Determination of Critical Micelle Concentration and Thermodynamic Evaluations of Micellization of GMS

Abstract

The uncontrolled distribution of surfactants which are commonly used as household and industrial products like soaps, lubricants and detergents in the global market have provoked this study. The determination of critical micelle concentration (CMC) of glycerol monostearate surfactant (GMS) was evaluated using Conductivity and UV-Visible Spectroscopic techniques respectively. The effect of solubility was quantified and the Krafft temperature was obtained. The thermodynamic feasibility parameters were evaluated using Erying and Vant Hoff’s equations. The CMC values were taken from the sharp breaks in the plots of absorbance versus surfactant concentrations and conductivity versus surfactant concentration respectively. The result showed that as the temperature increases, the CMC initially decreases and then followed by slight increase owing to the smaller probability of hydrogen bond formation at higher temperatures. The result showed that the critical micelle concentration of GMS obtained using Conductivity and UV-Visible techniques were 4.50 × 10-2 and 2.40 × 10-2 moldm-3 respectively and the Krafft temperature (KT) was obtained at 50°C. The Gibbs free energy change of micellization (ΔG° CMC) was found to decrease as temperature increases over the whole temperature range. The entropy change of micellization (ΔS° (CMC)) showed positive values throughout the temperature range tested while the large enthalpy change, ΔH° (CMC) means that in the micellization process, the attractive interaction among hydrophobic chains was opposed by the strong interaction of the oxyethylene chains of glycerol monostearate with water molecules. The study revealed that the use of UV-Visible Spectroscopy technique was a very good and easy way of determining the critical micelle concentration of GMS. This study is also a valuable industrial tool for the production of soap related products and its applications in domestic and industrial processes.