Study On Preparation Of TiO₂ Nanotube And Photocatalytic Activity

Along with our society development, people have been paying more and more attention to the environmental protection. Some traditional methods of wastewater treatment had some shortcomings, for example, having large amounts of byproduct, complicated treatment for the after processing and bringing second pollution, therefore the applications of these traditional methods was limited. The photocatalytic oxidation technique of TiO₂ is a new wastewater treatment technology, has been paid more and more attention to it because of its advantages, such as high treatment efficiency, easily operating controlling, degradation organic pollution without selectivity and without second pollution.In this paper, the TiO₂ nanotube arrays were prepared by electrochemical anodization of titanium foils. We have concentrated on the factors affected on the growth of titania nanotube arrays, such as the anodization duration, the anodization voltage and the pH value in different electrolytic solutions,The experiments showed that the nanotubes of titanium oxide would grow longer with the anodization duration and the pH value increased, and the diameter of TiO₂ nanotube arrays would grow wider with the anodization voltage increased. From the comparison of inorganic and organic electrolytes, it is clear that better high-aspect-ratio TiO₂ nanotube arrays can be fabricated in organic electrolytes. The most suitable process conditions in aqueous electrolytes containing fluoride should be as follows: the pH value of electrolytes was 5, anodization duration was 3 hours, and anodization voltage was between 10V and 20V; In organic electrolytes containing fluoride, the most suitable process conditions should be as follows: the pH value of electrolytes was 6, anodization duration was 10 hours, and anodization voltage was between 35V and 60V.TiO₂ nanotube arrays were calcined with different tempature, the XRD experiments showed that the crystal type of TiO₂ nanotube arrays would be transformed from anatase to rutile as the calcining temperature increased. The photocatalytic activity of titania nanotube arrays was very excellent, when annealing temperature of TiO₂ nanotube arrays was 550℃,C-doped TiO₂ nanotube arrays were prepared by calcining directly in air, beacause of the large amount of organic carbon and the excellent adsorptive activeness of TiO₂ nanotubes in organic electrolytes. The EDS indicated that the C-doped TiO₂ nanotube arrays were prepared successfully. The experiments of methylene blue photocatalytic degradation showed that the photocatalytic activity could be greatly improved with the dope of C.In this paper, degrading methylene blue under different conditions was discussed. And they are the joined quantity of TiO₂ nanotubes, the illumination time, the concentration of methylene blue, the pH value of methylene blue and adscititious H2O₂. The experiments indicated that the most suitable process conditions should be as follows: the joined quantity of TiO₂ nanotubes was 1 cm², the illumination time was 3 hours, the concentration of methylene blue was 4×10^-6mol/L. And the photocatalytic activity in alkalescence condition was better than in neutral condition and acidity condition. The photocatalytic activity of titania nanotube arrays would be improved with adscititious H₂O₂.The study on dynamics of photocatalytic degradation for methylene blue indicated that it was all in agreement with one order dynamics model whether un-doped TiO₂ nanotubes and C-doped TiO₂ nanotubes used as photocatalysts.