# 25 ppm gold solution



## Atto (Mar 17, 2014)

Hello, 

I Would like to know if anyone has an idea to how remove gold at low concentrations in cyanide solutions. 
I have approximately 4000 liters of a solution containing 25 ppm of gold. Reduction with zinc and NaOH is no longer working. 
Activated carbon would be a good choice? 

Thank you again!


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## 4metals (Mar 17, 2014)

Is it possible your free cyanide is too low? Try adding cyanide to a sample and use the zinc again. If you know you were at 25 ppm before you must have a lab capable of determining if there is an improvement after adding free cyanide.


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## Lou (Mar 17, 2014)

At this point, skip the zinc and get an ion exchange resin suited for RIP for cyanide gold solutions.


Lou


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## goldsilverpro (Mar 17, 2014)

In the mining industry, lead, usually in the form of lead acetate, is commonly used with the zinc to increase the efficiency when cementing gold from cyanide. I don't think it takes much. I have never done this but there's lots of info on the internet. Were I you, I would do a lot of studying and then do small experiments with analysis of the results. If this can be made to work, it sounds like the simplest way to me. You have over 1000 gallons containing about $4000-$5000 worth of gold.

https://www.google.com/search?q=gold+recovery+cyanide+lead+acetate+zinc&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-USfficial&client=firefox-a&channel=sb


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## freechemist (Mar 18, 2014)

After my experience there exist at least 2 procedures, to solve your problem:

*1.) Addition of ammonium chloride, followed by cementation of gold with zinc-powder:*
Reducing dissolved gold with zinc-powder, means also to oxidize metallic zinc to Zn2+-cations, and to keep these dissolved by a suitable complexing agent. 4metals suggests to add some cyanide, to form soluble cyano-complexes of Zn(II).
In my practice, I preferred to add an excess of ammonium chloride, which, in a cyanide-solution will form ammonia, NH3 and hydrocyanic acid, HCN. The ammonia in turn, together with ammonium ions, will help to oxidize/dissolve metallic zinc and keep it in solution as a soluble ammine-complex, [Zn(NH3)4]2+.

*2.)RIP-(resin in pulp)-process, suggested by Lou:*
The complex anion [Au(CN)2]- is absorbed on a strongly basic anion-exchange resin. In my practice I used successfully quartenary ammonium type resin, in chloride form. Such a resin can be loaded with at least 10% of it's weight in gold until the solution in equilibrium with it contains much more than 1 ppm of dissolved gold.
Take about 4 liters of your cyanidic gold-solution, corresponding to 100 mg of gold, add 1 g of resin beads and stir constantly for a few hours at room temperature. Then separate the beads by decantation/filtration, wash thoroughly with water, dry, and incinerate completely to spongeous
metallic gold.


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## Atto (Mar 19, 2014)

thank you all, I will start testing


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