One-dimensional titania nanotubes annealed at various temperatures for the photocatalytic degradation of low concentration gaseous pollutants

摘要

In this study,one-dimensional titania nanotubes(TNTs) were synthesized using a combined process of chemical and hydrothermal treatments,and their activities for the photocatalytic reactions of selected gaseous pollutants at sub-ppm levels were determined.Additionally,the properties of the TNTs were examined using selected spectroscopic methods.The annealed TNTs showed higher photocatalytic activities for the four target compounds than did the unannealed TNTs.For all the target compounds except benzene,the effect of the annealing temperature on the degradation efficiency was difficult to determine because all degradation efficiencies were very high.However,for benzene,which decomposed with a low efficiency,the degradation activities of the TNTs increased as the treatment temperature was increased from 250 to 300 ℃,while they decreased slightly when the temperature was increased from 300 to 400 ℃.These findings confirm the presence of an optimal annealing temperature for the synthesis of TNTs.Moreover,the average degradation extents for benzene,toluene,ethylbenzene,and o-xylene decreased from92%,96%,99%,and 98%to 77%,86%,92%,and 94%,respectively,as the airstream flow rate increased within the range of 1-4L/min.The average degradation extents decreased from 12%,75%,87%,and 88%to 3%,29%,46%,and 51%,respectively,as the input concentration increased from 0.4 to 1.9 ppm.Overall,these findings suggest that one-dimensional TNTs can be effectively utilized for the degradation of gaseous pollutants under optimal operational conditions.