Molecular Scale Speciation of First‐Row Transition Elements Bound to Ligneous Material by Using X‐ray Absorption Spectroscopy

Abstract

To develop a solid scientific basis for maintaining soil quality and formulating effective remediation strategies, it is critical to determine how environmentally-important trace metals are sequestered in soils at the molecular scale. The speciation of Mn, Fe and Cu in soil organic matter has been determined by synchrotron-based techniques: extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES). We show the structural similarity between the surface complexes of Mn(II), Fe(III) and Cu(II). These cations are bound to the surface through oxygen atoms. Each one presents a more or less tetragonal-distorted octahedral geometry. The use of X-ray absorption spectroscopy provides a relevant method for determining trace-metal speciation in both natural and contaminated environmental materials.

Co‐Adsorption of Copper(II) and 3‐Amino‐1,2,4‐triazole at a Water–Natural Macromolecular Compound Interface: Molecular Structure from Adsorption Isotherms Combined with X‐ray Absorption Measurements

“…The concentration was determined by EDTA titration {with PAN [1-(2-pyridyl-azo)-2-naphthol] as indicator}. The LS was extracted from wheat straw by two successive acid-base treatments, [24] and was fully characterized. [28] Protometric: Potentiometric titrations were carried out as described previously.…”

“…Even the EXAFS spectra seem identical, although a faint difference can be observed on the first beating of the sinusoid around 4 Å -1 , which is also observed for the Cu II -O/N distances. Indeed, the Cu-O/N distance in the Cu-LS surface complex is equal to 1.93 Å, [24] that in the Cu(LH) 2…”

Competitive sorption of metal ions onto a north-eastern France soil. Isotherms and XAFS studies

“…The χ(k) functions were extracted from the data with a linear pre-edge background, a combination of polynomials and spline atomic-absorption background, and normalized using the Lengeler-Eisenberg method (Lengeler and Eisenberg, 1980). The extraction procedure was conducted as previously described (Guillon et al, 2003). The major peak below 2 Å − 1 in the Fourier transformed curve was isolated and back transformed.…”

Coordination chemistry and hydrolysis of Fe(III) in a peat humic acid studied by X-ray absorption spectroscopy

“…In a study of the reaction between Fe and fulvic acids at pH 4 van Schaik et al (2008) found that Fe(III) formed mononuclear complexes with fulvic acids in solution with Fe-C distances in the range 2.82-2.98 Å . For humic acids and ligneous material only first shell contributions have been reported, showing that Fe(III) is coordinated by six O atoms at a distance of approximately 2.0 Å (Davies et al, 1997;Guillon et al, 2003). Obviously there is a relatively large variation in reported Fe-C distances (2.76-3.02 Å ), but whether this indicates actual differences in coordination environments is not entirely clear.…”