Preparation Of Bi₂WO₆ Photocatalyst And Its Degradation Performance

With the rapid development of economy,the problems of environmental pollution and energy crisis are becoming more and more prominent.Therefore,the issue of environment-al pollution control has become the focus of nowadays research.Among the many sewage treatment methods,photocatalytic technology is considered as a new efficient and conveni-ent water pollution treatment technology because of its own advantages.In many Photocat-alyst,Bi2WO6 as a new photocatalyst,the narrow band gap(2.7-3.1eV),can be stimulated by visible light,compared with TiO2 traditional photocatalyst,can better use of visible light,and also effectively degrade the organics in waste water,attracted wide attention of researchers.In this paper,Bi2WO6 was synthesized by hydrothermal method,solvothermal method and mixed solvent method using bismuth nitrate(Bi(NO3)3·5H2)and sodium tungstate(Na2WO4·2H2O)as the reaction materials,and La/Bi2WO6 prepared by the modification of the metal element La3+.the structure and morphology of the prepared samples were characterized by XRD,SEM and UV-vis DRS by adjusting the reaction time and the pH value of the precursor solution.The structure and morphology of the prepared samples were compared with those of the photocatalytic performance The specific research contents are as follows:(1)Ensure the molar ratio of Bi and W for the 2:1 condition,in the reaction temperat-ure is 180? by hydrothermal method,solvothermal method and mixed solvent method.Different Bi2WO6 nanomaterials were prepared under the reaction time of 8h,12h and 16h,respectively.The structure,morphology and photocatalytic properties were analyzed.Rhodamine B solution(RhB)was used to simulate the dye wastewater.The effects of different preparation methods and different reaction time on the photocatalytic activity of Bi2WO6 were compared.The results show that adopt hydrothermal method,the reaction time of Bi2WO6 photocatalyst prepared by 12h showed the best photocatalytic activity,the degradation efficiency reached 94%at 180min,which may be related to its special flower structure and larger specific surface area.The photocatalytic activity of Bi2WO6 prepared by solvothermal method with ethylene glycol as reaction solvent and the reaction time of 16h also showed the excellent photocatalytic activity,and the degradation efficiency reached 93.1%at 180min,and the structure of block structure particles.The photocatalytic activity of Bi2WO6 prepared by mixed solvent thermal method showed poor photocatalytic activity,and the highest degradation efficiency was 75%.(2)The reaction temperature was 180 ? and the reaction time was 12h(corresponding to the solvothermal reaction time was 16h)by hydrothermal method and solvothermal method.The Bi2WO6 photocatalyst was prepared under different pH conditions.The samples were characterized.The results showed that hydrothermal or solvothermal method the precursor solution pH will not change in the structure of the sample,but the effect on the morphology of the sample has a greater impact and thus affect its photocatalytic performance.The photocatalytic activity of Bi2WO6 synthesized by hydrothermal method at pH = 7 was the best,and the degradation efficiency of Rhodamine B solution reached 95%at 180 min.The photocatalytic activity of Bi2WO6 powder synthesized by solvothermal method at pH = 10 was the best,and the degradation efficiency was 85%at 120 min.180min degradation efficiency reached 97%.(3)The different contents of lanthanum nitrate doped with hydrothermal method were used to characterize the samples.The results show that La3+ element doping has a significant effect on the photocatalytic activity and microstructure of the sample,and the photocatalytic activity is enhanced mainly due to the appropriate bandgap energy of La/Bi2WO6 sample,the decrease in the recombination rate of the electron-hole pairs and the increase in the photo-generated electron transport rate,When the La3+ doping amount is 10%,the crystallinity is the best,the particles are uniform,the band gap is 2.86eV,and the smaller band gap leads to strong visible light absorption performance.Under the xenon lamp irradiation,10%La/Bi2WO6 exhibited the highest photocatalytic activity and the photocatalytic degradation of Rhodamine B was 91%at 120 min,relative to pure Bi2WO6,10%La/Bi2WO6 with 1.5 times the photocatalytic efficiency.