Membrane Adsorbers with Copolymer Coatings for the Separation of Actinides from Lanthanides (UO₂²⁺ and La³⁺)

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.