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Query: HUMANGGP:003739 (CO2)
 48,959 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to detect and assess the spastic components in airway obstruction of workers exposed to inhalation of different nonorganic and organic dusts, 129 workers of metal industry and 135 workers of textile industry were examined. The workers of metal industry were exposed to the following respiratory noxa: toluol, paint aerosol, mineral dusts (SiO2 up to 10%), asbestos dust, metalic dust and several chemical noxa (acetone, CO, CO2, ZnO, FeO and petrol). In textile industry the dust of vegetal origin was detected with unfavourable micro climatic factors. In both groups the similar results were found with very high percent of spastic components. After bronhodilatatory testing the most significant differences were found in the following tests: Raw, FMF25-75, FEF75-85, components. Several significant spastic components were present in workers of metal industry which are due to the polluted working area. In relation to the mean values of tests, the greatest number of different results was found in FEF75-85 and Raw tests. It is suggested that the workers with these results should be tested as well.
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PMID:[Results of bronchodilation tests in workers exposed to occupation respiratory noxae]. 221 18

Due to their insolubility in water and high adsorption coefficient, liquid polydimethylsiloxanes (PDMS) discharged as effluent will adsorb to particulate matter and, therefore, will become a component of sewage sludge during waste water treatment. The subsequent environmental fate of PDMS will depend on the fate of the sludge. Due to increasing practices of soil amendment with sewage sludge the principal environmental compartment receiving PDMS fluids is the soil. Degradation of PDMS is a common process taking place in many different types of soils. It occurs through a unique combination of environmental degradation processes. Initial hydrolysis of PDMS is catalysed by clay minerals, the principal component of soil. The primary hydrolysis product, dimethylsilanediol (DMSD), is then either biodegraded, or evaporated into the atmosphere, where it is subsequently oxidised in the presence of sunlight. The end products in both cases are expected to be CO2, SiO2 and H2O.
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PMID:Degradation of polydimethylsiloxane fluids in the environment--a review. 1007 Jul 32

A combination of ab initio molecular dynamic simulations and fully relaxed total energy calculations is used to predict that molecular CO2 should transform to nonmolecular carbonate phases based on CO4 tetrahedra at pressures in the range of 35 to 60 gigapascals. The simulation suggests a variety of competing phases, with a more facile transformation of the molecular phase at high temperatures. Thermodynamically, the most stable carbonate phase at high pressure is predicted to be isostructural to SiO2 alpha-quartz (low quartz). A class of carbonates, involving special arrangements of CO4 tetrahedra, is found to be more stable than all the other silica-like polymorphs.
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PMID:Pressure-induced solid carbonates from molecular CO2 by computer simulation 1022 7

The kinetics for the oxidation of carbon monoxide in the presence of excess oxygen over Pt-Rh alloy catalysts were studied by using the reversed-flow gas chromatography technique. Suitable mathematical analysis equations were derived by means of which the rate constants for the oxidation reaction of carbon monoxide, as well as for the adsorption and desorption of the reactant CO on the catalysts pure Pt, 75 atom% Pt+25 atom% Rh, 50 atom% Pt+50 atom% Rh, 25 atom% Pt+75 atom% Rh and pure Rh supported on SiO2 were determined. All the catalysts show a maximum rate constant for the production of CO2 at a characteristic temperature close to that found in the literature. The rate constants for the adsorption of CO increase generally with increasing temperature, while those for the desorption decrease with increasing temperature. From the variation of the rate constants with temperature activation energies for the oxidation reaction and adsorption of CO were determined, which are sensitive to the composition of the catalytic surface. The appearance of CO2 and carbon, when introducing pure CO into the column with the catalysts, verified a partial dissociative adsorption (e.g., disproportionation) of CO on the catalysts used. The latter indicates a mechanism for the CO oxidation through a partial dissociative adsorption of CO followed by the reaction of adsorbed CO molecules with adsorbed O atoms.
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PMID:Gas chromatographic kinetic study of carbon monoxide oxidation over platinum-rhodium alloy catalysts. 1048 88

A supercritical fluid extraction (SFE) method using carbon dioxide for the determination of organic pollutants in Yellow River water was developed. In this paper, organic contaminants in 3 L Yellow River water were concentrated on 1 g GDX-301 adsorbent and then eluted from the adsorbent with supercritical CO2. The analytes extracted by SFE were collected into 1 mL alcohol collecting solvent through a SiO2 restrictor (35 cm x 50 microns i.d.). Finally, the collecting solvent was analyzed by Gas Chromatography/Infrared Spectrometry/Mass Spectrometry. The SFE conditions which were optimized for removal of the analytes from adsorbent were 20 MPa, 60 degrees C and 40 min. The extraction efficiencies of SFE were directly compared to those obtained by using 15 mL dichloromethane elution. Efficiencies of SFE under conditions of 20 MPa, 60 degrees C and 40 min were generally higher than those of solvent elution.
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PMID:[Determination of organic pollutants in water by off-line supercritical fluid extraction-Gas Chromatography/Infrared Spectrometry/Mass Spectrometry]. 1132 2

The formation of carbonyl sulfide (COS) by catalytic oxidization of carbon disulfide (CS2) over atmospheric particle catalysts was explored through FT-IR, MS (mass spectrometry), and a fixed-bed stainless steel reactor. Also the crystallizing conditions and specific surfaces (areas) of the catalysts were investigated by means of X-ray diffraction (XRD) and BET. Some oxides such as CaO, Fe2O3, Al2O3, and SiO2 were investigated under the conditions similar to the atmospheric particles as a comparison. The results showed that atmospheric particles and the oxide catalysts exhibited considerable oxidizing activity for CS2 at ambient temperature to form COS. Elemental sulfur as well as COS was one of the main products; even CO2 could be produced by a secondary reaction on some catalysts. Among the catalysts, CaO showed the strongest catalytic activity for oxidizing CS2. The catalytic activities of Fe2O3 and Al2O3 decreased considerably as compared with CaO, and SiO2 had the weakest catalytic activity. Atmospheric particles' catalytic activity is between Fe2O3's and Al2O3's. The atmospheric particles we collected mainly consist of Ca(Al2Si2O8).4H2O, which is also the main component of cement. COS, the main product, is formed by the catalytic oxidizing reaction of CS2 with adsorbed "molecular" oxygen overthe catalysts' surfaces. The concentration of adsorbed oxygen over catalysts' surfaces may be the key factor contributed to the oxidizing activities. This paper first revealed that CS2 could be catalytically oxidized over atmospheric particles to form COS. It induced that this reaction may be another important source of atmospheric COS from CS2.
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PMID:Carbonyl sulfide derived from catalytic oxidation of carbon disulfide over atmospheric particles. 1143 61

Gas-phase photocatalysis of 1,4-dichlorobut-2-enes and 3,4-dichlorobut-1-ene (DCB) has been studied using TiO2 and 3% WO3/TiO2 supported on SiO2. DCB was found to oxidize efficiently over these catalysts; however, only low rates of CO2 formation were observed. With these chlorinated hydrocarbons, the catalysts were found to deactivate over time, probably via the formation of aldol condensation products of chloracetaldehyde, which is the predominant intermediate observed. The variation in rate and selectivity of the oxidation reactions with O2 concentration is reported and a mechanism is proposed. Using isotope ratio mass spectrometry, the initial step for the DCB removal has been shown not to be a carbon bond cleavage but is likely to be hydroxyl radical addition to the carbon-carbon double bond.
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PMID:Gas-phase photocatalytic oxidation of dichlorobutenes. 1145 16

Lead pollution of the environment is synonymous with civilization. It has no known biological function, and is naturally present in soil, but its presence in food crops is deemed undesirable. The concern regarding Pb is mostly due to chronic human and animal health effects, rather then phytotoxicity. However, not much is known about the chemistry and speciation of Pb in soils. We determined the activity of Pb2+, in near neutral and alkaline soils, representative of alluvial, desertic and calcareous soils of Egypt, using the competitive chelation method. Lead activity ranged from 10(-6.73) to 10(-4.83) M, and was negatively correlated with soil and soil solution pH (R2 = -0.92, P < 0.01 and R2 = -0.89, P < 0.01, respectively). It could be predicted in soil solution from the equation: log(Pb2+) = 9.9 - 2pH. A solubility diagram for the various Pb minerals found in soil was constructed using published thermodynamic data obtained from the literature, and our measured Pb2+ activities compared with this information. The measured Pb2+ activities were undersaturated with regard to the solubility of PbSiO3 in equilibrium with SiO2 (soil). However, they were supersaturated with regard to the solubilities of the Pb carbonate minerals PbCO3 (cerussite) and Pb3(CO3)2(OH)2 in equilibrium with atmospheric CO2 and hydroxide Pb(OH)2. They were also supersaturated with regard to the solubilities of the Pb phosphate minerals Pb3(PO4)2, Pb5(PO4)3OH, and Pb4O(PO4)2 in equilibrium with tricalcium phosphate and CaCO3. The activity of Pb2+ was not regulated by any mineral of known solubility in our soils, but possibly by a mixture of Pb carbonate and phosphate minerals.
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PMID:Soil solid-phase controls lead activity in soil solution. 1184 Oct 61

The degradation of 4-chlorophenol with near-UV light by silica-immobilized polyoxometalate (POM-in-SiO2) catalysts has been studied. The silica-immobilized Na6W7O24 (SW7), H4W1032 (SW10), H3PW12O40 (SPW12), and H6P2W18O62 (SP2W18) were prepared by means of the sol-gel hydrothermal technique through the hydrolysis of tetraethoxysilane in aqueous solution of the corresponding polyoxometalate, respectively. The degradation of 4-chlorophenol was monitored by measuring Cl- and CO2 concentrations and analyzing reaction intermediates by GC/MS analysis. During irradiation, 4-chlorophenol first dechlorinated to form hydroquinone and p-benzoquinone, and then these intermediates further mineralized to form CO2 and H2O. The degree to which 4-chlorophenol was mineralized by photocatalytic oxidation was investigated. Results indicate less than 15% for SW7 but nearly complete mineralization for SW10 after 60 min of photoirradiation. The present studies suggest that POM-in-SiO2 catalysts may be a novel type of photocatalyts for the purification of the environmentally chlorophenol-contaminated water.
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PMID:Photocatalytic degradation of aqueous 4-chlorophenol by silica-immobilized polyoxometalates. 1194 88

A coherent layer of zeolite A has been applied to a SiO2-supported Pt-Fe oxidation catalyst, using total surface charge-reversal. The zeolite has tracked the metals into the pore structure of the support, covering the active sites. The zeolite channel size is large enough to allow access of CO and O2 to the active sites, and to allow CO2 to emerge, but it excludes larger molecules. The presence of the zeolite membrane transforms the supported Pt-Fe into a highly specific catalyst, which can discriminate between CO and butane, even after the macroscopic catalyst particles are crushed.
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PMID:Active-site coating for molecular discrimination in heterogeneous catalysis. 1453 77


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