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Degradation of Re(IV)-EDTA in the Environment as Analogue of 99Tc-EDTA for Safe Disposal in the Geological Repository
- 언어ENG
- URLhttps://db.koreascholar.com/Article/Detail/430482
p.196
Mechanism and kinetics of Rhenium complexes as a surrogate of Technetium-99 (99Tc) is worthy of study from radioactive waste safe disposal perspective. Re(IV)-EDTA was synthesized via the reduction of Re(VII) with Sn(II) in the presence of Ethylenediaminetetracetic acid (EDTA). The Re(IV)-EDTA was then degraded by H2O2 (7–30%) at pH of 3–11 in ionic strength I = 0–2 M solution. The Re- EDTA was observed to degrade more rapidly at pH of ≤ 3–4 than one of ≥ 10–11 and remained stable at pH = 7–9. At a low acidic pH, the complex degradation process was facilitated by protonation and corresponded to the exponential model (y = k. e–nt). In contrast, at an alkaline pH, the degradation was facilitated OH– complexation with Re(IV) and corresponded to a linear model (y = –mt + C). Complex degradation followed the zero-order rate kinetics for the H+ and Re-EDTA parameters, apart from a pH of 3, for which degradation was a better fit to first order kinetics. A higher Re(IV)-EDTA stability at a pH of 7–9 demonstrated that Re(IV)-EDTA (or 99Tc(IV)-EDTA) tends to be more persistent in natural environmental conditions.
