氯化过程次生有机氯胺的稳定性及其与酚类化合物的反应活性

Stability of secondarily formed organic chloramines during water chlorination processes and their reactivity with phenolic compounds

氯消毒过程中,氯会与水中的溶解性有机氮反应生成有机氯胺.本文研究了以脂肪胺、氨基酸和酰胺为前体物次生有机氯胺的稳定性及其与酚类化合物的反应活性.结果表明,以乙胺、甘氨酸、尿素为前体物生成的有机氯胺在接近中性p H条件下可稳定存在.有机氯胺与间苯二酚、邻苯二酚的反应活性高于苯酚.在20℃、p H 8的反应条件下,对于间苯二酚,反应活性遵循:N-氯代乙胺(二级反应速率常数k=1.82×10^(-1)L·mol^(-1)·s^(-1))>N-氯代甘氨酸(k=7.05×10^(-2)L·mol^(-1)·s^(-1))>无机一氯胺(k=5.25×10^(-2)L·mol^(-1)·s^(-1))>N-氯代尿素(k=4.21×10^(-3)L·mol^(-1)·s^(-1));对于邻苯二酚,反应活性遵循:N-氯代尿素(k=1.28×10^(-1)L·mol^(-1)·s^(-1))>无机一氯胺(k=6.10×10^(-2)L·mol^(-1)·s^(-1))>N-氯代乙胺(k=3.96×10^(-2)L·mol^(-1)·s^(-1))>N-氯代甘氨酸(k=2.88×10^(-3)L·mol^(-1)·s^(-1)).随p H值升高(p H 6~10),N-氯代乙胺与间苯二酚、N-氯代尿素与邻苯二酚的k增大.尽管有机氯胺通常被认为是“伪氯胺”,但以胺类、尿素为前体物的有机氯胺与酚类化合物的反应活性高于无机一氯胺,因此,氯化水处理过程中次生有机氯胺可与水中基质反应,影响水质安全,需予以关注.

During water chlorination,chlorine reacts with dissolved organic nitrogen (DON) to form organic chloramines.This study aimed to investigate the stability of organic chloramines formed with precursors including aliphatic amines,amino acids,and amides,and their reactivity with phenolic compounds.Results showed that organic chloramines formed during chlorination of ethylamine,glycine,and urea were stable.The reactivity of organic chloramines towards resorcinol and catechol was obviously higher than phenol.At p H 8 and 20℃,the second-order rate constants for the reactions between organic chloramines and resorcinol followed the order of N-chloroethylamine (k=1.82×10^(-1) L·mol^(-1)·s^(-1))>N-chloroglycine (k=7.05×10^(-2) L·mol^(-1)·s^(-1))>monochloramine (k=5.25×10^(-2) L·mol^(-1)·s^(-1))>N-chlorourea (k=4.21×10^(-3) L·mol^(-1)·s^(-1)),while the second-order rate constants for the reactions between organic chloramines and catechol followed the order of N-chlorourea (k=1.28×10^(-1) L·mol^(-1)·s^(-1))>monochloramine (k=6.10×10^(-2)L·mol^(-1)·s^(-1))>N-chloroethylamine (k=3.96×10^(-2) L·mol^(-1)·s^(-1))>N-chloroglycine (k=2.88×10^(-3) L·mol^(-1)·s^(-1)).Moreover,the rate constants for the reactions between organic chloramines (e.g.,N-chloroethylamine and N-chlorourea) and phenolic compounds (e.g.,resorcinol and catechol) increased with increasing p H (p H 6~10).Even though organic chloramines are generally regarded as“pseudo-chloramines”,organic chloramines formed with amines and urea as precursors exhibit higher reactivity towards phenolic compounds than monochloramine.Hence,the formation of organic chloramines during water chlorination and their reactions with coexisting substances can induce potential risk,which warrants attention and further study.