TEMPERATURE EFFECT ON THE SURFACE-CHARGE PROPERTIES OF GAMMA-AL2O3

A comprehensive study of the surface properties of the gamma-AL(2)O(3) in KNO3 as a function of temperature was undertaken potentiometricall y. Surface charge, ionization and complexation constants, and PZC were calculated from the potentiometric titration data in the temperature range 293-333 K. A difference between the PZC and CIP was observed as a result of the adsorption of NO3- ions. A simple graphical procedure based on the mass action law was used to determine the number of surfa ce sites and equilibrium constants. Thermodynamic parameters, which sh owed a decrease in the role of nitrate NO3- ion in the charging mechan ism of gamma-Al2O3, were also evaluated, whereas that of K+ ion increa sed with the increase in temperature. (C) 1998 Academic Press.