Amount Of Dioxide Research Articles

Adsorption/desorption of NOx on MnO 2/ZrO 2 oxides prepared in reverse microemulsions

A series of MnO 2/ZrO 2 mixed oxides were prepared in reverse microemulsions for NOx adsorption and abatement. The results show that the amount of NOx adsorbed was increased with increasing MnO 2 content in various MnO 2/ZrO 2 samples. The maximum uptake value of NOx was 27.66 mg NOx/g adsorbent on the 40% Mn–Zr sample at 200 °C with NOx initial adsorption rate as 2.63 mg/(g adsorbent min). TPD results show that the complete desorption of NOx was easily obtained by heating the sample to 450 °C, and the temperature for the complete desorption can be further decreased to 210 °C by adding carbon monoxide into the argon desorption streams. Furthermore, water vapor was found to reduce NOx adsorption capacity because of its stronger competitive adsorption with NOx species. It is noteworthy that a small amount of sulfur dioxide could significantly increase the initial rate of NOx adsorption although it slightly decreased the NOx adsorption capacity.

Analysis of Titanium Dioxide in Synthetic Fibers Using Raman Microspectroscopy

The ability of Raman microspectroscopy to distinguish between rutile and anatase forms of the inorganic pigment titanium dioxide (TiO(2)) and to make quantitative measurements of titania loading in fibers is demonstrated. Issues that affect the validity of the Raman measurements include the spatial heterogeneity of TiO(2) in the fiber, the polarization of the laser beam, and the polarizing properties of the fiber itself. The amount of titanium dioxide in single delustered polyamide fibers was quantitated at concentration levels ranging from 0 to 7.1% TiO(2). Fiber polarization and orientation effects were shown to be minimized by scrambling the polarization of the laser.

Ruthenium(II)-tris-bipyridine/titanium dioxide codoped zeolite Y photocatalyst: Performance optimization using 2,4-xylidine (1-amino-2,4-dimethyl-benzene)

The heterogeneous photocatalysts of the ruthenium(II)-tris-bipyridine/titanium dioxide/zeolite Y ([Ru(bpy) 3] 2+/TiO 2/zeolite Y) family perform in a manner very similar to a “Fenton-catalyst” in the oxidative degradation of the model pollutant 2,4-xylidine (1-amino-2,4-dimethyl-benzene). Upon photoexcitation using visible light, an electron-transfer reaction to hydrogen peroxide is observed. The oxidation rate of 2,4-xylidine follows a distinct percolation behavior, which is dependent on the amount of titanium dioxide incorporated as nanoparticles into the zeolite Y's framework. The maximum of the photocatalytic degradation of 2,4-xylidine at pH 3.0 was found to be at 34.5 ± 0.5% TiO 2 per weight. The optimization of the performance parameters of this particular [Ru(bpy) 3] 2+/TiO 2/zeolite Y photocatalyst was undertaken in a pilot reactor ( V = 3.25 L), equipped with a medium pressure mercury lamp (TQ 718). Important factors in the apparent photocatalytic efficiency have been determined: (a) the availability of dissolved oxygen, (b) the substrate concentration and (c) the concentration of the dispersed photocatalyst. At higher starting concentrations of 2,4-xylidine (>200 mg C L −1), the photocatalytic oxidation process is hampered by parasitic light absorption by an azo-dye formed and, especially, by competitive adsorption of hydrogen peroxide and 2,4-xylidine at the nanoscopic TiO 2-centers. It is noteworthy that 2,4-dimethylphenol and oxalic acid were the main reaction products, when 200 mg C L −1 of 2,4-xylidine were oxidatively degraded, whereas a multitude of reaction intermediates were detected when the starting concentration of 2,4-xylidine was 500 mg C L −1. Evidence is given that hydroxylamine is formed during the oxidation of 2,4-xylidine, which subsequently is either reduced to ammonium or generated from the disproportionation of hydroxylamine to ammonium and nitrogen. In the discussion section of this report, the observed reaction behavior is rationalized, based on the elementary chemical reactions occurring in the irradiated heterogeneous reaction mixture.

Fotodegradación heterogénea de bisfenol A en agua con dióxido de titanio

contaminated by industrial remainder flow. In this article heterogeneous photo degradation of a solution of BPA in water solution using a catalytic photo reactor with UV light and titanium dioxide (TiO 2 ) was evaluated. High performance liquid chromatography (HPLC) was used to analyze the photo degradation of BPA solutions. The influence of titanium dioxide amount, BPA concentration, reaction temperature and the catalyst state like suspension and immobilized were also determinated. The highest elimination of BPA was 83.2%, in 240 min, beginning with 0.05 mM of BPA and 100 mg/L of TiO 2 in suspension.

Antibacterial electrospun chitosan/poly(vinyl alcohol) nanofibers containing silver nitrate and titanium dioxide

AbstractChitosan/poly(vinyl alcohol) (PVA) nanofibers with antibacterial activity were prepared by the electrospinning of a chitosan/PVA solution with a small amount of silver nitrate (AgNO3) and titanium dioxide (TiO2). Nanofibers with diameters of 270–360 nm were obtained. The yield of low‐viscosity chitosan (LCS)/PVA nanofibers was higher than that of high‐viscosity chitosan (HCS)/PVA, and the water content of the HCS/PVA nanofibers and the LCS/PVA nanofibers were 430 and 390%, respectively. The nanofibers developed in this study exhibited antibacterial activities of 99 and 98% against Staphylococcus aureus and Escherichia coli, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Retrieval of Gas Pollutants Vertical Profile in the Boundary Layer by Means of Multiple-Axis DOAS

This paper presents a methodology for the retrieval of the vertical profile of atmospheric gas pollutants in the boundary layer from ground-based remote sensing measurements. Nitrogen dioxide (NO2) and ozone (O3) slant column amounts were obtained with the differential optical absorption spectroscopy (DOAS) technique used in the multiple-axis configuration (referred to as multiaxis DOAS). The measurements were carried out in the Presidential Estate at Castel Porziano (near Rome) from September to November 2006, within a program started in 1994 for studying and monitoring the Estate's environment. The retrieval of information on trace gas vertical profiles from the slant column amounts requires as follows: (1) the simulation of the radiative transfer in the atmosphere for air mass factor calculation and (2) the application of inversion schemes. This paper illustrates and discusses the vertical profiles of NO2 and O3 obtained from multiaxis DOAS measurements and their daily evolution on October 29, 2006.

Spineli Catalysts for the Catalitic Combustion of Toluen

Three spinels catalysts with copper were synthetized: Cr2CuO4, Fe2CuO4 and (Fe,Cr)2CuO4 using the coprecipitation method, with a tartrate precursor type. The catalysts were characterized by atomic absorption spectrometry, X-ray diffraction spectrometry and IR and UV-Vis spectroscopy. The three catalysts were tested in toluene oxidation reaction and theirs performances were assessed by carbon dioxide amounts resulted from reactions.

Ten-year measurements of gaseous pollutants in urban air by an open-path analyzer

Object of this study is the versatility of a remote-sensing measurement system through experimental survey of the levels of primary and secondary pollutants in urban areas. For the first time a long-range measurement of different pollutant for a long period are reported in the urban area of Rome. Over 10 years of data collection, levels of NO2, O3, SO2, benzene and toluene are measured and discussed by means of a differential optical absorption spectroscopy (DOAS) system installed at ground level.The period is interesting because it represents one of the most important life-changes in Europe and in Italy: in fact, during the 1990s some significant decrees introduced the catalytic pots and limited the amount of benzene and sulfur dioxide in the fuel. The paper will describe how the main primary and secondary pollutants are changed during all the period: particularly, benzene and SO2 are not over a big social problem for the human health whereas the secondary pollutants, ozone and nitrogen dioxide, have the same trends during the period, meaning a no contribution to their evolution from the atmospheric processes.The DOAS technique is resulted very useful and versatile: comparisons with other traditional analyzers (i.e., GC-PID for benzene and toluene investigations) demonstrate how it allows to have information over all the territory saving the qualitative trends and giving a similar quantitative result. In this respect the authors show that the difference is due to the different sampling ways (the traditional analyzers are punctual whereas the DOAS is a remote-sensing technique covering a wide area) and does not influence the atmospheric process interpretation.Finally, it should be considered that the pollutant trends have been interpreted using the concentration measurements of natural radioactivity as tracer of the dynamic properties of the atmospheric boundary layer.

Advances in Chemical Oxidation of Total Reduced Sulfur from Kraft Mills Atmospheric Effluents

Chemical oxidation techniques in use for the reduction of malodorous total reduced sulfur (TRS) emissions in the kraft mills atmospheric effluents were reviewed with an emphasis on recent industrial improvements in chlorine dioxide (ClO2) oxidation of TRS as well as on laboratory developments of an iron-based chemistry process. The ClO2 approach was implemented successfully at the industrial scale in two Québec kraft mills. The approach consisted in mixing the non-condensable gases (NCG) containing the TRS with gaseous chlorine dioxide obtained either as a residue from a bleach plant vent stream or through vaporization of fresh solution. Full-scale tests have shown that the amount of chlorine dioxide injected or mixed in the NCG was sufficient to reduce the TRS load below the 10 ppmv-regulated levels in a cost efficient way as compared with incineration. A prospective approach validated in laboratory conditions and using the iron redox chemistry for alkaline oxidative scrubbing of TRS is being investigated at Laval University to reduce the odor pollution and to convert TRS into valuable sulfur. Two configurations were evaluated, one consisting of homogeneous Fe(III) sequestered in trans-1,2-diaminocyclohexanetetraacetic acid (cdta) chelates and another of heterogeneous Fe(III) as Fe/Ce oxides-hydroxides mixtures. The relative performances, advantages and weaknesses of the various chemical oxidation processes were discussed. In addition, the fundamentals of the alkaline oxidative scrubbing of TRS using the iron-based alkaline approach were summarized in terms of the gas-liquid thermodynamic equilibria and of the homogeneous and heterogeneous iron redox reactions.

Characterization of the oxidative inactivation of xylanase by laccase and a redox mediator

The biomass-processing enzymes laccase and xylanase can each be used to moderately reduce the amount of chlorine dioxide required for bleached pulp production. Although combined enzyme treatment is anticipated to be appealing to biomass-converting industries seeking to implement green processes, simultaneous incubation of these enzymes in the presence of a laccase mediator such as 1-hydroxybenzotriazole (HBT) results in rapid loss of xylanase activity. To characterize this inactivation, Thermomyces lanuginosus xylanase was treated with Trametes versicolor laccase in the presence of HBT. The time-dependent loss of xylanase activity showed first order kinetics, and a plot of inactivation rate constant versus HBT concentration exhibited saturation kinetics. Further, the xylanase substrate xylan protected against the inactivation. These results are consistent with an active-site directed modification, and the change in the xylanase UV absorbance and fluorescence emission spectra upon inactivation suggests tryptophan oxidation. To further characterize the nature of the modification, inactivated xylanase was digested with chymotrypsin and the resulting peptides were analyzed via mass spectrometry. The laccase-generated HBT oxidant was demonstrated to oxidize tryptophan residues to oxindolealanine residues, including Trp17 and known xylan-binding Trp18. Mechanistic detail of the oxidative inactivation will provide the basis for future studies focused on construction of redox-resistant xylanases.

Material properties of portland cement paste with nano-montmorillonite

The nano-montmorillonite, which has characteristics of high aspect ratio and interaction between polymer chains and dispersed nanolayers, has been widely used in the development of new reinforced nanocomposite polymers to improve their mechanical properties. Since a potential pozzolanic reaction may occur between Portland cement paste and high amount of silicon dioxide (SiO2) in nano-montmorillonite, the effects of introduction of montmorillonite to Portland cement-based material on the improvement of matrix properties of cement paste is of great interest in the construction industry. In this study, a liquid-form of nano-montmorillonite particle with a planar diameter of about 100 nm were incorporated into the Portland cement paste at five different dosages and analyzed at four different ages to identify the nanosizing effects on material properties of such cement-based composite. Experimental results show that the composite with 0.60% and 0.40% of added nano-montmorillonite by weight of cement have the optimum compressive strength and permeability coefficient, respectively, in which the increase of compressive strength is about 13.24%, and the decrease of permeability coefficient about 49.95%. Microstructural properties through the analyses of XRD, DSC, NMR, and MIP also indicate that the microstructures of cement paste with nano-montmorillonite contain more dense solid material and more stable bonding framework.

Preventing mercury emissions from coal-fired power plants using environmentally preferable coal purchasing practices

Electric utilities in the United States will soon be required under the federal Environmental Protection Agency's Clean Air Mercury Rule to significantly reduce mercury emissions. Coal-fired power plants, including the Lower Colorado River Authority's (LCRA) Fayette Power Project (FPP) have demonstrated that the selective purchasing of coal with low mercury content can result in significant reduction of pollution. This selective activity, commonly known as “green purchasing”, has been applied to the procurement of coal. For example, the use of low-sulfur coal from the Powder River Basin deposits of Wyoming results in the prevention of a significant amount of sulfur dioxide (SO 2) releases to the atmosphere when compared to other sources of coal in the United States. This same philosophy (selective purchasing of coal) can be employed to prevent mercury emissions and substantially reduce mercury removal costs for electric utilities burning coal. Data analysis confirms that low-mercury coal is available and that selective purchasing of low-mercury coal is possible. LCRA has implemented an extensive pollution prevention program and their green purchasing efforts have been expanded to influence coal purchasing choices. Coal purchasing is limited to the Gillette Coal Field from the Powder River Basin (PRB) of Wyoming. Three sets of coal quality data which include LCRA's Coal Quality Database (CQD), a database created from the Information Collection Request (ICR) conducted by the EPA in 1999, and the U.S. Geological Survey (USGS) Coal Quality (COALQUAL) Database were analyzed. Lab accuracy issues were found to have undermined the reliability of certain records in both the CQD and ICR databases, however, both remain valuable resources. The independent sets of coal quality data and technical reports show measurable differences in mercury concentration in coal in the Gillette Coal Field, both geographically (coal mine) and by depth (coal seam). A preliminary cost benefit analysis indicates that substantial cost savings in operating and maintaining mercury control equipment will be realized with low-mercury coal. Currently, low-mercury coal can be purchased without a significant premium.

Measurement of ambient ozone using newly developed porous glass sensor

An accumulated sensor with an hourly resolution has been developed for ambient ozone monitoring. The sensor operates by employing the reaction of ozone with indigo carmine. This reaction results in colorless reaction products in pores that can be determined by measuring the transmittance of the color change. Transparent porous glass is used as a substrate whose very large surface area is an advantage for gas sensing. Direct, on-site measurements are possible because of the use of the transparent substrate, and no chemical analyses are needed. The sensor is used to analyze exposure to ozone. The detection limit of the sensor is about 3 ppb for a 1 h exposure. The interference from nitrogen dioxide amounts to about 25%. The method is suitable for hourly to daily mean measurements of ambient ozone. Under indoor conditions, the correlation coefficient between the hourly ozone concentration indicated by our sensor and by a UV-photometric monitor for 3 months was 0.84, indicating good agreement.

Interactions between sulphides and manganese dioxide in thiosulphate leaching of gold ores

The interactions between manganese dioxide and pyrite or chalcopyrite were investigated in both the ammoniacal and ammoniacal thiosulphate leaching systems. Pyrite and chalcopyrite dissolved at enhanced rates in the presence of manganese dioxide in both ammoniacal and ammoniacal thiosulphate solutions. The interactions between manganese dioxide and sulphides were also applied in the thiosulphate leaching of gold from a pyrite concentrate and a sulphide ore. The addition of a small amount of manganese dioxide in the thiosulphate leaching of the sulphide bearing gold ores improved both the kinetics and the overall gold extractions without much impact on thiosulphate consumption. A pre-treatment process with copper ammoniacal solutions enhanced gold extractions from the sulphide bearing ores and reduced thiosulphate consumption to a large extent. The sulphides partially degraded in the pre-treatment process likely exposing gold to leach solutions. SEM images of the surface corrosion of pyrite and chalcopyrite in contact with manganese dioxide showed that the pre-treatment with manganese dioxide enhanced the degradation of the sulphide matrices, thus achieved a better gold leaching from the sulphide bearing ores.

Preparation of rectorite-TiO2 and its application in the solar photocatalytic degradation of dye wastewater

A photocatalyst consisting of TiO2 powder and rectorite was prepared and activated utilizing solar light and used for degradation of simulated dye wastewater (methyl solution). The effects of roasting temperature, the way of adding rectorite, and the amount of the rectorite on the photocatalytic activity have been investigated. The results indicated that rectorite-TiO2 photocatalyst prepared with the right proportional amount of rectorite and titanium dioxide, could effectively degrade the methyl orange solution in sunlight. After reacting in sunlight for 8 hours, the methyl orange decolorization reached 96%. The photocatalytic activity of rectorite-TiO2 was much better than that of TiO2 in sunlight.

Rare sulfur and triple oxygen isotope geochemistry of volcanogenic sulfate aerosols

We present analyses of stable isotopic ratios 17O/ 16O, 18O/ 16O, 34S/ 32S, and 33S/ 32S, 36S/ 32S in sulfate leached from volcanic ash of a series of well known, large and small volcanic eruptions. We consider eruptions of Mt. St. Helens (Washington, 1980, ∼1 km 3), Mt. Spurr (Alaska, 1953, <1 km 3), Gjalp (Iceland, 1996, 1998, <1 km 3), Pinatubo (Phillipines, 1991, 10 km 3), Bishop tuff (Long Valley, California, 0.76 Ma, 750 km 3), Lower Bandelier tuff (Toledo Caldera, New Mexico, 1.61 Ma, 600 km 3), and Lava Creek and Huckleberry Ridge tuffs (Yellowstone, Wyoming, 0.64 Ma, 1000 km 3 and 2.04 Ma 2500 km 3, respectively). This list covers much of the diversity of sizes and the character of silicic volcanic eruptions. Particular emphasis is paid to the Lava Creek tuff for which we present wide geographic sample coverage. This global dataset spans a significant range in δ 34S, δ 18O, and Δ 17O of sulfate (29‰, 30‰, and 3.3‰, respectively) with oxygen isotopes recording mass-independent ( Δ 17O > 0.2‰) and sulfur isotopes exhibiting mass-dependent behavior. Products of large eruptions account for most of‘ these isotopic ranges. Sulfate with Δ 17O > 0.2‰ is present as 1–10 μm gypsum crystals on distal ash particles and records the isotopic signature of stratospheric photochemical reactions. Sediments that embed ash layers do not contain sulfate or contain little sulfate with Δ 17O near 0‰, suggesting that the observed sulfate in ash is of volcanic origin. Mass-dependent fractionation of sulfur isotopic ratios suggests that sulfate-forming reactions did not involve photolysis of SO 2, like that inferred for pre-2.3 Ga sulfates from Archean sediments or Antarctic ice-core sulfate associated with few dated eruptions. Even though the sulfate sulfur isotopic compositions reflect mass-dependent processes, the products of caldera-forming eruptions display a large δ 34S range and exhibit fractionation relationships that do not follow the expected equilibrium slopes of 0.515 and 1.90 for 33S/ 32S vs. 34S/ 32S and 36S/ 32S vs. 34S/ 32S, respectively. The data presented here are consistent with modification of a chemical mass-dependent fractionation of sulfur isotopes in the volcanic plume by either a kinetic gas phase reaction of volcanic SO 2 with OH and/or a Rayleigh processes involving a residual Rayleigh reactant—volcanic SO 2 gas, rather than a Rayleigh product. These results may also imply at least two removal pathways for SO 2 in volcanic plumes. Above-zero Δ 17O values and their positive correlation with δ 18O in sulfate can be explained by oxidation by high- δ 18O and high- Δ 17O compounds such as ozone and radicals such as OH that result from ozone break down. Large caldera-forming eruptions have the highest Δ 17O values, and the largest range of δ 18O, which can be explained by stratospheric reaction with ozone-derived OH radicals. These results suggest that massive eruptions are capable of causing a temporary depletion of the ozone layer. Such depletion may be many times that of the measured 3–8% depletion following 1991 Pinatubo eruption, if the amount of sulfur dioxide released scales with the amount of ozone depletion.

Adsorption of Sulfur Dioxide from Coal Combustion Gases on Natural Zeolite

In this study, better efficiency of SO2 removal in flue gas from lignite coal combustion by adding of NZ in the gas phase was achieved. Natural zeolite was exposed to flue gas containing sulfur dioxide at varying conditions of relative humidity and temperature. It was found that the amount of sulfate on the zeolite increased with increasing relative humidity and temperature. The percents of adsorbed sulfur dioxide were 86, 74, 56, and 35, while the values of relative humidity (RH) were 75, 60, 45, and 30% for 40 minutes, respectively. The percents of adsorbed sulfur dioxide sharply increased within the first 40 min for the values of RH were 75 and 60, and after 40 min, slightly increased, then reached a plateau. In general, as increasing the RH increased the amount of sulfur dioxide adsorbed by natural zeolite. The amounts of adsorbed sulfur dioxide increased with exposure time. It increased and reached 30.2 mg/g for 40 min. After 40 min, it slightly increased and then reached a plateau. The NZ adsorbs 35.1 mg SO2 per gram adsorbent with 75% RH at 298 K from a simulated coal combustion flue gas. The amounts of adsorbed sulfur dioxide increased with increasing temperature. The NZ adsorbs 71.5 mg SO2 per gram adsorbent with 75% RH for 100 min exposure time from the flue gas mixture.

Inorganic Reactions in Chlorine Dioxide Bleaching of Softwood Kraft Pulp

A softwood kraft pulp (27 kappa) was bleached with chlorine dioxide to various end pH values. The formation of chlorite, chlorate, and chloride was measured to quantify the amount of chlorine dioxide wasted as a function of pH during a Do (pre‐bleaching) stage. Chlorate formation increased with a decrease in final pH. Conversely, residual chlorite increased with an increase in the final pH. After 120 min of bleaching the total residual chlorite and chlorate showed that no substantial increase in residual oxidant occurs when bleaching to an end pH below 3.4. As a result, the brightness and permanganate numbers for low pH chlorine dioxide bleached pulps did not differ when bleaching to an end pH between 3.4 and 1.8. However, decreasing the pH below 3.4 did result in increased organic chloride formation. The results are contrary to previous studies where the maximum bleaching efficiency for a D1 stage was reported to occur when the end pH was between 3 and 4.

還元型酸窒化チタン系黒色基板に二酸化チタンを被覆した光干渉顔料の調製とその光学的特性

マイカ基板に二酸化チタンを被覆した粒子から二酸化チタンを剥離して得た二酸化チタン板状粒子を出発原料として用い, それを還元処理して黒色基板とし, さらにそれに所定量の二酸化チタンを被覆させることによって白色台紙上でも各種の光于渉発色する顔料を得ることができた。このように基板を黒色化することで塗膜とした際の下地に黒色を用いた場合と同じように透過光を吸収する光干渉発色顔料を得ることができた。得られた顔料の色相制御は, 原料の黒色基板に滴下した四塩化チタンの滴下量の増加に従い, すなわち黒色基板に被覆された二酸化チタン量の増加とともに分光反射率曲線の反射ピークは長波長側にシフトし, 140nm厚さの原料基板を用いた場合には青紫色から青色, 緑色, 黄色, 金色, 赤色へと変化し, 220nm厚さの原料基板の場合には赤紫色から青紫色, 緑色へと変化した。これらの顔料粒子の星さを調べた結果, 顔料粒子全体の厚さと干渉発色の色相との間に相関性を認めた。また, 原料とした二酸化チタン基板には局い光触媒性を有していたが, 黒色化する際の還元処理およびシリカ被覆処理によって, その光触媒性を低下させることができることも明らかにした。

Evaluation of Recycling Technology of Insulation of Cross-linked Polyethylene Insulated Cable using Supercritical Alcohol

The material recycling of the insulation of cross-linked polyethylene cable was studied. We successfully obtained thermoplastic recycled polyethylene from silane cross-linked polyethylene by using chemical reaction in supercritical alcohol.Here, the continuous process for the recycling of silane cross-linked PE using supercritical alcohol was constructed. The mechanical and electrical properties of recycled polyethylene satisfied the requirement of the cable insulation. These results indicate that the cable to cable and wire to wire recycling of silane cross-linked polyethylene will possibly be accomplished by supercritical technology using extruder.Moreover the environmental effect of this technology was evaluated by the amount of the carbon dioxide generated from the continuous process. These results indicate that recycling method using supercritical alcohol was useful for the reduction of the environmental pollution.