Ferrous iron sorption by hydrous metal oxides

Genevieve Villaseñor Nano, Timothy J. Strathmann

Research output: Contribution to journalArticlepeer-review

Abstract

Ferrous iron is critical to a number of biogeochemical processes that occur in heterogeneous aquatic environments, including the abiotic reductive transformation of subsurface contaminants. The sorption of Fe(II) to ubiquitous soil minerals, particularly iron-free mineral phases, is not well understood. Colloidal TiO2, γ-AlOOH, and γ-Al2O3 were used as model hydrous oxides to investigate Fe(II) sorption to iron-free mineral surfaces. Rapid Fe(II) sorption during the first few hours is followed by a much slower uptake process that continues for extended periods (at least 30 days). For equivalent solution conditions, the extent of Fe(II) sorption decreases in the order TiO2 >γ-Al2O3 ≫γ-AlOOH. Short-term equilibrium sorption data measured over a wide range of conditions (pH, ionic strength, Fe(II)-to-sorbent ratio) are well described by the diffuse double layer model. Fe(II) sorption to TiO2 is best described by a single-site model that considers formation of two surface complexes, {triple bond, long}SOFe+ and {triple bond, long}SOFeOH0. For γ-AlOOH and γ-Al2O3, sorption data are best described by a two-site model that considers formation of {triple bond, long}SOFe+ complexes at weak- and strong-binding surface sites. Accurate description of sorption data for higher Fe(II) concentrations at alkaline pH conditions requires the inclusion of a Fe(II) surface precipitation reaction in the model formulation. The presence of common groundwater constituents (calcium, sulfate, bicarbonate, or fulvic acid) had no significant effect on Fe(II) sorption. These results demonstrate that iron-free soil minerals can exert a significant influence on Fe(II) sorption and speciation in heterogeneous aquatic systems.

Original languageEnglish (US)
Pages (from-to)443-454
Number of pages12
JournalJournal of Colloid And Interface Science
Volume297
Issue number2
DOIs
StatePublished - May 15 2006
Externally publishedYes

Keywords

  • Aluminum oxide
  • Anoxic environments
  • Ferrous iron
  • Metal oxide
  • Sorption
  • Surface complexation
  • Titanium dioxide

ASJC Scopus subject areas

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

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