Adsorption behavior of levofloxacin hydrochloride on non-degradable microplastics aging with H₂O₂

Plastics pollutants, especially microplastics (MPs, <5 mm in diameter) and levofloxacin hydrochloride (Lev-HCl) often co-exist in the aquatic environment. To explore the adsorption processes and mechanisms of Lev-HCl by non-degradable MPs, in this study, H₂O₂ oxidation was used to age polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET) MPs. The results demonstrated that the equilibrium adsorption capacity increased significantly after aging, as H₂O₂-PET (1.167 mg/g) > PET (0.995 mg/g), H₂O₂-PS (1.057 mg/g) > PS (0.957 mg/g), H₂O₂-PVC (1.107 mg/g) > PVC (0.975 mg/g). After H₂O₂ aging, the hydrogen bond (-OH) was more obvious, and π-π interactions were significantly enhanced. These non-degradable MPs mainly adsorbed Lev-HCl by micropore filling (contributions: PVC 65.9%, PS 56%, PET 63.5%). The current study highlights the potential of non-degradable MPs to act as a vector for Lev-HCl in the aquatic environment, especially after H₂O₂ aging. PRACTITIONER POINTS: Adsorption behavior of Lev-HCl onto three non-degradable MPs was elucidated. The adsorption capacity increased significantly after aging for PVC, PS, and PET MPs. The hydrogen bonding and π-π interactions of H₂O₂-aged MPs were more significant. Multi-layer adsorption on non-homogeneous surfaces via micropore filling was revealed.