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Fe(II) Sorption on a Synthetic Montmorillonite. A combined Macroscopic and Spectroscopic Study

Type of publication Peer-reviewed
Publikationsform Review article (peer-reviewed)
Author Soltermann Daniela, Marques Fernandes Maria, Baeyens Bart, Dähn Rainer, Miehé-Brendlé Jocelyne, Wehrli Bernhard, Bradbury Michael H.,
Project The influence of Fe(II) on clay properties, the sorption of Fe(II) on clays and competitive sorption investigations: a combined macroscopic and microscopic study
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Review article (peer-reviewed)

Journal Environmental Science & Technology
Volume (Issue) 47(13)
Page(s) 6978 - 6986
Title of proceedings Environmental Science & Technology

Open Access

Abstract

Extended X-ray absorption fine structure (EXAFS) and Mössbauer spectroscopy combined with macroscopic sorption experiments were employed to investigate the sorption mechanism of Fe(II) on an iron-free synthetic montmorillonite (Na-IFM). Batch sorption experiments were performed to measure the Fe(II) uptake on Na-IFM at trace concentrations as a function of pH and as a function of sorbate concentration at pH 6.2 and 6.7 under anoxic conditions (O2 < 0.1 ppm). A two-site protolysis nonelectrostatic surface complexation and cation exchange sorption model was used to quantitatively describe the uptake of Fe(II) on Na-IFM. Two types of clay surface binding sites were required to model the Fe(II) sorption, the so-called strong (SSOH) and weak (SWOH) sites. EXAFS data show spectroscopic differences between Fe sorbed at low and medium absorber concentrations that were chosen to be characteristic for sorption on strong and weak sites, respectively. Data analysis indicates that Fe is located in the continuity of the octahedral sheet at trans-symmetric sites. Mössbauer spectroscopy measurements confirmed that iron sorbed on the weak edge sites is predominantly present as Fe(II), whereas a significant part of surface-bound Fe(III) was produced on the strong sites (∼12% vs ∼37% Fe(III) species to total sorbed Fe).
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