Patent ID: 7976710

Claim:
A method for recovering sulfuric acid from a feed mixture comprising predominantly sulfuric acid and water, the method comprising: processing said feed mixture using a polymeric membrane to form a first retentate containing a greater concentration of acid than said feed mixture and a first permeate containing a greater concentration of water than said feed mixture, said polymeric membrane selectively excluding permeance of acid over the water in the feed mixture and further characterized as a crosslinked polyvinyl alcohol (PVA) membrane having a crosslinking density from about 1.0% to about 25.0% and is crosslinked with a crosslinking agent selected from: (a) aliphatic diisocyanate; (b) non-aliphatic diisocyanate; and (c) mixtures of (a) and (b); wherein the processing of said feed mixture using said polymeric membrane is performed under reverse osmosis conditions wherein said feed mixture is at a pressure of about 100 psi to about 5000 psi when contacting said polymeric membrane, and said feed mixture contains less than about 50 percent by weight acid.