ZETA-POTENTIAL AND SURFACE-CHARGE OF MONODISPERSED COLLOIDAL YTTRIUM(III) OXIDE AND BASIC CARBONATE

Zeta potentials of yttrium oxide and basic carbonate dispersions of narrow size distribution were determined by the microelectrophoresis method as a function of the pH and the ionic strength. The isoelectric point (iep) changed with the temperature of calcination and was found to be at pH = 8.6 for YOHCO3 and 9.1 for Y2O3 calcined at 900°C, and it was independent of the concentration of sodium perchlorate. Net electrical surface charge was determined by potentiometric titrations using two different experimental techniques described in the literature. One of them takes into account the solubility reactions in calculating the real surface charge from potentiometric titration data, while the other does not. The value of the point of zero charge (pzc) was also dependent on the temperature of calcination of yttrium basic carbonate and changed from 7.7 for YOHCO3 to 9.1 for yttrium oxide calcined at 900°C. The dissociation constants of surface - YOH groups were calculated. © 1992.