Extraction of titanium dioxide from Malagasy ilmenite: influence of leaching conditions on structural and optical properties

Abstract In this paper, we report results of the synthesis and characterizations of TiO 2 extracted from Madagascar ilmenite with different hydrochloric acid concentrations (2.5–10 M) and leaching times (5, 10, and 20 h). XRF analysis confirmed that the ilmenite is mainly composed of titanium dioxide (TiO 2 : 49.34%) and iron oxide (Fe 2 O 3 : 35.41%) with many minor elements that contain less than 1%. Ilmenite was subjected to a series of chemical treatments to extract titanium dioxide by using HCl leaching, followed by calcination at 1000 °C for 12 h. The obtained TiO 2 was characterized by x-ray diffraction (XRD), Raman, photoluminescence (PL), and UV–vis spectroscopies. Highly crystalline TiO 2 nanoparticles with sizes ranging from ∼23 to ∼68 nm were obtained. PL results suggest enhanced green emission due to oxygen vacancies, especially at 7.5 M acid concentration and longer leaching durations. Optical band gap energies are around 3.12–3.2 eV depending on processing conditions. The obtained results prove that Madagascar ilmenite can serve as a viable precursor for producing optoelectronically active TiO 2 , with tunable properties achieved through controlled leaching conditions.