Physico-chemical characteristics of Fe3O4/TiO2 и Fe3O4/SiO2/TiO2, nanocomposites synthesized by the hydrothermal peroxide method

In the present paper the composite materials based on Fe3O4/TiO2 and Fe3O4/SiO2/TiO2 oxides, synthesized by the hydrothermal peroxide method, were studied. At the first stage, magnetite nanoparticles were precipitated by ammonium hydroxide from a mixture of aqueous solutions of iron(II) sulfate and iron(III) chloride under continuous exposure to ultrasound, after which they were washed with distilled water. At the second stage, the resulting hydrated magnetite particles were stabilized with polyvinyl alcohol (PVA) by dispersing them under the action of ultrasound in a hot saturated aqueous PVA solution. At the third stage, the photocatalytically active particles based on titanium oxide were introduced into the composite by mixing the stabilized magnetite suspension with an aqueous solution of peroxotitanic acid (optionally introducing a sol of silicic acid), followed by hydrothermal treatment of the mixture at 180°C for 24 hours, washing, and drying under vacuum followed by calcination in a muffle furnace. The effect of the molar content of iron and titanium on the properties of the samples, the introduction of silicon dioxide into them, as well as various calcination temperatures, were studied. The photocatalytic properties of the synthesized samples during photodegradation of methyl orange and methylene blue, as well as their magnetic recovery from suspension, were studied. The physicochemical characterization of the samples was performed using high-resolution scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, powder X-ray diffraction, low-temperature nitrogen sorption porosimetry, inductively coupled plasma mass spectrometry, thermal analysis (TG-DSC), combined with mass spectrometry of gaseous thermolysis products. The optimal conditions for the synthesis of composites exhibiting the best combination of photocatalytic and magnetic properties were determined. The resulting photocatalysts can be used to purify water from dyes, followed by extraction using a magnet.