The mechanisms of reduction of hexavalent chromium by green rust sodium sulphate: Formation of Cr-goethite

L. L. Skovbjerg, S. L.S. Stipp, S. Utsunomiya, R. C. Ewing

研究成果: Contribution to journalArticle査読

93 被引用数 (Scopus)

抄録

The molecular-level processes that control green rust sodium sulphate (GRNa, SO4) reaction with chromate were studied using high-resolution techniques. Changes in solid morphology, structure and composition were observed with atomic force microscopy, transmission electron microscopy and X-ray diffraction. The results suggest the following mechanisms: Chromate replaces sulphate in the GR interlayer and is reduced by Fe(II). Formation of sparingly soluble Cr(III)-solid blocks further chromate entry, but Cr(VI) reduction continues at the GR solid/solution interface. Electron transfer from the centre of the GR crystals to the surface facilitates rapid reaction. Less stable zones of the reacted GRNa, SO4 dissolve and amorphous Cr(III),Fe(III)-solid forms. During equilibration, Cr-substituted goethite evolves in association with remaining GRNa, SO4, fed by material from the amorphous phase and dissolving oxidised GR. In contrast, previous Cr(VI) experiments with the carbonate form of GR, GRCO3, have suggested only reaction and deposition at the surface. From the perspective of environmental protection, these results have important implications. Goethite is sparingly soluble and the inclusion of Cr(III) as a solid-solution makes it even less soluble. Compared to Cr adsorbed at the surface of an Fe(III)-phase, Cr(III) incorporated in goethite is much less likely to be released back to groundwater.

本文言語英語
ページ(範囲)3582-3592
ページ数11
ジャーナルGeochimica et Cosmochimica Acta
70
14
DOI
出版ステータス出版済み - 7 15 2006
外部発表はい

All Science Journal Classification (ASJC) codes

  • 地球化学および岩石学

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