Abstract: A process for recovering uranium values from a sulphate solution containing dissolved uranium and molybdenum and with a pH not exceeding about 5.5, includes reacting the solution with ammonia at a pH in the range of from about 8 to about 10, without the solution existing for any significant time at a pH of around 7, with resultant precipitation of uranium values relatively uncontaminated by molybdenum. The uranium containing precipitate is separated from the remaining solution while maintaining the pH of the remaining solution within the same range.

Abstract: Selenium (IV) and selenium (VI) are removed from acidic copper-nickel sulphate solutions in a two-stage process by adjusting and maintaining the sulphuric acid content of the solution in a range of 10 to 50 g/L and, in a first stage, contacting the solution with sulphur dioxide or a sulphite-containing solution at an elevated temperature in the range of about 140.degree. to 175.degree. C. and, in a second stage, maintaining the said solution at an elevated temperature in the range of about 140.degree. to 200.degree. C. and pressure within the range of about 400 to 1750 kPa in an essentially oxygen-free atmosphere for a sufficient retention time to reduce and precipitate selenium (VI) as cuprous selenide.

Abstract: A process for removing arsenic from an aqueous solution containing arsenic in the form of a soluble arsenate includes adjusting the pH of the solution if necessary to at least about 10, adding a soluble barium salt to precipitate arsenic as barium arsenate, and removing the precipitated barium arsenate from the solution.

Abstract: A process for removing dissolved selenium IV values from an acidic aqueous copper sulphate solution includes passing the solution through a tubular member in a plug flow manner and injecting sulphur dioxide or a sulphite solution into the solution as it enters the tubular member. When the sulphate solution also contains dissolved selenium (VI) values, the ratio of dissolved selenium (IV) values to dissolved selenium (VI) values is preferably at least 3 to 1.

Abstract: A process for the recovery of copper and zinc values from copper and zinc containing sulphidic ore includes subjecting ground ore to a flotation operation. An initial copper concentrate is floated in a first flotation step, and the initial copper concentrate is fed to a second flotation step to float a relatively zinc free copper concentrate. Remaining ore from the first flotation step is fed to a third flotation step to float an initial zinc concentrate, and remaining ore from the third flotation step is fed to a fourth flotation step to float a copper and zinc containing material. An intermediate concentrate containing from about 5 to about 25% copper and from about 2 to about 25% zinc, with a total of at least about 12% copper and zinc, is produced by selecting at least the remaining ore from the second flotation step, and a zinc concentrate containing at least about 20% zinc is produced by at least selecting a portion of the initial zinc concentrate.

Abstract: A process for purifying copper sulfate solution by converting contained hexavalent selenium to tetravalent selenium which is amenable to removal from solution by heating and maintaining the solution at a temperature in the range of about 135.degree. to 220.degree. C. under a non-oxidizing atmosphere in the presence of bivalent iron. The converted selenium is removed from the solution either by co-precipitation with ferrous iron oxidized and hydrolyzed to ferric oxide at a temperature in the range of 135.degree. to 220.degree. C. and under an oxygen pressure of about 140 to 450 kPa or by cementation with a metal powder at a temperature in the range of about 25.degree. to 85.degree. C. at about ambient pressure under a non-oxidizing atmosphere.

Abstract: A process for treating thermally activated metal sulfides containing copper, iron and zinc for separate recovery of zinc as zinc sulfide in which the metal sulfides are subjected to a two-stage countercurrent acid leach for the formation of copper sulfide containing acid leach residue and ferrous sulfate solution. The second-stage acid leach is performed in two steps; the first step is operated at a relatively high pulp density and high acid concentration for iron and zinc extraction, the resulting slurry diluted, and the second step is operated at a relatively low pulp density and low acid concentration for dissolution of precipitated ferrous sulfate and precipitation of any dissolved copper values by H.sub.2 S. The diluent solution for the slurry from the second-stage first step preferably is generated sulfuric acid solution from a jarosite precipitation and iron and zinc-containing solution from a subsequent activation leach.

Abstract: A process for recovering nickel from an impure nickel compound which contains a major proportion of nickel values and a minor proportion of other metal values which are relatively soluble in ammoniacal ammonium sulphate solution, and a minor proportion of nickel values and other metal values which are relatively insoluble in the solution. The impure nickel compound is treated with ammoniacal ammonium sulphate solution so that the relatively soluble nickel and other metal values are dissolved in the solution with the relatively soluble nickel values being dissolved substantially as nickel diammine sulphate, and so that the relatively insoluble nickel and other metal values form an undissolved residue.

Abstract: A process for recovering metallic cobalt from an aqueous ammoniacal solution containing dissolved cobalt and other metals as ammine sulphates with substantially all the dissolved cobalt being in cobaltic form. The process includes contacting the solution with a water immiscible liquid ion exchange reagent dissolved in an inert organic diluent to selectively substantially completely extract the other metals from the solution and produce an organic extractant loaded with the other metals and an aqueous cobalt bearing raffinate substantially free of the other metals. The cobalt bearing raffinate is separated from the loaded organic extractant and the loaded organic extractant is washed to remove substantially all ammonia therefrom. The other metals are stripped from the washed organic extractant which is then recycled to treat further solution. Cobalt is recovered from the raffinate.