Surfactant-Containing Foam Effectively Enhanced the Removal of Polycyclic Aromatic Hydrocarbons from Heavily Contaminated Soil.

Surfactant remediation has an excellent record of removing polycyclic aromatic hydrocarbons (PAHs). By using simulation experiments, we investigated the properties and mechanism of a surfactant-containing foam and its effect on PAH removal. Our results suggest that the optimal conditions by foam washing are as follows: 40 mmol·L of rhamnolipid and fulvic acid mixed surfactant (V: V = 3:1), with 70:3 and 20:3 foam gas-liquid ratio for naphthalene and phenanthrene, respectively (pH 6, 50°C, 2 h). Under the optimal conditions, 60.1% and 56.68% removal efficiencies were achieved against naphthalene and phenanthrene from contaminated soil, respectively. These values were lower than those from the simulated media (76.69% and 70.43% for naphthalene and phenanthrene, respectively). The strong PAH adsorption on the soil particles antagonized volatilization, the key PAH removal mechanism by foam leaching. Therefore, this research provides relevant information for using surfactant foam to remediate heavily PAH-contaminated soils.