Mechanisms of rare earth element and aluminum leaching with magnesium sulfate based on coupled seepage–chemical–diffusion simulations in microporous networks
来源：Science Direct
In situ leaching of ionic rare earth ore by magnesium sulfate (MgSO4) generally involves long leaching cycles, low leaching rates, low rare earth element concentrations and high contents of impurity ions in the leachate liquor. In this paper, on the basis of the microporous network of rare earth ores and theories of fluid dynamics, chemical reaction kinetics, and mass transfer, we adopt coupled seepage–chemical–diffusion simulations to investigate the leaching mechanisms of rare earth elements and aluminum in ionic rare earth ores. 1) Based on the numerical simulation of rare earth ore microporous network leaching, the nonuniformity of the ore particle size and the disorder of the particle distribution are fully considered. The spatial and temporal evolution of rare earth ion (RE3+) and aluminum ion (Al3+) migration is intuitively analyzed. 2) An increase in the MgSO4 concentration increases the equilibrium constant and significantly increases the concentrations of RE3+ and Al3+ in the leachate and their leaching efficiency, whereas the effect on the rate constant is weak. The equilibrium coefficient of magnesium ions displacing RE3+ is greater than that of Al3+, which is the main reason why the leaching rate and efficiency of aluminum are lower than those of rare earth elements. 3) The high injection strength increases the diffusion of ions, and the leached ions at the mineral surface are transferred faster, resulting in an increase in the concentration gradient of RE3+ and Al3+ in the leaching diffusion layer, which decreases the leaching time of rare earth elements and aluminum. In this study, the influences of agent concentration and injection strength on the leaching behavior of rare earth elements and aluminum were analyzed, and the effects of the equilibrium constant, rate constant, and ion diffusion coefficient on the leaching behavior were explored, which provides a theoretical basis for the green and efficient extraction of rare earth resources.