REMOVAL OF SEMIVOLATILES FROM SOILS BY STEAM STRIPPING .2. EFFECTS OFDIFFUSION KINETICS

The validity of steady-state models for steam stripping of volatile an d semivolatile organic compounds (VOCs and SVOCs) is explored within t he framework of a simple one-compartment approach. The steady-state ap proximation appears to be valid after a relatively short warming phase . A mathematical model for the in-situ steam or hot-air stripping of v olatile and semivolatile compounds from vadose zone soils at hazardous waste sites is presented. The model assumes that the pneumatic permea bility of the soil is constant and isotropic, and that the adsorption isotherm of the contaminant on the soil is linear. Diffusion kinetics are included in the model; it is assumed that the contaminant is adsor bed in porous low-permeability lenses of clay, till, or silt, and must diffuse to the surfaces of these structures in order to be removed by the advecting vapor phase. The dependence of results on model paramet ers is explored.