Developing Materials for Rare-Earth–Element Chelation: Synthesis, Solution Thermodynamics, and Applications

Abstract

Rare Earth Elements (REEs: La–Lu, Y, and Sc) are critical components for technological innovations, therefore more effective methods for the domestic extraction and purification of REEs are in ever-increasing demand. Metal-chelating polymers have great potential in these applications due to their relatively low cost and high affinity for target elements. However, while much research has focused on specific ligands attached to polymers, little is known about the effect of polymer architecture itself on metal chelation. This dissertation reports recent progress in the design, synthesis, and application of polymers for the chelation of various REEs. In addition to synthesizing a series of metal-chelating polymers, we elucidated the thermodynamics of binding using isothermal titration calorimetry (ITC) to gain insight into the specific relationship between polymer structure and metal binding. ITC enables the direct measurement of the binding affinity (Ka), enthalpy changes (ΔH), and stoichiometry of the interactions between macromolecules and metal ions in solution. The thermodynamics of metal chelation underpins many technologies for REE extraction. Consequently, elucidating these parameters enables the rational design of future materials.