How Much Copper Powder Do I Use In My Stock Pot?

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scrapparts

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Hello members,

I have some copper powder (about 15 lbs) so far I recovered from my waste solutions after using copper metal bar/pipe pieces to cement out any precious metals. I have some more stockpot solution and I was wanting to use my copper powder instead of metal copper bar.

My questions are...

1. How much copper do I use to cement out any possible precious metals?
2. How do I know when I've added enough or too much copper powder to my stockpot?
3. Should I use an air bubbler when adding the copper powder?
4. How long after adding the copper powder can the solution be filtered?

So far, I've been dealing with my stockpot and waste solutions responsibly since I started dealing with my waste solutions. Right now, the only way I know I cemented out everything is when I clean off the copper bar and then put it back in the stockpot for a few days. If nothing builds up on it or very little, that's when I know I cemented out everything. I also know I neutralized the spent nitric acid too because the copper piece is still intact without weighing much less than last weight check.

My goal, if possible is to be able to cement out my stockpot from beginning in the morning, and being done by the evening, if that's reasonably possible.

Because of some extra solutions I made, I have (2) 5-gallon buckets that are ready for copper.

Any advice or recommendations welcome!

scrapparts
 

Lino1406

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Copper cements noble metal according to:
Me(n+) + n/2 Cu = Cu(++) +Me. 63.54g copper will reduce 2/n of Me gatom
where n is valence (Au -3 Pd -2 ..etc)
hence, weight of copper needed:
63.54 x 2/n x weight (Me)/atomic weight (Me)
 

g_axelsson

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Almost impossible to say. The largest problem I see is that all the powder will sit on the bottom and not contact the solution and it will be hard to separate the cemented precious metal from the copper powder if you use too much. A mechanical stirrer would probably be needed to keep the powder agitated.
A mechanical stirrer is better than a bubbler in my mind, adding air to agitate the solution only creates a copper chloride etch and it will consume more copper. Copper II chloride can dissolve palladium too which can make it hard to cement palladium if you add air.

Would it be possible to melt the powder to make solid chunks that can be suspended from a string (drilled hole) above the bottom? Then you can easily remove the copper and watch for any cemented metal.

If you use the copper powder as it is then you can always hang a solid pipe or wire over the edge to watch the reaction to determine when the precious metals are out of solution, you don't need it the whole time, just for testing.

Göran
 

Lou

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If you have enough money tied up to worry about it, get an ORP meter and test your waste solutions to get an idea of the value. Just shaking a known volume with copper powder until no stannous/DMG is a good way to get total recoverable value. That can then be fire assayed or otherwise worked up to look for Au/Pt/Pd.

This can let you know if your pH is right (1-3 or whatever doesn't let Fe fall out as that nasty red hydroxide) and make sure that your solution is reducing.

Another thing too that can be done is reduction in situ of any copper in solution with aluminum or zinc. This kitchen sinks it all but then the freshly generated copper starts trading out for the cemented copper.
 

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