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

Ying Xu, Thipnakarin Boonfueng, Lisa Axe, Sungmin Maeng, Trevor Tyson

Research output: Contribution to journalArticlepeer-review

81 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)28-40
Number of pages13
JournalJournal of Colloid And Interface Science
Volume299
Issue number1
DOIs
StatePublished - Jul 1 2006

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

Keywords

  • Adsorption
  • Amorphous oxide
  • EXAFS
  • Hydrous ferric oxide
  • Hydrous manganese oxide
  • Intraparticle diffusion modeling
  • Lead
  • XANES

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