**Adrián Carrillo García 1, Mohammad Latifi 1,2, Ahmadreza Amini <sup>1</sup> and Jamal Chaouki 1,\***


Received: 8 October 2020; Accepted: 13 November 2020; Published: 17 November 2020

**Abstract:** Rare earth elements (REE), originally found in various low-grade deposits in the form of different minerals, are associated with gangues that have similar physicochemical properties. However, the production of REE is attractive due to their numerous applications in advanced materials and new technologies. The presence of the radioactive elements, thorium and uranium, in the REE deposits, is a production challenge. Their separation is crucial to gaining a product with minimum radioactivity in the downstream processes, and to mitigate the environmental and safety issues. In the present study, different techniques for separation of the radioactive elements from REE are reviewed, including leaching, precipitation, solvent extraction, and ion chromatography. In addition, the waste management of the separated radioactive elements is discussed with a particular conclusion that such a waste stream can be employed as a valuable co-product.

**Keywords:** rare earth elements; thorium; uranium; separation methods; precipitation; solvent extraction; leaching; membrane
