The Preparation, Modification, Characterization And Application In Wastewater Treatment Of Novel Photocatalysts

With the booming development of the industry, the wastewater has been increasingly serious as a thorny environmental problem. How to effectively deal with the problem has become one of the most urgent issues in environmental purification. Photocatalytic technology, as a simple and efficient method, is mild and green in degradation of organic pollutants and can reduce the cost, therefore, it has been the hot research in catalysis and environmental protection. Traditional photocatalyst, such as TiO2, can only convert the ultraviolet part of the solar spectrum (about 3%) due to the overlarge band gap (about 3.2 eV). On the other hand, as an under-size powder, it is hard to recollected and reused, leading to the high cost and second pollution and being limited in the application of wastewater problem. Therefore, the two issues are urgent to deal with in photocatalysis: looking for novel visible-light-responding photocatalyst and solving the recycle and reusability.In this paper, the Mo-doped ZnWO4 nanoparticles were synthesized by a facile and effective hydrothermal method. The photocatalytic activities of the as-prepared pure ZnW04 nanoparticles and Mo-doped ZnWO4 nanoparticles were compared by the degradation of RhB. The doping effects with different molar ratios of molybdenum ions on the properties of ZnWO4 nanoparticles such as particle size, specific surface area, band gap as well as the photocatalytic performance were systematically studied, and the possible mechanism was also discussed.The magnetic nanoparticle Fe3O4 was firstly prepared through co-precipitation method, using iron (Ⅲ) chloride hexahydrate, iron (Ⅱ) sulfate heptahydrate, ammonia solution and hydrochloric acid as the main sources. Then, the Fe3O4 magnetic nanoparticles were covered by a layer of compact carbon, which was made by glucose through hydrothermal method. The formed core-shell structured Fe3O4@C was detected by TEM, proving to be that the Fe3O4 nanoparticles have been successfully coated with a thin carbon layer, the average thickness of which is about 2 nm. The as-prepared was dispersed in a Cl- solution, followed by addition of BiO+solution. The precipitation reaction of BiOCl would be carried out on Fe3O4@C, forming a ternary core-shell composite, which was proved to be dandelion-like through the following hydrothermal reaction.The magnetic nanoparticle Fe3O4 was alternatively covered by a SiO2 layer, which was made from TEOS through sol-gel method and detected to be about 30 nm in thickness by TEM. The formed core-shell Fe3O4@SiO2 was deposited by BiOBr with the following hydrothermal process, turning out to be a microsphere with the diameter from 1 to 2 μm. Another ternary core-shell composite Fe3O4@SiO2@Ag3PO4 was similarly prepared through the combination of Fe3O4@SiO2 as the core and Ag3PO4 as the shell.In this paper, the catalytic activities of the as-prepared Fe3O4@BiOCl, Fe3O4@SiO2@BiOBr and Fe3O4@SiO2@Ag3PO4 were evaluated by the degradation of rhodamin B (RhB), which was used as a model pollutant. The morphology and composition were characterized by X-ray diffraction、scanning electron microscopy and transmission electron microscopy. The properties were systemically studied by UV-Vis diffuse reflectance spectrum, photoluminescence spectrum, photocurrent spectrum and BET surface areas and the probable reaction mechanism was discussed.