ZINC LEACHING FROM SMITHSONITE ORE IN LACTIC ACID SOLUTION: STUDIES ON PARAMETRIC OPTIMIZATION, KINETIC AND MECHANISM

The solubility of low-grade zinc ores with a selective leaching environmentally friendly reagent has become a focus of great interest since zinc and its compounds have found wide application. For this purpose, lactic acid was used to investigate the selective leaching kinetics of smithsonite ore obtained from Kayseri region. The effects of particle size (137.5-725 μm), acid concentration (0.5-5 M), solid/liquid ratio (0.5/250-3/250 g mL-1), stirring speed (500-800 rpm) and temperature (40-70 °C) parameters on the smithsonite dissolution rate were experimentally studied. The results obtained show that leaching of about 99.8% of zinc is achieved using 425 μm particle size at a reaction temperature of 70 °C for 45 min reaction time with 2 M lactic acid, the solid/liquid ratio of 1/250 g mL-1 and stirring speed of 600 rpm. The statistical analysis of the experimental data obtained from the parameters revealed that smithsonite dissolution was the surface reaction-controlled with an apparent activation energy of 53.62 kJ.moL-1. The kinetic model describing the process was found as 1-(1-X) = 2.5×10-e t.