Kinetic modelling of the bromine-ammonia system: Formation and decomposition of bromamines

Reactions of Monobromamine and Dibromamine with Phenolic Compounds and Organic Matter: Kinetics and Formation of Bromophenols and Bromoform

“…Thus, the total oxidant (Br t ) concentrations of the NH 2 Br and NHBr 2 mixtures (N/Br = 2.5 or 10) were determined by the DPD method in the presence of KI. 33 Concentrations of NH 2 Br and NHBr 2 at pH 8.1 were predicted using the kinetic model developed by Mensah et al 17 Concentrations of the phenolic compounds were measured by high-performance liquid chromatography with ultraviolet detection (HPLC-UV) (see Supporting Information, Table S1 for detailed analytical conditions). The concentrations of CHBr 3 were determined by headspace gas chromatography (GC−MS) (see Table S2 in the SI for detailed analytical conditions).…”

“…All kinetic modeling was performed using Kintecus. 39 The kinetic model developed initially in the absence of organic compound 17 is shown in Table S3. showed that all plots were linear (R 2 > 98%), confirming that the reaction was first order with respect to NH 2 Br.…”

“…All kinetic modeling was performed using Kintecus . The kinetic model developed initially in the absence of organic compound is shown in Table S3.…”

“…19 Bromamines are unstable in aqueous solutions, and their distribution is mainly controlled by pH and the ammonia to bromine (N/Br) molar ratio. 17,20,21 NH 2 Br is more stable and predominant at high pH and high N/Br molar ratios (>100), while NHBr 2 predominates at nearly neutral pH and low N/Br molar ratios (<15). 20−22 During monochloramination, NH 2 Br reacts with monochloramine (NH 2 Cl) via an acid catalysis reaction, which leads to the formation of bromochloramine (NHBrCl).…”

“…Bromamines, i.e., monobromamine (NH 2 Br), dibromamine (NHBr 2 ), and tribromamine (NBr 3 ), can be formed during oxidative treatments, such as the chlorination of water containing bromide and ammonia. − Bromide (Br – ) is present ubiquitously in freshwaters at a concentration ranging from 0.01 to 2 mg L –1 − and at a concentration of about 67 mg L –1 in seawater. , During the oxidative treatment processes, Br – is rapidly oxidized into hypobromous acid/hypobromite ions (HOBr/OBr – ), − which then leads to rapid substitution reactions with ammonia to produce bromamines. ,,,− NH 2 Br and NHBr 2 could be formed during different scenarios such as oxidation treatments of ammonia-containing seawater (e.g., for biofouling control of cooling circuits, disinfection of ballast waters) or monochloramination of bromide-containing water for drinking water production. , The formation of bromamines is much greater with in-line chloramination than with preformed chloramination; bromamines are formed when ammonia is added after the prechlorination phase . Bromamines are unstable in aqueous solutions, and their distribution is mainly controlled by pH and the ammonia to bromine (N/Br) molar ratio. ,, NH 2 Br is more stable and predominant at high pH and high N/Br molar ratios (>100), while NHBr 2 predominates at nearly neutral pH and low N/Br molar ratios (<15). − During monochloramination, NH 2 Br reacts with monochloramine (NH 2 Cl) via an acid catalysis reaction, which leads to the formation of bromochloramine (NHBrCl) . The autodecomposition of NHBr 2 and the reaction of NHBr 2 with NHBrCl release HOBr, which can react with excess ammonia to regenerate bromamines.…”