Surface charging and points of zero charge of less common oxides: Beryllium oxide

Abstract

HypothesisThe surface charging and adsorption properties of beryllium oxide follow the same principles as the properties of other metal oxides. ExperimentsThe point of zero charge PZC was determined by potentiometric titration, and by salt addition method at 15, 25 and 35 °C. The ζ potential of beryllium oxide was measured at different concentrations of various 1-1 salts. The effect of ionic surfactants and of multivalent inorganic ions on the isoelectric point IEP was studied. FindingsThe PZC of beryllium oxide in the presence of NaCl is at pH 9.1 at 25 °C, and it decreases by 0.04 pH unit per 1 °C. The IEP of beryllium oxide in the presence of NaCl, KCl and KNO3 is at pH about 9, and it is independent of the electrolyte concentration and of aging. The presence of anionic surfactant (SDS) and of phosphate results in a shift in the IEP to low pH, and the presence of cationic surfactant (CTAB) results in a shift in the IEP to high pH. The IEP roughly matches the maximum in the particle size. The surface charging behavior of beryllium oxide confirms specific adsorption of ionic surfactants and of multivalent inorganic ions, and it is qualitatively similar to that of more common metal oxides (titania, alumina, hematite).