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Gold Recovery from Gold Cyanide Solution (3 replies and 5 comments)
I assume your PH is above 7 from cyanide and to minimize poisonous HCN gas. To react the peroxide to water at high PH I would experiment with sodium sulfite and heat. The sulfite should oxidize to sulfate while reducing H2O2 to H2O. This will occur more readily at lower PH so you could also try lowering the PH (Slowly) to under 7 by using sodium metabisulite NaHSO3.
Iron (ferric of ferrous) ions will catalyze the destruction of peroxide, as will cupric ions (copper II), liberating oxygen bubbles (so watch out).
Thanks for your reply. After lowering the PH what would be the best method to recover gold from cyanide solution? Can I use sodium hydro sulfite to recover gold ?
Thanks & Regards
First, I should have written above that Iron and copper ions mostly precipitate to hydroxides when above PH7 but there is some solubility. Also, they will speed the peroxide destruction of free cyanide by a significant amount, especially as PH lowers to between 9 and 7.
I would experiment in a small beaker with this first, by the way.
Once you get rid of the free cyanide and peroxide it will depend on what other ions are in your solution as how to proceed. If you have no citrates or chelating agents you should be able to drop the gold with hydrosulfite as you tried before, or maybe zinc at PH 2.0 to 2.5 at 90C. If there are complexing agents present then there is an excellent method posted somewhere on this site on how to use copper (I) ions at <7PH to precipitate a gold-copper-cyanide polymer that can be refined in several ways to pure metallic gold. I would hope the site proprietor knows which I am taking about and post the link. You make copper (I) with copper sulfate and sodium metabisulfate in a separate solution and mix warm in a dump into your gold solution. To be certain beforehand that you have killed most of the free cyanide you can test by seeing if a precipitate that forms will not dissolve when a drop of dilute silver nitrate and potassium iodide are added. If there is free cyanide the drops will be cloudy at first then dissolve.
Here is to the link to the article I referred to by David. https://www.911metallurgist.com/cyanide-chemistry-gold-extraction/
Ron G, I read the link you provided[cya-che-gold- extr] I dont understand most of it. I have no knowledge of chem. or smelt or acids. I am new to this. I do have 3 mines willed to me. I do have assay's 1gm per lb of cons. 75% is pyrites and sulfides. I am now going to try cyanide. Is there any where I can find step by step for laymen, how to use cyanide? The guy that suggested cy said grind, add 3% cy, add water to a pulp, forced air and mix for 48 hrs, pour off liquid toss in spoon of powder zinc, melt that, then AR. From reading I find keep Ph above 9.5 below 12 lime and soda. Is this it? Do I have to pre treat because of arsenic and sulfides? How? Thanks
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I want to recover gold from gold cyanide solution. This solution contains hydrogen peroxide also. I have tried metal displacement method. It does not give complete gold recovery. Please suggest me some chemical method through which I can recover all the gold from this solution.
Thanks!