THE MECHANICAL ACTIVATION AS AN EFFICIENT METHOD FOR THE IMPROVEMENT OF PEROVSKIT TECHNOLOGY

Abstract

The effect of high-voltage mechanical energy of planetary mill on a solid hydrated product isolated by the treatment of perovskite with nitric acid has been established. The transformation includes several physicochemical steps such as dispersion of the particles, amorphization of their surface and formation of structural defects. It leads to approximately twofold increases in the specific surface area and porosity of the particles. The best result of mechanical activation was achieved at rotation speed of 650 rpm for 4-5 hours due to high hardness of rutile and anatase contained in hydrated products. The mechanical activation markedly increases the chemical activity of the hydrated product at the step of treatment with sulfuric acid of 700-900 g/l H2SO4. The kinetic curves show the reduction in time of the induction period due to increasing in the dissolution rate of the amorphous layer in the hydrated product particles. Also the extraction of TiO2 into sulfuric acid liquid phase up to 85 % and 76 % respectively, depending on the conditions (in air atmosphere or in an autoclave). At the concentration of 700 g/l H2SO4 a stable liquid system is observed without any sulphate precipitates. Increase in H2SO4 concentration up to 900 g/l markedly accelerates the extraction process. However, increased acidity reduces the stability of the system and promotes formation of TiOSO4•H2O compound in the. The obtained results can be used to improve the nitric-sulfuric acid technology of perovskite