Liquid membrane system for the removal of nitrate from water

Claim 1

A process for the extraction of selected anions from an aqueous feed solution and deposition of said anions in an aqueous stripping solution comprising: (a) circulating said feed solution through a first compartment so that it contacts one side of a porous support, said support incorporating in a water-immiscible organic liquid a solution of a complexing agent selective for said anions, said solution substantially completely filling, and retained within the pores of said support, where said complexing agent is a quaternary ammonium salt of the formula: (R.sub.1)(R.sub.2)(R.sub.3)(R.sub.4)N.sup.+ ]X.sup.- wherein R 1 , R 2 , R 3 and R 4 are alkyl or cycloalkyl, N being substituted by a total number of carbon atoms between about 15-60 and wherein X - is an aromatic anion of the formula: ArO.sup.- or ArSO.sub.2 N.sup.- --Z wherein Ar is of the formula: ##STR6## wherein R 5 and R 6 are H or C 1 -C 5 alkyl, R 7 is H or C 1 -C 12 alkyl and Z is R 7 or CH 2 Ar, and wherein X - comprises at least 9 carbon atoms wherein said complexing agent exhibits a pKa of about 10-12 in aqueous solution, to form a complex comprising said complexing agent, hydrogen ions, and said anions in the feed solution; (b) diffusing said complex through the organic liquid to the opposide side of the support; and (c) circulating said aqueous stripping solution through a second compartment, wherein said aqueous stripping solution is maintained at a higher pH than said aqueous feed solution, so that the stripping solution contacts the opposite side of the support to liberate hydrogen ions and said anions into the stripping solution.