Cobalt and nickel recovery using carbon dioxide leach

Claim 1

A PROCESS FOR SELECTIVELY RECOVERING AT LEAST ONE METAL VALUE SELECTED FROM THE GROUP CONSISTING OF COBALT AND NICKEL FROM A MIXTURE OF ALKALINE SOLIDS CONTAINING AT LEAST ONE ACID-SOLUBLE COMPOUND OF SAID METAL VALUE AND OF AT LEAST ONE DILUENT METAL SELECTED FROM THE GROUP CONSISTING OF IRON AND ALUMINUM, WHICH PROCESS CONSISTS ESSENTIALLY OF: TREATING AN AQUEOUS SLURRY OF SAID MIXTURE AND WATER WITH CARBON DIOXIDE GAS AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 15* TO ABOUT 35* C., UNDER SUPERATMOSPHERIC PRESSURES, WHEREBY AT LEAST A PART OF SAID METAL VALUE IS SELECTIVELY DISSOLVED FROM SAID MIXTURE; MAINTAINING SAID PRESSURE WITH CARBON DIOXIDE UNTIL SAID METAL VALUE IS SUBSTANTIALLY COMPLETELY DISSOLVED; THEN WHILE MAINTAINING RESULTANT SLURRY UNDER AT LEAST SUFFICIENT PRESSURE TO PREVENT PRECIPITATION OF SAID DISSOLVED METAL VALUE, SEPARATING RESULTANT SOLUTION FROM RESIDUAL UNDISSOLVED SOLIDS; THEN AT LEAST PARTIALLY PRESSURE-RELIEVING THE RESULTANT SEPARATED SOLUTION, WHEREBY CARBON DIOXIDE IS RELEASED FROM THE PRESSURE-RELIEVED SOLUTION AND A PRECIPITATE IS OBTAINED IN WHICH THE MOL RATIO OF METAL VALUES TO DILUENT METAL IS INCREASED OVER THAT IN SAID MIXTURE; REMOVING RELEASED CARBON DIOXIDE AND COLLECTING SAID PRECIPITATE.