A STUDY ON THE PREPARATION OF POLYVINYL-ALCOHOL THIN-FILM COMPOSITE MEMBRANES AND REVERSE-OSMOSIS TESTING

Thin-film composite membranes were prepared by coating porous polysulf one membranes with a polyvinyl alcohol layer and further cross-linking its surface. Aldehydes, dialdehydes and malic acids were used as cros s-linking agents. The effects of additives to the PVA solution, of sol vents used for making PVA solutions, and of alcohols used for the memb rane post-treatment on the reverse osmosis performance were investigat ed. The effect of PVA solution coating, drying and heat-treatment on t he water permeability was also studied without cross-linking. It was f ound that heat-treatment had the strongest effect on the reduction of the water permeability. Hence, it was attempted to use cross-linking a gents that could react at room temperature. Attempts were also made to carry out the cross-linking reaction at the cross-linking solution/PV A layer interface by dissolving cross-linking agents in hydrophobic so lvents.