期刊
GEOCHIMICA ET COSMOCHIMICA ACTA
卷 172, 期 -, 页码 247-264出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.gca.2015.09.015
关键词
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资金
- U.S. Department of Energy, Office of Basic Energy Sciences [DE-AC02-05CH11231]
- U.S. National Science Foundation [EAR-1529937]
- Danish council for independent research
- U.S. DOE Office of Science, Office of Basic Energy Sciences [DE-AC02-98CH10886]
- DOE Office of Science [DE-AC02-06CH11357]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-76SF00515]
Iron oxides and oxyhydroxides form via Fe3+ hydrolysis and polymerization in many aqueous environments, but the pathway from Fe3+ monomers to oligomers and then to solid phase nuclei is unknown. In this work, using combined X-ray, UV-vis, and Mossbauer spectroscopic approaches, we were able to identify and quantify the long-time sought ferric speciation over time during ferric oxyhydroxide formation in partially-neutralized ferric nitrate solutions ([Fe3+] = 0.2 M, 1.8 < pH < 3). Results demonstrate that Fe exists mainly as Fe(H2O)(6)(3+), mu-oxo aquo dimers and ferrihydrite, and that with time, the mu-oxo dimer decreases while the other two species increase in their concentrations. No larger Fe oligomers were detected. Given that the structure of the mu-oxo dimer is incompatible with those of all Fe oxides and oxyhydroxides, our results suggest that reconfiguration of the mu-oxo dimer structure occurs prior to further condensation leading up to the nucleation of ferrihydrite. The structural reconfiguration is likely the rate-limiting step involved in the nucleation process. (C) 2015 Elsevier Ltd. All rights reserved.
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