Abstract: A method and apparatus are described for recovering gold from aqueous slurries of refractory gold ores containing sulfidic and/or carbonaceous matter. The method entails pretreating an ore slurry with chlorine in a multi-compartment autoclave operated at an elevated pressure. The chlorine used in this pressure chlorination pretreatment can be in either the gaseous or liquid state. Following the removal of residual chlorine from the pretreated ore slurry, said slurry is transferred to a conventional cyanide leach/carbon adsorption circuit to recover the gold values.

Abstract: A process for recovering gold from refractory gold-bearing ores uses sulfurous acid as the leaching agent to form a gold-sulfite complex. The ore is ground, slurried blended with a chelating agent and then subjected to a simultaneous dissolved SO.sub.2 leaching and anion exchange resin adsorption step in the presence of dissolved oxygen. The gold transfers to the resin which is later separated from the resin by chemical stripping.

Abstract: A process for recovering gold from gold-bearing ores includes the steps of forming a slurry of ground ore and treating the ore with an oxidizing and complexing agent such as hydrogen sulfide or a sulfide salt. A chelating agent, SO.sub.2, air, and an anion exchange resin are added to the slurry to subject the ore to a simultaneous sulfurous acid leaching and anion exchange resin adsorption step in the presence of dissolved oxygen. The gold transfers to the resin which is then removed from the slurry. The gold is then separted from the resin by chemical stripping. Alternately, the ground ore is blended with an oxidizing agent such as calcium hypochlorite and then with a gold-complexing agent. The ore blend is slurried in water, with the addition of a chelating agent, SO.sub.2, air and an anion exchange resin to effect the leaching and adsorption of gold values.

Abstract: In this invention sulfide compounds are added to mercury and precious metal-containing carbonaceous ore slurries prior to the slurry being processed by a carbon-in-pulp system. The sulfide compound inhibits the mercury from being adsorbed onto the activated carbon by reacting with the mercury to form mercuric sulfide and by inhibiting the dissolution of mercury from the ore. The mercuric sulfide precipitate displays no activity toward the activated carbon. The sulfiding procedure is performed with a sufficient amount of sulfide-providing compound to provide at least about 30 times the stoichiometric amount of sulfide ions required to react with the mercury in the ore slurry.

Abstract: This invention is a process for removing mercury from the desorption or cyanide liquor of a precious metal recovery, cyanide leach system. A sulfide ion-producing compound and a flocculating agent are added to the desorption liquor to form and flocculate mercuric sulfide. The desorption liquor typically has a cyanide concentration of between about 0.5 percent and about 2.0 percent by weight. The flocculated mercuric sulfide is separated from a substantially mercury-free precious metal-containing, cyanide solution.

Abstract: Residual hypochlorite contained in chlorinated slurries of either carbonaceous gold-containing ores or mixtures of carbonaceous and oxide gold-containing ores are reduced by reaction with sulfide ion-providing chemical compounds preferably sodium hydrosulfide, sodium sulfide or hydrogen sulfide. The hypochlorite "kill" step enables subsequent cyanide leach operations to be conducted more efficiently.

Abstract: A method and apparatus for high temperature-high pressure acid leaching of sulfide ores is described. The apparatus includes an autoclave having a plurality of pressurized compartments and a water removing-heat removing condenser. Means are described for the introduction of a neutralizing agent directly into the autoclave in order to maintain the acidity of the slurry at a level where substantially all of the iron present in the slurry will form an insoluble iron oxide precipitate. Means are described for removing the gaseous products resulting from the introduction of the neutralizing agent while avoiding contamination thereby of a substantial portion of the oxygen.

Abstract: A method is described for the oxidation-leaching of chalcopyrite concentrates at high temperatures and pressures for the extraction of copper values as copper sulfate in which temperatures are maintained between about 425.degree. and 450.degree.F, oxygen partial pressures of between about 50 and 200 psi are provided, and levels of acidity are permitted to increase above about 50 grams of H.sub.2 SO.sub.4 per liter in order to obtain maximum rates of extraction of virtually all of the copper. Thereafter, while maintaining the temperature and pressure at elevated levels, the acidity of the slurry is reduced to between about 10 and 40 grams of H.sub.2 SO.sub.4 per liter in order to obtain reduction of dissolved iron to optimal levels. The resulting slurry is then cooled and further processed for the production of a very pure copper sulfate solution.