| As a new type of catalyst,bismuth tungstate(Bi2WO6)has been extensively studied in recent years because of its excellent photocatalytic performance and stable structure.Benzidine is widely used as a common raw material and intermediate in industrial production.Its traditional treatment methods include physical adsorption,oxidation,and biological methods.However,these methods have incomplete treatment,high energy consumption,and secondary effects on the environment.Pollution issues,etc.Photocatalytic technology has many advantages,including simple and clear process flow,less energy consumption in the reaction,convenient and fast operation,thorough degradation so as to eliminate the possibility of secondary pollution.However,the traditional Bi2WO6 has defects such as easy recombination of photo-generated holes and photoelectrons,and poor absorption of light waves with wavelengths greater than 470 nm,which affect the degradation efficiency of Bi2WO6.In order to improve the degradation performance of Bi2WO6,this paper proposes a variety of modification methods for Bi2WO6 in response to the above-mentioned defects,and uses characterization methods to determine the specific modification mechanism.The aniline experiment proved the effectiveness and rationality of the modification methods,as well as a preliminary discussion on the mechanism of photocatalytic degradation of pollutants.The specific research contents are as follows:1.Using ethylene glycol as the reaction solvent and Bi(NO3)3·5H2O as the bismuth source,the original mesoporous microspherical Bi2WO6 was synthesized by solvothermal method,and the original Bi2WO6 was modified by O3.Oxygen vacancies,and XRD,SEM,BET,XPS,FT-IR,PL and Uv-vis were performed on the Bi2WO6 before and after modification.The results showed that O3 modification did not significantly damage the structure,band gap and surface area of Bi2WO6.After modification,the rich oxygen vacancies of Bi2WO6 acted as active centers,which effectively inhibited the migration of photo-generated holes and photo-generated electrons and increased the catalyst p-benzidine.The adsorption capacity of Bi2WO6 greatly improves the degradation capacity of Bi2WO6.Degradation experiments show that O3 treatment with a flow rate of 3 L/min and 4 h has the best effect,and the degradation rate is～2.7 times higher than that of the original Bi2WO6.Mechanism and cycle experiments confirmed that active substances have a certain role in the degradation process,of which ·OH plays a major role.After 4 repeated experiments,the catalytic effect did not show a significant decrease,indicating that the material is stable and easy to separate,and has good prospects for practical applications.2.Using ethylene glycol as the reaction solvent,Bi(NO3)3·5H2O as the bismuth source,and CTAB as the bromine source,the original bulk Bi2WO6 and Bi2WO6/BiOBr composite catalysts were synthesized by solvothermal method.And the Bi2WO6 before and after modification was characterized by XRD,SEM,BET,XPS,FT-IR,pL and Uvvis.The results show that,Under simulated sunlight conditions,it is found that the Bi2WO6/BiOBr composite catalyst with a composite ratio of Bi2WO6/BiOBr-1-1 has the best pollutant degradation effect,which is 2.4 times the degradation rate of the original Bi2WO6,and the initial concentration of 5 mg/L benzidine The degradation rate reached 99.8%.BiOBr composite affects the growth of Bi2WO6 crystal structure and changes the morphology and structure of the catalyst.After modification,the specific surface area of Bi2WO6/BiOBr decreases,resulting in a large number of microporous structures.The band gap of Bi2WO6 is significantly reduced,from 3.41 to 3.05 eV,and the absorption range is red-shifted,which can absorb more visible light,especially for light waves>470 nm,so the degradation effect is greatly improved.BiOBr compounded with Bi2WO6 to form a heterojunction.Compared with the original Bi2WO6,the heterojunction formed by the modified catalyst improves the separation rate of photogenerated charge carriers,which may help enhance the utilization efficiency of photogenerated carriers,thereby improving the degradation performance.Mechanism and cycle experiments confirmed that active substances have a certain role in the degradation process,of which O2-plays the main role.The Bi2WO6/BiOBr-1-1 sample was reused 4 times,and the catalytic effect did not show a significant decrease,indicating that the material is stable and easy to separate,and has a good practical application prospect.3.Using ethylene glycol as the reaction solvent,Bi(NO3)3·5H2O as the bismuth source,and three precursors of melamine,dihydrodiamine and thiourea as the nitrogen source,the original Bi2WO6 and g-C3N4 were prepared by solvothermal method.Bi2WO6 composite catalyst,and characterize the Bi2WO6 before and after modification by XRD,SEM,BET,XPS,FT-IR,pL and Uv-vis.The results show that the composite catalyst prepared with melamine as the precursor has the best degradation effect.Under simulated sunlight conditions,the g-C3N4/Bi2WO6-60%composite catalyst loaded with 60%g-C3N4 has the best pollutant degradation effect,which is 2.16 times the degradation rate of the original Bi2WO6,and 5 mg/L benzidine The degradation rate under the initial concentration reached 93%;the g-C3N4 composite affected the growth of the Bi2WO6 crystal structure and changed the morphology and structure of the catalyst.After modification,the specific surface area of g-C3N4/Bi2WO is reduced,and the band gap of Bi2WO6 is significantly reduced,from 3.16 to 2.63 eV.The absorption range is red-shifted and can absorb more visible light,especially for light waves>470 nm.The degradation effect is greatly improved;g-C3N4 composites with Bi2WO6 to form a heterojunction.Compared with the original Bi2WO6,the heterojunction formed by the modified catalyst improves the separation rate of photogenerated charge carriers,which may help enhance the utilization efficiency of photogenerated carriers,thereby improving the degradation performance.Mechanism and cycle experiments have confirmed that active substances have a certain role in the degradation process.The three active substances,photo-generated holes,·O2-and·OH,have certain roles in the degradation process,of which·O2-plays a major role.The g-C3N4-2/Bi2WO6-60%sample was reused 4 times,and the catalytic effect did not show a significant decrease,indicating that the material is stable and easy to separate,and has a good practical application prospect.Figure [48] table [8] reference [87]... |
PDF Full Text Request