Study On The Synthesis Of Ag-Zn₃?VO₄?₂ Photocatalyst And Its Photocatalytic Activity Under Visible Light Irradiation

At present,the environmental pollution problem is getting more and more serious.Thus,the preparation and application of visible-light photocatalysts to degrade organic pollutants are becoming a hot research in the field of environmental science,materials science and chemistry.In the early,most work is focused on the search for visible light sensitive photocatalysts by modifying wide band gap semiconductor photocatalysts,such as TiO2,whose development was far from the increasing demand of environmental remediation.Therefore,the preparation of novel narrow band gap semiconductor photocatalyst has become more and more attractive.Recently,vanadate,as one of the new photocatalyst,is gaining more attention of scholars.This thesis mainly covers the following aspects:(1)The visible-light photocatalyst Ag-Zn3(VO4)2 has been successfully synthesized by Zn(NO3)2·6 H2O,AgNO3 and NaVO3 through hydrothermal process.The prepared photocatalysts were characterized by XRD,SEM,TEM,UV-vis DRS and BET surface area analysis.Through the degradation of methyl orange,the results showed that Ag-Zn3(VO4)2 prepared under the condition of Ag+/Zn2+ molar ratio 0.15,pH=10,heated at 160 ? for 16 h and then annealed at 600 ? for 4 h possessed the best photocatalytic activity.(2)The results of degradation condition experiments of methyl orange showed that:The adsorption of methyl orange by Ag-Zn3(VO4)2 was small.Under the condition of neutral,the degradation rate of methyl orange was fastest and the decolourization ratio was highest.H2O2 promoted the degradation of methyl orange,but NaCl and Na2SO4 lowered the decoloration efficiency.And the inhibitory effcet of Na2SO4 was more apparent.With the increase of catalyst dosage,the decolourization ratio of methyl orange rose first and then fell.The results of repeated use showed that the stability of photocatalytic performance of Ag-Zn3(VO4)2 was good.(3)Choosing methylene blue and p-nitrophenol as test substrates further demonstrated the photocatalytic activity of Ag-Zn3(VO4)2.Similar with the results of methyl orange,the decolourization ratio of methylene blue and p-nitrophenol rose first and then fell as the catalyst dosage increased.(4)The degradation of methyl orange,methylene blue and p-nitrophenol all obeyed first-order kinetic equation.This topic research will further broaden the research field of vanadate photocatalyst,and the research result has a certain theories guides and realistic meaning to the treatment of dye wastewater and other refractory organic pollutants.