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 surf ace 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 Angstrom, was deposited on the surface of a germanium single crystal by rf/dc 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 cons istent with literature reports on the effect of pH on flotation recove ry of rutile from oleic acid solutions. (C) 1998 Elsevier Science B.V.