Evaluation of the absorption capacity of the natural clay from Bikougou (Gabon) to remove Mn (II) from aqueous solution.

Transcription

1 Vol. (),, 5-56 Evaluation of th absorption capacity of th natural clay from Bikougou (Gabon) to rmov Mn (II) from aquous solution. F. Eba * ; S. Guu ; A. Eya A-Mvongbot ; J. A. Ondo ; B. K. Yao ; J. Ndong Nlo ; R. Kouya Biboutou. Laboratoir Pluridisciplinair ds Scincs (LAPLUS) d l Ecol Normal Supériur d Librvill BP 79 Librvill (Gabon).. Laboratoir d procédés industrils, d synthès t d l nvironnmnt, Départmnt d Géni Chimiqu t Agroalimntair, INP HB BP 93 Yamoussoukro (Côt d Ivoir). Abstract : Th vntual us of th clay from Bikougou as an adsorbnt for th rmoval of mtal ions such as mangans, from aquous solution, was invstigatd by th man of batch tchniqu. Th rsults of adsorption wr fittd to th Langmuir, Frundlich and DKR modls. Satisfactory agrmnt btwn xprimntal data and th modl prdictd valus was xprssd by th corrlation cofficint (R ). Th Langmuir modl rprsntd th adsorption procss bttr than Frundlich and DKR modls, with corrlation cofficints (R ) valus rangd from.97 to.99. Th adsorption capacity (q m ) calculatd from Langmuir was mg/g for Mn (II) at ph 4 at 38K. Th intraction adsorbat-adsorbnt was found to b accompanid by positiv valus of nthalpy, ntropy and ngativ valus of Gibbs fr nrgy. Th kintics of Mn (II) ions adsorption followd th psudo scond-ordr modl, bcaus of its bst corrlation cofficints (rangd from.97 to.999) and highr agrmnt btwn q and q xp. Kywords: clay, adsorption capacity, isothrm psudo-scond-ordr. I. Introduction Havy mtals ar thrown out from production procsss of many industris. Mtallurgical, hydromtallurgical, and pyromtallurgical tchnologis, giv ris havy mtals in thir fflunts (Wojtowicz t al., ()). Th prsnc of havy mtals in aquatic nvironmnt bcaus of thir toxic natur and othr advrs ffcts on rciving cosystms has bn of grat concrn to scintific community (.g., Bin Yu t al., and Ahmad t al., 9). It follows that havy mtals nd to b rmovd bfor th fflunts stockd at adaptd sits or rvrsd at rivrs. Th tratmnt of rich havy mtal aquous solutions is ralizabl by man of many mthods including: ion xchang, chmical prcipitation, ultrafiltration, lctrochmical dposition, among which, adsorption on appropriat adsorbnt ( low cost and abundanc of th lattr) is on of th most fficint in trms of simplicity and fasibility of opration and low consumption of nrgy (Almida t al., 9). Adsorption procss, known sinc th 7 th cntury, charactriss som porous matrials to b capabl to adsorb gas or chmical spcis into solutions (Frnands t al., 7). During adsorption procsss, pollutants ar fixd at th surfac of th adsorbnts, sparating thm from liquid phas. Adsorption capacitis of many adsorbnts hav bn valuatd, such as sugar bt pulp and sawdust (.g., Ajmal t al., 998 and Chung t al., 99), coconut shll (Skar t al., 4), rd mud (Apk t al., 998), husk (Gupta t al., 6), doild soya (Gupta t al., 8), activatd carbon (Boubrka t al., 6). Clay matrials hav alrady bn shown to hav high adsorption capacity, which may vn xcd that of activatd carbon undr th sam conditions of tmpratur and ph, bcaus of thir high spcific surfac ara, high cation xchang capacity, Brönstd and Lwis aciditis and positiv or ngativ surfac chang against ph (Lin t al., ). Many studis hav bn rportd on th us of clays for mtal ions rmoval from aquous solutions: Zn(II) with natural bntonit (Mllah t al., 997); Zn(II), Cd(II), Pb(II), with raw smctit (Wojtowicz t al., ), Pb(II) with carbonat rich illit (Li t al., ), Pb(II), Cd(II) and Ni(II) with montmorillonit and kaolinit (Gupta t al., 8), Cd(II) and Zn(II) with montmorillonit (Bytia t al., 996), Pb(II), Ni(II), Cr(VI) and Cu(II) with palygorskit (Potgitr t al., 6), Cd(II) with palygorskit (Wang t al., 7), Cu(II) with kaolinit (Alkan t al., 8), lad(ii) with bntonit (.g. ISSN:

2 Vol. (),, 5-56 Ayari t al., 7 and Zhu t al., 8), Cd(II) with bntonit (Panday t al., 988), Pb(II) with palygorskit (Qiaohui Fan t al., 9), Cu(II) and Cd(II) with bntonit (Karapinar t al., 9), Ni(II) and Cu(II) with montmorillonit (Isagbmi t al., 9) and various forms of modifid clays also hav bn usd (.g. Zhu t al., 998 and Krishna t al., ). Th purpos of th prsnt study is to provid adsorption capacity of a natural mixtur kaolinit, montmorillonitillit sampl of clay from Bikougou dposit (Gabon 37 E and 58 N) to rmov Mn (II) from aquous in a singl batch systm undr various conditions. II. Matrials and mthods. II.. Adsorbnt. X Rays and chmical analyss xprimnts prformd at Nancy Univrsity (Franc) hav bn compltd by thos on dtrmination of spcific surfac ara (SSA), according to mthyln blu mthod (Pham Thi Hang t al., 97), cation xchang capacity by using ammonium actat mthods rspctivly (Rémy t al., 976) acid and alkalin surfac functional groups by mans of Bohm titration (Rockstraw, ) and point of zro charg with th mploymnt of potntiomtric titration (Isagbmi t al., 9). II.. Adsorbat and aquous solution. Mn (II) (MnCl, 4H O, MW 97, 9g.mol - ) was usd as th adsorbat in this study. Obtaind from Prolabo (Analytical grad), it was usd without furthr purification. Aquous solutions of Mn (II) wr prpard by dissolving an accuratly wighd amount of MnCl, 4H O in distilld watr to achiv concntrations of Mn (II) (rangd from 9mg/L to mg/l). II.3. Adsorption procdur. Th adsorption of Mn (II) ions on to clay from Bikougou was studid by th man of batch tchniqu. Th procdur usd for this study is dscribd as following: a known wight (.5 mg) of clay was quilibratd with 5 ml of th spikd mangans solution of known concntration, in a stoppd propyln flask, at a fixd tmpratur and in a thrmostatic shakr for a known priod tim. Aftr th quilibration using a constant stirring spd, th suspnsion was filtrd out and analysd for its mangans concntration, using atomic adsorption spctromtr (Analyst Prkin Elmr). Th ffct of svral paramtrs such as ph, contact-tim, initial concntration of mangans solutions and tmpratur on th adsorption was studid following diffrnt sts of xprimnts: Effct of ph: Clay: 5 g/l; Mn (II): 3.5 mg/l; tmpratur: 3K; intraction-tim: 45 min; ph: -8 and units intrvals. Effct of initial Mn (II) concntration and adsorption isothrm: Clay: 5 g/l; tmpratur: 38K, 33K and 38K; contact-tim: 45 min; ph: 4; Mn (II) solution: 9, 3, 3, 38, 67, 83, 98, 7 mg/l. Kintic studis: Clay: 5 g/l; tmpratur: 38K, 33K and 38K; Mn (II): 67 and 83 mg/l; ph: 4; intraction-tim: 5,, 5, 5, 35, 45 min II.4. Calculs. Th prcnt adsorption (% ads) and th amount of Mn (II) ions adsorbd pr unit mass of adsorbnt (q t ) wr calculatd by using rspctivly th following quations: and C C t (% ads) = C (i) ISSN:

3 Vol. (),, 5-56 q t = C V C t (ii) m whr C and C t ar th initial Mn(II) concntration and Mn(II) concntration at any tim contact of intraction adsorbat-adsorbnt; V is th volum of mangans solutions and m is th mass of clay. III. Rsults and discussion. III.. Charactrization of adsorbnt Th rsults concrning chmical analyss, modal composition, cation xchang capacity (CEC), spcific surfac ara (SSA), ph of point zro charg (PZC), acid and alkalin surfac functional groups, ar rportd in tabls, and 3 rspctivly; Th XRD pattrns of crud clay and clay fractions nabld us to dtrmin th qualitativ minralogical composition of th matrial. From X-ray diffraction pattrns (figurs and ), it appars that it compriss th following minrals: - Kaolinit; its ray at 7.9 Å in untratd clay is shiftd at.4 Å by hydrazin saturation (figur, curv H). Th lattr disappars on hating at 49 C (figur, curv C). In figur, othr rays of kaolinit ar at 3.59 Å,.56 Å and.73 Å; - Dioctahdral smctit: typical rays ar at 4.93 and 4.45 Å (figur ) or at 5.3 Å (Figur, curv U); basd on its d at 4.93 Å or at 5.3 Å, w suggst that calcium is th main intrlayr cation (Dr t al., 99). Th tratmnt with thyln-glycol shiftd th d at 7 Å (Figur, curv G) whras on hating this d is rducd to 9.8 Å (figur, curv C); - Fldspars ar rvald by rflctions at 3.8, 3., 4.4 Å. Th pattrn is typical of andsin or albit. - Illit-lik matrials displaying a d at 9.97 Å (figur ) or at. Å (figur, curv U), which is not affctd by th abov-mntiond tratmnts (figur ). Othr illit rays ar at 5. Å, 4.45 Å, 3.88 Å, 3.65 Å, 3.34 Å,.87 Å,.56 Å in figur. - Quartz; 3.34 Å, 4.7 Å,.8 Å ; - Calcit (3.5 Å, 3.86 Å). Whn th matrial is acid tratd (HCl, 5 %), ths rays disappar (figur ) ; - anatas; (3.5 Å,.37 Å,.89 Å); - maghmit; (.93 Å,.56 Å); - Ba, Sr-hydroxyapatit (4.45 Å, 3.76 Å,.8 Å,.3 Å,.93 Å). By combining th X-ray rsults and th whol-rock chmical analyss, th modal compositions of untratd clay can b stimatd according to a constraind multi-linar calculation as rportd by Njopwouo, (984) and Yvon t al., (99) using th following basic formula: n T(a) Mi Pi(a) whr T(a) = wt.% lmnt "a" in th sampl; Mi = wt.% minral "i" in th sampl, and Pi(a) = proportion of lmnt "a" in th minral "i". III.. Effct of ph. Th ffct of ph on th adsorption of Mn (II) ions on to clay from Bikougou was studid by varying it in th rang of -8 as shown in tabl 4. Th uptak of Mn (II) ions dpnds of ph, it incrass with th incras of ph, from to 8: (i) substantially from to 4, (ii) vry slowly from 4 to 6 and (iii) substantially again from 6 to 8. Ths rsults dmonstratd th importanc of ph on th mchanism govrning th adsorption charactristics of havy mtals on clays, known as givn by dissolution (wak ph), ion xchang adsorption and prcipitation (high ph) (Ho t al., ). Many studis rvald that th rmoval fficincy of havy mtals by clays dcrass at lowr ph valus ( ph< 4) and incrass at ph valus up of 4 (.g., Hasany t al., 998 ; Juang t al., 997 and Erdm t al., 4). This bhaviour is confirmd at this study. Th basis mchanism that govrns th adsorption charactristics of clay from Bikougou (i) at lowr ph than ph of point zro charg (PZC = 3. ±.) is adsorption and (ii) at highr ph than ph of point zro charg is adsorption and ion xchang. So at ths ph lvls (4-8), th alkalin, alkalin arth and acid cations ISSN:

4 Vol. (),, 5-56 locatd in th xchangabl sits of clay (Na +, K +, Ca +, Mg +, Al 3+, F 3+, H + ) ar rplacd by Mn (II) ions prsnt in prpard aquous solution. It appars that, as ph changs, th surfac functional also changs and th sorption of chargd spcis is affctd. It is convnint that at lowr ph valus (ph< PZC), whr thr is an xcss of H 3 O + ions, in th solution, a comptition xists btwn th positivly chargd hydrogn ion and Mn (II) ions for th availabl sits on th ngativly chargd clay surfac, according to Mathialagan t al., (). POH + H + + POH () This positiv surfac charg intracts rpulsivly with approaching Mn (II) cations and prvnts thm from raching th surfac and thus, th adsorption was not much at low ph. At highr ph (ph > PZC), th clay surfac bcoms ngativly chargd bcaus of dprotonation of functional group favouring Mn + uptak POH + OH - PO - + H O () As th ph incrass (4-7) and balanc btwn H 3 O + and OH - givs OH - xcss, mor of Mn (II) ions in th solution ar adsorbd on th ngativ clay surfac and thus th rmoval prcntag of Mn (II) ions adsorbd incrass. Whn th ph bcoms alkalin (ph> 7) possibl prcipitation of insolubl trioxid Mn O 3 may occur as highr mtal rmovd. From this considration, th xprimnts on th adsorption of Mn (II) ions on clay wr ralizd at a ph of 4. III.3. Effct of initial mangans concntration. Th ffct of initial Mn (II) ions concntration on th adsorption onto clay from Bikougou is rportd in tabl 5. Hnc, it is obsrvd that mor Mn (II) ions wr progrssivly rtaind by th clay, and th adsorption procss bcam fficint, as th initial Mn (II) ions concntration incrasd, up to obtain constant amounts adsorbd at highr initial concntration. Similar rsults hav also bn rportd by Gupta t al.,8.it appars that,at low Mn(II) ions concntration,numbr of availabl adsorption sits is vry high comparativly to that of Mn(II) ions,amounts of Mn(II) ions adsorbd is wak.whn th concntration of Mn(II) ions incrass, bcaus of prsnc of an lvatd numbr of Mn (II) ions in solution,th amount of Mn(II)ions incrass. Th adsorption quilibrium is stablishd whn th amount of Mn(II) ions fixd at th intrfac solid solution is in dynamic balanc with that on surfac. III.4. Effct of raction tim From fig 3., it can b sn that th adsorption of Mn (II) ions adsorbd incrasd with in crasing tim of quilibration. Th rmoval of Mn (II) incrasd with tim to obtain quilibrium at about 3 min. Aftr that, contact tim has not ffct in mtal rmoval prcntag. Vry high adsorption rats wr obsrvd at th bginning bcaus of th grat numbr of sits availabl for th sorption opration and adsorption quilibrium wr thn gradually achivd as rportd by Bdoui t al., 8. III.5. Adsorption isothrms studis. Th xprimntal adsorption data hav bn subjctd to diffrnt adsorption isothrms namly Langmuir (I. Langmuir, 98), Frundlich (Ho t al., ) and Dubinin-Kaganr-Radushkvich (DKR) (Hasany t al., 998) modls in th aims (I) to dtrmin th adsorption capacity of clay from Bikougou as adsorbnt and (II) to obtain both a good pictur of th surfac and bst intrprtation of adsorption procss. Th Langmuir isothrm, xprssd in its linarizd form by th quation: C q bq (III) m C q m is applicabl if th monolayr covrag of adsorbnt with adsorbat taks plac on a homognous adsorbnt surfac. Th Langmuir cofficints b and q m rprsnting rspctivly th adsorption quilibrium constant and maximum adsorption capacity hav bn dtrmind from th intrcpts and slops of th plots which ar linar. C vs C (Fig. 4), q ISSN:

5 Vol. (),, 5-56 Th absorption quilibrium constant b valus varid from 7.5 to 8 L/g and maximum adsorption capacity valus wr rangd from to.36 with th incras in tmpratur from 38K to 38K. Th corrlation cofficints (R ) wr rmaind btwn.99 and.97. Th study of Langmuir isothrm has bn compltd by that of dimnsionlss constant R L, calld quilibrium constant (Juang t al., 997). (IV) R L bc Th R L valus indicat th typ of isothrm: to b favourabl < R L <, linar (R L = ) or irrvrsibl (R L = ). Th R L valus issud from this study wr rangd btwn.35 and.38 at 38K and btwn.58 and.3 at 38K. Ths rsults hav indicatd that th dscription of adsorption procss by man of Langmuir modl is favourabl. Th linarizd form of th Frundlich isothrm is givn by th quation: lnq lnk lnc (V) F n This quation prdicts multilayr adsorption on htrognous surfac, charactrizd by an xponntial distribution of activ sits. Th Frundlich cofficints k F and n corrsponding rspctivly to adsorption capacity and adsorption intnsity hav bn obtaind from th intrcpts and slops of linar plots lnq against lnc (Fig. 5). Th adsorption capacity (k F ) and adsorption intnsity (n), wr found varying rspctivly from.4786 mg/g at 38K, to 7.36 mg/g at 38K and from.46 to 5. in rlation with th incrasing tmpratur from 38K to 38K and with corrlation cofficints (R ) rangd btwn.98 and.935. Th valus of th adsorption intnsity obtaind in conformity with th rquirmnt n > for physical adsorption procss (Ijagbmi t al., 9), charactrizd th natur favourabl of th adsorption of Mn (II) ions onto clay of Bikougou dscribd by th Frundlich isothrm. Th DKR quation has bn widly usd to xplain nrgtic htrognity of solid at low covrags as monolayr rgions in micropors (.g., Karapinar t al., 9 and Krishna t al., ). Th quation of th DKR modl is givn by th xprssion: lnq = lnx m βε (VI) whr β is th activity cofficint rlatd to man adsorption nrgy, X m th maximum of adsorption capacity and ε is th Polangi potntial, which is qual to ε = RTln(/C) (VII) with: R: as th gas constant (kj/mol/k) T: as th tmpratur (K) Th saturation limit X m may rprsnt th total micropor volum of th adsorbnt. Th adsorption potntial is indpndnt of tmpratur but varis according to th natur of adsorbnt and adsorbat. Th adsorption nrgy E xprssd by th quation: E = - (VIII), 5 Rvals th natur of adsorption. If th valu of adsorption nrgy E is rangd btwn - and -8 kj/mol, adsorption procss is physical, and if th valu of E is rangd btwn -9 and -6 kj/mol, it is chmical adsorption. Th DKR paramtrs E and X m wr calculatd from th slops and intrcpts of th linar plots linar of lnq vrsus ε (Fig.6). Th adsorption nrgy E valus obtaind:- 6. kj/mol at 38K, kj/mol at 33K and -.kj/mol at 38K, wr in th sam rang of thos obtaind from th adsorption of Mn + (- 8.8 kj/mol at 33K) on natural zolits (Erdm t al., 4) whn physioadsorption (- - 8 kj/mol) controlld th procss (Sad, 3). Chmical procss ISSN:

6 Vol. (),, 5-56 (E rangd btwn - 9 and -6 kj/mol) appard sinc 38K. Th adsorption capacity in DKR quation was found to b varying from.8 mg/g at 38K to 9.87 mg/g at 38K with corrlation cofficints up.9 (.9 at 38K,.96 at 33K and.99 at 38K). Th comparativ tsting of isothrm modls prformd by th considration both of th bst corrlation cofficints and th satisfactory agrmnt btwn maximum adsorption capacity (q m in Langmuir modl, K F in Frundlich modl and X m in DKR modl) with xprimntal data, had dmonstratd that if ths thr modls could wll dscrib th adsorption procss, bst rsults hav bn obtaind with th Langmuir modl (Tabl 6) at any xplord tmpratur (38K, 33K and 38K). This illustrats that th adsorption occurs through th formation of a monolayr covrag of Mn(II) ions on th surfac of th clay. Nvrthlss, th amlioration of adsorption capacity for DKR modl (X m =.83 mg/g at 38K, 3.6 mg/g at 33K and 9.87 mg/g at 38K) and Frundlich isothrm (k F =.47 mg/g and n =.48 at 38K, K F =.79 mg/g and n =.49 at 33K;K F = 7.36 mg/g and n= 5.6 at 38K) up 33K, suggstd th adsorbnt surfac bcam progrssivly htrognous as a rsult of apparanc of chmical adsorption procss (Sad, 3). III.6. Thrmodynamics paramtrs. Th adsorption of Mn (II) ions on th clay from Bikougou, incrasd as function of tmpratur from 38K to 38K. Similar rsult was also found for th adsorption of coppr by kaolinit (Alkan t al., 8). Th procss is controlld by th adsorbat-adsorbnt intraction. Th Langmuir constant b, was usd to stimat th nthalpy, ntropy and Gibbs nrgy chargs accompanying adsorption, from th following rlationships: Δ ad G = -RTlnb (IX) and Lnb = Δ adh Δ ads (X) RT R Whr Δ ad H and Δ ad S ar rspctivly th variation of nthalpy and that of ntropy issud of adsorption procss. Th plot of lnb as a function of T (K) - is shown in figur 7. From th slop rand intrcpt of th corrsponding linar curv obtaind, th nthalpy Δ adh and ntropy Δ ads valus wr dtrminatd. Gibb fr nrgy Δ G ad was calculatd by using th widly known quation. Δ G Δ H TΔ S If that is th cas, th valus of thrmodynamics paramtrs wr: (i) ad Δ H ad ad ad =.57 kj/mol, (ii) Δ ads = J/K/mol. (iii) Δ G ad dcrasd from kj/mol at 38K to -7. kj/mol at 33K and -8.8 kj/mol at 38K.This rsult illustrats that th adsorption phnomnon is mor fficint with th incras in tmpratur. Th positiv valu of Δ H ad, indicats th ndothrmic natur of th adsorption procss. Th positiv chang of ntropy corrsponds to th fixation of Mn (II) ions at th xchang sits of th randomly distributd surfactant spcis and also that th adsorption is irrvrsibl (Ho t al., 999b). Th ngativ valu of Gibbs fr nrgy indicatd that th procss is spontanous. IV. Kintic studis. IV.. Adsorption ordr. Th modl of psudo first ordr and that of psudo scond ordr wr tstd for th dtrmination of adsorption procss ordr. Ths modls ar givn rspctivly by th quation: log k.33 q q logq t (XII) t ISSN:

7 and t q t F. Eba t al. / Intrnational Journal of Enginring Scinc and Tchnology Vol. (),, 5-56 t (XIII) k q q whr: (I) k and k ar rspctivly th rat constant of psudo first ordr adsorption (mn - ) and that of psudo scond ordr adsorption (g/mg*mn), (II) q and q t th amounts of Mn(II) ions adsorbnt at quilibrium (mg/g) and at various tims rspctivly. Th kintic paramtrs, obtaind from th slops and intrcpts of linar plots log (q q t ) vrsus t (Fig.8) and t/q t as a function of t (Fig.9) wr rportd in tabl 7. Th validity of kintic modl is supportd by th mploymnt of two paramtrs: (i) corrlation cofficints valus and (ii) good agrmnt btwn xprimntal data (q xp ) and modl prdictd valus of th amounts of Mn (II) ions adsorbd (q ). Satisfactory modl has good linarity of plots (R >.9) and highst agrmnt btwn q and q xp (small dviation). Th rsults showd (i) th high corrlation cofficints (R >.9 in all cass) for th psudo scond ordr comparativly of thos of psudo first ordr (R varying from.3 to.87 whn tmpratur incrass from 38K to 38K); (ii) A progrssiv bttr concordanc btwn q and q xp for th psudo scond ordr modl at 33K and 38K (dviation varying from +.5% to -.% at 33K, from.3% to -.7% at 38K) whil that of th psudo first ordr modl is vry wak (dviation varying from % to % at 33K, and from to % at 38K). Ths rsults indicatd that th adsorption kintic of Mn (II) ions on to clay of Bikougou followd th psudo scond ordr kintic modl. IV.. Kintic mchanism. Th mchanism of kintic adsorption had bn studid by applying xprimntal data to: (i) psudo scond ordr modl, (ii) liquid film diffusion modl (Boyd t al., 947) and (iii) intra-particl diffusion modl (Kith t al., 4) Thir corrsponding quations ar givn by th xprssions rspctivly: :for th intra-particl diffusion: q t = k 3 t,5 (XIV) q ln k 4t q t and: for th liquid diffusion: (XV) Whr k 3 and k 4 ar rspctivly th intra-particl diffusion and liquid film diffusion rat constants. Th paramtrs of ach modl hav bn calculatd from th slops and intrcpts of linar plots q t vs t.5 and - ln(- q t /q ) vs t rspctivly (Fig. and rspctivly). Th rsults ar rportd in tabl 8. If th intra-particl diffusion or th liquid film diffusion was th adsorption mchanism modl, th plots might hav zro intrcpt (varis from.96 to.56 for intra-particl diffusion modl and from.4 to.36 with liquid film diffusion modl) and passd through th origin (Gupta t al. 8). Dspit, th plots bing linar, th corrlation cofficints (R ) of intra-particl diffusion modl (.66 to.9) < of psudo scond ordr (.999 to.97) and of liquid film diffusion (.7 to.83) < of psudo scond ordr (.999 to.97), show that th xprimntal data did not fit th quation of intra-particl diffusion modl q t vs t.5 or that of liquid film diffusion modl - ln(-q t /q ) vs t. Larg intrcpts obtaind by using intra-particl diffusion modl suggstd that th procss was largly surfac adsorption and not intra-particl diffusion phnomna. Th small intrcpts of plots - ln(-q t /q ) vs t, could b considrd as a suggstion that liquid film diffusion modl might hav som rol to play in th kintics of adsorption of Mn(II) ions onto clay from Bikougou. Th tst of diffrnt modls of adsorption mchanism had prsntd that mchanism issud of psudo scond ordr modl had givn th bst fit of xprimntal data and consquntly, th adsorption of Mn (II) ion on to crud clay of Bikougou could b considrd following a mchanism rlatd to th psudo scond ordr kintic modl. V. Conclusion. This study provd that Mn (II) could b adsorbd and thus rmovd in significant amount by crud clay of Bikougou from aquous solutions. In batch mthod, rmoval of Mn (II) ions incrasd with th incras of contact tim (45 mn of contact-tim ar sufficint), amount of Mn (II) in solution, ph and tmpratur. ISSN:

8 Vol. (),, 5-56 Th quilibrium data could b dscribd by th Langmuir, Frundlich and DKR quations. Howvr, th Langmuir modl bttr rprsntd th adsorption procss than Frundlich and DKR modls. At a ph of 4 and tmpratur T (K) 38K, adsorption occurrd was found not to b a spontanous physioadsorption procss. Kintic modlling rsults showd that th psudo scond ordr quation was appropriat for th dscription of this typ of adsorption and rmoval both concrning th dtrmination of ordr and mchanism of raction. VI. Rfrncs. [] Ahmad, A.; Rafatullah, M.; Suliman, O.; Hakimi Ibrahim, M.; Yap Y, C.; Siddiqu Bazlul, M., (9). Rmoval of Cu (II) and Pb (II) ions from aquous solutions by adsorptions on sawdust of Mrantiwood: Dsalination, 47, [] Ajmal, M.; Khan, A.H.; Ahmad, S.; Ahmad A., (998). Rol of sawdust in th rmoval of coppr (II) from industrial wasts: Watr Rsarch, [3] Alkan, M.; Kalay, B.; Dogan, M.; Dmirbas, O., (8). Rmoval of coppr ion from aquous solutions by kaolinit and butch dsign: Journal of Hazardous Matrials, Vol. 53, N -, [4] Almida, C.A.P.; Dbachr, N.A.; Downs, A.J.; Cottt, L.; Mllo, C.A.D., (9). Rmoval of mthyln blu from colord fflunts by adsorption on montmorillonit clay: Journal of colloïd and intrfac scinc 33, [5] Apk, R.; Tutn, E.; Hugul, M.; Hizal M., (998). Havy mtal cations rtntion by unconvntional sorbnts (rd muds and fly ashs): Watr Rsarch, 3, [6] Ayari, F.; Srasra, E.; Trablsi-Ayadi, M., (7). Rtntion of lad from aquous solution by us of bntonit as adsorbnt for rducting laching from industrials fflunts: Dsalination, Vol. 6, N -3, [7] Bdoui, K.; Bkri-Abbs, I.; Srasra, E., (8). Rmoval of Cadmium (II) from aquous solution using pur smctit and Lwatit S : th ffct of tim and mtal concntration: Dsalination, 3, [8] Bin Yu, Zhang, Y.; Shukla Alka; Shyam Sukla, S.; Dorris Knnth, L., (). Th rmoval of havy mtal from aquous solutions by sawdust adsorption-rmoval coppr: Journal of Hazardous Matrials B [9] Boubrka, Z.; Khnifi, A.; Bndrdouch, N.; Drrich, Z., (6). J. Hazard. Matr [] Boyd, G.E.; Adamson, A.W.; My, R.S.Jr, (947). Th xchang adsorptions of ions from aquous solutions on organic zolits: Journal of Amrican Socity, G [] Chung, Y.S.; L, K.W.; Yoon, Y.S.; Kwon, S.H.; Lim, K.S., (99). Th adsorption bhaviour of havy mtal ions on sawdust: Bulltin of th Koran Chmical Socity, 3-4. [] Dr, W. A.; Howi, R. A.; Zussman, J., (99). An introduction to th rock-forming minrals: Scond dition, London, 696 p. [3] Erdm, E.; Karapinar, N.; Donat, R., (4). Th rmoval of havy mtal cations by natural zolits: Journal of Colloïd Scinc, 8, [4] Frnands, A.N.; Almida, C.A.P.; Mnzs, C.T.B.; Dbachr, N.A.; Sirra, M.M.I., (7). J. Hazard. Matr. 44, 4. [5] Gupta Susmita, S.; Bhattacharyya, K., (8). Immobilization of Pb (II), Cd (II) and Ni (II) ions on kaolinit and montmorillonit surfac from aquous mdium: Journal of Environmntal Managmnt, 87, [6] Gupta, V.K.; Mittal, A.; Gajb, V.; Mittal, J., (8). Journal of Colloïd Intrfac Scinc, [7] Gupta, V.K.; Mittal, A.; Jain, R.; Mathur, M.; Sikarwar, S., (6). Journal of Colloïd Intrfac Scinc, 33, 8. [8] Hasany, S.M.; Chaudbry, M.H., (998). Fixation of Cr (III) tracs onto Haro rivrs and from acid solutions: J. Radioanal. Nucl.Chm., 3 N. [9] Ho, Y.S.; Huang, C.T., (). Equilibrium sorption isothrm for mtals ions on tr frn: Procss Biochmistry, 37, [] Ho, Y.S.; Mc Kay, G., (999)a. Psudo scond ordr modl for sorption procsss: Procss Biochmistry, 34, [] Ho, Y.S.; Mc Kay, G., (999)b. Batch lad (II) rmoval from aquous solution by pat: quilibrium and kintics. Transactions of th Institution of Chmical Enginrs 76B, [] Juang, R.S.; Wu, F.C.; Tsng, R.L., (997). Ability of activatd clay for th adsorption of dys from aquous solutions: Environ. Tchnol., 8, 535. [3] Karapinar, N.; Donat, R., (9). Adsorption bhaviour of Cu + and Cd + onto natural bntonit: Dsalination, Vol. 49, N, 3-9 [4] Kith, K.H.; Choy; Portr, J.F.; Mc Kay G., (4). Film-por diffusion modls analytical and numrical solutions: Chmical Enginring Scinc, 59, 5-5. [5] Krishna, B.S.; Murty, D.S.R.; Prakash, B.S.J., (9). Thrmodynamics of chromium (VI) anionic spcis sorption onto surfactantmodifid montmorillonit clay: J. Colloïd Intrf. Sci., 9 3. [6] Langmuir I., (98). Th adsorption of gass on plan surfacs of glass, mica and platinum: J. Am. Chm. Soc. Vol.4,(9), [7] Lin Su-Hsia; Juans Ruy-Shin, (). Havy mtal rmoval from wátr by sorption using surfactant-modifid montmorillonit: J. Hazard. Matr, B9, [8] Li, R.S.; Yong, R.N.; Li, L.Y., (). Mathmatical prdiction of lad rmoval from carbonat-rich illit: Gonvironmntal Enginring Vol. 6, N -4, [9] Mathialagan, T.; Viraraghavan, T., (). Adsorption of cadmium from aquous solution by prlit: Journal of Hazardous matrials, 94, [3] Mllah, A.; Chgrouch, S., (997). Th rmoval of zinc from aquous solutions by natural Bntonit: Watr Rsarch,Vol. 3, N 3, [3] Njopwouo, D., (984). Minéralogi t physico-chimi ds argils d Bomkoul t d Balngou (Camroun). Utilisation dans la polymérisation du styrèn t dans l rnforcmnt du caoutchouc naturl, Thès Doct. Etat. Fac. Sci., Univrsité d Yaoundé, 3 p. [3] Olakitan, I.C.; Mi-Hwa Bak ; Dong-Su, K., (9). Montmorillonit surfac proprtis and sorption charactristics for havy mtal rmoval from aquous solutions: Journal of Hazardous matrials, Vol. 66, n 4, [33] Panday, K.K.; Prasad, G.; Singh, V.N., (998). Environ. Tchnol. Ltt. 9, [34] Pham, T.H. ; Windly, G.W., (97). Mthyln blu absorption by clay minrals. Dtrmination of surfac ara and cation xchang capacitis: Clays and clays minrals, Vol. 8, 3-. ISSN:

9 Vol. (),, 5-56 [35] Potgitr, J. H.; Potgitr-Vrmaak, S.S.; Kalibantonga, P.D., (4). Havy mtal rmoval from solution by palygorskit clay: Minrals Enginring, Vol. 9, N 5, [36] Quiohui Fan; Zhan Li; Haoguizhao; Zhog Jia; Jungzhng Xu; Wangsuo Wu, (9). Applid Clay Scinc, Vol. 45, N 3, -6. [37] Rémi, J.C. ; Orsini, L., (976). Utilisation du chlorur d cobalthxamin pour la dtrmination simultané d la capacité d échang t ds bass échangabls dans ls sols: Scincs d sol, 4, [38] Rockstraw, D.A.; (). Charactrization of Pcan shll-basd carbon: Tchnical compltion Rport, Novmbr, Nw Mxico Stat Univrsity, Las Crucs, Chmical Enginring. [39] Sad, M.M., (3). J. Radioanal. Nucl. Chm., 56, [4] Skar, M.; Sakthi, V. ; Rngaraj, S., (4). Kintcis and quilibrium adsorption study of lad (II) onto activatd carbon prpard from coconut shll: Journal of Colloïd Intrfac Scinc, 79, [4] Shujing, Z.; Haobo, H.; Yongji, X., (8). Kintic and isothrmal studis of lad ion adsorption onto bntonit: Applid Clay scinc, Vol. 4, N -4, [4] Undabytia, T.; Morrillo, E.; Maquda, C., (996). Clays Clay Minr, 3, [43] Wang, W.; Chn, H.; Wang, A., (7). Adsorption charactristics of Cd (II) from aquous solution onto activatd polygorskit: Sparation and Purification Tchnology, Vol.55, N, [44] Wójtowicz, A.; Stoklosa, A., (). Rmoval of havy mtals on Smctit ion-xchang column: Polish Journal of Environmntal Studis, Vol. N, 97-. [45] Yvon, J.; Baudracco, J.; Cass, J.M.; Wiss, J., (99). Elémnts d minéralogi quantitativ n micro-analys ds argils. In: Matériaux Argilux, Structurs, Propriétés t Applications. SFMC GFA, Paris. Dcarrau A. éditur, ISBN , Parti IV, Chap. 3, [46] Zhu, L.; Rn, X.; Yu, S., (998). Us of ctyltrimthylammonium bromid-bntonit to rmov organic contaminants of varying polar charactr from watr: Environ. Sci. Tchnol. 3, Tabl Chmical composition of clay matrial from Bikougou SiO wt% 54.3 As ppm < L.D. Eu 5 Ni 9.6 U.4 Al O Ba Ga 7.45 Pb 7.6 V F O B.6 Gd.6 Pr 4.3 W 37.7 MnO. Bi < L.D. G.6 Rb 5.93 Y 9. MgO.6 Cd < L.D. Hf. Sb < L.D. Yb.75 CaO.53 C Ho.3 Sm 3.9 Zn Na O 3.9 Co 7.5 In < L.D. Sn.4 Zr 8.77 K O.89 Cr 6.45 La 9.86 Sr 55.6 TiO.9 Cs.5 Lu. Ta.4 P O 5.5 Cu Mo < L.D. Tb.35 LOI 8.35 Dy.87 Nb 6.4 Th.8 Total 99.6 Er.83 Nd 7.5 Tm. Tabl Modal compositions of untratd clay matrial and clay fraction (wt %), s txt. Th composition of untratd clay is dtrmind by combining qualitativ X-ray data and chmical analysis whil th composition of clay fraction is dtrmind from X-ray pattrn (Intnsitis masurmnts without absorption corrction). Minral Untratd clay Clay fraction Kaolinit Albit.3 Montmorillonit Illit.9 7. Quartz 9. Cabonats 3. Maghmit. Anatas.9 Ba-Sr hydroxyapatit.8 Zircon trac ISSN:

10 Vol. (),, 5-56 Tabl 3 Charactristics of Bikougou clay dposit ph of point zro Acidity nutralizations (mq/l) Surfac ara (m /g) charg (PZC) CEC (mq/g) NaOH NaHCO 3 Na CO Tabl 4 Amounts and prcntags of Mn(II) adsorbd as function of ph (clay 5g/L; concntration Mn(II) solution 3.5 mg/l, tim 45 mn). ph ph 4 ph 6 ph 8 q (mg/g) % ads q (mg/g) % ads q (mg/g) % ads q (mg/g) % ads Tabl 5 Amounts and prcntags of Mn(II) adsorbd as function of initial concntration (clay 5g/L ; contact tim 45 mn, ph4). Initial concntration Mn(II) ions solution (mg/l) q (mg/g) % ads Tabl 6 Langmuir, Frundlich and DKR paramtrs and statistical for adsorption of Mn(II) ions at 38K, 33K and 38K (initial concntration of Mn(II) ions solution 67, 83, 98, 7 mg/l, ph4, tim 45 mn). Langmuir Isothrm Frundlich Isothrm DKR Modl T(K) q xp mg/g) to to to 6.36 q m (mg/g) b (L/mg) R L R K F (mg/g) n R X m (mg/g) E (kj/mol) to to to R Tabl 7 Psudo first ordr, psudo scond ordr constants (rat constant, amount of Mn adsorbd) and statistical for adsorption of Mn(II) ions (clay 5g/L, ph4) dtrmination of raction ordr. T(K) Initial Psudo first ordr Psudo scond ordr concntration q xp q c % dviation k * R q % dviation k * R (mg/l) (mg/g) (mg/g) (mn - ) (mg/g) (g/mg.min) ISSN:

11 Vol. (),, 5-56 Tabl 8 Intraparticl diffusion and liquid film diffusion rat constants cofficints (clay 5g/L, ph4). Modls Intraparticl diffusion Liquid film diffusion Paramtrs and statistical Initial concntration of Mn (II) ions solutions (mg/l) K 33K 38K 33K k 3 (mg/g.min.5 ) Intrcpts R k 4 (mn - ) * Intrcpts R Fd Lgnd An: Anatas, Ap: Ba, Sr-hydroxyaptit C : calcit, F d : F ld sp ar, Il: illit K : kao lin it, M : m o n tm o rillo n it Q: quartz M 7.9 K Il 3.34 Il, Q Counts Il Il 4.45 Il 4.6 Q 4.4 And 3.88 Il 3.76 Ap 3.5 An Fd C.93 Ap.87 Il.56 Q, K.37 An.3 Ap.89 An, C.8 Ap, Q Two Thta ( ) Fig. XRD pattrns of crud clay from Bikougou dposit Fig. XRD pattrns of clay fraction from Bikougou dposit ISSN:

12 Vol. (),, 5-56 % rmoval Co (3,56 mg/l) Co (4,67 mg/l) Co3 (5,6 mg/l) Co4 (6 mg/l) tim (min) Fig.3 Equilibrium sorbd prcntag of Mn(II) according to adsorption tim for various initial concntrations at ph4 and 38K Mn (II) C /Q (mg/l) T=38 K T=33 K T=38 K C Fig.4 Langmuir plots for Mn (II) ions adsorbd on clay at 38K (initial concntration 66.66, 83.33, and 6.66 mg/l) at ph4 ISSN:

13 log Q.5 T=38 K T=33 K T=38 K F. Eba t al. / Intrnational Journal of Enginring Scinc and Tchnology Vol. (),, 5-56 Mn (II) log C Fig.5 Frundlich plots for Mn (II) ions adsorbd on clay at 38K and at ph4 (initial concntration of Mn(II) ions 66.66, 83.33, and 6.66 mg/l) Ln Q 4 T=38 K T=33 K T=38 K Mn (II) Fig.6 DKR plots for Mn (II) ions adsorbd on clay at 38K and at ph4 (initial concntration of Mn (II) ions 66.66, 83.33, and 6.66 mg/l) ISSN:

14 Vol. (),, 5-56 ln(b) ,3,34,36,38,3,3,34,36 /T(K) Fig.7 Rlationship btwn Langmuir sorption quilibrium constant and tmpratur for Mn (II) ions adsorbd on clay at ph4 log (q-qt),5 -, K 33K 38K -,5 tim (min) Fig. 8 First-ordr plots for Mn(II) ions adsorbd on clays at diffrnt tmpratur (initial concntration mg/l at ph4) ISSN:

15 Vol. (),, Mn (II) PH4 T=38 K t/q t 3 CO CO CO3 CO tim (min) Fig.9 Scond-ordr plots for Mn (II) ions adsorbd on clay at 38K and at ph4 (initial concntration: CO=66.66 mg/l; CO=83.33 mg/l; CO3=98.48 mg/l; CO4=6.66 mg/l) Mn (II) T= 38 K q t (mg/l) C C C Tim(min).5 Fig. Intra-particl diffusion plots for Mn (II) ions adsorbd on clays at 38K and at ph4 (initial concntration: CO=66.66 mg/l; CO=83.33 mg/l; CO3=98.48 mg/l) ISSN:

16 Vol. (),, C C -ln(-qt/q) tim (min) Fig. Liquid film diffusion plots for Mn (II) ions adsorbd on clay at 38K and at ph4 (initial concntration: CO=66.66 mg/l; CO=83.33 mg/l) ISSN: