APPLICATION OF DIFFERENT ISOTHERM MODELS ON LEAD IONS SORPTION ONTO ELECTRIC FURNACE SLAG

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1 L. Ćurković t al. Application of Diffrnt Isothrm Modls on Lad Ions Sorption... ISSN UDC =111 Rcivd: Accptd: Original scintific papr APPLICATION OF DIFFERENT ISOTHERM MODELS ON LEAD IONS SORPTION ONTO ELECTRIC FURNACE SLAG LIDIJA ĆURKOVIĆ, ALENKA RASTOVĈAN-MIOĈ ¹, MARIJANA MAJIĆ, JOSIP ŽUPAN Faculty of Mchanical Enginring and Naval Tchnology, Univrsity of Zagrb, Croatia ¹Faculty of Mtallurgy, Univrsity of Zagrb, Croatia Th ffct of tmpratur on th uilibrium sorption of Pb 2+ from auous solution onto a low-cost lctric furnac slag was invstigatd. In this papr, two-paramtr isothrm modls namly th and th Frundlich and thr-paramtr isothrm modl namly Rdlich Ptrson wr applid to dscrib th isothrms and to calculat thir constants. Th bst stimation of th paramtrs of ths modls by a non-linar rgrssion analysis was obtaind. A comparison btwn two-paramtr and thr-paramtr isothrms was rportd. Th charactristic paramtrs for ach isothrms and rlatd cofficint of dtrmination (R 2 ) hav bn dtrmind using MATLAB 6.5. All th cofficints of dtrmination (R 2 ) of th non-linar mthod ar clos to unity. Th Rdlich Ptrson isothrm producd a highr cofficint of dtrmination valus in comparison to all th isothrms studid. Ky words: lad, lctric furnac slag, sorption isothrm. Primjna razliĉitih modla izotrma za sorpciju olova na lktropćnoj troski. U radu j ispitan utjcaj tmpratur na sorpciju Pb 2+ iona na lktropćnoj troski kao jftinom sorbnsu. Izotrm su opisan uporabom dvoparamtarskih i Frundlich modla, t tro-paramtarskog Rdlich Ptrson modla. Paramtri navdnih izotrmi odrđni su nlinarnom rgrsijskom analizom. Karaktristični paramtri izotrmi i koficijnti odrđivanja (R 2 ) odrđni su uporabom MATLAB 6.5. Sv vrijdnosti koficijnata odrđivanja (R 2 ) su bizu jdan. Najvća vrijdnost koficijnta odrđivanja (R 2 ) postignuta j za Rdlich Ptrson modl. Kljuĉn rijĉi: olovo, lktropćna troska, sorpcijska izotrma. INTRODUCTION Havy mtals and othr mtal ions ar rlasd into th nvironmnt in a numbr of ways, such as auous wast strams of many industris, coal combustion, swag wastwatrs, automobil missions, battry industry, mining activitis, and th utilization of fossil fuls, tc. Havy mtals such as lad, mrcury, arsnic, coppr, zinc, cadmium ar highly toxic whn adsorbd into th body [1]. Thy can caus accumulativ poisoning, cancr, brain damag, tc. [2]. Effctiv mthods for mtal ions rmoval that hav bn usd includ ion xchang, rvrs osmosis, lctrochmical tratmnt, vaporativ rcovry and adsorption. Cost is an important paramtr for comparing th adsorbnt matrials. Thrfor, thr is incrasing rsarch intrst in using altrnativ low-cost adsorbnts. In rcnt yars, considrabl attntion has bn focusd on th rmoval of mtal ions from auous solution using adsorbnts drivd Th Holistic Approach to Environmnt 1(211)1, Pag 13

2 L. Ćurković t al. Application of Diffrnt Isothrm Modls on Lad Ions Sorption... from low-cost matrials, such as blast furnac slag [3] and lctric furnac slag [4]. Important physicochmical aspct for th valuation of sorption procsss as a unit opration is th sorption uilibrium. Sorption uilibrium is stablishd whn th concntration of sorbat in th bulk solution is in dynamic balanc with that of th intrfac concntration. Euilibrium rlationships btwn sorbnt and sorbat ar dscribd by sorption isothrms, usually th ratio btwn th uantity sorbd and that rmaining in th solution at a fixd tmpratur at uilibrium [5]. Th analysis of xprimntal uilibrium data by fitting into diffrnt isothrm modls is an important stp to propos suitabl modl for procss dsign. Th most widly applid two-paramtr isothrms ar Frundlich [6] and modls [7]. Furthr, othr two-paramtr modls such as Tmkin, Dubinin, Jovanovic, Halsy and Hurkins- Jura ar also usd in th litratur [8]. Thrparamtr isothrm modls namly Rdlich Ptrson, Toth, Radk Prausnitz, Fritz Schlundr, Vith Sladk and Sips ar also usd [9]. Linar or non-linar rgrssion can b usd to dtrmin th bst fitting isothrm. Nonlinar mthod has bn suggstd a bttr way to obtain th uilibrium isothrm paramtrs, but linar rgrssion is most fruntly usd to invstigat th most fittd isothrm [1]. In this study, a non-linar mthod of thr widly usd isothrms,, Frundlich, and Rdlich-Ptrson, wr compard in an xprimnt xamining Pb 2+ ion sorption onto lctric furnac slag as low cost sorbnt. EXPERIMENTAL All sorption xprimnts wr prformd on lctric furnac slag from th Flis foundry in Sisak, Croatia. Th chmical composition of lctric furnac slag was dtrmind by th standard chmical analysis and rsults in mass % ar: CaO-3 %, MgO-,2 %, MnO-19 %, SiO 2-19 %, Al 2 O 3-1,3 %, FO-3 %. All xprimnts hav bn mad with a fraction of particl siz of.5 to.7 mm. Sorption procss of lad onto EFS has bn prformd by th static, so calld batch procss. Th sampls of EFS (.25 g) hav bn uilibratd within 8 hours with 5. ml of th Pb 2+ solution of diffrnt initial concntration (1, 25, 5, 75 and 1 mg/l). Exprimnts wr prformd at diffrnt tmpraturs (293, 33 and 313 K) and uantity of Pb 2+ ions rmaining in th liuid phas aftr uilibration has bn masurd by mans of atomic absorption spctrophotomtry (AAS, AA-68, Shimadzu). Th diffrnc btwn th initial and uilibrium mass concntrations of Pb 2+ ions is usd for calculation of th uantity of lad sorbd on unit mass of lctric furnac slag (, mg Pb 2+ /g of th EFS), taking into considration th data rlatd to th EFS wight, volum and mass concntration of th solution. Th amount of Pb 2+ sorbd onto th lctric furnac slag was calculatd from th following xprssion: ( V ) (1) m whr is th uilibrium Pb 2+ concntration sorbd on th lctric furnac slag (mg/g), V is th initial volum of th Pb 2+ solution usd (L), m is th mass of lctric furnac slag usd (g), is th initial concntration of Pb 2+ in th solution (mg/l) and is th concntration of Pb 2+ in th solution at uilibrium (mg/l). Th Holistic Approach to Environmnt 1(211)1, Pag 14

3 L. Ćurković t al. Application of Diffrnt Isothrm Modls on Lad Ions Sorption... RESULTS AND DISCUSSION Th rlationship btwn th amount of Pb 2+ sorbd and th Pb 2+ concntration rmaining in solution is dscribd by an isothrm. Various isothrm uations can b usd to dscrib th uilibrium charactristics of sorption. Th rsults obtaind on th sorption of lad on lctric furnac slag wr analysd by th wll-known modls givn by, Frundlich, and Rdlich-Ptrson isothrm modls. modl is th simplst thortical modl for monolayr sorption onto a surfac with finit numbr of idntical sits. Th modl [7] is givn by th uation: K m L (2) 1 K L whr K L is th sorption uilibrium constant (L/mg). Th Frundlich [6] xprssion is an mpirical uation applicabl to non-idal sorption on htrognous surfac as wll as multilayr sorption, and is xprssd by th following uation: 1/ n KF (3) whr K F ((mg/g)(l/mg) 1/n )) and n ar th Frundlich constants rlatd to th sorption capacity and sorption intnsity, rspctivly. Th Frundlich xponnt, n, should hav valus in th rang of 1 to 1 for classification as favourabl adsorption. Rdlich and Ptrson (1959) incorporatd thr paramtrs into an mpirical isothrm. Th Rdlich-Ptrson isothrm modl combins lmnts from both th and Frundlich uations, and th mchanism of adsorption is a hybrid uniu and dos not follow idal monolayr adsorption [11]. It can b dscribd as follows: R (4) 1 K a Whr (mg/g) is th solid-phas sorbat concntration at uilibrium, (mg/l) is th concntration of adsorbat in uilibrium with liuid phas, K R (L/g) and a R (L/mol) ar th Rdlich-Ptrson isothrm constants, whil β is th xponnt, which lis btwn and 1. Whn xponnt β =, E. (4) transforms to Hnry`s law uation. For xponnt β = 1, E. (4) convrts to th form. In ordr to asss diffrnt isothrms and thir ability to corrlat with xprimntal rsults, th thortical plots from ach isothrm hav bn fittd with th xprimntal data for sorption of Pb 2+ ions on lctric furnac slag. Th xprimntal data of th amount Pb 2+ sorbd onto th EFS at diffrnt tmpraturs wr fittd to th isothrm modls using MATLAB 6.5 and th graphical rprsntations of ths modls ar prsntd in Figurs 1A, 1B and 1C. All isothrm paramtrs obtaind using th nonlinar mthod for th sorption of Pb 2+ ions onto lctric furnanc slag at diffrnt tmpraturs wr prsntd in Tabl 1. All th cofficints of dtrmination (R 2 ) of th non-linar mthod ar clos to unity. Th xprimntal data yildd xcllnt fits within th following isothrms ordr: Rdlich Ptrson > > Frundlich, basd on its R 2 valus. R Th Holistic Approach to Environmnt 1(211)1, Pag 15

4 L. Ćurković t al. Application of Diffrnt Isothrm Modls on Lad Ions Sorption A 35 3 B 2 25 [mg/g] K Frundlich Rdlich-Ptrson [mg/g] K Frundlich Rdlich-Ptrson [mg/l] [mg/l] [mg/g] 35 C K Frundlich Rdlich-Ptrson [mg/l] Figur 1. Exprimntal data (points) and th non-linar sorption isothrm modls (lins) for Pb 2+ with EFS at: (A) T = 293 K, (B) T = 33 K and (C) 313 K. Slika 1. Eksprimntalni podatci (točk) i modli nlinarn sorpcij (linij) Pb 2+ iona na lktropćnoj troski pri: (A) T = 293 K, (B) T = 33 K i (C) 313 K. Th Holistic Approach to Environmnt 1(211)1, Pag 16

5 L. Ćurković t al. Application of Diffrnt Isothrm Modls on Lad Ions Sorption... Tabl 1. Isothrm paramtrs obtaind using th non-linar mthod for th sorption of Pb 2+ ions onto lctric furnanc slag at diffrnt tmpraturs. Tablica 1. Paramtri izotrmi dobivni nlinarnom mtodom za sorpciju Pb 2+ iona na lktropćnoj troski pri različitim tmpraturama. Tmpratur (K) Isothrm Paramtr Frundlich n K F ((mg/g)(l/mg) 1/n )) R m (mg/g) K L (L/mg) R β Rdlich-Ptrson a R (L/mol) K R (L/g) R CONCLUSIONS Th prsnt invstigation shows that th lctric furnac slag is an ffctiv adsorbnt for th rmoval of Pb 2+ ions from auous solutions. Th sorption of Pb 2+ on th lctric furnac slag was found to b initial concntration and it is physical sorption. Th amount of Pb 2+ rmovd incrass with th incras tmpratur and initial Pb 2+ concntration. Th uilibrium data hav bn analyzd using, Frundlich and Rdlich-Ptrson isothrms. Th charactristic paramtrs for ach isothrm and rlatd cofficints of dtrmination (R 2 ) hav bn dtrmind using MATLAB 6.5. Th xprimntal data yildd xcllnt fits within th following isothrms ordr Rdlich Ptrson > > Frundlich, basd on thir cofficint of dtrmination (R 2 ) valus. Th Rdlich Ptrson isothrm producd a highr cofficint of dtrmination valus (.9999, and.9995 for xprimnts prformd at 293, 33 and 313 K, rspctivly) in comparison to all th isothrms studid. Th Holistic Approach to Environmnt 1(211)1, Pag 17

6 L. Ćurković t al. Application of Diffrnt Isothrm Modls on Lad Ions Sorption... REFERENCES 1. L. Ćurković, Š. Crjan-Stfanović, T. Filipan, Watr Rsarch, 31, 1997, J. Prić, M. Trgo, N. Vukojvić Mdvidović N, Watr Rsarch, 38, 24, S.V. Dmitrova, Wat. Rs., 3, 1996, L. Ćurković, Š. Crjan-Stfanovic, A. Rastovčan-Mioč, Watr Rsarch, 35, 21, Y.S. Ho, A.E. Ofomaja, Procss Biochmistry, 4, 25, H.Z. Frundlich, Th Journal of Physical Chmistry, 57A, 196, I., Journal of th Amrican Chmical Socity, 4, 1918, M. R. Samarghandi, M. Hadi, S. Moaydi, F. Barjasth Askari, Iranian Journal of Environmntal Halth Scinc and Enginring, 6, 29, 4, K. Vasanth Kumar, K. Porkodi, Journal of Hazardous Matrials, 138, 26, 3, Y.S. Ho, Polish Journal of Environmntal Studis 15, 26, 1, O. Rdlich, D.L. Ptrson, Th Journal of Physical Chmistry, 63, 1959, Th Holistic Approach to Environmnt 1 (211) 1, Pag 18