The sorption behavior of triclosan on microplastics: aging effects and mechanisms

• Various aging processes significantly altered surface morphology of MPs. • Aging increased TCS sorption capacity on PE but reduced it on PP, while changes in PS capacity varied depending on the aging method. • TCS sorption on aged MPs was mainly driven by hydrophobic and electrostatic interactions. • Oxygen-containing functional groups and the surface charge of MPs are key factors influencing TCS sorption. The interactions between microplastics (MPs) and organic pollutants have recently emerged as a critical area of research. While MPs aging is inevitable in natural ecosystems, the mechanisms underlying the heterogeneity of MP aging and its impact on pollutant sorption remain poorly understood. This study investigates the sorption behavior of triclosan (TCS) on both pristine MPs, including polyethylene (PE), polypropylene (PP), and polystyrene (PS), and aged MPs subjected to oxidative aging (Fenton oxidation, heat-activated potassium persulfate, and river-abrasive wear). Aging significantly altered MP sorption capacity. Aged PE exhibited reduced sorption, whereas aged PP showed an increase. Structural analysis revealed that aging modified MP surface morphology, hydrophobicity, and surface charge density, accompanied by an increase in oxygen-containing functional groups. Density functional theory (DFT) calculations further demonstrated that these changes influenced intermolecular interactions, including hydrogen bonding, van der Waals forces, and electrostatic effects. Spectroscopic analysis and DFT computations confirmed that hydrophobic and electrostatic interactions primarily govern the sorption of MPs and TCS. This study advances our understanding of MP–pollutant interactions and provides insights into the ecological risks associated with composite pollution.