ADSORPTION BEHAVIOR OF ALKYLARYLETHOXYLATED ALCOHOLS ON SILICA

The effect of ethoxylation of long chain alcohols on their adsorption behavior is investigated in this study for a series of alkylarylethoxylated alcohols. The degree of ethoxylation affects markedly both the maximum plateau adsorption and the uptake of the surfactant at lower concentrations. Hydrogen bonding is considered to provide the initial driving force for adsorption. Surfactants with lower ethoxylation show preferential adsorption on silica compared with those with higher ethoxylation because of the steric effect of ethylene oxide chains on the hydrocarbon chain-chain interaction at the solid/liquid interface. The hydrophobicity of silica surface after surfactant adsorption has been found to be dependent on the structure of surfactant as well as the adsorption density. While both C8EO10 and C8EO40 impart hydrophobicity to silica surface above a threshold concentration, C8EO40 shows a return to hydrophilicity near the CMC. These changes in hydrophobicity are interpreted by considering changes in orientation of the hydrocarbon chain of the adsorbed surfactant. © 1991.