Sorption of polycyclic aromatic hydrocarbons to mineral surfaces

S. Müller, K. U. Totsche, I. Kögel-Knabner

Research output: Contribution to journalArticlepeer-review

100 Scopus citations

Abstract

Minerals contribute crucially to the retention of polycyclic aromatic hydrocarbons (PAHs) in subsurface environments. To investigate the sorption behaviour to mineral surfaces batch sorption experiments were conducted using three PAHs (phenanthrene, pyrene, benzo(a)pyrene) and three mineral sorbents that were representative of subsurface materials (quartz, goethite-coated quartz, quartz-montmorillonite mixture). Sorption kinetics showed an instantaneous, considerable PAH sorption to all minerals, except for phenanthrene sorption to quartz at small aqueous-phase concentrations. Apparent sorption equilibrium was achieved after 4 hours of contact time. The sorption characteristics were fitted to six isotherm models by applying Monte Carlo simulation and nonlinear regression. Best-fit models were obtained by a model discrimination approach. Phenanthrene and pyrene sorption were best described by the Freundlich isotherm model, with the exception of phenanthrene sorption to quartz (linear isotherm). Good fit results for quartz were also obtained for the combined linear-Freundlich isotherm. Benzo(a)pyrene sorption to all minerals followed linear high-affinity isotherms. In the case of phenanthrene and pyrene, the Monte Carlo simulations resulted in mean values with small standard deviations for the isotherm parameters, indicating a negligible influence of the experimental uncertainties on the accuracy of the fitted parameters. For phenanthrene, (i) linear isotherms to quartz and goethite-coated quartz and (ii) a nonlinear concave-shaped isotherm to quartz-montmorillonite, assuming a pore-filling process to micropores formed by clay aggregates, were confirmed. For pyrene, nonlinear convex-shaped isotherms to the mineral surfaces were assessed. A specific sorption affinity of pyrene to the goethite surface indicated a non-covalent cation-π interaction. Small sorption affinities to quartz-montmorillonite support an unfavourable partitioning into the adjacent water.

Original languageEnglish
Pages (from-to)918-931
Number of pages14
JournalEuropean Journal of Soil Science
Volume58
Issue number4
DOIs
StatePublished - Aug 2007

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