COMPOSITE SEMIPERMEABLE MEMBRANE, PROCESS FOR PRODUCING THE SAME, AND METHOD OF PURIFYING WATER WITH THE SAME

摘要

A composite semipermeable membrane which comprises a microporous supporting film and an ultrathin layer of a crosslinked polyamide formed thereon by condensation-polymerizing a polyfunctional amine, a polyfunctional acid halide, and a polyfunctional acid anhydride halide, characterized by having a water permeability of 0.8 to 4.0 m<3>/m<2>. day and a percentage of humic acid removal of 98% or higher as measured at an operation pressure of 0.3 MPa, a temperature of 25 DEG C, and a pH of 6.5. The composite semipermeable membrane is especially effective in selectively separating and removing pollutants, harmful substances present in a slight amount, precursors of these, etc. from the raw water being treated in a water purification plant, while permitting silica to pass therethrough to prevent silica precipitation thereon. Hence, drinking water can be recovered in a high yield.