Synthesis of TiO2 nano-powders prepared from purified sulphate leach liquor of red mud

Highlights: → Ti can be recovered from red mud leach liquor by 40% Cyanex 272 in toluene. → 3 stages are required for Ti extraction at pH = 0.3, T = 25 oC and A/O = 1.5. → Ti can be stripped from loaded Cyanex 272 with diluted HCl at 25 oC. → TiO2 is precipitated as anatase at pH = 6 and T = 95 oC, using MgO pulp. → Fe in the precipitate did not exceed 0.3%, whereas no Al was detected. - Abstract: The research work presented in this paper is focused on the development of a purification process of red mud sulphate leach liquor for the recovery of titanium oxide (TiO2) nano-powders in the form of anatase. Initially, titanium was extracted over iron and aluminium from the leach liquor by solvent extraction using Cyanex 272 in toluene, at pH: 0.3 and T: 25 oC, with 40% extractant concentration. Stripping of the loaded, with titanium, organic phase was carried out by diluted HCl (3 mol/L) at ambient temperature. Finally, the recovery of titanium nano-powder, in the form of anatase, was performed by chemical precipitation at pH: 6 and T: 95 oC, using 10 wt% MgO pulp as neutralizing agent. The produced precipitates were characterized by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric/differential thermal analysis (TGA/DTA). Their morphological characteristics and microstructure were studied by scanning electron microscopy (SEM). High grade titanium white precipitate, in the form of anatase, was obtained. Iron concentration in the precipitate did not exceed 0.3%, whereas no aluminium was detected.