Sun Bo, Reddy Ettireddy P, Smirniotis Panagiotis G
Chemical and Material Engineering Department, University of Cincinnati, Cincinnati, Ohio 45221-0012, USA.
Environ Sci Technol. 2005 Aug 15;39(16):6251-9. doi: 10.1021/es0480872.
Here we report the simultaneous Cr(VI) reduction and 4-chlorophenol (4-CP) oxidation in water under visible light (wavelength > 400 nm) using commercial Degussa P25 TiO2. This remarkable observation was attributed to a synergistic effect among TiO2, Cr(VI), and 4-CP. It is well known that TiO2 alone cannot remove either 4-CP or Cr(VI) efficiently under visible light. Moreover, the interaction between Cr(VI) and 4-CP is minimal if not negligible. However, we found that the combination of TiO2, Cr(VI), and 4-CP together can enable efficient Cr(VI) reduction and 4-CP oxidation under visible light. The specific roles of the three ingredients in the synergistic system were studied parametrically. It was found that optimal concentrations of Cr(VI) and TiO2 exist for the Cr(VI) reduction and 4-CP oxidation. Cr(VI) was compared experimentally with other metals such as Cu(ll), Fe(lll), Mn(IV), Ce(IV), and V(V). Among all these metal ions, only Cr(VI) promotes the photocatalytic oxidation of 4-CP. The amount of 4-CP removed was directly related to the initial concentration of Cr(VI). The system was also tested with four other chemicals (aniline, salicylic acid, formic acid, and diethyl phosphoramidate). We found that the same phenomenon occurred for organics containing acid and/or phenolic groups. Cr(VI) was reduced at the same time as the organic chemicals being oxidized during photoreaction under visible light. The synergistic effect was also found with pure anatase TiO2 and rutile TiO2. This study demonstrates a possible economical way for environmental cleanup under visible light.
在此，我们报道了使用商用德固赛P25二氧化钛在可见光（波长>400nm）下水中同时进行的六价铬（Cr(VI)）还原和4-氯苯酚（4-CP）氧化。这一显著现象归因于二氧化钛、Cr(VI)和4-CP之间的协同效应。众所周知，单独的二氧化钛在可见光下不能有效地去除4-CP或Cr(VI)。此外，Cr(VI)与4-CP之间的相互作用即使不可忽略也是极小的。然而，我们发现二氧化钛、Cr(VI)和4-CP共同作用能够在可见光下实现高效的Cr(VI)还原和4-CP氧化。对协同体系中这三种成分的具体作用进行了参数研究。结果发现，对于Cr(VI)还原和4-CP氧化存在Cr(VI)和二氧化钛的最佳浓度。将Cr(VI)与其他金属如铜（II）、铁（III）、锰（IV）、铈（IV）和钒（V）进行了实验比较。在所有这些金属离子中，只有Cr(VI)能促进4-CP的光催化氧化。4-CP的去除量与Cr(VI)的初始浓度直接相关。该体系还使用其他四种化学品（苯胺、水杨酸、甲酸和二乙基磷酰胺）进行了测试。我们发现，对于含有酸和/或酚基的有机物也出现了相同的现象。在可见光下的光反应过程中，Cr(VI)在有机化学品被氧化的同时被还原。纯锐钛矿型二氧化钛和金红石型二氧化钛也发现了协同效应。这项研究展示了一种在可见光下进行环境净化的可能的经济方法。
