Do ZnO nd Al2O3 Nnoprticles Improve the Anti-Bcteril Properties of Cellulose Acette-Chitosn Memrne? Titik Istirokhtun,,*, Ulv Yuni, Pertiwi Andrni, Heru Susnto,c Deprtment of Environmentl Engineering, Diponegoro University, Indonesi Memrne Reserch Center(Mer-C), Center of Reserch nd Services-Diponegoro University c Deprtment of Chemicl Engineering, Fculty of Engineering, Diponegoro University Astrct. Biofouling, due to the existence of cteri in wter, ecomes one of the rriers in cellulose cette (CA) memrne pplictions. Although chitosn hs een incorported into CA memrnes, its ntimicroil ctivity hs not een improved significntly yet. In this study, cellulose cette-chitosn memrnes were prepred y modifiction using ZnO nd Al2O3 nnoprticles during phse seprtion method. The memrnes were then chrcterized in term of wter permeility, nd surfce morphology. The nti-cteri property ws exmined y using grm-negtive cteri. Modifiction of cellulose cette-chitosn memrnes with ZnO nd Al2O3 nnoprticles hve not shown optiml results where no cler zones round the memrne re visile. 1. Introduction Memrne technology hs een proposed s promising technology in the lst few centuries to remove vrious contminnts from wter nd wste wter [1-3]. Cellulose cette (CA) is considered s n ttrctive rw mteril for the memrne preprtion due to its rw mteril vilility in lrge quntities tht commonly found in nture. CA memrne hs een widely developed due to its superior chrcteristics such s nontoxic, inexpensive, iodegrdle (therefore, they re susceptile to fouling) [4, 5]. Fouling memrne is criticl prolem tht inhiits memrne performnce in wter tretment processes nd until now it hs not yet hndled. The min consequence of iofouling is the decrese of flux during filtrtion process [6,7]. Memrne fouling cn e distinguished y orgnic fouling, inorgnic fouling, nd iologicl fouling (i.e., iofilm formtion) [8]. Between these types of fouling, memrne iofouling, the ccumultion of microorgnisms nd extrcellulr polymers on the memrne surfce, is the mjor prolem in wter tretment. Memrne iofouling is formed when dhesion occurs from one or more cteri on the memrne surfce. Then it followed y growth nd multipliction of sessile cells, which then form iofilms on the memrne surfce [9,10]. Unlike physicl nd chemicl fouling, iofouling is more difficult to e removed nd it cuses decrese in permeility, resulting in irreversile dmge to memrne [11]. Chitosn (CS), lso known s the most importnt derivtive of chitin, which is its existence very undnt in Indonesi. Chitosn hs een lredy used in memrne production due to its interesting chrcteristics such s hydrophilicity [12], non-toxicity [13], nd ntimicroil ctivity [14]. Previous reserch hs dded chitosn to improve ntiiofouling performnce on cellulose cette memrnes. Unfortuntely, it resulted low ntimicroil ctivity ecuse the memrne loses its positive chrge [15]. Another resercher stted tht chitosn incresed the memrne resistnce ginst microil fouling, ut its microil ctivity could only e seen vi memrne surfce visuliztion, nd could not e seen y inhiition method. Furthermore, ddition of chitosn lso reduced the hydrophilicity of CA memrne [16]. Therefore, lterntives re needed for preventing iofouling, incresing hydrophilicity, nd in the sme time improving nticteril ctivity of CA-CS memrne. Memrne modifiction using dditives such s inorgnic nnoprticles, is one of the lterntive wys to control iofouling y improving sic polymer properties such s hydrophilicity nd fouling resistnce (perm-selectivity) [17,18]. In this study, Al2O 3 ws used to enhnce the mechnicl resistnce nd hydrophilicity of the memrne [19]. Al 2O 3 nnoprticle lso improves memrne nti-dhesive cpility thus reducing the iofilm lyer nd in the sme time incresing memrne hydrophilicity [20]. Zink oxide is nother mteril which is completely hydrophilic nd possesses nticteril nture. Moreover, ZnO lso hve ultrvioresistnt property which might potentil enefit the ntifouling performnce of memrne. However, little ttention is pid to the ppliction of ZnO on memrne friction [21]. Therefore, the ZnO ws lso used in this study to improve * Corresponding uthor: titik.istirokhtun@live.undip.c.id The Authors, pulished y EDP Sciences. This is n open ccess rticle distriuted under the terms of the Cretive Commons Attriution License 4.0 (http://cretivecommons.org/licenses/y/4.0/).
hydrophilicity nd ntifouling properties of memrnes [22-25]. In this reserch, modifictions of cellulose cettechitosn memrnes were prepred y dding Al 2O 3 (0-4%), nd ZnO (0-4%) to improve the hydrophilicity nd nti-iofouling properties of memrnes. 2. Mterils nd Methods 2.1 Mterils Commercil cellulose cette ((C 6H 7O 2(OCOCH 3))x ws purchsed from from Sigm Aldrich, Germny. Nnoprticles Al 2O 3 nd ZnO were otined from Merck, Germny. Chitosn (C 6H 11NO 4)n ws purchsed from Biotech Surendo, Indonesi. Acetic cid (CH 3COOH) ws otined from Merck, Germny. Distilled wter produced from home-mde pure wter unit ws used for ll experiment. Escherichi coli cteri cultures were otined from Microiology, Diponegoro University. 2.2 Methods 2.2.1 Memrne preprtion Preprtion of memrne ws conducted y wet phse inversion. Memrne csting solution ws mde from 12% cellulose cette s memrne se mteril, mixture of cetic cid nd distilled wter (3:1) s solvent, 0.1% chitosn, nnoprticles Al 2O 3 nd ZnO with concentrtion of 0-4% s dditives. First of ll, chitosn ws introduced into the solvent nd stirred using mgnetic stirrer until ll chitosn dissolved. Then the nnoprticles were dded to the solution with concentrtion vritions of 0-4% until dissolved. The finl step ws ddition cellulose cette then stirring until ll the ingredients were homogenously mixed. After completion, csting solution ws left without stirring until no ule ws oserved. Memrne molding process ws crried out y following the method which hs een conducted y Istirokhtun et l. [26] s follows, the solution ws firstly cst on glss sustrte using csting knife, then left in room temperture. Therefter, the cst memrne ws solidified in cogultion th contining wter for 30 min to remove remined cidity. The resulting memrne ws wshed nd rinsed y soking in wter for t lest 24 h efore drying. 2.2.2. Memrne Chrcteriztions The wter permeility of the memrnes ws evluted through series of filtrtion using ded end stirred cell filtrtion system (Amicon model 8010), which ws pressurized y nitrogen gs. Prior to ech filtrtion memrne were pre-compcted y filtrtion of pure wter t high pressure for t lest 0.5-1 h to void effect of compction. Therefter, the pressure ws lowered to the desired pressure for wter permeility mesurements (1 r). The next step ws mesuring the permete weight to know the volume. This permete volume ws then used s sis for clculting wter flux. The equtions used to clculte the pure wter flux re: JJ = QQ AA.tt (1) Where: Q : The volume of fluid pssing through the memrne (permete) (L) t : Time (hour) J : Flux (L/m 2.hour) A : Memrne Are (m 2 ) 2.2.3. Anticteril ctivity test The nticteril ctivity of the memrne ws exmined y n inhiition method, wherein grm-negtive cteri Escherichi Coli ws used. This method hs lredy een descried y Istirokhtun et l nd M et l [16,27]. To determine nticteril ctivity, ll memrnes were sterilized in utoclve t 121 o C, 2 rs for 15 min. Sterilized memrnes were then plced on the surfce nutrient gr (NA) contining Escherichi Coli solution nd then incuted for 24 hours t 37 o C. The dimeter of the cler zone formed round the memrne ws noted s n indictor of nticteril ctivity. 3. Result nd Discussion 3.1 Memrne Chrcteriztion 3.1.1 Effect of nnoprticles concentrtion on wter permeility Memrne permeility cn e determined y mesuring flux. The results of the pure wter flux test from Cellulose Acette-Chitosn (CA-CS) memrne modified with ZnO nd Al 2O 3re shown in Figure 3.1. Flux (L/m 2.h) 2500 2000 1500 1000 500 0 Al2O3 ZnO 0% 1% 2% 3% 4% Nnoprticle Concentrtion Figure 3.1 Wter permeility of CA-CS memrnes s function of nnoprticles concentrtion It is oviously seen tht compred with 0% concentrtion of nnoprticles, ddition of oth ZnO nd Al 2O 3hs significnt effect on promoting memrne permeility. These phenomen occurred might e due to complete hydrophilicity of ZnO nd Al 2O 3. CA-CS memrne with ddition of ZnO reched the highest flux (1,984.71 L/m 2.hour) t 2% of ZnO concentrtion, while 2
ddition of Al 2O 3 chieved the highest flux (1,891.98 L/m 2.hour) t 3% of Al 2O 3 concentrtion. It is lso importnt to note tht overdoses of oth nnoprticles could decrese flux [21], s cn e oserved in the decrese of flux when percent concentrtion of ZnO nd Al 2O 3 were 3% nd 4% respectively. These results re consistent with studies conducted y Yn et l. [20] which conclude the increse of Al 2O 3 concentrtion long with the increse of permete flux to certin concentrtion level. According to Ivrs et l. [28], memrne permeility incresed long with the incresing of nnoprticles in the csting solution. It cused y the ffinity of nnoprticles, therefore, the porosity nd pore size of modified CA-CS memrnes were higher thn unmodified memrnes. However, the results of this study differ from reserch conducted y (He nd Hong, [29] which sttes tht the ddition of nnoprticle the PVDF memrne reduces the flux of pure wter nd pore size of the memrne. The presence of nnoprticles in the memrne mtrix enhnces strength nd stiffness, therml stility, permeility, hydrophilicity, flux recovery nd ntifouling properties of memrnes [30-32]. The presence of nnoprticles improves the memrne hydrophilicity due to high surfce energy thus incresing the sorption of wter molecules on the memrne surfce [33]. In ddition, the hydrophilicity of nnoprticles lso ffects memrne flux. Incresed hydrophilicity of the memrne surfce nd memrne pore could decrese the memrne fouling s it strongly intercts with wter molecules nd resulting greter flux [34,35]. However, higher concentrtion of nnoprticles could negtively ffect the memrne permeility due to gglomertion of the inorgnic nnoprticles on the memrne surfce during memrne preprtion. These clumping nnoprticles s consequence of Vn der Wls forces etween nnoprticles cused y high surfce energy to chieve stle conditions. It my clog some pores nd possily desrese the memrne hydrophilicity, thus cusing decrese in the wter flux [34,36]. sed on the results otined in this study the pore size of memrne modifiction of Al 2O 3 nnoprticles ws greter thn the memrnes without modifiction of nnoprticles. This result is in ccordnce with the reserch conducted y Liu et l. [19] which sttes tht higher concentrtion of Al 2O 3 nnoprticles resulting lrger pore size of memrne. Figure 3.2 SEM of memrne surfce () CA-CS () CA- CS/Al2O3 1% (c) CA-CS/Al2O3 3% with mgnifiction 7.500x The surfce morphology of the CA-CS/ZnO memrne is shown in Figure 3.3. As well s the ddition of Al 2O 3, the ddition of ZnO lso resulted lumps of nnoprticles on the memrne surfces. It is lso oserved tht CA-CS/ZnO memrnes hve smller pores thn CA-CS/Al 2O 3 memrnes. This could e cused y the presence of oxide metl nnoprticles in the polymer to increse the viscosity of the solution therey the rte of solvent diffusion into the non-solvent during the phse inversion process decresed, which eventully led to the formtion of tightly pore memrnes [38]. c 3.1.2. Scnning Electron Microscopy (SEM) Figure 3.2 show SEM results from the surfce of CA-CS nd CA-CS/Al 2O 3 memrnes. It ws oserved qulittively tht ddition of Al 2O 3 influences surfce morphology of ech memrne. On the surfces of CA- CS/Al 2O 3 memrnes, oth 1% nd 3% concentrtions pper gglomertions of nnoprticle covering the memrne pores. The incresed concentrtion of Al 2O 3 resulted thicker gglomertion. This SEM result supports preceding explntion on the results of wter permeility tht the presence of nnoprticles cusing clumps tht covered the memrne pores. Yn et l. [20] stted in his reserch tht the ddition of Al 2O 3 nnoprticles in PVDF memrnes does not ffect thesurfce structure, cross section nd pore size of memrnes. Mximous et l. [37] lso stted tht there ws no significnt pore size difference with the ddition of Al 2O 3 nnoprticles in the PES memrne. However, c Figure 3.3 SEM of memrne surfce () CA-CS () CA- CS/ZnO 1% (c) CA-CS/ZnO 2% with mgnifiction 7.500x 3.2 Anticteril Activity Test The nti-cteril test ws exmined to find out the ntiiofouling properties of CA-CS memrnes fter the ddition of Al 2O 3 nd ZnO nnoprticles. The nticteril test ws performed y mesuring the 3
dimeter of the cler zone formed ner memrne fter E. coli incution. The results re presented in Figure 3.4. not occurred perfectly, evidenced y the presence of the gglomertions of nnoprticles on memrne surfces. The higher the concentrtion of nnoprticles, the more ovious the ppernce of the lumps. An nticteril test using inhiition zone method ws performed. Nevertheless, it produced unidel result, where no cler zone round the memrne were visile. The uthors would like to thnks to Engineering Fculty, Diponegoro University for the finncil support of this study. Figure 3.4 Anti-cteril test on () CA-CS/ZnO memrne nd () CA-CS/Al 2O 3 memrne In the CA-CS memrne (Figure 3.4.), the width of the cler zone formed round the memrne ws 3 mm. The width of the cler zone formed y CA-CSnnoprticle memrne ws 2 mm nd 1 mm for Al 2O 3 1% nd Al 2O 3 2% respectively. Menwhile, the cler zone widths formed y CA-CS memrne with ZnO (Figure 3.4.) were 1 mm nd 0.5 mm t concentrtions of 1% ZnO nd 2% ZnO respectively. These results suggest tht the effect of ddition ZnO on memrne mtrix resulted in smller cler zone compred to CA-CS memrne which modified y Al 2O 3, while the modified CA-CS memrne with the ddition of nnoprticles hs smller cler zone thn the CA-CS memrne. Anticteril ctivity cn e seen from the dimeter of the cler zone. The cler zone is n effective wy for memrne to demonstrte nticteril ctivity [39]. The greter the cler zone formed round on the memrne the etter nticteril properties. From this study, it cn e concluded tht the ddition of nnoprticles further reduced the cler zone round memrne. In other words, the ddition of nnoprticles during memrne preprtion hs not een successful in improving nticteril properties. These results differ from those stted y Al-nmni et l. [24] nd Mlini et l. [25] tht modified the chitosn memrne with the ddition of ZnO nd found tht the ddition of ZnO incresed the nticteril cpcity of the memrne significntly. In nother study [40], Shenghn nd Ruichng, reported tht the memrne of cellulose/nnoprticles produces etter nti-cteril properties thn the cellulose/chitosn memrne. However, in these results, it is seen tht higher nnoprticle concentrtions resulted smller inhiition zones. This might e due to the ccumultion of nnoprticles dded to the memrne which further decresed their nticteril ctivity. 4. Conclusion Modifiction of CA-CS memrne y dding ZnO nd Al 2O 3 incresed flux. The mximum flux of the modified memrne ws reched y 2% ZnO (1,984.71L.m -2.h -1 ) nd 3% Al 2O 3 (1,891.98 L.m -2.h -1 ). In ddition, the presence of nnoprticles lso enhnced hydrophilicity of CA-CS memrnes. The SEM results showed tht ddition nnoprticle during phse seprtion process hs References [1] G. Kng, Y. Co. J. Memr. Sci. 463, 145-165 (2014) [2] J. Hong, Y. He. Deslintion 332, 67-75 (2014) [3] J. Kim, B.V. Bruggen. Environ. Pollut. 158, 2335-2349 (2010) [4] D. Bhongsuwn nd T. Bhongsuwn, 2008. J. Nt. Sci. 42, 311-317 (2008) [5] J. Puls, S.A. Wilson, D. Holter.J. Polym. Environ. 19, 152-165 (2011) [6] J. Hong, Y. He. Deslintion 302, 71-79 (2012) [7] L.H. Kim, M.S. Shin, S. Kim, C. Kim, K. Che, In. S. Kim. J. Memr. Sci. 477, 86-92 (2015) [8] L. Dong, H. Yng, S. Liu, X. Wng, Y.F Xie. Deslintion 365, 70-78 (2015) [9] C.X Liu, D.R Zhng, Y. He, X.S. Zho, R. Bi. J. Memr. Sci. 346.121-130 (2010) [10] N. Hill, V. Kochkodn, L. Al-Khti, T. Levdn. Deslintion. 167, 293-300 (2004) [11] H. Rji, N. Ghemi, S.S. Mdeni, P. Drel, B. Astinchp, S. Zindini, S.S. Rzvizdeh. Appl. Surf. Sci. 349, 66-77 (2015) [12] T.C. Yng, C.C. Chou, C.F. Li. Int. J. Food Microiol. 97, 237-245 (2005) [13] G. M, D. Yng, Y. Zhou, M. Xio, J.F. Kennedy, J. Nie. Polym. 74, 121-126 (2008) [14] H. Mellegrd, S.P. Strnd, B.E. Christensen, P.E. Grnum, S.P. Hrdy. Int J. Food Microiol 148, 48-54 (2011) [15] C. Qin, H. Li, Q. Xio, Y. Liu, J. Zhu, Y. Du. Crohyd. Polym. 63, 367-374 (2006) [16] T. Istirokhtun, N. Rokhti, D. Nurleli, N.N. Arifiningsih, Sudrno, Syfrudin, H. Susnto. Int. J. Environ. Sci. Technol. 10, 56-67 (2017) [17] F. Kr, E.A Aksoy, Z. Yuksekdg, N. Hsirci, S. Aksoy. Crohyd. Polym. 112, 39-47 (2014) [18] J.G. Ivrs, M.I. Iorr-Clr, M.I. Alcni-Mirnd, B.V. Bruggen. J. Memr. Sci. 492, 709-722 (2015) [19] F. Liu, M.R.M. Aed, K. Li. J. Memr. Sci. 366, 97-103 (2011) [20] L.Yn, Y.S. Li, C.B. Xing, S. Xind. J. Memr. Sci. 276, 162-167 (2006) [21] S. Ling, K. Xio, Y. Mo, X. Hung. J. Memr. Sci. 394-395, 184-192 (2012) [22] D. Shrm, J. Rjput, B.S. Kith, M. Kur, S. Shrm. Thin Solid Films. 519, 1224-1229 (2010) [23] G.S. Dhillon, S.Kur, S.K. Brr. Int. Nno. Lett. 4, 107 (2014) [24] L. Al-nmni, S. Doretsov, J. Dutt, J.G. Burgess. Chemosphere. 168, 408-417 (2017) 4
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