ELECTROACOUSTIC STUDY OF ADSORPTION OF IONS ON ANATASE AND ZIRCONIA FROM VERY CONCENTRATED ELECTROLYTES

The reduction of absolute values of negative zeta potentials (basic br anch) of anatase with the concentration of 1-1 salts (alkali halides, nitrates, and perchlorates) is much more pronounced than that of the p ositive zeta potentials (acidic branch). The extent of this effect inc reases in the series Cs < K < Na < Li for a given anion and CH3COO < C l < NO3 < ClO4 < Br < I for a given cation. For sufficiently high conc entrations of most lithium and sodium salts, e.g., 0.53 mol dm(-3) NaI , there is no isoelectric point (iep) and the zeta potentials are posi tive over the entire available pH range. For potassium and cesium salt s, an iep is always observed, even at very high concentrations, but it is substantially shifted toward the higher pH values. Small cations s how a differentiating effect: the course of zeta(pH) curves for partic ular lithium and sodium salts at a given high ionic strength is very s ensitive to the nature of the anion, but the effect of the nature of t he anion is relatively insignificant when different potassium salts ar e considered. Large anions (iodide) show a differentiating effect, whi le smaller anions (chloride) do not.