Study On Preparation And Characterization Of Ion Doped TiO₂ Nanotube Arrays And Its Application In The Photocatalytic Oxidation Treatment Of Papermaking Wastewater

TiO₂ nanotube arrays?TNAs?has shown a great potential of application in photocatalytic degradation of organic pollutions due to its large specific surface area,adsorption capacity,charge separation efficiency,non-toxicity and high chemical stability.However,the large bandgap?3.2 eV?and high electron hole recombination limit the photocatalytic efficiency of TNAs.In order to overcome these obstructions,there are many efforts to focus on improving its visible-light absorption scope and quantum yield.Among these methods,the ion doping has attracted considerable attention due to its simple requirement and better modified effect.In this study,TNAs were fabricated via the electrochemical anodization process.The microstructure of TNAs was controlled by adjusting the preparation parameter.The influence of the microstructure of TNAs on its visible-light photocatalytic activity was studied.The ion doped TNAs and Zn-N codoped TNAs were fabricated by impregnation method and the samples were characterized by SEM,XRD,UV-Vis,PL,XPS and photocatalytic experiment.Finally,the TNAs were used for the photocatalytic degradation of papermaking wastewater and the effect of titanium nanotube length on its photocatalytic efficiency was evaluated.The main results are as follows:?1?The tube diameter and the tube length both had a linear relation with anodization voltage and anodization time within a certain range.The TNAs showed up the best photocatalytic activity when the actual tube length was near the penetration depth of UV light.?2?The visible-light absorption ability of highly ordered TNAs improved with its nanotube length increased.However,the recombination rate of photo-generated electron and hole pairs increased with the tube length increased.The photocatalytic activity of TNAs increased with the tube length increased.?3?The visible-light absorption ability of TNAs could be enhanced by doping certain concentration of transition metal(Fe³⁺,Ni²⁺,Co²⁺and Zn²⁺).However,the actual photocatalytic degradation efficiency of TNAs decreased due to the increased recombination rate of photo-generated electron and hole pairs.?4?The effect of visible-light absorption ability of TiO₂ increased much better by Zn-N codoped TNAs than single metal ions doping.Besides,the photocatalytic degradation efficiency of Zn-N codoped TNAs increased with the increased of Zn²⁺concentration.But there exists an optimal concentration,which was 0.005 M in this experiment.The highest removal rate of RhB after visiable-light photocatalytic reaction for 200 min reached 44.77%.?5?The TNAs has the ability on photocatalytic degradation papermaking wastewater.The highest removal rate of COD_cr after photocatalytic reaction reached 53.0%when the nanotube length was 1500 nm and the COD_cr was reduced to 40 mg/L.The removal rate of BOD₅,TOC and turbidity were 43.75%,70.91%and 39.18%respectively.