Effect of Chemical Activation of Natural Clay by FRRIC Chloride on Adsorption of Nitrobenzene

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1 IOSR Journal of Enginring (IOSRJEN) ISSN (): , ISSN (p): Vol. 08, Issu 8 (August. 2018), V (V) PP Effct of Chmical Activation of Natural Clay by FRRIC Chlorid on Adsorption of Nitrobnzn Imd Elmir (1), Mohamd Baguan (2) Dpartmnt of Chmical Enginring, laboratory of intraction fluid and pors matrials National school of nginrs of Gabs-Tunisia, Univrsity of Gabs Strt of Mdnin, 6011, Gabs, Tunisia, Corrsponding Author: Imd Elmir Abstract: Natural clays hav a high capacity of adsorption aftr activation. Ths matrials ar usd to tratmnt of organics dys solutions, uss minrals oils and dgradation of non biodgradability compounds such us nitrobnzn, chlorobnzn, phnol... tc. Th aim of this work is th ffct of chmical activation of natural clay by frric chlorid (FCl 3 ) on adsorption of nitrobnzn onto thss nw prpard activatd clays. Th quilibrium was rachd at th nd of 4 hours. Th adsorption isothrm was wll dscribd by th Dubinin- Radushkvich modl. Th high fficincy of tratmnt by activatd clay is %, was obtaind at th optimum conditions of activation: activation tmpratur Ta = 15 C, activation mass ratio (quantity of FCl 3 /quantity of natural clay) R m = 0.3, activation tim ta = 15 min and activation frric chlorid concntration C = 15 g/l. Kywords: Activatd clay, Adsorption, Natural clay, Nitrobnzn, Optimization Dat of Submission: Dat of accptanc: I. INTRODUCTION Wastwatrs containing nitrobnzn is a srious nvironmntal problm and ths liquids cannot simply b rlasd into th nvironmnt without tratmnt. Nitrobnzn is prsnt in th fflunt from industris ngagd in th manufactur of varity of chmicals such as dys, plastic, psticids, xplosivs, pharmacuticals and intrmdiats in chmical synthsis industris for yars. Aftr us, nitrobnzn in solution is gnrally dischargd to wast tratmnt plants whr a largr proportion of it cannot b rmovd and finally is dischargd into th aquatic nvironmntal, which tnds to prsist in th nvironmnt and poss a potntial toxic thrat to cological and human halth [1, 2]. Thrfor, a varity of possibl tratmnt tchnologis such as ozonation, Fnton procss, advancd oxidation procss and adsorption hav bn takn into account for purification of nitrobnzn contaminatd watr [3, 4, 5, 6, 7]. It is wll known that clay minrals can b usd to dcoloriz oils bcaus of its high adsorptiv capacity [8].In othr to nhanc this adsorptiv proprty, acid activation of clay is th most commonly usd tchniqu. This ara of clay modification has rcivd normous intrst from various rsarchrs [9, 10]. This papr aims at studying th dgradation of nitrobnzn from aquous solutions by adsorption onto activatd clay. It is ncssary to product activatd clay by chmical activation of natural clay by frric chlorid. Influncing paramtrs such as tim, tmpratur and amounts of frric chlorid and natural clay ar valuatd to charactriz th ffct of kind of chmical activation on dgradation of nitrobnzn by adsorption onto ths nw prpard matrials. Kintic study and adsorption isothrm of nitrobnzn by activatd clay wr prsntd in this works. II. MATERIALS AND METHODS 2.1. Matrials Adsorbat (nitrobnzn) Analytical grad nitrobnzn from ACROS (rfrnc: ) was usd in th xprimnts. Aquous solutions of nitrobnzn wr prpard using bi-distilld watr. Th initial ph of background solution was adjustd by introducing appropriat amounts of bas (NaOH 2M) solutions. 62 P a g

2 Tabl 1 prsnts th principal physic-chmicals proprtis of nitrobnzn. Tabl1. Principal physic-chmicals proprtis of nitrobnzn (ACROS ) Molcular formula C 6 H 5 NO 2 Physical stat Liquid Molcular mass (g/mol) Fusion point ( C) 5.7 Boiling point at 1 atm ( C) Solubility in watr at 20 C (g/l) 1.9 Dnsity at 20 C Adsorbnts (Natural Clay: NC and Activatd Clay: AC) Starting matrial natural clay was collctd from Elhamma-Gabs (south of Tunisia). Th prparation of th adsorbnt was as followd: 1000g of natural clay wr washd for 24 h with bi-distilld watr on a shakr at 1000 rpm, drid at 80 C for 24h, crushd and sivd[7]. Aftr ths stps, obtaind matrial is activatd by mtallic solution (frric chlorid) [11, 12]. On introduc in a ractor of 1 L capacity: -500 ml of bi-distilld watr; -A masss of NC (m NC ) and frric chlorid (m FCl3 ). Ths amounts ar addd as th ratio R m (m FCl3 / m NC) : 0.15 R m 1 (w/w). Th mixtur is puttr in agitation at 1000 rpm, at tmpratur T a (15 T a 75 C) and for tims t a (15 min t a 4 h). ph and conductivity (χ ) of natural clay and activatd clay solutions (1 g/l) wr analyzd by ph-mtr (HANNA instrumnts) and conduct-mtr (ino LAB) of laboratory rspctivly. Apparnt dnsity (ρ) of two matrials was analyzd by pycnomtri mthod (NFT Mthod B). Th chmical composition and principal physic-chmicals proprtis of th matrials ar prsntd rspctivly in tabl 2 and tabl 3. Tabl2. Chmical composition of NC and AC (Analyzd by Inductivly Coupld Plasma) Elmnt Masss composition (%) NC AC Al 2 O SiO FO MgO CaO Na 2 O MnO ZnO Humidity Tabl3. Principal physic-chmicals proprtis of NC and AC Proprtis Matrial NC AC Apparnt dnsity ρ(kg/l) ph Conductivity χ(µs/cm) Mthods Adsorption studis Adsorption studis wr conductd in a routin mannr by batch tchniqu. For batch xprimnts a variabl amount (50 m AC 600 mg) of AC wr placd into 250 ml flasks containing 100 ml solution with diffrnt initial concntrations ( mg/l) of nitrobnzn solution. Th flasks wr shackd on a shakr at 280 rpm with a constant shaking rat for th tim ndd to rach quilibrium from th prliminary kintic invstigation (4 hours) thn th sampl was filtrd on filtrs micro-pors of diamtr 0.45 µm and th nitrobnzn concntration was dtrmind. Th studis wr prformd at a constant tmpratur of 298K to b rprsntativ of nvironmntally rlvant conditions and at ph = 8[7]. Th amount of nitrobnzn adsorbd pr volum unit of solution onto AC is dtrmind by th diffrnc btwn th initial concntration (C 0 ) and th quilibrium concntration (C ). 63 P a g

3 Th amounts of nitrobnzn adsorbd pr gram of AC, q (mg/g), and fficincy of adsorption onto AC, at quilibrium, wr calculatd rspctivly from quations (1) and (2). ( C0 C ) V q (1) mac C0 C (%) 100 (2) C 0 Th amount of nitrobnzn adsorbd pr gram of AC at tim (t), q t (mg/g), was calculatd by quation (3). ( C0 Ct ) V qt (3) m AC Whr C t rprsnts th instantanous nitrobnzn concntration (mg/l) and V is th volum of nitrobnzn solution (ml) Analytical mthod Th concntration of nitrobnzn was dtrmind by high prformanc liquid chromatography (Agilnt 1100) quippd with Ultra Violt dtction at a wavlngth of 261 nm, using a hyprsil column G1316A (4 125 mm). Th injction volum was 20 µl and th mobil phas was a mixtur of acitonitril watr (80% v: 20% v) with a rat of 1 ml/min. Undr ths conditions, th rtntion tim of nitrobnzn in th column was 1.69 min. III. RESULTS AND DISCUSSION 3.1. Effct of activation tim on adsorption of nitrobnzn Figur1. Effct of activation tim on adsorption of nitrobnzn by activatd clays Conditions of adsorption: C 0 = 246 mg/l; ph = 8; N = 280 rpm; t q = 4 h; T = 25 C Th abov Figur shows th ffct of activation tim on adsorption of nitrobnzn by diffrnt activatd clays. It is obsrvd that th dgradation fficincis of nitrobnzn incrass with th dcras in activation tim for all th adsorbnt usd hrin. For th dgradation of nitrobnzn, all activatd clays prsnt similar volution of th rtntion capacitis vrsus doss. Th volution of high dgradation fficincy (η h ) vrsus activation tim at dos of 100 mg of AC is rprsntd in tabl 4. According to tabl 4, th optimum valu of activation tim of natural clay is 0.25h (15 min). Tabl4. High adsorption fficincy of nitrobnzn by activatd clays at diffrnt activation tim at dos of 100 mg ta (h) η h (%) P a g

4 3.2. Effct of activation mass ratio on adsorption of nitrobnzn Th ffct of frric chlorid-natural clay ratio on activation was studid at 25 C, with 15 g/l FCl 3, for 15 min. Th rsults ar shown in fig. 2. Conditions of adsorption: C 0 = 246 mg/l; ph = 8; N = 280 rpm; t q = 4 h; T = 25 C Whn th ratio was incrasd from 15 to 30% w/w, dgradation prformanc of nitrobnzn incrasd from 46.5 to 60.61% at 100 mg of activatd clay, an incras of about 14.11% implying a grat ffct on bnficiation of natural clay obtaind at th xpns of incrasd of pors du to formation of H + clay. Th kind of clays was an acid charactr which incrass his activity [13]. Efficincy of dgradation of nitrobnzn by diffrnt activatd clay dcrass whn activation ratio incrass from 50 to 100%. Th volution of high dgradation fficincy (η h ) vrsus activation ratio at doss of 50 mg and 100 mg of AC is rprsntd in tabl 5. According to tabl 5, th optimum valu of activation ratio of natural clay is 30%. Tabl5. High adsorption fficincy of nitrobnzn by activatd clays at diffrnt activation ratio of FCl 3 /Natural clay R m (%) m AC (mg) η h (%) Effct of activation tmpratur on adsorption of nitrobnzn Th ffct of tmpratur on activation of natural clay was invstigatd with 15 g/l FCl 3, 0.3 frric chlorid-natural clay ratio (w/w) for 15 min. Th rsults ar shown in fig P a g

5 Conditions of adsorption: C 0 = 246 mg/l; ph = 8; N = 280 rpm; t q = 4 h; T = 25 C Th abov figur shows that activation of natural clay by frric chlorid was improvd by dcrasing tmpratur. This was probably du to incrasd spd of th molculs in th systm which nhancd contact btwn clay surfac and frric chlorid [14]. Whn th tmpratur was dcrasd from 25 to 15 C, dgradation prformanc of nitrobnzn incrasd from to 79.62% at 100 mg of activatd clay, an incras of about 19.01% implying a grat ffct on bnficiation of natural clay obtaind at th xpns of incrasd of pors du to ractivity of frric chlorid in prsnc of hydrogn proxid including in stps of prparation of activatd clays [15, 16]. Th attack raction of natural clay by frric chlorid has ndothrmic charactr. Th volution of high dgradation fficincy (η h ) vrsus activation tmpratur at doss of 50 mg and 100 mg of AC is rprsntd in tabl 6. According to tabl 6, th optimum valu of activation tmpratur of natural clay is 15 C. Finally, th optimums conditions of activation of natural clay of Elhamma-Gabs by frric chlorid ar: -activation tim ta = 15 min; -activation ratio (FCl 3 /NC) R m = 0.3 (w/w); -activation tmpratur Ta = 15 C Kintic study of adsorption of nitrobnzn by activatd clay Effct of initial concntration of nitrobnzn As illustratd by fig. 4, th amount adsorbd incrass with th concntration of solution. Whn th initial nitrobnzn concntration was incrasd from 61.5 to 246 mg/l, th adsorption uptak of activatd clay incrasd. Th ffct of contact tim on th rmoval of nitrobnzn at initial concntrations 61.5 to 246 mg/l showd rapid adsorption of nitrobnzn in th first 60 min bcaus th adsorption taks plac primarily at asily accssibl surfac sits[1, 13]. And a hydrophobic intraction btwn adsorbnt and organic compounds may b attributd to th rapid adsorption rat [1]. Th adsorption rat dcrasd gradually and th adsorption rachd quilibrium in about 4 hours for all th initial concntrations usd. Th high fficincy of dgradation of nitrobnzn is 32.79%, 44.8% and 60.61% at concntrations 61.5, 123 and 246 mg/l rspctivly. Figur4. Effct of initial concntration of nitrobnzn on adsorption by activatd clay Conditions: t a =15 min; R m =0.3(w/w); T a =T = 25 C; m AC =100 mg; ph = 8; N = 280 rpm Kintic modls Svral kintic modls (diffusion on homognous surfac, diffusion pors, htrognous modl of diffusion and modl of Elovich) ar tstd on our xprimntal rsults in ordr to dscrib th mchanism of th procss of adsorption of nitrobnzn by activatd clay. Th psudo-first-ordr Lagrgrn quation is givn as [17]: 66 P a g

6 Ln( q q ) Lnq k t (4) t 1 Whr q and q t ar dtrmind by quations (1) and (3), rspctivly and k 1 is th rat of constant of psudofirst-ordr adsorption procss (min -1 ). Th slop and intrcpt of plots of Ln (q q t ) vrsus t wr usd to dtrmin th first-ordr rat constant k 1 and q. Th psudo-scond-ordr kintic modl by Ho and McKay [18], with th linar form: t q t 1 1 t (5) 2 k q q 2 Whr k 2 is th rat of constant of psudo-scond-ordr adsorption procss (g/mg min). If th psudo-scondordr is applicabl, th plot of t/q t vrsus t givs a linar rlationship, and thn k 2 and q can b calculatd from th slop and intrcpt of th lin. Th Elovich quation [19] is tstd with th linar form: 1 1 Ln( ) Ln( t) (6) q t Whr α is th initial sorption rat constant (mg/g min), and th paramtr β is rlatd to th xtnt of surfac covrag and activation nrgy for chmisorptions (g/mg). Th constant can b obtaind from th slop and intrcpt of th plot of q t vrsus Ln (t). Th intra-particl diffusion modl was tstd. Th modl is illustratd by quation (7) [20]: 1/ 2 C k int t (7) q t Whr k int (mg/g min 1/2 ), and C (mg/g) ar th intra particl rat constant, and constant of modl rspctivly. Th factor of corrlation R 2 of for quations and constants th kintics of ach modl ar prsntd in tabl 7. Tabl7. Constants of th kintic modls of adsorption of nitrobnzn by activatd clay Modl Constant of modl and corrlation cofficint k 1 (min -1 ) Lagrgrn q (mg/g) R k 2 (g/mg min) Psudo-scond-ordr q (mg/g) R α (mg/g min) 3.8 Elovich β (g/mg) R K int (mg/g min 1/2 ) Layr diffuss C (mg/g) R W can conclud that th rtntion of nitrobnzn by activatd clay is bttr rprsntd by scond-ordr kintic (fig. 5) with xtrm high valus of corrlation cofficint (tabl 7). But it can b also rprsntd by a diffusion intra particl modl. 67 P a g

7 3.5. Isothrm of adsorption Th adsorption isothrm is th variation at quilibrium of th quantity (q ) of compound adsorbd on a solid according to concntration of adsorbat (C ) in th liquid in contact, at a constant tmpratur q = f (C ). To dtrmin th typ and th natur of th adsorption isothrm of nitrobnzn by activatd clay, w varid th initial concntration of nitrobnzn from 35 to 246 mg/l. Th adsorption isothrm is illustratd in fig. 6. According to th fig. 6, th amount adsorbd incras with incrasing initial concntration of nitrobnzn (tabl 8). This isothrm is typ III. This typ shows a prsnc of hydrophobic intractions btwn nitrobnzn and activatd clay and an isothrm with transition from mono-layr to multi-layr [21, 22]. Efficincy of dgradation of nitrobnzn (η) by this tchnical at diffrnt initial concntration is rprsntd in tabl 8. In ordr to dscrib th adsorption isothrm, thr important mathmatic modls of isothrm ar slctd in this study, Frundlich, Dubinin-Radushkvich and Tmkin [22, 23, 24]. Tabl8. Efficincy of dgradation of nitrobnzn by activatd clay at diffrnt initial concntration C 0 (mg/l) η (%) Th Frundlich modl can b xprssd by this quation: 1 Lnq Lnk F LnC n (8) Whr K F and n F ar th Frundlich adsorption constants. Dubinin-Radushkvich (D-R) isothrm was usd to fit with th xprimntal data, and it can b rprsntd as: 1 Lnq Lnq m 2BRTLn (1 ) (9) C Whr q m is th maximum adsorption capacity (mg/g) and B is th D-R adsorption constant. F 68 P a g

8 Th Tmkin isothrm quation is givn as: q BLnA BLnC (10) Whr A and B ar th Tmkin adsorption constants. Corrlation cofficints and paramtr valus for th thr isothrms wr prsntd in tabl9. Tabl9. Valus of th usd isothrm paramtrs Isothrm modl Paramtr Corrlation cofficint R 2 Frundlich n F = K F = D-R B = mol/j q m = mg/g Tmkin A = B = mg/g Basd on th corrlation cofficint (tabl 9), th applicability of th isothrms was compard. Th xprimntal rsults indicat that th adsorption of nitrobnzn onto activatd clay followd Dubinin-Radushkvich (D-R) isothrm modl (fig. 7). Th thortical valu of th maximum adsorption capacity of activatd clay at quilibrium q m = mg/g is lightly suprior that xprimntal valu which is of mg/g. IV. CONCLUSION Activatd clay was producd from activatd natural clay using frric chlorid as a chmical activation agnt. Th adsorption bhavior of th producd activatd clay was tstd with nitrobnzn in aquous solutions. Th optimums conditions of activation of natural clay by this tchnical ar: activation tim ta = 15 min, activation ratio (FCl 3 /NC) R m = 0.3 (w/w) and activation tmpratur Ta = 15 C. Th adsorption of nitrobnzn by activatd clays rachd quilibrium in 4 hours. Th kintics of rtntion is bttr rprsntd by a scond ordr kintic. Th xprimntal rsults show an isothrm of typ III and fit to th Dubinin-Radushkvich modl. W found that with a initial concntration of nitrobnzn of 246 mg/l, a tmpratur of 298 K, a mixing vlocity of 280 rpm, a dos of 0.1 g adsorbnt/100 ml of solution (1 g/l) and ph = 8, th fficincy of rtntion rachd 79.62%. Th rmoval of nitrobnzn by activatd clay is much bttr that by natural clay only bcaus fficincy of tratmnt incrasd from 37.5% (conditions: C 0 = 246 mg/l, t q = 8 hours, ph = 8 and dos of natural clay 1g/L) with natural clay only [7] to 79.62% with activatd clay (conditions: C 0 = 246 mg/l, t q = 4 hours, ph = 8 and dos of activatd clay 1g/L). ACKNOWLEDGMENTS Th authors acknowldg GCT and FSG of Gabs for supporting this rsarch. Th authors acknowldg also, Chabbi. Asma, Kardamin. Manl, Elmasboub. Lila, Hmidi. Aff, Lhiaui Mouna and Bllazrg Houda for prforming som of th xprimntal work. 69 P a g

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