Kinetics on leaching rare earth from the weathered crust elution-deposited rare earth ores with ammonium sulfate solution

In this paper, the kinetic of leaching rare earth from the weathered crust elution-deposited rare earth ores with ammonium sulfate solution was investigated. The effects of the main leaching parameters such as temperature and ore particle size on leaching process were examined and discussed in order to elucidate the kinetics and mechanism of leaching rare earth. It was found that the higher the leaching temperature or the smaller the ore particle size, the faster the leaching progress. The leaching mechanism was analyzed with different kinetics models. The results show that the leaching process can be described by the shrinking-core model, the leaching rate was controlled by the inner diffusion of reactants and leaching products through mineral porous layer, the leaching process follows the kinetic model 1 − 2/3α − (1 − α)2/3 = kt, the apparent activation energy was 9.24 kJ/mol obtained from calculating the experimental data and the order of the ore particle size found to be approximately 2. An empirical equation relating the rare earth leached rate constant with ore particle size and leaching temperature was established as 1–2/3α–(1–α)2/3=1.50⋅r0−2⋅e9240RT⋅t.