One Step Synthesis of ZnO/g-C3N4 Composite for Photocatalytic Degradation of Methylene Blue and Emerging Contaminants Under Sunlight

A key factor limiting the photocatalytic performance of pure graphitic carbon nitride (g-C 3 N 4 ) is the swift recombination of photogenerated electron–hole pairs. To address this issue, the ZnO/g-C 3 N 4 composites were synthesized via a one-step calcination method. Their structure, composition, and morphology being characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). An L 16 (4 5 ) orthogonal array was employed to investigate the effects of various factors on the removal efficiency. The results exhibit that under optimal conditions (sunlight irradiation time: 20.0 h, pH: 7.00, catalyst dosage: 40 mg, ZnO/g-C 3 N 4 mass ratio: 4:1), the methylene blue removal rate reached 92.36%. Comparative experiments demonstrated removal efficiencies of 43.64% for phenol, 52.13% for tetracycline, and 40.26% for pyridine, respectively. Moreover, the removal rate of methylene blue can still reach 90.12% after five cycles. Trapping experiments for active species confirmed that photogenerated electrons and holes are critical for methylene blue degradation. ZnO doping g-C 3 N 4 improves the methylene blue removal performance of g-C 3 N 4 , providing a facile strategy for developing g-C 3 N 4 /metal oxide heterostructure to deal with emerging contaminants in the future.