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Abstract

A composite polyamide reverse osmosis membrane and method of producing same. In one embodiment, the membrane is made by coating a porous polysulfone support for about 40 seconds with an aqueous solution containing (i) a polyfunctional primary or secondary amine in the form of 1.6 wt. % of meta-phenylenediamine (MPD), (ii) a polyfunctional tertiary amine in the form of 0.4 wt. % N,N,N',N'-tetramethyl-1,6-hexanediamine (TMHD), and (iii) a polar solvent in the form of 0.2 wt. % 2-ethyl-1,3-hexanediol (EHD). Next, the excess aqueous solution is removed, and the coated support is dipped for about 1 minute in a 0.1 wt. % organic solvent solution of trimesoyl chloride (TMC) in a mixture of alkanes having from 8 to 12 carbon atoms. After draining the organic solvent solution off, the resulting composite membrane is air dried at room temperature for about 1 minute and then rinsed in a 0.2% Na.sub.2 CO.sub.3 aqueous solution for 30 minutes at room temperature. The resultant membrane exhibits a flux of 46.5 gfd and a salt rejection of 97.1% when used at 225 psi for an aqueous solution containing 2000 ppm of NaCl. In another embodiment, instead of including a polyfunctional tertiary amine in the aqueous solution, there is included the reaction product of a polyfunctional tertiary amine and a strong acid, preferably in a ratio ranging from greater than 1:0, respectively, to less than or equal to 1:(0.95)n, respectively, where n is the number of tertiary functional groups in the polyfunctional tertiary amine.

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