Probing molecular interactions between polycyclic aromatic hydrocarbons and metal cations in solution and at hydrated mineral surfaces
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One group of hydrophobic organic contaminants currently receiving considerable attention are PAH, probably the most widespread of all environmental chemical contaminants. A comprehensive understanding of interactions between co-contaminants such as PAH and metals would be useful in elucidating the biogeochemical behavior of these types of contaminant mixtures. An NSF project, which seeks to determine whether cation- interactions can be important in biogeochemical systems, was presented. Naphthalene, pyrene, perylene, and benzene were used as representative aromatic ring systems. These compounds were selected to cover a wide range of hydrophobicities/solubilities and because of their unique spectroscopic characteristics. Linear sorption isotherms for naphthalene and pyrene were observed for all minerals tested, thus allowing for comparison using simple distribution coefficients (Kd) normalized by the mineral surface areas. The one with the highest exchange capacity (vermiculite) had the highest Kd values, while the mineral with the smallest exchange capacity (kaolinite) had the lowest Kd values.