Bromophenols (BPs) are ubiquitous phenolic contaminants and typical halogenated disinfection byproducts (DBPs) that are commonly detected in aquatic environments. The transformation of 2,4-dibromophenol (2,4-DBP) during chlorination process was fully explored in this research. It was found that active chlorine can react with 2,4-DBP effectively in a wide pH range of 5.0-11.0, with an apparent second-order rate constant (k_app) varying from 0.8 M⁻¹·s⁻¹ to 110.3 M⁻¹·s⁻¹. The addition of 5 mM ammonium ions almost completely suppressed the reaction via competitive consumption of free chlorine. With the concentration of HA increasing from 1.0 to 10.0 mg·L^-1, the inhibition on the degradation of 2,4-DBP increased from 8.7% to 63.4%. By contrast, bromide ions at a concentration of 5 mM accelerated the process by about 4 times, due to the formation of hypobromous acid. On the basis of the eleven products (with eight nominal masses) identified by LC-TOF-MS, electrophilic substitution reactions and single-electron transfer reactions were mainly involved in the chlorination process. The concentration of primary chlorine-substituted products was about 4 times that of the dimer products, demonstrating that electrophilic substitution reaction was predominant during chlorination of 2,4-DBP. Density functional theory (DFT) based calculations revealed that HOCl is the dominant active oxidizing species for elimination of 2,4-DBP and coupling reaction occurs more easily at para and ortho position of hydroxyl group in the phenolic moiety. These findings could provide some new insights into the environmental fate of bromophenols during chlorine disinfection of water and wastewaters.

溴酚（BPs）是普遍存在的酚类污染物，是通常在水生环境中检测到的典型卤化消毒副产物（DBP）。本研究充分探讨了氯化过程中2,4-二溴苯酚（2,4-DBP）的转化。发现活性氯可以在5.0-11.0的宽pH范围内与2,4-DBP有效反应，表观二阶速率常数（k _app）在0.8 M ^-1 ·s ^-1至110.3 M之间变化。^-1 ·s ^-1。通过竞争性消耗游离氯，添加5 mM铵离子几乎可以完全抑制反应。随着HA浓度从1.0增加到10.0 mg·L ^-1，对2,4-DBP降解的抑制作用从8.7％增加到63.4％。相反，由于次溴酸的形成，浓度为5 mM的溴离子使该过程加速了约4倍。根据LC-TOF-MS鉴定的11种产品（具有8个标称质量），亲电取代反应和单电子转移反应主要参与了氯化过程。氯取代的初级产物的浓度约为二聚产物的4倍，表明在2，4-DBP氯化过程中，亲电取代反应占主导地位。基于密度泛函理论（DFT）的计算表明，HOCl是消除2的主要活性氧化物质。4-DBP和偶联反应更容易在酚部分中羟基的对位和邻位发生。这些发现可以为水和废水的氯消毒过程中溴酚的环境命运提供一些新见解。