Separation of Rare Earth Elements using a Novel Chromatographic Method

Background

To address the global issue of climate change and to meet the goals set in the Paris agreement, decarbonization of the energy sector is necessary. This includes among other things a significant transition in the source of energy from fossil-based to renewable. The electrification of the transport sector is also required. Vital to such green technologies and to other technological advancements are specialty metals like the rare earth elements (REEs). The world bank has projected scenarios where the need for neodymium (a REE) would increase from the current 7000 tons/year to 400 000 tons/year [1]. However, to meet these rising demands, more and more REE minerals would have to be mined out of the Earth’s crust. This is an unsustainable scenario, since mining can have adverse effects on the environment which could offset the benefits from the decarbonization or cause new environmental concerns. Therefore, it is important to increase the efficiency of extraction from mining waste, as well as develop methods for recycling of end-of-life products containing these valuable metals.

REEs are however difficult to separate from each other by conventional methods owing to their similarity in chemical properties, and to the low concentrations of each element. Using traditional solvent extraction, large quantities of organic solvents are usually needed. Extraction chromatography offers a much better alternative, where a similar extractant as used in a solvent extraction process is adsorbed on a column and used for metal extraction, thereby drastically decreasing the organic waste created. Additionally, the chromatographic process can in principle achieve complete separation in a single step in contrast to the solvent extraction process which needs several mixer-settler units to achieve the same separation. Despite its benefits, extraction chromatography is yet to be used at a commercial scale, mainly due to the challenges to achieve sufficient productivity. It is thus crucial to push the total mass load onto the column to the limit where an acceptable separation is still feasible.

The project

In this project, a separation method based on extractive chromatography, which has shown promise as a powerful technique to separate otherwise difficult to separate REEs [2-4], will be developed, for the purpose of recycling of REE-containing waste sources. Thus, the project contributes to the solution of global energy problems and offers the opportunity to work with a powerful, novel separation technique. The project is supervised by Dr:s Meher Sanku, Michael Svärd and Kerstin Forsberg, and carried out in collaboration with both industrial and academic partners. Funded by Formas.

For questions or to express your interest, please contact:

Meher Sanku (mgsanku@kth.se) or Michael Svärd (micsva@kth.se)

References

[1] “The Growing Role of Minerals and Metals for a Low Carbon Future - World bank,” 2017. [Online]. Available: http://documents1.worldbank.org/curated/en/207371500386458722/pdf/117581-WP-P159838-PUBLIC-ClimateSmartMiningJuly.pdf.

[2] M. G. Sanku, K. Forsberg, and M. Svärd, “Extraction Chromatography for Separation of Rare Earth Elements,” in Azimi G. et al. (Eds); Rare Metal Technology 2021 - Proceedings of the TMS Annual Meeting & Exhibition (2021), pp. 155–161.

[3] D. Kifle, “Separation of rare earth elements and other precious metals by high performance liquid chromatography and solid phase extraction,” University of Oslo, 2013.

[4] M. Max-Hansen, “Modeling and Optimization of Rare Earth Element Chromatography,” Lund University, 2014.