Showing papers on "Chlorine published in 1990"

Effects of ozone, chlorine dioxide, chlorine, and monochloramine on Cryptosporidium parvum oocyst viability.

Abstract: Purified Cryptosporidium parvum oocysts were exposed to ozone, chlorine dioxide, chlorine, and monochloramine. Excystation and mouse infectivity were comparatively evaluated to assess oocyst viability. Ozone and chlorine dioxide more effectively inactivated oocysts than chlorine and monochloramine did. Greater than 90% inactivation as measured by infectivity was achieved by treating oocysts with 1 ppm of ozone (1 mg/liter) for 5 min. Exposure to 1.3 ppm of chlorine dioxide yielded 90% inactivation after 1 h, while 80 ppm of chlorine and 80 ppm of monochloramine required approximately 90 min for 90% inactivation. The data indicate that C. parvum oocysts are 30 times more resistant to ozone and 14 times more resistant to chlorine dioxide than Giardia cysts exposed to these disinfectants under the same conditions. With the possible exception of ozone, the use of disinfectants alone should not be expected to inactivate C. parvum oocysts in drinking water.

Chlorination of humic materials: byproduct formation and chemical interpretations

Abstract: Ten aquatic humic and fulvic acids were isolated and studied with respect to their reaction with chlorine. Yields of TOX, chloroform, trichloroacetic acid, dichloroacetic acid, dichloroacetonitrile, and 1,1,1-trichloropropanone were measured at pH 7 and 12. Humic acids produced higher concentrations than their corresponding fulvic acids of all byproducts except 1,1,1-trichloropropanone. Chlorine consumption and byproduct formation were related to fundamental chemical characteristics of the humic materials. A statistical model was proposed for activated aromatic content based on {sup 13}C NMR and base titration data. The values estimated from this model were found to be well correlated with chlorine consumption. Specific by-product formation was related to UV absorbance, nitrogen content, or the activated aromatic content.

Disinfecting Biofilms in a Model Distribution System

Abstract: This study examined the disinfection efficiency of free chlorine and monochloramine for improve water quality, but if sources of controlling biofilm organisms in a model pipe system The composition of the pipe material microbial contamination (eg, sediment, was found to be a major influence on disinfection efficiency Bacteria grown on galvanized, tubercles, flocculated materials) are not copper, or PVC pipe surfaces were readily inactivated by a 1-mg/L residual of free chlorine or eliminated, deterioration will soon monochloramine Biofilms grown on iron pipes treated with free chlorine doses as high as 4 recurlO In practice, it is difficult to mg/L (3-mg/L residual) for two weeks did not show significant changes in viability, but if effectively apply these procedures to treated with 4 mg/L of monochloramine for two weeks, these biofilms exhibited a more than transmission mains and trunk lines 3-log die-off Accumulation of corrosion products on iron pipes was found to interfere with without extreme effort, high costs, and free chlorine disinfection

Minimizing Chlorite Ion and Chlorate Ion in Water Treated With Chlorine Dioxide

Abstract: The use of sulfur dioxide-sulfite ion chemistry to quantitatively remove chlorite ion to below the 0.11-mg/L level is described, along with the use of free chlorine to remove the sulfur dioxide-sulfite ion. The stoichiometry and the rate law are described for pH values of 5.5 to 8.5 so that the chemistry can be applied directly in existing drinking water treatment facilities

A neutron-diffraction study of tetramethylammonium chloride in aqueous solution

Abstract: Neutron diffraction with isotope substitution of nitrogen, chlorine and hydrogen nuclei is used to investigate the hydration region of both ions and the possibility of ion pairing in aqueous solutions of tetramethylammonium chloride (TMACl) at 0·5 m, 1·0 m and approximately 2·0 m concentration. The use of a maximum-entropy method to calculate the radial distribution functions is discussed. The H-H correlation function for the water in the 1·0 m solution is measured and compared with that for pure water. The nitrogen-substitution results are also compared with a hard-sphere model calculation. The results show that the TMA hydration is apolar rather than ionic, and is consistent with a disordered water-cage structure, while the water in the hydration sphere does not appear to be more ordered than in bulk water. There is no significant change in the hydration structure measured at the different concentrations, although at the highest concentration there may be evidence of the close approach of the anion and ...

Structures, relative stabilities, and vibrational spectra of isomers of chlorine oxide dimer (Cl2O2): the role of the chlorine oxide dimer in antarctic ozone depleting mechanisms

Abstract: Quantitative ab initio molecular orbital calculations have been applied to he description of the structures, relative stabilities, and vibrational spectra of isomers of Cl{sub 2}O{sub 2} The highest level of calculations performed (MP2/6-31+G (3d)//MP2/6-31G*) suggests that C{sub 2} symmetry ClOOCl (chlorine peroxide) is the lowest energy form but that the hypervalent, C{sub s} symmetry species ClClO{sub 2} (chloryl chloride) is only about 1 kcal/mol higher in energy A third form, C{sub 1} symmetry ClOClO (chlorine chlorite), lies higher in energy by 7 kcal/mol The theoretical results are compared with experimentally determined thermochemical and vibrational data, and the role of the chlorine oxide dimer in Antarctic ozone depleting mechanisms is discussed

Production of polycyclic aromatic hydrocarbons in chlorine containing environments

Abstract: The factors affecting the formation and growth of polycyclic aromatic hydrocarbons (PAHs) in chlorine-containing environments are investigated. The experimental results obtained in shock-tube pyrol-ysis of chlorinated C1, and C2, hydrocarbons are re-analyzed in terms of Cl-to-H molar ratio of the mixture and it is found that the sooting tendency and hence PAH production are increased with the increase in [C1]/[H] ratio. Based on the analysis of the reaction kinetics and results or detailed modeling, two basic factors are suggested to be responsible for this phenomenon: (1) the enhanced, chlorine-catalized molecular degradation that promotes the formation of aromatic-ring compounds; and (2) the large concentration of CI atoms that accelerates the abstraction of aromatic H from stable PAH molecules, which activates them for further growth. The modeling results also provide an evidence against existence of a correlation between PAHs and CO in flame environments.

Disinfection of bacteria in water systems by using electrolytically generated copper:silver and reduced levels of free chlorine.

Abstract: As an alternative disinfectant to chlorination, electrolytically generated copper:silver (400 and 40 μg/L copper and silver, respectively) with and without free chlorine (0.3 mg/L) was evaluated ov...

Application of soot formation model : effects of chlorine

Abstract: Soot formation in the combustion of hydrocarbon fuels is the net effect of competition between molecular weight growth and destruction mechanisms involving free radicals. Chlorine addition to the fuel can alter the concentrations of radicals in a manner that enhances soot formation. In diffusion flames and purely pyrolysis systems, the presence of chlorine increases the fractional conversion of carbon to soot, while in premixed flames and well-stirred combustion the presence of chlorine lowers the critical equivalence ratio for the onset of soot formation. These effects tend not to be of major importance in premixed and well-stirred systems unless substantial amounts of chlorine are added. The chlorine has a strong tendency to go to HO, which may or may not significantly lower the concentration of H atoms, and in turn affect the concentrations of OH and O, depending on whether the atomic Cl/H ratio is comparable to or much less than unity. The observed effects of chlorine on soot formation are qu...

Method and apparatus for chlorine dioxide manufacture

Abstract: A method and apparatus for the generation, use, and disposal of chlorine dioxide is disclosed. A solid sodium chlorite composition having impurities, at least one of which is sodium hydroxide, is contacted with an agent to consume essentially all of the sodium hydroxide. Chlorine dioxide gas is then generated by contacting the resultant composition with chlorine in a humidified inert carrier gas. The resultant chlorine dioxide gas mixture may then be treated to remove chlorine gas present therein by contacting the same with soda-lime in particulate form. After using the chlorine dioxide gas mixture in the desired manner, chlorine dioxide present in the spent effluent gas may be substantially removed via the introduction of the effluent gas into an aqueous solution of sodium thiosulfate having a sufficient amount of an inorganic base to maintain the alkalinity of the solution during consumption of thiosulfate by chlorine dioxide.

Inactivation of human and simian rotaviruses by chlorine dioxide.

Abstract: The inactivation of single-particle stocks of human (type 2, Wa) and simian (SA-11) rotaviruses by chlorine dioxide was investigated. Experiments were conducted at 4 degrees C in a standard phosphate-carbonate buffer. Both virus types were rapidly inactivated, within 20 s under alkaline conditions, when chlorine dioxide concentrations ranging from 0.05 to 0.2 mg/liter were used. Similar reductions of 10(5)-fold in infectivity required additional exposure time of 120 s at 0.2 mg/liter for Wa and at 0.5 mg/liter for SA-11, respectively, at pH 6.0. The inactivation of both virus types was moderate at neutral pH, and the sensitivities to chlorine dioxide were similar. The observed enhancement of virucidal efficiency with increasing pH was contrary to earlier findings with chlorine- and ozone-treated rotavirus particles, where efficiencies decreased with increasing alkalinity. Comparison of 99.9% virus inactivation times revealed ozone to be the most effective virucidal agent among these three disinfectants.

Method of treating water

Abstract: A method of treating and removing volatile organic contaminants from ground water by treating the water with effective amounts of a water-soluble polymeric sequesterant comprising polymers derived from acrylic acid or organic acid, followed by the addition of a biocide, eg, chlorine, and then subsequently passing the treated water through a packed column or air stripper wherein the volatile organic contaminants are removed by passing air in a counter-direction to the flow of water at temperatures ranging from about 40° to about 200° F

Recovery of gold, silver and platinum group metals with various leachants at low pulp densities

Abstract: In the recovery of noble metals, including gold, silver and members of the platinum group, the ores or tailings are subjected to the action of various leaching agents, namely, sodium cyanide, thiourea, chlorine and aqua regia and optionally a leaching aid, such as chloride ions. The resulting slurry is then diluted to an optimum pulp density of 0.1 to 10.0% and allowed to stand in a holding tank for periods up to 30 minutes, preferably 15 minutes, with the optional addition of a dispersant, such as sodium silicate, sodium carbonate, trisodium polyphosphate or sodium hexametaphosphate. The pulp is then centrifuged to remove solids if necessary and is then passed at a pH <9 through a column containing activated carbon or ion exchange resin/fibre to adsorb any precious metal in solution in the liquor. This is followed by desorption and the cycle repeated as often as warranted by the economics of the process. Alternatively, the pulp is filtered and the filtrate subjected to various recovery techniques, such as cementation, solvent extraction, electrowinning and precipitation.

Comparative Subchronic Toxicity Studies of Three Disinfectants

Abstract: In separate subchronic toxicity studies, male and female Sprague-Dawley rats received various dosages of chlorine, monochloramine, or chlorine dioxide in their drinking water for 90 consecutive days. None of the disinfectants caused premature death at any of the concentrations used. The highest dose of chlorine tested (250 mg/L) was concluded to be a no observable adverse effect level. At 200 mg/L (the lowest observable adverse effect level), monochloramine produced decreased body and organ weights in both sexes and a small decrease in red blood cell count and serum calcium in males. Chlorine dioxide produced dosage-related decreases in body and organ weight at concentrations as low as 25 mg/L, but its most significant toxic effect was the induction, at all concentrations, of nasal lesions.

Nonaqueous liquid automatic dishwasher detergent composition containing a dual bleach system

Abstract: The invention discloses an aqueous liquid dishwashing detergent composition having improved cleaning performance against both proteinaceous and carbohydrate soils comprising at least one ingredient selected from the group consisting of organic detergent, detergent builder, from inhibitors and mixtures thereof, and a dual bleach system comprising a hypochlorite source sufficient to provide 0.5 to 5 wt. % available chlorine and a bromide compound which bromide compound is insoluble or only sparingly soluble in the product liquid wherein the mole ratio of bromide compound to available chlorine is 0.04 to 1.04.

Polymer-bound active chlorine: disinfection of water in a flow system. Polymer supported reagents. 5

Abstract: Resins were prepared by reaction of sulfochlorinated, macroporous styrene-divinylbenzene copolymer, >15% DVB, with excess α,ω-alkanediamines or methylamine in aqueous solution. The resulting polymers having N-alkylarenesulfonamide functional groups were chlorinated by using hypochlorous acid to form N-chloro-N-alkylarenesulfonamide function groups. Water containing E. coli at concentrations of 10 5 -10 8 colonies/100 mL was pumped through beds of the N-chlorinated resins at low pressure drops and residence times on the order of minutes. Up to 175 L of water could be treated by 30 g of resin with more than 99.8% of the E. coli being killed

The selective chlorination of iron from llmenite ore by CO-Cl2 mixtures: Part I. intrinsic kinetics

Abstract: The intrinsic kinetics of the selective chlorination of iron from ilmenite ore using carbon monoxide as the reducing agent were studied in a shallow fluidized bed. Experiments on the effects of chlorination temperature, carbon monoxide and chlorine gas partial pressures, and particle size were conducted in the absence of mass- and heat-transfer influences. Results indicate that the kinetics in the temperature range 923 to 1123 K are represented by the following pore-blocking rate law: λ[ exp (XFe/λ) − 1 ] = 33.7 exp (− E/RT)pco0.5220.32t where E is 37.2 kJ/mol and p and t are in atm (=101.3 kPa) and minutes, respectively. The partial pressure of carbon monoxide was found to affect the chlorination rate more strongly than that of chlorine. A reaction mechanism in which iron in ilmenite reacts with chlorine before the liberated oxygen is removed by carbon monoxide is proposed.

The Effect of Compound Structure on the Elemental Responses in Gas Chromatography-Microwave Induced Plasma Atomic Emission Spectrometry

Abstract: In this paper the effects of chemical structure and microwave power on the GC-MIP elemental response of carbon, hydrogen, chlorine, and bromine are investigated using alkanes, alkenes, aromatics, polynuclear aromatic and alcohol homologs, mixtures of saturated and nonsaturated hydrocarbons, mixtures of oxygen-containing compounds, and various chlorohydrocarbons and bromohydrocarbons as testing compounds

Doppler spectroscopy of chlorine atoms generated from photodissociation of hydrogen chloride and methyl chloride at 157 and 193 nm

Abstract: Hydrogen chloride and methyl chloride are photodissociated at 193 and 157 nm. Branching ratios for production of the resulting chlorine atoms in the 2P1/2 state relative to the 2P3/2 state are determined to be 0.20±0.02 at 193 nm and 0.35±0.05 at 157 nm for HCl and 0.23±0.02 at 193 nm and 0.26±0.05 at 157 nm for CH3Cl. The Doppler profiles of the chlorine fragments have been measured and are interpreted by assuming their anisotropy parameters and translational energies. HCl undergoes a perpendicular optical transition at each of the two wavelengths. For CH3Cl, the transition is parallel at 193 nm and a mixture of parallel and perpendicular types at 157 nm.

Method for preparing stabilized aqueous chlorine dioxide solution

Abstract: A compact manufacturing method of an aqueous stabilized chlorine dioxide comprising adding to an aqueous 0.1-5% alkali metal chloride solution an aqueous alkali metal hypochlorite solution at 5-40 ppm, while before and after the addition of the hypochlorite solution an organic acid such as citric acid or an inorganic acid such as hydrochloric acid is used to adjust pH to 7-9 or 2-5.6, respectively, which is useful as disinfectant or deodorant.