Surface complexation modeling and spectroscopic evidence of antimony adsorption on iron-oxide-rich red earth soils

Meththika Vithanage, Anushka Upamali Rajapaksha, Xiaomin Dou, Nanthi S. Bolan, Jae E. Yang, Yong Sik Ok

Research output: Contribution to journalArticle

71 Citations (Scopus)

Abstract

Few studies have investigated surface complexation of antimony (Sb) on natural sorbents. In addition, intrinsic acidic constants, speciation, and spectroscopic data are scarce for Sb sorption in soil. Only simple sorption models have been proposed to describe the sorption of Sb(V) on specific mineral surfaces. This study therefore assessed the mechanisms of Sb(III) and Sb(V) adsorption on natural red earth (NRE), a naturally occurring iron coated sand, at various pHs and Sb loadings. The Sb(V) adsorption followed typical anion adsorption curve with adsorption reaching maximum around pH 4-5, while no pH dependence was observed for Sb(III) sorption. The FT-IR spectra revealed that shifts in absorbance of the hydroxyl groups in iron-oxide were related to the Fe. O. Sb bonds and provided evidence for inner sphere bond formation. Direct evidence on the strong interaction of Sb(III) and Sb(V) with Fe. O and Al. O was observed from the decrease in Fe-2p, Al-2p, and Si-2p peaks of the X-ray photoelectron spectroscopy (XPS) data before and after Sb(V) and Sb(III) adsorption on NRE. Successful data modeling using the 2-pK diffuse double layer model (DDLM) with the FITEQL revealed that sorption occurs through the formation of bidentate mononuclear and binuclear complexes. Model simulations showed a high affinity to the FeOH sites at high Sb loadings, whereas at low loadings, both FeOH and AlOH sites showed similar affinities to Sb. In the case of Sb(V), multilayer formation was also revealed in addition to surface complexation by the isotherm data fitted with the Freundlich model and two sites Langmuir equations, which indicated heterogeneous multilayer adsorption of Sb(V) on NRE.

Original languageEnglish
Pages (from-to)217-224
Number of pages8
JournalJournal of Colloid and Interface Science
Volume406
DOIs
Publication statusPublished - 2013 Sep 15
Externally publishedYes

Keywords

  • Adsorption edge
  • Anion adsorption
  • Ionic strength
  • Surface charge
  • Surface precipitation

ASJC Scopus subject areas

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

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