Advanced Catalytic and Hybrid Biomass-Based Materials for Microplastic Removal and Oxidative Degradation in Aquatic Environments

Microplastic remediation by catalytic materials is challenged by the chemical resistance of polymers and by the difficulty of distinguishing particle capture from actual polymer conversion. This review critically examines biomass-derived carbons, biochars, silica-rich residues, biogenic ligands, and hybrid catalysts for aquatic microplastic treatment. Rather than comparing reported removal percentages alone, it organizes the evidence along a sequence from particle transport and interfacial contact to surface oxidation, fragmentation, depolymerization, and mineralization. It evaluates photocatalytic, Fenton-like, persulfate-activation, electrochemical, and integrated approaches while distinguishing direct evidence obtained with biomass-containing catalysts from mechanisms inferred from conventional benchmark systems. Across the literature, catalyst composition and porosity may improve adsorption or reactive-species generation, but these properties do not by themselves establish polymer-carbon conversion. Reliable claims require polymer-specific characterization, particle-size analysis, transformation-product identification, carbon balances, and assessment of catalyst leaching and toxicity. The review identifies the need for reproducible reporting, tests in realistic water matrices, and life-cycle and techno-economic evaluation before sustainability or scale-up advantages can be established. Data-driven catalyst design may help prioritize formulations, provided that sufficiently comparable experimental datasets become available.