for diamond mining, effluent water treatment is still continuing for gold recovery, example Panna gold mine India.
Ion exchange resins are a good solution. Gold-selective resins have a higher selectivity for gold over base metals than activated carbon. This allows higher gold loadings since resin capacity is not "wasted" on undesirable base metals. A further result of the reduced affinity of resins for base metals is that these metals can be preferentially eluted from the resin before gold and silver, thereby ensuring a cleaner eluate, higher cell-house efficiency, and higher-purity bullion. Copper is the biggest problem due to the similarity between the gold-cyanide and copper-cyanide complexes. High concentrations of copper result in high cyanide consumption. Excess-free cyanide must be maintained to minimize the Cu(CN)2- complex formation and avoid significant copper loading onto the activated carbon. Measures such as selective mining or removal of copper via acid leach have been tried but are only effective to a point. Anglo Asia's Gedabek mine in Azerbaijan chose the gold-selective Dowex-Minix resin over activated carbn, due to the high copper content of the ore.
More at:
https://www.purolite.com/index/core-technologies/industry/hydrometallurgy/developments-ion-exchange-recovery-of-gold
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