Department of Environmental Engineering and Soil Environment Research Center, Chonbuk National University, 567 Baekje-daero, Deokjin, Jeonju, Jeollabukdo 561-756, Republic of Korea.
Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
Chemosphere. 2018 May;199:453-458. doi: 10.1016/j.chemosphere.2018.02.074. Epub 2018 Feb 12.
During the measurement of total organic carbon (TOC), dissolved organic carbon is converted into CO by using high temperature combustion (HTC) or wet chemical oxidation (WCO). However, the criteria for selecting the oxidation methods are not clear. In this study, the chemical structures of organic material were considered as a key factor to select the oxidation method used. Most non-degradable organic compounds showed a similar oxidation efficiency in both methods, including natural organic compounds, dyes, and pharmaceuticals, and thus both methods are appropriate to measure TOC in waters containing these compounds. However, only a fraction of the carbon in the halogenated compounds (perfluorooctanoic acid and trifluoroacetic acid) were oxidized using WCO, resulting in measured TOC values that are considerably lower than those determined by HTC. This result is likely due to the electronegativity of halogen elements which inhibits the approach of electron-rich sulfate radicals in the WCO, and the higher bond strength of carbon-halogen pairs as compared to carbon-hydrogen bonds, which results in a lower degree of oxidation of the compounds. Our results indicate that WCO could be used to oxidize most organic compounds, but may not be appropriate to quantify TOC in organic carbon pools that contain certain halogenated compounds.
在总有机碳（TOC）的测量过程中，使用高温燃烧（HTC）或湿式化学氧化（WCO）将溶解的有机碳转化为 CO。然而，选择氧化方法的标准尚不清楚。在本研究中，有机材料的化学结构被认为是选择所用氧化方法的关键因素。大多数不可降解的有机化合物在这两种方法中表现出相似的氧化效率，包括天然有机化合物、染料和药物，因此这两种方法都适用于测量含有这些化合物的水中的 TOC。然而，只有一部分卤代化合物（全氟辛酸和三氟乙酸）中的碳被 WCO 氧化，导致测量的 TOC 值明显低于 HTC 确定的值。这一结果可能是由于卤元素的电负性抑制了 WCO 中富电子硫酸根自由基的接近，以及与碳氢键相比，碳-卤键的键强度更高，导致化合物的氧化程度较低。我们的结果表明，WCO 可用于氧化大多数有机化合物，但可能不适合定量含有某些卤代化合物的有机碳库中的 TOC。
