Study On Modification Of Bi₂MoO₆ Photocatalyst And Its Degradation Of Tetracycline Wastewater

Since the discovery of antibiotics,they have been used in the medical industry and animal husbandry,etc.,which play a great role in promoting human development and the growth of animals and plants.However,with the widespread use and even abuse of antibiotics,it has caused serious harm to the water environment and threatened the stability of the entire ecosystem.Removal of antibiotic contaminants in water bodies through reasonable and efficient means has gradually become the focus of research,and has a role in promoting the healthy and harmonious development of human economy and society.Photocatalytic technology is gradually applied to water pollution treatment due to its advantages of high processing efficiency,relatively mild reaction conditions,low energy consumption,and no secondary pollution.Bi₂MoO₆,a perovskite oxide with a stable Aurivillius structure,stands out from many photocatalysts due to its excellent visible light response and high quantum yield.However,it still faces the common problem with many photocatalysts,and its high recombination rate of photogenerated carriers will seriously limit the improvement of its photocatalytic activity.This article uses three different ways to modify it,including doping of metal strontium（Sr）ions,compounding with non-stoichiometric strontium iron oxide(SrFeO_2.73),compounding with lanthanum cobaltate（LaCoO₃）.The composite materials were analyzed and discussed through XRD,FT-IR,XPS,SEM,UV-vis characterization methods,and the photocatalytic activity was evaluated by the degradation efficiency of tetracycline（TC）,and the degradation mechanism and reaction process were analyzed.The main research contents are as follows:（1）Sr（NO₃）₂ is used as a strontium source and added during the solvothermal synthesis of Bi₂MoO₆ to form Sr-Bi₂MoO₆ with different doping amounts.When the doping mass ratio is 3 wt%,the degradation efficiency of TC reaches the highest.It can degrade 79.5%of TC in120 min.According to UV-vis analysis,after doping with Sr,the band gap width of Bi₂MoO₆becomes narrower,the light absorption is enhanced,and the quantum yield is increased.Moreover,the generation of Sr ions and defect sites will trap a part of the electrons,inhibiting the recombination of electrons and holes,thereby improving the photocatalytic activity.（2）SrFeO_2.73 was synthesized by sol-gel method,and was compounded with Bi₂MoO₆by ultrasonic dispersion to form TypeⅡheterojunctions with different composite ratios.With the continuous increase of the composite content of SrFeO_2.73,the photocatalytic degradation activity of TC increased first and then decreased.The best effect is that 30 wt%SrFeO_2.73/Bi₂MoO₆ can degrade 77.0%of TC in 100 minutes,which is mainly due to the arrangement of the energy bands of the two semiconductors in a staggered manner,which improves the separation rate of photogenerated electrons and holes,thereby improving the photocatalytic activity.（3）The citric acid was used to synthesize LaCoO₃ by solvothermal method.During the synthesis of Bi₂MoO₆,LaCoO₃ was added by ultrasonic dispersion to form p-n heterojunction LaCoO₃/Bi₂MoO₆ with different compound ratios.When the composite content of LaCoO₃ is5 wt%,the photocatalytic activity of Bi₂MoO₆ increases the most.It can degrade 86.1%TC in100 min,which is 28.3%and 65.2%higher than pure substances Bi₂MoO₆ and LaCoO₃,respectively,and also has good stability.This is mainly due to the formation of a p-n heterojunction,resulting in the establishment of an internal electric field,the life of photogenerated charges is extended and the separation rate of carriers is increased,thereby increasing the output of strong oxidizing active substances h⁺、·OH和·O₂^-.