Influencing Mechanisms of Exogenous and Endogenous Dissolved Organic Matter on the Adsorption of Tetracycline on UV ‐Light Aged Microplastics

Abstract Microplastics (MPs), as emerging pollutants, may interact with frequently detected antibiotics and ubiquitous dissolved organic matter in groundwater. In this study, the influencing mechanisms of humic acid and microplastic‐derived dissolved organic matter (MP‐DOM) on tetracycline (TC) adsorption onto UV‐light aged MPs were investigated through batch experiments and microscopic characterization. Compared with the pristine polyethylene (PE) and polystyrene (PS), the specific surface areas of UV‐light aged polyethylene (U‐PE) and polystyrene (U‐PS) increased by 1.35 and 1.46 m 2 /g, respectively. There was a release of small hydrophilic MP‐DOM containing benzene rings from U‐PS, and the released amount was positively proportional to salinity and solution pH. PS interacts with the aromatic structure of TC through π–π interactions. The main adsorption mechanism of TC to PE was van der Waals force, and aging of MPs resulted in the appearance of hydroxyl groups, which can form H‐bonds with the amide groups of TC. Exogenous and endogenous DOM could form complexes with TC or compete for active adsorption sites on MPs. The findings of this study are helpful for the assessment of the environmental impacts of MPs after UV‐light aging and antibiotic pollution control.