Chlorine release induced by contact electrification between polyvinyl chloride microplastics and moist air

Polyvinyl chloride (PVC) microplastics (MPs) are prevalent in the atmosphere and, as they migrate, inevitably interact with flowing moist air. Despite this, our understanding of the surface chemistry of MPs remains limited. In this study, friction experiments were conducted using a custom-designed model to simulate the interaction between PVC MPs and moist air. The physicochemical changes and reactive species were systematically characterized using ion chromatography, electron spin resonance, and X-ray photoelectron spectroscopy. Results demonstrate that PVC MPs release chloride ions when subjected to friction with moist air in dark conditions. The release of chloride ions is primarily driven by the reduction of C Cl bonds, induced by hydrogen radicals generated through electron transfer from water to the polymer during friction. Furthermore, these released chloride ions are subsequently converted into atomic chlorine due to the generation of hydroxyl radicals, a process facilitated by contact electrification between water vapor and the polymer under solar irradiation. Our findings suggest that PVC MPs could act as a source of reactive chlorine, influencing redox processes and potentially impacting air quality in the atmosphere. • PVC microplastic friction with moist air induces contact electrification. • PVC microplastic releases and accumulates chloride during moist air friction. • PVC microplastic releases chloride via •H generation during moist air friction. • PVC microplastic friction with moist air promotes reactive chlorine formation under sunlight.