lazersteve said:
Harold,
I have a question about burning filters:
What if the filters have residual chemicals such as copper chloride in them? Do you recommend washing them clean with water before the burning process or do you just suggest burning them as is in a very well ventilated area?
I have lots of filters that need to be processed.
Steve
I did nothing to my wastes aside from drying and incinerating. It's a waste of time otherwise. Future processing of the ash is a much easier way to deal with them. Values will tend towards being low, and you rely on volume to make it worth while.
If I was to process a volume of filters, as you've described, what I'd do is incinerate them until there was no carbon present. That will involve heating the pan to a red heat. Carbon burns at 1,100° F if I recall correctly. Goodwill stores generally sell old stainless frypans for about a buck. I used them for this purpose. There's a small one that was used, I think, by the boy scouts. It's perfect for such an application. It's much easier to heat to redness than a large one.
After full incineration, place the ash in a beaker (or container of your choosing) and do a wash with HCL. I liked to take it to a boil and allow it to work for some time, maybe 15 minutes. I would then take up the solution with water and allow it to settle well. Decant, and rinse (tap water) again if the solution was very dirty. When you're satisfied that the mud is clean, you can either incinerate a second time, then follow up with a wash in nitric, or you can go directly to AR, or dissolve the contents with your preferred method. The second incineration is essential to kill traces of chlorides, so you avoid dissolving values when not intended. You're likely to have considerable residue from this operation, which should eventually see a furnace. Some of it is likely to be silver chloride, which is assured if you've done any inquartation, or otherwise worked with silver.
Best overall procedure is to incinerate, then melt the waste with the proper fluxes. This is best done in a crucible, not a melting dish with a torch. You'll reduce the majority of values to metallics, and a lot of the base metals and all of the remaining garbage will go off with the flux. It's important that the flux be quite fluid so the prills will agglomerate, which may involve the use of fluorspar. Don't rely on soda ash alone to make the flux fluid. If you have included any silver chloride, it will act as a collector for the balance of the values.
The furnace operation should be done out of doors, or in a room with an efficient air exchange system. I ran my furnace directly under a large funnel shaped hood that was powered by a 1 hp 1,000 cfm blower to insure that the resulting gasses were discharged where they weren't breathed.
I may not have answered to your satisfaction. If you have any particular question(s), please ask. I'm an open book where refining is involved. I have no secrets.
Harold