scholarly journals SO2Gas Physicochemical Removal through Pulse Streamer Discharge Technique Assisted by Vapor Additive

2015 ◽  
Vol 2015 ◽  
pp. 1-10
Author(s):  
Xiaojun Wang ◽  
Lianshui Zhang
Keyword(s):  
Pulse Duration ◽  
Removal Efficiency ◽  
Pulse Discharge ◽  
Emission Spectra ◽  
Reaction Model ◽  
Electron Collision ◽  
Oh Radicals ◽  
Streamer Discharge ◽  
Physicochemical Reaction ◽  
Discharge Duration

SO2removal has drawn extensive attentions for air pollution treatment. In this paper, the pulse streamer discharge technique is investigated. Emission spectra diagnosis experimentally indicates that the SO2molecule has been physically dissociated into SO and O radicals by electron collision and can be remediated through further chemical reactions during and after discharge. In order to quantitatively analyze the removal physical chemistry kinetics, a zero-dimensional physicochemical reaction model is established. Without H2O vapor additive, the SO2removal efficiency is leanly low and only 0.296% has been achieved under pulse discharge duration of 0.5 μs. Through increasing the electrical concentration six times, the removal efficiency has been slightly heightened to 1.796% at pulse duration of 3 μs. Contrarily, vapor additive can effectively improve the removal kinetics, and removal efficiency has been remarkably heightened to 13.0195% at pulse duration of 0.5 μs with H2O/SO2initial concentration ratio of 0.1 : 1. OH radicals decomposed from H2O through electron collision are the essential factor to achieve such improvement, which have effectively adjusted the chemical removal process to the favorite directions. The major productions have been transformed from HSO3and HOSO2to H2SO4when vapor ratio increased above 1.27 : 1.

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.

scholarly journals Photocatalytic degradation of volatile chlorinated organic compounds with ozone addition

2017 ◽  
Vol 43 (1) ◽  
pp. 65-72 ◽  
Author(s):  
Hossein Ebrahimi ◽  
Farshid Ghorbani Shahna ◽  
Abdulrahman Bahrami ◽  
Babak Jaleh ◽  
Kamal ad-Din Abedi
Keyword(s):  
Removal Efficiency ◽  
Residence Time ◽  
Ozone Concentration ◽  
Photocatalytic Oxidation ◽  
Synergetic Effect ◽  
Expanded Graphite ◽  
Active Species ◽  
Oh Radicals ◽  
Chlorinated Organic Compounds ◽  
Combined System

Abstract The decomposition of hydrocarbons using combined advanced oxidation methods is largely considered owing to abundant production of OH radicals and the potential economic advantages. In this study, the synergetic effect of ozonation on photocatalytic oxidation of chloroform and chlorobenzene over expanded graphite-TiO2&ZnO Nano composite was investigated. The effect of introduced ozone concentration and residence time was also examined on removal efficiency. The results showed that the removal efficiency was significantly enhanced by the combined system resulting from the additional oxidation process causing active species to be increased. Increasing the introduced ozone concentration which generates more reactive compounds had a greater effect on the removal efficiency than that of residence time. However, from the mineralization point of view, the residence time had a dominant effect, and the selectivity towards CO2 was dramatically declined when the flow rate increased. Based on these results, the combined system is preferred due to higher removal efficiency and complete mineralization.

Research on Micro-Size Electrical Discharge Machining Polycrystalline Diamond

2019 ◽  
Vol 943 ◽  
pp. 14-19 ◽  
Author(s):  
Yun Hai Jia ◽  
Jian Mei Guo ◽  
Yan Guo ◽  
Fan Yu
Keyword(s):  
Pulse Duration ◽  
High Efficiency ◽  
Electrical Discharge Machining ◽  
Pulse Discharge ◽  
Cutting Tools ◽  
Polycrystalline Diamond ◽  
Green Manufacturing ◽  
Single Pulse ◽  
Pit Depth ◽  
Thermal Influence

With the demand of modern cutting technology for ‘high efficiency, precise, flexibility and green manufacturing’, polycrystalline diamond materials as cutting tools have been widely used in automobile, aerospace and non-metal processing. Electro-spark erosion is one of the most effective ways to machine polycrystalline diamond materials. Single pulse discharge is one of the research foundations of micro-EDM. Using 2 micron granularity polycrystalline diamond as experiment material, the influence of single pulse discharge technology on the removal efficiency of materials was studied, such as pit radius, pit depth and radius-depth ratio, etc. The experimental results show that, with the extension of the pulse duration, the radius of the discharge pit begins to increase rapidly, then slowly increases, and finally to slow down; while the radius of thermal influence zone increases rapidly and then continues to increase slowly. With the extension of pulse duration, the ratio of pit depth to radius changes within the range of 0.05 ~ 0.25, which shows a downward trend basically.

Sonochemical Composition of Humic Substances with Magnetic Nanoparticles and H2O2

2014 ◽  
Vol 522-524 ◽  
pp. 439-444
Author(s):  
Song Lin Wang ◽  
Ming Dan ◽  
Si Wu ◽  
Ning Zhou ◽  
Qi Zhang
Keyword(s):  
Magnetic Nanoparticles ◽  
Humic Acid ◽  
Humic Substances ◽  
Removal Efficiency ◽  
Enhancement Effect ◽  
Oh Radicals ◽  
Acid Degradation ◽  
Adsorption Surface

The experiments of TOC and UV254 removal of humic acid (HA) solution by ultrasound (US) irradiation with the presence of H2O2 and Fe3O4 nanoparticles (NP) were carried out. The comparison of enhancement effect of humic acid sonolysis by H2O2 and NP was investigated. It was found that removal efficiency of TOC and UV254 increased significantly in the order of US< US/NP< US/H2O2< NP/H2O2< US/NP/H2O2. During US/NP/H2O2 combining process, the contribution of H2O2 should be presenting most OH radicals for humic acid degradation, Fe3O4 nanoparticles would supply adsorption surface for humic acid to have more chance to be oxidized, and ultrasonic would work as main energy for OH radicals generation and offer sonochemical environment.

Molecular Dynamics Simulation of Pressure Generated inside Melting Area in EDM

2014 ◽  
Vol 625 ◽  
pp. 525-529 ◽  
Author(s):  
Xiao Dong Yang ◽  
Xiao Han ◽  
Masanori Kunieda
Keyword(s):  
Molecular Dynamics ◽  
Hydrostatic Pressure ◽  
Pressure Distribution ◽  
Pulse Discharge ◽  
Dynamics Simulation ◽  
Tool Electrode ◽  
Melting Area ◽  
Depth Direction ◽  
Discharge Duration ◽  
Narrow Space

Electrical discharge phenomena in EDM occur in a very short time period and in a very narrow space, thus making both observation and theoretical analysis extremely difficult. For this reason, the material removal mechanism in EDM has yet to be understood clearly. EDM is a thermal process. Thermal energy is generated by a pulse discharge between the workpiece and the tool electrode. It results in melting and evaporating followed by removal of both the workpiece and tool electrode, forming a discharge crater on both surfaces. In this paper, the hydrostatic pressure distribution in melting area was simulated by Molecular Dynamics (MD) methods. The analysis shows that after discharge is ignited, extremely high pressure is generated inside the melting area. The pressure distribution along the central axis of the melting area at different times indicates that during the discharge duration, the hydrostatic pressure quickly increases to a peak value along the depth direction of melting area and then reduced to 0 GPa in the unaffected area. It was also found that with the passage of time, the depth of the point where the pressure peaks increases with the formation of the discharge crater, accompanied by the decrease in the peak pressure. In addition, the ejected material atoms at different times during the removal process were also analyzed. It was found that the material ablation occurs mostly during the discharge duration.

Research on Micro-Size Electrical Discharge Grinding Polycrystalline Cubic Boron Nitride Based on Single Pulse

2021 ◽  
Vol 1035 ◽  
pp. 778-784
Author(s):  
Yun Hai Jia ◽  
Yan Hua Cia ◽  
Qin Jian Zhang
Keyword(s):  
Boron Nitride ◽  
Pulse Duration ◽  
Electrical Discharge ◽  
High Efficiency ◽  
Pulse Discharge ◽  
Cubic Boron Nitride ◽  
Single Pulse ◽  
Polycrystalline Cubic Boron Nitride ◽  
Corrosion Pit ◽  
Corrosion Pits

Polycrystalline cubic boron nitride (PcBN) was a high temperature and high pressure composite material with high hardness. With its high wear resistance and good chemical stability, it conforms to the basic characteristics of modern advanced cutting technology of "high efficiency, high precision, high efficiency and green". Currently, it was widely used in the field of ferrous metal cutting tools. Electrical discharge grinding was one of the most effective methods for machining polycrystalline cubic boron nitride cutters. It was especially suitable for machining complex shapes and thin edge cutters. Single pulse electrical discharge grinding is the basis of continuous EDG machining and an effective method to study micro-scale electrical discharge grinding. In this study, the morphology of single pulse discharge corrosion pits and the relationship between discharge parameters and material removal rate, such as the deep-diameter ratio of the corrosion pits, the pulse width and the deep-diameter relationship of the corrosion pits, were studied with the polycrystalline cubic boron nitride composite sheet of 2 micron particle size as the test material and the independently developed single pulse discharge power supply as the device. The experimental results show that the radius and heat affected area of the discharge corrosion pit increase rapidly, then slowly, and finally gradually with the extension of pulse duration. The corrosion depth generally varies gently in the range of 0.2 ~ 0.5 micron, and the pulse duration has no obvious effect on the depth of the discharge corrosion pit. With the extension of pulse duration, the ratio of radius to depth of the corrosion pit changed in the range of 13 ~ 20, and the ratio basically declined.

scholarly journals Degradation of Bisphenol A by CeCu Oxide Catalyst in Catalytic Wet Peroxide Oxidation: Efficiency, Stability, and Mechanism

2019 ◽  
Vol 16 (23) ◽  
pp. 4675
Author(s):  
Zhaojie Jiao ◽  
Ligong Chen ◽  
Guilin Zhou ◽  
Haifeng Gong ◽  
Xianming Zhang ◽  
...  
Keyword(s):  
Bisphenol A ◽  
Removal Efficiency ◽  
Oxide Catalyst ◽  
Ph Value ◽  
Reaction System ◽  
Complex Method ◽  
Oh Radicals ◽  
Peroxide Oxidation ◽  
Wet Peroxide Oxidation ◽  
Catalytic Wet Peroxide Oxidation

The CeCu oxide catalyst CC450 was prepared by citric acid complex method and the catalytic wet peroxide oxidation (CWPO) reaction system was established with bisphenol A (BPA) as the target pollutant. By means of characterization, this research investigated the phase structure, surface morphology, reducibility, surface element composition, and valence of the catalyst before and after reuse. The effects of catalyst dosage and pH on the removal efficiency of BPA were also investigated. Five reuse experiments were carried out to investigate the reusability of the catalyst. In addition, this research delved into the changes of pH value, hydroxyl radical concentration, and ultraviolet-visible spectra of BPA in CWPO reaction system. The possible intermediate products were analyzed by gas chromatography-mass spectrometry (GC-MS). The catalytic mechanism and degradation pathway were also discussed. The results showed that after reaction of 65 min, the removal of BPA and total organic carbon (TOC) could reach 87.6% and 77.9%, respectively. The catalyst showed strong pH adaptability and had high removal efficiency of BPA in the range of pH 1.6–7.9. After five reuses, the removal of BPA remained above 86.7%, with the structure of the catalyst remaining stable to a large extent. With the reaction proceeding, the pH value of the reaction solution increased, the concentration of OH radicals decreased, and the ultraviolet-visible spectrum of BPA shifted to the short wavelength direction, that is, the blue shift direction. The catalysts degraded BPA rapidly in CWPO reaction system and the C–C bond or O–H bond in BPA could be destroyed in a very short time. Also, there may have been two main degradation paths of phenol and ketone.

scholarly journals Removal Dynamics of Nitric Oxide (NO) Pollutant Gas by Pulse-Discharged Plasma Technique

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Lianshui Zhang ◽  
Xiaojun Wang ◽  
Weidong Lai ◽  
Xueliang Cheng ◽  
Kuifang Zhao
Keyword(s):  
Air Pollutants ◽  
Reaction Kinetic ◽  
Emission Spectra ◽  
Nonthermal Plasma ◽  
Plasma Electron ◽  
Discharge Voltage ◽  
Electron Collision ◽  
No Removal ◽  
Plasma Technique ◽  
Major Reaction

Nonthermal plasma technique has drawn extensive attentions for removal of air pollutants such as NOxand SO2. The NO removal mechanism in pulse discharged plasma is discussed in this paper. Emission spectra diagnosis indicates that the higher the discharge voltage is, the more the NO are removed and transformed into O, N, N2, NO2, and so forth. Plasma electron temperatureTeis ranged from 6400 K at 2.4 kV discharge voltage to 9500 K at 4.8 kV. After establishing a zero-dimensional chemical reaction kinetic model, the major reaction paths are clarified as the electron collision dissociation of NO into N and O during discharge and followed by single substitution of N on NO to form N2during and after discharge, compared with the small fraction of NO2formed by oxidizing NO. The reaction directions can be adjusted by N2additive, and the optimal N2/NO mixing ratio is 2 : 1. Such a ratio not only compensates the disadvantage of electron competitive consumption by the mixed N2, but also heightens the total NO removal extent through accelerating the NO oxidization process.

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