Opportunities and challenges for treating rare-earth elements

Abstract

Rare-earth elements (REEs) have become an important group of metals used in various high-tech industries. In this paper, the authors have first reviewed and discussed various mineral-processing techniques used in the processing of these REE-containing ores. Because the majority of minerals from which REEs are extracted are monazite, bastnasite, and xenotime, the discussion has focused around the ores containing these three minerals. Following this discussion, various leaching technologies have been reviewed and problems associated with leaching technologies have been assessed again in the context of the afore-mentioned three minerals. The leaching technologies discussed here include leaching using various acids, and also leaching after acidic and alkaline roasting of the ores. Because of chemical similarities of these REEs, it is very difficult to separate the individual elements from each other. Various technologies used in this regard including chemical precipitation, ion exchange, and solvent extraction have been reviewed and discussed in detail. The effect of speciation of REEs in the solutions on the selective recovery has also been investigated.