A Comparison of the Adsorption Behavior of Bisphenol A by Microplastics From Different Sources

Microplastics (MPs) are pervasive carriers of aquatic pollutants, yet their adsorption behaviors, especially after environmental aging, remain incompletely understood. This study systematically investigated the adsorption of bisphenol A (BPA) onto four common MPs: polyvinyl chloride (PVC), polyolefin resin (PO), polypropylene (PP), and polyethylene (PE), and their ultraviolet (UV)-aged counterparts. We found that UV aging universally enhanced the adsorption capacity, with increases of up to 19% compared to pristine MPs. Aged PVC (A-PVC) exhibited the highest overall affinity. Adsorption mechanisms diverged: PO, PP, A-PVC, and A-PE followed multilayer chemical adsorption, whereas PE, A-PO, and A-PP exhibited monolayer chemical adsorption; only pristine PVC followed monolayer physical adsorption. Importantly, UV aging altered these adsorption mechanisms by modifying the surface physicochemical properties of MPs. Environmental factors significantly modulated adsorption, which increased with contact time and initial BPA concentration but decreased with higher MPs dosage and pH, peaking at 25°C and remaining unaffected by salinity. These results reveal that UV aging not only intensifies adsorption capacity but can also alter the fundamental adsorption mechanism, thereby reshaping the role of MPs as transport vectors for endocrine-disrupting compounds like BPA in aquatic environments. This study provides crucial insights for ecological risk assessment of coexisting MPs and organic pollutants.