Traditional methods of quantifying alpha- and beta-emitting radionuclides in environmental water samples involve time-intensive, batch style analytical techniques that utilize bulky instruments.  A recent development in environmental sensing is a portable, flow cell detector that utilizes extractive scintillating resin.  The extractive scintillating resin serves the dual purpose of (1) concentrating the radionuclide of interest and (2) serving as a radiation transducer by transmitting a photo-signal proportional to the radionuclide's activity.  Nowadays, such resins are produced by physically absorbing organic extractants and fluorophores into a polymer matrix.  Unfortunately, this approach yields resins with poor stability as the active components leach from the resin over time. This contribution describes our work to synthesize a new class of extractive scintillating resin in which the fluorophore is incorporated into the polymer matrix during particle formation and the extractive ligand is bound covalently within the matrix.  Suspension polymerization was used to prepare porous poly[styrene-co-divinylbenzene-co-(4-vinylbenzyl chloride)] resin beads with 2-(1-naphthyl)-5-phenyloxazole as the fluorophore. The resin was functionalized with a uranium-selective bisphosphonate ligand through a nucleophilic substitution reaction and then hydrolyzed to its bis(phosphonic acid) form. It was characterized by FTIR, confocal laser scanning microscopy to observe the distribution of the fluorophore, and titrations to quantify the accessible binding sites. The binding capacity and uptake kinetics were investigated for both the bisphosphonate and bis(phosphonic acid) functionalized resins. Uranium uptake experiments were performed for both resins at pH values above and below the pKa1 and pKa2 of the phosphonic acid groups to compare the resin uptake for two binding mechanisms: chelation and cation exchange. Findings from this research provide the foundation for a new class of chemically stable extractive scintillating resin for use in field-deployable environmental sensors.

Synthesis and characterization of extractive scintillating resin for ultra-trace-level quantification of alpha- and beta-emitting radionuclides in aqueous media

248th National Meeting (2014)

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