Eco-friendly biosurfactant saponin for the solubilization of cationic and anionic dyes in aqueous system

This study demonstrates the solubilization of two different dyes, methylene blue and eosin yellow by one biosurfactant, saponin. This eco-friendly natural surfactant was extracted from the pericarps of sapindus mukorossi (reetha) fruit. The physicochemical properties of extracted aqueous saponin were characterized using various techniques, such as, FTIR spectroscopy, UV-spectroscopy, MALTI-TOF-MS, optical microscope, particle size analyzer, and surface tension measurement. The size of saponin micelle was observed in the range of 10-11.5 nm, whereas, the agglomerates of saponin having higher size, ranging from 132 to 235 nm, 390-990 nm, and 5155-8520 nm were also present in the aqueous system. The batch solubilization experiments were performed and the solubilization capacity of dyes in saponin micelles was measured in terms of solubilization power. The solubilization of dyes was the combined effect of micellar solubilization by saponin micelle, as well as sorption of dyes by saponin agglomerates. The partition coefficient of both the dyes between the aqueous solution and saponin micelles were calculated. The Gibbs free energy of solubilization was evaluated for both the dyes and found that the solubilization process was thermodynamically feasible. The outcome of this study explores the potential of saponin in various surfactant based processes such as, MEUF, SER, and CPE etc. (C) 2017 Elsevier Ltd. All rights reserved.