Electrochemical behavior and electro-aging of microplastics: interaction with enrofloxacin and Pb.

Microplastic in wastewater and its aging change the fate of pollution transformation during electrochemical treatment, making the treatment effectiveness and environmental risks unpredictable. This study systematically revealed the effect of microplastics on the fate of enrofloxacin (ENR) and lead (Pb) during the electrochemical process, associated aging phenomena and mechanisms of the microplastics. The presence of polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) microplastics affected electron transfer at the electrode interface and electrogenerated reactive oxygen species (ROS). These effects reduced ENR anodizing efficiency by a maximum of 23.67 % compared to the control, and lowered the Pb inhibition threshold for ENR anodizing. PS and PVC, in addition to PP, also impeded the rate of Pb cathodic reduction. Significant microplastic aging occurred during electrochemical processes. Although the sequence of functional group changes varied between anodic and cathodic treatments, both increased oxygen-containing groups and altered electrochemical properties. Meanwhile, ENR promoted microplastic aging via electrogenerated ROS, while Pb inhibited it. Additionally, Pb compounds deposited on microplastics during cathodic reduction, leading to increased Pb re-release and inhibited ENR oxidation when the microplastics were transferred to the anode. This study deepens understanding of environmental behavior and microplastic aging in treatment systems.