Synergistic Effect of Saponin and Rhamnolipid Biosurfactants Systems on Foam Behavior

Abstract In this study, the synergistic effect of saponin and rhamnolipid biosurfactant on foam properties at an air-water interface was investigated. In order to reach the optimum hydrophilic lipophilic balance (HLB) value, samples of 2 wt% of rhamnolipid and saponin biosurfactants with different HLB values (9.6, 10, 10.4, 10.8, 11.2, 11.6, and 12) in 5 ml of DI water were prepared. Results showed that the optimum HLB value of the microemulsion system was 10.8 for the mixture of 84% rhamnolipid and 16% saponin. At that optimum HLB value and a total surfactant concentration of 2 wt%, the maximum foaming ability and foam stability of the mixed system was 48 mm and 72 min respectively. During the experiment, it was observed that at optimum HLB value the foaming ability of the system increased by increasing the concentration of rhamnolipid and saponin. Comparing the foaming ability and foam stability of biosurfactant system with the properties of SDS, Tween80 and Span80 showed that the biosurfactants have a good foaming ability. The CMC value of the biosurfactant mixtures at the optimum HLB value was lower than that of other synthetic surfactants. The results show that, the biosurfactant mixtures had a synergistic effect on foaming ability and foam stability compared to the individual biosurfactants and synthetic surfactants. Therefore, the mixture of rhamnolipid and saponin is proposed as a potential alternative for detergent, cosmetic and petroleum industry.