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The field of non-aqueous solvent extraction has received increased attention in the past years, as it showed to enhance metal separations significantly compared with the more conventional aqueous solvent extraction systems. SOLVOMET/SIM² researchers have now published a critical review paper in Industrial & Engineering Chemistry Research on the concept and different systems and mechanisms of non-aqueous solvent extraction.

The increasing use of many critical metals like rare earths in permanent magnets and cobalt, nickel, and manganese in the cathode materials of lithium-ion batteries calls for a more efficient and sustainable method for the extraction, separation and purification of these elements.

Conventional SX

While conventional aqueous solvent extraction (SX) has been widely used by the metallurgical industry for this purpose, it has clear limitations in terms of chemicals consumption and separation efficiency.

Non-aqueous solvent extraction, a solvent extraction technique in which the aqueous phase is replaced largely by a non-aqueous solvent, can offer a solution for some of the issues encountered in conventional processes.

Critical review

The review summarises the works published on this innovative approach, focusing on enhanced metal separations and the chemistry behind the improved extraction performance.

The aim of this review is to provide a framework that should allow to develop future solvometallurgical processes. This framework includes an overview on the use of molecular solvents, the use of ionic solvents, and the introduction of complexing agents.

This should help the efforts to develop fully solvometallurgical processes or non-aqueous systems that can be integrated practically into existing metallurgical flowsheets, enhancing or replacing conventional techniques and resulting in more sustainable extraction processes. An exciting journey lies ahead.

Full reference of paper

Zheng Li, Brecht Dewulf, and Koen Binnemans, Nonaqueous Solvent Extraction for Enhanced Metal Separations: Concept, Systems, and Mechanisms, Ind. Eng. Chem. Res. 2021, 60, 48, 17285–17302, https://doi.org/10.1021/acs.iecr.1c02287

Acknowledgements

Z.L. was supported by the Senior FWO Postdoctoral Fellowship (No. 181203/12ZI920N). K.B. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme: Grant Agreement 694078 – Solvometallurgy for critical metals (SOLCRIMET).