Spectroelectrochemical Sensor for Technetium: Preconcentration and Quantification of Pertechnetate in Polymer-Modified Electrodes

摘要

A remote Spectroelectrochemical sensor and instrumentation package is being developed for the detection of technetium as aqueous pertechnetate (TcO_4~-) in the vadose zone and associated groundwater. This sensor would be used to monitor the integrity of low-level and high-level nuclear waste containment at U.S. Department of Energy sites. Electrochemical studies of TcO_4~- reduction at bare indium doped tin oxide (ITO) optically transparent electrodes (OTEs) show a poorly formed reduction wave for cyclic voltammetry and precipitation of technetium oxide (TcO_2) on the electrode surface. Similar experiments at ITO OTEs coated with thin films containing cationic polymers show partitioning of TcO_4~-into the films. Three films were investigated: poly(dimethyldiallylammonium chloride) (PDMDAAC) and quaternized poly(4-vinylpyridine) (QPVP), both immobilized in porous glass by the sol-gel process, and poly(vinylbenzyltrimethylammonium chloride) (PVTAC) copolymerized with poly(vinylalcohol). The largest enhancement in cyclic voltammetry reduction wave for TcO_4~-was for QPVP. The electrochemical mechanism changes to favor the formation of a relatively long-lived soluble species that ultimately converts to TcO_2. The electrodeposition of technetium oxide in these films was shown to be a method for the quantitative spectroelectrochemical determination of TcO_4~-and has been verified using radiochemistry dose measurements and scanning electron microscopy.