Synthesis,Modification Of Bi₂WO₆ And Photocatalytic Degradation Of Antibiotics

Antibiotics have been widely used in many fields such as medical treatment andaquaculture since they were invented.The water pollution caused by the extensive use,improper handling and massive discharge of antibiotics has become increasingly serious.As a new type of green and efficient degradation technology,photocatalysis technology has attracted attention.Recently,Bi₂WO₆ has been widely used in the field of photocatalysis due to its suitable band gap（2.7～2.9 e V）,easy preparation process,visible light response and non-toxic.However,Bi₂WO₆ still has the disadvantages of high recombination probability of photogenerated carriers and limited absorption of visible light.To solve the above problems,Bi₂WO₆ were synthesized by hydrothermal method in this dissertation.And its photocatalytic degradation performance of antibiotics was improved in a variety of ways through the construction of oxygen vacancies and the compound of Mo S₂ quantum dots.The main researches are as follows:（1）Synthesized of Bi₂WO₆ by hydrothermal method and photocatalytic degradation of antibiotics.Bi₂WO₆ photocatalysts were synthesized by hydrothermal method at120℃,140℃,160℃and 180℃,with Bi（NO₃）₃·5H₂O and Na₂WO₄·2H₂O as precursors.The crystal structure,elemental composition and morphology of Bi₂WO₆photocatalysts were systematically characterized by XRD,XPS,SEM,TEM and BET measurements.The photocatalytic degradation for tetracycline hydrochloride（TC）and levofloxacin（LVFX）of Bi₂WO₆ were studied,and the photocatalytic degradation mechanism were analyzed.The research results show that the Bi₂WO₆ obtained at 140℃hydrothermal temperature exhibits the best photocatalytic activity.The photocatalytic degradation rate of TC was 93.16%after 40 min of visible light irradiation,and that of LVFX was 93.80%under visible light irradiation for 2 h.（2）Synthesized of Bi₂WO₆ with rich oxygen vacancies and photocatalytic degradation of antibiotics.The Bi₂WO₆ samples were alkali-etched with Na OH solution,and oxygen vacancies were constructed by controlling the concentration of Na OH solution.The crystal structure,elemental composition and morphology of Bi₂WO₆ with rich oxygen vacancies were systematically characterized by XRD,XPS,Raman spectroscopy,SEM and TEM measurements.The photocatalytic degradation for levofloxacin（LVFX）of Bi₂WO₆ with rich surface oxygen vacancies were studied,and the photocatalytic mechanism were tested.The obtained results proved that the band gap decreased from 2.68 e V to 2.44 e V after the oxygen vacancies were constructed.When the concentration of Na OH is 0.5 M,the photocatalytic degradation rate of Bi₂WO₆ for LVFX reached 95%.The surface oxygen vacancy constructed after alkaline etching can introduce a shallow defect level at the top of the valence band of Bi₂WO₆,which improves the visible light absorption capacity,so that improve the photocatalytic performance of Bi₂WO₆ photocatalytic.（3）Synthesized of Mo S₂ quantum dots/Bi₂WO₆ composites and photocatalytic degradation of antibiotics.The Mo S₂/Bi₂WO₆ composite photocatalysts were fabricated via an electrostatic self-assembly method through-loading Mo S₂ quantum dots on the surface of Bi₂WO₆.The crystal structure,elemental composition and morphology of the Mo S₂/Bi₂WO₆ composite photocatalysts were systematically characterized by XRD,SEM,TEM and XPS measurements.The photocatalytic degradation for levofloxacin（LVFX）of Mo S₂/Bi₂WO₆ composite photocatalysts were studied,and the photocatalytic mechanism was analyzed.The obtained results indicated that both the visible light absorption capacity and the photogenerated carrier migration rates of Mo S₂/Bi₂WO₆ composite photocatalysts were significantly improved after loading Mo S₂ quantum dots.The photocatalytic degradation rate of the optimal Mo S₂/Bi₂WO₆ composite photocatalyst for LVFX reached 83%,while the degradation rate of Bi₂WO₆ was only 69%under visible light irradiation for 2 h.The degradation kinetic constant of the composite photocatalyst was 0.0183 min^-1,which was 1.22 times than that of Bi₂WO₆.（4）Synthesized and photocatalytic degradation of antibiotics by Mo S₂ quantum dots combined with rich oxygen vacancies Bi₂WO₆.Mo S₂ quantum dots were loaded on the surface of Bi₂WO₆ with rich oxygen vacancies for the preparation of composite photocatalysts.The crystal structure,elemental composition and morphology of the composite photocatalysts were systematically characterized by XRD,SEM,TEM and XPS measurements.The photocatalytic degradation performance of levofloxacin（LVFX）was studied.Compared with Bi₂WO₆ with rich oxygen vacancies,the visible light absorption capacity of the composite photocatalysts were slightly improved after loading Mo S₂ quantum dots.However,the composite photocatalysts decreased 8%than that of the Bi₂WO₆ with rich oxygen vacancies for the photodegradation of LVFX.Therefore,the construction of oxygen vacancies on the surface and the construction of heterojunction loaded with Mo S₂ quantum dots do not achieve synergistic effect in the photocatalytic degradation of LVFX.