Abstract
Thermal desorption techniques, destined for removing organic pollutants from contaminated soil, are reviewed with some emphasis on the removal of persistent organic pollutants (POPs) and other semi-volatiles. Treatment temperature and time are the two key factors determining removal efficiency (RE), which is also influenced by soil texture, total pressure, carrier gas composition and heating rate. Polychlorinated biphenyls (PCB) are selected as the most typical as well as widespread representative of semi-volatile POPs. In the presence of oxygen, PCB is converted into PCDF, leading to a rise in total TEQ (toxic equivalency quantity) even in case total PCB is diminishing. Thermal desorption and contaminant destruction and removal efficiency can be promoted by adding additives. The main mechanism of contaminants removal is desorption/evaporation, presumably accompanied by soil-catalysed dechlorination and decomposition. Thus, the soil treated is purified, yet the remaining contaminants are partly transferred to the gas phase. Dust extraction, condensation, and adsorption are frequently used to decrease the contaminant concentration in off-gas.
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