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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Leaching of gold ore containing mercury (5 replies and 1 comment)

6 years ago
Wadzanayi 6 years ago

I would like to know how I can modify the cyanidation process to leach a gold ore which has got the following characteristics:

 Au grade 3-4 g/t 

 Hg grade  1-2.5 g/t

 Cu, As,Sb grades: trace

FeS: trace

The ore has produced unsatisfactory results after milling to 85%  passing 75 microns and processing in a CIP plant under the conditions of  49% solids,pH 8,NaCN  1kg/ton and 24 hours residence time.

6 years ago
Aminpro 6 years ago

It would have been nice to hear some more about this ore.  I see there are sulphides in the ore.  Have you tried flotation? or leaching the pyrite with sulfuric to then leach it with CN?


6 years ago

The process is as follows
crushing and milling down to 80% passing 75 microns to liberate the gold. The gravity circuit is as follows:
1. Mill discharge is then passed over a 12 inch Knelson concentrator
2. KC concentrates are processed in an amalgam barrel using mercury
3.KC tails( grind of 65% passing 75 microns are deposited on a makeshift slimes dam)
4.KC tails are then transported to a toll treatment facility
5. Tails from amalgamation usually with an assay grade of around 300g/t Au and 2 g/t Hg are periodically feed into the CIP plant to recover the gold contained through intensive leaching

The ore leaches quite statisfatorily ( head grade 2.7-3 g/t Au tail- 0.4-0.54 g/t Au) but the gold doesnt show in the final product

6 years ago
Rheomet 6 years ago

It appears that the pH is way too low at 8. This causes quick depletion of cyanide, even though your are adding plenty upfront...about one quarter of that (0.5 g/L free NaCN should suffice, if maintained). I suggest that you bring the pH up to 10.5-11 with lime. If does not work, it could also be due to the grind being too coarse. Best would be to run 3 bottle roll tests, one as it is now (pH 8, 2 g/L NaCN, 75 microns) and two at pH 10.5-11, 0.5 g/L NaCN, at two grind-sizes, 75 microns and 50 microns.

 Good luck.


Vault Dweller
6 years ago
Vault Dweller 6 years ago

Yummy, Mercury - Out of interest what recovery configuration will you use? 

6 years ago
moka97 6 years ago

I am asking about gold amalgam freezing with chemical additives to increase gold extraction? what is this types of chemicals ?  

6 years ago
Auexplorer 6 years ago

I am curious, Please excuse my question, Why the amalgamation circuit when grinding to 75 micron, seems like an extra circuit. Any free_mill material would be caught in the grinding and classification circuit and viable for direct smelt. Again, please excuse my question. I have a similar ore.


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