Presence Of Bromide Ions Research Articles

SERS Enhancement Factors Studies of Silver Nanoprism and Spherical Nanoparticle Colloids in The Presence of Bromide Ions

Surface-enhanced Raman Scattering (SERS) of R6G has been observed in two different silver colloids in the presence of KBr. It was found in spherical nanoparticles with an average diameter of 10 ± 2 nm and in their photoinduced conversion products with sodium light irradiation, silver nanoprisms, with an average edge length of 70 ± 30 nm and thickness of about 10 ± 2 nm. The SERS intensity of R6G (4.5 × 10−9 M) in the silver nanoprism colloid was 20× stronger than in the spherical nanoparticle colloid with the addition of KBr (0.05 M). Comparing the Raman signal intensity of water (55.5 M) and the SERS intensity of R6G (4.5 × 10−9 M) in the same spectrum showed that the analytical enhancement factors (AEF) in the truncated silver nanoprism colloid and spherical nanoparticle colloid are about 1.6 × 105 and 8 × 103, respectively. Monitoring the fluorescent intensity of R6G versus the concentration of R6G in two colloids in the absence of KBr displayed that the nanoprisms had better fluorescence quenching ability than the spherical nanoparticles by a factor of around 3. It implied that light irradiation not only converted the morphology of the spherical nanoparticles to nanoprisms, but also changed the surface character to have a higher affinity to the dye molecule. The surface enhancement factors (SEF) can also be calculated from AEF and the percentage of dye molecules adsorbed on the surface in the presence of KBr. The SEF of the nanoprism and spherical nanoparticle colloids are about 3.2 × 105 and 9 × 103, respectively. The UV−vis−NIR spectra and TEM images show that the spherical nanoparticles remained dispersed, while the nanoprisms were sculptured by the bromide ions after the addition of KBr.

Formation of polybrominated and polychlorinated ethylphenoxyethylphenols (PXEPEPs) during aqueous chlorination of 4-ethylphenol solutions in the presence of bromide ions

This investigation was undertaken to determine the effect of the bromide concentration on the formation of polyhalogenated ethylphenoxyethylphenols (PXEPEPs), including predioxins, during the chlorination of 4-ethylphenol in solution. An aqueous solution of 4-ethylphenol was treated with hypochlorite in the presence of various concentrations of bromide ions. The changes in the compositions of the halogenated products in hexane extracts of the chlorinated solution were analyzed by gas chromatograph (GC) and a flame ionization detector (FID) and mass spectrometry (MS). 4-Ethylphenol was shown to from several halogenated compounds, including PXEPEPs, as by-products of chlorination. The number of substituted chlorine or bromine atoms ranged from 0 to 4. The formation of bromine-substituted PXEPEPs was observed in the presence of 0.1 equivalents of bromide ions per mole of 4-ethylphenol. The number of substituted bromine atoms increased with the amount of co-existing bromide ions. In the presence of more than one equivalent of bromide ions per mole of 4-ethylphenol, the number of bromine atoms substituted in the PXEPEPs increased, whereas the number of chlorine atoms substituted in the PXEPEPs decreased. GC-MS total ion chromatograms confirmed the formation of polybrominated and polychlorinated predioxins during the aqueous chlorination of 4-ethylphenol in the presence of bromide ions. However, at ten equivalents of bromide ions per mole of 4-ethylphenol, no predioxins were observed in the hexane extract obtained from the aqueous 4-ethylphenol solution after being treated with chlorine. The formation of PXEPEPs during the chlorination of 4-ethylphenol in the presence of bromide ions was also influenced by the reaction pH.

Characterization of Polyhalogenated Phenoxyphenols (Br/Cl-Predioxins) Formed during Aqueous Chlorination of Phenol in the Presence of Bromide Ion

Aqueous phenol solution with bromide ion was treated with sodium hypochlorite at 20°C under various experimental conditions. Changes in the composition and the concentration of the halogenated products in water were determined by gas chromatographic (GC) and GC-mass spectrometric (GC/MS) analyses of diethyl ether extracts. Phenol was shown to produce a variety of halogenated compounds, including polybrominated/chlorinated phenoxyphenols (PXPPs, Br/Cl-predioxins), having three to five halogen atoms, as byproducts in the chlorine-treated water. Production of these PXPPs is dependent on the number of equivalent chlorine atoms per mole of compound and on the reaction pH. These findings suggest that the chlorinetreatment of water contaminated with phenol and bromide ion leads to the formation of Br/Cl-predioxins, which are precursors of the highly toxic halogenated dibenzo-p-dioxins.

A new induction period based reaction rate method for determination trace amounts of phenylhydrazine in water samples

A simple, selective, and sensitive kinetic spectrophotometric method is described for the determination of trace amounts of phenylhydrazine, which is based on its inhibition effect on the reaction between meta cresol purple (MCP) and periodate in the presence of bromide ions. The reaction was monitored spectrophotometrically by measuring the change in absorbance of MCP at 525 nm. The calibration graph was linear in the range of 1.0–10.0 μM. The detection limit (3 σ) was 0.020 μM. The relative standard deviations for 10 replicate measurements of 3.0, 5.0 and 7.0 μM of phenylhydrazine were 2.0%, 1.4%, and 0.90%, respectively. The potential interfering substances were studied in the presence of phenylhydrazine. The proposed method was applied to the analysis of water samples.

Formation and distribution of disinfection by-products during chlorine disinfection in the presence of bromide ion

The influences of contact time and pH value on the formation and distribution of four species of trihalomethanes and five species of haloacetic acids during chlorination in the presence of bromine were investigated. Results showed that the distribution of molar fraction of trihalomethanes varied with contact time due to the change of bromide ion concentration during chlorination. Most of the trihalomethanes comprising bromine-containing species and the favored products of the haloacetic acids were chlorine-containing species after 24 h of chlorination. The extent of bromine incorporation in trihalomethanes and haloacetic acids both decreased with time. The contact time also had influence on the formation rate of different species of haloacetic acids. The formation and distribution of trihalomethanes and haloacetic acids strongly depended on the chlorination pH value. All of the trihalomethanes species formation increased with the increase of pH value except the bromoform that had not been detected. The molar fraction of bromodichloromethane and dibromochloromethane containing bromine increased with pH value while chloroform without bromine decreased. Under the pH range studied in this experiment, the predominant haloacetic acids species were trichloroacetic acid and dichloroacetic acid which all decreased with the increase of pH value and the level of TCAA was higher than that of DCAA.

Carbohydrates as trihalomethanes precursors. Influence of pH and the presence of Cl − and Br − on trihalomethane formation potential

Upon chlorination carbohydrates can give trihalomethanes (THMs). In the present work, we have studied the influence of pH, chloride or bromide concentration on the formation of THMs from carbohydrates. We have observed that THMs are not formed at acidic pH, while basic pH values only increase slightly the THM content, although the consumption of chlorine increases up to 100% with respect to pH 8. The presence of chloride in ppm increases the THM formation from carbohydrates without influence of the chlorine consumption. In the same manner, the presence of bromide ions in ppb also increases remarkably the THMs formed upon chlorination of saccharides. Even more, we have observed that at bromide concentrations below 100 ppb, complete incorporation of bromide in THMs occurs. Overall, the results obtained show that saccharides widely present in natural waters can give rise to significant THM concentrations in the disinfection process by chlorine.

Reaction of 2′-deoxycytidine with peroxynitrite in the presence of ammonium bromide

Peroxynitrite, a reactive nitrogen species generated from nitric oxide and superoxide anion radical, is an endogenous potential risk factor for human cancer. When 2′-deoxycytidine was incubated with peroxynitrite at neutral pH and 37 °C, the reaction was greatly enhanced by the addition of ammonium bromide. Both ammonium ion and bromide ion were required to exert the enhancing effect. In addition to ammonium ion, methylamine and dimethylamine exerted the enhancing effect in the presence of bromide ion. Two major products were identified as 5-hydroxy-2′-deoxycytidine and 5-bromo-2′-deoxycytidine. Hypochlorite solution and bromine water reacted with 2′-deoxycytidine generating 5-hydroxy-2′-deoxycytidine and 5-bromo-2′-deoxycytidine in the presence of ammonium bromide with the yields similar to those of the reaction of peroxynitrite with ammonium bromide. Fenton reaction of 2′-deoxycytidine was suppressed by the addition of ammonium bromide. Nitrogen dioxide gas did not react with 2′-deoxycytidine in the presence or the absence of ammonium bromide. These results suggest that in the presence of ammonium ion or amines, bromide ion interacts with peroxynitrous acid, which is a protonated form of peroxynitrite, but not with hydroxyl radical or nitrogen dioxide generated by homolysis of peroxynitrous acid, to form hypobromous acid. In the presence of ammonium ion or amines, bromide ion may play a role in enhancing the genotoxic effects of peroxynitrite in humans.

Characterization of Polyhalogenated 4-Methylphenol Dimers (Br/Cl-Predioxins) Formed during Aqueous Chlorination of 4-Methylphenol Solution in the Presence of Bromide Ion

Aqueous 4-methylphenol solution with bromide ion was treated with hypochlorite at 20°C under various experimental conditions. Changes in the composition of the halogenated products in water were determined by gas chromatographic (GC) and GC-mass spectrometric (GC/MS) analyses of diethyl ether extracts. 4-Methylphenol was shown to produce a variety of halogenated compounds, including polybrominated/chlorinated phenoxyphenols (Br/Cl-predioxins), having one to four halogen atoms, as by-products in the chlorine-treated water. Production of these predioxins is dependent on the number of equivalent of chlorine atoms per mole of compound and on the reaction pH. These results suggest that the chlorine treatment of water contaminated with 4-methylphenol and bromide ion leads to the formation of Br/Cl-predioxins, which are precursor of the highly toxic halogenated dibenzo-p-dioxins.

Thermodynamic model of natural brines accounting for the presence of trace components: II. System Na+, K+, Mg2+ ‖ Cl−, Br−-H2O

This paper reports the calculations of parameters for the Pitzer equation and thermodynamic potentials of solid phases crystallizing in water-salt systems modeling chloride brines taking into account the presence of bromide ions in them. Solubility diagrams were calculated for corresponding ternary and quaternary systems containing chlorides and bromides of sodium, potassium, and magnesium at 25°C. The results of calculations are in adequate agreement with the available published experimental data on solubility and can be used to model salt crystallization during the concentration of seawater and brines.

Reactivity at the film/solution interface of ex situ prepared bismuth film electrodes: A scanning electrochemical microscopy (SECM) and atomic force microscopy (AFM) investigation

Bismuth film electrodes (BiFEs) prepared ex situ with and without complexing bromide ions in the modification solution were investigated using scanning electrochemical microscopy (SECM) and atomic force microscopy (AFM). A feedback mode of the SECM was employed to examine the conductivity and reactivity of a series of thin bismuth films deposited onto disk glassy carbon substrate electrodes (GCEs) of 3 mm in diameter. A platinum micro-electrode ( ϕ = 25 μm) was used as the SECM tip, and current against tip/substrate distance was recorded in solutions containing either Ru(NH 3) 6 3+ or Fe(CN) 6 4− species as redox mediators. With both redox mediators positive feedback approach curves were recorded, which indicated that the bismuth film deposition protocol associated with the addition of bromide ions in the modification solution did not compromise the conductivity of the bismuth film in comparison with that prepared without bromide. However, at the former Bi film a slight kinetic hindering was observed in recycling Ru(NH 3) 6 3+, suggesting a different surface potential. On the other hand, the approach curves recorded by using Fe(CN) 6 4− showed that both types of the aforementioned bismuth films exhibited local reactivity with the oxidised form of the redox mediator, and that bismuth film obtained with bromide ions exhibited slightly lower reactivity. The use of SECM in the scanning operation mode allowed us to ascertain that the bismuth deposits were uniformly distributed across the whole surface of the glassy carbon substrate electrode. Comparative AFM measurements corroborated the above findings and additionally revealed a denser growth of smaller bismuth crystals over the surface of the substrate electrode in the presence of bromide ions, while the crystals were bigger but sparser in the absence of bromide ions in the modification solution.

A Novel Route to a Bromo‐Cyano‐Substituted Azulene and Its Exploitation in the Construction of an Acetylenic Scaffold

AbstractA novel route to functionalized azulenes is devised from a dihydroazulene precursor. Thus, bromination of 1,1‐dicyano‐2‐phenyl‐1,8a‐dihydroazulene followed by heating in the presence of bromide ions provides an efficient way to generate 3‐bromo‐1‐cyano‐2‐phenylazulene. Formation of this somewhat unexpected product was confirmed by X‐ray crystallographic analysis. It undergoes a palladium‐catalyzed cross‐coupling reaction with trimethylsilylacetylene, affording a new azulene building block for acetylenic scaffolding. Oxidative homo‐coupling hereof provides an azulene dimer, for which the optical and electrochemical properties are compared to the other azulenes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Diffusion-controlled size-selective chloride ion sensing in the presence of bromide ion using a thin, nanoporous, plasma-polymerized coating on an Ag/AgCl electrode

We have developed a diffusion-controlled size-selective method for sensing chloride ion in the presence of bromide ion, based on a thin, nanoporous, plasma-polymerized coating of hexamethyldisiloxane on an Ag/AgCl electrode. Sub-nanometer-sized pores responsible for a highly cross-linked polymer network in the plasma-polymerized coating allowed diffusion-controlled permeation of chloride ion while blocking the larger bromide ion. An electrode coating of thickness greater than 70 nm enabled chloride detection in the concentration range 1–10 mM in the presence of 0.63 mM bromide ion. Advantages of this approach are: (1) simple design compared with ionophore-based strategies and (2) compatibility with microfabrication and mass production processes.

Kinetics of reactions between chlorine or bromine and the herbicides diuron and isoproturon

AbstractThe chemical oxidation of two herbicide derivatives of the phenylurea group—diuron and isoproturon—has been carried out by means of chlorine, in the absence and in the presence of bromide ion. Apparent second‐order rate constants for the reactions between chlorine and the herbicides were determined to be below 0.45 L mol−1 s−1. Hypobromous acid reacts faster with the investigated herbicides, especially with isoproturon (kapp = 24.8 L mol−1 s−1 at pH 7). While pH exerts a negative effect on the bromination rate, the maximum chlorination rate was found to be at circumneutral pH. In a second stage, the oxidation of each compound was conducted in different natural waters, in order to simulate the processes which take place in water purification plants. Again, chlorine was used as an oxidant, and bromide ion was added in some experiments with the aim of producing the more reactive HOBr oxidant. The herbicide oxidation rate was inversely proportional to the organic matter content of the natural water. However, the formation of trihalomethanes (THMs) was directly proportional to the organic matter content and constitutes a limitation for the application of chlorine during drinking water treatment. Finally, the evolution of herbicide concentration was modeled and predicted by applying a kinetics approach based on the rate constants for the reactions between the herbicides and the active oxidants. Copyright © 2007 Society of Chemical Industry

The Impact of Ammonia Photo-Oxidation Under UV Light from Low Pressure Mercury Lamps on Bromate Decay in Water

This research examines the influence of ammonia photo-oxidation on the reduction of the water contaminant, bromate (BrO3-) as a potential removal strategy. It has long been recognized that aqueous ammonia (NH3) has the potential to accelerate the photodecomposition of bromate. This phenomenon has never been studied in dilute solutions whereby its impact during water treatment with UV low-pressure lamps may be used advantageously. It is hypothesized that the accelerated rate of BrO3- photodecomposition in the presence of NH3 is attributed to the generation of an additional supply of electrons as ammonia photo-oxidation occurs. The findings revealed that the rate of bromate photo-decay is increased in the presence of ammonia even in dilute ammonia and BrO3- solutions and the reaction is further accelerated in basic solutions and solutions containing chloride ions. Nitrate is the final stable reaction product formed with prolonged irradiation, followed by a depression of pH. Hypobromous acid was undetected at these concentrations. It was also found that ammonia oxidation occurred in the presence of bromide ions even in acidic solution. The hypothesis that electrons are made available for electron scavengers when ammonia oxidation occurs was verified using sulphur hexafluoride as an electron scavenger.

Effect of bromide and chloride ions for the dissolution of colloidal gold

Gold organosol has been synthesized in toluene employing two-phase (water–toluene) extraction of AuCl 4 − followed by its reduction with sodium borohydride in presence of cationic surfactants with variable counter ions. The influence of the counterions of the phase transfer reagent and stabilizing ligand on the photochemical stability of the gold colloids in toluene has been investigated. The counterions of the surfactants, i.e. bromide or chloride ions at times generate the corresponding radicals under UV-irradiation, which oxidize the gold clusters. It is explored that photodiscoloration process is faster for bromide system as compared to chloride. The slower discoloration in presence of only chloride system has been explained in the light of electron affinity of chlorine and stability of chlorocomplex. The photodiscoloration is facilitated in chloroform. It has further been observed that HCl oxidizes the gold nanoparticles under ambient condition. Finally the thermal activation facilitates the oxidation process in presence of bromide ions.

The synergistic inhibition of the cold rolled steel Corrosion in 0.5 M sulfuric acid by the mixture of OP and bromide ion

The synergistic inhibitive effect of the mixture of OP and NaBr on the corrosion of cold rolled steel in 0.5 M sulfuric acid has been investigated using weight loss and polarization method. The results reveal that corrosion of cold rolled steel has been efficiently inhibited by OP in the presence of NaBr in sulfuric acid, and inhibition efficiency increases with increasing concentration of OP at a constant temperature. A synergistic effect has been observed for OP with NaBr at all investigated temperatures (except 30 °C). The polarization curves show that the mixture of OP and NaBr is a cathodic inhibitor. The experimental results suggest that the presence of bromide ion in the solution stabilizes the adsorption of OP molecules on the metal surface and improves the inhibition efficiency of OP. Langmuir adsorption isotherm equation is obeyed at all the temperatures studied. The results obtained from weight loss and polarization method are in good agreement. The present study is important for the practical use of surfactant as corrosion inhibitor for steel in acidic media.

Accurate‐mass identification of chlorinated and brominated products of 4‐nonylphenol, nonylphenol dimers, and other endocrine disrupters

LC/ToF-MS was used to identify new chlorination and bromination products of 4-nonylphenol (4-NP), such as 4-NPBr2, 4-NPBrCl, 4-NP dimer (2 isomers), 4-NPCl dimer (2 isomers), 4-NPBr dimer, and a series of methoxy bromo and chloro 4-NPs from a laboratory study of nonylphenol chlorination. The identification procedure used the exact mass, exact mass of the isotope cluster, and their relative intensities, at an average mass accuracy of approximately 1 ppm. The products were produced by a simulated study of industrial cleaning procedures where 4-NP, nonylphenol ethoxylate (NPEO-1 and 2), and nonylphenol carboxylate (NPEC-1) were in contact with sodium hypochlorite solutions (with and without bromide) of various strengths (possible environmental scenarios) at neutral pH. The formation of the products was measured as a function of chlorine concentration, and it was found that 4-NP was the most reactive, producing 4-NPCl, 4-NPCl2, 4-NP (dimers), and the 4-NPCl (dimers). In the presence of bromide ions, a mixture results with products of 4-NPBr2, 4-NPCl, 4-NPCl2, 4-NPBrCl, 4-NPBr, and a 4-NPBr dimer. Less reactive to halogenation was NPEO, which formed only the monochloro and monobromo products, and the least reactive was NPEC. A simple stereochemical model is used to explain halogenation reactivity for the family of 4-NPs and NPEOs at neutral pH. The presence of halogenated 4-NP dimers (bromo and chloro diphenyl ethers) is discussed as a possible source of new endocrine disrupters.

Formation of bromo-substituted triclosan during chlorination by chlorine in the presence of trace levels of bromide

The side reactions of triclosan (2,4,4′-trichloro-2′-hydroxydiphenyl ether, TC) and chlorine in the presence of sodium chloride were investigated. In the absence of sodium chloride, three chloro-derivatives of TC, 2′,3,4,4′-tetrachloro-2-hydroxydiphenyl ether (3-Cl-TC), 2′,4,4′,5-tetrachloro-2-hydroxydiphenyl ether (5-Cl-TC), and 2′,3,4,4′,5-pentachloro-2-hydroxydiphenyl ether (3,5-Cl 2-TC) were formed, whereas in the presence of sodium chloride, 3-bromo-2′,4,4′-trichloro-2-hydroxydiphenyl ether (3-Br-TC), 5-bromo-2′,4,4′-trichloro-2-hydroxydiphenyl ether (5-Br-TC), (3 or 5)-bromo-2′,4,4′,(5 or 3)-chloro-2-hydroxydiphenyl ether ((3,5)-(BrCl)-TC), and 3,5-dibromo-2′,4,4′-trichloro-2-hydroxydiphenyl ether (3,5-Br 2-TC) were additionally formed. Radiochemical neutron activation analysis indicated that 1 g of commercially available sodium chloride contained 73 μg of bromide and the bromide ion was determined to be the source of the side reactions. The rate of decrease of TC due to reaction with chlorine was greatly accelerated by the presence of bromide ion in the system: the rate with only 1×10 −5 M bromide ion was three times the rate in the absence of bromide.

The synergistic inhibition between hexadecyl trimethyl ammonium bromide (HTAB) and NaBr for the corrosion of cold rolled steel in 0.5 M sulfuric acid

The synergistic effect of the mixture of hexadecyl trimethyl ammonium bromide (HTAB) and various concentrations of NaBr on the corrosion of cold rolled steel in 0.5 M sulfuric acid has been investigated using weight loss method and polarization method. The results reveal that the corrosion of cold rolled steel has been efficiently inhibited by HTAB in the presence of NaBr in sulfuric acid, and inhibition efficiency increases with increasing concentration of NaBr at the same temperature. A synergistic effect has been observed for HTAB with NaBr at every experimental temperature. The polarization curves show that the complex of HTAB and NaBr is a mixed-type inhibitor. The experimental results suggest that the presence of bromide ion in the solution stabilizes the adsorption of HTAB molecules on the metal surface and improves the inhibition efficiency of HTAB. Langmuir adsorption isotherm equation was obeyed at all the temperatures studied. The synergism parameters have been calculated and discussed. The results obtained from weight loss method and polarization method are in good agreement.

Preparation and Formation Mechanism of Mesoporous Titania Particles Having Crystalline Wall

Mesoporous titania particles having anatase-type crystalline wall were prepared using a low-temperature crystallization technique. Crystalline mesoporous titania was obtained through the sol−gel process of titanium oxysulfate sulfuric acid hydrate (TiOSO4·xH2SO4·xH2O) at 333 K in the presence of cetyltrimethylammonium bromide (C16TAB), a cationic surfactant. The mesoporous titania with hexagonal structure was formed according to the following mechanism. Nuclei of ultrafine titanium hydroxide oxide (TiO(OH)2) were formed from TiOSO4 on the periphery of the surface of cationic C16TAB micelles at the primary stage of sol−gel reaction. Then, heat treatment at 333 K induced the transformation of the particle wall from TiO(OH)2 to anatase nanocrystal, which resulted in the formation of mesoporous titania with a crystalline wall. Moreover, the presence of bromide ion (Br-), the counterion of C16TAB, was shown to suppress the collapse of mesostructure by retarding the transition from anatase to rutile.