Composite semi-permeable membrane for separation of organic substances from drinking water

摘要

Composite semi-permeable membrane exhibiting selective retention of organic substances comprise: (A) a porous substrate; and (B) an ultrafine layer with selective permeability formed in situ on the porous support. (B) is the reaction product of an interfacial reaction between (a) an organic solution of an aromatic polyacyl halide (I) and (b) an aqueous solution containing a mixture of 0.001-0.5 wt.% piperazine and 0.0001-1.0 wt.% of a water-soluble polar additive (II) which causes (B) to allow the hardness in an aqueous feed solution applied to the membrane to pass through the latter in a ratio of at least 1.5-1 w.r.t. the passage of small organic molecules contained in it. Also claimed is a process for preparing the membranes by first contacting the porous support with the aqueous solution containing piperazine and the (II), and then with the organic solution containing the (I).