Study of dye–surfactant interaction: Aggregation and dissolution of yellowish in N-dodecyl pyridinum chloride

Among several known technique for investigating dye–surfactant interactions, the conductivity measurement and spectroscopy are simple and accessible methods for determining the degree of interaction between dye and surfactant. An abrupt change in measured specific conductance of dye–surfactant mixture is attributed to the formation of dye–surfactant ion pair at six different temperatures. Thermodynamic parameters were also evaluated. The results have shown that low temperature favors the tendency for ion pair formation, as the equilibrium constant decreases with increase in temperature. To enhance the scope of the present study, a gradual transition in absorbance from pre-miceller to post-miceller region of surfactant were monitored. Spectral behavior of dye–surfactant mixture with varying concentration of surfactant confirms that electrostatic interaction between dye and surfactant occurs up to a certain level. Beyond this concentration only the dissolution of dye–surfactant aggregate was observed. The association tendency of opposite charged surfactant is used to recover dye from dye–surfactant mixture.