Contaminants containing cationic amine moieties are regularly released into the environment posing concern over human and ecosystem exposure.  Understanding sorption of contaminant substructures is key to anticipating environmental fate. Experimental studies involving substituted anilines, benzylamines, and cyclohexanemethylamine revealed nonlinear S-shaped isotherms for sorption to Na+- and Ca2+-montmorillonite. Through the assessment of sorption isotherms using deterministic equations and nonlinear regression, the Langmuir-Freundlich equation was identified as the best fit model.  For each compound studied, h (measuring nonlinearity) and KLF (measuring affinity) were extracted from the model fit to sorption data. Trends in h values matched trends in structural criteria (e.g., cationic amine charge, electron density at the center of the aromatic ring, and hydrophobicity) that favor intermolecular p-interactions between sorbed and adjacent amines. Ongoing studies of benzylamine sorption to soils are aimed at identifying how soil properties influence the nature and extent of sorption nonlinearity.

Effect of molecular structure and soil properties on nonlinear sorption of cationic amines

245th National Meeting (2013)

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