PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Chlorine Compounds”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36Linked to original sources
PubMed1999

Long-term performance monitoring for a permeable reactive barrier at the U.S. Coast Guard Support Center, Elizabeth City, North Carolina.

A continuous hanging iron wall was installed in June, 1996, at the U. S. Coast Guard (USCG) Support Center near Elizabeth City, NC, United States, to treat overlapping plumes of chromate and chlorinated solvent compounds. The wall was emplaced using a continuous trenching machine whereby native soil and aquifer sediment was removed and the iron simultaneously emplaced in one continuous excavation and fill operation. To date, there have been seven rounds (November 1996, March 1997, June 1997, September 1997, December 1997, March 1998, and June 1998) of performance monitoring of the wall. At this time, this is the only full-scale continuous 'hanging' wall installed as a permeable reactive barrier to remediate both chlorinated solvent compounds and chromate in groundwater. Performance monitoring entails the following: sampling of 10-5 cm PVC compliance wells and 15 multi-level samplers for the following constituents: TCE, cis-dichloroethylene (c-DCE), vinyl chloride, ethane, ethene, acetylene, methane, major anions, metals, Cr(VI), Fe(II), total sulfides, dissolved H(2), Eh, pH, dissolved oxygen, specific conductance, alkalinity, and turbidity. Electrical conductivity profiles have been conducted using a Geoprobe to verify emplacement of the continuous wall as designed and to locate upgradient and downgradient wall interfaces for coring purposes. Coring has been conducted in November, 1996, in June and September, 1997, and March, 1998, to evaluate the rate of corrosion on the iron surfaces, precipitate buildup (particularly at the upgradient interface), and permeability changes due to wall emplacement. In addition to several continuous vertical cores, angled cores through the 0.6-m thick wall have been collected to capture upgradient and downgradient wall interfaces along approximate horizontal flow paths for mineralogic analyses.

Corrosion↗
PubMedDate not supplied

Producing 13C NMR, infrared absorption, and electron ionization mass spectrometric data models of the monodechlorination of chlorobenzenes, chlorophenols, and chloroanilines.

We have developed four spectroscopic data-activity relationship (SDAR) models of monodechlorination of 32 chlorinated benzene compounds in anaerobic estuarine sediment. The SDAR models were based on combinations of 13C nuclear magnetic resonance (NMR), infrared absorption (IR), and electron ionization mass spectrometric (EI MS) data. The SDAR models segregated the 32 compounds into 17 readily monodechlorinated compounds and 15 not readily monodechlorinated compounds. The SDAR model based on 13C NMR, IR, and EI MS data gave a leave-one-out cross-validation of 93.8%. The SDAR model based on a composite of 13C NMR and IR data gave a leave-one-out cross-validation of 90.6%. The SDAR model based on a composite of IR and EI MS data gave a leave-one-out cross-validation of 84.4%. The SDAR model based on a composite of 13C NMR and EI MS data gave a leave-one-out cross-validation of 84.4%. These reliable SDAR models provide a rapid and simple way to predict whether a chlorinated benzene compound will readily go through monodechlorination. The FDA has filed a patent application on methods of using any combination of spectral data (NMR, MS, UV-vis, IR, and fluorescence, phosphorescence) to model a chemical, physical, or biological endpoint.

Carbon Isotopes↗
PubMed2001

Organochlorine formation in magnesium electrowinning cells.

The formation of organochlorines during the electrolytic production of magnesium was investigated using a laboratory-scale electrolytic cell having a graphite anode, a liquid aluminium alloy cathode, and a molten chloride electrolyte. The cell was operated at current densities ranging from 3000 to 10,000 A m(-2) and at temperatures ranging from 660 degrees C to 750 degrees C. Organochlorines were adsorbed from the cell off-gases onto silica gel, extracted with hexane, and determined by gas chromatography. All compounds identified were fully chlorinated aliphatic and aromatic compounds, the major components being hexachlorobutadiene, hexachlorobenzene, hexachloroethylene, and octachlorostyrene. The total amount of organochlorines per tonne of magnesium produced decreased with electrolysis time and with current density and increased with operating temperature; it was also dependent on the type of graphite employed. The output of organochlorines varied from 5 to 20 g t(-1) of magnesium.

Chlorine Compounds↗
PubMed1983

Metabolic breakdown of Kaneclors (polychlorobiphenyls) and their products by Acinetobacter sp.

Biodegradability of commercial polychlorobiphenyl mixtures (Kaneclors, KC 200 to KC 500) and their metabolic products by Acinetobacter sp. strain P6 were studied by gas chromatography-mass spectrometry analysis. KC 200 (primarily dichlorobiphenyls) rapidly degraded after 4 h of incubation with the P6 resting cells, showing predominant accumulation of monochlorobenzoic acids. KC 300 (primarily trichlorobiphenyls) were also degraded after 4 h of incubation, producing various metabolic intermediates such as mono- and dichlorobenzoic acids, dihydroxy biphenyl compounds with two and three chlorines, and the ring meta-cleavage compounds with two and three chlorines. KC 400 (primarily tetrachlorobiphenyls) were also susceptible to biodegradation by the same organism. Chlorobenzoic acids (chlorine number 1 to 3), dihydroxy compounds (chlorine number 2 to 4), and the ring meta-cleavage compounds (chlorine number 2 to 3) were observed as the products from KC 400. In addition to such products, a large amount of unknown compounds with two chlorines in the molecule, which can be derived from 2,3,2',3' - or 2,3,2',5'-tetrachlorobiphenyls or both, accumulated. In contrast to KC 200, KC 300, and KC 400, KC 500 (primarily pentachlorobiphenyls) were resistant to degradation and hardly metabolized. Only dihydroxy compounds of certain pentachlorobiphenyls were detected.

Acinetobacter↗
PubMed2004

Structural diversity in the coordination of amidines and guanidines to monovalent metal halides.

A series of structurally characterised, monovalent metal-halide complexes incorporating neutral amidine and guanidine ligands is reported. N,N'-diphenylbenzamidine reacted with copper(I) chloride to afford the bis-ligand complex [CuCl(PhC[NPh][NHPh])2]2 (1), that exists as a chlorine bridged dimer in the solid state, with a non-symmetrical distribution of NH...Cl interactions within the 'Cu2Cl2' metallacycle. In contrast, only one equivalent of the guanidine, Me2NC[NiPr][NHiPr] (2), is coordinated in the copper(I) iodide complex [CuI(Me2NC[NiPr][NHiPr])]2 (3), which was also isolated as the dimer with bridging halide atoms. The molecular structure of the bicyclic guanidine, 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-alpha]pyrimidine (hppH), is reported, revealing a hydrogen bridged dimer with extensive delocalisation throughout the ligand framework. Coordination of hppH to lithium chloride afforded the dimeric bis-ligand complex [LiCl(hppH)2]2 (4) in which each hppH molecule interacts with a different chlorine atom of the central 'Li2Cl2' core of the molecule via NH...Cl hydrogen bonding. In contrast the 2:1 ligand to metal complex is formed with silver(I) chloride to afford AgCl(hppH)2 (5), a unique example of a monomeric, three-coordinate silver chloride supported by nitrogen-based ligands. The series of mixed ligand complexes [CuX(hppH)(PPh3)]n (6, X = Cl, n= 1; 7, X = Br, n= 2; 8 X = I, n= 2) have also been synthesised and structurally characterised, allowing comparisons of the relative coordinating behaviour of hppH and PPh3 as neutral donors at copper(I) centres to be made.

Amidines↗
PubMed2004

[Kinetics and mechanism of aniline oxidation with chlorine dioxide in water].

Reaction kinetics of aniline oxidation with chlorine dioxide in water were investigated systematically by detecting concentrations of aniline with HPLC at regular intervals. Results showed that the reaction was first-order with respect to both chlorine dioxide and aniline, and the entire reaction was of second-order. Under condition of pH 6.86 and water temperature (Tw) 287 K, the second-order reaction rate constant k was 0.11 L x (mol x s)(-1). Reaction activation energy was 73.11 kJ x mol(-1), revealing that the reaction could take place under usual water treatment conditions. The reaction rate constants in acidic and alkali media were greater than that in neutral medium. Effect of chlorite ion on the reaction rate was insignificant. P-aminophenol and azobenzene were detected by GC MS as intermediates. Oxidation pathways were proposed and discussed elementarily.

Aniline Compounds↗
PubMed2004

Biodegradation of PCE and TCE in landfill leachate predicted from concentrations of molecular hydrogen: a case study.

The Refuse Hideaway Landfill (23-acre) received municipal, commercial, and industrial waste between 1974 and 1988. It was designed as a "natural attenuation" landfill and no provision was made to collect and treat contaminated water. Natural biological degradation through sequential reductive dechlorination had been an important mechanism for natural attenuation at the site. We used the concentration of hydrogen to forecast whether reductive dechlorination would continue over time at particular locations in the plume. Based on published literature, reductive dechlorination and natural attenuation of PCE, TCE, and cis-DCE can be expected in the aquifer if the concentration of molecular hydrogen in monitoring wells are adequate (> 1 nanomolar). Reductive dechlorination can be expected to continue as the ground water moves down gradient. Natural attenuation through reductive dechlorination is not expected in flow paths that originate at down gradient monitoring wells with low concentrations of molecular hydrogen (< 1 nanomolar). In three monitoring wells at the margin of the landfill and in five monitoring wells down gradient of the landfill, ground water maintained a molecular hydrogen concentration, ranging from 1.30 to 9.17 nanomolar, that is adequate for reductive dechlorination. In three of the monitoring wells far down gradient of the landfill, the concentration of molecular hydrogen (0.33 to 0.83 nanomolar) was not adequate to support reductive dechlorination. In wells with adequate concentrations of hydrogen, the concentrations of chlorinated volatile organic compounds were attenuated over time, or concentrations of chlorinated volatile organics were below the detection limit. In wells with inadequate concentrations of hydrogen, the concentrations of chlorinated organic compounds attenuated at a slower rate over time. In wells with adequate hydrogen the first order rate of attenuation of PCE, TCE, cis-DCE and total chlorinated volatile organic compounds varies from 0.38 to 0.18 per year. In wells without adequate hydrogen the rate varies from 0.015 to 0.006 per year.

Biodegradation, Environmental↗
PubMed2001

Combination of advanced oxidation processes and gas absorption for the treatment of chlorinated solvents in waste gases.

Treatment of chlorinated organic compounds in waste gases is difficult because of several reasons: these compounds are dioxin precursors when incinerated, and also biological treatment is difficult because of a limited number of suitable microbial degradation pathways. On the other hand, since the 1990s, a new generation of chemical oxidation techniques has been introduced in water treatment. Advanced Oxidation Processes (AOPs) are based on a combination of UV/H202, UV/O3 or H2O2/O3. The combinations result in the generation of OH-radicals, which subsequently attack the organic pollutants. In this work, the treatment of a gas stream (240 L/h) loaded with 20-40 ppmv trichloroethylene (TCE) is presented. Therefore, a combination of an absorption process in a bubble column with a liquid H2O2/O3 initiated oxidation, was investigated. Removal efficiencies, depending on the dosed H2O2 and O3, up to 94% were found. The production of chloride ions was investigated: the Cl-atoms from the removed TCE could be found back as chloride ions. Next to the experimental work, attention was paid to the mechanisms taking place in the proposed concept. Here, a simulation model was developed, considering gas/liquid mass transfer of TCE and ozone, axial liquid dispersion, advective gas and liquid transport and about 29 chemica reaction steps. The modelling allowed a better understanding of the technique and gives insight in its possibilities and limitations. Finally, it can be concluded that the proposed technique shows interesting perspectives: it is able to transform chlorine in chlorinated solvents into chloride ions effectively at ambient temperature conditions.

Absorption↗
PubMed2004

Kinetics of aniline oxidation with chlorine dioxide.

For the first time, kinetics of aniline oxidation with chlorine dioxide (ClO2) were investigated systematically by detecting concentration of aniline with HPLC at regular intervals. Results showed that the reaction was first-order both in ClO2 and in aniline, and the oxidation reaction could be described as second-order reaction. Stoichiometric factor eta was experimentally determined to be 2.44. The second-order-reaction rate constant k was 0.11 L/(mol x s) under condition of pH 6.86 and water temperature (Tw) 287K. Reaction activation energy was 72.31 kJ/mol, indicating that the reaction could take place under usual water treatment conditions. The reaction rate constants in acidic and alkali media were greater than that in neutral medium. Chlorite ion could slightly increase reaction rate in acidic medium. p-aminophenol and azobenzene were detected by GC-MS as intermediates.

Aminophenols↗
PubMed1999

Detection of chlorinated and brominated byproducts of drinking water disinfection using electrospray ionization-high-field asymmetric waveform ion mobility spectrometry-mass spectrometry.

The lower limit of detection for low molecular weight polar and ionic analytes using electrospray ionization-mass spectrometry (ESI-MS) is often severely compromised by an intense background that obscures ions of trace components in solution. Recently, a new technique, referred to as high-field asymmetric waveform ion mobility spectrometry (FAIMS), has been shown to separate gas-phase ions at atmospheric pressure and room temperature. A FAIMS instrument is an ion filter that may be tuned, by control of electrical voltages, to continuously transmit selected ions from a complex mixture. This capability offers significant advantages when FAIMS is coupled with ESI, a source that generates a wide variety of ions, including solvent clusters and salt adducts. In this report, the tandem arrangement of ESI-FAIMS-MS is used for the analysis of haloacetic acids, a class of disinfection byproducts regulated by the US EPA. FAIMS is shown to effectively discriminate against background ions resulting from the electrospray of tap water solutions containing the haloacetic acids. Consequently, mass spectra are simplified, the selectivity of the method is improved, and the limits of detection are lowered compared with conventional ESI-MS. The detection limits of ESI-FAIMS-MS for six haloacetic acids ranged between 0.5 and 4 ng/mL in 9:1 methanol/tap water (5 and 40 ng/mL in the original tap water samples) with no preconcentration, derivatization, or chromatographic separation prior to analysis.

Acetates↗
PubMed2000

Comparison of aqueous chemical treatments to eliminate Salmonella on alfalfa seeds.

Several outbreaks of salmonellosis associated with alfalfa sprouts have been documented in the United States since 1995. This study was undertaken to evaluate various chemical treatments for their effectiveness in killing Salmonella on alfalfa seeds. Immersing inoculated seeds in solutions containing 20,000 ppm free chlorine (Ca[OCl]2), 5% Na3PO4, 8% H2O2, 1% Ca(OH)2, 1% calcinated calcium, 5% lactic acid, or 5% citric acid for 10 min resulted in reductions of 2.0 to 3.2 log10 CFU/ g. Treatment with 1,060 ppm Tsunami or Vortex, 1,200 ppm acidified NaClO2, or 5% acetic acid were less effective in reducing Salmonella populations. With the exceptions of 8% H2O2, 1% Ca(OH)2, and 1% calcinated calcium that reduced populations by 3.2, 2.8, and 2.9 log10 CFU/g, respectively, none of treatments reduced the number of Salmonella by more than 2.2 log10 CFU/g without significantly reducing the seed germination percentage. Treatment with 5% acetic, lactic, or citric acids substantially reduced the ability of seeds to germinate. Treatment with 1% Ca(OH)2 in combination with 1% Tween 80, a surfactant, enhanced inactivation by 1.3 log10 CFU/g compared to treatment with 1% Ca(OH)2 alone. Presoaking seeds in water, 0.1% EDTA, 1% Tween 80, or 1% Tween 80 plus 0.1% EDTA for 30 min before treatment with water, 2,000 ppm NaOCl, or 2% lactic acid had a minimal effect on reducing populations of Salmonella. Results indicate that, although several chemical treatments cause reductions in Salmonella populations of up to 3.2 log10 CFU/g initially on alfalfa seeds when analyzed by direct plating, no treatment eliminated the pathogen, as evidenced by detection in enriched samples.

Acetic Acid↗
PubMed1990

Metal-ligand vibrations of cyanoferric myeloperoxidase and cyanoferric horseradish peroxidase: evidence for a constrained heme pocket in myeloperoxidase.

The low-frequency FeCN vibrations of cyanoferric myeloperoxidase (MPO) and horseradish peroxidase (HRP) have been measured by resonance Raman spectroscopy. The ordering of the frequencies of the predominantly FeC stretching and FeCN bending normal vibrational modes in the two peroxidases differs. These normal mode vibrations are identified by their wavenumber shifts upon isotopic substitution of the cyanide ligand. For MPO, the stretching mode nu 1 (361 cm-1) occurs at a lower frequency than the bending mode delta 2 (454 cm-1). For HRP, the order is reversed as nu 1 (456 cm-1) is at a higher frequency than delta 2 (404 cm-1). Normal coordinate analyses and model complexes have been used to address the origin of this behavior. The nu 1 stretching frequencies in cyanide complexes of iron porphyrin and iron chlorin model compounds are similar to one another and to that of HRP. Thus, the inverted order and altered frequencies of the nu 1 and delta 2 vibrations in MPO, relative to those in HRP and the model compounds, are not inherent to the proposed iron chlorin prosthetic group in MPO but, rather, are attributed to distinct distal environmental effects in the MPO active site. The normal coordinate analyses for MPO and HRP showed that the nu 1 and delta 2 vibrational frequencies are not pure; the potential energy distributions for these modes respond not only to the geometry but also to the force constants of the nu(FeC) and delta(FeCN) internal coordinates.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed2004

Toxicity of model aliphatic amines and their chlorinated forms.

Aliphatic amines can be found in many wastewater effluents from industry, agriculture, pharmacy, and food processing. Amines can induce toxicological responses that are relevant in biochemical treatment processes, as well as in natural waters. This research compared the toxicity and inhibition caused by three aliphatic amines (n-propylamine, ethylmethylamine, and trimethylamine) and their chlorinated derivatives. The chemistry of chlorine interactions with these compounds was characterized by using membrane introduction mass spectrometry (MIMS). Acute toxicity assays were conducted by using a Microtox system with Phosphobacterium phosphoreum (also known as Vibrio fischeri) for the aliphatic amine compounds and their corresponding chlorinated derivatives, as identified by MIMS. Inhibition tests were conducted by using the oxygen utilization rate test with an enhanced nitrifier culture. The median effective concentration (EC50) values for chloropropylamine, chloroethylmethylamine, and chlorodimethylamine obtained by Microtox with a contact time of 15 min were 12.68, 19.72, and 15.92 microM, respectively. The EC50 values of these aliphatic chloramines from the Microtox test decreased by roughly one order of magnitude as a result of chlorination. Inhibition of nitrifiers also was observed in these amines. Trimethylamine and n-propylamine caused greater inhibition to nitrifiers than did ethylmethylamine under similar concentrations. Nitrifier inhibition from these amines increased after chlorination. The results of these tests indicated that aliphatic amines and their chlorinated derivatives could induce environmentally relevant toxicity responses in treatment settings and in receiving waters.

Amines↗