Synthesis and characterization of sago / polyvinyl alcohol blend pervaporation membrance for ethyl acetate recovery

Abstract

Pervaporation is a membrane separation technology with high selectivity, efficiency and energy saving benefits that make it the method of choice for separation of mixtures. The application for pervaporation includes removal of dilute organic compounds from aqueous solution and dehydration of organics such as dehydration of ethyl acetate-water mixture. The best successful application that has been used for pervaporation is dehydration of organic liquid from water using hydrophilic polymer membrane. In this work, material used for membrane separation was sago and polyvinyl alcohol. However, during the separation process, excessive affinity of water towards hydrophilic polymer membrane led to an increase in the swelling of the membrane. To control the degree of swelling the membranes were cross-linked to improve the intrinsic properties of hydrophilic polymer membranes. Sago starch was used as based polymer to prepare membranes with polyvinyl alcohol (PVA) with various morphologies such as homogenous, composite and blended ration of sago and PVA. Sago/PVA membranes were cross-linked using three different approaches: firstly, using glutaraldehyde, secondly using thermal treatment (80 °C) and thirdly by using both glutaraldehyde and thermal treatment. The effects of various cross-linking methods on the intrinsic properties of hydrophilic polymer membrane were investigated. Before applying the cross-linking to sago/PVA membranes for separation of ethyl acetate-water mixture, a physicochemical characterization was carried out using Fourier transform infrared spectroscopy, differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), atomic force microscopy and swelling experiments. The investigation on the effect of cross-linking on the sago/PVA membranes showed an increase in surface hydrophobicity from contact angle measurements. DSC measurements showed an increase in melting temperature of the polymer membranes after cross-linking. In addition, TGA showed an increase in the stability of the polymer membranes after cross-linking. The effects of operating condition such as feed temperature and feed concentration on the permeation flux and separation factor were also investigated. For the pervaporation of ethyl acetate-water mixture, a decrease in flux and an increase in the separation factor were observed with chemical and combination of chemical and thermal cross-linking. Finally, central composite designs (CCD) of response surface methodology was applied to analyse pervaporation performance of thermal cross-linked membrane. Regression models were developed for permeation flux and separation factor as a function of feed temperature, feed concentration and permeate pressure