Biomaterial-Based Magnetic Nanobiochar for Remediation of Trichloroethylene: Environmental Fate, Toxicity, Mechanistic Insights, and Technological Advancements

Trichloroethylene (TCE) is a carcinogenic, persistent groundwater contaminant against which conventional remediation techniques like pump-and-treat, soil vapor extraction, and chemical oxidation falter badly especially at dense non-aqueous-phase-liquid (DNAPL) source zones. Magnetic nanobiochar composites (MNBCs) fuse biochar’s tunable porosity with the redox power of embedded nanometals (e.g., nZVI), uniting adsorption, catalytic oxidation, and reductive dechlorination in one magnetically recoverable material. Biochar is chosen over activated carbon, carbon nanotubes, and graphene on hard comparative grounds: comparable or superior TCE removal at strikingly lower production cost, embodied energy, and environmental burden. This review delivers the first integrative structure–mechanism–outcome assessment of MNBCs for TCE, linking fabrication parameters directly to the removal mechanisms they produce and to field-scale performance and risk closing a gap in which prior reviews treat biochar synthesis, magnetic functionalization, and TCE degradation as separate studies. We reveal that the vast majority of reported TCE removal data derive from laboratory-scale studies, with field validation concentrated in only a handful of biochar- and activated-carbon-supported nZVI trials, and we benchmark these against genuine field and pilot deployments to draw a sharp line between what is field-proven and what is merely laboratory-demonstrated. Strikingly, environmental risk assessment for MNBCs remains far underdeveloped relative to their performance characterization, a gap made vivid by a concrete benchmarking example in which iron leaching from a stabilized nZVI-carbon composite matches the EPA’s secondary drinking-water threshold for iron, exposing the quantitative risk assessment this field still lacks. This review concludes by pinpointing the specific data gaps—not generic scale-up challenges—that must close before MNBCs can advance from bench-scale demonstration to field-ready TCE remediation technology.