Degradation of acrylamide during chlorination as a precursor of haloacetonitriles and haloacetamides
Degradation of acrylamide during chlorination as a precursor of haloacetonitriles and haloacetamides
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氯化过程中丙烯酰胺的降解作为卤代乙腈和卤代乙酰胺的前体
DOI：
10.1016/j.scitotenv.2017.09.141
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发表时间：
2018
影响因子：
9.8
通讯作者：
Gao Nai-Yun
中科院分区：
文献类型：
--
作者：
Wang An-Qi;Lin Yi-Li;Xu Bin;Hu Chen-Yan;Zhang Min-Sheng;Xia Sheng-Ji;Zhang Tian-Yang;Chu Wen-Hai;Gao Nai-Yun
丙烯酰胺是聚丙烯酰胺的单体，作为絮凝剂广泛应用于水处理过程中。本研究研究了丙烯酰胺氯化过程中的降解动力学和消毒副产物 (DBP) 的形成。氯和丙烯酰胺之间的反应遵循伪一级动力学。建立了丙烯酰胺氯化的动力学模型，计算出各主要基元反应（即丙烯酰胺与 ClO− 的碱催化反应以及丙烯酰胺与 HOCl 和 ClO− 的反应）的速率常数为 7.89 × 107M− 2h− 1、7.72 × 101M− 1h− 1，以及分别为 1.65×103M−1h−1。水中存在的 Br− 会导致 HOBr 的形成，并加速氯对丙烯酰胺的降解速度。计算得出丙烯酰胺与HOBr的反应速率常数为1.33×103M−1h−1。根据超高效液相色谱和电喷雾四极杆飞行时间质谱(UPLC-Q-TOF/MS)鉴定的中间体，提出了丙烯酰胺氯化的降解途径。丙烯酰胺氯化过程中鉴定出五种氯化 DBP，包括氯仿 (CF)、二氯乙腈 (DCAN)、三氯乙腈 (TCAN)、二氯乙酰胺 (DCAcAm) 和三氯乙酰胺 (TCAcAm)。随着反应时间的延长，CF、DCAN、DCAcAm和TCAcAm的形成量不断增加，而TCAN的形成量先增加后减少。随着氯剂量从 0.75 mM 增加到 4.5 mM，DCAN 成为主要的 DBP。在碱性 pH 条件下形成大量 CF、DCAN 和 TCAN。 DCAN 和 TCAN 的水解分别导致 DCAcAm 和 TCAcAm 的形成。这项研究的结果表明，丙烯酰胺可能是饮用水处理过程中形成卤代乙腈 (HAN) 和卤代乙酰胺 (HAcAms) 的前体。
Acrylamide is a monomer of polyacrylamide, which is widely used in the water treatment process as a flocculant. The degradation kinetics and formation of disinfection by-products (DBPs) during acrylamide chlorination were investigated in this study. The reaction between chlorine and acrylamide followed a pseudo-first-order kinetics. A kinetic model regarding acrylamide chlorination was established and the rate constants of each predominant elementary reaction (i.e., the base-catalyzed reaction of acrylamide with ClO−as well as the reactions of acrylamide with HOCl and ClO−) were calculated as 7.89 × 107M− 2h− 1, 7.72 × 101M− 1h− 1, and 1.65 × 103M− 1h− 1, respectively. The presence of Br−in water led to the formation of HOBr and accelerated the rate of acrylamide degradation by chlorine. The reaction rate constant of acrylamide with HOBr was calculated as 1.33 × 103M− 1h− 1. The degradation pathways of acrylamide chlorination were proposed according to the intermediates identified using ultra-performance liquid chromatography and electrospray ionization-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS). Five chlorinated DBPs including chloroform (CF), dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN), dichloroacetamide (DCAcAm), and trichloroacetamide (TCAcAm) were identified during acrylamide chlorination. The formation of CF, DCAN, DCAcAm, and TCAcAm kept increasing, while that of TCAN increased and then decreased with increasing reaction time. As the chlorine dosage increased from 0.75 to 4.5 mM, DCAN became the dominant DBP. Large amounts of CF, DCAN, and TCAN were formed at basic pHs. The hydrolysis of DCAN and TCAN led to the formation of DCAcAm and TCAcAm, respectively. The results of this study elucidated that acrylamide can be a precursor for the formation of haloacetonitriles (HANs) and haloacetamides (HAcAms) during drinking water treatment.