Sorption kinetics and thermodynamics of trichloroethylene in humic acid

To identify the resistant fraction for the desorption of trichloroethylene (TCE) from humic substances and to quantity the sorption/desorption rates, time courses for the TCE sorption to compressed humic acid disks were investigated. The gravimetric experiments have been used to study the sorption/desorption of TCE in Aldrich humic acid. The averaged apparent diffusivities of TCE in humic acid are 8.7 × 10−9 cm2/s for sorption and 2.6 × 10−9 cm2/s for desorption at 25 °C. The activation energies are 11.0 and 10.7 kcal/mol for the sorption and desorption process, respectively. The sorption rate of TCE in the humic acid increased with increase of the system temperature. The sorption of TCE into humic acid was reversible and controlled mainly by diffusion. These findings offer a better understanding of the sorption kinetics of chlorinated volatile organic compounds associated with humic acid and soil organic matter.