Leaching of Rare Earth Elements: Review of Past and Present Technologies

doi:10.1016/B978-0-12-802328-0.00021-8

Rare Earths Industry

Technological, Economic, and Environmental Implications

2016, Pages 319-334

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Abstract

The recycling of rare earth elements (REEs) from mine tailings and REE containing end-of-life (EoL) scrap, two promising secondary resources, offers great opportunities to secure an REE supply in Europe. The relatively low concentration of REE in mine tailings (1000–1500 ppm) and the variety of contaminants in the EoL scrap have made the extraction of REE from these resources challenging. This chapter provides a review of past and present technologies for REE leaching used in primary REE production and of current REE recycling as an important part of hydrometallurgical REE processing. Detailed studies of the existing processes are essential to properly understand and resolve difficulties in REE recycling from these secondary resources. Known processes range from acid leaching with H₂SO₄, HCl, or HNO₃ for primary ores to leaching with NaCl or (NH₄)₂SO₄ of ion adsorbed clays and combined base and acid leaching for EoL lamp phosphors. A comprehensive understanding of these processes is the key to applying them to REE recycling from secondary resources.

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Chapter 21 - Leaching of Rare Earth Elements: Review of Past and Present Technologies

Abstract