madelyn said:
Is it possible to skimm most or all base metals from the top of the melt until you are only left with silver alloy?
I am melting e waiste into bars with my induction furnace and was wondering if I could do this to reduce the bar size and then move to nitric acid.
I don't know if I will loose precious metal value when skimming of base metals.
Can anyone please advise if this is optional?
No. It won"t work if the copper and other base metals are in a metallic form, as they would be as molten alloys. If you could provide a source of oxygen, the base metal oxides that form, being lighter than the molten metal, would float on top of the metal as a slag. Then, you could pour everything into a mold, let it cool, and break the copper bearing slag on the top away from the solidified metal which has settled in the bottom.
Problems in doing this:
(1) Unfortunately, since copper is, by far, the main constituent, and since copper oxide is much lighter weight than copper metal, you would end up with a proportionately huge volume of slag, all of which is inclined to trap jillions of very small BB's of gold. I would guess that copper oxide will occupy at least 10 times more space than the copper metal.
(2) Probably, the most efficient way of doing this is to bubble bottled oxygen into the molten metal via a pipe which will not be wasted away by the molten metal. About the only other way would be to add, say, niter, as the oxidizing agent, Unfortunately, the niter reaction destroys expensive crucibles.
(3) With oxygen, considering the vast amount of copper to convert, it would probably take days, at best.
(4) You'll never be able to convert it all for reasons I won't go into.
(5) Considering everything, it would be overly expensive.
You might be able to add some other compound that would combine with the copper and report in the slag but I can't think of anything expect maybe a very controlled amount of sulfide. However, even if it worked, you would have the same problems.
To make a long story short, this is a bad idea. It's a dream. If there was any merit in it, it would have been done centuries ago and everybody would be doing it now.
As Barren said, in general, it's a bad idea to melt everything together (unless you want to sell it on eBay and screw your buyers). You make a lot more work for yourself and lose more money than you normally would.
If you must refine that type of material, use a traditional method, like acid/peroxide (AP). It's been discussed 1000's of times of this forum.