Presence Of Bromide Research Articles

Granular Activated Carbon Treatment May Result in Higher Predicted Genotoxicity in the Presence of Bromide.

Certain unregulated disinfection byproducts (DBPs) are more of a health concern than regulated DBPs. Brominated species are typically more cytotoxic and genotoxic than their chlorinated analogs. The impact of granular activated carbon (GAC) on controlling the formation of regulated and selected unregulated DBPs following chlorine disinfection was evaluated. The predicted cyto- and genotoxicity of DBPs was calculated using published potencies based on the comet assay for Chinese hamster ovary cells (assesses the level of DNA strand breaks). Additionally, genotoxicity was measured using the SOS-Chromotest (detects DNA-damaging agents). The class sum concentrations of trihalomethanes, haloacetic acids, and unregulated DBPs, and the SOS genotoxicity followed the breakthrough of dissolved organic carbon (DOC), however the formation of brominated species did not. The bromide/DOC ratio was higher than the influent through much of the breakthrough curve (GAC does not remove bromide), which resulted in elevated brominated DBP concentrations in the effluent. Based on the potency of the haloacetonitriles and halonitromethanes, these nitrogen-containing DBPs were the driving agents of the predicted genotoxicity. GAC treatment of drinking or reclaimed waters with appreciable levels of bromide and dissolved organic nitrogen may not control the formation of unregulated DBPs with higher genotoxicity potencies.

Click 1,4-regioselective synthesis, characterization, and antimicrobial screening of novel 1,2,3-triazoles tethering fluorinated 1,2,4-triazole and lipophilic side chain

Base-catalyzed alkylation of 5-(4-fluorophenyl)-2,4-dihydro-1,2,4-triazole-3-thione (3) with one or two equivalents of propargyl bromide in presence of triethylamine as catalyst selectively produced the thiopropargylated 1,2,4-triazole 7 in 90 % yield. Under the same reaction conditions, 4-ethyl-5-(4-fluorophenyl)-3-(prop-2-yn-1-ylthio)-1,2,4-triazole (8) was produced. Conversely, when the propargylation was carried out in presence of sodium bicarbonate, a mixture of S,N 4- (24) and S,N 2-bis(propargylated) triazoles (25) was obtained in 85 % overall yield. The click 1,3-dipolar cycloaddition reaction of the mono- (7, 8) and/or bis(propargylated)-1,2,4-triazoles (24) with a variety of long-chain alkyl azides, conducted in t-BuOH:H2O (10:1) in presence of sodium ascorbate and copper(II) sulfate at room temperature, afforded the regioselective 1,4-disubstituted mono- (14–18) and bis(1,2,3-triazole) derivatives (26–30) containing a fluorinated 1,2,4-triazole moiety and a lipophilic side chain. The structures of the new products were elucidated by infrared (IR), 1H and 13C nuclear magnetic resonance (NMR), and mass spectrometry. They were also assessed in vitro for their antimicrobial potency against six bacteria (Bacillus subtilis, Streptococcus pneumonia, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia) and two fungi (Aspergillus fumigatus and Candida albicans). The bioassay results revealed that some of the tested compounds displayed promising antimicrobial activity.

Natural Organic Matter Exposed to Sulfate Radicals Increases Its Potential to Form Halogenated Disinfection Byproducts.

Sulfate radical-based advanced oxidation processes (SR-AOPs) are considered as viable technologies to degrade a variety of recalcitrant organic pollutants. This study demonstrates that o-phthalic acid (PA) could lead to the formation of brominated disinfection byproducts (DBPs) in SR-AOPs in the presence of bromide. However, PA does not generate DBPs in conventional halogenation processes. We found that this was attributed to the formation of phenolic intermediates susceptible to halogenation, such as salicylic acid through the oxidation of PA by SO4(•-). In addition, reactive bromine species could be generated from Br(-) oxidation by SO4(•-). Similar in situ generation of phenolic functionalities likely occurred by converting carboxylic substituents on aromatics to hydroxyl when natural organic matter (NOM) was exposed to trace level SO4(•-). It was found that such structural reconfiguration led to a great increase in the reactivity of NOM toward free halogen and, thus, its DBP formation potential. After a surface water sample was treated with 0.1 μM persulfate for 48 h, its potential to form chloroform, trichloroacetic acid, and dichloroacetic acid increased from 197.8, 54.3, and 27.6 to 236.2, 86.6, and 57.6 μg/L, respectively. This is the first report on possible NOM reconfiguration upon exposure to low-level SO4(•-) that has an implication in DBP formation. The findings highlight potential risks associated with SO4(•-)-based oxidation processes and help to avoid such risks in design and operation.

Effects of UV/PS and UV/H2O2 pre-oxidations on the formation of trihalomethanes and haloacetonitriles during chlorination and chloramination of free amino acids and short oligopeptides

Free amino acids (AAs) can form trihalomethanes (THMs) and haloacetonitriles (HANs) during chlorination in drinking water treatment plants, but they account for a small fraction of dissolved organic nitrogen (DON) pool in natural waters. In contrast, combined AAs contribute to a greater identifiable DON portion, but the information on the formation and control of THMs and HANs from them is limited. Ultraviolet/hydrogen peroxide (UV/H2O2) and ultraviolet/persulfate (UV/PS), two typical UV-based advanced oxidation processes (UV-AOPs), are both promising drinking water technologies for the reduction of trace organic contaminants. The objective of this study is to examine the effects of the two UV-AOP pre-treatments on the formation of carbonaceous and nitrogenous disinfection by-products (C- and N-DBPs), which were indicated by THMs and HANs, respectively, during post-chlorination and chloramination of tyrosine (Tyr) in free and combined forms. Results showed that direct UV photolysis, PS pre-oxidation alone or H2O2 pre-oxidation alone did not significantly impact the THM and HAN formation during subsequent chlorination. However, the two UV-AOP pre-treatments could somewhat alter the DBP formation. In general, under the identical doses (UV irradiation dose and molar oxidant dose), UV/PS pre-treatment better controlled the HANs than UV/H2O2 during AA post-chlorination, though UV/PS might slightly promote the formation of chloroform. In contrast, the two UV-AOP pre-treatments did not obviously affect the THM and HAN formation when post-chloramination was applied. In addition, a marked difference was observed in the speciation of DBPs formed from free AAs and short oligopeptides in the presence of bromide. For free Tyr, more brominated THMs were formed than brominated HANs; but for short oligopeptides, more bromine was incorporated into HANs than THMs.

Water temperature significantly impacts the formation of iodinated haloacetamides during persulfate oxidation

The use of persulfate oxidation processes is receiving increasing interest for the removal of aquatic contaminants. However, it is unknown whether its application in the presence of iodide has the potential to directly form iodinated DBPs. This study investigated formation of six chlorinated, brominated and iodinated di-haloacetamides (DHAcAms) during persulfate oxidation in the presence of bromide and iodide. Formation of the same DHAcAms during chlorination was monitored for comparison. Persulfate oxidation of natural water formed diiodoacetamide (DIAcAm), and heat-activated persulfate, at 45 °C and 55 °C, generated bromoiodoacetamide (BIAcAm) and dibromoacetamide (DBAcAm), besides DIAcAm. At an ambient iodide concentration of 0.3 μM, total DHAcAms increased slightly from 0.43 to 0.57 nM as the water temperature increased from 4 °C to 35 °C, respectively (only DIAcAm detected), then significantly increased to 1.6 nM at 55 °C (DIAcAm, BIAcAm and DBAcAm detected). Equivalent total DHAcAm concentrations in the presence of 3.0 μM iodide were 0.5, 0.91 and 2.1 nM, respectively. Total DHAcAms formed during chlorination, predominantly dichloroacetamide (DCAcAm) and bromochloroacetamide (BCAcAm), were always significantly higher than that during persulfate oxidation. However, an integrated risk assessment showed the toxicity resulting from the DHAcAms was higher during persulfate oxidation than chlorination. An increase in water temperature from 25 °C to 55 °C significantly increased the integrated toxic risk values for both persulfate oxidation and chlorination. Use of persulfate oxidation should be weighed against the formation of high-toxicity iodinated HAcAms in waters with high ambient iodide concentrations.

Ternary Model of the Speciation of I-/Br-/Cl-Trihalomethanes Formed in Chloraminated Surface Waters.

This study examined the effects of the iodide concentration and pH on yields and speciation of the entire group of 10 species of iodine-, bromine-, and chlorine-containing trihalomethanes (THMs) formed at pH values from 6.5 to 8.5 in chloraminated surface waters in the presence of bromide and iodide. Pathways of iodine, bromine, and chlorine incorporation in the active sites in dissolved organic matter (DOM) were examined on the basis of a ternary halogenation/THM speciation model. The model assumed the occurrence of sequential three-step halogenation of the active site and competition of iodine, bromine, and chlorine species at each node of the halogenation sequence. A comparison of experimentally measured and modeled speciation coefficients and also iodine and bromine incorporation factors calculated for 10 THM species showed that the developed approach was sufficient to closely model the observed trends. Interpretation of preferred iodine incorporation pathways associated with the generation of THMs in all examined conditions showed that the susceptibility of the halogenated intermediates to iodine incorporation increases rapidly with the number of iodine atoms that have already been incorporated into the reaction site. In contrast, the incorporation of bromine and chlorine atoms in the intermediates involved in the generation of THMs makes them largely inactive in iodine incorporation reactions. The presented approach allows for a further understanding of the mechanisms of DOM/halogen interactions and prediction of the speciation of THMs formed at varying pH values, iodide concentrations, and other system conditions.

Auxiliary Part of Ligand Mediated Unique Coordination Chemistry of Copper (II)

AbstractSix N,N,O‐donor Schiff‐base ligands, HL1‐HL6, [HL1/HL2/HL3={2‐(2‐piperazin‐1‐yl)ethylimino)methyl)‐4‐(Cl/H/Me)‐phenol}; HL4/HL5/HL6={2‐(2‐morpholine/piperidine/ pyrrolidine −1‐yl)ethylimino)methyl)‐4‐chlorophenol}, have been designed by combining 5‐R‐2‐hydroxy‐benzaldehyde, (R=Cl/H/Me) and N‐(2‐aminoethyl)‐Y, (Y=piperazin/morpholine/ piperidine/pyrrolidine) with the view to explore the role of R and X (part of Y excluding coordinating N) on the coordination chemistry of Cu(II) in presence of bromide as counter anion. HL1‐HL6 formed in situ on reaction with Cu(II)Br2 produce complexes 1–6, respectively. Complex 1, [Cu(II)2Cu(I)2(L1)(MeOH)2Br7.30], is a mixed valence Cu(I)‐Cu(II) species having phenyl ring brominated at ortho position with 0.65 occupancy. Complexes 2–4 are mononuclear species with general formula [Cu{L2/L3/L4)}Br2]. Complexes [Cu3(L5)Br4] (5) and [Cu3(L6)Br4] (6) are trinuclear species having similar structure but exhibit different magnetic property, 5 is ferro‐ (J= +16.64 cm−1 ) and 6 is antiferromegnetic (J=–11.76 cm−1). The influence of R and X on bromonation, magnetic property and nuclearity issues have been rationalized by DFT calculations.

Effects of Halide Ions on the Carbamidocyclophane Biosynthesis in Nostoc sp. CAVN2.

In this study, the influence of halide ions on [7.7]paracyclophane biosynthesis in the cyanobacterium Nostoc sp. CAVN2 was investigated. In contrast to KI and KF, supplementation of the culture medium with KCl or KBr resulted not only in an increase of growth but also in an up-regulation of carbamidocyclophane production. LC-MS analysis indicated the presence of chlorinated, brominated, but also non-halogenated derivatives. In addition to 22 known cylindrocyclophanes and carbamidocyclophanes, 27 putative congeners have been detected. Nine compounds, carbamidocyclophanes M−U, were isolated, and their structural elucidation by 1D and 2D NMR experiments in combination with HRMS and ECD analysis revealed that they are brominated analogues of chlorinated carbamidocyclophanes. Quantification of the carbamidocyclophanes showed that chloride is the preferably utilized halide, but incorporation is reduced in the presence of bromide. Evaluation of the antibacterial activity of 30 [7.7]paracyclophanes and related derivatives against selected pathogenic Gram-positive and Gram-negative bacteria exhibited remarkable effects especially against methicillin- and vancomycin-resistant staphylococci and Mycobacterium tuberculosis. For deeper insights into the mechanisms of biosynthesis, the carbamidocyclophane biosynthetic gene cluster in Nostoc sp. CAVN2 was studied. The gene putatively coding for the carbamoyltransferase has been identified. Based on bioinformatic analyses, a possible biosynthetic assembly is discussed.

Diastereoselective reaction of 1,3-dihydroxy calixarene with acylisocyanates: new and easy approach for preparing inherently chiral calyx[4]arenes

The facile method of generating internal chirality into the calixarene with two hydroxy groups at the lower rim via an attached chiral substituent has been proposed. The reaction with acylisocyanates, catalyzed by a small amount of triethylamine, proceeds forming predominantly one of the two possible calixarene carbamates. The best diastereomeric excess (60 %) has been achieved in the reaction of trichloroacyl isocyanates with 1,3-hydroxycalixarene substituted with the chiral phenylethyl amide moiety. The individual diastereomers of trichloroacetyl-carbamoylcalix[4]arenas were isolated by crystallization, and their absolute configuration was determined by X-ray diffraction study. The most favored conformations predicted for 1,3-dihydroxy calixarene structures by quantum chemical calculations possess very similar stability. However, the triethylamine molecule preferably connects to the one hydroxyl group of the two available ones, providing the most favorable adduct, which predominantly participates in the reaction with acylisocyanates. This gives rise to the observed diastereomeric excess. The subsequent treatment of the formed carbamoyl with n-propyl bromide in presence of NaH and hydrolysis of the product of alkylation easily provide a persistent internally chiral calixarene.

Kinetics of Chlorination of Benzophenone-3 in the Presence of Bromide and Ammonia

The aim of this study was to assess the impact of chlorination on the degradation of one of the most commonly used UV filters (benzophenone-3 (BP-3)) and the effects of bromide and ammonia on the kinetics of BP-3 elimination. Bromide and ammonia are rapidly converted to bromine and chloramines during chlorination. At first, the rate constants of chlorine, bromine and monochloramine with BP-3 were determined at various pH levels. BP-3 was found to react rapidly with chlorine and bromine, with values of apparent second order rate constants equal to 1.25(±0.14) × 10(3) M(-1)·s(-1) and 4.04(±0.54) × 10(6) M(-1)·s(-1) at pH 8.5 for kChlorine/BP-3 and kBromine/BP-3, respectively, whereas low monochloramine reactivity was observed (kNH2Cl/BP-3 = 0.112 M(-1)·s(-1)). To assess the impact of the inorganic content of water on BP-3 degradation, chlorination experiments with different added concentrations of bromide and/or ammonia were conducted. Under these conditions, BP-3 degradation was found to be enhanced in the presence of bromide due to the formation of bromine, whereas it was inhibited in the presence of ammonia. However, the results obtained were pH dependent. Finally, a kinetic model considering 18 reactions was developed using Copasi to estimate BP-3 degradation during chlorination in the presence of bromide and ammonia.

Development and validation of three spectrophotometric methods for determination of pyridostigmine bromide in the presence of its alkaline-induced degradation product

Three simple, accurate and validated spectrophotometric methods were developed for the determination of pyridostigmine bromide (PB) in presence of its alkaline-induced degradation product, 3-hydoxy- N -methylpyridinium bromide (3-OH NMP) in powder form and in pharmaceutical formulations. Method A, is first derivative method ( 1 D), which is based on measuring the peak amplitude of the first derivative spectra ( 1 D) of PB at 260 nm. Method B, is first derivative of ratio spectra ( 1 DD) which allows the determination of PB at 267.4 nm using (50 µg/mL) of 3-OH NMP as a suitable devisor. Finally, method C depends on mean centering of ratio spectra (MCR) of PB with different concentrations, which were recorded over 200-400 nm and divided by the spectrum of 20 µg/mL of 3-OH NMP as a devisor. The obtained ratio spectra were mean centered and the concentrations of PB were then determined from the calibration graphs obtained by measuring the amplitudes at 338 nm. The proposed methods were successfully applied for assay of PB both in pure form and in pharmaceutical formulations. The proposed methods were validated in compliance with International Conference on Harmonization (ICH) guidelines. The results obtained by the developed methods were statistically compared to those obtained by the reported HPLC method using F- and student's t-tests showing no significant difference regarding both accuracy and precision.

Peptide bonds affect the formation of haloacetamides, an emerging class of N-DBPs in drinking water: free amino acids versus oligopeptides.

Haloacetamides (HAcAms), an emerging class of nitrogenous disinfection by-products (N-DBPs) of health concern, have been frequently identified in drinking waters. It has long been appreciated that free amino acids (AAs), accounting for a small fraction of the dissolved organic nitrogen (DON) pool, can form dichloroacetamide (DCAcAm) during chlorination. However, the information regarding the impacts of combined AAs, which contribute to the greatest identifiable DON portion in natural waters, is limited. In this study, we compared the formation of HAcAms from free AAs (tyrosine [Tyr] and alanine [Ala]) and combined AAs (Tyr-Ala, Ala-Tyr, Tyr-Tyr-Tyr, Ala-Ala-Ala), and found that HAcAm formation from the chlorination of AAs in combined forms (oligopeptides) significantly exhibited a different pattern with HAcAm formation from free AAs. Due to the presence of peptide bonds in tripeptides, Tyr-Tyr-Tyr and Ala-Ala-Ala produced trichloroacetamide (TCAcAm) in which free AAs was unable to form TCAcAm during chlorination. Moreover, peptide bond in tripeptides formed more tri-HAcAms than di-HAcAms in the presence of bromide. Therefore, the peptide bond may be an important indicator to predict the formation of specific N-DBPs in chlorination. The increased use of algal- and wastewater-impacted water as drinking water sources will increase health concerns over exposure to HAcAms in drinking water.

Electrogenerated chemiluminescence resonance energy transfer between lucigenin and CdSe quantum dots in the presence of bromide and its sensing application

Electrogenerated chemiluminescence (ECL) of lucignein often suffered from weak signal at positive potential in neutral condition. In the present study, strong anodic ECL was obtained in neutral lucigenin solution at a CdSe quantum dots modified glassy carbon electrode. Electrochemical results suggested that CdSe quantum dots can catalyze the oxidation of lucigenin and bromide, which can generate the anodic ECL. The fluorescence and the ECL spectra revealed that ECL resonance energy transfer (ECL-RET) can occur between lucigenin and CdSe quantum dots. The oxidation product of bromide can promote ECL-RET and increase the anodic ECL signal significantly. The mechanisms of the anodic ECL based on the ECL-RET were proposed. Cytochrome C exhibited apparent inhibiting effect on the anodic ECL emission, based on which a sensitive ECL sensor for the detection of cytochrome C was established.

Mechanistic Study on the Formation of Cl-/Br-/I-Trihalomethanes during Chlorination/Chloramination Combined with a Theoretical Cytotoxicity Evaluation.

Chlorination followed by chloramination can be used to mitigate the formation of potentially toxic iodinated disinfection byproducts (I-DBPs) while controlling the formation of regulated chloro-bromo-DBPs (Cl-/Br-DBPs). Water samples containing dissolved organic matter (DOM) isolates were subjected to 3 disinfection scenarios: NH2Cl, prechlorination followed by ammonia addition, and HOCl alone. A theoretical cytotoxicity evaluation was carried out based on the trihalomethanes (THMs) formed. This study demonstrates that the presence of bromide not only enhances the yield and rate of iodate formation, it also increases the formation of brominated I-THM precursors. A shift in the speciation from CHCl2I to the more toxic CHBr2I, as well as increased iodine incorporation in THMs, was observed in the presence of bromide. For low bromide concentrations, a decrease in I-THM formation and theoretical cytotoxicity was achieved only for high prechlorination times, while for high bromide concentrations, a short prechlorination time enabled the full conversion of iodide to iodate. For low DOM concentrations or DOM with low reactivity, Br-/I-THMs were preferentially formed for short prechlorination times, inducing high cytotoxicity. However, for high chlorine exposures, the cytotoxicity induced by the formation of regulated THMs might outweigh the benefit of I-THM mitigation. For high DOM concentrations or DOM with higher reactivity, mixed I-THMs were formed together with high concentrations of regulated THMs. In this case, based on the cytotoxicity of the THMs formed, the use of NH2Cl is recommended.

On the Effects of Halides on the Hydrogen Peroxide Reduction Reaction in Aqueous Electrolytes

The influence of adsorbed species on the kinetics and mechanism of a number of redox reactions has been recognized for decades1. In particular, the adsorption of both chloride and bromide on Pt electrodes in acidic electrolytes, is known to promote the two-electron reduction of oxygen to peroxide instead of the desired four-electron reduction to water 2,3. This contribution seeks to gain insights into the reduction of H2O2 on a polycrystalline Pt electrode in 0.1 M HClO4 solutions containing a few ppm of either Cl- or Br-. The strategy employed makes use of a chronoamperometric method recently developed in our laboratories to determine independently, the effects of potential, E, and coverage of the adsorbate, q, on the peroxide reduction reaction on a Pt rotating disk electrode, RDE EXPERIMENTAL All measurements were performed in an all-glass, three-compartment cell in a 1 mM H2O2 in 0.1 M HClO4 solution either neat or containing 10 µM NaCl or 10 µM KBr. Experiments were performed with a rotating Pt ring-Pt disk electrode, Pt|Pt RRDE, (Pine Instruments, (A = 0.164 cm2) using a bipotentiostat (Pine Instruments). A Pt foil and a reversible hydrogenelectrode in the same solution (RHE) were used as counter and reference electrodes, respectively. RESULTS AND DISCUSSION Shown in Fig.1 are polarization curves recorded at a scan rate, ν = 10 mV/s for a Pt disk electrode in 0.1 M HClO4 containing 1 mM H2O2in the absence (black curve) and in the presence of either 10 mM NaCl or 10 μM KBr (red curve). In contrast to the rather subtle effects of chloride, the presence of bromide gives rise to a substantial, ca. 0.3 V, shift in the onset for peroxide reduction. Chronoamperometric curves, i.e. disk current, idisk vs time, obtained in upon stepping the potential from a value Eo, at which its coverage q is negligible 0, to a value Eads at which q attains a finite value are displayed in Fig. 2. The results of these experiments make it possible to correlate the disk current, i, as a function of Eads at fixed q, or as a function of q for a fixed Eadsas illustrated in Panels A and B in Fig. 3, respectively. Implications of these results on the effects of these impurities on the oxygen reduction reaction (ORR) will be discussed. ACKNOWLEDGEMENTS This work was supported by a grant from NSF (CHE-0911621). REFERENCES Marković, N. M.; Ross Jr, P. N., Surf. Sci. Reports 2002, 45, 117-229.Stamenkovic, V.; M. Markovic, N.; Ross Jr, P. N., J. Electroanal. Chem. 2001, 500, 44-51.Schmidt, T. J.; Paulus, U. A.; Gasteiger, H. A.; Behm, R. J., J. Electroanal. Chem. 2001, 508, 41-47. Figure 1

Chlorination of polyvinyl pyrrolidone–polysulfone membranes: Organic compound release, byproduct formation, and changes in membrane properties

In this work, the release of organic compounds, the variations of membrane properties and the formation of toxic byproducts during chlorine treatment of polyvinyl pyrrolidone–polysulfone (PVP–PSF) membranes were investigated. Chlorine treatment decreased bovine serum albumin rejection, permeability and hydrophilicity of PVP–PSF membranes and resulted in the release of organic compounds as measured by total organic carbon (TOC). More organic compounds were released from the membranes at higher chlorine concentrations and higher initial values of chlorine contact pH. The presence of bromide that can be oxidized to bromine by chlorine also increased the release of organic matter from the membranes and contributed to the formation of high toxic brominated byproducts. Five toxic volatile chlorinated byproducts, chloroform, chloral hydrate, 1,1-dichloro-2-propanone, 1,1,1-trichloro-2-propanone and trichloronitromethane, were formed during chlorination of the organic compounds from the PVP–PSF membranes. Three brominated byproducts including bromodichloromethane, dibromochloromethane and bromoform were determined in the presence of bromide. The PVP appears to be more susceptible than PSF to chlorine destruction in the PVP–PSF membranes as analysis of the chlorinated byproducts derived from PVP precursors.

Chlorination of bensulfuron-methyl: Kinetics, reaction factors and disinfection by-product formation

The kinetics of bensulfuron-methyl chlorination were studied at pH 4–9 at room temperature (25 ± 1 °C), which can be described well by a second-order kinetic model, first-order in chlorine and first-order in bensulfuron-methyl concentrations. Bensulfuron-methyl reacted very rapidly with aqueous chlorine with the maximum reaction rate constant at pH 6 and minimum at pH 9. The superior reactions were the reactions between HOCl and ionized/nonionized bensulfuron-methyl. The reaction factors including bromide and ammonium concentrations as well as temperature were also evaluated. It was found that bromide accelerated the chlorination of bensulfuron-methyl and the reaction rate increased linearly with the increase of bromide concentration. In contrast, the presence of ammonium inhibited the degradation of bensulfuron-methyl due to its quick conversion of chlorine to chloramines. Bensulfuron-methyl chlorination is an endothermic reaction with the activation energy being estimated as 13.74 kJ/mol using the Arrhenius equation. Four volatile disinfection by-products (DBPs) were identified after bensulfuron-methyl chlorination, including chloroform, dichloroacetonitrile, 1,1,1-trichloroacetone and nitrotrichloromethane. Trihalomethanes were the dominant species with a maximum reached at pH 8, which could cause potential risks to public health during bensulfuron-methyl chlorination, especially with the presence of bromide because the concentration and species of brominated DBPs increased with increasing bromide concentration.

A new and sensitive reaction rate method for spectrophotometric determination of trace amounts of thiourea in different water samples based on an induction period

Thiourea (TU) has various industrial, agricultural and analytical applications. TU has been labeled as having carcinogenic activity. Hypothyroidism was induced in animals by using TU. A simple and sensitive spectrophotometric reaction rate method was proposed for the determination of trace amounts of TU. The method is based on the inhibitory effect of TU on the rate of meta cresol purple (MCP) with bromate in the presence of bromide. The reaction progress was followed by monitoring the absorbance of MCP at 525 nm. The effects of different variables on the sensitivity of the proposed method were studied and optimized. Under optimum conditions a linear relationship between induction period time and TU concentration was found in the concentration range of 0.10 – 6.0 μg mL−1 of TU. The detection limit (3σ) of 0.020 μg mL−1 was found. The relative standard deviations for six replicate determinations of 0.10, 2.0 and 5.0 μg mL−1 of TU were 2.3%, 1.8% and 1.1%, respectively. In this study a new reaction system was proposed for the kinetic spectrophotometric determination of TU in water samples. The new method not only benefit from high selectivity and sensitivity, but also it has the advantage of fast and simple operation.

Removal and inactivation of virus by drinking water treatment in the presence of bromide or iodide

The inactivation of virus in raw water was conducted in a continuous flow pilot scale system. Coliphage MS2 was used as model organism for human enteric virus. The effect of disinfection technologies (single or combined process of ozonation and chlorination) and interfering substances (bromide or iodide) on inactivation of virus, and the removal performance of virus in raw water by the pilot scale system (Train A and B) were investigated. The results indicated that bromide or iodide in water was detrimental to ozonation but beneficial to chlorination for virus inactivation. After bromide or iodide was added, the removal of MS2 by ozonation unit was much lower than before (p < 0.01), the removal of MS2 by chlorination unit was significantly higher than before (p < 0.05). Both Train A and B could remove and inactivate MS2 in raw water completely even at high concentration of bromide (675.24 μg/dm3) and iodide (52.33 μg/dm3). The processes of Train A and B can effectively guarantee the virological safety of drinking water.

Synthesis and biological activities of some benzimidazolone derivatives.

The reaction of 5-nitrobenzimidazolone with phenoxyethyl bromide in presence of potassium carbonate in dimethyl formamide obtained 6-nitro-1,3-bis(2-phenoxyethyl)-1,3-dihydro-2H-benzimidazol-2-one. It was reduced using stannous chloride to get 6-amino -1,3-bis(2-phenoxyethyl)-1, 3-dihydro-2H-benzimidazol -2-one, which was further treated with aromatic sulphonyl chloride to obtain benzimidazolone derivatives, 6a-k. These compounds were tested for antibacterial, antituberculosis and antifungal activity. Most of them have shown very good activity against some gram positive and gram negative microorganisms and fungal strains. Some of them have shown moderate activity against Mycobacterium tuberculosis.