Sustainable utilization of bio-waste for surface functionalization of mesoporous silica with titania to enhance photocatalytic activity

• Bioenergy obtained from rice husk helps reduce greenhouse gas emissions. • Photocatalyst composite was synthesized from alkali extraction of rice husk ash. • Calcination temperature strongly influenced photoactivity of titania catalysts. • Interaction of TiO 2 with SiO 2 with mesostructure results in high photoactivity. • Both adsorption and photolysis enhanced the catalyst’s degradation efficiency. Rice husk (RH) is a bio-waste that can be harnessed as bioenergy because of its rich lignocellulose content. However, in addition to bioenergy, RH produces a large amount of RH ash (RHA) after undergoing combustion, which can lead to environmental pollution. RHA is rich in silica; accordingly, this used recycled silica from RHA to prepare Santa Barbara Amorphous-15 mesoporous materials and then used these materials as a support to synthesize nano-TiO 2 photocatalyst composites. XRD and TEM analyses revealed that the TiO 2 synthesized in this study mainly exhibited an anatase structure and was evenly dispersed within the holes of the silica support. The size of the TiO 2 nanoparticles was 5.41–7.50 nm. XPS and FTIR confirmed that TiO 2 was tightly bound to the SiO 2 materials. The pore volumes of ​​the photocatalyst composites were 0.389–0.578 cm 3 /g, the surface areas were 269–426 m 2 /g, and the pore diameters were 6.31–9.29 nm. Photocatalytic degradation experiments were conducted using methyl orange. The optimal catalysis conditions are TiO 2 ratio of 30 %, calcination temperature of 800 °C, catalyst weight of 1.0 g/L, and solution pH of 2. The photocatalyst removal efficiency was nearly 100 % after 120 min. The photocatalytic efficiency remained >80 % after five cycles. This paper also discusses the photocatalytic reaction mechanism. Converting RHA into highly active photocatalyst composites materials not only provides an effective solution for managing agricultural waste but also contributes to wastewater treatment technology to fully achieve green resource recycling.