Products of hexavalent chromium reduction by green rust sodium sulfate and associated reaction mechanisms

Andrew N. Thomas, Elisabeth Eiche, Jörg Göttlicher, Ralph Steininger, Liane G. Benning, Helen M. Freeman, Knud Dideriksen, Thomas Neumann

Research output: Contribution to journalArticleResearchpeer-review

13 Citations (Scopus)


The efficacy of in vitro Cr(VI) reduction by green rust sulfate suggests that this mineral is potentially useful for remediation of Cr-contaminated groundwater. Previous investigations studied this reaction but did not sufficiently characterize the intermediates and end products at chromate (CrO42−) concentrations typical of contaminant plumes, hindering identification of the dominant reaction mechanisms under these conditions. In this study, batch reactions at varying chromate concentrations and suspension densities were performed and the intermediate and final products of this reaction were analyzed using X-ray absorption spectroscopy and electron microscopy. This reaction produces particles that maintain the initial hexagonal morphology of green rust but have been topotactically transformed into a poorly crystalline Fe(III) oxyhydroxysulfate and are coated by a Cr (oxy) hydroxide layer that results from chromate reduction at the surface. Recent studies of the behavior of Cr(III) (oxy) hydroxides in soils have revealed that reductive transformation of CrO42− is reversible in the presence of Mn(IV) oxides, limiting the applicability of green rust for Cr remediation in some soils. The linkage of Cr redox speciation to existing Fe and Mn biogeochemical cycles in soils implies that modification of green rust particles to produce an insoluble, Cr(III)-bearing Fe oxide product may increase the efficacy of this technique.

Original languageEnglish
Article number58
Number of pages19
JournalSoil Systems
Issue number4
Publication statusPublished - Dec 2018
Externally publishedYes


  • Chromium
  • Green rust sulfate
  • Metal redox cycles

Programme Area

  • Programme Area 2: Water Resources


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