Adsorption of sodium dodecyl sulfate (SDS) at ZnSe and α-Fe2O3 surfaces: Combining infrared spectroscopy and batch uptake studies

Xiaodong Gao, Jon Chorover

Research output: Contribution to journalArticle

51 Scopus citations

Abstract

Adsorption of sodium dodecyl sulfate (SDS) at the solid/aqueous interface was examined as a function of pH and SDS concentration ([SDS]) using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and batch uptake experiments. Two types of sorbent surfaces were compared: (i) a hydrophobic zinc selenide (ZnSe) ATR internal reflection element (IRE) and (ii) the same surface coated with hydrophilic nanoparticulate α-Fe2O3 (hematite). The results indicate that adsorption to the ZnSe IRE is affected by both electrostatic attraction and hydrophobic interaction. Batch adsorption and ATR-FTIR spectral results are consistent with SDS forming outer-sphere complexes at the α-Fe2O3 surface. There is also no evidence for ligand (SDS)-promoted dissolution of hematite. Adsorption to hematite is dominated by anion exchange and surfactant self-assembly. ATR-FTIR data indicate that adsorption to both surfaces shows a strong pH dependence at low [SDS] and negligible pH dependence when [SDS] exceeds the critical micelle concentration (cmc). Adsorption to ZnSe IRE shows small variation with [SDS], apparently due to a lack of surfactant self-assembly at the interface. Adsorption to α-Fe2O3 is a rapid process; equilibrium is reached within a few minutes. Conversely, adsorption to the ZnSe IRE shows strong longer time dependence; evidently, hydrophobic interfacial reactions constitute a much slower process.

Original languageEnglish (US)
Pages (from-to)167-176
Number of pages10
JournalJournal of Colloid And Interface Science
Volume348
Issue number1
DOIs
StatePublished - Aug 1 2010

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Keywords

  • ATR-FTIR spectroscopy
  • Adsorption
  • Hematite
  • SDS
  • ZnSe IRE

ASJC Scopus subject areas

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

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