The environmental fate of emerging contaminants, such as pharmaceuticals and pesticides, is influenced by the sorption affinities of these compounds for soils and sediments. Cationic pyridine groups are a relevant substructure in emerging contaminants, as well as in industrial contaminants and natural organic matter. The goal of this study was to develop a predictive framework for the sorption of substituted cationic pyridines to aluminosilicate clays by establishing the influence of compound and clay structure on the extent of sorption. To this end, isotherms were obtained for the sorption of methyl- and dimethyl-pyridines to aluminosilicates (illite and montmorillonite) using a recently developed high through-put method of pulse input chromatography. Sorption coefficients (Kd values) were determined from the linear range of the sorption isotherm. Work to date on illite has shown that pyridine sorption is less than methyl-pyridine sorption, which correlates with differences in compound hydrophobicity. Further, the trend of pyridine Kd &lt; 2-methylpyridine Kd &lt;&lt; 3-methylpyridine Kd &lt; 4-methylpyridine Kd is consistent with the orientation of the pyridines on Na-illite and related steric effects. Ongoing work focuses on the determination of structural correction factors (Kxs) that account for the excess sorption exhibited by substituted pyridines in comparison to the base structure, pyridine. These factors, which are a function of substituent size, its location on the pyridine ring, and synergistic/antagonistic effects of multiple substituents, can be used to predict the Kd values of larger contaminants possessing cationic pyridine groups.

Sorption of substituted pyridines to aluminosilicate clays: Building predictive models for cationic amines

253rd National Meeting (2017)

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