Preparation of rutile titanium dioxide pigment from low-grade titanium slag pretreated by the NaOH molten salt method

Low-grade titanium slag with a high accumulation of Mg, Al, Si, and the refractory structure of spinel, was sodiumized-oxidized to make it usable in the sulfate process for TiO2 pigment production. In the sodiumized-oxidized process, the Ti3O5 and Mg2SiO4 transform into Na2TiO3 and Na2MgSiO4, respectively. From combined ICP-OES with XRD refinement of the molten NaOH intermediate, the ideal stoichiometric ratio of NaOH to slag was calculated to be 0.9:1. After acidolysis of the intermediate, the obtained TiOSO4 solution, with Mg2+ and Al3+ impurities, was hydrolyzed to prepare metatitanic acid (H2TiO3) with a suitable particle size D(0.5) of 1.0-1.5 μm. The particle size D(0.5) of the hydrolyzed H2TiO3 decreased, while the concentration of Mg2+ and Al3+ increased. Finally, under optimal doping and calcination conditions, the rutile content of the prepared sample was 97.0%, and the achromic abilities of TCS and SCX were 1937 and 1.54, respectively.