Solubilization properties of polycyclic aromatic hydrocarbons by saponin, a plant-derived biosurfactant

The enhanced solubilization of polycyclic aromatic hydrocarbons (PAHs) by saponin, a plant-derived non-ionic biosurfactant, was investigated. The results indicated that the solubilization capabilities of saponin for PAHs were greater than some representative synthetic non-ionic surfactants and showed strong dependence on solution pH and ionic strength. The molar solubilization ratio (MSR) of saponin for phenanthrene was about 3–6 times of those of the synthetic non-ionic surfactants, and decreased by about 70% with the increase of solution pH from 4.0 to 8.0, but increased by approximately 1 times with NaCl concentration increased from 0.01 to 1.0 M. Heavy metal ions can enhance saponin solubilization for phenanthrene and the corresponding MSR values increased by about 25% with the presence of 0.01 M of Cd2+ or Zn2+. Saponin is more effective in enhancing PAHs solubilization than synthetic non-ionic surfactants and has potential application in removing organic pollutants from contaminated soils.

► The enhanced solubilization of PAHs by saponin was investigated in this study.
► Saponin showed great solubilization capability for PAHs.
► Saponin is more effective in enhancing HOCs solubilization at lower solution pH.
► Increasing ionic strength can enhance HOCs solubilization in saponin solution.
► Heavy metal ions can also enhance phenanthrene solubilization in saponin solution.