Production of titanium dioxide pigment from high titanium dioxide content slags

Claim 1

A METHOD OF PRODUCING TITANIUM DIOXIDE PIGMENT FROM A SLAG CONTAINIGN AT LEAST ABOUT 65% OF TITANIUM OXIDE, FROM ABOUT 1% TO ABOUT 16% OF IRON EXPRESSED AS FEO, AND FROM ABOUT 30% TO ABOUT 5% OF FLUX RESIDUES WHICH COMPRISES COMMINUTING SAID SLAG TO A PARTICLE SIZE DISTRIBUTION SUCH THAT SUBSTANTIALLY ALL THEREOF IS SMALLER THAN 70-74 MICRONS IN AVERAGE DIAMETER, AT LEAST 92% IS NOT MORE THAN ABOUT 44 MICRONS IN AVERAGE DIAMETER, AND NOT MORE THAN ABOUT 25-30% IS SMALLER THAN 10 MICRONS IN AVERAGE DIAMETER, MIXING SAID COMMINUTED SLAG WITH 85%-98% SULFURIC ACID, THE AMOUNT OF ACID EMPLOYED BEING EQUIVALENT TO ABOUT 1.5 PARTS TO ABOUT 2.2 PARTS BY WEIGHT OF 100% H2SO4 FOR EACH PART BY WEIGHT OF TIO2 PLUS THAT NECESSARY TO REACT WITH THE OTHER ACID-REACTIVE CONSTITUENTS CONTAINED IN THE SLAG, HEATING THE MIXTURE TO INITIATE REACTION BETWEEN THE ACID AND SLAG, REACTING THE ACID AND SLAG TO SOLUBILIZE THE TITANIUM CONTENT OF THE SLAG, SLURRYING THE ACID-REACTED MATERIAL WITH SUFFICIENT WATER TO OBTAIN AN AQUEOUS MIXTURE HAVING A SPECIFIC GRAVITY OF FROM ABOUT 1.4 TO ABOUT 1.55, ADDING TO THIS AQUEOUS MIXTURE FROM ABOUT 0.02% TO ABOUT 0.07% OF ANIMAL GLUE AND FROM ABOUT 0.004% TO ABOUT 0.01% OF ANTIMONY OXIDE DISSOLVED IN A 10% AQUEOUS SODIUM SULFIDE SOLUTION, BOTH ADDITIONS BEING BASED ON THE WEIGHT OF THE AQUEOUS SLURRY, ALLOWING THE MIXTURE TO STAND UNTIL THE INSOLUBLE MATERIAL THEREIN HAS BEEN FLOCCULATED, FILTERING THE MIXTURE, THEREAFTER HEATING THE CLARIFIED SOLUTION TO A BOIL AND BOILING IT UNTIL THE TITANIUM CONTENT HAS PRECIPITATED IN THE FORM OF HYDROUS TITANIUM DIOXIDE, AND THEN CALCINING THE HYDROLYSATE TO OBTAIN A TITANIUM PIGMENT.