Preparation Of Tungsten Selenide Nano-composites And Study On Photocatalytic Degradation Of Organic Compounds

With the development of chemical industry,papermaking,textile and other industries,the issue of water pollution is constantly being reported by the media,which has attracted people's attention.Photocatalytic oxidation technology is a hot spot in recent years.It can not only use clean and pollution-free solar energy but also selectively oxidize organic pollutants,and the final product is pollution-free.Tungsten diselenide?WSe₂?is a very excellent photocatalytic semiconductor material,which has great potential in the field of photocatalysis.In this thesis,a visible light catalyst WSe₂ and its compound WSe₂/nitrogen doped graphene?NG?and Fe₃O₄-WSe₂/NG were designed and synthesized,and the degradation effect of these photocatalysts on the MB was studied.The details are as follows:?1?With Se powder and Na₂WO₄·2H₂O as raw materials,the rod like WSe₂nanomaterials were prepared by hydrothermal method,after the photocatalytic degradation test of the simulated dye wastewater MB,the preparation conditions were optimized.The photocatalyst WSe₂ was characterized by XRD,SEM,EDS and TEM.The experimental results showed that the photocatalytic activity of WSe₂ is the highest when the concentration of hydrochloric acid is 3.75 mol/L,and the reaction is 48h at 200?.At the same time,the affected by the amount of catalyst,MB initial concentration,the light intensity and the reaction time on the photocatalytic degradation of MB under visible light were studied.Finally,the results indicated that in the 500W light power,adding 0.05g WSe₂ to the concentration 2.0×10^-5mol/L of MB solution,the removal rate reaches the maximum,up to79.7%at the reaction time of 60 minutes.?2?Graphene oxide?GO?was synthesized by Hummers method,and then the WSe₂/NG composites photocatalyst with different mass fraction of NG were prepared by hydrothermal method using GO and WSe₂ as raw materials and urea as the nitrogen source.The morphology,structure and composition of the samples were analyzed by SEM,EDS,TEM,UV-vis DRS,XRD and elemental analysis.Using the MB organic dye as the degradation target,the degradation effect of WSe₂/NG under visible light irradiation and photocatalytic degradation mechanism was investigated under optimal photocatalytic conditions.The experimental results showed that the 50%NG mass fraction of WSe₂/NG composite photocatalyst reacted at 200?for 12h has the best degradation effect on the MB solution with a concentration of 6×10^-55 mol/L,and the removal rate was 99.3%.?3?Spherical nanometers Fe₃O₄ was prepared by liquid phase coprecipitation.Then the Fe₃O₄-WSe₂/NG composite photocatalyst with different mass fraction was synthesized with WSe₂,Fe₃O₄,GO and urea as nitrogen source.The photocatalysts were characterized by XRD,SEM,TEM,UV-vis DRS,XPS methods.The degradation effect of compounds to MB simulated dye wastewater and the degradation mechanism were studied under optimum photo-degradation conditions.The results showed that the Fe₃O₄-WSe₂/NG with Fe₃O₄ mass fraction of 30%reacted at 200?for 12 h,and under the condition of value 3 and H₂O₂3.0mM the degradation of 8.0×10^-5mol/L MB solution was the highest.The k_apppp is 0.05589min^-1,and the degradation efficiency was 98.8%.Moreover,it has high superparamagnetic property and good reusability,after four repeated experiments,the removal rate of MB was over 85%.