Extraction of the cefluosil from rare earth slag by pressurized filtration

Bayan Obo blast furnace slag (i.e., rare earth slag) is rich in rare earth elements. However, current methods for the separation and extraction of rare earth elements often suffer from lengthy production processes, high energy consumption, and significant environmental pollution, making large-scale applications difficult. Therefore, the separation, purification, and comprehensive utilization of rare earth elements from rare earth slag have become urgent priorities. In this study, gas pressure filtration technology was employed to purify and separate cerium fluorosilicate crystals from a quaternary system of CaO-SiO2-CaF2-Ce2O3 rare earth slag. The pressure filtration mechanism was investigated, and both constant rate filtration and constant pressure filtration cake models were established. Additionally, the nucleation behavior of the cefluosil crystals was studied, and the optimal nucleation temperature under theoretical conditions was estimated to be 1145 °C. Furthermore, the effects of different separation conditions on the separation efficiency were examined, and it was concluded that successful separation of the cefluosil crystals was achieved under the optimal separation conditions (i.e., filtration temperature of 1150 °C, filtration pressure of 0.35 MPa, and filtration times of 4). After the pressure filtration separation, the recovery rate of Ce, a rare earth element, in the upper crucible reached 88.83%. This study confirms the effectiveness of pressure filtration for solid-liquid separation of rare earth slag and provides new insights for the separation and purification of high-value rare earth elements in rare earth slag.