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Article type Paper. Submitted 23 Jul For ease of comparison, these results were also listed in Table 1. Combining the observations in second-derivative spectra and the theoretical IR vibration frequencies, a Gaussian line shape was employed in the curve-fitting analysis of the overlapping peaks.
Such data analysis has been performed before. According to Axe et al. Fitting of the entire data set resulted in a poor-quality fit. In Fig. The frequency was consistent with the quantum mechanical frequency of binuclear bidentate oxalate complexes 51 and the narrow FWHM indicated a low heterogeneity of the binding.
With increasing reaction time, the absorption intensities were increased to different extents. However, the spectroscopic observation was not sensitive sufficiently to reveal the dynamic changes of different oxalate species with time. To clarify the transformation sequence of different oxalate species adsorbed on ferrihydrite, 2D-FTIR correlation spectroscopy analysis was performed and the results are displayed in Fig. The shaded and unshaded areas in the 2D spectra represent negative and positive peaks, respectively.
Asynchronous map was employed to investigate the sequential order of specific events along external perturbations. No cross peak was observed at , , indicating that these two bands changed simultaneously.
According to Michel et al. Fe1 and Fe2 are octahedrally coordinated, while Fe3 is tetrahedrally coordinated. Recently, Hiemstra proposed a modified Michel model surface depletion model 55 , in which the ferrihydrite consists of a defect-free mineral core and a defect- and water-rich surface layer.
Fe2 and Fe3 polyhedra on the surface are depleted, and Fe1 octahedra are present in rows. This binuclear bidentate binding mode of oxalate was also observed with goethite by Filius et al. As indicated in Fig. Similar observations have been reported in previous studies of oxalate adsorption on boehmite 28 , Axe and Persson 29 ascribed these changes of peak shape and position to the asymmetric solvation effect on the oxalate adsorbed in an outer-sphere mode.
A similar conclusion was made for the adsorption of oxalate on goethite micro- and nano-rods at pH 3 by Cwiertny et al. Inorganic ligands adsorbed in an binuclear bidentate mode tend to inhibit mineral dissolution, whereas ligands adsorbed as mononuclear bidentate complexes can enhance dissolution Our ATR-FTIR results showed that the aggregation state of ferrihydrite determines the surface coordination mode of oxalate, which in turn affects the dissolution behavior of ferrihydrite.
This was ascribed to the fact that after the adsorption of small amounts of oxalate to ferrihydrite aggregate surfaces, the positive surface charge of pure ferrihydrite is neutralized, resulting in the domination of attractive forces over repulsive forces A recent study has shown that citrate coating on ferrihydrite may cause electrostatic repulsion between small sub-aggregates within large ferrihydrite aggregates and the formation of a stable colloidal suspension In our experiments, the electrostatic repulsion probably stemmed from binuclear bidentate oxalate complexes.
ATR-FTIR results showed that the inner-sphere mononuclear bidentate oxalate complexes on ferrihydrite surface dominated over inner-sphere binuclear bidentate complexes Fig.
Here, the enhancement of colloidal particles dissolution was ascribed to the formation of the mononuclear bidentate oxalate complexes. Furrer and Stumm 21 , 22 have proposed that mononuclear bidentate oxalate complexes resulted in the polarization and weakening of bridging metal-oxygen bonds in positions trans to each metal-anion bond, which makes the release of complexed metal cations from the surface relatively easy.
The mononuclear bidentate oxalate complexes also caused the transfer of considerable electron density into the coordination sphere of the surface metal cations In this scenario, reductive dissolution could occur, and Fe II as the reduction product of Fe III at the ferrihydrite surface is more susceptible to be released into the solution. Based on these results, the proposed relationship between oxalate coordination modes and the dissolution behavior of ferrihydrite is shown in Fig.
At sufficiently low oxalate concentrations, the oxalate is strongly bound to the surface of ferrihydrite aggregates in the form of binuclear bidentate complex, which causes electrostatic repulsion, resulting in the liberation of colloidal particles from the large aggregates. With the increase in the available surface area, the oxalate is bound to the surface of ferrihydrite in the form of mononuclear bidentate complex, which leads to the further breaking-up of large aggregates and dissolution of colloidal particles into dissolved Fe.
Schematic illustration of the relationship between oxalate coordination modes and the dissolution behavior of ferrihydrite. In this study, we concluded that the change in oxalate concentrations or dissolution time is likely to induce the change in the surface coordination mode of oxalate, which results in the change in the ratio of dissolved and colloidal fractions of Fe during the dissolution of ferrihydrite aggregates.
A chemical perturbation caused by the change in oxalate concentrations has been observed in certain environments. For instance, in soils where Chinese fir of different developmental stages are planted, the oxalate content is substantially higher in mature forest soil than in young forest soil and decreases with increasing soil depth in soils form forests of the same age A chemical perturbation could cause different environmental behaviors of iron hydroxides. First, the disintegration of ferrihydrite aggregates into colloidal particles plays an important role in iron transmission.
Second, previous studies have shown that the metal pollutants bound to metal oxides such as Co, Ni and Cu are released in the ligand-promoted and reductive dissolution of metal oxides 4. The change in oxalate concentration may result in the redistribution of metal pollutants in the solution and available surfaces by controlling the fate of ferrihydrite in the environment. Stumm, W. Reichard, P. Dissolution mechanisms of goethite in the presence of siderophores and organic acids.
Geochimica Et Cosmochimica Acta 71 , — Kraemer, S. Effect of hydroxamate siderophores on Fe release and Pb II adsorption by goethite. Geochimica Et Cosmochimica Acta 63 , — Liang, L.
Ligand-induced dissolution and release of ferrihydrite colloids. Geochimica Et Cosmochimica Acta 64 , — Strobel, B. Influence of vegetation on low-molecular-weight carboxylic acids in soil solution—a review. Geoderma 99 , — Ryan, P. Function and mechanism of organic anion exudation from plant roots [Review]. Lackovic, K. Modeling the adsorption of citric acid onto Muloorina illite and related clay minerals. Journal of Colloid and Interface Science , 49—59 Fu, H.
Complexes of fulvic acid on the surface of hematite, goethite, and akaganeite: FTIR observation. Chemosphere 63 , — Cornell, R. Colloid and Polymer Science , — Borer, P. Photolysis of citrate on the surface of lepidocrocite: an in situ attenuated total reflection infrared spectroscopy study. The Journal of Physical Chemistry C , — Zhang, L. Oleic acid coating on the monodisperse magnetite nanoparticles.
Applied Surface Science , — Mikutta, C. Effect of citrate on the local Fe coordination in ferrihydrite, arsenate binding, and ternary arsenate complex formation. Geochimica et Cosmochimica Acta 74 , — Wang, Z. Synergistic effect of reductive and ligand-promoted dissolution of goethite. Iron oxide dissolution and solubility in the presence of siderophores. Aquatic Sciences 66 , 3—18 Qiu, H. Oxalate-promoted dissolution of hydrous ferric oxide immobilized within nanoporous polymers: Effect of ionic strength and visible light irradiation.
Chemical Engineering Journal , — Paul, B. Journal of Physical Chemistry C , — Article Google Scholar. Influence of solution saturation state on the kinetics of ligand-controlled dissolution of oxide phases.
Geochimica Et Cosmochimica Acta 61 , — Lin, Q. Effect of low-molecular-weight organic acids on hematite dissolution promoted by desferrioxamine B. Zinder, B. The coordination chemistry of weathering: II. Dissolution of Fe III oxides. Geochimica et Cosmochimica Acta 50 , — Cwiertny, D. Journal of Physical Chemistry C Furrer, G. The coordination chemistry of weathering: I. Geochimica Et Cosmochimica Acta 50 , — Johnson, S.
Outer-sphere adsorption of maleate and implications for dissolution processes. Langmuir 20 , — Langmuir 21 , — Yoon, T. Implications of surface dissolution for adsorption of oxalate. Effects of adsorbed natural organic matter analogues on mineral dissolution.
Ha, J. Langmuir 24 , B, Jr. Geochimica Et Cosmochimica Acta 68 , — Axe, K. Geochimica Et Cosmochimica Acta 65 , — Persson, P. Adsorption of oxalate and malonate at the water-goethite interface: Molecular surface speciation from IR spectroscopy. Geochimica Et Cosmochimica Acta 69 , — Inorganic Chemistry , 46 19 , Chisholm,, Jason S. D'Acchioli,, Christopher M. Hadad, and, Nathan J.
Inorganic Chemistry , 45 26 , Liu,, Carlos A. Inorganic Chemistry , 45 2 , Byrnes,, Malcolm H. Chisholm, and, Nathan J. Inorganic Chemistry , 44 25 , Chisholm,, Florian Feil,, Christopher M. Journal of the American Chemical Society , 51 , Chisholm,, Judith A. Journal of the American Chemical Society , 49 , Barybin,, Malcolm H. Chisholm,, Naresh S. Dalal,, Thomas H.
Holovics,, Nathan J. Patmore,, Randall E. Robinson, and, David J. Journal of the American Chemical Society , 43 , Chisholm, , Ann M. Chemical Reviews , 8 , Bursten,, Malcolm H. Chisholm, and, Jason S. Inorganic Chemistry , 44 16 , Rakowski DuBois.
Organometallics , 24 18 , Organometallics , 24 11 , D'Acchioli,, Brian D. Pate, and, Nathan J. Patmore, , Naresh S. Dalal and, David J. Theoretical, Spectroscopic, and Structural Investigations. Inorganic Chemistry , 44 4 , Chisholm,, Robin J. Clark,, Judith C. Gallucci,, Christopher M. Inorganic Chemistry , 43 20 , Clark,, Judith Gallucci,, Christopher M.
Journal of the American Chemical Society , 26 , Bradley,, Laura T. Smith,, Judith L. Eglin, and, Claudia Turro.
Inorganic Chemistry , 42 23 , Albert Cotton,, Chun Y. Journal of the American Chemical Society , 44 , Organometallics , 22 20 , Murillo, and, Xiaoping Wang. Inorganic Chemistry , 42 15 , Cotton,, James P. Donahue,, Carlos A. Murillo,, Lisa M. Journal of the American Chemical Society , 29 , Albert Cotton,, James P. Murillo, and, Lisa M. Journal of the American Chemical Society , 18 , Structural Chemistry , 31 2 ,
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