Department of Chemistry, Shaoxing University, Zhejiang Shaoxing 312000, China.
Chemosphere. 2012 Oct;89(4):420-5. doi: 10.1016/j.chemosphere.2012.05.076. Epub 2012 Jun 12.
There have been serious concerns about polybromodiphenyl ethers (PBDEs) in the environment because of their global distribution and bioaccumulation. Owing to strong hydrophobicity of PBDEs, the regular photocatalytic system, in which the substrate is solvated in the bulk solution, is not applicable to the removal of the PBDEs in water. In this work, the photocatalytic reduction degradation of decabromodiphenyl ether (BDE209), the most-used PBDEs, was investigated in aqueous system, by pre-adsorbing it on the surface of photocatalyst. It was found that the preloaded BDE209 underwent efficient reductive debromination in aqueous system under irradiation with wavelength larger than 360 nm in the presence of electron donors such as methanol. Our experiments further show that such a preloaded system exhibits different characteristics from that in the organic solution. The meta-debrominated intermediate is predominant in the present system, while the ortho-debrominated one is the main nona-BDE products in the organic solution. In addition, different from other photocatalytic system, the pH has little effect on the photocatalytic reaction. We propose that these differences are originated from the formation of overlayer of hydrophobic BDE209 to limit the motion of BDE209 and the access of water and H(+)/OH(-) to the TiO(2) surface.
由于多溴二苯醚（PBDEs）在全球范围内的分布和生物累积性，人们对其环境安全性一直存在严重的担忧。由于 PBDEs 具有很强的疏水性，常规的光催化体系（其中底物溶解在本体溶液中）不适用于水中 PBDEs 的去除。在这项工作中，通过预先吸附在光催化剂表面上，研究了在水溶液中光催化还原降解十溴二苯醚（BDE209），这是最常用的 PBDEs。结果发现，在波长大于 360nm 的光照射下，在甲醇等电子供体的存在下，预负载的 BDE209 在水溶液中可有效地进行还原脱溴反应。我们的实验进一步表明，这种预加载系统表现出与有机溶液中不同的特性。在本体系中，间位脱溴中间产物占优势，而在有机溶液中，邻位脱溴产物是主要的非九溴二苯醚产物。此外，与其他光催化体系不同，pH 值对光催化反应的影响很小。我们提出，这些差异源于疏水性 BDE209 的覆盖层的形成，限制了 BDE209 的运动以及水和 H(+)/OH(-)进入 TiO(2)表面的通道。
