Phosphonic acid and alkyl phosphate-derivatized resins for the simultaneous concentration and detection of uranium in environmental waters

The objective of this study was to synthesize extractive scintillating resins for the direct, real-time analysis of uranium in neutral pH environmental waters. In the first synthetic approach, a methyl phosphonic acid-derivatized resin was prepared by suspension polymerization to create a matrix containing a covalently bound fluorophore and 4-vinylbenzyl chloride, followed by phosphorylation and hydrolysis to add phosphonic acid functionality. In the second approach, methyl phosphate-derivatized resin was synthesized in a one-step suspension polymerization, resulting in matrix containing a covalently bound fluorophore and ethylene glycol methacrylate phosphate ligand. Uranium binding capacity and detection efficiency of the resins were evaluated in pH 4, 6 and 8 simulated ground water and compared. The ability of both resins to detect uranium from neutral pH simulated ground water was evaluated through a Shewart-3σ control statistic applied to real-time data collected in a flow-cell detector. Resins exhibited similar binding capacities (0.18 mmol g−1) and detection efficiencies; however, the methyl phosphate resin concentrated uranium more rapidly from simulated ground water than the phosphonic acid resin. The pH dependence on the volume to detection was interpreted through changes in uranium speciation and binding mechanism supported by computational simulations.