Mechanisms of oxidative removal of 1,4-dioxane via free chlorine rapidly mixing into monochloramine: Implications on water treatment and reuse
Mechanisms of oxidative removal of 1,4-dioxane via free chlorine rapidly mixing into monochloramine: Implications on water treatment and reuse
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DOI：
10.1016/j.jhazmat.2022.129760
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发表时间：
2022-08-12
影响因子：
13.6
通讯作者：
Liu, Haizhou
中科院分区：
文献类型：
--
作者：
Wu, Liang;Patton, Samuel D.;Liu, Haizhou
游离氯（HOCl）和一氯胺（NH 2Cl）是水处理中最常用的两种水消毒剂;然而，HOCl快速混合到NH 2Cl中以诱导氧化反应以有效去除污染物的能力在很大程度上仍然未知。在这项研究中，1，4-二氧六环（1，4-D）的去除进行了定量的HOCl到NH 2Cl的快速混合过程中，溶液的pH值和HOCl-NH 2Cl比的影响进行评估，并确定反应物种在系统中产生的机制。结果表明，在pH值为6，HOCl与NH 2Cl摩尔比为1. 5，接近中性的条件下，1，4-D的去除率最高。羟基自由基（HO中心点）对1，4-D降解的贡献率为60- 70%，它的产生是通过在快速混合下向NH_2Cl中加入HOCl时NH_2Cl和NHCl（2）的水解衰变以及随后的过氧亚硝酸根（ONOO-）和过氧亚硝酸（ONOOH）的转化而开始的。结果还证实了ONOO-/ONOOH的形成需要溶解氧的存在，ONOO-是反应性自由基产生的关键前体。这些研究结果提供了深入了解与快速混合HOCl到NH 2Cl系统的反应机理与潜在的优化和应用，有效的痕量有机物去除水处理和回用。
Free chlorine (HOCl) and monochloramine (NH2Cl) are two of the most commonly used water disinfectants in water treatment; however, the capability of rapid mixing of HOCl into NH2Cl to induce oxidative reactions for efficient removal of contaminants remains largely unknown. In this study, 1,4-dioxane (1,4-D) removal was quantified during the rapid mixing of HOCl into NH2Cl, to evaluate the effects of solution pH and HOCl-to-NH2Cl ratio, and to identify mechanisms by which reactive species are generated in the system. Results showed that the highest 1,4-D removal was observed at the near-neutral pH of 6 with the HOCl-to-NH2Cl molar ratio of 1. Hydroxyl radical (HO center dot) contributed to 60-70 % of 1,4-D degradation and its generation was initiated by the hy-drolytic decay of NH2Cl and NHCl(2 )upon HOCl addition to NH2Cl with rapid mixing, and subsequent transformation of peroxynitrite (ONOO-) and peroxynitrous acid (ONOOH). The results also confirmed that the presence of dissolved oxygen was required to form ONOO-/ONOOH, and ONOO- was a crucial precursor for reactive radical generation. These findings provide insight into the reaction mechanism associated with the system of rapidly mixed HOCl into NH2Cl with the potential optimization and application for efficient trace organics removal in water treatment and reuse.