Bio‐Derived Carbon Nanoparticles: A Green Amendment for Alleviating Heavy Metals in Soil–Plant Systems

ABSTRACT Heavy metal (HM) contamination of soil–plant systems poses persistent ecological and health risks, driving interest in nanoparticle‐based remediation. Although conventional chemically synthesized nanoparticles (CSNPs) are effective, their energy‐intensive production and residual toxicity limit sustainable deployment. Bio‐derived carbon nanoparticles (BCNPs), synthesized from plant, algal, and microbial biomass via pyrolysis, hydrothermal carbonization, or extraction, offer a potentially greener alternative. However, the literature linking their bio‐derived origin to a distinct remediation advantage over CSNPs remains fragmented. This review consolidates bibliometric and mechanistic evidence to evaluate BCNPs as HM remediation amendments in soil–plant systems. BCNPs immobilize HMs through adsorption, ion exchange, complexation, co‐precipitation, redox transformation, and electrostatic attraction mediated by oxygen‐containing surface functional groups and high surface area. Comparative data show several BCNPs (e.g., Ag‐GONA, rGOH) match or exceed CSNP adsorption capacities while avoiding hazardous reagent use. Beyond immobilization, BCNP amendment enhances plant nutrient uptake (N, P, K increase up to 133%, 41%, and 92%), strengthens antioxidant defenses, and reduces HM translocation into edible tissues by 6.6%–66%. However, performance is strongly modulated by edaphic factors (pH, redox status, ionic strength, and organic matter), and evidence indicates that BCNP “green” origin does not inherently guarantee environmental safety, since ecotoxic risk can be reintroduced at the feedstock, thermal‐conversion, and functionalization stages. Hence, this review highlights that BCNP‐HM interaction mechanisms, plant physiological benefits, and life‐cycle safety considerations must be evaluated jointly and identifies standardized multi‐metal testing, field‐scale validation, and mechanistic subcellular studies as priorities for translating BCNPs from laboratory promise into reliable field‐scale remediation technology.