Dissolution Kinetics and Leaching of Rutile Ore in Hydrochloric Acid

Experiments on the dissolution kinetics and leaching of rutile ore by hydrochloric acid have been carried out. The influence of acid concentration, temperature, stirring speed and particle diameter on the leaching of the ore were examined. The dissolution rates were greatly influenced by the hydrogen ion concentration, temperature, stirring speed and particle diameter. Kinetic data analysis showed that the dissolution mechanism followed a diffusion controled shrinking core model with the surface chemical reaction as the rate controlling step. The study showed that with 4M HCl solution, about 82.3 % of 10g rutile ore per litre of leachant at 80oC was dissolved within 120min., using 0.045-0.075mm particle diameter at a stirring speed of 360rpm. The reaction order with respect to hydrogen ion concentration was found to be 1.0, while 42.28kJ/mol was calculated for the activation energy of the dissolution process. Finally, the X-ray diffraction spectrum showed that the residual solid which amounted to 18 % of the initial solid material contained silica (-SiO2) and are formed around the shrinking core of the unreacted material