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) ofte n 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 fro m a kinetic analysis of new experimental data. Intraparticle diffusion and external mass transfer limitations played a minor role in the mec hanisms of adsorption and desorption. Screening studies have also been carried out in order to determine the efficacy of 15 single organic s olvents 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-molec ular weight alcohols to more viscous solvents greatly increased the ca pacity for TCDD removal.