Dissolving silver braze from tungsten carbide

I'm working out the best process to chemically strip silver brazing from tungsten carbide (WC) bits. My main objective is to recover the silver as a relatively pure metal. When I use $\ce{HNO3}$ at anywhere from 20-70%, it dissolves the solder and I end up with a red solution. When I try to use cementation (putting copper metal in the solution) to precipitate the $\ce{Ag}$ as sponge, it isn't working. 


Can any one help me figure out what's going on here? The brazing being used should be 50-60% $\ce{Ag}$ by weight. I'm not sure yet if there is $\ce{Pd}$ or not.




Most common silver brazes are 50 to 90 % silver with copper or maybe zinc. A complication may be the WC; it is sintered with 2 to 20 % cobalt ( usually).


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No expert here, but it seems that if the copper added becomes coated with a monolayer of silver from your very complicated solution, more silver may not deposit as it does from pure solutions of silver nitrate.


One way to keep silver depositing would be to use two copper electrodes and electrolyze your solution with a relatively low voltage. The most inactive metals (Ag, Pd) will plate out first onto the negative electrode, and the positive electrode will lose an equivalent amount of copper. Finally, your solution will have been depleted of silver and enriched in copper, and the silver will be on the negative electrode. If you start with a silver wire, you will have a purer result, but that may be unimportant. If you electrolyze too fast, you will plate out copper with the silver.


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