Porous block polymer composite membranes for uranium uptake

Adsorptive membranes are an effective solution to capture uranium from seawater and contaminated water supplies. Current fibrous membrane-based sorbents usually suffer from a low density of binding ligands at the solid–liquid interface and broad pore size distributions. These issues lead to problems of low binding capacity and gradual breakthrough curves during flow-through adsorption. We sought to address these challenges by developing highly permeable (i.e., ∼3.5 × 104 L m−2h−1 bar−1) amidoxime-functionalized polystyrene-b-poly(acrylic acid) (PS-PAA)/polysulfone (Psf) composite membranes. A surface-segregation and vapor-induced phase separation (SVIPS) method was used to fabricate membranes that have an interconnected pore structure with PAA-lined pore walls. The PAA brushes offer a high density of reactive carboxyl sites that enable the surface chemistry to be tailored with nitrile groups and converted to amidoxime (AO) ligands for high-capacity uranium adsorption. The functionalized Psf/PS-PAO membrane removes uranium from dilute solution with a capacity of 150 mg g−1. Flow-through experiments demonstrate rapid mass transfer of the membranes, which adsorb over 90 % of the uranyl ions from flowing solutions at feed concentrations of 0.1 and 1.0 mg/L. Batch sorption–desorption experiments also indicate reusability of membranes over several cycles. Therefore, this membrane-based sorbents offers a chemically tailored platform for high-efficient uranium capture under trace concentrations.