The Influence of Biochar Content on the Structure and Photocatalytic Activity of TiO₂/g-C₃N₄/Biochar Composite Materials

Abstract

In this study, the ternary composite material TiO₂/g-C₃N₄/biochar (TCNBC), derived from reed stalks, was successfully synthesized using a simple hydrolysis method. The study demonstrates that biochar has a significant impact on the structure and photocatalytic activity of the obtained composite material. Biochar plays a crucial role in inhibiting crystal growth, increasing the specific surface area, narrowing the band gap energy, and enhancing the visible light absorption capability of TiO₂. The TCNBC composite exhibits an average crystal size of 5.5 nm and a lower band gap energy of 0.62 eV, while its specific surface area (32.6 m²/g) is significantly higher than that of pure TiO₂ (33.7 nm, 3.02 eV, and 2.1 m²/g). The synthesized photocatalyst composite was used as an effective catalyst for the photodegradation of doxycycline (DC) from aqueous solutions. The hybrid TCNBC catalyst exhibited approximately 7.48 times higher photocatalytic activity compared to pure TiO₂. The TCNBC composite synthesized with a TiOSO₄/g-C₃N₄/biochar mass ratio of 4/1.5/0.5 achieved the highest DC photodegradation efficiency, reaching 91.93% within 120 minutes of visible light irradiation. These findings indicate that the synthesized catalysts hold great promise for the treatment of DC in wastewater.