Recovery of metal values from nickel-copper mattes

Claim 2

The process of claim 1 wherein the pH of the resultant pressure leached slurry is less than 5.35 at 80* C. and the reagent to raise the pH to the optimum pH for separation of nickel and copper is nickel carbonate.

Claim 3

The process of claim 1 wherein the pH of the resultant pressure leached slurry is greater than 5.35 at 80* C. and the reagent to lower the pH to the optimum pH for separation of nickel and copper is sulfuric acid.

Claim 4

The process of claim 1 wherein the insoluble nickel depleted residue separated from the pH adjusted oxidative leach solution is treated for further recovery of nickel values by the steps comprising, slurrying such residue in water, equilibrating such slurry at a pH of 5.35 + or - 0.3, and separating the solution containing additional nickel values from the residue.

Claim 5

The process of claim 1 wherein the sulfur content of the matte dispersed in the water is adjusted by the addition of elemental sulfur powder as the sulfur-bearing material and the slurry is heated to a temperature in the range of about 75* C. + or - 10*.

Claim 6

A process for extracting nickel and copper metal values from a matte consisting essentially of nickel, copper, sulfur and minor amounts of iron and precious metals and containing a molar ratio of nickel to sulfur in excess of 1:1, which process comprises: a. dispersing the matte in finely divided form in water to form an aqueous slurry and adding sufficient sulfur-bearing material to adjust the Ni:S molar ratio to about 1:1, b. subjecting the slurry to an oxidative pressure leach, at an elevated temperature, c. equilibrating the resultant pressure leached slurry at a pH of 5.35 + or - 0.3 to selectively separate nickel values from the slurry, d. separating at the equilibration conditions the pH adjusted nickel containing solution from the nickel depleted insoluble residue, e. subjecting the insoluble nickel depleted residue to a mild acid leach and equilibration at a pH of 3.5 + or - 0.7 to dissolve the copper values therefrom, and f. separating at the equilibration conditions the mild acid leach solution containing the copper values from the residue containing the precious metals.

Claim 7

The process of claim 7 wherein the mild acid leach is effected at a temperature in the range of 75* C. + or - 10*.

Claim 8

The process of claim 7 wherein the pH of the mild leach solution is adjusted with sulfuric acid.

Claim 9

The process of claim 8 wherein the mild acid leach solution is subjected to mild oxidation conditions to oxidize Fe to Fe .

Claim 10

The process of claim 9 wherein the separated mild acid leach solution is further treated for the recovery of additional nickel values by concentrating said solution to effect crystallization of copper sulfate therefrom, and recycling the mother liquor to the pressure leached slurry.

Claim 11

The process of claim 7 wherein the residue containing precious metals is treated for the recovery of precious metals.