Amount Of Active Oxygen Research Articles

Promoted oxygen release from copper-ceria interfacial sites for selective hydrogen production

The modulation of oxygen species is an effective strategy for selective H2 production with relevant chemical looping processes. This paper describes the promoted oxygen release from CuO-CeO2 redox catalysts for selective H2 production in chemical looping oxidative steam reforming of methanol (CL-OSRM). Despite the complete oxidation of methanol from CuO, the excess H2 production of CL-OSRM with respect to methanol steam reforming (MSR) increases linearly with the amount of active oxygen in CeO2 induced by the copper-ceria interaction. In situ spectroscopic characterizations and mechanistic study demonstrate that copper-ceria interfacial sites induce oxygen release from CeO2 to facilitate the partial oxidation of methoxy to formate species, which promotes the H2 production rate. This study provides an instructive strategy for the construction of redox catalysts for selective H2 production with chemical looping processes.

Effect of the Porcine STC-1 Gene on Autophagy and Mitochondrial Function as Induced by Serum Starvation.

Stanniocalcin-1 (STC-1) is a glycoprotein hormone involved in calcium/phosphorus metabolism and direct inhibition of bone and muscle growth. The aim of this study was to investigate the STC-1 gene with respect to the regulatory mechanisms of porcine growth metabolic pathways involving autophagy. Western blotting was used to detect the expression of autophagy and mitochondrial function-related proteins, and flow cytometry was used to detect mitochondrial function-related. Changes in the autophagosome and mitochondrial were observed by electron microscopy. The expression of the autophagy-related proteins was detected by confocal microscopy. The results showed that Pink1, Parkin and LC3B expression was increased; SQSTM1/P62 expression was reduced. Electron microscopy revealed that the cells in the serum starvation group all produced autophagosomes. The fluorescence intensity of GFP-LC3B and GFP-Parkin increased. The Bax/Bcl-2 ratio, Pink1 and Parkin protein levels were profoundly reduced in the STC-KO. In addition, the increase in Mfn2, OPA1, DRP1 and LC3B proteins was attenuated; the increase in the apoptosis rate and amount of active oxygen was attenuated; the decrease in membrane potential; the decrease in ATP was reversed; the fluorescence intensity of GFP-LC3B and GFP-Parkin was increased. These results indicate that autophagy can be caused by serum starvation. Knocking out the porcine STC-1 gene had an obvious antiapoptotic effect on cells, the inhibition of serum starvation-induced autophagy. This is the first study to show that the porcine STC-1 gene confers self-protection in the absence of nutrients. To provide a theoretical basis for studying the effect of STC-1 on pig growth and development.

Mechanisms of Cd and Cr removal and tolerance by macrofungus Pleurotus ostreatus HAU-2

Fungi bioaccumulation is a novel and highly promising approach to remediate polluted soil. The present study revealed a high ability to tolerate Cd and Cr in the fungus Pleurotus ostreatus HAU-2. However, high concentrations of Cd and Cr can suppress fungal growth and result in a variation of hypha micromorphology. Batch experiments were performed to investigate Cd and Cr stress effects on the amount of active oxygen in fungi, activity of antioxidant enzyme, as well as the removal efficiency of Cd and Cr. The results revealed that Cd and Cr caused increasing active oxygen and malonaldehyde (MDA) concentrations. Antioxidant enzymes play a central role in removing active oxygen, while glutathione (GSH) aids the Cd detoxification within cells. In fluid culture, fungal removal rates of Cd and Cr ranged from 44.85% to 80.36% and 14.49% to 45.55%, respectively. Intracellular accumulation and extracellular adsorption were the major removal approaches. Bag cultivation testing indicated that the fungus absorbed Cd and Cr contained within soil. In particular, the accumulation ability of Cd (15.6mgkg−1) was higher compared to that of Cr (8.9mgkg−1). These results successfully establish P. ostreatus HAU-2 as promising candidate for the remediation of heavy-metal polluted soils.

Effects of Surface Area of Co–Mn–O Catalysts on the Selective CO Oxidation in H2

A series of CoxMn1−xOy catalysts were prepared via the co-precipitation method by varying the cobalt content, and were applied to selective CO oxidation in the presence of H2, CO2, and H2O. The prepared catalysts were characterized by means of N2 physisorption, X-ray diffraction, temperature-programmed reduction, and temperature-programmed desorption of oxygen. Among the evaluated catalysts, the highest catalytic activity was achieved with the formulation Co0.8Mn0.2Oy. The surface area of the Co0.8Mn0.2Oy catalyst could be maximized by utilizing a lower feeding rate of the precipitant solution and calcination temperature in the preparation process. The catalytic reducibility and the amount of active oxygen were enhanced by increasing the Co content of the Co–Mn–O catalyst only except for Co1.0Mn0.0Oy catalyst. The catalytic activity was effectively enhanced by increasing the catalyst surface area, which is proportional to the amount of active surface oxygen.

Determination of Mechanism for Soot Oxidation with NO on Potassium Supported Mg‐Al Hydrotalcite Mixed Oxides

AbstractSoot oxidation with NO (in the absence of gas phase O2) on potassium‐supported Mg‐Al hydrotalcite mixed oxides (K/MgAlO) was studied using a temperature‐programmed reaction and in situ FTIR techniques. Nitrite and the ketene group were identified as the reaction intermediates and thus a nitrite‐ketene mechanism was proposed in which surface active oxygen on K sites of K/MgAlO is transferred to soot by NO through nitrites. In the absence of gas phase O2, soot oxidation with NO at lower temperatures (below 450 °C) is limited by the amount of active oxygen on the K sites. This kind of active oxygen is not reusable but can be replenished in the presence of gas phase O2.

Interaction of activated carbon electrodes with sulfuric acid solutions

Impedance and potentiodynamic studies have been carried out to investigate reversible processes on the surface of electrodes based on activated carbon (AC). Relationships have been found between the reversible capacity and true resistance, on the one hand, and the potential, on the other. Stoichiometric characteristics of AC charging in sulfuric acid have been obtained. A mechanism of the reversible surface process is suggested. It is concluded that Faraday pseudocapacity makes a considerable contribution to charging of AC electrolytes. The amount of gas liberated in the course of AC wetting in electrolyte has been measured. It is assumed that the amount of liberated gas depends on the amount of active oxygen involved in the current-forming reaction. Based on the data obtained, a redox surface reaction is substantiated in general form.

Synthesis ofAFeO2.5+x(0≤x≤0.5;A=Sr, Ca) Mixed Oxides from the Oxidative Thermal Decomposition ofA[Fe(CN)5NO]·4H2O

The low-temperature formation of Sr and Ca ferrates by thermal oxidative decomposition of tetrahydrates of Sr and Ca nitroprussides (pentacyanonitrosilferrates(II)) is reported. IR spectroscopy, X-ray diffraction (including Rietveld analysis), and thermal analysis were used to follow the process. The amount of active oxygen (concentration of Fe(IV)) in the products was chemically determined. For the Sr compound, the final product was an oxygen-deficient perovskite that could be produced with a very low content of carbonate in the temperature range 750–850°C. For the calcium compound, only Ca2Fe2O5with the brownmillerite type structure was obtained.

Application of PIXE analysis to determination of trace elements in colonic tumor disease

In order to investigate the validity of the cancer development, the presence of active oxygen need to be taken into account since active oxygen participates in the initiation and promotion of cancer. However, it is impossible to measure the amount of active oxygen in vivo directly. Therefore, the levels of trace elements such as Zn, Cu and Mn in enzyme which eliminates active oxygen were measured at each stage of cancer development by PIXE. The large differences between the normal mucosa and colonic adenoma in the amount of Zn, Cu and Mn within the enzyme eliminating free radicals were observed. There was a significant relationship among trace element levels, active oxygen and the development of tumor in connection with the levels of Zinc and Copper.

The Making and Characterization of BaO- and BaCl2-Promoted Y2O3Catalysts for the OCM Reaction

The performances of the 30 mol%MO/Y2O3(M=Mg, Ca, Sr, Ba) catalysts in OCM reactions have been investigated. The BaO-promoted one has out-performed the others. We found that the 30 mol% BaX2/Y2O3(X=F, Cl, Br) catalysts could do even better. Both BaF2and BaCl2are good materials to promote Y2O3.At 800°C and with CH4:O2:N2=2.47:1:11.4, total flow rate=50 ml min−1, contact time=0.6 g s ml−1, and weight of catalyst=0.5 g, the C2yields over the catalysts were respectively 19.7 and 22.3%. In this paper, we concentrate on the BaCl2/Y2O3catalysts and compare them with the BaO/Y2O3ones. It is obvious that the 30 mol% BaCl2/Y2O3catalyst is superior to the 30 mol% BaO/Y2O3one both in C2selectivity and C2H4/C2H6ratio.XRD examinations revealed that the addition of 10–50 mol% of BaO or BaCl2has greatly altered the surface and bulk natures of Y2O3. Crystal phase of orthorhombic BaCO3was found to exist in the 30 mol% BaO/Y2O3catalyst. Although no significant amount of any barium compound was detected over the fresh 30 mol% BaCl2/Y2O3catalyst, crystal phases of orthorhombic Ba3Cl4CO3and BaCO3were detected after OCM reactions. Also, the cubic Y2O3lattices of the BaO- and BaCl2-promoted catalysts were found to have undergone expansion which is a result of ionic substitution(s). The reactivity of the 30 mol% BaCl2/Y2O3catalyst has been monitored for 40 h at 750°C and found to be stable. Although XPS results suggested no significant change in surface chlorine concentration, analysis of Cl content of the catalyst revealed that up to ca 15.5% of the original content of chlorine was lost after 20 h of reaction.Y2O3by itself lacks active oxygen for the oxidation reaction. O2TPD and reduction studies of the fresh 30 mol% BaO- and BaCl2-promoted catalysts showed that the amount of active oxygen in the former was at least 4 times that in the latter. However, during OCM reaction, the 30 mol% BaCl2/Y2O3catalyst was changing somewhat like a 30 mol% BaO/Y2O3catalyst. It is apparent that the presence of Cl−ions in the 30 mol% BaCl2/Y2O3catalyst is the reason for the superiority in C2selectivity over the BaCl2-promoted Y2O3catalysts. We conclude that the presence of Ba2+ions can enhance the amount of oxidative oxygen for CH4activation while the presence of Cl−suppresses deep oxidation. A careful balance of the two can optimize the performance of the Y–Ba–Cl catalysts in the OCM reaction.

Oxidative degradation of AOX and COD by different advanced oxidation processes: a comparative study with two samples of a pharmaceutical wastewater

Using two samples of a pharmaceutical wastewater, the efficiency of three advanced oxidation processes (AOPs) (H2O2/UV, O3/UV and H2O2/Fe(II)) for the removal of adsorbable organic halogen (AOX) and chemical oxygen demand (COD) were compared on a laboratory scale. The AOX contents of these samples ranged from 3 to 5 mg/L. Generally the results showed that all three methods are suitable for the degradation of AOX and COD. UV irradiation involved a high selectivity for the degradation of AOX compared to COD. On the other hand, processes based on hydroxyl radicals were less selective but considerably more effective in COD degradation. This explains why the combined methods H2O2/UV and O3/UV lead both to a complete destruction of AOX and a large removal of COD. During ozone treatment – without UV radiation – a decrease of AOX was also observed, although to a lower degree. Using Fenton's reagent both AOX and COD could be removed almost completely. The reaction time needed for this kind of treatment was very low compared to the other two AOPs. O3/UV treatment showed the largest consumption of “activated” oxygen (AO) during COD degradation. H2O2/Fe(II) treatment required almost the same amount of AO as H2O2/UV.

Oxidative degradation of aox and cod by different advanced oxidation processes: A comparative study with two samples of a pharmaceutical wastewater

Using two samples of a pharmaceutical wastewater, the efficiency of three advanced oxidation processes (AOPs) (H2O2/UV, O3/UV and H2O2/Fe(II)) for the removal of adsorbable organic halogen (AOX) and chemical oxygen demand (COD) were compared on a laboratory scale. The AOX contents of these samples ranged from 3 to 5 mg/L. Generally the results showed that all three methods are suitable for the degradation of AOX and COD. UV irradiation involved a high selectivity for the degradation of AOX compared to COD. On the other hand, processes based on hydroxyl radicals were less selective but considerably more effective in COD degradation. This explains why the combined methods H2O2/UV and O3/UV lead both to a complete destruction of AOX and a large removal of COD. During ozone treatment - without UV radiation - a decrease of AOX was also observed, although to a lower degree. Using Fenton's reagent both AOX and COD could be removed almost completely. The reaction time needed for this kind of treatment was very low compared to the other two AOPs. O3/UV treatment showed the largest consumption of “activated” oxygen (AO) during COD degradation. H2O2/Fe(II) treatment required almost the same amount of AO as H2O2/UV.

Surface modification of polyolefins for hydrophilicity and bondability: Ozonization and grafting hydrophilic monomers on ozonized polyolefins

AbstractOzonization is a very efficient, economical, and potentially practical method to modify polypropylene (PP) as well as polyethylene (PE) surfaces. Carbonyl, carboxyl, and hydroperoxide groups can be very conveniently generated by reacting these polymers with ozone. In the case of fibers and powders, surface treatment with ozone in an aqueous medium offers advantages: water can be used as a carrier in commercial processes, and since water enhances generation of hydroperoxide it may be used for potential reaction purposes. The extent of reaction of polyolefins with ozone depends on the extent of agitation of the slurry, the slurry temperature, solid consistency, and ozone concentration in the gas. Within the limits of the present work, the ozone uptake of fibers increases linearly with time. The carbonyl (%) and carboxyl (meq/g) contents are approximately 0.08 and 0.04 times the ozone uptake (%) of the PP fibers. Hydroperoxide generation is found optimum at a slurry temperature of 60–80°C, and the amount of active oxygen (%) at 60°C is about 0.1 times the ozone uptake (%) of the PP pulp. Spurted polypropylene fibers show two different kinds of crystallinity in X‐ray diffraction analysis, namely monoclinic and smectic. The type of fibers produced depends on the spurting conditions. The monoclinic fibers have a mostly rodlike structure while the smectic fibers have a ribbonlike appearance. The fiber types give different sheet properties in blends with cellulose, and show different grafting rate behavior. The smectic fibers provide relatively stronger sheets, and graft acrylamide monomers at a higher rate. Ozonization degrades the chain length of polyolefins as shown by intrinsic viscosity of treated material. It is possible to have an additive in the polymer to reduce degradation rate of the chain length. Further work in this area is needed, however, for better understanding of the reaction, and to achieve complete control over the degradation process to make the product commercially viable. Effects of some additives on ozone reaction to enhance the generation of functional groups also opens an area for further study. Handsheets were prepared with blends of 30% ozonized polypropylene pulp and 70% wood pulp. About 90% of the strength of a 100% wood pulp sheet can be achieved by either grafting acrylamide (25–30%) on the polypropylene pulp, or by disk refining with 5% of a bonding resin. Polypropylene pulp significantly raises the bulk, opacity, and brightness of the sheets. High levels of acrylamide grafted to pulp reduce opacity and caliper of sheets. Grafting with a redox system of hydrophilic monomers, such as acrylamide, to ozonized pulps containing a reasonable amount of hydroperoxide (0.1–0.5% active oxygen) also provides an effective method for surface modification. The surface of both ozonized and grafted pulps becomes highly hydrophilic. Polyethylene, in the limited results obtained in this work, behaves very similarly to polypropylene. The activation energy of ozone reaction with both polypropylene and polyethylene is approximately 7 kcal/mol.

Development of supported manganese oxides for partial oxidation: CO Oxidation and oxygen availability

The total oxidation properties of supported MnOx [MnOx/S; S = TiO2, Al2O3, CeO2 and MgAl2O4] using the oxidation of carbon monoxide as a model reaction were analyzed. For this purpose, steady-state and transient operation of a flow micro-reactor (P = I atm; T = 333 – 433 K) were used, as well as TPD of oxygen. It was determined that the rate of oxidation of CO is a strong function of the support for highly dispersed overlayers of MnOx. The rate of CO oxidation is a positive function of both P02 on all the catalysts of the series, but only on MnOx/TiO2 is the reaction rate independent of PCO2, indicating that the CO2 adsorption sites are different from reaction intermediates formation sites on this catalyst. Both reduction and reoxidation of the surfaces are steps of comparable rates. The amount of active oxygen on the catalyst surfaces is directly proportional to the catalytic activity, and is less than 10% of the total surface oxygen.

Development of supported manganese oxides for partial oxidation: CO oxidation and oxygen availability

The total oxidation properties of supported MnO x [MnO x/S; S = TiO 2, Al 2O 3, CeO 2 and MgAl 2O 4] using the oxidation of carbon monoxide as a model reaction were analyzed. For this purpose, steady-state and transient operation of a flow micro-reactor (P = I atm; T = 333 – 433 K) were used, as well as TPD of oxygen. It was determined that the rate of oxidation of CO is a strong function of the support for highly dispersed overlayers of MnO x. The rate of CO oxidation is a positive function of both P02 on all the catalysts of the series, but only on MnO x/TiO 2 is the reaction rate independent of PCO 2, indicating that the CO 2 adsorption sites are different from reaction intermediates formation sites on this catalyst. Both reduction and reoxidation of the surfaces are steps of comparable rates. The amount of active oxygen on the catalyst surfaces is directly proportional to the catalytic activity, and is less than 10% of the total surface oxygen.