Synthesis Of Nanotube Arrays On Titanium Alloys And The Photocatalytic Degradation Properties For Dibutyl Phthalate Under Visible Light Irradiation

In recent years,with the popularity of plastic products,the consumption of plasticizers has grown exponentially.The main components of plasticizers are phthalate esters,which is a kind of non-biodegradable endocrine disruptors for environment.Dibutyl phthalate?DBP?is the representative of phthalate esters and one of the priority pollutants in China,the United States and other countries.Though the concentration of DBP in the water environment is at ng/L^?g/L level,it is sufficient to induce estrogen responses and arouse abnormalities of aquatic development.If those refractory organic pollutants cannot be removed effectively,they will be gradually enriched and eventually cause serious damage to the ecological environment.Photocatalysis is powered by solar energy and can completely mineralize pollutants without secondary pollution,which has become one of the key research technologies in the field of environmental purification.However,its application is still constrained by key bottlenecks such as low quantum efficiency,narrow optical response range,and difficulty in recycling of powder materials.Based on the view that distinct morphologies own different properties and visualization through semiconductors compound can enhance photocatalytic activities,this paper chose refractory DBP as the target contaminant and in-situ synthesis alloy oxide nanotube arrays with visible light response and special morphologies through anodization on the TC4?6Al4V?alloy substrate.With TC4 alloy as substrate,alloy nanotube arrays with visible light response was fabricated in situ through improved anodizing and calcining methods.Adjusted the conditions of anodizing such as voltage,time,electrolyte and composition.The optimal preparation conditions of materials with the best visible light photocatalytic performance were obtained as follows:70 V of anodizing voltage,3 h of time,and ethylene glycol electrolyte with 0.5 wt%NH₄F and 2 vol%H₂O.Based on condition experiments,the visible-light responsive alloy oxide nanotube array with a special porous double-walled morphology was discovered for first time.The structure,composition and surface properties of the alloy oxide nanotube arrays were characterized by SEM,TEM,N₂ adsorption/desorption isotherms,elemental analysis and XPS.The results show that the double-walled alloy oxide nanotube array has a porous inner wall with a diameter of about 100 nm,a wall thickness of 20 nm,and a smooth outer wall with diameter of about 180 nm,a wall thickness of 20 nm.The alloy elements Al and V were distributed in the wall of the nanotubes in the form of Al₂O₃ and V₂O₅,forming a close-packed compound semiconductor with TiO₂,thereby realizing the visible light response of the nanotube arrays.At the same time,the rich pore structure between the double walls provides sufficient adsorption and photocatalytic active sites for photocatalytic reaction,thereby greatly improving the photocatalytic activity of the material.With visible light irradiation for 3 h,the removal rate of DBP was 96.1%and the degradation rate constant was 49.7 times as high as that of pure titanium oxide nanotube array.With TA28?3Al?and TC10?6Al6V?alloy as substrates,different morphologies alloy oxide nanotube arrays with visible light response were fabricated in-situ through improved anodizing and calcining methods.The morphological structure,composition and visible light response ability of different alloy oxide nanotube arrays were characterized by SEM,TEM,N₂ adsorption/desorption isotherms,elemental analysis and XPS.The results show that the type and content of alloy elements are important influent factors for the formation of double-walled nanotubes.The corrosion resistance of alloy can be destroyed with the presence of Al and enhanced through appropriate addition of V,but further weaken by the high total content addition of Al and V.The corrosion resistance of alloy directly affects the thickness of the C,F-riched layer in nanotube walls formed after anodization.The special morphology of the porous inner and smooth outer wall is attributed to the fact that the inner wall gets in touch with the electrolyte longer than the outer wall during the formation of the nanotube array.Thereby,a rich pore structure inner walls was created after the removal of C,F elements through calcined at high temperatures.This provides a new idea for the preparation of photocatalytic materials with special morphology and excellent visible light response.