Cyanide(CN) under the right conditions forms covalent complexes with metal cations such as Ag, Au, Cd, Ni, Hg, Fe, Cr etc,. If there is a large number of competing metal ions in the ore, you have to frig around with the conditions to try and maximize the economic metals coming out, but minimize the competing metals, and minimize the amount of cyanide used to lower costs in initial leaching and subsequent precipitating steps.
How much you crush is also part of the process. You may be able to extract more with a finer crush, but this will cost you more to accomplish in power, additional handling, additional equipment costs, and increased leach pit management costs. You may also increase the yield of competing metal ion production, which may increase overall processing and refining costs.
It is a balancing act and usually requires many months and years of frigging to get the highest dollar yield from the leachate, with the lowest costs to process. It may be that the best final profit is obtained by only extracting 65% of the total Au.
Just as you get things right, the blend of crushed inputs changes a bit in composition and frigs everything up on you again. |
