Investigation of operating conditions for soil remediation by subcritical water

Abstract

The aim of the present research is to investigate the application of subcritical water to naphthalene removal from soils. The extraction curves obtained show no clear patterns relating the operating conditions to the extraction time. This is mainly due to anomalies that occurred during some extraction runs. The analysis of the results shows an extraction time rather constant as function of the operating conditions (pressure, temperature, and mass flow). The extraction efficiency, on the other hand, is found to increase at higher hot water flows and lower temperatures, while no dependence is recorded from the pressure or the density. The data interpretation suggests that the film transfer resistance is the extraction rate limiting factor in the flow range considered. Finally, the relationships between the extraction efficiency and the operating conditions, together with the non-achievement of 100% efficiency, seems to confirm some authors' theory on the resistance to desorption due to the presence in the soil of "resistant" and slowly desorbing fractions, constituted by immobile fluid in pores.