Adsorción de fenobarbital en carbones activados comerciales. Equilibrio cinético e isotermo de adsorción

Transcription

1 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. Adsorción d fnobarbial n carbons acivados comrcials. Euilibrio cinéico isormo d adsorción Carlos Albro Ry-Mafull, Julio Csar-Llopiz, Albro Iglsias-Crvo, Dachamir Hoza, Raul Garcia-Gallardo* Insiuo d Cincia y Tcnología d Marials d La Univrsidad d la Habana (Cuba) * Faculad d Física d La Univrsidad d la Habana (Cuba) ** Univrsidad Fdral d Sana Caarina, Florianópolis, (Brasil) *** Laboraorio Rinaldo Guiérrz (Cuba) Rcibido: 8 d marzo d 014. Acpado: 13 d novimbr d 014. Palabras clav: carbón acivado, adsorción, fnobarbial, cinéica, isormas. Kywords: acivad carbon, phnobarbial, adsorpion, kinic, isohrms. RESUMEN. La adsorcion in viro d fnobarbial n fluido gásrico simulado (FGS), ph 1, y 310 K, fu sudiada a parir d rs carbons acivados comrcials: Nori USP XX, Ch3J (ambos usados como anídoos) y M1. Las isormas d adsorción corrspondins furon analizadas por cuaro modlos: Langmuir (Tipo I y II), D-R, Frundlich y Tmkin; la cinéica d adsorción por si modlos: Elovich, psudo-primr ordn, psudo-sgundo ordn, ordn cro, primr ordn, sgundo ordn inraparícula. Los mjors ajuss n ambos casos furon obnidos por l modlo d monocapa d Langmuir y psudo-sgundo ordn rspcivamn. Es modlo cinéico propon u la vlocidad d adsorción sá conrolada por mcanismos d uimisorción nr l adsorbao y l adsorbn. El coficin d corrlación (R ) obnido por Langmuir n odos los casos, fu suprior a El sudio cinéico mosró u la adsorción d fnobarbial n los rs adsorbns alcanzó sus mjors rsulados con l modlo d psudo-scond ordr TI (R > 0.98) y TII (R 0.9). La variación d la nrgía libr d Gibbs (ΔG < 0) xplica l carácr sponáno dl procso d adsorción. Todos los marials sudiados musran poncials capacidads para la adsorción d fnobarbial. ABSTRACT. Th in viro adsorpion of phnobarbial by diffrn adsorbns in simulad gasric fluid (SGF) a ph 1. and 310 K, was drmind on hr yps of commrcial sampls of acivad carbon (AC): Nori USP XX, Ch3J (boh usd as anidos) and M1. Th uilibrium isohrms for h adsorpion of phnobarbial wr analyzd by four modls: Langmuir (Typ I and II), D-R, Frundlich and Tmkin isohrms uaions and h kinic curvs obaind wr fid using svn uaions (Elovich, psudo-firs ordr, psudo-scond ordr, zro ordr, firs ordr, scond ordr and h inraparicl modl) o drmin kinic paramrs of adsorpion. Th psudo-scond ordr and h Langmuir modl rspcivly showd h bs fiings. Th psudo-scond ordr suggrd ha h ovrall ra of h adsorpion was conrolld by chmisorpion which involvd valncy forcs hrough sharing or xchang of lcrons bwn h sorbn and adsorba Th corrlaion cofficins (R ) obaind from Langmuir modl for h linar rgrssion in all cass wr highr han Kinic sudis showd ha h adsorpion of phnobarbial on h hr adsorbns obaind h bs rsuls wih h psudo-scond ordr modl TI (R > 0.98) and TII (R 0.9) rspcivly. Th variaion of h fr Gibbs nrgy (ΔG < 0), in all cass, xplaind h sponanous characr of h adsorpion procss. Dspi h diffrn bhaviors all marials sd hav ponial for raing phnobarbial inoxicaions. INTRODUCTION Whil hisory provids ha h firs sudis on acivad carbon, from h rsarch poin of viw bgan in 1800, i was no unil 1980 ha sablishd sysmaic sudis of h applicaion of his marial in h ara of oxicological rsarch. 1 Th us of acivad carbon o adsorb drugs akn in ovrdos by humans is known only in h broads sns. By dialysis can prvn gasroinsinal absorpion of oxic nrohpaic circulaion and subsun passag 17

2 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. ino h bloodsram. Th xprincs in h clinical sudy (in vivo) of h applicaion of acivad carbon o pains in hospials and poison cnrs suppor hir us bu dos no dlv ino h xplanaion of why and how h procss of adsorpion. This mans ha ar unknown inracions in siu bwn his marial and drugs, so ha hy ar no wll lucidad y. Th in viro or prclinical sudy, which is par of his work, allowd undr crain condiions, sablish a baslin bhavior of h drug (phnobarbial) and is rlaionship wih crain adsorbn (acivad carbon) sag projcing is acion hrough h us of simulad gasric fluids [SGF]. 1-3 Th sarch for an anido o poison h slciv adsorpion is no inndd, bu h vrsail abiliy of adsorpion of hs adsorbns (univrsal characr). Tha is, h sam marial is abl o rain h gras numbr and variy of mdicins or drugs in a complx nvironmn. All of his imposs hr facors which ar dcisiv for h us of hs adsorbns: high chmical puriy, fas adsorpion kinics and high adsorpion capaciy. Ths facors was analyzd in his sudy mploying diffrn uaions known as: Langmuir (TI and TII), Dubinin-Radushkvich, Frundlich and Tmkin, bu is horical foundaions ar diffrn, as o how o addrss h phnomnon of adsorpion, which is gnrally vry conradicory and complx. Kinic sudis ar also addrssd in ordr o clarify which is or may b h mchanisms involvd during h adsorpion of h molcul on acivad carbons phnobarbial. Wll-known modls wr mployd, including: fracional powr, zro ordr, firs ordr, scond ordr, psudo scond ordr (TI, TII, TIII and TIV), Elovich and inraparicl diffusion. 4-7 Phnobarbial was slcd in his sudy du o i is a wll sudid molcul by and hr is updad informaion from in viro sudis, also bcaus i has a long prolongd half lif of 110 h for disposal, which drmind ha popl who ings i in ovrdos may b subjcd o a prolongd coma. Th minimum plasma drug concnraion ha has bn associad wih faal ovrdos was 60 mg/l. In associaion wih alcohol and ohr dprssans Cnral Nrvous Sysm (CNC) is causd dah a doss blow hos ha produc slp MATERIALS AND METHODS Acivad carbon Th acivad carbon mployd hr was h indusrial grad o applicaion in mdical and pharmacuical fild. Nori USP XX (Holland) and Ch3J (Chinss) akn as rfrncs. Th acivad carbon M1 was supplid by h Baracoa Acivad Carbon Plan from Cuban and purifid by acid/basic ramn. 11, 1 All sampls m h sandards s by USP Phnobarbial Phnobarbial [> 99 %] has bn purchasd from Sigma-Aldrich. I is a wak acid pk a = 7.4. Th solubiliy incrass wih incrasing ph. Form sodium sals (sodium phnobarbial), C 1 H 11 N NaO 3 = 54.. Nonionizd drugs adsorb rapidly in h somach by diffusion. Th Food and Drug Adminisraion (FDA) provids spcrophoomry UV in auous acid λ max. = 54 nm, as rfrnc mhod for is uanificaion. Th phnyl group a posiion 5 of phnobarbial givs h spcific anipilpic aciviy. 1,,8,9 Simulad gasric fluid (SGF) Th simulad gasric fluid was prpard according o h USP 30-NF 5, 13 was prpard wih h aciv ingrdin of phnobarbial as dscribd: g of NaCl wr dissolvd in 7 ml of concnrad HCl, nrazing o 1 L wih disilld war fr of CO by adjusing h ph of h soluion o 1.. Phnobarbial concnraion usd was 1000 mg/l. Th calibraion curv of phnobarbial in SGF was prformd using a spcrophoomr UV/VIS [Ulrospc 100 pro from Amrsham Bioscincs]. Th opical dnsiy of all sampls was drmind wih maximum absorbanc a λ max. = 54 nm in h zon of Lambr Br ransmianc. Th calibraion curv was adjusd using h linar rgrssion analysis or las suars uadraic. Each xprimn was prformd by riplica. Bach uilibrium adsorpion xprimns and analyical mhod Sock soluion of phnobarbial a h concnraion of 1000 mg/l was prpard by dissolving phnobarbial in 1 L of SGF radjusd o ph 1.. Th sampls of ACs wr analyzd granulomrically w disribuion, 100 % < 50 mµ. During adsorpion procss h amoun of carbon usd varid in h rang of 0.00 o 0.3 g and was addd o small vials prviously prpard wih phnobarbial dissolvd in SFG would b kp undr consan sirring of 150 r/min for 4 h a room mpraur [37 C ± 0.1 C]. Onc his im nding h sampls wr filrd o spara h solid phas and h liuid xrac 5 ml soluion for rading in h UV/VIS [Ulrospc pro from Amrsham Bioscincs]. Sampling was filrad by rmoving 5 ml aliuos nding h xprimnal. Exprimnal soluions a dsird concnraions wr obaind by diluion of h sock soluion wih SGF pradjusd o ph 1.. Prviously sablishd linar Br- Lambr rlaionships wr usd in h concnraion analysis. For h soluions wih highr concnraions, diluion was ruird o opra h analysis in h Br-Lambr rgion. Absorbanc % radings ar akn from h calibraion curv which drmins h uilibrium concnraion corrsponding o ach of h poins of h isohrm. Th amoun of adsorpion a uilibrium, [mg/g], was calculad by E

3 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. = ( C C ) 0 M V (1) whr: C 0 [mg/ml] iniial concnraion a [ = 0]. C [mg/ml] uilibrium [=4 h]. V [L] volum of h soluion and M [g] is h wigh of carbon. Kinics uilibrium adsorpion During adsorpion procss h amoun of acivad carbon usd was fixd 0.5 g and was addd o 50 ml glass bakr prviously prpard wih phnobarbial dissolvd in SFG (ph = 1.) would b kp undr consan sirring of 150 r/min a room mpraur [37 C ± 0.1 C]. Sampls aliuos wr collcd a diffrn ims and wr filrd wih 0. µm syring filrs. Th rmoval fficincy (RE) was calculad by E. : RE = ( C0 C ) x 100 C 0 whr: C (mg/ml) concnraion of adsorba a im (s). C 0 [mg/ml] iniial concnraion a [ = 0]. () Adsorpion isohrms modls An uilibrium isohrm xprsss h rlaion bwn h amouns of adsorba rmovd from soluion a uilibrium by uni of mass of adsorbn a consan mpraur. In his sudy, uilibrium daa of h phnobarbial adsorpion wr procssing by fiv wo-paramr isohrms including: Langmuir Typ I and II, Frundlich, Dubinin Radushkvich and Tmkin, Linar xprssion of hs isohrm uaions and h way o obain h isohrm paramrs ar givn in Tabl 1. Th daa valus wr plod according o h ruirmns of hs modls. Th linar rgrssion mhod of las suars is usd for drawing h rnd lins. Th characrisic paramrs wr drmind from h linar form corrsponding o ach Tabl 1. Isohrms and hirs linarizd xprssions. Isohrms Exprssions Linar xprssions Plos Langmuir = m K LC 1 K LC + ΔG = RTln Frundlich 1/n = K FC Dubinin- Radushkvich = max (D-R) Tmkin xp Dε [ ] K L TI TII ln ln 1 C C = + K LI m m = + K LII m C 1 = lnk F + n lnc = ln Dε max 1 ε = RTln 1 + C E = [ D] 0.5 RT = BlnKTK + BlnC = ln[ K TKC ] b RT B = b 1 m C vsc 1 1 vs C ln vslnc ln vsε vslnc 174

4 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. Kinic modls sudis Th sudis of adsorpion uilibrium ar imporan in drmining h ffcivs of adsorpion; howvr, i is also ncssary o idnify h yps of adsorpion mchanism in givn sysm. In his sudy i was usd diffrns modls, 14-6 o prdic h adsorpion kinic of phnobarbial, (Tabl ) Zro ordr, firs ordr and scond ordr ar h simpls modls and from h plos bwn, vs., ln vs. ln and -1 vs. was obaind h rlaiv kinics paramrs, whr K 0 [mg g -1 s -1 ], [mg g -1 ] ; K 1 [s -1 ], [mg g -1 ] and K [mg -1 s -1 ], [mg g -1 ] rspcivly. Tabl. Kinics modls and hir linarizd xprssions. Kinic modls Exprssions Linar xprssions Plo Zro ordr = K o = K o Firs ordr (K1) = xp Scond ordr Fracional powr = ( 1+ K ) ν FP =K = βln αβ vs ln ln = K1 vs 1 1 = K 1 vs + ln = lnk FP + νln Elovich ( ) 1 1 = ln( αβ) + ln Psudo scond ordr = K p ( 1+ K ) Inraparicl 0.5 =Kp TI TII 1 TIII TIV β 1 = K p p + β 1 1 = + K 1 = K p = K p K =K p 0.5 p 1 ln vsln vsln vs 1 1 vs vs vs 0.5 vs Th fracional powr or modifid Frundlich uaion, whr [mg g -1 ] is h amoun sorbd, K FP [mg g -1 s -ν ] and ν [g mg -1 ] ar consans and ν is posiiv and smallr han on, and [s] is im. This xprssion is gnrally mpirical, xcp for h cas in which ν = 0.5, whr i bcoms indisinguishabl from h parabolic-diffusion uaion. 7 Elovich uaion is on of h mos usful modls for dscribing chmisorpions. I has rcnly bn usd o modl h adsorpion of polluans from auous soluion, whr α [mg g -1 s -1 ] is h iniial sorpion ra and β [g/mg] is rlad o h xn of surfac covrag and acivaion nrgy for chmisorpion. Th paramrs α and β can b obaind from h slop and inrcp of h linar plo of vrsus ln. Psudo scond ordr modl assums ha h sorpion ra is conrolld by chmical sorpion and h sorpion capaciy is proporional o h numbr of sis on h sorbn. This modl has bn succssfully usd in many adsorpion procsss h whol im rang. Whr K p [g mg -1 s -1 ] is h ra consan of scond ordr adsorpion. Th linar plo of / vrsus gav 1/ as h slop and 1/K p as inrcp. This procdur is mor likly o prdic h bhavior ovr h whol rang of adsorpion. Th inraparicl diffusion modl, is basd on h hory proposd by Wbr and Morris 8 was mployd o idnify h diffusion This hory assums an mpirically basd funcional rlaionship, common o mos adsorpion procsss, whr upak varis almos proporionally o ½ han o h conac im. I s was usd o drmina h ra conrolling sp of h adsorpion kinic. Plos of vrsus 0.5 may prsn muli-linariy corrspond o succssiv sps in h adsorpion phnomnon. 9 Th kinic paramrs ar K p [g mg -1 s 0.5 ] and [mg g -1 ] 175

5 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. RESULTS AND DISCUSSION Adsorpion isohrms of phnobarbial. Adsorpion isohrms dscrib h uilibrium rlaionships adsorbn-adsorba and ach poin on i rprsns a condiion of hrmodynamic uilibrium. Hnc, xprssing a spcific bhavior for ach adsorbn, (Figurs 1 o 5). All h isohrms wr concav owards h axis of h adsorpion capaciy [mg/g]. Th isohrms obaind ar yp I according IUPAC classificaion for microporous marials wih rlaivly small xrnal surfac. 30 Phnobarbial can inrac wih h basal carbon plan (non spcific inracion) and wih a paricular polar funcional group on h surfac (spcific inracion). Th surfac OH - groups ar h spcific sis for phnobarbial adsorpion. 8,31 Also, h phnobarbial is a mulifuncional molcul and his maks i asir bing abl o bind o diffrn pars of is srucur, (Figur 1). Mainly by amino groups R-NH and carbonyl -C = O radical pron o h formaion of hydrogn links. As soon raisd suggss ha his yp of link is h mos likly o occur bwn h drug and h surfac of h coals. Th ionizd sa of phnobarbial dcrass hir abiliy o bond wih h hydroxyl groups C-OH o los h amino group hydrogn o form C = N bing h N ngaivly chargd. This condiion may also drmin ha h adsorpion of h molcul of phnobarbial in is favor bu no ionizd a acid ph han a ph basic, bu also incras h solubiliy of inonizado sa, du o h incrasd ph, dcrasd adsorpion capaciy of acivad carbon.,31 Fig 1. Exprimnal daa of adsorpion of Phnobarbial ono Nori USP XX [ ] Ch3J [ ] M1[ ]. Th Langmuir adsorpion modl, dscribs monolayr adsorpion of adsorba ono a homognous adsorbn surfac. Morovr, hr is ngligibl inracion bwn h adsorbd molculs and adsorpion sis having uniform nrgis. Th Langmuir isohrm, [Figur. (a,b)], accouns for surfac-covrag by balancing h rlaiv ras of upak and rlas, h formr bing proporional o h fracion of h surfac is opn, whil h lar is proporional o h fracion ha is covrd. Th uilibrium consan for hos ras is K L [L/mg] which also corrsponds o h Hnry s law cofficin. Whn h fluid concnraion is vry high, a monolayr forms on h adsorbn surfac, having a loading of max [mg/g], (Tabl 3). Th ssnial characrisics of Langmuir uaion can L ( 1+ K C ) b xprssd in rms of dimnsionlss sparaion facor, L 0 R Th rm R L indicas h shap of h isohrm as follows: whn h paramrs, R L > 1 (unfavourabl isohrm), R L = 1 [linar isohrm], 0 < R L < 1 [favourabl isohrm]. In all cass 0 < R L < 1, and valus wr calculad as 7, [NXX], 7, 10-4 [Ch3J] and 7, [M1] rspcivly, which xprsss h isohrm has a favorabl bhavior. 3,33 Th Dubinin-Radushkvich uaion assums ha h amoun adsorbd corrsponding o any adsorba concnraion is a Gaussian funcion of h Polanyi ponial. Th dvlopmn of his hory is basd on h concp of h characrisic curv and Polanyi adsorpion ponial [ E/ T= 0] is applid o dscrib h adsorpion in micropors. 34,35 A linar plo of ln vs. ε [KJ/mol], Figur. c, from h inrcp and slop would giv h valu of max.. [mg/g] and D [mol/kj] Tabl 3. Th calculad valu of E [KJ/mol] is showd in h Tabl 4. 36,37 Characrisic curv, (Figur d), shows ha h valus nrgy bhav in h nvironmn prviously prdicd. To h xn ha h dgr of covrag dcrass o valus of 0.3 h valus of h nrgis can b found bwn 11 o 1 KJ/mol. =

6 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. Achiving nrgy valus according o Tabl 6 for dgrs of covrag of 50 %. Th Tmkin modl considrd h ffcs of som indirc adsorbn/adsorba inracions on adsorpion isohrms, (Fig. ) As a rsul of adsorbn/adsorba inracions, h ha of adsorpion of all h molculs in h layr would dcras linarly wih covrag is h corrcion of Langmuir uaion, which is basd on Langmuir uaion and inroducs h influnc of mpraur on h adsorpion, whr B is h Tmkim consan rlad o ha of sorpion and K TK is h uilibrium binding consan ha corrsponds o h maximum binding nrgy [ml/g], (Tabl 3). Th mpirical Frundlich modl: is basd upon h assumpion of mulilayr formaion of adsorba on h hrognous solid surfac of h adsorbn and assums ha h srongr binding sis ar occupid firs and ha h binding srngh dcrass wih h incrasing dgr of si occupaion. Th valus K F (mg/g) (L/g) 1/n and n ar Frundlich consans rlad o adsorpion capaciy and innsiy of adsorpion, rspcivly, (Figur. f) Th lowr fracional valu of 1/n [0 < (1/n) < 1] indicas ha wak adsorpiv forcs ar ffciv on h surfac of acivad carbon. Valu of n > 1 rprsns a favourabl adsorpion condiion. I is considrd suiabl for highly hrognous surfacs. In his sudy, h valus found for n wr > 1, which prov ha h adsorpion is favourabl and procss could b physical in naur, howvr h valu of rgrssion cofficin is no good, (Tabl 3). 38,39 Fig. Adsorpion isohrms from Nori USP XX [ ] Ch3J [ ] M1[ ] fid by: a) Langmuir TII b) Langmuir TII c) D-R d) Characrisic curvs ) Tmkin f) Frundlich. From h Langmuir, Tmkin and D-R uaions, sponaniy of h sysms and h nrgy involvd during h adsorpion procss wr simad. (Tabl 4) 40 Gnrally, h ΔG is in h rang of 0 o 0 KJ/mol and 80 o 400 KJ/mol for physical and chmical adsorpion Th valus of ΔG calculad ar in h rang of physical adsorpion, (Tabl 4). Th valus simad of h molcular cross scional ara of phnobarbial by Langmuir, D-R and Frundlich uaions had bn rpord (Tabl 5) To calculad h molcular cross scional ara of phnobarbial h follow uaion was mployd. AspMW A = 1,,8 0 N K 0, Whr: A sp [m /g] spcific surfac ara of h acivad carbon. MW molcular wigh of phnobarbial. K numbr of mols of phnobarbial adsorbd pr gram of adsorbn a maximum surfac covrag (m.s.c). N 0 Avogadro s numbr. 177

7 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. Tabl 3. Consans and corrlaion cofficins of adsorpion isohrms for h adsorpion of phnobarbial ono acivad carbon commrcials. Langmuir Frundlich D-R Tmkin Adsorba TI TII Paramrs R Paramrs R Paramrs R Paramrs R Paramrs R max. = max. = K F = max. = b = Nori USP XX K LI = 1.7 K LII = 53 n = 4.93 D = K TK = 649 Ch3J M1 max. = 78 K LI = 1 max. = 370 K LI = max. = 33 K LII = max.. = 345 K LII = K F = 388 n = K F = 39 n = max. = 337 D = max. = 358 D= b = K TK = b = K TK = 310 Th ffcivnss of h dgr of compacion of h molcul of phnobarbial on h surfac of h acivad carbon is rlad o h opimal disribuion of h sis of adsorpion o h maximum xn of packaging of his molcul. Basd on h adsorpion sudis, h apparn aras occupid pr phnobarbial molcul on h surfacs of hydroxyl groups spacd mor closly han approximaly on pr Å will b inffciv a adsorbing addiional phnobarbial. If h surfac of an acivad carbon is complly and prfcly covrd wih phnobarbial, h ara occupid pr molcul is xpcd o b approximaly 110 o 10 Å. Tabl 4. Fr nrgy chang Gibss [ΔG] calculad by Langmuir and Tmkin uaions and characrisic nrgy [E 0 ] calculad by h Dubinin Radushkvich s uaion. Modls Paramrs Nori USP XX Ch3J M1 Langmuir TI ΔG [KJ/mol] Tmkin ΔG [KJ/mol] D-R E o [KJ/mol] Th drminaion of h ara of h molcul of phnobarbial, (Tabl 5) in hir non-ionizd sa in SGF, shows a br orinaion on h surfac of acivad carbon, in ordr of prioriy wih rgarding o h avrag rlaiv rror as follows: Nori USP XX [6.3 %] >Ch3J [14.5 %]> M1[10.7 %]. Th caus could b a br disribuion of h aciv sis of adsorpion, in boh xural and funcional plan rspcivly. Howvr, wih rlaion o h modls, h simad calculaion shows h following ordr: Frundlich [18.7 %] > Langmuir [16.8 %] > D-R [16 %]. Tabl 5. Esimaing h apparn aking as rfrnc h valu 110 Å ara of h phnobarbial molcul on h surfac of h acivad carbons. Langmuir D-R Frundlich Adsorbn m.c.s [Å ] rlaiv rror [%] m.c.s [Å ] rlaiv rror [%] m.c.s [Å ] rlaiv rror [%] Nori USP XX Ch3J M

8 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. Kinics analyss Th adsorpion kinics was xprssd as C 0 -C/C 0 [%] vs. [s] (Figur. 3) Th adsorpion of phnobarbial is ui fas. Th fas adsorpion may b ascribd o h highr driving forc ha maks fas ransfr of phnobarbial o h surfac of adsorbn paricls along wih h availabiliy of h uncovrd ara, h aciv sis and hir disribuion on h adsorbn. Th adsorbns wih hs kinic propris ar vry usful in cass of poisoning sinc hy rain in h solid phas vry rapidly oxic nrohpaic sysm which prvns h sam happns wih a concnraion unfavorabl o h bloodsram. I can b sn walking round h lbow of h curv and immdialy bgins o pass his ara sabilizaion sysm which is characrisic of good affiniy and rapid kinics. Th plaau is rachd vry fas ha longr ims carry no ffciv adsorpion, bu o rach full sauraion in h sysm xcding 3 min. Similar sysms o his ar rpord and in all cass hr is a good fi wih h kinic psudo scond ordr modl Fig. 3 Exprimnal adsorpion daa ono Nori USP XX [ ] Ch3J [ ] M1[ ]a) Kinic xprimnal daa ph 1. and 310 K. b) Psudo scond ordr kinics modl for adsorpion of phnobarbial. c) Exprimnal xp. vs h calculad amoun calc.. Th kinic adsorpion daa wr procssd o sudy h dynamics of h adsorpion procss in rms of h ordr of ra consan, (Tabl 6 and figurs 3 o 5). Rgrssion lins buil o obain h kinic paramrs. Th uilibrium adsorpion capaciis do no agr wih xprimnal valus o h follows modls: Elovich, fracional powr, zro ordr, firs ordr, scond ordr and psudo scond ordr [TII, TIII and TIV] and inraparicl diffusion, du o low corrlaions cofficin [< 0.934]. This confirms ha do no giv a good rgrssion. Th corrlaion cofficin of linarizd form of psudo-scond ordr uaion wr > (Tabl 6). Furhrmor, h calculad calc. [mg/g] valu hrough his modl is clos o h xp. [mg/g] xprimnal wih R > 95. This dmonsrad ha h sorpion of phnobarbial ono acivad carbon is mos approprialy rprsnd by a psudo-scond ordr kinic modl, (Figur 4) This modl supposs ha wo racions ihr in sris or in paralll ar occurring, h firs on is fas and rachs uilibrium uickly and h scond is a slowr racion ha can coninu for a long priod of im. 48 Th produc K p is h iniial sorpion ra rprsnd as, h=k p [mg/g s], and was calculad for ach AC as follow: 0.44 [Nori USP XX], 0.59 [Ch3J] and 0.7 [M1] rspcivly. 179

9 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. Fig. 4. Kinic xprimnal daa ( ) and prdicd daa (---) from psudo scond ordr modl TI a ph 1. and T = 37 C. Th produc K p is h iniial sorpion ra rprsnd as, h=k p [mg/g s], and was calculad for ach AC as follow: 0.44 [Nori USP XX], 0.59 [Ch3J] and 0.7 [M1] rspcivly. Th psudo-scond ordr TI modl was h mos suiabl uaion o dscrib h adsorpion of phnobarbial ono acivad carbon. This suggrd ha h ovrall ra of h adsorpion was conrolld by chmisorpion which involvd valncy forcs hrough sharing or xchang of lcrons bwn h sorbn and adsorba. Analyss of h inraparicl modl. Wbr Morris plos show ha h adsorpion procss of phnobarbial is a hr sp procss. Th firs sp, vry shor, corrsponds o a limiaion of adsorpion by xrnal diffusion, (Fig.5) Fig. 5 Wbr-Morris plos for phnobarbial adsorpion ono Nori USP XX [ ] Ch3J [ ] M1[ ]. 180

10 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. Th scond sp corrspond o a gradual adsorpion sag during h inraparicl diffusion is h ra limiing facor. Th hird sp is h final uilibrium in which adsorba concnraion in auous soluion bcoms vry wak, hus slowing down h inraparicl diffusion phnomnon. Th valu of h inrcp indicas whhr xrnal diffusion limis h adsorpion phnomnon: if h sraigh lin passs hrough h origin, inraparicl diffusion is h ra limiing facor; ohrwis xrnal diffusion opras simulanously o conrol h ra of adsorpion. I was obsrvd ha any h linar lins did no pass hrough h origin, which rvald ha h inraparicl diffusion was par h adsorpion bu was no h only ra conrolling sp. Som ohr mchanisms as complxs may also involvd in h ra of adsorpion. Tabl 6. Kinic modls paramrs by linar rgrssion mhod for h sorpion of phnobarbial by acivad carbon. Kinic modls Paramrs Adsorbn Nori USP XX Ch3J M1 Elovich Fracional Powr Zro ordr Firs ordr Scond ordr Psudo scond ordr TI TII TIII TIV Inraparicl α β R K FP ν R K 0 R K 1 R K R K P R K P R K P R K P R x K p 1.76 R x CONCLUSIONS Th Langmuir isohrm modl fid h uilibrium daa br han D-R isohrm modl, rvaling ha h adsorpion of phnobarbial ono h acivad carbon was monolayr adsorpion. Th hrmodynamic paramrs ΔG and E 0 calculad from h xprimnal daa show ha acivad carbons hav inracions boh spcific and non spcific vry similar. This shows ha hs marials bhav agains phnobarbial adsorpion similarly and procss sponanous (ΔG<0). Th adsorpion kinic rsuls dmonsra ha h adsorpion procss of phnobarbial ono acivad carbon follows closly h psudo-scond ordr kinic modl. Wbr Morris plos show ha h adsorpion procss of phnobarbial is a hr sp procss. Also hs plos indica ha h inraparicl diffusion is no h ralimiing sp for h whol racion. ACKNOWLEDGEMENTS Th auhors hank o Programa d Esudans-Convênio d Pós-Graduação (PEC/PG), Coordnação d Aprfiçoamno d Pssoal d Nívl Suprior (Caps), Brazil. 181

11 Rvisa CENIC Cincias Químicas, Vol. 45, pp , 014. REFERENCE BIBLIOGRAPHIC 1. Nuvonn P. and Olkkola K. Oral Acivad Charcoal in h Tramn of inoxicaions. Rol of singl and rpad doss, Mdical Toxicol. 1988:(3): Wurs D, Burk G, Brg M, Vng P, and Scholiuas D. Phnobarbial Adsorpion from Simulad Insinal Fluid, USP., and Simulad Gasric Fluid, USP., by Two Acivad Charcoals. Pharm Rs. 1988:(5): Hogbrg LC, Chrisophrsn AB, Chrisnsn HR, Anglo HR., Comparison of h adsorpion capaciis of an acivad-charcoal yogur mixur vrsus acivad-charcoal war slurry in vivo and in viro, Clin. Toxicol. 005:43: Srividya K,, Kausubha M. Influnc of Tmpraur on Euilibrium, Kinic and Thrmodynamic Paramrs of Biosorpion of Cr(VI) ono Fish Scals as Suiabl Biosorbn, J War Rsourc and Procion. 011: 3: Thio C., Mirna M., Sudaryano Y. and Ismadji S. Adsorpion of basic dy ono acivad carbon prpard from durian shll: Sudis of adsorpion uilibrium and kinics, Chm Eng J. 007:17: Yanhui Li. Prparaion of acivad carbon from Enromorpha prolifra and is us on Caionic rd X-GRL rmoval, Applid Surfac Sci. 011: 57: Qing-Song Liu. Adsorpion isohrm, kinic and mchanism sudis of som subsiud phnols on acivad carbon fibrs, Chm Eng J. 010:157: Aburub A. and Wurs D., Phnobarbial inracions wih drivaizd acivad carbon surfacs. J. Colloid. Inrf. Sci. 006:96: Burk, G., Wurs, D., Brg, M., Vng, P. and Scholiuas D. Surfac Characrizaion of Acivad Charcoal by X-Ray Phoolcron Spcroscopy (XPS): Corrlaion wih Phnobarbial Adsorpion Daa. Pharm Rs. 199:9: Burk, G., Wurs, D., Brg M., Vng P. and Scholiuas, D., Modl slcion for h Adsorpion of Phnobarbial by Acivad Charcoal, Pharm Rs. 1991:8: Carlos RM, Csar JLL, Iglsias A. Esudio comparaivo dl carbón acivado M1 d producción nacional para su uso como anídoo, Rvisa CENIC Cincias Químicas. 007:38: Carlos RM, Iglsias A, García RG, Muñiz RA. Procdimino cnológico para la obnción d carbón acivado calidad USP 30 para uso médico farmacéuico, Rvisa CENIC Cincias Químicas. 010:41: Unid Sad Pharmacopia, USP, USP30-NF5, p. 1701, Acivad Charcoal 14. Ali, B. and Mohammad M., Euilibrium and kinic sudis on fr cyanid adsorpion from auous soluion by acivad carbon, J Hazardous Marials. 009:170: Isaribl, Q. Comparaiv adsorpion of lvodopa from auous soluion on diffrn acivad carbons, Chm Eng J. 009:15: Dominiu, R. al, Adsorpion of complx phnolics compounds on acivad charcoal: Adsorpion capaciy and isohrms, Chm Eng J. 009:148: Mohd, A. and Nazira, K., Euilibrium, kinics and hrmodynamic of Rmazol Brillan Orang 3R dy adsorpion on coff husk-basd acivad carbon. Chm Eng J. 011:170: Xiaodong, X. Adsorpion of bnzoic acid from auous soluion by hr kinds of modifid bnonis, J. Colloid Inrf. Sci. 011:359: I.A.W.Tan, A.L.Ahmad and B.H. Hamd, Adsorpion isohrms, kinics, hrmodynamics and dsorpion sudis of,4,6-richlorophnol on oil palm mpy frui bunch-basd acivad carbon, J Hazardous Marials Hamdi M.H and Ashraf A. El-Sayd, Acivad carbon from agriculural by-producs for h rmoval of Rhodamin-B from auous soluion, J Hazardous Marials. 009:168: Chaim, A. Kinics of Soil Chmical Racions: Rlaionships bwn Empirical Euaions and Diffusion Modls. Soil Sci Soc Am J. 1991:55: Lunhong, A. Rmoval of mhyln blu from auous soluion wih magni loadd muli-wallcarbon nanoub: Kinic, isohrm and mchanism analysis, J Hazardous Marials. 011:198: M.N. Sahmoun, K. Louhab and A. Boukhiar, Kinic and uilibrium modls for h biosorpion of Cr (III) on Srpomycs riosas, Rs J Applid Sci. 008:3: Ho, Y.S., McKay, G., Th kinics of sorpion of divaln mal ions ono sphagnum moss pa, War Rs. 000:34: Ho, Y.S., McKay, G., Psudo-scond ordr modl for sorpion, Proc Biochm. 1999:34: Chiou, M.S., Li, H.Y.Adsorpion bhavior of raciv dy in auous soluion on chmical cross-linkd chiosan bads, Chmosphr. 003:50: Wu, F.C., Tsng, R.L. and Juang, R.S., Kinic modling of liuid phas adsorpion of raciv dys and mal ions on chiosan. War Rs. 001:35:

12 Rvisa CENIC Cincias Químicas, Vol. 45, pp , Chaim, A. Kinics of Soil Chmical Racions: Rlaionships bwn Empirical Euaions and Diffusion Modls. Soil Sci Soc Am J. 1991:55: Y. Onal, Kinics of adsorpion of dys from auous soluion using acivad carbon prpard from was aprico, J Hazardous Marials. 006:137: Wu, F.C., R Tsng, L. and Juang, R.S., Comparisons of porous and adsorpion propris carbons acivad by sam and KOH. J Colloid Inrf Sci. 005:: IUPAC Manual of Symbols and Trminology, Appndix, Par. 1, Colloid and Surfac Chmisry Pur and App. Chm. 3. Dal, E. W., Akham, A., Th Effcs of Surfac Lacon Hydrolysis and Tmpraur on h Spcific and Nonspcific Inracions Bwn Phnobarbial and Acivad Carbon Surfacs. J Pharm Sci. 95 (006). 33. Ali, B. and Mohammad M., Euilibrium and kinic sudis on fr cyanid adsorpion from auous soluion by acivad carbon. J Hazardous Marials. 009:170: Isaribl, Q. al., Comparaiv adsorpion of lvodopa from auous soluion on diffrn acivad carbons, Chm Eng J. 009:15: Sockli, F. al., Por siz disribuions of aciv carbons assssd by diffrn chnius. Carbon. 000:38: McEnany, B., Esimaion of h dimnsions of micropors in acivad carbons using h Dubinin- Radushkvich uaion. Carbon. 1987:5: I.A.W.Tan, A.L.Ahmad and B.H. Hamd, Adsorpion isohrms, kinics, hrmodynamics and dsorpion sudis of,4,6-richlorophnol on oil palm mpy frui bunch-basd acivad carbon. J Hazardous Marials. 009:164: Hong, Z. Sorpion isohrm and kinic modling of anilin on Cr-brnyoni. J Hazardous Marials. 009:167: Mohd, A. and Nazira, K., Euilibrium, kinics and hrmodynamic of Rmazol Brillan Orang 3R dy adsorpion on coff husk-basd acivad carbon. Chm Eng J. 011:170: Lunhong, A., al, Rmoval of mhyln blu from auous soluion wih magni loadd muliwallcarbon nanoub: Kinic, isohrm and mchanism analysis. J Hazardous Marials. 011:198: Indra, D., Vimal, C., Niin Kumar, A. and, Indra M., Rmoval of congo rd from auous soluion by bagass fly ash and acivad carbon: Kinic sudy and uilibrium isohrm analyss, Chmosphr. 005:61: Y. Liu, Is h fr nrgy chang of adsorpion corrcly calculad?. J Chm Eng Daa. 009:54: Li, Y.H. al., Adsorpion hrmodynamic, kinic and dsorpion sudis of Pb + on carbon nanoubs. War Rs. 005:39: Qing-Song, L., al., Adsorpion isohrm, kinic and mchanism sudis of som subsiud phnols on acivad carbon fibrs. Chm Eng J. 010:157: Alxandro M.M. Vargas, André L. Caza, Marcos H. Kunia, Taís L. Silva, Vior C. Almida. Adsorpion of mhyln blu on acivad carbon producd from flamboyan pods (Dlonix rgia): Sudy of adsorpion isohrms and kinic modls. Chm Eng J. 011:168: Li, W., al., Adsorpion of Pb(II) on acivad carbon prpard from Polygonum orinal Linn.: Kinics, isohrms, ph, and ionic srngh sudis. Biorsourc Tch. 010:101: Gomz, M.S. and Larrchi, M.P., Kinic and adsorpion sudy of acid dy rmoval using acivad carbon. Chmosphr. 007:69: Niyaz Mohammad Mahmoodi, Raziyh Salhi and Mokhar Arami, Binary sysm dy rmoval from colord xil waswar using acivad carbon: Kinic and isohrm sudis, Dsalinaion. 011:7: Khambhay, Y., Mody, K., Basha, and Jha, S. B., Kinics uilibrium and hrmodynamic sudis on biosorpion of hxavaln chromium by dad fungal biomass of marin Asprgillus nigr. Chm Eng J. 009:145: Mohd Azmir Ahmad, Rasyidah Alrozi, Rmoval of malachi grn dy from auous soluion using rambuan pl-basd acivad carbon: Euilibrium, kinic and hrmodynamic sudis. Chm Eng J. 011:171: