AIR STRIPPING OF HYDROCARBON-CONTAMINATED SOILS - INVESTIGATION OF MASS-TRANSFER EFFECTS

Bench-scale experiments were carried out to simulate air stripping of soil contaminated with a semi-volatile hydrocarbon, n-octane. The expe riments were conducted in an 8-cm diameter glass column, packed with t wo types of packings: glass beads to represent non-adsorbing materials and soil particles to represent adsorbing materials. Effects of gas s uperficial velocity, particle size and soil organic matter on the colu mn outlet concentration and temperature profile were studied. Nitrogen adsorption/desorption experiments were performed to establish the des orption characteristics of the soil sample. Additionally, a mathematic al model is presented which treats the interphase contaminant transpor t as a mass transfer rate-limited process. The predictions from the ma thematical model are shown to be in good agreement with the experiment al results. Most importantly, the numerical results show that, contrar y to the common assumption of local equilibrium, the interphase contam inant transport (from the sorbed to the vapour phase and/or from the l iquid to the vapour phase) is mass transfer controlled.