Preparation Of Bi₅O₇I-Based Composite Catalysts And Their Photocatalytic Degradation Of Tetracycline Hydrochloride

In recent years,while antibiotics have provided protection for human and animal life and health,they have also brought environmental pollution and damage to the ecological balance of water.If antibiotic pollution is not handled in time,it will inevitably endanger the ecological balance seriously and pose a serious threat to human life and health.Antibiotics are structurally stable,difficult to biodegrade,and biologically toxic,which makes it difficult for traditional biological treatment technologies and physical treatment technologies to effectively treat antibiotic wastewater and control antibiotic pollution.Therefore,the development of an efficient technology for the treatment of antibiotic wastewater is of great significance to the protection of the ecological environment and the promotion of human life and health.The photocatalytic oxidation method has the advantages of simple operation,green pollution-free,high degradation efficiency,energy saving and environmental protection,etc.,so it has a good application prospect in the treatment of antibiotic wastewater and the treatment of antibiotic pollution.In this paper,the element doping method and different semiconductor compound methods were used to successfully prepare the composite catalyst Bi₅O₇I/g-C₃N₄ and the composite catalyst Bi₅O₇I/g-C₃N₄-Ce,which were used in the photocatalytic degradation of tetracycline hydrochloride.The main research contents are as follows:（1）Bi OI and g-C₃N₄ were prepared by hydrothermal precipitation method and high temperature calcination method,and then a series of composite catalysts Bi₅O₇I/g-C₃N₄ with different mass ratios were prepared by high temperature calcination method and used for photocatalytic degradation of tetracycline hydrochloride.The results show that when the weight of g-C₃N₄ in the composite catalyst is 5%,the photocatalytic activity of the composite catalyst Bi₅O₇I/g-C₃N₄ is the highest.The prepared composite catalyst Bi₅O₇I/g-C₃N₄ was characterized,and the results showed that the composite of Bi₅O₇I and g-C₃N₄ did not affect the crystal structure and molecular structure of Bi₅O₇I.The composite catalyst Bi₅O₇I/g-C₃N₄ was composed of nano flakes and it has a certain hollow structure.In addition,its light absorption range has been successfully expanded.The photocatalytic mechanism analysis results show that the main active substances in the photocatalytic degradation of tetracycline hydrochloride by the composite catalyst Bi5O7I/g-C3N4 are superoxide radicals（·O₂^-）and holes（h⁺）.（2）Using element doping method to modify g-C₃N₄,successfully prepared a series of modified g-C₃N₄-Ce with different Ce element doping amount,and degrading tetracycline hydrochloride by photocatalysis.The results showed that when Ce element doping amount At 2%,its photocatalytic activity is the highest.The prepared modified g-C₃N₄-Ce was subjected to material characterization,and the results showed that Ce doping not only does not affect the molecular structure and crystal structure of g-C₃N₄-Ce,but also reduces its photo-generated electron-hole Recombination rate,thereby improving its photocatalytic activity.（3）Fully mix the modified g-C₃N₄-Ce and Bi OI with the highest catalytic activity,and then prepare a series of composite catalysts Bi₅O₇I/g-C₃N₄-Ce with different mass ratios by high-temperature calcination,and use them for photocatalytic degradation of tetracycline hydrochloride.The results show that when the weight of g-C₃N₄-Ce in the composite catalyst is 5%,the photocatalytic activity of the composite catalyst Bi₅O₇I/g-C₃N₄-Ce is the highest.The prepared composite catalyst Bi₅O₇I/g-C₃N₄-Ce was characterized,and the results showed that the composite of Bi₅O₇I and g-C₃N₄-Ce did not affect the crystal structure and molecular structure of Bi₅O₇I.The composite catalyst Bi₅O₇I/g-C₃N₄-Ce is a kind of nano flakes with a smaller size.In addition,its light absorption range has been successfully broadened.The results of photocatalytic mechanism analysis showed that the main active substances of the composite catalyst Bi₅O₇I/g-C₃N₄-Ce in the photocatalytic degradation of tetracycline hydrochloride are superoxide radicals（·O₂^-）and holes（h⁺）.（4）The optimal conditions and material stability of the composite catalyst Bi₅O₇I/g-C₃N₄-Ce for degradation of tetracycline hydrochloride were explored.The experimental results show that the optimal photocatalyst dosage of the composite catalyst Bi₅O₇I/g-C₃N₄-Ce is 1.0g/L,and the lower the initial concentration of tetracycline hydrochloride,the higher the photocatalytic activity.In addition,the photocatalytic activity of the composite catalyst Bi₅O₇I/g-C₃N₄-Ce can still be maintained at a high level after being recycled for 4 times.