Degradation Of Organic Pollutants By Z-scheme Composite Photocatalysts

In recent years,due to the rapid development of semiconductor photocatalysts,its application in wastewater treatment and environmental remediation has attracted more and more attention.In this paper,the Z-scheme heterojunction composite photocatalyst was prepared.The treatment process of tetracycline hydrochloride wastewater was explored by photocatalytic technology under the condition of no external oxidant at room temperature.The Z-schemeα-Fe₂O₃/g-C₃N₄photocatalyst was constructed by hydrothermal synthesis.The preparedα-Fe₂O₃/g-C₃N₄photocatalyst has better degradation performance of tetracycline hydrochloride under visible light than pureα-Fe₂O₃and g-C₃N₄,and the degradation rate can reach59.62%after 140 min.In addition,the adsorption of antibiotics conformed to the Pseudo-second-order kinetics equation according to the adsorption experiments.In the active species experiment,it is proved that a Z-scheme heterojunction is formed on the highly exposed redox active center,which enhances the separation of electron-hole pairs and the conversion of light energy,and maintains the original redox capacity without changing the redox potential.This study further broadens the application of Z-scheme photocatalyst in the treatment of TC-HCl and TC-HCl related antibiotic wastewater.The Z-scheme heterojunction Bi₂O₃/g-C₃N₄composite photocatalyst was prepared by hydrothermal synthesis.The physical and chemical properties of the prepared samples were studied by XRD,SEM,and UV-vis DRS.Compared with a single g-C₃N₄and Bi₂O₃,the composite photocatalyst has higher photocatalytic activity.The performance improvement of Bi₂O₃/g-C₃N₄-20composite photocatalyst can be attributed to the improvement of its reactive sites,the increase of light absorption,and the migration of photogenerated carriers following the Z-scheme heterojunction scheme.The degradation kinetics of TC-HCl is basically in line with the first-order reaction kinetics model with an external xenon lamp as the light source,the light intensity is maintained at 300 W（λ>420 nm）,and the initial p H.The highest apparent rate constants of Bi₂O₃/g-C₃N₄-20 catalyst for TC-HCl are 4.26 and 2.68 times that of pure g-C₃N₄and Bi₂O₃,respectively.After 3 cycles of testing,the degradation rate of the TC-HCl solution was only reduced by 3.06%,which may be attributed to the loss of the recovered catalyst,indicating that the material has high stability and has the potential for industrial application.The single factor test method was used to degrade TC-HCl,(solution concentration is 20 mg·L^-1).The optimal process conditions after considering the cost were:Bi₂O₃/g-C₃N₄-20 as the catalyst,initial p H 7,50 mg as-prepared catalyst,light intensity of 300 W.The degradation rate of TC-HCl is 68.67%after 140min of reaction.This study will provides a new idea for the degradation of antibiotic wastewater by a composite photocatalyst with a Z-scheme heterojunction under visible light irradiation,and further broadens its application.