was

a much more effective photocatalyst than TiO2FeCl3 The

increase in COD value in WFlax effluent probably wasconnected with the presence of a very persistent substance(s)that did not undergo the oxidation during the COD deter-mination On the other hand the photocatalytic processleads to degradation of these substances and the obtainedproducts are much less chemically resistant In this aspectthe observed phenomenon is not negative In our publication[33] we have reported similar to other authors [34] that thecomplete photocatalytic degradation of contaminants duringthe treatment of effluents is still not economically feasible dueto high operating costs Therefore the reduction of time ofphotocatalytic process only to the time necessary to initialdegradation of nonbiodegradable substances (eg azo dyes)towards the most readily biodegradable intermediates is themost reasonable It is obvious that one single treatment stepcannot remove all pollutants contained in dyes effluents Theoptimal solution is the combination of different treatmentprocesses for example the photocatalytic degradation usingsunlight as the source of UV light with a biological processIt may significantly decrease the overall cost of the dyeeffluents treatment Additionally the photocatalytic pre-treatment of dyeing effluents can lead to improvement oftheir biodegradability for example initial toxicity inducedby photodegradation of textile antraquinone dye to Vibriafisheri progressively decreased during the course of pro-cess [35] In this way a significant decrease in the overall

cost of the treatment of dyes effluents is expected mainlythrough the combination of several AOPs for example thephotocatalytic degradation as a pretreatment method withbiological processes [36] An increase of biodegradability ofthese effluents would facilitate their subsequent biologicaltreatment and an effective removal of undesirable andorrecalcitrant pollutants making the complete mineralizationunnecessary

4 The Mechanism of WastewaterDecolorization Processes

The experiments confirmed that TiO2caused decolorization

of wastewatermainly due to photocatalytic process Howeverthe decolorization ofWLeat could be a result of dyes sorptiononto TiO

2surface (Table 3)

As previously described FeCl3alone could not be the

cause of decolorization of wastewater during the photocat-alytic process On the other hand the addition of FeCl

3

accelerated undoubtedly the photocatalytic degradation ofanionic dyes According to Mestankova et al this effectwas mainly the result of the synergism of photochemicalactivity between TiO

2and FeCl

3[24] However the results

of experiments showing that FeCl3alone did not exhibit the

photochemical activity in wastewater and it decreased thephotodegradation rate of cationic dyes may indicate otherpossible mechanism It should be noted that even moreimportant is the above described process of intensification ofsorption of dyes coordinated with FeCl

3onto TiO

2surface

[23] The other reason could be the fact that the additionof FeCl

3and simultaneously decrease of pH cause agglom-

eration of suspensions in wastewaters and also increase instability and photoavailability of the TiO

2used [30]

5 Conclusions

Dyeing effluents irradiated in the presence of FeCl3alone

were decolorized but azo dyes almost completely did notundergo degradation On the country the photocatalyticprocess carried out with TiO

2and TiO

2FeCl3as photo-

catalysts was the effective method of decolorization anddyes photodegradation in the investigated effluents (exceptsamples containing high concentration of very stable azodye) During the photocatalytic degradation of anionic dyesa mixture of TiO

2FeCl3was more effective while in the case

of cationic dyes more suitable seems to be TiO2alone

Acknowledgment

This work was supported by the Medical University of Silesia(Grant no KNW-1-043P20)

References

[1] R G Saratale G D Saratale J S Chang and S P GovindwarldquoDecolorization and biodegradation of reactive dyes and dyewastewater by a developed bacterial consortiumrdquo Biodegrada-tion vol 21 no 6 pp 999ndash1015 2010

10 International Journal of Photoenergy

[2] 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

[3] J C Garcia J L Oliveira A E C Silva C C OliveiraJ Nozaki and N E de Souza ldquoComparative study of thedegradation of real textile effluents by photocatalytic reactionsinvolvingUVTiO

2H2O2andUVFe2+H

2O2systemsrdquo Journal

of Hazardous Materials vol 147 no 1-2 pp 105ndash110 2007[4] I M C Goncalves A Gomes R Bras M I A Ferra M T

P Amorim and R S Porter ldquoBiological treatment of effluentcontaining textile dyesrdquoColoration Technology vol 116 pp 393ndash397 2000

[5] M Asgher H N Bhatti S A H Shah M J Asad and R LLegge ldquoDecolorization potential of mixed microbial consortiafor reactive and disperse textile dyestuffsrdquo Biodegradation vol18 no 3 pp 311ndash316 2007

[6] B H Hameed A L Ahmad and K N A Latiff ldquoAdsorptionof basic dye (methylene blue) onto activated carbon preparedfrom rattan sawdustrdquo Dyes and Pigments vol 75 no 1 pp 143ndash149 2007

[7] H Selcuk ldquoDecolorization and detoxification of textile wastew-ater by ozonation and coagulation processesrdquo Dyes and Pig-ments vol 64 no 3 pp 217ndash222 2005

[8] A S Stasinakis ldquoUse of selected advanced oxidation processes(AOPs) for wastewater treatmentmdashamini reviewrdquoGlobal NESTJournal vol 10 pp 376ndash385 2008

[9] R Aplin and T D Waite ldquoComparison of three advancedoxidation processes for degradation of textile dyesrdquo WaterScience and Technology vol 42 no 5-6 pp 345ndash354 2000

[10] I Arslan-Alaton G Tureli and T Olmez-Hanci ldquoTreatmentof azo dye production wastewaters using Photo-Fenton-likeadvanced oxidation processes optimization by response surfacemethodologyrdquo Journal of Photochemistry and Photobiology Avol 202 no 2-3 pp 142ndash153 2009

[11] J M Herrmann ldquoHeterogeneous photocatalysis state of the artand present applicationsrdquoTopics in Catalysis vol 34 no 1ndash4 pp49ndash65 2005

[12] I K Konstantinou and T A Albanis ldquoTiO2-assisted photocat-

alytic degradation of azo dyes in aqueous solution kinetic andmechanistic investigations a reviewrdquo Applied Catalysis B vol49 no 1 pp 1ndash14 2004

[13] W Feng and D Nansheng ldquoPhotochemistry of hydrolyticiron (III) species and photoinduced degradation of organiccompounds A minireviewrdquo Chemosphere vol 41 no 8 pp1137ndash1147 2000

[14] I P Pozdnyakov Y A Sosedova V F Plyusnin et al ldquoPho-todegradation of organic pollutants in aqueous solutions causedby (OH)2+aq photolysis evidence of OH radical formationrdquoInternational Journal of Photoenergy vol 6 no 2 pp 89ndash932004

[15] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalyticdegradation of organic contaminants over titanium dioxidea review of fundamentals progress and problemsrdquo Journal ofPhotochemistry and Photobiology C vol 9 no 1 pp 1ndash12 2008

[16] O K Dalrymple D H Yeh and M A Trotz ldquoRemovingpharmaceuticals and endocrine-disrupting compounds fromwastewater by photocatalysisrdquo Journal of Chemical Technologyand Biotechnology vol 82 no 2 pp 121ndash134 2007

[17] R Rajeswari and S Kanmani ldquoA study on degradation of pes-ticide wastewater by TiO

2photocatalysisrdquo Journal of Scientific

and Industrial Research vol 68 no 12 pp 1063ndash1067 2009

[18] Z F Guo R X Ma and G J Li ldquoDegradation of phenolby nanomaterial TiO

2in wastewaterrdquo Chemical Engineering

Journal vol 119 pp 55ndash59 2006[19] C Jia YWang C Zhang and Q Qin ldquoUV-TiO

2photocatalytic

degradation of landfill leachaterdquo Water Air and Soil Pollutionvol 217 no 1ndash4 pp 375ndash385 2011

[20] V Sarria M Deront P Peringer and C Pulgarin ldquoDegradationof a biorecalcitrant dye precursor present in industrial wastew-aters by a new integrated iron(III) photoassisted-biologicaltreatmentrdquoApplied Catalysis B vol 40 no 3 pp 231ndash246 2003

[21] L Poulain G Mailhot P Wong-Wah-Chung and M BolteldquoPhotodegradation of chlortoluron sensitised by iron(III) aqua-complexesrdquo Journal of Photochemistry and Photobiology A vol159 no 1 pp 81ndash88 2003

[22] C Catastini S Rafqah G Mailhot and M Sarakha ldquoDegra-dation of amitrole by excitation of iron(III) aquacomplexes inaqueous solutionsrdquo Journal of Photochemistry and PhotobiologyA vol 162 no 1 pp 97ndash103 2004

[23] W Baran A Makowski and W Wardas ldquoThe influence ofFeCl3on the photocatalytic degradation of dissolved azo dyes

in aqueous TiO2suspensionsrdquo Chemosphere vol 53 no 1 pp

87ndash95 2003[24] H Mestankova J Krysa J Jirkovsky G Mailhot and M

Bolte ldquoThe influence of Fe(III) speciation on supported TiO2

efficiency example of monuron photocatalytic degradationrdquoApplied Catalysis B vol 58 pp 185ndash191 2005

[25] J Zhang D Fu Q Peng L Deng and X Yang ldquoFe3+-assistedphotocatalytic oxidation of sulfamethazine in TiO

2suspended

solutionrdquo Fresenius Environmental Bulletin vol 20 no 4 pp1051ndash1056 2011

[26] I A Alaton I A Balcioglu and D W Bahnemann ldquoAdvancedoxidation of a reactive dyebath effluent Comparison of O

3

H2O2UV-C and TiO

2UV-A processesrdquo Water Research vol

36 no 5 pp 1143ndash1154 2002[27] P A Pekakis N P Xekoukoulotakis and D Mantzavinos

ldquoTreatment of textile dyehouse wastewater by TiO2photocatal-

ysisrdquoWater Research vol 40 no 6 pp 1276ndash1286 2006[28] C C Liu Y H Hsieh P F Lai C H Li and C L Kao ldquoPho-

todegradation treatment of azo dye wastewater by UVTiO2

processrdquo Dyes and Pigments vol 68 no 2-3 pp 191ndash195 2006[29] J C Garcia J I Simionato A E C Silva J Nozaki and N E de

Souza ldquoSolar photocatalytic degradation of real textile effluentsby associated titanium dioxide and hydrogen peroxiderdquo SolarEnergy vol 83 no 3 pp 316ndash322 2009

[30] W Baran E Adamek and A Makowski ldquoThe influence ofselected parameters on the photocatalytic degradation of azo-dyes in the presence of TiO

2aqueous suspensionrdquo Chemical

Engineering Journal vol 145 no 2 pp 242ndash248 2008[31] ldquoMethods for Chemical Analysis of Water and Wastes Chem-

ical Oxygen Demand Titrimetric Methods 4101-3rdquo US EPAUnited States Environmental Protection Agency Office ofResearch and Development Washington DC USA EPA6004-79020 pp 443ndash451 March 1983 httpnepisepagov

[32] W Baran A Makowski and W Wardas ldquoChanges in CODvalues in aqueous solutions of the selected azo dyes duringthe photocatalytic degradation processrdquo in Micropollution inthe Human Environment vol 51 pp 215ndash221 CzestochowaUniversity of Technology Publishing House CzestochowaPoland 2003

[33] W Baran J Sochacka andWWardas ldquoToxicity and biodegrad-ability of sulfonamides and products of their photocatalytic

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

10 International Journal of Photoenergy

[2] 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

[3] J C Garcia J L Oliveira A E C Silva C C OliveiraJ Nozaki and N E de Souza ldquoComparative study of thedegradation of real textile effluents by photocatalytic reactionsinvolvingUVTiO

2H2O2andUVFe2+H

2O2systemsrdquo Journal

of Hazardous Materials vol 147 no 1-2 pp 105ndash110 2007[4] I M C Goncalves A Gomes R Bras M I A Ferra M T

P Amorim and R S Porter ldquoBiological treatment of effluentcontaining textile dyesrdquoColoration Technology vol 116 pp 393ndash397 2000

[5] M Asgher H N Bhatti S A H Shah M J Asad and R LLegge ldquoDecolorization potential of mixed microbial consortiafor reactive and disperse textile dyestuffsrdquo Biodegradation vol18 no 3 pp 311ndash316 2007

[6] B H Hameed A L Ahmad and K N A Latiff ldquoAdsorptionof basic dye (methylene blue) onto activated carbon preparedfrom rattan sawdustrdquo Dyes and Pigments vol 75 no 1 pp 143ndash149 2007

[7] H Selcuk ldquoDecolorization and detoxification of textile wastew-ater by ozonation and coagulation processesrdquo Dyes and Pig-ments vol 64 no 3 pp 217ndash222 2005

[8] A S Stasinakis ldquoUse of selected advanced oxidation processes(AOPs) for wastewater treatmentmdashamini reviewrdquoGlobal NESTJournal vol 10 pp 376ndash385 2008

[9] R Aplin and T D Waite ldquoComparison of three advancedoxidation processes for degradation of textile dyesrdquo WaterScience and Technology vol 42 no 5-6 pp 345ndash354 2000

[10] I Arslan-Alaton G Tureli and T Olmez-Hanci ldquoTreatmentof azo dye production wastewaters using Photo-Fenton-likeadvanced oxidation processes optimization by response surfacemethodologyrdquo Journal of Photochemistry and Photobiology Avol 202 no 2-3 pp 142ndash153 2009

[11] J M Herrmann ldquoHeterogeneous photocatalysis state of the artand present applicationsrdquoTopics in Catalysis vol 34 no 1ndash4 pp49ndash65 2005

[12] I K Konstantinou and T A Albanis ldquoTiO2-assisted photocat-

alytic degradation of azo dyes in aqueous solution kinetic andmechanistic investigations a reviewrdquo Applied Catalysis B vol49 no 1 pp 1ndash14 2004

[13] W Feng and D Nansheng ldquoPhotochemistry of hydrolyticiron (III) species and photoinduced degradation of organiccompounds A minireviewrdquo Chemosphere vol 41 no 8 pp1137ndash1147 2000

[14] I P Pozdnyakov Y A Sosedova V F Plyusnin et al ldquoPho-todegradation of organic pollutants in aqueous solutions causedby (OH)2+aq photolysis evidence of OH radical formationrdquoInternational Journal of Photoenergy vol 6 no 2 pp 89ndash932004

[15] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalyticdegradation of organic contaminants over titanium dioxidea review of fundamentals progress and problemsrdquo Journal ofPhotochemistry and Photobiology C vol 9 no 1 pp 1ndash12 2008

[16] O K Dalrymple D H Yeh and M A Trotz ldquoRemovingpharmaceuticals and endocrine-disrupting compounds fromwastewater by photocatalysisrdquo Journal of Chemical Technologyand Biotechnology vol 82 no 2 pp 121ndash134 2007

[17] R Rajeswari and S Kanmani ldquoA study on degradation of pes-ticide wastewater by TiO

2photocatalysisrdquo Journal of Scientific

and Industrial Research vol 68 no 12 pp 1063ndash1067 2009

[18] Z F Guo R X Ma and G J Li ldquoDegradation of phenolby nanomaterial TiO

2in wastewaterrdquo Chemical Engineering

Journal vol 119 pp 55ndash59 2006[19] C Jia YWang C Zhang and Q Qin ldquoUV-TiO

2photocatalytic

degradation of landfill leachaterdquo Water Air and Soil Pollutionvol 217 no 1ndash4 pp 375ndash385 2011

[20] V Sarria M Deront P Peringer and C Pulgarin ldquoDegradationof a biorecalcitrant dye precursor present in industrial wastew-aters by a new integrated iron(III) photoassisted-biologicaltreatmentrdquoApplied Catalysis B vol 40 no 3 pp 231ndash246 2003

[21] L Poulain G Mailhot P Wong-Wah-Chung and M BolteldquoPhotodegradation of chlortoluron sensitised by iron(III) aqua-complexesrdquo Journal of Photochemistry and Photobiology A vol159 no 1 pp 81ndash88 2003

[22] C Catastini S Rafqah G Mailhot and M Sarakha ldquoDegra-dation of amitrole by excitation of iron(III) aquacomplexes inaqueous solutionsrdquo Journal of Photochemistry and PhotobiologyA vol 162 no 1 pp 97ndash103 2004

[23] W Baran A Makowski and W Wardas ldquoThe influence ofFeCl3on the photocatalytic degradation of dissolved azo dyes

in aqueous TiO2suspensionsrdquo Chemosphere vol 53 no 1 pp

87ndash95 2003[24] H Mestankova J Krysa J Jirkovsky G Mailhot and M

Bolte ldquoThe influence of Fe(III) speciation on supported TiO2

efficiency example of monuron photocatalytic degradationrdquoApplied Catalysis B vol 58 pp 185ndash191 2005

[25] J Zhang D Fu Q Peng L Deng and X Yang ldquoFe3+-assistedphotocatalytic oxidation of sulfamethazine in TiO

2suspended

solutionrdquo Fresenius Environmental Bulletin vol 20 no 4 pp1051ndash1056 2011

[26] I A Alaton I A Balcioglu and D W Bahnemann ldquoAdvancedoxidation of a reactive dyebath effluent Comparison of O

3

H2O2UV-C and TiO

2UV-A processesrdquo Water Research vol

36 no 5 pp 1143ndash1154 2002[27] P A Pekakis N P Xekoukoulotakis and D Mantzavinos

ldquoTreatment of textile dyehouse wastewater by TiO2photocatal-

ysisrdquoWater Research vol 40 no 6 pp 1276ndash1286 2006[28] C C Liu Y H Hsieh P F Lai C H Li and C L Kao ldquoPho-

todegradation treatment of azo dye wastewater by UVTiO2

processrdquo Dyes and Pigments vol 68 no 2-3 pp 191ndash195 2006[29] J C Garcia J I Simionato A E C Silva J Nozaki and N E de

Souza ldquoSolar photocatalytic degradation of real textile effluentsby associated titanium dioxide and hydrogen peroxiderdquo SolarEnergy vol 83 no 3 pp 316ndash322 2009

[30] W Baran E Adamek and A Makowski ldquoThe influence ofselected parameters on the photocatalytic degradation of azo-dyes in the presence of TiO

2aqueous suspensionrdquo Chemical

Engineering Journal vol 145 no 2 pp 242ndash248 2008[31] ldquoMethods for Chemical Analysis of Water and Wastes Chem-

ical Oxygen Demand Titrimetric Methods 4101-3rdquo US EPAUnited States Environmental Protection Agency Office ofResearch and Development Washington DC USA EPA6004-79020 pp 443ndash451 March 1983 httpnepisepagov

[32] W Baran A Makowski and W Wardas ldquoChanges in CODvalues in aqueous solutions of the selected azo dyes duringthe photocatalytic degradation processrdquo in Micropollution inthe Human Environment vol 51 pp 215ndash221 CzestochowaUniversity of Technology Publishing House CzestochowaPoland 2003

[33] W Baran J Sochacka andWWardas ldquoToxicity and biodegrad-ability of sulfonamides and products of their photocatalytic

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

International Journal of Photoenergy 11

degradation in aqueous solutionsrdquo Chemosphere vol 65 no 8pp 1295ndash1299 2006

[34] E Bizani K Fytianos I Poulios andV Tsiridis ldquoPhotocatalyticdecolorization and degradation of dye solutions and wastewa-ters in the presence of titanium dioxiderdquo Journal of HazardousMaterials vol 136 no 1 pp 85ndash94 2006

[35] C Lizama J Freer J Baeza and H D Mansilla ldquoOptimizedphotodegradation of reactive blue 19 on TiO

2and ZnO suspen-

sionsrdquo Catalysis Today vol 76 no 2ndash4 pp 235ndash246 2002[36] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-

ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of