Potential interferences on the pertechnetate-sulfide immobilization reaction

摘要

The potential interference from competing inorganic anions, chelating agents, and low molecular weight organic acids (LMWOAs), and the potential surface effects of selected minerals on the TcO4--sulfide immobilization reaction (to form Tc2S7) were investigated. The presence of the common inorganic anions, such as nitrate, studied did not affect the TcO4--sulfide immobilization process even though their concentrations were 20 times higher than that of sulfide. The chelating agents relevant to nuclear waste sites (e.g., ethylenediaminetetraacetic acid) did not compete with the TcO4--sulfide reaction even in high excess. Of the ten selected LMWOAs investigated, only maleic acid and fumaric acid were able to inhibit the immobilization process by forming anionic water-soluble complexes with pertechnetate at concentrations significantly higher than found in the environment. None of the non-reducing minerals (e.g., goethite) investigated interfered with the immobilization reaction. X-ray absorption spectroscopy showed that the product obtained in the presence of the selected co-existing species was predominantly Tc2S7.