Kinetic model for direct leaching of zinc sulfide concentrates at high slurry and solute concentration

• Direct leaching was studied experimentally.
• Experimental results were used in the modeling of direct leaching.
• Reliability of the model parameters was studied with MCMC-methods.
• The results demonstrate the importance of experimental data and modeling aspects.

In this study, direct leaching of zinc sulfide concentrate was investigated in a solution that resembles the composition of solutions used in industrial leaching processes. The effect of different factors (temperature, Fe2 +–Fe3 +-concentration, H2SO4-concentration, SO4-concentration, pressure, size of the concentrate particles) on the rate of the zinc sulfide concentrate leaching was studied experimentally. H2SO4-concentration had no influence on the leaching kinetics. The obtained experimental data were used to model the reaction kinetics with mechanistic models as well with a more empirical model, and the reliability and the accuracy of the model parameters were studied with Markov Chain Monte Carlo (MCMC) methods. The model that best describes the leaching system (R2 = 97%) takes into account the reactions between the zinc sulfide concentrate and oxidizing agents at the reacting surface of the concentrate particles, the decrease in the active surface area of the concentrate particles as the leaching proceeds, the particle size distribution of the concentrate particles, the composition of the solution, and the oxidation rate of Fe2 + to Fe3 +. The experimental results together with the modeling results clearly demonstrate that it is important to have experimental data for the kinetics of the leaching at the conditions of the reactor.