The Isoelectric Point of an Exotic Oxide: Tellurium (IV) Oxide

The pH-dependent surface charging of tellurium (IV) oxide has been studied. The isoelectric point (IEP) of tellurium (IV) oxide was determined by microelectrophoresis in various 1-1 electrolytes over a concentration range of 0.001–0.1 M. In all electrolytes studied and irrespective of their concentration the zeta potential of TeO(2) was negative over the pH range 3–12. In other words the IEP of TeO(2) is at pH below 3 (if any). TeO(2) specifically adsorbs ionic surfactants, and their presence strongly affects the zeta potential. In contrast the effect of multivalent inorganic ions on the zeta potential of TeO(2) is rather insignificant (no shift in the IEP). In this respect TeO(2) is very different from metal oxides.