Influence of hydrophobic tail on the adsorption of isomeric alcohols at air/water interface

Abstract

This study investigated the influence of molecular structures of alcohols on adsorption behaviour. The adsorption isotherm of nonanols, octanols and hexanols at air–water interface was determined using the Wilhelmy plate method, in combination with an automatic dispenser. The experimental data were fitted with Frumkin–Langmuir isotherms by applying least-squares techniques in Solver (MS Excel) to identify the adsorption parameters. These parameters can be used to quantify and compare the surface behaviours of all the investigated surfactants. It has been found that with the same concentration, the straight chain alcohols had stronger surface activity than the corresponding branched alcohols. The adsorption activity was also strongly related to the position of the hydroxyl group, with primary alcohols showing strongest adsorption. Overall, it was found that the surface activity decreased with increasing bulkiness of the alcohol structure. The results also highlighted the significance of low concentration data in determining the adsorption isotherm of alcohols.