Leaching of rare earths from mechanochemically decomposed bastnaesite

The leaching process of rare earths from mechanochemically decomposed bastnaesite was investigated. The effects of temperature, HCl concentration and liquid-solid ratio on leaching kinetics were studied. The results show that the leaching efficiency of rare earths quickly reaches 90.7% after 10 min (50 °C; 2.5 mol/L HCl; liquid-solid ratio 10:1). The changes of specific surface area, pore volume and morphology during mechanochemical decomposition and leaching processes were examined by SEM and BET analyzer. To give a better description for the leaching kinetics, the models considered the variations of H+ concentration with leaching, particle shape and residual amount, indicating that the leaching process was controlled by chemical reaction. The mechanochemical processing loosened the surface structure as well as increased effective reaction area, so improving leaching rate and enhancing leaching process.