Natural surfactant extracted from Sapindus mukurossi as an eco-friendly alternate to synthetic surfactant – a dye surfactant interaction study

Abstract

The comparative study between synthetic and natural surfactants was carried out using spectrophotometry, conductometric and surface tension measurement. The value of critical micelle concentration for the natural surfactant was determined. The influence of temperature on conductance was observed and the interaction is found favorable at low temperature. The comparative interaction behavior of the surfactants was studied by reacting them individually with an oppositely charged dye. The concentration of both the surfactants was varied from pre to post micellar region to examine spectral changes. It was detected that the variation in the concentration of surfactant leads to the changes in the spectra of dye. The study showed that the initial increase in surfactant concentration leads to the formation of stable ion-pair, but increasing concentration beyond its critical micelle concentration caused the dissolution of dye surfactant aggregates. The surface tension measurement was also performed. The values for equilibrium constant and Gibbs free energy were calculated based on the theoretical model. On the basis of these values, it is stated that the interaction between natural surfactant and dye is thermodynamically favorable and competitive. The use of natural surfactant in place of synthetic surfactant is suggested as an inexpensive, environmental friendly and cleaner substitute.