Coupled Oxidation and Fragmentation of Synthetic Fabrics in Chlorinated Environments: A Hidden Source of Microplastics and Disinfection Byproduct Precursors

Chlorination is widely employed in medical and water treatment systems; however, its impact on polymer aging and the coupled release of microplastics (MPs) and dissolved organic matter (DOM) remains poorly understood. Existing studies have primarily focused on polymer degradation under UV irradiation or thermal conditions, largely overlooking the roles of active chlorine species and unique oxidative pathways present in practical disinfection environments. Here, we directly simulated representative chlorination conditions to investigate the degradation kinetics of polyethylene terephthalate (PET), polyamide 6 (PA6), and a model blended textile (PU–PA6). A multi-scale analytical framework combining field-emission SEM (FESEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and three-dimensional excitation–emission matrix fluorescence spectroscopy combined with parallel factor analysis (3D-EEM–PARAFAC) was established to elucidate the mechanistic links among surface oxidation, chain scission, and DOM optical property evolution. Our results reveal a previously unreported, material-dependent “two-stage degradation” mechanism in the blended system: the PU soft segments undergo rapid hydrolytic cleavage, triggering accelerated MPs release, followed by progressive PA6 hard-segment fragmentation that drives DOM evolution from low-molecular-weight amine-like species toward humic-like, high-molecular-weight components. This interfacial degradation process governs MPs size distribution and generates abundant submicron fragments. Unlike UV photochlorination mechanisms, which involve 1O₂-mediated aromatic rearrangements, chlorination in this study is characterized by Cl•/ClO•-initiated chain scission and enrichment of oxygen-containing functional groups, without observable surface reconstruction. Importantly, our findings demonstrate that even in the absence of light or thermal input, chlorination alone can substantially induce secondary MPs formation and produce DOM with high aromaticity and strong potential as disinfection byproduct (DBPs) precursors. This study extends the paradigm of polymer aging research by proposing a chlorination-driven, interface-mediated mechanism for coupled MPs-derived DOM (MPs–DOM) release, offering critical insights for DBPs risk assessment and control in medical and drinking water disinfection scenarios.