Scintillating adsorptive membrane for preconcentration and determination of anionic radionuclides in aqueous samples

Abstract

A composite polymer membrane containing liquid anion exchanger and scintillator molecules was developed for preconcentration and quantitative determination of anionic radionuclides like pertechnetate and iodide ions. The radiation emitted by the radionuclides sorbed in the membrane lead to scintillation signals. This scintillating adsorptive membrane was prepared by immobilizing trioctylmethyl ammonium chloride (liquid anion-exchanger) along with 2,5-diphenyl oxazole (primary scintillator), and 4-bis(methylstyryl)benzene (wavelength shifter) in the plasticized polystyrene matrix. The anion selectivity of the membrane follows Hofmeister series i.e. hydrophobic anions are preferentially sorbed in the membrane matrix. It was observed that TcO₄⁻ ions were transferred quantitatively to the membrane matrix from equilibrating aqueous solutions having pH 2–8 and multicomponent feed solution like seawater. The amount of TcO₄⁻ ions preconcentrated in the membrane was directly quantified by counting the scintillations produced by β-particles in the membrane matrix. The scintillating membrane developed in the present work was optimized in terms of its scintillation efficiency, β-scintillation pulse height, anion-exchange capacity and reusability.