Degradation Of Ciprofloxacin And Tetracycline By Graphene Quantum Dots Composite Bi2w06

Antibiotic wastewater is a kind of wastewater which is difficult to treat.It has complex and diverse organic substances which are difficult to degrade and biotoxic.It has a wide range of sources and serious harm to human beings,animals and plants,so it is urgent to treat antibiotic wastewater.At present,there are endless studies on antibiotic wastewater treatment methods.Among them,adsorption and photocatalysis have the advantages of simple operation,low cost and environmental protection.So this paper chooses these two methods to degrade ciprofloxacin and tetracycline,which are widely used in China.The main results are as follows:(1)Graphene quantum dots/bismuth tungstate(GQDs/Bi2WO6)composites with different proportions were prepared by one-step hydrothermal method and two-step hydrothermal method respectively.The basic structure of the composites is still bismuth tungstate.The morphology of the composites prepared by one-step method is more complete than that by two-step method.The specific surface area of the composites is larger and the fluorescence intensity is lower.Among the materials prepared by one-step method,0.2GQDs/Bi2WO6 has the largest specific surface area and the lowest fluorescence intensity.(2)The influence factors of degradation of ciprofloxacin and tetracycline by GQDs/Bi2WO6 composites were studied.It was found that the degradation performance of the composites prepared by one-step method was better than that of the composites prepared by two-step method.Among the materials prepared by one-step method,0.2GQDs/Bi2WO6 had the highest total degradation rate of the target pollutants,and the total degradation rate of ciprofloxacin was 91.8%.The total degradation rate was 92.3%.When the initial concentration of the solution is 10 mg/L,the solution pH is 7,and the material dosage is 50 mg,the degradation effect of 0.2GQDs/Bi2WO6 composite material on ciprofloxacin and tetracycline is the best.(3)From the comparison of adsorption performance and photocatalytic adsorption performance,it was found that the adsorption performance of the modified material was improved faster than that of photocatalysis,indicating that the'addition of graphene quantum dots had a greater impact on the adsorption performance than that of photocatalysis.The adsorption process of 0.2GQDs/Bi2WO6 for ciprofloxacin and tetracycline was easy to carry out,and the adsorption capacity of the material for tetracycline was larger than that of ciprofloxacin.(4)N-GQDs/Bi2WO6 with different N/Bi ratios were prepared by hydrothermal method.By means of XRD,SEM,BET,FT-IR and PL,the material composition,morphology and structure,specific surface area and fluorescence intensity were analyzed.XRD and FT-IR analysis showed that the characteristic peaks of N-GQDs/Bi2WO6 composites did not change significantly compared with single Bi2WO6.SEM shows that the morphology of N-GQDs/Bi2WO6 is more complete than that of undoped N atoms,but there is no obvious change in the structure.It shows that the doping of N atoms does not change the basic structure of GQDs/Bi2WO6.From BET analysis,we can see that the specific surface area of 0.2N-GQDs/Bi2WO6 is slightly larger than that of 0.2GQDs/Bi2WO6,but the difference is very small,which indicates that the doping of N atoms does not lead to a significant change in particle size.From PL analysis,it can be seen that the fluorescence intensity of 0.2N-GQDs/Bi2WO6 is obviously lower than that of pure Bi2WO6 and 0.2N-GQDs/Bi2WO6.This indicates that the fluorescence intensity of the composites decreases after N atom doping,which promotes the formation of photogenerated hole-electron pairs and improves the photocatalytic degradation effect.After four reuses,0.2N-GQDs/Bi2WO6 also maintained good degradation effect(5)The single factor experiments were carried out to investigate the factors affecting the degradation of ciprofloxacin and tetracycline by 0.2N-G.QDs/Bi2WO6 composites.It was found that the degradation rate of ciprofloxacin by 0.2N-GQDs/Bi2WO6 composites reached 97.2%when the dosage of material was 50mg,the initial concentration of solution was 10mg/L and the pH of solution was 7.When the tetracycline was degraded,the maximum degradation rate of tetracycline was 99.4%when the material dosage was 75 mg,the initial concentration of solution was 20 mg/L and the solution pH was 7.On the basis of the single factor influence data,the model was used to analyze the effect of the interaction between factors on the degradation of ciprofloxacin and tetracycline.The results showed that the interaction of the three factors affected the degradation reaction.The optimum reaction conditions for the degradation of ciprofloxacin by 0.2N-GQDs/Bi2WO6 were optimized by the model:material dosage is 56.34mg,initial concentration is 10.33mg/L,solution pH is 6.51.The optimum reaction conditions for tetracycline degradation are follow:material dosage is 74.31mg,initial concentration of solution17.46mg/L,solution pH is 6.82(6)By the comparison of adsorption and photocatalytic properties between 0.2N-GQDs/Bi2WO6 and 0.2GQDs/Bi2WO6,It can be seen that after N atom doping,the adsorption and degradation of ciprofloxacin and tetracycline have no obvious change,but the photocatalytic degradation of ciprofloxacin and tetracycline has increased significantly.It shows that after N atom doping,the material not only maintains the good adsorption properties of GQDs/Bi2WO6 itself,but also reduces the fluorescence intensity of the material and promotes The formation of photogenerated holes-electron pairs improves the photocatalytic efficiency and the total degradation rate.