Department of Chemical Engineering, University of Illinois at Chicago, 929 West Taylor Street, Chicago, Illinois 60607, United States.
Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 North Park Street, Madison, Wisconsin 53706, United States.
Environ Sci Technol. 2020 Oct 6;54(19):12673-12683. doi: 10.1021/acs.est.0c03916. Epub 2020 Sep 17.
This research investigated chlorinated byproduct formation at TiO anodes. Resorcinol was used as a model organic compound representative of reactive phenolic groups in natural organic matter and industrial phenolic contaminants and was oxidized in the presence of NaCl (0-5 mM). Resorcinol mineralization was >68% in the presence and absence of NaCl at 3.1 V/SHE (residence time = 13 s). Results indicated that ∼4.3% of the initial chloride was converted to inorganic byproducts (free Cl, ClO, ClO) in the absence of resorcinol, and this value decreased to <0.8% in the presence of resorcinol. Perchlorate formation rates from chlorate oxidation were 115-371 mol m h, approximately two orders of magnitude lower than reported values for boron-doped diamond anodes. Liquid chromatography-mass spectroscopy detected two chlorinated organic products. Multichlorinated alcohol compounds (CHClO and CHClO) at 2.5 V/SHE and a monochlorinated phenolic compound (CHOCl) at 3.1 V/SHE were proposed as possible structures. Density functional theory calculations estimated that the proposed alcohol products were resistant to direct oxidation at 2.5 V/SHE, and the CHOCl compound was likely a transient intermediate. Chlorinated byproducts should be carefully monitored during electrochemical advanced oxidation processes, and multibarrier treatment approaches are likely necessary to prevent halogenated byproducts in the treated water.
这项研究调查了 TiO2 阳极上氯化副产物的形成。间苯二酚被用作天然有机物和工业酚类污染物中反应性酚基的模型有机化合物，并在存在 NaCl（0-5 mM）的情况下被氧化。在 3.1 V/SHE（停留时间=13 s）下，间苯二酚存在和不存在 NaCl 时的矿化率均>68%。结果表明，在没有间苯二酚的情况下，约有 4.3%的初始氯转化为无机副产物（自由氯、ClO、ClO），而在有间苯二酚存在的情况下，这一数值降至<0.8%。由氯酸盐氧化生成高氯酸盐的速率为 115-371 mol m h，大约比硼掺杂金刚石阳极报道的值低两个数量级。液相色谱-质谱检测到两种氯化有机产物。在 2.5 V/SHE 处检测到多氯醇化合物（CHClO 和 CHClO），在 3.1 V/SHE 处检测到单氯酚化合物（CHOCl），它们被认为是可能的结构。密度泛函理论计算估计，所提出的醇产物在 2.5 V/SHE 下不易直接氧化，而 CHOCl 化合物可能是一种瞬态中间体。在电化学高级氧化过程中应仔细监测氯化副产物，并且可能需要采用多屏障处理方法来防止处理水中的卤代副产物。
