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Separating lanthanides from actinides is a common task in rare earth element mining and processing, medical isotope purification, nuclear forensics, and radioanalytical chemistry. Membrane adsorbers are emerging as a promising platform to perform such adsorptive separations. In this work, functional membrane adsorbers are synthesized by coating poly(ether sulfone) microfiltration membranes with polymeric ligands that contain ethylene glycol methacrylate phosphate (EGMP) as the ion-coordinating moiety. The composition of the polymeric ligands is controlled by copolymerizing EGMP with butyl methacrylate (BuMA) and 2-hydroxy ethyl methacrylate (HEMA). Equilibrium and time-resolved adsorption data were modeled to understand the thermodynamics and kinetics of complexation of UO22+ at pH 1 and pH 4. The data are compared to previously reported data for La3+ and the feasibility of on-column separation of UO22+ over La3+ is assessed by transport modeling in MATLAB. All synthesized membranes are selective for UO22+ over La3+. At pH 1, the separation is improved with the presence of a nonbinding comonomer. At pH 4, the separation is worsened by the presence of a nonbinding comonomer. 

Rare earth elements (REEs) are crucial for clean energy technologies but are predominantly purified by solvent extraction using strong acids. This work explores two adsorbents with selective chemistry based on lanmodulin-derived peptides. Two membrane adsorber platforms were synthesized: (1) a poly(vinylbenzyl chloride) membrane with a grafted poly(allyl methacrylate) network and (2) a poly(arylene ether sulfone)membrane with allyl pendant groups. Both membrane adsorbers were functionalized with LanM1 peptides via a thiol−ene click reaction. The morphology, surface chemistry, and adsorption of select trivalent lanthanides (La, Ce, Pr, Nd) were characterized in pH 4−5 solutions, mimicking phosphogypsum waste streams. Results from the adsorption experiments indicate that the lanmodulin peptide sequence maintains its ability to bind when it is immobilized on the surface of polymer fibers for some ions. Despite the different adsorbent designs, the measured capacity of both adsorbents is on the same order of magnitude, which may be explained by differences in the surface area of the fibers