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

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

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Cyanide levels to minimise copper loading on carbon (2 replies)

3 years ago
ManUtd67 3 years ago


I am looking for operating experiences for controlling and minimizing copper loading on activated carbon in a gold CIP circuit.

The project under consideration is still in design phase.  The ore has some copper associated with chalcopyrite which causes copper in leach solutions to run at around 60ppm Cu.  

There is plenty of literature that shows by running at high pH >10 and sufficient free cyanide, Cu(CN)3 and Cu(CN)4 prevails and does not load significantly on carbon.  Maarsden recommends a 4:1 CN:Cu molar ratio which implies a free cyanide level of 185ppm is required.

Cu that does load on C can be removed by a cold cyanide wash.

Can I please get some operating examples to confirm this:

Cu in solution - ppm

Free cyanide level - ppm

Au loading on C - gAu/t

Cu loading on C - gCu/t



Todd H
3 years ago
Todd H 3 years ago

The cyanide level is not the most critical part, the adsorption pH is more important in my experience. Also not using excess free cyanide in the leach - stagewise additions helps reduce the copper dissolution driving force.  Any copper adsorbed on the carbon can be eluted with an acid wash not a cyanide wash.  You risk losing gold using cyanide.  I have only one recent example that I can recall from a plant:

Cu in solution 50 ppm, free cyanide 50 ppm, gold loading 3,500 ppm, pH 10.5, copper adsorbed 50%.  We were trying to convince them to make some changes to this circuit to reduce the copper loading.






Todd Harvey - Global Resource Engineering http://www.global-resource-eng.com

3 years ago
Reactor 3 years ago


If you are still in design mode we may be able to help. We have many years of success with in-solution metals and cyanide recovery using membranes.



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