Magnetic capture and process-oriented upcycling of PET nanoplastics enabled by mesocrystalline iron oxide nanoflowers

Nanoplastics are widely recognized as persistent environmental pollutants that require removal from aquatic systems. Here, we propose an alternative strategy based on the functional valorization of polyethylene terephthalate (PET) nanoplastics through their integration into magnetic hybrid materials. Mesocrystalline iron oxide nanoflowers (NF) were synthesized via a rapid microwave-assisted polyol route, producing multicore magnetic architectures capable of efficiently capturing dispersed PET nanoplastics. The NFs exhibit a capture capacity of up to 10,000 mg of NanoPET per gram of magnetic collector, enabling rapid magnetic harvesting of nanoplastics from aqueous media. Instead of treating the collected plastic as waste, the captured NanoPET is incorporated into PET/NF hybrid materials, where the nanoplastics become a structural and functional component of the system. FTIR analysis reveals the interfacial interactions responsible for NanoPET/NF formation, confirming the adhesion of the nanoflowers to the PET surface. The resulting NanoPET/NF combine magnetic recoverability (v s= 1.35 × 10 −4 m/s with ∇H = 24 T/m) with adsorption and catalytic functionalities, exhibiting adsorption capacities of 25 mg/g for methylene blue and achieving a 11% higher degradation than at 25 °C under alternating magnetic field activation (200 kHz, 24 kA/m), through localized magnetic heating without bulk heating of the medium. The sample retained both their magnetic recoverability and catalytic activity over multiple reuse cycles. This work provides a pathway to valorize plastic nanowaste into recoverable systems for magnetically-assisted advanced water treatment.