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Magnetic modified and Fe/Zn modified biochar enhanced removal of polystyrene microplastics in constructed wetlands: Performance and mechanism insights
Summary
Scientists engineered special charcoal filters (treated with iron and zinc) that can capture up to 88% of tiny plastic particles from water passing through constructed wetlands—far better than plain gravel or untreated charcoal. This matters because microplastics are increasingly found in our water, food, and even our bodies, and better filtration methods like this could help reduce the amount of plastic pollution that ends up in the water we drink and the ecosystems we depend on.
Microplastics (MPs) pollution poses a growing threat to aquatic ecosystems. Constructed wetlands (CWs) can intercept MPs, but traditional fillers suffer from saturation and lack functional interfaces. To address this, this study proposed a material-interface-microbe coupling strategy and prepared magnetic modified biochar (MBC) and Fe/Zn modified biochar (FZBC) as CW fillers. Material characterization showed increased specific surface area, oxygen-containing groups, and metal oxide sites on modified biochar. In 180-day experiments with influent polystyrene microplastics (PS-MPs) at 10, 100, and 1000 μg/L, MBC and FZBC achieved removal rates of 69.27-88.82% and 60.47-88.15%, respectively, significantly outperforming gravel (CK, 20.36-79.75%) and raw biochar (BC, 40.53-84.75%). Microbial analysis revealed enrichment of functional genera, includingPseudomonas,Bacillus, andStenotrophomonas. It also showed higher predicted abundances of key degradation enzymes (e.g., alkane monooxygenase, aldehyde dehydrogenase) and electron transport chain-related genes. These observations suggest that enhanced PS-MPs removal by modified biochar may result from a combination of adsorption and microbial metabolic support, implying a potential abiotic-biotic coupling process that requires direct verification. Overall, this study provides a promising strategy for MPs pollution control in aquatic environments using modified biochar-based CWs.