DISSOLUTION OF POLYCYCLIC AROMATIC-HYDROCARBONS FROM WEATHERED CONTAMINATED SOIL

Dissolution of PAHs from soil contaminated with multi-component coal t ar was investigated using a polymeric adsorbent, Tenax-TA and a nonion ic surfactant, Brij 30. Tenax created maximum concentration gradient a t the soil/water interface, thus maximizing interfacial mass transfer. Even in the presence of Tenax, the release of PAHs from the weathered soil was a very slow, noneqilibrium process. The rate-limiting step i n the release of PAH was identified as diffusional mass transfer withi n the contaminant-soil matrix. Based on model analyses, the key parame ter controlling dissolution of PAHs from the soil was found to be the diffusivities of PAHs within the soil/tar matrix. Brij 30 solution (5. 5 g/L) substantially increased the rate of PAH dissolution from the so il. The enhanced mass transfer rates of PAHs by Brij 30 were attribute d to their enhanced matrix diffusivities rather than their increased a queous solubilities. Matrix diffusivities of PAHs in Brij 30 solution increased by two orders of magnitude compared with those with Tenax. S welling of the weathered tar matrix of the soil by infiltrating surfac tant molecules was suggested as the mechanism responsible for the obse rved diffusivity enhancement. Copyright (C) 1996 IAWQ.