Preparation of high-value TiO2 nanowires by leaching of hydrolyzed titania residue from natural ilmenite

In this work, a simple and efficient process is developed to synthesize high-value TiO2 nanowires from natural ilmenite, combining acid and alkali leaching together. Valuable Fe and Ti were selectively divided from ilmenite by hydrochloric acid leaching, and then the obtained hydrolyzed titania residue with mainly precipitated hydrated TiO2 was leached by sodium hydroxide and hydrogen peroxide. Ti and Si were monitored by ICP and EDS during the process. The effects of NaOH to-hydrolyzed titania residue (Na+/Ti4 +) molar ratio, H2O2 to-hydrolyzed titania residue (O22 −/Ti4 +) molar ratio, leaching temperature and leaching time on leaching of hydrolyzed titania residue were investigated. Results indicated that the recovery of Ti was 96.39% and dissolution of Si was 67.9% under the optimal conditions: Na+/Ti4 + molar ratio of 8/1, O22 −/Ti4 + molar ratio of 6/1, leaching temperature of 30 °C and leaching time of 30 min. And then simple boiling divided the Ti and Si very efficiently resulting in high-purity of synthetic TiO2 within 0.47% of SiO2. Meanwhile, the high-value TiO2 exhibited echinus-like structure with aggregations of nanowires and well-crystallized anatase phase at 400 °C.