Solution PPM Silver needed for Plating Silver onto Copper

A. I don't have personal experience with electrolytic recovery of silver from thiosulphate, so I have to speak in terms of similar processes rather than this specific one. I don't see any reason why you cannot plate the silver out, but there is no particular concentration at which silver stops plating out; rather, it's a continuum where the Faraday efficiency keeps dropping as the concentration drops. By the time you reach 50 ppm you may find the efficiency to have already dropped below 5 percent. Electrolytic recovery is the right technology for dealing with high concentrations of metals but the wrong technology for dealing with low concentrations unless you use higher technology to achieve huge surface areas, extreme agitation, and very tight anode to cathode spacing.

You can probably remove all of the silver on ion-exchange resin, but if you don't want to then burn the resin, but regenerate it, that's probably difficult.

A. James,

As the silver concentration decreases, the deposition efficiency of silver decreases and black sulfur [affil links] compounds deposit instead. The sulfur will produce poor deposits and will fall off of the cathode. Also, the higher the cathode current density, the lower will be the percentage of silver in the deposit - the rest is sulfur [affil links]. In a fixer solution, the silver complex is negative and is therefore attracted to the anode and is repelled by the cathode. Without excellent agitation to replenish silver to the cathode, the situation will be identical to low silver concentration and the deposit will be mainly sulfur.

Use lots of mechanical agitation (not air). In a professional unit, the silver is plated onto a revolving stainless steel drum. This rotation is good because it acts directly on the cathode surface. A circulating pump should also be used - you might even try to direct the outlet onto the cathode. If the current is too high, it will deplete the cathode film of silver faster than it can be replenished. You must, therefore, continually reduce the current in some relationship to the decreasing silver content.

All in all, you'll never get all of the silver out using a plating setup. To get it to legal limits, you'll probably have to final "polish" the solution in a steel wool [on eBay or Amazon] or expanded metal canister, which are both available from the film industry. You can also get the final silver out with 325 mesh zinc dust [on eBay or Amazon] - it doesn't take much. Of course, the solution will now contain zinc.

A. I have isolated silver from photographic waste by using a special reagent taking time less as in minutes.

Thanks Dr. Naliapara. If you are willing to publicly describe what that reagent is, and how to make it, please do; we have all the room in the world for complete details. If you are offering that knowledge for sale, or the reagent for sale, please become an advertiser here. Thanks.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 2015

A. It would be my guess that Dr. Naliapara's principal ingredient is sodium sulfide, which would precipitate the silver quickly as silver sulfide. At present, I am convinced the this method is about the best, especially for the novice. Complete instructions can be found by searching goldrefiningforum.com

Chris Owen
- Nevada, Missouri, USA
June 21, 2015