Journal of Industrial and Engineering Chemistry

Transcription

1 Journl of Industril nd Engineering Chemistry 7 () 5 59 Contents lists ville t ScienceDirect Journl of Industril nd Engineering Chemistry journl homepge: Removl of Cu(II)-ion over mine-functionlized mesoporous silic mterils Hyung Won Lee, Hye Jung Cho, Jin-Heong Yim, Ji Mn Kim c, Jong-Ki Jeon d, Jung Min Sohn e, Kyung-Seun Yoo f, Seung-Soo Kim g, Young-Kwon Prk,h, * Grdute School of Energy nd Environmentl System Engineering, University of Seoul, Seoul 3-73, Repulic of Kore Division of Advnced Mterils Engineering, Kongju Ntionl University, Cheonn 33-77, Repulic of Kore c Deprtment of Chemistry, BK School of Mterils Science, Deprtment of Energy Science, Sungkyunkwn University, Suwon -7, Repulic of Kore d Deprtment of Chemicl Engineering, Kongju Ntionl University, Cheonn 33-77, Repulic of Kore e Deprtment of Minerl Resources & Energy Engineering, Chonuk Ntionl University, Jeonju 5-75, Repulic of Kore f Deprtment of Environmentl Engineering, Kwngwoon University, Seoul 39-7, Repulic of Kore g Deprtment of Chemicl Engineering, Kngwon Ntionl University, Smcheok 5-7, Repulic of Kore h School of Environmentl Engineering, University of Seoul, Seoul 3-73, Repulic of Kore ARTICLE INFO ABSTRACT Article history: Received July Accepted 9 Septemer Aville online April Keywords: Cu(II)-ion Amine functionlized Mesoporous silic mterils The cpility for the dsorption of Cu(II)-ion with mesoporous silic mterils, such s MCM-, SBA-5 nd XPD-, fter functionlizing with mine groups, such s minopropyltriethoxysilne (APTES), N(-minoethyl) g-minopropylmethyl dimethoxysilne (AEAPMDMS) nd N -(3-(trimethoxysilyl)- propyl) diethylenetrimine (TMSPDETA), ws investigted in this study. N dsorption, XRD nd elementl nlysis methods were performed to gin n understnding of the structure nd surfce properties of the mesoporous silic mterils. Of the sorent mterils, MCM-, functionlized with APTES, showed the est ctivity for the dsorption of Cu(II)-ion. Compred with the mesoporous silic mterils functionlized with APTES, those functionlized with AEAPMDMS nd/or TMSPDETA showed lower dsorption cpilities, which my hve een due to the loctions of the mine groups. Most of the mine-orgnic domins were suggested should exist ner the opening of chnnels or externl surfces. Furthermore, the rte of dsorption of Cu(II)-ions mtched well with pseudo-second-order kinetic model. ß The Koren Society of Industril nd Engineering Chemistry. Pulished y Elsevier B.V. All rights reserved.. Introduction Rpid industriliztion nd the increse in the world popultion hve incresed pollution of ecosystems due to hevy metls with high toxicities. Hevy metl ions hve grdully incresed ecotoxicologicl hzrds, with much ttention hving een pid to these issues []. Copper is widely used s metl for smelting, in the mnufcture of rss, electroplting industries nd petroleum refining, with the excessive use of copper-sed grichemicls. These industries produce much wste wter nd sludges contining vrious concentrtions of Cu(II)-ions, which hve negtive effects on the wter environment []. Even very low concentrtion of Cu(II)-ions cn e hrmful to humns. An excess dsorption of Cu cuses Wilson s disese, nd Cu(II)-ions re deposited in the rin, skin, liver, pncres nd myocrdium [3]. Conventionl methods for the removl of hevy metl ions in queous solutions include chemicl precipittion, ion exchnge, reverse osmosis, * Corresponding uthor. Tel.: + 53; fx: + 5. E-mil ddress: ctlic@uos.c.kr (Y.-K. Prk). electrochemicl tretment nd dsorption. Especilly, dsorption is known s one of est methods for the removl of low concentrtions of metl ions []. Although ctivted cron is used s generl sorent for oth inorgnic nd orgnic compounds, the development of new sorents to improve the effectiveness of dsorption t very low pollutnt concentrtions re required. For this purpose, new hyrid orgnic inorgnic mesoporous ordered structures hve recently een proposed s lterntive sorents for the removl of hevy metl ions. Since their initil preprtion in 99, mesoporous silic mterils hve een pplied to mny fields. Mesoporous silic mterils, such s MCM- nd SBA-5, hve lrge surfce res nd homogeneous pore sizes [5 ]. In ddition, the surfce of mesoporous silic mterils cn e redily modified with orgnic groups to chnge their chrcteristics nd chieve specific purposes [,]. Amine groups re reported to improve the dsorption efficiency of hevy metls when dded to the surfce of the dsorent [3]. Amino functionl mesoporous silic SBA-5 mterils were lso pplied for removl of queous hevy metls such s Cu(II), Ni(II), P(II), Cd(II) nd Zn(II) []. However, only few comprisons of the ddition of vrious mine functionl groups to mesoporous silic -X/$ see front mtter ß The Koren Society of Industril nd Engineering Chemistry. Pulished y Elsevier B.V. All rights reserved. doi:./j.jiec..9.

2 H.W. Lee et l. / Journl of Industril nd Engineering Chemistry 7 () mterils, with different pore structures, hve een reported for the dsorption of Cu(II)-ions. In this study, MCM- (pore size: typiclly 3 nm, ordered hexgonl pore structure) ws functionlized with three different mine groups, i.e. 3-minopropyltriethoxysilne (APTES), N(mino ethyl) g-mino propyl methyl dimethoxy silne (AEAPMDMS) nd N -(3-(trimethoxy silyl)-propyl) diethylene trimine (TMSPDETA), with one, two nd three mine groups, respectively. Furthermore, the dsorption ility of the functionlized MCM- mterils ws compred with those of functionlized SBA-5 (pore size: typiclly nm) nd morphous silic (pore size: typiclly nm, worm-like disordered structure), which hve different pore sizes nd structures.. Experimentl.. Preprtion of mesoporous silic mterils The MCM- smples were synthesized s descried elow. The CTAB (.3 g) ws completely dissolved in g of distilled wter in drying oven ( C), fter which, g of sodium silicte solution (SiO wt% in H O) ws dded drop wise t room temperture. After stirring for h to form gel, the mixture ws ged t C for h. Acetic cid (5 wt%) ws dded until the ph of the mixture ws ph, with the mixture further ged t C for h. The ph of the mixture ws redjusted to using the previous method. The finl solid product ws otined y filtrtion, wshed severl times with distilled wter, nd then clcinted t 55 C for h. The molr rtio of SiO :CTAB:H O ws.5:.:3. The SBA-5 ws synthesized s follows. A trilock copolymer, Pluronic P3 (EO PO7 EO, Aldrich), ws used s templte. The P3 (.5 g) ws completely dissolved in mixture of 9. ml queous. M HCl, with stirring. TEOS (. g) ws then dded drop wise to the mixture, mintined t 35 C in wter th. The resulting solution ws stirred until milky, with the mixture then ged for h t 35 C. The solution ws susequently trnsferred into n oven ( C) nd ged for h. The product ws filtered, without wshing, nd the solid product vcuum-dried t C for h. The s-synthesized SBA-5 ws clcinted t 55 C for 5 h. The molr rtio of P3:TEOS:HCl ws ::35. Commercil morphous silic (XPO-) ws purchsed from Grce Dvison Compny... Synthesis of mine functionlized mterils y the post synthesis method A typicl post-synthesis method, entiled refluxing in nonpolr solvent in the presence of orgnosilnes, ws employed [,,5]. The detils of the experimentl procedure re s follows:.5 g of the s-clcinted mterils were dispersed in ml of toluene for.5 h, t 5 C, with stirring. P-toluene sulfonic cid (3.5 mg) nd the orgnosilnes (. mmol) were then dded. The mixture ws refluxed t C for h, with stirring. After h, the solid product ws filtered, wshed three times with ethnol nd the resulting solid dried t C for h..3. Chrcteriztion of mesoporous silic mterils Nitrogen dsorption desorption isotherms were determined using Micrometrics ASAP t 9 C. For the mesurements, the smples were degssed t 35 C for 3 h. The surfce re ws clculted ccording to the Brunuer Emmett Teller (BET) eqution. The pore volume ws otined from the t-plot method. The pore size distriution ws determined y Brrett Joyner Hlend (BJH) method. Smll-ngle powder X-ry diffrction (XRD) ptterns were recorded on Rigku D/mx-5 X-ry diffrctometer. The nitrogen contents of the mterils were determined vi n elementl nlysis (EA) using Flsh EA, series (CE Instruments)... Cu(II)-ion dsorption experiment The dsorption tests were performed in tch type tests in ml Erlenmeyer flsks t C, with stirring t 5 rpm. Typiclly, 5 mg of the mine-functionlized mesoporous silic [(Fig._)TD$FIG] Quntity dsored (cm 3 g - STP) Quntity dsored (cm 3 g - STP) Quntity dsored (cm 3 g - STP) c Reltive pressure (P/P ) SBA-5 SBA-5 / APTES SBA-5 / AEAPMDMS SBA-5 / TMSPDETA.. Reltive pressure (P/P ) XPO- XPO- / APTES XPO- / AEAPMDMS XPO- / TMSPDETA.. Reltive pressure (P/P ) MCM- MCM- / APTES MCM- / AEAPMDMS MCM- / TMSPDETA Fig.. Nitrogen dsorption desorption isotherms of mesoporous silic dsorents

3 5 H.W. Lee et l. / Journl of Industril nd Engineering Chemistry 7 () 5 59 mteril ws plced in flsk, contining ml of n queous solution of copper (II) nitrte trihydrte (Junsei Chemicl Co., Ltd.), which ws used s the copper source. The initil Cu concentrtion ws mg L, t ph After h of vigorous stirring, to ssuring equilirium, the suspension ws filtered, with the filtrte otined nlyzed using n ICP (Inductively Coupled Plsm, ICPE- 9 SHIMADZU). A wvelength of 3. nm ws used in this study for the nlysis of the copper. The metl concentrtions in the liquid phse were determined t the eginning (C i ) nd t equilirtion (C e ), nd represented s mg L. The following eqution ws used to compute the dsorent uptke cpcity t equilirium, q e (mg g ): q e ¼ ðc i C e ÞV w where V is the volume of the copper in solution (ml), C i nd C e re the initil nd equilirium concentrtions of copper in solution (mg L ), respectively, nd w is the mss of the mine-functionlized mesoporous silic mteril (g). 3. Results nd discussion 3.. Chrcteriztion of mesoporous silic mterils N dsorption/desorption ws conducted to oserve the effect of the functionliztion with vrious mine groups on the specific surfce re nd size of pore. Figs. nd showed the dsorption desorption isotherms nd pore size distriutions of MCM-, SBA- 5 nd XPO-. All smples mtched the type IV hysteresis loop of the IUPAC clssifiction. Although the mount of N dsored decresed, the shpe of the hysteresis loop ws mintined, which mens tht the pore shpe hd not een chnged during the silne functionliztion. The specific surfce res nd pore sizes of the sorents, oth with nd without functionliztion with mine groups, re presented in Tle. The specific surfce re nd pore size of the non-functionlized MCM-, with n ordered hexgonl pore structure, were 5 m /g nd.9 nm, respectively. After dding the functionl mine groups, the surfce re ws decresed to 777 m /g. With incresing length of the formed mine chin, the surfce re decresed; the pore size lso decresed. Without functionliztion, the pore size of SBA-5 ws 5.5 nm, nd the surfce re the lrgest, m /g, which decresed to 3 m /g s incresing the chin length of the mine group. The surfce re of the non-functionlized XPO- ws 5 m /g, with pore size of.7 nm nd n ordered hexgonl pore structure. Conversely, the smller surfce re of the XPO- /TMSPDETA with the three mine group chin ws m /g. These results inferred tht locking of pores nd decresed surfce re hd een cused due to the functionliztion with mine groups. As shown in Fig., the shpe of hysteresis ws lso Tle Surfce re nd pore volume of vrious mine-functionlized dsorents. Adsorent V tot (cm 3 /g) S BET (m /g) Pore size (nm) MCM MCM-/APTES.7.5 MCM-/AEAPMDMS MCM-/TMSPDETA SBA SBA-5/APTES SBA-5/AEAPMDMS SBA-5/TMSPDETA XPO XPO-/APTES.9 3. XPO-/AEAPMDMS. 7. XPO-/TMSPDETA chnged y functionliztion with mine group. By locking of pores with mine group, the size nd volume of pores ws decresed nd then the smller hysteresis loop in dsorption desorption isotherm ws oserved. More smooth desorption isotherm ws oserved compred to mesoporous mterils without mine groups. These results greed with previous pper reported y Grosmn nd Orteg []. The results of the elementl nlyses of the sorents re summrized in Tle. The mount of nitrogen (N) dsored incresed with functionliztion with mine groups. From the [(Fig._)TD$FIG] dv/dlog(d) Pore volume (cm 3 g - ) dv/dlog(d) Pore volume (cm 3 g - ) c dv/dlog(d) Pore volume (cm 3 g - ) 5 3 Pore dimeter (nm) Pore dimeter (nm) XPO- XPO- / APTES XPO- / AEAPMDMS XPO- / TMSPDETA Pore dimeter (nm) MCM- MCM- / APTES MCM- / AEAPMDMS MCM- / TMSPDETA SBA-5 SBA-5 / APTES SBA-5 / AEAPMDMS SBA-5 / TMSPDETA Fig.. Pore size distriutions of mesoporous silic dsorents.

4 [(Fig._3)TD$FIG] H.W. Lee et l. / Journl of Industril nd Engineering Chemistry 7 () Tle Amine (N) content of vrious dsorents. Ctlyst N (wt%) MCM-. MCM-/APTES. MCM-/AEAPMDMS 3. MCM-/TMSPDETA 5.3 SBA-5. SBA-5/APTES.7 SBA-5/AEAPMDMS 3. SBA-5/TMSPDETA.9 XPO-. XPO-/APTES.5 XPO-/AEAPMDMS.9 XPO-/TMSPDETA 3. intensity MCM- / TMSPDETA MCM- / AEAPMDMS MCM- / APTES By elementl nlysis. MCM- mount of N dsored, the numer of functionlized mine groups could e clculted. The lrgest numer of mine groups ws functionlized on the MCM-, with the smllest numer on the XPO-. The longer the mine chin, the more mine groups the sorents contined. An X-ry diffrction (XRD) nlysis ws crried out to investigte the surfce structure of the sorents contining the vrious mine groups, the results of which re shown in Fig. 3. From the XRD results, no ovious chnges were oserved in the structures due to functionliztion with the vrious mine groups. 3 θ Adsorption test of Cu(II)-ion on mine-functionlized mesoporous silic dsorents An dsorption experiment ws performed to investigte the effects of the mine groups, introduced vi the post-synthesis grfting method, on the mesoporous silic mterils. Comprtive experiments were performed using the sme method for the mesoporous silic mterils without functionliztion. As shown in Fig., the cpcities for Cu(II)-ion dsorption y the nonfunctionlized sorents were reltively low. When ll the mesoporous silic mterils were functionlized with APTES, the mounts of Cu(II)-ion dsored were gretly incresed. However, the mounts of Cu(II)-ion dsored onto the mesoporous silic sorents functionlized with AEAPMDMS nd/or TMSPDETA were lower thn tht for APTES. The longer the mine group chin, the lower the dsorption ility for Cu(II)-ion. This could men tht the mine groups, such s AEAPMDMS nd TMSPDETA, when functionlized onto the sorents could not ecome effective dsorption sites for Cu(II)-ions. A similr result ws reported for the dsorption of Co (II)-ions y n mino-functionlized MCM- [3], for which the following explntions were suggested; the Cu(II)-ions in n queous solution cn form complexes with wter nd/or other molecules. Since the sizes of those complexes re less thn nm, nd the pore sizes of the mesoporous silic sorents functionlized with AEAPMDMS nd TMSPDETA re out.3.5 nm (Tle ), these complexes will e le to esily diffuse to the mine groups in the pores of the sorents. However, the mount of Cu(II)-ions dsored did not increse with incresing numer of mine groups. Amine-orgnolkoxysilnes my rect minly with the surfce silnol locted t the entry to the chnnels or externl surfces of the sorents. In these cses, the orgnic mine moieties will e concentrted on the pore entries, resulting in non-homogeneous distriution of the orgnic mine moieties inside the pores. This my cuse the concentrtion of orgnic mine moieties t the pore entries; therefore, the ctul effective pore size will e decresed. The possiility for Cu(II)-ions to come into contct with the mine groups on the inside of pores would e decresed. Furthermore, mine groups forming specific domin cn esily interct with djcent mine groups vi hydrogen [(Fig._)TD$FIG] Amount of copper dsored [mg/l] intensity M θ 3 SBA-5 / TMSPDETA SBA-5 / AEAPMDMS Fig. 3. XRD ptterns of mesoporous dsorents. M- M- M-3 S S- S- S-3 SBA-5 / APTES X X- SBA-5 Fig.. Cu(II)-ion dsorption test over mesoporous silic dsorents fter h (M: MCM-, S: SBA-5, X: XPO-, -: fucntionlized with APTES, -: funtionlized with AEAPMDMS, -3: funtionlized with TMSPDETA). X- 5 X-3

5 5 H.W. Lee et l. / Journl of Industril nd Engineering Chemistry 7 () 5 59 onding, leding to decresed rectivity [7]. FT-IR spectr of mine functionlized mesoporous mterils with nd without Cu(II)-ion dsorption re shown in Fig. 5. It ws reported tht the pek round 3 cm ws nd chrcteristics of NH scissor nds []. The decrese of pek in this region fter Cu(II)-ion dsorption indictes tht the N H virtion ws ffected due to the Cu(II)-ion dsorption. The dsorption onto the MCM- functionlized with APTES ws the gretest of ll the sorents tested, which ws scried to the lrge surfce re nd greter numer of mine group. From these results, it my e preferle to use n dsorent with lrge surfce re nd high single mine content Adsorption kinetics of Cu(II)-ion on APTES functionlized mesoporous silic dsorents Adsorption kinetics experiments were performed on the mesoporous silic mterils functionlized with APTES, which ws chosen s representtive mteril to monitor the ehvior of the entire rnge of these dsorent types. The rte of dsorption ws nlyzed using two common semi-empiricl kinetic models sed on the dsorption equilirium cpcity: the pseudo-firstorder nd pseudo-second-order equtions, proposed y Lgergren [9] nd Ho nd McKy [], respectively, which re s follows: Pseudo-first order model The sorption kinetics my e descried y pseudo-first order, where the differentil eqution is s follows: [(Fig._5)TD$FIG] dq t ¼ k ðq d q t Þ () t Trnsmittnce(A.U.) MCM-/APTES MCM-/APTES copper loded Integrting Eq. () for the oundry conditions; t =tot = t nd q t =toq t = q t, gives: q log ¼ k t () q q t :33 which is the integrted rte lw for pseudo-first order rection, where q is the mount of Cu(II)-ions sored t equilirium, mg g, q t is the mount of Cu(II)-ions sored t time t,mgg nd k is the equilirium rte constnt of pseudo-first order sorption, min. Eq. () cn e rerrnged to liner form: k t logðq q t Þ¼logðq Þ (3) :33 In order to otin the rte constnts, stright line plots of log(q q t ) ginst t for different Cu(II)-ion concentrtions under different experimentl conditions were nlyzed. The rte constnt, k, nd correltion coefficients, r, for Cu(II)-ions under different conditions were clculted from these plots Pseudo-second order model The sorption kinetics my e descried s pseudo-second order. The differentil eqution is s follows: dq dt ¼ kðq e q t Þ () Integrting Eq. () for the oundry conditions t = tot = t nd q t =toq t = q t, gives: ¼ q e q t q e þ kt which is the integrted rte lw for pseudo-second order rection, where q e is the mount of Cu(II)-ion sored t equilirium, mg g, nd k is the equilirium rte constnt for pseudo-second order sorption, g mg min. Eq. (5) cn e rerrnged to liner forms: t ¼ þ t () q t kq e q e nd (5) h ¼ kq e (7) [(Fig._)TD$FIG] where h is the initil sorption rte, mg g min. Trnsmittnce(A.U.) Wvenumer (cm - ) SBA-5/APTES SBA-5/APTES copper loded Amount of copper dsored [mg/l] MCM-/APTES SBA-5/APTES XPO-/APTES Wvenumer (cm - ) 35 3 Contct time (min) 5 Fig. 5. FT-IR spectr of mine functionlized dsorents with nd without Cu(II)-ion dsorption. () MCM- () SBA-5 Fig.. Effect of contct time on Cu(II)-ion uptke over mesoporous silic dsorents fucntionlized with APTES.

6 [(Fig._7)TD$FIG] H.W. Lee et l. / Journl of Industril nd Engineering Chemistry 7 () Time, (min) MCM-APTES SBA5-APTES XPO-APTES Tle 3 The pseudo-first-order nd pseudo-second-order model constnts, nd their respective coefficients for the dsorption of Cu(II)-ion from its queous solutions. Pseudo-first-order Pseudo-second-order r k [min ] r k [g mg min ] h [mg g min ] log(q e -q t )..5 MCM-/APTES SBA-5/APTES XPO-/APTES Conclusions t/q t, (min g/mg) Time, (min) 5 MCM-APTES SBA5-APTES XPO-APTES 7 Fig. 7. Cu(II)-ion dsorptin kinetics over mesooporous dsorents fucntionlized with APTES. Liner plots of () pseudo-first-order model; () pseudo-second-order model. Stright line plots of t/q t ginst t were lso constructed to otin the rte prmeters. The k, q nd correltion coefficients, r, vlues for Cu(II)-ions under different conditions were clculted from these plots. The liner rrngements, i.e. Eqs. (3) nd (), re commonly used to check the vlidity of models nd to otin the model prmeters when the corresponding liner plot is dequte. Fig. shows tht the dsorption of Cu(II)-ions with contct time; wheres, Fig. 7 shows oth liner plots. From Tle 3 it ws cler tht the pseudo-first-order model is not suitle to descrie the kinetic profile due to the pprent sence of liner ehvior. Conversely, the rtes for the dsorption of queous Cu(II)-ions were le to e ccurtely descried y the pseudo-second-order eqution, s shown in Tle 3, where the experimentl t/q t nd t dt re provided with liner correltions. The rte constnt, k, nd initil sorption rte, h, were highest for XPO- nd lowest for MCM-, which my e due to the initil diffusion eing reltively esy with the lrger pore size. Mesoporous silic mterils, such s MCM-, SBA-5 nd XPO-, were functionlized with APTES, AEAPMDMS nd TMSPDETA, with their performnces for the dsorption of Cu(II)- ions evluted. Of the three different mterils tested for the dsorption of Cu(II)-ions, MCM- functionlized with APTES showed the est performnce. However, the mesoporous silic mterils functionlized with AEAPMDMS nd TMSPDETA showed lower Cu(II)-ion dsorption ilities thn those functionlized with APTES, which might hve een due to the loction of the mine groups; most orgnic mine moieties re likely to concentrte ner the openings of chnnels nd/or on the externl surfces. In ddition, the rtes for the dsorption of queous Cu(II)- ions were successfully reproduced using pseudo-second-order kinetic model. References [] E.A. Deliynni, E.N. Pelek, K.A. Mtis, J. Hzrd. Mter. (7) 7. [] N. Li, N. Bi, Sep. Purif. Technol. (5) 37. [3] B. Volesky, Biosorption of Hevy Metls, CRC Press, Boc Rton, FL, 99. [] S. Krulut, A. Krkn, A. Denizli, Y. Yurum, Sep. Purif. Technol. () 77. [5] H.J. Prk, J.K. Jeon, J.M. Kim, H.I. Lee, J.H. Yim, J. Prk, Y.K. Prk, J. Nnosci. Nnotechnol. () 539. [] K.H. Prk, H.J. Prk, J. Kim, R. Ryoo, J.K. Jeon, J. Prk, Y.K. Prk, J. Nnosci. Nnotechnol. () 3. [7] H.J. Prk, H.S. Heo, J.K. Jeon, J. Kim, R. Ryoo, K.E. Jeong, Y.K. Prk, Appl. Ctl. B: Environ. 95 () 35. [] J.K. Jeon, Y.K. Prk, S. Kim, S.S. Kim, J.H. Yim, J.M. Sohn, J. Ind. Eng. Chem. 3 (7) 7. [9] S.H. Lee, H.S. Heo, K.E. Jeong, J.H. Yim, J.K. Jeon, K.Y. Jung, Y.S. Ko, S.S. Kim, Y.K. Prk, J. Nnosci. Nnotechnol () 759. [] H.I. Lee, J.M. Kim, J.Y. Lee, Y.K. Prk, J.K. Jeon, J.H. Yim, S.H. Prk, K.J. Lee, S.S. Kim, K.E. Jeong, J. Nnosci. Nnotechnol. () 33. [] D.I. Kim, J.H. Prk, S.D. Kim, J.Y. Lee, J.H. Yim, J.K. Jeon, S.H. Prk, Y.K. Prk, J. Ind. Eng. Chem 7 (). [] J.H. Yim, D.I. Kim, J.A. Be, Y.K. Prk, J.H. Prk, J.K. Jeon, S.H. Prk, J.H. Song, S.S. Kim, J. Nnosci. Nnotechnol () 7. [3] T. Yokoi, H. Yoshitke, T. Ttsumi, J. Mter. Chem. () 95. [] J. Agudo, J.M. Arsug, A. Arencii, M. Lindo, V. Gscon, J. Hzrd. Mter. 3 (9) 3. [5] J.A. Be, S.H. Hwng, K.C. Song, J.K. Jeon, Y.S. Ko, J.H. Yim, J. Nnosci. Nnotechnol. () 9. [] A. Grosmn, C. Orteg, Lngmuir () 397. [7] M.W. McKittrick, C.W. Jones, Chem. Mter. 5 (3) 3. [] A.M. Showkt, Y.P. Zhng, M.S. Kim, A.I. Gopln, K.R. Reddy, K.P. Lee, Bull. Koren Chem. Soc. (7) 95. [9] S. Lgergren, Hdndlingr (9). [] Y.S. Ho, G. Mcky, Adsorpt. Sci. Technol. (99) 3.