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Preparation of nano-ZnO and its photocatalytic degradation of dyeing wastewater

2019; Science Press; Volume: 36; Issue: 04 Linguagem: Inglês

10.3724/sp.j.1249.2019.04367

1000-2618

Lijuan Wang, Xiaoning LI, Aiwu CHEN, Ying Wang, Butao JIANG,

Nanoparticles: synthesis and applications

The nano-ZnO powder is synthesized by using the direct precipitation method through the reaction between zinc chloride and ammonia water, and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Under the simulated ultraviolet and visible light conditions, methylene blue (MB) is used as the target contaminantin dyeing wastewater to investigate the photocatalytic activity of nano-ZnO. The effects of the calcination temperature, nano-ZnO dosage, photocatalytic reaction time, initial pH and initial concentration on the MB removal efficiency are studied. The results show that when the calcination temperature is 400 ℃ (the morphology of ZnO is spherical and flake-likemixed), the nano-ZnO dosage is 2 g/L, the initial mass concentration of the solution is 5 mg/L, and pH=9, the maximum removal rate of MB by nano-ZnO can reach 93.11% after UV irradiation for 3 h, and the maximum removal ratio of MB is 65.49% after exposure to visible light for 3 h. The removal ratio of MB after nano-ZnO recycling for 4 times under ultraviolet light can still reach 88%. The results of free radical quenching experiments show that the holes are the primary controlling factor for the degradation of MB by nano-ZnO. Because nano-ZnO is small in size, large in specific surface area, small in forbidden band gap, high in recycling rate, and environmentallyfriendly, it would have broad application prospects in water treatment.