Desorption kinetics of volatile organic contaminants from aquifer materials

Sorption and desorption of volatile, halogenated hydrocarbons from aquifer material are investigated using a frontal gas chromatography technique. One of the aquifer materials studied was silty sand with 0.15% organic C from the Santa Clara Valley, California; the other was a fine grained sand containing 0.02% organic C from Borden, Ontario. The time to recover 90% of the hydrocarbon was significantly higher for the water containing samples than for the dry solids despite the fact that the dry solids sorbed much more strongly. These findings suggest that mass transfer limitations are due to diffusion through the aqueous phase in the intraparticle domain, and that remediation of contaminated soil using soil air extraction techniques is typically operated under nonequilibrium conditions. Removal of the solid-bound contaminants is much slower than the concentration decrease in the mobile phase. -from Authors