Preparation of Poly-Aniline-Magnetic Porous Carbon Composite for Using as Uranium Adsorbent

Transcription

1 Amrican Journal of Matrials Synthsis and Procssing 2017; 2(3): doi: /j.ajmsp Prparation of Poly-Anilin-Magntic Porous Carbon Mohamd Abdallah Gado, Ahmd Morsy Gology of Isotops Dpartmnt, Nuclar Matrials Authority, Cairo, Egypt addrss: (A. Morsy) To cit this articl: Mohamd Abdallah Gado, Ahmd Morsy. Prparation of Poly-Anilin-Magntic Porous Carbon Composit for Using as Uranium Adsorbnt. Amrican Journal of Matrials Synthsis and Procssing. Vol. 2, No. 3, 2017, pp doi: /j.ajmsp Rcivd: April 7, 2017; Accptd: April 24, 2017; Publishd: Jun 19, 2017 Abstract: Ric husk as on of th agricultural by-products has bn usd as a starting matrial for th production of porous carbon (PC), th obtaind porous carbon has bn modifid by poly anilin and magntizd to form poly anilin magntic porous carbon composit (PA-MPC). Th prpard PA-MPC has bn charactrizd and xamind for uranium adsorption from its prgnant solutions. Th ffct of th controlling paramtrs (ph; Contact tim, tmpratur, initial uranium concntration, and adsorbnt dosag) hav bn optimizd. Th obtaind rsults indicat that th adsorption is ph dpndant. Th quilibrium data wr wll dscribd by langmuir isothrm with thortical capacity 94.3 mg/l at room tmpratur. Ths rsults dmonstrat th potntial us of this adsorbnt for uranium ions rmoval from its prgnant solutions. Kywords: Agricultur Wast, Ric Husk, Poly-Anilin, Uranium, Adsorption 1. Introduction Ric is considrd as on of th most important agricultur product all ovr th world. It plays an important rol in food municipal consumption. Through ric rfining procss, ric husk is obtaind as a by- product, which is charactrizd by low humidity and simpl opration [1]. Ric husk ash charactrizs by th prsnc 87-97% silica [2] as wll as bing highly porous and light in wight, also its surfac ara is vry high. Svral studis hav bn prformd on ric husk, whr many rsarchrs usd ric husk in diffrnt applications rlaying on its chmical and physical proprtis. From such uss ar as a ful in powr plant [3 and 4], formation of activatd carbon [5], sourc of silica and silicon compounds [6 and 7], insulating fir brick using RH [8], also in th manufacturing of building matrials [9] and it has bn usd ful in lctricity gnrating [10]. Th burning of husk ld to th formation of ric husk charcoal, which has multilatral uss. Carbon and silica ar th main constitunts of ric husk and ric charcoal, so both ric husk and ric charcoal can b usd as starting matrials for th prparation of diffrnt adsorbnt. Th prparation of activatd porous carbon from ric husk passs through two stps, carbonization thn activation, th latr can b don ithr physically and\or chmically [11]. Th aim of this work is to mploy ric husk in th prparation of porous carbon, th latr has bn usd in th prparation of magntic poly-anilin porous carbon composit. Th prpard composit has bn tstd as adsorbnt for uranium ions rmoval. In this study, IR tchniqu, TGA tchniqu and BET thory hav bn applid to dtrmin th physical charactrization of prpard adsorbnt. Batch adsorption tchniqu has bn don to xamin th prpard composit for uranium adsorption. Equilibrium isothrms as wll as kintic and thrmodynamic studis for U (VI) adsorption hav bn don. 2. Matrials and Mthods 2.1. Ragnts Th chmicals usd for diffrnt xprimnts ar of analar grad. A stock solution from uranium (VI) (1000ppm) has bn prpard by dissolving 2.11 gm of UO 2 (NO 3 ) 2.6H 2 O in d-ionizd watr bsids adding 1 ml of concntratd HNO Porous Carbon Prparation Th porous carbon has bn prpard from ric husk as follow: th ric husk has bn washd, drid and carbonizd at 450 C in vacuum with nitrogn flow rat of 200 cm 3 /min.

2 33 Mohamd Abdallah Gado and Ahmd Morsy: Prparation of Poly-Anilin-Magntic Porous Carbon Th carbonizd product was hatd with adquat wight from potassium hydroxid at 400 C for 60 min in ordr to dhydrat th mixtur and incras th surfac ara. Th mixtur was activatd by incrasing th tmpratur in th rang from 650 to 850 C for about on hour. Finally, th activatd product was ground, washd with watr and drid at 120 C to form th porous carbon (PC) Prparation of Magntic Porous Carbon Th magntic porous carbon has bn prpard using th modifid mthod of Massart [12], whr about 100 ml from frric solution (0.2M) has bn mixd with 100 ml from frshly prpard 0.1 M frrous solution undr stirring with tn gram from th producd porous carbon. Aftr that, about 100 ml from ammonia solution (30%) has bn pourd to th F +3 /F +2 /PC mixtur and stirrd vigoursly. A black prcipitat was formd which was lft to crystalliz for 30 min undr stirring. Th crystallizd product was thn washd with doxygnatd watr undr magntic dcantation until ph of suspnsion bcam blow 7.5. Th prcipitat was drid at room tmpratur to giv a black powdr and markd as M- PC Polyanilin / Magntic Porous Carbon Prparation On gram from KIO 3 had bn addd to 100 ml from sulphuric acid (1 M) and stirrd for about 30 min. to form homognizd solution. Thn th mixtur and 3 ml from frsh distilld anilin monomr wr mixd with about two gram from porous carbon. Th raction was prformd for about 5 hrs at room tmpratur with stirring in ordr to maintain th complt polymrization of anilin. Aftr that, th rsultd polymr was filtrd on filtr papr, washd svral tims with 0.2 M hydrochloric acid, thn with acton to sparat th oligomrs and impuritis [13]. Th final product was drid in ovn at 60 C tmpratur for about 24 h and markd ad PA-MPC Matrials Charactrization Th prpard porous carbon and poly-anilin porous carbon composit has bn charactrizd using th following tchniqus: (1) Fourir Transform Infrard Spctromtr (FTIR): (FTIR) modl Thrmo Scintific Nicolt IS10, Grmany has bn usd for th dtrmination of th structural charactristics of th prpard sorbnt (2) Th N 2 adsorption dsorption isothrms hav bn usd to prdict th por siz distribution. Th spcific surfac ara (SBET) has bn rcognizd from th linar sgmnt of th N 2 adsorption isothrms by applying Brunaur Emmtt Tllr (BET) thory. (3) Thrmal stability and th functional group contnt 2.6. Batch Adsorption Exprimnts To figur out th contribution of th controlling factors on th adsorption prformanc, svral xprimnts hav don using fixd amount from PA-MPC (0.1 gm), placd on a cappd flask which was st on a watr bath shakr. Each of th controlling factors has bn studid alon by varying its rang and kping all th othr factors fixd. Th rangs of ach factor ar as follow: ph from 1 to 9, contact tim from 15 to 240 min, initial concntration from 50 to 1400 mg/l, tmpratur from 25 to 80 C, and solid dosag from 0.05 to 0.4g. Th ph was maintaind using 0.1 M from HCl and /or 0.1 M from NaOH. Th ffct of compting ions was invstigatd using diffrnt concntrations from ths ions ranging from 50 to 500 mg/l and ach has bn studid solly. Th adsorbd uranium amounts obtaind from diffrnt invstigation ar dtrmind using th following function q ( C ) C V o o = (1) M Whr q is th adsorption amount in mg/g, M is th wight of th adsorbnt (g), V is th volum of solution (L) and C o and C ar th initial and quilibrium concntrations of mtal ions in solution Adsorption Isothrm To dscrib th adsorption bhavior of U (IV) ions onto PA-MPC, classical isothrm modls hav bn studid. Ths modls ar: Langmuir Adsorption Isothrm [14]: which dpicts th formation of a monolayr adsorbat on th outr surfac of th adsorbnt [15] using th following quation: C C 1 = + (2) q Q Q b m m Whr Q m is th saturatd monolayr adsorption (mg/g), b is th Langmuir constant rlatd to th affinity of binding sits and is a masur of th adsorption nrgy (ml/mg). Frundlich Adsorption Isothrm [16] which figurs th adsorption charactristics for th htrognous surfac [17] by applying linarizd quation: log q = 1 log K + f n log C (3) Whr K F is th adsorption capacity (mg/g) and 1/n is th Frundlich constant indicating adsorption intnsity Kintics Study To invstigat th mchanism of adsorption, psudo first ordr and psudo scond- ordr modls hav bn stimatd. Ths modls can b xprssd in linar forms rspctivly [18 and 19] Psudo first ordr: ln Psudo scond ordr: ( t ) ln 1 q q = q K t (4)

3 Amrican Journal of Matrials Synthsis and Procssing 2017; 2(3): t q t = 1 t K q + q (5) 2 Whr q t and q ar th amounts of thorium ions adsorbd (mg/g) at tim t (min) and at quilibrium tim, rspctivly; k 1 (min 1 ) and k 2 (g/mg min) ar th psudo-first-ordr and th psudo scond- ordr sorption rat constant, rspctivly 2 3. Rsults and Discussion 3.1. Matrials Charactrization FTIR Spctroscopy Th figurd data of FT-IR for PA-MPC prsnts in figur t (1) show that, paks at 1566 and 1478 cm 1 ar corrsponding to quinon and bnzn, slightly shiftd ringstrtching dformations of PANI ar also dtctd in th nano-composit. Th band at 1304 cm 1 blongs to th C-N strtching of a scondary aromatic amin strngthnd by protonation of PANI, and is also prsnt in spctra of composit. Furthrmor, th charactristic paks of PANI ar sn at 2926 cm 1 (N H in bnznoid ring) and 800 cm 1 (out-of-plan dformations of C H). Ths paks can also b sn in th spctra of PAn/RHC nano-composits. All bands in nano-composits ar slightly shiftd, which indicat that thr is som intraction btwn PANI and th mtal oxids of RH. Th most important thing on th chart B is th apparanc of uranium pak on 920 cm 1. Figur 1. FT-IR spctra of PA-MPc bfor and aftr uranium ions adsorption Raman Spctra Th scond tool usd for composit charactrization is Raman spctroscopy which is considrd on of th most usful tools for carbonacous matrials charactrization. From figur (2), th typical G-band in Raman spctrum for PC consists of a strong lin situatd at 1574 cm -1, th band of PC has a shouldr xtnding to highr wav numbrs for disordr carbons additional bands appars at 1355 cm -1 (D1-band) [20], Th scond-ordr Raman band is assignd to ovrton at 2643 cm -1 broadnd with incrasing disordr. Aftr th polymrization of PC with PANI, th spctrum of this polymr dominats in all sampls. This obsrvation confirms that polymrization occurs btwn PC and PANI. Th paks in th spctra ar typical of protonatd PANI and ar locatd at1593, 1504, 1330, and 1171 cm -1 [21]. Thir positions rmain practically unchangd aftr polymrization with obsrvd incras of th intnsity of th paks. Figur 2. Raman spctra of prpard adsorbnt.

4 35 Mohamd Abdallah Gado and Ahmd Morsy: Prparation of Poly-Anilin-Magntic Porous Carbon Thrmal Stability Studis Thrmo gravimtric analysis (TGA) of PC and PANI show dcomposition in th tmpratur rang from 190 to 590 C and rsidual wight aftr this tmpratur is ngligibl (figur 3), whil in th cas of PC/PANI composit shows thrmal stability up to 640 C and bcom compltly dcomposd abov 750 C, th TGA profil also confirmd that a significant amount of th functional groups hav bn chmically graftd on th carbon surfac, and th rsulting matrial has xcllnt thrmal stability [22 and 23]. Figur 3. Thrmo gravimtric analysis of prpard adsorbnt Surfac Ara and Porosity Figur (4) shows th N 2 adsorption isothrms and th corrsponding por siz distribution curvs of th porous carbon and th PC/poly-anilin composit sorbants, rspctivly. Th BET surfac ara, total por volum and por siz of ths matrials ar prsntd in tabl 1. It is notworthy that whn poly-anilin was introducd into porous carbon substrats, th BET surfac ara and total por volum of PC/poly-anilin significantly dcrasd to approximatly half th lvl of porous carbon. Figur 4. N 2 adsorption-d-sorption isothrms for th porous carbon and porous carbon/ poly-anilin composit. Figur (5) shows that th valu of th dv/dd gratly dcrasd in th por siz rang of 1 20 nm, but th pak shiftd slightly to a lowr valu as poly-anilin was incorporatd into Porous carbon. Ths rsults suggst two possibilitis: (1) th surfac of th nano-pors of porous carbon is modifid with poly-anilin or (2) som parts of th nano-pors of porous carbon ar filld with poly-anilin.

5 Amrican Journal of Matrials Synthsis and Procssing 2017; 2(3): Figur 5. Th corrsponding por siz distribution for th porous carbon and porous carbon/ poly-anilin composit. Tabl 1. Th BET surfac ara, total por volum and por siz of porous carbon and porous carbon/ poly-anilin composit. Sampl S BET(m 2 /g) V t(ml/g) V micro(ml/g) V <1nm(ml/g) Porous carbon PA Composit Effct of Controlling Factors Effct of ph Th solution ph is considrd as th most dominant factor that has a clar ffct on th adsorption phnomna in most cass, bcaus ph not only affcts th solubility and spciation of mtal ions in solution but also on th nt charg of th adsorbnt. Th uranium spcis found in th solution dpnds on th ph as wll as th composition of th solution [24]. Th plottd rsults in figur (6) assur that th solution ph is a controlling factor in th uranium adsorption onto th surfac of PA-MPc. In th high acidic mdia th uranium adsorption is minimum (ph 1), with th incras in th ph from 2 to 5, th prcnt of adsorption incrass and th maximum adsorption has bn attaind at ph 5. With th incras in th ph of th solution th adsorption prcnt dcras (figur 6). Figur 6. Effct of ph on uranium ions adsorption onto PA-MPC surfac.

6 37 Mohamd Abdallah Gado and Ahmd Morsy: Prparation of Poly-Anilin-Magntic Porous Carbon Th adsorption onto PA-MPC occurs mainly through two ways: physical (which is back to th proprtis of th adsorbnt surfac) and/ or chmically through complxation with th functional group (mainly oxygn-containing groups) on th carbon surfac which is affctd by th solution ph. Complxation playd an important rol whr at lowr ph, th surfac functional groups linkd to th H +, making ths inaccssibl for uranium ions. With incrasing th ph valu, th d-protonation of th functional groups providd th chanc to mak a complx with uranium ions rsulting in highr adsorption capacity. Similar rsults had bn obsrvd for uranium adsorption on hmatit, and amorphous iron hydroxid [25 and 26] Effct of Initial Uranium Concntration Th ffct of initial uranium concntration on th adsorbd quantity undr thr diffrnt tmpratur has bn shown in figur (7). It can b sn from th figur that th prcnt of adsorbd uranium dcras with th incras in th uranium concntration at diffrnt tmpratur dgrs. This may b back to th following, at lowr initial concntrations; sufficint adsorption sits ar fr for mtal ions adsorption, which givs an indication that th fractional adsorption is mtal ions initial concntration indpndnt. At highr concntrations, th uranium ions ar rlativly highr compard to availability of adsorption sits. Hnc, th adsorption prcnt dpnds on th initial mtal ions concntration and dcrass with incras in initial mtal ions concntration. Also th obtaind rsults show that th tmpratur has a positiv ffct on th uranium adsorption prcnt. Figur 7. Effct of initial uranium concntration on uranium ions adsorption fficincy onto PA-MPC. Adsorption Isothrms Th obtaind rsults of uranium adsorption isothrms tabulatd in tabl (2) show that undr th xprimntal conditions listd prviously, th obtaind data fits wll with langmuir isothrm rathr than frundlich isothrms, although th corrlation cofficint (R 2 ) for frundlich isothrms is abov 0.99, but th xprimntal data hr is th controlling factor. Th maximum adsorption valu obtaind in accordanc to langmuir is 94.3 mg/g at room tmpratur. Th obtaind valu of n in frundlich isothrm (tabl 2), is lss than 1 indicating normal adsorption [27]. Tmpratur Tabl 2. Paramtrs for plotting Langmuir, Frundlich adsorption Isothrms of uranium ions onto PA-MPC. Langmuir pararmtrs Frunlich pararmtrs q max(mgg 1 ) B (Lmg -1 ) R 2 quation K f (mg g- 1 ) n R 2 quation Y=0.0106x y = x Y=0.0097x y = x Y=0.0085x y = x Effct of Adsorbnt Dos In ordr to invstigat th ffct of adsorbnt dosag on uranium adsorption, svral xprimnts hav bn prformd with constant uranium concntration (1500 mg/l) and diffrnt PA-MPC dosag ranging from to g/l. Th obtaind xprimntal rsults of adsorption plottd in Fig. (8) show that th adsorption capacity incrasd with incrasing adsorbnt amount and thn bcam constant indicating that 0.05 g for vry 20 ml was th optimum adsorbnt dosag and will b usd in th following sorption xprimnts.

7 Amrican Journal of Matrials Synthsis and Procssing 2017; 2(3): Figur 8. Effct of adsorbnt dosag on uranium adsorption fficincy onto PA-MPC Effct of Contact Tim Figur (9) shows th influnc of contact tim on adsorption fficincy of PA-MPC for uranium ions. Th xprimntal data indicat that, th adsorption capacity of PA-MPC incrasd by incrasing contact tim. This is probably du to th highr contact btwn th surfac of PA-MPC and uranium ions [28]. Th obtaind data also rvals that th initial uranium concntration has a significant rol on th adsorption capacity, whr by incrasing th concntration of uranium ions th adsorption capacity incrass. At all concntrations th systm rachd quilibrium stat aftr 60 minut. Figur 9. Effct of contact tim on uranium ions adsorption fficincy onto PA-MPC. Adsorption Kintics Th obtaind rsults of uranium adsorption kintics listd in tabl 3, show that th corrlation cofficint (R 2 ) of th psudo-scond-ordr ar 0.98, 0.98 and 0.95 and th thortical capacity ar 49,104.1 and mg g -1 which is clos to th xprimntal valu for th invstigatd concntrations 100, 400 and 600 mg g -1 rspctivly. Whil th thortical capacity calculatd from psudo first ordr is far away from th ral xprimntal capacitis. Ths rsults indicat that th adsorption procss of uranium ions on PA- MPC can b xprssd by psudo-scond-ordr kintic modl.

8 39 Mohamd Abdallah Gado and Ahmd Morsy: Prparation of Poly-Anilin-Magntic Porous Carbon Tabl 3. Kintic modl paramtrs applid to uranium ions sorbd onto PA-MPC. concntration First ordr Scond ordr mg/l q (mgg -1 ) K 1 (min 1 ) R 2 quation q (mgg -1 ) K 2 (g mg- 1.min -1 ) R 2 quation y = x * y = x y = x * y = x y = x * y = x Influnc of Coxisting Cations Th adsorption bhavior of uranium ions in th prsnc of diffrnt cations lik Ca 2+, Na +, F 3+, Mn 2+ and Mg 2+ has bn tstd using fixd concntrations of ths cations (100 mg/l). Adsorption xprimnt has bn prformd using ths cations gathrd togthr and th xtraction fficincy has bn dtrmind. Th obtaind rsults show that ths cations hav no influnc on uranium adsorption fficincy, whr th adsorption fficincy is almost th sam 92 % xcpt for iron which is slightly incrasd to rach 94 %. This may b back to th following: F 3+ has also th capacity of adsorption. From this point of viw, adsorbd F 3+ on PA- MPC has rol in th adsorption procss. Ths rsults is in agr Kütahyalı and Eral [29], whr thy found that F 3+ has a positiv ffct on th uranium adsorption by using chmical modifid activatd carbon Influnc of Coxisting Anions Th adsorption bhavior of uranium ions in th prsnc of diffrnt anions lik Cl -, CO 3 2-, HCO 3 -, SO 4 2-, OH - and NO 3 - has bn xamind. Th invstigatd anions concntrations hav bn fixd at 100 ppm and th ph of th solution was kpt constant at 5. Sodium ion was usd as th cationic componnt for th invstigatd anions. Th obtaind rsults show that PA- MPC show good affinity for uranium xtraction vn in th prsnc of high concntration of anionic complxing agnts and common lctrolyt spcis th uranium xtraction fficincy was 20, 92, 90, 55, 95 and 72 % for th invstigatd anions CO 3 2-, HCO 3 -, SO 4 2-, OH - and NO 3 - rspctivly. Th prsnc of som anions can nhanc th adsorption capacity by pairing with th uranium spcis, hnc, rducing th rpulsion btwn adjacnt uranium molculs adsorbd on th surfac. This nabls th carbon to adsorb mor of th positiv uranium ions sinc th rpulsiv forcs btwn th surfac and uranium ions and rpulsiv forc among positiv uranium ions ar rducd. It has bn noticd that, although carbonats ions ar th most known anions which intrfr with th sorption of U (V1) du to th formation of stabl tricarbonat complx, UO 2 (CO 3 ) 3 4-, but it did not intrfr with th uranium adsorption at ph 5. This can b xplaind as follow: for ph highr than 7.5 and ph lowr than 3.5, th uranium complxs with phosphats and carbonats prdominat. In th rgion btwn 5.5 and 7.5, th prdominant spcis wr th polynuclar hydroxocomplxs whil for 3.5 < ph < 5.5, th uranyl ion was th major uranium spcis formd [30]. D-sorption and rusability On of th paramtrs usd in th judgmnt of th prpard adsorbnt is its rgnration or rusability ability in ordr to improv its cost ffctivnss for russ in multipl cycls. As dsorbing agnt, HCl and H 2 SO 4 solutions wr usd for dsorbing prviously adsorbd U (VI) ions onto PA- MPC. Various concntrations from HCl and H 2 SO 4 ranging btwn and 0.2 M wr tstd for adsorbd U (VI) ions lution from PA-MPC. It was found that that HCl was bttr than H 2 SO 4 as dsorbing agnt. Th obtaind U (VI) d-sorption prcnt was 70.1, 89.2, 98.2, 98.5 and 98.9% with 0.01, 0.05, 0.10, 0.15 and 0.2 moll -1 HCl, rspctivly. Thrfor, th bst optimum concntration was st as 0.1 mol L - 1 in trms of conomical procss. Th rgnration-rus proprty is important for th application of adsorbnts in ral work, bcaus an appropriat adsorbnt should prsnt not only xcllnt slctiv adsorption capability but also rgnration rus proprty. In this papr, th rusability of PA-MPC composits was invstigatd by washing with 0.1 mol/l HCl and rinsd with watr thoroughly Th rgnratd PA-MPC composits showd similar rmoval prcntag of U (VI) as compard with pristin PA- MPC composits. It indicats that PA-MPC composits can b asily rgnratd by trating U (VI)-loadd PA-MPC composits with convntional acidic solution (0.1 mol/l HCl). Morovr, ths high adsorption capacitis of rgnratd PA- MPC composits wr kpt vn aftr (at last) six cycls of rgnration rus applications. 4. Conclusion Poly-anilin magntic porous carbon composit has bn prpard, charactrizd and xamind for uranium adsorption from its prgnant solution. Th controlling factors hav bn dtrmind and th obtaind rsults rval th following: th adsorption of uranium ions onto PA-MPC is ph dpndnt with maximum adsorption at ph 5 and raching th quilibrium aftr 60 minuts. Th xprimntal maximum adsorption capacitis of PA-MPC is found to b 94, 103 and 117 at 298, 313 and 343 K rspctivly, which indicats that th tmpratur has a positiv ffct on uranium adsorption. HCl can b usd as dsorbing agnt for uranium ions from th surfac of PA-MPC. Rfrncs [1] P. Jintanawasan, W. Clowutimon, and P. Assawasangrat, Adsorption of congo rd by ric husk, prsntd at th TIChE Confrnc, Songkhla, Thailand, (2011), [2] M. Rozain, S. P. Ngo, A. A. 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