Process for acid recovery from waste water
AssigneeGeneral Electric Company
InventorBang M. Kim
Life of this patent
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Abstract
Anions such as chromate ions are removed from a stream of waste water through an anion selective membrane and are subsequently combined with hydrogen ions transferred across a cation selective membrane in a two-phase Donnan dialysis acid recovery process. In a preferred embodiment chromate ions recovered from an electroplating process rinse solution are recycled to an associated electroplating bath as chromic acid while the chromate ion-depleted rinse solution is recycled to an associated rinse tank.
Claims11
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.
A process as in claim 1 or 4 in which the first anionic radical is CrO.sub.4.sup.--.
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.
Dependencies are inferred from the claim text.