The kinetic study of refractory silver ore in acidified potassium chloride - hypochlorite media

In this study, the dissolution of refractory silver ore samples obtained from the Kütahya Gümüşköy region in HCl/NaOCl and KCl system was investigated. Chemical and morphological analyzes of the sample show that ore consists mainly of quartz, dolomite, barite and clay. Silver is dispersed as free fine particles or locked in barite and quartz minerals. The leaching tests were carried out under ambient conditions with direct contact of the solvent reagent and sample. Temperature, time, and KCl concentration were examined as leaching parameters to elucidate their effects on silver extraction. The results obtained in leaching tests indicated that dissolution of silver occurs very quickly, almost linearly, within the first minute of the reaction. After this point, the dissolution rate decreases and reaches equilibrium after 10 minutes. It was found that increasing both temperature and KCl concentrations have a positive effect on extraction. These effects become more evident in first stage, especially at high salt concentrations (1 M). The experimental results showed that the highest silver extraction of 53.15% was obtained under the following conditions: Temperature of 85oC, leaching time of 10 min, concentrations of 0.5 M and 0.1 M for KCl and NaOCl, respectively, solid ratio of 30%, and particle size (d80) 15 µm. The kinetics of AgCl dissolution was specificially studied using aforementioned leaching system as well. The reaction rates, kinetic orders and activation energies were calculated. Correspondingly, a general kinetic model describing leaching systems based on shrinking core was proposed as a rate-controlling model for the dissolution mechanism.