Differential morphological and physicochemical responses of polyvinyl chloride and Polyamide-12 micro- and nanoplastics to Fenton oxidation

Oxidative aging can modify the physicochemical properties of micro- and nanoplastics (MNPs), altering their environmental behavior and potential biological interactions. In this study, we investigated how a hydroxyl radical–driven Fenton oxidation process affects the morphology, size distribution, and surface chemistry of polyvinyl chloride (PVC) and polyamide-12 (PA-12) MNPs using multimodal characterization. Oxidation caused extensive aggregation and surface restructuring in PVC, whereas PA-12 retained greater colloidal stability but showed clear evidence of surface oxidation. Both polymers exhibited increases in oxygen-containing functional groups, along with polymer-specific elemental loss consistent with dechlorination in PVC and amide degradation in PA-12. These transformations indicate that oxidative aging can generate nanoscale debris, increase surface reactivity, and shift particle behavior in ways relevant to environmental fate and human exposure pathways. The results emphasize the importance of including chemically aged MNPs, rather than only pristine particles, in studies examining transport, sorption, and toxicological potential, particularly in contexts where advanced oxidation treatments are used. Overall, this work highlights polymer-specific differences in oxidative transformation and provides a foundation for future studies that connect degradation chemistry with exposure and risk assessment. • PVC and PA-12 micro/nanoplastics were oxidized via Fenton reaction to mimic aging. • PVC aggregated and roughened, while PA-12 stayed well-dispersed after oxidation. • Oxidized PVC size rose from ~350 nm to ~800 nm, increasing polydispersity. • PVC chlorine decreased and PA-12 nitrogen decreased after oxidation. • FTIR showed hydroxyl, ether, and carbonyl group formation from backbone oxidation.