Recent advances in biochar-mediated mitigation of microplastics: A comprehensive review on removal mechanisms, toxicity alleviation strategies, and synergistic environmental impacts

Biodegradable plastics are broadly applied in different industries because of their biodegradability, pliability and durability. The improper disposal of their waste has triggered serious plastic contamination, with microplastics (MPs) becoming ubiquitous pollutants in the environment worldwide, adversely impairing soil ecosystems, aquatic ecosystems, the atmosphere and human health. Biochar is considered a prospective candidate for MPs removal and toxicity reduction due to its high specific surface area, abundant porosity and widespread availability. This study overviews the interception, filtration, adsorption and degradation of MPs via biochar-mediated processes facilitated by its honeycomb-like porous structure. How biochar-MPs interactions influence environmental systems and the mechanisms behind are discussed, including hydrophobic interactions, π-π stacking, electrostatic attraction, microbial community restructuring and modulation of oxidative stress. Notably, biochar has been shown to remove more than 90% of MPs and mitigate the emission of greenhouse gases (e.g., CO and NO) generated by MPs-induced microbial processes. Biochar-derived dissolved organic matter (BDOM) synergistically facilitates the photoaging of MPs by promoting oxidative reactions at surface-active sites. Collectively, this review consolidates current knowledge on biochar-mediated remediation of MPs, with a focus on their environmental fate, associated environmental impacts and potential human health risks. Building upon the proven efficacy of biochar, this review advocates for integrated strategies to mitigate MPs pollution and their cross-media effects to ultimately protect global environment.