Benzene Transport through Landfill Liners Containing Organophilic Bentonite

Abstract

The mineral surface of Wyoming bentonite was modified by replacing inorganic ions by different quaternary ammonium compounds of known molecular structure by an ion‐exchange process. The resulting organically modified bentonites (organobentonites) were evaluated for their suitability as components of compacted earthen liners for waste‐disposal sites. Varying weight percentages of an Ottawa sand, either of five types of organobentonites, untreated bentonite, and water were mixed uniformly and compacted to simulate sand‐and‐bentonite liners for waste‐disposal facilities. The hydraulic conductivities of the compacted soil specimens were measured in triplicate. The hydraulic conductivities of compacted specimens composed of 88% (by mass) Ottawa sand, 8% untreated bentonite, and 4% organobentonite were on the order of 10⁻⁸ cm/s. Benzene sorption from water to Ottawa sand, bentonite, and two of the organobentonites was measured experimentally. Benzene sorption to each organobentonite was significantly greater than benzene sorption to bentonite or Ottawa sand. The sorption and permeability data were input into a one‐dimensional solute transport model to simulate benzene transport through a conventional earthen liner and two liners containing organobentonites. Results of the simulations indicate that earthen liners containing organobentonites significantly retard the transport of benzene relative to a conventional liner.