COMPOSITE SEMIPERMEABLE MEMBRANE

摘要

PURPOSE:To obtain a composite semipermeable membrane which is effective in both the softening of hard water and the selective separation of a multivalent ion and a monovalent ion and is excellent in water permeability even under the operation conditions in low pressure by coating the surface of an activated layer consisting of a cross-linked organic polymer having a negative fixed charge group by the organic polymer having a positive fixed charge group. CONSTITUTION:A composite membrane where in a cross-linked organic polymer having a negative fixed charge type group is made to an activated layer is obtained for example by allowing piperazine and trimesic acid chloride to react with a support of fiber-reinforced polysulfone by interfacial polycondensation, controlling the interfacial reaction in this case and introducing a carboxyl group into cross-linked pipe-razine polyamide. Then a reverse osmosis method is performed by using this membrane and adding an organic polymer having a positive fixed charge group such as polyethyleneimine to raw water and the organic polymer having the positive fixed charge type group is adsorbed on the surface of the membrane and thereby a composite semipermeable membrane where the activated layer is coated by the organic polymer having positive fixed charge type group is obtained.