Magnetic Harvesting and Degradation of Microplastics using Iron Oxide Nanoflowers prepared by a Scaled-up Procedure

Abstract

Addressing the ecological risks and human health threats posed by emerging contaminants requires the development of reproducible and scalable materials and technologies. In this context, the performance of multicore flower-shaped nanoparticles (NFs) with approximately 40 nm diameters was assessed for extracting and degrading polyethylene microplastics from cosmetics in water samples. These NFs, exhibiting cooperative magnetic behavior and high magnetic moment per particle, were scaled to grams of product in a larger reactor (1 L), yielding a 91 % mean reproducibility for structural, colloidal and magnetic properties. The NFs were directly attached to microplastic surfaces via ultrasonic treatment and separated using a permanent magnet, demonstrating removal capacities of up to 1000 mgMP/gNF under optimal conditions (pH 7, 10 mg NFs, 30 min, field strength 320 kA/m). Subsequently, microplastics in aqueous suspensions were hydrolyzed at 150 °C followed by mineralization through a Fenton-like reaction catalyzed by the NFs where reactive oxygen species produced, in the presence of H2O2, break the organic molecules. Mineralization yields ranged from 20 % to 75 % at 25 and 90 °C, respectively, with a further increase to 78 % achieved under an alternating magnetic field (60 mT, 100 kHz), obviating the need for high temperatures. These results highlight the potential of NFs and associated technologies in effectively addressing the challenges associated with emerging contaminants, offering promising avenues for environmental remediation and human health protection.