Green synthesis of ZnNi/ZIF-8 composites for efficient anionic dye removal: A sustainable approach to wastewater treatment

Given the scarcity of water resources and the irreversible environmental impact of wastewater discharge, metal-organic frameworks (MOFs) have been studied using an environmentally friendly approach known as solvent-free or green synthesis. In this study, ZIF-8 crystals embedded with nickel metal (ZnNi/ZIF-8) were synthesized using a green approach to enhance their performance, promote synergistic effects, and improve environmental friendliness. The crystal structure, functional groups, surface area, and morphology of ZIF-8 and ZnNi/ZIF-8 nanocomposites were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N 2 adsorption-desorption isotherms (BET), and scanning electron microscopy (SEM). These nanocomposites were employed to remove Acid Blue 92, an anionic dye, from aqueous solutions. The adsorption kinetics of Acid Blue 92 followed a pseudo-second-order model, with a high correlation coefficient of 0.99. The adsorption isotherms of ZIF-8 and the nanocomposite (ZnNi/ZIF-8) were described by the Langmuir model, with maximum adsorption capacities of 403 and 458 mg/g, respectively. Under optimal conditions, including an initial concentration of 25 mg/L, a pH of 3, a contact time of 120 minutes, and a dose of 6 mg, the ZnNi/ZIF-8 nanocomposite exhibited an adsorption capacity of 387 mg/L and a removal efficiency of 93.6%. Due to its environmentally friendly nature, the prepared ZnNi/ZIF-8 nanocomposite is a promising candidate for efficient treatment of anionic wastewater. The adsorption mechanism primarily involves hydrogen bonds, dipole-induced dipole bonds, π-π donor-acceptor interactions, and the hydrophobic effect. • The highest Ab92 dye adsorption capacity was 387.6 mg/g • The NiZ composites illustrated increased dye removal performance. • The analysis of the isotherm model was fitted with the Langmuir adsorption model and the kinetic model was fitted with the pseudo-second-order model.