Effects of nonionic surfactant (TX-100) on solubilizing power of cationic surfactants (CTAB and CPC) for Direct Red 13

Abstract

In present study, the solubility of anionic dye, Direct Red 13, has been, spectroscopically and conductometrically, investigated in micellar media of cationic surfactants; Cetylpyridinium chloride (CPC), Cetyltrimethylammonium bromide (CTAB) and mixed micellar media of each with nonionic surfactant, Tritron X-100. The spectral behavior of dye in presence of surfactants was regularly monitored from pre- to post-micellar region of concentration. The UV–vis spectroscopy was applied for estimation of extent of solubilization in terms of partition coefficient (Kx), binding constant (Kb) and Gibbs free energy of corresponding processes. The addition of nonionic surfactant in ternary solution of dye was made to elucidate the role of mixed micelles on solubility of dye. The electrical conductivity data, measured at different temperatures, was used for detection of CMC and calculation of different thermodynamic parameters like; entropy (ΔSm), enthalpy (ΔHm) and Gibbs free energy change (ΔGm) of micellization of selected surfactants. Results reveal the spontaneity of binding and partitioning of dye in aqueous and micellar phase for all the used surfactant systems.