HOME FAQs BOOKS JOBS: Help Wanted Suggestions you are here: Hotline/Forum => Letter 51059
Recovering Gold from Used Gold Bath
January 25, 2009
We are engaged into Electroplating for Electronic Industries. Some qty of Au Solution is available for Recovery.
Balganchi Venkatram PrasannaPlating Industry - Bangalore, Karnataka, India
^- Privately contact this inquirer -^
First of two simultaneous responses -- January 28, 2009
Basically the easiest way is to plate the Gold onto a sacrificial Cathode for recovery as metal in a process typically known as Electrowinning. Typically this is done by very low Volts/Amps onto a large surface area over extended time. In the US, a common product for this application is the "Gold Bug". We have plated out baths to very low residual gold content using this method.
Paul Slater- Cedar Rapids, IA, USA
Second of two simultaneous responses -- January 28, 2009
For someone who has extensive experience and the proper equipment, there is a way to drop the gold out of solution with the use of aqua regia and filtering.
For someone with little or no experience, running the solution through a resin column would probably be the most cost effective and safest way to recover the gold. Gold bugs also work pretty well
(small compact electrolytic recovery units). With these units the gold can be recovered and processed right off a cathode pad or plate. The gold bearing resin or gold bearing cathode would then be sent to a refiner. The recovery units are supplied by precious metal vendors or plating equipment mfgs. It is a good idea to do gold metal analysis before and after the recovery process so you know how much gold you have. Some refiners lack honesty. Good Luck!
Fellow Plater - Syracuse, N.Y., USA
April 18, 2009
Dear Prasanna,
Gold Bug method is very good process, but this is expensive process. You can go for zinc, caustic soda method. Your solution should not have any oxidizing agent and free cyanide, If it is there first kill the oxidizing agent by formaldehyde and kill the free cyanide with sodium hypo chloride. Then you add caustic soda up to 11 pH. We should know how much of gold in solution, based on this add double quantity of zinc and live it over night. All gold will deposit in bottom. If you add more zinc, it deposited along with gold filter the gold and adds concentrated hydrochloric acid. The excess zinc will removed as zinc chloride. Finally you will get gold powder. Good luck.
- Coimbatore, India