SORPTION OF TRACE ORGANICS TO COLLOIDAL CLAYS, POLYMERS, AND BACTERIA

Sorption to dissolved macromolecules and colloidal particles may enhance the transport of environmental contaminants in subsurface environments. Some properties of sorbent and solute that may influence the adsorption behavior, especially in saturated soils with low organic C concentrations, were examined in a series of stirred reaction cell experiments, using acetophenone and ionizable 4-chloroaniline and pentachlorophenol as solutes and substituted bio- and geopolymers and suspended clays as sorbents. The distribution coefficient was most variable, by a factor of 5500 from one sorbent to another, for the anionic pentachlorophenol and least variable, by a factor of 250, for acetophenone. These variations could be ascribed to differences io binding properties of the solute and sorbent functional groups. Sorption to clay minerals was generally low and approximated sorption to an aquifer soil suspension; the exception was a local clay with 12% organic C, which increased sorption of the phenolate ion more than 30 times compared with the low-organic-C clays. The most efficient sorbent was cells of bacteria isolated from aquifer material. The linear distribution coefficient for sorption on bacteria varied from 0.5 x 10(3) mL g(-1) for acetophenone to 5 x 10(4) mL g(-1) for neutral pentachlorophenol. The implications of sorption varying with solute and sorbent functional groups on movement of solutes through an aquifer were examined by a transport model, which divides the mobile system into an aqueous and a colloidal phase. The relative mobility of pentachlorophenol associated with colloidal sorbents can vary by as much as 90% as a result of variations of the distribution coefficient to the polymers and clays examined.