Improved solubilities of PAHs by multi-component Gemini surfactant systems with different spacer lengths

Mixed micellization, interface and enhanced solubilization aspects of a series of single cationic Gemini surfactants (alkanediyl-α,ω-bis (dodecyldimethylammonium bromide) as well as their equimolar bi and ternary combinations have been investigated. Several theoretical treatments have been employed to evaluate and compare the mutual interaction parameter, counterion binding, surface excess, free energies of micellization, etc. for finding out synergistic effect of mixed surfactant systems. Nonideality is found to increase with the enlarged difference of spacer length of components in mixtures. Water solubility enhancement of polycyclic aromatic hydrocarbons (PAHs), naphthalene and pyrene, by selected single, equimolar bi and ternary Gemini surfactant systems, has been evaluated from measurements of the molar solubilization ratio, the micelle–water partition coefficient, the deviation ratio and the free energy of solubilization. The spacer length of selected single and mixed Gemini surfactant systems has a different effect on their solubilization capabilities towards PAHs relative to micellar and interfacial behaviors. The results have shown that the solubilization power not only depends on the micellar and interfacial properties of surfactant but also has an association with hydrophilic/hydrophobic properties of solutes. Such studies on binary and ternary Gemini surfactant combinations with the same charge are limited.