Improving Permanganate Oxidations: Speciation, Pathways, Rates, and Products

1067075StonePermanganate广泛用于自来水厂，用于去除铁和锰、气味和气味化合物、内分泌干扰物和蓝藻毒素。它在水产养殖中被用作杀菌剂。据报道，高锰酸盐使一些有机底物脱卤化，但这种能力尚未在实践中得到利用。高锰酸盐氧化可涉及六种锰氧化态：+II、+III、+IV、+V、+VI、+VII。锰的形态和对环境化学的反应活性控制着底物消耗的速率和氧化产物的特性。许多高锰酸盐氧化是自催化的；中间体或产物催化正向反应。更好地了解环境化学对高锰酸盐氧化的形态、途径、速率和产物的影响，将使我们能够(I)加速高锰酸盐的氧化，从而提高效率，(Ii)预测和避免氧化产物可能有毒或有问题的情况。本研究的目的是为提高高锰酸盐的氧化性能提供科学/技术基础。同时具有高锰酸盐氧化的经典中心(例如烯基)和非经典中心(氧和氮杂环)的新兴污染物将被包括为代表性底物。官能团同一性和分子结构的微小变化将使我们能够探索反应机理并建立结构-反应性关系。毛细管电泳联用UV检测，高效液相色谱联用UV和ESI-MS/MS检测，将用于鉴定和定量反应中间体和产物。自催化可能源于(I)吸附到水合锰氧化物(HMOS)时底物反应的增强，(Ii)高锰酸盐与低氧化态(+II，+III，+IV)之间的歧化反应，从而提高了Mn(V)和Mn(VI)的浓度，(Iii)高锰酸盐-底物反应在表面或在溶液中产生新的氧化剂。试剂探针，以及探索pH值和主要离子组成的影响，将有助于解决可能的机制。高分辨电子显微镜(HRTEM)、选区电子衍射(SAED)和电子能量损失谱(EELS)将用于表征高锰酸盐氧化生成的氢氧化锰固体。他们将探索利用毛细管电泳法识别和定量的中间氧化态锰物种。PI的实验室需要独特的专业知识组合，即无机反应机理、有机反应机理和异质形态测定，以解决所提出的科学/技术问题。通过提高高锰酸盐氧化的效率，以及揭示高锰酸盐氧化产物的特性和产率，拟议的工作将对水质领域做出重大贡献。PI的实验室在水中金属-有机相互作用领域开发了几个关键概念和工具。9名女性和5名男性已经在PI的实验室完成了他们的博士培训，其中包括8名目前持有终身教职的人。少年派在巴尔的摩的罗林斯音乐学院帮助组织了外展活动，并每月在音乐学院领导“科学示范”。

1067075StonePermanganate is widely employed in water supply plants to remove iron and manganese, taste and odor compounds, endocrine disruptors, and cyanobacterial toxins. It is employed in aquaculture as a fungicide. Permanganate reportedly dehalogenates some organic substrates, but this capability is not yet utilized in practice. Permanganate oxidations can involve six manganese oxidation states: +II, +III, +IV, +V, +VI, +VII. Manganese speciation and reactivity in response to ambient chemistry govern rates of substrate consumption and the identities of oxidation products. Many permanganate oxidations are autocatalytic; an intermediate or product catalyzes forward reaction. Better understanding of the effects of ambient chemistry on the speciation, pathways, rates, and products of permanganate oxidations would enable us to (i) accelerate permanganate oxidations, thereby improving effectiveness, and (ii) anticipate and avoid situations where oxidation products might be toxic or otherwise problematic.The objective of this research to provide the scientific/technical basis for improving the performance of permanganate oxidations. Emerging contaminants that possess both classical sites of permanganate oxidation (e.g. alkene groups) and nonclassical sites (oxygen and nitrogen heterocycles) will be included as representative substrates. Small changes in functional group identity and molecular structure will enable us to probe reaction mechanisms and develop structure-reactivity relationships. Capillary electrophoresis with UV detection, and HPLC with both UV and ESI-MS/MS detection, will be used to identify and quantify reaction intermediates and products. Autocatalysis may arise from (i) heightened substrate reactivity upon adsorption to hydrous manganese oxides (HMOs), (ii) disproportionation reactions between permanganate and lower Mn oxidation states (+II, +III, +IV) that boost Mn(V) and Mn(VI) concentrations, (iii) permanganate-substrate reactions that generate novel oxidants on surfaces or in solution. Reagent probes, as well as exploration of pH and major ion composition effects will help resolve among possible mechanisms. High resolution transmission electron microscopy (HRTEM), combined with selective area electron diffraction (SAED) and electron energy loss spectroscopy (EELS), will be used to characterize manganese (hydr)oxide solids generated by permanganate oxidations. They will explore the intermediate oxidation state manganese species identified and quantified using capillary electrophoresis.The unique combination of expertise in the PI's lab, i.e. inorganic reaction mechanisms, organic reaction mechanisms, and heterogeneous speciation determination, is needed to address the scientific/technical issues posed. By improving the efficiency of permanganate oxidations, and by shedding light on permanganate oxidation product identity and yields, the proposed work will make a significant contribution to the field of water quality.The PI's laboratory has developed several key concepts and tools in the area of metal-organic interactions in water. Nine women and five men have completed their Ph.D. training in the PI's laboratory, including eight currently holding tenure track appointments. The PI has helped organize outreach activities at the Rawlings Conservatory in Baltimore, and leads monthly "Science Demonstrations" at the Conservatory.