EFFECT OF N-ALCOHOLS ON THE SURFACE-CHARGE DENSITY AND ADSORPTION OF SUPPORTING ELECTROLYTE ON ALUMINAS

The presence of n-alcohols (ethanol up to 12, propanol up to 10, and butanol up to 4% weight) does not affect the course of the σ0 vs. pH curves and the adsorption of Na+ and Cl- ions from 0.1, 0.01, and 0.001 M solutions in the system alumina-NaCl solution. For the sample of alumina containing mainly α-corundum the values of pzc and cip coincide at pH = 8. This sample adsorbs considerable amounts of counterions in relation to the values of σ0 but adsorption of these ions at pHpzc is negligible within experimental error. For the sample containing mainly γ-alumina, PHcip = 8.2 and σ0 = -0.3 C/g for cip. This sample adsorbs considerable amounts of chloride ions even at pHpzc but adsorption of sodium ions appears for the pH values above pHpzc. © 1990.