Temperature Effect on the Surface Charge Properties of gamma-Al2O3

A comprehensive study of the surface properties of the gamma-Al2O3 in KNO3 as a function of temperature was undertaken potentiometrically. 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 NO-3 ions. A simple graphical procedure based on the mass action law was used to determine the number of surface sites and equilibrium constants. Thermodynamic parameters, which showed a decrease in the role of nitrate NO-3 ion in the charging mechanism of gamma-Al2O3, were also evaluated, whereas that of K+ ion increased with the increase in temperature. Copyright 1998 Academic Press.