SORPTION PROCESSES OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN ON SOIL IN THE PRESENCE OF ORGANIC LIQUIDS

Soil contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) often contains organic solvents as co-contaminants or as part of the clean-up process. The rate constants for adsorption and desorption of TCDD to Norfolk loamy sand in four organic liquids have been determined from a kinetic analysis of new experimental data. Intraparticle diffusion and external mass transfer limitations played a minor role in the mechanisms of adsorption and desorption. Screening studies have also been carried out in order to determine the efficacy of 15 single organic solvents and seven solvent mixtures in TCDD removal from Norfolk loamy sand. Low-molecular weight and low-viscosity solvents removed the most TCDD during the duration of the experiment. The addition of low-molecular weight alcohols to more viscous solvents greatly increased the capacity for TCDD removal.