Lab-scale removal of PAHs in contaminated soil using electrical resistance heating: Removal efficiency and alteration of soil properties.

Electrical resistance heating (ERH) is a promising thermal remediation method for treating volatile soil pollutants. However, the remediation of soil contaminated by polycyclic aromatic hydrocarbons (PAHs) based on lab-scale ERH devices must be extensively studied to determine the factors affecting the remediation. Therefore, this study used a lab-scale ERH equipment to investigate the influence factors of ERH, PAH removal efficiency, and changes in soil properties through the treatment process. The results suggested that moisture and salinity were basic factors affecting electric conductive capability; heating 15 g of soil to the target temperature required at least 4 g solution of 0.1% salt. Meanwhile, higher electric strength can ensure heating efficiency and maximum temperature. The removal efficiency of PAHs, which is highly related to boiling point, was significantly affected by its benzene rings and bond structure; during 90 min ERH treatment, more than 40% of the pollutants were removed synchronously with the evaporation of water. Hence, co-boiling with water was confirmed to be the primary mechanism of ERH. The influence of the treatment on soil properties (organic matter, particle size, fertility, enzymatic activity) was limited, suggesting that soil functionality can be retained by ERH.