Roger L Anderson

US Patent:

51123924, May 12, 1992

Filed:

Jun 21, 1991

Appl. No.:

7/719201

Inventors:

Roger W. Anderson - Farragut TN
Wayne A. Neff - Knoxville TN

Assignee:

Martin Marietta Energy Systems, Inc. - Oak Ridge TN

International Classification:

B01D 1504

US Classification:

106 122

Abstract:

A process for removing, from spent electroless metal plating bath solutions, accumulated byproducts and counter-ions that have deleterious effects on plating. The solution, or a portion thereof, is passed through a selected cation exchange resin bed in hydrogen form, the resin selected from strong acid cation exchangers and combinations of intermediate acid cation exchangers with strong acid cation exchangers. Sodium and nickel ions are sorbed in the selected cation exchanger, with little removal of other constituents. The remaining solution is subjected to sulfate removal through precipitation of calcium sulfate hemihydrate using, sequentially, CaO and then CaCO. sub. 3. Phosphite removal from the solution is accomplished by the addition of MgO to form magnesium phosphite trihydrate. The washed precipitates of these steps can be safely discarded in nontoxic land fills, or used in various chemical industries. Finally, any remaining solution can be concentrated, adjusted for pH, and be ready for reuse.