Determination of the trichloroethylene diffusion coefficient in water

Trichloroethylene (TCE) is a halogenated aliphatic organic compound frequently detected as pollutant in soils and ground water. To study the fate of TCE in water and to devise effective remediation strategies, a series of advection-diffusion (dispersion) models, where the diffusion coefficient of TCE (D-TCE) is an important parameter, have been developed. However, D-TCE in water has never been experimentally determined and only theoretical values ( similar or equal to 1x10-5 cm(2) s(-1) at 25 degrees C) are present in the literature. A new method based on the Taylor dispersion technique, which allows to measure D-TCE in a broad range of temperature and, in principle, in any solvent is presented. At 25 degrees C D-TCE= 8.16 +/- 0.06x10-6 cm(2) s(-1) and the value increases almost linearly with the temperature, while, in the limit of the experimental error, is independent from [TCE] for dilute solutions. From the temperature dependence of D-TCE, it was possible to calculate the specific TCE fitting constant in the well-known Wilke and Chang theoretical relation and the activation energy of the diffusion process through the Arrhenius plot.