Environmental challenges and identification of the knowledge gaps associated with REE mine wastes management

In the last decade, the rare earth elements (REE) attracted tremendous attention from the scientific and industrial communities. The increasing needs for REE in our society triggered the development of several REE mine projects. Beside primary sources of REE, recycling of REE from electrical and electronic wastes is also an important source. These secondary resources allow to reduce the supply risks related to the mining industry of REE. However, REE recycling is challenging because of various problems associated with material collecting and processing. During the mining and refining activities of REE ores, significant quantities of liquid and solid wastes are generated (e.g., waste rocks, tailings, treatment sludges, and other effluents). The lack of suitable environmental management techniques for these wastes could cause serious environmental damages, leading to contamination of drainage waters in REE and radioactive elements. Thus, it becomes necessary to predict the metal leaching potential of REE-bearing future mine wastes as early as possible in the design and development of mining projects. The mine drainage water quality is controlled by the geochemical reactions that occur naturally during waste-water interactions. Mine water quality prediction not only favors the social acceptability of mining projects, but also the development of waste management strategies. Currently, there remains significant knowledge gaps related to REE release in the environment from mine wastes and their toxicity. This critical review addresses these knowledge gaps and discusses: (i) the typology of REE deposits, (ii) the REE-bearing minerals reactivity, (iii) the REE ore processing and characterization of the associated waste, and (iv) the REE behayior in natural environments. (C) 2018 Elsevier Ltd. All rights reserved.