Rates and Mechanisms of Co(II)EDTA~(2-)Interactions with Sediments from the Hanford Site

摘要

The migration of ~(60)Co from buried radioactive waste in the Hanford subsurface may be facilitated by chelation with organics such as EDTA. The goal of this research was to quantify the rates and mechanisms of Co(II)EDTA2' interactions with twenty Hanford subsurface sediments using kinetic batch experiments. Our results suggested that oxidation to Co(III)EDTA" occurred in all sediments, oxidizing up to 75% of the initial Co(II)EDTA2' concentrations. Oxidation was sustained over 30 days, though rates typically decreased as a function of time. Dissociation of the Co(II)EDTA2" complex and adsorption/precipitation of free Co2+ tended to increase with contact time. Correlations were derived between sediment Mn content and 1) the rate of Co(II)EDTA2' disappearance, and 2) the production of Co(III)EDTA". These correlations will provide an improved mechanistic understanding and predictive capability of the interactions of chelated metals in the Hanford subsurface.