Abstract: Based on the    significant impact of  natural aging on the adsorption behavior of microplastics, we selected commercial polystyrene (PS) coffee cup lids as the microplastic source. Naturally aged microplastics were obtained through an outdoor natural process. Nonylphenol (NP) was chosen as the target pollutant. The adsorption kinetic and thermodynamic characteristics of NP by PS microplastics before and after natural aging were investigated. The influence mechanism of natural aging on the adsorption of NP by microplastics was studied  by combining with various characterization methods,  such as scanning electron microscopy, specific surface area analyzer, infrared spectroscopy, and X-ray photoelectron spectroscopy. The results show that the pseudo second-order (PSO) kinetic model can well fit the kinetic process of NP adsorption by PS microplastics. Both the Henry model and the Freundlich model can well fit the adsorption isotherms of NP by PS microplastics. The adsorption mechanism of NP by PS microplastics includes partitioning,  van der Waals forces,  hydrogen bonding,  π-π interactions and hydrophobic interactions. After  aging,   the π-π interactions and hydrophobic interactions between PS and NP are weakened,  thereby inhibiting the adsorption of NP. The research results provide a theoretical basis for accurately assessing the ecological risks of PS microplastics and NP.

Key words: microplastics,  , polystyrene,  , natural aging,  , nonylphenol,  , adsorption