Recovery of selenate values contained in sulfuric acid solutions

Claim 1

IN A PROCESS FOR RECOVERING ELEMENTAL SELENIUM FROM AN ALKALI SLAG CONTAINING SELENITES AND SELENATES OF AN ALKALI METAL INVOLVING LEACHING SAID SLAG TO DISSOLVE SAID SELENIUM VALUES THEREFROM, ACIDIFYING THE LEACH SOLUTION SELENIUM VALUES THEREFROM, ACIDIFYING THE LEACH SOLUTION ACIDIFIED SOLUTION TO REDUCE THE SELENITE VALUES THEREIN TO ELEMENTAL SELENIUM, AND RECOVERING THE LATTER FROM THE SOLUTION, THE IMPROVEMENT WHICH COMPRISES REDUCING SELENATE VALUES REMAINING IN THE RESIDUAL ACID SOLUTION FROM SAID SELENITE REDUCTION STEP TO ELEMENTAL SELENIUM IN THE PRESENCE OF THIOUREA IN SAID RESIDUAL SOLUTION, RECOVERING THE THUS PRECIPITATED ELEMENTAL SELENIUM FROM SAID RESIDUAL SOLUTION, INCORPORATING SAID LAST MENTIONED ELEMENTAL SELENIUM INTO A MOLTEN ALKALI SLAG, CONTROLLING THE OXIDATION CONDITIONS IN THE LATTER TO CONVERT THE SELENIUM VALUES THEREIN TO VALUES COMPRISING AN ALKALI METAL SELENITE, AND REPEATING SAID SELENITE REDUCTION STEP AND THE RECOVERY OF THE ELEMENTAL SELENIUM PRECIPITATED THEREIN.