Interaction between an Anionic Surfactant and Some Oil Soluble Azo Dyes at Oil/Water Interface

Abstract

The adsorption behavior of 5 Azo oil dyes and sodium dodecyl sulfate (SDS) at n-dodecane/water interface were studied. In the case of surfactant free systems, interfacial tension decreased with increasing hydrophilicity of the dye. By applying the Gibbs adsorption equation to the interfacial tension data, the interfacial excesses of Azo oil dyes and SDS were evaluated. The interfacial densities and orientation angles of the dyes at the interface were dependent on the type and replacement positions of the hydrophilic groups.In the presence of a surfactant, both the dye and a strongly hydrophilic group interacted with SDS to a considerable extent.The distribution coefficients of the dyes in n-dodecane and sodium dodecyl sulfate micelle solutions were larger for dyes containing strongly hydrophilic groups than those with weakly hydrophilic groups.