Adsorption of copper and nickel by a stannum-functionalized 3D graphene composite: Synthesis, characterization and optimization studies

Heavy metals are among the most hazardous pollutants in aquatic systems, posing significant risks to both the environment and human health. This research presents a newly developed three-dimensional (3D) graphene-based composite functionalized with stannum (GSn) for the targeted removal of heavy metal ions, specifically copper and nickel, from aqueous environments. A variety of spectroscopic and microscopic techniques were applied to characterize the structural and chemical properties of the GSn material. To assess its adsorption performance, a series of batch experiments were conducted, examining the effects of major operational variables such as GSn dosage, metal concentration, temperature, pH and contact time. A central composite design approach was used to investigate the interactive effects of these variables and optimize the adsorption conditions. The optimum parameters for copper adsorption were determined to be 20 mg of GSn, 80 mg/L copper and a contact time of 40 min at 40 °C, attaining a maximum adsorption capacity of 87.57 mg/g. For nickel, the optimum performance was achieved with 20 mg of GSn, 60 mg/L nickel and 40 min at 45 °C, yielding a maximum adsorption capacity of 75.96 mg/g. The adsorption kinetics closely followed the pseudo-second-order kinetic model, while the equilibrium data conformed to the Dubinin-Radushkevich isotherm, suggesting a chemisorption-driven mechanism. Furthermore, the GSn composite exhibited promising reusability, maintaining effective performance over four adsorption-desorption cycles. These findings highlight the potential of GSn as a sustainable and cost-effective nanomaterial for heavy metal removal in wastewater treatment applications.