RadChem 2018

Retention of Tc(VII) by pyrite nanoparticles

15 May 2018, 17:15

1h 30m

Gallery (Casino Conference Centre)

Poster Radionuclides in the Environment, Radioecology Poster RER

Speaker

Diana Marcela Rodríguez Hernández (Helmholtz Zentrum Dresden Rossendorf)

Description

One of the major pollutants in nuclear waste is ⁹⁹Tc, a redox-sensitive fission product from ²³⁵U and ²³⁹Pu with a long half-life of 2.14 X 10 ⁵ years. Under environmental oxidizing conditions, ⁹⁹Tc mainly exists in aqueous solution as pertechnetate, TcO₄^-, which is a highly water-soluble ion that does not sorb significantly on minerals or sediments [1], so that, it is considered as inert with high risk to migrate through the environment. Under reducing conditions, Tc mobility is hampered by formation of Tc(IV) with significantly lower solubility [2]. Pyrite, on one hand, is a good sorbent for Tc(VII) due to the presence of the functional groups FeOH and FeSH, and on the other hand, Tc(VII) is reduced to Tc(IV) by the interaction with structural Fe²⁺ and possibly with sulfur atoms. Moreover, Bruggeman et al. [3] found considerably increased Tc sorption when adding pyrite to boom clay in the presence of humic substances, which also favor the Tc retention [4,5].

In this work synthetized pyrite nanoparticles [6] were used to investigate Tc sorption in classical batch sorption experiments.

References

1. Lieser, K. H. & Bauscher, C. H. Technetium in the hydrosphere and in the geosphere. Radiochimica Acta 42, 205–214 (1987).
2. Meena, A. H. & Arai, Y. Environmental geochemistry of technetium. Environ. Chem. Lett. 15, 241–263 (2017).
3. Bruggeman, C., Maes, A. & Vancluysen, J. The identification of FeS2 as a sorption sink for Tc(IV). Phys. Chem. Earth 32, 573–580 (2007).
4. Maes, A., Geraedts, K., Bruggeman, C., Vancluysen, J., Rossberg, A. & Hennig, C. Evidence for the Interaction of Technetium Colloids with Humic Substances by X-ray Absorption Spectroscopy. Environ. Sci. Technol. 38, 2044–2051 (2004).
5. Geraedts, K. & Maes, A. Determination of the conditional interaction constant between colloidal technetium(IV) and Gorleben humic substances. Appl. Geochemistry 23, 1127–1139 (2008).
6. Bai, Y., Yeom, J., Yang, M., Cha, S., Sun, K. & Kotov, K. Universal synthesis of single-phase pyrite FeS2 nanoparticles, nanowires, and nanosheets. J. Phys. Chem. C 117, 2567–2573 (2013).