Soybean residues assisted g-C3N4/SiC photocatalyst prepared from waste materials: Synthesis, characterization, and application of tetracycline photodegradation irradiated with simulated sunlight

Abstract This study employed the reproduced carbon black, waste silicon materials, and soybean residue to develop an environmentally friendly O-gC₃N₄/SiC composite photocatalyst and evaluated the corresponding photodegradation performance of tetracycline (TC). Initially, the reproduced carbon black was soaked in nitric acid to eliminate impurities, which resulted in the lowest ash content (7.86%). Soybean residue is a vital replacement for melamine during the preparation of graphitic carbon nitride. The characteristics of the synthesized SiC, O-gC₃N₄, and O-gC₃N₄/SiC photocatalysts were verified through TEM, XRD, and Fourier-transform infrared spectroscopy. The characteristic wavelength of the O-gC₃N₄/SiC photocatalysts was 523–541 nm, indicating that visible light triggers the photocatalytic reaction. The composites of soybean residue and SiC enhanced TC degradation, resulting in the best degradation rate of 89.5% with an initial first-order reaction rate constant of 2.01 × 10⁻ ² 1/min for O0.10M0.90SC₅ photocatalysts. Free radical trapping experiments determined the electron holes (h⁺) and OH· as the primary free radicals responsible for TC degradation, whereas O₂⁻· played a relatively minor role. A photodegradation mechanism for O-gC₃N₄/SiC was also proposed. The prepared O-gC₃N₄/SiC photocatalysts are promising candidates for sustainable applications.