Adsorption Performance of Zn(II)-Based Coordination Polymer (ZnMOF) Reinforced Magnetic Activated Biochar (CmBC-Fe₃O₄@ZnMOF) Hybrid Composites

Evaluation of organic wastes originating from livestock as biochar is of great importance in terms of both economic and environmentally friendly sustainable material production. In this study, cow manure (C_m), an animal waste, was used for biochar (BC) production. The obtained biochar was activated with Fe₃O₄ and given magnetic properties (CmBC-Fe₃O₄), then modified with a Zn(II)-based coordination polymer (ZnMOF) to synthesize a hybrid material, CmBC-Fe₃O₄@ZnMOF. The synthesis of this innovative hybrid material was carried out in two stages: In the first stage, CmBC-Fe₃O₄ was obtained by in situ synthesis method. In the second stage, it was modified with ZnMOF synthesized by solvothermal method to obtain the innovative adsorbent of CmBC-Fe₃O₄@ZnMOF hybrid material. The synthesized CmBC-Fe₃O₄, ZnMOF, and CmBC-Fe₃O₄@ZnMOF were characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometry (SEM–EDX), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), TG/DTA, and BET analyses. Based on kinetic feasibility, CmBC-Fe₃O₄@ZnMOF has the highest removal efficiency. The removal efficiencies of Pb(II), Cd(II), Cu(II), and Mn(II) in the synthetic water sample were found to be 81.39%, 69.52%, 58.47%, and 32.53%, respectively. On the other hand, the corresponding removal efficiencies in the milk sample were found to be 64.63%, 43.02%, 30.62%, and 19.27%, respectively. Isotherm (Dubinin–Radushkevich, Freundlich, and Langmuir) and kinetic (Elovich, Ho-McKay, and Lagergren) models were used and mostly fit with Ho-McKay second-order rate equation and the Freundlich isotherm model. In addition, the reusability studies were carried out in three cycles, and it was observed that it can be used after three cycles without losing its efficiency. It was concluded that the CmBC-Fe₃O₄@ZnMOF hybrid material is an effective adsorbent with the potential to remove heavy metals from both water and milk solutions and its selectivity for Pb(II) and Cd(II) is higher than that for Cu(II), and Mn(II). Summary: Hybrid material (CmBC-Fe₃O₄@ZnMOF) structures combining unit cells with different adsorption capacities. Zn(II)-based coordination polymer (ZnMOF) and activated magnetic biochar (CmBC-Fe₃O₄) were used to evaluate their performance on heavy metal removal from milk and synthetic water samples. CmBC-Fe₃O₄ was synthesized by a one-step in situ synthesis method and ZnMOF by solvothermal method. CmBC-Fe₃O₄@ZnMOF showed excellent and selective adsorption capacity especially for Pb(II) and Cd(II). The removal efficiencies for Pb(II), Cd(II), Cu(II), and Mn(II) in synthetic water sample were found to be 81.39%, 69.52%, 58.47%, and 32.53%, respectively. The removal efficiencies for Pb(II), Cd(II), Cu(II), and Mn(II) in milk sample were found to be 64.63%, 43.02%, 30.62%, and 19.27%, respectively.