Surface complexation of Pb(II) on amorphous iron oxide and manganese oxide: Spectroscopic and time studies

Document Type

Article

Publication Date

7-1-2006

Abstract

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. © 2006 Elsevier Inc. All rights reserved.

Identifier

33646811212 (Scopus)

Publication Title

Journal of Colloid and Interface Science

External Full Text Location

https://doi.org/10.1016/j.jcis.2006.01.041

ISSN

00219797

First Page

28

Last Page

40

Issue

1

Volume

299

Grant

DE-AC02-98CH10886

Fund Ref

National Science Foundation

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