Green-synthesized metal and metal-oxide nanomaterials for pesticide removal: Synthesis, strategies, mechanistic insights, performance evaluation, and scale-up prospects

Pesticide contamination of aquatic systems remains a persistent environmental and public-health concern, while many conventional treatment technologies are limited by high energy demand, secondary waste generation, and incomplete mineralization. This review critically evaluates green-synthesized metal-based nanomaterials (GS-MBNMs), comprising metallic nanoparticles, and their biofunctionalized or supported nanocomposites, for pesticide remediation by linking biological precursor chemistry, synthesis conditions, nanostructure, surface properties, removal mechanisms, durability, environmental safety, and scale-up readiness. Adsorption, photocatalytic oxidation, reactive oxygen species-mediated transformation, Fenton-like reactions, and redox degradation are examined alongside the effects of particle size, morphology, porosity, crystallinity, defect density, and biomolecular corona composition. Available studies confirm strong laboratory-scale adsorption and degradation performance; however, direct comparison remains constrained by inconsistent operating conditions, incomplete reporting of surface area and kinetic parameters, and frequent reliance on parent-pesticide disappearance rather than mineralization, transformation-product identification, or toxicity reduction. Green synthesis can reduce hazardous reagent use and provide beneficial surface functionality, but biological-feedstock variability, difficult purification, uncertain yield, nanoparticle leaching, and limited batch reproducibility restrict practical deployment. Hybrid nanostructures and machine-learning-assisted optimization offer potential gains in selectivity, charge transfer, recovery, and process control, yet evidence remains limited for pesticide-specific systems. A source-to-deployment framework is proposed, integrating standardized synthesis, mechanistic validation, real-matrix testing, regeneration, continuous-flow operation, life-cycle assessment, techno-economic analysis, and regulatory evaluation to support safe and commercially credible scale-up. The evidence therefore supports technical promise, but not universal superiority over conventionally synthesized counterparts.