Toxic metal-ion contamination in wastewater is a key environmental concern. Equally important is that many metal contaminants are valuable materials themselves, thus metal recovery from industrial wastewaters can be a sustainable process for metal production. Rare Earth Elements (REEs: La–Lu, Y, and Sc) are critical components for innovations in green energy and technology, therefore more effective technologies 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. We will report on our most recent progress in the design, synthesis, and application of polymers for the selective 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 structure-metal binding relationships of these materials. 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. Furthermore, we synthesized a polymer resin and evaluated the ability of this material to extract REEs from a simulated mining waste solution (i.e., a solution with realistic concentrations of REEs for a waste stream) and compared the resin performance to our ITC data. By elucidating the thermodynamic profile of each chelating material, we have gained insight into each materials’ properties as a metal chelator.

Elucidating chelation thermodynamics between rare-earth elements and polymeric chelators

ACS Spring Meeting 2021

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