Active Bromine Species Research Articles

The diverse roles of bromide in the degradation of tinidazole during UV-LED/chlorine process at different wavelengths: Kinetics, radical contribution, and degradation pathway

Bromide (Br–) is widely present in aquatic environment and plays important roles in pollutant degradation during advanced oxidation processes. This work systematically investigated the effect of Br– on the degradation of tinidazole (TNZ) during ultraviolet light-emitting diode (UV-LED)/chlorine process at different wavelengths (265 and 365 nm). The observed pseudo-first-order constant (k') for the TNZ degradation during UV-LED (365 nm)/chlorine process in the presence of 0.4 mM Br– (0.1125 min−1) was 1.56 times that during UV-LED (365 nm)/chlorine process in the absence of Br–. However, the k' value during UV-LED (265 nm)/chlorine process was reduced by 49.=7 % in the presence of 0.4 mM Br–. At 0–0.4 mM Br−, elevated levels of hydroxyl radicals (HO·) and active bromine species promoted TNZ degradation during UV-LED (365 nm)/chlorine/Br– process, whereas reduced HO· concentration was the main reason for the inhibition of TNZ degradation during UV-LED (265 nm)/chlorine/Br– process. With increasing solution pH from 5.8 to 7.8, the k' value of both processes decreased in the presence of Br–. Meanwhile, the k' value increased with increasing chlorine dosage and decreased with increasing initial TNZ concentration during both processes in the presence of Br–. The presence of Cl− and HCO3– presented negligible effects on the degradation of TNZ. According to the density functional theory calculation and detected intermediates, the degradation pathway of TNZ during both processes in the presence of Br– was proposed. The toxicity evaluation demonstrated that some of the degradation products of TNZ presented lower predicted toxicity values than TNZ. Overall, this work provides a thorough insight into the role of Br– in TNZ degradation during UV-LED/chlorine process at different wavelengths.

Engineering halogen ligand in Fe-based ionic liquid for elemental mercury removal from flue gas

The application of Fe-based ionic liquids (ILs) in elemental mercury (Hg0) removal from flue gas is limited by the low oxidative activity of the Fe(III) center. Here, a strategy of engineering halogen ligand to enhance the oxidative activity of Fe-based ILs for mercury removal was proposed. We developed a series of ionic liquids [Bmim][FeCl4-xBrx] (x = 0–4) with varying ratios of Cl− and Br− ligand substitutions. Mercury removal performance evaluations demonstrated a positive correlation between the oxidative activity towards Hg0 and the number of Br ligand substitutions in the ILs. [Bmim][FeBr4] achieved ∼99 % removal efficiency in the temperature range of 50–150 °C, with a saturated adsorption capacity reaching 205.4 mg/g (at 150 °C). In-situ Raman spectroscopy, DFT calculations, Hg-TPD, and XPS collectively revealed that the introduction of Br significantly lowered the excitation energy of the ligand–metal p-d orbital electron transitions, which facilitates the generation of active bromine species with unfilled 4p orbital, consequently enhancing the oxidative removal performance of Fe-based ILs for Hg0. This work provides an application of metal-based ILs in the realm of mercury removal and broadens the scope of ligand–metal interaction for IL design.

Regulated adsorption capability by Interface–Electric–Field enabling promoted electrochemical kinetics of Zinc–Bromine flow batteries

Zinc–bromine flow batteries (ZBFB) are gaining significant attention for large–scale energy storage due to the high energy density and affordable cost. Nevertheless, the diffusion of Br2 and the relatively low activity of Br2/Br− impede their broader application. Herein, a bi–phasic rutile/anatase–TiO2 embedded in carbon composite with hollow sphere structure (R/A–TiO2@HCS) is proposed as the catalyst for the Br2/Br− electrode. The internal electric field (IEF) formed between rutile–TiO2 and anatase–TiO2 regulates the adsorption capability for active bromine species. The appropriate adsorption capability can rapidly transfer the generated Br2 complex (QBrn) to the adsorbent component R/A–TiO2 during charging, liberating the carbon active sites, and release QBrn back to the carbon reaction sites timely during discharging, satisfying the both adsorption and desorption requirements of QBrn in different processes. The kinetics for oxidation and reduction are simultaneously enhanced. Moreover, the hollow construction offers storage space for QBrn, relieving its penetration problem. Under the synergistical cooperation, the ZBFB assembled with R/A–TiO2@HCS demonstrates the energy efficiency (EE) of 83.6 % at 80 mA cm−2, without significant decay over 500 cycles. And the EE still maintains 70.0 % even under 160 mA cm−2. This work highlights the significance of tailored electrocatalyst for ZBFB.

Halogenated aliphatic and phenolic disinfection byproducts in chlorinated and chloraminated dairy wastewater: Occurrence and ecological risk evaluation

The increasing demand for dairy products has led to the production of a large amount of wastewater in dairy plants, and disinfection is an essential treatment process before wastewater discharge. Disinfection byproducts (DBPs) in disinfected dairy wastewater may negatively influence the aquatic organisms in receiving water. During chlorine and chloramine disinfection of dairy wastewater, the concentrations of aliphatic DBPs increased from below the detection limits to 485.1 μg/L and 26.6 μg/L, respectively. Brominated and iodinated phenolic DBPs produced during chlor(am)ination could further react with chlorine/chloramine to be transformed. High level of bromide in dairy wastewater (12.9 mg/L) could be oxidized to active bromine species by chlorine/chloramine, promoting the formation of highly toxic brominated DBPs (Br-DBPs), and they accounted for 80.3% and 71.1% of the total content of DBPs in chlorinated and chloraminated dairy wastewater, respectively. Moreover, Br-DBPs contributed 49.9–75.9% and 34.2–96.4% to the cumulative risk quotient of DBPs in chlorinated and chloraminated wastewater, respectively. The cumulative risk quotient of DBPs on green algae, daphnid, and fish in chlorinated wastewater was 2.8–11.4 times higher than that in chloraminated wastewater. Shortening disinfection time or adopting chloramine disinfection can reduce the ecological risks of DBPs.

Chlorination of phenol, bisphenol A, and methylparaben in the presence of bromide: Kinetic simulation and formation of brominated aromatic byproducts

The seawater intrusion caused by the rising sea level increased the bromide (Br−) levels in the source waters of coastal cities. Adding bromide could significantly improve the degradation of phenol, bisphenol A, and methylparaben by chlorine. Bromide in water was first oxidized to active bromine species, which further reacted with phenols to generate brominated aromatic byproducts. A kinetic model including the reactions of chlorine oxidizing bromide, chlorine with phenol, and active bromine with phenol was established. The reaction rate constants of active bromine with phenols were calculated by fitting the degradation of phenols by chlorine in the presence of different bromide concentrations via the kinetic model. The rate constants of active bromine with phenols (1.5 × 104 to 2.9 × 104 M−1s−1 at pH 7.0) were higher than those of chlorine with phenols (4.0 × 101 to 8.9 × 101 M−1s−1 at pH 7.0), resulting in a bromide enhancement effect. The kinetic model could accurately simulate the evolution of total oxidant concentration with time (R2 > 0.96). Various brominated aromatic byproducts were identified in the chlorine/phenols/bromide systems, and they were first produced and then further degraded by chlorine. The technology of removing bromide and phenolic components from source water should be developed to control the formation of toxic brominated aromatic byproducts.

Unprecedented formation of reactive BrO– ions and their role as mediators for organic compounds degradation: The fate of bromide ions released during the anodic oxidation of Bromophenol blue dye

AbstractBased on the existing literature, active chlorine‐mediated electrochemical oxidation has been extensively studied when Cl‒ is added or Cl‒ is already present in the water matrices, as well as when Cl‒ is released from the target organic pollutants during their degradation. However, no attempts have been published concerning the fate and role of bromide (Br‒) ions released during the anodic oxidation (AO) of organobromine compounds. Therefore, the AO of bromophenol blue dye (BPB) was investigated in a parallel plate flow reactor using a boron‐doped diamond (BDD) anode. The effect of the applied current on the color removal efficiency and mineralization of BPB solution was examined and compared with AO of phenol red (PR) which has a similar molecular structure to BPB (but without Br) in order to understand the role of Br heteroatoms on the mineralization of BPB. Faster and higher mineralization and discoloration were achieved when treated with BPB solution compared to PR under similar experimental conditions. This behavior was associated with the electrogeneration of BrO‒, from the heteroatom Br which is released as the bromide ion (Br‒), during the degradation of BPB. The active bromine species are formed via direct and indirect oxidation approaches which were proposed based on ion chromatography and linear scanning voltammetry analysis.

New insight into electropolymerization of melamine. II: Low onset potential deposition of polymelamine with trace active bromine

In the present work, electrodeposition of polymelamine (pMel) was realized at relative low onset potentials in melamine aqueous solution containing additives of trace bromide ion (Br−), which can greatly drive the polymerization reaction by anodically generated active bromine species. The experimental results showed that in neutral monomer solutions containing even as low as 1 mmol/L Br−, the pMel film on glassy carbon electrode was effectively deposited at the anodic potential negatively shifted ca. 0.4 V than in 100 mmol/L chloride containing solutions. The effects of Br− on the electropolymerization of melamine were studied by cyclic voltammetry, potentiostatic control, in situ electrochemical Raman spectra and atomic force microscopy (AFM) techniques, respectively. Based on above results, this method was utilized for electrochemical polymerization of pMel on gold substrates under mild conditions, making it casting a pMel film on noncarbonaceous materials for the first time.

Role of hypobromous acid in the transformation of polycyclic aromatic hydrocarbons during chlorination

Hypobromous acid (HOBr), a highly reactive active species, can be formed and impact reaction processes with organic pollutants in source water during chlorination disinfection of the water containing bromide (Brˉ). In this study, we investigated the transformation kinetics of 10 parent polycyclic aromatic hydrocarbons (PAHs) and formation mechanisms of transformation products in the presence of Brˉ during chlorination. The results indicated that HOBr can accelerate the processes of electrophilic substitution (ES) and single electron transfer (ET) reactions in PAHs, and the second-order rate constants of HOBr are 102–103 times higher than those of hypochlorous acid (HOCl) with PAHs. HOBr was more conductive to induce ES reactions than HOCl. In water containing Brˉ, HOBr and HOCl dominate the reaction processes with PAHs, although other active bromine species may still affect reaction processes. In terms of transformation products, higher reactivity of HOBr results from faster formation of oxygenated PAHs (OPAHs) and halogenated PAHs (HPAHs) than HOCl. As an example of 3 model PAHs, anthracene transforms faster to its oxygenated products at a higher concentration, while pyrene and fluorene transform faster to halogenated products. These fundamental results were essential to understanding the transformation kinetics of PAHs and the formation of toxic disinfection by-products in the presence of Brˉ.

Enhanced ozone loss by active inorganic bromine chemistry in the tropical troposphere

Bromine chemistry, particularly in the tropics, has been suggested to play an important role in tropospheric ozone loss although a lack of measurements of active bromine species impedes a quantitative understanding of its impacts. Recent modelling and measurements of bromine monoxide (BrO) by Wang et al. (2015) have shown current models under predict BrO concentrations over the Pacific Ocean and allude to a missing source of BrO. Here, we present the first simultaneous aircraft measurements of atmospheric bromine monoxide, BrO (a radical that along with atomic Br catalytically destroys ozone) and the inorganic Br precursor compounds HOBr, BrCl and Br2 over the Western Pacific Ocean from 0.5 to 7 km. The presence of 0.17–1.64 pptv BrO and 3.6–8 pptv total inorganic Br from these four species throughout the troposphere causes 10–20% of total ozone loss, and confirms the importance of bromine chemistry in the tropical troposphere; contributing to a 6 ppb decrease in ozone levels due to halogen chemistry. Observations are compared with a global chemical transport model and find that the observed high levels of BrO, BrCl and HOBr can be reconciled by active multiphase oxidation of halide (Br− and Cl−) by HOBr and ozone in cloud droplets and aerosols. Measurements indicate that 99% of the instantaneous free Br in the troposphere up to 8 km originates from inorganic halogen photolysis rather than from photolysis of organobromine species.

A rechargeable non-aqueous Mg-Br2 battery

Owing to its low cost and high volumetric capacity, Mg is a promising anode material for energy storage applications. Previous research has identified the cathode chemistry as a major challenge that must be addressed for further development of Mg-based batteries. In response to this challenge, here we show Br2-based conversion chemistry is a potential route toward rechargeable Mg-batteries. Compared with Mg-ion or Mg-air chemistries, the Mg-Br2 system features fast kinetics and good cyclability. To solve the issues of poor electrolyte stability, a non-aqueous, dual-electrolyte scheme was employed for this proof-of-concept demonstration. The anolyte consisted of Mg(TFSI)2 dissolved in a monoglyme and diglyme mixture. The catholyte was composed of Mg(TFSI)2 in PYR14TFSI ionic liquid mixed with active bromine species. When Mg was used as the anode, an open circuit voltage of 3.0V (vs. Mg2+/Mg) was measured. The prototypical cell was successfully discharged and charged for over 20 cycles with consistently high coulombic efficiencies (ca. 96%).

Homogeneous mercury oxidation with bromine species released from HBr-modified fly ash

This research studies the release of bromine species from HBr-modified fly ash and the subsequent homogeneous oxidation of gaseous elemental mercury (Hg0) by active gaseous bromine species during heating. Tests utilize an innovative bench-scale experimental system specialized for the homogeneous Hg0 oxidation reaction and confirm that the released bromine species from the fly ash can oxidize Hg0 in the gas-phase. Low reaction temperatures are believed to favor the formation of intermediate products and effectiveness of Van der Waals forces resulting in improved mercury oxidation efficiency. Higher reactant concentrations improved oxidation performance, most likely because the oxidation reaction occurs via multiple reaction steps. Furthermore, O2 may not facilitate the Hg0 oxidation at the specified reaction temperature. Both FT-IR and UV/vis confirmed the release of HBr and Br2 from brominated fly ash. TG/MS results provided additional evidence of thermal stability and the identity of the released materials. At 140°C, HBr was detected by both FT-IR and TG-MS. UV/Vis detected increasing Br2 levels with increased heating temperature (especially above 200°C). The suggested mechanism is that the hydrogen atom of the released HBr is attracted to the lattice oxygen, forming active bromine species, such as Br∗. The Br∗ can then recombine to form Br2, which desorbs at higher temperatures and improves homogeneous Hg0 oxidation.

Experimental design as a tool for studying trihalomethanes formation parameters during water chlorination

Chlorination systems are widely used to ensure municipal drinking water's safety, providing defense against disease-causing organisms. However, previous studies indicated that, depending on the conditions of this treatment, a group of byproducts known as trihalomethanes (THMs), such as chloroform, may be formed and represent a considerable health risk. In this study, the effect of five variables (substrate and ClO− concentration, presence of KBr, temperature, and pH) on THMs' formation during chlorination of aqueous solutions of humic acid is discussed using a factorial design. Results showed that in the absence of KBr, only traces of brominated THMs are produced, probably due to contamination of ClO− by active bromine species. In the presence of KBr, the formation of chloroform is negligible, whereas within the group of brominated THMs, bromoform is produced in higher concentrations. Most relevant results are related to the existence of numerous higher-order effects, which shows the complexity of the involved reactions and also that THMs formation is not simply a function of substrate and ClO− molar ratio but also depends on the number of reactive sites available for chlorination in the substrate.

Bromide Ion Effect on N-Nitrosodimethylamine Formation by Monochloramine

N-Nitrosodimethylamine (NDMA) formation experiments conducted in phosphate buffer demonstrated that in waters containing monochloramine, the presence of bromide ion enhanced NDMA formation at the relatively high pH values of 8 and 9 after 24 h of reaction time, which was consistent with literature results. However, at relatively low to neutral pH (6 to 7), the presence of bromide resulted in lower NDMA formation as compared to results obtained in the absence of bromide. The hypothesis that bromamines were the species directly responsible for enhanced NDMA formation at high pH was tested and was shown not to be valid. Additional active bromine species were also tested, including hypobromous acid, hypobromite ion, and tribromide ion, with no species showing an ability to directly enhance NDMA formation. Analysis of the UV spectral data corresponding to the NDMA experiments suggest that the mechanism by which bromide enhances NDMA formation lies in the formation of a haloamine compound, possibly the mixed dihaloamine bromochloramine.

The Oxidative Bromination of Methane Over Rh/SiO2 Catalyst

Methyl bromide was synthesized by reacting methane with oxygen and hydrogen bromide over Rh/SiO2 catalyst. The reaction started from the oxidation of HBr to form active bromine species (Br• radicals and Br* surface species), which in turn reacted with CH4 to form CH 3 • radicals and $$\hbox{CH}_{3}^{\ast}$$ surface species. These CH 3 • and $$\hbox{CH}_{3}^{\ast}$$ species reacted with the active bromine species to form CH3Br and CH2Br2. The presence of HBr inhibited the deep oxidation and the steam reformation of CH4 and therefore, guaranteed the high selectivity of CH3Br. In the presence of HBr, CO was formed from the oxidation and steam reformation of CH3Br, while CO2 was formed from the oxidation and steam reformation of CO over Rh/SiO2 at reaction temperature higher than 560 °C.

Methods for the photometric determination of reactive bromine and chlorine species with ABTS

New methods for the determination of reactive bromine and chlorine species are presented. Hypobromous acid (HOBr) and all three bromamines species (NH 2Br, NHBr 2, NBr 3) are analyzed as a sum parameter and hypochlorous acid (HOCl), monochloramine (NH 2Cl) and chlorine dioxide (ClO 2) can be determined selectively. However, no distinction is possible between HOCl and the active bromine species. The bromine and chlorine species react with ABTS (2,2-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid-diammonium salt) to a green colored product that is measured at 405 or 728 nm. Free chlorine and NH 2Cl can be measured in the presence of ozone. The method is therefore suitable if combinations of disinfectants are used, such as chlorine/chlorine dioxide or chlorine/ozone. In natural waters, the method provides a detection limit for all chlorine/bromine species of less than 0.1 μM. The colored reaction product is very stable and allows a fixation of the chlorine/bromine species in the field and subsequent determination of the absorption in the laboratory.

Oxidations of Dihydroxyalkanoates to Vicinal Tricarbonyl Compounds with a 4-BzoTEMPO-Sodium Bromite System or by Indirect Electrolysis Using 4-BzoTEMPO and Bromide Ion

Abstract An efficient access to vicinal dioxoalkanoates, one of structural elements of potent competitive inhibitors of hydrolytic enzyme, from 2,3-dihydroxyalkanoates has been developed, which features an one-step procedure with a mild oxidizing system using recyclable 2,2,6,6-tetramethylpiperidine-1-oxyl in combination with NaBrO2·3H2O or electrogenerated active bromine species as a real oxidant.

Surface ozone depletion in Arctic spring sustained by bromine reactions on aerosols

NEAR-TOTAL depletion of the ozone in surface air is often observed in the Arctic spring, coincident with high atmospheric concentrations of inorganic bromine1–5. Barrie et al.1 suggested that the ozone depletion was due to a catalytic cycle involving the radicals Br and BrO (ref. 6); however, these species are rapidly converted to the nonradical species HBr, HOBr and BrNO3, quenching ozone loss. McConnell et al.7 proposed that cycling of inorganic bromine between aerosols and the gas phase could maintain sufficiently high levels of Br and BrO to destroy ozone, but they did not specify a mechanism for aerosol-phase production of active bromine species. Here we propose such a mechanism, based on known aqueous-phase chemistry, which rapidly converts HBr, HOBr and BrNO3 back to Br and BrO radicals. This mechanism should be particularly efficient in the presence of the high concentrations of sulphuric acid aerosols observed during ozone depletion events3.

Indirect electrooxidation of alcohols by a double mediatory system with two redox couples of [R2N+:O]/R2NO.cntdot. and [Br.cntdot. or Br+]/Br- in an organic-aqueous two-phase solution

An indirect electrooxidation method for alcohol to aldehyde to ketone conversion has been developed. This method, applicable to chemoselective oxidation, employs two redox couples, consisting of 2,2,6,6-tetremathyl-piperidine-1-oxyl derivatives and active bromine species

Indirect Electrooxidation of Alcohols by a Double Mediatory System with [R2N+= O]/R2N-O . and [Br. or Br+]Br-Redoxes

A double mediatory system consisting of N-oxoammonium salts and active bromine species, generated from 2,2,6,6-tetramethylpiperidine-1-oxyl derivatives and bromide ion as recyclable reagents, is useful for the selective electrooxidation of primary and secondary alcohols to aldehydes and ketones, respectively, in an aqueous-organic two-phase system.