An uranyl sorption study inside functionalised nanopores

Sorption mechanism of uranyl by poly(bis[2-(methacryloyloxy)ethyl] phosphate) (PB2MP) functionalised polyvinylidene fluoride (PVDF) track-etched membranes, PB2MP-g-PVDF, was investigated. It was found that uranyl sorption obeyed Langmuir isotherm model giving a maximum U(VI) membrane uptake of 6.73 μ mol g −1 and an affinity constant of 9.85 ⋅ 10 6 L mol −1 . XPS and TRPL measurements were performed to identify sorbed uranyl oxidation state and its environment. Uranyl was found to be mainly in its hexavalent state, i.e . U(VI), showing that the trapping inside the PB2MP-g-PVDF nanoporous membranes did not change the ion speciation. Two sorbed uranyl life-times ( τ 1 = 8.8 μ s and τ 2 = 102.8 μ s) were measured by TRPL which pointed out different complexations taking place inside the nanopores. Uranyl sorption by PB2MP-g-PVDF membranes was also found to be pH dependent demonstrating the highest performance at circumneutral pH. In addition, TRPL was demonstrated to be not only a remarkable technique for U(VI) characterization, but also an alternative to voltammetry detection for trace on-site uranyl monitoring using PB2MP-g-PVDF nanoporous membranes.