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1
Svenson, Doug R., Hou-min Chang, Hasan Jameel e John F. Kadla. "The role of non-phenolic lignin in chlorate-forming reactions during chlorine dioxide bleaching of softwood kraft pulp". Holzforschung 59, n. 2 (1 febbraio 2005): 110–15. http://dx.doi.org/10.1515/hf.2005.017.
Testo completoAbstract (sommario):
Abstract The affect of phenolic hydroxyl groups on the reaction efficiency during chlorine dioxide pre-bleaching of a softwood kraft pulp was investigated. The removal of phenolic hydroxyl groups via pulp methylation did not adversely affect the chlorine dioxide bleaching efficiency or the amount of chlorate formed during exposure to chlorine dioxide. Ion analysis of the reaction systems revealed that the formation of chloride and chlorite ions during the bleaching process were very similar between the kraft and methylated kraft pulps. These results indicate that the kinetic rates of lignin oxidation by chlorine dioxide and its reduction products, chlorite and hypochlorous acid, are much faster than the rate of inorganic reactions leading to chlorate formation.
2
MOKIIЕNKO, Andrii, Larysa SPASONOVA e Oleksandr BONDARCНUK. "ANALYSIS OF METHODS FOR DETERMINATION OF CHLORINE DIOXIDE, CHLORITE AND CHLORATE ANIONS IN DRINKING WATER". Herald of Khmelnytskyi National University. Technical sciences 317, n. 1 (23 febbraio 2023): 294–99. http://dx.doi.org/10.31891/2307-5732-2023-317-1-294-299.
Testo completoAbstract (sommario):
The analysis shows that the primary measure for the purification of drinking water is its reliable disinfection with oxidants, which are chlorine and its compounds, chlorine dioxide, ozone. The aim of the article is to analyze the existing methods for determination of chlorine dioxide, chlorite, hypochlorite and chlorate anions in drinking water. To analyze the chlorine dioxide strength solutions (to control the generator performance) the iodometric method (determination of chlorine dioxide concentration, concentration of free chlorine, chlorite and chlorate anions; relative error ≤ 5%) and the method of direct absorption at 445 nm (determination of chlorine dioxide concentration in the range of concentrations of 100-700 mg / l; relative error ≤ 2%) were used. To analyze the residual concentrations of chlorine dioxide, chlorite and hypochlorite anions in their joint presence the titrimetric and photometric methods with N,N-діетил-1,4-фенилендіамінсульфатом (DFD) (error of determination is of 0.05 mg/l) were used as well as iodometric method with photometric determination of iodine at 350 nm in the concentration range 0.01-0.5 mg/l. To analyze the residual concentrations of chlorine dioxide (selective methods), such methods were used: the photometric method with chlorophenol red in the concentration range of 0.02-0.7 mg/l; relative error ≤ 5%; photometric method with chromic violet acid in the concentration range of 0.1-1.5 mg/l. The method of ion chromatography was used to analyze the residual concentrations of chlorite and chlorate anions. Given the necessity for harmonization of domestic regulatory and guidance documentation with European one, it should be considered as necessary to control chlorites and chlorates in drinking water by method of ion chromatography. It is appropriate to conduct research on the approbation of ion chromatography method for the simultaneous determination of chlorites and chlorates in samples of water after its disinfection by various oxidants (sodium hypochlorite, ozone, chlorine dioxide).
3
Paun, Iuliana, Florentina Laura Chiriac, Vasile Ion Iancu, Florinela Pirvu, Marcela Niculescu e Nicoleta Vasilache. "Disinfection by-products in drinking water distribution system of Bucharest City". Romanian Journal of Ecology & Environmental Chemistry 3, n. 1 (25 giugno 2021): 10–18. http://dx.doi.org/10.21698/rjeec.2021.102.
Testo completoAbstract (sommario):
Chlorine is widely used in Romania and all over the world as a disinfectant of drinking water. During the chlorination process, the natural organic matter and inorganic ions react with chlorine forming disinfection by-products (DBPs). The predominant organic disinfection by-products are trihalomethanes (THMs) while the main inorganic disinfection by-products are chlorate and chlorite ions. THMs were detected in all investigated drinking water samples from Bucharest distribution system with values from 27.8 µg/L up to 75.1 µg/L, which are below the maximum concentration value admitted by Romanian drinking water legislation of 100 µg/L. Chloroform constitutes the major component in total THMs concentration found in all tested drinking water. Chlorate and chlorite anions were not detected in any of the investigated drinking water samples. THMs concentration was correlated with total organic carbon (TOC), residual chlorine and chloride.
4
Lapina, E. A., S. A. Zverev, S. V. Andreev e K. A. Sakharov. "Determination of chlorine-containing compounds in disinfectants using ion-exchange chromatography". Fine Chemical Technologies 18, n. 3 (2 agosto 2023): 254–64. http://dx.doi.org/10.32362/2410-6593-2023-18-3-254-264.
Testo completoAbstract (sommario):
Objectives. To develop a method for the determination of hypochlorite, chloride, chlorite, chlorate, and perchlorate ions in solution; to determine the limits of detection and quantitation for ClO−, Cl−, ClO2−, ClO3−, and ClO4− ions; to evaluate the applicability of the developed method and its suitability for disinfectant analysis.Methods. Ionic chromatography using a conductometric detection system in isocratic elution mode.Results. The method developed for chromatographic determination of chlorine-containing ions can be used to quantify the content of hypochlorite, chloride, chlorite, chlorate, and perchlorate ions. In isocratic elution mode at 7.5 mM NaOH and a flow rate of 0.4 mL/min, the content of chlorine-containing ions can be determined with high sensitivity. The presented method does not require the use of expensive equipment for the ultrasensitive analysis of the studied compounds.Conclusions. A novel method for the simultaneous determination of hypochlorite, chloride, chlorite, chlorate, and perchlorate ions in case of their combined presence is proposed. The technique can be used to carry out routine control of the content of these disinfectant components during use, increasing their effectiveness at the same time as managing associated toxicological risks.
5
Gambardella, Mario, Santad Kongpricha, James J. Pitts e Albert W. Jache. "Disproportionation of chlorine in hydrogen fluoride and related media". Canadian Journal of Chemistry 67, n. 11 (1 novembre 1989): 1828–31. http://dx.doi.org/10.1139/v89-283.
Testo completoAbstract (sommario):
Chlorine can be made to disproportionate to chlorine monofluoride and chloride, taking advantage of Le Chatelier's principle in several different ways. It will disproportionate to form insoluble silver chloride and chlorine monofluoride when silver fluoride is present. It will disproportionate in a melt of alkali metal fluorides to form alkali metal chlorides and chlorine monofluoride. The alkali metal chlorides will react with hydrogen fluoride to regenerate the metal fluorides and hydrogen chloride. Chlorine will also disproportionate in hydrogen fluoride containing antimony pentafluoride to yield antimony pentafluoride adducts of chlorine monofluoride and of hydrogen chloride. These adducts are readily decomposed to yield the disproportionation products and the original antimony pentafluoride. Keywords: hydrogen fluoride, disproportionation, chlorine, waterlike, solvent system.
6
Xu, Cuisheng, Ningke Hao, Lei Zhan, Shiwei Wang, Shuangquan Yao, Shuangxi Nie e Shuangfei Wang. "High Purity Chlorine Dioxide Generation Based on the Mixed Reductant: From the Laboratory to Industry". Journal of Biobased Materials and Bioenergy 13, n. 4 (1 agosto 2019): 517–22. http://dx.doi.org/10.1166/jbmb.2019.1885.
Testo completoAbstract (sommario):
Methanol was used as reducing agent in the chlorine dioxide generation technology, and sodium chlorate was reduced to form chlorine dioxide under acidic conditions. The side reaction during the preparation process would produce chlorine, which results in a high content of chlorine in the product and leads to an increase in the amount of AOX formation during pulp bleaching. In this work, the chlorine dioxide generation technology based on the mixed reductant was developed. On the basis system based on the methanol method, a high-purity chlorine dioxide for pulp bleaching was successfully produced using a vertical generator by adding a mixed reducing agent that contain hydrogen peroxide and sodium chloride. This invention can not only solve the problems of low conversion rate of sodium chlorate and high content of chlorine in the traditional methanol reduction method, but also reduces the production cost. The chlorine content in the chlorine dioxide solution is reduced to less than 0.2 g/L.
7
Moore, Nathan, Shelir Ebrahimi, Yanping Zhu, Chengjin Wang, Ron Hofmann e Susan Andrews. "A comparison of sodium sulfite, ammonium chloride, and ascorbic acid for quenching chlorine prior to disinfection byproduct analysis". Water Supply 21, n. 5 (2 marzo 2021): 2313–23. http://dx.doi.org/10.2166/ws.2021.059.
Testo completoAbstract (sommario):
Abstract This study compared 3 commonly used quenching agents for dechlorinating samples prior to disinfection byproduct (DBP) analysis under typical drinking water sampling conditions for a representative suite of chlorination byproducts. Ascorbic acid and sodium sulfite quenched the residual free chlorine to below detection within 5 seconds. Ammonium chloride did not quench the chlorine to below detection with up to a 70% molar excess, which agrees with published ammonium chloride-chlorine chemistry. With respect to the DBPs, ascorbic acid worked well for the trihalomethanes and haloacetic acids, except for dibromoiodomethane, which exhibited 2.6–28% error when using ascorbic acid compared to non-quenched control samples. Sodium sulfite also worked well for the trihalomethanes (and performed similarly to ascorbic acid for dibromoiodomethane) and was the best performing quenching agent for MX and the inorganic DBPs, but contributed to the decay of several emerging DBPs, including several halonitromethanes and haloacetamides. Ammonium chloride led to considerable errors for many DBPs, including 27–31% errors in chloroform concentrations after 24 hours of storage. This work shows that ascorbic acid is suitable for many of the organic DBPs analyzed by gas chromatography-electron capture detection and that sodium sulfite may be used for simultaneous chlorite, chlorate, and bromate analysis.
8
Wu, Ming Song, Xun Xu, Xin Yang Xu, Shu Juan Chen, Zi Wei Huang, Deng Biao e Ya Jie Hu. "High-Purity Chlorine Dioxide Generation Process from Sodium Chlorate by Using Waste Molasses". Advanced Materials Research 955-959 (giugno 2014): 3924–27. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.3924.
Testo completoAbstract (sommario):
A new chlorate-based chlorine dioxide generation process was developed by using waste molasses as reductant in the presence of sulfuric acid catalyst. The optimum technological condition was determined as 80 oC, 50% sulfuric acid, molasses and sodium chlorite weight ratio of 1:4. The best conversion rate and purity of chlorine dioxide was 73.8% and 95.1%, respectively. Chlorite was found in the reacting mixtures, and major reactions of in process were inferred. The results obtained provides a new way for waste molasses comprehensive utilization and chlorine dioxide generation.
9
Monteiro, Mayra K. S., Ángela Moratalla, Cristina Sáez, Elisama V. Dos Santos e Manuel A. Rodrigo. "Production of Chlorine Dioxide Using Hydrogen Peroxide and Chlorates". Catalysts 11, n. 12 (2 dicembre 2021): 1478. http://dx.doi.org/10.3390/catal11121478.
Testo completoAbstract (sommario):
Chlorine dioxide was produced by the reduction of chlorate with hydrogen peroxide in strongly acidic media. To avoid reaction interference during measuring procedures, UV spectra were acquired to monitor the chlorate reduction. This reduction led to the formation of chlorine dioxide and notable concentrations of chlorite and hypochlorous acid/chlorine, suggesting that the hydrogen peroxide:chlorate ratio is important. Once chlorates are transformed to chlorine dioxide, the surplus hydrogen peroxide promoted the further reaction of the chlorinated species down to less-important species. Moreover, chlorine dioxide was stripped with the outlet gas flow. A linear relationship was established between the amount of limiting reagent consumed and the maximum height of the absorption peak at 360 nm after testing with different ratios of hydrogen peroxide and chlorate, allowing calculations of the maximum amount of chlorine dioxide formed. To verify the reproducibility of the method, a test with four replicates was conducted in a hydrogen peroxide/chlorate solution where chlorine dioxide reduction was not promoted due to the presence of surplus chlorate in the reaction medium after the test. Results confirmed the efficient formation of this oxidant, with maximum concentrations of 8.0 ± 0.33 mmol L−1 in 400–450 min and a conversion percentage of 97.6%. Standard deviations of 0.14–0.49 mmol L−1 were obtained during oxidation (3.6–6.5% of the average), indicating good reproducibility.
10
Mikkelsen, Marie K., Jesper B. Liisberg, Maarten M. J. W. van Herpen, Kurt V. Mikkelsen e Matthew S. Johnson. "Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols: a combined experimental, quantum chemical, and chemical equilibrium model study". Aerosol Research 2, n. 1 (19 marzo 2024): 31–47. http://dx.doi.org/10.5194/ar-2-31-2024.
Testo completoAbstract (sommario):
Abstract. Prior aerosol chamber experiments show that the ligand-to-metal charge transfer absorption in iron(III) chlorides can lead to the production of chlorine (Cl2/Cl). Based on this mechanism, the photocatalytic oxidation of chloride (Cl−) in mineral dust–sea spray aerosols was recently shown to be the largest source of chlorine over the North Atlantic. However, there has not been a detailed analysis of the mechanism that includes the aqueous formation equilibria and the absorption spectra of the iron chlorides nor has there been an analysis of which iron chloride is the main chromophore. Here we present the results of experiments measuring the photolysis of FeCl3 ⋅ 6H2O in specific wavelength bands, an analysis of the absorption spectra of FeCln3-n (n=1 … 4) made using density functional theory, and the results of an aqueous-phase model that predicts the abundance of the iron chlorides with changes in pH and iron concentrations. Transition state analysis is used to determine the energy thresholds of the dissociations of the species. Based on a speciation model with conditions extending from dilute water droplets and acidic seawater droplets to brine and salty crust, as well as the absorption rates and dissociation thresholds, we find that FeCl2+ is the most important species for chlorine production for a wide range of conditions. The mechanism was found to be active in the range of 400 to 530 nm, with a maximum around 440 nm. We conclude that iron chlorides will form in atmospheric aerosols from the combination of iron(III) cations with chloride and that they will be activated by sunlight, generating chlorine (Cl2/Cl) from chloride (Cl−) in a process that is catalytic in both chlorine and iron.
11
Chandrasekara Pillai, K., Tae Ok Kwon, Bo Bae Park e Il Shik Moon. "Using RuO2 anode for chlorine dioxide production in an un-divided electrochemical cell". Water Science and Technology 61, n. 8 (1 aprile 2010): 2151–60. http://dx.doi.org/10.2166/wst.2010.131.
Testo completoAbstract (sommario):
Chlorine dioxide is a well known powerful disinfectant. Although there are several chemical and electrochemical methods developed for on-line chlorine dioxide generation, the details are mostly confined as patents. We studied in this work the electrochemical generation of dissolved chlorine dioxide from an un-buffered solution of sodium chlorite and sodium chloride mixture in an un-divided electrochemical cell set-up with RuO2-coated-Ti anode and Pt-coated-Ti cathode under constant current mode. Various process parameters including feed flow rate (10 to 150 ml/min), feed solution pH (2.3 to 9.4), concentration of sodium chloride (0 to 170 mM), concentration of sodium chlorite (0 to 7.7 mM), and the applied current (100 to 1,200 mA) were optimized. Experiments were conducted by performing single pass experiments, with no circulation. The current efficiency and the power consumption were calculated for the optimized conditions, and compared with IrO2 electrode of our previous investigation.
12
Li, Xue, Zhijing Zhao, Zheng Qu, Xinyu Li, Zengli Zhang, Xiaojun Liang, Jingsi Chen e Jiafu Li. "A Review of Traditional and Emerging Residual Chlorine Quenchers on Disinfection By-Products: Impact and Mechanisms". Toxics 11, n. 5 (26 aprile 2023): 410. http://dx.doi.org/10.3390/toxics11050410.
Testo completoAbstract (sommario):
Disinfection by-products (DBPs) are the most common organic contaminants in tap water and are of wide concern because of their highly developmental toxic, cytotoxic, and carcinogenic properties. Typically, to control the proliferation of pathogenic microorganisms, a certain concentration of residual chlorine is retained in the factory water, which reacts with the natural organic matter and the disinfection by-products that have been formed, thus affecting the determination of DBPs. Therefore, to obtain an accurate concentration, residual chlorine in tap water needs to be quenched prior to treatment. Currently, the most commonly used quenching agents are ascorbic acid, sodium thiosulfate, ammonium chloride, sodium sulfite, and sodium arsenite, but these quenching agents can cause varying degrees of DBPs degradation. Therefore, in recent years, researchers have attempted to find emerging chlorine quenchers. However, no studies have been conducted to systematically review the effects of traditional quenchers and new ones on DBPs, as well as their advantages, disadvantages, and scope of application. For inorganic DBPs (bromate, chlorate, and chlorite), sodium sulfite has been proven to be the ideal chlorine quencher. For organic DBPs, although ascorbic acid caused the degradation of some DBPs, it remains the ideal quenching agent for most known DBPs. Among the studied emerging chlorine quenchers, n-acetylcysteine (NAC), glutathione (GSH), and 1,3,5-trimethoxybenzene are promising for their application as the ideal chlorine quencher of organic DBPs. The dehalogenation of trichloronitromethane, trichloroacetonitrile, trichloroacetamide, and bromochlorophenol by sodium sulfite is caused by nucleophilic substitution reaction. This paper takes the understanding of DBPs and traditional and emerging chlorine quenchers as a starting point to comprehensively summarize their effects on different types of DBPs, and to provide assistance in understanding and selecting the most suitable residual chlorine quenchers during DBPs research.
13
Marchesi, Isabella, Greta Ferranti, Annalisa Bargellini, Patrizia Marchegiano, Guerrino Predieri, Janet E. Stout e Paola Borella. "Monochloramine and chlorine dioxide for controlling Legionella pneumophila contamination: biocide levels and disinfection by-product formation in hospital water networks". Journal of Water and Health 11, n. 4 (2 settembre 2013): 738–47. http://dx.doi.org/10.2166/wh.2013.079.
Testo completoAbstract (sommario):
Legionella colonization in hospital hot water distribution networks was evaluated following 36 months of continuous treatment with monochloramine and compared with chlorine dioxide. Nitrite, nitrate, chlorite, chlorate, bromide, trihalomethanes and haloacetic acids as well as the biocide concentration at sampled points were measured. Only 8/84 samples treated with monochloramine were found contaminated and after the first 8 months of treatment no Legionella was isolated. Chlorine dioxide was associated with a strong reduction in Legionella contamination compared to pre-treatment, but differences according to the device were observed. Monochloramine between 2 and 3 mg l−1 and chlorine dioxide between 0.50 and 0.70 mg l−1 were needed to control Legionella colonization. Comparing no- and post-flush samples, a higher frequency of no-flush positive samples was noted using chlorine dioxide, suggesting an increased risk for patients when they open the tap. No increase in chlorite levels and no water nitrification occurred by using monochloramine. Chlorite at levels exceeding the limit requested for drinking water was measured when chlorine dioxide was applied. In conclusion, we highlight that continuous injection of monochloramine should be considered as an effective alternative to chlorine dioxide in controlling legionellae contamination inside hospital water distribution systems.
14
Hicks, Scott D., Silei Xiong, Curt J. Bougher, Grigori A. Medvedev, James Caruthers e Mahdi M. Abu-Omar. "Mechanistic study of a manganese porphyrin catalyst for on-demand production of chlorine dioxide in water". Journal of Porphyrins and Phthalocyanines 19, n. 01-03 (gennaio 2015): 492–99. http://dx.doi.org/10.1142/s1088424615500376.
Testo completoAbstract (sommario):
A water-soluble manganese porphyrin complex was examined for the catalytic formation of chlorine dioxide from chlorite under ambient temperature at pH 5.00 and 6.90. Quantitative kinetic modeling allowed for the deduction of a mechanism that accounts for all experimental observations. Catalysis is initiated via an OAT (Oxygen Atom Transfer) reaction resulting in formation of a putative manganese(V) oxo species, which undergoes ET (Electron Transfer) with chlorite to form chlorine dioxide. As chlorine dioxide accumulates in solution, chlorite consumption slows down and ClO 2 reaches a maximum as the system reaches equilibrium. In phosphate buffer at pH 6.90, manganese(IV) oxo accumulates and its reaction with ClO 2 gives ClO 3-. However, at pH 5.00 acetate buffer proton coupled electron transfer (PCET) from chlorite to manganese(IV) oxo is fast and irreversible leading to chlorate formation only via the putative manganese(V) oxo species. These differences underscore how PCET rates affect reaction pathways and mechanism. The ClO 2 product can be collected from the aqueous reaction mixture via purging with an inert gas, allowing for the preparation of chlorine dioxide on-demand.
15
Krenzelok, Edward, e Rita Mrvos. "Chlorine/Chloramine". Journal of Toxicology: Clinical Toxicology 33, n. 4 (gennaio 1995): 355–57. http://dx.doi.org/10.3109/15563659509028922.
Testo completo
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Rodriguez, Rocio Aranda, Boniface Koudjonou, Brian Jay, Guy L. LeBel e Frank M. Benoit. "Disinfection By-Products (DBPs) in Drinking Water from Eight Systems Using Chlorine Dioxide". Water Quality Research Journal 43, n. 1 (1 febbraio 2008): 11–22. http://dx.doi.org/10.2166/wqrj.2008.003.
Testo completoAbstract (sommario):
Abstract A study was initiated to determine the presence of organic disinfection by-products (DBPs) in drinking water treated with chlorine dioxide (ClO2). One potential advantage for the use of ClO2 as a disinfectant is the reduced formation of organic DBPs. Generally, water treated with ClO2 produces chlorite and chlorate ions, but there is limited information regarding the presence of halogenated organic DBPs. Eight systems that use chlorine dioxide as part of the water disinfection process were investigated. All systems in this study applied chlorine as a primary or secondary disinfectant in addition to ClO2. To evaluate seasonal and spatial variations, water samples were collected during cold water (February to March 2003) and warm water (July to August 2003) months at five sites for each system: raw water (R, before treatment), treated water (T, after treatment but before distribution), and three points along the same distribution line (D1, D2, D3). Sampling and analysis were conducted according to established protocols. A suite of 27 organic DBPs including haloacetic acids (HAA), trihalomethanes (THM), haloacetonitriles (HAN), haloketones, haloacetaldehydes (HA), chloropicrin, and cyanogen chloride were examined. In addition, the concentration of oxyhalides (chlorite and chlorate ions) and auxiliary parameters were also determined. Chlorite was found in treated (T) and distributed (Dx) waters. The chlorite ion levels decreased along the distribution system (T > D1 > D2 > D3). At T sites, the levels ranged from 10 to 870 µg/L (winter), and from 300 to 1,600 µg/L (summer). Chlorite was not found in treated or distributed water in the one system that used ozone. Chlorate ion levels ranged from 20 to 310 µg/L (winter), and 80 to 318 µg/L (summer). Chlorate levels remained relatively constant throughout the distribution system. THM and eight HAA (HAA8) accounted for approximately 85% of the total DBPs (wt/wt) analyzed, followed by total HA (up to 7%) and HAN (3%). THM in distributed water were found at concentrations between 1.8 and 30.6 µg/L (winter), and 3.3 and 93.6 µg/L (summer). For HAA8, the levels ranged from 13 to 52 µg/L (winter), and 16 to 111 µg/L (summer). Chloral hydrate ranged from 0.2 to 5.2 µg/L (winter), and 0.4 to 12.2 µg/L (summer). The temporal and spatial variations observed in previous studies were confirmed in the current study as well.
17
Narkis, N., e A. Katz-Stoller. "Back to pre-disinfection of highly polluted waters". Water Supply 2, n. 3 (1 luglio 2002): 219–26. http://dx.doi.org/10.2166/ws.2002.0106.
Testo completoAbstract (sommario):
The initial pre-disinfection was one of the stages that most contributed to the formation of a large number of halogenated disinfection by-products (DBPs). The threat and awareness to the formation of chlorine disinfection by-products, refrained from using pre-disinfection with chlorine in the treatment of contaminated raw waters, to be used as drinking water. The main purpose of this research was to study whether chlorine dioxide can be used for pre-disinfection in the treatment of highly polluted wastewaters and surface waters. Chlorine dioxide was found suitable, as a replacement for chlorine, for disinfection of water containing natural organic substances, effluents’ organic materials and ammonium ions, due to its advantages, and especially because it is an effective disinfectant for killing pathogenic microorganisms and destroying viruses. Chlorine dioxide does not form THMs and barely creates chloroorganic compounds. However, the main disadvantage of the chlorine dioxide is the creation of undesirable chlorite and chlorate ions, which are suspected of being toxic. This research showed that the undesirable chlorite ions can be removed completely by adding Fe+2, which reduces ClO2- to the harmless Cl-, and is oxidized to Fe+3, to form the ferric polyhydroxo complexes, that can be used as the flocculant, in the next flocculation step, for the achievement of safer drinking water.
18
Borziak, O., V. Zhuravel e M. Hudymenko. "The influence of chloride ion diffusion on the structure of cement composites containing carbonate additives". IOP Conference Series: Earth and Environmental Science 1376, n. 1 (1 luglio 2024): 012023. http://dx.doi.org/10.1088/1755-1315/1376/1/012023.
Testo completoAbstract (sommario):
Abstract One way to reduce the diffusion of chlorides deep into concrete is to bind chlorine ions into stable hydration products. It is known that systems containing carbonates have an increased binding capacity towards chlorides. The goal of this work is to study the effect of carbonate additives on the depth of diffusion of chlorine ions in cement composites (mortars). As controls, samples of mortar were made using cement CEM I 42.5 R as binder. In the main samples, 15% of cement was replaced by carbonates - chalk and limestone. The strength characteristics of mortar samples kept in water and in a sodium chloride solution were studied. According to test data, it was established that the compressive strength of samples with the addition of chalk or limestone practically does not change under the influence of a chloride solution. The compressive strength of samples without additives in the salt solution decreased by 8%. The depth of diffusion of chlorine ions deep into cement composites was also studied. It has been established that replacing part of the binder with carbonate additives does not reduce the permeability of porous cement composites for chloride ions.
19
Ferchichi, Olfa, Najoua Derbel, Thibaud Cours e Alexander Alijah. "Dichlorine peroxide (ClOOCl), chloryl chloride (ClCl(O)O) and chlorine chlorite (ClOClO): very accurate ab initio structures and actinic degradation". Physical Chemistry Chemical Physics 22, n. 7 (2020): 4059–71. http://dx.doi.org/10.1039/c9cp06875a.
Testo completoAbstract (sommario):
The structural parameters of the three most stable isomers with formula Cl2O2, dichlorine peroxide, chloryl chloride and chlorine chlorite, were determined by high-level ab initio theory. The photodissociation pathways were investigated.
20
Moratalla, Ángela, Mayra K. S. Monteiro, Cristina Sáez, Elisama V. Dos Santos e Manuel A. Rodrigo. "Full and Sustainable Electrochemical Production of Chlorine Dioxide". Catalysts 12, n. 3 (9 marzo 2022): 315. http://dx.doi.org/10.3390/catal12030315.
Testo completoAbstract (sommario):
With the final purpose of manufacturing electrochemically-based devices that produce chloride dioxide efficiently, this paper focuses on the production of chlorates and hydrogen peroxide in two different electrochemical cells, in which operation conditions are selected to obtain high efficiencies, and in the subsequent combination of both electrochemically manufactured solutions to produce chlorine dioxide. Results demonstrate that suitable reagents can be produced by electrolyzing 20 g L−1 sodium chloride solutions at 50 mA cm−2 and 50 °C, and 3000 mg L−1 NaClO4 solutions at 5.0 mA cm−2 and 15 °C with current efficiencies of 30.9% and 48.0%, respectively. Different tests performed with these electrolyzed solutions, and also with commercial hydrogen peroxide and chlorate solutions, demonstrate that the ratio between both reagents plays a very important role in the efficiency in the production of chlorine dioxide. Results clearly showed that, surplus chlorate should be contained in the reagent media to prevent further reduction of chlorine dioxide by hydrogen peroxide and consequently, loses of efficiency in the process. During the reaction, a gas with a high oxidation capacity and consisting mainly in chloride dioxide is produced. The results contributed to the maximum conversion reached being 89.65% using electrolyzed solutions as precursors of ClO2, confirming that this technology can be promising to manufacture portable ClO2 devices.
21
Mitrofanova, S. A., e I. V. Murav’eva. "Determination of chlorine in dusty waste in ferronickel production: Analysis and estimation of uncertainty". Izvestiya. Ferrous Metallurgy 65, n. 9 (2 ottobre 2022): 629–36. http://dx.doi.org/10.17073/0368-0797-2022-9-629-636.
Testo completoAbstract (sommario):
A key stage in ferronickel production is sulfate-chlorination roasting, after which and at subsequent stages (up to the final product) exhaust gases are formed in the system accompanied by dust and metal chloride vapors outlet in roasting furnace. Enrichment of wastes during their removal with condensed chlorides indicates a decrease in the efficiency of sulfate-chlorination roasting. Therefore, the control of mineral chlorine in filter sediments is important both from the standpoint of environmental monitoring and evaluation of the technological process efficiency. In order to determine mineral chlorine in dusty waste during the ferronickel production, a quantitative chemical analysis procedure based on the ionometric method was developed in the testing laboratory of the South Ural Nickel Plant. This paper proposes a procedure for estimating the results uncertainty in determining chlorine in the sample. It consists of the following steps: compiling a mathematical model to determine the chloride-ion mass fraction, estimating the input quantities in the mathematical model and their uncertainties, estimating the output quantities in the mathematical model and their uncertainties, budgeting for uncertainty, determining the expanded uncertainty and presenting the results. The paper considers the results of calculating the total expanded uncertainty in determining the chloride-ion mass fraction – U(XCl – ) = ±9.4 % (kp = 2, P = 95 %) – for the samples with chlorine mass fraction from 0.4 to 0.8 %. Application of the proposed methodology in calculating uncertainty ensures reliable results in determining chlorine in dusty wastes of ferronickel production, which has a positive effect on the technological process and environmental monitoring efficiency.
22
Tang, Honghu, Lihua Zhao, Yue Yang, Haisheng Han, Li Wang e Wei Sun. "Dissolution Kinetics of Chlorine from Iron Ore Sintering Dust". Metals 11, n. 8 (26 luglio 2021): 1185. http://dx.doi.org/10.3390/met11081185.
Testo completoAbstract (sommario):
Chlorine is generated during iron ore sintering, mostly in the form of alkali chlorides and primarily accumulates in sintering dust, which must be removed before reusing. In this study, an in-situ monitor leaching system based was designed to detect chloride ion water leaching behaviors in real-time and improve the understanding of chlorine dissolution kinetic behaviors in water. Various parameters, including water leaching temperature, solid/liquid ratio, stirring speed, particle size and surfactant addition have been studied. Meanwhile their chlorine dissolution data exhibited a good fit to Stumm’s kinetic models. The results of kinetics analysis and transition state theory calculation on apparent activation energy demonstrated that the dissolution process was controlled by diffusion at low S/L ratio, while changed to be controlled by surface chemical reaction as the S/L ratio increased. Furthermore, increasing both temperature and stirring speed improved the chlorine removal speed. Moreover, reducing the particle size and adding 0.2% nonionic surfactant Triton X-100 reduced the surface energy and accelerated surface chemical reaction, which were also beneficial for removing chlorine from sintering dust. In addition, the SEM-EDS examination inferred that the existence of laurionite (PbOHCl) limited the chlorine dissolution rate to less than 97%, while beneficiation or hydrometallurgy treatment was needed to further remove chlorine.
23
Fosu, Allen Yushark, Bastien Demeusy, Frédéric Diot, Tiina Lavonen, Veronika Meriläinen, Danièle Bartier, Yann Foucaud e Ndue Kanari. "Selective Extraction of Valuable and Critical Metals in Cassiterite Concentrate by Dry Chlorination, Part I: Thermodynamic and Modelling Perspective". Materials 17, n. 17 (23 agosto 2024): 4186. http://dx.doi.org/10.3390/ma17174186.
Testo completoAbstract (sommario):
The chlorination of oxides of major concern in cassiterite concentrate with various chlorinating agents is investigated in light of their thermodynamic feasibilities to extract and recover their valuable metal components. Mechanisms responsible for the processes and their Gibbs free energy changes as a function of temperature to selectively separate and/or recover the metal(s) of interest and unwanted ones as their metallic chlorides are identified. Attention is given to gaseous (Cl2 and Cl2 + CO mixture) and solid (CaCl2 and MgCl2) chlorine sources, from which Cl2 + CO shows no reaction selectivity for any of the oxides but a feasible metal chloride formation for all. Chlorine gas (Cl2), on the other hand, could selectively form chlorides with metals of +2 oxidation state in their oxides, leaving those of high oxidation state unreacted. MgCl2, unlike CaCl2, is found capable of producing calcium, ferrous, and stannic chloride from their metallic oxides with enhanced reaction tendencies in the presence of silicon dioxide (SiO2). An overall study of the thermodynamic feasibility of all chlorine sources looked at alongside operational and environmental viabilities suitably suggests MgCl2 for a selective extraction of the valuable metal components in a cassiterite concentrate, in which case, moderate temperatures seem promising.
24
Coates, John D., Urania Michaelidou, Royce A. Bruce, Susan M. O’Connor, Jill N. Crespi e Laurie A. Achenbach. "Ubiquity and Diversity of Dissimilatory (Per)chlorate-Reducing Bacteria". Applied and Environmental Microbiology 65, n. 12 (1 dicembre 1999): 5234–41. http://dx.doi.org/10.1128/aem.65.12.5234-5241.1999.
Testo completoAbstract (sommario):
ABSTRACT Environmental contamination with compounds containing oxyanions of chlorine, such as perchlorate or chlorate [(per)chlorate] or chlorine dioxide, has been a constantly growing problem over the last 100 years. Although the fact that microbes reduce these compounds has been recognized for more than 50 years, only six organisms which can obtain energy for growth by this metabolic process have been described. As part of a study to investigate the diversity and ubiquity of microorganisms involved in the microbial reduction of (per)chlorate, we enumerated the (per)chlorate-reducing bacteria (ClRB) in very diverse environments, including pristine and hydrocarbon-contaminated soils, aquatic sediments, paper mill waste sludges, and farm animal waste lagoons. In all of the environments tested, the acetate-oxidizing ClRB represented a significant population, whose size ranged from 2.31 × 103 to 2.4 × 106 cells per g of sample. In addition, we isolated 13 ClRB from these environments. All of these organisms could grow anaerobically by coupling complete oxidation of acetate to reduction of (per)chlorate. Chloride was the sole end product of this reductive metabolism. All of the isolates could also use oxygen as a sole electron acceptor, and most, but not all, could use nitrate. The alternative electron donors included simple volatile fatty acids, such as propionate, butyrate, or valerate, as well as simple organic acids, such as lactate or pyruvate. Oxidized-minus-reduced difference spectra of washed whole-cell suspensions of the isolates had absorbance maxima close to 425, 525, and 550 nm, which are characteristic of type c cytochromes. In addition, washed cell suspensions of all of the ClRB isolates could dismutate chlorite, an intermediate in the reductive metabolism of (per)chlorate, into chloride and molecular oxygen. Chlorite dismutation was a result of the activity of a single enzyme which in pure form had a specific activity of approximately 1,928 μmol of chlorite per mg of protein per min. Analyses of the 16S ribosomal DNA sequences of the organisms indicated that they all belonged to the alpha, beta, or gamma subclass of the Proteobacteria. Several were closely related to members of previously described genera that are not recognized for the ability to reduce (per)chlorate, such as the generaPseudomonas and Azospirllum. However, many were not closely related to any previously described organism and represented new genera within the Proteobacteria. The results of this study significantly increase the limited number of microbial isolates that are known to be capable of dissimilatory (per)chlorate reduction and demonstrate the hitherto unrecognized phylogenetic diversity and ubiquity of the microorganisms that exhibit this type of metabolism.
25
KAUR, SIMRAN, DAVID J. SMITH e MARK T. MORGAN. "Chloroxyanion Residue Quantification in Cantaloupes Treated with Chlorine Dioxide Gas". Journal of Food Protection 78, n. 9 (1 settembre 2015): 1708–18. http://dx.doi.org/10.4315/0362-028x.jfp-14-576.
Testo completoAbstract (sommario):
Previous studies show that treatment of cantaloupes with chlorine dioxide (ClO2) gas at 5 mg/liter for 10 min results in a significant reduction (P < 0.05) in initial microflora, an increase in shelf life without any alteration in color, and a 4.6- and 4.3-log reduction of Escherichia coli O157:H7 and Listeria monocytogenes, respectively. However, this treatment could result in the presence of chloroxyanion residues, such as chloride (Cl−), chlorite (ClO2−), chlorate (ClO3−), and perchlorate (ClO4−), which, apart from chloride, are a toxicity concern. Radiolabeled chlorine dioxide (36ClO2) gas was used to describe the identity and distribution of chloroxyanion residues in or on cantaloupe subsequent to fumigation with ClO2 gas at a mean concentration of 5.1 ± 0.7 mg/liter for 10 min. Each treated cantaloupe was separated into rind, flesh, and mixed (rind and flesh) sections, which were blended and centrifuged to give the corresponding sera fractions. Radioactivity detected, ratio of radioactivity to mass of chlorite in initial ClO2 gas generation reaction, and distribution of chloroxyanions in serum samples were used to calculate residue concentrations in flesh, rind, and mixed samples. Anions detected on the cantaloupe were Cl− (~90%) and ClO3− (~10%), located primarily in the rind (19.3 ± 8.0 μg of Cl−/g of rind and 4.8 ± 2.3 μg of ClO3−/g of rind, n = 6). Cantaloupe flesh (~200 g) directly exposed to 36ClO2 gas treatment showed the presence of only Cl− residues (8.1 ± 1.0 μg of Cl−/g of flesh, n = 3). Results indicate chloroxyanion residues Cl− and ClO3− are only present on the rind of whole cantaloupes treated with ClO2 gas. However during cutting, residues may be transferred to the fruit flesh. Because Cl− is not toxic, only ClO3− would be a toxicity concern, but the levels transferred from rind to flesh are very low. In the case of fruit flesh directly exposed to ClO2 gas, only nontoxic Cl− was detected. This indicates that ClO2 gas that comes into contact with edible flesh would not pose a health concern.
26
Kitaeva, D. Kh, A. G. Buyanovskaya, O. A. Levinskaya e S. L. Dzvonkovski. "Determination of low chlorine content in organic compounds and polymers using an «Expert-006» coulometer". Industrial laboratory. Diagnostics of materials 84, n. 7 (8 agosto 2018): 16–20. http://dx.doi.org/10.26896/1028-6861-2018-84-7-16-20.
Testo completoAbstract (sommario):
A method of visual mercurimetric titration of chloride ions is widely used in elemental microanalysis for determination of chlorine content in organic substances after their combustion in an oxygen-filled flask. However, when chlorine content is less than 0.5%, the mercurimetric method fails to provide essential accuracy, and a more sensitive method of chlorine coulometric titration by electrogenerated silver ions appeared favorable. We consider a possibility of determining the microgram content of chloride-ions in solutions using a digital coulometric analyzer («Expert-006» produced by «Econics-Expert» (Moscow)) supplemented with an electrolytic cell with silver electrodes. The coulometer was tested in different operation modes to select the optimal electrochemical parameters of ion chloride titration and develop a technique for coulometric determination of chloride ions which in combination with the preliminary burning of the analyzed substances in an oxygen-filled flask provides determination of the residual chlorine in organic matrices at a level of 0.1 – 0.5%. The proposed technique was used to determine the residual chlorine in a number of polymers. The relative error did not exceed 5% at chlorine concentrations of 0.16 – 0.28%.
27
Gao, Weiwei, Thomas A. Baker, Ling Zhou, Dilini S. Pinnaduwage, Efthimios Kaxiras e Cynthia M. Friend. "Chlorine Adsorption on Au(111): Chlorine Overlayer or Surface Chloride?" Journal of the American Chemical Society 130, n. 11 (marzo 2008): 3560–65. http://dx.doi.org/10.1021/ja077989a.
Testo completo
28
Chowdhury, Shakhawat, e Pascale Champagne. "Selecting Water Disinfection Processes using Fuzzy Synthetic Evaluation Technique". Water Quality Research Journal 43, n. 1 (1 febbraio 2008): 1–10. http://dx.doi.org/10.2166/wqrj.2008.002.
Testo completoAbstract (sommario):
Abstract Drinking water treatment strategies generally involve treatment processes such as screening, coagulation/flocculation, sedimentation, and filtration/adsorption followed by disinfection. Disinfection approaches include chlorine/chlorine (chloramine), granular activated carbon with post chlorine (chloramine), ozone/chlorine (chloramine), chlorine dioxide/ chlorine (chloramine), chloramine/chloramine, and ultraviolet radiation/chlorine (chloramine). However, comparative evaluation of these disinfection methodologies and their application to a particular source of water is rare. In this study, a framework for multicriteria decision making has been developed. Human health risk, cost, technical feasibility, and disinfection performance have been incorporated as the criteria for evaluation of the disinfection approach. A fuzzy synthetic evaluation technique has been incorporated where fuzzy triangular membership functions were developed to capture the uncertainties of the basic attributes. This paper compares three disinfection approaches: chlorination, granular activated carbon with post chlorination, and chloramination through a multistage hierarchy risk management model in which the analytical hierarchy process has been used to determine the relative importance of various attributes at different hierarchy levels. The evaluation process was found to be sensitive to the assignment of relative importance of the attributes. Chlorination was evaluated as the best disinfection approach in most of the cases.
29
Schwan, A. M., R. Martin e W. Goessler. "Chlorine speciation analysis in blood by ion chromatography-inductively coupled plasma mass spectrometry". Analytical Methods 7, n. 21 (2015): 9198–205. http://dx.doi.org/10.1039/c5ay02426a.
Testo completoAbstract (sommario):
The present work describes the development of a robust method for the determination of traces of the anionic chlorine species chlorite and chlorate in blood matrices (estimated detection limits ∼0.5–1.0 mg Cl L−1) by ion chromatography coupled to inductively coupled plasma mass spectrometry.
30
Novoselova, Alena, Vladimir Shishkin e Vladimir Khokhlov. "Redox Potentials of Samarium and Europium in Molten Lithium Chloride". Zeitschrift für Naturforschung A 56, n. 11 (1 novembre 2001): 754–56. http://dx.doi.org/10.1515/zna-2001-1110.
Testo completoAbstract (sommario):
Abstract The samarium (III)/(II) and europium (III)/(II) redox potentials in molten lithium chloride were measured using the direct potentiometric method in the temperature range from 923 to 1094 K. Glassy carbon was used as the indifferent working electrode, and the standard chlorine electrode as a reference. The total concentration of rare-earth chlorides dissolved in molten lithium chloride did not exceed 4.5 mol%.
31
Rav-Acha, Ch, A. Serri, E. (Goldstein) Choshen e B. Limoni. "Disinfection of Drinking Water Rich in Bromide with Chlorine and Chlorine Dioxide, While Minimizing the Formation of Undesirable By-Products". Water Science and Technology 17, n. 4-5 (1 aprile 1985): 611–21. http://dx.doi.org/10.2166/wst.1985.0164.
Testo completoAbstract (sommario):
Although chlorine dioxide does not form trihalomethanes (THM) and produces very few non-volatile haloorganic materials in drinking water, intensive investigations bearing on the formation of chlorite by ClO2 disinfection reveal that the rate of chlorite formation reflects the rate of ClO2 consumption and as long as the amount of ClO2 applied is behind its demand, about 60% of the chlorine dioxide consumed is converted into chlorite. Mixtures of Cl2 and ClO2, which may successfully reduce the formation of haloorganic compounds, as well as of chlorite in the absence of bromide, fail to do this where water rich in bromide is concerned. As a result of bromide oxidation by chlorine, bromine is formed, which in turn reacts more intensively with organics than does chlorine and thus favours the formation of THM and other halogenated organic materials. This problem can, however, be circumvented if ClO2 is allowed to react in water with the organic precursors before chlorine is introduced. A pre-treatment with 1 ppm of ClO2 two hours before the application of 2 ppm Cl2, was found to reduce the formation of THM by 60% relative to its formation by chlorine alone, and the chlorite is reduced in this case by up to 90% relative to its formation by chlorine dioxide alone. This is of particular importance since it can solve some of the major problems bearing on the impact of disinfection upon the formation of undesirable by-products.
32
Diyamandoglu, V. "Nitrate and chloride formation in chloramination". Water Science and Technology 30, n. 9 (1 novembre 1994): 101–10. http://dx.doi.org/10.2166/wst.1994.0453.
Testo completoAbstract (sommario):
The formation of nitrate and chloride as end-products of chloramination (combined chlorination) was investigated at pH ranging between 6.9 and 9.6 at 25°C. The experimental results comprised concentration-time profiles of combined chlorine residuals along with nitrate and chloride. Nitrite, if present, was always below the detectibility limit of the analytical method used (25 ppb). Mass balances on chlorine species depicted that chloride formed during the slow decay of combined chlorine residuals does not account for all the chlorine lost. This substantiates the formation of other reaction end-products which are yet to be identified. A kinetic model for chloramination is proposed based on the kinetic data obtained in this study.
33
Shin, H. S. "Simultaneous reduction of by-products of chlorine dioxide and chlorine using Fe(II)–Al(III) coagulant mixture". Water Supply 11, n. 3 (1 luglio 2011): 318–23. http://dx.doi.org/10.2166/ws.2011.054.
Testo completoAbstract (sommario):
Ferrous iron has been considered very useful for removal of chlorite, a by-product of chlorine dioxide. However, a serious problem can occur associated with high residual iron concentrations in water after Fe(II) treatment, especially at weak acidic condition (pH 6), having a higher capacity of chlorite reduction. Simultaneous removal of chlorite, dissolved iron, and humic acids was achieved with a Fe(II) –Al(III) (1:5) coagulant mixture. Moreover, a significant reduction of chlorine by-products formed after subsequent post chlorination was observed. The by-products of chlorine dioxide and chlorine could be dramatically reduced by the simple addition of the coagulant mixture without the additional problem of dissolved iron.
34
Guo, Qianjun, Zaili Zhang, Zhengbo Ma, Yongmei Liang e Wei Liu. "Fluorescence characteristics of natural organic matter in water under sequential exposure to UV irradiation/chlor(am)ination". Water Supply 14, n. 1 (12 settembre 2013): 22–30. http://dx.doi.org/10.2166/ws.2013.166.
Testo completoAbstract (sommario):
The organic matter in International Humic Substances Society Natural Organic Matter (IHSS NOM) water exposed to ultraviolet (UV) irradiation and chlor(am)ine sequentially under practically relevant conditions was characterized based on fluorescence spectra. IHSS NOM water exposed to UV irradiation or chlor(am)ine alone was also evaluated. Both chlor(am)ine alone and UV/chlor(am)ine exposure showed similar chlor(am)ine demand and fluorescence spectra. UV irradiation and UV/chlorine exposure diminished the fluorescence intensity of IHSS NOM water, while UV/chloramine exposure resulted in increased fluorescence intensity. When compared with the results obtained following chlor(am)ination alone, IHSS NOM water showed decreased chlorine decay and increased chloramine decay after UV irradiation/chlor(am)ination. Additionally, IHSS NOM water exposed to UV/chloramine and chloramine showed less disinfection by-product (DBP) formation than water subjected to UV/chlorine and chlorine. Overall, these findings indicate that UV irradiation degrades NOM molecules to low-molecular-weight fractions, facilitating the subsequent reaction with chlor-(am)ine. However, chlorine and chloramine play different roles in the reaction. Chlorine degradation and substitution dominates the process of UV/chlorine exposure, while chloramine substitution is the major reaction during UV/chloramine exposure.
35
Gao, Kangning, Jie Lu, Xi Wang, Dengxin Li e Shihong Xu. "Effect of cations on the removal rate of chloride ions and mechanism analysis in high-salt wastewater". Water Science and Technology 83, n. 9 (17 marzo 2021): 2232–41. http://dx.doi.org/10.2166/wst.2021.098.
Testo completoAbstract (sommario):
Abstract Precipitation dechlorination has the advantage of being a simple process with a low cost. However, there are few reports on the effect of cations on dechlorination. In this study, we investigated the effect of cations in high-salt wastewater on the removal of chlorine ions by cuprous chloride precipitation and analysed the corresponding mechanism. A series of investigations revealed that Fe3+ could oxidise sulphite, thereby reducing the removal rate of chlorine ions. The reaction between magnesium and sulphite results in precipitation, which has a slightly adverse effect on the removal of chloride ions. Hexavalent chromium oxidises the chloride ion, resulting in the formation of chlorine gas, which improves the removal rate. Ferrous and manganese, however, do not have a notable effect on chlorine removal.
36
Qiu, Yinan, Yan Yang, Na Yang, Lige Tong, Shaowu Yin, Lang Yu e Li Wang. "Corrosion of Iron Covered with Iron Oxide Film by Chlorine and Hydrogen Chloride Gases: A Molecular Dynamics Simulation Study Using the ReaxFF". Energies 15, n. 12 (9 giugno 2022): 4237. http://dx.doi.org/10.3390/en15124237.
Testo completoAbstract (sommario):
Flue gas produced by biomass fuel combustion contains various chlorine-containing substances and is an important factor causing biomass boiler corrosion. The corrosion processes of chlorine, hydrogen chloride and water on iron covered with an intact/damaged oxide film were investigated under the high temperature of 1300 K through reactive molecular dynamics simulation. The results show that the diffusion processes of oxygen and chlorine are similar and can be divided into three stages: rapid diffusion, continuous diffusion, and no oxide film (stable). Oxygen diffusion in Fe2O3 into a pure iron layer is the main cause of gas corrosion in iron/iron oxide systems. A complete oxide film can hinder iron corrosion by chlorine and hydrogen chloride. Damage in an oxide film significantly affects oxygen and chlorine diffusion and iron corrosion. However, such influence is gradually reduced. The integrity of a protective film is the key to alleviating corrosion. Water facilitates the dissociation of chlorine and hydrogen chloride, and it reacts with iron at high temperatures to enhance corrosion. This study improves the understanding of the iron oxide/iron corrosion from chlorine-containing gases from a microscopic perspective and is of great significance to metal corrosion protection and biomass combustion technologies.
37
Janků, Josef, Jiří Burkhard e Luděk Vodička. "Reaction of adamantanone, diamantanone, and their derivatives with thionyl chloride". Collection of Czechoslovak Chemical Communications 52, n. 8 (1987): 2028–34. http://dx.doi.org/10.1135/cccc19872028.
Testo completoAbstract (sommario):
In reaction of adamantanone, diamantanone, and their chloro or oxo derivatives with thionyl chloride the oxo group is replaced with two chlorine atoms under formation of geminal dichloro derivatives. The presence of a chlorine atom or an oxo group in both ketones reduces the reaction rate. The reaction rate decreases with decreasing distance between the substituent and the carbonyl group. Ketones with chlorine atom in α- or β-axial position do not react with thionyl chloride. The reaction is accelerated by hydrogen chloride whereas in the presence of pyridine no reaction was observed.
38
Wiesenthal, K. E., M. J. McGuire e I. H. Suffet. "Characteristics of salt taste and free chlorine or chloramine in drinking water". Water Science and Technology 55, n. 5 (1 marzo 2007): 293–300. http://dx.doi.org/10.2166/wst.2007.191.
Testo completoAbstract (sommario):
Abstract Salty taste with or without chlorine or chloramine flavour is one of the major consumer complaints to water utilities. The flavour profile analysis (FPA) taste panel method determined the average taste threshold concentration for salt (NaCl) in Milli-Q water to be 640±3 mg/L at pH 8. Chlorine and chloramine disinfectants have no antagonistic or synergistic effects on the taste of NaCl, salt, in Milli-Q water. The flavour threshold concentrations for chlorine or chloramine in Milli-Q water alone or in the presence of NaCl could not be estimated by the Weber-Fechner curves due to the chlorine or chloramine flavour outliers in the 0.2–0.8 mg/L concentration range. Apparently, NaCl is not equilibrated with the concentration of ions in the saliva in the mouth and the concentration of free chlorine or chloramines cannot be tasted correctly. Therefore, dechlorinated tap water may be the best background water to use for a particular drinking water evaluation of chlorine and chloramine thresholds. Laboratory FPA studies of free chlorine found that a 67% dilution of Central Arizona Project (CAP) (Tucson, AZ) water with Milli-Q water was required to reduce the free chlorine flavour to a threshold value instead of a theoretical value of 80% (Krasner and Barrett, 1980). No synergistic effect was found for chlorine flavour on the dilution of CAP water with Milli-Q water. When Central Avra Valley (AVRA) groundwater was used for the dilution of CAP water, a synergistic effect of the TDS present was observed for the chlorine flavour. Apparently, the actual mineral content of drinking water, and not just NaCl in Milli-Q water, is needed for comparative flavour tests for chlorine and chloramines.
39
Zhuravel, Vitalii, Teresa Rucińska e Olga Borziak. "Investigation of the Diffusion of Chloride Ions in Blended Cement Pastes". ce/papers 6, n. 6 (dicembre 2023): 1265–68. http://dx.doi.org/10.1002/cepa.2970.
Testo completoAbstract (sommario):
AbstractWhen exposed to aggressive environments containing chlorides, the chlorine ion partially binds to the usual Portland cement mortar and changes its mineralogy. Chlorine ions entering the system displace sulfate from the monosulfoaluminate. Such systems form Kusel's salt at low chloride concentrations and Friedel's salt at higher concentrations. Unbound chloride ions remain dangerous for reinforcing steel, which diffuse deep into the concrete and destroy the passivating layer on the reinforcement. To assess the protective properties of concrete in relation to metal reinforcement, it is proposed to investigate the process of displacement of the diffusion front in cement composites of various compositions. It is also important to study changes in such characteristics as porosity and filtration properties, which significantly affect the penetration depth of an aggressive medium. The study of the structure, mineral and chemical composition is carried out in layers.
40
Miles, Jeffrey, Laurent Mossé e Jim Grau. "Formation Chlorine Measurement From Spectroscopy Enables Water Salinity Interpretation: Theory, Modeling, and Applications". Petrophysics – The SPWLA Journal of Formation Evaluation and Reservoir Description 61, n. 6 (1 dicembre 2020): 549–69. http://dx.doi.org/10.30632/pjv61n6-2020a2.
Testo completoAbstract (sommario):
Many methods of calculating water saturation require knowing the chloride concentration in formation water. Chlorides have a strong effect on water properties, and they impact saturation estimates that are based on resistivity, dielectric dispersion, or thermal neutron absorption. Here we introduce a new direct quantitative measurement of formation chlorine from nuclear spectroscopy, enabling a continuous log of water salinity within a limited radial depth. Neutron capture spectroscopy is sensitive to chlorine and is a natural fit for measuring its concentration, except that the spectrum contains chlorine from both the formation and borehole. The borehole chlorine background can be large and is highly variable. Historical efforts to derive water salinity from spectroscopy have relied on ratios of chlorine and hydrogen, which are affected by the borehole and hydrocarbons. The direct use of chlorine provides a more reliable basis for salinity interpretation after isolating its formation signal. We partition the borehole and formation components of chlorine via two unique spectral standards. The contrast between the two standards arises from differences in gamma ray scattering based on their point of origin. The shape of the borehole chlorine standard must be adjusted along depth to account for environmentally dependent scattering, which we achieve with a continuously varying function of borehole and formation properties. The algorithm is derived from 129 laboratory measurements and 2,995 numerical simulations spanning a diverse range of conditions. The remaining signal is converted into a log of formation chlorine concentration. In combination with total porosity, chlorine concentration sets a minimum value for water salinity. Adding an organic carbon measurement enables the simultaneous estimation of water volume and salinity. Chlorine concentration can also be combined with a selected water salinity to compute a water volume for comparison with other methods. Finally, chlorine concentration enables calculation of a maximum expected sigma, which can identify the presence of excess thermal absorbers in the matrix. The systematic uncertainty on the chlorine concentration ranges from 0.03 to 0.07 wt%, depending on borehole size. The resulting salinity accuracy is inversely proportional to porosity. A potential limitation of the measurement is its depth of investigation, reaching 8 to 10 in. for 90% of the signal. The chlorine concentration is sensitive to filtrate or connate water, depending on formation permeability and invading fluids. We first present the technique to measure formation chlorine, supported by modeling, laboratory data, and core-log comparisons. We then propose petrophysical workflows to interpret the chlorine concentration.
41
Gobinddass, M. L., J. Molinie, S. Richard, K. Panechou, A. Jeannot e S. Jean-Louis. "Coastal Sea Salt Chlorine Deposition Linked to Intertropical Convergence Zone (ITCZ) Oscillation in French Guiana". Journal of the Atmospheric Sciences 77, n. 5 (29 aprile 2020): 1723–31. http://dx.doi.org/10.1175/jas-d-19-0032.1.
Testo completoAbstract (sommario):
Abstract Sea salt chloride is a major component of atmospheric aerosol and its behavior is an essential element in determining the climate. Two atmospheric chlorine deposition measurement procedures were performed between 2004 and 2008 by the French Guiana Regional Air Observatory (ORA), in the coastal plain of Sinnamary. The main goal was to determine the background spatial distribution of marine chlorine in order to evaluate the impact of Ariane rocket hydrogen chloride emission. To determine the chlorine concentration level, weekly samples from 10 sites were analyzed. A seasonal pattern was identified. For every site, a high sea salt chlorine deposition level was observed from December to April and a low level from July to October. The ratio of high to low mean chloride concentration RHC/LC shows that just under half of the variation in chlorine deposition can be linked to the variation of sea salt production with low-level wind speed. Equations relating mean sea salt chlorine concentration and the distance to shore were studied, taking into account parameters found in other tropical regions, with a focus on neighboring Brazil. The wind rotation between the two seasons, and the sea salt chlorine loss per kilometer equation found for dry deposition, were used to calculate RHC/LC. It appears that the observed rotation (60°) explains 88% of RHC/LC. Finally, inland sea salt chlorine deposition behavior in this region was linked to intertropical convergence zone oscillation through variations in wind speed and direction.
42
Srinivasan, Arjun, Gregory Bova, Tracy Ross, Karen Mackie, Nicholas Paquette, William Merz e Trish M. Perl. "A 17-Month Evaluation of a Chlorine Dioxide Water Treatment System to Control Legionella Species in a Hospital Water Supply". Infection Control & Hospital Epidemiology 24, n. 8 (agosto 2003): 575–79. http://dx.doi.org/10.1086/502254.
Testo completoAbstract (sommario):
AbstractObjective:To assess the safety and efficacy of a chlorine dioxide water treatment system in controlling Legionella in a hospital water supply.Design:For 17 months following installation of the system, we performed regular water cultures throughout the building, assessed chlorine dioxide and chlorite levels, and monitored metal corrosion.Results:Sites that grew Legionella species decreased from 41% at baseline to 4% (P = .001). L. anisa was the only species recovered and it was found in samples of both hot and cold water. Levels of chlorine dioxide and chlorite were below Environmental Protection Agency (EPA) limits for these chemicals in potable water. Further, enhanced carbon filtration effectively removed the chemicals, even at chlorine dioxide levels of more than twice what was used to treat the water. After 9 months, corrosion of copper test strips exposed to the chlorine dioxide was not higher than that of control strips. During the evaluation period, there were no cases of nosocomial Legionella in the building with the system, whereas there was one case in another building.Conclusions:Our results indicate that operation of a chlorine dioxide system effectively removed Legionella species from a hospital water supply. Furthermore, we found that the system was safe, as levels of chlorine dioxide and chlorite were below EPA limits. The system did not appear to cause increased corrosion of copper pipes. Our results indicate that chlorine dioxide may hold promise as a solution to the problem of Legionella contamination of hospital water supplies.
43
Jiang, Deng Ling, Bo Wen Chen e Guo Wei Ni. "Application of Chlorine Dioxide in Drinking Water Disinfection". Advanced Materials Research 461 (febbraio 2012): 497–500. http://dx.doi.org/10.4028/www.scientific.net/amr.461.497.
Testo completoAbstract (sommario):
Chlorine dioxide was applied to drinking water for reducing the quantity of organic pollutants such as chloroform and the taste and odor problems. A modified mode for operation in tap water plant was proposed following an investigation of the reaction mechanism by which ClO2 reacts with aquatic organic materials. By using such techniques, by-products such as chlorite and chlorate were effectively minimized and high quality drinking water was produced with reduced production cost of water treatment.
44
Ortenberg, E., L. Groisman e C. Rav-Acha. "Taste and odour removal from an urban groundwater establishment – a case study". Water Science and Technology 42, n. 1-2 (1 luglio 2000): 123–28. http://dx.doi.org/10.2166/wst.2000.0302.
Testo completoAbstract (sommario):
A deep groundwater well was established in a village near Tel-Aviv, in order to supply drinking water for its 30,000 inhabitants. Although all water characteristics were within the range permitted by the Israeli regulations, operators received complaints about a funny taste and a rotten-egg odour in the water. This was attributed to the presence of 0.38 mgL–1 hydrogen sulfide. Removing the odour by the usual method of aeration was impossible because of the populated surroundings. Therefore it was decided to examine chemical oxidants for taste and odour removal. A treatment with 8 mgL–1 of chlorine successfully oxidized hydrogen sulfide but the complaints continued. This was attributed to the formation of elemental sulfur, whichis converted into polysulfide that may hydrolyze to regenerate the odourous hydrogen sulfide. Treatment with 2 mgL–1 of chlorine dioxide successfully eliminates odour completely, but produces chlorite and chlorate which are above the permitted levels. A partial solution to this problem was found by a consequential treatment with 2 mgL–1 of ClO2 for 10 min. followed by 1.5 mgL–1 of chlorine (30 min.). In this case the chlorite is reduced substantially to be within the permitted level. In addition, such treatment regenerates some of the chlorine dioxide thereby increasing its residual. The odourous H2S can also be eliminated with 3 mgL–1 of ozone. Advantages and disadvantages of the above treatments are discussed.
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Kim, Gwangmok, e Sangwon Park. "Chloride Removal of Calcium Aluminate-Layered Double Hydroxide Phases: A Review". International Journal of Environmental Research and Public Health 18, n. 6 (10 marzo 2021): 2797. http://dx.doi.org/10.3390/ijerph18062797.
Testo completoAbstract (sommario):
Chlorine is a critical element with respect to the use of fossil fuel, recycling of industrial wastes, and water purification. Chlorine could form toxic chemical compounds, corrode pipe systems and boilers, and contaminate surface and ground waters. Calcium aluminate-layered double hydroxides are one of the most promising materials to remove chlorides due to the chemisorption mechanism, since the phases have positively charged interlayers. Many studies on the synthesis and the characterization of calcium aluminate-layered double hydroxides have been extensively conducted, whereas few studies have been conducted on the chloride removal characteristics of the phases. The state-of-the-art studies on the synthesis methods and the structural characteristics of CaAl-LDH phases, the underlying mechanism on the removal of chlorides, and the potential removal rate and the capacity in the present study were thoroughly reviewed.
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Motupally, Sathya, Dennie T. Mah, Francisco J. Freire e John W. Weidner. "Recycling Chlorine from Hydrogen Chloride: A New and Economical Electrolytic Process". Electrochemical Society Interface 7, n. 3 (1 settembre 1998): 32–36. http://dx.doi.org/10.1149/2.f07983if.
Testo completoAbstract (sommario):
In the chemical industry, chlorine is one of the most widely used chemicals. The chlorine molecule is often used as a modifier or as an aid to manufacture other chemicals. Oftentimes, some or all of the chlorine used is reduced to hydrogen chloride, a waste byproduct.
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Новицький Д. Ю., Костюк В. А. e Кобилянський В. Я. "ДІОКСИД ХЛОРУ В АСПЕКТІ МІКРОБІОЛОГІЧНОЇ БЕЗПЕКИ ВОДОПРОВІДНОЇ ВОДИ". Science Review, n. 4(21) (31 maggio 2019): 9–14. http://dx.doi.org/10.31435/rsglobal_sr/31052019/6487.
Testo completoAbstract (sommario):
In the article the use of chlorine dioxide for disinfection of water from Dnipro River are considered. The results of the industrial testing of disinfection chlorine dioxide technology with using of De NORA Model T70G4000 Chlorine Dioxide Generator for Kyiv water supply system are presented. The Model T70G4000 chlorine dioxide generator is a two-chemical system, utilizing commercially available concentrations of hydrochloric acid (32-33%) and sodium chlorite (24-25%) in the production of chlorine dioxide. No chlorine gas is required. Use of solutions of chlorine dioxide for treatment of tap water with concentrations 1,5 mg/dм3 at first stage and 0,3 mg/dм3 at second stage were effective. The use of chlorine dioxide for water disinfection increases the microbiological safety of drinking water supply.
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Taylor, Robert H., Joseph O. Falkinham, Cheryl D. Norton e Mark W. LeChevallier. "Chlorine, Chloramine, Chlorine Dioxide, and Ozone Susceptibility of Mycobacterium avium". Applied and Environmental Microbiology 66, n. 4 (1 aprile 2000): 1702–5. http://dx.doi.org/10.1128/aem.66.4.1702-1705.2000.
Testo completoAbstract (sommario):
ABSTRACT Environmental and patient isolates of Mycobacterium avium were resistant to chlorine, monochloramine, chlorine dioxide, and ozone. For chlorine, the product of the disinfectant concentration (in parts per million) and the time (in minutes) to 99.9% inactivation for five M. avium strains ranged from 51 to 204. Chlorine susceptibility of cells was the same in washed cultures containing aggregates and in reduced aggregate fractions lacking aggregates. Cells of the more slowly growing strains were more resistant to chlorine than were cells of the more rapidly growing strains. Water-grown cells were 10-fold more resistant than medium-grown cells. Disinfectant resistance may be one factor promoting the persistence of M. avium in drinking water.
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Narkis, N., A. Katz, F. Orshansky, Y. Kott e Y. Friedland. "Disinfection of effluents by combinations of chlorine dioxide and chlorine". Water Science and Technology 31, n. 5-6 (1 marzo 1995): 105–14. http://dx.doi.org/10.2166/wst.1995.0574.
Testo completoAbstract (sommario):
The behaviour of both chlorine dioxide and chlorine, either as an individual or as combined disinfectants were studied on effluents from activated sludge. The results of the disinfection efficiency, residual disinfectants and their by-products, obtained by treating the same effluents at the same day with identical dosing sequence of chlorine dioxide and chlorine, alone and in a combined dosing, were compared after periods of the same contact. In most cases, it seems that each disinfectant maintains its individual capabilities when used in a combined manner. The combination produced a relatively stable high residual of both disinfectants. The important finding is the fact that the combinations of chlorine dioxide and chlorine decreased the concentration of the undesirable chlorite ion and increased the concentration of the newly formed chlorine dioxide. A greater advantage is obtained by using chlorine dioxide prior to chlorine. Therefore, combined disinfection in this sequence is recommended.
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MOKIENKO, A., L. SPASIONOVA e Yu BONDARCHUK. "CURRENT ISSUES OF MONITORING THE CHLORITE AND CHLORITE CONTENT IN DRINKING WATER AFTER OXIDATION DISINFECTION". HERALD OF KHMELNYTSKYI NATIONAL UNIVERSITY 299, n. 4 (ottobre 2021): 7–10. http://dx.doi.org/10.31891/2307-5732-2021-299-4-7-10.
Testo completoAbstract (sommario):
The use of oxidants (chlorine, chlorine dioxide and ozone) is a priority way of safe water supply. However, their use involves control of the formation, determination and normalization of chlorites and chlorates as by-products of disinfection. The aim of the work was to characterize the topical issues of monitoring the content of chlorites and chlorates in drinking water after disinfection with oxidants. Research methods included bibliometric and analytical. The results are as follows. The analysis of foreign and domestic normative documents testifies to the need to harmonize the current DSanPiN 2.2.4-171-10 “Hygienic requirements for drinking water suitable for human consumption” regarding the standardization of chlorites and chlorates in accordance with international requirements. It should be noted that these values, namely the normative values for chlorites and chlorates at the level of 0.7 and 0.7 mg / l, respectively, were included in the latest version of the above-mentioned normative document DSanPiN 2.2.4-171-20. An analysis of the experience gained in Europe (European federation of national associations of water services) shows that the main source of chlorite and chlorate formation is not chlorine dioxide, as previously thought, but sodium hypochlorite. According to the WHO, chlorate is a typical by-product of disinfection in the treatment of water with oxidants (sodium hypochlorite, chloramines, chlorine dioxide, ozone). Currently, research on the development of technological principles for minimizing the content of chlorites and chlorates as by-products of water disinfection by oxidants in Ukraine has not been conducted. The above necessitates the implementation of the following tasks: generalization of research results of chlorite content in drinking water from centralized drinking water supply systems, where chlorine dioxide is used; development, testing and implementation of the method of determination of chlorates in drinking water; determination of the content of chlorites and chlorates in the finished sodium hypochlorite, which is supplied to water utilities, depending on the shelf life; monitoring the content of chlorites and chlorates in drinking water of settlements where sodium hypochlorite is used in the process of water treatment; determination of chlorate content in chlorinated tap water after its treatment with ozone; substantiation of optimal modes of water treatment with oxidants to minimize the content of chlorites and chlorates in drinking water from the water distribution network; development of technological principles for minimizing the content of chlorites and chlorates in drinking water after disinfection with oxidants.