Agile synthesis and automated, high-throughput evaluation of diglycolamides for liquid–liquid extraction of rare-earth elements

Abstract

Liquid–liquid extraction is one of the most scalable processes to produce rare-earth elements (REEs) from natural and recycled resources. Accelerating the research, development, and deployment (RD&D) of sustainable processes to manufacture REEs requires both facile synthesis of extractive ligands at scale and fast evaluation of process conditions. Here, we establish an integrated RD&D methodology comprised of agile ligand synthesis and automated high-throughput extraction studies. Using diglycolamides (DGAs) as an example, we first developed a method for DGA synthesis (scalable to 200 g) by directly coupling diglycolic acid and secondary amines via the solvent-free melt-amidation reaction. A substrate scope of the melt-amidation synthesis was demonstrated for 9 different DGAs with good yields (85–96%) and purities (88–96%) without any post-reaction workup or purification process. Life cycle assessment shows that our synthesis method outperforms the prior-art pathway in each environmental impact category, especially showing a 67% reduction in global warming potential. Furthermore, we investigate the structure–activity relationship of various alkyl-substituted DGAs using an automated, high-throughput workflow for liquid–liquid extraction, achieving over 180 runs in 48 hours. The acquired data enables the development of a promising flowsheet for separating light and heavy REEs. The integrated RD&D method of agile synthesis and automated, high-throughput extraction studies paves the way for future iterative development of sustainable production of REEs and other critical materials to meet the needs for clean energy transformation.

Graphical abstract: Agile synthesis and automated, high-throughput evaluation of diglycolamides for liquid–liquid extraction of rare-earth elements

Supplementary files

Article information

Article type
Paper
Submitted
06 Mar 2024
Accepted
09 May 2024
First published
22 May 2024
This article is Open Access
Creative Commons BY-NC license

Green Chem., 2024, Advance Article

Agile synthesis and automated, high-throughput evaluation of diglycolamides for liquid–liquid extraction of rare-earth elements

L. An, Y. Yao, T. B. Hall, F. Zhao and L. Qi, Green Chem., 2024, Advance Article , DOI: 10.1039/D4GC01146E

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