Eawag, Swiss Federal Institute of Aquatic Science and Technology CH-8600, Dübendorf, Switzerland.
Environ Sci Technol. 2013 Oct 1;47(19):11147-56. doi: 10.1021/es402516b. Epub 2013 Sep 16.
In water treatment dissolved organic matter (DOM) is typically the major sink for chemical oxidants. The resulting changes in DOM, such as its optical properties have been measured to follow the oxidation processes. However, such measurements contain only limited information on the changes in the oxidation states of and the reactive moieties in the DOM. In this study, we used mediated electrochemical oxidation to quantify changes in the electron donating capacities (EDCs), and hence the redox states, of three different types of DOM during oxidation with chlorine dioxide (ClO2), chlorine (as HOCl/OCl(-)), and ozone (O3). Treatment with ClO2 and HOCl resulted in comparable and prominent decreases in EDCs, while the UV light absorbances of the DOM decreased only slightly. Conversely, ozonation resulted in only small decreases of the EDCs but pronounced absorbance losses of the DOM. These results suggest that ClO2 and HOCl primarily reacted as oxidants by accepting electrons from electron-rich phenolic and hydroquinone moieties in the DOM, while O3 reacted via electrophilic addition to aromatic moieties, followed by ring cleavage. This study highlights the potential of combined EDC-UV measurements to monitor chemical oxidation of DOM, to assess the nature of the reactive moieties and to study the underlying reaction pathways.
在水处理中，溶解的有机物 (DOM) 通常是化学氧化剂的主要吸收体。已经测量了 DOM 的这些变化，例如其光学性质，以跟踪氧化过程。然而，此类测量仅包含有关 DOM 的氧化态和反应性部分变化的有限信息。在这项研究中，我们使用介导的电化学氧化来量化三种不同类型的 DOM 在与二氧化氯 (ClO2)、氯 (HOCl/OCl(-)) 和臭氧 (O3) 氧化过程中电子供体容量 (EDC) 的变化，从而确定其氧化还原状态。ClO2 和 HOCl 的处理导致 EDC 可比且明显降低，而 DOM 的紫外吸光度仅略有下降。相反，臭氧化仅导致 EDC 的微小降低，但 DOM 的吸收损失明显。这些结果表明，ClO2 和 HOCl 主要通过从 DOM 中富电子的酚类和对苯二酚部分接受电子来作为氧化剂反应，而 O3 则通过亲电加成到芳族部分，然后进行环裂解进行反应。这项研究强调了结合 EDC-UV 测量来监测 DOM 的化学氧化、评估反应性部分的性质以及研究潜在反应途径的潜力。
