Synthesis Of Bismuth Molybdate Photocatalyst Based On Yeast-template And Their Performance In The Treatment Of Printing And Dyeing Wastewater

With the development of printing and dyeing industry,printing and dyeing wastewater pollution has aroused widespread concern in the society.Semiconductor photocatalysis is an effective way to treat printing and dyeing wastewater.Among various semiconductor photocatalytic materials,Bi₂MoO₆ photocatalytic material has a typical Olive Chis layered structure.With response ability to visible light,Bi₂MoO₆has excellent performance in photocatalytic degradation of pollutants and hydrogen production.However,the application of Bi₂MoO₆ in photocatalysis is restricted due to the lack of quantum efficiency and low visible light response.We will focus on the optimization of the photocatalytic performance of bismuth molybdate.The morphology of Bi₂MoO₆ was controlled by biological templates method.On this basis,different process conditions were used to construct heterojunctions with semiconductor carbon nitride and bismuth sulfide to improve the photocatalysis of simulative dyeing wastewater.The possible photocatalytic mechanism was proposed based on the related characterization and experiments.The specific research contents and conclusions are as followed:（1）Bi₂MoO₆ microspheres photocatalytic material was prepared using yeast cells as biological templates.The differences among Bi₂MoO₆ prepared by hydrothermal method,precipitation method and biological templates method was analyzed and compared.The photocatalytic performance of bismuth molybdate microsphere for visible light driven degradation of simulated dye wastewater was tested.The crystal structure,morphology features,optical property of the materials were characterized by XRD,SEM and UV-Vis.Taking methylene blue as the target pollutant,the photocatalytic activity of Bi₂MoO₆microspheres was evaluated by the degradation of methylene blue simulated dye wastewater under visible light.The effects of different factors on the photocatalytic performance of Bi₂MoO₆ microspheres were investigated.The results showed that the Bi₂MoO₆microspheres with a diameter of about 8μm had good dispersity.Compared with Bi₂MoO₆ particles obtained by hydrothermal method or precipitation,the photocatalytic activity of Bi₂MoO₆microspheres synthesized through biological templates method has been significantly improved.It is proved that the microsphere morphology of Bi₂MoO₆ contributes to the improvement of its photocatalytic performance.The photocatalytic reaction is affected by temperature and catalyst dosage.The degradation rate of methylene blue reached 60%after120 min of visible light irradiation.It was proved that superoxide radical was the main active substance in the reaction process.（2）Based on biological templates synthesis of Bi₂MoO₆ microspheres,g-C₃N₄/Bi₂MoO₆composite materials were prepared via hydrothermal-template sacrifices method.The crystal structure,morphology,light absorption and physicochemical properties of the sample were characterized by XRD,SEM,TEM,EDS,FT-IR,BET,UV-vis and photocurrent response.The results showed that the hydrothermal-sacrificial template method realized the successful combination of g-C₃N₄ and Bi₂MoO₆ on the surface of biological template.The as-obtained microspheres with a diameter of about 8μm had good dispersity and exhibited flower-like nano-clusters and a specific surface area of 11.6007 m²/g.The degradation efficiency of MB was over 96%under visible light irradiation for 120 min.Mechanism analysis demonstrated that Z-type heterojunction formed between g-C₃N₄ and Bi₂MoO₆ reduced the recombination rate of electronic-hole effectively and enhanced the visible-light driven photocatalytic efficiency significantly.（3）Based on biological templates synthesis of Bi₂MoO₆ microspheres,Bi₂S₃/Bi₂MoO₆photocatalytic materials were prepared via biotemplate-anion exchange method.The crystal structure,microstructure and light absorption properties of the sample were characterized by XRD,SEM,TEM,XPS and UV-vis.The results showed that Bi₂S₃ and Bi₂MoO₆ were composited successfully by anion-exchange method.The morphology of the sample wasin the form of microspheres with a diameter of about 12μm with good dispersity.The formation of heterojunction improves the light absorption capacity significantly and reduces the band gap.The methylene blue was completely degraded after 120min of visible light irradiation.The main reactive substances in the reaction were determined by radical capture experiment.The possible photocatalytic mechanism was studied with aid of characterization and the data of experiment.