New insight into the co-adsorption of oxytetracycline and Pb(II) using magnetic metal-organic frameworks composites in aqueous environment: co-adsorption mechanisms and application potentials.

Abstract

The present study aimed to investigate the co-adsorption and application of water stabilized Fe3O4@ZIF-8 composite with magnetic cubic crystal structure. This new material was successfully prepared by facile modification strategy and rational design, which was used for simultaneous adsorption of oxytetracycline (OTC) and Pb(II) in aqueous solution. The co-adsorption behavior and mechanism of the composite for OTC and Pb(II) were systematically investigated by characterization techniques and batch experiments, and its application potential was effectively evaluated. The results showed that the synthesized Fe3O4@ZIF-8 composite innovatively retained the cubic crystal structure of ZIF-8 and was successfully loaded on the surface of Fe3O4 particles with small particle size to form a core-shell structure. The Fe3O4@ZIF-8 composite possessed a large specific surface area (1722 m2/g), magnetic separation performance (13.4emu/g), and rich functional groups. The co-adsorption of OTC and Pb(II) on Fe3O4@ZIF-8 had fast reaction kinetics (equilibrium within 90min) and large adsorption capacity (310.29mg/g and 276.06mg/g respectively). The adsorption process for both contaminants followed pseudo-second order kinetics and Langmuir isotherm models and had synergistic and competitive effects at the same time. π-π stacking and electrostatic interaction were the main mechanisms of adsorption. Fe3O4@ZIF-8 had good adsorption performance after cyclic adsorption for 4 times and it performed well in the treatment of real waste water. This study provided a new sight for the control of combined pollution of OTC and Pb(II) and proved Fe3O4@ZIF-8 composites have great application potentials for complex wastewater treatment.