Kinetics of the dissolution of ilmenite in oxalic and sulfuric acid solutions

In this study, the effects of particle size, type and concentration of acid solution on dissolution kinetics of ilmenite are investigated. The results showed that both oxalic and sulfuric acid and their concentrations had relatively high effects on the dissolution rate of titanium, which increased with an increase in acid concentration. About 86.4% of titanium could be leached in 10 h when using 4 M oxalic acid, 1: 20 solid/liquid ratio, 90 °C temperature and particle size less than 45 μm. Under similar experimental conditions with the exception of sulfuric acid concentrations of 4, 8 and 12 M, the titanium solubilization was 16.1%, 48.2% and 52.0%, respectively. The experimental data followed reaction kinetics and indicated that the shrinking particle model controlled the chemical reaction. The observed titanium dissolution rates could be expressed as 1 - (1 - x)^1/3 = 0.0092C ^1.2022t for oxalic acid for concentration varying between 1 and 4 M and 1 - (1 - x)^1/3 = 0.0006C^1.5977t for sulfuric acid for concentration varying between 2 and 12 M, respectively. The fitted models for estimating the titanium dissolution rate from the experimental data indicated good accuracy with coefficient of determination (R²) higher than 0.96.