Thermal Desorption of Hazardous and Toxic Organic Compounds from Soil Matrices

Thermal desorption is a physical separation process, although chemical transformations may occur, depending on thermal stability of the organic compounds and operating temperature. 1 Nearly complete desorption of many organic pollutants from soil is possible for relatively small desorption oven residence times at temperatures near the boiling point of the pollutant. The principal advantage of the technique is that moderate temperatures, and therefore moderate energy inputs to the system with an inexpensive carrier gas such as CO 2 exhaust or N 2 , are sufficient to place the organic compounds into the vapor phase. Subsequent incineration of the organic compounds in the vapor phase could then be accomplished in an afterburner. 2 This two-stage technique requires significantly less energy input and therefore less cost than direct incineration of the entire soil mass. It is, therefore, intended to be considered as an alternative to incineration for soil cleanup, and is in fact “the” method of choice. It is important that knowledge of the thermal decomposition behavior of hazardous organic materials is first obtained under controlled, environmentally safe laboratory conditions before expensive scale-up and permanent construction. 3-5 Then, many problems associated with full-scale thermal destruction may be avoided. Conventional equipment such as an asphalt kiln or a rotary kiln may be utilized during full-scale operations.