抄録
The effects of casting conditions of cellulose acetate membrane (Batch-47 type) on its reverse osmosis properties have been investigated by x-ray diffraction, electron microscopy, water vapor sorption and reverse osmosis performance. It was found that the membrane consisted of a thin dense layer and a porous substructure. The variation of diffusion coefficient of water calculated from the sorption data corresponded to the change of water flux by a reverse osmosis. This indicates that as soon as a casting solvent is lost from the membrane surface, the dense layer is formed. The membrane annealed at about 75°C showed a steep increase in salt rejection but a decrease in water flux. Some changes in the compaction effect and membrane shrinkage were noted in the same temperature range as described above. X-ray diffraction and deuteration methods revealed no distinct increase in crystallinity upon annealing (40-80°C). This may be due to the pore size reduction on the surface accompanied by the shrinkage and also to the increase of degree crystallinity in the dense layer.
