Partitioning Behavior of Trichloroethlyene in Cyclodextrin–Water–Granular-Activated Carbon Systems

Abstract

The purpose of this study was to collect experimental data and develop a mathematical model describing the equilibrium phase distribution of a common organic chemical, trichloroethylene (TCE), among cyclodextrin (CD), water, and granular-activated carbon (GAC). Batch tests and a modified linear regression model were applied to assess the partitioning behavior in this multiphase (CD pseudophase–water–GAC) system. Results showed that CD lowers TCE availability for dissolution in water and adsorption to GAC, demonstrated by reduced TCE partitioning to GAC with increasing CD concentration. Presence of CD does not significantly affect the distribution of TCE between water and GAC. Rescaled Freundlich adsorption isotherms for the GAC–water (CD-free) and GAC–CD solution systems were not significantly different and overlapping normalized isotherms were observed. This is an important indicator that the distribution of TCE within the dissolved and GAC phase is independent of the presence of CD. It further indicates that the distribution within CD–water–GAC systems can be aptly described by standard TCE Freundlich isotherms for water–GAC dual-phase systems and water–CD partitioning coefficients. A linear relationship between the logarithms of apparent Freundlich isotherm coefficients and solubility enhancement factors (R2=0.99) was verified theoretically and experimentally. This study provides important information to optimize the design, assess the performance of GAC treatment systems containing CD solutions, and possibly aid in prediction the lifetime of GAC in a full-scale operation.