Recovery of nickel

Claim 1

IN THE METHOD OF RECOVEING HIGH PURITY NICKEL CHLORIDE BY HYDROCHLORIC ACID LEACHING OF FINELY DIVIDED NICKEL-COPPER MATTE CONTAINING ACID-SOLUBLE IMPURITIES SUCH AS IRON AND COBALT, THE IMPROVEMENT WHICH COMPRISES ESTABLISHING A MIXTURE OF THE MATTE IN A STOICHIOMETRIC EXCESS OF HYDROCHLORIC ACID TO FORM A REACTING SLURRY EVOLVING HYDROGEN SULPHIDE, FEEDING MATTE AND A STOICHIOMETRIC EXCESS OF HYDROCHLORIC ACID TO THE MIXTURE, MAINTAINING THE MIXTURE AS AN AGITATED SUSPENSION TO CONVERT THE MICKEL AND ACID SOLUBLE IMPURITIES TO THEIR DISSOLVED CHLORIDES BUT TO MAINTAIN THE COPPER AS INSOLUBLE COPPER SULPHIDE RESIDUE, MAINTAINING THE MATTE IN CONTACT WITH THE EXCESS ACID UNTIL THE NICKEL IS SUBSTANTIALLY COMPLETELY REACTED TO FORM NICKEL CHLORIDE, WITHDRAWING REACTED SLURRY FROM THE SUSPENSION SUBSTANTIALLY AS FAST AS MATTE AND ACID ARE FED TO THE SUSPENSION, SEPARATING THE INSOLUBLE RESIDUE FROM THE RESULTING NICKELIFEROUS ACID IN THE REACTED SLURRY, SUBJECTING THE NICKELIFEROUS ACID TO THE ACTION OF AN OXIDIZING AGENT SELECTED FROM THE GROUP OXYGEN AND CHLORINE TO REMOVE RESIDUAL HYDROGEN SULPHIDE AND TO CONVERT FERROUS IRON TO FERRIC IRON, MAINTAINING THE MICKELIFEROUS AID SUFFICIENTLY STRONG TO CONVERT THE FERRIC IRON AS WELL AS THE COBALT TO THEIR CHLORIDE ANION COMPLEXES, BRINGING THE NICKELIFEROUS ACID INTO CONTACT WITH ORGANIC MATERIAL INSLUBLE IN THE ACID BUT CAPABLE OF ABSORBING METAL CHLORIDE ANION COMPLEXES, ADDING HYDROGEN CHLORIDE TO THE NICKELIFEROUS ACID TO PROMOTE SELECTIVE CRYSTALLIZATION OF NICKEL CHLORIDE, CRYSTALLIZING NICKEL CHLORIDE TO FORM HIGH PURITY NICKEL CHLORIDE CRYSTALS AND BARREN ACID CONTAINING RESIDUAL ACID SOLUBLE IMPURITIES, SEPARATING THE CRYSTALLIZED NICKEL CHLORIDE FROM THE BARREN ACID, DISTILLING HYDROGEN CHLORIDE FROM THE BARREN ACID THEREBY ADJUSTING ITS ACID CONCENTRATION SUBSTANTIALLY TO ITS ORIGINAL STRENGTH, USING THE HYDROGEN CHLORIDE TO PROMOTE THE SELECTIVE CRYSTALLIZATION OF NICKEL CHLORIDE BY ADDITION TO FURTHER QUANTITIES OF NICKELIFEROUS ACID, AND USING THE ADJUSTED BARREN ACID TO TREAT FURTHER AMOUNTS OF THE FINELY DIVIDED MATTE THUS MAINTAINING A LEACHING CIRCUIT.