Abstract
Aqueous solutions of anionic surfactant sodium dodecylsulfate (SDS) and cationic surfactant cetyltrimethyammonium bromide (CTAB) were prepared at room temperature in order to investigate the influences of surfactants mixing on the solubilization of 2-naphthol-6-sulfonate and toluene. The phase behavior of CTAB/SDS was firstly investigated to obtain the optimum ratio of CTAB/SDS that result in an isotropic solution before reaching the two phase region. From the conductivity and surface tension measurements, the critical micelle concentrations (CMC) of single and mixed surfactant solutions were obtained and the interaction parameter (beta) were evaluated. Water solubility enhancement of (0-3 wt.%) toluene by micellar solutions of single surfactant SDS, CTAB and mixed solutions of SDS-CTAB surfactants were then investigated by establishing the phase behavior and measuring the absorption and the emission spectra of these solutions. The toluene was completely solubilized by the micellar solution of single surfactants, whereas turbidity was observed at toluene concentration of about 1.5 wt.% in the micellar solution of SDS-CTAB. The fluorescence behavior of 2-naphthol-6-sulfonate (2NO6S) and toluene in the single and mixed surfactant solutions was also compared. The solubilization of toluene in surfactant solutions was explained in terms of hydrophobic interaction occurring within the surfactant core and the palisade layers.