Solubilization of cationic dye in single and mixed micellar media

Abstract

The effect of mixed-micellization of anionic/non-ionic surfactants on the solubilization of a cationic dye (Methylene blue) is presented in this manuscript. Interactions of dye with the single anionic surfactant sodium dodecyl sulfate (SDS), and its mixture with the non-ionic surfactant (Triton X-100), were investigated. The non-ionic surfactant was initially screened, and then its concentration was kept constant at its critical micellar concentration. The critical micellar concentration, entropy, enthalpy, and free energy of micelle formation (ΔGmic°) were determined by electrical conductivity measurements. The solubilization parameters in terms of the partition coefficient (Kx) and binding constant (Kbind) were assessed by UV–Visible spectroscopy. The role of non-ionic surfactants on the electrostatic interactions of cationic dye and surfactant was also elaborated. Mixed micellization significantly enhanced the solubility of dye molecules as shown by conductivity and absorbance analysis. The disruption of structured water in the vicinal environment of hydrophobic groups of surfactants was responsible for the increase in critical micelle concentration (CMC). The negative values of energies of binding, partitioning, and micellization indicated the spontaneity and feasibility of micellar systems. The experimental outcomes supported the superiority of anionic/non-ionic mixed micellar solubilization over a single anionic surfactant. Thus, the mixed micellar system (SDS + TX-100) assured a higher degree of solubilization than the corresponding single system (SDS).