Using Copper to clean up mess

[Marvinm4u]

After MUCH reading here, I'm cleaning up a couple of messes of my own doing. Oddly, my first 2 oz of 24k sold gold went well, although with a massive excess of chemicals. My 2nd and 3rd, not so well.

I've now figured out that I moved to the "refining" stage WAYYYY to early and didn't do nearly enough "recovery".

That said, I "boiled" down my (negative for gold) black liquid to the point that when I took the liquid off the heat, it all slowly became a moist, grainy solid mass. On rehydrating with distilled water, I ended up with a LOT of white precipitate, which I assume is silver chloride, and probably some lead nitrate, et al. I've set this 200 g of solid aside. As for the fairly clear green liquid after this bath, I've dropped copper chunks into it to see if MAYBE I can get some gold to fall out. QUESTION: Do I need to acidify this liquid with nitric or HCL? Or just let it sit and hope for the best? Any thoughts on if I'll find my gold?

On 3rd (semi-concurrent) recovery, I (again) went from a stannous positive for gold, to SMB (StumpOut), with zero reaction....and then a negative stannous test. Can I just add copper chunks to this and hope to get the gold to fall out?

As far as lesson learned, on my first batch, I spent days with gold-filled in dilute nitric. I probably did 10 baths to no reaction. The 2nd and 3rd, I was too smart by half and went to AR well before all of the base metals were gone. Now I know. This is a learning process and I've learned much from this forum and external reading.

Thanks,
MarvinM

 

[butcher]

The displacement reaction with copper will work better under acidic pH conditions, although if the solution Has a high oxidation-reduction potential or highly oxidizing acidic conditions you will dissolve copper in the solution and still have a high enough ORP to keep the gold in the solution until the solutions become saturated with copper and the ORP reduces to the point where the newly dissolved copper ions displace gold from the solution (instead of just dissolving copper into the solution with your gold ions, once the oORPis reduced to the point where the copper ions give up their electrons to the gold ions as opposed to the copper dissolving in solution giving up its electrons or sharing them in the strongly oxidizing acid or solution...

To put it simply it will work better under acidic conditions, but not too high of oxidizing conditions, any excess acid or oxidizer just consumes more copper before it will precipitate gold.

Example: With a solution of gold ions dissolved in a cupric chloride solution (wrongly called acid peroxide or AP) (which has a lower ORP than say aqua regia), in this acid solution you can precipitate gold without the solution dissolving a copious amount of copper before doing so.

With aqua regia and with its high oxidation-reduction potential and with copious amounts of free acid and oxidizers in the solution you will dissolve a lot more copper (and dissolve more gold if involved, or redissolve it or just keeping it dissolved) before the ORP is low enough for the copper to displace the gold, but eventually, it will dissolve enough copper to displace ( cement) the gold from solution.

under these conditions, we use up more copper in the cementing process but we can also recover the copper we used when we treat our waste solution to recover the copper metal.

MarvinM, it all seems so simple, and it is once you begin to understand the basic principles, but that takes time and a lot of work and study and working through a lot of messes and failures, inpatients to get going and to get gold, before gaining a fairly good understanding which leads to failures can also help us learn some, but the more we study and practice and the more of an understanding the easier it becomes,

PS You get more gold from educating yourself than you will ever get from the acid or the earth or from some newly found treasure map, or by stumbling around in the dark without an understanding of the principles.

Keep working on gaining more understanding, and the gold will follow you will not have to look so hard to find it if it is hidden...

 

[Marvinm4u]

Thanks for the response

I absolutely agree that impatience was my biggest error. My first batch took 3 weeks, off and on. I condensed to 3 days...then to 3 hours. I understand the "steps", but am learning more and more on what each step actually does and how to know it's complete.

 

[butcher]

"That said, I "boiled" down my (negative for gold) black liquid to the point that when I took the liquid off the heat, it all slowly became a moist, grainy solid mass. On rehydrating with distilled water, I ended up with a LOT of white precipitates, which I assume is silver chloride, and probably some lead nitrate, et al. I've set this 200 g of solid aside. As for the fairly clear green liquid after this bath, I've dropped copper chunks into it to see if MAYBE I can get some gold to fall out. QUESTION: Do I need to acidify this liquid with nitric or HCL? Or just let it sit and hope for the best? Any thoughts on if I'll find my gold?"


Maybe you just the wrong term, when you describe the process, but you should slowly evaporate a solution you suspect contains gold but never bring it to its boiling point, evaporating the solutions rather than boiling the acidic solution.

It sounds like you drove off any free acids, concentrating the salts of the metals, saturating the solution to the point of precipitating them from solution and reducing their valence charge, some of the metals will begin to change oxidation valences at this point, cupric chloride CuCl2 can be converted to cuprous chloride CuCl making the solution darker and precipitating the white salts of copper, other metals like iron can also change valences under these saturated conditions Fe ³⁺ can be reduced to Fe²⁺and so on.

Evaporating a fairly pure gold clean solution (not saturated with base metals) this far down would not be much of a problem, but when you have a soup of base metals with a possibly a salt grain of gold flavoring the soup, well your already seeing the results.

If you would have rehydrated with HCl (instead of water) much of those base metal salts would have dissolved, using water to rehydrate can leave many of the less water-soluble salts undissolved, using water to rehydrate the saturated base metal salts can also reduce other base metal salts lowering their valence charges making them less soluble (CuCl2 -->CuCl, Fe3+ --> Fe2+...).

Yes, you can put the salts back into the solution (using HCl) to change valences of the base metals, also making the solution somewhat acidic, and then use a copper bar of metal to recover any gold from the solution in a displacement reaction to cement the gold, or better said to reduce the gold valence to a metallic form (although a dirty black) precipitate, note you will have other metals or their salts follow and the gold will need another refining and note there may be very little of it (black dirty gold powders) and may be hard to see (depending how much gold is in solution and may take time to settle and be very easily disturbed when decanting...

SnCl2 The stannous chloride is extremely sensitive, it can detect only slight traces of gold in solution, traces too small to worry about trying to get out of a waste solution at some points, as this small trace would be better recovered during waste treatment of your stockpot, rather than wasting your time and your acids and other reagents, spending your days chasing a speck of gold salt in a large kettle soup composed of base metals around your laboratory.

 

[Marvinm4u]

UPDATE: I managed to "find" enough to dissolve in dilute nitric, then dissolve the gold in AR, then drop with SMB to get 15.6 grams of 24k melted end product.

What could you buy at Lowe's/Home Depot that would be actual iron? I want to experiment with it to drop metals for disposal.

 

[FrugalRefiner]

rebar.

Dave