Remediation of Polycyclic Aromatic Hydrocarbon-Contaminated Soils by Nonionic Surfactants: Column Experiments

Using flushing solutions with different nonionic surfactants, this study investigated the remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soils with different organic carbon contents. Naphthalene and anthracene are the two delegates of PAHs used in the study. Contaminated soil packed in a stainless-steel column was continuously flushed with a surfactant solution at room temperature at a constant flow rate. Results are of practical interest in developing effective surfactant remediation technology applied in ex situ or in situ PAH-contaminated soils. Nonionic surfactants can be used effectively to remediate hydrophobic organic compound-contaminated soils. For soil with 500 ppm PAH, enhanced solubility reached as high as 30 times that of water solubility. Compared with the efficiency in using sodium nitrate solution, desorption efficiencies of Tween 80 (T80) and Triton X-100 (TX-100) solutions in the naphthalene-contaminated soil were 2.4and 2.0-fold higher, respectively. For different soils contaminated with anthracene, which is more hydrophobic than naphthalene, enhanced desorption efficiencies were 11 and 24 times greater than that of sodium nitrate solution when using T80 in Kun-Shan and Yun-Nun soils, respectively, and 14 and 27 times greater when using TX-100. It should be noted that the surfactant may cause colloid mobilization and then clog soil pores; therefore, the possibility of clogging should be taken into account during site remediation. Result demonstrates that the concentration of 0.1% of T80 and TX-100 is suitable for soil remediation in the field. It was also found that the sorption of surfactants to the soil affects the time and efficiency of remediation.