Selective extraction of rare earth elements from florencite-rich sedimentary rare earth ore by sulfation

Abstract

Simultaneous recovery of lanthanum (La), cerium (Ce), and niobium (Nd) from sedimentary rare earth ores (SREO) has been carried out by a hydrometallurgical process using a sulfation roasting - leaching process (SRLP). Response surface methodology (RSM) was used to optimize the process parameters. The optimum condition for rare earth elements (REE) recovery was determined to be roasting temperature 700 °C, roasting liquid/solid ratio (L/S) 1.35 mL/g, roasting time 15 min, leaching temperature 90 °C, leaching L/S 20 mL/g, and leaching time 4.24 h. The maximum predicted recoveries for La, Ce, and Nd were 80.93 %, 74.48 %, and 97.49 %, respectively. The leaching verification experiments showed that the % leaching under the optimal conditions were La 88.02 %, Ce 78.87 %, and Nd 89.75 %, respectively. The % leaching relative deviation between the experimental and predicted values was less than 10 %, confirming the reliability of the experiments. Mechanism analysis shows that after SRLP, the florencite and kaolinite in SREO are more likely to be selectively converted to aqueous solution by H2SO4, thus achieving the separation of La, Ce, and Nd from SREO. This provides a valuable reference for the recovery of REE from florencite-base rare earth ore.