Mechanisms of competitive adsorption of naphthalene, phenanthrene, and benzo[ghi]perylene on UV-aged polyvinyl chloride microplastics.

This study systematically investigated the adsorption of polycyclic aromatic hydrocarbons (PAHs) (naphthalene (NAP), phenanthrene (PHE), benzo[ghi]perylene (BghiP)) on UV-aged polyvinyl chloride (PVC) microplastics (MPs) in single/coexistent systems, clarifying their competitive adsorption mechanisms via macroscopic experiments and microscopic spectroscopy. UV aging modified PVC's physical structure and enhanced its PAHs adsorption capacity. The adsorption process may be jointly controlled by physical pore filling and interfacial chemical interactions, and the relative contribution of the latter tends to increase after UV aging. In competition, adsorption affinity followed BghiP > PHE > NAP (matching hydrophobicity) with pore-filling as a key factor. Two-dimensional correlation spectroscopy (2D-COS) revealed different response priorities of CCl and CH bonds in single and competitive adsorption systems, and selective Cl-π polar coupling between polarized CCl bonds and PAH conjugated planes further governs the benzene-ring vibration response sequence: BghiP > NAP > PHE. UV aging regulates the adsorption pathways and kinetics of PAHs on PVC MPs but does not alter the competitive priority determined by PAHs' intrinsic physicochemical properties. These findings provide new insights into the composite pollution behavior and ecological risks of MPs in natural environments.