green synthesis of silver nanoparticles using chromolaena odorata leaf extract for adsorptive removal of heavy metals and textile dyes from aqueous systems

Heavy metal and dye pollution in water resources presents a pressing global challenge due to its adverse impacts on environmental quality and human health. conventional treatment methods, while effective, are often costly, energy-intensive, and generate secondary waste. in this study, silver nanoparticles (agnps) were synthesized via an eco-friendly green method using chromolaena odorata leaves collected from nueva vizcaya, philippines. the phytochemical-rich extract served as both a reducing and stabilizing agent. the synthesized nanoparticles were characterized by ultraviolet–visible (uv–vis) spectroscopy, with a distinct surface plasmon resonance (spr) peak observed at 428 nm, confirming nanoparticle formation and stability. adsorption experiments were conducted to evaluate the removal efficiency of agnps against selected heavy metals (pb2+, fe2+, cu2+, co2+) and textile dyes (methyl orange, methyl red, methyl blue, congo red) using simulated wastewater prepared from analytical grade reagents. results revealed high removal efficiencies, with pb2+ (92.3%) and methyl orange (89.7%) exhibiting the highest adsorption under optimal conditions, while other contaminants ranged between 74.5% and 86.8%. kinetic analysis demonstrated that adsorption followed a pseudo-second-order model (r² > 0.99), indicating chemisorption as the dominant mechanism, with equilibrium reached within 90–100 minutes. isotherm modeling confirmed monolayer adsorption, with pb2+ showing the highest maximum adsorption capacity (50 mg/g), followed by fe2+ (46 mg/g), cu2+ (43 mg/g), and co2+ (44.5 mg/g). dye adsorption capacities ranged from 40 to 42 mg/g. thermodynamic parameters revealed negative gibbs free energy (–18 to –25.5 kj/mol), positive enthalpy (15–18 kj/mol), and positive entropy (118–140 j/mol·k), confirming that the process was spontaneous, endothermic, and entropy-driven. these findings highlight the potential of c. odorata-derived agnps as sustainable and effective adsorbents for wastewater remediation. limitations include testing under controlled conditions, requiring studies in real wastewater, and evaluations of nanoparticle reusability and scalability. overall, the study advances green nanotechnology for cost-effective, eco-friendly water treatment.