Magnetically active MOF-based adsorbent for efficient diclofenac sodium adsorption

A novel magnetically active ZnFe₂O₄@MIL-53(Al)-NH₂ composite was prepared for the first time, and its adsorption performance for diclofenac sodium (DS) in solution was investigated systemically. Structural analyses by XRD and FTIR confirmed the successful integration of ZnFe₂O₄ nanoparticles within the MIL-53(Al)-NH₂ framework, while magnetic hysteresis loop measurements revealed excellent magnetic responsiveness, enabling rapid recovery under an external magnetic field within 60 s. The composite exhibited a maximum DS adsorption capacity of 217.85 mg/g at pH 6.44, 298 K, and 60 min contact time, significantly higher than those of most recent benchmarks, including Lignin‑Based Magnetic Nanoparticle (106.4 mg/g), Ni_0.5Zn_0.5Fe₂O₄ (52.91 mg/g) and Na-X zeolite (6.68 mg/g). The DS adsorption process is primarily spontaneous and endothermic, dominated by electrostatic attraction, hydrogen bonding, and π-π interactions. The high stability, negligible ion leaching, and efficient magnetic recyclability underscore its potential for scalable wastewater treatment applications. This study provides valuable insights into the mechanism of magnetism-enhanced adsorption and offers a promising pathway for developing multifunctional MOF-based adsorbents for environmental remediation.