Presence Of Bromide Research Articles

Combining high resolution mass spectrometry with a halogen extraction code to characterize and identify brominated disinfection byproducts formed during ozonation

Ozonation is widely used during water treatment but can generate a variety of toxic disinfection byproducts, especially in the presence of bromide. In the present study, our halogen extraction code was extended and modified to identify bromine isotopic patterns and combined with the R package MFAssignR in selectively identifying brominated disinfection byproducts (Br-DBPs) from high resolution mass spectra. In total, 127 Br-DBPs formed from a Suwannee River natural organic matter (SRNOM) solution were successfully detected from tens of thousands of mass spectrometry peaks. Kendrick mass defect analysis and structural characterization identified 17 structures, 15 of which were identified as brominated carboxylic acids and firstly reported here. Computational model predictions indicated that these brominated carboxylic acids may possess high toxic potencies and raise valid concerns. The adapted halogen extraction code described in this study is a powerful tool for a wider application of analyzing Br-DBPs in complex water matrices and provides an effective technique to characterize and identify these compounds in future studies.

Toxicity of disinfection byproducts formed during the chlorination of sulfamethoxazole, norfloxacin, and 17β-estradiol in the presence of bromide.

Brominated disinfection byproducts (Br-DBPs) are formed during the disinfection process of water containing bromine ions, such as marine aquaculture water. Little attention has been paid to Br-DBPs with anthropogenic chemicals as precursors. This study summarized the sodium hypochlorite (NaClO) oxidation of three frequently used pharmaceuticals, including two antibiotics, norfloxacin (NOR) and sulfamethoxazole (SMX), and the growth hormone estrogen 17β-estradiol (E2). Transformations of the pharmaceuticals were found to be faster in marine aquaculture water than in distilled water. Several Br-DBPs and Cl-DBPs were identified for NOR, SMX, and E2. It was shown that the carboxyl group, piperazine ring, C3, and C8 atoms were the primary reaction sites on NOR. The aniline moiety and S-N bond were identified to be the reaction sites on SMX. The C2, C4, C9, and C16 atoms were the potential reaction centers on E2. Preliminary calculation by QSAR model indicated that the value of logKow significantly increased with an increase in the number of bromine atoms in the Br-DBPs. The results of the bioconcentration factors (BCF) analysis suggested that the bioaccumulation of Br-DBPs were greater than that chlorinated DBPs (Cl-DBPs) in distilled water.

Bromate and brominated oxidation byproducts formation in the UVA/TiO2/peroxydisulfate system: Mechanism, kinetic model and control methods

In this research, the formation of bromate and brominated oxidation byproducts (Br-OBPs) by the UVA/TiO2/peroxydisulfate (PDS) process in the presence of bromide was investigated. Bromate formation, undetectable in the UVA/TiO2 and UVA/PDS systems, was found to be significant in the UVA/TiO2/PDS system. The PDS concentration and TiO2 dosage were positively correlated with bromate formation, while the conversion of bromide to bromate was inhibited by the initial concentration of bromide itself. A lag phase was observed when the initial concentration of bromide was 7.0 mg/L. Extreme pH (4 or 10), humic acid, or ammonium completely inhibited the formation of bromate. Chloride, sulfate, and bicarbonate could suppress the bromate formation. Three Br-OBPs were detected in the UVA/TiO2/PDS system spiked with bromide when humic acid was used as the precursor, with a total concentration lower than 4 μg/L. The fluorescence change of humic acid in bromide solution during oxidation by the UVA/TiO2/PDS process could be dissected into three dissimilar components via parallel factor analysis (PARAFAC) of excitation-emission matrix (EEM) spectra. The results of this study demonstrate that bromate and Br-OBPs formation by the UVA/TiO2/PDS process could be well controlled in the presence of humic acid or ammonium.

Dispersive micro-solid phase extraction with a magnetic nanocomposite followed by electrothermal atomic absorption measurement for the speciation of thallium

A magnetic dispersive micro-solid phase extraction procedure for the determination of the thallium content in waters is presented. The incorporation in the sample (10 mL) of a small amount of graphene-Fe3O4 composite (3.6 mg) in the presence of 10−4 mol L−1 Aliquat 336 at pH 2 results in the complete retention of both thallium(I) and thallium(III). After separation with a magnet, the micro-solid phase recovered is treated with 0.05 mL of a 0.1 mol L−1 sodium ethylenediaminetetracetate solution at pH 9, and the supernatant obtained after application of the magnet is introduced in the electrothermal atomizer of an atomic absorption spectrometer to obtain the signal corresponding to the total thallium content. For speciation, the trivalent form in a second sample aliquot is separated by means of a liquid-liquid extraction stage with chloroform and methyl trioctyl ammonium in the presence of bromide, and the signal corresponding to the monovalent form is obtained, the concentration of thallium(III) being obtained by difference. The enrichment factor is 185, which permits a detection limit as low as 0.01 μg L−1 of the analyte to be achieved. The relative standard deviation for five measurements at the 0.1 μg L−1 thallium level is below 5%. The reliability of the procedure is verified by analysing five certified reference samples for which speciation data are also given.

Hydrogen peroxide formation in water during the VUV/UV irradiation process: Impacts and mechanisms of selected anions

Understanding the formation and transformation of radicals generated by a low pressure mercury lamp emitting both 254 nm ultraviolet (UV254) and 185 nm vacuum UV (VUV185) is currently challenging due to the complexity of concurrent redox reactions occurring in this complex system. Because hydrogen peroxide (H2O2) is a common product of both oxidizing and reducing radicals generated during the VUV irradiation process, monitoring the variations in H2O2 levels can help us better understand the presence and relative dominance of different radicals. In this study, we systematically evaluated the effects of several selected anions on the formation of H2O2 under a variety of pH and dissolved oxygen (DO) conditions. Results show that although addition of these anions inhibited the formation of H2O2, their H2O2-inhibition mechanisms are markedly different. At low concentrations (≤1.0 mg/L), chloride reduced the generation of H2O2 primarily by consuming hydroxyl radicals (•OH); however, in high concentrations (11.0 mg/L), its light-screening effect was dominant. In comparison, the presence of bromide (≤1.0 mg/L) inhibited H2O2 formation mainly by reacting rapidly with both •OH and H2O2. Carbonate and phosphorous species exerted influence mainly by consuming •OH. Along with irradiation, increasing pH significantly decreased H2O2 levels, confirming that H2O2 was formed mainly by •OH. In contrast, raising DO did not raise H2O2 maximum yields, confirming that reducing radicals like aqueous electrons (e-aq) and hydrogen atoms (•H) are not the key precursors of H2O2 in this process. Mathematically, the evolutions of H2O2 can be reliably modeled (R2 ≥ 0.80) using a kinetics model incorporating H2O2 formation and decomposition kinetics. The results of this study may contribute to better understanding the use of VUV technology in water/wastewater treatment.

Determination of Pyridostigmine Bromide in Presence of its Related Impurities by Four Modified Classical Least Square Based Models: A Comparative Study

: Quantitative determination of pyridostigmine bromide in the presence of its two related substances; impurity A and impurity B was considered as a case study to construct the comparison. Introduction: Novel manipulations of the well-known classical least squares multivariate calibration model were explained in detail as a comparative analytical study in this research work. In addition to the application of plain classical least squares model, two preprocessing steps were tried, where prior to modeling with classical least squares, first derivatization and orthogonal projection to latent structures were applied to produce two novel manipulations of the classical least square-based model. Moreover, spectral residual augmented classical least squares model is included in the present comparative study. Methods: 3 factor 4 level design was implemented constructing a training set of 16 mixtures with different concentrations of the studied components. To investigate the predictive ability of the studied models; a test set consisting of 9 mixtures was constructed. Results: The key performance indicator of this comparative study was the root mean square error of prediction for the independent test set mixtures, where it was found 1.367 when classical least squares applied with no preprocessing method, 1.352 when first derivative data was implemented, 0.2100 when orthogonal projection to latent structures preprocessing method was applied and 0.2747 when spectral residual augmented classical least squares was performed. Conclusion: Coupling of classical least squares model with orthogonal projection to latent structures preprocessing method produced significant improvement of the predictive ability of it.

Effects of residual disinfectants on the redox speciation of lead(ii)/(iv) minerals in drinking water distribution systems.

This study investigated the reaction kinetics on the oxidative transformation of lead(ii) minerals by free chlorine (HOCl) and free bromine (HOBr) in drinking water distribution systems. According to chemical equilibrium predictions, lead(ii) carbonate minerals, cerussite PbCO3(s) and hydrocerussite Pb3(CO3)2(OH)2(s), and lead(ii) phosphate mineral, chloropyromorphite Pb5(PO4)3Cl(s) are formed in drinking water distribution systems in the absence and presence of phosphate, respectively. X-ray absorption near edge spectroscopy (XANES) data showed that at pH 7 and a 10 mM alkalinity, the majority of cerussite and hydrocerussite was oxidized to lead(iv) mineral PbO2(s) within 120 minutes of reaction with chlorine (3 : 1 Cl2 : Pb(ii) molar ratio). In contrast, very little oxidation of chloropyromorphite occurred. Under similar conditions, oxidation of lead(ii) carbonate and phosphate minerals by HOBr exhibited a reaction kinetics that was orders of magnitude faster than by HOCl. Their end oxidation products were identified as mainly plattnerite β-PbO2(s) and trace amounts of scrutinyite α-PbO2(s) based on X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopic analysis. A kinetic model was established based on the solid-phase experimental data. The model predicted that in real drinking water distribution systems, it takes 0.6-1.2 years to completely oxidize Pb(ii) minerals in the surface layer of corrosion scales to PbO2(s) by HOCl without phosphate, but only 0.1-0.2 years in the presence of bromide (Br-) due the catalytic effects of HOBr generation. The model also predicts that the addition of phosphate will significantly inhibit Pb(ii) mineral oxidation by HOCl, but only be modestly effective in the presence of Br-. This study provides insightful understanding on the effect of residual disinfectant on the oxidation of lead corrosion scales and strategies to prevent lead release from drinking water distribution systems.

Dimensional Structures and Electrocatalytic Activities of Platinum(II)-Palladium(II)-Manganese(II) Coordination Polymers Controlled by Chloride versus Bromide.

Here we report the synthesis and structural characterization of heterotrimetallic (PtII2PdII2MnII2)n coordination polymers that show different dimensionalities and electrocatalytic activities depending on chloride and bromide employed in the system. The reaction of the PtII2PdII2 tetranuclear complex [Pd2Pt2(NH3)4(d-pen)4] (1), bearing free carboxylate groups, with Mn2+ in the presence of chloride produced the (PtII2PdII2MnII2)n coordination polymer [Mn2Cl2(H2O)6(1)]Cl2 (2Cl), in which the PtII2PdII2 units of 1 are linked by [MnCl(H2O)3]+ moieties in a 1:2 ratio to form a 2D sheetlike structure. The corresponding reaction in the presence of bromide also gave the (PtII2PdII2MnII2)n coordination polymer [Mn2(H2O)6(1)]Br4 (3Br), but 3Br adopted a 3D network structure via a 1:1 linkage of the PtII2PdII2 units with [Mn2(H2O)6]4+ moieties. These complexes showed appreciably different electrocatalytic activities for H2 evolution.

Hexavalent Chromium Release in Drinking Water Distribution Systems: New Insights into Zerovalent Chromium in Iron Corrosion Scales.

Upon cast iron corrosion in contact with residual disinfectants, drinking water distribution systems have become potential geogenic sources for hexavalent chromium Cr(VI) release. This study investigated mechanisms of Cr(VI) release from cast iron corrosion scales. The oxidation of the corrosion scales by residual disinfectant chlorine released Cr(VI) and exhibited a three-phase kinetics behavior: an initial 2 h fast reaction phase, a subsequent 2-to-12 h transitional phase, and a final 7-day slow reaction phase approximately 2 orders of magnitude slower than the initial phase. X-ray absorption spectroscopy analysis discovered that zerovalent Cr(0) coexisted with trivalent Cr(III) solids in the corrosion scales. Electrochemical corrosion analyses strongly suggested that Cr(0) in the corrosion scales originated from Cr(0) in the cast iron alloy. Cr(0) exhibited a much higher reactivity than Cr(III) in the formation of Cr(VI) by chlorine. The presence of bromide in drinking water significantly accelerated Cr(VI) release because of its catalytic effect. Meanwhile, chlorine consumption was mainly attributed to the oxidation of organic matter and ferrous iron. Findings from this study point to a previously unknown but important pathway of Cr(VI) formation in drinking water, that is, direct oxidation of Cr(0) by chlorine, and suggest new strategies to control Cr(VI) in drinking water by inhibiting Cr(0) reactivity.

Comprehensive GC×GC-qMS with a mass-to-charge ratio difference extraction method to identify new brominated byproducts during ozonation and their toxicity assessment

Ozonation might increase the risk of wastewater due to byproduct formation, especially in the presence of bromide. In this study, a new analytical method was developed to identify new brominated disinfection byproducts (Br-DBPs) during ozonation, using comprehensive two-dimensional gas chromatography-single quadrupole mass spectrometry (GC×GC-qMS) connected with an electron capture detector in parallel. The obtained data were analyzed using a mass-to-charge ratio (m/z) difference extraction method. Over 1304 DBPs were detected in an ozonated phenylalanine solution. Further screening of 635 DBPs was conducted using the m/z difference extraction method. Finally, the structures for 12 Br-DBPs were confirmed and for 4 Br-DBPs were tentatively proposed by comparison with the NIST library and standard compounds. Eight of the confirmed Br-DBPs are first reported and identified: 2-bromostyrene, 1-bromo-1-phenylethylene, 2-bromobenzaldehyde, 3-bromobenzaldehyde, 4-bromobenzaldehyde, 2-bromophenylacetonitrile, 3-bromophenylacetonitrile and 4-bromophenylacetonitrile. These DBPs and 2,4,6-tribromophenol were detected at nanogram- to microgram-per-liter concentrations during ozonation of authentic water samples like algal bloom waters, wastewater treatment plant effluents, and surface water. The toxicities of these compounds were generally higher than that of bromate. The developed analytical method is a powerful technique for analyzing complex compounds and provides a novel way of identifying byproducts in future studies.

Effect of copper oxide on monochloramine decomposition in bromide-containing waters

Copper oxide (CuO), a common corrosion product found in copper pipes, has been shown to catalyse the decay of different oxidants in drinking water, including chlorine, bromine, iodine, and chlorine dioxide. However, its impact on monochloramine (NH2Cl), a disinfectant commonly used in long distribution system worldwide is still unknown. In this study, the effect of CuO on NH2Cl decay in the absence or presence of bromide was investigated. Results showed that in the presence of CuO and the absence of bromide, NH2Cl slightly decayed under acidic conditions. When bromide was present in NH2Cl solutions, the total oxidant concentration (sum of the different bromo-chloro-amines) was significantly decreased by CuO. This was primarily due to the degradation of bromochloramine (NHBrCl) by CuO which was evidenced by membrane inlet mass spectrometry. The decomposition rate of the total oxidant was similar for different CuO dosages (0.02–0.2 g/L) but increased with increasing bromide concentration (0–80 μM) and decreasing pH (6.5–8). An apparent second-order rate constant of 0.73 M−1 s−1 was determined with respect to NH2Cl and bromide concentrations for a CuO concentration of 0.05 g/L. Our findings suggest that, during water transportation in copper pipes or in distribution systems where copper oxide is present, special attention should be given to the stability of chloramines when bromide-containing waters are chloraminated.

Formation of disinfection byproducts during chlorination of mixed nitrogenous compounds in swimming pools

Disinfection byproducts (DBPs) in swimming pool waters are receiving increasing attention because of their toxicity and widespread occurrence. Current studies rarely investigate the formation of DBPs from typical precursors in swimming pools under mixed exposure. They also rarely investigate the formation of carbonaceous DBPs (C-DBPs) and nitrogenous DBPs (N-DBPs) simultaneously. In this study, the formation of C-DBPs and N-DBPs were investigated during chlorination of mixed precursors (i.e., tryptophan, urea, creatinine, and ammonia). The effects of precursors and operation parameters were also investigated. Among the four precursors, tryptophan had the highest DBP formation potential. Urea and ammonia restrained the formation of C-DBPs but promoted the formation of more toxic N-DBPs. C-DBP yields were significantly higher than N-DBP yields under all experimental conditions. Longer reaction time and higher chlorine dosage promoted the formation of C-DBPs, while higher temperature decreased the concentration of N-DBPs. The presence of bromide not only improved the sum yields of DBPs, but also shifted chlorinated DBPs to brominated species.

Synthesis and characterization of indolizine and 5,6-benzo-fused indolizine derivatives with their pharmacological applications

A efficient synthesis of novel Indolizine and 5,6-benzo-fusedindolizine derivatives are achieved by using substituted pyridine and substituted quinoline with electron-deficient acetylene and phenacyl bromides in presence of TEA base with acetonitrile solvent. The structures of newly synthesized compounds have been confirmed by spectroscopic techniques like 1H-NMR, 13C-NMR, LC-MS, IR and Elemental analysis. All the synthesized compounds were studied their lipid peroxidation activity. Synthesized compounds showed mild to moderate lipid peroxidase inhibitory activity. Compound 1a to 1e showed moderate activity and 1f, 2a and 2d showed minimal activity compared to ascorbic acid.

Oxidation of betrixaban to yield N-nitrosodimethylamine by water disinfectants

Degradation of betrixaban, an oral anticoagulant recently approved by the U.S. Food and Drug Administration (FDA), and its N-nitrosodimethylamine (NDMA) formation potential were studied mechanistically in the presence of monochloramine (NH2Cl), free chlorine, and ozone. Upon monochloramination, the formation of NDMA exceeded 1% at basic pH and was significant at circumneutral pH as well. The kinetic studies revealed that the reaction between betrixaban and monochloramine followed pseudo-first-order reaction kinetics. Increasing monochloramine concentration, its reaction time, and pH all significantly enhanced the NDMA formation yield, which also increased three-fold in the presence of bromide during monochloraminantion. The presence of nitrite inhibited the formation of NDMA under the same conditions. This study revealed a new potent and significant precursor of NDMA, indicating that monochloramination of waters containing betrixaban can lead to the formation of NDMA and other disinfection by-products such as dichloroacetonitrile (DCAN) and dimethylformamide (DMF). Moreover, chlorination of betrixaban by hypochlorite also yielded NDMA, albeit at two orders of magnitude lower yield than chloramination, while no NDMA formation was observed from ozonation of betrixaban.

Tracing nitrogenous byproducts during ozonation in the presence of bromide and ammonia using stable isotope labeling and high resolution mass spectrometry

Ammonia has been widely used to inhibit bromate formation during ozonation. However, our recent study found that during ozonation in the presence of bromide and ammonia, toxicity increased under certain conditions that might be attributed to the formation of nitrogenous byproducts. Herein, a typical structural moiety of natural organic matter (NOM), hydroquinone, was evaluated for its potential to form nitrogenous byproducts. During ozonation of the hydroquinone solution containing bromide and ammonia, toxicity of organic byproducts increased significantly. As organic bromine was hardly detected, organic nitrogen was responsible for the increased toxicity. An effective method combining ultra-performance liquid chromatography in tandem with high resolution mass spectrometry (UPLC-HRMS) with an isotope labeling strategy was used to trace nitrogenous byproducts. Four newly formed nitrogenous byproducts were detected, two of which were also detected in Suwannee River natural organic matter (SRNOM) solution treated under the same ozonation condition. Furthermore, the molecular structures and formation pathways of these nitrogenous byproducts were proposed. This study highlights that, despite the widespread use, adding ammonia to inhibit bromate formation during ozonation might increase the toxicity posed by nitrogenous byproducts. During ozonation in the presence of bromide and ammonia, particular attention should be paid to nitrogenous byproducts.

Enhanced ozonation of ciprofloxacin in the presence of bromide: Kinetics, products, pathways, and toxicity

Although the ozonation of common antibiotics, such as ciprofloxacin (CIP), in water has been well studied, the influence of bromide that is present at high levels in seawater, is essentially unknown. In this study, we investigated the effect of bromide on the reaction kinetics, formation of transformation products (TPs), reaction pathways, and toxicity in the ozonation of CIP. Bromide significantly accelerated the transformation of CIP by ozone, likely due to the formation of reactive bromine species. Based on time-of-flight high-resolution mass spectrometry and suspect screening, a total of 26 TPs, including 13 previously unknown products, were identified in artificial seawater, while only 9 of them were found in pure water without bromide. The transformation of CIP in artificial seawater was found to involve four major processes: oxidation at the piperazinyl moiety with the addition of hydroxyl group(s) to the ring and ring cleavage, oxidation at the quinolone moiety, and bromination. In contrast, the ozonation of CIP in pure water occurred only at the piperazinyl moiety. In addition, bromide also enhanced the removal of toxicity towards Escherichia coli. This study suggests that careful consideration should be taken when using ozone to treat antibiotics contaminated water in the presence of bromide.

Synthesis and Structural Analysis of Novel Phosphonium Hexatungstate Complexes

Sodium tungstate reacted with tetramethyl- and tetrabutyl-phosphonium bromide in presence of hydrochloric acid to afford two new phosphonium hexatungstate compounds ((CH3)4P)2W6O19, 1, and ((CH3CH2CH2CH2)4P)2W6O19, 2, respectively. Under similar conditions, sodium tungstate reacted with methyltriphenyl-, allyltriphenyl-, butyltriphenyl- and benzyltriphenyl-phosphonium bromides to yield four new phosphonium hexatungstate compounds (CH3Ph3P)2W6O19, 3, (CH2CHCH2Ph3P)2W6O19, 4, (CH3CH2CH2CH2Ph3P)2W6O19, 5, and (C6H5CH2Ph3P)2W6O19, 6, respectively. All six compounds appeared to be stable in air, and were structurally characterized by a combination of FTIR, elemental analyses, and single-crystal X-ray diffraction analyses. The steric effect of the phosphonium cation was investigated and found to cause no significant change on the average bond distances of the hexatungstate anion. The crystal structure analyses of these compounds showed that hexatungstate anions were isolated and the distance between the anions increases with increase in the bulkiness of the surrounding phosphonium cations. Moreover, thermal stability and heat absorption of all six compounds were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).

Ag doped ZnO nanorods catalyzed photo-triggered synthesis of some novel (1H-tetrazol-5-yl)-coumarin hybrids

Herein, we reported a facile synthetic strategy for the synthesis of 1,5-disubstituted tetrazole (1,5-DST) based chromone derivatives with different through photocatalyzed one-pot multicomponent reactions between aldehyde derivatives 7a-c, sodium azide, chromenocyl bromide in presence of triethylamine using ZnO nanorods (NRs) and Ag-doped ZnO nanocomposites (NCs) as photocatalysts. The reaction optimization was developed under ambient conditions at room temperature in dark and under visible light irradiation which revealed that Ag/ZnO NCs showed efficient catalytic activity towards the synthesis of new 1,5-DST through photocatalytic [3 + 2] cycloaddition reaction. The products 10a-f were afforded in excellent yields (90%–97%). The as-prepared tetrazole derivatives were subjected under cytotoxic evaluation towards MCF-7, HepG2, A549 and Wi38 cancer cell lines. It was revealed that compounds 10e and 10f showed potent anticancer activity.

Roles of bromine radicals, HOBr and Br2 in the transformation of flumequine by the UV/chlorine process in the presence of bromide

In the presence of bromide (Br−), new reactive species, such as bromine and reactive bromine species (RBS), are formed by the UV/chlorine process. In this study, the effects of Br− on the kinetics, products, and pathways of flumequine (FLU) transformation by the UV/chlorine process were investigated. The pseudo first-order rate constant (k′) for FLU degradation in the UV/chlorine process was enhanced by 2.5 times by 50 μM Br− at pH 7, as HOBr, Br2, RBS and HO• were formed, and they contributed 29.2%, 7.8%, 57.4% and 4.8% to k′, respectively. The second-order rate constants (k) of FLU reacting with HOBr, OBr−, Br2 and Br• were determined to be 115.6 M−1 s−1, negligible, 1.5 × 106 M−1 s−1 and 2.4 × 108 M−1 s−1, respectively. The contribution of Br2 was enhanced at a higher Br− level and a lower pH, which accounted for 48.2% of k′ at pH 6. The overall k′ value decreased by 97.9% from pH 6 to 9, during which k′ by HOBr, Br2 and RBS decreased significantly. The formation of brominated products was mainly attributed to HOBr and Br2, while RBS and HO• primarily promoted hydroxylation and ketonization during UV/chlorine treatment with Br−. The formation of total organic bromine (TOBr) by the UV/chlorine process with Br− was comparable to that during dark chlorination with Br−, while the yield of brominated disinfection byproducts in the former was much higher, further indicating that RBS and HO• promoted the formation of small-molecule products. In addition, the acute toxicity of FLU was significantly reduced during the UV/chlorine process with Br−. This is the first study to reveal the significant roles of Br2 and Br• in the degradation of micropollutants by the UV/chlorine process in Br−-containing water.

Kinetics and formation of disinfection byproducts during iohexol chlor(am)ination

In this study, the degradation kinetics, and the formation of disinfection byproducts (DBPs) during iohexol chlor(am)ination were studied. The chlorination kinetics can be described using a second-order model. As the pH of the solution increased, the apparent second-order rate constant of iohexol chlorination increased considerably. The reaction rate constants of iohexol with HOCl and OCl− were calculated as (3.75±0.70)×10-4 and (1.39±1.19)×10-4 M−1 s−1, respectively. In addition, the chloramination of iohexol followed tertiary kinetics, and the maximum apparent rate constant of 3.78×10-6 M−1 s−1 occurred at pH 7. NH4+ can promote the degradation of iohexol during chlorination, whereas Br− inhibits iohexol degradation during chloramination. The formation of conventional carbonated DBPs and emerging nitrogenated DBPs during chlor(am)ination of iohexol was measured. However, in the presence of bromide, the conversion of iohexol to toxic iodinated DBPs increased significantly during chlorination, and chlorination resulted in higher formation of toxic I-DBP compared to chloramination. Therefore, chloramine disinfection is preferred for treating raw water containing high bromide concentrations in terms of DBP formation control.