TRANSPORT OF HYDROPHOBIC ORGANICS BY COLLOIDS THROUGH POROUS-MEDIA .1. EXPERIMENTAL RESULTS

The transport of two hydrophobic organic compounds (HOCs), namely, phenanthrene and pyrene, through model porous media (glass microspheres and quartz sand) in the presence of a homogeneous colloid (polystyrene latex) was studied. The sorption and desorption of colloids were dependent on the pH and ionic strength of the porewater. The sorption of colloids was only partially reversible even after modifying the aqueous solution chemistry, viz. the ionic strength and pH. The organic sorption on the porous media was directly related to the behavior of colloids. In the absence of an electrolyte, the HOCs showed an early breakthrough in the presence of the colloids compared to that without colloids. At higher ionic strength, the colloids were deposited on the porous medium. Owing to their high sorbed mass on the colloids, the HOCs remained on the porous material, thus decreasing their mobility in the column. Mobile colloids in porewater have been shown to impact the transport of HOCs through porous media.