Process for acid recovery from waste water

Claim 2

A plating process in which a first anionic radical is removed from a plating solution to a rinse solution during the transfer of an object from a plating bath to a rinse tank, and in which the first anionic radical is recycled to the plating solution by: passing rinse solution containing the first anionic radical in contact with a first side of an anion selective membrane; simultaneously passing a sweep solution containing a second anionic radical and having a greater anionic radical chemical potential than the rinse solution in contact with an opposite side of the membrane; maintaining the rinse and sweep solutions in contact with the anion selective membrane for sufficient time to effect the transfer of a quantity of the first anionic radical across the membrane from the rinse solution to the sweep solution; removing the resulting rinse solution from contact with the membrane; and passing the resulting sweep solution containing the first anionic radical to the plating bath.

Claim 3

A process as in claim 1 in which the resulting sweep solution containing the first anionic radical is acidified before being passed to the plating bath by: passing the resulting sweep solution in contact with a first side of a cation selective membrane; simultaneously passing an acidic sweep solution having a greater cationic radical chemical potential than the resulting sweep solution in contact with an opposite side of the cation selective membrane; maintaining the resulting and acidic sweep solutions in contact with the cation selective membrane for sufficient time to effect the transfer of a quantity of hydrogen ions across the membrane to the resulting sweep solution, thereby transforming the resulting sweep solution into an acidic product solution containing the first anionic radical; and passing the product solution to the plating bath.

Claim 4

A process as in claim 1 in which the resulting rinse solution is removed from contact with the anion selective membrane and is recycled to the rinse tank.

Claim 5

A process as in claim 1 or 4 in which the first anionic radical is CrO 4 -- .

Claim 6

A process as in claim 1 in which the first anionic radical is selected from the group comprising CrO 4 2- , PO 4 3- , HPO 4 2- , P 2 O 7 4- , A s O 4 3- , and CN - .

Claim 7

A arocess as in claim 1 in which the second ionic radical is Cl - .

Claim 8

A process as in claim 1 in which the second ionic radical is OH - .

Claim 9

A process as in claim 2 in which the acidic sweep solution includes H 2 SO 4 .

Claim 10

A process as in claim 4 in which the acidic sweep solution includes HCl.

Claim 11

A process for recovering an acid from a feed solution containing the anionic radical of said acid and comprising the steps of: passing the feed solution in contact with a first side of an anion selective membrane; simultaneously passing a sweep solution containing a second anionic radical and having a greater anionic radical chemical potential than the waste stream in contact with an opposite side of the anion selective membrane; maintaining the feed and sweep solutions in contact with the anion selective membrane for sufficient time to effect the transfer of a substantial quantity of the feed solution anionic radical across the membrane to the sweep solution; passing the resulting sweep solution containing the transferred anionic radical in contact with a first side of a cationic selective membrane; simultaneously passing an acidic solution having a greater cationic radical chemical potential than the resulting sweep solution in contact with the opposite side of the cationic selective membrane; maintaining the resulting and acidic sweep solution in contact with the cation selective membrane for sufficient time to effect the transfer of a quantity of hydrogen ions across the membrane, thereby transforming the resulting sweep solution into an acidic product solution; and removing the acidic product solution from contact with the membrane.

Claim 12

A process for recovering an acid from a feed solution containing the anionic radical of said acid and comprising the steps of: passing the feed solution in contact with a first side of an anion selective membrane; simultaneously passing a sweep solution containing a second anionic radical and having a greater anionic radical chemical potential than the waste stream in contact with an opposite side of the anion selective membrane; maintaining the feed and sweep solutions in contact with the anion selective membrane for sufficient time to effect the transfer of a substantial quantity of the feed solution anionic radical across the membrane to the sweep solution; passing the resulting sweep solution containing the transferred anionic radical in contact with a first side of a cationic selective membrane; simultaneously passing an acidic solution having a greater cationic radical chemical potential than the resulting sweep solution in contact with the opposite side of the cationic selective membrane; maintaining the resulting and acidic sweep solution in contact with the cation selective membrane for sufficient time to effect the transfer of a quantity of hydrogen ions across the membrane, thereby transforming the resulting sweep solution into an acidic product solution; and removing the acidic product solution from contact with the membrane.

Claim 13

A process as in claim 10 in which the anionic radical contained in the waste stream is taken from the group comprising CrO 4 2- , CN - , PO 4 3- , HPO 4 2- , and P 2 O 7 4- and A s O 4 3- .