Thermodynamic Analysis of Dye-Surfactant Interactions in Aqueous Solution Using Conductometric and Surface Tension Techniques

(Nihad Abdullah Al-Omair)

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Abstract

The interaction between anionic dye C.I. Acid Orange 5 (AO5) and anionic surfactant sodium dodecyl sulfate (SDS), along with the effect of increasing the proportion of the dye in the surfactant solutions as well as the impact of increased temperature on these interactions were examined using both conductometric and surface tension techniques. The results revealed that the Critical Micelle Concentrations (CMC) have reflected a tendency towards increasing in the values with increasing in the proportion of the dye in the surfactant solutions. Correspondingly, the CMC values of the dye-surfactant mixture solutions increased with the increase of temperature. A theoretical model of calculations has been implemented to measure the standard Gibbs free energy changes of micellization, , the standard enthalpy changes of micellization, , and the standard entropy changes of micellization, . Moreover, the interactions of dye-surfactant are spontaneous based on the negative values of for all systems. Significantly, the negative values of revealed that the interactions of dye-surfactant system are exothermic. The entropy contribution of micelle formation shows positive values. Key Words: Conductivity; Dye; Micellization; Surface Tension; Surfactant.
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