Photocatalytic Degradation Performance And Mechanism Of Antibiotics In Water By Photosensitized Bismuth Vanadate

Antibiotics have been included in the"Key Control New Pollution List（2023 Edition）"inChina.Photocatalytic degradation technology is one of the most promising methods for treating typical antibiotic discharge sources such as urban wastewater treatment plants,due to its economic and efficient advantages.The design of catalysts with high photocatalytic activity and stability is the core of photocatalytic degradation technology.Bismuth vanadate（Bi VO₄）has been widely used in the preparation of photocatalysts due to its good chemical stability and light response range.However,how to overcome the limitations of low light utilization efficiency and high photogenerated carrier recombination rate of Bi VO₄ on photocatalytic performance is the focus of current research.Photosensitizers can effectively improve the light response intensity and charge separation efficiency of the catalyst and enhance photocatalytic activity.Therefore,this study has constructed an excellent organic photosensitized photocatalytic system（x ACP-PDDA-Bi VO₄）with Bi VO₄ as the framework,which can be used for the photocatalytic degradation of typical antibiotics such as sulfamethazine（SMZ）in water.The main results of this thesis are as follows:（1）Monoclinic crystalline Bi VO₄ catalyst（x ACP-PDDA-Bi VO₄）sensitized with poly dimethyl diallyl ammonium chloride（PDDA）and acetophenone（ACP）was prepared by ultrasonic impregnation method.Single PDDA or acetophenone sensitized Bi VO₄（PDDA-Bi VO₄ and ACP-Bi VO₄）were used as control catalysts for the catalytic degradation of SMZ under xenon lamp irradiation.The results showed that the ACP-PDDA-Bi VO₄ sensitized system had good photocatalytic activity,and the photocatalytic degradation efficiency of the catalyst（0.02ACP-PDDA-Bi VO₄）was the highest when the amount of PDDA was 0.02wt.%.When the dosage of 0.02ACP-PDDA-Bi VO₄ catalyst was 1.0 g/L,the maximum degradation rate of SMZ in water reached 98.24%within 50 min,and the catalyst maintains high photocatalytic activity under solution p H conditions ranging from 5 to 9.The results of catalyst recycling experiment showed that the catalyst has excellent stability and reusability.（2）The results of the photocatalytic influence factor experiment showed that Ca²⁺could accelerate the charge separation in the catalyst and promote the photocatalytic degradation of SMZ,and the degradation rate was 98.91%within 60 min;Cl^-,NO₃^-,Na⁺,K⁺,and Mg²⁺all showed slight inhibition on SMZ degradation,with degradation efficiency ranging from92.15%～97.42%within 60 min;HPO₄^2-almost completely inhibited SMZ degradation with a degradation rate of only 8.46%.Organic acids strongly inhibited the photocatalytic degradation of SMZ by competing energy,free radicals,and surface active sites,and the inhibition intensity was citric acid>maleic acid>fulvic acid>malic acid.（3）The actual photocatalytic results of sewage treatment plant tail water showed that0.02ACP-PDDA-Bi VO₄ could rapidly degrade various antibiotics under xenon lamp irradiation.The degradation efficiency of SMZ,sulfadiazine（SDZ）,sulfamethazine（SMR）,tetracycline（TC）,doxycycline（DOX）,oxytetracycline（OTC）,and chlortetracycline（CTC）were 88.98%～99.01%within 60 min,and the degradation rates were 6.0～64.4 times that of the control group（without catalyst）,respectively.Under sunlight irradiation,the degradation rate of seven antibiotics in the tail water reached 60.2%～99.8%within 60 min by 0.02ACP-PDDA-Bi VO₄.（4）The results of fluorescence spectrum and electrochemical workstation characterization showed that the organic photosensitization system constructed in this study mainly improved the photocatalytic performance of Bi VO₄ by improving the light response intensity,promoting the separation of photogenerated carriers and interfacial charge transfer.The free radical quenching experiment and electron paramagnetic resonance spectroscopy confirmed that the main active substances of the 0.02ACP-PDDA-Bi VO₄ photocatalytic system were superoxide radicals（·O₂^?）and photogenerated holes（h⁺）.（5）Thirteen possible intermediates of SMZ were identified by liquid chromatography tandem quadrupole time of flight mass spectrometry（LC-QTOF-MS）,and three possible photodegradation pathways of SMZ were deduced,including oxidation,desulfurization,and rearrangement reactions.The toxicity prediction results from the ECOSAR system indicate that the catalytic system effectively reduces the ecological risk of SMZ（sulfamethazine）.The overall toxicity of the intermediates generated during SMZ degradation shows a decreasing trend,and the final products exhibit non-toxic characteristics towards aquatic organisms such as fish.