Highly permeable composite reverse osmosis membrane, method of producing the same

Abstract

This invention provides a composite reverse osmosis membrane having a polyamide type skin layer whose average surface roughness is at least 55 nm, and the polyamide type skin layer comprises the reaction product of a compound having amino groups and polyfunctional acid halide compound having acid halide groups. The composite reverse osmosis membrane of this invention is superior in salt rejection and water permeability. A polymer film is formed on a supporting film by contacting a solution containing e.g., m-phenylenediamine with a porous polysulfone supporting film so as to form a layer of the solution on the supporting film, then contacting the film with a solution of trimesic acid chloride and holding the film in a hot air dryer so that a polymer film is formed on the supporting film. The surface of the polyamide type skin layer can also be treated with quaternary ammonium salt and coated with a crosslinked layer of an organic polymer having positively-charged groups. Raw liquid is transmitted from a raw liquid tank to a membrane module for the first stage through a first transmission pump, and the first stage of reverse osmosis treatment is carried out. The composite reverse osmosis membrane coated with the crosslinked layer is used when another reverse osmosis treatment is carried out by using another membrane module for the second stage.

Dependencies are inferred from the claim text.