Dual-function TiO2/biochar composites for NH3 capture and decomposition

As ammonia (NH 3 ) is a significant atmospheric pollutant, its removal is crucial for ensuring human and environmental safety. This study aimed to address this issue by combining traditional adsorption technology with photocatalysis to develop a novel method for preparing a TiO 2 /biochar photocatalytic composite. The composite was synthesized through hydrothermal carbonization followed by low-oxygen calcination. The results demonstrated that the composite exhibited notable adsorption and degradation performance for NH 3 . Specifically, when NH 3 at a concentration of 10 ppm was continuously injected at a flow rate of 1 L min −1 , 0.5 g of the composite quickly reduced the NH 3 concentration to 3.73 ppm under ultraviolet light. The composite showed excellent stability, reusability and daylight availability. Hydrothermal carbonization effectively retained oxygen-containing functional groups on the hydrochar and stably bound metals oxides to the carbon carrier. Low-oxygen calcination substantially enhanced the composite's porosity and promoted the formation of TiO 2 active sites. The synergistic effects of high specific surface area, hierarchical porosity and abundant oxygen-containing functional groups on the carbon carrier significantly boosted NH 3 adsorption. Furthermore, the carbon carrier's exceptional electron-storage capability promoted efficient electron-hole separation, thereby elevating photocatalytic efficiency. When TiO 2 was fixed on the carbon carrier, the formation of Ti-O-C bonds reduced the band gap energy, enhancing its response to visible light. The combination of hydrothermal carbonization and low-oxygen calcination simultaneously improved the composite's adsorption and photocatalytic degradation abilities. This study introduces a new approach for NH 3 removal and broadens the application of sunlight in environmental remediation.