Utilizing rice husk for sustainable production of mesoporous titania nanocomposites with highly adsorption and photocatalysis

Rice husks are a lignocellulosic biowaste that can be used to produce valuable renewable energy. However, combustion of rice husks produces rice husk ash. Rice husk ash should be effectively utilized to reduce environmental pollution and create a circular economy. In the study, rice husk ash was employed to extract silica for the preparation of mesoporous Santa Barbara Amorphous-15 (RH-SBA-15) materials, and a titanium precursor was then added to obtain a TiO₂/RH-SBA-15 photocatalyst. X-ray diffraction and transmission electron microscopy confirmed that mesostructure of silica inhibits TiO₂ grain growth and is conducive to the generation of anatase-phase TiO₂. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed that Ti–O–Si bonds are generated during synthesis of catalyst. A photodegradation experiment was conducted using methyl orange for near-ultraviolet light tests. RH-SBA-15 provides many adsorption sites, thereby improving photoactivity of TiO₂. The photocatalytic efficiency of catalyst increases with an increase of initial dye concentration, catalyst mass, and calcination temperature but decreases with an increase in the pH of dye solution. The optimal catalysis conditions are initial dye concentration of 50 ppm, catalyst weight of 200 mg, solution pH value of 2, calcination temperature of 800 °C, and TiO₂ ratio of 30 %. The photocatalytic mechanism was elucidated through kinetic analysis and a free-radical-scavenging test. Recycling of rice husk ash to produce high-value-added mesoporous photocatalysts can help to address environmental pollution problems such as those related to agricultural waste storage and wastewater treatment.