Sol–Gel‐Prepared N–ZnO/TiO 2 Composite Photocatalysts: Optimization of Degradation Conditions for Tetracycline Hydrochloride and Stability Assessment

ABSTRACT The sol–gel method is employed to prepare N–ZnO, which is coupled with TiO 2 to successfully synthesize the N–ZnO/TiO 2 composite photocatalyst. Various characterization techniques, including x‐ray diffraction (XRD), Fourier‐transform infrared (FT‐IR), SEM, and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), were used to investigate the catalyst's structure, morphology, and optical properties. Tetracycline hydrochloride (TCH), a typical tetracycline antibiotic, serves as the degradation target. Three factors with the most significant influence on the photocatalytic effect are selected for single‐factor analysis. On the basis of the Box–Behnken Design (BBD) experimental design, the factors most affecting the photocatalytic degradation of TCH by N–ZnO/TiO 2 and the optimal degradation conditions are explored. The results show that the degradation efficiency of N–ZnO/TiO 2 on TCH solution is influenced by pH > dosage > initial TCH concentration. When the N–ZnO/TiO 2 dosage is 1.35 g L −1 , the initial TCH concentration is 33.85 mg L −1 , and the solution pH is 8.79, the optimal degradation rate of TCH wastewater reaches 95.81%. Possible degradation mechanisms and stability are investigated through radical capture experiments and cyclic stability tests. RhB, NOR, SMX, and other types of water pollutants are selected for photodegradation experiments to broaden the application scope of N–ZnO/TiO 2 .