Design Of Double Perovskite Composite Catalyst And Activity For 2,4-dichlorophenol Degradation Under Visible Light

With the rapid economic growth,the pollution generated by the chemical industry has a worsening impact on the environment.Among them,the highly toxic and refractory phenol-containing wastewater has been listed as a hazardous pollutant requiring priority treatment.The low concentration of phenol-containing wastewater is the most common,so it is an urgent task to treat the phenol-containing wastewater with an efficient,economical and environmentally friendly method.The technology of photocatalytic oxidation with advantages of environmental protection,high efficiency,good stability and reusable,etc.It is considered to be the most promising treatment method in environmental remediation for the degradation of organic pollutants.Therefore,the development of photocatalysts with visible light response is an effective way to solve low-concentration phenol-containing wastewater.In this paper,double perovskites are prepared by sol-gel method,including La₂CuMnO₆?La₂FeMnO₆ and La₂ZnZrO₆,and then designs and prepared a series of composite catalysts La₂CuMnO₆/Bi₂O₃?La₂FeMnO₆/BiOCl and La₂ZnZrO₆/Bi₂O₃,and explored the degradation rate and stability of 2,4-dichlorophenol under visible light.A series of characterizations were conducted by XRD?SEM?TEM?BET?Uv-vis DRS?PL?FT-IR,etc.The comprehensive analysis results are as follows:Firstly,a series of La₂CuMnO₆/Bi₂O₃ composite catalysts was prepared by hydrothermal synthesis method,The XRD and TEM results show that the two catalysts are well compounded,the results of activity test shows that 80%-La₂CuMnO₆/Bi₂O₃ has the best activity of photocatalytic degradation,the2,4-dichlorophenol degradation rate was 85.02%for 60 min under visible light,which is 1.35 times of pure perovskite La₂CuMnO₆ and 1.85 times of pure phase Bi₂O₃,the 80%catalyst is still very stable after 5 recycling runs.It was concluded that the main reasons for the good activity were its narrow band gap?2.19eV?and high surface adsorption of active oxygen content?55.17%?.Secondly,a series of La₂FeMnO₆/BiOCl composite catalysts were prepared by hydrothermal method.When the La₂FeMnO₆ content was 10%wt,the degradation rate of the composite catalyst for 2,4-dichlorophenol reached up to 82.87%within 50min under visible light,which is 1.42 times and 1.52 times of the perovskite La₂FeMnO₆ and pure BiOCl,Respectively.The analysis showed that the reason for the optimized activity was mainly the inhibition of the recombination of photogenerated carriers,and the band gap energy of BiOCl is narrowed from 3.39 eV to 2.98 eV.The catalyst surface of 10%-La₂FeMnO₆/BiOCl has 25.64%adsorbed oxygen and 51.49%hydroxy oxygen.Thirdly,The La₂ZnZrO₆?Bi₂O₃ and La₂ZnZrO₆/Bi₂O₃ composite catalyst were successfully prepared,the results of activity test shows that 60%-La₂ZnZrO₆/Bi₂O₃has the best activity of photocatalytic degradation,the 2,4-dichlorophenol degradation rate was 82%within 2 hours under visible light,which is 1.54 times and 1.38 times of the perovskite La₂ZnZrO₆ and Bi₂O₃,and its band gap energy is 2.63eV,photogenerated carrier recombination rate is significantly reduced.The reaction process is in line with the first order reaction kinetics.After analyzing the characterization results,we put forward the mechanism of photocatalytic reaction.