Synthesis of Functionalized Magnetic Fe ₃ O ₄ Composites for Robust and Selective Capture of Pb(II) from Wastewater

Water pollution caused by Pb(II) is a significant environmental problem that has hazardous effects on ecological safety and human health. Adsorption is an attractive method for the remediation of Pb(II) pollution. The synthesis of an efficient adsorbent to achieve selective adsorption of Pb(II) is the focus of extensive research. Herein, functionalized magnetic Fe3O4 composites were constructed for the selective adsorption of Pb(II) by employing diethylenetriamine (DETA), aminomethylpyridine (AMP), arginine (ARG), and thiosemicarbazide (TSC) as functional groups. The adsorption performance and mechanism of the composites for Pb(II) were systematically investigated. The composites display a satisfactory adsorption capacity for Pb(II). The normalized adsorption capacity of DETA-functionalized composites for Pb(II) is 1.33 mmol·mmol–1, which is 2.11, 2.13, and 1.52 times that of AMP-, ARG-, and TSC-functionalized composites. The optimal adsorption pH for Pb(II) is 6. The adsorption can be promoted by raising the Pb(II) concentration and temperature. Adsorption kinetics indicates film diffusion is the rate-controlling step and the adsorption follows a pseudo-second-order model. The composites exhibit a marked adsorption selectivity for Pb(II). The increase of concentration, column bed height, and reduced flow rate of solution can promote the dynamic adsorption for Pb(II). The composites also display good adsorption performance and reusability in simulated industrial wastewater. The adsorption capacity of DETA-functionalized composites can retain 97.00% after 3 cycles of regeneration. The adsorption mechanism demonstrates the capture of Pb(II) is mainly dependent on amino, oxygen, and sulfur groups. The work not only provides a feasible method to quantitatively evaluate the adsorption ability of different functional groups but also paves a new way for the preparation of efficient adsorbents to realize the efficient adsorption of Pb(II) from aqueous solutions.