Facile Synthesis of Magnetic ZIF-67@Fe3O4 Composite with Synergistic Properties for Monolayer Adsorption of Pb(II) Pollutants

Abstract

The development of efficient and easily recoverable adsorbents for heavy metal removal remains a significant challenge in wastewater treatment. In this study, a magnetic ZIF-67@Fe3O4 (ZIFO) composite was successfully synthesized via a simple methanol-assisted in situ method at ambient temperature for the removal of Pb(II) from aqueous solution. The physicochemical properties of the synthesized material were comprehensively characterized using XRD, FTIR, FESEM-EDS, HR-TEM, Raman spectroscopy, BET surface area analysis, XPS, and zeta potential, confirming the successful integration of Fe3O4 into the ZIF-67 framework. Batch adsorption experiments were conducted to evaluate the effects of pH, contact time, and initial Pb(II) concentration on adsorption performance. The results showed that Pb(II) uptake was strongly dependent on solution pH, with optimal removal achieved at pH 6. Under the optimized conditions, ZIFO exhibited an experimental adsorption capacity of 212.69 mg g⁻¹ and achieved up to 99.86% Pb(II) removal. Kinetic analysis revealed that the adsorption process was best described by the pseudo-second-order model (R² = 0.99535), indicating that chemisorption dominated the adsorption mechanism. The equilibrium data were well-fitted by the Langmuir isotherm model (R² = 0.9887), with a maximum monolayer adsorption capacity of 158.73 mg g⁻¹. These findings demonstrate that ZIFO is a fast, efficient, and magnetically separable adsorbent with strong potential for the practical treatment of Pb(II)-contaminated wastewater.