Theoretical study on the degradation mechanism of methamidophos and chloramine phosphorus with OH radicals

2015 ◽  
Vol 115 (17) ◽  
pp. 1187-1193 ◽  
Author(s):  
Shengmin Sun ◽  
Kun Zhang ◽  
Yang Lu ◽  
Ping Liu ◽  
Hui Zhang
Keyword(s):  
Theoretical Study ◽  
Degradation Mechanism ◽  
Oh Radicals

Theoretical study on the degradation mechanism of carbamate pesticides with OH radicals

2015 ◽  
Vol 134 (3) ◽  
Author(s):  
Shengmin Sun ◽  
Kun Zhang ◽  
Hui Zhang
Keyword(s):  
Theoretical Study ◽  
Degradation Mechanism ◽  
Oh Radicals ◽  
Carbamate Pesticides

Theoretical Study on the Reaction of OH Radicals with Polychlorinated Dibenzo-p-dioxins

2004 ◽  
Vol 108 (4) ◽  
pp. 607-614 ◽  
Author(s):  
Jung Eun Lee ◽  
Wonyong Choi ◽  
Byung Jin Mhin ◽  
Krishnan Balasubramanian
Keyword(s):  
Theoretical Study ◽  
Oh Radicals

An experimental and theoretical study of the kinetics of the reaction between 3-hydroxy-3-methyl-2-butanone and OH radicals

RSC Advances ◽  
2015 ◽  
Vol 5 (34) ◽  
pp. 26559-26568 ◽  
Author(s):  
Angappan Mano Priya ◽  
Gisèle El Dib ◽  
Lakshmipathi Senthilkumar ◽  
Chantal Sleiman ◽  
Alexandre Tomas ◽  
...  
Keyword(s):  
Rate Constants ◽  
Theoretical Study ◽  
Oh Radicals ◽  
First Time ◽  
Kinetics Of

Absolute experimental and theoretical rate constants are determined for the first time for the reaction of 3-hydroxy-3-methyl-2-butanone with OH as a function of temperature. The atmospheric implications are discussed.

scholarly journals The MCM v3.3 degradation scheme for isoprene

2015 ◽  
Vol 15 (6) ◽  
pp. 9709-9766 ◽  
Author(s):  
M. E. Jenkin ◽  
J. C. Young ◽  
A. R. Rickard
Keyword(s):  
Boundary Layer ◽  
Free Radical ◽  
Degradation Mechanism ◽  
Closed Shell ◽  
Chemical Mechanism ◽  
Formation Mechanisms ◽  
Oh Radicals ◽  
Atmospheric Conditions ◽  
Radical Species ◽  
Master Chemical Mechanism

Abstract. The chemistry of isoprene degradation in the Master Chemical Mechanism (MCM) has been systematically refined and updated to reflect recent advances in understanding, with these updates appearing in the latest version, MCM v3.3. The complete isoprene degradation mechanism in MCM v3.3 consists of 1935 reactions of 605 closed shell and free radical species, which treat the chemistry initiated by reaction with OH radicals, NO3 radicals and ozone (O3). A detailed overview of the updates is provided, within the context of reported kinetic and mechanistic information. The revisions mainly relate to the OH-initiated chemistry, which tends to dominate under atmospheric conditions, although these include updates to the chemistry of some products that are also generated from the O3 - and NO3-initiated oxidation. The revisions have impacts in a number of key areas, including HOx recycling, NOx recycling and the formation of species reported to play a role in SOA-formation mechanisms. The performance of the MCM v3.3 isoprene mechanism has been compared with those of earlier versions (MCM v3.1 and MCM v3.2) over a range of relevant conditions, using a box model of the tropical forested boundary layer. The results of these calculations are presented and discussed, and are used to illustrate the impacts of the mechanistic updates in MCM v3.3.

scholarly journals Electrochemical Reaction in Hydrogen Peroxide and Structural Change of Platinum Nanoparticle-Supported Carbon Nanowalls Grown Using Plasma-Enhanced Chemical Vapor Deposition

2019 ◽  
Vol 5 (1) ◽  
pp. 7
Author(s):  
Masakazu Tomatsu ◽  
Mineo Hiramatsu ◽  
Hiroki Kondo ◽  
Kenji Ishikawa ◽  
Takayoshi Tsutsumi ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Degradation Mechanism ◽  
Chemical Vapor ◽  
Oh Radicals ◽  
Platinum Nanoparticle ◽  
H2o2 Reduction ◽  
Carbon Nanowalls ◽  
Cv Measurements

Hydrogen peroxide (H2O2) reactions on platinum nanoparticle-decorated carbon nanowalls (Pt-CNWs) under potential applications were investigated on a platform of CNWs grown on carbon fiber paper (CFP) using plasma-enhanced chemical vapor deposition. Through repeated cyclic voltammetry (CV), measurements of 1000 cycles using the Pt-CNW electrodes in phosphate-buffered saline (PBS) solution with 240 μM of H2O2, the observed response peak currents of H2O2 reduction decreased with the number of cycles, which is attributed to decomposition of H2O2. After CV measurements for a total of 3000 cycles, the density and height of CNWs were reduced and their surface morphology changed. Energy-dispersive X-ray (EDX) compositional mapping revealed agglomeration of Pt nanoparticles around the top edges of CNWs. The degradation mechanism of Pt-CNWs under potential application with H2O2 is discussed by focusing on the behavior of OH radicals generated by the H2O2 reduction.

scholarly journals A rapid and efficient removal approach for degradation of metformin in pharmaceutical wastewater using electro-Fenton process; optimization by response surface methodology

2019 ◽  
Vol 80 (4) ◽  
pp. 685-694 ◽  
Author(s):  
Maryam Dolatabadi ◽  
Saeid Ahmadzadeh
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Removal Efficiency ◽  
Degradation Mechanism ◽  
Pharmaceutical Products ◽  
Oh Radicals ◽  
Order Kinetic ◽  
Pharmaceutical Wastewater ◽  
Efficient Removal ◽  
Solution Ph

Abstract Presence of emerging contaminants such as pharmaceutical products in aquatic environments has received high concern due to their undesirable effect on wildlife and human health. Current work deals with developing a treatment model based on the electro- Fenton (EF) process for efficient removal of metformin (MET) from an aqueous medium. The obtained experimental results revealed that over the reaction time of 10 min and solution pH of 3, the maximum removal efficiency of 98.57% is achieved where the value of MET initial concentration, current density, and H2O2 dosage is set at 10 mg.L−1, 6 mA.cm−2, and 250 μL.L−1, respectively, which is in satisfactory agreement with the predicted removal efficiency of 98.6% with the desirability of 0.99. The presence of radical scavengers throughout the mineralization of MET under the EF process revealed that the generation of •OH radicals, as the main oxidative species, controlled the degradation mechanism. The obtained kinetics data best fitted to the first order kinetic model with the rate constant of 0.4224 min−1 (R2 = 0.9940). The developed treatment process under response surface methodology (RSM) was employed for modeling the obtained experimental data and successfully applied for efficient removal of the MET contaminant from pharmaceutical wastewater as an adequate and cost-effective approach.

Ultrasonic Irradiation Of The Removal Of Linear Alkylbenzene Sulphonates (LAS) From Wastewater

2012 ◽  
Author(s):  
Mohd Ariffin Abu Hassan ◽  
Dionissios Mantzavinos ◽  
Ian S. Metcalfe
Keyword(s):  
Ultrasonic Irradiation ◽  
Surfactant Concentration ◽  
Degradation Rate ◽  
Degradation Mechanism ◽  
Low Frequency ◽  
Degradation Pathway ◽  
H2o2 Production ◽  
Oh Radicals ◽  
Linear Alkylbenzene ◽  
Batch Time

Kesan frekuensi rendah (20 kHz) penyinaran ultrasonik untuk penyingkiran Linear Alkylbenzene Sulphonates (LAS) daripada larutan berair telah dikaji. Penyinaran ultrasonik terhadap tiga kepekatan berbeza LAS iaitu 500 μgmol/l, 750 μgmol/l and 1000 μgmol/l telah dijalankan. Kesemua eksperimen telah dijalankan pada suhu 30°C, pada frekuensi 20 kHz, kuasa pada 125 W dan masa eksperimen selama 120 minit tanpa pengawalan terhadap pH. Hasil kajian mendapati OH· radikal mendominasi proses pengdegradasian LAS. Kadar degradasi awal bertambah dengan bertambahnya kepekatan LAS di dalam skop kajian. Penghasilan H2O2 didapati rendah dengan proses penyinaran ultrasonik terhadap LAS pada kepekatan LAS yang tinggi. Keputusan penyinaran ultrasonik terhadap LAS dengan kehadiran Br¯ sebagai pemakan radikal membuktikan bahawa OH· radikal mendominasi pengdegradasian LAS. Kata kunci: Surfaktan, ultrasonik, sisa air, jumlah karbon organik (TOC) The effect of low frequency (20 kHz) ultrasonic irradiation on the removal of sodium Linear Alkylbenzene Sulphonates (LAS) from aqueous solutions has been investigated. Sonication of three different initial concentrations of LAS, 500 μgmol/l, 750 μgmol/l and 1000 μgmol/l, were performed. All experiments used a temperature of 30°C, frequency of 20 kHz, power of 125 W, a batch time of 120 min and the pH was left uncontrolled. It was found that the main degradation of LAS at micromolar concentrations proceeded via a reaction with OH· radicals. The initial degradation rate increased with an increase in the surfactant concentration over the whole concentration range studied. The sonolysis of LAS showed a strong inhibition of H2O2 production at a higher concentration. Sonication of LAS in the presence of Br¯ suggested that OH· radicals induced degradation pathway was the dominating sonochemical degradation mechanism. Key words: Surfactants, ultrasonic, wastewater, total organic carbon (TOC)

scholarly journals Theoretical Study of the Iron Complexes with Lipoic and Dihydrolipoic Acids: Exploring Secondary Antioxidant Activity

Antioxidants ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 674
Author(s):  
Roger Monreal-Corona ◽  
Jesse Biddlecombe ◽  
Angela Ippolito ◽  
Nelaine Mora-Diez
Keyword(s):  
Antioxidant Activity ◽  
Electron Transfer ◽  
Rate Constant ◽  
Thermodynamic Stability ◽  
Rate Constants ◽  
Theoretical Study ◽  
Oh Radicals ◽  
Single Electron Transfer ◽  
Coordination Numbers ◽  
Ph Conditions

The thermodynamic stability of twenty-nine Fe(III) complexes with various deprotonated forms of lipoic (LA) and dihydrolipoic (DHLA) acids, with coordination numbers 4, 5 and 6, is studied at the M06(SMD)/6-31++G(d,p) level of theory in water under physiological pH conditions at 298.15 K. Even though the complexes with LA- are more stable than those with DHLA−, the most thermodynamically stable Fe(III) complexes involve DHLA2−. The twenty-four exergonic complexes are used to evaluate the secondary antioxidant activity of DHLA and LA relative to the Fe(III)/Fe(II) reduction by O2•− and ascorbate. Rate constants for the single-electron transfer (SET) reactions are calculated. The thermodynamic stability of the Fe(III) complexes does not fully correlate with the rate constant of their SET reactions, but more exergonic complexes usually exhibit smaller SET rate constants. Some Cu(II) complexes and their reduction to Cu(I) are also studied at the same level of theory for comparison. The Fe(III) complexes appear to be more stable than their Cu(II) counterparts. Relative to the Fe(III)/Fe(II) reduction with ascorbate, DHLA can fully inhibit the formation of •OH radicals, but not by reaction with O2•−. Relative to the Cu(II)/Cu(I) reduction with ascorbate, the effects of DHLA are moderate/high, and with O2•− they are minor. LA has minor to negligible inhibition effects in all the cases considered.

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