Journal
JOURNAL OF COLLOID AND INTERFACE SCIENCE
Volume 588, Issue -, Pages 692-704Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcis.2020.11.085
Keywords
Ferrous iron; Calcium silicate hydrates; X-ray absorption spectroscopy; Sorption
Categories
Funding
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-76SF00515]
- Swiss National Science Foundation [200021_162342]
- European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant [701647]
- project CALIPSOplus from the EU Framework Programme for Research and Innovation HORIZON 2020 [730872]
- Swiss National Science Foundation (SNF) [200021_162342] Funding Source: Swiss National Science Foundation (SNF)
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The study found that Fe(II) oxidation rate is fast under alkaline conditions, and a methodology was developed to stabilize Fe(II) for sorption experiments and spectroscopy analysis. Results showed that C-S-H can uptake a small portion of Fe(II), while Fe(II) incorporation by AFm phases was not indicated. XAFS spectroscopy revealed Fe(II) binding in an octahedral coordination environment with C-S-H.
Fe(II) interaction with cement phases was studied by means of co-precipitation and sorption experiments in combination with X-ray absorption fine structure (XAFS) spectroscopy. Oxidation of Fe(II) was fast in alkaline conditions and therefore, a methodology was developed which allowed Fe(II) to be stabilised in the sorption experiments and to prepare samples for spectroscopy. X-ray diffraction (XRD) of the co-precipitation samples showed uptake of a small portion of Fe(II) by calcium-silicate-hydrates (C-S-H) in the interlayer indicated by an increase in the interlayer spacing. Fe(II) incorporation by AFm phases was not indicated. Wet chemical experiments using Fe-55 radiotracer revealed linear sorption of Fe(II) irrespective of the Ca/Si ratio of C-S-H and equilibrium pH. The K-d values for Fe(II) sorption on C-S-H are more than three orders of magnitude lower as compared to Fe(III), while they are comparable to those of other bivalent metal cations. XAFS spectroscopy showed Fe(II) binding by C-S-H in an octahedral coordination environment. The large number of neighbouring atoms rules out the formation of a single surface-bound Fe(II) species. Instead the data suggest presence of Fe(II) in a structurally bound entity. The data from XRD and XAFS spectroscopy suggests the presence of both surface- and interlayer-bound Fe(II) species. (C) 2020 The Author(s). Published by Elsevier Inc.
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