Department of Environmental Science and Engineering, Nanjing Agricultural University, Nanjing, 210095, China.
Ministry of Environmental Protection of PRC, Nanjing Institute of Environmental Science, Nanjing, 210042, China.
Environ Sci Pollut Res Int. 2017 Oct;24(29):23219-23225. doi: 10.1007/s11356-017-9935-z. Epub 2017 Aug 22.
The objective of this research was to compare the transformation of Br and formation of brominated byproducts in UV/persulfate (PS) and UV/HO processes. It was revealed that Br was efficiently transformed to free bromine which reacted with humic acid (HA) or dihydroxybenzoic acid resulting in the formation of brominated byproducts such as bromoacetic acids (BAAs) in UV/PS system. In contrast, no free bromine and brominated byproducts could be detected in UV/HO system, although the oxidization of Br was evident. We presumed that the oxidation of Br by hydroxyl radicals led to the formation of bromine radicals. However, the bromine radical species could be immediately reduced back to Br by HO before coupling to each other to form free bromine, which explains the undetection of free bromine and BAAs in UV/HO. In addition to free bromine, we found that the phenolic functionalities in HA molecules, which served as the principal reactive sites for free chlorine attack, could be in situ generated when HA was exposed to free radicals. This study demonstrates that UV/HO is more suitable than UV/PS for the treatment of environmental matrices containing Br. Graphical abstract Graphical abstract.
本研究旨在比较 UV/过硫酸盐 (PS) 和 UV/过氧氢 (HO) 工艺中 Br 的转化和溴代副产物的形成。结果表明，Br 被有效地转化为游离溴，它与腐殖酸 (HA) 或二羟基苯甲酸反应，导致溴代副产物如溴乙酸 (BAA) 的形成，这在 UV/PS 体系中发生。相比之下，在 UV/HO 体系中，尽管 Br 的氧化是明显的，但不能检测到游离溴和溴代副产物。我们推测，由羟基自由基引起的 Br 的氧化导致溴自由基的形成。然而，溴自由基物种可以在与彼此结合形成游离溴之前，被 HO 立即还原回 Br，这解释了在 UV/HO 中不能检测到游离溴和 BAA 的原因。除了游离溴之外，我们还发现，当 HA 暴露于自由基时，HA 分子中的酚官能团可以原位生成，这些官能团是游离氯攻击的主要反应位点。这项研究表明，对于含有 Br 的环境基质的处理，UV/HO 比 UV/PS 更合适。
