scholarly journals Rapid Removal of Tetrabromobisphenol A by Ozonation in Water: Oxidation Products, Reaction Pathways and Toxicity Assessment

PLoS ONE ◽  
2015 ◽  
Vol 10 (10) ◽  
pp. e0139580 ◽  
Author(s):  
Ruijuan Qu ◽  
Mingbao Feng ◽  
Xinghao Wang ◽  
Qingguo Huang ◽  
Junhe Lu ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Toxicity Assessment ◽  
Oxidation Products ◽  
Reaction Pathways ◽  
Tetrabromobisphenol A ◽  
Rapid Removal

Investigating the NO-dependent photooxidation of limonene by OH and O3 using the atmosphere simulation chamber SAPHIR

2021 ◽  
Author(s):  
Yat Sing Pang ◽  
Martin Kaminski ◽  
Anna Novelli ◽  
Philip Carlsson ◽  
Ismail-Hakki Acir ◽  
...  
Keyword(s):  
Organic Aerosol ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Reaction Pathways ◽  
Oh Radicals ◽  
Oh Radical ◽  
Simulation Experiments ◽  
Master Chemical Mechanism ◽  
Simulation Results ◽  
Atmosphere Simulation Chamber

<p>Limonene is the fourth-most abundant monoterpene in the atmosphere, which upon oxidation leads to the formation of secondary organic aerosol (SOA) and thereby influences climate and air quality.</p><p>In this study, the oxidation of limonene by OH at different atmospherically relevant NO and HO<sub>2</sub> levels (NO: 0.1 – 10 ppb; HO<sub>2</sub>: 20 ppt) was investigated in simulation experiments in the SAPHIR chamber at Forschungszentrum Jülich. The analysis focuses on comparing measured radical concentrations (RO<sub>2</sub>, HO<sub>2</sub>, OH) and OH reactivity (k<sub>OH</sub>) with modeled values calculated using the Master Chemical Mechanism (MCM) version 3.3.1.</p><p>At high and medium NO concentrations, RO<sub>2</sub> is expected to quickly react with NO. An HO<sub>2</sub> radical is produced during the process that can be converted back to an OH radical by another reaction with NO. Consistently, for experiments conducted at medium NO levels (~0.5 ppb, RO<sub>2</sub> lifetime ~10 s), simulated RO<sub>2</sub>, HO<sub>2</sub>, and OH agree with observations within the measurement uncertainties, if the OH reactivity of oxidation products is correctly described.</p><p>At lower NO concentrations, the regeneration of HO<sub>2</sub> in the RO<sub>2</sub> + NO reaction is slow and the reaction of RO<sub>2</sub> with HO<sub>2</sub> gains importance in forming peroxides. However, simulation results show a large discrepancy between calculated radical concentrations and measurements at low NO levels (<0.1 ppb, RO<sub>2</sub> lifetime ~ 100 s). Simulated RO<sub>2</sub> concentrations are found to be overestimated by a factor of three; simulated HO<sub>2</sub> concentrations are underestimated by 50 %; simulated OH concentrations are underestimated by about 35%, even if k<sub>OH</sub> is correctly described. This suggests that there could be additional RO<sub>2</sub> reaction pathways that regenerate HO<sub>2</sub> and OH radicals become important, but they are not taken into account in the MCM model.</p>

Function-switchable metal/semiconductor junction enables efficient photocatalytic overall water splitting with selective water oxidation products

2020 ◽  
Vol 65 (16) ◽  
pp. 1389-1395 ◽  
Author(s):  
Daixing Wei ◽  
Yubo Tan ◽  
Yiqing Wang ◽  
Tingting Kong ◽  
Shaohua Shen ◽  
...  
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Oxidation Products ◽  
Overall Water Splitting ◽  
Semiconductor Junction

scholarly journals Water oxidation catalysis on reconstructed NaTaO3 (001) surfaces

2019 ◽  
Vol 7 (28) ◽  
pp. 16770-16776 ◽  
Author(s):  
Hassan Ouhbi ◽  
Ulrich Aschauer
Keyword(s):  
Surface Reconstruction ◽  
Water Oxidation ◽  
Oxidation Catalysis ◽  
Reaction Pathways ◽  
Catalytic Activities ◽  
Water Oxidation Catalysis

Surface reconstruction of polar NaTaO3 (001) surfaces is shown to strongly affect reaction pathways and catalytic activities.

scholarly journals Evidence for roles of radicals in protein oxidation in advanced human atherosclerotic plaque

1998 ◽  
Vol 333 (3) ◽  
pp. 519-525 ◽  
Author(s):  
Shanlin FU ◽  
Michael J. DAVIES ◽  
Roland STOCKER ◽  
Roger T. DEAN
Keyword(s):  
Hydroxyl Radical ◽  
Protein Modification ◽  
Indirect Evidence ◽  
Transition Metal Ions ◽  
Oxidation Products ◽  
Reaction Pathways ◽  
Radical Attack ◽  
Radical Damage ◽  
Human Carotid

Oxidative damage might be important in atherogenesis. Oxidized lipids are present at significant concentrations in advanced human plaque, although tissue antioxidants are mostly present at normal concentrations. Indirect evidence of protein modification (notably derivatization of lysine) or oxidation has been obtained by immunochemical methods; the specificities of these antibodies are unclear. Here we present chemical determinations of six protein-bound oxidation products: dopa, o-tyrosine, m-tyrosine, dityrosine, hydroxyleucine and hydroxyvaline, some of which reflect particularly oxy-radical-mediated reaction pathways, which seem to involve mainly the participation of transition- metal ions. We compared the relative abundance of these oxidation products in normal intima, and in human carotid plaque samples with that observed after radiolytically generated hydroxyl radical attack on BSA in vitro. The close similarities in relative abundances in the latter two circumstances indicate that hydroxyl radical damage might occur in plaque. The relatively higher level of dityrosine in plaque than that observed after radiolysis suggests the additional involvement of HOCl-mediated reactions in advanced plaque.

scholarly journals Identifying the Spectroelectrochemical Characteristics of Hematite Photoanodes for Water Oxidation

2021 ◽  
Author(s):  
Jifang Zhang ◽  
Qiyuan Lin ◽  
Zhenlei Wang ◽  
Haowen Liu ◽  
Yuegang Zhang
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Surface States ◽  
Reaction Pathways ◽  
Reaction Intermediates ◽  
Fermi Level Pinning ◽  
Solar Water Splitting ◽  
Interfacial Processes ◽  
Active Reaction ◽  
Recombination Processes

Achieving efficient solar water splitting using hematite (α-Fe2O3), one of the most promising candidates for photoanodes, requires photogenerated holes to be efficiently used for water oxidation. However, this goal is obstructed by multiple undesirable recombination processes, as well as insufficient fundamental mechanistic understandings of water oxidation kinetics, particularly as to the nature of reaction pathways and possible reaction intermediates. Here we spectroelectro-chemically identify some of the most critical interfacial processes which determine the photoelectrocatalytic efficiencies of water oxidation, for hematite films with varied surface properties by tailoring the doping level of titanium. The spectroscopic signals of the processes inactive for water oxidation, including oxidation of intra-gap Fe2+ states and Fermi level pinning, are successfully distinguished from that of the active reaction intermediate, Fe(IV)=O. In addition, our kinetic analyses reveal two water oxidation pathways, of which the direct hole transfer mechanism becomes dominant over the surface states-mediated mechanism when the hematite surface is reconstructed by high levels of titanium dopants.

scholarly journals Comparison of Material Activity and Selectivity in the Electrocatalytic Oxidation of Dibenzothiophene

2021 ◽  
Author(s):  
Victoria Kompanjiec ◽  
John R Swierk
Keyword(s):  
Water Oxidation ◽  
Electrocatalytic Oxidation ◽  
Oxidative Desulfurization ◽  
Oxidation Products ◽  
Faradaic Efficiency ◽  
Lower Activation ◽  
Bulk Electrolysis ◽  
Percent Conversion ◽  
Increasing Demand ◽  
Electrochemical Catalysts

Abstract There is an increasing demand for efficient methods to remove sulfur from oil products, such as oxidative desulfurization. In this work, a set of five materials (gold, glassy carbon, nickel, palladium and platinum) were evaluated as electrochemical catalysts for the oxidation of dibenzothiophene (DBT). Bulk electrolysis performed without water present, produced DBT dimer, while the addition of 2 M water, produced dibenzothiophene sulfoxide (DBTO), both more polar than DBT. LC-MS and NMR were used to characterize the oxidation products. Faradaic efficiencies ranged from 18.4–56.5% for DBT consumption without water present, and there was a correlation between higher rate constants, lower activation energies and more efficient DBT oxidation. With water present, selectivity for DBTO formation was highest using gold, with a Faradaic efficiency of 87.9%. Group ten metals demonstrated low Faradaic efficiencies due to competitive water oxidation. Though there were differences in the observed selectivity for DBT oxidation, all catalysts reduced the concentration of DBT in solution by similar amounts. Our findings indicate that the overall percent conversion does not give a complete picture of catalytic activity. Of the materials tested, gold was the most selective for oxidation to DBTO, with the presence of water improving the overall reaction activity.

scholarly journals Oxygenated products formed from OH-initiated reactions of trimethylbenzene: Autoxidation and accretion

2020 ◽  
Author(s):  
Yuwei Wang ◽  
Archit Mehra ◽  
Jordan E. Krechmer ◽  
Gan Yang ◽  
Xiaoyu Hu ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Flow Reactor ◽  
Time Of Flight ◽  
Oxidation Products ◽  
Urban Atmosphere ◽  
Reaction Pathways ◽  
Peroxy Radicals ◽  
Flight Mass Spectrometer

Abstract. Gas-phase oxidation pathways and products of anthropogenic volatile organic compounds (VOCs), mainly aromatics, are the subject of intensive research with attention paid to their contributions to secondary organic aerosol (SOA) formation and potentially, new particle formation (NPF) in the urban atmosphere. In this study, a series of OH-initiated oxidation experiments of trimethylbenzene (TMB, C9H12) including 1,2,4-TMB, 1,3,5-TMB, 1,2,3-TMB, and 1,2,4-(methyl-D3)-TMBs (C9H9D3) were investigated in an oxidation flow reactor (OFR), in the absence and presence of NOx. Products were measured using a suite of state-of-the-art instruments, i.e., a nitrate-based chemical ionization – atmospheric pressure interface time-of-flight mass spectrometer (Nitrate CI-APi-TOF), an iodide-adduct chemical ionization – time-of-flight mass spectrometer (Iodide CI-TOF) equipped with a Filter Inlet for Gases and AEROsols (FIGAERO), and a Vocus proton-transfer-reaction mass spectrometer (Vocus PTR). A large number of C9 products with 1–11 oxygen atoms and C18 products presumably formed from dimerization of C9 peroxy radicals were observed, hinting the extensive existence of autoxidation and accretion reaction pathways in the OH-initiated oxidation reactions of TMBs. Oxidation products of 1,2,4-(methyl-D3)-TMBs with deuterium atoms in different methyl substituents were then used as a molecular basis to propose potential autoxidation reaction pathways. Accretion of C9 peroxy radicals is the most significant for aromatics with meta-substituents and the least for aromatics with ortho-substituents, if the number and size of substituted groups are identical. The presence of NOx would suppress the formation of C18 highly oxygenated molecules (HOMs) and enhance the formation of organonitrates, and even dinitrate organic compounds. Our results show that the oxidation products of TMB are much more diverse and could be more oxygenated than the current mechanisms predict.

Removal of Organic Matters in Pesticide Wastewater by Supercritical Water Oxidation

2014 ◽  
Vol 955-959 ◽  
pp. 2340-2348 ◽  
Author(s):  
Dong Hai Xu ◽  
Shu Zhong Wang ◽  
Chuan Bao Huang ◽  
Xing Ying Tang ◽  
Yang Guo ◽  
...  
Keyword(s):  
Chemical Oxygen Demand ◽  
Residence Time ◽  
Supercritical Water ◽  
Water Oxidation ◽  
Oxygen Demand ◽  
Reaction Pathways ◽  
Experimental Plant ◽  
Supercritical Water Oxidation ◽  
High Concentration ◽  
Organic Matters

Supercritical water oxidation (SCWO) is an alternative to effectively dispose many varieties of organic wastewaters. In this article, a high concentration pesticide wastewater with very complicated components was handled by SCWO in a batch experimental plant at 25 MPa, 410–580 °C within the oxidant coefficient of 1.1–4.0 and the residence time of 1.0–10.0 min. The results show that reaction temperature, oxidant coefficient, residence time can improve XCOD(removal efficiency of chemical oxygen demand) of reactor effluent. XCODreaches up to 99.89% at 550 °C, 25 MPa with the oxidant coefficient of 3.0 and the residence time of 5.0 min, and the corresponding COD concentration is 73 mg/L. Residence time indicates a relatively more important influence on COD1at higher reaction temperatures and OCs. Furthermore, possible reaction pathways for SCWO of organic matters in the pesticide wastewater were also proposed primarily.

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