Process for recovering precious metals from refractory minerals

Claim 1

THE METHOD OF TREATING A REFRACTORY, METAL BEARING MATERIAL WHICH CONTAINS SULPHUR, AT LEAST ONE PRECIOUS METAL, AND AT LEAST ONE METAL OR METALLOID COMPOUND OF THE GROUP CONSISTING OF LEAD, ARSENIC AND ANTIMONY, WHICH COMPRISES ROASTING THE METAL BEARING MATERIAL IN COMMINUTED STATE IN A NON-OXIDIZING ATMOSPHERE AND AT A TEMPERATURE ABOVE ABOUT 900* F. BUT BELOW THE FUSION TEMPERATURE OF THE PARTICLES TO REMOVE AT LEAST PART OF AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF ARSENIC AND ANTIMONY BY DISTILLATION, REMOVING TREATED METAL BEARING PARTICLES FROM THE ROASTING STEP AND DISPERSING THEM IN AN AQUEOUS ACID SULPHATE SOLUTION TO FORM A WATER AND AQUEOUS ACID SULPHATE SOLUTION TO FORM A SLURRY, AGITATING AND REACTING THE SLURRY WITH A FREE OXYGEN BEARING GAS AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 200* F. TO ABOUT 375* F. AND UNDER A PARTIAL PRESSURE OF OXYGEN ABOVE ABOUT 10 POUNDS PER SQUARE INCH TO CONVERT AT LEAST A PORTION OF THE SULPHUR CONTAINED IN THE METAL BEARING MATERIAL TO ELEMENTAL SULPHUR IN THE FORM OF LIQUID SULPHUR GLOBULES WITH OCCLUDED METAL BEARING PARTICLES, CONVERTING LIQUID SULPHUR GLOBULES TO SOLID SULPHUR PELLETS, SEPARATING SOLID SULPHUR PELLETS FROM THE SLURRY, RE-CYCLING SULPHUR PELLETS AND OCCLUDED METAL BEARING MATERIAL TO THE ROASTING STEP OF THE METHOD, AND RECOVERING PRECIOUS METALS FROM THE UNDISSOLVED, OXIDIZED RESIDUE FROM THE SLURRY.

Claim 2

THE METHOD OF TREATING A REFRACTORY, METAL BEARING MATERIAL WHICH CONTAINS SULPHUR, AT LEAST ONE PRECIOUS METAL, AND AT LEAST ONE METAL OR METALLOID COMPOUND OF THE GROUP CONSISTING OF LEAD, ARSENIC AND ANTIMONY, WHICH COMPRISES ROASTING THE METAL BEARING MATERIAL IN COMMINUTED STATE IN A NON-OXIDIZING ATMOSPHERE AND AT A TEMPERATURE ABOVE ABOUT 900* F. BUT BELOW THE FUSION TEMPERATURE OF THE PARTICLES TO REMOVE AT LEAST PART OF AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF ARSENIC AND ANTIMONY BY DISTILLATION, REMOVING TREATED METAL BEARING PARTICLES FROM THE ROASTING STEP AND DISPERSING THEM IN AN AQUEOUS ACID SULPHATE SOLUTION TO FORM A WATER AND AQUEOUS ACID SULPHATE SOLUTION TO FORM A SLURRY, AGITATING AND REACTING THE SLURRY WITH A FREE OXYGEN BEARING GAS AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 200* F. TO ABOUT 375* F. AND UNDER A PARTIAL PRESSURE OF OXYGEN ABOVE ABOUT 10 POUNDS PER SQUARE INCH TO CONVERT AT LEAST A PORTION OF THE SULPHUR CONTAINED IN THE METAL BEARING MATERIAL TO ELEMENTAL SULPHUR IN THE FORM OF LIQUID SULPHUR GLOBULES WITH OCCLUDED METAL BEARING PARTICLES, CONVERTING LIQUID SULPHUR GLOBULES TO SOLID SULPHUR PELLETS, SEPARATING SOLID SULPHUR PELLETS FROM THE SLURRY, RE-CYCLING SULPHUR PELLETS AND OCCLUDED METAL BEARING MATERIAL TO THE ROASTING STEP OF THE METHOD, AND RECOVERING PRECIOUS METALS FROM THE UNDISSOLVED, OXIDIZED RESIDUE FROM THE SLURRY.