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

Magnetic microspheres with an Fe 3 O 4 core and a SiO 2 –TiO 2 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.