Systematic choice of crosslinker and filler for pervaporation membrane: A case study with dehydration of isopropyl alcohol–water mixtures by polyvinyl alcohol membranes Paramita Das, S.K. Ray ⇑ , S.B. Kuila, H.S. Samanta, N.R. Singha Department of Polymer Science and Technology, University of Calcutta, India article info Article history: Received 29 May 2011 Received in revised form 13 July 2011 Accepted 14 July 2011 Available online 23 July 2011 Keywords: Polyvinyl alcohol Crosslinker Filler Pervaporation Membrane abstract Poly vinyl alcohol (PVOH) membrane, was crosslinked with 2, 4 and 6 mass% of four different kinds of crosslinkers i.e. glutaraldehyde (GLU), oxalic acid (OA), dimethylol urea (DMU) and tetra ethyl ortho silicate (TEOS) to produce four different kinds of crosslinked PVOH membranes termed here as PVGLU, PVOA, PVDMU and PVTEOS membrane, respectively. These membranes were first used for pervaporative separation of azeotropic feed concentration of 87.7 mass% of isopropyl alcohol (IPA) in water. Among all of these membranes PVOH membrane crosslinked with 2 mass% (of PVOH) GLU i.e. PVGLU2 was found to show optimum flux and water selectivity (79.75 g/m 2 h and 45.23, respectively, at 40 °C) for separation of this IPA–water azeotropic mixture. This PVGLU2 membrane was further filled with 2, 4, and 6 mass% hydrophilic aluminosilicate filler to produce three different filled membranes i.e. F2PVGLU2, F4PVGLU2 and F6PVGLU2, respectively. These three filled membranes were used for separation of the same azeotro- pic IPA–water mixtures and F6PVGLU2 membrane was found to show optimum flux and selectivity (109.84 g/m 2 h and 72.71, respectively, at 40 °C). This F6PVGLU2 membrane crosslinked with 2 mass% glutaraldehyde and filled with 6 mass% aluminosilicate filler showing optimum flux and selectivity for azeotropic IPA–water mixture was used for dehydration of IPA using IPA–water mixtures containing 75.87–99.36 mass% IPA in water. All of the filled and unfilled membranes synthesized were also characterized by various conventional methods. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Isopropyl alcohol (IPA) is a very important chemical intermedi- ate and mixtures of IPA–water are encountered in many applica- tions. Concentrated IPA solution in water is widely used as cleaning agent in chemical and electronic industries [1]. However, IPA–water mixtures form azeotrope (87.7 mass% IPA in water at atmospheric pressure) and thus in recent times various mem- branes have been tried for pervaporative (PV) separation of IPA–water mixtures. PVOH membranes with different degree of hydrolysis were crosslinked with amic acid and used for PV sepa- ration of IPA–water mixtures. The partial flux of water and IPA was found to be inversely proportional to the degree of hydrolysis of PVOH while water selectivity of these membranes was found to be proportional to the hydrolysis level of PVOH [2]. The perfor- mance of commercially available crosslinked PVOH membrane (PERVAP2510) and microporous silica membranes (PERVAP SMS) was compared with respect to the dehydration of binary mixtures of IPA/water for 0–20 mass% IPA in water. Water fluxes through the SMS membranes were found to be up to three times larger than those of the PERVAP2510 membrane. However, IPA fluxes through the SMS membrane were also observed to be higher than those through a PERVAP2510 membrane, resulting in a substantial de- crease in separation performance [3]. Membranes made from PVOH–polyacrylic acid (PAA) blends containing 5–20 mass% of PAA were also used for IPA dehydration [4]. With increasing amount of PAA in the blend the membranes were found to show higher water selectivity but lower flux. PVOH membranes contain- ing nano size polyaniline particles were found to show very high water selectivity for IPA–water mixtures. However, fluxes of these filled PVOH membranes were very low in comparison to unfilled PVOH membranes [5]. Mixed matrix membranes of PVOH filled with different amounts of phosphomolybdic heteropolyacid (HPA) were found to show higher flux and water selectivity than the pristine unfilled PVOH membranes [6]. PVOH membrane cross- linked with trimesoyl chloride was also studied for PV separation of IPA–water mixtures at different temperatures. In this case per- meation flux and water selectivity were found to be independent 1383-5866/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.seppur.2011.07.020 ⇑ Corresponding author. Fax: +91 33 351 9755. E-mail address: samitcu2@yahoo.co.in (S.K. Ray). Separation and Purification Technology 81 (2011) 159–173 Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur