Jump to main content
Jump to site search

Issue 1, 2016
Previous Article Next Article

Formation of environmentally persistent free radical (EPFR) in iron(III) cation-exchanged smectite clay

Author affiliations

Abstract

Environmentally persistent free radicals (EPFRs) have been found at a number of Superfund sites, with EPFRs being formed via a proposed redox process at ambient environmental conditions. The possibility of such a redox process taking place at ambient environmental conditions is studied utilizing a surrogate soil system of phenol and iron(III)-exchanged calcium montmorillonite clay, Fe(III)CaM. Sorption of phenol by the Fe(III)CaM is demonstrated by Fourier-transformed infra-red (FT-IR) spectroscopy, as evidenced by the peaks between 1345 cm−1 and 1595 cm−1, and at lower frequencies between 694 cm−1 and 806 cm−1, as well as X-ray diffraction (XRD) spectroscopy, as shown by an increase in interlayer spacing within Fe(III)CaM. The formation and characterization of the EPFRs is determined by electron paramagnetic resonance (EPR) spectroscopy, showing phenoxyl-type radical with a g-factor of 2.0034 and ΔHP-P of 6.1 G at an average concentration of 7.5 × 1017 spins per g. EPFRs lifetime data are indicative of oxygen and water molecules being responsible for EPFR decay. The change in the oxidation state of the iron redox center is studied by X-ray absorption near-edge structure (XANES) spectroscopy, showing that 23% of the Fe(III) is reduced to Fe(II). X-ray photoemission spectroscopy (XPS) results confirm the XANES results. These findings, when combined with the EPFR concentration data, demonstrate that the stoichiometry of the EPFR formation under the conditions of this study is 1.5 × 10−2 spins per Fe(II) atom.

Graphical abstract: Formation of environmentally persistent free radical (EPFR) in iron(iii) cation-exchanged smectite clay

Back to tab navigation

Publication details

The article was received on 26 Oct 2015, accepted on 25 Nov 2015 and first published on 25 Nov 2015


Article type: Paper
DOI: 10.1039/C5EM00554J
Citation: Environ. Sci.: Processes Impacts, 2016,18, 42-50
  •   Request permissions

    Formation of environmentally persistent free radical (EPFR) in iron(III) cation-exchanged smectite clay

    U. G. Nwosu, A. Roy, A. L. N. dela Cruz, B. Dellinger and R. Cook, Environ. Sci.: Processes Impacts, 2016, 18, 42
    DOI: 10.1039/C5EM00554J

Search articles by author

Spotlight

Advertisements