Degradation Behavior And Mechanism Of Tetracycline Antibiotics In Aqueous Solution By Carbon Nitride Catalyst

Tetracycline antibiotics,broad-spectrum bacteriostatic agent,are widely used in the treatment of livestock and human bacterial infection.However,the antibiotic is easily soluble in water and difficult to degrade,which can easily accumulate and eventually pose a threat to humans.In the field of environmental remediation,photocatalytic oxidation technology is considered to have great potential because of its green and easy operation.Finding a kind of high efficiency and wide spectrum material for photocatalytic oxidation has become a researc h hotspot.Graphite carbon nitride（g-C₃N₄）has become a research hotspot due to its characteristics of cheap and easy preparation,strong electrical conductivity and stability,and easy electronic structure adjustment.In this paper,the reasonable design of g-C₃N₄ to improve its catalytic performance,so that it can effectively remove antibiotics in water.Then,the morphology and properties of the material were further studied through characterization technology,and the reasons for the improvement of catalytic performance were verified.In the end,the degradation behavior and anti-interference of the material were studied.The main research contents are as follows:（1）Oxygen structure was introduced into g-C₃N₄ to adjust its electronic structure and strengthen the light absorption.Further,oxygen vacancy bismuth tungstate/oxygen rich carbon nitride（BWO-OV/OCN）heterojunction composite was prepared by hydrothermal method to degrade tetracycline pollutants in water.Different characterization techniques proved that the composite was successful,and the specific surface area of the composite was larger than that of the monomer,the absorption of visible light was stronger,and the separation ability of electron hole pair was stronger.The photocatalytic degradation results display that the tetracycline degradation by the composite material can reach 96.16%,which is far higher than 30.22%of OCN and62.94%of BWO-OV.The improvement of the catalytic efficiency may be due to the large specific surface area profit supplying a mass of reaction sites,and the black body nature of the material conducive to the absorption of visible light.The formed heterojunction is favorable for photogenic electron transfer.（2）Iron was directly doped in g-C₃N₄ which could regulate the electronic structure of g-C₃N₄ to improve insufficient visible light absorption of g-C₃N₄ and prevent rapid recombination of photogenerated electron holes.The oxygen-rich precursor synthesized by ferric chloride and dicyandiamide hydrothermal method showed a stronger visible light response range.The weakly acidic ethylenediaminetetraacetic acid and weakly alkaline hydrothermal dicyandiamide self-assembled to form a new precursor and calcined to form iron-doped porous carbon nitride（Fe/PCN）.The characterization results show that Fe/PCN has higher specific surface area and stronger absorption capacity in the full spectral region,which can improve the utilization of solar energy and generate more electron hole pairs.In addition,due to the characteristics of the catalyst,in combination with Fenton reaction,iron species can activate hydrogen peroxide to generate hydroxyl radical and achieve the regeneration of iron bivalent through the cycle,showing higher catalytic oxidation performance.The degradation experiments showed that the re moval efficiency of oxytetracycline in the photo-Fenton system was 99.24%,and the degradation rate was up to 0.072 min^-1,which showed strong stability and anti-interference.The possible degradation pathway and mechanism of oxytetracycline were put forwa rd.The toxicity assessment showed that the process was green and friendly to the environment.