In Terms Of The Mechanism For Photocatalytic And Auto-oxidation Of Pollutants By Bismuthate Nanoparticles

Advanced Oxidation Technology?AOPs?has developed rapidly in recent years.It can produce low-activity selective oxygen?ROS?such as·OH and·O₂^-with strong oxidizing properties,and completely mineralizes pollutants into CO₂,H₂O and inorganic ions.It has great application potential in dealing with various refractory pollutants.However,most materials do not work alone.AOPs usually require additional high energy or a large amount of additives,which greatly increases operating costs and limits its application to actual environmental pollution control.Therefore,a new bismuth-based material with excellent degradation efficiency but without expensive additives was studied.The main research contents and results of this paper are as follows:?1?In this paper,Bi-NaBiO₃ was prepared by simple ion exchange method.The photocatalytic activity and degradation mechanism of Bi-NaBiO₃ were studied through degradation of liquid 4-chlorophenol?4-CP?,gaseous toluene and a series of material characterization.Under visible light irradiation,0.2 Bi-NaBiO₃?0.2 represents the molar ratio of Bi in Bi?NO₃?₃·5H₂O to Bi in NaBiO₃?has excellent catalytic performance and high stability due to the photogenerated hole electrons.Material characterization showed that Bi doping improved visible light utilization rate of NaBiO₃ and separation efficiency of photogenic carriers.¹O₂,·O₂^-and·OH radicals are the main active oxygen?ROS?in photocatalytic reactions,and the oxygen vacancy formed by NaBiO₃ lattice oxygen release promoted the formation of ROS.In addition,Bi₂?CO₃?O₂ continuously generated in the reaction process also exhibited some photocatalytic activity.?2?The catalytic activity of Bi-NaBiO₃ nanoparticles in the absence of light was further investigated,4-CP was used as the target pollutant for experiments.The results show that the doping of Bi ions can greatly enhance the oxidative degradation ability of NaBiO₃.After treatment for 30 minutes in dark condition,the removal rate of 4-CP by 0.2 Bi-NaBiO₃ can reach 83.7%,which is 5.13 times that of pure NaBiO₃.According to the EPR test and material characterization,in the absence of light or any other additional oxidant,the lattice oxygen released by Bi-NaBiO₃ nanoparticles can be activated to form reactive oxygen species and further generate a large amount of ¹O₂.Thereby oxidizing organic pollutants.?3?In this paper,another new type of oxide was prepared by a simple ball milling.The material was optimized by adjusting the dosage of the initial raw material and preliminary characterization results confirmed the successful synthesis of Ag₄Bi₂O₅.Gaseous toluene was selected as the model compound to evaluate the photocatalytic performance of Ag₄Bi₂O₅ catalyst.Under visible light irradiation,Ag₄Bi₂O₅ performed excellent photocatalytic activity and high stability.According to the EPR test,¹O₂,·O₂^-and·OH radicals was the reason for the gaseous tolene oxidation.The oxygen vacancy formed on Ag₄Bi₂O₅ is involved in the production of ROS,which promotes the transfer of photogenerated electron and improves the photocatalytic activity.