Showing papers on "Chlorine published in 2010"

A large atomic chlorine source inferred from mid-continental reactive nitrogen chemistry

Abstract: Chlorine atoms can profoundly affect the composition of the atmosphere. Notoriously, as chlorofluorocarbons, they were implicated in ozone depletion in the stratosphere. New observations suggest that chlorine may be a more potent force lower down in the atmosphere than was thought. The presence of gaseous chlorine atom precursors in the troposphere is generally considered a marine air phenomenon. But measurements made near Boulder, Colorado, reveal significant production of atmospheric nitryl chloride (ClNO2) in a continental setting, 1,400 km from the nearest coastline. This finding, incorporated into model studies, suggests that nitryl chloride production in the contiguous United States alone — probably arising from anthropogenic pollutants — is at a level similar to previous global estimates for marine regions. The presence of gaseous chlorine atom precursors within the troposphere was thought only to occur in marine areas but now nitryl chloride has been found at a distance of 1,400 km from the nearest coastline. A model study shows that the amount of nitryl chloride production in the continental USA alone is similar to previous global estimates for marine regions. A significant fraction of tropospheric chlorine atoms may arise directly from anthropogenic pollutants. Halogen atoms and oxides are highly reactive and can profoundly affect atmospheric composition. Chlorine atoms can decrease the lifetimes of gaseous elemental mercury1 and hydrocarbons such as the greenhouse gas methane2. Chlorine atoms also influence cycles that catalytically destroy or produce tropospheric ozone3, a greenhouse gas potentially toxic to plant and animal life. Conversion of inorganic chloride into gaseous chlorine atom precursors within the troposphere is generally considered a coastal or marine air phenomenon4. Here we report mid-continental observations of the chlorine atom precursor nitryl chloride at a distance of 1,400 km from the nearest coastline. We observe persistent and significant nitryl chloride production relative to the consumption of its nitrogen oxide precursors. Comparison of these findings to model predictions based on aerosol and precipitation composition data from long-term monitoring networks suggests nitryl chloride production in the contiguous USA alone is at a level similar to previous global estimates for coastal and marine regions5. We also suggest that a significant fraction of tropospheric chlorine atoms6 may arise directly from anthropogenic pollutants.

Manganese Porphyrins Catalyze Selective C-H Bond Halogenations

Abstract: We report a manganese porphyrin mediated aliphatic C−H bond chlorination using sodium hypochlorite as the chlorine source. In the presence of catalytic amounts of phase transfer catalyst and manganese porphyrin Mn(TPP)Cl 1, reaction of sodium hypochlorite with different unactivated alkanes afforded alkyl chlorides as the major products with only trace amounts of oxygenation products. Substrates with strong C−H bonds, such as neopentane (BDE =∼100 kcal/mol) can be also chlorinated with moderate yield. Chlorination of a diagnostic substrate, norcarane, afforded rearranged products indicating a long-lived carbon radical intermediate. Moreover, regioselective chlorination was achieved by using a hindered catalyst, Mn(TMP)Cl, 2. Chlorination of trans-decalin with 2 provided 95% selectivity for methylene-chlorinated products as well as a preference for the C2 position. This novel chlorination system was also applied to complex substrates. With 5α-cholestane as the substrate, we observed chlorination only at the...

Photocatalytic study of BiOCl for degradation of organic pollutants under UV irradiation

Abstract: BiOCl exhibited high photocatalytic activities for the degradation of rhodamine B, methyl orange and phenol. Surface chloride ions were adverse to the BiOCl photocatalysis and dissociated from BiOCl via reaction with photogenerated holes and electrons under UV irradiation. Conduction band electrons of BiOCl directly reduced either chlorine radical or the azo-bond of MO during the photocatalytic process. Hydroxyl radical was the main oxidative species in the BiOCl photocatalysis, whose generation can be accelerated via enhancing the conduction band electron consumption by MO. After the photocatalytic reaction, the dissolved chloride ion would spontaneously recombine back to the BiOCl photocatalyst, hence qualifies BiOCl as a practical high-activity photocatalyst with long lifetime.

Chlorine monoxide (Cl2O) and molecular chlorine (Cl2) as active chlorinating agents in reaction of dimethenamid with aqueous free chlorine.

Abstract: HOCl is often assumed to represent the active oxidant in solutions of free available chlorine (FAC). We present evidence that Cl2O and Cl2 can play a greater role than HOCl during chlorination of the herbicide dimethenamid. Reaction orders in [FAC] were determined at various solution conditions and ranged from 1.10 ± 0.13 to 1.78 ± 0.22, consistent with the concurrent existence of reactions that appear first-order and second-order in [FAC]. Solution pH, [Cl−], [FAC], and temperature were systematically varied so that the reactivity and activation parameters of each FAC species could be delineated. Modeling of kinetic data afforded calculation of second-order rate constants (units: M−1 s−1) at 25 °C: kCl2O = (1.37 ± 0.17) × 106, kCl2 = (1.21 ± 0.06) × 106, and kHOCl = 0.18 ± 0.10. Under conditions typical of drinking water chlorination, Cl2O is the predominant chlorinating agent of dimethenamid. To the extent that Cl2O represents the active species in reactions with other disinfection byproduct (DBP) precu...

Method for purifying a chlorine supply

Abstract: This invention provides a method for purifying a chlorine supply that includes a chlorine component, a bromine component, and nitrogen trichloride. The method includes the steps of introducing the chlorine supply into a vaporizer, heating the chlorine supply in the vaporizer to form a vapor, and introducing the vapor into a distillation system to provide purified chlorine gas, a distillate that includes liquid chlorine and the bromine component, and a bottoms component including the nitrogen trichloride. The method also includes the steps of condensing the vapor in a reflux condenser, heating the condensate in a reboiler, removing the purified chlorine gas from the distillation system, and removing the distillate from the distillation system.

Perchlorate formation by ozone oxidation of aqueous chlorine/oxy-chlorine species: role of ClxOy radicals.

Abstract: The environmental occurrence of perchlorate (ClO4−) can be related to either natural or anthropogenic sources. Recent studies highlighted the ubiquitous occurrence of natural ClO4− in the environment including wet deposition in the United States. Limited studies have investigated potential mechanisms responsible for natural ClO4− production in the environment. These studies have neither addressed the influence of relevant reaction conditions nor have they evaluated the rates of ClO4− production. The purpose of this study was to determine the comparative yields and rates of ClO4− production from O3 mediated oxidation of Cl−, OCl−, ClO2−, ClO3−, and ClO2. The influence of reactant (O3 and ClOx−) concentration and pH were evaluated. The comparative rate and efficiency of ClO4− production is generally greater for higher oxidation states of Cl (2.7 to 0.5% for ClO2−/ClO2 and 0.02 to 0.005% for OCl−/HOCl oxidation) with the notable exception of ClO3− which does not react with O3. The very slow rate of ClO4− pro...

Effects of chemically and electrochemically dosed chlorine on Escherichia coli and Legionella beliardensis assessed by flow cytometry

Abstract: The present study reports the disinfection effects of chemically and electrochemically dosed chlorine on two models for typical water-borne bacteria (Escherichia coli and Legionella beliardensis) by plating and flow cytometry (FCM) in combination with different fluorescence dyes. The residual effect on various cell functions, including cultivability, esterase activity, membrane polarization, and integrity, was tested at different free chlorine concentrations. In comparison, chemical disinfection yielded on average 60% more E. coli cells entering the viable but nonculturable (VBNC) state than electrochemical disinfection. Here, VBNC is defined as those cells with intact cell membrane but which cannot be cultured on solid nutrient agar plates. L. beliardensis was about five times more resistant to chlorine disinfection than E. coli. The results also suggested the two methods result in different disinfection mechanisms on L. beliardensis, i.e., chemically dosed chlorine targeted cell membrane integrity before enzyme activity, while electrochemically dosed chlorine acted the other way round. In addition, both bacteria lost the integrity of their cell membranes at three times lower chlorine concentration over a longer contact time (i.e., 40 vs. 10 min) by the chemical method. Our results showed that FCM is an appropriate tool to evaluate the effects of water disinfection and the percentage of cells in VBNC in a matter of hours. Electrochemical disinfection is suggested to be a favorable alternative for chemical disinfection.

Chlorine Oxides and Chlorine Oxygen Acids

Abstract: The article contains sections titled: 1. Introduction 2. Hypochlorous Acid 3. Solid Hypochlorites 3.1. Properties 3.2. Production 3.3. Quality Specifications 3.4. Uses 4. Hypochlorite Solutions 4.1. Chemical Production 4.1.1. From Chlorine 4.1.2. From Bleaching Powder 4.2. Electrosynthesis 4.2.1. Reaction Fundamentals 4.2.2. Industrial Cells 4.3. Storage 4.4. Uses 4.5. Economic Aspects 4.6. Plant Safety 5. Chlorine Dioxide 5.1. Introduction 5.2. Physical and Chemical Properties 5.3. Resources and Raw Materials 5.4. Production 5.4.1 Chlorate-Based Processes Using Methanol as Reducing Agent 5.4.2 Chlorate-Based Processes Using Hydrogen Peroxide as Reducing Agent 5.4.3 Chlorate-Based Processes Using Sulfur Dioxide as Reducing Agent 5.4.4 Chlorate-Based Processes Using Chloride as Reducing Agent 5.4.5 Chlorite-Based Processes 5.4.6 Electrochemical Methods 5.4.7 Stabilized Chlorine Dioxide Products 5.5 Uses 5.5.1 Pulp Bleaching 5.5.2 Other Uses 5.6 Quality Specifications 5.7 Analysis 5.8 Storage and Transportation 5.9 Economic and Legal Aspects, Trade Names 5.10 Environmental Protection 5.11 Toxicology and Environmental Health 6. Sodium Chlorite 6.1. Properties 6.2. Production 6.3. Uses 7. Chloric Acid and Chlorates 7.1. Properties 7.2. Production Fundamentals 7.2.1. Chlorate-Generating Reactions 7.2.2. Loss Reactions 7.3. Industrial Electrosynthesis Systems 7.3.1. Electrolysis Cell Types 7.3.2. Electrodes 7.3.3. Operational Parameters 7.3.4. Brine Purification 7.4. Crystallization 7.5. Construction Materials 7.6. Environmental Protection 7.7. Quality Specifications 7.8. Storage, Transportation, and Safety 7.9. Uses 7.10. Economic Aspects 8. Perchloric Acid and Perchlorates 8.1. Physical and Chemical Properties 8.1.1. Perchloric Acid 8.1.2. Perchlorates 8.2. Production 8.2.1. Perchloric Acid 8.2.2. Perchlorates 8.3. Environmental Protection 8.4. Chemical Analysis 8.5. Storage, Transportation, and Safety 8.6. Uses 8.7. Economic Aspects 9. Toxicology and Occupational Health

Release and Removal of Microcystins from Microcystis during Oxidative-, Physical-, and UV-Based Disinfection

Abstract: Cyanotoxins released from cyanobacteria (or blue-green algae) pose an increasing public health risk worldwide. In this study, the release of the cyanotoxin microcystin, from Microcystis aeruginosa due to oxidative, ultraviolet (UV), and physical impacts during water treatment was studied. Additionally, the relative and absolute rates of chemical oxidation of the six microcystins were determined for selected oxidants. Cell viability was measured based on treatment dosage using a fluorescence method. The specific chemical oxidants studied were free chlorine ( HOCl/ OCl− ) , chlorine dioxide, ozone, permanganate, and monochloramine. UV energy was at 254 nm. For chemical oxidants and UV, the exposures or doses examined were selected based on typical disinfection dosages. Other treatments examined included low and high salinity, ultrasonics, and physical blending. Free chlorine, permanganate, chlorine dioxide, monochloramine, and ozone were observed to at least partially disinfect the cyanobacteria, while the ...