Presence Of Active Oxygen Species Research Articles

Synthesis of surficial-modified green biochar catalyst generated by biogas residue biochar and potential application for catalytic ozonation degradation of ciprofloxacin

This study synthesized novel, green, and easily recoverable surface-modified economical catalysts via hydrothermal treatment (HT) successfully, utilizing biogas residue biochar (BRB), a food waste product from anaerobic fermentation, pyrolyzed at 500 °C for 50 min. Using autoclaves, a total of six solutions were prepared, each having 1 g fine-grinded BRB, surficial modified by adding glycerol (GL) (10 or 20 mL) and SDI water (70 or 60 mL), and heated in an oven at 240 °C, 180 °C, and 120 °C for 24 h. Afterward, the catalysts showed the potential for degradation of widely used emerging pollutants like ciprofloxacin. Taking advantage of catalytic surface modification, the catalytic ozonation degradation was more effective than that of a single ozonation. However, under similar conditions, catalyst amount 0.20 g, ozone dose 15 mg L−1, and ciprofloxacin 80 mg L−1, the performance of the 10 mL GL-180 °C catalyst was excellent. It showed a 92.45%–94.41% optimum removal rate in the 8–10 min interval. After five continuous cycles, the 10 mL GL-180 °C catalyst exhibited excellent stability and reusability. XPS, FT-IR, BET, XRD, and SEM before and after the reaction confirmed the successful synthesis and degradation mechanism. A possible degradation pathway was unrevealed based on a liquid chromatography-mass spectrometer (LC-MS) and scavenger test, proving the significant roles of superoxide radicals (O2•-), hydroxyl radicals (•OH), and singlet oxygen (1O2). Further, Electron paramagnetic resonance (EPR) analysis confirmed the presence of active oxygen species. Subsequently, 10 mL GL-180 °C showed promising degradation for the actual water environment, such as groundwater (73.55%) and river water (64.74%). This work provides a valuable economic strategy to convert biogas residue biochar into a low-cost catalyst for organic pollutant decomposition.

Co3O4 hollow nanotubes for the catalytic oxidation of C2-chlorinated VOCs

Structured Co3O4 catalysts with a hollow nanotube morphology were prepared by several synthesis routes based on the Kirkendall effect. The resulting samples were kinetically evaluated in the gas-phase oxidation of vinyl chloride and 1,2-dichloroethane, two model C2-chlorinated volatile organic compounds; and exhaustively characterised by means of BET measurements, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetry and temperature-programmed techniques (adsorption of ammonia and chlorinated VOC, O2-TPD, H2-TPR and TPO). The performance of the prepared nanotubes was essentially controlled by the presence of active oxygen species at the surface, which in turn depended on the Co2+/Co3+ molar ratio, and the adsorption capacity of the catalyst for the chlorocarbon. Both pollutants were efficiently converted to deep oxidation products at relatively low temperatures. In addition, the optimal catalyst exhibited an appreciable stability when operating during 120 h.

Cerium oxide nano-particles application for self-cleaning building material

Photocatalytic degradation has gained attraction in the self-cleaning construction materials applications because of its ability to be used to protect surface of cementitious materials and minimize the negative effects of environmental conditions on building, and to remove the dyes and other organic pollutants from water and wastewater. In this study, the influence of nano-Ceria particles on the photocatalytic degradation of methylene blue dye of cement mortar samples was investigated. In this work, nanoceria was prepared via simple co-precipitation method. Nanoceria is a powerful photocatalyst due to its high visible-light absorptivity, strong redox ability, high oxygen storage/release capacity, eco-friendly nature, photostability and cost effectiveness. Nano ceria showed a photocatalytic and self-cleaning activity in the presence of sun radiation. Nano ceria particles were characterized by X-ray diffraction, High resolution transmission electron microscope, and Ultra-violet visible spectroscopy. The presence of active oxygen species detected on nano- ceria surface was identified as cause of the photobleaching of dyes in presence of UV-irradiated.

Oxidative reforming of n-heptane in gliding arc plasma reformer for hydrogen production

The exploration of novel technologies to reduce the air pollution and greenhouse gas emissions has been of great interest. Gliding arc plasma reformer at atmospheric pressure has been developed for converting n-heptane to hydrogen. The system has been evaluated by H2 yield and energy yield via continuous n-heptane oxidative reforming at room temperature. Effects of some process parameters (discharge gap, input power, residence time, and O/C) have been studied on the reaction performance. The maximum H2 yield and energy yield are 50.1% and 94.5 L (kW h)−1. To investigate the role of inert gas (N2, Ar) in the plasma oxidative reforming system, the performance of C7H16/air, C7H16/N2/O2/Ar and C7H16/O2/Ar have been investigated. The results show that N2 (B3Πg) and Ar∗ can accelerate the formation of active oxygen species (such as O+, O (1D) and O). The presence of active oxygen species promotes the progress of the oxidative reforming reaction. What's more, N2 (B3Πg) is also conducive to the direct conversion of n-heptane. The reaction mechanism of hydrogen production from gliding arc plasma oxidative reforming of n-heptane was proposed based on the analysis of the OES and GC–MS.

Synthesis and Characterization of Li+, Ag2+and Cu2+ metals doped MgO nanostructured in Gel Method

The MgO nano particles doped with alkali, Nobel and transition metals (Li+, Ag2+, Cu2+) were synthesized by gel method. The structures, morphologies and size of synthesized samples were characterized and confirmed by Powder X-ray diffraction (PXRD), Scanning Electron Microscope (SEM) and High Resolution Transmission Electron Microscope (HR-TEM). The antibacterial activity for pure and doped MgO nano particles were studied against S.auerus. Among the results, the Li+ and Cu2+ doped MgO nano particles are best inhibition against the bacterial strains due to the presence of active oxygen species.

Giant improvement in the rectifying performance of oxidized Schottky contacts to ZnO

The rectifying performance of platinum, palladium, and iridium Schottky contacts on ZnO(0001) surfaces was dramatically improved by their deliberate in-situ oxidation using an O2:Ar rf plasma during fabrication. For example, oxidized Pt Schottky contacts exhibited current rectification of 12 orders-of-magnitude, effective barrier heights of up to 1.30 eV, and stable high-temperature operation at 180 °C, compared to the ohmic behavior (i.e., zero rectification/barrier height) of unoxidized contacts. Oxidized Pd and Ir Schottky contacts also showed similar dramatic improvements compared to their plain metal counterparts. These very large performance gains are attributed to the presence of active oxygen species during Schottky contact formation that produces the following beneficial effects: (1) the removal of the hydroxyl-induced surface potential well and associated electron accumulation layer, (2) the passivation of interfacial oxygen vacancies, and (3) an increase in the work function and electronegativity of the oxidized Schottky contacts.

Incomplete ozone recovery effect in the presence of active oxygen species

The degree of ozone recovery after pulsed UV laser photolysis of O2-O3-Ar mixture is measured using time-resolved absorption spectroscopy. The effect of incomplete ozone recovery in the presence of molecular singlet oxygen O2(a1Δ) and atomic oxygen is detected. This effect is caused by the reaction between the vibrationally excited ozone molecule formed due to recombination and atomic oxygen. The branching factor for the chemical channel of reaction products is γr = 0.81 ± 0.13.

Malondialdehyde-modified low-density lipoproteins as biomarker for atherosclerosis

Background. Cardiovascular diseases are accompanied by the presence of active oxygen species and organic free radical generation. The aim of this study was to examine the possibility of using malondialdehyde (MDA)-modified low-density lipoprotein (LDL) analyses as a diagnostic and prognostic biomarker. Design and methods. A cross-sectional epidemiological study of a random sample of the male population of Tallinn aged 20–64 was carried out in 2007–2008. A total of 413 subjects were included in the study. The screening procedure included standard epidemiological methods. Oxidative stress was assessed by measuring the kinetics of glutathione oxidation and the level of oxidized of MDA-modified LDL. Results. A strong positive correlation between levels of MDA-modified LDL- and total cholesterol was indicated, as well as LDL-cholesterol in blood of patients with postinfarct cardiosclerosis (r=0.82 and r=0.83, respectively, p<0.05). Hypercholesterolemia and hyperglyceridemia were accompanied by significant increase in oxidized LDL plasma level. Conclusion. MDA-modified LDL estimation has a diagnostic accuracy and may be used as an independent biochemical marker for atherosclerosis.

Preparation and properties of sulfur-containing tetraazaporphyrin iron supported on anion-exchange resin

An anion-resin carrying the catalyst iron(II) tetra(1,4-dithin)porphyrazine, ( Fe (II) Pz ( dtn )4/resin), may effectively interact with the lone-pair electron of the sulfur in the Fe (II) Pz ( dtn )4 to keep the absorption for the catalyst molecule, which can efficiently activate molecular oxygen coordinated with iron(II) on the axial orientation of Fe (II) Pz ( dtn )4 through electron transfer in a heterogeneous process. On the other hand, the hydrophilic property of the resin also facilitates adsorption of the anion-substrates in the aqueous solution onto the unoccupied resin surface to increase the substrate concentration around the Fe (II) Pz ( dtn )4 and the contact probability between the substrate with activated molecular oxygen to promote the oxidative degradation of these adsorbed substrates. The stability and repeatability of the Fe (II) Pz ( dtn )4/resin were determined by some control experiments. The results indicate that Fe (II) Pz ( dtn )4 was stable enough in the presence of active oxygen species under irradiation of visible light and could degrade recalcitrant organic pollutants such as rhodamine B and p-nitrobenzoic acid. It can be reused at least 5 cycling runs without losing activity.

Detection of 3-hydroxykynurenine in a plant pathogenic fungus.

A redox-active compound has been purified from the barley powdery mildew fungus Blumeria ( Erysiphe ) graminis f. sp. hordei. A combination of spectrophotometry, MS and NMR has identified it as 3-hydroxykynurenine (3OHKyn). This compound, never previously detected in any fungus or pathogen, is best known for its role in vertebrate cataracts. It is found abundantly in developing and germinating spores and also in runner hyphae. Two roles for 3OHKyn are discussed: first, the presence of active oxygen species would enable 3OHKyn to cross-link the spore chemically with the plant. Secondly, it may be acting as an UV protectant and an antioxidant.

Mechanism of catechin chemiluminescence in the presence of active oxygen.

The photon emission (chemiluminescence; CL) of catechin in the presence of active oxygen species (hydrogen peroxide, hydroxyl radical tert-butyl hydroperoxide and tert-butyl oxyl radical) and acetaldehyde was confirmed to occur non-enzymatically at room temperature in aqueous neutral conditions. The CL intensity [P] in the presence of active oxygen species (X), catalytic species (Y) and receptors (Z) is predicted by [P] = k [X] [Y] [Z]. The calculated photon constants (k) of 8 catechins and gallic acid were 8.23 x 10(6) M-2 s-1 counts ((-)-epigallocatechin), 2.78 x 10(8) ((-)-epigallocatechin gallate), 4.66 x 10(5) ((-)-gallocatechin gallate), 4.36 x 10(5) ((-)-gallocatechin), 2.70 x 10(5) ((-)-epicatechin), 6.44 x 10(4) ((-)-catechin), 585 x 10(4) ((-)-epicatechin gallate), 4.78 x 10(4) (gallic acid) and 3.54 x 10(4) ((-)-catechin gallate), respectively. The system of active oxygen species, catalytic species and receptors is proposed to be a scavenging mechanism for active oxygen species. In the presence of acetaldehyde, (-)-epigallocatechin (maximum k value among catechins tested) reacted with tert-BuOOH to form tert-BuOH as determined by HPLC analysis.

Chemiluminescence of soybean saponins in the presence of active oxygen species

Natural active oxygen scavengers (Y; catalytic compounds) exhibit chemiluminescence (CL) in the presence of an X (active oxygen compounds) and a Z (receptive compounds). The CL derived from soyasaponins Ab and βg, major components of group A and DDMP saponins present at high level in the hypocotyl of soybean seeds, was compared with (−)-epigallocatechin (EGC) as the most effective Y and acetaldehyde (MeCHO) as the most effective Z in the presence of H 2O 2 as X. We have found that soyasaponin Ab and soyasaponin βg are Y equivalent to EGC and Z equivalent to MeCHO, respectively. In the presence of soyasaponin Ab as Y, CL of soyasaponin βg showed about 100-fold than that of MeCHO as Z. These results suggest that group A and DDMP saponins play an important role in the scavenging function of active oxygen.

LIQUID PHASE OXIDATION OF OCTANAL BY CUMENE HYDROPEROXIDE

Abstract Reactions that lead to fuel instability can be closely linked to the presence of active oxygen species. An increasing body of evidence links oxidation reactions of hydroperoxides to the instability observed in fuels. The active oxygen compounds present in fuels are alkyl and aromatic hydroperoxides. Cumene hydroperoxide represents a logical choice for an active oxygen compound that could be present in a middle distillate fuel. This paper reports on the reactions of cumene hydroperoxide with octanal in benzene solvent at 140°C for various time periods. The complete slate of products is presented along with a suggested mechanism to explain the observed products and the implications for fuel instability reactions.

Photo-oxidative damage to lenticular GAPDH and its relationship to aldehyde metabolism

These studies show that GAPDH from the calf lens and human lens epithelium undergoes size and charge modifications in the presence of active oxygen species generated from methylene blue and light. The histidine content of the enzyme was reduced by one third. No evidence of increased proteolysis was observed suggesting a nonenzymatic cleavage of enzyme by the photo-oxidants.