COMPETITIVE AND DISPLACEMENT ADSORPTION OF POLYVINYL-ALCOHOL AND THE AMMONIUM SALT OF A POLYACRYLIC-ACID ON BATIO3

Adsorption isotherms for polyvinyl alcohol (PVA) and the ammonium salt of a polyacrylic acid (NH4-PAA) on BaTiO3 have been measured with separate solutions, with mixtures and after sequential addition. Size-exclusion chromatography was used to measure the amounts adsorbed from the depleted supernatants. The amounts adsorbed from separate solutions reach plateaux at 0.19 mg m-2 for PVA and 0.40 mg m-2 for NH4-PAA. Both polymers adsorb from mixtures as long as the amount of NH4-PAA is not enough to reach the plateau adsorption. Above this level no adsorption of PVA is found. If PVA is adsorbed first and the NH4-PAA added afterwards, both polymers are adsorbed at amounts almost equal to the separate plateau values. After long contact times the amount of PVA adsorbed decreases slightly to 0.17 mg m-2.