Abstract
Phosphorous (P) sorption on mineral surfaces largely controls P mobility and bioavailability, hence its pollution potential, but the sorption speciation and mechanism remain poorly understood. We have identified and quantified the speciation of both phosphate and phytate sorbed on ferrihydrite with various P loadings at pH 3-8 using differential atomic pair distribution function (d-PDF) analysis, synchrotron-based X-ray diffraction (XRD), and P and Fe K-edge X-ray absorption near edge structure (XANES) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. With increasing P sorption loading for both phosphate and phytate, the sorption mechanism transits from bidentate-binuclear surface complexation to unidentified ternary complexation and to precipitation of amorphous FePO4 and amorphous Fe-phytate. At a given P sorption loading, phosphate precipitates more readily than phytate. Both phosphate and phytate promote ferrihydrite dissolution with phytate more intensively, but the dissolved FeIII concentration in the bulk solution is low because the majority of the released FeIII precipitate with the anions. Results also show that amorphous FePO4 and amorphous Fe-phytate have similar PO4 local coordination environment. These new insights into the P surface complexation and precipitation, and the ligand-promoted dissolution behavior improve our understanding of P fate in soils, aquatic environment and water treatment systems as mediated by mineral-water interfacial reactions.
Original language | English |
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Pages (from-to) | 2193-2204 |
Number of pages | 12 |
Journal | Environmental Science: Nano |
Volume | 4 |
Issue number | 11 |
DOIs | |
State | Published - 2017 |
Externally published | Yes |
Funding
This work was supported by the Wyoming Agricultural Experimental Station Competitive Grants Program and the Wyoming Reclamation and Restoration Center. X.W. and X.F. thanks National Natural Science Foundation of China (No. 41601228, 41471194) for its partial support. Use of the Advanced Photon Source, Argonne National Laboratory, supported by U.S. DOE-BES under Contract DE-AC02- 06CH11357. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. A portion of the research described in this work was performed at the Canadian Light Source, which is supported by the Natural Sciences and Engineering Research Council of Canada, the National Research Council Canada, the Canadian Institutes of Health Research, the Province of Saskatchewan, Western Economic Diversification Canada, and the University of Saskatchewan.