THERMAL ANNEALING EFFECT ON CELLULOSE-ACETATE REVERSE-OSMOSIS MEMBRANE-STRUCTURE

The structure variation of cellulose acetate (CA) reverse osmosis (RO) membranes due to thermal annealing was investigated by using gas adso rption. When the CA membranes were dehydrated by freeze-drying, the mo rphology of the unannealed membrane was similar to that of the anneale d membrane. On the contrary, with air-drying which induced structure c ollapse of the CA membranes, gas adsorption behavior of the unannealed membrane showed a significant difference from that of the annealed me mbrane. The CA RO membrane in an unannealed state totally collapsed du ring air-drying, but the membrane that was annealed for 10 min at 90 d egrees C showed significantly reduced collapsing compared to the unann ealed one. However, even though the CA membranes were annealed, use of methanol as the wetting agent caused complete collapsing during air-d rying.