Hu Lanhua, Flanders Phillip M, Miller Penney L, Strathmann Timothy J
Department of Civil & Environmental Engineering, Newmark Laboratory, MC-250, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Water Res. 2007 Jun;41(12):2612-26. doi: 10.1016/j.watres.2007.02.026. Epub 2007 Apr 12.
The widespread detection of pharmaceutically active compounds, including many synthetic antimicrobial agents, in aquatic environments is raising public health concerns. As a result, there is growing interest in the development of innovative technologies to efficiently transform these compounds to non-toxic and pharmaceutically inactive byproducts. This work examines the photocatalytic degradation of sulfamethoxazole (SMX) and related sulfonamide antimicrobial agents in aqueous suspensions of nanophase titanium dioxide (TiO(2)). Experimental results demonstrate that SMX is mineralized by TiO(2) irradiated with ultraviolet-A light (UVA: 324<<lambda<<400 nm). Rates of UVA-TiO(2) photocatalyzed SMX degradation are dependent upon several variables, including the initial SMX concentration, catalyst phase identity and concentration, electron acceptor identity and concentration, and the presence of non-target water constituents. In contrast, reaction rates are not sensitive to changes in sulfonamide structure. Although pH has little direct effect on reaction rates, the presence of natural organic matter (NOM) inhibits photocatalytic degradation of SMX to a much greater extent at pH 5 than pH 9. In addition, the presence of bicarbonate leads to enhanced SMX photocatalysis at pH 9. Kinetic trends are consistent with a mechanism involving sulfonamide oxidation by hydroxyl radicals (()OH) generated via TiO(2) band gap excitation by UVA radiation. Identified transformation intermediates and products are consistent with SMX mineralization initiated by ()OH attack on either the aromatic or heterocyclic rings or the sulfonamide bond. Results demonstrate that UVA-TiO(2) photocatalysis can be a very effective approach for degrading sulfonamide micropollutants, particularly in natural waters exhibiting either alkaline pH or low concentrations of NOM, or both conditions.
在水生环境中广泛检测到包括许多合成抗菌剂在内的具有药物活性的化合物，这引发了公众对健康问题的担忧。因此，人们对开发创新技术以有效将这些化合物转化为无毒且无药物活性的副产物的兴趣与日俱增。这项工作研究了纳米相二氧化钛（TiO₂）水悬浮液中磺胺甲恶唑（SMX）及相关磺胺类抗菌剂的光催化降解。实验结果表明，SMX在紫外-A光（UVA：324＜λ＜400nm）照射的TiO₂作用下发生矿化。UVA-TiO₂光催化SMX降解的速率取决于几个变量，包括初始SMX浓度、催化剂相的性质和浓度、电子受体的性质和浓度以及非目标水体成分的存在。相比之下，反应速率对磺胺类结构的变化不敏感。尽管pH对反应速率几乎没有直接影响，但天然有机物（NOM）的存在在pH为5时比pH为9时对SMX光催化降解的抑制作用要大得多。此外，碳酸氢盐的存在导致在pH为9时SMX光催化作用增强。动力学趋势与一种机制一致，该机制涉及通过UVA辐射激发TiO₂带隙产生的羟基自由基（·OH）氧化磺胺类。鉴定出的转化中间体和产物与·OH攻击芳香环或杂环或磺胺键引发的SMX矿化一致。结果表明，UVA-TiO₂光催化可以是降解磺胺类微污染物的一种非常有效的方法，特别是在呈现碱性pH或低浓度NOM或两种情况皆有的天然水体中。
