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How to extract gold from a carbonaceous ore? (2 replies)

3 weeks ago
markoramiusiii 3 weeks ago

Having the following mineralogy: Free gold, 30% coarse greater than 208 microns, 40% less than 208 microns but greater than 54 microns, 30% less than 54 microns. Any idea would be a great help. Thank you. 

Paul Morrow
3 weeks ago
Paul Morrow 3 weeks ago

If you have free gold, use gravity.  Is this a real already running plant or a Laboratory job?

How much carbon do you have?  Any sulphides/sulfur?

Greg Henderson
3 weeks ago
Greg Henderson 3 weeks ago

Before getting too excited about carbon, do some bottle cyanide leach tests with (10 g/l) and without activated carbon to see what the relative drop in adsorption is.  It is possible to have carbon present that is not preg-robbing, in which case you don't have a problem.  If there is an issue you can then move on to diagnostic leach tests (at your optimised grind size, P80 = 75 um is a good start) to quantify deportment of gold in the various minerals present.  If the carbon is "active", you will need to use acetonitrile for the gold leach between oxidation steps.  Any decent lab will know how to adapt the standard diagnostic leach to cater for preg-robbers.  After this you can get into the more expensive metallurgical tests.

I agree with Paul Morrow, you can recover most of the gold that is coarser than 54 microns with gravity provided that it is liberated.  Mines in Siberia and Ghana have to deal with these type of ores and favour a combination of gravity and flotation.  With flotation, it is important to operate at a low pulp density, around 20% solids w/w, and to use strong depressants such as guar gum to depress the carbon minerals and possibly a dispersant such as sodium silicate, along with a specialised gold promoter and selective collector.  Cleaner stages should be columns with in froth washing, Woodgrove Technologies Staged Flotation Reactors could be a good device for this application.  If the carbon still co-floats with the gold (and sulphides if present), resin-in-pulp (RIP) using modern resins such as Puragold or Minix, in conjunction with pre-treatment with kerosene to foul the carbon prior to cyanide leaching, should be effective. 

If you need more detailed help please drop me a line on greg.henderson@amecfw.com


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