(113g) Rare Earth Element Recovery Is Only a ‘Click’ Away: Recovering Lanthanides with Peptide-Functionalized Polyvinylidene (PVDF) Membranes

Rare earth elements (REEs) are a vital part of many technologies – particularly electronics, but there are no established means to recover and recycle them from waste streams. Membrane adsorbers are a promising way to recover REEs due the potential for high water throughput and high specificity. In this work, membrane adsorbers were synthesized by first covalently grafting glycidyl methacrylate (GMA) from polyvinylidene fluoride (PVDF) membranes through AGET ATRP, a controlled polymerization that produces monodisperse poly(GMA) brushes on the surface and pores of the PVDF membrane. A polymerization time of 30 minutes was chosen to optimize the amount of GMA on the membrane (lower times had less GMA) and ensure an even distribution of GMA across the surface (higher times were nonuniformly distributed). Azide moieties were then introduced through a ring opening reaction of GMA. Finally, alkyne-appended peptides derived from EF-hand loop I of calmodulin were conjugated to the azide-containing brushes through copper catalyzed azide alkyne cycloaddition (CuAAC) click chemistry. The appearance of characteristic peaks in the ATR-FTIR spectrum supports the presence of GMA (1700 cm^-1), azide (2100 cm^-1), and peptide (1650 cm^-1). As the CuAAC reaction proceeds, the peak ratio of GMA:azide increases, further supporting successful peptide attachment. The distribution of GMA and azide within the membrane is mapped using energy dispersive X-ray spectroscopy (EDS). The distribution of accessible azide sites to CuAAC is determined by confocal microscopy on using fluorescent labeling. The binding ability of peptide functionalized membranes was explored with single-species equilibrium adsorption for Ce³⁺. The conjugation strategy employed in this work can be used to functionalize membranes with peptides or other alkyne-appended binding groups with specificity for a wide variety of ions and small molecules.