Adsorption of levofloxacin hydrochloride by microplastics with or without oxygen functional groups

Functional groups can alter the properties of microplastics (MPs), thereby affecting their adsorption of antibiotics.This study selected oxygen free plastics polyvinyl chloride (PVC), polystyrene (PS), and oxygen containing plastics polyethylene terephthalate (PET) as representative MPs to investigate the adsorption behavior of MPs on levofloxacin hydrochloride (LEV) before and after ultraviolet (UV) aging.The research results indicated that the adsorption capacity of PET before and after aging was the strongest (from 0.430 to 0.859 mg/g), followed by PVC (from 0.406 to 0.733 mg/g) and PS (from 0.326 to 0.526 mg/g). After aging, PVC and PS generated C = O, and –OH functional groups, and the content of PET -COOR and –OH has increased. As the pH increases from 2 to 12, the saturated adsorption capacity of MPs first increased and then decreased. The adsorption capacities were suppressed with the presence of NaCl. Pb2+ and Cd2+ inhibited adsorption, as the complexation of oxygen-containing functional groups with metals reduced the saturation adsorption. In the mechanism calculation, the contribution of microporous filling was the most, while the contribution of functional groups was small. The increase of oxygen-containing functional groups enhanced the electrostatic interaction and hydrogen bond.