The ilmenite-to-TiO₂: A greener way to prepare titanium dioxide by hydrometallurgical hydrochloric route

Hydrochloric acid process is a new titanium dioxide (TiO₂) production process, which is more environmentally friendly than the existing production process (sulfate process and chloride process) in the fields of pollutant discharge and energy consumption. Ilmenite was digested with hydrochloric acid to obtain ilmenite hydrochloric acid leaching solution, the leaching efficiency of ilmenite reached approximately 97 %. In the study of extractant and diluent, the process of separating Fe(Ⅲ) and Ti(Ⅳ) from leaching solution by two-step method was determined. In the investigation of diluents, analysis of the carbonyl peak shift in the FT-IR spectra of the extractant complex suggested that isooctanol formed hydrogen bonds with the extraction complex. This interaction resolved phase separation issues in the loaded organic phase. Finally, a solution containing Ti(Ⅳ) with a purity of 99.78 % was obtained, and the preparation conditions of TiO₂ were explored. The experimental results showed that the preparation of TiO₂ by hydrolysis of Ti(Ⅳ) was an endothermic process in acidic chloride medium. Furthermore, by changing hydrolysis time, the crystal growth process could be divided into three distinct stages: nucleation, growth, and agglomeration. The effect of H⁺ , Cl^- and Ti(Ⅳ) ion concentration on hydrolysis was in the order of H⁺>Cl^->Ti(Ⅳ). Through the study of the extraction system and exploration of hydrolysis conditions, rutile-type TiO₂ was successfully prepared from ilmenite with a purity more than 99.78 %.