John Wiley & Sons, Ltd.

Sorption of polycyclic aromatic hydrocarbons to polystyrene nanoplastic

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Microplastic has become an emerging contaminant of global concern. Bulk plastic can degrade to form smaller particles down to the nano‐scale (<100 nm), which are referred to as nanoplastics. Due to their high surface area, nanoplastic may bind hydrophobic chemicals very effectively, increasing their hazard when such nanoplastics are taken up by biota. Here we report distribution coefficients for sorption of polycyclic aromatic hydrocarbons (PAH) to 70 nm polystyrene in freshwater, and PAH adsorption isotherms spanning environmentally realistic aqueous concentrations of 10‐5 to 1 µg/L. Nano‐polystyrene aggregate state was assessed using dynamic light scattering. The adsorption isotherms were non‐linear and the distribution coefficients at the lower ends of the isotherms were very high with values up to 109 L/kg. The high and non‐linear sorption was explained from π‐π interactions between the planar PAH and the surface of the aromatic polymer polystyrene, and was higher than for micrometer sized polystyrene. Reduction of nano‐polystyrene aggregate sizes had no significant effect on sorption, which suggests that the PAH could reach the sorption sites on the pristine nanoparticles regardless of the aggregation state. Pre‐extraction of the nanopolystyrene with C18 polydimethylsiloxane decreased sorption of PAH, which was explained from removal of the most hydrophobic fraction of the nanopolystyrene. This article is protected by copyright. All rights reserved

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