Facile Syntheses of Fe ₃ O ₄ @TiO ₂ @PDA Composites for the Highly Efficient Removal of Methylene Blue

ABSTRACT Ultrasonic‐ and microwave‐assisted methods are progressive techniques used in synthesizing nanocomposites on different inorganic, organic, or hybrid supports. In this study, one‐step synthesis of Fe 3 O 4 @TiO 2 (FT) core‐shell nanoparticles was conducted by combining ultrasound‐ and microwave‐assisted solvothermal methods. The composites were fabricated using a central magnetic Fe 3 O 4 core, with in situ formation of the outer TiO 2 coating. The surface of FT was further modified via polydopamine(PDA), and the as‐prepared Fe 3 O 4 @TiO 2 @PDA composites (FTP) were successfully used as photocatalysts to effectively remove methylene blue (MB) in an aqueous solution. The pH, photocatalyst dosage, initial MB concentration, and temperature influences were investigated under 254 nm UV light. Additionally, the changes in the physicochemical properties of the nanocomposites were analyzed using transmission and scanning electron microscopy, Fourier transform infrared spectroscopy, x‐ray powder diffraction, and vibrating sample magnetometry. The as‐prepared FTP composites exhibited excellent efficiencies (99.9%) in the adsorption and photocatalytic degradation of 20 ppm MB in neutral or basic conditions over 30 min. Compared with previous reports about Fe 3 O 4 @TiO 2 composites, the modified PDA layer enriched MB molecules via hydrogen bonds and strong electrostatic interactions, and simultaneously trapped photogenerated electrons of TiO 2 to inhibit carrier recombination with an apparent reaction rate constant of 0.0816 min − 1 . Therefore, the use of ultrasonic and microwave co‐irradiation in rapidly preparing magnetic composites is simple and viable.