An increasing number of modern lanthanide (Ln) applications incorporate multiple metals within devices such as cell phones, batteries, or magnets. To enable these applications, mining industries excavate rare earth ores composed of various Lns. As a result, Ln separation and recycling have become growing areas of research. Our work has focused on the preparation of tripodal carbamoylmethylphosphine oxide (CMPO) ligands designed to selectively target Ln cations and facilitate their extraction from aqueous solution. In previous work from our group, a tripodal TREN-capped CMPO ligand, TREN-CMPO-OEt, displayed increased extraction affinity for terbium(III) relative to other select Lns included in the study. Encouraged by this preliminary result, systematic analyses of the ligand architecture along with additional extraction experiments were employed in this study to further probe the unique selectivity. A new extractant analogous to the TREN-capped structure but with a larger ligand cap was therefore synthesized to investigate the dependence of terbium(III) selectivity on the central capping scaffold. Ln extractions from acidic solution into an organic phase using this new agent saw decreased extraction throughout the entire Ln series. In performing extraction experiments, each ligand was tested in the presence of individual Lns as well as with rare earth metal mixtures to assess selectivity when exposing the ligand to multiple metals at the same time. The effect of ligand concentrations on extraction selectivity was also explored by varying the ratio of ligand to metal. Finally, solid state FT-IR analyses were used to probe metal coordination environments, and to help rationalize extraction behavior, molecular modeling studies were conducted via conformational energy minimizations.<br/>

Assessing CMPO-based ligands for selective lanthanide extraction from acidic solution

253rd National Meeting (2017)

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