Abstract: A method for recovering a precious metal from a host material, comprises the steps of subjecting the host material to an oxidative pressure leach process, in the presence of a halide ion constituent which is reactive with the precious metal, and at a temperature sufficient to cause at least a portion of the precious metal to be extracted by a leach solution; and recovering the precious metal from the leach solution.

Abstract: A process for treatment of precious metal ores in which gold is leached from an oxidized ore slurry using a thiosulfate salt lixiviant and copper catalyst. Gold and copper are subsequently loaded onto an ion exchange resin. Copper is recovered from the resin by elution with a thiosulfate solution; gold is recovered from the resin by elution with a thiocyanate colution. Gold is recovered from the eluate by precipitation, electrowinning, or cementation.

Abstract: A process for recovering gold in which an ore slurry of refractory sulfidic and refractory carbonaceous ore having preg-robbing characteristics due to the presence of organic carbon is subjected to pressure oxidation in an autoclave. The oxidized ore slurry is mixed with a thiosulfate salt lixiviant, which mixture is maintained at a pH between 7 and 8.7 while the slurry is agitated in a stirred tank reactor system having agitated leach tanks. Gold is recovered from the gold-bearing leachate by cementation, adsorption on an adsorbent, or cyanidation.

Abstract: The specification discloses a process for removing radionuclides from zircon. The process involves thermally decomposing the zircon in the presence of suitable additives, extracting the radionuclides chemically and recovering zirconia and silica. Suitable additives include fluxes, silica and any oxide capable of forming a silicate with silica when heated. Chemical treatments disclosed include leaching with mineral acids and strong organic acids. Methods of stabilizing the radionuclides extracted by leaching are also disclosed. One method involves spray roasting. Another method involves neutralization of leach liquor and recovery of radionuclide solids by filtration or other suitable liquid/solid separation techniques.

Abstract: A hydrometallurgical process for treating copper ores or concentrates containing gold by simultaneously leaching both copper and gold into an aqueous cyanide solution, recovering copper and gold in metallic form by electrowinning or cementation and regenerating cyanide ions is provided.

Abstract: Increased efficiency of extraction of silver and gold from ore materials thereof containing active carbonaceous material is obtained by conducting the extraction in two stages. In a first stage a portion of the silver and of the gold when present is extracted in a cyanide leach solution. The leached solids residue is contacted with activated carbon so that the silver and the gold when present are adsorbed on the activated carbon at elevated temperature (most preferably at about 35.degree. C. to about 100.degree. C.). In a modification, a slurry of the ore material is treated with cyanide and the precious metal adsorbed directly from the cyanided slurry with activated carbon at elevated temperature up to about 70.degree. C.

Abstract: A method of regenerating strong-base anion exchange resins which have been used in the extraction of complex anions followed by elution with a thiocyanate strip solution is provided. The method involves the use of ferric ions in a regenerating solution together with a substitute anion for attachment of the resin, the regeneration taking place under conditions in which ferric-thiocyanate complex cations are formed and washed from the resin by the regenerating solution. The thiocyanate can be recovered by neutralizing the regenerating solution to precipitate ferric hydroxide and leave thiocyanate in solution.