Oxygen Bubbling Research Articles

Evaluation of in-service oxidative stability and antioxidant additive consumption in corn oil based natural ester insulating fluid

The Rancimat method was used to evaluate the consumption of antioxidant additive in a natural ester insulating fluid (NEI). NEI samples were aged in the laboratory with and without oxygen bubbling. NEI samples were also collected from a transformer in operation. Samples of NEI (unused, aged in the laboratory and collected from transformer in operation) were analyzed by Fourier-transform infrared spectroscopy (FTIR) and by the Rancimat method for induction time (IT) measurement. The results showed that it is possible to evaluate the consumption of antioxidant additive in NEI in service by the Rancimat method. Laboratory tests were also performed to extend the lifetime of NEI in service by adding new loads of antioxidant additive. The results showed that the addition of new antioxidant additive loads when the IT of in-service NEI (determined by Rancimat method) reaches about 3 h extends the lifetime of this oil.

Spectroscopic properties of cerium-doped aluminosilicate glasses

The spectroscopic properties of cerium ions in various aluminosilicate glasses modified by Mg2+, Ca2+, Ba2+ and Na+ were investigated in order to optimize these for the potential utilization as Ce3+/Yb3+ quantum cutting material. An increasing optical basicity of the glasses results in a shift in the peak position of the 5d-4f emission of Ce3+ to longer wavelengths and in a decrease in the Ce3+ fluorescence intensity due to decreasing Ce3+/Ce4+ ratios. Argon-bubbling of the melt and supplying argon as melting atmosphere and/or using small amounts of metallic aluminum powder as raw material led to an almost complete reduction of Ce4+ to Ce3+. This resulted in much higher intensities of the Ce3+ fluorescence emission which runs parallel to a decreasing charge transfer absorption of Ce4+. From the absorption spectra of these samples extinction coefficients for Ce4+ and Ce3+ were calculated. For this purpose, an additional sample was prepared by using oxygen bubbling of the melt. An increasing cerium concentration shifts the Ce3+ emission peak position to longer wavelengths, while up to 2·1020 ions per cm3 only a slight increase in the Ce3+ emission intensity was observed. At higher dopant concentrations, a drastic decrease in the Ce3+ fluorescence emission is observed which is most likely attributed to an increasing Ce4+ concentration. High intensity Ce3+ blue emission matching the spectroscopic requirements for potential quantum cutting in Ce3+/Yb3+ codoped glasses could be achieved with a barium aluminosilicate glass.

Degradation of Alizarin Red by Hybrid Gas-Liquid Dielectric Barrier Discharge

A system based on dielectric barrier discharge (DBD) with improved discharge stability and homogeneity was used for the degradation of Alizarin Red (AR). This special structure of the DBD system is characterized by the high voltage electrode, which is covered with a quartz tube and partially immersed in water, and by directly using the water as the ground electrode. A transition was realized from the filamentary mode for the conventional structure of the DBD to the semi-homogeneous mode for such a configuration of the plasma discharge. The spectra of plasma are dominated by N2 molecular lines in the ultraviolet-A radiation region. Plasma degradation of AR in this system exhibited pseudo-first-order reaction kinetics. The degradation rate of AR reached 95% or so after 14 min treatment under favorable conditions. Alkaline conditions are favorable for the degradation of AR. The increase of conductivity of the solution, input power and usage of oxygen bubbling could enhance AR degradation.

Selective flotation of chalcopyrite and molybdenite with plasma pre-treatment

For pretreatment of selective flotation, plasma treatment of chalcopyrite and molybdenite was applied then the minerals were washed by solution at pH 9 with oxygen bubbling. Surface characteristics of these minerals were investigated with AFM, XPS, zeta potential and contact angle measurements. Contact angle of chalcopyrite and molybdenite decreased a lot by plasma treatment. When they were washed with pH 9 solution with oxygen bubbling, contact angle of molybdenite increased whereas chalcopyrite one kept low. Adhesion force measurements indicated similar behavior. Result of flotation experiments indicated low recovery of both chalcopyrite and molybdenite after plasma treatment and only molybdenite recovery became higher after washing. Selective flotation of chalcopyrite and molybdenite could be achieved with this process. However, flotation of mixture of chalcopyrite and molybdenite after these treatments indicated both chalcopyrite and molybdenite were depressed. Addition of emulsified kerosene changed the flotation results where molybdenite was floated and chalcopyrite was depressed. Possible mechanism of selective flotation was proposed from the results of XPS, AFM, etc.

Titanium-oxo cluster with 9-anthracenecarboxylate antennae: a fluorescent and photocurrent transfer material.

Attention has been paid to titanium-oxo clusters (TOCs) modified with functional molecules, because they can be considered as model systems for dye-sensitized titanium oxides in terms of their information in structures and electron transfer. We select 9-anthracenecarboxylate (9-AC) as a photoactive ligand and prepare two model compounds, [Ti6O6(O(i)Pr)6(9-AC)6] (1) and [Ti6O4(O(i)Pr)6(cat)4(9-AC)2] (2) (where cat = catecholate). Structures of the TOCs and the dye-TOC linkage are characterized by single-crystal analysis. Solvent-induced fluorescence change is observed for the cluster solution, and the fluorescence can be turned off by irradiating and on by oxygen bubbling. Photoinduced Ti(III) is responsible for the fluorescence extinction. The photocurrent conversion property of the clusters is examined by use of a three-electrode cell with cluster-coated indium tin oxide (ITO) electrodes. The results indicate that 9-AC is an effective photosensitizer and cluster 1 shows higher photocurrent intensity for its multiantenna structure in comparison with that of 2. Density of states for cluster 1 is calculated, in which the discrete energy bands of Ti6O24 include a number of new energy levels for the contribution of 9-AC molecules.

Extraction of arsenic from arsenic-containing cobalt and nickel slag and preparation of arsenic-bearing compounds

The arsenic extraction from the arsenic-containing cobalt and nickel slag, which came from the purification process of zinc sulfate solution in a zinc smelting factory, was investigated. The alkaline leaching method was proposed according to the mode of occurrence of arsenic in the slag and its amphoteric characteristic. The leaching experiments were conducted in the alkaline aqueous medium, with bubbling of oxygen into the solution, and the optimal conditions for leaching arsenic were determined. The results showed that the extraction rate of arsenic was maximized at 99.10% under the optimal conditions of temperature 140 °C, NaOH concentration 150 g/L, oxygen partial pressure 0.5 MPa, and a liquid-to-solid ratio 5:1. Based on the solubilities of As2O5, ZnO and PbO in NaOH solution at 25 °C, a method for the separation of As in the form of sodium arsenate salt from the arsenic-rich leachate via cooling crystallization was established, and the reaction medium could be fully recycled. The crystallization rate was confirmed to reach 88.9% (calculated on the basis of Na3AsO4) upon a direct cooling of the hot leachate down to room temperature. On the basis of redox potentials, the sodium arsenate solution could be further reduced by sulfur dioxide (SO2) gas to arsenite, at a reduction yield of 92% under the suitable conditions. Arsenic trioxide with regular octahedron shape could be prepared successfully from the reduced solution, and further recycled to the purification process to purify the zinc sulfate solution. Also, sodium arsenite solution obtained after the reduction of arsenate could be directly used to purify the zinc sulfate solution. Therefore, the technical scheme of alkaline leaching with pressured oxygen, cooling crystallization, arsenate reduction by SO2 gas, and arsenic trioxide preparation, provides an attractive approach to realize the resource utilization of arsenic-containing cobalt and nickel slag.

Sequestration of Cd(II) with nanoscale zero-valent iron (nZVI): Characterization and test in a two-stage system

Abstract Nanoscale zero-valent iron (nZVI) for removal of cadmium from polluted water was investigated. Batch experiments were conducted at 1:100 mass ratio of Cd to nZVI to investigate low, medium and high concentration levels of species. Effect of solution pH was importantly evaluated on the removal efficiency of Cd(II) by nZVI. The removal process is fast and can reach equilibrium in less than 30 min. The cadmium removal efficiency increases rapidly with rising pH in the range of 3.0–8.6, maximum removal capacity of 66.9 mg Cd(II)/g nZVI was observed. Benchmark tests were also conducted with oxidized nZVI (nZVI oxidized with oxygen bubbling), which had much lower removal efficiency of Cd(II) under identical conditions. Flow experiments with a two-stage reactor were performed to examine the effects of hydraulic retention time, influent cadmium concentration, nZVI recycle ratio and nZVI dose. Removal efficiency over 91% was achieved within a residence time of 20 min in a two-stage flow reactor. Higher nZVI recycle ratio and longer hydraulic retention time enhanced removal efficiency. Transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray powder diffraction were employed to characterize nZVI before and after the reactions. Data suggest that Cd(II) is sequestrated within nZVI by adsorption or surface complex formation with no apparent reduction of Cd(II).

산소-플라즈마 방전을 이용한 수중의 페놀 제거

Decomposition of non-biodegradable contaminants such as phenol contained in water was investigated using a dielectric barrier discharge (DBD) plasma reactor in the aqueous solutions with continuous oxygen bubbling. Effects of various parameters on the removal of phenol in aqueous solution with high-voltage streamer discharge plasma are studied. In order to choose plasma gas, gas of three types (argon, air, oxygen) were investigated. After the selection of gas, effects of 1st voltage (80 ~ 220 V), oxygen flow rate (2 ~ 7 L/min), pH (3 ~ 11), and initial phenol concentration (12.5 ~ 100.0 mg/L) on phenol degradation and change of absorbance were investigated. Absorbance of can be used as an indirect indicator of phenol degradation and the generation and disappearance of the non-biodegradable organic compounds. Removal of phenol and COD were found to follow pseudo first-order kinetics. The removal rate constants for phenol and COD of phenol were and , respectively.

Molecular oxygen as a regulator of primary chain length of branched polymers formed in 3D radical polymerization. Oxidative polymerization of styrene

On the example of oxidative polymerization of styrene, explored was the feasibility of regulating the length of polymer chain upon variation in the amount of oxygen dissolved in the liquid phase. Due to the use of rapidly decomposing 2,2′-azo-bis-(isobutyronitrile) (AIBN) as an initiator, the polymerization reaction (at 95 °С) proceeded in two stages. At the first one, a source of radicals was AIBN; while at the second stage, the peroxide groups formed in a course of reaction. Based on literature data for rate constants of elementary reactions, suggested was a mathematical model for calculating the running concentration of dissolved oxygen in reaction solution. At [AIBN] = 0.01 M and a rate of oxygen bubbling (VO2) of 62.4 × 10−3 M/min, the polymer exhibited a relatively low chain length (Мn = 700, Mw = 1600) but contained a large number of peroxide groups. Meanwhile, at [AIBN] = 0.05 M and VO2 = 6.0 × 10−3 M/min, the polymer chains were longer (Мn = 1700, Mw = 5800) while the amount of peroxide groups, low.

Oxidative and photochemical processes for the removal of galaxolide and tonalide from wastewater

Synthetic musks have been reported in wastewaters at concentrations as high as tens of micrograms per litre. The two most significant polycyclic musk fragrance compounds are 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta(g)-2-benzopyran (HHCB, trade name galaxolide®) and 7-acetyl-1,1,3,4,4,6-hexamethyltetrahydronaphthalene (AHTN, trade name tonalide®). We report the result of several irradiation and advanced oxidation processes carried out on samples of the effluent of a wastewater treatment plant located in Alcalá de Henares, Madrid. Wastewater samples were pre-ozonated and spiked with 500 ng/L of tonalide or galaxolide in order to obtain final concentrations in the same order as the raw effluent. The treatments assayed were ozonation with and without the addition of hydrogen peroxide (O3, O3/H2O2), ultraviolet (254 nm low pressure mercury lamp) and xenon-arc visible light irradiation alone and in combination with ozone (UV, O3/UV, Xe, O3/Xe) and visible light photocatalytic oxidation using a Ce-doped titanium dioxide photocatalyst performed under continuous oxygen or ozone gas bubbling (O2/Xe/Ce–TiO2, O3/Xe/Ce–TiO2). In all cases, samples taken at different contact times up to 15 min were analyzed. An analytical method based on stir bar sorptive extraction (SBSE), followed by comprehensive two-dimensional gas chromatography (SBSE-GC × GC–TOF-MS), was used for the automatic searching and evaluation of the synthetic musks and other nonpolar or semipolar contaminants in the wastewater samples. In all cases tonalide was more easily removed than galaxolide. The best results for the latter (more than 75% removal after 5 min on stream) were obtained from ozonation (O3) and visible light photocatalytic ozonation (O3/Xe/Ce–TiO2). A significant removal of both pollutants (∼60% after 15 min) was also obtained during visible light photocatalysis (O2/Xe/Ce–TiO2). UV radiation was able to deplete tonalide (+90%) after 15 min but only reduced the concentration of galaxolide to about half of its initial concentration. The toxicity of treated samples decreased for O3/UV and O3/Ce–TiO2, but increased during irradiation processes UV, Xe and Xe/Ce–TiO2. Ozone treatments tend to decrease toxicity up to a certain dosage, from which point the presence of toxic transformation products has adverse effects on aquatic microorganisms.

Modified Carbon Nanoball on Electrode Surface Using Plasma in Enzyme-Based Biofuel Cells

Biofuel cells performed similarly to those conventional fuel cells are regarded as one of potential substitute for fossil fuel. Developments of biofuel cells demonstrate the advantages on reduction of greenhouse gas emissions as well as increasing energy security. Enzyme-based biofuel cells is one kind of the biofuel cells, enzyme-based biofuel cells convert chemical energy into electrical energy via specific enzymes as biocatalysts. Glucose oxidase and laccase were immobilized onto carbon paper as bioanode and biocathode, respectively in enzyme-based biofuel cells system. Mediator and enzyme were mixed in phosphate buffer (pH 7) and citrate buffer (pH 5) solutions, respectively. A Nafion membrane117 was inserted to separate the two half cells. The power density with respect to different operating voltages was obtained with a glucose concentration of 10mM. Potassium hexacyanoferrate III and ABTS (2, 2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) as mediators were added to the bioanode and biocathode cell, respectively. Carbon nanoballs were coated on the carbon paper and enormous enhancement of power density was achieved.The power-voltage with the CNB surface modifying by using plasma was with oxygen bubbling in cathode directly in the cell achieved up to 0.114V. The power density was 65.5μW/cm2. The assembled enzyme-based biofuel cells were studied under nitrogen at 37°C in bioanode.

Electrochemical oxidation of phenol on boron-doped diamond electrode

The process of phenol oxidation on a boron-doped diamond electrode (BDD) is studied in acidic electrolytes under different conditions of generation of active oxygen forms (AOFs). The scheme of phenol oxidation known from the literature for other electrode materials is confirmed. Phenol is oxidized through a number of intermediates (benzoquinone, carboxylic acids) to carbon dioxide and water. Comparative analysis of phenol oxidation rate constants is performed as dependent on the electrolysis conditions: direct anodic oxidation, with oxygen bubbling, and addition of H2O2. A scheme is confirmed according to which active radicals (OH·, HO2·, HO2−) are formed on a BDD anode that can oxidize the substrate which leads to formation of organic radicals interacting with each other and forming condensation products. Processes with participation of free radicals (chain-radical mechanism) play an important role in electrochemical oxidation on BDD. Intermediates and polymeric substances (polyphenols, quinone structures, and resins) are formed. An excess of the oxidant (H2O2) promotes a more effective oxidation of organic radicals and accordingly inhibition of the condensation process.

ChemInform Abstract: Comparisons Between Haydeeite, α‐Cu3Mg(OD)6Cl2, and Kapellasite, α‐Cu3Zn(OD)6Cl2, Isostructural S = 1/2 Kagome Magnets.

AbstractThe title compounds are prepared by refluxing Cu powder in a solution of MgCl2 or ZnCl2 in D2O with four ground glass beads, each with an approximate radius of 1 mm and a surface area of 12.5 mm2 (as a nucleation surface) and slow oxygen bubbling.

Electrodeposition of SnO2 Thin Films from Aqueous Tin Sulfate Solutions

Tin oxide (SnO2) thin films were successfully electrodeposited on indium tin oxide (ITO) coated glass substrate from an acidic aqueous solution containing SnSO4 at room temperature. Oxygen bubbling was employed so that dissolved oxygen serves as oxygen precursor. With O2 bubbling and short deposition time, transparent films were obtained. The composition ratios of the films were measured by Auger electron spectroscopy. The n-type conductivity and the photosensitivity of the films were confirmed from photoelectrochemical measurement.

Luminescence Spectroscopic Observation of Singlet Oxygen Formation in Extra Virgin Olive Oil as Affected by Irradiation Light Wavelengths, 1,4‐Diazabicyclo[2.2.2]octane, Irradiation Time, and Oxygen Bubbling

A spectrofluorometer equipped with a highly sensitive near-IR InGaAs detector was used for the direct visualization of singlet oxygen emission at 1268 nm in olive oil during light irradiation with various different wavelengths. The virgin olive oil in methylene chloride (20% w/v, oxygen saturated) was irradiated at the 301, 417, 454, 483, and 668 nm, then the emission at 1268 nm, singlet oxygen dimole decaying was observed. The result showed the highest production of (1)O(2) with light irradiation at 417 nm, and followed by at 668 nm in virgin olive oil, indicating that pheophytin a and chlorophyll a were the most responsible components for the production of singlet oxygen. The UV light irradiations at the wavelength of 200, 250, and 300 nm did not induce any detectable luminescence emission at 1268 nm, but 350 nm produced weak emission at 1269 nm. The quantity of (1)O(2) produced with excitation at 350 nm was about 1/6 of that of irradiation at 417 nm. Addition of an efficient (1)O(2) quencher, 1,4-diazabicyclo[2.2.2]octane, in virgin olive oil in methylene chloride greatly decreased the luminescence emission at 1268 nm, confirming the singlet oxygen production in olive oil. Singlet oxygen production was more efficient in oxygen-purged virgin olive oil than in oxygen non-purged olive oil. This represents first report on the direct observation of singlet oxygen formation in olive oil as well as in real-food system after visible light illumination. Practical Application: The present results show the positive evidence of the singlet oxygen involvement in rapid oxidative deterioration of virgin olive oil under visible light. This paper also shows the effects of different wavelength of light irradiation on the formation of singlet oxygen in olive oil. The present results would provide important information for the understanding of the mechanism involved in rapid oxidative quality deterioration of virgin olive oil under light illumination and for searching the preventive methods of deterioration of olive oil quality under light.

ChemInform Abstract: Electroinitiated Oxygenation of Alkenyl Sulfides and Alkynes in the Presence of Thiophenol.

Electrolysis of alkenyl sulfides in the presence of thiophenol with bubbling of molecular oxygen gave the corresponding α-(phenylthio) carbonyl compounds with the consumption of a catalytic amount of electricity. An electroinitiated radical chain mechanism has been proposed. The reaction also took place without electrochemical initiation, but much (5-50 times) longer reaction time was required for the completion of the reaction. The potential utility of the present reaction in organic synthesis is demonstrated by the net 1,2-transposition of a phenylthio group and a carbonyl group. The electroinitiated oxygenation of ketene dithioacetals also proceeded smoothly to give the corresponding α-(phenylthio) thiol esters. It was also found that the electroinitiated oxygenation of alkynes in the presence of thiophenol gave α-(phenylthio) carbonyl compounds. A mechanism involving the initial formation of alkenyl sulfides has been proposed

Surface-passivation effects on the photoluminescence enhancement in ZnS:Mn nanoparticles by ultraviolet irradiation with oxygen bubbling

This study examined the effects of surface-passivation on the photoluminescence (PL) properties of ZnS:Mn nanoparticles treated by ultraviolet (UV) irradiation with oxygen bubbling. Compared to the pristine Mn-doped zinc-sulfide nanocrystals (quantum efficiency: ∼16%), the UV-irradiated ZnS:Mn showed significantly enhanced luminescence properties (quantum efficiency: ∼35%). The photoinduced surface passivation was characterized by x-ray diffraction, x-ray photoelectron spectroscopy, and time-resolved PL. The optimum thickness of the passivation layer for the quantum efficiency was examined considering the nanocrystal size, local strain, and radiative/nonradiative recombination rates.

Effect of Oxygen Bubbling on the Dissolution of Brass in Acidified Sodium Sulfate Solution under Free Corrosion Conditions

The effect of oxygen bubbling on the dissolution of brass was studied. Brass samples were immersed in acidified sodium sulfate solution at different temperatures (25-80°C) and subjected to bubbled oxygen during the testing period of 7 h. Samples of solution experiment were taken every hour and analyzed for zinc and copper using Inductively Coupled Plazma (ICP) technique. After experiment, sample surfaces were examined using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS).Results show no appreciable dissolution either in inert atmosphere or in open atmosphere without bubbling. On the other hand, oxygen bubbling results in the enhancement of brass dissolution. This enhancement increases largely upon increasing the temperature from 25 to 50°C. Further increase in temperature has slightly negative effect on dissolution. The results of SEM and EDS support those of ICP. [DOI: 10.1380/ejssnt.2010.17]

The Aerobic Oxidation of Benzylic Alcohols with F-MSS Catalyst

A magnetically active core-shell-structured γ-Fe2O3-mesoporous silica sphere (F-MSS) catalyst was developed for the aerobic oxidation of benzylic alcohols. Thus, F-MSS was prepared by transferation of Fe3O4 (chloroform dispersion) from chloroform to water with cetyltrimethylammonium bromide (CTBA) as a phase-transfer agent, followed by formation of silica sol-gel on Fe3O4 with tetraethyl orthosilicate (TOES) and calcination at 500 ˚C. The aerobic oxidation of benzylic alcohols was performed with oxygen bubbling in the presence of F-MSS in PEG-200 to give the corresponding aldehydes in 60-94% conversion with 84-98% selectivity (3 examples).

A method for electrochemical growth of homogeneous nanocrystalline ZnO thin films at room temperature

We report the electrodeposition at room temperature (25 °C), in a potentiostatic mode, of cohesive nanocrystalline ZnO thin films from an oxygenated zinc chloride bath. It is shown that the bath saturation by molecular oxygen precursor is a key parameter to grow the oxide at low temperature. After low O 2 bubbling the solution is not saturated and the surface is more or less passivated by an amorphous Zn(OH) 2 veil-like thin layer. After intense and long molecular oxygen bubbling, the current density rapidly increases after an induction period of about 800 s. At the foot of the current onset, crystallized ZnO seeds appear entrapped in the initial amorphous layer. The film nucleation is a delayed process. The electrode is subsequently covered by a homogeneous ZnO film with structures of several hundreds of nanometers in length composed of nanocrystals with size of about 17 nm. The room-temperature photoluminescence spectrum of the film is dominated by a strong UV emission at 3.25 eV due to the recombination of excitons. The visible emission centered at 2.36 eV, due to deep defects, is less intense than the UV one showing the good structural quality of the ZnO nanocrystallized film. The films have interesting properties to be used as a seed layer for instance.