Synthesis of Mixed Metal Nano-Oxides (MMNOs) for Cu (II) adsorption with remarkable removal efficiency: Isothermal, kinetics, and thermodynamics studies

The growing problem of copper pollution in the world's water supply threatens both aquatic ecosystems and human health. This study sought to assess the effectiveness of zinc/iron nano-oxides, which represent Mixed Metal Nano-Oxides (MMNOs), and their suitability for improving Cu (II) adsorption from wastewater. MMNOs in various ratios were effectively generated using the hydrothermal process. MMNOs adsorption ability was assessed in batch systems with varying initial Cu (II) ions from, which include availability and affordability. The generated precursors were characterized by energy-dispersive X-ray analysis (EDX), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Atomic absorption spectroscopy (AAS) is used to determine the quantity of metal ions and their concentrations in filtrates. MMNOs possess distinctive properties, including a large surface area, enhanced stability, superior adsorption capabilities, low production costs, and straightforward separation processes. These MMNOs are effective adsorbents because of their porous nanostructures and particle size, surface characteristics, and crystallinity, all of which play essential roles in determining their physicochemical properties, as well as their exceptional ability to adsorb Cu (II) ions. The presence of irregular porous MMNOs can impact adsorption, according to SEM studies, which reveal a remarkable removal efficiency of around 99.2 % of Cu (II) ions across the MMNOs (10:1) precursor. The adsorption capacity reached 7.079 mg/g. The batch adsorption technique was optimized, resulting in (pH = 5.5, temperature = 30 °C, dose = 0.05 gm, concentration = 10 mg/L, time = 120 min). Additionally, MMNOs' surface roughness after Cu (II) adsorption improved dispersion capabilities and mild electrostatic contact with Cu (II). Linear and non-linear kinetic models, as well as isotherm models, were also studied. The pseudo-second-order model proved to be the best fit among the kinetic models, while the Freundlich model is the best for isothermal models. The reusability investigation, on the other hand, demonstrated that the adsorbent may be used for multiple cycles, with removal efficiency decreasing from 99.2 % to 87.3 % after four cycles and to 67 % after ten cycles. As a result of selectivity, Cu 2+ adsorption decreased from 99.2 % to 94 % in the presence of Co 2+ and Ni 2+ ions.