Magnetic Fe3O4/ZIF-8 composite as an effective and recyclable adsorbent for phenol adsorption from wastewater

Recovery of phenol in wastewater is a matter of concern. Metal organic frameworks (MOFs) are promising adsorbents for the removal of organic pollutants from water phase owing to their rich pore structure and high chemical activity. However, most MOFs are in the form of microcrystalline powders, making them difficult to be separated and recycled. Therefore, it is important to explore the facile fabrication of magnetic adsorbents with high adsorption efficiency, fast equilibrium adsorption time, and excellent recoverability. A regenerable magnetic Fe3O4/ZIF-8 composite was prepared for phenol removal with ZIF-8 as adsorption mainstay and Fe3O4 nanoparticle as magnetic component. Through self-assembly process design, the advantages of the combination and its synergistic effect were exhibited. The effects of pH, binding time, and initial concentration on the adsorption behaviors of Fe3O4/ZIF-8 towards phenol were investigated to assess adsorption capacity and reusability. Owing to the dual effect of high adsorption activity and abundant pore structures, Fe3O4/ZIF-8 demonstrated prominent adsorption capacity (129.8 mg g−1) and rapid adsorption rate (20 min) towards phenol. The pseudo-second-order kinetic model fits the adsorption data well. The thermodynamic adsorption curves conform to the Langmuir model. The adsorption mechanism involves the critical contribution of hydrogen bonding interaction, π-π interaction, pore adsorption, and electrostatic attraction. Moreover, the magnetic adsorbent shows excellent reusability. This work provides a new sight on the synthesis of high efficiency adsorbents for organic pollutant separation.