Kinetics of hydrothermal sulfidation of synthetic hemimorphite with elemental sulfur

The kinetics of hydrothermal sulfidation of synthetic hemimorphite with elemental sulfur was investigated. The effects of stirring speed (100-600 r/min), temperature (120-220 degrees C), sulfur dosage (mole ratio of 0.6-1.6), and particle size (48-246 mu m) on the hemimorphite conversion rate were studied. The results show that the conversion rate of hemimorphite increases with increasing temperature and decreasing particle size. A stirring speed above 400 r/min and a sulfur dosage above 1 have very little effect on the conversion rate. The kinetics analyses of the experimental data under various conditions indicate that the sulfidation process is controlled by the chemical reaction at the early stage of process with activation energy of 50.23 kJ/mol, and then controlled by diffusion through the product layer with activation energy of 11.12 kJ/mol.