Hyperaccumulator-derived biochar catalysts for persulfate activation: Structure-activity relationships and regulation strategies.

Persulfate-based advanced oxidation processes (PS-AOPs) are applied for water pollution control. This review examines the formation, activation mechanisms, and environmental applications of hyperaccumulator-derived biochar (HDB) for persulfate activation. Before pyrolysis, endogenous metals in hyperaccumulator plants undergo uptake, translocation, chelation, and subcellular compartmentalization, creating predispersion and coordination environments. During pyrolysis, these metals co-evolve with the biomass-derived carbon matrix, regulating metal dispersion, coordination, defects, carbon restructuring, and the formation of highly dispersed active sites and, under appropriate conditions, atomically dispersed sites. These interfaces govern persulfate adsorption, electron transfer, and reactive oxygen species generation. Unlike previous reviews on phytoremediation, biochar modification, or general PMS/PDS activation, this review links precursor characteristics, structural evolution, activation mechanisms, and application performance. It compares endogenous and exogenous metal fabrication routes, distinguishes PMS and PDS activation pathways, and evaluates stability, persulfate utilization efficiency, complex-water performance, and environmental impacts. Our case-specific life cycle assessment indicates that the global warming potential of the endogenous-metal HDB route is 73.7% lower than that of an exogenous-metal catalyst synthesis route under defined boundaries and conditions, suggesting potential environmental advantages. This review connects hyperaccumulator precursor properties, HDB formation mechanisms, and PS-AOP performance to guide sustainable catalyst design and environmental applications.