An interpolymer anionic composite reverse osmosis membrane derived from poly(vinyl alcohol) and poly(styrene sulfonic acid)

An interpolymer anionic composite membrane for reverse osmosis was prepared from poly(vinyl alcohol) and poly(styrene sulfonic acid). The effects of composition of a casting solution, heat-curing periods, and casting thickness on the reverse osmosis performance of resulted membranes have been examined. A mixture of water and ethyl alcohol (12/7, wt %) was found to be a proper solvent for casting an interpolymer membrane on the supporter. The composite membrane was formed by casting the polymer solution in ultrathin film on a microporous polypropylene supporter, evaporating the solvent, and heat-curing at 120°C for a proper period. the optimum composition of a casting solution was as follows: wt % of poly(vinyl alcohol)/poly(styrene sulfonic acid)/solvent was 3/2/95. The membrane heat-cured at 120°C for 2 h has a good performance for reverse osmosis, viz., water flux of 9.1–28.4 L/m².h at salt rejection level of 88.1–93.4% under applied pressure of 80 kg/cm² with 0.5% NaCl aqueous solution. The formation mechanism of a water-insoluble membrane was discussed.