Tan Xiaoli, Fang Ming, Wang Xiangke
Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, 230031, PR China.
J Nanosci Nanotechnol. 2008 Nov;8(11):5624-31. doi: 10.1166/jnn.2008.242.
The TiO2/multiwalled carbon nanotube (MWCNT) composites were prepared by hydrothermal deposition. Batch experiments were carried out to study the removal of Cr(VI) from aqueous solution to TiO2, MWCNTs and TiO2/MWCNTs. Scanning electron microscopy and X-ray diffraction were utilized to characterize the prepared TiO2/MWCNT composites. The introduction of MWCNTs onto TiO2 catalyst led to a remarkable increase of Cr(VI) removal through adsorption and photocatalytic reduction under ultraviolet irradiation. Results of X-ray photoelectron spectroscopy analysis of chromium species adsorbed on TiO2/MWCNTs phase revealed that the removal mechanism of Cr(VI) by TiO2/MWCNTs under UV-irradiation was the reduction of Cr(VI) into Cr(III). The adsorption and photocatalytic activity of Cr(VI) decreased with increasing in pH, and was not affected by the concentration of sulphate obviously. In the ternary systems humic acid (HA)/fulvic acid (FA)-Cr(VI)-TiO2/MWCNTs, the increasing of FA/HA concentration did not cause any drastic changes in the adsorption capacity in terms of Cr(VI) concentration in the dark, but a minor increasing trend for the photocatalytic reduction of Cr(VI). The presence of humic substances enhanced the photocatalytic reduction and adsorption of Cr(III) to TiO2/MWCNTs.
采用水热沉积法制备了TiO₂/多壁碳纳米管（MWCNT）复合材料。进行了批量实验，以研究TiO₂、MWCNTs和TiO₂/MWCNTs从水溶液中去除Cr(VI)的情况。利用扫描电子显微镜和X射线衍射对制备的TiO₂/MWCNT复合材料进行了表征。在TiO₂催化剂上引入MWCNTs后，在紫外光照射下，通过吸附和光催化还原显著提高了Cr(VI)的去除率。对吸附在TiO₂/MWCNTs相上的铬物种进行X射线光电子能谱分析的结果表明，TiO₂/MWCNTs在紫外光照射下对Cr(VI)的去除机制是将Cr(VI)还原为Cr(III)。Cr(VI)的吸附和光催化活性随pH值升高而降低，且不受硫酸盐浓度的明显影响。在腐殖酸（HA）/富里酸（FA）-Cr(VI)-TiO₂/MWCNTs三元体系中，FA/HA浓度的增加对暗处Cr(VI)浓度的吸附容量没有引起任何剧烈变化，但对Cr(VI)的光催化还原有轻微的增加趋势。腐殖物质的存在增强了Cr(III)对TiO₂/MWCNTs的光催化还原和吸附。
