State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
Environ Sci Pollut Res Int. 2018 Jan;25(3):2265-2272. doi: 10.1007/s11356-017-0614-x. Epub 2017 Nov 8.
It has recently been demonstrated that the addition of nanoscale zero-valent iron (nZVI) to oxygen-containing water or soil aquifers results in the oxidation of organic compounds. However, there has been little insight about the generation of the reactive oxygen species (ROS) that play a vital role in the transformation of contaminants in the presence of nZVI. This study investigated (i) the degradation of 2-chlorobiphenyl (2-CB) by nZVI; (ii) the generation and role of ROS in this process. Under anaerobic and aerobic conditions, the removal efficiency of 2-CB was 65.5 and 59.4%, respectively, after 4 h at a pH of 5.0. The results demonstrated that both the reductive and oxidative processes account for 2-CB degradation under aerobic conditions. Hydroxyl radicals (·OH) generated by nZVI at low pH could efficiently degrade 2-CB, the main reductive dechlorination product was biphenyl. Two other hydroxylation products (2-chlorophenol and 2-hydroxybiphenyl) were also examined. There was a higher degradation efficiency of 2-CB under acidic conditions than basic conditions because more ·OH was generated by nZVI. The presence of natural organic matters (NOMs), including humic acid (HA), salicylic acid (SA), galic acid (GA), and tannic acid (TA), increased the degradation efficiency of 2-CB (k values ranged from 0.0041 to 0.0042 min), because NOMs can mediate the electron transfer from the nZVI surface to O, and facilitate the production of Fe and HO that subsequently form ·OH. The mechanisms of these processes have provided new insights into the role of nZVI in the transformation of organic compounds.
最近的研究表明，将纳米零价铁 (nZVI) 添加到含氧水或土壤含水层中会导致有机化合物的氧化。然而，对于在 nZVI 存在下对污染物转化起着至关重要作用的活性氧物质 (ROS) 的生成，人们的了解甚少。本研究考察了 (i) nZVI 对 2-氯联苯 (2-CB) 的降解；(ii) 在这个过程中 ROS 的生成和作用。在 pH 值为 5.0 时，在厌氧和有氧条件下，2-CB 的去除效率分别为 65.5%和 59.4%，经过 4 小时。结果表明，在有氧条件下，2-CB 的降解既涉及还原过程也涉及氧化过程。在低 pH 值下，nZVI 生成的羟基自由基 (·OH) 可以有效地降解 2-CB，主要的还原脱氯产物是联苯。还检测到另外两种羟化产物（2-氯苯酚和 2-羟基联苯）。由于 nZVI 生成的·OH 更多，因此在酸性条件下 2-CB 的降解效率更高。天然有机物 (NOMs) 的存在，包括腐殖酸 (HA)、水杨酸 (SA)、没食子酸 (GA) 和单宁酸 (TA)，增加了 2-CB 的降解效率（k 值范围从 0.0041 到 0.0042 min），因为 NOMs 可以介导电子从 nZVI 表面转移到 O，并促进 Fe 和 HO 的生成，进而形成·OH。这些过程的机制为 nZVI 在有机化合物转化中的作用提供了新的见解。
