An overview on membrane strategies for rare earths extraction and separation

Emission pollutants in rare earths hydrometallurgy industry have been the main constraint restricting its development. Membrane technology, as a sustainable green strategy with easy operation, is receiving great attentions in metal separation and wastewater treatment. Numerous membrane strategies for rare earths separation have been designed but few reviews could be found. The present article makes a state-of-the-art summary on current membrane techniques in rare earths separation including both liquid and non-liquid membranes. Further understandings of the crucial scientific and technical issues, such as REEs transport features, extraction performances, separation efficiency, transport models and mechanisms, membrane stability, operation modes and transport apparatus were discussed in details. Evaluations of each strategy and critical perspectives for future researches were suggested. Novel developments in non-liquid membrane techniques, such as polymer inclusion membranes, imprinted membranes, nanocomposite membranes and metal-organic framework membranes, were recommended and highlighted as potential strategies for rare earths separation in the near future. We hope that this overview would be a stimulator providing more opportunities for reference in membrane techniques for rare earths separation.