Preparation Of Modified TiO₂ Nanotube Arrays And Their Application On Photoelectrocatalytic Degradation Of Sulfadiazine

In recent years,antibiotics have increasingly polluted the water environment,endangering human health and threatening the survival of animals and plants,which have obtained more and more attention.Traditional wastewater treatment methods have many shortcomings and are not practical.As a green chemistry technology,photocatalytic technology has wide prospect in degradation of organic pollutants.As an excellent semiconductor material,TiO₂ nanotube arrays have attracted wide spread attention due to their highly ordered structure,large specific surface area,and excellent electron transfer performance.However,the forbidden band width of TiO₂ is 3.2 eV,which can only respond in the ultraviolet region.In addition,the photo-generated electrons and holes generated by TiO₂ nanotube arrays are easy to recombine,leading to the low quantum efficiency.These two problems limit the practical application of TiO₂ nanotube arrays.In this paper,TiO₂ nanotube arrays electrode were fabricated by anodic oxidation method,then modified by MoS₂ nanosheets and Ag₃PO₄ nanoparticles,respectively.And the morphology,structure and optical properties of the composite material were analyzed by Scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?XPS?,X-ray diffraction?XRD?,ultraviolet-visible absorption spectrum?UV-vis?,and electrochemical characterization methods.The photoelectrocatalytic activities were researched for the modified TiO₂ nanotube arrays electrode by degrading methylene blue?MB?and sulfamethazine?SD?in visible light.Subsquently,the photoelectrocatalytic degradation mechanism of modified TiO₂ nanotube arrays electrode were discussed.The research contents and results were as follows:Firstly,MoS₂/TiO₂ nanotube arrays electrode were fabricated and its photoelectro-catalytic activity in visible light was examined.The MoS₂/TiO₂ nanotube arrays electrode were fabricated by the photo-assisted electrochemical deposition process.The experimental results showed that the MoS₂/TiO₂ nanotube arrays electrode prepared by photo-assisted electrodeposition for 20 min can significantly improve the efficiency of photocatalytic degradation in visible light,and the degradation efficiency of MB and SD in photoelectrocatalytic?PEC?process could reach 60%and 65%in 240 min.In this study,the effects of the reaction temperature,concentration of pollutants,pH of the solution and other conditions were systematically investigated.The mechanism of degradation of MB was investigated by additing different scavengers,and the results suggested that the major reactive species were holes?h⁺?,O₂^?-,and ¹O₂.Secondly,Ag₃PO₄/MoS₂/TiO₂ nanotube arrays electrode were prepared and its photoelectrocatalytic activity in visible light was tested.On the basis of MoS₂/TiO₂nanotube array electrodes,Ag₃PO₄ nanoparticles were loaded on the MoS₂/TiO₂ nanotube arrays electrode by chemical impregnation method.The loading of the Ag₃PO₄nanoparticles and the MoS₂ nanosheets can extend the response of TiO₂ nanotube array electrode to visible light region.Compared with pure TiO₂ nanotube arrays,the SD degradation efficiency of Ag₃PO₄/MoS₂/TiO₂ nanotube arrays electrode were improved significantly in visible light.The PEC activity of the Ag₃PO₄/MoS₂/TiO₂ nanotube arrays electrode are mainly attributed to the fact that Ag₃PO₄ can absorb visible light,and the recombination of photo-generated charges and holes can be effectively suppressed.Therefore,the photogenerated carriers can prolong and the degradation efficiency of pollutants can effectively improve.In addition,the concentration changes of SO₄^2-and NO₃^-in solution were identified by ion chromatography,the intermediate products were tested by LC-MS technique.And the possible degradation pathways were explored.The mechanism of SD on Ag₃PO₄/MoS₂/TiO₂ nanotube arrays electrode was investigated by examining the reactive oxygen species produced during the degradation process.