Construction Of Z-scheme Photocatalytic System And Photocatalytic Degradation Of Antibiotics Under Visible Light

With the rapid development of the pharmaceutical industry,all kinds of antibiotics have been widely used in the prevention and treatment of human and livestock diseases.However,antibiotics are not easily biodegradable,resulting in a large number of residues were released into natural water.The antibiotics in the environment have accelerated the resistance genes and resistant bacteria,which will transfer through a variety of ways and pose a serious threat to the health of human and the balance of ecological system.Therefore,treatment of antibiotic wastewater is of vital importance.In recent years,photocatalysis technology has been recognized as one of the most effective advanced oxidation processes?AOPs?in the removal of organic contaminants in water due to its high efficiency,energy conservation,and low cost.However,single-phase semiconductor catalysts often have problems such as easy recombination of carriers and small range of light response.Therefore,it is necessary to establish a compound photocatalytic system to improve the photocatalytic activity of the catalyst,among of which the Z-scheme catalyst system is an effective way.Moreover,in order to effectively utilize most of the visible light in the solar energy,the narrow-band semiconductors were selected to construct the visible-light-driven Z-scheme photocatalytic system with narrow-band semiconductor to compound the visible light.In this work,Z-scheme photocatalytic system Ag/FeTiO₃/Ag/BiFeO₃ was constructed and applied to photocatalytic degradation of norfloxacin under visible light.On this basis,a double-channel Z-scheme photocatalytic system,Ag/ZnFe₂O₄/Ag/BiTa_1-xV_x O₄ was also constructed.The separation efficiency of carriers was further improved by doping transition metals into the semiconductor in the photooxidation system to form a recombination center for cyclic redox reactions.And applied to photocatalytic degradation of sulfanilamide.In this work,Z-scheme Ag/FeTiO₃/Ag/BiFeO₃ photocatalytic system was constructed by ultraviolet photo-reduction method.With norfloxacin as the target pollutant,the photocatalytic activities of Ag/FeTiO₃/Ag/BiFeO₃ and FeTiO₃/BiFeO₃nanocomposites were compared.The effects of loaded content of Ag,the mass ratio?FeTiO₃:BiFeO₃?,and light irradiation time on the photocatalytic activities were assessed.Ag/FeTiO₃/Ag/BiFeO₃has higher photocatalytic activity than FeTiO₃/BiFeO₃,and the loading of Ag improves the photocatalytic activity of catalysts.The photocatalytic degradation extent reaches 96.5%within 150 min,when using Ag/FeTiO₃/Ag/BiFeO₃ at 2.0 wt.%Ag?FeTiO₃:BiFeO₃=1.0:0.5?.In addition,Ag/FeTiO₃/Ag/BiFeO₃ can be reused with excellent photocatalytic stability.The active species such as·OH,h⁺,and·O₂^-are generated during the photocatalytic process using Ag/FeTiO₃/Ag/BiFeO₃.Hence,the Z-scheme Ag/FeTiO₃/Ag/BiFeO₃photocatalytic system could effectively and rapidly degrade antibiotics such as norfloxacin in water,and had a good application prospect in the treatment of organic wastewater.In addition,double channel Z-scheme Ag/ZnFe₂O₄/Ag/BiTa_1-x-x V_xO₄ photocatalytic system was constructed.With sulfanilamide as the target pollutant,the photocatalytic activities of ZnFe₂O₄/BiTaO₄,Ag/ZnFe₂O₄/Ag/BiTaO₄,ZnFe₂O₄/BiTa_1-xV_x O₄ and Ag/ZnFe₂O₄/Ag/BiTa_1-xV_xO₄ nanocomposites were compared.The effects of the mass ratio?ZnFe₂O₄:BiTaO₄?,loaded content of Ag,doped content of V and light irradiation time on the photocatalytic activities were assessed.Ag/ZnFe₂O₄/Ag/BiTa_1-xV_xO₄ has higher photocatalytic activity.The photodegradation extent reaches 100% within6.0h,when using Ag/ZnFe₂O₄/Ag/BiTa_1-xV_xO₄ at ZnFeO₄:BiTaO₃=1.0:0.5,2.0 wt.%Ag and 0.5 wt.%of V.In addition,Ag/ZnFe₂O₄/Ag/BiTa_1-xV_x O₄ can be reused with excellent photocatalytic stability.The active species such as·OH,h⁺,and·O₂^-are generated during the photocatalytic process using Ag/ZnFe₂O₄/Ag/BiTa_1-x-x V_xO₄.Hence,the Z-scheme Ag/ZnFe₂O₄/Ag/BiTa_1-xV_xO₄ photocatalytic system could effectively and rapidly degrade antibiotics such as sulfanilamide in water,and had a good application prospect in the treatment of organic wastewater.