Sol–Gel Synthesis of C3N4-Decorated AlFeO3 Photocatalyst and Environmental Purification of Methyl Orange Wastewater

The C₃N₄/AlFeO₃ photocatalysts were synthesized successfully via a sol-gel route and low temperature calcination process. When C₃N₄ is coupled with AlFeO₃ to form a special heterojunction, the crystal structure, composition and optical band gap of the main lattice phase are not changed. However, its surface morphology, optical absorption coefficient and photocatalytic activity are greatly improved compared with pure C₃N₄ and AlFeO₃. Photocatalytic experiments confirmed that the C₃N₄/AlFeO₃ photocatalyst showed high photocatalytic activity for degradation of methyl orange under visible light irradiation, and its degradation rate was 9.40 times that of C₃N₄ and 5.13 times that of AlFeO₃. The optimal catalyst content, dye concentration and pH value are 1 g/L, 20 mg/L and 5, respectively. Capture and stability experiments confirmed that the C₃N₄/AlFeO₃ photocatalyst is recyclable, and holes, hydroxyl radicals and superoxide radicals are the main active species in the photocatalysis process.