Phase separation, binding nature, and physico-chemical variables of TX-100 + crystal violet mixture: effects of the electrolytes and hydrotropes

This study has explored the potential interactions between Triton X-100 (TX-100) and crystal violet dye (CV) in the presence of different electrolytes and hydrotrope (HDT) solutions by using cloud point (CP) measurement and UV–visible spectroscopic techniques. The studied electrolytes are sodium chloride (NaCl), sodium acetate (NaOAc), and sodium sulfate (Na₂SO₄), whereas the HDTs are sodium salicylate (NaSal), sodium benzoate (NaBenz), and 4-amino benzoic acid (4-ABA). There was a sharp increase in the CP values of the system studied in NaSal and NaBenz media due to “salting-in” effect, whereas the lowering in the magnitudes of CP was recorded in aqueous solutions of NaCl, NaOAc, Na₂SO₄, and 4-ABA as a result of “salting-out” effect. The extents of CP in the experimental system were varied with the enhancement of different electrolytes and HDTs concentration which followed the trend as \(\normalsize {\text{CP}}_{\text{aq. NaSal}}>{\text{CP}}_{\text{aq. NaBenz}}>{\text{CP}}_{\text{aq. NaOAc}}>{\text{CP}}_{\text{aq. NaCl}}>{\text{CP}}_{{\text{aq. Na}}_{2}{\text{SO}}_{4}}>{\text{CP}}_{aq.4-\text{ABA}}\). The binding constant (\({K}_{b}\)) for the complexation of CV and TX-100 was determined by using the Benesi–Hildebrand equation with the help of UV–Vis spectroscopic method. The degree of \({K}_{b}\) was found to be dependent on the presence of salts and variation in temperatures. The recorded \({\Delta G}_{c}^{0}\) and \({\Delta G}_{b}^{0}\) values for the phase segregation and binding were found as positive and negative, respectively, in all experimental cases. The positive magnitudes of \({\Delta G}_{c}^{0}\) showed a decreasing trend by the boost of electrolytes and HDT concentrations. The appearances of \(-{\Delta H}_{c}^{0}\) and \({-\Delta S}_{c}^{0}\) values in the solutions of different electrolytes confirmed the H-bonding and dipole–dipole interactions being in function amid the surfactant/dye mixtures in the aqueous media, whereas \(+{\Delta H}_{c}^{0}\) and \(+{\Delta S}_{c}^{0}\) values found in aq. NaSal and aq. NaBenz media were indicative of hydrophobic interactions to be have occurred between TX-100 and CV dye species. Both \({\Delta H}_{b}^{0}\) and \({\Delta S}_{b}^{0}\) values of binding were found to be positive revealing the presence of ion–dipole and hydrophobic interactions which were responsible for the binding of the respective components within the experimental surfactant–dye system. These significant results will be of great resource of knowledge to the researchers in the respective fields as well as highly useful for the formulations of quality products in various textiles and pharmaceutical industries.

Graphical Abstract