Preparation Of Heterojunction Bismuth Photocatalytic Material And Its Research On Degradation Of Pollutants

Semiconductor photocatalysis is considered to be one of the most potential technologies for solving environmental pollution due to its characteristics of simplicity,high efficiency,no secondary pollution and no selective oxidation.As a new type of bismuth-based semiconductor photocatalyst,Bi OCOOH has potential application value in the field of photocatalysis due to its unique structure,which has gradually attracted researchers'attention.However,BiOCOOH has a large band gap,which can only absorb the ultraviolet band in the solar spectrum,and its low coefficient of utilization of solar energy limits its practical application.In view of this,this paper improves the photocatalytic degradation activity of BiOCOOH by controlling the synthesis temperature of BiOCOOH and adopting semiconductor coupling.XRD,FESEM,FT-IR and UV-vis DRS are used to characterize the phase,morphology,structure and light absorption properties of the catalyst.Under ultraviolet-visible light,tetracycline is used as the degradation target product,and the optimal coupling ratio is selected,and it is used for the study of photocatalytic stability and catalytic degradation mechanism.Research indicates:1.BiOCOOH photocatalytic material prepared by hydrothermal method has a sheet-like structure,its crystallinity and light absorption performance are affected by the synthesis temperature;BiOCOOH synthesized at 180?has the best photocatalytic activity,the input of 50 mg can almost completely degrade 50 mL of 10 mg/L tetracycline within 50 min;the main active species involved in the photocatalytic degradation of tetracycline by BiOCOOH are holes?h⁺?and superoxide radicals?·O?^-?;the reusability of the photocatalyst is good.2.Coupling g-C₃N₄ with BiOCOOH to prepare a composite photocatalyst with n-n heterojunction g-C₃N₄/BiOCOOH has significantly improved degradation performance.When the mass ratio of g-C₃N₄ to Bi OCOOH is 1:5,it exhibits the best photocatalytic activity,and its degradation rate is 4.84 and 7.83 times that of g-C₃N₄and Bi OCOOH,respectively;holes?h⁺?and superoxide radicals?·O?^-?is the main active species for degradation;the reusability of the photocatalyst is good.3.Coupling Bi₂WO₆ with BiOCOOH to prepare Bi₂WO₆/BiOCOOH composite photocatalyst with p-n heterojunction.Due to the existence of the p-n heterojunction,the separation efficiency of photogenerated carriers is improved,and the photocatalytic activity of the composite material is significantly improved.When the mass ratio of the two is 1:1,the photocatalytic activity is the best,and the degradation rate is 4.34 times and 9.09 times that of Bi₂WO₆ and BiOCOOH;the hole?h⁺?and superoxide radical?·O?^-?are main active species of the degradation process;external factors such as the amount of catalyst,concentration of tetracycline solution,salt effect,and pH of the solution must have influence on the photocatalytic degradation activity;the reusability of the photocatalyst is good.4.one-step hydrothermal method to prepare a p-n heterojunction composite photocatalyst BiOCOOH/BiOX?X=Cl,Br,I?has excellent photocatalytic activity.Due to the existence of the p-n heterojunction,the separation efficiency of photogenerated carriers is improved,and the photocatalytic activity of the composite material is significantly improved.When the added amounts of KCl,KBr,and KI were 1.0,1.0,and 0.7 mmol,respectively,the prepared photocatalyst show the best photocatalytic activity,and the input of 50 mg is able to effectively degrade 50 mL 20 mg/L of tetracycline within 35 min;the main active species that degrade tetracycline are superoxide radicals?·O?^-?and holes?h⁺?;the reusability of the photocatalyst is good.