The Solubilization Capability of Polycyclic Aromatic Hydrocarbons Enhanced by Biosurfactant Saponin Mixed With Conventional Chemical Surfactants

Abstract

Water solubilities of anthracene and phenanthrene were measured by adding a plant-derived biosurfactant Saponin and/or synthetic surfactants correspondingly below and above their critical micelle concentrations (CMCs). The results showed that the solubilities of anthracene and phenanthrene in water were greatly enhanced following a linear fashion if adding Saponin, TX100 and Brij35, respectively. The enhancing solubility capacities for Polycyclic aromatic hydrocarbons (PAHs) followed the order as: Saponin > Brij35 > TX100 at the concentrations below their CMC. It also proved that biosurfactant Saponin exhibited much higher enhancement efficiency for PAHs solubilization than the synthetic ones at the concentrations below the CMC. However, the solubility enhancement efficiencies of surfactants above the CMC turned to be the following order as Brij35 > Saponin > TX100. Furthermore, this study has confirmed that PAHs are synergistically solubilized in the mixed biologic-synthetic surfactant solutions, especially at the low surfactant concentrations.Synergistic effect of a prepared mixed-surfactant solution on different PAH compounds also appeared to be linear related to the surfactant concentrations. The synergistic power of mixed surfactants were examined as Saponin-Brij35 > Saponin-TX100 while the efficiencies of synergistic solubilization ranged from 27% to 137%. The noted solubilization for the single and mixed surfactants could be attributed to the formation of single and mixed micelles, the lower CMC of the single and mixed surfactant solutions, and the increase of the solubilization ratio or micellar partition coefficients.