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Synergetic polyethylene microplastic photodegradation over core–shell TiO2/biochar: unraveling the dual roles of interfacial bonding and biochar-derived DOM
Original title: Synergetic polyethylene microplastic photodegradation over core–shell TiO2/biochar: unraveling the dual roles of interfacial bonding and biochar-derived DOM
Summary
Scientists created a new material from walnut shell waste and a light-activated compound (TiO2) that breaks down plastic mulch film fragments in soil almost 3 times faster than previous methods, shrinking them from visible specks to nearly invisible pieces in less than two days. Importantly, the breakdown products were tested and found to be low-toxicity, meaning this approach could help clean up farmland plastic pollution without creating new harmful substances that might enter our food and water. While this is early-stage lab research, it points toward practical, waste-based solutions for reducing the microplastics that end up in soil, crops, and eventually our
Abstract The pervasive accumulation of polyethylene (PE) microplastics (MPs) from agricultural mulch films represents a critical threat to soil health and ecological stability. In this study, we developed a sustainable “waste-to-resource” strategy by engineering biomass-derived biochar/core–shell TiO2 (BC/CST) composites for the efficient remediation of PE-MPs. Walnut shell biochar-optimized core–shell structural TiO2 composites (12TJBC) achieved superior performance, reducing PE-MPs size from 500 μm to <70 μm within 40 h, outpacing pristine TiO2 by 2.8-fold. Systematic characterization revealed that the superior activity originates from the synergistic effects of Ti–O–C interfacial bonding and bandgap narrowing (from 3.19 to 2.74 eV), which facilitates efficient charge separation and visible-light harvesting. Mechanistic investigations identified hydroxyl radicals (•OH) as the dominant reactive oxygen species (ROS), with steady-state concentrations reaching 8.84 μM. A unique focus was placed on the environmental chemistry of biochar-derived dissolved organic matter (JDOM). We found that JDOM acts as a co-catalyst to amplify degradation by enhancing electron-accepting capacity, effectively counteracting its inherent light-shielding effects. Furthermore, the chemical fate of PE-MPs was elucidated through two-dimensional correlation spectroscopy (2D-COS) and GC–MS, revealing a sequential oxidation pathway from long-chain alkanes to low-toxicity oxygenated intermediates. Ecotoxicological assessments via ECOSAR confirmed the environmental safety of the products. This work provides a dual-phase synergistic framework for mitigating plastic pollution while ensuring ecotoxicological integrity in agricultural ecosystems. Graphical Abstract