Research Group in Advanced Oxidation Processes (AdOx), Department of Chemical Engineering, University of São Paulo, Av. Prof. Luciano Gualberto, tr. 3, 380, São Paulo, SP, Brazil.
Chemical Systems Engineering Center, Department of Chemical Engineering, University of São Paulo, Av. Prof. Luciano Gualberto, tr. 3, 380, São Paulo, SP, Brazil.
Environ Sci Pollut Res Int. 2021 May;28(19):23887-23895. doi: 10.1007/s11356-020-11715-x. Epub 2020 Nov 24.
This study aimed at investigating the photochemical behavior of sulfa drugs containing five and six-membered heterocyclic substituents (sulfamethoxazole (SMX) and sulfadiazine (SDZ), respectively), in an aqueous medium. Despite their importance, studies devoted to the use of photochemical models to predict the environmental phototransformation of pollutants in surface waters, by combining laboratory results and natural aquatic systems parameters, are still scarce in the scientific literature. In this work, the second-order reaction rate constants of SDZ and SMX with hydroxyl radicals (OH), singlet oxygen (O), and triplet excited states of chromophoric dissolved organic matter (CDOM*) were experimentally determined at pH 7, using the competition kinetics approach. The results show that OH and CDOM* are the key species involved in sulfonamide degradation, with anionic SMX, most prevalent at pH 6-9, being degraded much slower than the anionic form of SDZ. Moreover, SDZ and SMX photodegradation in natural water samples (spring-fed natural pond, public supply reservoir, and sea water) was significantly enhanced relative to depletion in pure water. Finally, from mathematical simulations of the sunlight-driven sulfonamide degradation, half-life times were predicted for these drugs varying from less than 2 to about 90 days, depending on the water depth, concentration of key species (DOC, HCO, NO, CO) in natural aqueous systems, as well as on the particular heterocyclic substituent.
本研究旨在研究含有五元和六元杂环取代基的磺胺类药物（分别为磺胺甲恶唑 (SMX) 和磺胺嘧啶 (SDZ)）在水介质中的光化学反应行为。尽管它们很重要，但在科学文献中，仍缺乏使用光化学模型来结合实验室结果和自然水系统参数来预测地表水中污染物的环境光转化的研究。在这项工作中，使用竞争动力学方法，在 pH 7 下，实验确定了 SDZ 和 SMX 与羟基自由基 (OH)、单线态氧 (O) 和发色溶解有机物质的三重激发态 (CDOM*) 的二级反应速率常数。结果表明，OH 和 CDOM*是磺胺类药物降解中涉及的关键物质，带负电荷的 SMX（pH 6-9 时最常见）的降解速度比带负电荷的 SDZ 慢得多。此外，与在纯水中的消耗相比，天然水样（泉水自然池塘、公共供水水库和海水）中的 SDZ 和 SMX 光降解明显增强。最后，通过对阳光驱动的磺胺类药物降解的数学模拟，预测了这些药物的半衰期从不到 2 天到约 90 天不等，具体取决于水的深度、自然水系统中关键物质（DOC、HCO、NO、CO）的浓度，以及特定的杂环取代基。
