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RECOVERY OF STRIPPING SOLUTION FOR SILVER

April 17, 2009

We do silver plating on brass utensils using cyanide solution. We have to strip the silver from defective pieces or old plated utensils given to us for replating. We use concentrated sulfuric acid in a stainless steel tank. The tank is jacketed with hot water at about 95 C. Initially some Sodium Nitrate [affil links] is added to start stripping action. Initially the action is very fast. 20 microns of silver are removed in about 15 minutes. If action slows down sodium nitrate is added to speed up the process. However, over the time the action slows down so much that any addition of sodium nitrate does not help. We remove this spent solution. To recover silver we first neutralize it to about 2 pH. Then suspend copper plates to remove silver. After silver mud is removed the solution is further neutralized to 12 pH. This precipitates copper. Top clear solution is removed,neutralized to 7 pH and discarded. My questions are as follows,

1) Is there any method of reusing the same acid?

2) Is there any better method for treatment of spent acid?

Vishwas Deval
owner of plating shop - Pune, Maharashtra, India

Normally it is not cost effective to try to recover the spent acid as there is no way to make it acid again after the high pH treatment to remove the copper.

James Watts
- Navarre, Florida
April 21, 2009