Photodegradation under Ultraviolet Light Irradiation of RhB by ZnO–ZnCr₂O₄/g-C₃N₄ Nanocomposites Fabricated by Urea Combustion Method

Due to the rapid national development of various countries, organic dyes have been applied in manufacturing products such as leather, textiles, paper, and cosmetics. However, the wastewater produced by these industries is harmful to the environment and organisms. Moreover, organic dyes contain toxic carcinogens and cause the reduction of the oxygen content in water, which is harmful to nature and the water resources people use. Photodegradation is a low-cost, highly efficient, and low-energy way to remove these substances. Zinc-based materials were applied as a degradation catalyst in this study. ZnO–ZnCr2O4/g-C3N4 nanocomposites were fabricated by the urea combustion method and used as photocatalysts for rhodamine B (RhB) degradation under ultraviolet A (UVA) light irradiation. ZnO–ZnCr2O4/g-C3N4 was investigated by XRD, FESEM, BET, UV-Vis, and TEM to confirm the crystalline microstructure. Based on the various annealing temperatures of ZnO–ZnCr2O4/g-C3N4 nanocomposite, the specific surface area varied from 36.33 m2/g to 107.55 m2/g. In addition, the photocatalytic activities of ZnO–ZnCr2O4/g-C3N4 nanocrystals were investigated through the degradation of RhB under UV light for 12 hours. After 12 hours, 95.45% of the RhB was degraded under UV light irradiation. ZnO–ZnCr2O4/g-C3N4 nanocomposites annealed at 500°C exhibited the highest rate constant, up to 6.11 × 10−3 min−1, and ZnO–ZnCr2O4/g-C3N4 revealed excellent stability based on the results of the cyclic test.