Remediation of phenanthrene contaminated soil by coupling soil washing with Tween 80, oxidation using the UV/S2O82- process and recycling of the surfactant

Surfactant-enhanced soil washing was applied to phenanthrene (PHE) contaminated soil, followed by a sulfate radical based advanced oxidation process. In this study, soil washing experiments were conducted with the nonionic surfactant Tween 80 (TW 80) and the influence of washing temperature, TW 80 concentration and liquid to soil ratio on the removal of PHE was investigated. The maximum PHE removal of 90.0% was achieved with TW 80 (15 g/L) and a 10:1 (mL/g) liquid to soil ratio at 20 degrees C. Furthermore, the UV/S2O82- process was used for the selective oxidation of PHE from the effluent and the recovery of TW 80. The regenerated effluent was re-employed in the soil washing process and the results showed that the removal efficiency was almost the same as with fresh surfactant solution. The reaction mechanism of the UV/S2O82- process was also investigated, the possible intermediate products were detected by liquid chromatography-mass spectrometry (LC-MS) and the corresponding degradative pathway of the target contaminant was proposed. Overall, the result indicates that soil washing with TW 80 and the subsequent selective UV/S-2 O-8(2-) oxidation process may provide a potential option for the remediation of soil contaminated with polycyclic aromatic hydrocarbons (PAHs).