Hi!
As many probably know, brazing rods can contain a lot of silver. Up to 55%
Rest is an almost even mixture of copper and zinc, with low amounts of tin. Or Cd - pre ROHS. I don't know the age of all the stuff, so I often have to assume Cd in solution. Which is a pain!
Sometimes P in the lower Silver content rods.
What is the best way to recover the silver from these?
My most experience is with running "wastefree" hydrometallurgic processes. I am thinking on the following route.
As many probably know, brazing rods can contain a lot of silver. Up to 55%
Rest is an almost even mixture of copper and zinc, with low amounts of tin. Or Cd - pre ROHS. I don't know the age of all the stuff, so I often have to assume Cd in solution. Which is a pain!
Sometimes P in the lower Silver content rods.
What is the best way to recover the silver from these?
My most experience is with running "wastefree" hydrometallurgic processes. I am thinking on the following route.
- Dissolving in CuCl2/HCl, or Nitric. I prefer the first as nitric is harder to come by. But silver content may be too high to dissolve in a chloride environment. Up to which %Ag will a piece dissolve in CuCl2/HCl, leaving behind particulate AgCl?
- Drop out the Silver on excess copper when using nitric. Or filter out the AgCl.
- When Silver is gone, add an excess of sulphuric acid and distill off the acid (both for HCl and Nitric routes). Every metal should be in the sulfate form now.
- Electrolyse sulfate solution to recover metals and Sulfuric acid. Copper is very easy, Tin is easy, Zinc is a bit of a pain in the acidic conditions requiring low concentrations and slow electrolysis.
- Any completely different approaches?
- How do I deal with metastannic acid on the Nitric route?
- How do I deal with Cd in solution? So far I have just worked on explicitly Cd free material.