Enhancement of Polynuclear Aromatic Hydrocarbon Desorption by Complexing Agents in Weathered Soil

Abstract

Successful remediation of hydrophobic organic contaminants, such as polynuclear aromatic hydrocarbons (PAHs), at contaminated sites has been hindered by slow desorption kinetics. This work explored the use of complexing agents, such as sodium citrate, EDTA, sodium oxalate, and tetrasodium pyrophosphate, in enhancing the desorption of 16 PAH compounds from soil collected at a former manufactured gas plant (MGP) site. Based on equilibrium and kinetic experiments, it was evident that both the rate a nd extent of PAH desorption can be significantly enhanced using complexing agents. Efficacy of the desorption process depended on such factors as the nature of the PAH, type of ligand, and time allowed for reaction. It was hypothesized that complexing agents act by disrupting humic–metal–mineral linkages in the soil, resulting in the mobilization of soil organic matter (SOM) and colloids. This facilitates the solubilization of sorbed PAH molecules.