Zn2+ and Sr2+ adsorption at the TiO2 (110)-electrolyte interface: Influence of ionic strength, coverage, and anions

Z. Zhang*, P. Fenter, L. Cheng, N. C. Sturchio, M. J. Bedzyk, M. L. Machesky, L. M. Anovitz, D. J. Wesolowski

*Corresponding author for this work

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

The X-ray standing wave technique was used to probe the sensitivity of Zn2+ and Sr2+ ion adsorption to changes in both the adsorbed ion coverage and the background electrolyte species and concentrations at the rutile (α-TiO2) (110)-aqueous interface. Measurements were made with various background electrolytes (NaCl, NaTr, RbCl, NaBr) at concentrations as high as 1 m. The results demonstrate that Zn2+ and Sr2+ reside primarily in the condensed layer and that the ion heights above the Ti-O surface plane are insensitive to ionic strength and the choice of background electrolyte (with <0.1 Å changes over the full compositional range). The lack of any specific anion coadsorption upon probing with Br-, coupled with the insensitivity of Zn2+ and Sr2+ cation heights to changes in the background electrolyte, implies that anions do not play a significant role in the adsorption of these divalent metal ions to the rutile (110) surface. Absolute ion coverage measurements for Zn2+ and Sr2+ show a maximum Stern-layer coverage of ∼0.5 monolayer, with no significant variation in height as a function of Stern-layer coverage. These observations are discussed in the context of Gouy-Chapman-Stern models of the electrical double layer developed from macroscopic sorption and pH-titration studies of rutile powder suspensions. Direct comparison between these experimental observations and the MUltiSIte Complexation (MUSIC) model predictions of cation surface coverage as a function of ionic strength revealed good agreement between measured and predicted surface coverages with no adjustable parameters.

Original languageEnglish (US)
Pages (from-to)50-64
Number of pages15
JournalJournal of Colloid And Interface Science
Volume295
Issue number1
DOIs
StatePublished - Mar 1 2006

Keywords

  • Adsorption
  • Electrical double layer
  • Ionic strength
  • Multisite complexation
  • Oxide-aqueous interface
  • Rutile
  • X-ray standing wave

ASJC Scopus subject areas

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

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