J. Phys. IV France
Volume 104, March 2003
Page(s) 417 - 420

J. Phys. IV France
104 (2003) 417
DOI: 10.1051/jp4:20030112

Reduction of selenite on iron surfaces: A micro-spectroscopic study

A.M. Scheidegger1, D. Grolimund1, D. Cui2, J. Devoy2, K. Spahiu3, P. Wersin4, I. Bonhoure1 and M. Janousch1

1  Paul Scherrer Institut, 5232 Villigen, Switzerland
2  Studsvik Nuclear AB, 61182 Nyköping, Sweden
3  SKB, 10240 Stockholm, Sweden
4  National Cooperative for the Disposal of Radioactive Waste (Nagra), Wettingen, Switzerland

Under anoxie conditions zero-valent iron can react with water to produce hydrogen gas and magnetite or green rust, a highly reactive mineral phase that can induce reduction processes and thus control the speciation, the solubility, toxicity and the mobility of redox sensitive elements in (nuclear) waste repositories. In this study micro X-ray fluorescence (micro-XRF) and micro X-ray absorption spectroscopy (micro-XAS) were used to investigate the speciation of selenium that immobilized in the presence of Fe(0) and an anoxie synthetic groundwater solution. The selenium immobilization was accompanied by the formation of a green rust corrosion layer. Micro-XRF revealed that a Se-rich layer is present along the iron surfaces that were exposed to the Se(IV) solution. Micro-XAS experiments at the Se K-edge showed that Se(IV) was reduced to elemental Se(0). Thus, the reactivity of zero-valent and green rust should to be considered in assessing the long-term fate of selenium in nuclear waste repositories.

© EDP Sciences 2003