A green method of respectively recovering rare earths (Ce, La, Pr, Nd) from rare-earth tailings under super-gravity

摘要

A green method was proposed for respectively recovering rare earths (REEs) under super-gravity from rare-earth tailings which are massively stockpiled in the Bayan Obo tailings dams. Firstly, the REEs (Ce, La, Pr, Nd) were discovered to be precipitated as the rare earth oxyfluoride, rare earth ferrate and britholite phases respectively at various temperature ranges of 1773-1673 K, 1673-1473 K and 1473-1373 K. However, the Re-rich phases were intimately intertwined with each other in the normal-gravity. Consequently, respective recovery of REEs (Ce, La, Pr, Nd) at their corresponding precipitation temperatures was conducted under the super-gravity. 98.38% of (Ce) were firstly enriched into the rare earth oxyfluoride and separated from the tailings as driven by the super gravity, 97.70% of (La) were enriched into the rare earth ferrate and separated subsequently, and the residual REEs were precipitated further into britholite. Accordingly, high-purity of rare earth oxyfluoride, rare earth ferrate and britholite phases were attained respectively, achieving the green and efficient recovery of REEs (Ce, La, Pr, Nd) from the tailings with no additives, no hazardous wastes and no secondary pollution.