Efficient photocatalytic defluorination of perfluorooctanoic acid over BiOCl nanosheets via a hole direct oxidation mechanism

2017 ◽  
Vol 317 ◽  
pp. 925-934 ◽  
Author(s):  
Zhou Song ◽  
Xuelin Dong ◽  
Nan Wang ◽  
Lihua Zhu ◽  
Zhihong Luo ◽  
...  
Keyword(s):  
Oxidation Mechanism ◽  
Perfluorooctanoic Acid ◽  
Direct Oxidation

scholarly journals A facile and effective method for preparation of 2.5-furandicarboxylic acid via hydrogen peroxide direct oxidation of 5-hydroxymethylfurfural

2017 ◽  
Vol 19 (1) ◽  
pp. 11-16 ◽  
Author(s):  
Shuang Zhang ◽  
Long Zhang
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction Time ◽  
Oxidation Mechanism ◽  
Molar Ratio ◽  
Alkaline Condition ◽  
Optimal Parameters ◽  
Direct Oxidation ◽  
Reaction Parameters ◽  
Alkaline Conditions ◽  
Furandicarboxylic Acid

Abstract In this paper, 2,5-furandicarboxylic acid (FDCA) was efficiently prepared by the direct oxidation of 5-hydroxymethylfurfural (5-HMF) using hydrogen peroxide (H2O2) in alkaline conditions without any catalysts. The effects of reaction parameters on the process were systematically investigated and the optimal parameters were obtained as follows: molar ratio of 5-HMF:KOH:H2O2 was 1:4:8, reaction temperature and reaction time were determined as 70°C and 15 minutes, respectively. Under these conditions, the yield of FDCA was 55.6% and the purity of FDCA could reach 99%. Moreover, we have speculated the detailed oxidation mechanism of 5-HMF assisted by hydrogen peroxide in alkaline condition to synthesize FDCA.

THE SILVER CATALYZED OXIDATION OF ETHYLENE: III. KINETICS OF ETHYLENE OXIDE OXIDATION

1954 ◽  
Vol 32 (4) ◽  
pp. 432-442 ◽  
Author(s):  
A. Orzechowski ◽  
K. E. MacCormack
Keyword(s):  
Ethylene Oxide ◽  
Initial Rate ◽  
Oxidation Mechanism ◽  
Kinetic Studies ◽  
Main Step ◽  
Direct Oxidation ◽  
Flow Rates ◽  
Rate Determining Step ◽  
Kinetics Of ◽  
Catalyzed Oxidation

A flow type apparatus was used for kinetic studies of the silver catalyzed oxidation of ethylene oxide (EtO) by oxygen at 274 °C. Using N2 as diluent the concentrations of O2 and ethylene oxide were varied independently from 9.9 to 79% and 2.35 to 9.4% respectively while a total pressure of 1 atmosphere was maintained. Flow rates were varied to give a range of contact times varying from 0.06 to 0.25 sec. It was shown that EtO is oxidized without previous dissociation into C2H4 and O2. The dependence of the initial rate of oxidation of EtO on reactant concentrations excludes isomerization of EtO (to acetalde hyde) as a main step in its oxidation, and a direct oxidation mechanism is suggested. The results of a few experiments to determine the extent of isomerization of EtO to acetaldehyde in the absence of oxygen are presented. No steady state could be achieved but the results may be used semiquantitatively to support the belief that isomerization is not the rate determining step in the oxidation of ethylene oxide.

scholarly journals Insights into the Kinetics of Intermediate Formation during Electrochemical Oxidation of the Organic Model Pollutant Salicylic Acid in Chloride Electrolyte

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1322 ◽  
Author(s):  
Ambauen ◽  
Muff ◽  
Mai ◽  
Hallé ◽  
Trinh ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Electrochemical Oxidation ◽  
Density Functional ◽  
Oxidation Mechanism ◽  
Intermediate Formation ◽  
Anode Surface ◽  
Order Kinetic ◽  
Direct Oxidation ◽  
Boron Doped Diamond ◽  
Chloride Electrolyte

The present study investigated the kinetics and formation of hydroxylated and chlorinated intermediates during electrochemical oxidation of salicylic acid (SA). A chloride (NaCl) and sulfate (Na2SO4) electrolyte were used, along with two different anode materials, boron doped diamond (BDD) and platinum (Pt). Bulk electrolysis of SA confirmed the formation of both hydroxylated and chlorinated intermediates. In line with the density functional theory (DFT) calculations performed in this study, 2,5- and 2,3-dihydroxybenzoic acid, 3- and 5- chlorosalicylic acid and 3,5-dichlorosalicylic acid were the dominating products. In the presence of a chloride electrolyte, the formation of chlorinated intermediates was the predominant oxidation mechanism on both BDD and Pt anodes. In the absence of a chloride electrolyte, hydroxylated intermediates prevailed on the Pt anode and suggested the formation of sulfonated SA intermediates on the BDD anode. Furthermore, direct oxidation at the anode surface only played a subordinate role. First order kinetic models successfully described the degradation of SA and the formation of the observed intermediates. Rate constants provided by the model showed that chlorination of SA can take place at up to more than 60 times faster rates than hydroxylation. In conclusion, the formation of chlorinated intermediates during electrochemical oxidation of the organic model pollutant SA is confirmed and found to be dominant in chloride containing waters.

scholarly journals Degradation Reactive Black 5 dye from aqueous solutions using ozonation with pumices and pumices modified by nanoscale zero valent iron (nZVI)

2020 ◽  
Keyword(s):  
Batch Reactor ◽  
Oxidation Mechanism ◽  
Zero Valent Iron ◽  
Radical Mechanism ◽  
Main Role ◽  
Reactive Black 5 ◽  
Direct Oxidation ◽  
Solution Ph ◽  
Nanoscale Zero Valent Iron ◽  
Textile Industries

<p>Reactive Black 5 (RB5) dyes are a dye widely used in textile industries. The nanocatalytic ozonation of RB5 solution in the presence of pumice modified with nanoscale zero valent iron (nZVI) catalysts and pumice raw investigated in a laboratory scale batch reactor. The effects of solution pH (3-11), reaction time, pumice dosage (10, 15 and 20 g/L) and COD removal were evaluated. Natural mineral raw pumice and pumice-nZVI was used directly in nanocatalytic ozonation of dye of RB5 solution. Compared with raw pumice, pumice-nZVI into the ozonation reactor greatly accelerated the rate of RB5 degradation. The results indicate that with increasing (pH, and pumice dosage) increased rate RB5 degradation. Molecular ozone direct oxidation mechanism was proved in nanocatalytic ozonation with pumice, and hydroxyl radical mechanism was demonstrated to play a main role in nanocatalytic ozonation with nZVI.</p>

scholarly journals The Oxidation Mechanism of Aniline by Ozone Water and Ozone Micro-nano Bubble Water and Its Influencing Factors

2022 ◽  
Author(s):  
Zeming Xie ◽  
Jiali Shentu ◽  
Yuyang Long ◽  
Li Lu ◽  
Dongsheng Shen ◽  
...  
Keyword(s):  
Treatment Process ◽  
Mass Transfer Rate ◽  
Oxidation Mechanism ◽  
Utilization Rate ◽  
Groundwater Treatment ◽  
Direct Oxidation ◽  
Negative Effect ◽  
Aniline Oxidation ◽  
Oxidation Efficiency ◽  
Oxidation Effect

Abstract Aniline is a kind of refractory contaminant that is difficult to be degraded by microorganisms. Ozone is a green and efficient reagent to oxidize aniline, while the ozone oxidation efficiency is restricted by the low ozone mass transfer rate. Micro-nano bubble ozonation has been developed as a new method to significantly improve the ozone utilization rate, while the characteristics of ozone micro-nano bubble when compared with dissolved ozone is not clear. The paper carried out batch experiments to research the oxidation effect of aniline by ozone water (OW) and ozone micro-nano bubble water (OMNBW), and found that the degradation rate of aniline by OMNBW was 2.8~5.9% higher than that by OW. The increase of pH had a negative effect on the degradation of aniline by OW and OMNBW. SO42-, Cl-, HCO­3- and Mg2+ could inhibit the degradation efficiency by 0.04%, 0.99%, 0.44% and 10.4% for OW, while the ratios were 1.1%, 6.4%, 4.1% and 1.5% for OMNBW. The addition of humic acid and fulvic acid could decrease the oxidation rate of aniline by 35% and 49% for OW, while the ratios were 41% and 62% for OMNBW. Through quenching experiment, it was found that the direct oxidation by ozone molecules and the indirect oxidation by superoxide radicals were main pathways for aniline oxidation by OW and OMNBW. This work provided a practical guide for the application of OMNBW in wastewater and groundwater treatment process.

scholarly journals Limits of Versatility of Versatile Peroxidase

2016 ◽  
Vol 82 (14) ◽  
pp. 4070-4080 ◽  
Author(s):  
Doriv Knop ◽  
Dana Levinson ◽  
Arik Makovitzki ◽  
Avi Agami ◽  
Elad Lerer ◽  
...  
Keyword(s):  
Active Site ◽  
Aromatic Compounds ◽  
Pleurotus Ostreatus ◽  
Active Sites ◽  
Oxidation Mechanism ◽  
White Rot ◽  
White Rot Fungus ◽  
Reactive Black 5 ◽  
Direct Oxidation ◽  
Content Type

ABSTRACTAlthough Mn2+is the most abundant substrate of versatile peroxidases (VPs), repression ofPleurotus ostreatusvp1expression occurred in Mn2+-sufficient medium. This seems to be a biological contradiction. The aim of this study was to explore the mechanism of direct oxidation by VP1 under Mn2+-deficient conditions, as it was found to be the predominant enzyme during fungal growth in the presence of synthetic and natural substrates. The native VP1 was purified and characterized using three substrates, Mn2+, Orange II (OII), and Reactive Black 5 (RB5), each oxidized by a different active site in the enzyme. While the pH optimum for Mn2+oxidation is 5, the optimum pH for direct oxidation of both dyes was found to be 3. Indeed, effectivein vivodecolorization occurred in media without addition of Mn2+only under acidic conditions. We have determined that Mn2+inhibitsin vitrothe direct oxidation of both OII and RB5 while RB5 stabilizes both Mn2+and OII oxidation. Furthermore, OII was found to inhibit the oxidation of both Mn2+and RB5. In addition, we could demonstrate that VP1 can cleave OII in two different modes. Under Mn2+-mediated oxidation conditions, VP1 was able to cleave the azo bond only in asymmetric mode, while under the optimum conditions for direct oxidation (absence of Mn2+at pH 3) both symmetric and asymmetric cleavages occurred. We concluded that the oxidation mechanism of aromatic compounds by VP1 is controlled by Mn2+and pH levels both in the growth medium and in the reaction mixture.IMPORTANCEVP1 is a member of the ligninolytic heme peroxidase gene family of the white rot fungusPleurotus ostreatusand plays a fundamental role in biodegradation. This enzyme exhibits a versatile nature, as it can oxidize different substrates under altered environmental conditions. VPs are highly interesting enzymes due to the fact that they contain unique active sites that are responsible for direct oxidation of various aromatic compounds, including lignin, in addition to the well-known Mn2+binding active site. This study demonstrates the limits of versatility ofP. ostreatusVP1, which harbors multiple active sites, exhibiting a broad range of enzymatic activities, but they perform differently under distinct conditions. The versatility ofP. ostreatusand its enzymes is an advantageous factor in the fungal ability to adapt to changing environments. This trait expands the possibilities for the potential utilization ofP. ostreatusand other white rot fungi.

Mechanism of photocatalytic oxidation of gaseous ethanol

2007 ◽  
Vol 61 (1) ◽  
Author(s):  
C. Shao ◽  
D. Pan ◽  
R. Zhang ◽  
H. Hou
Keyword(s):  
Water Vapour ◽  
Photocatalytic Oxidation ◽  
Oxidation Mechanism ◽  
Ethyl Formate ◽  
Direct Oxidation ◽  
Partial Pressures ◽  
Film Reactor ◽  
Carrier Gases ◽  
Positive Hole ◽  
Dioxide Film

AbstractA photocatalytic film reactor with a titanium dioxide film was used for oxidation of gaseous ethanol at 253.7 nm. The influences of partial pressures of oxygen and water vapour in different carrier gases were studied. The rate of photocatalytic oxidation of ethanol was significantly affected by the content of oxygen but water vapour had no effect. It was suggested that the photocatalytic transformation of ethanol follows a direct oxidation mechanism where the interaction of ethanol with positive hole gives first cationic free radical of ethanol, which is converted by multipathway reactions with oxygen to acetaldehyde, ethyl formate, and ethyl acetate.

scholarly journals Intrareticular charge transfer regulated electrochemiluminescence of donor–acceptor covalent organic frameworks

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Rengan Luo ◽  
Haifeng Lv ◽  
Qiaobo Liao ◽  
Ningning Wang ◽  
Jiarui Yang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Density Functional ◽  
Oxidation Mechanism ◽  
Emission Mechanism ◽  
Direct Oxidation ◽  
Functional Theory ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Anions And Cations ◽  
Mediated Oxidation

AbstractThe control of charge transfer between radical anions and cations is a promising way for decoding the emission mechanism in electrochemiluminescence (ECL) systems. Herein, a type of donor-acceptor (D-A) covalent organic framework (COF) with triphenylamine and triazine units is designed as a highly efficient ECL emitter with tunable intrareticular charge transfer (IRCT). The D-A COF demonstrates 123 folds enhancement in ECL intensity compared with its benzene-based COF with small D-A contrast. Further, the COF’s crystallinity- and protonation-modulated ECL behaviors confirm ECL dependence on intrareticular charge transfer between donor and acceptor units, which is rationalized by density functional theory. Significantly, dual-peaked ECL patterns of COFs are achieved through an IRCT mediated competitive oxidation mechanism: the coreactant-mediated oxidation at lower potential and the direct oxidation at higher potential. This work provides a new fundamental and approach to improve the ECL efficiency for designing next-generation ECL devices.

NANOELECTROCATALYSTS BASED PALLADIUM FOR FUEL CELLS WITH DIRECT OXIDATION OF FORMIC ACID

2019 ◽  
Vol 6 (3) ◽  
pp. 104-107
Author(s):  
Marina Vladimirovna Lebedeva ◽  
Alexey Petrovich Antropov ◽  
Alexander Victorovich Ragutkin ◽  
Nicolay Andreevich Yashtulov
Keyword(s):  
Formic Acid ◽  
Palladium Nanoparticles ◽  
Oxidation Reaction ◽  
Electrode Materials ◽  
Formic Acid Oxidation ◽  
Energy Sources ◽  
Acid Oxidation ◽  
Direct Oxidation ◽  
Atomic Force ◽  
Formic Acid Oxidation Reaction

In paper electrode materials with palladium nanoparticles on polymer matrix substrates for energy sources have been formed. Nanocomposites were investigated by atomic force and scanning electron microscopy. The catalytic activity of formed electrodes in the formic acid oxidation reaction was evaluated by voltammetry method.

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