rewalston said:
Steve, I've seen mentioned numerous times that all of our washes should be put into a stock pot for later processing to catch any minute amounts of PM's. I've seen mentioned to put HCL washes, water washes, etc into the pot. What kind of container would be good to use as a stock pot? Also can all of the chemicals that we are using go into the pot? I'm assuming that nitric won't go in there because most often we are boiling off the nitric or chlorine before precipitation. I'm asking because once I'm done reading and digesting everything I can, that I don't want to put into the stock pot anything that would cause a mess later...or worse explode or catch fire or fume like a failed lab experiment.
thanks
Rusty
Rusty,
Great question.
I don't know how everyone else does it, but I keep a few five gallon buckets for the various by products. One for copper nitrate, one for SMB left overs, sulfuric cell dilution settling bucket, etc. I typically let them sit uncovered in an open air outdoor space which is protected from the rain. I add the same type of reaction left overs to the appropriate bucket.
Once a bucket is full or evaporated to saturation (a crust starts forming), I siphon off the bulk of the liquid and process it for disposal or recycling as the case may be. The sediment in the bottoms of these buckets is processed for precious metals along with any PM's that I harvest from the solution as part of the disposal process.
Once the disposal or recycling routine is completed, I combine the neutralized liquids and responsibly dispose of the separated solids as appropriate. The combined solutions are put in 35 - 55 gal fiber drums for hauling.
The only exception to this is solutions that contain the ammonium ion. These are immediately acidified, settled, siphoned, and then combined with the appropriate bucket of waste liquid. The solids are processed for PMs (usually silver).
Here's a simplified overview of the buckets and their uses and or by products:
1. Copper Nitrate solutions from sterling silver dissolution:
a. recycled as silver cell electrolyte by reverse plating out copper sponge
b. recycled as dilute nitric acid by precipitating silver chloride with HCl
c. metallic copper sponge from a. above.
d. recycle as Aklai nitrate by neutralizing with base.
e. by product of d. above is hazardous hydroxide or carbonate of base metal. Can be fluxed to form base metals in large furnace or disposed of on amnesty day at landfill.
f. Regenerate nitric acid by destructive distillation of the copper nitric in a glassware apparatus. Brown gas is bubbled into cold distilled water. Copper Oxides can be converted to Acid Peroxide with HCl.
2. AR or HCl-Cl solutions after SMB:
a. Residual PMs precipitated by Cu saturation, let settle, and siphon, PMs in black powder.
b. Mixed metal Copper sponge cemented with scrap iron.
c. Neutralized with Lime, filtered, disposed of in drums.
d. Filtered Iron hydroxides / carbonates dehydrated to solids.
3. Sulfuric acid Cell diluted electrolyte
a. Siphon bulk of liquid off of settled residual black impure gold powder.
b. Copper harvested by carbon electrodes from diluted liquid.
c. Recycled as cell electrolyte by dehydration until concentrated.
4. Acid Peroxide Solutions:
a. Regenerate with air bubbler or peroxide additions.
b. Regenerate with electricity forming copper sponge.
c. Treat as 2 above for complete disposal.
5. PGM solutions:
a. 1-2 L beaker as appropriate for volume of PGM leftovers.
b. Dehydrates over time forming colored salts.
c. When enough colored salts are present, rehydrate and process with zinc.
d. Zinc left over solutions combined and dehydrated.
There are more left over solution types, but these are the most common ones. As a general rule of thumb, don't mixed residual solutions from different types of reactions. Lie stays with like.
Hopefully some of the other guys will post there 'stock pot' set ups ofr comparison.
Steve
