Magnetic iron oxide is a typical narrow-band gap semiconductor photocatalyst, but its inherent magnetic aggregation effect and high electron–hole recombination rate seriously affect its photocatalytic performance. Here, α-Fe2O3/SiO2 composite aerogels were prepared by combustion technology for the first time. The unique structure of α-Fe2O3/SiO2 composite aerogels with amorphous silica coated with nanocrystalline iron oxide was confirmed. The composite aerogels exhibited a high specific surface area (479 m2 g−1 when calcined at 500 °C), so that they have excellent adsorption properties for organic pollutants (MB, RhB and TC) and Cr(VI). The composite aerogels with a Fe : Si molar ratio of 1 : 2 showed the best visible light photocatalytic properties for MB, RhB and TC. Based on the study of the band gap width, photocurrent density, transient photocurrent response, impedance of photocatalysts, and the unique structure of the composite aerogels, the mechanism of photocatalytic enhancement of composite aerogels was proposed. Finally, the mechanism of the preparation of α-Fe2O3/SiO2 composite aerogels by combustion synthesis was analyzed. It is a potential technology for preparing high performance composite aerogel photocatalysts by high efficiency combustion technology.
SiO 2 aerogel is a typical thermal insulation material suitable for varied high temperature industrial applications. However, its radiative transparency seriously hampers its application scenario. Herein, we integrated infrared (IR) opacified Fe 2 O 3 nanoparticles into silica aerogel system and developed a Fe 2 O 3 /SiO 2 composite aerogel (FSA) by using industrial water glass and ambient pressure drying process. Especially, we chelated Fe 3+ with disodium ethylenediaminetetraacetic (EDTA-2Na) to avoid the loss of Fe 3+ in the gelling, solvent-exchanging and hydrophobic modification processes. FSA powders with 3–11% concentration exhibited an amorphous structure, high porosity with small nanopores (11–12 nm). The EDS analysis confirmed the presence of Fe in the aerogel samples. The high-temperature thermal insulation properties of the FSA powders were enhanced compared with the pure SiO 2 aerogel powders, yielding a cold surface temperature of 456 ℃ after heating at 600 ℃ for 30 min, 26 ℃ lower than pure SiO 2 aerogel. The EDTA-2Na chelating agent improved the dispersion of Fe 3+ and further reduced the temperature by 6 ℃, demonstrating its positive effect on the insulation performance.
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