Studies on pervaporation characteristics of polyacrylonitrile–b-poly(ethylene glycol)–b-polyacrylonitrile block copolymer membrane for dehydration of aqueous acetone solutions

A novel polyacrylonitrile–b-poly(ethylene glycol)–b-polyacrylonitrile (PAN–b-PEG–b-PAN) block copolymer was synthesized by water-phase precipitation copolymerization, using ceric ammonium nitrate–PEG pair as an initiator. Structure and composition of the block copolymer were characterized by FT-IR, 1H NMR, differential scanning calorimetry and elemental analysis. Block copolymer membranes were prepared by solution casting method and morphologies of the membranes were examined by transmission electron micrographs. Dehydration of aqueous acetone solution with 5 wt% water is considerably improved by using block copolymer membrane and pervaporation performance is greatly dependent on the PEG molecular weight (MPEG) and weight content (WPEG) in the block copolymer. Maximum separation factor and minimum permeate flux displayed for the block copolymer membrane with MPEG = 6000 and WPEG = 7.3 wt%. Effect of feed temperature and feed composition on pervaporation was analyzed in two pairs of parameters, separation factor, flux and selectivity, permeability and it was found that the latter pair can better correlate pervaporation performance with membrane structure. These pervaporation characteristics of the membrane were explained mainly in terms of PEG micro-phase separation behavior in the PAN–b-PEG–b-PAN block copolymer and PEG solubility characteristics in water with temperature.