High thermostable ordered mesoporous SiO2–TiO2 coated circulating-bed biofilm reactor for unpredictable photocatalytic and biocatalytic performance

• A novel photocatalytic circulating biofilm bed reactor is fabricated successfully.
• The macro/mesoporous SiO2–TiO2/PUF as the carrier is a key point for the PCBBR.
• The ordered mesoporous SiO2–TiO2 has the high crystallinity and large surface area.
• Synergic effect between photocatalysis and biocatalysis in PCBBR is vital.

Utilizing high thermostable ordered mesoporous SiO2–TiO2 as a precursor, macroporous polyurethane foam (PUF) as a floating biofilm carrier, the photocatalytic circulating-bed biofilm reactor (PCBBR) is fabricated via ultrasonic vibration and deposition approach. The prepared SiO2–TiO2/PUF carrier is characterized in detail by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, N2 adsorption, scanning electron microscopy and energy dispersive spectroscopy. The results indicate that the ordered mesoporous SiO2–TiO2 network can be maintained and the presence of SiO2 can inhibit the anatase-to-rutile phase transformation during 800 °C calcinations. Furthermore, the prepared SiO2–TiO2/PUF carrier presents a hierarchical macro/mesoporous structure, filling the bacterium to the channels. The PCBBR exhibits good synergic effect for the refractory phenolic wastewater, and the total organic carbon removal ratio of high toxic 2,4,5-trichlorophenol is up to 97.5% after hydraulic retention time for 3 h, which is ascribed to the hierarchical macro/mesoporous structure in favor of pollutants adsorption, efficient photon utilization and microorganism loading. This novel ordered mesoporous SiO2–TiO2 coated circulating-bed biofilm reactor is promising in the environmental field.

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