Electrochemical oxidation of polyethylene microplastics: from efficient removal to sustainable valorization

Abstract

The persistence of polyethylene microplastics in aquatic systems has become one of the most urgent environmental challenges of the twenty-first century, driven by their extreme chemical inertness and resistance to oxidative degradation. This work demonstrated the electrochemical oxidation of polyethylene microspheres (1–4 μm) using niobium-supported boron-doped diamond anodes, achieving removal efficiencies of up to 98% within only three hours of treatment. By coupling complementary analytical techniques – including pyrolysis coupled with gas chromatography and mass spectrometry, turbidity monitoring, non-purgeable organic carbon analysis, ion chromatography, and scanning electron microscopy – a comprehensive, multi-scale evaluation of degradation pathways was achieved. The results revealed that electrochemical processes not only fragmented and reduced polyethylene but also selectively generated low-molecular-weight carboxylic acids, particularly formic and acetic acid. This discovery highlights a paradigm shift: instead of aiming exclusively at full mineralization into carbon dioxide, electrochemical oxidation can be steered toward the production of value-added chemicals, positioning microplastic remediation within the broader framework of circular economy and resource recovery. Radical scavenging experiments confirmed hydroxyl radicals as the dominant species driving polyethylene degradation. The absence of persistent solid residues, the rapid and near-complete removal of microplastics, and the concurrent generation of economically relevant intermediates underscore the dual environmental and technological significance of boron-doped diamond electrodes. These findings advanced the emerging concept of organic electro-refineries, establishing electrochemical oxidation as a transformative approach for mitigating microplastic pollution while simultaneously creating sustainable routes for chemical valorization of plastic waste.