Preparation of Magnetic Composite Hollow Microsphere and Its Adsorption Capacity for Basic Dyes

Magnetic microspheres with an Fe3O4 core and a SiO2-TiO2 hybrid shell were prepared by a surfactant-assisted aerosol process and subsequent etching treatment. The core-shell spheres with robust and chemically stable Ti-O-Si shells exhibit excellent adsorption performance toward basic dyes. The maximum adsorption capacities were obtained at 147 mg/g for methylene blue (MB) and 124.6 mg/g for basic fuchsin. MB with an initial concentration of 20 mg/L can be completely removed in 5 min at a dosage of 0.5 mg/L, and the equilibrium time is 90 min in the MB concentration range 20-250 mg/L. The adsorption kinetics follows the pseudo-second-order model. Furthermore, the dye saturated microspheres can be easily recycled by an external magnetic field and regenerated using 1-3 wt % NaOH aqueous solution. After six recycle runs, 98% of the adsorption capacity was still retained. The low-cost magnetic hollow spheres with good adsorption capacity are a promising candidate for water treatment.