Journal of Chemical and Pharmaceutical Research, 2012, 4(6): Research Article

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1 Avilble online Journl of Chemicl nd Phrmceuticl Reserch, 212, 4(6): Reserch Article ISSN : CODEN(USA) : JCPRC5 Photoctlytic degrdtion of midoblck-1b using nnophotoctlyst * E K Kirupvsm nd G Allen Gnn Rj Deprtment of Chemistry nd Reserch Centre, Scott Christin College, (Autonomous) Ngercoil, Tmil Ndu ABSTRACT This study involves the photoctlytic degrdtion of midoblck- 1B (AB - 1B) in wter using nnosized silver doped TiO 2, with the use of solr light s the stimulting source. It hs been investigted tht, when the full rnge of emitted photons is used, decolouriztion nd complete minerliztion of the solution is chieved with stisfctory rtes, depending on initil dye concentrtion. The rte of degrdtion follows first order kinetics. The photoctlytic degrdtion of dye depends on concentrtion of dye, mount of ctlyst, silver doped TiO 2, ph of the solution. The mechnism of the photodegrdtion process under visible light illumintion involves n electron excittion into the conduction bnd of the modified TiO 2 semiconductor leding to the genertion of very ctive oxygented species tht ttck the dye leding to photodegrdtion Photoctlytic ctivity of Ag-doped TiO 2 ws lso incresed by using H 2 O 2 s electron scvenger. Keywords: Amidoblck-1B, Photodegrdtion, Ag doped TiO 2, Visible light. INTRODUCTION Dye pollutnts produced from textile industries re becoming mjor source of environmentl contmintion [1]. Among the different types of dyes used in textile industries, 6-7 % is zo compounds. These dyes hve chromophore of N= N unit in their moleculr structure nd re lost in wter during dyeing opertion. These soluble zodyes when incorported into the body re split into corresponding romtic mines which cn cuse cncer in humn [2-3]. Vrious physicl nd chemicl processes such s cogultion, dsorption on ctivted chrcol, reverse osmosis re not destructive, but only trnsfer the dye from one phse to nother. Among the vrious photo ctlysts employed TiO 2 hs ttrcted much interest in recent yers for its highly ctive photoctlytic functions, like the bility to decompose the chemicl compounds s well s super hydrophilic nd ntibcteril properties [4-6]. The only drwbck of TiO 2 semiconductor is tht it bsorbs smller portion of solr spectrum in the UV region. Therefore modifiction of TiO 2 photoctlyst for pollutnt degrdtion using visible light is demnding re of reserch. Dye sensitiztion seems to be one of the vible methods for deling with this issue. Severl studies of photoctlytic degrdtion of dyes hve been reported [4-8]. Dipti Vy hs investigted the effect of trnsition metl ions such s Mo (VI) doped ZnO for photoctlytic bleching of eosin Y[9]. Abofrh reported[1] the photoctlytic degrdtion of monozo nd dizodyes in wstewter on nnometer sized TiO 2. Krishnkumr [11] studied the solr photoctlytic degrdtion of cid blck 1 with ZnO. The photoctlytic bleching of textile zo dye Rective Yellow 86 hs been crried out in the presence of semiconductor TiO 2 nd the progress of rection ws observed spectrophotometriclly by Preeti Meht[12]. The optimum conditions for the photobleching of (Direct Yellow 12) hs been estblished by Menk Surn[13]. The potentil of Polylthi longifoli (PL) seed powder to dsorb methylene blue (MB) from queous solution hs been investigted through btch experiments by Mundhe.[14]. Mirkhni investigted tht the photoctlytic degrdtion of zodyes ctlyzed 2979

2 by Ag- doped TiO 2 photoctlyst is higher thn ordinry TiO 2. In this study surfce modified TiO 2 with Ag, (Ag- TiO 2 ) prticles were used for the photoctlytic degrdtion of midoblck-1b (AB -1B) using solr light. EXPERIMENTAL SECTION The commercil zodyes midoblck-1b (8 % of dye) ws obtined from sigm nd ws used without purifiction (λmx=62nm). TiO 2 powder which ws in ntse crystlline form of surfce re of bout 5 m 2 /g ws obtined from Merck. The dye solutions were prepred using double distilled wter. The ph of the solution ws djusted with diluted HNO 3 or by NOH. Solvents nd other mterils such s AgNO 3, H 2 O 2, nd N 2 CO 3 were lso purchsed from Merck. The silver doped photoctlyst (Ag-TiO 2 ) ws prepred dding clculted mount of TiO 2 to solution of AgNO 3 (.1 M). To this slurry solution of (1. % W/V) sodium crbonte ws dded nd the suspension dried t room temperture nd heted t 4 o C for 6h [15]. The visible light photo ctivity of Ag-TiO 2 cn be explined by new energy level produced in the bnd gp of TiO 2, by the dispersion of metl nnoprticles in the TiO 2 mtrix. The photoctlytic experiments were crried out under similr condition on sunny dys between 11 m to 2 pm. An open borosilicte glss beker of 25 ml cpcity ws used s the rection vessel for sunlight exposure in n open tmosphere. The suspensions contining dye nd the photoctlyst were mgneticlly stirred in the drk for 3 minutes to chieve the dsorption equilibrium of AB-1B on the surfce of the ctlyst. All irrdition experiments were performed under constnt stirring. Smples were withdrwn regulrly for every 3 minutes nd the photoctlyst were removed by centrifuge. Then bsorption spectr were recorded nd the rte of decolouriztion ws observed in terms of chnge in intensity t bsorption mximum i.e., 62 nm for AB 1B. The percentge of decolouriztion ws clculted s, % Decolouriztion = 1 x (C -C)/C Where C represents initil concentrtion of dye, C - concentrtion of dye fter irrdition. To mesure the structurl vrition, XRD ptters were obtined using n X-ry genertor (Shimdzu XD-D1, Shimdzu Corportion, Kyoto, Jpn). Fig.1 shows the XRD ptterns of silver doped TiO 2. Fig. 1: XRD Pttern of Ag-TiO 2 Photoctlyst Counts outside work2_ Position [ 2Thet] (Copper (Cu)) 298

Crystllite size of nnoprticles cn be clculted by Scherer s eqution D=.9λ/βcosθ. Where D is the verge crystllite size,.9 is the shpe fctor of the grin. λ is the wvelength of X-ry (.

3 Crystllite size of nnoprticles cn be clculted by Scherer s eqution D=.9λ/βcosθ. Where D is the verge crystllite size,.9 is the shpe fctor of the grin. λ is the wvelength of X-ry (.15451nm) for Cukα rdition nd is the FWHM of the diffrction pek, θ. is the incident ngle of X-ry. By the diffrction dt in Fig.1, the prticle size of Ag-TiO 2 is bout 36 nm. Scnning electron microscopy ws used to observe the surfce stte nd structure of the photoctlyst composites. Scnning electron microscopy (SEM, JSM- 52, Joel, nd Tokyo, Jpn) long with Energy dispersive X-ry spectroscopy (EDX) ws lso used for elementl nlysis of the smples. The SEM imge of 1.15At % Ag-TiO 2 nnoprticles is shown in Fig 2. Some porous surfces dispersed mong culiflower-like clusters of grins were observed. Fig. 3 shows EDX nlysis on 1.15At % Ag-TiO 2 ctlyst. 2981

4 The silver signls re found t round 3. Kev. Though the peks of silver re in significnt due to its content in TiO 2 mtrix; it cn be the indictive of the silver prticles in the ctlyst. Degrdtion products of dye ws confirmed using GC-MS nlysis crried out by thermo GC-trce ultrver 5., thermo MS DSQ equipment, TR 5- MS cpillry stndrd, non polr column 3 m length,.25 mm dimeter. RESULTS AND DISCUSSION The degrdtion of AB 1B ctlyzed by modified TiO 2 with Ag metl (1% w/w) in queous solution under irrdition with solr light hs been investigted. The synthesized Ag TiO 2 were chrcterized by X-ry diffrction (XRD), scnning electron microscope (SEM) nd EDX. The effect of vrious prmeters such s mount of photoctlyst, effect of substrte concentrtion, ph, clcintions temperture nd the presence of electron cceptors such s H 2 O 2 were crried out. The kinetic of photo degrdtion of AB 1B using nnosized Ag Tio 2 ws lso exmined. GC MS ws pplied to the nlysis of the intermedites coming from the photo ctlytic degrdtion of AB 1B. Effect of ctlyst concentrtion An importnt prmeter tht cn ffect the degrdtion rte is the ctlyst concentrtion. Fig.4 shows the effect of ctlyst loding on the degrdtion of AB - 1B t ph =

5 % D e g r d t i o n Fig 4 Effect ofctlyst concentrtion on % degrdtion of AB-1B 2ppm+.1gAg TiO2 2ppm+.2g Ag -TiO2 2ppm+.3gAg-TiO2 2ppm+.4g Ag-TiO2 2ppm+.5gAg-TIO Time in min. It hs been seen tht rte of photodegrdtion increse with ctlyst loding (.1 to.5g L -1 ), bove this loding, increse in turbidity of the solution reduces the light trnsmission through the solution. Mny uthors hve investigted the rection rte s function of ctlyst loding under different experimentl conditions [16]. The enhncement of the removl rte is due to the increse in the mount of ctlyst weight which increses the number of dye molecules dsorbed, nd the density of prticles in the re of illumintion [17]. Hence it is concluded tht higher dose of ctlyst my not be useful both in view of possible ggregtion s well s reduced irrdition field due to increse in light scttering. Therefore ctlyst dose (.5 g L -1 ) ws fixed for further studies. Effect of ph In order to study the effect of ph on the degrdtion efficiency, experiments were crried out t vrious ph vlues from for constnt dye concentrtions (2 mgl -1 ) nd ctlyst loding (.5 g L -1 ). Fig. 5 shows the color removl efficiency of AB-1B s function of ph. % D e g r d t i o n Fig 5 Effect of ph on % of degrdtion ph=1.2 ph =7.6 ph =9.6 ph=12 Time in min. The efficiency of degrdtion increses with incresing ph exhibiting mximum rte of degrdtion t ph7.6. Similr behvior ws reported for the photoctlytic efficiency of Ag-TiO 2 for degrdtion of zo dyes. The 2983

6 mphoteric behvior of most semiconductor oxides influences the surfce chrge of the photoctlyst [18]. Due to the mphoteric behvior of most metl hydroxides the following two equilibri re considered. M - OH + H + + M - OH 2 M - OH MO - + H + Photoctlyst surfce is positively chrged in cidic medi, wheres it is negtively chrged under lkline medi. Thus for zo dyes with sulphonic cid group in their structures t low ph rnge, surfce dsorption of ctlyst is more effective thn photoctlytic degrdtion of dyes. In the lkline solution, dyes re not bsorbed onto the negtive surfce of photoctlyst effectively. Hence in the ph rnge of 1-7.6, the formtion of more hydroxyl rdicl would enhnce the photodegrdtion of dyes [19]. Effect of concentrtion of dye After optimizing the experimentl conditions, t ph 7.6, Ag-TiO 2 (.5 mg L -1 ), the photoctlytic degrdtion of AB-1B ws crried out by vrying the initil concentrtions of the dye from 2 mg L -1, the rte of photodegrdtion decrese indicting either to increse the ctlyst dose or time spn. Fig. 7 clerly shows tht for dye solution of 2 mg L -1, 97 % degrdtion ws observed in 15 min, wheres for 3, 4, nd 5 mg L -1 of dye solution, the degrdtion efficiency ws 86 %, 81 % nd 64 % respectively. % D e g r d t i o n Fig6 Effect of dye concentrtion on the % of degrdtion 2ppm+.5gTiO2 3ppm+.5gTiO2 4ppm+.5gTiO2 5ppm+.5gTiO Time in min The possible explntion for this behvior is tht s the initil concentrtion of the dye increses, the pth length of the photons entering the solution decreses nd in low concentrtion the reverse effect is observed, thereby incresing the number of photon bsorption by the ctlyst in lower concentrtion[2]. Effect of H 2 O 2 concentrtion The effect of vrying the H 2 O 2 concentrtion ws investigted. Increse of H 2 O 2 concentrtion (from 5 mm to 1.5 mm) incresed the degrdtion of AB-1B dye. An increse in H 2 O 2 concentrtion up to 1.5 mm leds to n importnt rise in the dye degrdtion rte. The optimum mount of H 2 O 2 is (1.5 mm), nd the percentge of degrdtion is incresed to 94 % within 9 min. Fig. 7 shows the effect of H 2 O 2 concentrtion on degrdtion of the AB - 1B. 2984

7 % D e g r d t i o n Fig 7 Effect of H2O2 on the % of degrdtion Presence ofh2o2 Absence of H2O Time in min. This behvior is due to the hydroxyl rdicls generted upon photolysis of hydrogen peroxide i ndicted by the following eqution. H 2 O 2 + hr 2OH. This rdicl is very powerful oxidizer, ble to rect with inorgnic s well with romtic orgnic compounds cusing the degrdtion of dye. 2985

8 Kinetic study Fig. 8 shows the kinetics of degrdtion of AB-1B for n initil concentrtion of 2 mg L -1 under optimized conditions for the dyes. The results show tht the photoctlytic degrdtion of the dye in Ag-TiO 2 cn be described by the first-order kinetic model, ln Co/C= kt, where C o is the initil concentrtion nd C is the concentrtion t ny time t. The semilogrithmic plots of the concentrtion dt gve stright line. The correltion constnt for the fitted line ws clculted to be r 2 =.9976 for AB-1B. The rte constnts were clculted to be.72 min -1. Identifiction of AB-1B dye degrdtion intermedites. For identifiction of intermedite products, 2 ml of queous solution of AB-1B dye contining Ag-TiO 2 (5g L -1 ) ws irrdited with solr light for 2 h nd the photoctlyst ws removed by filtrtion. The filtrte ws extrcted using chloroform nd ws subsequently dried over nhydrous sodium sulphte. The solvent ws removed under reduced pressure to get the residul mss, which ws nlyzed by GC-MS. Irrdition of AB-1B dye using Ag- TiO 2 results in the formtion of nphthlene type molecules such s 2-npthol, coumrin, s the primry degrdtion products obtined by the oxidtive clevge of the dye molecule in the vicinity of zobond long with phthlic cid nd benzene dicrboxylic cid s intermedites s reported[21]. This is ccompnied by the formtion of low moleculr cids such s formic cid which eventully decompose to give crbondioxide by photo-kolbe rection. Efficiency of the turn over frequency Photoctlysis is clen technology, which normlly does not involve ny wste disposl problem. The ctlyst cn be recycled. Ag-TiO 2 cn be used t lest thrice without significnt chnge in the efficiency[22]. The economy of the photoctlytic process depends upon how mny times ctlyst cn be reused without scrificing its efficiency nd the type of regenertion it requires. The photodegrdtion efficiency of turn over frequency were exmined nd it ws found tht the turn over frequency ws found to be 97 % s tht obtined with the fresh ctlyst under the sme experimentl conditions. The used ctlyst ws regenerted to get Ag-1 first by treting with boiling distilled wter till colorless wsh liquid ws obtined nd then drying it in hot ir oven t temperture of bout 1 ºC. The decrese in turn over frequency my be ttributed to the deposition of photosensitive hydroxides on the photoctlyst surfce blocking its ctive sites. CONCLUSION The results of degrdtion experiments show tht photoctlyst cn effectively degrde the dye into nontoxic forms using sunlight. Experimentl results indicted tht the degrdtion of dyes is fcilitted in the presence of ctlyst Ag-TiO 2. The initil rte of photodegrdtion incresed with increse in ctlyst dose up to n optimum loding. Further increse in ctlyst dose showed no effect. As the initil concentrtion of dyes ws incresed, the rte of degrdtion is decresed. However in the presence of hydrogen peroxide, the degrdtion efficiency is lso incresed. The photoctlytic degrdtion of dye showed pseudo first order kinetics. This method is lso one of the chepest nd n ecofriendly method for degrdtion of dye. REFERENCES [1]Yingxuehen;Kngwng; LipingLou; J. Photochem Photobiol.A:Chem., 24, 163, 281. [2] I Arsln;IA Bleioglu; DW Bhnermnn; Dyes nd Pigments., 2, 47, 27. [3]V Mirkhni; S Tngestninejd; M Moghdm; MH Hbibi; A.Rostmi-Vrtooni., J. Irn. Chem.Soc., 29, 3, 578. [4]A Fujishim; TN Ro ; DA Tryk;J Photochem.Photobiol A :chem., 2, 1, 1. [5]S Al- Qrdwi; SP Slmn; J. Photochem. Photobiol.A: Chem., 22, 148, 161. [6]D Chtterjee; S Dsgupt; J. Photochem. Photobiol. A: chem., 25, 186,123. [7]A Syoufin; K Nkshem;, J. Coll nd Inter. Sci., 28,317, 512. [8]HY Shu;MC Chng;H Fn; J. Energy mter sol.cells., 23,77,21. [9]Dipti Vy; nd VK Shrmb ; J. Chem. Phrm. Res., 21, 2, [1] SA Abofrh; J. of Americn Science;21, 6, 11. [11] Preeti Meht; Rjeev Meht; Menk Surn; B V Kbr; J. Chem. Phrm. Res; 21,2, [12] Menk Surn; Preeti Meht; Kvit Pmech; B V Kbr; J. Chem. Phrm. Res., 21, 2, [13]K Mundhe; S Gikwd;RC Torne,NR Deshpnde nd RV Kshlkr; J. Chem.Phrm. Res.,212, 4 ; [14]B Krishnkumr; M Swminthn; Ind. J.Chem. 21, 49, 135. [15]M Kondo; W Jrdim;wter Res., 1991, 25, 823. [16]RW Mtthews, Wter Res., 199, 24, 653. [17]M Murugndhm; M Swminthn; Dyes nd pigments. 24, 62,

9 [18]S Skthivel; B Neppolin; MV Shnkr; MV Arbindoo; M Plnichmy; V Murugesn;, Mter. Sol. Cells., 23, 77, 65. [19]Z Shourong; H Qigguo; Z Jun;W Bingturn, J.Photochem.Photobiol A:Chem., 1997,13, 235. [2]JH Bxendle ; JA Wilson; Trns. Frdy. Soc., 1957, 53, 344. [21]ID Mristylidi; Kondrides; Xenophon.E.Verykios; I.J of Photoenergy., 23, 5, 6. [22]S Chkrbrti;B.K.Dutt; J.Hzrd.Mter., 24, 156,

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