Pyrolusite surface transformations measured in real-time during the reactive transport of Co(II)EDTA{sup 2{minus}}

Journal Article · Fri Oct 01 04:00:00 EDT 1999 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(99)00232-X· OSTI ID:20003964

Fendorf, S; Jardine, P M; Patterson, R R; Taylor, D L; Brooks, S C

Oxidation of Co(II)EDTA{sup 2{minus}} to Co(III)EDTA{sup {minus}} by manganese and iron hydrous oxide minerals enhances the transport of {sup 60}Co in subsurface environments. Until now, reduction of the oxidant MnO{sub 2} has not been identified in hydrodynamic systems, leaving the fate and transport mechanisms involving {sup 60}Co in natural environments unresolved. The authors investigated the transport of Co(II)EDTA{sup 2{minus}} through packed beds of {beta}-MnO{sub 2} and identified the reaction mechanism using a novel hydrodynamic flow cell coupled with X-ray absorption near edge structure (XANES) spectroscopy. Using this technique the authors are able to determine both solution and solid-phase species of cobalt and manganese in real-time. Co(II)EDTA{sup 2{minus}} is produced while Mn(IV) is reduced to Mn(III) which forms an {alpha}-Mn{sub 2}O{sub 3} layer on pyrolusite. This layer passivates the surface after an initial reaction period and ultimately limits the production of Co(III)EDTA{sup {minus}}. As a consequence, the enhanced transport of {sup 60}Co by oxidative processes may be diminished by continual exposure to pyrolusite--an advantage from an environmental quality perspective. It has also been clarified that Mn(III) is formed rather than Mn(II) resulting in formation of a stable trivalent manganese solid ({alpha}-Mn{sub 2}O{sub 3}).

• Research Organization: Univ. of Idaho, Moscow, ID (US)
• Sponsoring Organization: US Department of Energy; National Institutes of Health
• DOE Contract Number: AC05-96OR22464
• OSTI ID: 20003964
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 19-20 Vol. 63; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
COBALT 60
EDTA
ENVIRONMENTAL TRANSPORT
MANGANESE OXIDES
MINERALS
RADIONUCLIDE MIGRATION
SURFACES