Formation Of Bromine Research Articles

Effect of bromide on the degradation kinetics of antibiotic resistance genes during water chlorination

Degradation of antibiotic resistance genes (ARGs) in water chlorination can be influenced by bromide (Br−), a common component in water matrices; however, detailed kinetic information on this process is limited. This study investigated the degradation kinetics tetA and blaTEM-1 genes, contained within the plasmid pWH1266, when exposed to bromine, chlorine, and chlorine with varying concentrations of Br− across a pH range of 7.0–8.5. The degradation of four ARG amplicons, measured using quantitative polymerase chain reaction, was observed to pursue second-order kinetics with bromine, exhibiting k of 4.0 × 102 − 1.6 × 103 M−1 s−1 at pH 7.0 and 2.6 × 102 − 9.6 × 102 M−1 s−1 at pH 8.5. These k values increased linearly with the length of the ARG sequences (209–1136 bps), yielding sequence-independent k of 1.2 and 7.4 × 10−1 (M AT + GC)−1 s−1 at pH 7.0 and 8.5, respectively. The degradation rate of ARGs during chlorination increased with rising Br− concentration due to the bromine formation through the reaction between chlorine with Br−, which subsequently degrades ARGs more rapidly than chlorine. This behavior was successfully simulated using a kinetic model derived from the reaction kinetics of bromine and chlorine reactions with ARGs. The existence of dissolved organic matter extracts only marginally decreased the enhanced degradation of ARGs with Br−, while ammonia significantly inhibited this process during chlorination, both with and without Br−, due to the low reactivity of NH2Cl and NH2Br toward ARGs. These findings highlight the importance of Br− in ARG degradation during water chlorination and the need for further studies in diverse water matrices.

Ferrate(VI) assists in reducing cytotoxicity and genotoxicity to mammalian cells and organic bromine formation in ozonated wastewater

Ozonation of wastewater containing bromide (Br−) forms highly toxic organic bromine. The effectiveness of ozonation in mitigating wastewater toxicity is minimal. Simultaneous application of ozone (O3) (5 mg/L) and ferrate(VI) (Fe(VI)) (10 mg-Fe/L) reduced cytotoxicity and genotoxicity towards mammalian cells by 39.8% and 71.1% (pH 7.0), respectively, when the wastewater has low levels of Br−. This enhanced reduction in toxicity can be attributed to increased production of reactive iron species Fe(IV)/Fe(V) and reactive oxygen species (•OH) that possess higher oxidizing ability. When wastewater contains 2 mg/L Br−, ozonation increased cytotoxicity and genotoxicity by 168%-180% and 150%-155%, respectively, primarily due to the formation of organic bromine. However, O3/Fe(VI) significantly (p < 0.05) suppressed both total organic bromine (TOBr), BrO3−, as well as their associated toxicity. Electron donating capacity (EDC) measurement and precursor inference using Orbitrap ultra-high resolution mass spectrometry found that Fe(IV)/Fe(V) and •OH enhanced EDC removal from precursors present in wastewater, inhibiting electrophilic substitution and electrophilic addition reactions that lead to organic bromine formation. Additionally, HOBr quenched by self-decomposition-produced H2O2 from Fe(VI) also inhibits TOBr formation along with its associated toxicity. The adsorption of Fe(III) flocs resulting from Fe(VI) decomposition contributes only minimally to reducing toxicity. Compared to ozonation alone, integration of Fe(VI) with O3 offers improved safety for treating wastewater with varying concentrations of Br−.

Bromide Ion Impurity-Induced Reaction between Selenium(IV) and Acidic Bromate: Prototype of a Cycle with Autocatalytic Behavior.

The selenium(IV)-bromate reaction in an acidic medium using phosphoric acid/phosphate buffer was investigated by UV-vis spectroscopy monitoring the formation of bromine. In an excess of bromate, the absorbance-time curves measured at 450 nm display a characteristic sigmoidal shape having a fairly long induction period, while in the opposite case, when selenium(IV) species is used in excess, the measured data follow the rise and fall behavior. Depending on the excess of Se(IV) the final bromine-containing product is either an elementary bromine or bromide ion. Simultaneous evaluation of the measured kinetic traces clearly indicated that, surprisingly, no direct reaction takes place between the reactants. Instead of that, a trace amount of bromide ion impurity in the stock bromate solution is sufficient to drive the system via the oxidation of the bromide ion by bromate producing elementary bromine followed by the subsequent selenite-bromine reaction reestablishing the bromide ion to open a new cycle. As a result, the concentration of bromide ions increases in a sigmoidal fashion during the course of the reaction unless enough selenium(IV) species is present; hence, the overall synergetic effect observed is the autocatalytic rise of bromide ions. Therefore, the cycle mentioned above may be considered as a prototype of autocatalytic cycles. This observation prompted us to clarify the explicit difference between an autocatalytic cycle and an autocatalytic reaction.

Evolution of the Bromate Electrolyte Composition in the Course of Its Electroreduction inside a Membrane-Electrode Assembly with a Proton-Exchange Membrane.

The passage of cathodic current through the acidized aqueous bromate solution (catholyte) leads to a negative shift of the average oxidation degree of Br atoms. It means a distribution of Br-containing species in various oxidation states between -1 and +5, which are mutually transformed via numerous protonation/deprotonation, chemical, and redox/electrochemical steps. This process is also accompanied by the change in the proton (H+) concentration, both due to the participation of H+ ions in these steps and due to the H+ flux through the cation-exchange membrane separating the cathodic and anodic compartments. Variations of the composition of the catholyte concentrations of all these components has been analyzed for various initial concentrations of sulfuric acid, cA0 (0.015-0.3 M), and two values of the total concentrations of Br atoms inside the system, ctot (0.1 or 1.0 M of Br atoms), as functions of the average Br-atom oxidation degree, x, under the condition of the thermodynamic equilibrium of the above transformations. It is shown that during the exhaustion of the redox capacity of the catholyte (x pass from 5 to -1), the pH value passes through a maximum. Its height and the corresponding average oxidation state of bromine atoms depend on the initial bromate/acid ratio. The constructed algorithm can be used to select the initial acid content in the bromate catholyte, which is optimal from the point of view of preventing the formation of liquid bromine at the maximum content of electroactive compounds.

Quantitative separation of thorium from rare earth elements and uranium in a rare earth element sulfuric acid leachate using cloud point extraction

A new cloud point extraction (CPE) method was created for extracting and concentrating thorium from a sulfuric acid leachate of rare earth elements (REESL). The method employs P,P′-di(2-ethylhexyl) methanediphosphonic acid (H2DEH[MDP]) as a chelating agent that has a strong attraction for actinides. By using Triton X-100 as a non-ionic surfactant and cetyl trimethyl ammonium bromide (CTAB) as an ionic surfactant, thorium is quantitatively extracted (over 98%) into a small volume of the surfactant-rich phase through heating and centrifugation. The method is based on in situ bromine formation to improve phase separation at highly acidic pH values resulting from the leaching steps. The method yielded a preconcentration factor of 22 when tested on REESL. To our knowledge, it is the first paper dealing with the use of CPE to selectively separate Th(IV) from rare earth elements and U from mining leachates.

Contribution of Embedded Bromine Molecules to the Dielectric Properties of Fluorinated Graphite Intercalation Compounds

Here, we study the dielectric properties of fluorinated graphites C2Fx with different fluorine contents (x ≈ 1.05, 0.85, and 0.60) and embedded bromine molecules by impedance spectroscopy. An analysis of the results using the Maxwell-Garnett approximation made it possible to estimate the contributions of the fluorinated graphite matrix and bromine guests to the dielectric permittivity of the compound. The permittivity of the C2Fx matrix increases with decreasing fluorine content and does not depend on temperature. The change in the permittivity upon cooling/heating of the samples is provided by the polarization of bromine molecules Br2. The significant temperature-dependent dielectric response of C2F0.60 is associated with the formation of bromine and polybromide ions, such as Br2– and Br3–, in the interlayer space of the matrix. The decrease in the permittivity at low temperature is explained by the freezing of the ion mobility.

Apparent Reactivity of Bromine in Bromochloramine Depends on Synthesis Method: Implicating Bromine Chloride and Molecular Bromine as Important Bromine Species.

The chloramination of bromide containing waters results in the formation of bromine containing haloamines: monobromamine (NH2Br), dibromamine (NHBr2), and bromochloramine (NHBrCl). Many studies have directly shown that bromamines are more reactive than chloramines in oxidation and substitution reactions with organic water constituents because the bromine atom in oxidants is more labile than the chlorine atom. However, similar studies have not been performed with NHBrCl. It has been assumed that NHBrCl has similar reactivity as bromamines with organic constituents in both oxidation and substitution reactions because NHBrCl, like bromamines, rapidly oxidizes N,N-diethyl-p-phenylenediamine. In this study, we examined the reactivity of NHBrCl with phenol red to determine if NHBrCl reacts as readily as bromamines in an isolated substitution reaction. NHBrCl was synthesized two ways to assess whether NHBrCl or the highly reactive intermediates, bromine chloride (BrCl) and molecular bromine (Br2), were responsible for bromine substitution of phenol red. NHBrCl was found to be much less reactive than bromamines with phenol red and that BrCl and Br2 appeared to be the true brominating agents in solutions where NHBrCl is formed. This work highlights the need to reexamine what the true brominating agents are in chloraminated waters containing bromide.

Chlorination of methotrexate in water revisited: Deciphering the kinetics, novel reaction mechanisms, and unexpected microbial risks

Chlorination of a typical anticancer drug with annually ascending use and global prevalence (methotrexate, MTX) in water has been studied. In addition to the analysis of kinetics in different water/wastewater matrices, high-resolution product identification and in-depth secondary risk evaluation, which were eagerly urged in the literature, were performed. It was found that the oxidation of MTX by free available chlorine (FAC) followed first-order kinetics with respect to FAC and first-order kinetics with respect to MTX. The pH-dependent rate constants (kapp) ranged from 170.00 M−1 s−1 (pH 5.0) to 2.68 M−1 s−1 (pH 9.0). The moiety-specific kinetic analysis suggested that 6 model substructures of MTX exhibited similar reactivity to the parent compound at pH 7.0. The presence of Br− greatly promoted MTX chlorination at pH 5.0–9.0, which may be ascribed to the formation of bromine with higher reactivity than FAC. Comparatively, coexisting I− or humic acid inhibited the degradation of MTX by FAC. Notably, chlorination effectively abated MTX in different real water matrices. The liquid chromatography-high resolution mass spectrometry analysis of multiple matrix-mediated chlorinated samples indicated the generation of nine transformation products (TPs) of MTX, among which seven were identified during FAC oxidation for the first time. In addition to the reported electrophilic chlorination of MTX (the major and dominant reaction pathway), the initial attacks on the amide and tertiary amine moieties with C-N bond cleavage constitute novel reaction mechanisms. No genotoxicity was observed for MTX or chlorinated solutions thereof, whereas some TPs were estimated to show multi-endpoint aquatic toxicity and higher biodegradation recalcitrance than MTX. The chlorinated mixtures of MTX with or without Br− showed a significant ability to increase the conjugative transfer frequency of plasmid-carried antibiotic resistance genes within bacteria. Overall, this work thoroughly examines the reaction kinetics together with the matrix effects, transformation mechanisms, and secondary environmental risks of MTX chlorination.

Enhanced removal of ammonia in Fe(VI)/Br− oxidation system: Kinetics, transformation mechanism and theoretical calculations

This work systematically examined the capability of ferrate (Fe(VI)) for ammonia oxidation, revealing for the first time that bromide ions (Br−) played an important role in promoting the removal of ammonia in Fe(VI) system. In the presence of 10.0 mM Br−, the removal efficiency of ammonia was nearly 3.4 times that of the control, and 1.0 mM ammonia was almost completely removed after two rounds addition of 1.0 mM Fe(VI) in 60 min. PMSO probe test, electron paramagnetic resonance spectra and radical quenching experiments were employed to interpret the underlying promotion mechanism of Br−, and it was proposed that the formation of active bromine (HOBr/OBr−) played a dominant role in the enhanced oxidative removal of ammonia by Fe(VI). Further kinetic model simulations revealed that HOBr/OBr− and Fe(VI) were the two major reactive species in Fe(VI)/Br− system, accounting for 66.7% and 33.0% of ammonia removal, respectively. As the target contaminant, ammonia could quickly consume the generated HOBr/OBr−, thereby suppressing the formation of brominated disinfection byproducts. Finally, NO3− was identified as the dominant transformation product of ammonia, and density functional theory (DFT) calculations revealed that six reaction stages were involved in ammonia oxidation with the first step as the rate-limiting step. This work would enable the full use of coexisting bromides for effective removal of ammonia from natural waters or wastewaters by in situ Fe(VI) oxidation method.

An Iodine-Functionalized Metal–Organic framework for catalytic alkene bromination

An iodine-functionalized metal–organic framework (MOF), UiO-68-I, was synthesized. UiO-68-I showed good catalytic activity for dibromination of alkenes and alkynes with a low catalyst loading of 1% and was able to be recycled and recovered efficiently. Mechanistic studies suggest that UiO-68-I may trigger the formation of molecular bromine through a radical intermediate and thus accelerate the reaction. The activity and stability of UiO-68-I outperforms most earlier reports on organoiodine catalysts, showing the great potential of iodine-functionalized MOFs as recyclable heterogeneous hypervalent iodine reagents or catalysts.

Bromide significantly promoted the abatement of micropollutants by peroxymonosulfate: Roles of HOBr and Br2

Peroxymonosulfate (PMS) is extensively investigated for water treatment, which can inevitably interact with bromide (Br−) in water to form bromine species. This study differentiated specific roles of bromine species for carbamazepine degradation during PMS treatment with Br− (PMS/Br−) via experiments and modeling. The second-order rate constants of HOBr, OBr−, Br2, Br2O, BrCl, and BrOCl with carbamazepine were first determined to be 59.5 M−1 s−1, 14.3 M−1 s−1, 1.1 × 104 M−1 s−1, 2.2 × 105 M−1 s−1, 1.4 × 107 M−1 s−1, and 2.7 × 106 M−1 s−1, respectively. By modeling, HOBr and Br2 substantially contributed to carbamazepine degradation. The contribution of Br2 was enhanced at higher Br− level and lower pH, and reached 99% at pH 3. Interestingly, Cl− significantly enhanced while HCO3− slightly enhanced the removal of carbamazepine. NOM was a sink for bromine, thereby retarding carbamazepine degradation in PMS/Br−. The maximum of total organic carbon (TOC) removal rate reached 43%, and the conversion ratio from the consumed bromine to total organic bromine (TOBr) formation was only 9% at 10 min in PMS/Br−. The primary transformation pathways of carbamazepine were hydroxylation and deacetylation, whereas bromination happened as the minor pathway. The acute toxicity was significantly reduced, and the total yields of known brominated disinfection by-products including tribromomethane and dibromoacetonitrile only accounted for 0.6% of TOBr at 10 min in PMS/Br−. This study firstly quantified specific roles of bromine species for micropollutant degradation under environmentally relevant conditions during PMS treatment of Br−-containing water.

Bromate formation during oxidation of bromide-containing water by the CuO catalyzed peroxymonosulfate process

Bromate formation has been found in the SO4•−-based oxidation processes, but previous studies primarily focused on the bromate formation in the homogeneous SO4•−-based oxidation processes. The kinetics and mechanisms of bromate formation are poorly understood in the heterogeneous SO4•−-based oxidation processes, although which have been widely studied in the eliminations of micropollutants. In this work, we found that the presence of CuO, a common heterogeneous catalyst of peroxymonosulfate (PMS), appreciably enhanced the bromate formation from the oxidation of bromide by PMS. The conversion ratio of bromide to bromate achieved over 85% within 10 min in this process. CuO was demonstrated to play a multiple role in the bromate formation: (1) catalyzed PMS to generate SO4•−, which then oxidizes bromide to bromate; (2) catalyzed the formed free bromine to disproportionate to bromate; (3) catalyzed the formed free bromine to decomposed back into bromide. In the CuO-PMS-Br system, bromate formation increases with increasing CuO dosages, initial CuO and bromide concentrations, but decreases with increasing bicarbonate concentrations. The presence of NOM (natural organic matter) resulted in a lower formed bromate accompanied with organic bromine formation. Notably, CuO catalyzes PMS to transform more than 70% of initial bromide to bromate even after recycled used for six times. The formation of bromate in the PMS catalysis by CuO system was also confirmed in real water.

해수 오존처리시 브로민 생성과 소독효과

Pathogenic and/or invasive organisms are problematic in ballast water, desalination plants and aquaculture systems for both ecological and economic reasons. In a desalination plant, the presence of microorganisms can lead to biofouling of the ultrafiltration and seawater reverse osmosis membrane equipment. Meanwhile, in the aquaculture industry, some pathogenic organisms cause serious fish diseases, which can result in mass die-offs. Various disinfection techniques such as ozonation, ultraviolet irradiation, electrolysis and chlorination, have been applied to remove pathogenic organisms from seawater environments. The purpose of this study was to develop a kinetic model for the prediction of residual ozone and bromine concentrations in seawater following ozonation, taking into consideration the ozone dose, water salinity, and pH. Ozone chemistry in saltwater is considerably different from that in fresh water because saltwater contains much higher concentrations of dissolved anions and cations (e.g., chloride, bromide, magnesium, sulfate) than fresh water. Salinity greatly affects the formation of residual ozone and bromine during saltwater ozonation. Unlike freshwater ozonation, there is no hydroxyl radical formation in seawater ozonation because ozone decomposition is considerably faster in water containing bromide. Therefore, seawater ozonation involves the initial unstable oxidant (ozone) and a secondary, more stable oxidant (bromine) for disinfection. This study also aimed to evaluate the performance of ozone and bromine disinfection using E. coli. The log inactivation of E. coli with ozone and bromine was 2.5 and 4 log, respectively. The log inactivation of E. coli with seawater ozonation was 5.8 log.

Toxicity of Ozonated Wastewater to HepG2 Cells: Taking Full Account of Nonvolatile, Volatile, and Inorganic Byproducts.

Wastewater ozonation forms various toxic byproducts, such as aldehydes, bromate, and organic bromine. However, there is currently no clear understanding of the overall toxicity changes in ozonated wastewater because pretreatment with solid phase extraction cannot retain inorganic bromate and volatile aldehydes, yet contributions of known ozonation byproducts to toxicity are unknown. Moreover, compared with bromate, organic bromine did not receive widespread attention. This study evaluated the toxicity of ozonated wastewater by taking aldehydes, bromate, and organic bromine into consideration. In the absence of bromide, formaldehyde contributed 96-97% cytotoxicity and 92-95% genotoxicity to HepG2 cells among the detected known byproducts, while acetaldehyde, propionaldehyde, and glyoxal had little toxicity. Both formaldehyde and dibromoacetonitrile drove toxicity among the known byproducts when bromide was present. Toxicity assays in HepG2 cells showed that when secondary effluents contained no bromide, the cytotoxicity of the nonvolatile organic fraction (NVOF) was reduced by 56-70%, and genotoxicity was completely removed after ozonation. However, the formed aldehydes (volatile organic fraction, VOF) led to increased overall toxicity. In the presence of bromide, compared with the secondary effluent, ozonation increased the cytotoxicity of the NVOFBr from 3.4-4.0 mg phenol/L to 10.3-13.9 mg phenol/L, possibly due to the formation of organic bromine. In addition, considering the toxicity of VOFBr (VOF in the presence of bromide, including aldehydes, tribromomethane, etc.), the overall cytotoxicity and genotoxicity became much higher than those of the secondary effluent. Although bromate had a limited impact on cytotoxicity and genotoxicity, it caused an increase in oxidative stress in HepG2 cells. Therefore, when taking full account of nonvolatile, volatile, and inorganic fractions, ozonation generally increases the toxicity of wastewater.

Investigation of electrochemical oxidation technology for selective bromine extraction in comprehensive utilization of concentrated seawater

Comprehensive utilization of concentrated seawater is a significant means to promote the development of the desalination industry, and then effectively relieve the freshwater crisis in coastal areas. Bromine exists in (concentrated) seawater as the main element, and is an important basic chemical. Its extraction becomes an important aspect of comprehensive utilization of concentrated seawater. Selective oxidation of bromide using a three-electrode system and an electrolyzer, was applied to extract bromine from concentrated seawater. It was feasibility for selective oxidation of bromide at the anode potential between 1.0 V and 1.5 V (with respect to the standard hydrogen electrode, SHE). Within this potential range, the formation of bromine was favored over that of chlorine and oxygen with the graphite rod electrode used in this study. Chloride was difficult to be oxidized at the selected anode potential (1.350 V vs. SHE) even though its concentration was very high. Both chloride and sulfate as coexisting ions showed a promoting effect on the electro-oxidation of bromide due to their contribution to the total conductivity of the solution. However, hardness ions such as calcium ion and magnesium ion had little effect on selective oxidation of bromide. Taking yield of bromine, current efficiency and energy consumption into overall consideration, operation time from 4 h to 10 h might be optimal in the process of treating concentrated seawater.

Bromine Vacancy Redistribution and Metallic‐Ion‐Migration‐Induced Air‐Stable Resistive Switching Behavior in All‐Inorganic Perovskite CsPbBr3 Film‐Based Memory Device

AbstractAll‐inorganic halide perovskites have attracted a great deal of attention for applications in resistive switching (RS) memory devices due to their superior stability compared to organic–inorganic hybrid halide perovskites. RS memory devices utilizing air‐stable all‐inorganic halide perovskite cesium lead bromide (CsPbBr3) film as the switching layer, which are successfully prepared by spin coating at low temperature, are demonstrated. Memory devices based on CsPbBr3 film exhibit typical reproducible bipolar RS behavior and superior switching characteristics, including the high ON/OFF ratio (≈104), long data retention (&gt;5 × 104 s), and environmental stability. In addition, multilevel storage capability can be achieved through controlling the different compliance currents. The formation and rupture of bromine (Br) vacancy conducting filaments (CFs) is proposed to explain the switching behavior in the Pt‐anode‐based memory devices, which is verified by XPS depth‐profiling analysis. Moreover, the coexistence of Br vacancies and Ag metallic CFs is suggested to be responsible for the switching behavior in Ag‐anode based device. These results demonstrate that the all‐inorganic halide perovskite CsPbBr3 film will be the promising switching material for nonvolatile memory devices.

Degradation of triclosan in a peroxymonosulfate/Br− system: Identification of reactive species and formation of halogenated byproducts

Peroxymonosulfate (PMS), a widely used in situ chemical oxidation agent, has attracted increasing attention in ground water/soil remediation. PMS is relatively stable with lifetime from months to even years in subsurface. The residual PMS can react with various of organics or inorganics species in environment, which may pose long term environmental effects. In this study, reaction between PMS and bromide (Br−) in water, and thus to the transformation of triclosan (TCS), an antibiotic agent, was studied. We found that TCS cannot be degraded by PMS alone but was efficiently removed in the presence of both PMS and Br−. This was due to the formation of free bromine upon the oxidation of Br− by PMS. Formation of bromine radical (Br) in PMS/Br− system was unlikely according to quenching tests. Reaction between free bromine and TCS generated brominated TCS intermediates which underwent further degradation to brominated disinfection byproducts (DBPs), of which bromoform (CHBr3) and dibromoacetic acid (DBAA) were the most prominent ones. Their yields reached 1.31 µM and 0.49 µM in 24 h, respectively, when 1 mg/L TCS was treated with 100 µM PMS and 100 µM Br−. Presence of humic acid (HA) remarkably enhanced the formation of monobromoacetic acid (MBAA), DBAA, and bromochloroacetic acid (BCAA) but inhibited the formation of CHBr3 and dibromochloromethane (CHClBr2). Thus, even though certain phenolic contaminants like TCS can be effectively removed in PMS/Br− system, formation of free bromine and DBPs makes it not a good treatment strategy. Particular attention should be paid when Br− is presented in PMS-based oxidation process.

Oxidative bromination of non-activated aromatic compounds with AlBr3/KNO3 mixture

Bromination of non-activated aromatic compounds with reaction mixture containing KNO3 and AlBr3 was studied in liquid substrates and in solvent. Aluminium bromide has three different roles in this reaction mixture. First, it is a source of bromide ions, which are essential in oxidative bromination application. Second, it acts as a catalyst, and lastly, it forms acidic environment via its hydrolysis, which is necessary for enhancement of the oxidising properties of nitrate ions. It was shown that when changing the reaction conditions, different side reactions (like nitration or Friedel–Crafts type arylation) can occur. However, it is possible to guide the reaction path and receive the desired outcome by choosing the suitable reaction conditions. In addition, it was shown that there has to be water content in this reaction mixture as the bromine formation rate depends on it, while there exists an optimal volume of water, where bromine formation is the fastest.

Oxidative debromination of 2,2-bis(bromomethyl)-1,3-propanediol by UV/persulfate process and corresponding formation of brominated by-products

This study investigated the oxidative debromination of 2,2-bis(bromomethyl)-1,3-propanediol (BBMP), a widely used brominated flame retardant, and the corresponding formation of brominated by-products by the UV/persulfate process. The debromination of BBMP by the UV/persulfate process was primarily driven by sulfate radicals (SO4−) at pHs 4.0–6.0 and hydroxyl radicals (HO) at pHs 9.0–12.0. The debromination rate increased with increasing pH from 4.0 to 9.0 and remained the same at pHs 9.0 and 12.0. Bromate was formed through the oxidation of bromide released from BBMP mainly by SO4−, with free bromine as a key intermediate. Bromate formation increased with increasing pH from 4.0 to 6.0, while it remarkably decreased with increasing pH from 6.0 to 12.0. This was mainly due to the transformation of SO4− to HO and also the quenching of bromine atoms that were the key intermediate for the formation of free bromine, by hydroxyl ions at the alkaline pH. In addition, the oxidative debromination of BBMP resulted in a significant decrease in the concentrations of total organic bromine, but the formation of brominated acetic acids and unknown brominated organic by-products. The concentrations of brominated organic by-products firstly increased and then decreased with prolonged reaction time. Also, the formation of brominated organic by-products and genotoxicity at pH 9.0 were much lower than that at pH 6.0. In this study, we propose that the UV/persulfate process under mildly alkaline conditions not only debrominates BBMP efficiently but also eliminates the formation of bromate and brominated organic by-products and genotoxicity.

Evolution of Anolyte Composition in the Oxidative Electrolysis of Sodium Bromide in a Sulfuric Acid Medium

The oxidation of a 10 mM aqueous solution of sodium bromide in a sulfuric acid medium on the surface of a platinum electrode in a cell with separated spaces was studied. The process is important in view of the use of the bromine–bromide redox couple in redox flow batteries. The study was performed by cyclic voltammetry, potentiostatic chronoamperometry with optical absorption spectrum recording, and measurements of the potential of the redox reference electrode. A numerical procedure for processing the experimental spectra of the solution was developed to separate them into the spectrum of molecular bromine and the residual signal. The latter was attributed to the absorption of the tribromide anion based on the literature data. The experimental dependences of the Br2 and Br3- concentrations for the oxidative electrolysis of the NaBr solution in the sulfuric acid medium agreed well with the theoretical predictions. The current efficiency of bromine formation was evaluated.