scholarly journals Development of mesh-type Fenton-like Cu/Fex/γ-Al2O3/Al catalysts and application for catalytic degradation of dyes

2020 ◽  
Vol 81 (10) ◽  
pp. 2057-2065
Author(s):  
Huang Qian ◽  
Shao Qianwen ◽  
Zhang Qi ◽  
Ni Yanhui ◽  
Wu Yongqiang
Keyword(s):  
Degradation Rate ◽  
Bimetallic Catalyst ◽  
Radical Scavenging ◽  
Resonance Spectroscopy ◽  
Degradation Of Dyes ◽  
Spin Resonance ◽  
Temperature Programmed ◽  
Reactive Oxidant ◽  
Redox Ability

Abstract The application of nanoparticle heterogeneous Fenton-like catalysts is limited due to the requirement of filtration after reaction and possible secondary pollution. In this work, a novel mesh-type monolithic Fenton-like Cu/Fex/γ-Al2O3/Al catalyst was developed for the degradation of dyes. The Cu and Fe species are uniformly dispersed on the mesh-type anodic monolithic γ-Al2O3 supports, and the results of scanning electron microscopy and X-ray diffractometry analysis show that Fe can reduce the particle size of Cu over γ-Al2O3. The activity results show that the degradation rate of rhodamine B (RhB) reached 99.5% within 1 h using 4 × 6 cm Cu12.0/Fe2.0/γ-Al2O3/Al catalyst with 1,200 ppm H2O2 at 50 °C. The important role of •OH as a reactive oxidant was confirmed through electron spin-resonance spectroscopy and radical scavenging experiment. The hydrogen temperature programmed reduction suggests the high redox ability of Cu/Fe bimetallic catalyst is beneficial to the production of •OH. The Cu/Fe bimetallic catalyst shows excellent recyclability in a 10-cycle experiment, the degradation rate of RhB was maintained at 98% and the leaching amount of metals was lower than 0.7 mg/L. The mesh-type catalyst will be easily applied for the continuous wastewater treatment because it does not need filtration for recovery.

scholarly journals Environmentally persistent free radicals are ubiquitous in wildfire charcoals and remain stable for years

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Gabriel Sigmund ◽  
Cristina Santín ◽  
Marc Pignitter ◽  
Nathalie Tepe ◽  
Stefan H. Doerr ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Free Radicals ◽  
Reactive Oxygen ◽  
Resonance Spectroscopy ◽  
Oxygen Species ◽  
Pyrogenic Carbon ◽  
Spin Resonance ◽  
Long Time ◽  
High Concentrations

AbstractGlobally landscape fires produce about 256 Tg of pyrogenic carbon or charcoal each year. The role of charcoal as a source of environmentally persistent free radicals, which are precursors of potentially harmful reactive oxygen species, is poorly constrained. Here, we analyse 60 charcoal samples collected from 10 wildfires, that include crown as well as surface fires in forest, shrubland and grassland spanning different boreal, temperate, subtropical and tropical climate. Using electron spin resonance spectroscopy, we measure high concentrations of environmentally persistent free radicals in charcoal samples, much higher than those found in soils. Concentrations increased with degree of carbonization and woody fuels favoured higher concentrations. Moreover, environmentally persistent free radicals remained stable for an unexpectedly long time of at least 5 years. We suggest that wildfire charcoal is an important global source of environmentally persistent free radicals, and therefore potentially of harmful reactive oxygen species.

scholarly journals Pneumocystis Melanins Confer Enhanced Organism Viability

2006 ◽  
Vol 5 (6) ◽  
pp. 916-923 ◽  
Author(s):  
Crystal R. Icenhour ◽  
Theodore J. Kottom ◽  
Andrew H. Limper
Keyword(s):  
Fungal Pathogen ◽  
Pneumocystis Carinii ◽  
Environmental Stressors ◽  
Resonance Spectroscopy ◽  
Reverse Transcription Pcr ◽  
Spin Resonance ◽  
Opportunistic Fungal Pathogen ◽  
Adverse Environmental Conditions ◽  
Previous Identification

ABSTRACT Pneumocystis continues to represent an important opportunistic fungal pathogen of those with compromised immunity. Thus, it is crucial to identify factors that affect its viability and pathogenicity. We previously reported the first identification of melanins in Pneumocystis. In the present study, we sought to further characterize these components and define the function for these melanins. Melanins extracted from Pneumocystis and melanized Pneumocystis cells were analyzed by electron spin resonance spectroscopy, revealing spectra consistent with melanins from other fungi. Immunofluorescence assays using anti-melanin monoclonal antibodies showed that melanins are widely present across Pneumocystis host species, including mouse-, ferret-, and human-derived Pneumocystis organisms, as well as Pneumocystis carinii derived from rat. Using immunoelectron microscopy, melanins were found to localize to the cell wall and cytoplasm of P. carinii cysts, as well as to intracystic bodies within mature cysts. Next, the role of melanins on the maintenance of Pneumocystis viability was determined by using quantitative reverse transcription-PCR measurement of the heat shock protein mRNA under adverse environmental conditions. Using a new method to promote the melanization of Pneumocystis, we observed that strongly melanized Pneumocystis retained viability to a greater degree when exposed to UV irradiation or desiccation compared to less-pigmented organisms. These studies support our previous identification of Pneumocystis melanins across the genus, further characterize these Pneumocystis components, and demonstrate that melanins protect Pneumocystis from environmental stressors.

The Presence and Role of Paramagnetic Impurities in the Degradation of Paper

1996 ◽  
Vol 462 ◽  
Author(s):  
Donato Attanasio ◽  
Donatella Capitani ◽  
Maria C. Emanuele
Keyword(s):  
Electron Spin Resonance ◽  
Point Defects ◽  
Systematic Investigation ◽  
Electron Spin Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Paramagnetic Impurities ◽  
Quantitative Monitoring ◽  
Spin Resonance ◽  
Paramagnetic Centres

ABSTRACTElectron Spin Resonance spectroscopy has been used to carry out a systematic investigation of the paramagnetic impurities present in antique and modern paper. Up to eleven different paramagnetic centres, which include different transition ions (Fe3+, Mn2+, Cu2+), organic free radicals, and paramagnetic point defects have been detected, in concentrations ranging from few ppm to several hundreds. Experiments performed on new and deteriorated samples strongly indicate that some of these impurities participate directly or are produced during the aging and degradation processes. They can be used as quality indicators or probes for quantitative monitoring of the degradation of paper.

Defect Creation and Photoablation in Stoichiometric and Sub-Stoichiometric SiO2

1985 ◽  
Vol 60 ◽  
Author(s):  
R. A. B. Devine ◽  
C. Fiori
Keyword(s):  
Point Defects ◽  
Defect Structure ◽  
Measurement Techniques ◽  
Electrical Measurement ◽  
Resonance Spectroscopy ◽  
Physical Mechanisms ◽  
Spin Resonance ◽  
Different Types ◽  
Comparison Of The Results

AbstractIt is demonstrated that microscopic point defects can be created in amorphous silica using pulsed ultraviolet irradiation (λ = 248 nm) at energy densities ∼ 100 times less than those normally estimated to lead to damage creation. Identification of the physical character of the defects has been made using electron spin resonance spectroscopy and electrical measurement techniques. Continued irradiation of the SiO2 is found to lead to photoablation. Results obtained for bulk dry SiO2, thermal SiO2 and vacuum deposited SiOx are presented. The important role of non-stoichiometry (defect structure) in the process of photoablation is clearly manifested by comparison of the results obtained for the different types of SiO2. Possible physical mechanisms involved are discussed.

Effect of K2S2O8 on Material Removal Rate in Abrasive-Free Polishing of Hard Disk Substrate

2013 ◽  
Vol 690-693 ◽  
pp. 3222-3225 ◽  
Author(s):  
Rong Zhao ◽  
Hong Lei
Keyword(s):  
Material Removal Rate ◽  
Material Removal ◽  
Removal Rate ◽  
Hard Disk ◽  
Resonance Spectroscopy ◽  
Electrochemical Test ◽  
Spin Resonance ◽  
Hard Disk Substrate ◽  
Disk Substrate

The role of K2S2O8 (KPS) initiator on the material removal rate (MRR) of hard disk substrate in the H2O2-based slurry was investigated. Experiment results indicate that the MRR of slurry containing KPS and H2O2 is higher than that of slurry containing only H2O2 under the same testing conditions. The electrochemical test shows that KPS can increase the corrosion rate of hard disk substrate in the H2O2-based slurry. The electron spin-resonance spectroscopy (EPR) analysis shows that KPS, as an initiator, can increase the number of OH• free radical. Further, the reaction mechanism of KPS in abrasive-free polishing of hard disk substrate is discussed.

Pyrite-enhanced degradation of chloramphenicol by low concentrations of H2O2

2015 ◽  
Vol 72 (2) ◽  
pp. 180-186 ◽  
Author(s):  
Deli Wu ◽  
Yanxia Liu ◽  
Zhiyong Zhang ◽  
Luming Ma ◽  
Yalei Zhang
Keyword(s):  
Energy Dispersive Spectrometry ◽  
Gas Chromatography Mass Spectrometry ◽  
Resonance Spectroscopy ◽  
Low Concentrations ◽  
Spin Resonance ◽  
Initial Ph ◽  
Catalyzed Reactions ◽  
Natural Pyrite ◽  
Enhanced Degradation

A pyrite-catalyzed reaction was used to degrade chloramphenicol. Chloramphenicol could be almost 100% removed within 60 minutes when 1 mM H2O2 and 0.1 g/L pyrite were added at an initial pH = 3. During oxidation, intermediates such as nitrobenzaldehyde and dichloroacetamide were identified by gas chromatography/mass spectrometry (GC/MS). The •OH was identified by electron spin-resonance spectroscopy. Pyrite was digested to determine elements by ICP (inductive coupled plasma emission spectrometer). To understand the reaction mechanism and the role of natural pyrite in these processes, techniques including scanning electron microscopy and energy dispersive spectrometry were employed to characterize the solid sample. The results explain that pyrite acts as a ‘bond’ between Fe3+ and H2O2, and this pathway continues to form •OH and inhibit the quenching reaction. Therefore, pyrite-catalyzed reactions would proceed even in low concentrations of H2O2.

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