Electrosorption and reduction of pertechnetate by anodically polarized magnetite

The radionuclide technetium is a common surface and groundwater contaminant at many nuclear fuels processing facilities. This research investigated a new method for removing pertechnetate from contaminated waters based on the low aqueous solubility of reduced technetium species. The removal method involved electrostatic adsorption of pertechnetate at an anodically polarized magnetite electrode, followed by reduction of the adsorbed Tc(VII). This method was capable of reducing technetium associated β activity below the 900 pCi/L drinking water maximum contaminant level set by the US EPA for manmade β activity. Upon termination of the applied polarization, the reduced technetium species remained adhered to the magnetite electrode under anaerobic conditions. Under aerobic conditions, the technetium was slowly released back into solution, indicating that the reduced technetium is afforded a degree of cathodic protection due to preferential oxidation of the magnetite. The advantages of this electrosorption/reduction technique over direct cathodic reduction are an increase in the stability of the reduced technetium, removal to lower aqueous concentrations, and greatly increased removal kinetics.