The Hydrometallurgical Approach in the Production of a High Content of Titanium Dioxide (TiO 2 ) from Ilmenite, Direct Hydrochloric and Sulfuric Acid Leaching and Pre-Treatment Methods: A Review

Titanium dioxide, which is found in the mineral ilmenite as a feedstock, has the highest refractive index of any known white pigment. Therefore, two commercial techniques have been developed to produce TiO2 pigment using pyrometallurgical processes, such as melting cast iron while shrinking ilmenite. Although the leaching of ilmenite with sulfuric or hydrochloric acids to remove impurities like iron to create TiO2 pigment or SR is included in the second group of methods. In addition to studying various methods of pre-treatment acid leaching of ilmenite, such as oxidation, reduction, mechanical activation, KOH decomposition, alkali roasting, and the Becher process, with assessing the impact of leaching variables including temperature, duration, acid concentration, particle size, acid to ilmenite ratio, extra stirring speed, and other additional factors. This research attempts to explain these aims with a review of recent articles on ilmenite leaching, which means accelerating iron extraction and Ti dissolving to obtain a high content of TiO2 in the final process with low cost, ecologically friendly, and a limited number of contaminants that can be used in the pigment industry or other usage. As well, the mechanism of HCl and H2SO4 acid leaching of ilmenite has been precisely investigated.