Strong Degradation Effect Research Articles

Inquisition on enhanced photocatalytic performance of ternary cerium manganese nickel metal oxide nanocomposites

The hydrothermal approach was used to successfully incorporate ternary Cerium Manganese Nickel mixed metal oxides (CMN-MMOs) with various Ce/Mn/Ni ratios. The improved crystallanity of incorporated CMN-MMOs was discovered using powder X-ray diffraction. From Ultra Violet (UV)–visible diffuse reflection spectroscopy (DRS), CMN-MMOs displays a broad absorption in the visible range. Scanning Electron Microscope (SEM) reveals that CMN-MMOs exhibit in nanoslab. Image of Transmission Electron Microscope (TEM) expose that synthesized samples are in hexagonal structure with average size of 20–30 nm. The photocatalytic activity was appraised for calcined samples of CMN-MMOs (1: 1: 2). It indicates the greatest photocatalysic activity with 89 % degradation of methylene blue (MB) dye. CMN- MMOs (1: 1: 2) also had a strong degradation effect on the non-dye contaminant phenol. Methylene Blue degradation followed a pseudo-first-order kinetic trend. The mechanism of photo degradation of CMN- MMOs was also explored.

Synergy of stress and corrosion in a 12Cr ferritic/martensitic steel exposed to static liquid lead-bismuth eutectic at 550 °C

In this work, uniaxial creep tests under 300, 350 and 380 MPa were performed to study the synergy of stress and corrosion in a 12Cr ferritic/martensitic (F/M) steel exposed to static liquid lead-bismuth eutectic (LBE) at 550 °C. The results showed that LBE had a strong degradation effect especially under low-oxygen condition, leading to drastic acceleration of creep deformation as compared to that in air. Although oxide scales, such as magnetite, Fe-Cr spinel and chromium oxide, could slow down crack initiation and propagation, this effect is load and oxygen concentration dependent. The overall creep behavior is governed by multiple competing mechanisms.

Photocatalytic Degradation of Tetracycline Hydrochloride by Zinc oxide/Polypyrrole/Carbon nanotubes

AbstractIn this study, the intermediates of the photocatalytic degradation of tetracycline hydrochloride (TC‐HCl) were analyzed by high performance liquid chromatography‐mass spectrometry. The doping of polypyrrole (PPy) and carbon nanotubes (CNTs) increased the reaction rate of TC‐HCl degradation by ZnO. The prepared ZnO has a large specific surface area, which can improve the adsorption performance. The introduction of PPy and CNTs can promote electron transfer and reduce the recombination of photogenerated electron hole pairs in the composite material ZnO/PPy/CNTs(ZPC), and the photocatalytic performance of the composite sample is improved. In addition, the new visible light catalyst has strong degradation effect on TC‐HCl. Using tetracycline hydrochloride as a pollutant, the photocatalytic degradation performance of each sample was analyzed. After 240 min of photoreaction, the Degradation rate of TC‐HCl (DTC‐HCl) by ZnO was 24.1 %, while that by ZPC was 91.5 %. Meanwhile, the intermediates of photocatalytic degradation of TC‐HCl were analyzed by high performance liquid chromatography‐mass spectrometry. The peak intensity of TC‐HCl from adsorption equilibrium to the end of the photocatalytic reaction occurred at a retention time of about 10.05 min and decreased with the increase of the reaction time. This indicates that TC‐HCl is broken down into small molecules during the reaction. Through the analysis of intermediates and active species, the degradation pathway of tetracycline hydrochloride was deduced.

Effective Tumor Targeting by EphA2-Agonist-Biotin-Streptavidin Conjugates.

We recently reported on a potent synthetic agent, 135H11, that selectively targets the receptor tyrosine kinase, EphA2. While 135H11 possesses a relatively high binding affinity for the ligand-binding domain of EphA2 (Kd~130 nM), receptor activation in the cell required the synthesis of dimeric versions of such agent (namely 135H12). This was expected given that the natural ephrin ligands also need to be dimerized or clustered to elicit agonistic activity in cell. In the present report we investigated whether the agonistic activity of 135H11 could be enhanced by biotin conjugation followed by complex formation with streptavidin. Therefore, we measured the agonistic EphA2 activity of 135H11-biotin (147B5) at various agent/streptavidin ratios, side by side with 135H12, and a scrambled version of 147B5 in pancreatic- and breast-cancer cell lines. The (147B5)n-streptavidin complexes (when n = 2, 3, 4, but not when n = 1) induced a strong receptor degradation effect in both cell lines compared to 135H12 or the (scrambled-147B5)4-streptavidin complex as a control, indicating that multimerization of the targeting agent resulted in an increased ability to cause receptor clustering and internalization. Subsequently, we prepared an Alexa-Fluor-streptavidin conjugate to demonstrate that (147B5)4-AF-streptavidin, but not the scrambled equivalent complex, concentrates in pancreatic and breast cancers in orthotopic nude-mouse models. Hence, we conclude that these novel targeting agents, with proper derivatization with imaging reagents or chemotherapy, can be used as diagnostics, and/or to deliver chemotherapy selectively to EphA2-expressing tumors.

A Novel PHEMA-Based Bismuth Oxide Composite with High Photocatalytic Activity

The Stober method was used to synthesize silicon sphere carriers with uniform size. The surface of the silicon sphere carrier was treated with 3-aminopropyltrimethoxysilane and 2-bromopropionyl bromide as atom transfer radical polymerization (ATRP) initiator and grafted with polyhydroxyethyl methacrylate (PHEMA) by ATRP. Bismuth nitrate was used as bismuth source to form polymer-metal complex with PHEMA. Sodium borohydride was used to reduce the bismuth ions in the composite material to metallic bismuth, and the metal bismuth on the surface of the composite material was oxidized in air atmosphere at 450 °C to obtain the inorganic–organic bismuth oxide composite. The morphology, elemental composition and photocatalytic degradation efficiency of Rhodamine B by bismuth oxide composite were characterized by various measurements. The TG and TEM results show that the composite material has good thermal stability, and Bi2O3 has very good dispersibility and stability in the prepared Bi2O3 composite. When the pH value is 4 with a catalyst dosage of 1.2 g/L, the degradation efficiency of Rhodamine B can reach 99.3% after 4 h of light irradiation, which is 24.2% higher than that of pure bismuth oxide. After 5 cycles, Bi2O3 composites still have a strong degradation effect with a degradation rate of 90.1% for Rhodamine B dye solution, which illuminates that the prepared Bi2O3 composite has good cyclic degradation performance.

Microwave-hydrothermal synthesis of beta-bismuth (III) oxide nanopowders and their enhanced photocatalytic properties

Facile microwave-hydrothermal method was successfully used to synthesize Beta-bismuth (III) oxide (β-Bi2O3) nanopowders under the low calcination temperature (350 °C) with a demonstrated diameter of about 40–200 nm. UV–vis diffuse reflection spectroscopy revealed that the resulting β-Bi2O3 nanopowders exhibited a broad absorption with a low band gap of about 2.64–2.85 eV. When the reaction temperature of microwave-hydrothermal process was 180 °C (the sample is named as 180 MH), an optimal methyl orange (MO) degradation efficiency of 95.0% was achieved after visible light irradiation of 120 min. β-Bi2O3 nanopowders also had a strong degradation effect on the tetracycline (TC). Kinetic studies indicated that the photocatalytic degradation process of MO and TC could be well fitted to the pseudo-first-order kinetics. The mechanisms for the enhanced photocatalytic degradation were disclosed as well, and the h+ and O2•- were dominating radicals for MO degradation. This paper provides a way to synthesize nanostructural materials for wide applications.

Microwave irradiation activated persulfate and hydrogen peroxide for the treatment of mature landfill leachate effluent from a membrane bioreactor

This study systematically compared the effect of microwave irradiation activated persulfate (MW/PS) and hydrogen peroxide (MW/H2O2) on organic matter removal in mature landfill leachate effluent from a membrane bioreactor (MBR), the reactive oxygen species (ROS) produced, and the degradation and transformation mechanisms of organic substances. An obvious synergistic effect was identified in the MW/PS and MW/H2O2 processes. The synergistic effect of the MW and PS (synergy coefficient F = 23.67) was significantly higher than that of the MW and H2O2 (synergy coefficient F = 11.43). The MW/PS process had a stronger degradation effect on organic substances than the MW/ H2O2 process, even when the PS dosage was significantly lower than the H2O2 dosage. The removal rate and kobs (initial reaction rate) of the two processes could be raised by increasing the oxidant dosage. Increasing the MW output power improved the removal rate of organics by the two processes, but an excessive MW output power only improved the kobs of the two processes, while the effect on organic matter removal was not significant. The MW/H2O2 process only removed organics expeditiously under acidic conditions, while the MW/PS process resulted in a strong degradation of organic matter under a wide range of pH values. A quenching experiment using alcohols indicated that both SO4•- and •OH existed in the MW/PS process, with SO4•- playing a leading role in the degradation of organics, while •OH played a leading role in the MW/H2O2 process. A spectrum analysis based on the quenching experiment demonstrated that the two processes destroyed the characteristic structure of humus and refractory organics in the leachate (i.e., humic acid-like (HAL) and fulvic acid-like (FAL) substances), mainly through the free radical oxidation mechanism. The SO4•- degraded HAL substances efficiently, while •OH had a better degradation effect on FAL substances. Therefore, the MW/PS process had a stronger degradation effect on organics than the MW/H2O2 process due to the enhancement of ROS production. The final energy consumption analysis revealed that the energy conserved by the MW/PS process was about 614.2 kWh per unit volume of effluent compared to the MW/H2O2 process. This study provides a useful reference for the use of the MW/PS and MW/H2O2 processes to eliminate refractory organics in leachate effluent from an MBR.

Thermal degradation of poly(lactic acid)–zeolite composites produced by melt-blending

Various zeolites (4A, Y, 13X) and related fillers (molecular sieves and coal fly ash) were used to prepare PLA composites and to assess their degrading effect on the polyester matrix under different processing conditions, at various zeolite/filler loadings. In this objective, untreated fillers, as well as washed and thermally activated zeolites, were used. PLA–zeolite composites were produced by melt-blending step followed by the evaluation of rheological information and molecular and thermal characteristics. The degradation of PLA during the preparation and processing of PLA–zeolite composites, or due to the presence of fillers, was evidenced by specific analyses (SEC, DSC, TGA, TG-FTIR). PLA degradation was mainly dependent on the nature of zeolite, filler loading, and thermal and processing history. The results of the study suggest that a stronger degradation effect is obtained by the addition of zeolite 4A into PLA (at loading of 5–10%) with respect to other zeolites (e.g., 13X and Y). It was also revealed the key roles of the temperature and residence time (as parameters in melt-mixing process), free alkalinity level, and water uptake in determining the ultimate characteristics of composites. The washing and thermal activation pretreatments of fillers have diminished in some cases the degradation of PLA matrix. Finally, the study also highlights the zeolite grades capable of being used to produce new PLA composites with competitive properties and those that could be of interest to improve PLA recycling by pyrolysis.

Improving enzymatic saccharification of eucalyptus with a pretreatment process using MgCl2

Pretreatment using an acid salt is a novel technology for biomass conversion, which not only improves the following enzymatic efficiency but also decreases the equipment corrosion. In the present work, MgCl2 was used as a pretreatment for enzymatic saccharification. After pretreatment, the solid substrate (SS) and pretreatment liquor (PL) were characterized, and the SS was enzymatically hydrolyzed to evaluate the conversion yield of cellulose (CYC). The results showed that the pretreatment using MgCl2 had a strong degradation effect on hemicellulose, whose removal rate was nearly 100% in certain cases. After pretreatment, the efficiency of the enzymatic SS saccharification increased, such that the CYC was as high as 99.5%. The degradation kinetics of hemicellulose and cellulose both followed first-order homogeneous reactions, and the reaction activation energies Ea were 46.63 kJ/mol and 82.26 kJ/mol, respectively. The suitable pretreatment conditions were as follows: 0.2 mol/L MgCl2 at 210 °C for 20 min.

Microcystis aeruginosa inhibition by Zn–Fe–LDHs as photocatalyst under visible light

Visible light-responsive Zn–Fe layered double hydroxide (Zn–Fe LDHs) algaecide that could remove Microcystis aeruginosa when combined with visible light was prepared by the combination of Zn2+ and Fe2+coprecipitation method and H2O2 oxidation. A laboratory scale experiment for Microcystis aeruginosa removal was carried out under visible light to assess the effect of Zn–Fe LDHs on algae degradation by photocatalysis process. XRD, IR SEM and TEM results showed that Zn–Fe LDHs exhibited integrated crystal structure and homogeneous granularity. Zn–Fe LDHs had a strong degradation and inhibition effect on Microcystis aeruginosa under visible light and achieved a removal rate of 80%. TEM morphology of Microcystis aeruginosa and the variation of chlorophyll a level, total soluble protein content and the concentration of malondialdehyde a product of lipid peroxidation of algae cell membrane demonstrated that Zn–Fe LDHs damaged the cell membrane and degraded cell inclusions due to its visible light catalytic activity, therefore, inhibited the proliferation of Microcystis aeruginosa. Zn–Fe LDHs could be a potential algaecide used to control harmful blooms in natural water sources with solar radiation.

The AMINO experiment: RNA stability under solar radiation studied on the EXPOSE-R facility of the International Space Station

AbstractCareful examination of the present metabolism and in vitro selection of various catalytic RNAs strongly support the RNA world hypothesis as a crucial step of the origins and early life evolution. Small functional RNAs were exposed from 10 March 2009 to 21 January 2011 to space conditions on board the International Space Station in the EXPOSE-R mission. The aim of this study was to investigate the preservation or modification properties such as integrity of RNAs after space exposition. The exposition to the solar radiation has a strong degradation effect on the size distribution of RNA. Moreover, the comparison between the in-flight samples, exposed to the Sun and not exposed, indicates that the solar radiation degrades RNA bases.

Effect of Heating, UV Irradiation and pH on Stability of the Anthocyanin Copigment Complex

The influences of temperature, UV irradiation, pH and copigment concentration on the stability of a copigmentation complex were investigated. The copigments selected for the study included: Catechin, Chlorogenic acid and Gallic acid. Five levels of copigment concentration as: 0, 120, 240, 480, 960 mg L(-1) were examined. The copigmentation effect increased with copigment contain. UV irradiation had a stronger degradation effect on the copigmentation complex than heating at 80 degrees C. The suitable pH for copigmentation complex was in pH 3.5. In this study, catechin predominate among copigments.

The effects of heating, UV irradiation, and storage on stability of the anthocyanin–polyphenol copigment complex

The influences of temperature, UV irradiation, and 3 months of storage (in the presence and absence of light) on the stability of a copigmentation complex were investigated. The copigments selected for the study included: quercetin-5′-sulphonic acid (QSA), sodium salt of morin-5′-sulphonic acid (NaMSA), rutin, quercetin, chlorogenic acid, tannic acid, and unknown flavones from roots of the Chinese origin herb Scutellaria baicalensis Georgi. The copigmentation effect increased with the copigment content. UV irradiation had a stronger degradation effect on the copigmentation complex than heating at 80 °C. Direct sunlight was found to be a significant factor, determining instability of the anthocyanin–copigment complex during storage. The Scutellaria flavones predominated over other copigments.

Effects of multiple impulse currents on the microstructure and electrical properties of metal-oxide varistors

The multiple impulse currents that are associated with a lightning ground flash have a stronger degradation effect on the electrical properties of metal oxide varistors than single pulses. It has been found that this degradation is associated with the formation of cracks extending between the contact surfaces of the devices which are filled with an amorphous material. These defects probably develop because of the formation of highly localized conduction paths during the application of the current pulses.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>