Comparative solubilization of reactive dyes in single and mixed surfactants

Abstract

Physicochemical attributes and solubilization of reactive dyes in single and mixed micellar media are elaborated in this study. The enhanced entrapment of reactive dyes was observed in the mixed-micellar media of cationic surfactant, cetyltrimethylammonium bromide (CTAB) and nonionic surfactant, (Triton X-100) as compared to single-micellar media of CTAB. Two reactive dyes viz. Reactive Black 5 (RB) and Reactive Yellow 145 (RY) were used for this interactional study. The solubilization in terms of partition constant (Kc ), partition coefficient (Kx ), binding constant (Kb ), Gibbs free energies (ΔGp and ΔGb ) and the approximate location of dye molecules in the micelles, was assessed by UV–Vis spectroscopy. From the experimental findings, it was concluded that the mixing of CTAB with a nonionic surfactant is recommended to achieve a superior degree of entrapment of dye molecules as compared to the single surfactant. The RB, the magnitude of Kx was 520 × 105 in CTAB media, whereas this value lowered to 195 × 105 in the mixed-micellar system (MMS). A similar trend was observed in RY and the single and MMSs showed respective Kx values of 207 × 105 and 19.7 × 105. The higher negative magnitudes in the case of single surfactant indicated greater partitioning of dyes while the mixed system caused deep penetration of dyes. The lower values of Gibb’s free energies of partition and binding were indicative of greater penetration of dyes within the micelles.