A Simple Method for Separating Phenanthrene from Soil by Cloud-Point Extraction

Contamination of soil by polycyclic aromatic hydrocarbons (PAHs) is currently widespread in urban and industrial areas, and the decontamination of PAHs remains a challenge. In addition, recovering PAHs from large volumes of soil washings is costly. Therefore, in this study, we focused on cloud-point extraction (CPE) without centrifugation, which separates PAHs from the washing solution through gravitational sedimentation. Specifically, we examined the conditions for the separation of phenanthrene (a typical PAH pollutant) from soil using CPE. After evaluating the water and phenanthrene solubilities of 23 commercially available nonionic surfactants, Brij 30 was found to be optimal. We simulated contaminated soil by adding phenanthrene to three soils with different particle sizes and varying amounts of organic matter. We examined the Brij 30 washing conditions and the effects of salt additives that promote phase separation during CPE. The addition of either sodium chloride or sodium sulfate enabled CPE at 25 degrees C, but sodium sulfate was found to be more effective at lower concentrations than sodium chloride. A phenanthrene recovery rate of 58-88% was observed for each laboratory-simulated contaminated soil by CPE using salt additives. This method is economical and effective for processing large amounts of contaminated soil.