TY - JOUR
T1 - Surface complexation of Pb(II) on amorphous iron oxide and manganese oxide
T2 - Spectroscopic and time studies
AU - Xu, Ying
AU - Boonfueng, Thipnakarin
AU - Axe, Lisa
AU - Maeng, Sungmin
AU - Tyson, Trevor
N1 - Funding Information: The authors gratefully acknowledge the support of the DuPont Young Professor's Grant and the National Science Foundation under Grant No. BES 0089903. The authors thank James A. Dyer and Noel C. Scrivner of DuPont Engineering Technology for their input and support. The authors also acknowledge the technical support provided by staff at beamline X11A and X11B, National Synchrotron Light Source (NSLS), Brookhaven National Laboratory (BNL). Research carried out at NSLS BNL is supported in part by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences, under Contract DE-AC02-98CH10886. Beamline X11 at NSLS is supported by the Office of Naval Research. The authors gratefully acknowledge the helpful comments and XRD analyses from Dr. Robert C. Ford of National Risk Management Research Laboratory, USEPA. Two anonymous reviewers are also acknowledged for the helpful comments.
PY - 2006/7/1
Y1 - 2006/7/1
N2 - Hydrous Fe and Mn oxides (HFO and HMO) are important sinks for heavy metals and Pb(II) is one of the more prevalent metal contaminants in the environment. In this work, Pb(II) sorption to HFO (Fe2O3ṡnH2O, n = 1 - 3) and HMO (MnO2) surfaces has been studied with EXAFS: mononuclear bidentate surface complexes were observed on FeO6 (MnO6) octahedra with Pb{single bond}O distance of 2.25-2.35 Å and Pb{single bond}Fe(Mn) distances of 3.29-3.36 (3.65-3.76) Å. These surface complexes were invariant of pH 5 and 6, ionic strength 2.8 × 10-3 to 1.5 × 10-2, loading 2.03 × 10-4 to 9.1 × 10-3 mol Pb / g, and reaction time up to 21 months. EXAFS data at the Fe K-edge revealed that freshly precipitated HFO exhibits short-range order; the sorbed Pb(II) ions do not substitute for Fe but may inhibit crystallization of HFO. Pb(II) sorbed to HFO through a rapid initial uptake (∼77%) followed by a slow intraparticle diffusion step (∼23%) resulting in a surface diffusivity of 2.5 × 10-15 cm2 / s. Results from this study suggest that mechanistic investigations provide a solid basis for successful adsorption modeling and that inclusion of intraparticle surface diffusion may lead to improved geochemical transport depiction.
AB - Hydrous Fe and Mn oxides (HFO and HMO) are important sinks for heavy metals and Pb(II) is one of the more prevalent metal contaminants in the environment. In this work, Pb(II) sorption to HFO (Fe2O3ṡnH2O, n = 1 - 3) and HMO (MnO2) surfaces has been studied with EXAFS: mononuclear bidentate surface complexes were observed on FeO6 (MnO6) octahedra with Pb{single bond}O distance of 2.25-2.35 Å and Pb{single bond}Fe(Mn) distances of 3.29-3.36 (3.65-3.76) Å. These surface complexes were invariant of pH 5 and 6, ionic strength 2.8 × 10-3 to 1.5 × 10-2, loading 2.03 × 10-4 to 9.1 × 10-3 mol Pb / g, and reaction time up to 21 months. EXAFS data at the Fe K-edge revealed that freshly precipitated HFO exhibits short-range order; the sorbed Pb(II) ions do not substitute for Fe but may inhibit crystallization of HFO. Pb(II) sorbed to HFO through a rapid initial uptake (∼77%) followed by a slow intraparticle diffusion step (∼23%) resulting in a surface diffusivity of 2.5 × 10-15 cm2 / s. Results from this study suggest that mechanistic investigations provide a solid basis for successful adsorption modeling and that inclusion of intraparticle surface diffusion may lead to improved geochemical transport depiction.
KW - Adsorption
KW - Amorphous oxide
KW - EXAFS
KW - Hydrous ferric oxide
KW - Hydrous manganese oxide
KW - Intraparticle diffusion modeling
KW - Lead
KW - XANES
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U2 - 10.1016/j.jcis.2006.01.041
DO - 10.1016/j.jcis.2006.01.041
M3 - Article
C2 - 16483594
SN - 0021-9797
VL - 299
SP - 28
EP - 40
JO - Journal of Colloid And Interface Science
JF - Journal of Colloid And Interface Science
IS - 1
ER -