XX-th ARS SEPARATORIA Szklarska Poręba, Poland 2005

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1 XX-th ARS SEPARATORIA Szklrsk Porę, Polnd 25 DIALYSIS OF METAL IONS THROUGH ULTRAFILTRATION POLYSULFONE MEMBRANES ENHANCED BY POLY(ACRYLIC ACID) Gryzeld POŹNIAK Wroclw University of Technology, Deprtment of Chemistry Wyrzeże Wyspińskiego 27, 5-3 Wrocłw There re numerous pplictions requiring removl of multivlent ions from wter solutions. These include clen up of groundwter (elimintion of wter hrdness) nd of wstewter from metllurgicl industry (removl of vlule hevy metls) [1-5]. Dilysis is trditionl memrne process for removl of metl ions from wter in which the ions move cross nonporous ion-exchnge memrnes sed on Donnn equilirium principle [6]. Dilysis is diffusion phenomenon which is governed y the difference of concentrtion of metl on the two sides of the memrne. The solute flux is stopped when the concentrtions re equl in the two comprtments. The mount of metl crossing the memrne cn e incresed y modifiying the chemicl potentil of the metl in one of the two comprtments. If some wter-solule polymer is dded in the feed comprtment, decrese of free metl ions concentrtion would led to decrese of the trnsfer rte of metl ions [7]. To the contrry, if polyelectrolyte is dded in the receipt comprtment, the interction of the metl ions should e responsile for n increse of the mount trnsferred. In the cse very stle interction formed, it should e possile to recover the totl mount of metl in the receipt comprtment [8]. The im of this work is to compre two kind of ultrfiltrtion memrne: polysulfone nd sulfonted polysulfone in dilysis of Mg(II), Zn(II) nd Ni(II) enhnced y of poly(crylic cid). EXPERIMENTAL The polysulfone (PSU) ws sulfonted using mixture of chlorosulfonic cid (CSA) nd 1,2-dichloroethne (t room temperture, 2 hours). Concentrtion of polymer in DCE ws 1%-wt., the initil molr rtio of CSA to PSU ws.75:1. Porous symmetric memrnes from PSU nd SPSU were formed y phseinversion method from 15%-wt., nd %-wt. solution in N,N-dimethylformmid, respectively, wter ws cogultion th. The dilysis cell ws divided in two indenticl comprtments (35 cm 3 ) y the memrne. One of them contining the metl slt (MgCl 2, ZnCl 2 or NiCl 2 ) n the other the sodium slt of poly(crylic cid), M w = kd. The concentrtions of metl ions in oth queous phses were determined y ASA method (AAnlyst 1, Perkin-Elmer). The diffusion coefficient of metl, D, ws clculted from the eqution [9]: 65

2 where: XX-th ARS SEPARATORIA Szklrsk Porę, Polnd [ cm ],3 tgα V d D = s 2 S 2 tgα = log(c /C -2C t ) = f(t) C nd C t re the initil concentrtion of Mg (II), Zn(II) or Ni(II) in the feed nd in the receipt comprtment t time t, respectively; V is the volume of ech comprtment; d is thickness of the memrne; S is the ctive memrne surfce. RESULTS AND DISCUSSION Polysulfone with good therml, mechnicl, iologicl nd chemicl stility is the most frequently used polymer for ultrfiltrtion memrne preprtion. Ionic groups cn e introduct to the polymer y chemicl modifiction [1]. CH 3 O C CH 3 O S O X - X = SO 3 n A porous structure of PSU nd SPSU memrnes is similr (verge pore dimeter out 35 nm, flux of wter under.1 MP trnsmemrne pressure out 15 dm 3 /cm 2 h) ut in SPSU memrne concentrtion of sulfonic groups is equl to 45%-mol. The dilysis of solution which contins poly(crylic cid) t concentrtion 1-2 mol/cm 3 shows tht only 3% of the polymer is found in the receipt solution fter 24 hours. This mens tht the polymer cnnot cross the memrnes despite the gret differences etween verge pore dimeter of our memrnes nd the moleculr size of the poly(crylic cid). The metl flux depends on molr concentrtion rtio of the polymer to the ction nd on the ph of the receipt phse [8]. In our experiments, concentrtion of Mg(II) nd Ni(II) in feed solution ws equl to 1-3 mol/dm 3, concentrtion of polymer in receipt solution ws equl to 1-2 mol/dm 3 nd ph = 9 (the verge pk for croxylte groups is round 5. Dependence of metl ions concentrtion in feed nd receipt comprtments on dilysis time is presented in Figs

3 XX-th ARS SEPARATORIA Szklrsk Porę, Polnd 25 Mg concentrtion, % Mg concentrtion, % Fig.1. Evolution of the feed nd receipt Mg(II) concentrtions in the sence nd in the presence of polyelectrolyte (PE):. PSU memrne, SPSU memrne 1 1 Zn concentrtion, % 5 2 Zn concentrtion, % Fig.2. Evolution of the feed nd receipt Zn(II) concentrtions in the sence nd in the presence of polyelectrolyte (PE):. PSU memrne, SPSU memrne 1 1 Ni concentrtion, % 5 2 Ni concentrtion, % Fig.3. Evolution of the feed nd receipt Ni(II) concentrtions in the sence nd in the presence of polyelectrolyte (PE):. PSU memrne, SPSU memrne 67

4 XX-th ARS SEPARATORIA Szklrsk Porę, Polnd 25 For the experiments performed without polyelectrolyte, nturl dilysis of metl ions is oserved; concentrtion of Mg (II),Zn(II) nd Ni(II) in receiver is lower thn 5%. The trnsport of ll investigted metl ions is higher out 1% in the cse of sulfonted polysulfone memrne thn in the cse of polysulfone memrne. This effect is due to ction-exchnge property of sulfonted polysulfone memrne. In the presence of polyelectrolyte, concentrtion of ll metl ions in receipt solution is higher thn 5% for PSU memrne nd incresed to lmost 1% for SPSU memrne. The comprison of Mg (II), Zn(II) nd Ni (II) trnsport shows tht the est results one cn otined for SPSU memrne with dded polyelectrolyte. However, trnsport of investigted metl ions goes with vrious rtes; metl concentrtion in receiver reches mximum fter 4, 3 nd 2 hours of dilysis for Mg(II), Zn (II) nd Ni(II), respectively (Figs 1, 2 nd 3). It my rise from differences in rte of onding etween polyelectrolyte nd investigted metls for which electrochemicl potentil is equl to: V for Mg(II), -.76 V for Zn(II) nd -,22 V for Ni(II). The sme dependence is oserved for diffusion coefficient of these metls (T. 1). Tle 1. The diffusion coefficient of investigted metls SPSU 1 5 D, cm 2 s -1 memrne Mg (II) Zn(II) Ni (II) without PAA with PAA Appliction of porous memrnes for dilysis is more dvntgeous thn solid memrnes minly from the trnsport rte point of view. The diffusion coefficient of metl trnsport through porous ultrfiltrtion memrnes is out 1 times higher thn through nonporous dilytic memrnes [9,11]. CONCLUSION 1. The dilysis of metls through polysulfone ultrfiltrtion memrne cn e enhnced y mens of poly(crylic cid), which is le to ond the metl ctions. 2. Properties of ction-exchnge memrnes mde of sulphonted polysulfone mke possile trnsfer of metls to the receiver in 1%. 3. Diffusion rte depends on electrochemicl potentil of trnsported metl. 68

5 XX-th ARS SEPARATORIA Szklrsk Porę, Polnd 25 ACKNOWLEDGEMENT This work ws supported y the Polish Committee for Scientific Reserch grnt 3 T9B REFERENCES 1. A. Tti, J.F. Scmehorn, S.D. Christin, Wter softening using polyelectrolyte-enhnced ultrfiltrtion, Sep. Sci. Technol. (1995) A. Tti, J.F. Scmehorn, S.D. Christin, Economic fesiility study of polyelectrolyte-enhnced ultrfiltrtion for wter softeninh 3. J. Ste, M. Pujol, J. Llorens, Two-phses model for clcium removl from queous solution y polymer enhnced ultrfiltrtion, J. Memr. Sci. 24 (22) R. Wódzki, G. Sionkowski, G. Poźnik, Recovery nd concentrtion of metl ions.iv. Uphill trnsport of Zn(II) in multimemrne hyrid system, Sep. Sci. Technol., 34 (1999) C.A. Kozlowski, W. Wlkowik, Removl of chromium(vi) from queous solutions y polymer inclusion memrnes, Wter Res., 36 (22) F.G. Donnn, Theory of memrne equilirium, Chem. Rev. 1 (1924) J-K. Wng, Preferentil trnsport ehviors of ternry system ferric-cupricnickel ions through ction exchnge memrne with complex gent y dilysis, Deslintion, 161 (24) J. Mrty, M. Persin, J. Srrzin, Dilysis of Ni (II) through n ultrfiltrtion memrne enhnced y polymer complextion, J. Memr. Sci. 167 (2) G. Poźnik, W. Trochimczuk, Tuulr interpolymer ion exchnge memrnes, Angew. Mkromol. Chem., 127 (1984) G. Poźnik, M. Bryjk, W. Trochimczuk, Sulfonted polysulfone memrnes with ntifouling ctivity. Angew. Mkromol. Chem. 233 (1995) G. Poźnik, W. Trochimczuk, Tuulr interpolymer ion-exchnge memrnes. Donnn dilysis through strong-se memrnes, J. Memr. Sci., 49 (19)