高锰酸钾氧化去除水中芳胺类药物:效能、机理及低价态锰的作用

Recently, application of chemical oxidation processes to control trace emerging micropollutants such as endocrine disrupting chemicals and pharmaceuticals in aqueous solution has received great attention, with respect to these contaminants' adverse effect on aquatic ecology and drinking water quality. Oxidants including ozone, chlorine, chlorine dioxide, and ferrate can be applied, and the reaction kinetics and mechanims as well as effects of water background matrices have been widely documented. However, to date little information is known on the common and green oxidant permanganate [KMnO4; Mn(VII)].Our recent studies showed that Mn(VII) could readily oxidize phenolic endorine disrupting chemicals such as steroidal estrogens and bisphenol A. Our data strongly supported a novel mechanism responsible for the promoting effect of ligands. That was, aqueous highly active manganese intermediates (e.g., Mn(V) and Mn(III))formed in situ upon Mn(VII) reduction cound be stabilized to a certain extent in the presence of some ligands and subsequently invovled in further oxidation of target phenolics, whereas without stabilizing agents manganese intermediates would otherwise autodecompose or disproptionate spontaneously. The final product manganese oxides also had the ability to enhance Mn(VII) oxidation through a catalytic role. This work was desgined to comparatively examine the oxidation kinetics and mechanisms of aromatic amine containing pharmaceuticals by permanganate in synthetic and real waters, with a focus toward futher understanding the formation of manganese intermediates/oxides and their role in promoting Mn(VII) oxidation. These data will also provide a fundamental basis for developing novel technologies of low valence manganese enhanced Mn(VII) oxidation to effectively remove some emerging micropollutants during water and wastewater treatment.

国内外对化学氧化(臭氧、次氯酸、二氧化氯、高铁酸钾)去除水中微量新兴污染物-内分泌干扰物与药物已经做了大量的研究，包括动力学、反应机理、水质背景影响等,但到目前为止，有关绿色氧化剂高锰酸钾[KMnO4; Mn(VII)]的应用基础研究却还很缺乏。申请人前期研究工作表明，高锰酸钾可以高效的氧化去除水中酚类内分泌干扰物(如：雌激素、双酚A)，苯环上的羟基是高锰酸钾氧化进攻的活性位。而且原位产生的中间价态锰[如：Mn(V)、Mn(III)]在络合稳定剂的作用下能够强化除污染，最终固相产物二氧化锰(MnO2)也能够催化高锰酸钾氧化。本课题在前期工作的基础上，对比研究高锰酸钾氧化芳胺类药物的效能与机理，揭示锰氧化物催化作用的内在本质，研究高活性中间价态锰的生成规律，探讨中间态锰除污染特性，掌握不同价态锰的氧化特点；为低价态锰强化高锰酸钾氧化技术用于去除水中典型新兴污染物提供重要理论支持。

高锰酸钾（KMnO4，Mn(VII)）易氧化进攻有机污染物分子中电子云密度较大的官能团（如：烯烃、巯基和酚羟基）。但高锰酸钾与另一类不饱和官能团——胺类有机污染物的化学反应还缺乏系统深入的研究。本项目研究成果表明：高锰酸钾可以高效的氧化去除水中一级、二级、三级芳香胺类有机污染物，而且二级反应动力学随pH值的升高而降低，并与高锰酸钾氧化降解酚类有机污染物的动力学规律进行对比；高锰酸钾氧化降解芳胺类/酚类有机物的动力学规律可以用稳态动力学模型进行很好的描述，该模型假设了芳胺类/酚类有机物首先形成络合物。在弱酸性条件下，锰氧化物能够催化高锰酸钾氧化芳香胺类有机污染物，催化过程遵循表面络合机理：即芳胺类有机物首先与锰氧化物表面键合的锰离子形成表面络合物，然后表面络合物再被高锰酸钾迅速氧化；上述锰氧化物的催化现象与酚类污染物得出的催化规律相似。一些络合稳定剂（焦磷酸、EDTA、NTA）抑制了二氧化锰的生成但形成了溶解性三价锰，由于溶解性三价锰氧化芳胺类污染物的效率不是很高，所以络合稳定剂抑制了高锰酸钾对芳胺的氧化效率。相反，络合稳定剂极大的促进了高锰酸钾对酚类污染物的氧化。三重四级杆串联线性离子肼液相质谱联用仪（LC-MS/MS）检测分析结果表明：高锰酸钾氧化芳胺类污染物主要产生聚合、开环产物，释放铵离子。在实际水体中，背景成分对高锰酸钾氧化芳胺类有机污染物的影响较小；相反，实际水体背景成分能够强化高锰酸钾氧化酚类有机污染物的效能。