Bio-based magnetic metal-organic framework nanocomposite: Ultrasound-assisted synthesis and pollutant (heavy metal and dye) removal from aqueous media

In the recent decade, Metal-Organic Frameworks (MOFs) and their most popular subclasses (zeolitic imidazolate frameworks (ZIFs)) are widely studied for removing contaminants from the effluent. Herein, the magnetic bionanocomposite (eggshell membrane-zeolitic imidazolate framework) was synthesized using a facile, efficient, and green ultrasound-assisted method. Zeolitic imidazolate frameworks-67 (ZIF-67) crystals were stabilized on the surface of magnetic eggshell membrane (Fe₃O₄@ESM) support to prepare the ZIF-67@ Fe₃O₄@ESM composite as a novel adsorbent with the high surface area (1263.9 m²/g). Several analyses such as XRD, FTIR, SEM/EDS/Mapping, VSM, and BET were used to confirm the characterization and structural changes of ZIF-67 crystals before and after the composition process. Thereafter, copper cation (Cu²⁺) capture and dye (Basic Red 18: BR18) adsorption process were designed and thoroughly studied using the prepared adsorbents. It was found that the adsorption rate and removal percentage of the ZIF-67@Fe₃O₄@ESM composite are faster and higher than that of the pure ZIF-67 for both types of contaminants. Moreover, the magnetic feature of the composite adsorbent caused to a facile separation from liquid media. The results showed that the Langmuir adsorption isotherm well explained the obtained equilibrium data with a maximum adsorption capacity of 344.82 and 250.81 mg/g for Cu²⁺ and BR18, respectively. Kinetic studies showed that the pseudo-second order model was capable to fit the experimental data of the simultaneous removal of heavy metal ion and dye molecule.