<p>In the article results of kinetic studies of autoclave-carbonate decomposition of scheelite concentrates are presented. Studies are carried out in temperature range of 368–523 K, at mixing with a speed of 100–400 revolutions per minute. Solutions of sodium carbonate, mol/ dm<sup>3</sup>: 0.5, 0.75, 1.0, 1.25, 1.5, 2.0 was used to determine the dependence of the degree of tungsten leaching from scheelite on concentration. It was established, that with increase of concentration of sodium carbonate leaching degree increases and at the concentration of 1.5–2.0 mol/dm<sup>3</sup> it is reached rapid, within 45–60 min, 80−90% of leaching, and the almost complete leaching of tungsten (95.2–99.3%) achieved in 2 h. For interaction of WO<sub>3</sub> with Na<sub>2</sub>CO<sub>3</sub> solution it was obtained the kinetic mode. In this case there is practically no concentration gradient of sodium carbonate at an oxide surface. It is obvious, that increase of the hydrolysis takes place due to the fact that to oxides reaction with a reagent-solvent precedes hydration of their surface. In the adsorbed water molecules due to their interaction with the oxide surface intramolecular bonds are weakened, thereby hydrolysis of<br /> oxide ions coming to the hydrated surface flows more fully.</p>
Simultaneous removal of Cr(III) and V(V) and enhanced synthesis of high-grade rutile TiO2 based on sodium carbonate decomposition