Experimental Study on Direct Acid Leaching of Vanadium-containing Steel Slag Using New Sulfuric Acid and Titanium White Waste Acid

Direct acid leaching of vanadium-containing steel slag with new sulfuric acid and titanium white waste acid was carried out.The compositions and structure of the vanadium-containing steel slag were analyzed firstly.The results show that the vanadium-containing steel slag is mainly composed of Ca₂SiO₄,（MgO）_0.593（FeO）_0.407,Ca₃Fe₂（SiO₄）₃,Ca₃（V,Ti）₂O₇.Vanadium is dispersed in a variety of minerals in vanadium-containing steel slag.Relatively dense and large particle of vanadium titanium calcium oxide（Ca₃（V,Ti）₂O₇） is the main vanadium-enriched phase.It is hard to damage the structure of Ca₃（V,Ti）₂O₇ by direct acid leaching.To improve the leaching rate of vanadium,ball milling of the vanadium-containing steel slag is required.A lower content of vanadium is dispersed in dicalcium silicate,while V in the phase can be easily leached directly by the acid.79% of V is extracted by new acid direct leaching at optimum conditions of 200 r/min of stirring speed,30% of sulfuric acid concentration,65% of particles smaller than 124 μm,7∶1 of liquid-solid ratio and 1 h of leaching time.At the same conditions mentioned above,74% of V can be leached at 5∶1 of liquid-solid ratio using titanium white waste acid.Due to the high content of CaO and FeO,new sulfuric acid leaching of the slag will lead to a high cost.Titanium dioxide waste acid is a waste and cannot be directly discharged.Neutralizing the titanium white waste acid by vanadium-containing steel slag can greatly reduce the consumption of calcium carbonate for treating the waste acid.Simultaneously,vanadium can be extracted from the slag,realizing the high value utilization of the vanadium-containing steel slag.