FTIR internal reflection spectroscopy studies of the effect of pH on adsorption of oleate/oleic acid at the surface of a TiO2 thin film deposited on a Ge single crystal

The adsorption of oleate/oleic acid from aqueous solutions at the surface of titanium dioxide was examined by Fourier transform infrared (FT-IR) spectroscopy using a germanium internal reflection element coated with a thin film of TiO2. This thin film, with a thickness of 100–200 Å, was deposited on the surface of a germanium single crystal by View the MathML source magnetron reactive sputtering. It was found that significant adsorption of oleate/oleic acid from a 0.03 mM aqueous solution occurs at neutral and close-to-neutral pH, from about pH = 4.5 to pH = 8.5. The surface density vs. pH relationship obtained in this study is consistent with literature reports on the effect of pH on flotation recovery of rutile from oleic acid solutions.