Adsorption of cupric, cadmium and cobalt ions from the aqueous stream using the composite of iron(II,III) oxide and zeolitic imidazole framework-8.

In recent research, the composite of FeO and metal-organic frameworks have shown great potential in removing potentially toxic metals from water. We conducted the adsorption studies of potentially toxic metal ions (Cu, Co and Cd) using the composite of FeO and zeolitic imidazole framework-8 (FeO@ZIF-8) for the first time. The solvothermal technique was used to synthesize the FeO. The magnetic ZIF-8 offers high thermal stability, greater adsorption surface, good removability, and high chemical and thermal stability. Characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the synthesized samples. The SEM and XRD results revealed the high purity and structural integrity of ZIF-8 crystallites. To remove potentially toxic metals (Cu, Co and Cd), the influence of adsorbent dosage, contact time, pH, and adsorbate concentration on the adsorption performance of FeO@ZIF-8 was investigated. The Langmuir isotherm accurately represented the adsorption processes, with absorption magnitudes of FeO@ZIF-8 determined to be 46.82 mg g, 71.29 mg g and 54.49 mg g for Cu, Co and Cd, respectively. According to the adsorption mechanism analysis, the primary Cu, Co and Cd removal methods of FeO@ZIF-8 were ion exchange and coordination bonds. The uptake capacity of Cu, Co and Cd solution by FeO@ZIF-8 were not significantly affected by the presence of counter ions. The material exhibited superior regenerative properties for Cu, Co and Cd ions from water for up to three cycles. This study concluded that the FeO@ZIF-8 could be a viable candidate for eliminating potentially toxic metals (Cu, Co and Cd).