research article fenton-like oxidation of malachite green...

Hindawi Publishing CorporationJournal of ChemistryVolume 2013 Article ID 809318 7 pageshttpdxdoiorg1011552013809318

Research ArticleFenton-Like Oxidation of Malachite Green SolutionsKinetic and Thermodynamic Study

Saeedeh Hashemian

Chemistry Department Islamic Azad University Yazd Branch P O Box 89195155 Yazd Iran

Correspondence should be addressed to Saeedeh Hashemian sa hashemianyahoocom

Received 25 May 2013 Revised 19 June 2013 Accepted 25 June 2013

Academic Editor Oleksandr A Loboda

Copyright copy 2013 Saeedeh HashemianThis 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

Oxidation by Fenton-like (Fe3+H2O2) reactions is proven to be an economically feasible process for destruction of a variety of

hazardous pollutants in wastewater In this study the degradation and mineralization of malachite green dye are reported usingFenton-like reaction The effects of different parameters like pH of the solution the initial concentrations of Fe3+ H

2O2 and

dye temperature and added electrolytes (Clminus and SO42minus) on the oxidation of the dye were investigated Optimized condition was

determinedThe efficiency of 955 degradation of MAG after 15 minutes of reaction at pH 3 was obtained TOC removal indicatespartial and insignificant mineralization of malachite green dye The results of experiments showed that degradation of malachitegreen dye in Fenton-like oxidation process can be described with a pseudo-second-order kinetic model The thermodynamicconstants of the Fenton oxidation process were evaluatedThe results implied that the oxidation process was feasible spontaneousand endothermic The results will be useful for designing the treatment systems of various dye-containing wastewaters

1 Introduction

Dyes in wastewater are of particular environmental concernsince they not only give an undesirable color to the waters butalso in some cases are harmful compounds and can originatedangerous by-products through oxidation hydrolysis orother chemical reactions taking place in the waste phaseEnvironmental research has paid special attention to dyecompounds because of the extensive environmental con-tamination arising from dyeing operations Various attemptshave been made for the removal of dyes from water andwastewater There are several methods applicable for thereclamation of dyeing wastewaters [1 2] Commonly appliedtreatmentmethods for color removal fromdye-contaminatedeffluents consist of various processes involving biologicalphysical and chemical decolorizationmethodsThebiologicaltreatment is not a complete solution to the problem dueto biological resistance of some dyes [3] The traditionaltreatment techniques were applied in wastewaters such asozonation [4]membrane [5] oxidation [6 7] photochemical[8] and adsorption [9ndash13] Various Fenton processes wereused for oxidation of dyes Homogenous Fenton reaction(Fe2+H

2O2) is one of the most important processes to

generate hydroxyl radicals ∙OH [14ndash16] These processesare involved in the generation of highly reactive radicals(especially hydroxyl radicals) in enough quantity to affectwater purification and their use is justified by the low organiccontent of the wastewaters to be treated They have lowreaction temperatures and thus require the presence of veryactive oxidation agents In particular the oxidation usingFentonrsquos reagent has proved to be a promising and attractivetreatment method for the effective destruction of a largenumber of hazardous and organic pollutants [17ndash21]

The Fenton process completely destroys contaminantsand breaks them down into harmless compounds suchas carbon dioxide water and inorganic salts However itsapplications are limited due to the generation of excessiveamounts of ferric hydroxide sludge that requires additionalseparation process and disposal [22]

Malachite green is classified in the dyestuff industry asa triarylmethane dye Malachite green (MAG) is usuallyused as a dye for materials such as silk leather and paperRemoval of malachite green by different methods such asoxidation [23] catalytic oxidation [24] electrooxidation [25]and adsorption by agro-industry waste [26] peel [27] andsolid agricultural waste [28 29] was studied

2 Journal of Chemistry

Fentonrsquos reagent is a mixture of ferrous ion and hydrogenperoxide generating hydroxyl radical (∙OH) in situ accordingto the following equation

Fe2+ +H2O2997888rarr Fe3+ +OHminus + ∙OH (1)

Fe(III) can catalyze the decomposition of H2O2 The

reaction of H2O2with Fe3+ (the so-called Fentonrsquos-like

reagent) goes through the formation of hydroperoxyl radicalHO2

∙ [30]

Fe3+ +H2O2997888rarr Fe2+ +HO

2

∙+H+ (2)

Fe3+ +HO2

∙997888rarr Fe2+ +H+ +O

2(3)

Fe2+ + ∙OH 997888rarr Fe3+ + minusOH (4)∙OH+ H

2O2997888rarr HO

2

∙+ H2O (5)

Fe2+ +HO2

∙997888rarr Fe3+ +HO

2

minus (6)∙OH+ HO∙ 997888rarr H

2O2

(7)

The specific objectives of this study are the investiga-tion of removal efficiencies of malachite green (MAG) byFenton-like process Important variables such as oxidationtime effect of pH dosages of H

2O2 and ferrous ions were

examined The kinetics and thermodynamic of process alsowere determined

2 Experimental

21 Material and Methods The basic dye MAG has molec-ular formula C

23H25ClN2and molar mass 364911 gmol

with 120582max 620 nm and was used as received without fur-ther purification to prepare simulated wastewater 50 times10minus3 stock solution of MAG was prepared and work-ing solutions are prepared by the dilution Experimen-tal solutions of the desired concentration were obtainedby successive dilutions The chemical structure of mala-chite green (4-[(4-dimethylaminophenyl)phenyl-methyl]-NN-dimethylaniline) is shown in Figure 1

All the reagents used in the experimentswere in analyticalgrade (Merck) and were used without further purificationAll the experiments were conducted at room temperatureThe dye oxidation was achieved by Fenton-like reagent whichwas composed of a mixture of Fe

2(SO4)3sdot7H2O and H

2O2

(30) The necessary quantities of Fe3+ and H2O2were

added simultaneously in the dye solution All experimentswere conducted in a 500mL thermostated batch glass reactorequipped with the magnetic stirrer The kinetics of oxidationwas followed by taking samples at regular time interval

The residual concentration of the MAG in the solutionat different times of sampling was determined The residualconcentration of the dye was deducted from the calibrationcurves which were produced at wavelength correspondingto the maximum of absorbance (620 nm) on an UV-visiblespectrophotometer apparatus (Shimadzu 160A) The cellsused were in quartz 1 cm thick The discoloration efficiency

N

N

Figure 1 Chemical structure of malachite green (MAG)

of the dye (X) with respect to its initial concentration iscalculated as

X = ([MAG]0 minus [MAG] [MAG]0) times 100 (8)

where [MAG]0and [MAG] are the initial and appropriate

concentrations of dye at any reaction time 119905 respectively

3 Results and Discussion

31 Effect of pH on Decolorization pH has a major effect onthe efficiency of MAG treatment The oxidation was done for120min under controlled pH condition with constant doseof Fe3+ (10 times 10minus4M) and H

2O2(5 times 10minus2M) The effect

of pH on the removal of malachite green using 50mg Lminus1of dye was studied The oxidation of MAG as a functionof pH is shown in Figure 2 It is evident that change inthe pH of the solution to Fenton-like value of 3 leads toincreases in the extent of MAG oxidation It is apparent fromthat extent of decolorization decreases with increase in pHand at pH 30 almost gt95 color removal was observedTherefore the results demonstrate that the pH value for themost effective oxidation of MAG is approximately 3 Thedecrease in oxidation rate at pH gt 3 could be explained bythe formation of Fe(OH)

3 which has lower catalytic activity

in the decomposition of H2O2[30]The low activity detected

for high pH has been reported and the results closely agreedwith those in the literature [19 30ndash32]

32 Effect of Fe3+ Ferrous Dosage The concentration of Fe3+is one of the critical parameters in Fenton processes In thepresent study the influence of different iron concentrations(Fe3+ = 10 times 10minus6ndash10 times 10minus3M) expressed asMAG removal isillustrated in Figure 3 The concentration of hydrogen perox-ide is fixed as 005M andMAG concentration is 30times 10minus5MIt can be seen from results that MAG degradation increasedwith increasing Fe+3 concentrations This is due to the factthat Fe+3 plays a very important role in the decompositionsof H2O2to generate the ∙OH in the Fenton process The

lower degradation capacity of Fe3+ at small concentrationis probably due to the lowest ∙OH radicals producing avariable for oxidation [16 19] for higher concentration ofFe+3 oxidation of dye will decrease This can be explained by

Journal of Chemistry 3

100

80

60

40

20

00 30 60 90 120

Time (min)

Deg

rada

tion

effici

ency

()

pH 3pH 7pH 2

pH 9pH 5pH 10

Figure 2 Effect of pH on the discoloration efficiency for Fenton-like oxidation process ([Fe3+] = 10 times 10minus4M [H

2O2] = 50 times 10minus2M

[MAG] = 30 times 10minus5M)

100

80

60

40

20

00 30 60 90 120

Time (min)

Deg

rada

tion

effici

ency

()

10minus3 10minus4

10minus5 10minus6

Figure 3 Effect of Fe3+ concentration on the discoloration efficiencyfor Fenton-like oxidation process ([H

2O2] = 50times 10minus2 [MAG] = 30

times 10minus5M)

the fact that when the concentrations of Fe3+ are high canreact with the HO

2

∙ and finally reduce consumed the veryreactive ∙OH radical according to (3)

33 Effect of H2O2Concentration H

2O2plays the role of

an oxidizing agent in this process The selection of anoptimal H

2O2concentration for the decolorization of MAG

is important from practical point of view due to the cost ofH2O2[33]

Oxidation of dyes by Fenton and Fenton-like process iscarried out by ∙OH radicals that are directly produced fromthe reaction between H

2O2 Fe2+ and Fe3+ To determine

the concentration of H2O2giving the maximum MAG

discoloration efficiency experiments were conducted andresults detained are represented in Figure 4Thediscolorationefficiency according to time for different concentrations of

100

80

60

40

20

00 30 60 90 120

Time (min)

Deg

rada

tion

effici

ency

()

5 times 10minus3

5 times 10minus210 times 10minus2

1 times 10minus1

Figure 4 Effect of H2O2concentration on the discoloration

efficiency for Fenton-like oxidation process ([MAG] = 30 times 10minus5M[Fe+3] = 10 times 10minus4])

H2O2shows that the dye degradation yield increases with

increasing concentration of H2O2 For the oxidation process

the addition of H2O2from 50 times 10minus3ndash10 times 10minus1M increases

the decolorization from 68 to 95 at 10min The increasein the decolorization is due to the increase in hydroxylradical concentration by addition of H

2O2[17] However at

higherH2O2concentration efficiency of dye removal showed

no significant efficiency which is due to recombination ofhydroxyl radicals and scavenging the OH radicals will occurwhich can be expressed by (2) (5) and (6)

34 Effect of Relation [Fe3+][H2O2] Themain process vari-

ables affecting the rate of a Fenton-like reaction are the molarconcentrations of the oxidant (H

2O2) and catalyst (Fe3+)

particularly the Fe3+ H2O2molar ratio Therefore color

removal as a function of the initial molar ratio of Fe3+H2O2

was investigated The different ratios of [Fe3+][H2O2] 1ndash400

are reported from the literature The experimental resultsshowed that the optimum Fe3+ H

2O2molar ratio for the

removal of MAG was 1 50 [19 34] The reaction of Fe3+with H

2O2leads to the formation of Fe2+ ions which can

further react with H2O2to produce OH radical Therefore

a low Fe3+ concentration decreases MAG degradation MAGremoval actually ceased when the Fe3+ H

2O2molar ratio

increased from 1 50 to 1 500 for 1mM Fe3+ indicating thatH2O2was overdosed when its concentration rose tenfold In

the presence of 50mM of H2O2 the ionic liquid is probably

eliminated solely by the reaction with ∙OH but at 500mM asit is expectedmost of theH

2O2dosage appliedwas consumed

in the first stage of the fast reaction The oxidation of ionicliquids was done not only by reaction with ∙OH radicals butalso by other radical species generated in vigorous Fe+3H

2O2

reactions such FeO3+ [35] and Fe3+HO2

2+ [30] which thendecrease

35 Effect of Dye Concentration The efficiency of the Fenton-like process as a function of initial concentration of dye was


evaluated Figure 5 shows the changes ofMAG concentrationwith the reaction time The results indicated that decoloriza-tion efficiency increased when the initial dye concentrationincreased Concentration plays a very important role in reac-tions according to the collision theory of chemical reactionsTwo reactants were in a closed container All the moleculescontained within are colliding constantly By increasing theconcentration of one or more reactants the frequency ofcollisions between reactant molecules is increased and thefrequency of effective collisions that causes a reaction to occurwill also be high The lifetime of hydroxyl radicals is veryshort (only a fewnanoseconds) and they can only reactwherethey are formed therefore as increasing the quantity of dyemolecules per volume unit logically enhances the probabilityof collision between organic matter and oxidizing speciesleading to an increase in the decolorization efficiency [36]

36 Effect of Temperature The influence of reaction tempera-ture on the decolorization efficiency ofMAGwas investigatedby varying temperature from 20∘C to 70∘C Temperature iscritical to the reaction rate product yield and distributionThe result is illustrated in Figure 6 It can be seen that raisingthe temperature has a positive impact on the decolorizationofMAGThe decolorization efficiency within 10min reactionincreased from 78 to 95 as the different temperaturesThis is due to the fact that higher temperature increased thereaction rate between hydrogen peroxide and the catalystthus increasing the rate of generation of oxidizing speciessuch as ∙OH radical or high-valence iron species [34] Inaddition a higher temperature can provide more energyfor the reactant molecules to overcome reaction activationenergy [37] Although the decolorization efficiency for 119879 =30∘C is lower than those obtained at 119879 = 40∘C the valuesof dyes removal achieved at 30∘C might be consideredsatisfactory At higher temperature the efficiency of MAGoxidation decreases This phenomenon may be due to thedecomposition of H

2O2at the relatively high temperatures

(9)This is consistent with results found in the literature [38]

2H2O2997888rarr H

2O +O

2 (9)

37 Mineralization Study The complete mineralization of1mol MAG dye molecule implies the formation of the equiv-alent amount (23 moles) of CO

2at the end of the treatment

However the depletion in TOC (shown in Figure 7) clearlyindicates that the reaction does not go to completion Extentof mineralization of the dye by Fenton-like process can beevaluated by measuring Total Organic Carbon (TOC) Todetermine the change in the TOC of reactionmedium initialTOC (pure dye solution) and the TOC of a sample at differentintervals during the reaction were measured TOC reductionwas determined as follows

TOCremoval =1 minus TOC

119905

TOC0

times 100 (10)

where TOC119905and TOC

0(mg Lminus1) are values at time (119905) and

at time (0) respectively 70 TOC reduction is achievedfor MAG dye in 30min In fact after 30min of reaction

100908070605040302010

00 20 40 60 80 100 120

Time (min)

Deg

rada

tion

effici

ency

()

1 times 10minus6

5 times 10minus5

1 times 10minus5

1 times 10minus4

3 times 10minus5

Figure 5 Effect of MAG concentration on the discoloration effi-ciency for Fenton-like oxidation process

100

90

80

70

60

50

400 30 60 90 120

Time (min)

30∘C40∘C70∘C

50∘C20∘C60∘C

Deg

rada

tion

effici

ency

()

Figure 6 Effect of temperature on the discoloration efficiency forFenton-like oxidation process

about 70 of the initial organic carbon had been transformedinto CO

2 which implied the existence of other organic

compounds in the solution and the partial mineralization ofdyes [39 40]

38 Effect of Clminus and SO4

2minus on Fenton Effectiveness Clminus

and SO4

2minus are common coexisting anions with dyes inwastewater therefore the effect of Clminus and SO

4

2minus ions onMAG removal by Fenton-like process was investigated It wasfound that the presence of Clminus at the concentration range of0ndash01mol Lminus1 did not have a significant effect on removingMAG The effect of SO

4

2minus on the removal of MAG wassignificant at the concentration range of 0ndash01mol Lminus1 Theremoval ofMAGdecreased at a concentration of 002mol Lminus1


80

70

60

50

40

30

20

10

00 50 100 150

TOC

rem

oval

()

Time (min)

Figure 7 TOC removal for MAG dye by Fenton-like oxidationprocess

of SO4

2minus The removal of MAG decreased to 45 for concen-tration of 002mol Lminus1 of SO

4

2minus

39 Kinetic of Fenton Reaction The general elementary ratelaw for reaction of a target organic compound (MAG) can bewritten as follows

minusd119862MAGd119905= 119896HO119896∙OH119896RH + Σ119870oxi119862oxi119862RH (11)

where oxi represents oxidants other than ∙OH that may bepresent such as ferryl hydroxyl radical which is usuallyregarded as the sole or most important reactive species Then

minusd119862MAGd119905= 119896HO119896∙OH119896MAG (12)

And by integration the rate law of first-order reaction can bewritten as follows

ln119862MAG = ln119862(MAG)0 minus 119896app119905 (13)

where 119862MAG and 119862(MAG)0 are initial concentration of MAG

and concentration of MAG at any time A plot of ln119862MAGversus time generated a straight linewith a negative slopeTheslope of this line corresponds to the apparent rate constantvalue for the degradation of the organic target compound Inour case we follow the rate of decolourization of the MAGdye Consequently (13) was converted to

ln119862MAGln119862(MAG)0= minus119896app119905 (14)

Figure 8 shows the plot of first-order Fenton reactionRate law of the second-order reaction can be written asfollows

1

[119862MAG]minus

1

[119862(MAG)0]

= 119896119905 (15)

The plot of 1[119862] against 119896 shows the rate constant ofsecond-order Fenton reaction (Figure 9) The results from1198772 of Figures 8 and 9 show that the kinetic of Fenton-like

reaction for degradation of MAG was second-order reaction[41]

minus45

minus35

minus25

minus15

0 20 40 60 80 100 120

y = minus0017x minus 22362

R2 = 09439

Time (min)

lnC

Figure 8 Pseudo-first-order model for Fenton-like oxidation ofMAG

R2 = 09951

0

10

20

30

40

50

60

70

0 30 60 90 120Time (min)

y = 04613x + 2616

1C

Figure 9 Pseudo-second-order model for Fenton-like oxidation ofMAG

310 Thermodynamic of Fenton Reaction Thermodynamicparameters including Gibbs free energy Δ119866∘ standardenthalpy Δ119867∘ and standard entropy Δ119878∘ are the parametersto better understand the temperature effect on degradationof dye which was studied Gibbs free energy Δ119866∘ by usingequilibrium constant119870

119862is calculated

Δ119866∘= minus119877119879 ln119870

119862 (16)

119870119862value is calculated from the following formula

119870119862=

119862Ae119862Se (17)

119862Ae is amount of degradation dye at equilibrium and 119862Seequilibrium concentration of dye at the solution

Standard enthalpy Δ119867∘ and standard entropy Δ119878∘ are asvanrsquot Hoff equation

ln119870119862=

minusΔ119867∘

119877119879

+

Δ119878∘

119877

(18)

In this equation 119877 is the gas constant equal to thepublic (8314 Jmolminus1 kminus1) The amounts of degradation dyeat equilibrium at different temperatures 25ndash55∘C have beenexamined to obtain thermodynamic parameters for Fenton-like reaction of MAG Δ119867∘ and Δ119878∘ were calculated asthe slope and intercept of vanrsquot Hoff plots of ln119870

119862versus


Table 1 Thermodynamic parameters for Fenton oxidation of MAG([MAG]= 30times 10minus5 M [Fe3+] = 10times 10minus4 M [H2O2] = 50times 10

minus2 M)

Δ119878∘

(Jmolminus1kminus1)Δ119867∘

(Jmolminus1)Δ119866∘

(KJmolminus1 ) 119870119862 119879 (K)

432823 9610

minus3255minus3408minus4213minus5680

3803870480733

293303323333

Fentonlike

oxidation

1119879 The results of thermodynamic parameters are givenin Table 1 As observed in Table 1 negative value of Δ119866∘at different temperatures shows the oxidation process to bespontaneousTheΔ119867∘ positive value indicates that the uptakeis endothermic [42]

4 Conclusion

The results of Fenton-like oxidation process of MAG showedthe following

(1) The optimal parameters for Fenton-like process are

[MAG] = 3 times 10minus5M [Fe3+] = 10 times 10minus3M

[H2O2] = 5 times 10

minus2M pH = 3(19)

(2) Fenton-like process not only completes decoloriza-tion of MAG dye (95) but also mineralizes it (70)

(3) The oxidation process of MAG follows pseudo-second-order kinetic model

(4) The negative values of Δ119866∘ and positive value ofΔ119867∘ obtained indicated that the MAG dye oxidation

by Fenton reaction processes is spontaneous andendothermic

(5) The overall equation of MAG degradation and pro-duction of carbon dioxide and nitrate ion is as follows

C23H25ClN2+ 52H

2O 997888rarr 23CO

2+ 129H+

+ 2NO3

minus+ Clminus + 126eminus

(20)

References

[1] AWang J Qu J RuH Liu and J Ge ldquoMineralization of an azodye Acid Red 14 by electro-Fentonrsquos reagent using an activatedcarbon fiber cathoderdquoDyes and Pigments vol 65 no 3 pp 227ndash233 2005

[2] J Pierce ldquoColour in textile effluentsmdashthe origins of the prob-lemrdquo Journal of the Society of Dyers amp Colourists vol 110 no 4pp 131ndash133 1994

[3] C Galindo P Jacques and A Kalt ldquoPhotochemical and pho-tocatalytic degradation of an indigoid dye a case study of acidblue 74 (AB74)rdquo Journal of Photochemistry and Photobiology Avol 141 no 1 pp 47ndash56 2001

[4] M Muthukumar and N Selvakumar ldquoStudies on the effectof inorganic salts on decolouration of acid dye effluents byozonationrdquoDyes and Pigments vol 62 no 3 pp 221ndash228 2004

[5] R Sabry A Hafez M Khedr and A El-Hassanin ldquoRemoval oflead by an emulsion liquid membrane Part IrdquoDesalination vol212 no 1ndash3 pp 165ndash175 2007

[6] P K Malik and S K Saha ldquoOxidation of direct dyes withhydrogen peroxide using ferrous ion as catalystrdquo Separation andPurification Technology vol 31 no 3 pp 241ndash250 2003

[7] E E Ebrahiem M N Al-Maghrabi and A R MobarkildquoRemoval of organic pollutants from industrial wastewater byapplying photo-Fenton oxidation technologyrdquo Arabian Journalof Chemistry In press

[8] I Fatimah S Wang and DWulandari ldquoZnOmontmorillonitefor photocatalytic and photochemical degradation ofmethylenebluerdquo Applied Clay Science vol 53 no 4 pp 553ndash560 2011

[9] S Hashemian ldquoMnFe2O4bentonite nano composite as a novel

magnetic material for adsorption of acid red 138rdquo AfricanJournal of Biotechnology vol 9 no 50 pp 8667ndash8671 2010

[10] S Hashemian ldquoRemoval of acid red 151 from water by adsorp-tion onto nano-composite MnFe

2O4kaolinrdquo Main Group

Chemistry vol 10 no 2 pp 105ndash114 2011[11] S Hashemian ldquoStudy of adsorption of acid dye from aqueous

solutions using bentoniterdquo Main Group Chemistry vol 6 pp97ndash107 2007

[12] S Hashemian and M Salimi ldquoNano composite a potentiallow cost adsorbent for removal of cyanine acidrdquo ChemicalEngineering Journal vol 188 pp 57ndash63 2012

[13] S Hashemian andMMirshamsi ldquoKinetic and thermodynamicof adsorption of 2-picoline by sawdust from aqueous solutionrdquoJournal of Industrial and Engineering Chemistry vol 1 pp 2010ndash2015 2012

[14] A R Khataee V Vatanpour and A R Amani GhadimldquoDecolorization of CI Acid Blue 9 solution by UVNano-TiO2 Fenton Fenton-like electro-Fenton and electrocoagu-

lation processes a comparative studyrdquo Journal of HazardousMaterials vol 161 no 2-3 pp 1225ndash1233 2009

[15] J Ma W Song C Chen W Ma J Zhao and Y Tang ldquoFentondegradation of organic compounds promoted by dyes undervisible irradiationrdquo Environmental Science and Technology vol39 no 15 pp 5810ndash5815 2005

[16] F Chen W Ma J He and J Zhao ldquoFenton degradation ofmalachite green catalyzed by aromatic additivesrdquo Journal ofPhysical Chemistry A vol 106 no 41 pp 9485ndash9490 2002

[17] M S Lucas and J A Peres ldquoDecolorization of the azo dyereactive black 5 by Fenton and Photo-Fenton oxidationrdquo Dyesand Pigments vol 71 no 3 pp 236ndash244 2006

[18] W-P Ting M-C Lu and Y-H Huang ldquoKinetics of 26-dimethylaniline degradation by electro-Fenton processrdquo Jour-nal of Hazardous Materials vol 161 no 2-3 pp 1484ndash14902009

[19] H-J Fan S-THuangW-HChung J-L JanW-Y Lin andC-C Chen ldquoDegradation pathways of crystal violet by Fenton andFenton-like systems condition optimization and intermediateseparation and identificationrdquo Journal of Hazardous Materialsvol 171 no 1ndash3 pp 1032ndash1044 2009

[20] E Neyens and J Baeyens ldquoA review of classic Fentonrsquos peroxida-tion as an advanced oxidation techniquerdquo Journal of HazardousMaterials vol 98 no 1-3 pp 33ndash50 2003

[21] C Bouasla M E-H Samar and F Ismail ldquoDegradation ofmethyl violet 6B dye by the Fenton processrdquo Desalination vol254 no 1ndash3 pp 35ndash41 2010

[22] N Masomboon C Ratanatamskul and M-C Lu ldquoKineticsof 26-dimethylaniline oxidation by various Fenton processesrdquoJournal of HazardousMaterials vol 192 no 1 pp 347ndash353 2011


[23] M H Baek C O IJagbemi and D S Kim ldquoSpectroscopicstudies on the oxidative decomposition ofmalachite green usingozonerdquo Water Science and Technology vol 62 no 6 pp 1304ndash1311 2010

[24] H ZhengH Zhang X Sun P Zhang T Tshukudu andG ZhuldquoThe catalytic oxidation of malachite green by the microwave-Fenton processesrdquo Dyes Pigments vol 62 no 1 pp 1ndash10 2004

[25] P A Soloman C A Basha M Velan and N BalasubramanianldquoElectro oxidation of malachite green and modeling usingANNrdquoChemical and Biochemical EngineeringQuarterly vol 24no 4 pp 445ndash452 2010

[26] V K Garg R Kumar and R Gupta ldquoRemoval of malachitegreen dye from aqueous solution by adsorption using agro-industry waste a case study of Prosopis cinerariardquo Dyes andPigments vol 62 no 1 pp 1ndash10 2004

[27] T Santhi and S Manonmani ldquoMalachite green removal fromaqueous solution by the peel of Cucumis sativa fruitrdquo CleanmdashSoil Air Water vol 39 no 2 pp 162ndash170 2011

[28] S P S Syed ldquoStudy of the removal of malachite green fromaqueous solution by using solid agricultural wasterdquo ResearchJournal of Chemical Sciences vol 881 no 1 pp 88ndash104 2011

[29] G H Sonawanea and V S Shrivastava ldquoKinetics of decolour-ization of malachite green from aqueous medium by maize cob(Zea maize) an agricultural solid wasterdquoDesalination vol 250pp 94ndash105 2009

[30] B Ensing F Buda and E J Baerends ldquoFenton-like chemistryin water oxidation catalysis by Fe(III) and H

2O2rdquo Journal of

Physical Chemistry A vol 107 no 30 pp 5722ndash5731 2003[31] M Neamtu A Yediler I Siminiceanu and A Kettrup ldquoOxi-

dation of commercial reactive azo dye aqueous solutions bythe photo-Fenton and Fenton-like processesrdquo Journal of Photo-chemistry and Photobiology A vol 161 no 1 pp 87ndash93 2003

[32] M Perez F Torrades X Domenech and J Peral ldquoFenton andphoto-Fenton oxidation of textile effluentsrdquoWater Research vol36 no 11 pp 2703ndash2710 2002

[33] J-H Sun S-P Sun G-L Wang and L-P Qiao ldquoDegradationof azo dye Amido black 10B in aqueous solution by Fentonoxidation processrdquo Dyes and Pigments vol 74 no 3 pp 647ndash652 2007

[34] D R de Souza E T F Mendonca Duarte G de Souza Girardiet al ldquoStudy of kinetic parameters related to the degradationof an industrial effluent using Fenton-like reactionsrdquo Journal ofPhotochemistry and Photobiology A vol 179 no 3 pp 269ndash2752006

[35] M L Kremer ldquoComplex versus ldquoFree Radicalrdquo mechanism forthe catalytic decomposition of H

2O2by Fe3+rdquo International

Journal of Chemical Kinetics vol 17 pp 1299ndash1314 1985[36] H Hassan and B H Hameed ldquoFenton-like oxidation of acid

red 1 solutions using heterogeneous catalyst based on ball clayrdquoInternational Journal of Environmental Science vol 2 no 3 pp1ndash5 2011

[37] H-Y Xu M Prasad and Y Liu ldquoSchorl a novel catalyst inmineral-catalyzed Fenton-like system for dyeing wastewaterdiscolorationrdquo Journal of Hazardous Materials vol 165 no 1ndash3 pp 1186ndash1192 2009

[38] G R Mahdavinia and R Zhalebaghy ldquoRemoval kinetic ofcationic dye using poly (sodium acrylate)-carrageenanNa-montmorillonite nanocomposite superabsorbentsrdquo Journal ofMaterials and Environmental Science vol 3 no 5 pp 895ndash9062012

[39] S HashemianM Tabatabaee andMGafari ldquoFenton oxidationof methyl violet in aqueous solutionrdquo Journal of Chemistry vol2013 Article ID 509097 6 pages 2013

[40] J J Pignatello E Oliveros andAMacKay ldquoAdvanced oxidationprocesses for organic contaminant destruction based on thefenton reaction and related chemistryrdquo Critical Reviews inEnvironmental Science and Technology vol 36 no 1 pp 1ndash842006

[41] G E A Mahmoud and L F M Ismail ldquoFactors affecting thekinetic parameters related to the degradation of direct yellow50 by Fenton and Photo-Fenton Processesrdquo Journal of Basic andApplied Chemistry vol 1 no 8 pp 70ndash79 2011

[42] L Nunez J A Garcıa-Hortal and F Torrades ldquoStudy of kineticparameters related to the decolourization and mineralizationof reactive dyes from textile dyeing using Fenton and photo-Fenton processesrdquo Dyes and Pigments vol 75 no 3 pp 647ndash652 2007

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

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Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

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Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


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Medicinal ChemistryInternational Journal of


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Fentonrsquos reagent is a mixture of ferrous ion and hydrogenperoxide generating hydroxyl radical (∙OH) in situ accordingto the following equation

Fe2+ +H2O2997888rarr Fe3+ +OHminus + ∙OH (1)

Fe(III) can catalyze the decomposition of H2O2 The

reaction of H2O2with Fe3+ (the so-called Fentonrsquos-like

reagent) goes through the formation of hydroperoxyl radicalHO2

∙ [30]

Fe3+ +H2O2997888rarr Fe2+ +HO

2

∙+H+ (2)

Fe3+ +HO2

∙997888rarr Fe2+ +H+ +O

2(3)

Fe2+ + ∙OH 997888rarr Fe3+ + minusOH (4)∙OH+ H

2O2997888rarr HO

2

∙+ H2O (5)

Fe2+ +HO2

∙997888rarr Fe3+ +HO

2

minus (6)∙OH+ HO∙ 997888rarr H

2O2

(7)

The specific objectives of this study are the investiga-tion of removal efficiencies of malachite green (MAG) byFenton-like process Important variables such as oxidationtime effect of pH dosages of H

2O2 and ferrous ions were

examined The kinetics and thermodynamic of process alsowere determined

2 Experimental

21 Material and Methods The basic dye MAG has molec-ular formula C

23H25ClN2and molar mass 364911 gmol

with 120582max 620 nm and was used as received without fur-ther purification to prepare simulated wastewater 50 times10minus3 stock solution of MAG was prepared and work-ing solutions are prepared by the dilution Experimen-tal solutions of the desired concentration were obtainedby successive dilutions The chemical structure of mala-chite green (4-[(4-dimethylaminophenyl)phenyl-methyl]-NN-dimethylaniline) is shown in Figure 1

All the reagents used in the experimentswere in analyticalgrade (Merck) and were used without further purificationAll the experiments were conducted at room temperatureThe dye oxidation was achieved by Fenton-like reagent whichwas composed of a mixture of Fe

2(SO4)3sdot7H2O and H

2O2

(30) The necessary quantities of Fe3+ and H2O2were

added simultaneously in the dye solution All experimentswere conducted in a 500mL thermostated batch glass reactorequipped with the magnetic stirrer The kinetics of oxidationwas followed by taking samples at regular time interval

The residual concentration of the MAG in the solutionat different times of sampling was determined The residualconcentration of the dye was deducted from the calibrationcurves which were produced at wavelength correspondingto the maximum of absorbance (620 nm) on an UV-visiblespectrophotometer apparatus (Shimadzu 160A) The cellsused were in quartz 1 cm thick The discoloration efficiency

N

N

Figure 1 Chemical structure of malachite green (MAG)

of the dye (X) with respect to its initial concentration iscalculated as

X = ([MAG]0 minus [MAG] [MAG]0) times 100 (8)

where [MAG]0and [MAG] are the initial and appropriate

concentrations of dye at any reaction time 119905 respectively

3 Results and Discussion

31 Effect of pH on Decolorization pH has a major effect onthe efficiency of MAG treatment The oxidation was done for120min under controlled pH condition with constant doseof Fe3+ (10 times 10minus4M) and H

2O2(5 times 10minus2M) The effect

of pH on the removal of malachite green using 50mg Lminus1of dye was studied The oxidation of MAG as a functionof pH is shown in Figure 2 It is evident that change inthe pH of the solution to Fenton-like value of 3 leads toincreases in the extent of MAG oxidation It is apparent fromthat extent of decolorization decreases with increase in pHand at pH 30 almost gt95 color removal was observedTherefore the results demonstrate that the pH value for themost effective oxidation of MAG is approximately 3 Thedecrease in oxidation rate at pH gt 3 could be explained bythe formation of Fe(OH)

3 which has lower catalytic activity

in the decomposition of H2O2[30]The low activity detected

for high pH has been reported and the results closely agreedwith those in the literature [19 30ndash32]

32 Effect of Fe3+ Ferrous Dosage The concentration of Fe3+is one of the critical parameters in Fenton processes In thepresent study the influence of different iron concentrations(Fe3+ = 10 times 10minus6ndash10 times 10minus3M) expressed asMAG removal isillustrated in Figure 3 The concentration of hydrogen perox-ide is fixed as 005M andMAG concentration is 30times 10minus5MIt can be seen from results that MAG degradation increasedwith increasing Fe+3 concentrations This is due to the factthat Fe+3 plays a very important role in the decompositionsof H2O2to generate the ∙OH in the Fenton process The

lower degradation capacity of Fe3+ at small concentrationis probably due to the lowest ∙OH radicals producing avariable for oxidation [16 19] for higher concentration ofFe+3 oxidation of dye will decrease This can be explained by


100

80

60

40

20

00 30 60 90 120

Time (min)

Deg

rada

tion

effici

ency

()

pH 3pH 7pH 2

pH 9pH 5pH 10




100

80

60

40

20

00 30 60 90 120

Time (min)

Deg

rada

tion

effici

ency

()

10minus3 10minus4

10minus5 10minus6



times 10minus5M)


2











100

80

60

40

20

00 30 60 90 120

Time (min)

Deg

rada

tion

effici

ency

()

5 times 10minus3


1 times 10minus1







2O2[17] However at















2O2molar ratio






2O2









2H2O2997888rarr H

2O +O

2 (9)





119905

TOC0

times 100 (10)




100908070605040302010

00 20 40 60 80 100 120

Time (min)

Deg

rada

tion

effici

ency

()

1 times 10minus6

5 times 10minus5

1 times 10minus5

1 times 10minus4

3 times 10minus5


100

90

80

70

60

50

400 30 60 90 120

Time (min)

30∘C40∘C70∘C

50∘C20∘C60∘C

Deg

rada

tion

effici

ency

()







and SO4


4


4



80

70

60

50

40

30

20

10

00 50 100 150

TOC

rem

oval

()

Time (min)


of SO4


4

2minus











1

[119862MAG]minus

1

[119862(MAG)0]

= 119896119905 (15)



minus45

minus35

minus25

minus15

0 20 40 60 80 100 120


R2 = 09439

Time (min)

lnC


R2 = 09951

0

10

20

30

40

50

60

70

0 30 60 90 120Time (min)

y = 04613x + 2616

1C



119862is calculated

Δ119866∘= minus119877119879 ln119870

119862 (16)


119870119862=

119862Ae119862Se (17)



ln119870119862=

minusΔ119867∘

119877119879

+

Δ119878∘

119877

(18)


119862versus



minus2 M)

Δ119878∘



(KJmolminus1 ) 119870119862 119879 (K)

432823 9610


3803870480733

293303323333

Fentonlike

oxidation


4 Conclusion




[H2O2] = 5 times 10

minus2M pH = 3(19)






C23H25ClN2+ 52H

2O 997888rarr 23CO

2+ 129H+

+ 2NO3


(20)

References




































2O2rdquo Journal of

























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


100

80

60

40

20

00 30 60 90 120

Time (min)

Deg

rada

tion

effici

ency

()

pH 3pH 7pH 2

pH 9pH 5pH 10




100

80

60

40

20

00 30 60 90 120

Time (min)

Deg

rada

tion

effici

ency

()

10minus3 10minus4

10minus5 10minus6



times 10minus5M)


2











100

80

60

40

20

00 30 60 90 120

Time (min)

Deg

rada

tion

effici

ency

()

5 times 10minus3


1 times 10minus1







2O2[17] However at















2O2molar ratio






2O2









2H2O2997888rarr H

2O +O

2 (9)





119905

TOC0

times 100 (10)




100908070605040302010

00 20 40 60 80 100 120

Time (min)

Deg

rada

tion

effici

ency

()

1 times 10minus6

5 times 10minus5

1 times 10minus5

1 times 10minus4

3 times 10minus5


100

90

80

70

60

50

400 30 60 90 120

Time (min)

30∘C40∘C70∘C

50∘C20∘C60∘C

Deg

rada

tion

effici

ency

()







and SO4


4


4



80

70

60

50

40

30

20

10

00 50 100 150

TOC

rem

oval

()

Time (min)


of SO4


4

2minus











1

[119862MAG]minus

1

[119862(MAG)0]

= 119896119905 (15)



minus45

minus35

minus25

minus15

0 20 40 60 80 100 120


R2 = 09439

Time (min)

lnC


R2 = 09951

0

10

20

30

40

50

60

70

0 30 60 90 120Time (min)

y = 04613x + 2616

1C



119862is calculated

Δ119866∘= minus119877119879 ln119870

119862 (16)


119870119862=

119862Ae119862Se (17)



ln119870119862=

minusΔ119867∘

119877119879

+

Δ119878∘

119877

(18)


119862versus



minus2 M)

Δ119878∘



(KJmolminus1 ) 119870119862 119879 (K)

432823 9610


3803870480733

293303323333

Fentonlike

oxidation


4 Conclusion




[H2O2] = 5 times 10

minus2M pH = 3(19)






C23H25ClN2+ 52H

2O 997888rarr 23CO

2+ 129H+

+ 2NO3


(20)

References




































2O2rdquo Journal of

























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of






2H2O2997888rarr H

2O +O

2 (9)





119905

TOC0

times 100 (10)




100908070605040302010

00 20 40 60 80 100 120

Time (min)

Deg

rada

tion

effici

ency

()

1 times 10minus6

5 times 10minus5

1 times 10minus5

1 times 10minus4

3 times 10minus5


100

90

80

70

60

50

400 30 60 90 120

Time (min)

30∘C40∘C70∘C

50∘C20∘C60∘C

Deg

rada

tion

effici

ency

()







and SO4


4


4



80

70

60

50

40

30

20

10

00 50 100 150

TOC

rem

oval

()

Time (min)


of SO4


4

2minus











1

[119862MAG]minus

1

[119862(MAG)0]

= 119896119905 (15)



minus45

minus35

minus25

minus15

0 20 40 60 80 100 120


R2 = 09439

Time (min)

lnC


R2 = 09951

0

10

20

30

40

50

60

70

0 30 60 90 120Time (min)

y = 04613x + 2616

1C



119862is calculated

Δ119866∘= minus119877119879 ln119870

119862 (16)


119870119862=

119862Ae119862Se (17)



ln119870119862=

minusΔ119867∘

119877119879

+

Δ119878∘

119877

(18)


119862versus



minus2 M)

Δ119878∘



(KJmolminus1 ) 119870119862 119879 (K)

432823 9610


3803870480733

293303323333

Fentonlike

oxidation


4 Conclusion




[H2O2] = 5 times 10

minus2M pH = 3(19)






C23H25ClN2+ 52H

2O 997888rarr 23CO

2+ 129H+

+ 2NO3


(20)

References




































2O2rdquo Journal of

























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


80

70

60

50

40

30

20

10

00 50 100 150

TOC

rem

oval

()

Time (min)


of SO4


4

2minus











1

[119862MAG]minus

1

[119862(MAG)0]

= 119896119905 (15)



minus45

minus35

minus25

minus15

0 20 40 60 80 100 120


R2 = 09439

Time (min)

lnC


R2 = 09951

0

10

20

30

40

50

60

70

0 30 60 90 120Time (min)

y = 04613x + 2616

1C



119862is calculated

Δ119866∘= minus119877119879 ln119870

119862 (16)


119870119862=

119862Ae119862Se (17)



ln119870119862=

minusΔ119867∘

119877119879

+

Δ119878∘

119877

(18)


119862versus



minus2 M)

Δ119878∘



(KJmolminus1 ) 119870119862 119879 (K)

432823 9610


3803870480733

293303323333

Fentonlike

oxidation


4 Conclusion




[H2O2] = 5 times 10

minus2M pH = 3(19)






C23H25ClN2+ 52H

2O 997888rarr 23CO

2+ 129H+

+ 2NO3


(20)

References




































2O2rdquo Journal of

























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



minus2 M)

Δ119878∘



(KJmolminus1 ) 119870119862 119879 (K)

432823 9610


3803870480733

293303323333

Fentonlike

oxidation


4 Conclusion




[H2O2] = 5 times 10

minus2M pH = 3(19)






C23H25ClN2+ 52H

2O 997888rarr 23CO

2+ 129H+

+ 2NO3


(20)

References




































2O2rdquo Journal of

























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










2O2rdquo Journal of

























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

research article fenton-like oxidation of malachite green...

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