Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction 2017-04-04T06:57:36+00:00
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Gold Cyanidation (6 replies)

1 year ago

What are the reasons why high cyanide concentration does have a decelerating effect in gold dissolution? Our process is batch type, maintaining pH of 10.5-11, leached for 24 hours. The ore contains: Gold, silver, high in quartz, high with pyrite, and small amount of Cu, As, Pb.

Bob Mathias
1 year ago
Bob Mathias 1 year ago

Many different reasons have been proposed, but a generally regard one is the change in pH by increased amounts of cyanide.

Marshal Meru
1 year ago
Marshal Meru 1 year ago

Send more details on your process, cyanide concentrations, batch/continuous, DO, leach time, pro-ox etc. Maybe we can make more sense and even come up with some improvements.

1 year ago
Oberstorm 1 year ago

I studied this extensively while working in Ecuador and do not believe that higher pH is the cause of the decelerating effect of gold solubility in higher concentrations of cyanide because we held the pH constant (at 10, at 10.5 and at 11 with lime and also with NaOH) in our studies. We found only that the solubility of copper increased dramatically with higher cyanide concentrations hence that may have been the cause.

Helena Russell
1 year ago
Helena Russell 1 year ago

I think, that first at all, we need to know, what is the operational context?, In this metallurgical process, there is so much copper, silver, mercury, and what about the oxygen concentration on the barren solution. The gold cyanidation, is a electrochemical process, so it´s very important to evaluate, with other electrochemical factors.

Dizzy Flores
1 year ago
Dizzy Flores 1 year ago

Interesting problem - probably passivation caused by the interaction between pyrite and cyanide (ferro-cyanides-iron hydroxides). High DO levels are also not good for gold dissolution in the presence of pyrite. Need to keep the CN and DO levels quite moderate.

Are you using lead nitrate to passivate the pyrite and what DO levels are you achieving?
Are you sure that it is pyrite and not marcasite or some pyrrhotite present?

These versions of iron sulphide can have a dramatic impact unless handled in specific ways (e.g. aeration prior to cyanide addition).

1 year ago
Sturmbann 1 year ago

I think it's because of other secondary reactions that consume CN.

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