Uranium isolation and concentration using membranes for nuclear foresics applications

This presentation describes the development of reactive membranes for the isolation and concentration of uranium from circumneutral pH solutions by ultrafiltration (UF). Polyethersulfone (PES) UF membranes were modified by grafting uranium-selective polymer films from surface of the membrane via UV-initiated polymerization. The resulting uranium-selective membranes (USMs) were used as a substrate for direct alpha spectrometric analysis of bound uranium isotopes. To guide membrane synthesis, we studied growth kinetics of the selective polymer film by measuring thickness as a function of UV-irradiation time using ellipsometry with a model PES substrate that simulates the surface of USMs. Alpha spectroscopy pulse height spectra were analyzed to determine the optimal selective layer thickness that would result in the highest uranium uptake without sacrificing energy resolution. Batch uptake experiments were conducted to determine uranium binding capacity of USMs at different concentrations. Flow through uptake experiments were conducted to identify the residence time for optimum detection efficiency at selected pH values. Results from this work are being used to develop a detection method for the rapid analysis of radionuclides in water using a field portable device, which would be a powerful nuclear forensics tool.