Abstract

TiO₂ nanotubes were synthesized by hydrothermal reaction using commercially available TiO₂ powder at 150 °C for 24 h. The transmission electron microscopy, X-ray diffraction, nitrogen adsorption-desorption isotherms and Fourier Transform-Infrared spectroscopy were used to characterize the nanotubes. Anatase phase was not transformed into rutile phase in the range of calcination temperature studied. Increase in calcination temperature result in enhancement of crystallinity and reduction in BET surface area. Photocatalytic removal of Reactive Red 239 (RR239) was investigated using prepared TiO₂ nanotubes. Effects of pH, TiO₂ nanotube dosage, initial RR239 concentration and calcination temperature were studied. 99%, 97% and 55% of removal efficiency values were attained at pH = 3, 5 and 7, respectively within 60 min or reaction time. With an increase in dosage of TiO₂ nanotube in the range of 0.25–0.75 g dm⁻³, removal rate increased by a steeper slope. Complete removal of RR239 was observed at 20 mg dm⁻³ RR239 concentrations within 30 min but longer time was required for complete removal at higher concentrations. Langmuir-Hinshelwood kinetic expression was proposed based on nonlinear regression analysis. The removal efficiency of nanotubes calcined at 300 − 450 °C significantly increased but further increase in calcination temperature caused to decrease the efficiency.100% and 85% removal efficiency values were observed using actual solar light within 120 min of reaction time in July and January, respectively. Experiments conducted with scavengers showed that holes and adsorbed hydroxyl radicals were the major species involved in removal of RR239. A pathway for degradation of RR239 was suggested according to detected intermediate compounds.

摘要

TiO ₂纳米管是使用市售的TiO ₂粉末在150℃下通过水热反应24小时合成的。透射电子显微镜、X 射线衍射、氮吸附-脱附等温线和傅里叶变换-红外光谱用于表征纳米管。在所研究的煅烧温度范围内，锐钛矿相没有转变为金红石相。煅烧温度的增加导致结晶度的提高和BET表面积的减少。_{使用制备的 TiO 2}纳米管研究了活性红 239 (RR239) 的光催化去除。_{pH、TiO 2}的影响研究了纳米管用量、初始RR239浓度和煅烧温度。在 pH = 3、5 和 7 时，在 60 分钟或反应时间内分别达到 99%、97% 和 55% 的去除效率值。_{随着TiO 2}纳米管用量在0.25–0.75 g dm ^-3范围内的增加，去除率以更陡峭的斜率增加。^{在 20 mg dm -3}时观察到 RR239 完全去除RR239 浓度在 30 分钟内，但在更高浓度下完全去除需要更长的时间。基于非线性回归分析提出了Langmuir-Hinshelwood动力学表达式。在 300 ~ 450 °C 下煅烧的纳米管的去除效率显着提高，但进一步增加煅烧温度会导致效率降低。在 7 月和 1 月的反应时间 120 分钟内使用实际太阳光观察到 100% 和 85% 的去除效率值， 分别。用清除剂进行的实验表明，空穴和吸附的羟基自由基是参与去除 RR239 的主要物质。根据检测到的中间化合物，提出了 RR239 的降解途径。