Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

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How to process silver gold amalgam with acids (2 replies)

2 years ago
7CHEESE8 2 years ago

I have refined gold with ar with success. I have gold silver amalgam that I'm not sure what the steps are to separate the metals.  Gold and silver amalgam come from where I'm working. I started by retorting the amalgam. I'm guessing a nitric bath. The solution turned black. Rinse with distilled water with a little heat. I'm honestly not sure what to do with this. Please help! 

2 years ago
Jorge 2 years ago

It is important to eliminate the mercury by distillation. The product containing silver should be ground, approx. 80-90% passing 200 mesh. Then, dry the material to evaluate the effect of hot nitric acid on silver dissolution.

- You can try different temperatures (e.g. 50, 75, 90 oC).

- Nitric acid strength is other variable to consider, a good starting point is 40% w/w, based on the result you can try 60% w/w or higher concentration.

- Solid/Liquid ratio, 1/3, 1/4, 1/6

The optimum parameters will product a pregnant solution, which can be treated by cementation with copper to precipitate silver.

Nonoy Celera
2 years ago
Nonoy Celera 2 years ago

Retort the amalgam to removed the hazardous mercury. The mercury-free sludge can be melted in an appropriate flux to slag-out base metals in the sludge. You will produce a silver-gold dore'. If you need to produce separately gold from silver the next step is to remelt the dore and while in molten state pour this in a vigorously stirred vat of water to produce granulated dore. Put the granulated dore into a stainless steel basin and pour nitric acid while heating the basin. Dark brown smoke is the reaction of the nitric acid and the silver. Stir occasionally then pour the solution into a container. Repeat the process 3 time until no more brown smoke is observed which could indicate that all the silver is dissolve. Ground the charge every after pouring the silver nitrate solution to exposed more surfaces for the next acidification. The residue can be remelted with just a borax to cover the fines gold granules. This will produce > 95% pure gold bullion. Add sodium chloride to the silver nitrate solution to precipitate the silver, filter the silver chloride precipitate and smelt it with necessary flux to produce >98% silver bullion.


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