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AssigneeSulpetro Minerals Limited
InventorUlrich Dienstbach
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This invention relates to environmentally sound hydrometallurgical methods and processes for extraction of cobalt, nickel and silver from complex concentrates. The finely ground minerals are converted during an oxidative caustic leach at elevated pressures and temperatures to insoluble metal hydroxides and are separated from soluble sodium arsenate and sodium sulphate. Cobalt and nickel are extracted from the caustic cake during a two-stage sulphuric acid leach. Solution purification for cobalt and nickel recovery proceeds on the basis that only one waste residue and one liquid effluent are generated which meet strict environmental standards. A small amount of cyanidation residue is generated after silver extraction by cyanidation from the acid leach residue. Metal values extraction reaches +99.0%. Arsenic and sulphur can be recovered in an innovative recycle system as sodium, zinc or copper arsenate chemicals and as anhydrous sodium sulphate.
In a method for extracting and recovering cobalt, nickel or silver from feedstock derived from complex ore concentrates containing other mineralization including arsenic and sulphur and having a finely particulate character, the step of subjecting such feedstock to a first stage oxidative caustic leach at elevated temperatures and pressures and wherein the caustic introduced is calculated to produce in the converted reactants a pH of the order of 13 or greater followed by the steps of separating and recovering the liquor and solids phases therefrom respectively, followed by the further step of subjecting such recovered solids phase to a second stage oxidative caustic leach at elevated temperatures and pressures and wherein the caustic introduced is calculated to produce in the converted reactants a pH of the order of 13 or greater followed by the still further steps of separating and recovering the liquor and solids phases therefrom respectively.
In a method for extracting and recovering cobalt, nickel and silver from feedstock derived from complex ore concentrates containing other mineralization including arsenic and sulphur and having a finely particulate character of the order of -400 mesh or thereabouts, the step of subjecting such feedstock to a two-stage oxidative caustic leach, commenced by heating the slurried intial reactants of feedstock and caustic to an elevated temperature of the order of between 85.degree.-100.degree. C., followed by the introduction of finely dispersed oxygen at a pressure of the order of between 120-140 psig and at a temperature of the order of between 120.degree.-150.degree. C. until the reactions are substantially complete followed by the steps of separating and recovering the liquor and solid phases therefrom, and reslurrying said recovered solids with caustic and repeating the introduction of finely dispersed oxygen at said range of pressures and at said range of temperatures until the reactions are substantially complete followed by the steps of separating and recovering the liquor and solids phases therefrom said caustic introduced in each of the aforementioned stages being an amount sufficient to produce in the converted reactants respectively a pH of the order of 13 or greater.
Dependencies are inferred from the claim text.