Electrochemical removal of Brilliant green and Condo red dye from aqueous solutions

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1 INSTITUTE OF TECHNOLOGY, NIRA UNIVERSITY, AHEDABAD 38 48, 8- DECEBER, Electrchemical remval f Brilliant green and Cnd red dye frm aqueus slutins Venkat S. ane and P. V. Vijay Babu. Abstract - The single-chamber electrchemical methd used in the waste water treatment mainly fcused n andic xidatin, but hydrgen prduced n the cathde and indirect electrchemical treatment invlves applicatin f an electrical current t the wastewater cntaining chlride t cnvert int chlrine/hypchlrite. In this paper the perfrmance f an electrchemical degradatin f Brilliant green and Cng red dye was investigated by using graphite and stainless steel electrdes in the presence f NaCl electrlyte. Experiments are carried ut in a batch electrchemical cell cvering wide range in perating cnditins. Due t the strng xidizing ptential f the chemicals prduced, the effluent clr is reduced substantially in this treatment technique. The influences f initial ph, treatment time, electrlyte cncentratin and current density n the clr remval were critically examined. It was bserved that the ptimum ph fr Brilliant green remval.9 and that f Cng red 7. In the study, the remval f dyes increased with the increase in NaCl cncentratin. It can be nticed that the rate f degradatin increases with applied current density. The energy cnsumptin shwed increasing trend with increasing applied current density. The results indicate that the electrchemical methd is a feasible and effective technique fr remval f Brilliant green and Cng red dye frm aqueus slutins. Keywrds: Brilliant Green; Cng Red; Electr-xidatin; Dye remval I. INTRODUCTION T he day-t-day human activities and industrial revlutin have influenced the flw and strage f water and the quality f available fresh water. Dyes are used in textiles, fd and beverage industries and printing prcesses []. The ttal dye cnsumptin f the textile industry wrldwide is in excess f 7 kg per year. Hwever, apprximately millin kg/yr f dyes are discharged int water streams by the textile industry []. Dye prducers and users are interested in stability and fastness and, cnsequently, are prducing dyestuffs that are mre difficult t degrade after use. Unless prperly treated, the dyes present in wastewaters can affect phtsynthetic activity due t reduced light penetratin and may als be txic t certain frms f aquatic life [3]. The dye effluents are usually treated by cagulatin, anaerbic reductin and aerbic xidatin and adsrptin methds. Due t large variatins in the effluent cmpsitin, mst f these traditinal methds are inadequate. Althugh the bilgical degradatin is the mst ecnmic prcess, it is ineffective t degrade mlecules f refractive nature. Als, the survival f anaerbic bimass in the presence f high cncentratin f az dyes and heavy metals (metal-cmplex dyes) is tugh [4]. In this cntext, researchers are trying varius alternative prcesses, such as electrchemical technique, wet xidatin, znizatin, phtcatalytic methd fr the degradatin f rganic cmpunds. Amng these advanced xidatin prcesses, the electrchemical treatment has been receiving greater attentin in recent years due t its unique features, such as versatility, energy efficiency, autmatin and cst effectiveness [5]. Electrchemical technlgy and its applicatin in wastewater treatment have been increasingly paid mre attentin t, because f its advantage f clr remval [6]. Accrding t traditinal electrchemistry and recent study, electrlytic effect culd be influenced by electrlyte cncentratin (cnductivity), ph, temperature and electric vltage, etc [6]. Additin f higher initial amunts f NaCl and HCl resulted in an imprved remval f clr. It is clear frm the reprted researches that mst f the investigatins favred t degrade rganic pllutants using high salt cncentratin, high vltages and large electric current. Cnsequently, the efficiency f energy supplied during electrlysis decreased. S, it is necessary t describe the influence f electrlyte cncentratin and vltage n electrlytic effect and find its ptimal utilizatin parameters [7]. In electrchemical technique, the main reagent is the electrn, called Clean Reagent degrades all the rganics present in the effluent withut generating any secndary pllutant r by-prduct/sludge. The electrchemical technique ffers high remval efficiencies and has lwer temperature requirements cmpared t nn-electrchemical treatment. In additin t the perating parameters, the rate f pllutant degradatin depends f the ande material. When electrchemical reactrs perate at high cell ptential, the andic prcess ccurs in the ptential regin f water discharge, hydrxyl radicals are generated. On the ther hand, if chlride is present in the electrlyte, an indirect xidatin via active chlrine can be perative. Earlier researchers have demnstrated several ande materials, such as graphite and nble metal andes successfully fr the mediated xidatin f rganic pllutants [8]. Andic xidatin efficiency depends strngly n the electrde materials. As a whle, the andes fr rganics xidatin shuld have high-ver ptential fr xygen evlutin. Otherwise, a great deal f current will be wasted t prduce xygen. Graphite has been used as an ande during electrchemical treatment, as it is relatively ecnmical and gives satisfactry results [9]-[]. Brilliant Green (BG) dye is drless yellw-green t green pwder used fr the prductin f cver paper in the paper industry. Abut.8. kg f BG is cnsumed per tnne f paper prduced. Hwever, in humans BG causes irritatin t

2 INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN TECHNOLOGY, NUiCONE the gastrintestinal tract; symptms include nausea, vmiting and diarrhea. It als causes irritatin t the respiratry tract, leading t cugh and shrtness f breath. Skin cntact causes irritatin with redness and pain []- []. Als Cng red (CR) (-naphthalenesulfnic acid, 3,3-(4,4-biphenylenebis (az)) bis (4-amin-) disdium salt) is a benzidine-based aninic disaz dye [3]. This dye is knwn t metablize t benzidine, a knwn human carcingen. The bjective f the present wrk is thus t study the electrchemical treatment f Brilliant green and Cng red dye frm aqueus slutin using graphite as ande and stainless steel as cathde. The influencing factrs, electrlyte cncentratin and current density have great effect n electrlysis results. II. THEORY The mechanism f electrchemical xidatin f wastewater is a cmplex phenmenn invlving cupling f electrn transfer reactin with a dissciate chemisrptins step. Basically tw different prcesses ccur at the ande; n ande having high electr-catalytic activity, xidatin ccurs at the electrde surface (direct electrlysis); n metal xide electrde, xidatin ccurs via surface mediatr n the andic surface, where they are generated cntinuusly [indirect electrlysis]. In direct electrlysis, the rate f xidatin is depending n electrde activity, pllutants diffusin rate and current density. On the ther hand, temperature, ph and diffusin rate f generated xidants determine the rate f xidatin in indirect electrlysis. In indirect electr-xidatin, chlride salts f sdium r ptassium are added t the wastewater fr better cnductivity and generatin f hypchlrite ins [4]. The reactins f andic xidatin f chlride ins t frm chlrine is given as [Vlyssides] accrding t the fllwing reactins: R OX( OH) ROO H e O X () Cl k Cl e () R OX RO O() x () The liberated chlrine frm hypchlrus acid (Eq. ()) The physisrbed rute f xidatin is the preferable way k Cl HO H HOCL () fr waste treatment. It is () prbable that dixygen participates and further dissciated t give hypchlrite in (Eq. (3)). als in the cmbustin f rganics accrding t the reactins, such as frmatin f rganic radicals by a hydrgen 3 HOCL k H OCL (3) abstractin mechanism: RH OH R H O reactin f (3) The generated hypchlrite ins act as main xidizing rganic radical with dixygen frmed at the ande: agent in the pllutant degradatin. The direct electrxidatin R O ROO and further abstractin f a hydrgen atm rate f rganic pllutants depends n the catalytic with frmatin f an rganic hydrgen perxide (ROOH) and activity f the ande, n the diffusin rate f the rganic cmpunds in the active pints f ande and applied current density. A generalized scheme f the electrchemical cnversin/cmbustin f rganics f pllutant [5] n nble xide cated catalytic ande (Ox) is given belw. In the first step, H O is discharged at the ande t prduce adsrbed hydrxyl radicals accrding t the reactin. anther radical; ROO R' H ROOH R'. Since the O H O O ( OH) H e (4) X X In the secnd step, generally the adsrbed hydrxyl radicals may interact with the xygen already present in the xide ande with pssible transitin f xygen frm the adsrbed hydrxyl radical t the xide frming the higher xide Ox+. O ( OH) O x + H e (5) X At the ande surface, the active xygen can be present in tw states. Either as physisrbed (adsrbed hydrxyl radicals ( OH) r/and as chemisrbed (xygen in the lattice, O x+ ). In the absence f any xidizable rganics, the active xygen prduces dixygen accrding t the fllwing reactins: O ( OH) O O H e (6) x X O x Ox O (7) When NaCl is used as supprting electrlyte Cl in may react with O x ( OH) t frm adsrbed OCl radicals accrding t the fllwing [6] : Ox ( OH) Cl Ox ( OCl) H e (8) Further, in presence f Cl in, the adsrbed hypchrite radicals may interact with the xygen already present in the xide ande with pssible transitin f xygen frm the adsrbed hypchrite radical t the xide frming the higher xide O x+ accrding t the fllwing reactin and als O x ( OCl) simultaneusly react with chlride in t generate active xygen (dixygen) and chlrine accrding t the fllwing reactins: Ox ( OH) Cl Ox ( OCl) H e (9) Ox ( OCl) Cl OX Cl e () In the presence f xidizable rganics the physisrbed active xygen ( OH) shuld cause predminantly the cmplete cmbustin f rganics and chemisrbed will participate in the frmatin f selective xidatin prducts rganic hydrgen perxides frmed are relatively unstable, decmpsitin f such intermediates leads t mlecular breakdwn and frmatin f subsequent intermediates with lwer carbn numbers. These sequential reactins cntinue until the frmatin f carbn dixide and water. In this case the diffusin rate f rganics n the ande area cntrls the cmbustin rate [7]. In the same way indirect electrchemical xidatin mechanism has been prpsed fr metal xide with chlride as supprting electrlyte fr wastewater treatment. The rle f hypchlrite in electrchemical treatment f dye effluent via chlrine generatin is k4 Dye OCl CO HO Cl P (3)

3 INSTITUTE OF TECHNOLOGY, NIRA UNIVERSITY, AHEDABAD 38 48, 8- DECEBER, 3 Since dye mlecules f the effluent are electrchemically inactive, the reactin ccurs at the andes is chlride in xidatin with the liberatin f Cl, which is a rbust xidizing agent. As regards t the reactins in the bulk, gaseus Cl disslves in the aqueus slutins due t inizatin as indicated in Eq. (). The rate reactin is less in acidic slutin due t OH instability and cnsiderably mre in basic slutin due t ready frmatin f OCL in in Eq. (3) implying that the basic r neutral ph cnditins are mre favrable fr cnducting reactins invlving Cl. A cycle f chlride chlrine hypchlrite chlride takes place, which prduces OCL. The pseud steady state thery can be applied t each f the intermediates prducts HOCl and OCL taking part in the bulk slutin. Kinetic equatin fr the xidatin f dye can be written as ( c) ln kt (4) ( c) where C is the cncentratin f dye at unit time and C is the initial dye cncentratin. The slpe f the plt f ln(c/c)versus electrlysis time gives the value f first rder reactin rate cnstant k in h - [8]. III. ATERIALS AND ETHODS The Brilliant Green (BG) dye [C.I. = 44, chemical frmula = C 7 H 34 N O 4 S, FW = 48.6; nature = basic green 4] was supplied by S.D. Fine Chemicals, umbai, India. The Cng Red dye [C.I. =, chemical frmula = C 3 H N 6 Na O 6 S, FW = 696.7, max = 5 nm] was supplied by the Sigma Chemical Cmpany, USA. Stck slutin ( mg/l) f each dye was prepared by disslving an accurately weighed quantity f dye in duble-distilled water. Experimental slutins f the desired cncentratins were then btained by successive dilutins with distilled water. The experimental setup cnsists f a glass beaker f 7 liter capacity with PVC lid having prvisin t fit a cathde and an ande. Salt bridge with reference electrde was inserted thrugh prvided in the lid. Prper prvisins are als made in the lid fr insertin f thermmeter and fr peridic sampling. The cathde was stainless steel plate and the ande taken was cmmercially available graphite f area.6 m. Experiments were carried ut under galvanstatic cnditins using a DC-regulated pwer surce f.8a and 33.8V. Stirring was dne with a magnetic stirrer. Electrlysis was carried ut under batch mde. The six liter dye cntaining aqueus slutin; supprting electrlyte with natural ph fr each dye was taken fr all experiments. Electrlysis was carried ut at different current densities, viz..97,.94,.9and 3.88 A/m. During electrlysis, samples were cllected at different time intervals and the clr was measured. IV. ANALYTICAL EASUREENTS The Brilliant green and Cng red in the aqueus slutin was analyzed by using a UV spectrphtmeter (Perkin Elmer Lambda 35). A standard slutin f the Brilliant green as well as Cng red was scanned t determine the wavelength ( max ) crrespnding t maximum absrbance. The wavelengths crrespnding t maximum absrbance were 63 nm and 5 nm fr Brilliant green and Cng red respectively. By using these wavelengths standard graphs f absrbance versus cncentratin f Brilliant green and Cng red was prepared. These graphs shwed a linear variatin up t mg/l cncentratin. Therefre, the samples with higher cncentratin f Brilliant green as well as Cng red (> mg/l) were diluted with distilled water whenever necessary t make the cncentratin less than mg/l fr the accurate determinatin f the Brilliant green and Cng red cncentratin. Clr remval was calculated by fllwing frmula: % clr remval ABS ABS ABS where ABS is the average f absrbance values at its maximum absrbency value f visible wavelength (λmax). ABS and ABS are the values befre and after the degradatin prcess. V. RESULTS AND DISCUSSIONS The ph value affects the structural stability f Brilliant green and Cng red and, therefre, its cncentratin. The effect f ph was studied with blank slutins f C = 5 mg/l having natural ph =.7 fr Brilliant green and ph 7 fr Cng red. The slutin was kept fr h, after which the absrbance f the slutin was determined. There was insignificant change in absrbance f Brilliant green and Cng red slutin after h with respect t that after 5 min. Therefre, stability f brilliant green and Cng red was examined nly fr slutins held fr h. It is inferred that the brilliant green and Cng red slutin is stable at the natural ph =.9 and 7 respectively, and it becmes unstable if the slutin ph is either increased r decreased. Brilliant green and Cng red instability due t ph change alne may be due t the structural changes taking place in the brilliant green mlecules. The change in natural ph f brilliant green and Cng red slutin, therefre, changes the structure f brilliant green and, hence, destabilizes the slutin. Therefre, further electrchemical experiments were carried ut at ph.9 fr Brilliant green and ph 7 fr Cng red. The rate f clr reductin has been pltted as versus electrlysis time. It can be ascertained frm Figs. and that the rate f Clr reductin decreases with electrlysis time fr Brilliant green and Cng red respectively. The rate f degradatin is high at the beginning f the prcess and reduces gradually t a mntnical value at the end f the prcess. Further, it can be nticed frm the figure that the rate f degradatin increases with applied current density. This can be explained that the rate f generatin f hypchlrite

4 4 INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN TECHNOLOGY, NUiCONE in increased with current density, which eventually increases the pllutant degradatin. Ntice that the rate f degradatin increased significantly when the current density increased frm.97 t 3.88 A/m. It was bserved that the rate f degradatin is very fast in first 3 min and after reduces slwly and remains cnstant at certain interval f time NaCL: g/l NaCL: g/l NaCL: 3 g/l NaCL:.5 g/l NaCL: g/l A/m.94 A/m.9 A/m 3.88 A/m Fig.. Influence f the current density n C t/c with electrlysis time; Brilliant green initial cncentratin 5 mg/l; supprting electrlyte cncentratin.75 NaCL: g/l NaCL: g/l NaCL: 3 g/l NaCL:.5 g/l NaCL: g/l Fig. 3 The effect f supprting electrlyte cncentratin n Brilliant green degradatin; Initial dye cncentratin 5 mg/l; current density 3.88 A/m NaCL: g/l NaCL: g/l NaCL: 3 g/l NaCL:.5 g/l NaCL: g/l Fig. 4. The effect f supprting electrlyte cncentratin n Cng red degradatin; Initial dye cncentratin 5 mg/l; current density 3.88 A/m Fig.. Influence f the current density n C t/c with electrlysis time; Cng red initial cncentratin 5 mg/l; supprting electrlyte cncentratin g/l; ph 6.8. The influence f supprting electrlyte (NaCl) cncentratin n the Brilliant green and Cng red degradatin rate has been tested with initial dye cncentratins f 5 mg/l and the current density f 3.88 A/m as ahwn in Figs. 3 and 4. It can be nticed that the rate f degradatin increased with supprting electrlyte cncentratin. At lwer chlride cncentratin, the pllutant degradatin is small cmpared t higher chlride cncentratin. This is are due t the fact that the xide cated electrdes have lw verptential fr xygen evlutin and then this secndary reactin is favred in cmparisn with rganic xidatin. Als it was bserved frm Fig. 3 and Fig. 4, supprting electrlyte cncentratin required is less fr Cng red than that f Brilliant green fr same degradatin rate. The Fig. 5 shws the effect f current density n clr remval. It was bserved that the clr remval increases with increase in current density. Fig. 6 shws the variatin f reactin rate cnstant with current density. Figs. 7 and 8 shws the energy cnsumptin during electrchemical xidatin. The energy demand measured in kilwatt hurs per kilgram f clr remved [9]. Thus, fr,.5,, and 4 g/l f NaCl fr degradatin f Brilliant green and Cng red the energy cnsumptin was measured. The Figs. 7 and 8 shws that energy cnsumptin is less fr high dse f NaCl at same time. The rate cnstant, k was estimated frm the plt f ln versus electrlysis time. The rate cnstant has been estimated fr all the experimental runs carried ut in the present investigatin as shwn in Table. Fig. 6 shws the variatin f reactin rate cnstant with current density.

5 kwh/kg clr remved K (min - ) % Clr remval kwh/kg clr remved INSTITUTE OF TECHNOLOGY, NIRA UNIVERSITY, AHEDABAD 38 48, 8- DECEBER, Brilliant green dye Cng red dye 5 NaCl : g/l NaCl :.5 g/l NaCl : g/l NaCl : g/l 5 5 NaCl : 3 g/l Current density A/m Fig. 5. Variatin f Clr reductin with current density; supprting electrlyte cncentratin 3 g/l fr Brilliant green and g/l fr Cng red degradatin Brilliant green dye Cnd red dye Current Density A/m Fig. 6. Variatin f transfer cefficient with current density; supprting electrlyte cncentratin 3 g/l fr Brilliant green and g/l fr Cng red degradatin NaCl: g/l NaCl:.5 g/l NaCl: g/l NaCl: g/l NaCl : 3 g/l 5 5 time, min Fig. 7. Energy cnsumptin during the electrlysis treatment f Brilliant green. 5 5 time, min Fig.8. Energy cnsumptin during the electrlysis treatment f Cng red. VI. CONCLUSION The results f the present studies shwed that electrchemical prcess culd be efficiently used t degrade the Brilliant green and Cng red frm aqueus slutin. The results indicated that the degree f degradatin f Brilliant green and Cng red was bviusly affected by the current density and amunt f NaCl as an electrlyte. It was bserved that the clr remval increases as the current density increases. Als clr remval increases with increase in electrlyte cncentratin. The reductin in clr has been achieved abut 9 % fr bth Brilliant green and Cng red. VII. REFERENCES [] R. Ahmad and R. Kumar, Adsrptive remval f cng red dye frm aqueus slutin using bael shell carbn, Appl. Surf. Sci. vl. 57, pp ,. [] A.R. Cestari, F.S. Vieira, G.S. Vieira and L.E. Almeida, Aggregatin and adsrptin f reactive dyes in the presence f an aninic surfactant n mesprus aminprpyl silica, J. Cllid Interf. Sci. vl. 39, pp. 4 4, 7. [3] J. Ga, Q. Zhang, K. Su, R. Chen and Y. Peng, Bisrptin f Acid Yellw 7 frm aqueus slutin by nn-living aerbic granular sludge, J. Hazard. ater. vl. 74, pp. 5 5,. [4]. uthukumar,. T. Karuppiah and G. B. Raju, Electrchemical remval f CI Acid range frm aqueus slutins, Sep. Purif. Technl. vl. 55 pp. 98 5, 7. [5] N. han, N. Balasubramanian, C. Ahmed Basha, Electrchemical xidatin f textile wastewater and its reuse, J. Hazard. ater. vl. 47 pp , 7. [6] P. Kariyajjanavara, N. Jgttappa and Y. Arthba Nayaka, Studies n degradatin f reactive textile dyes slutin by electrchemical methd, J. Hazard. ater. vl. 9, pp , June [7] C. A. Basha, K. V. Selvakumar, H. J. Prabhub, P. Sivashanmugam and C. W. Lee, Degradatin studies fr textile reactive dye by cmbined electrchemical, micrbial and phtcatalytic methds, Sep. Purif. Technl. vl. 79, pp , June [8] J. Naumczyk, L. Szpyrkwicz,. De Faveri and F. Z. Grandi, Electrchemical treatment f tannery wastewater cntaining high strength pllutants, Trans. I ChemE, vl. 74 pp , 996. [9] Z.. Shen, D. Wu, J. Yang, T. Yuan, W.H. Wang and J.P. Jia, ethds t imprve electrchemical treatment effect f dye wastewater, J. Hazard. ater. vl. B3, pp.9 97, 6. []. A. Sanrman,. Pazs,. T. Ricart, C. Cameselle, Declurisatin f Textlie indig dye by Direct electric current, Engineering Gelgy, vl. 77, pp. 53-6, 5.

6 6 INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN TECHNOLOGY, NUiCONE [] V. S. ane and P.V. Vijay Babu, Studies n the adsrptin f Brilliant Green dye frm aqueus slutin nt lw-cst NaOH treated saw dust, Desalinatin, vl. 73, pp. 3 39,. [] V. S. ane, I. D. all and V. C. Shrivastava, Use f bagasse fly ash as an adsrbent fr the remval f brilliant green dye frm aqueus slutin, Dyes Pigments, vl. 73, pp. 69, 7. [3] I.D. all, V.C. Shrivastava, N.K. Agarwal and I.. ishra, Remval f Cng red frm aqueus slutin by bagasse fly ash and activated carbn: Kinetic study and equilibrium istherm analyses, Chemsphere, vl. 6 pp. 49 5, 5. [4] K. Rajeshwar and J. G. Ibanez, Envirnmental Electrchemistry, Academic Press, Inc., 997. [5]. Panizza and G. Cerisla, Electrchemical xidatin as a final treatment f synthetic tannery wastewater, J. Envirn. Sci. Technl. Vl. 38, pp , 4. [6] S. Raghu and C. A. Basha, Electrchemical treatment f Prcin Black 5B using cylindrical flw reactr a pilt plant study, J. Hazard. ater. vl. B39, 38 39, 7. [7] A.G. Vlyssides, E.. Baramputi and S. ai, Degradatin f methyl parathin in aqueus slutin by electrchemical xidatin, J. Envirn. Sci. Technl. Vl. 38, 65 63, 4. [8] V. Lpez-Grimau and.c.gutierrez, Declurizatin f simulated reactive dyebath effluents by electrchemical xidatin assisted by UV light, Chemsphere, vl 6, pp. 6-, 6. [9] A. G. Vlyssides,. Lizidu, P.K.Karlis, A.A Zrpas and D. Papaiannu, Electrchemical xidatin f textile dye wastewater using a Pt/Ti electrde, J. Hazard. ater. vl. B 7, pp. 4-5, 999.