The effect of sulfuric acid concentration on titanium leaching from an ilmenite ore

• 78 % is the critical concentration for the low concentration acid leaching of ilmenite. • The heat effect of the reaction serves as an important factor influencing low concentration acid leaching. • Shrinking core models was employed to derive the kinetic relationships for the leaching of titanium at various sulfuric acid concentrations. • The leaching process of titanium can be divided into three stages, and each stage exhibits different rate controlling steps. In the sulfate process used to produce titanium dioxide pigments, high-concentration sulfuric acid is usually used for acid leaching. Lowering the sulfuric acid feed concentration allows waste acid to be reused, reducing waste acid emissions and the amount of fresh sulfuric acid required. In this work, the leaching reaction mechanism in which the sulfuric acid concentration affects the ilmenite acid leaching reaction was investigated using theoretical and experimental methods. The results show that 78 % is the critical concentration for the low concentration acid leaching of ilmenite. The reaction between sulfuric acid and ilmenite can be roughly divided into three stages, and each stage has a different rate control mechanism. The sulfuric acid feed concentration has a significant effect on the reaction rate, reaction heat effect, particle size and crystallite size of ilmenite. Also, particle size was added to the shrinkage core model (SCM), the kinetic equations of different sulfuric acid concentrations were derived, and the acid leaching reaction mechanism of ilmenite under different sulfuric acid feed concentrations and the root causes of affecting titanium leaching efficiency were revealed. This work provides theoretical support for the low concentration acid leaching of ilmenite.