Soil washing feasibility at a manufacturing gas plant site.

Bench-scale treatability tests were carried out in order to evaluate performances of "physical" soil washing (particle size classification aimed at "concentrating" contamination in the fine fraction of the soil) and of a surfactant-aided soil-washing process on a brownfield soil, contaminated by high-molecular-weight Polycyclic Aromatic Hydrocarbons (PAHs). In the first case, soil was classified by wet particle separation using water, whereas it was extracted by water + surfactant in the second case. The chemical agent was selected among non-ionic synthetic and anionic biogenic surfactants (Triton X-100, Igepal CA-720, Brij-30, JBR 325), evaluating the kinetics of the desorption process and the extraction efficiency for different time of contact with soil. Surfactant concentration was selected by evaluating the extraction efficiency at the optimal time of contact. A surfactant-aided soil-washing process was tested, where soil was sequentially treated by fresh soil-washing solution (water + surfactant), and soil-washing solution was recycled for other contaminated soil. Transfer efficiency of PAHs and recovery of surfactant solution were evaluated