title: Sorption of nonionic organic solutes from water to tetraalkylammonium bentonites: Mechanistic considerations and application of the Polanyi-Manes potential theory.
abstract: This work describes the role of quaternary alkylammonium amendment length on sorption mechanisms of modified bentonites for four nonionic organic compounds; benzene, carbon tetrachloride, TCE, and 1,2-DCB. Tetramethyl to tetrabutyl alkyl amendments were studied and an important mechanistic shift occurred at the propyl chain length for all four solutes studied. Three- and four-carbon-chain functional groups on the ammonium cation resulted in a linear, rather than a curvilinear isotherm. The uptake on tetrapropyl and tetrabutylammonium clays was noncompetitive in binary systems and showed negligible sensitivity to temperature variations, indicating the linear isotherms describe a partitioning uptake mechanism for these organoclays. The adsorptive organoclays (tetramethyl and tetraethylammonium clays) were fit with the Dubinin-Radushkevich equation to investigate the application of the Polanyi-Manes potential theory to organoclay adsorption. It was found that TCE and carbon tetrachloride, with similar physical and chemical characteristics, behaved according to the Polanyi-Manes theory. Benzene showed an anomalously high adsorption volume limit, possibly due to dense packing in the adsorption space or chemisorption to the short chain alkyl groups.
authors.affiliation: Department of Civil and Environmental Engineering, University of Virginia, P.O. Box 400742, Charlottesville, VA 22904-4742, USA.
authors.forename: Megan
authors.initials: M
authors.lastname: Fuller
authors.forename: James A
authors.initials: JA
authors.lastname: Smith
authors.forename: Susan E
authors.initials: SE
authors.lastname: Burns