Ultrasonic vibration potential and point of zero charge of some rare earth oxides in water

The surface charge of rare earth metal oxides in water was examined using ultrasonic vibration potential (UVP) technique for the dilute colloid. Sonic irradiation induced an alternative current in suspensions of oxide powders in water. The observed potential largely varied, depending on the surface charge density of oxide powders, for suspensions at different pH as well as the kind of rare earth metals used. The paper described the measurement results and comparison for several rare earth oxides. The effect of pH and its swing and the kinds of rare earth element in oxides were reported. The point of zero charge (p.z.c., pH of zero charge for powders in water) strongly depended on the kinds of metal elements forming oxides and valence of metal ions. For a series of rare earth elements, dependence of atomic number can be observed; however, the distinguishing feature was the difference between trivalent rare earth metal oxides and tetravalent Ce oxide. The p.z.c. of CeO2 was 6.7, while those of oxides of trivalent rare earth were 8.3-8.8. (c) 2005 Elsevier B.V. All rights reserved.