| Popis: |
The kinetics of leaching zinc from hemimorphite was investigated. The factors that influence hemimorphite leaching were also evaluated, and a kinetic model was built. In addition, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used to investigate the changes of surface morphology before and after leaching. By decreasing particle size and increasing temperature, 5-sulfosalicylic acid concentration, and stirring speed, the leaching rate of hemimorphite can be enhanced. The shrinkage nucleus model describes the surface chemistry of leaching. The activation energy of hemimorphite by 5-sulfosalicylic acid in the leaching process was determined as 55.244 kJ/mol. The reaction rate based on the shrinkage nucleus model can be expressed by the semi-empirical formula:1−1−x1/3 =[k0C0.3385(r0)−0.6083(SS)0.4992exp(−55.244/RT)]t. At the condition of 50 °C of leaching temperature, 0.175 mol/L of 5-sulfosalicylic acid concentration, 82.5 μm of particle size and 650 rpm of stirring speed, the high leaching rates of zinc were obtained. After the reaction time of 15 min, the leaching rate of zinc reached more than 95%. According to the SEM-EDS results, the hemimorphite and leaching residue are distributed in blocks, but the particle size of the leaching residue is smaller, and the atomic concentrations of Zn and Si in the leaching residue are significantly lower than those in the hemimorphite, so the leaching effect is remarkable. Therefore, 5-sulfosalicylic acid solution would be an excellent leaching agent for zinc extraction from hemimorphite. |
