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Regeneration of Ammonium Persulphate Solution

IP.com Disclosure Number: IPCOM000091659D
Original Publication Date: 1968-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Matzke, S: AUTHOR [+2]

Abstract

Exhausted ammonium persulphate etching solution for printed circuits is neutralized with ammonia and then passed through a cation exchanger to remove copper ions. The solution is then oxidized into ammonium persulphate.

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Regeneration of Ammonium Persulphate Solution

Exhausted ammonium persulphate etching solution for printed circuits is neutralized with ammonia and then passed through a cation exchanger to remove copper ions. The solution is then oxidized into ammonium persulphate.

An exhausted ammonium persulphate solution, consisting of ions of copper, ammonium, sulphate and persulphate, gathered in container 1, is thoroughly mixed in container 3 with ammonia from tank 2 until a pH value of 7.5 to 8.5 is obtained. A pH meter 5 controls ammonia valve 6.

The neutralized solution is guided through an oxidation-proof and preferably strongly acid cation exchange 7 which is saturated with ammonium ions. Copper ions are exchanged against ammonium ions and the copper ions remain in exchange 7. The solution at the outlet of exchange 7 contains ions of ammonium, sulphate and persulphate and is brought to container 8 for anodic oxidation by electrodes 9 and 10 to produce ammonium persulphate. Copper ions at exchange 7 are eluted with diluted mineral acid, such as 20% sulphuric acid concentration, from container 12. The eluate is brought to container 11 from which the copper can be obtained by electrolysis or cementation.

Deionized water from container 13 is used to rinse exchange 7 until the pH values at inlet and outlet are the same and between 5 and 7. Cation exchange 7 is saturated with ammonium persulphate solution of approximately 10-20% concentration from container 15 and then rinse...