From teak waste to functional nanomaterials: A green nanotechnology approach for sustainable wastewater remediation

Tectona grandis L.f. (teak) wastes, including leaves, seeds, bark, sawdust, and wood residues, represent an underutilized lignocellulosic biomass resource for developing sustainable nanomaterials and carbon-based adsorbents for wastewater remediation. Previous reviews have discussed plant-mediated nanoparticle synthesis and biomass-derived adsorbents in general; however, a focused review linking teak biomass valorization with green nanotechnology and water-treatment applications remains limited. The present review provides an integrated evaluation of teak-derived nanoparticles, biochar, activated carbon, hydrochar, and functional adsorbents, with emphasis on synthesis routes, characterization features, pollutant-removal mechanisms, and sustainability-related limitations. The phytochemical composition of teak, including phenolics, flavonoids, tannins, and quinone-based compounds, supports green nanoparticle formation by acting as reducing, capping, and stabilizing agents. Reported teak-mediated metal and metal oxide nanoparticles generally show nanoscale dimensions, diverse morphologies, and photocatalytic or antimicrobial activity, while teak-derived carbon materials exhibit adsorption potential due to their porous structure, aromatic carbon domains, and oxygen-containing functional groups. Current applications are mainly concentrated on dye degradation, heavy-metal adsorption, phosphate removal, antimicrobial water treatment, and selected organic pollutant removal. Pharmaceutical wastewater remediation remains poorly explored; the main direct evidence is tetracycline adsorption using iron-modified teak biochar with a reported capacity of 62.5 mg g⁻¹ , indicating pharmaceutical pollutant removal as a key future research gap rather than an established application. Critical analysis shows that bark-mediated synthesis, composite development, regeneration, toxicological assessment, real-wastewater validation, and scale-up studies remain insufficient. In addition, direct comparison among reported studies is limited by differences in pH, pollutant concentration, adsorbent dose, irradiation conditions, contact time, and wastewater matrix. Overall, teak waste offers a promising circular-bioeconomy route for producing potentially low-cost and environmentally preferable materials for wastewater treatment.