A method of recovering a metal from a low-grade ore which is subjected to cyanide leaching to produce a PLS which contains a metal cyanide which is removed from the PLS by ultrafiltration and nano-filtration, and then acidified and sulphidised to produce a metal sulphide from which the metal is extracted, and hydrogen cyanide which is recycled to the cyanide leaching step.

THIS invention relates to a method and heap for recovering metal values from ore in a heap leach process. The method includes the steps of depositing and stacking crushed ore 16 on an impermeable pad 12 to form a heap, and enclosing the heap with a substantially impermeable coating 18 to both gas and liquid; to form a sealed heap. The sealed heap is irrigated with a leachant added inside the top of the heap, allowing the leachant to percolate through the heap and removing leachant at the base of the heap, either for recirculation or subsequent processing. Oxygen containing gas is added to the base of the sealed heap.

THIS invention relates to a method and heap for recovering metal values from ore in a heap leach process. The method includes the steps of depositing and stacking crushed ore 16 on an impermeable pad 12 to form a heap, and enclosing the heap with a substantially impermeable coating 18 to both gas and liquid; to form a sealed heap. The sealed heap is irrigated with a leachant added inside the top of the heap, allowing the leachant to percolate through the heap and removing leachant at the base of the heap, either for recirculation or subsequent processing. Oxygen containing gas is added to the base of the sealed heap.

A method and system for converting copper cyanide to copper oxide is provided. The method includes contacting a copper cyanide solution with an acidic solution in a precipitation tank under reaction conditions sufficient to produce a copper cyanide slurry, removing the copper cyanide slurry from the precipitation tank, separating solid copper cyanide from the copper cyanide slurry in a first separation device, removing the solid copper cyanide from the first separation device, contacting the solid copper cyanide with a sodium hydroxide solution in a production tank under reaction conditions sufficient to produce a copper oxide slurry, removing the copper oxide slurry from the production tank, separating solid copper oxide from the copper oxide slurry in a second separation device, and removing from the second separation device any residual sodium hydroxide not reacted during the process of contacting the solid copper cyanide with the sodium hydroxide solution in the production tank.

Disclosed is selective removal of mercury from aqueous feeds also including precious metals. In particular, the present invention is useful for removal of mercury from processing waters produced during precious metal mining processes. The process includes contacting the aqueous feed solution with a solid sorbent material including thiol and/or thiolate functional groups, wherein (i) the aqueous feed solution includes at least 10 ppm of free cyanide ions; and/or (ii) the sorbent material is contacted with an aqueous cyanide solution after contact with the aqueous feed solution to selectively desorb precious metal from the sorbent material.

Disclosed is selective removal of mercury from aqueous feeds also including precious metals. In particular, the present invention is useful for removal of mercury from processing waters produced during precious metal mining processes. The process includes contacting the aqueous feed solution with a solid sorbent material including thiol and/or thiolate functional groups, wherein (i) the aqueous feed solution includes at least 10 ppm of free cyanide ions; and/or (ii) the sorbent material is contacted with an aqueous cyanide solution after contact with the aqueous feed solution to selectively desorb precious metal from the sorbent material.

A process is disclosed for recovering cyanide used to leach gold or silver from ore. In the course of leaching gold or silver from ore, a barren solution is generated. A portion of the barren solution containing sodium cyanide is recycled to the cyanidation process while blowdown from the barren solution is subjected to pre-treatment, UV photodissociation and pH adjustment. Ultimately, a volatile hydrocyanic acid is formed and is absorbed into a sodium hydroxide solution through the employment of a gas-filled membrane. This forms sodium cyanide that can be recycled and used in the cyanidation process to leach gold or silver from ore.

A process is disclosed for recovering cyanide used to leach gold or silver from ore. In the course of leaching gold or silver from ore, a barren solution is generated. A portion of the barren solution containing sodium cyanide is recycled to the cyanidation process while blowdown from the barren solution is subjected to pre-treatment, UV photodissociation and pH adjustment. Ultimately, a volatile hydrocyanic acid is formed and is absorbed into a sodium hydroxide solution through the employment of a gas-filled membrane. This forms sodium cyanide that can be recycled and used in the cyanidation process to leach gold or silver from ore.

The present disclosure relates to a method using a reagent having a thiocarbonyl functional group to liberate a precious metal such as gold from a material comprising a sulfide, wherein the sulfide encapsulates the precious metal. Such a method comprises contacting the material under acidic conditions with the reagent comprising the thiocarbonyl functional group and optionally producing a residue comprising the precious metal. The present disclosure also relates to the use of a reagent having a thiocarbonyl functional group in methods for extracting a precious metal from a material comprising a sulfide, wherein the sulfide encapsulates the precious metal, the method comprising leaching the precious metal from a residue comprising the precious metal produced from such a method for liberating a precious metal.

A process to recover nickel, cobalt and copper by co-processing copper-containing sulphide concentrate feed containing one or more of arsenic, antimony, and bismuth, and laterite ore feed containing nickel and cobalt by pressure oxidative leaching. The sulphide concentrate and oxygen are controlled to produce sulphuric acid to leach nickel, cobalt, copper and acid soluble impurities into a liquid phase of an acidic leach slurry, to precipitate iron compounds and a majority of the arsenic, antimony and bismuth as solids, and to produce heat to heat the incoming feeds to a temperature above 230 C. Reacted slurry is withdrawn, solids are separated, and the PLS solution contains the nickel, cobalt, copper and acid soluble impurities. A first solution purification stage on the PLS neutralizes free acid, precipitates one or more of iron, aluminum, chromium and silicon, and, separates as solids, the precipitated impurities and other solids from a first purified solution. Copper is separated from the first purified solution with a solvent extraction step to produce a raffinate solution reduced in copper and a copper loaded organic phase. The organic phase is stripped and copper is recovered with electrowinning. A second solution purification stage is conducted on the raffinate by one or both of neutralizing free acid and precipitating one or more of iron, aluminum, chromium and silicon, followed by separating as solids, the precipitated impurities and other solids from a second purified solution. Nickel and cobalt are recovered as mixed hydroxides or mixed sulphides from the second purified solution.