Conductometric Investigation of the Interaction of Natural and Synthetic Surfactant with Cationic Dye in Water-Alcohol Mixed Solvent

摘要

The association of dye and surfactant in aqueous solution alters various properties of these molecules. Alcohol as a part of a water-alcohol mixed solvent is thought to affect dye surfactant interaction. A conductance measurement was performed for the interaction of cationic dye with two anionic surfactants in a water alcohol mixed solvent. The specific conductance was measured at five different temperatures containing (5, 10, 15, 20, and 25) wt % of ethanol or propanol. On the basis of the theoretical model, the equivalent conductances and the equilibrium constants for the reactions were calculated. Thermodynamic parameters were also determined. The results showed that the tendency of ion-pair formation reduced with the percentage of alcohol in a solvent mixture due to decrease in the dielectric constant of the solvent. A nonlinear trend of thermodynamic parameters was observed. The formation of an ion-pair in the water-alcohol mixed solvent was an enthalpy driven process. The values of enthalpy for neutral red and sodium dodecyl sulfate (NR-SDS), and neutral red and anionic natural surfactant (NR-ANS) systems were in the range of -15 kJ mol(-1) to -21 kJ mol(-1) and -46 kJ mol(-1) to -52 kJ mol(-1). It was found that both long-range and short-range interactions are involved during dye surfactant interaction.