and Reliability Act (CERCLA). The aromatic fraction of This study investigates the clay-aromatic interactions with a gasoline's hazardous constituents includes benzene, toluene, view to the use of bentonite clay for binding benzene, toluene, ethylbenzene, and xylene (commonly called the BTEX comethylbenzene, and o-xylene (BTEX compounds) in contaminated pounds). soils. BTEX compounds are the most toxic aromatic constituents Today, several options such as chemical degradation, soil of gasoline present in many underground storage tanks. Modified flushing, thermal treatment, soil vapor extraction, and bio-(organophilic) and ordinary bentonites are used to remove these degradation are available to treat aromatic wastes and the organics. The organophilic bentonites are prepared by replacing matrices they contaminate, particularly soils (3). The appli-
the exchangeable inorganic cations present in bentonite particles cation of these techniques entails high costs. In addition, the with a quaternary ammonium salt. Various clay-to-soil ratios were applied to determine the efficiency of the modified bentonite in present methods of disposing of these wastes (i.e., placement enhancing the cement-based solidification/stabilization (S/S) of in drums for burial, pooling for evaporation, and storage in BTEX contaminated soils. Toxicity characteristics leaching procelined disposal sites) are not reliable and do not provide a dure (TCLP) tests were performed on soil samples to evaluate the permanent solution for containment. It is essential that a leaching of the organics. In addition, X-ray diffraction analyses safe and cost-effective cleanup process be developed as an were conducted to assess the changes in the basal spacing of the alternative to the current treatment and disposal practices. clays as a result of their interaction with BTEX compounds. The One such treatment process could be developed using findings of this study reveal that organophilic bentonite can act modified (organophilic) clays to adsorb aromatic comas a successful adsorbent for removing the aromatic organics from pounds from contaminated soils and prevent them from polcontaminated soil. Thus, this material is viable for enhancing the luting the groundwater. Research conducted (4-6) on the performance of cement-based S/S processes, as an adsorbent for adsorption of organics by clays indicates that quaternary petroleum spills, and for landfill liners and slurry walls. α§ 1997 Academic Press ammonium cations such as hexadecyltrimethylammonium Key Words: bentonite; aromatic compounds (BTEX); organo-(HDTMA) interact with clays and replace the exchangeable philic clay; cement-based solidification/stabilization (S/S) proinorganic cations on their surfaces, forming a stationary cess; basal spacing; XRD analysis.
phase in the clay particles. In addition, as a result of the larger size of the HDTMA cations compared with that of the replaced cations, the interlamellar distance (basal spac-