Presence Of Bromide Ions Research Articles

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.

Micellization of CTAB in the presence of silicate anions and the exchange between bromide and silicate at the micelle surface: A step to understand the formation of mesoporous molecular sieves at extremely low surfactant and silicate concentrations

The effect of silicate anions, from dilute aqueous tetramethylammonium silicate (TMASi) solutions (0–3.0 mmol L −1 in silicon), on the formation of hexadecyltrimethylammonium bromide (CTAB) micelles was investigated by means of a series of simple conductivity experiments. These two compounds are used in the preparation of mesoporous silicate molecular sieves. An increase in the monovalent silicate anion concentration decreases the critical micelle concentration (cmc) of CTAB, as might be expected from the decreased repulsive forces between the polar heads of the surfactant molecules. However, the decrease in cmc values is less pronounced than that observed in the presence of bromide ions, suggesting that Br − binds more strongly than Si(OH) 3O − at the micelle surface. Through the ion-exchange formalism, a selectivity coefficient for Si(OH) 3O −/Br − exchange of 0.30 ± 0.03 was estimated from the conductivity data. This value compares well with that of 0.4 ± 0.1 also determined in this work by the pyrene fluorescence quenching method. The experimental results were used to rationalize the formation of a surfactant supramolecular-templated mesoporous molecular sieve at extremely low surfactant (0.63 mmol L −1) and silicate (4.00 mmol L −1) concentrations.

Underpotential deposition of Tl on Ag in the presence of bromide ions – Estimation of specific capacitance for design of electrochemical supercapacitors

The analysis of underpotential deposition (UPD)-based systems for the development of electrochemical supercapacitors is investigated employing the UPD of Tl on Ag in the presence of bromide ions, as an illustrative example. The specific capacitance is estimated with the help of multi-cycle voltammograms, galvanostatic charge/discharge experiments and impedance spectroscopy. The equivalent circuit for the system is constructed and the parameters are deduced from the simulation. The deduced magnitude of ∼102 F g−1 in conjunction with the satisfactory number of charge/discharge cycles obtained from galvanostatic experiments indicate the feasibility of these systems as supercapacitors.

TLC Fractionation and Characterization of Ames Mutagenic Substances in Chlorine-treated 4-methylphenol Solution in the Presence of Bromide Ion

The diethyl ether extracts from aqueous 4-methylphenol solutions in the presence of bromide ion after treatment with chlorine were mutagenic to the Ames salmonella test strain TA100 in the absence of rat liver homogenate. Gas chromatography/mass spectrometry (GC/MS) showed the occurrence of halogenated products in the extracts: bromo-4-methylphenols, bromo-4-methylquinones and brominated 4-methylphenol dimers. The diethyl ether extracts were fractionated into several fractions by polyamide thin-layer chromatography (TLC) . The fractionated components were examined for mutagenicity by means of Ames assays, and were identified by GC/MS. TLC fraction of the extracts revealed that two components present in the extracts are mutagenic. GC/MS analysis indicated the presence of 2, 6-dibromo-4-hydroxy-4-methylcyclohexa-2, 5-lien-1-one (2, 6-dibromotolquinol) as the major mutagen and brominated 4-methylphenol dimers as minor mutagenic compounds in the chlorinated 4-methylphenol solutions containing bromide ion. Production of 2, 6-dibromotolquinol in water was found to be dependent on the equivalents of chlorine per mole of compound and the reaction pH.

Photodegradation of Dimethyl Sulfide (DMS) in Natural Waters: Laboratory Assessment of the Nitrate-Photolysis-Induced DMS Oxidation

The interaction of sunlight and dissolved chromophoric matter produces reactive chemical species that are significant in the removal of dimethyl sulfide (DMS) in the surface ocean. Using artificial solar radiation, we examined the role of several inorganic components of seawater on the kinetics of NO3- -photolysis-induced DMS removal in aqueous solution. This study strongly suggests that NO3- photolysis products react significantly with DMS in aqueous solution possibly via an electrophilic attack on the electron-rich sulfur atom. This supports previous field observations that indicate that NO3- photolysis has a substantial control on DMS photochemistry in nutrient-rich waters. A key finding of this research is that the oxidation rate of DMS induced by NO3- photolysis is dramatically enhanced in the presence of bromide ion. Moreover, our results suggest that bicarbonate/carbonate ions are involved in free radical production/scavenging processes important for DMS photochemistry. These reactions are pH dependent. We propose that DMS removal by some selective free radicals derived from bromide and bicarbonate/carbonate ion oxidation is a potentially important and previously unrecognized pathway for DMS photodegradation in marine waters.

Retention profile, kinetics and sequential determination of selenium(IV) and (VI) employing 4,4′-dichlorodithizone immobilized-polyurethane foams

Polyurethane foams (PUFs) loaded with the chromogenic reagent 4,4′-dichlorodithizone (Cl 2H 2D Z ) have been investigated for the quantitative retention, chemical speciation and sequential determination of traces of inorganic selenium(IV) and (VI) from aqueous media containing bromide ions. The retention profile of selenium(IV) onto the reagent loaded foam followed a dual-mode sorption mechanism involving both absorption related to “solvent extraction” and an added component for surface adsorption. The kinetics and thermodynamic characteristics of selenium(IV) uptake onto PUFs have been studied. The kinetics of selenium(IV) sorption onto PUFs was found fast, reached equilibrium in few minutes and followed a first-order rate constant in presence of bromide ions in the extraction media. The thermodynamic parameters, Δ H, Δ S and Δ G, indicated the exothermic and spontaneous nature of the sorption process. The sorption and the recovery percentages of inorganic selenium(IV) from fresh water by the proposed loaded foam columns were achieved quantitatively. The height equivalent to theoretical plate (HETP), the number of layers ( N), breakthrough capacity and the critical capacity for selenium(IV) uptake onto Cl 2H 2D Z loaded foams columns were found to be 1.3, 103, 8.6 and 7.2 mg/g, respectively. The method was successfully applied for the chemical speciation and sequential determination of inorganic selenium(IV) and/or (VI) species spiked to fresh and industrial wastewaters.

On-line electrochemically controlled solid-phase extraction interfaced to electrospray and inductively coupled plasma mass spectrometry

Electrochemically controlled solid-phase extractions of anions were interfaced on-line to electrospray mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS), using polypyrrole coated electrodes and a thin-layer electrochemical (EC) flow cell. The results indicate that electrochemically controlled solid-phase extraction (EC-SPE) can be used as a versatile potential controlled sample preparation technique for a range of anions and that the properties of the polypyrrole coatings can be modified by altering the electrodeposition conditions. In the present study, the influence of interfering anions (i.e., fluoride and sulfate), and the anion used during the electropolymerisation, on the bromide extraction recovery was investigated for EC-SPE interfaced to ICP-MS. The results of these experiments show that the interference due to the presence of similar concentrations of sulfate can be reduced when using a polypyrrole coating electropolymerised in the presence of bromide ions. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were also used to study the morphology of the coatings, as well as the variations in the film thickness within the coatings. The effect of different desorption techniques on the bromide preconcentration factor in the ICP-MS on-line flow system was also examined. Stopped-flow desorption was found to give rise to significantly increased preconcentration factors in comparison with desorptions in flowing solutions. While the desorption efficiency depends on the type of desorption electrolyte (the electrolyte in which the desorption takes place), due to the competing influx of cations, the influence of the pH on the switching charge of the polypyrrole coating was found to be small, at constant ionic strength. To study the applicability of the EC-SPE technique with respect to real samples, investigations were also made with tap water samples spiked with different bromide concentrations. The results of these experiments, which were carried out using a modified thin-layer EC flow cell allowing in situ polymerisation of polypyrrole yielding a polymer plug covering the cross section of the channel, demonstrate that 3 microM concentrations of bromide could be detected in the tap water sample. This demonstrates that the extraction technique allows extractions of low concentrations of ions in the presence of significantly higher concentrations of other similar ions. The fact that the extraction and desorption steps are electrochemically controlled makes EC-SPE particularly well suited for inclusion in miniaturised lab-on-a-chip systems.

Dioxycarbene complexes derived from reactions of tetrairidium carbonyl clusters with oxirane: X-ray crystal structures of and

Some novel cyclic-dioxycarbene derivatives of general formula ▪ (L = P t Bu 3, n = 1 ( 2), PPh 3: n = 1 ( 3), 2 ( 4)) and ▪ (L–L = PPh 2PCH 2PPh 2, n = 1 ( 5), norbornadiene, n = 1 ( 6) and 1,5-cyclooctadiene, n = 1 ( 7), 2 ( 8)) have been obtained by reaction of oxirane ▪ with the tetrairidium cluster derivatives [Ir 4(CO) 11(L)] and [Ir 4(CO) 10(L–L)] in the presence of bromide ion as catalyst. Elemental analysis, IR, and NMR spectra ( 1H, 31P{ 1H}, 13C{ 1H}), and for compounds 2 and 5 also the X-ray crystal structures, were carried out for their characterisation. All the derivatives have 3 edge-bridging CO’s on the basal face of the iridium tetrahedron with non-CO ligands in axial and/or radial positions. For the mixed-ligand cluster compounds, two or three stereoisomers were observed in solution by 1H, 31P and 13C NMR spectroscopies at low temperature. All these clusters are fluxional at room temperature.

Kinetics of the formation and decomposition of chlorination by-products in surface waters

The presence of organic chlorination by-products (CBPs) in drinking waters has caused great public health concerns. One of the most important factors affecting their formation during the disinfection procedure is reaction time. The kinetics of the formation of CBPs can be different for the different categories or species of compounds, depending also on the chlorine dose, organic matter content and the presence of bromide ion. Decomposition of some CBPs also occurs due to hydrolysis or reactions with residual chlorine. Therefore, the final concentrations of individual species of CBPs reaching the consumers’ tap may deviate from the predictions. The aim of the present investigation was the determination of formation or decomposition kinetics of CBPs during chlorination of natural waters. 24 CBPs were studied in chlorinated water from three different sources. Different speciation of CBPs and different formation rates were observed for different water quality regarding bromide ion presence and organic matter content. Decomposition of some CBPs occurred, specifically haloketones, BCA and DBA, after an initial formation step. The percentages of incorporation of chlorine and organic matter into CBPs indicated that other halogenated compounds not identified during the present study have also been formed during chlorination. The importance of chlorine dose for the formation of CBPs and for the incorporation of organic matter was highlighted. Moreover, linear correlations were observed between the concentrations of chloroform-MCA, chloroform-DCA and chloroform-TCA as well as between total THMs and total HAAs, in all waters studied.

Vanadium haloperoxidase-catalyzed bromination and cyclization of terpenes.

Marine red algae (Rhodophyta) are a rich source of bioactive halogenated natural products, including cyclic terpenes. The biogenesis of certain cyclic halogenated marine natural products is thought to involve marine haloperoxidase enzymes. Evidence is presented that vanadium bromoperoxidase (V-BrPO) isolated and cloned from marine red algae that produce halogenated compounds (e.g., Plocamium cartilagineum, Laurencia pacifica, Corallina officinalis) can catalyze the bromination and cyclization of terpenes and terpene analogues. The V-BrPO-catalyzed reaction with the monoterpene nerol in the presence of bromide ion and hydrogen peroxide produces a monobromo eight-membered cyclic ether similar to laurencin, a brominated C15 acetogenin, from Laurencia glandulifera, along with noncyclic bromohydrin, epoxide, and dibromoproducts; however, reaction of aqueous bromine with nerol produced only noncyclic bromohydrin, epoxide, and dibromoproducts. The V-BrPO-catalyzed reaction with geraniol in the presence of bromide ion and hydrogen peroxide produces two singly brominated six-membered cyclic products, analogous to the ring structures of alpha and beta snyderols, brominated sesquiterpenes from Laurencia, spp., along with noncyclic bromohydrin, epoxide, and dibromoproducts; again, reaction of geraniol with aqueous bromine produces only noncyclic bromohydrin, epoxide, and dibromoproducts. Thus, V-BrPO can direct the electrophilic bromination and cyclization of terpenes.

Solvolysis of chiral cyclohexylidenemethyl triflate. Evidence against a primary vinyl cation intermediate

AbstractSolvolysis of (R)‐4‐methylcyclohexylidenemethyl triflate (6) was examined at 140 °C in various aqueous methanol and some other alcoholic solvents. The main product was (R)‐4‐methylcycloheptanone that maintains the stereochemical purity of 6, with accompanying 4‐methylcyclohexanecarbaldehyde. In the presence of bromide ion, the bromide substitution product was also obtained, mostly with inversion of configuration. It is concluded that the solvolysis does not involve the formation of the primary vinyl cation but proceeds via σ‐bond participation to form the rearranged cycloheptenyl cation as an intermediate. Copyright © 2002 John Wiley & Sons, Ltd.

Sensitive detection and quantitation of mouse eosinophils in tissues using an enzymatic eosinophil peroxidase assay: its use to rapidly measure pulmonary eosinophilia during experimental respiratory syncytial virus infection of mice

Eosinophils are granular proinflammatory leukocytes implicated in the pathogenesis of several inflammatory processes including allergy, asthma, and in the development of enhanced disease during respiratory syncytial virus (RSV) infection. Here, we adapted a colorimetric assay to measure eosinophil peroxidase (EPO) activity in inflamed mouse lung tissue in order to quantitate pulmonary eosinophilia during experimental RSV infection. Using the substrate o-phenylenediamine dihydrochloride (OPD) in the presence of bromide ions, we show that this assay is able to quantitate limiting numbers of eosinophils in lung tissue homogenates even in the presence of large numbers of infiltrating neutrophils and macrophages. The ability of the EPO assay to selectively quantitate eosinophils in a complex tissue inflammatory infiltrate demonstrates the usefulness of this enzymatic assay as a rapid and sensitive method to quantitate the influx of eosinophils into inflamed mouse tissue such as the lung during experimental RSV infection without reliance on morphologic criteria to identify murine eosinophils in tissues or bronchial lavage fluid.

Photochemical behavior of sitafloxacin, fluoroquinolone antibiotic, in an aqueous solution.

Sitafloxacin (STFX) hydrate, an antimicrobial agent, is photo-labile in aqueous solutions. The photodegradation rates (k) in neutral solutions were higher than those observed in acidic and alkaline solutions and maximum at the maximum absorption wavelength of STFX. The structures of photodegradation products were elucidated as 7-[7-amino-5-azaspiro[2.4]heptan-5-yl]-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid and 1-(1-amino-2-[16-fluoro-1-(2-fluoro-1-cyclopropyl)-1,4-dihydro-4-oxo-3-quinolin-7-yl]-amino]ethyl)cyclopropanecarbaldehyde. This implies that dechlorination is the key step in the photodegradation of STFX. The effect of halide ions on the photodegradation of STFX was estimated by observing the increments in the photostability of STFX with the addition of chloride ions. In contrast, in the presence of bromide ions, instead of increased photostability of the STFX rate, a new photodegradation product in the presence of bromide ion was observed. The structure of this new photodegradation product was an 8-bromo form of STFX, which was substituted for chlorine at the 8-position, so the dissociation of C-Cl bond at the 8-position of STFX was the rate-limiting step in the initial process of the photodegradation. STFX generated .C (carbon centered radical) and .OH (hydroxyl radical) in the process of photodegradation in a pH 4.0 buffer. On the contrary, STFX did not generate C in the presence of chloride ion in a pH 4.0 buffer. The .C was generated and then degraded into the above degradation products by photoirradiation in the absence of chloride ion, but the .C immediately reacted with chloride when it was present. As a result, the C-Cl bond was recovered leading to a possible increase in the apparent photostability.

Formation of organic by-products during chlorination of natural waters

Natural water from six sources in Mytilene, Greece, was chlorinated in order to identify and quantify some of the organic by-products formed. The compounds examined were trihalomethanes, haloacetic acids, haloacetonitriles, haloketones, chloral hydrate and chloropicrin. The factors tested were time and chlorine dose. The presence of bromide ion in some of the waters studied resulted in significant changes in the by-product speciation, with enhanced brominated species formation. In addition, UV absorbance, measured at three wavelengths, led to correlation of organic matter content with the concentrations of by-products produced. The species formed, varying among different water sources, increased with increasing chlorine dose. Most of the species also increased with increasing contact time, although there were some exceptions due to hydrolysis reactions.

Estimation of thallium(III) alone and in mixture with thallium(I) titrimetrically

The reduction of thallium(III) with glyoxal is catalyzed by light especially in the presence of bromide ions. The reaction is also catalyzed at higher temperature. Based on this reaction, a convenient method is described for the estimation of thallium(III) alone and in mixtures with thallium(I).

Role of halogen(I) cation-transfer mechanisms in water chlorination in the presence of bromide ion.

Bromide ion is rapidly converted to HOBr via BrCl by reaction with HOCl. The subsequent slow reactions of (HOCl, OCl-)/(HOBr, OBr-) mixtures are monitored directly by multiwavelength UV-vis absorbance methods and simultaneously by ion chromatographic measurement of ClO2-, ClO3-, and BrO3- (p[H+] 5.6-7.6). A first-order loss of HOCl is observed which is catalyzed by trace concentrations of Br- and BrCl. Chlorite ion forms first and is subsequently oxidized to ClO3-. The loss of HOBr is slower and is second-order in HOBr, so that BrO3- formation takes longer than ClO3- formation. Under the conditions of this work, the relative yield of BrO3- increases with increase in pH. The decomposition of HOCI by bromide proceeds primarily by a series of halogen(I) cation-transfer reactions with subsequent halide release. The presence of HOCI increases the BrO3- yield three-fold from HOBr decay alone.

Simultaneous Determination of Halogenated Derivatives of Alkylphenol Ethoxylates and Their Metabolites in Sludges, River Sediments, and Surface, Drinking, and Wastewaters by Liquid Chromatography−Mass Spectrometry

A quantitative solid-phase extraction-liquid chromatography/mass spectrometry (SPE-LC/MS) method is described for the simultaneous analysis of halogenated byproducts of alkylphenolic compounds and their degradation products formed during chlorine disinfection in the presence of bromide ions. Compounds analyzed include brominated and chlorinated nonylphenol ethoxylates (XN-PEOs); octylphenol ethoxylates (XOPEOs); nonylphenols (XNP); nonylphenoxycarboxylates (XNPECs) and their precursors nonionic surfactants, alkylphenol ethoxylates (APEOs); and their metabolites formed during sewage treatment, alkylphenoxycarboxylates (APECs) and alkylphenols (APs). Target compounds were concentrated from water samples using a C18 SPE procedure. Extracts were analyzed using reversed phase LC/MS. The performances of both atmospheric pressure chemical ionization (APCI) and electrospray (ESI) interfaces were compared. ESI offered better sensitivity and specificity for a higher range of oligomers. Detection limits (LODs) for water samples were from 20 to 100 ng/L; and for sediment samples, from 2 to 10 microg/kg. Slightly higher LODs were obtained for sludge samples (5-25 microg/kg). Halogenated byproducts were found in sludge from Barcelona drinking water treatment plant in concentrations of 220 microg/kg for BrNP, 430 microg/kg for BrNPEOs (nEO = 1 - 2), and 1600 microg/kg for BrNPEOs (nEO = 3 - 15). The concentration of ClNPEOs was estimated to be in the order of 660 microg/kg (assuming the same response as BrNPEOs). Halogenated OPEOs were also identified, and their concentration was approximately 50 times lower than the concentration of NPEOs analogues. To our knowledge, this is the first method described that allows simultaneous determination of alkyphenol ethoxylates and halogenated derivatives, including degradation products.

Effect of bromide ions on genotoxicity of halogenated by-products from chlorination of humic acid in water

Genotoxicity of halogenated by-products obtained by chlorination of humic acid in water was evaluated in the presence of bromide ions (Br −). After the halogenated humic acid solution was made to flow through CSP800 cartridge, absorbed substances were eluted with dimethyl sulfoxide or acetone, and subjected to mutagenicity assays and to analysis of trihalomethanes (THMs). Mutagenic activity was measured by Ames tests using S. typhimurium TA100 strain without metabolic activation, and by the frequencies of micronuclei formation using cultured Chinese hamster lung cells (CHL/IU) in vitro. A powerful effect of bromide ions in chlorinated humic acid solutions was observed on the reverse mutation and micronuclei formations. The formations of total THMs and more brominated THMs were also enhanced in the presence of bromide ions. The ratio of [Br −/Cl −] regulated the composition and concentrations of THMs intensely, and the rate of substitution of Br − was greater than that of chloride ions (Cl −). The increments of the mutagenicity and total THMs formed in chlorinated solutions were observed in parallel with the concentration of Br − or Cl −. From the observations, it was concluded that the increasing mutagenicity might be caused by the increasing chlorinated and/or brominated by-products.

Characteristics of Municipal Wastewater Treatment Using Non - Thermal Plasma in the Presence of Bromide Ion

Abstract – This study was carried out to find the possibility of the new physical and chemical municipal wastewater treatment such as denitrification of ammonia and degradation of organics by ionized gas in presence of bromide ion as a bench-scale reactor. Removal efficiencies of organics and SS were not related to bromide ion concentration but Removal efficiencies of organics and SS increased as the rate of influent gas flow were higher. With higher bromide ion concentration and lower influent gas flow rate, the higher removal efficiency of total nitrogen was obtained. Municipal wastewater treatment using non-thenna1 plasma in the presence of bromide ion could be considered as an effective method for the removal of organic matter and ammonia nitrogen.

By-products formation during degradation of isoproturon in aqueous solution. II: chlorination

After a previous study in which the considered oxidant was ozone (Part I), a laboratory investigation has been carried out to study the degradation of the herbicide isoproturon during its reaction with another oxidant, i.e. chlorine, in aqueous solution (Part II; this paper). The specific aim was to identify the by-products formed. The effects of pH and the presence of bromide ions were studied. Reactions have been carried out at room temperature, in phosphate buffered aqueous solutions, at four pHs (6, 7, 8 and 9). By-products identification was first performed using relatively high initial reagent concentrations which were analytically convenient ([isoproturon]=40 mg/l, [HClO+ClO −]=160 mg Cl/l, [Br −]=80 mg/l). In follow-up studies, the by-products identified during this preliminary step were searched for when using concentration values closer to those actually encountered at real water treatment plants ([isoproturon]=0.4 and 0.004 mg/l, [HClO+ClO −]=1.6 mg Cl/l, [Br −]=0.8 and 0.008 mg/l). Under all of the studied conditions, the results showed that isoproturon is completely degraded and that it decays much faster in the presence of bromide. The pH has a negligible influence when bromide ions are absent. On the contrary, if bromide ions are present, the isoproturon decay is slower at higher pH values. High-performance liquid chromatography-mass spectrometry (HPLC-MS) analyses have led to the identification of several by-products as a result of simultaneous oxidation and substitution reactions, both occurring on the aromatic ring of the herbicide. However, the more abundant by-products are those resulting from the oxidation of the isoproturon aromatic ring. As far as halogenated by-products are concerned, the higher the bromide ion concentration the higher the ratio of brominated to chlorinated by-products. On the basis of the analytical results, a pathway for isoproturon degradation under the studied conditions is proposed.