Leaching of reduced ilmenite concentrate from the Samotkan deposit using sulfuric acid solutions

A strongly altered ilmenite concentrate from the Samotkan deposit was reduced with coal at 12000C for 4 hours, yielding a product in which 90% of iron was reduced to the metallic state. Iron was leached from the reduced ilmenite using 6–22% sulfuric acid solutions at temperatures of 20–700C for three hours. It was found that the leaching of metallic iron by acidic solutions proceeds rapidly in the initial period, following a first-order reaction mechanism with an apparent activation energy of 40.2–42.6 kJ/mol, indicating kinetic control of the process. The reaction order with respect to hydrogen was determined to be 0.36–0.42. After approximately 57% of iron was extracted, the leaching mechanism changed, causing a sharp slowdown in the process. Laboratory modeling of a two-stage countercurrent process was conducted to produce synthetic rutile by leaching the reduced ilmenite with titanium white waste acid. By metering the feed of reduced ilmenite, the rapid iron dissolution stage can be utilized to regulate the acidity of the waste to a level of 3–5 g/L H2SO4. The required level of impurity removal was achieved by exposing the partially leached reduced ilmenite to an excess of the initial 22% titanium white waste acid for 3 hours at 700C. Calcination of the solid residue at 8000C yielded synthetic rutile containing 92% TiO2 and 2.6% FeO. After the crystallization of iron sulfate, the residual slightly acidic solution, containing iron(II), aluminum, magnesium, and titanium(III) sulfates, was found to contain about 22–24 mg/L of scandium.