Heterogeneous Reduction of 2-Chloronitrobenzene by Co-substituted Magnetite Coupled with Aqueous Fe2+: Performance, Factors, and Mechanism

Xiaoliang Liang, Ying Li, Gaoling Wei, Hongping He, Joseph W. Stucki, Lingya Ma, Linda Pentrakova, Martin Pentrak, Jianxi Zhu

Research output: Contribution to journalArticle

Abstract

Reductive transformation is the predominant degradation pathway for nitrobenzene (NB) derivatives in natural matrices. Magnetite coupled with aqueous Fe2+ (Fe2+aq) displays reducing capability toward NB derivatives, but it is still unclear whether the substitution of redox-active metals in magnetite has significant influence on the reducing capability of the coupled system. This study investigated the potential of the heterogeneous reduction of 2-chloronitrobenzene (2-Cl-NB) by co-substituted magnetite (Fe3-xCoxO4, 0.00 ≤ x ≤ 1.00) coupled with Fe2+aq. Both reaction kinetics and extent of electron transfer illustrated that appropriate Co substitution (x ≤ 0.77) significantly promoted the reduction activity of Fe3-xCoxO4/Fe2+aq systems, while excess Co (x > 0.77) retarded the process. A good linear correlation (R2 ≥ 0.94) was established between the electrical conductivity of Fe3-xCoxO4 and the rate constant (kobs), calculated from a three-parameter single-exponential decay model. The improvement of the reduction activity was ascribed to the redox pairs Co(II)/Co(III) and Fe(II)/Fe(III) on the octahedral sites, which accelerated the electron transfer in magnetite. As Co substitution increased up to x = 0.85, however, structural Fe(II) occupying the octahedral sites of magnetite was too low, resulting in a decrease of the reducing capability of the coupled system. During the redox reaction, adsorbed Fe2+aq and structural Fe(II) were oxidized gradually, while the spinel structure of Fe3-xCoxO4 was maintained. These results shed light on the role of magnetite group minerals and their impact on the fate of contaminants in anoxic environments.

Original languageEnglish (US)
Pages (from-to)728-737
Number of pages10
JournalACS Earth and Space Chemistry
Volume3
Issue number5
DOIs
StatePublished - May 16 2019

Keywords

  • aqueous Fe
  • co-substituted magnetite
  • electron transfer
  • heterogeneous reduction
  • reduction stability

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Atmospheric Science
  • Space and Planetary Science

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