Abstract: A process for the recovery of zinc from zinc-containing sulphidic material which also contains iron and from zinc oxide containing material, at least one of the materials containing lead and/or silver values. The process includes leaching zinc-containing sulphidic material and zinc oxide containing material under pressurized oxidizing conditions at a temperature in the range of from about 130.degree. to about 170.degree. C. in aqueous sulphuric acid solution with a stoichiometric excess of sulphuric acid relative to the zinc content of the materials of from about 40 to about 100% to produce a residue containing a major proportion of lead and/or silver values and a leach solution containing a major proportion of the zinc and iron. The residue is separated from the leach solution and treated to recover lead and/or silver values.

Abstract: A water permeability contrast correction process to improve the sweep efficiency of waterflooding which involves the sequential injection of (1) an optional aqueous preflush slug to adjust connate water salinity, (2) an aqueous thickened slug comprising a sequestered polyvalent metal cation such as aluminum citrate and a gelable polymeric viscosifier such as polyacrylamide, (3) carbon dioxide to decrease the pH of the polymer slug which triggers the delayed in-situ gelation of said thickened slug to preferentially decrease water permeability in highly permeable thief zones, and (4) an aqueous drive fluid.

Abstract: A process for the production of fine copper powder with particles having a size less than about 5 micrometers, comprises providing an ammoniacal cuprous salt solution, and neutralizing ammonia in said solution with acid in a substantially oxygen-free environment to produce substantially oxygen-free fine spherical copper powder.

Abstract: A process for the recovery of silver from a residue essentially free of elemental sulphur obtained by acidic pressure oxidation leaching or iron-containing sulphidic material which comprises forming a slurry of the residue with lime at a temperature of at least about 80.degree. C. to raise the pH of the slurry to at least about 9. The slurry is maintained at this temperature for from about 0.5 to about 4 hours, and the resultant slurry is subjected to silver recovery treatment.

Abstract: A process for recovering gold from refractory auriferous iron containing sulphidic material which comprises treating an aqueous slurry of the material in a pressure oxidation step at a temperature in the range of from about 135.degree. to about 250.degree. C. under a total pressure of from about 500 to about 5000 kPa to oxidize sulphide sulphur to sulphate form and release gold from a refractory state. The pH of the resultant oxidized slurry is adjusted to a value suitable for cyanidation. The pH adjusted slurry is subjected to a cyanidation step in which gold is dissolved in a cyanide solution. The cyanided slurry is diluted to a pulp density in the range of from about 2 to about 10% solids by weight. The diluted slurry is subjected to a liquid-solids separation step to produce a gold containing solution and a relatively high pulp density gold-containing slurry, and gold from the gold-containing solution and from the high pulp density gold-containing slurry is separately recovered.

Abstract: A process for the pressure oxidation leaching of non-ferrous metal sulphidic material which comprises providing an autoclave assembly which has a series of successive compartments, the first compartment of which being substantially larger in size than each of the remaining compartments. An oxygen partial pressure is provided in the autoclave assembly in the range of from about 50 to about 2000 kPa. An aqueous slurry of the material is fed into the relatively large first compartment with resultant flow of the material through the successive smaller compartments causing the temperature in the first and successive compartments to be sufficient to produce autogeneous oxidation of the sulphidic material. The oxidized slurry from the last compartment of the series is discharged.

Abstract: A process for separately recovering gold and silver from a solution containing dissolved gold and silver by carbon adsorption which comprises passing the solution sequentially through a series of carbon adsorption stages and passing carbon sequentially through the series countercurrent to the solution to cause gold and silver to be loaded onto the carbon. A portion of the loaded carbon is removed partway along the series, and silver is recovered from the removed portion of the loaded carbon. Loaded carbon is removed from the beginning of the series, and gold is recovered from the carbon removed from the beginning of the series. Carbon from which gold and silver have been removed is returned to the end of the series for re-use.

Abstract: A process for the recovery of gold from refractory auriferous iron-containing sulphidic material which comprises providing an aqueous feed slurry of fresh feed material and oxidized solids from a subsequent pressure oxidation step. The feed slurry has a pulp density in the range of from about 30 to about 60% by weight. The slurry is subjected to pressure oxidation at a temperature of from about 120.degree. to about 250.degree. C. under a total pressure of from about 360 to about 6000 kPa to produce a slurry of oxidized solids. A portion of the oxidized solids is recycled to the feed slurry, and gold is recovered from the remaining oxidized solids.

Abstract: A process for recovering cobalt and nickel values from cobalt and nickel containing sulphidic material also containing iron includes roasting the sulphidic material to produce a calcine containing water soluble cobalt and nickel sulphate, and leaching the calcine in aqueous sulphate solution under oxidizing conditions at an oxygen overpressure in the range of from about 50 kPa to about 1500 kPa and at a temperature in the range of from about 100.degree. to about 180.degree. C. to produce an iron-containing residue and a cobalt and nickel containing solution. The residue is separated from the solution, and cobalt and nickel values are recovered from the solution.

Abstract: A process for recovering gold from refractory auriferous iron-containing sulphidic ore which comprises feeding ground ore as an aqueous slurry to an acidic pretreatment step. The ground ore in the acidic pretreatment step is treated with aqueous sulphuric acid solution to decompose carbonate and acid consuming gangue compounds, and subjecting the treated slurry to a first liquid-solids separation step to produce a sulphate solution and separated solids. Water is added to the separated solids in a first repulping step to form a slurry having a pulp density in the range of from about 25 to about 60% by weight solids. The first repulped slurry is oxidized in a pressure oxidation step at a temperature in the range of from about 135.degree. to about 250.degree. C.

Abstract: A process for recovering gold from refractory auriferous iron-containing concentrate includes feeding the concentrate as an aqueous slurry to an acidic pretreatment step and treating the concentrate in the acidic pretreatment step with aqueous sulphuric acid solution to decompose carbonate and other acid consuming gangue compounds. The treated slurry is oxidized in a pressure oxidation step at a temperature in the range of from about 135.degree. to about 250.degree. C. under a pressurized oxidizing atmosphere while maintaining a free acid concentration of from about 5 to about 40 g/L sulphuric acid to cause dissolution of iron, formation of sulphuric acid and oxidation of substantially all oxidizable sulphide compounds to sulphate form with less than about 20% of oxidized sulphur being present as elemental sulphur during the oxidation step.

Abstract: A process for separately recovering platinum group metal values, nickel values and copper from nickel-copper-iron sulphidic matte containing platinum group metals includes leaching ground matte at atmospheric pressure in acidic nickel-copper sulphate solution at a temperature in the range of from about 75.degree. to about 105.degree. C. and at a pH below about 4 initially under oxidizing conditions and subsequently under neutral or non-oxidizing conditions to cause dissolution of nickel and iron, precipitation of copper as a copper sulphide and precipitation of dissolved platinum group metals. The copper, nickel and platinum group metal containing solids are separated from the nickel and iron containing sulphate solution and are leached in acidic nickel-copper sulphate solution under pressurized oxidizing conditions at a temperature of from about 120.degree. to about 180.degree. C. to cause dissolution of nickel and copper with minor dissolution of platinum group metals.

Abstract: A process for separately recovering zinc and lead values from zinc and lead containing sulphidic ore which also contains iron comprises subjecting ground ore to a first flotation step to float an initial lead concentrate containing zinc and produce zinc and iron containing tailings. The zinc and iron containing tailings are subjected to a second flotation step to float an initial zinc concentrate containing iron and also produce tailings. The initial zinc concentrate is subjected to a third flotation step to float a further zinc concentrate containing iron and also produce zinc and iron containing tailings. The zinc and iron containing tailings from the third flotation step and at least a lead and zinc containing portion of the initial lead concentrate are leached in a first leach step under oxidizing conditions at a temperature in the range of from about 130.degree. to about 170.degree. C.

Abstract: A process for recovering zinc from material containing zinc ferrite includes leaching the ferrite containing material together with zinc sulphide containing material in a leach step, with the relative amounts of ferrite material and zinc sulphide material being such that the zinc present as zinc ferrite is a minor proportion of the total zinc content of the ferrite material and the zinc sulphide material. The leach step is carried out in aqueous sulphuric acid solution at elevated pressure under oxidizing conditions and at a temperature above the melting point of sulphur, with the sulphuric acid to zinc molar ratio being less than about 1.2:1, to cause dissolution of a substantial amount of zinc from the ferrite material and from the sulphide material.

Abstract: A process for recovering zinc from zinc-containing sulphidic material which also contains iron and lead includes leaching the material under oxidizing conditions at a temperature in the range of from about 130.degree. to about 155.degree. C. in aqueous sulphuric acid solution with a stoichiometric excess of sulphuric acid relative to the zinc content of the material of from about 50 to about 100% to produce an undissolved residue containing a major proportion of the lead and a leach solution containing a major proportion of the zinc and iron. The sulphur and lead containing residue is separated from the zinc and iron containing leach solution. Elemental sulphur is physically separated from the remaining lead-containing residue, and the remaining lead-containing residue is recovered. The zinc and iron containing leach solution is treated to recover zinc by feeding the solution to another process in which zinc-containing material is treated to recover zinc and which includes an iron-precipitation step.

Abstract: A process for recovering zinc from zinc-containing sulphidic material also containing iron and from zinc oxide containing material. Zinc-containing sulphidic material is leached under oxidizing conditions at a temperature in the range of from about 130.degree. to about 170.degree. C. in aqueous sulphuric acid solution with an initial stoichiometric excess of sulphuric acid relative to the zinc content of the sulphidic material to form a leach slurry containing dissolved zinc and iron. The leach step is continued until a substantial amount of zinc has been dissolved from the sulphidic material. Zinc oxide containing material is then added to the leach slurry to raise the pH of the slurry to a value in the range of from about 4.5 to about 5.5 to precipitate dissolved iron and form an iron-containing residue and a relatively iron-free leach solution. The residue is separated from the leach solution, and the leach solution is treated to recover zinc.

Abstract: A process for recovering zinc from zinc containing sulphidic material which also contains iron together with lead and/or silver includes leaching the material under oxidizing conditions at a temperature in the range of from about 130.degree. to about 170.degree. C. in aqueous sulphuric acid solution with a stoichiometric excess of sulphuric acid relative to the zinc content of the material of from about 40 to about 100% to produce an undissolved residue containing a major proportion of lead and/or silver and a leach solution containing a major proportion of the zinc and iron. The residue is separated from the leach solution and treated to recover lead and/or silver values. The leach solution is treated to recover zinc by feeding the solution to another process in which zinc-containing material is treated to recover zinc and which includes an iron-precipitation step.

Abstract: A process for removing radium from a radium-containing aqueous sulphate solution also containing dissolved magnesium at a pH not greater than about 10 comprises treating the solution with a soluble barium salt to precipitate radium as barium radium sulphate. The pH of the solution is raised to at least about 11 to precipitate an insoluble magnesium compound which collects the barium radium sulphate precipitate, and substantially all of the precipitates are separated from the solution.

Abstract: A process for the recovery of uranium values from uranium-containing material which also contains iron, arsenic and siliceous matter, includes leaching the uranium-containing material in aqueous sulphuric acid solution under conditions to provide dissolved iron present in the resultant leach solution as predominantly ferrous iron rather than ferric iron and/or to provide a sulphuric acid concentration in the leach solution sufficiently high to substantially prevent the precipitation of arsenates. Uranium values are recovered from the leach solution by solvent extraction agent which has little affinity for arsenic.

Abstract: A process for selectively removing ions of copper and/or cadmium from a sulphate solution containing nickel and/or cobalt values. The solution is treated at a temperature in the range of from about 85.degree. to about 95.degree. C. and at a pH in the range of from about 4.5 to about 5.5 with hydrogen sulphide to precipitate copper and/or cadmium ions as copper and/or cadmium sulphide, and the precipitated copper and/or cadmium sulphide is separated from the solution.