Use of Surface Modified Silica gel factory Waste for Removal of 2,4-D Pesticide from Agricultural Wastewater: A case study

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1 In. J. Environ. Rs., 6(4): , Auumn 202 ISSN: Us of Surfac Modifid Silica gl facory Was for Rmoval of 2,4-D Psicid from Agriculural Waswar: A cas sudy Konr, S., Pal, A. 2 and Adak, A. 3* Dparmn of ivil Enginring, Jalpaiguri Govrnmn Enginring ollg, Jalpaiguri 73502, India 2 Dparmn of ivil Enginring, Indian Insiu of Tchnology, Kharagpur 72302, India 3 Dparmn of ivil Enginring, Bngal Enginring and Scinc Univrsiy, Shibpur, Howrah 703, India Rcivd 6 Aug. 20; Rvisd 9 Jun 202; Accpd 26 Jun 202 ABSTRAT: Th silica gl was (SGW), afr is collcion from a local facory (Kolkaa, India) was modifid wih caionic surfacan and was uilizd as an adsorbing mdia for h rmoval of 2,4- dichlorophnoxyacic acid (2,4-D) from agriculural runoff of a a gardn. haracrizaion of bas adsorbn and modifid adsorbn was carrid ou. Th fficacy of h adsorbn was valuad hrough boh bach and fixd bd mod. Kinics and isohrm sudy wr conducd and h paramrs wr compard wih 2,4-D baring disilld war sampls. Th valus of diffusion cofficins wr drmind. Prsnc of lcroly and soluion ph was found o affc h prformanc of h adsorbn significanly. Th rmoval fficincy of surfacan modifid silica gl was (SMSGW) in cas of waswar was found o b lowr han h 2,4-D baring disilld war sampl. Th daa of column run was analyzd using Logi modl. Bach dsorpion sudy was carrid ou using hanol and acon. Th sudis rvald surfacan coad SGW o b an fficin adsorbing mdia for 2,4-D rmoval. Ky words: Adsorpion, Hrbicid, was, Agriculural runoff INTRODUTION Th larg-scal applicaion of psicids in agriculur fild and forsry, fas growing of agrochmical indusris worldwid and h domsic aciviy of conrolling pass caus various psicids and hrbicids nring ino h surfac and ground war rsourcs (Ghadri al., 202). Ths rndr srious psicid polluion in h war rsourcs (Nasrabadi al., 20; Mhadhbi and Boumaiza, 202). Th laching runoff and indusrial dischargs ar rsponsibl for his conaminaion in surfac war (Gupa al., 2006; Ahsan and DlValls, 20; Assassi al., 20). On of h widly usd hrbicids in h world is 2,4-dichlorophnoxyacic acid (2,4-D). I is considrd as modraly oxic and ponially carcinognic (hao al., 2008). Du o is low pka valu (2.73), i xiss prdominanly in anionic form which can badly affc h auaic lif and hampr h cosysm and a h sam im h poor biodgradabiliy maks 2,4-D nvironmnally sabl (arr 2000). As a consunc, i has bn frunly dcd in war bodis in various rgions of h world. Th rmoval of psicids from war has hus bcom *orrsponding auhor asokadak@gmail.com on of h major nvironmnal concrns hs days (Hammd al., 2009). Th various ramn chnologis such as chmical oxidaion (hu al., 2004), phoodgradaion (Topalov al., 200; Kundu al., 2005), micllr flocculaion (Poras and Talns, 999), biological procss (H and Warham, 2009; Elfsiniois and Li, 2008) and sorpion chnius (Xi al., 200, Salman and Hammd 200; Hammd al., 2009; hao al., 2009; hao al., 2008; Gupa al., 2006; Goyn al., 2004; Aksu and Kbasakal; 2005 & 2004; Prado and Airodi, 200; Alam al., 2000; Akcay and Yurdakoc, 2000) ar availabl for rmoval of 2,4-D from war nvironmn. Among hs mhods adsorpion has bn provn o b an ffciv and araciv mchanism (Hamd al., 2009; Aksu and Kbasakal, 200). Rcnly, adsorpion of 2,4-D has bn carrid ou using various surfacan modifid mal oxids bcaus h us of surfacan baring sludg (surfacan xhausd sorbn) has bcom on of h cos-ffciv alrnaivs for organic polluan rmoval from waswar (Xi al., 200; Akcay and 995

2 Konr, S. al. Yurdakoc, 2000). Th ionic surfacans form monolayr or bilayr srucurs on h chargd mal oxid surfac dpnding on surfacan concnraion (Somasundaran and Fursnau, 966). Th surfacan layrs pos h abiliy o solubiliz diffrn organic molculs wihin is srucur. Again, during h las dcad, iniiaiv has bn akn by h many rsarchrs o us h indusrial wass as an adsorbing mdia for waswar ramn. Such us of was would no only rduc is disposal problm bu also would rduc h discharg of liuid was in h nvironmn. Thrfor us of such was as mal oxid would b usful. Silica gl is a marial ha is wll known for is high hrmal and chmical sabiliy, good slciviy, swlling rsisanc, possibiliy of rpad us and conomic viabiliy (Donia al., 2009). So h was gnrad from a silica gl facory could b usd as mal oxid. Morovr, in a rcn sudy carrid ou by h prsn auhors, i was obsrvd ha h was gnrad from a local silica gl facory was ffciv in adsorpiv rmoval of h caionic surfacan from waswar (Konr al., 20). Wih his in viw, h prsn sudy aims a furhr invsigaion of h ponial of ha was, afr is us as a sorbn for caionic surfacan (S), for h rmoval of 2,4-D from ral waswar collcd from an agriculural runoff of a a gardn. MATERIALS & METHODS Orang II (Hi-Mdia, India), cylrimhylammonium bromid (TAB) (Hi-Mdia, India), chnical grad 2,4-D (98% pur) (Mrck, Grmany) and chloroform (Mrck, India) wr usd as rcivd. All ohr chmicals usd in his sudy wr of high puriy and usd wihou furhr purificaion. All h chmicals wr of analyical ragn grad. An lcrical balanc (P 225D, Sarorious GMBH) was usd for wighing. Digial ph mr (PB-, Sarorious GMBH) was usd for ph masurmns. A spcrophoomr (UV 800, Rayligh, Bijing) was usd for absorbanc masurmn. For SEM and EDX analysis, JEOLJSM5800 scanning lcron microscop was usd. Th silica gl was was supplid by local facory locad a Kolkaa, India. Afr rcip of h marial i was horoughly washd wih ap war followd by disilld war o rmov h forign subsancs and drid a 00 o. I was hn sivd and abou 70% of h oal marial lid in h paricl siz bwn 50 and 300 µm and ha was usd for h sudy. Th final marial afr is washing and siving was masurd o b around 65% of h collcd was. Th silica gl was (SGW) was hn rad wih TAB, a rprsnaiv of S o form micll lik srucur on hir surfacs and hus surfacan-modifid silica gl was (SMSGW) was prpard. This marial was hn for 2,4-D rmoval from war nvironmn. Spcrophoomric mhod was usd for h drminaion of S in h concnraion rang 0-2 mg/l (Fw and Owil, 956). Orang II (0.4 x 0-3 M) chmically known as p-(β-naphol-azo) bnzn sulfonic acid as ion pairing agn wih S was usd and chloroform was usd as an xracion solvn from h soluion and h sam was akn for absorbanc masurmn a 485 nm wavlngh. 2,4-D was uanifid by spcrophoomric mhod in h concnraion rang of 0-35 mg/l a 230 nm wavlngh. Th ral waswar conaining 2,4-D was collcd from surfac runoff of a a gardn siuad in Jalpaiguri disric, Ws Bngal, India. To conrol h wds of h a gardn, 2,4-D hrbicid is applid in h form of 2,4-D sodium sal (80% w/w) which is commrcially known as SALIX sal. Afr applicaion of SALIX sal in h gardn, hr was a havy sorm of duraion 25 min and h runoff was collcd from on of h fild channls of h gardn during h sorm. Th characrisics of h waswar ar prsnd in Tabl. Th concnraion of 2,4-D in h waswar was masurd o b mg/l. Afr collcion, h waswar was passd hrough ordinary filr papr in ordr o rmov h suspndd paricls and hn i was akn for h sudy. Tabl. haracrisics of ral waswar (agriculural runoff) collcd from a gardn Paramr Valus 2,4- D 32.9 m g/l ph 8.5±0. Turbidiy 23 NTU Toal dissolvd solids 36 mg/l Toal suspndd solids 256 mg/l onduciviy 48.8 µs/cm Toal hardnss 44 mg/l as ao 3 OD 37 mg/l Th kinic xprimns wr carrid wih a fixd SMSGW dos of 8 g/l a 30 o aking h waswar and h sam was compard using synhic sampls of 2,4-D prpard in disilld war a h sam iniial concnraion and h sampls wr shakn in a mchanical shakr a an agiaion spd of 50 rpm. Th shaking im was varid from 0 o 30 min. Th uilibrium im was found o b 20 min and was usd for furhr sudis. 2,4-D baring ral waswar gnrally conains various dissolvd sals which may inrfr h prformanc of h adsorbn. Thrfor, i is ruird o invsiga h ffc of various inrfring subsancs on h 2,4-D rmoval procss. Thus, xprimns wr carrid ou o s h ffcs of various lcrolys and dissolvd sals lik sodium 996

3 In. J. Environ. Rs., 6(4): , Auumn 202 chlorid, sodium sulpha, calcium chlorid, magnsium sulpha (0.0N and 0.02N). Effc of ph (in h rang ) was also sudid. For hs sudis h iniial 2,4-D concnraion spikd in disilld war was akn as 50 mg/l and h adsorbn dos was 0 g/l. Th mpraur and conac im and ph wr 30 o, 20 min and 3.9±0. rspcivly. Bach dsorpion sudy was conducd using organic solvns. Four isohrm modls, namly Frundlich, Langmuir, Tmkin and Rdlich-Prson isohrm wr also sd for hir abiliy o dscrib h xprimnal rsuls a h mpraur of 30 o and h isohrm paramrs obaind for waswar wr compard wih disilld war spikd sampl. Fixd bd column sudy was conducd using a column of 2.5 cm inrnal diamr and 00 cm lngh. Th adsorbn was packd in h column bwn wo layrs of glass wool and h dph of bd was 20 cm. Th sudy was conducd in h up flow mod wih a volumric flow ra 0 ml/ min (~.22 m 3 /m 2 /hr). Th sampls wr collcd a crain inrvals and wr analyzd for rmaining 2,4- D concnraion. In ordr o invsiga h mchanism of solu adsorpion ono h adsorbn, four kinic modls viz., firs ordr racion modl (Bnfild and Randall 980) basd on h soluion concnraion, psudo-firs ordr uaion of Lagrgrn (898) basd on h solid capaciy, scond ordr racion modl basd on h soluion concnraion (Bnfild and Randall 980) and psudo-scond ordr racion modl of Ho and Mckay basd on h solid phas sorpion (Ho and Mckay 999) wr analysd and a comparison of h bs fi sorpion mchanism was mad. Th linarizd forms of diffrn racion modls ar shown blow. Firs ordr: ln = ln k () o d d Psudo firs ordr: k ( ) Scond ordr: Psudo scond ordr: = (2) S = k2 (3) o = + 2 (4) k S 2 Whr, = solu concnraion a any im o = solu concnraion a im =0 = amoun of solu adsorbd pr uni wigh of adsorbn a any im = amoun of solu adsorbd pr uni wigh of adsorbn a uilibrium k = firs ordr racion ra consan k S = psudo-firs ordr racion ra consan k 2 = scond ordr racion ra consan k S2 = psudo-scond ordr racion ra consan Th xprimnal racion kinic daa wr analysd using h abov four kinic modl. RESULTS & DISUSSION Bfor prparaion of SMSGW, i is imporan o find h maximum adsorpion capaciy and h iniial S concnraion a which i would occur. In h prsn sudy, TAB was usd as a rprsnaiv of S. Thrfor, h adsorpion isohrm sudy was carrid ou in h iniial TAB concnraion rang of mg/l. Th adsorbn dos was kp fixd a 30 g/l. Th conac im was akn as 30 min sinc his was h uilibrium conac im. Th mpraur and ph wr 302 o and 6.9±0. rspcivly. From his isohrm sudy, h maximum adsorpion capaciy was found o b 0.88 mmol/g (68.62 mg/g) and i occurrd whn iniial concnraion of TAB was 7500 mg/l. This condiion was usd for h prparaion of SMSGW. Thrfor, 80 g SGW (a a dos of 30 g/l) was shakn for on hour wih 6 lirs of TAB soluion having concnraion of 7500 mg/l. Afr shaking, h suprnaan was discardd and h SGW was washd horoughly iniially wih ap war and finally wih disilld war and hn drid a 60 o for 24 hours. Thus h SGW was convrd o SMSGW. Th characrizaion of h bas adsorbn was carrid ou afr propr washing and siving of h collcd was. Tabl 2 summarizs h diffrn propris of h bas adsorbn (SGW) and modifid adsorbn (SMSGW) such as siz, bulk dnsiy, ph poin of zro charg (ph pzc ), BET surfac ara and por volum. Th surfac morphology of h adsorbn was obaind from h Scanning Elcron Microscopy (SEM) sudis and h lmnal composiion from Enrgy Disprsiv X-ray (EDX) analyss. Th SEM phoograph showd ha h adsorbn paricls ar of ill dfind shaps having irrgular surfacs. I was also nod ha afr surfacan modificaion h surfac of SGW bcam smooh (Fig. ) and lowrd h surfac ara. EDX analysis is a usful ool for idnificaion of h kinds of lmns conaind in h solid spcimn wihin shor analysis priod. Th EDX analysis showd ha h SGW conaind 96% silica. Kinics sudis wr conducd o find ou h uilibrium conac im for 2,4-D upak from ral waswar as wll as disilld war spikd sampl by SMSGW. An adsorbn dos of 8 g/l and h shaking im ranging from 0 o 30 min was usd o conduc h kinic sudy. Fig. 2 shows h rsuls of ffc of 997

4 Rmoval of 2,4-D Psicid Tabl 2. haracrisics of SGW and SMSGW Paramr SGW SMSGW Paricl siz (µm) Bulk dnsiy (g/cc) ph pzc BET surfac ara (m 2 /g) Por volum (ml/g) (a) (b) Fig.. SEM imag of (a) SGW and (b) SMSGW (mmol/g) disilld war spikd sampl ral waswar onac im (min) Fig. 2. Effc of conac im on 2,4-D upak by SMSGW 998

5 In. J. Environ. Rs., 6(4): , Auumn 202 conac im. Th ra of adsorpion is vry rapid iniially. From h figur i is shown ha in 5 min h uilibrium rachd. Bu a conac im of 20 min considrd o b sur ha full uilibrium was rachd. Similar rnd was also obsrvd in cas of 2,4-D-spikd in disilld war sampl. Bu in cas of disilld war spikd sampl h rmoval fficincy was br han waswar du o prsnc of various lcrolys and probably highr ph of h waswar. Th uilibrium conac im, so found, indicad vry uick racion compar o ohr sudis lik 90 min (Gupa al., 2006), 450 min (Hamd al., 2009) and 7 days (Aksu and Kbasakal, 2004). Th pracical applicaion of his adsorbn in coninuous mod in h fild will b asir sinc i would facilia o rduc h racor volum du o such lowr valu of uilibrium conac priod. Th ra of sorpion was drmind by sing h four racion kinics modls as dscribd arlir. Afr analyzing h four modls, i was found ha h psudo-scond ordr modl (Fig. 3) fid bs among all h modls indicaing h ra limi sp o b chmisorpion or chmical adsorpion (Ho and Mckay 999). Th uaions, uilibrium upak capaciy, racion ra consan and h drmining cofficins (R 2 ) of h psudo-scond ordr modl ar shown in Tabl 3. Th valu of racion consan was found o b g/mg. min for ral waswar and g/ mg. min disilld war spikd sampl. Th racion consan, so found, could b usd for h dsign of diffrn yps of bach racors gnrally usd in h fild. Th diffusion cofficins for h prsn sudy wr drmind using firs ordr racion kinics daa. Assuming sphrical gomry of h sorbns, h firs ordr ra consan, K obaind from firs ordr kinics profils can b corrlad o h por diffusion and film diffusion cofficins (Hlffrich, 962). 2 r0 D p / 2 = (5) r 0δ 2 = D f (6) Whr, /2 = half im ro = radius of adsorbn paricl = cm Dp = por diffusion cofficin (cm2/sc) Df = film diffusion cofficin (cm2/sc) / disilld war spikd sampl ral waswar Linar (ral waswar) onac im (min) Fig. 3. Linar plo of psudo-scond ordr racion kinic modl Tabl 3. Euaions and R 2 valus of h linar fi lins of psudo-scond ordr racion modls for h rmoval of 2,4-D by SMSGW Sampl yp Ral waswar Disill d war spikd Euaion of linar fi lin Racion ra consan (g/mg?min) = = R 2 999

6 Konr, S. al. = concnraion of adsorba on h adsorbn = mg/l =concnraion of adsorba in soluion = 5.22 mg/l δ = film hicknss (cm) /2 can b calculad using h rlaion (Ashr al., 990) 2 [ln(0.5)] = (7) K Th valu of K in cas of ral waswar was found o b min-. Using h valu of K, h valus of /2 wr calculad and i was found o b sc. Assuming sphrical gomry of h sorbns, δ = 0.00 cm (Hlffrich, 962) and using calculad valus of /2 h film diffusion cofficins, Df and por diffusion cofficins, Dp for ral waswar wr calculad and hs wr.48x0-8 cm2/sc and 8.2x0-9 cm2/sc rspcivly. Now according o Michlson (975) for film diffusion o b h ra limiing sp in sorpion, h valu of film diffusion cofficin (Df) should b bwn 0-6 o 0-8 cm2/s, whr as for por diffusion o b ra limiing, h por diffusion cofficin (Dp) should b in h rang of 0- o 0-3 cm2/s. In h prsn sudy, h valu of Df was found o b nar o 0-8 ha indicad ha hr is also a possibiliy for h film diffusion o b h ra limiing sp. Th ffc of ph and lcrolys wr sudid aking iniial 2,4-D concnraion of 50 mg/l (spikd in disilld war sampl). Th adsorbn dos was 0 g/ l. From h Fig. 4, i is shown ha wih incras of ph, h capaciy of 2,4-D upak by SMSGW dcrasd sinc a highr ph h surfac of SMSGW (ph pzc = 0.2) bcam mor ngaiv and hrfor rsuld lowr affiniy of h adsorpion of anionic 2,4-D molculs (Gupa al., 2006; hao al., 2009; Hammd al., 2009). Bu for h prsn cas, as h dsorpion of TAB from h surfac of SMSGW occurrd a lowr ph, h adsorpion of 2,4-D a lowr ph also found o dcras (Konr al., 20). Th rsul for ffc of lcrolys is plod in Fig. 5. Thr was a rducion in rmoval fficincy in prsnc of hs sals. This was du o compiion of coxisnc of anions on posiivly chargd surfac. hao al. (2009) hav sudid ha h ngaiv ffc of anions -2 on 2,4-D rmoval was in h ordr of SO 4 > l -. Similar rsul was obaind in his cas also. I was also inrsing o s ha in prsnc of al 2 and MgSO 4, h rmoval fficincy was slighly incrasd compar o h rmoval fficincy in prsnc of Nal and Na 2 SO 4 rspcivly. This was probably du o prsnc of mulivaln caions ha incrasd h posiiv charg of SMSGW. A propr conac bwn h adsorba and adsorbn is ncssary for any adsorpion procss. Th concnraion gradin a h adsorbn surfac is maximum iniially. Howvr, wih im adsorba spcis sar migraing o h adsorbn surfac and concnraion gradin sars dcrasing. Afr som im concnraion gradin bcoms ngligibl and hr is no n ransfr ono h adsorbn. This sablishs h dynamic uilibrium bwn adsorba prsn in solid and liuid phas. Th adsorpion isohrm dfins his uilibrium sa. Svral modls hav bn dvlopd o dfin h adsorpion isohrm. Among hm four widly usd modls such as Frundlich modl (Frundlich 906), Langmuir modl (Langmuir 98), Tmkin modl (Tmkin and Pyzhv, 940) and Rdlich- Prson modl (Rdlich and Prson 959) hav bn sudid in h prsn sudy. 2,4-D rmoval (%) Iniial ph Fig. 4. Effc of iniial ph on 2,4-D upak by SMSGW 000

7 In. J. Environ. Rs., 6(4): , Auumn Zro lcroly 0.0(N) 0.02(N) 2,4-D rmoval (%) No lcroly Sodium chlorid Sodium sulpha alcium chlorid Magnsium sulpha Addd lcrolys (N) Fig. 5. Effc of lcrolys on 2,4-D upak by SMSGW Th Frundlich uaion is an mpirical xprssion ha ncompasss h hrogniy of h adsorbn surfac and h xponnial disribuion of sis and hir nrgis. Th xprssion for Frundlich modl is givn in uaion 8. f n = k (8) Whr, k f = Frundlich consan rlad o adsorpion capaciy = adsorpion innsiy n = amoun of adsorba on adsorbn a uilibrium (mg/g) = uilibrium concnraion (mg/l) Th linar form of Frundlich isohrm modl is rprsnd blow. ln = ln k f + ln (9) n Langmuir isohrm modl is known as idalizd monolayr modl. Th basic assumpions of Langmuir modl (i) a fixd numbr of accssibl sis having ual nrgy (homognous surfac) and (ii) rvrsibiliy of h adsorpion procss. Whn h ra of adsorpion bcoms ual o h ra of dsorpion of molculs from h surfac, uilibrium is rachd. Langmuir isohrm modl may b xprssd as K m L = (0) + K L Whr, m = maximum adsorpion capaciy (mg/g) K L = consan rlad o nrgy of h sorpion sysm (l/mg) Th linarizd form of h Langmuir isohrm modl is prsnd blow. = + () K m m L Tmkin isohrm considrd h ffc of indirc adsorba adsorbn inracions on adsorpion. Tmkin isohrm also rprsns h binding hrogniy wih a simpl xprssion, which has prdiciv powr ovr a wid rang of concnraion. Tmkin isohrm can b rprsnd as RT = ln( KT ) (2) b Whr, R is univrsal gas consan, T is absolu mpraur (K) and b and KT ar modls consans. I can b linarizd as = B ln( KT ) + B ln( ) (3) RT Whr, B = rlad o ha of adsorpion and b KT is h uilibrium binding nrgy consan (l/mg) corrsponding o h maximum binding nrgy. Th Rdlich-Prson isohrm modl incorporad hr paramrs and can b applid ihr in homognous and hrognous sysms. Jossns al. (978) includd h basic concps of Frundlich and Langmuir isohrms o mak a singl uaion and xprssd as K R = β (4) + ar 00

8 Rmoval of 2,4-D Psicid This uaion can b linarizd as ln( K R ) = ln( ar ) + β ln( ) (5) Whr, KR and ar ar h modl consans and β is h xponn which has h valu bwn 0 o. Dpnding on h valu of xponn β ihr in Langmuir or Hnry s law of isohrm. A rial and rror opimizaion chniu was adopd o solv h abov uaion using MATLAB. Tabl 4 rprsns h consans of h abov four isohrm modls for boh waswar and disilld war spikd sampls rspcivly. From h R2 valus of drmining cofficins (R2) i is sn ha Rdlich-Prson modl fid bs in comparison o ohr modls for h ral waswar. Similar rsul obaind in cas disilld war spikd sampl also. Th maximum adsorpion capaciy obaind from Langmuir isohrm was 7.73 mg/g (0.08 mmol/g) a 30o, which was found o b lowr han h disilld war spikd sampl (33.9 mg/g or 0.53 mmol/g). Such lowr valu of adsorpion capaciy and highr valu of opimum adsorbn dos han disilld war spikd sampl was du o h prsnc of dissolvd sals in h waswar. Morovr, h solubiliy of 2,4-D sodium sal (45000 mg/l a 25 o ) in war is 50 ims of 2,4-D acid (900 mg/ l a 25 o ). This highr solubiliy of h 2,4-D sal rsuld lowr affiniy owards adsorpion. Th capaciy obaind for upaking psicids (for disilld war spikd sampl) was found o b grar han ohr sorbns lik diocadcyl dimhylammonium bromid-modifid polysagri (Xi al., 200), blas furnac sludg and dus (Gupa al.,2006), acivad usd yrs (Hamadi al., 2004), oil shal ash (Al- Quodah al., 2007), biuminous shll (Ayar al., 2008), 3-rimhoxysilylpropylamin anchord silica gl (Prado and Airodi, 200) and was rubbr granuls (Alam al., 2000). Though his capaciy was lowr compar o carbonacous adsorbns drivd from da son (Hamd al., 2009) and frilizr was (Gupa al., 2006), granular and powdrd acivad carbon (Salman and Hammd, 200; Aksu and Kbasakal 2004 & 2005) and layrd doubl hydroxids (hao al., 2008; hao al., 2009). Th imporan par, howvr, in cas of 2,4-D rmoval by SMSGW was h uilizaion of xhausd was afr rmoval of S, which is known o b an nvironmnal polluan and rsisan o biodgradaion. Th us of an indusrial was for S rmoval and furhr us of xhausd was for 2,4-D rmoval mad h procss no only cos-ffciv bu also i causd was minimizaion. I is also vry imporan o b mniond ha h upak capaciy of SMSGW could b incrasd, if h adsorpion of TAB on h surfac of SGW was carrid ou in prsnc of lcrolys and wih ph adjusmn during h prparaion of SMSGW, sinc h prsnc of lcrolys and highr ph was found o nhanc h surfacan covrag on h surfac of silica paricls (Konr al., 20). So in acual applicaion in h fild hr is no possibiliy o achiv h adsorpion capaciy of SMSGW lowr han h capaciy obaind hr. Th ssnial characrisics of h Langmuir isohrm can b xprssd in rms of a dimnsionlss consan sparaion facor RL (Hall al., 966), which is givn by R L = + K o L (6) Tabl 4. Isohrm consans for 2,4-D rmoval from ral waswar and disilld war spikd sampls by SMSGW a 30 o Frundlich consans Sampl yp K f [(mg/g)(l/mg) /n ] /n R 2 Ral waswar Disilld war spikd Langmuir consans Sampl yp m (mg/g) K L (l/mg) R L R 2 Ral waswar 7.73 (0.08 mmol/g) Disilld war spikd (0.53 mmol/g) Tmkin consans Sampl yp K T (l/mg) B R 2 Ral waswar Disilld war spikd Rdlich-Prson consans Sampl yp K R (l/mg) a R β R 2 Ral waswar Disilld war spikd

9 In. J. Environ. Rs., 6(4): , Auumn 202 Whr, o is h iniial concnraion of 2,4-D (mg/l) and K L (l/mg) is Langmuir consan. Th valu of R L indicad naur of adsorpion; irrvrsibl (R L = 0), favourabl (0 < R L < ) and unfavourabl (R L = ). Th valu of R L (Tabl 4) indicad favourabl adsorpion. Th brakhrough curv for 2,4-D using SMSGW for h column run is shown in Fig. 6. Th brakhrough im (corrsponding o / o = 0.) and xhaus im (corrsponding o / o = 0.9) wr found o b 2 and 25 hours rspcivly. Th corrsponding volums of rad waswar wr 7.2 and 5 l rspcivly. Th propris of adsorpion zon or mass ransfr zon wr calculad using h column daa (Adak, 2006). High of adsorpion zon was found o b 6.45 cm and h ra of adsorpion zon movmn hrough h bd was.26 cm/h. Th prcnag of h oal column saurad a brakhrough was found o b 42%. Th fixd bd column was dsignd by Logi mhod (Oulman 980). Th logi uaion can b wrin as: / o / KNX = V + K ln o (7) o Whr, = Solu concnraion a any im o = Iniial solu concnraion V = Approach vlociy X = Bd dph K = Adsorpion ra consan N = Adsorpion capaciy cofficin Rarranging E / Tim (h) Fig. 6. Brakhrough curv for 2,4-D upak from waswar by SMSGW 3 2 ln [/ (0- )] ln [/ ( 0 - )] = () R 2 = Tim (h) Fig. 7. Linarizd form of Logi modl 003

10 Konr, S. al. KNX ln = + Ko (8) o V Plo of ln vs. givs a sraigh lin wih o KNX slop K o and inrcp from which, valu V of K and N could b calculad. Plo of vs. is shown in Fig 7. Th valu of adsorpion ra cofficin (K) and adsorpion capaciy cofficin (N) wr obaind as l/mg.h and 3473 mg/l rspcivly. Ths valus could b usd for h dsign of adsorpion columns. 2,4-D could b dsorbd from xhausd SMSGW surfac using hanol and acon. I was obsrvd ha in cas of acon and hanol mor han 80% and 75% dsorpion was achivd rspcivly. 0 g of xhausd SMSGW was akn in 50 ml of solvn (200 g/l) and hn agiad a 50 rpm for 60 min a a mpraur of 30 o ±2. Th rgnrad 2,4-D could b collcd and rusd. Th organic solvn could b disilld off using a Soxhl apparaus and h sam solvn could b rcycld for h sam purpos. ONLUSION SMSGW could ffcivly b usd for h rmoval of 2,4-D from ral waswar. A vry uick racion was found o occur for h adsorpion procss. Th rmoval fficincy and adsorpion capaciy was found o b lowr for waswar in comparison o disilld war. Th upak capaciy of SMSGW dcrasd in prsnc of various lcrolys and a highr ph. Inrsingly in a wid rang of ph, h rmoval was no significanly affcd. Th valu of diffusion cofficins indicad ha h film diffusion migh b h ra limiing sp for ral waswar. Th adsorpion of 2,4-D followd h R-P isohrm modl bs compard o ohr isohrm modls lik Frundlich, Langmuir and Tmkin isohrm modl. Th capaciy obaind from Langmuir isohrm can b compard wih many ohr adsorbns spcially which ar drivd from indusrial was. Thrfor, an indusrial was afr is us for rmoval of surfacan could b rusd for psicid rmoval from war nvironmn. Such ffciv us of a was mad h procss no only cos-ffciv bu also nvironmnfrindly. AKNOWLDEGEMENT W ar hankful o h SER Division, Dparmn of Scinc and Tchnology, Nw Dlhi, India for h financial suppor for his work. W ar also graful o M/S Kalpaaru Pv. Ld., Kolkaa, India for supplying us h silica gl was marial and Mr. Alaksh handra Mandal of Indian Insiu of Scinc, Bangalor, India for his kind hlp and valuabl advic. REFERENES Adak, A., Bandyopadhyay, M. and Pal, A. (2006). Fixd bd column sudy for h rmoval of crysal viol (. I. Basic Viol 3) dy from auaic nvironmn by surfacanmodifid alumina. Dys and Pigmns, 69, Ahsan, D. A. and Dl Valls, T. A. (20). Impac of Arsnic onaminad Irrigaion War in Food hain: An Ovrviw From Bangladsh. In. J. Environ. Rs., 5 (3), Akcay, G. and Yurdakoc, K. (2000). Rmoval of various phnoxyalcanoic acid hrbicids from war by organo-clays. Aca Hydochim. Hydrobio., 28, Aksu, Z. and Kabasakal, E. (2005). Bach adsorpion characrisics of 2,4-dichlorophnoxy-acic acid 2,4-D from auous soluion on powdrd acivad carbon. J. Environ. Sci Halh Par B, 40, Aksu, Z. and Kabasakal, E. (2004). Bach adsorpion characrisics of 2,4- dichlorophnoxy-acic acid (2,4-D) from auous soluion by granular acivad carbon. Sp. Purif. Tchnol., 35, Alam, J. B., Dikshi, A. K. and, Bandyopadhyay, M. (2000). Efficacy of adsorbns for 2,4-D and arazin rmoval from war nvironmn. Global Ns: Th Inrnaional J., 2, Al-Qodah, Z., Shawafh, A. T. and Lafi, W. K. (2007). Adsorpion of psicids from auous soluion using oil shal ash. Dsalinaion, 208, Assassi, M., Fourcad, F., Gns, F., Flonr, D., Maachi, R., Amran, A. (20). ombind lcrochmical and biological ramn for psicid dgradaion Applicaion o phosm. In. J. Environ. Rs., 5 (), Ashr, B. T., Sparks, D. L., Psk, J. D. and Fignbaum, S. (990). Analysis of adsorpion kinics using a sirrd-flow chambr: I Thory of criical ss. Soil Sci. Soc. Amrica J., 54, Ayar, N., Bilgin, B. and Aun, G. (2008). Kinics and uilibrium sudis of h hrbicid 2,4-dichlorophnxyacic acid adsorpion on biuminous shal. hm. Eng. J., 38, Bnfild, L. D. and Randall,. W. (980). Biological procss dsign for waswar ramn, firs d. Prnic- Hall Inc. USA. arr, A. D. (2000). Hrbicid movmn in soils: principls, pahways and procsss. Wd Rs., 40,

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12 Rmoval of 2,4-D Psicid Somasundaran, P. and Fursnau, D. W. (966). Mchanism of alkyl sulfona adsorpion a h alumina-war inrfac, J. Phys. hm., 70 (), Tmkin, M. I. and Pyzhv, V. (940). Kinics of ammonia synhsis onpromod iron caalyss. Aca Physicochimica, URSS, 2, Topalov, A., Abramovic, B., Molnár-Gábor, D., sanádi, J. and Arcson, O. (200). Phoocaalyic oxidaion of h hrbicid (4-chloro-2-mhylphnoxy) acic acid (MPA) ovr TiO 2, J. Phoochm. Phoobio. A: hm., 40, Xi, Y., Mallavarappu, M. and Naidu, R. (200). Adsorpion of h hrbicid 2,4-D on organo-palygorski. Appl. lay Sci., 49,