Recovery of gold, silver and platinum group metals with various leachants at low pulp densities

Abstract

In the recovery of noble metals, including gold, silver and members of the platinum group, the ores or tailings are subjected to the action of various leaching agents, namely, sodium cyanide, thiourea, chlorine and aqua regia and optionally a leaching aid, such as chloride ions. The resulting slurry is then diluted to an optimum pulp density of 0.1 to 10.0% and allowed to stand in a holding tank for periods up to 30 minutes, preferably 15 minutes, with the optional addition of a dispersant, such as sodium silicate, sodium carbonate, trisodium polyphosphate or sodium hexametaphosphate. The pulp is then centrifuged to remove solids if necessary and is then passed at a pH <9 through a column containing activated carbon or ion exchange resin/fibre to adsorb any precious metal in solution in the liquor. This is followed by desorption and the cycle repeated as often as warranted by the economics of the process. Alternatively, the pulp is filtered and the filtrate subjected to various recovery techniques, such as cementation, solvent extraction, electrowinning and precipitation.

Dependencies are inferred from the claim text.