Mechanism and kinetics study of sulfuric acid leaching of titanium from titanium-bearing electric furnace slag

Titanium(Ti)-bearing electric furnace slag (TEFS) was leached with sulfuric acid in this study. The influence of temperature, acid/solid ratio, particle size, and initial sulfuric acid concentration on the Ti extraction was evaluated. The leaching kinetics indicate that diffusion across the product layer and the interface transfer both affected the decomposition of the TEFS, and the apparent activation energy was24.01 kJ/mol. Reaction temperature was the most important factor that influenced the extraction of Ti, followed by the acid/solid ratio, sulfuric acid concentration, and particle size. The Ti leaching rate reached up to 89.46 % under the conditions of an average particle size of 31.5 μm, acid/solid ratio of 2.0:1, initial acid concentration of 88.0 wt%, reaction temperature of 513.15 K, and water leaching temperature of 333.15 K for 120 min. Fe was almost completely dissolved in the acid, whereas MgO (22.73 wt%) and Al2O3 (44.57 wt%) in spinel were retained in the leach residue, and SiO2 (45.94 wt%) and CaO (34.96 wt%) occurred in the form of diopside in the leach residue. During the leaching process, substantial TiOSO4 and CaSO4·2H2O were produced and coated the TEFS particles, which hindered the leaching of Ti.