Effect of thermal pre-treatment on the availability of PAHs for successive chemical oxidation in contaminated soils

This is the premier study designed to evaluate the impact of thermal pre-treatment on the availability of polycyclic aromatic hydrocarbons (PAHs) for successive removal by chemical oxidation. Experiments were conducted in two soils having different PAH distribution originating from former coking plant sites (Homécourt, H, and Neuves Maisons, NM) located in northeast of France. Soil samples were pre-heated at 60, 100, and 150 °C for 1 week under inert atmosphere (N₂). Pre-heating resulted in slight removal of PAHs (<10 %) and loss of extractable organic matter (EOM). Then, these pre-heated soil samples were subjected to Fenton-like oxidation (H₂O₂ and magnetite) at room temperature. Chemical oxidation in soil without any pre-treatment showed almost no PAH degradation underscoring the unavailability of PAHs. However, chemical oxidation in pre-heated soils showed significant PAH degradation (19, 29, and 43 % in NM soil and 31, 36, and 47 % in H soil pre-treated at 60, 100, and 150 °C, respectively). No preferential removal of PAHs was observed after chemical oxidation in both soils. These results indicated the significant impact of pre-heating temperature on the availability of PAHs in contaminated soils and therefore may have strong implications in the remediation of contaminated soils especially where pollutant availability is a limiting factor.