Surface and Bulk Properties of a Nonionic Surfactant in Ternary Water–Alcohol–Salt Systems

Surface tension method is a simple and popular method to study the surface as well as bulk properties of nonionic surfactants, including Brij‐35, which is a poly‐oxyethylated surfactant. In this study, the surface tension of the solutions of Brij‐35 in the presence of sodium nitrate and sodium sulfate in binary mixed media of alcohol–water was measured precisely. The alcohols used in this study were methanol, ethanol, and propan‐1‐ol. The surface properties such as surface excess concentration ( Γ max ) and minimum surface area ( A min ), bulk properties such as critical micelle concentration (CMC) and packing parameter (P), and thermodynamic properties and of micellization of the surfactant were determined using the surface tension data. The presence of inorganic salts is found to decrease the CMC of Brij‐35 in water–alcohol‐mixed media, whereas the presence of short‐chain alcohols separately increases the CMC values of Brij‐35. The alkyl part of the short‐chain alcohol also plays a significant role in the micellization of Brij‐35. The results were explained on the basis of molecular and ionic interactions, including ion–ion, ion–solvent, hydrophobic, and hydrophilic, among the various species in the system.