Composite magnetosusceptible photocatalysts based on the Fe3O4/SiO2/TiO2oxides

In the present study the composite materials based on the Fe3O4/SiO2/TiO2 oxides, synthesized by the sol-gel method, were investigated. At the first stage, magnetite nanoparticles were precipitated by sodium hydroxide from a mixture of aqueous solutions of iron(II) and iron(III) sulfates under continuous ultrasonic treatment, after which they were washed with distilled water and dried under vacuum. At the second stage, the resulting magnetite particles were coated with silicon oxide according to the Stober method by dispersing them under the ultrasonic treatment in a solution of tetraethoxysilane in n-propanol, followed by hydrolysis of tetraethoxysilane in the presence of aqueous ammonia, washing and drying the obtained materials under vacuum. At the third stage, photocatalytically active particles based on titanium oxide were introduced into the composite by the solvent replacement procedure via dispersing the samples in an aqueous solution of peroxotitanic acid and adding n-propanol, stirring vigorously, followed by activation based on boiling in the water/ethanol (1:1) mixture, washing and drying under vacuum. The properties of samples influenced by the citrate stabilization and separation of magnetite particles at the stage of their synthesis into “light” and “heavy” magnetic fractions, as well as calcination of samples at 450 °C, were studied. The photocatalytic properties of the synthesized samples were studied during photodegradation of methyl orange, as well as their magnetic extraction from the suspension. The physicochemical characterization of the samples was performed using a high-resolution scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray powder diffraction, thermal analysis (TG-DSC), combined with mass spectrometry of gaseous thermolysis products. It has been found that the composites based on the mixed titanium-silicon oxide have a higher photocatalytic activity than the composites based on the pure titanium dioxide obtained via a similar procedure. The resulting photocatalysts can be used to purify water from dyes, followed by their extraction using a magnet.