Method for the production of zinc

Claim 1

THE METHOD OF RECOVERING ZINC FROM ZINCIFEROUS MINERAL SULPHIDES WHICH COMPRISES THE STEPS OF DISPERSING FINELY DIVIDED ZINCIFEROUS MINERAL SULPHIDES IN AN AQUEOUS MEDIUM TO FORM A SLURRY, PROVIDING IN SAID SLURRY SULPHURIC ACID IN AMOUNT SUFFICIENT TO PRODUCE A PH VALUE WITHIN THE RANGE OF FROM ABOUT 0.5 TO ABOUT 2.5 AND TO COMBINE WITH THE ZINC CONTENT OF SAID MINERAL SULPHIDES AS ZINC SULPHATE, REACTING SAID SLURRY AT A TEMPERATURE ABOVE ABOUT 90*C. BUT BELOW THE MELTING POINT OF SULPHUR WITH A FREE OXYGEN CONTAINING GAS AT A POSITIVE PARTIAL PRESSURE OF OXYGEN ABOVE ABOUT 10 POUNDS PER SQUARE INCH, CONTINUING SAID REACTION WITHIN SAID TEMPERATURE AND PH RANGES TO EXTRACT ZINC FROM SAID MINERAL SULPHIDES AND DISSOLVE IT IN THE AQUEOUS SULPHURIC ACID SOLUTION AS ZINC SULPHATE WITH CONCURRENT OXIDATION OF SULPHIDE SULPHUR TO ELEMENTAL SULPHUR, SEPARATING ELEMENTAL SULPHUR FROM THE SLURRY, ADJUSTING THE PH VALUE OF SAID SLURRY TO WITHIN THE RANGE OF FROM ABOUT PH 4 TO ABOUT PH 5, SEPARATING ZINC SULPHATE SOLUTION FROM SAID SLURRY, PRECIPITATING ZINC SUBSTANTIALLY FREE FROM IMPURITIES FROM SAID SOLUTION BY ELECTROLYSIS, AND RE-CYCLING SPENT ELECTROLYTE WHICH CONTAINS ZINC AS A DISSOLVED SALT FROM SAID ELECTROLYSIS STEP TO THE FIRST MENTIONED OXIDATION STEP OF THE PROCESS.