Quest for an eco-friendly alternative surfactant: Surface and foam characteristics of natural surfactants

Abstract

Surfactants are amphiphilic molecules that reduce the surface tension of water and are extensively used for domestic and industrial purpose. Today it is increasingly desirable to replace synthetic surfactants with naturally derived molecules with a reduced environmental burden. About 60% of surfactants used enter the aquatic environment and cause immense damage. This study demonstrates the use of plant based natural surfactants as biodegradable and renewable alternatives. Traditionally used natural surfactants extracted from two plants, Pyagi Phool (Zephyranthes carinata Herbert.) and Ritha (Sapindus mukorossi Gaertn.) in aqueous solution have been studied. Surface tension, foaming and other relevant parameters have been investigated. While Ritha has been studied earlier, this is perhaps the first ever report on surfactant activities of Pyagi Phool. Ritha is acid balanced and exhibits a prominent surface tension reduction to 35.30 mN/m, high foaming, wetting and cleaning. Pyagi Phool is also acid balanced, reduces surface tension to 40.76 mN/m, possesses high viscosity and shows good dirt dispersion, making it a decent natural cleansing agent. The mechanism of foam formation affects the foaming ability and stability. Quantified dirt dispersion measurement shows that dirt dispersion reaches a maximum at Critical Micelle Concentration. Emulsion stability also decreases in the same region. The natural surfactants show better emulsification at higher concentrations as compared to synthetic surfactant. The results obtained suggest that both Ritha and Pyagi Phool have remarkable surface active properties and can be used as environmental friendly alternatives to synthetic surfactants.