• To participate in the 911Metallurgist Forums, be sure to JOINLOGIN
  • Use Add New Topic to ask a New Question/Discussion about Leaching.
  • OR Select a Topic that Interests you.
  • Use Add Reply = to Reply/Participate in a Topic/Discussion (most frequent).
    Using Add Reply allows you to Attach Images or PDF files and provide a more complete input.
  • Use Add Comment = to comment on someone else’s Reply in an already active Topic/Discussion.

Gold Cyanidation (6 replies)

9 months ago
Obergruppenfuhrer 9 months 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
9 months ago
Bob Mathias 9 months ago

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

Marshal Meru
9 months ago
Marshal Meru 9 months 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.

9 months ago
Oberstorm 9 months 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
9 months ago
Helena Russell 9 months 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
9 months ago
Dizzy Flores 9 months 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).

9 months ago
Sturmbann 9 months ago

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

Please join and login to participate and leave a comment.