Synthesis of Novel Magnetic Microspheres with Bimetal Oxide Shell for Excellent Adsorption of Oxytetracycline

Multifunctional magnetic microspheres (Mag@ZnO–Co3O4) with bimetal oxide shell were synthesized via a facile method. The Mag@ZnO–Co3O4 composite was characterized through a vibrating sample magnetometer, N2 adsorption analysis, Fourier transform infrared spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy analyses. The structural analysis showed that the as-prepared microsphere possessed a mean diameter of 150 nm, a bimetal oxide shell thickness of ∼10.0 nm, and a magnetic core, which endowed it with good dispersibility, strong magnetism, and excellent adsorption property for oxytetracycline (OTC). Several experimental conditions, such as solution pH, adsorption time, OTC concentration, and ionic strength were systematically investigated. The Mag@ZnO–Co3O4 composite exhibited a fast adsorption rate, that is, the equilibrium was reached within 90 min, when the concentration of OTC was between 10 and 30 mg/L. The composite showed favorable performance for the adsorption of OTC in the pH range 5–9. According to the adsorption isotherms and kinetics, the removal of OTC was efficient and obeyed the pseudo-second-order rate equation and Langmuir adsorption model.