Construction of Oxygen Vacancy Defects of γ-Al<sub>2</sub>O<sub>3</sub> and Application of UV-Vis Spectrophotometry in Its Performance Detection

In this paper, the precursor of γ-Al₂O₃ was prepared by hydrothermal method, AlOOH (pseudo-thin aluminium water), further mixed with melamine, calcined into oxygen-deficient γ-Al₂O₃ (OV-γ-Al₂O₃) by one-step pyrolysis method in an air atmosphere, and the morphology and structure of the samples were characterized by a series of characterization methods such as SEM and XRD. Ultraviolet-Vis spectrophotometry was used to determine the degradation efficiency of the catalyst to methylene blue. By controlling the annealing rate of melamine (CM) and g-C₃N₄(CN) after calcination of γ-Al₂O₃ precursors, the products of melamine thermal decomposition were investigated to form g-C₃N₄ or oxygen vacancies formed by γ-Al₂O₃. The results show that when the annealing rate is 5°C/min, g-C₃N₄ is formed, and when the annealing rate is 1°C/min, g-C₃N₄ decomposes to construct the oxygen vacancy of the carrier. When the doping ratio is 1.2:1, the total degradation effect of OV-γ-Al₂O₃ can reach 89%, which is 2.8 times that of ordinary Al₂O₃ and 1 times higher than that of γ-Al₂O₃. The stability of OV-γ-Al₂O₃ was proved by five cycle experiments and the degradation of different concentrations of MB solution, and the data were analyzed and discussed, in order to provide a theoretical basis and research ideas for the treatment of actual sewage. Finally, combined with various characterization and test results, the main active species of OV-γ-Al₂O₃ in the degradation process were predicted •OH.