Showing papers on "Chlorine published in 2006"
TL;DR: C and 35/37Cl NMR relaxation measurements on several model systems demonstrate that the solvation of cellulose by the ionic liquid 1-n-butyl-3-methylimidazolium chloride involves hydrogen-bonding between the carbohydrate hydroxyl protons and the IL chloride ions in a 1 ratio 1 stoichiometry.
696 citations
TL;DR: This paper describes the theory and practice of the cleaning and disinfecting operations based on the use of sodium hypochlorite solution and implies that the optimal pH region of the germicidal activity of sodium Hypochlorites differs from that of its cleaning activity.
Abstract: Sodium hypochlorite (NaOCl) is the most widely used disinfectant in the food industry despite the increasing availability of other disinfectants. Sodium hypochlorite fulfills many requirements as the ideal disinfectant and furthermore it has an excellent cleaning action. The effectiveness of sodium hypochlorite in the cleaning and disinfection processes depends on the concentration of available chlorine and the pH of the solution. Hypochlorous acid (HOCl) is a weak acid and dissociates to the hypochlorite ion (-OCl) and proton (H+) depending on the solution pH. It is generally believed that HOCl is the active species in the germicidal action, whereas the concentration of -OCl is a key factor determining the cleaning efficiency. This implies that the optimal pH region of the germicidal activity of sodium hypochlorite differs from that of its cleaning activity. This paper describes the theory and practice of the cleaning and disinfecting operations based on the use of sodium hypochlorite solution.
410 citations
TL;DR: Quantitative assessment of the results of this study showed a good agreement with kinetic data in the literature on the impact of bromide and iodide ions on the formation and speciation of disinfection byproducts.
Abstract: Two natural waters were fortified with various levels of bromide or iodide ions (0−30 μM) and chlorinated in the laboratory to study the impact of bromide and iodide ions on the formation and speciation of disinfection byproducts. Trihalomethanes (THMs), haloacetic acids (HAAs), total organic halogen (TOX), and its halogen-specific fractions total organic chlorine (TOCl), bromine (TOBr), and iodine (TOI), were measured in this work. The molar yields of THMs and HAAs increased as the initial bromide concentration increased. No significant change in TOX concentration was found for varying bromide concentrations. However, TOX concentrations decreased substantially with increasing initial iodide concentrations. At higher levels of bromide, there was a decreasing level of unknown TOX and unknown TOCl but an increasing level of unknown TOBr. The extent of iodine substitution was much lower than that of bromine substitution when comparing identical initial concentrations because a substantial amount of iodide wa...
401 citations
TL;DR: It can be concluded in general that the triazine containing higher molecular weight diazo compounds takes more time for complete de-colorization than the mono azo or anthraquinone containing dye compounds.
326 citations
TL;DR: In this article, the effect of exposure to solution of hypochloric acid (disinfecting agent) on the chemical and morphological properties of a crosslinked polyamide membrane (LFC1, Hydranautics©) was evaluated using AFM, XPS, FT-IR, contact angle and streaming potential analysis.
181 citations
TL;DR: Time-resolved measurements of As( III) loss during chlorination and ozonation of real waters were accurately modeled using the rate constants determined in this investigation, and each reaction was found to be first order in oxidant and in As(III), with 1:1 stoichiometry.
Abstract: Kinetics and mechanisms of As(III) oxidation by free available chlorine (FACthe sum of HOCl and OCl-), ozone (O3), and monochloramine (NH2Cl) were investigated in buffered reagent solutions. Each reaction was found to be first order in oxidant and in As(III), with 1:1 stoichiometry. FAC−As(III) and O3−As(III) reactions were extremely fast, with pH-dependent, apparent second-order rate constants, , of 2.6 (±0.1) × 105 M-1 s-1 and 1.5 (±0.1) × 106 M-1 s-1 at pH 7, whereas the NH2Cl−As(III) reaction was relatively slow ( = 4.3 (±1.7) × 10-1 M-1 s-1 at pH 7). Experiments conducted in real water samples spiked with 50 μg/L As(III) (6.7 × 10-7 M) showed that a 0.1 mg/L Cl2 (1.4 × 10-6 M) dose as FAC was sufficient to achieve depletion of As(III) to 75% As(III) oxidation could be achieved within 10 s of dosing 1−2 mg/L Cl2...
149 citations
TL;DR: A kinetic model that incorporates pH-based speciation of both oxidant species and sulfonamide antibiotics was developed and validated and used in kinetic experiments to identify kinetics and treatment effectiveness.
131 citations
01 Jan 2006
TL;DR: In this article, ammonium sulfate injection together with a so-called in situ alkali chloride monitor (IACM) was used to reduce the formation and corrosion of a biomass combustion boiler.
Abstract: Biomass and waste derived fuels contain relatively high amounts of alkali and chlorine, but contain very little sulfur. Combustion of such fuels can result in increased deposit formation and superheater corrosion. These problems can be reduced by using a sulfur containing additive, such as ammonium sulfate, which reacts with the alkali chlorides and forms less corrosive sulfates. Ammonium sulfate injection together with a so-called in situ alkali chloride monitor (IACM) is patented and known as “ChlorOut”. IACM measures the concentrations of alkali chlorides (mainly KCl in biomass combustion) at superheater temperatures. Tests with and without spraying ammonium sulfate into the flue gases have been performed in a 96MWth/25MWe circulating fluidized bed (CFB) boiler. The boiler was fired mainly with bark and a chlorine containing waste. KCl concentration was reduced from more than 15 ppm to approximately 2 ppm during injection of ammonium sulfate. Corrosion probe measurements indicated that both deposit formation and material loss due to corrosion were decreased using the additive. Analysis of the deposits showed significantly higher concentration of sulfur and almost no chlorine in the case with ammonium sulfate. Results from impactor measurements supported that KCl was sulfated to potassium sulfate by the additive. © 2007 Elsevier B.V. All rights reserved.
131 citations
TL;DR: The anodic oxidation of 1.8l of solutions with mecoprop (2-(4-chloro-2-methylphenoxy)-propionic acid or MCPP up to 0.64 g l(-1) in Na2SO4 as background electrolyte within the pH range 2.0-12.0 has been studied and a reaction pathway for M CPP mineralization involving all products detected is proposed.
115 citations
TL;DR: The results suggest that THMs in source water of Pearl River could be effectively reduced when pollution of human activity is greatly controlled.
109 citations
TL;DR: In this article, Rouaix et al. showed that fiber embrittlement is a determining criterium, especially for water treaters, which occurs by chain scission (determined by Size Exclusion Chromatography) with the hydroxyl radical OH formed in the bleach solution.
TL;DR: In this paper, the intrinsic rate coefficients for these processes were determined, and a simple mechanistic model was developed, which was used to forecast the fate of organophosphate (OP) pesticides under drinking water treatment conditions.
Abstract: Chlorpyrifos (CP) was used as a model compound to develop experimental methods and prototype modeling tools to forecast the fate of organophosphate (OP) pesticides under drinking water treatment conditions. CP was found to rapidly oxidize to chlorpyrifos oxon (CPO) in the presence of free chlorine. The primary oxidant is hypochlorous acid (HOCl), kr = 1.72 (±0.68) × 106 M-1h-1. Thus, oxidation is more rapid at lower pH (i.e., below the pKa of HOCl at 7.5). At elevated pH, both CP and CPO are susceptible to alkaline hydrolysis and degrade to 3,5,6-trichloro-2-pyridinol (TCP), a stable end product. Furthermore, hydrolysis of both CP and CPO to TCP was shown to be accelerated in the presence of free chlorine by OCl-, kOCl,CP = 990 (±200) M-1h-1 and kOCl,CPO = 1340 (±110) M-1h-1. These observations regarding oxidation and hydrolysis are relevant to common drinking water disinfection processes. In this work, intrinsic rate coefficients for these processes were determined, and a simple mechanistic model was dev...
TL;DR: In this paper, the thermodynamic properties of mixtures of polyvinyl chloride (PVC) and a variety of metal oxides including rare earth oxides were studied under helium atmosphere at 400 and 800°C.
TL;DR: The sequential application of ozone, chlorine dioxide, or UV followed by free chlorine was performed to investigate the synergistic inactivation of Bacillus subtilis spores and the greatest synergism observed by the chlorine dioxide/free chlorine pair suggested that common reaction sites might exist for these disinfectants.
TL;DR: In this article, the influence of gasification environment (gas type, temperature and time) on the transformations of sodium and the extent of vaporisation were studied. But, contrary to theoretical equilibrium calculations for the high levels of sulphur present in the coal, no sodium sulphide formation was found upon the transformation of carboxylate sodium.
TL;DR: It is shown that trace amounts of HCl induce formation of a disordered region, or quasi-liquid layer, at the ice surface at stratospheric temperatures and that surface disordering enhances the chlorine activation reaction of Hcl with chlorine nitrate (ClONO(2)) and also enhances acetic acid (CH(3)COOH) adsorption.
Abstract: Characterizing the interaction of hydrogen chloride (HCl) with polar stratospheric cloud ice particles is essential for understanding the processes responsible for ozone depletion. We studied the interaction of gas-phase HCl with ice between 243 and 186 K by using (i) ellipsometry to monitor the ice surface and (ii) coated-wall flow tube experiments, both with chemical ionization mass spectrometry detection of the gas phase. We show that trace amounts of HCl induce formation of a disordered region, or quasi-liquid layer, at the ice surface at stratospheric temperatures. We also show that surface disordering enhances the chlorine activation reaction of HCl with chlorine nitrate (ClONO2) and also enhances acetic acid (CH3COOH) adsorption. These results impact our understanding of the chemistry and physics of ice particles in the atmosphere.
TL;DR: The composition and content of sodium hypochlorite solutions had a profound effect on the ability of these solutions to dissolve pulp tissue in vitro, and one per cent solutions with added surfactant and which contained higher concentrations of sodium hydroxide were significantly more effective in dissolution of pulp tissue.
Abstract: Background: The solubility of dental pulp tissue in sodium hypochlorite has been extensively investigated but results have been inconsistent; due most likely to variations in experimental design, the volume and/or rate of replenishment of the solutions used and the nature of the tissues assessed. Traditionally, the sodium hypochlorite solutions used for endodontic irrigation in Australia have been either Milton or commercial bleach, with Milton being the most common. Recently, a range of Therapeutic Goods Administration (TGA) approved proprietary sodium hypochlorite solutions, which contain surfactant, has become available. Some domestic chlorine bleaches now also contain surfactants. The purpose of this study was to perform new solubility assessments, comparing Milton with new TGA approved products, Hypochlor 1% and Hypochlor 4% forte, and with a domestic bleach containing surfactant (White King). Methods: Ten randomly assigned pulp samples of porcine dental pulp of approximately equal dimensions were immersed in the above solutions, as well as representative concentrations of sodium hydroxide. Time to complete dissolution was measured and assessed statistically. Results: White King 4% showed the shortest dissolution time, closely followed by Hypochlor 4% forte. White King 1% and Hypochlor 1% each took around three times as long to completely dissolve the samples of pulp as their respective 4% concentrations, while Milton took nearly 10 times as long. The sodium hydroxide solutions showed no noticeable dissolution of the pulp samples. Conclusions: The composition and content of sodium hypochlorite solutions had a profound effect on the ability of these solutions to dissolve pulp tissue in vitro. Greater concentrations provided more rapid dissolution of tissue. One per cent solutions with added surfactant and which contained higher concentrations of sodium hydroxide were significantly more effective in dissolution of pulp tissue than Milton.
TL;DR: Results showed that antioxidant parameters of Cyprinus carpio could be used as biomarkers of oxidative stress when this species is exposed to disinfectants for water potabilization.
TL;DR: It is demonstrated that perchlorate can be generated as an end-product of photochemical transformation reactions of chlorine precursors such as aqueous salt solutions of hypochlorite, chlorite, and chlorate upon exposure to ultraviolet (UV) radiation.
TL;DR: Treatment with silicon tetrachloride improves the chemical resistance of H-ZSM-5 against hydrogen chloride, and TCM is more reactive compared to DCM but it produces more by-products due to its high chlorine content.
TL;DR: In this article, the second part of the studies of halogens in the air-acetylene flame attends to the determination of chlorine using high-resolution continuum source absorption spectrometry and molecular absorption.
TL;DR: ClO2 profiles showed depletion of disinfectant at 100 μm in the biofilm depth, indicating that ClO2 may not reach bacteria in a biofilm thicker than this using a 25 mg/l solution, and discarded microelectrodes proved useful for in situ direct measurement of biofilm thicknesses.
Abstract: Biofilms are considered a significant health risk in the food and dairy industries because they can harbor pathogens, and direct contact with them can lead to food contamination. Biofilm control is often performed using strong oxidizing agents like chlorine and peracetic acid. Although chlorine dioxide (ClO2) is being used increasingly to control microbiological growth in a number of different industries, not much is known about disinfection in biofilms using chlorine dioxide. In this study, a microelectrode originally made for chlorine detection was modified to measure the profiles of chlorine dioxide in biofilm as a function of depth into the biofilm. In addition, discarded microelectrodes proved useful for in situ direct measurement of biofilm thicknesses. The chlorine dioxide microelectrode had a linear response when calibrated up to a ClO2 concentration of 0.4 mM. ClO2 profiles showed depletion of disinfectant at 100 μm in the biofilm depth, indicating that ClO2 may not reach bacteria in a biofilm thicker than this using a 25 mg/l solution.
TL;DR: The production of NDMA in ammonia-containing systems was correlated with the concentration ofNDMA precursors in the wastewater effluent and the overall dose of chlorine applied, and much of the NDMA formation occurred in chlorine contact basins or in storage basins where water that contained chloramines was held after disinfection.
TL;DR: In this paper, the effect of monochloramine solutions on polyamide membranes in the reverse osmosis process was studied. But the authors did not consider the effects of iron and aluminum on the membrane degradation process.
01 Jan 2006
TL;DR: In this article, the results of full-scale corrosion tests in a 65 MW waste fired combined heat and power plant were presented, which indicated a chlorine induced corrosion mechanism involving volatile iron chloride with a high corrosion rate on the superheater materials typically used.
Abstract: Incineration of municipal solid waste is often associated with high temperature corrosion problems. This paper presents results of full-scale corrosion tests in a 65 MW waste fired combined heat and power plant. A failure case indicated alarmingly high corrosion rate of the superheater tubes. Corrosion tests with five different alloys were carried out within this work in order to determine plant specific corrosion rates on different superheater materials. Additional tests were done to determine the effect on the corrosion rate from adding chlorine containing polyvinyl chloride to the ordinary fuel mix. A corrosion probe with metal temperatures ranging from 320 °C to 460 °C was used to estimate corrosion loss and to collect deposits. The sampling was performed at a flue gas temperature of 470 °C for 10 days. The probe rings were analysed using scanning electron microscope and micrometer measurements to determine the deposit chemistry and corrosion rates. The results showed significant differences in corrosion rates depending on tube material. Chlorine was shown to have a key role in the corrosion process, even at these relatively low temperatures. The results indicated a chlorine induced corrosion mechanism involving volatile iron chloride with a high corrosion rate on the superheater materials typically used. Addition of extra polyvinyl chloride to the fuel mix had an increasing effect on the corrosion.
TL;DR: It was observed that with the COOH substitution of 3- HBA and 4-HBA tend to exhibit more CAA formation potential than resorcinol, and phloroglucinol, with one more OH substitution group than res orcinol tends to form significant amounts of CAA after chlorination.
TL;DR: The initial chlorine dose required to give any residual chlorine concentration can be calculated for any time within the experimental time window, from a single set of experimental data.
TL;DR: In this paper, the results of isothermal and thermocyclic high temperature oxidation tests of technical TiAl-alloys with and without halogen treatment are shown and compared with the untreated alloys.
TL;DR: In this paper, a systematic investigation of the relationship between chlorine exposure of a thin film composite crosslinked polyamide membrane and changes in membrane performance (water flux and salt rejection) is discussed.
Abstract: A systematic investigation of the relationship between chlorine exposure of a thin film composite crosslinked polyamide membrane (LE membrane, FilmTec©) and changes in membrane performance (water flux and salt rejection) is discussed here. Performance change of crosslinked polyamide membranes due to chlorination depended on pH and concentration of chlorine in the soaking bath. Membranes chlorinated at low pH and high chlorine concentration showed flux decreases at an early stage of filtration and then increases with filtration time. On the other hand, membranes chlorinated at high pH and low chlorine concentration showed flux increases at an early stage and then decreases with filtration time. Performance of chlorinated polyamide membranes was determined by the balance between rearrangement of polymer chains and the distortion of the chains due to chlorination. A conceptual model of performance change was proposed consistent with the chlorination of polyamide membranes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5895–5902, 2006
TL;DR: Results provide information on the effectiveness of sanitizers commonly used in the food processing industry in killing Bacillus spores in suspension, on a food-contact surface, and on a ready-to-eat food.