Composite polyamide membrane post treated with nitrious acid

A method for making a composite polyamide membrane comprising a porous support and a thin film polyamide layer, wherein the method comprises:

• i) applying a polar solution comprising a polyfunctional amine monomer and a non-polar solution comprising a polyfunctional acyl halide monomer to a surface of a porous support and interfacially polymerizing the monomers to form a thin film polyamide layer;
• ii) treating the thin film polyamide layer with a polyfunctional arene compound comprising 1 or 2 benzene rings collectively substituted with the follow four functional groups:
• (a) a first functional group (w) selected from the group consisting of:
• —NR4R5 and —OH,
• (b) a second functional group (x) selected from the group consisting of:
• —NR4R5, —OH, —COOH, and-SO3H,
• (c) a third functional group (y) is selected from the group consisting of:
• —H, —NR4R5, —OH, —COOH, and —SO3H,
• (d) a fourth functional group (z) selected from the group consisting of:
• —H, —CH3, —NR4R5, —OH, —COOH and —SO3H,
• wherein:
• (R4) and (R5) are independently selected from the group consisting of:
• —H and hydrocarbyl groups comprising from 1 to 10 carbon atoms;
• and
• iii) exposing the thin film polyamide layer to nitrous acid;
• wherein step ii) may occur before, during or after step iii) and, wherein the method is characterized by:
• (A) at least one of the polar and non-polar solutions further comprises a tri-hydrocarbyl phosphate compound represented by Formula I:
• wherein R1, R2 and R3 are independently selected from the group consisting of:
• hydrogen and hydrocarbyl groups comprising from 1 to 10 carbon atoms, with the proviso that no more than one of R1, R2 and R3 are hydrogen;
• and
• (B) the non-polar solution further comprises an acid-containing monomer comprising a C2-C20 hydrocarbon moiety substituted with at least one carboxylic acid functional group or salt thereof and at least one amine-reactive functional group selected from the group consisting of:
• acyl halide, sulfonyl halide and anhydride, wherein the acid-containing monomer is distinct from the polyfunctional acyl halide monomer.