THE ROLE OF THE ACTIVITY-COEFFICIENTS OF SURFACE GROUPS IN THE FORMATION OF SURFACE-CHARGE OF OXIDES .2. ION-EXCHANGE AND ZETA-POTENTIALS

A new method is developed to calculate the surface charge densities an d zeta potentials of oxides in contact with electrolyte solution as fu nctions of pH and ionic strength. For low ionic strength and not too f ar from p.z.c. (up to 3 pH units for 10(-3) mol dm(-3) NaCl) the previ ous model (Kosmulski, 1992) neglecting the ion exchange can be used bu t farther from p.z.c., correction for the ion exchange is necessary fo r some systems. This correction leads to increase of the calculated ti tration charge (that is not necessarily equal to the surface charge),b ut does not affect the diffuse charge and zeta potential.