31 Alexandre Loukanov

7/25/2019 31 Alexandre Loukanov

1/9

Analele Universit ii Constantin Brncui din Trgu Jiu, Seria Inginerie, Nr. 2/2011

Annals of the Constantin Brncui Universityof Trgu-Jiu,Engineering Series, Issue 2/2011

257

PARTICULE DE FIER ZERO-

VALENT PENTRU

DECOLORAREA

COLORANILOR AZOICI DINAPA REZIDUALTEXTIL

Alexandre Loukanov,Catedra deGeoecologie, Universitatea de Mine i

Geologie St. Ivan Rilski,, Sofia 1700,

BULGARIA

Nikolay Petrov,Catedra deGeoecologie, Universitatea de Mine i


BULGARIA

Anatoli Angelov,Catedra deGeoecologie, Universitatea de Mine i


BULGARIASeiichiro Nakabayashi, Catedra de

Chimie, Facultatea de tiine,

Universitatea Saitama, Saitama 338-

8570, JAPAN

ABSTRACT: Lucrarea de fa a fost realizat pentrudecolorarea negrului Reactiv 5, care este un colorantazoic prezent n apele reziduale textile prinnanoparticule de fier zerovalent sintetic (ZVIN).

Nanoparticulele (< 100 nm) discutate apar sub formaunei structuri tipice de miez-nveli(core-shell). Miezuleste alctuit din fier zero-valent sau metalic, iarnveliul este format din oxizi de fier (II) i fier (III). ncondiii ambientale nanoparticulele de fier zerovalentsunt reactive n api servesc ca un donor excelent deelectroni, ceea ce le face un material versatil pentrutratarea coloranilor azoici. Se poate concluziona ceficiena distrugerii a fost sporit prin doz denanoparticule de fier zerovalent i timp de reaciedatoritsuprafeei mari i activiti interioare mari. Rataconstant de reacie crete puternic odat cu scderea

pH-ului soluiei. Aceste descoperiri au demonstratndeprtarea rapid a coloranilor azoici din apelereziduale prin tratamentul cu nanoparticule de fierzerovalent.

CUVINTE-CHEIE: nanoparticule de fier zerovalent,Negru reactiv 5, decolorare a coloranilor azoici

ZERO-VALENT IRON

NANOPARTICLES FOR

DECOLORIZATION OF AZO

DYES FROM TEXTILE

WASTEWATER

Alexandre Loukanov,Dept. of Eng.geoecology, University of Mining and

Geology St. Ivan Rilski,, Sofia 1700,

BULGARIA

Nikolay Petrov,Dept. of Eng.geoecology, University of Mining and

Geology St. Ivan Rilski,, Sofia

1700, BULGARIA

Anatoli Angelov,Dept. of Eng.geoecology, University of Mining and

Geology St. Ivan Rilski,, Sofia

1700, BULGARIASeiichiro Nakabayashi,Dept. of

Chemistry, Faculty of Science,

Saitama University, Saitama 338-

8570, JAPAN

ABSTRACT: The present work was conducted fordecolorization of Reactive black 5, which is an azodye occurred in the textile wastewater, by syntheticzero-valent iron nanoparticles (ZVIN). Thenanoparticles (< 100 nm) discussed in this contributionexhibit in a typical core-shell structure. The coreconsists primarily of zero-valent or metallic iron,while the shell is formed from iron (II) and iron (III)oxides. Under ambient condition ZVIN are fairlyreactive in water and can serve as an excellent electrondonor, which makes them versatile material fortreatment of azo dyes. It could be concluded that thedestruction efficiency were enhanced with ZVINdosage and reaction time due to the high surface areaand high inherent activity. The reaction rate constantstrongly increases with decreasing pH of the solution.These findings demonstrated the fast removal of azo-dyes compound in wastewaters by treatment with

NZVI.

KEY WORDS: Zero-valent iron nanoparticles,Reactive black 5, Azo dye decolorization


2/9



258

1. INTRODUCERE

Industria textil sufer din cauzacantitilor mari de ape reziduale care sunt

foarte colorate cu diveri compui cum ar fichimicalele auxiliare organice, srurileanorganice, metalele grele i detergeniineionici (Pekakis et al. 2006, Mantzavinos iPsillakis 2004). Coloranii sintetici sunt ngeneral rezisteni la biodegradarea oxidativdin moment ce sunt realizai pentru a avea orezisten ridicat la splarea cauzat deoxidarea chimic, biologic i indus delumin. Dintre cele 10,000 de tipuri diferite de

pigmeni disponibili, coloranii azoici

reprezint peste 50 % din coloranii textilifolosii n industrie (Tang i An 1995). Unelestudii care folosesc noroi activat sugereazc

biotransformarea este nceatpentru coloraniiazoici solubili n ap (Hitz et al. 1978).Coloranii azoici se caracterizeaz prinlegturi duble azot-azot (-N=N-), rapiditatesuperioar la materialul aplicat i stabilitatefotolitic mare. Culoarea i toxicitatea lorinflueneaz calitatea apei i eficienaanumitor tehnici de tratare a apei. Stabilirea detehnologii de ndeprtare pentru coloraniiazoici este o problem urgent. Un singurtratament nu poate totui elimina toatesubstanele contaminante din apa rezidual.

Folosirea nanoparticulelor de fier zero-valent pentru decontaminarea agenilor decontaminare din sol i apa fost subiect pentrumulte studii. Majoritatea studiilor asupradegradrii chimicalelor organice s-auconcentrat pe iniierea unor mecanisme

reductoare (Tratnyek et al. 2002). Scopulacestei lucrri este s demonstreze utilizareananoparticulelor de fier zero-valent pentrudecolorarea negrului reactiv 5 (RB 5) ca uncolorant azoic reprezentativ n apele rezidualetextile. La temperatura ambiental i condiiide pH mediu i acid, fierul elementar oxideazuor fierul feros i elibereaz doi electroni.Aceti electroni ncep s funcioneze pentrutransformarea gruprii azoice n grupareamino. Distrugerea legturii azoice din

cromoforul RB 5 duce la decolorarea soluieide apcontaminat.

1. INTRODUCTION

The textile industry suffers from thegeneration of large quantities wastewater that

is highly colored with various compoundssuch as organic auxiliary chemicals,inorganic salts, heavy metals and non-ionicsurfactants (Pekakis et al. 2006, Mantzavinosand Psillakis 2004). The synthetic dyes aregenerally resistant to oxidative

biodegradation since they are designed toexhibit high resistance to fading caused bychemical, biological and light-inducedoxidation. Amongst the 10,000 different dyesand pigments available, azo dyes constitute

over 50 % of all textile dyes used in theindustry (Tang and An 1995). Some studiesusing activated sludge suggest that

biotransformation is slow for water-solubleazo dyes (Hitz et al. 1978). Azo dyes arecharacterized by nitrogen to nitrogen double

bonds (-N=N-), superior fastness to theapplied fabric and high photolytic stability.Their color and toxicity influence the qualityof water and the efficiency of some watertreatment techniques. Establishing removaltechnologies for azo dyes is an urgent

problem. One single treatment however cannot eliminate all contaminates in waste water.

The use of zero-valent ironnanoparticles for decontamination ofcommon soil and water contaminants has

been the subject of many studies. Moststudies of the degradation of organicchemicals have focused on the initiation ofreductive mechanisms (Tratnyek et al. 2002).

The aim of this work is to demonstrate theutilization of ZVIN for decolorization ofreactive black 5 (RB 5) as a representativeazo dyes in the textile wastewater. Underambient temperature and mild and acid pHconditions the elemental iron slowly oxidizesto ferrous iron and releases two electrons.These electrons begin to function oftransformation of the azo- to amine-group.The destruction of the azo bond in thechromophore of RB 5 leads to decolorization

of the contaminated waste solution.


3/9



259

2. SECIUNE EXPERIMENTAL

2.1. Chimicale

Toi reactivii chimici (FeCl3, NaOH, NaBH4,acid hidrocloric, Negru Reactiv 5) suntobinui din Sigma-Aldrich. Chimicalele suntde grad reactiv analitic. Soluiile au fost

preparate prin dizolvarea unor cantitiadecvate de compui din apa distilat. Apa afost purificat cu un distilator (modelRobotika DS-10).

2.2. Sinteza nanoparticulelor de fier

zero-valent.

Particulele de mrimea nano au fost sintetizateprin reducerea clorurii de fier (III) cu soluiealcalin de de borohidrid de sodiu. Soluieapoas 0.1 M FeCl3 a fost adugat prin

picurare unei soluii apoase preparate proaspt0.16 M NaBH4la temperatura camerei (25 C)i la presiunea aerului nconjurtor. Reacia afost inut la dispozitivul magnetic deamestecare timp de 30 min. Prepararea

soluiilor i schema de reacie sunt prezentaten Fig. 1. Rezultatul este formarea rapid deprecipitate negre fine de nanoparticule cu fierzero-valent.

2. EXPERIMENTAL SECTION

2.1.

Chemicals

All chemical reagents (FeCl3, NaOH, NaBH4,hydrochloric acid, Reactive Black 5) areobtained from Sigma-Aldrich. The chemicalsare of analytical reagent grade. The solutionswere prepared by dissolving of adequatequantities compound in distilled water. Waterwas purified by a water distiller (modelRobotika DS-10).

2.2. Synthesis of Zero Valent Iron

Nanoparticles.

Nano sized particles were synthesized byreduction of iron (III) chloride with alkalinesolution of sodium borohydrid. 0.1 M FeCl3aqueous solution was added drop wise to afreshly prepared 0.16 M NaBH4 aqueoussolution at room temperature (25 C) andambient air pressure. The reaction was keptunder magnetic stirrer for 30 min. The

preparation of solutions and reaction schemeare shown on Fig. 1. The result is rapidformation of fine black precipitates of zero-valent iron nanoparticles.

Figura 1. Schema procedeului experimental pentru prepararea nanoparticulelor de fier zero-valent prin reducereapoas. Procedura a inclus urmtoarele etape: (i) borohidrid de sodiu (NaBH4, 0.6 g) solid este dizolvat n 100mL de soluie de NAOH 0.1 M (0.16 M NaBH4in 0.1 M NaOH). (ii) 1.6 g de FeCl3anhidreste dizolvatn 100


4/9



260

mL ap distilat (0.1 M FeCl3). Precurosul NaBH4 ar putea fi fpcut fie n ap fie n soluie de NaOH; totuiNaBH4 este instabil n ap i poate duce rapid la pierderea puterii de reducie. Adiia de FeCl3 la soluia deNaBH4n prezena amestecrii magnetice puternice a dus la un precipitat negru de Fe

0potrivi reaciei (Eq. 2.1).Particulele au fost splate de 3 ori cu apdistilat(pH ~ 7) i depozitate sub formde concentrat de 4 mg Fe/ml la

pH neutru n frigider la < 4 C.

Figure 1. Scheme of the experimental procedure for preparation of zero-valent iron nanoparticles by aqueousreduction. The procedure involved the following steps: (i) sodium borohydride (NaBH4, 0.6 g) solid is dissolvedin 100 mL of 0.1 M NaOH solution (0.16 M NaBH4in 0.1 M NaOH). (ii) 1.6 g of anhydrous FeCl3is dissolvedinto 100 mL distilled water (0.1 M FeCl3). NaBH4precursor might be made either in water or NaOH solution;however NaBH4 is unstable in water and can quickly result in a loss of reduction power. Addition of FeCl3 to

NaBH4solution in the presence of vigorous magnetic stirring resulted in black precipitation of Fe0according the

reaction (Eq. 2.1). The particles were washed 3 times with distilled water (pH ~ 7) and storred as a 4 mg Fe/mlconcentrate at neutral pH in a refrigerator at < 4 C.

2FeCl3 + 6NaBH4 + 18H2O2Fe0 + 6B(OH)3 + 21H2 + 6NaCl

air

Eq. 2.12.1. Degradarea Negrului Reactiv 5

Pentru a testa activitatea de degradare ananoparticulelor de fier zero-valent, 4 mg de

precipitat a fost amestecat cu 100 mL soluiede RB 5 (conc. 5 mg/ ml). In toateexperimentele, spectrele de absorbie opticaufost msurate cu un spectrofotmetruSpektromom 410 (Ungaria) la o lungime de

undfixatde 600 nm. Eficiena decolorrii idegradrii a fost calculatca:

2.1. Degradation of Reactive Black 5

To test the degradation activity of ZVIN, 4mg precipitate was mixed with 100 mLsolution of RB 5 (conc. 5 mg/ ml). In allexperiments the optical absorbance spectrawere measured by spectrophotometerSpektromom 410 (Hungary) at fixedwavelength of 600 nm. The decolorization

and degradation efficiency have beencalculated as:

D =

C0 - C

C0

x 100

, Eq. 2.2unde C0 este concentraia iniial acolorantului i C este concentraia colorantuluidup tratarea cu nanoparticule de fier zero-valent n intervalul de timp selectat. Toate

testele de distrugere au fost realizate la rataconstant de amestecare (500 rpm) latemperaturi ambientale (25 C) i mai ridicate(>40 C).

3. REZULTATE I DISCUIE

3.1. Caracterizarea nanoparticulelor defier zero-valent

Particulele de fier zero-valent sunt sintetizateprin reducie apoas cu borohidrid de sodiucare nu permite controlul mrimii i

where C0 is the initial concentration of dyeand C is the concentration of dye aftertreatment with ZVIN in selected timeinterval. All destruction tests were performed

at constant stirring rate (500 rpm) at ambient(25 C) and higher (>40 C) temperatures.

3. RESULTS AND DISCUSSION

3.1. Characterization of zero-valent iron nanoparticles

The zero-valent iron nanoparticles are

synthesized by aqueous reduction withsodium borohydride, which does not enable


5/9



261

morfologiei lor. Acest rezultat este demonstratn Fig.2A, unde micrograful SEM alnanoparticulelor de Fe0 sintetic a indicatdistribuia lor polidispersat. Analiza la

micrograf confirm cnanoparticulele de fierzero-valent nu apar ca nanoparticule discrete,ci mai degrabca agregate cu diametru mediude aproximativ 60-70 nm (Fig. 2B).

to control their size and morphology. Thisresult is demonstrated on Fig.2A, whereSEM micrograph of synthetic Fe0nanoparticles showed their polydispersed size

distribution. The micrograph analysisconfirms that ZVIN do not appear as discretenanoparticles, rather as aggregations withaverage diameter about 60-70 nm (Fig. 2B).

0

10

20

30

40

50

60

70

1020

3040

5060

7080

90100

number

particle size, nm100 nm

A B

Figura 2. (A) Micrograful SEM de agregate de nanoparticule de fier zero-valent. (B)Distribuia polidispersat.Scara = 100 nm.

Figure 2. (A) SEM micrograph of aggregations of ZVIN. (B)Polydisperse size distribution. Scale bar = 100 nm.

Agregarea particulelor se datoreaz probabil

forelor magnetice care au aprut ntreparticule. Acest rezultat este asemntor cu celraportat n literatur (Shao-feng et al. 2005,Kanel et al. 2006). Reacia nanoparticulelor defier zero-valent cu RB 5 este realizat prinspargerea celei mai slabe grupri azoice dinmolecul (Fig. 3A). Legtura N=N bond estemai slab dect C-C iar gruparea azoic estemai uor de distrus n comparaie cu altegrupri, n special structurile cu inelearomatice. Se tie c gruparea N=N a

colorantului este motivul principal pentruculoarea sa vizibil. Lungimile de undmaxime vizibile pentru absorbie ale RB 5 este600 nm, aa cum se observn Fig. 3B. A foststudiat degradarea sistemului Fe-H2O-RB 5.Am observat cabsorbana vizibil a soluieide degradare scade.

The particles aggregation is probably due to

the magnetic forces which occurred betweenthe particles. This result is similar to thosereported in the literatures (Shao-feng et al.2005, Kanel et al. 2006). The reaction ofZVIN with RB 5 is pursued with breaking ofweakest azo group in the molecule (Fig. 3A).The N=N bond is weaker than the C-C andthe azo group is easier for destruction incomparison with other groups, especially thearomatic ring structures. It is well known that

N=N group of the dye is the basic reason

for its visible color. The maximum visibleabsorption wavelengths of RB 5 is 600 nmrespectively, as it is shown on Fig. 3B.Degradation of Fe-H2O-RB 5 system wasstudied. We observed that the visibleabsorbance of the degradation solution

become lower.


6/9



262

NaO3S

SO3Na

H2N

HO N

N

N

N

S

S

O

O

O

O

SO3Na

NaO3S

weak bond

weak bond

N=NA B

Figura 3. (A) Structura chimic, i spectrul de absorbie (B) UV-VIS al Negrului Reactiv 5.Figure 3. (A) Chemical structure, and (B) UV-VIS absorption spectrum of Reactive Black 5.

Distrugerea legturii azoice n RB 5 duce ladecolorarea soluiei de colorant. n condiiiambientale, nanoparticulele de fier zero-valentsunt reactive n ap i servesc ca un donorexcelent de electroni, ceea ce le face unmaterial versatil de remediere. Moleculacolorantului primete electroni de la fier (veziFig. 4A) i se combincu H+de la acid pentrua forma un produs de tranziie. In aceastreacie particula de fier este oxidatn timp cemolecula de RB 5 este redus. n plus, n

prezena Fe

0

, gruparea azoiceste convertitlaamine aromatice cum se indic n Fig. 4B.Aceti compui modificai sunt uor degradaide microorganisme (Nam i Tratnyek 2000).

The destruction of the azo bond in the RB 5leads to decolorization of the dye solution.Under ambient conditions ZVIN is fairlyreactive in water and can serve as anexcellent electron donor, which makes it aversatile remediation material. The dyemolecule receives electrons from the iron(seeFig. 4A) and combined with H+from theacid to form the transitional product. In thisreaction the iron particle is oxidized whileRB 5 molecule is reduced. Additionally, in

the presence of Fe

0

, the azo group isconverted to aromatic amines as it is shownon Fig. 4B. Such modified compounds areeasily degraded by microorganisms (Namand Tratnyek 2000).

N

NAr'

Ar''

Fe0

NN

Ar'

Ar''

Fe2+

H+/H2O

Fe2+Ar' NH2 H2N Ar''+ +

Fe0

FeO(OH)

NaO3S SO3Na

NH2 OH

NNNN

SS

O

O O

O

SO3Na

NaO3S

NH2

SO O

SO3Na

NaO3S SO3Na

NH2 OH

NH2NH2+

A B

Figura 4. Decolorarea negrului reactiv 5 n prezena nanoparticulelor de fier zero-valent. A) Mecanismul dedegradare n sistemul Fe0-H2O. (B) Modelul miez-nvelial nanoparticulelor de fier zero-valent. Miezul constnspecial n fier zero-valent i asigurputerea de reducie pentru reacia cu gruparea azoicdin apa rezidualtextil.nveliul este reprezentat de oxizi/hidroxizi de fier formi din oxidarea fierului zero-valent.Figure 4.Decolorisation of reactive black 5 in the presence of ZVIN. A) Degradation mechanism in Fe0-H2Osystem. (B) The core-shell model of ZVIN. The core consists of mainly zero-valent iron and provides the

reducing power for reaction with azo-group from the textile wastewater. The shell is largely ironoxides/hydroxides formed from the oxidation of zero-valent iron.Potrivit modelului miez-nveli, nveliul According to the core-shell model, the mixed


7/9



263

oxidului de fier cu valenmixteste insolubiln condiii de pH neutru i poate protejamiezul Fe0 de o posibil oxidare viitoarerapid. Reactivitatea ridicat se datoreaz

suprafeei totale mari, densitii mai mari dezone reactive pe suprafeele particulei.Raportul concentraiilor (C/C0) a fost

caluclat pentru a evalua degradareacoloranilor. Curbele de decolorare sunt

prezentate n Fig. 5. Procesul este puternicinfluenat de pH. Molecula de RB 5 existcaun anion n ap n jurul i peste pH 7, dincauza disocierii ionului de sodiu (Fig. 5A).Rata de decolorare este mai nceatpncndreacia ajunge la un echilibru, unde practic nu

se mai observ nicio schimbare. Dupadugarea a 50 l de acid hidrocloric laamestecul de reacie (volum = 100 mL)absorbana a fost redus cu peste 90 % ncteva minute (Fig. 5B). Rata reacieiireversibile este mult mai rapid rate.Rezultatele degradrii observate la pH iniial7.5 i 1.8 indicfaptul ccinetica degradrii ieficiena ndeprtrii finale a indicate RB 5 aucrescut odat cu scderea pH-ului soluiei.Creterea concentraiei ionilor de hidrogen vaspori reaciile de degradare prin reducie acompuilor azoici din cauz c ionii dehidrogen sunt implicai n reacia reductoare

prin nanoparticule de fier zero-valent.

valence iron oxide shell is largely insolubleunder neutral pH conditions and may protectFe0 core from future rapid oxidation. Thehigh reactivity is due to the large overall

surface area, greater density of reactive siteson the particle surfaces.The concentration ratio (C/C0) was

calculated to evaluate the degradation of thedyes. Decolorization curves are shown onFig. 5. The process is strongly influenced by

pH. RB 5 molecule exists as an anionic inwater at around and above pH 7, because ofthe dissociation of sodium ion (Fig. 5A). Thedecolorization rate is slower till the reactionreaches a equilibrium, where practically no

any changes are observed. After adding of 50l hydrochloric acid to the reaction mixture

(volume = 100 mL) the absorbance wasreduced greater than 90 % in a few minutes(Fig. 5B). The rate of the irreversible reactionis much faster. The observed degradationresults at initial pH 7.5 and 1.8 indicate thatthe degradation kinetics and the final removalefficiency of RB 5 increased with adecreasing of solution pH. The increase inconcentration of hydrogen ions wouldenhance the reduction degradation reactionsof azo-compounds because hydrogen ions areinvolved in the reductive reaction by ZVIN.

NNAr'

Ar''

Fe0

NN

Ar'

Ar''

Fe2+pH = 7.5

e0

NN

Ar'

Ar''

Fe2+

H+/H2O

Fe2+

Ar' NH2 H2N Ar''+ +

pH = 1.8

C0/C

C0/C

Time, min Time, min

A B

Figura 5.Cinetica degradrii negrului reactiv la un pH diferit = 7.5 (A) i 1.8 (B) la temperatura camerei.Figure 5.Degradation kinetics of reactive black at different pH = 7.5 (A) and 1.8 (B) at room temperature.

Constanta cineticii degradrii RB 5 creteodatcu creterea temperaturii de reacie. Este

necesar numai o energie activat sczutpentru a rupe gruparea azoiccu nanoparticule

The degradation kinetic constant of RB 5increases with increasing of reaction

temperature. Only a small activated energy isneeded to break the azo-group with ZVIN,


8/9



264

de fier zero-valent, sugernd un efect altemperaturii sczute pentru reacia dedescompunere.

4. CONCLUZIE I PERSPECTIVE

S-a studiat cinetica degradrii reductoare aNegrului Reactiv 5 cu nanoparticule de fierzero-valent n soluie apoas. Rezultatul aindicat c degradarea este foarte eficient ncondiii de pH acid timp de cteva minute.Aciditatea soluiei, temperatura i cantitatea defier (respectiv suprafaa sa) sunt factori careinflueneaz foarte mult ratele de degradare.

Aceste rezultate au elucidat clar c NegrulReactiv 5 poate fi decolorat rapid folosindnanoparticule de fier zero-valent i decifolosirea acestor oxizi nanostructurai ar puteafacilita ndeprtarea coloranilor azoici dinapele reziduale.

5. Mulumiri:

Autorii sunt recunosctori proiectului

DDVU 02-36/10 al Ministerului Bulgar alEducaiei i tiinei pentru sprijinul financiaracordat pentru aceastcercetare.

BIBLIOGRAFIE

[1]Pekakis, P., Xekoukoulotakis, N.,Mantzavinos, D. Tratamentul apei rezidualecu colorani textili prin fotocataliza TiO2,Cercetarea apei, Vol. 40(6), 1276-1286,2006.

[2]

Mantzavinos, D., Psillakis, E. Cretereabiodegradrii apelor reziduale industrialeprin pre-tratarea oxidrii chimice, J. Chem.Technol. Biotechnol., Vol. 79 (5), 431-454,2004.

[3]Tang, W., An, A. Oxidarea fotocataliticUV/TiO2a coloranilor comerciali n soluiiapoase, Chemosfer, Vol. 31 (9), 4157-4170, 1995.

[4]Hitz, H., Huber, W., Reed, H. Absorbia

coloranilor asupra noroiului activat, J. Soc.Dyers Colorists, Vol. 94, 71-76, 1978.

suggesting a small temperature effect for thedecomposition reaction.

4.CONCLUSION AND

PERSPECTIVES

The reducing degradation kinetic of ReactiveBlack 5 by zero-valent iron nanoparticles inaqeous solution was studied. The resultshowed that degradation is high effective inacidic pH conditions for few minutes. Thesolution acidity, temperature and ironquantity (respectively its surface area) arefactors greatly influencing the degradationrates. These results have clearly elucidatedthat Reactive Black 5 can be rapidlydecolorized by ZVIN and thus the use ofthese nanostructured oxides could facilitatethe removal of azo-dyes in wastewater.

5. Acknowledgements:

The authors are thankful to project

DDVU 02-36/10 of the Bulgarian Ministry ofEducation and Science of Bulgaria for thefinancial support of this investigation.

REFERENCES

[9]Pekakis, P., Xekoukoulotakis, N.,Mantzavinos, D. Treatment of textiledyehouse wastewater by TiO2

photocatalysis, Water Research, Vol.40(6), 1276-1286, 2006.

[10]

Mantzavinos, D., Psillakis, E.Enhancement of biodegradability ofindustrial wastewaters by chemicaloxidation pre-treatment, J. Chem.Technol. Biotechnol., Vol. 79 (5), 431-454, 2004.

[11] Tang, W., An, A. UV/TiO2photocatalytic oxidation of commercialdyes in aqueous solutions, Chemosphere,Vol. 31 (9), 4157-4170, 1995.

[12]

Hitz, H., Huber, W., Reed, H. Theadsorption of dyes on activated sludge, J.


9/9



265

[5]Tratnyek, P., Scherer, M., Johnson, T.,Matheson, L. Barierele reactive permeabileale fierului i altor metale zero-valente,Metode de degradare chimic pentru

deeuri i poluani: Aplicaii de mediu iindustriale (Ed, M.A. Tarr), Marcel Dekker,Inc, New York, 371-421, 2002.

[6]Shao-feng, N., Yong, L., Xin-hua, X.,Zhang-hua, L. ndeprtarea cromuluihexavalent din soluii apoase prinnanoparticule de fier, Journal of ZhejiangUniversity Science-B., Vol. 6 (10), 1022-1027, 2005.

[7]Kanel, S., Greneche, J., Choi, H.ndeprtarea arsenicului din apa de

suprafa folosind fierul nanovalent camaterial de barier reactiv coloidal,Environ. Sci. Technol., Vol. 40, 2045-2050,2006.

[8]Nam, S., Tratnyek, P. Reducereacoloranilor azoici cu fierul zero-valent,Cercetarea apei, Vol. 34(6), 1837-1845,2000.

Soc. Dyers Colorists, Vol. 94, 71-76,1978.

[13] Tratnyek, P., Scherer, M., Johnson,T., Matheson, L. Permeable reactive

barriers of iron and other zero-valentmetals, Chemical degradation methods forwaste and pollutants: Environmental andindustrial application (Ed, M.A. Tarr),Marcel Dekker, Inc, New York, 371-421,2002.

[14] Shao-feng, N., Yong, L., Xin-hua, X.,Zhang-hua, L. Removal of hexavalentchromium from aqueous solution by ironnanoparticles, Journal of ZhejiangUniversity Science-B., Vol. 6 (10), 1022-

1027, 2005.[15] Kanel, S., Greneche, J., Choi, H.

Arsenic(V) removal from groundwaterusing nano scale zero-valent iron as acolloidal reactive barrier material,Environ. Sci. Technol., Vol. 40, 2045-2050, 2006.

[16] Nam, S., Tratnyek, P. Reduction ofazo dyes with zero-valent iron, WaterResearch, Vol. 34(6), 1837-1845, 2000.

Documents

31 Alexandre Loukanov