Abstract
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.
© by Oldenbourg Wissenschaftsverlag, München, Germany
