Yan Wu

Dalian University of Technology, Lü-ta-shih, Liaoning, China

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Publications (61)106.23 Total impact

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    ABSTRACT: Ozonation of p-nitrophenol adsorbed on activated carbon fiber (ACF) was conducted in a semi-wet atmosphere, and its effect on the textural and chemical characteristics of ACF was examined. The decomposition kinetics of p-nitrophenol followed a pseudo first order reaction, and an increase in inputted O3 enhanced the removal of p-nitrophenol. Ozone slightly etched ACF and resulted in a decrease in the pores volume of ACF, but slightly different changes in pores diameter also occurred on virgin and spent ACF. An increase in the surface oxygen-containing groups (C=O, COOH, etc.) after ozonation might have influence on the adsorption capacity of ACF.
    Ozone Science and Engineering 07/2015; 37(2):178-185. DOI:10.1080/01919512.2014.942723 · 0.95 Impact Factor
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    ABSTRACT: The electrical characteristics of pulsed-discharge plasma for decoloration of dyes in water were systematically investigated with a view toward getting insight into discharge process. Methylene blue (MB) dye water was selected as the target object. The discharge behavior was found to depend on the power supply voltage, conductivity of MB solution, and pulse-forming capacity. A strong positive linear relationship existed between power supply voltage and initial capacitor voltage. The injection energy per pulse increased when increasing the power supply voltage and a maximal energy efficiency of injection of approximately 85% was obtained at power supply voltage of 50 V. The conductivity of MB solution had appreciable impact on the voltage-current characteristics and discharge time of pulse-forming capacitor. Remarkable increase of pulse current was observed as the pulse-forming capacity increasing, while it had slight effect on the pulse voltage. The pulsed corona discharge in MB solution could change into spark discharge by way of increasing the air flow rate and reducing the electrode distance. Increasing pulse-forming capacity and pulse frequency significantly accelerated the decoloration rate of MB in solution. This paper is expected to provide reference for improving the application of pulsed-discharge plasma in treating dye solution.
    IEEE Transactions on Plasma Science 02/2015; 43(2):580-586. DOI:10.1109/TPS.2015.2389238 · 0.95 Impact Factor
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    ABSTRACT: The remediation of dye-contaminated soil using silent discharge plasma in dielectric barrier discharge (DBD) reactor was reported in this study. Acid scarlet GR was selected as the representative of azo dye pollutants. Effects of applied voltage, discharge frequency, and gas flow rate on Acid scarlet GR treatment effect which were characterized by degradation efficiency and the change of chemical oxygen demand (COD) during the degradation were investigated. The decolorization rate of Acid scarlet GR in the soil increased with the applied voltage and discharge frequency, and the optimal gas flow rate was obtained at 1.0 L min(-1). The energy efficiency was clearly enhanced by way of increasing the amount of contaminated soil in the DBD reactor finitely. The degradation efficiency of Acid scarlet GR and the removal of COD value were achieved 93% and 74 % after 25-min discharge treatment, respectively. The results indicated that the DBD remediation system was able to degrade Acid scarlet GR in the soil quickly and efficiently. This study is expected to provide a possible pathway of Acid scarlet GR degradation in soil.
    Water Air and Soil Pollution 06/2014; 225(6). DOI:10.1007/s11270-014-1991-0 · 1.69 Impact Factor
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    ABSTRACT: The oxidation of elemental mercury (Hg-0) by dielectric barrier discharge reactors was studied at room temperature, where concentric cylinder discharge reactor (CCDR) and surface discharge plasma reactor (SDPR) were employed. The parameters (e.g. Hg-0 oxidation efficiency, energy constant, energy yield, energy consumption, and O-3 concentration) were discussed. From comparison of the two reactors, higher Hg-0 oxidation efficiency and energy constant in the SDPR system were obtained by using lower specific energy density. At the same applied voltage, energy yield in the SDPR system was larger than that in the CCDR system, and energy consumption in the SDPR system was much less. Additionally, more O-3 was generated in the SDPR system. The experimental results showed that 98% of Hg-0 oxidation efficiency, 0.6 J.L-1 of energy constant, 13.7 mu g.kJ(-1) of energy yield, 15.1 eV.molecule(-1) of energy consumption, and 12.7 mu g.J(-1) of O-3 concentration were achieved in the SDPR system. The study reveals an alternative and economical technology for Hg-0 oxidation in the coal-fired flue gas.
    Plasma Science and Technology 01/2014; 16(2). DOI:10.1088/1009-0630/16/2/12 · 0.60 Impact Factor
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    ABSTRACT: The use of non-thermal plasma (NTP) injection approach to oxidize elemental mercury (Hg(0)) in simulated flue gas at 110°C was studied, where a surface discharge plasma reactor (SDPR) inserted in the simulated flue duct was used to generate and inject active species into the flue gas. Approximately 81% of the Hg(0) was oxidized and 20.5μgkJ(-1) of energy yield was obtained at a rate of 3.9JL(-1). A maximal Hg(0) oxidation efficiency was found with a change in the NTP injection air flow rate. A high Hg(0) oxidation efficiency was observed in the mixed flue gas that included O2, H2O, SO2, NO and HCl. Chemical and physical processes (e.g., ozone, N2 metastable states and UV-light) were found to contribute to Hg(0) oxidation, with ozone playing a dominant role. The deposited mercury species on the internal surface of the flue duct was analyzed using X-ray photoelectron spectroscopy (XPS) and electronic probe microanalysis (EPMA), and the deposit was identified as HgO. The mercury species is thought to primarily exist in the form of HgO(s) by adhering to the suspended aerosols in the gas-phase.
    Journal of hazardous materials 01/2014; 268C:237-245. DOI:10.1016/j.jhazmat.2014.01.022 · 4.33 Impact Factor
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    ABSTRACT: A surface dielectric barrier discharge plasma reactor was employed to study Hg0 oxidation in coal-fired flue gas. The experimental results showed that 98 % of Hg0 oxidation efficiency and 13.7 μg kJ−1 of energy yield were obtained under a specific energy density (SED) of 7.9 J L−1. Increasing SED was beneficial for Hg0 oxidation due to higher production of active species. Higher initial concentration resulted in lower Hg0 oxidation efficiency, but higher amount of Hg0 oxidation. Water vapor inhibited Hg0 oxidation because the generation of O3 was suppressed. The presence of NO remarkably restrained Hg0 oxidation, while SO2 showed little effect on Hg0 oxidation. Roles of active species in Hg0 oxidation were examined under different gas atmospheres (O2 and air), indicating that O3 played an important role in Hg0 oxidation. Deposits on the internal surface of the reactor were analyzed by energy dispersive spectroscopy and the product was identified as HgO.
    Plasma Chemistry and Plasma Processing 01/2014; 34(1). DOI:10.1007/s11090-013-9496-y · 1.60 Impact Factor
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    ABSTRACT: A low temperature air plasma jet was generated by syringe needle-ring electrodes dielectric barrier discharge at atmospheric pressure. It was found that the air plasma jet length reached about 25 mm and the gas temperature was close to the room temperature. Besides, the optical emission spectrum showed that a large number of active species, such as O* (777.2 nm), O* (794.7 nm), O* (799.5 nm), O* (844.6 nm), N-2* (C-B), N-2* (B-A), N-2(+) (B-X), N* (750.7nm), N* (812.9 nm), etc., existed in the air plasma plume.
    Thin Solid Films 12/2013; 548:470-474. DOI:10.1016/j.tsf.2013.10.031 · 1.87 Impact Factor
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    ABSTRACT: In this study, the effects of electrode geometry on benzene degradation in a dielectric barrier/packed-bed discharge plasma reactor with different electrodes were systematically investigated. Three electrodes were employed in the experiments, these were coil, bolt, and rod geometries. The reactor using the coil electrode showed better performance in reducing the dielectric loss in the barrier compared to that using the bolt or rod electrodes. In the case of the coil electrode, both the benzene degradation efficiency and energy yield were higher than those for the other electrodes, which can be attributed to the increased role of surface mediated reactions. Irrespective of the electrode geometry, the packed-bed discharge plasma was superior to the dielectric barrier discharge plasma in benzene degradation at any specific applied voltage. The main gaseous products of benzene degradation were CO, CO2, H2O, and formic acid. Discharge products such as O3, N2O, N2O5, and HNO3 were also detected in the outlet gas. Moreover, the presence of benzene inhibited the formation of ozone because of the competing reaction of oxygen atoms with benzene. This study is expected to offer an optimized approach combining dielectric barrier discharge and packed-bed discharge to improve the degradation of gaseous pollutants.
    Journal of hazardous materials 09/2013; 262C:387-393. DOI:10.1016/j.jhazmat.2013.08.072 · 4.33 Impact Factor
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    ABSTRACT: Active species injection generated by a surface discharge plasma reactor (SDPR) was studied to oxidize elemental mercury (Hg0) in the flue gas. The reactor was inserted in the simulated flue duct. The effects of several operational parameters, such as applied voltage, inlet Hg0 concentration, applied frequency and air injection flow rate, were well investigated. Experimental results showed that Hg0 oxidation efficiency of 83.8% was achieved at specific energy density of 4.0 J L-1 and the flow rate of 1.6 L min-1. Increasing applied voltage and air injection flow rate was beneficial for Hg0 oxidation due to higher production of active species. Lower Hg0 oxidation efficiency was observed with an increase of initial concentration. With an increase of applied frequency, Hg0 oxidation efficiency significantly increased, but the energy yield dropped.
    09/2013; 807-809:1294-1297. DOI:10.4028/www.scientific.net/AMR.807-809.1294
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    ABSTRACT: Atmospheric argon plasma jets are generated with the rod-tube/tube high voltage electrode and a ring ground electrode at 8 kHz sinusoidal excitation voltage. It is found that the vibrational temperature, electronic excitation temperature, atomic oxygen density and spectral intensity with the rod-tube high voltage electrode are enhanced significantly than that with the tube high voltage electrode. The atomic oxygen density, molecular nitrogen density, and average electronic density are about magnitude of 1016 cm−3, 1015 cm−3, and 1012 cm−3 respectively, and the excited Ar, N2, OH and O are presented in the plasma plume with the rod-tube/tube high voltage electrode.
    Journal of Electrostatics 04/2013; 71(2):93–101. DOI:10.1016/j.elstat.2012.12.009 · 1.27 Impact Factor
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    ABSTRACT: The oxidation of ammonium sulfite in the ammonia-based flue gas desulfurization (FGD) process was investigated in a multi-needle-to-plate gas phase pulsed corona discharge reactor in this paper. The effect of several parameters, including capacitance and peak pulse voltage of discharge system, electrode gap and bubbling gas flow rate on the oxidation rate of ammonium sulfite was reviewed. The oxidation rate of ammonium sulfite could reach 47.2% at the capacitance, the peak pulse voltage, electrode gap and bubbling gas flow rate equal to 2 nF, -24.6 k V, 35 mm and 4 L min-1 within treatment time of 40 min The experimental results indicate that the gas phase pulsed discharge system with a multi-needle-to-plate electrode can oxide the ammonium sulfite. The oxidation rate increased with the applied capacitance and peak pulse voltage and decreased with the electrode gap. As the bubbling gas flow rate increased, the oxidation rate increased first and then tended to reach a stationary value. These results would be important for the process optimization of the (NH4)2SO3 to (NH4)2SO4 oxidation.
    Journal of Physics Conference Series 03/2013; 418(1):2128-. DOI:10.1088/1742-6596/418/1/012128
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    ABSTRACT: Soil contamination by organic compounds has become an issue of concern around the world. Currently, non-thermal plasma, especially pulsed corona discharge, has received a great attention in environmental protection field. As a result, the matching between a pulsed-power and corona discharge reactor containing different thickness of soil was a significant aspect in optimizing the pulse corona discharge. In this paper, some methods have been adopted to achieve the matching, including choosing a suitable capacity, adjusting the frequency, providing a suitable soil thickness and comparing the energy and energy utilization efficiency. The details of the matching and optimization discussed were based upon the theories of streamer formation and experimental results as well. The results indicated that energy injected into the reactor increased with the pulse forming capacity and pulse frequency. There existed an optimal energy utilization efficiency with the change of soil thickness and pulse frequency under the pulse forming capacity of 100 pF. The SED at pulse voltage of 19 kV and pulse frequency of 70 Hz was achieved 0.11 J g-1soil at the soil thickness of 3 mm, which was only 0.064 J g-1soil at the soil thickness of 9 mm; meanwhile, with the increase of pulse frequency from 50 Hz to 90 Hz, the SED increased from 0.075 J g-1soil to 0.146 J g-1soil at 19 kV and soil thickness of 3 mm. This study is expected to provide reference for the matching between a pulsed-power and reactor containing different thickness of soil for producing corona discharge.
    Journal of Physics Conference Series 03/2013; 418(1):2136-. DOI:10.1088/1742-6596/418/1/012136
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    ABSTRACT: A catalytic method using titanium dioxide (TiO2) under a dielectric barrier discharge (DBD) plasma was studied to improve the decomposition of phenol adsorbed on granular activated carbon (GAC) and the simultaneous regeneration of the saturated GAC. The TiO2–GAC hybrid was fabricated by an impregnation-desiccation method and characterised by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherms and Boehm titration to investigate its adsorption and catalytic characteristics before and after the adsorption and DBD processes. The adsorption experiments showed that the GAC and TiO2–GAC both followed pseudo-second-order kinetic models with adsorption isotherms that were well represented by the Langmuir model. TiO2–GAC exhibited remarkable catalytic activity, increasing the phenol degradation by 19% and TOC removal by 8.7% relative to GAC in DBD treatment. TiO2–GAC also exhibited better regeneration efficiency than GAC, and the reusability of the hybrid material was examined over four consecutive adsorption-regeneration cycles. The above results may be due to the enhanced generation of active species, such as hydroxyl radicals and hydrogen peroxide, on TiO2–GAC relative to GAC during the discharge process, and the main intermediate products were analysed to explore the mechanisms involved in DBD plasma.
    Carbon 03/2013; 53:380–390. DOI:10.1016/j.carbon.2012.11.028 · 6.16 Impact Factor
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    ABSTRACT: A surface Dielectric Barrier Discharge (DBD) reactor was utilized to degrade phenol in water. Different power supplies applied to the DBD reactor affect the discharge modes, the formation of chemically active species and thus the removal efficiency of pollutants. It is thus important to select an optimized power supply for the DBD reactor. In this paper, the influence of the types of power supplies including alternate current (AC) and bipolar pulsed power supply on the ozone generation in a surface discharge reactor was measured. It was found that compared with bipolar pulsed power supply, higher energy efficiency of O3 generation was obtained when DBD reactor was supplied with 50Hz AC power supply. The highest O3 generation was approximate 4 mg kJ-1 moreover, COD removal efficiency of phenol wastewater reached 52.3% after 3 h treatment under an AC peak voltage of 2.6 kV.
    Journal of Physics Conference Series 03/2013; 418(1):2131-. DOI:10.1088/1742-6596/418/1/012131
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    ABSTRACT: Low-temperature atmospheric-pressure argon-oxygen plasma jet is generated with syringe needle-ring electrodes, which is powered by a sinusoidal excitation voltage at 8 kHz. The volume percentage of the oxygen content in the argon gas is as high as 12.5%. It is found that the rotational temperature of nitrogen is in the range of 297-320 K, and the vibrational temperature is almost unchanged to be about 2475 K, which is obtained by comparing the simulated spectrum with the measured spectrum at the C3 Πu → B3Πg (Δv = -2) band transition. The electronic excitation temperature is in the range of 8587-8994 K as obtained by the Boltzmann's plot method, the electron temperature at the tip of syringe needle is about 7.3 eV as estimated by the Einstein's equation, and the densities of atomic oxygen and molecular nitrogen are, respectively, on the order of magnitude of 1016cm-3 as determined by actinometry method, respectively. Moreover, the 2-D and 1-D distributions of the electric field magnitude are estimated by the 2-D finite-element software. At a time of 45.7 μs and an instantaneous applied voltage of 8 kV, the electric field magnitude at the edge of the ring ground electrode is the largest, and it is 15.9 kV/cm at the tip of the syringe needle.
    IEEE Transactions on Plasma Science 03/2013; 41(3):545-552. DOI:10.1109/TPS.2013.2242876 · 0.95 Impact Factor
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    ABSTRACT: To understand the reactions taking place in the dielectric barrier discharge (DBD) plasma system of activated carbon regeneration, the determination of active species is necessary. A method based on High Performance Liquid Chromatography with radical trapping by salicylic acid, has been developed to measure hydroxyl radical (•OH) in the DBD plasma reactor. The effects of applied voltage, treatment time, and gas flow rate and atmosphere were investigated. Experimental results indicated that increasing voltage, treatment time and air flow rate could enhance the formation of •OH. Oxygen atmosphere and a suitable GAC water content were contributed to •OH generation. The results give an insight into plasma chemical processes, and can be helpful to optimize the design and application for the plasma system.
    Journal of Physics Conference Series 03/2013; 418(1):2104-. DOI:10.1088/1742-6596/418/1/012104
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    ABSTRACT: The application of corona discharge technology in gas purification and wastewater treatment has been received great attention in recent years. The configuration of discharge electrode and the discharge types directly affect the discharge power and the power density, and then affect the generation of active species as well as the removal efficiency of pollutants. A novel cylinder-type discharge reactor with saw-wheel-array electrodes was developed for removal of SO2/NOx from flue gas, and influence factors such as electrode structure (ratio of spacing of saw-wheel slices and discharge distance, herein defined as R) and power supply types (positive DC, negative DC, and pulse power) on discharge characteristics and the output power was discussed. The experimental results show that the current and output power of three types of discharges firstly increased with R increasing from 0.3-1.7, and then tended to a stability from 1.7-2.5 while the power density reached a maximum at the ratio of 1.7.
    Journal of Physics Conference Series 03/2013; 418(1):2098-. DOI:10.1088/1742-6596/418/1/012098
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    ABSTRACT: Configuration of plasma reactors influences the generation of active species including the energized electrons, active radicals and the distribution of active species in reactor, and thus influences the removal efficiency of pollutants. Oxidation efficiency of elemental mercury (Hg0) in two different DBD plasma reactors was studied in this paper. One plasma reactor is a surface discharge reactor (SDR) with a spiral stainless steel thread as the high voltage electrode, and the other plasma reactor is a concentric cylinder type DBD reactor (CCDR) with a copper screw rod as the high voltage electrode. The oxidation efficiencies of Hg0 under different specific energy density (SED), oxygen content, flue gas residence time and the temperature of flue gas indicate that SDR had a better performance than CCDR in oxidation of Hg0, which can be attributed to the higher generation efficiency of ozone in SDR than in CCDR.
    Journal of Physics Conference Series 03/2013; 418(1):2118-. DOI:10.1088/1742-6596/418/1/012118
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    ABSTRACT: Dielectric barrier discharge (DBD) is an effective method to produce active species including ozone for remediation of pollutants in water, gas, etc. In the present work, a DBD type surface discharge system was utilised to degrade phenol in solutions. The influence of experimental conditions including solution pH values, initial concentration of phenol and applied voltage on the degradation rate of phenol, the removal of COD and the byproducts was examined and discussed as well as the concentration change of ozone during phenol was examined. Experimental results reveal that high pH value advanced the degradation of phenol and COD removal, which maybe contributed to the enhanced generation of hydroxyl radicals under higher pH value; applied voltage influenced the transformation of phenol to byproducts which could be demonstrated by the different COD removal under different applied voltages. Under an optimization condition, the degradation rate of phenol reached 100% in 80 minutes and COD removal reached 68% in 120 minutes.
    Journal of Physics Conference Series 03/2013; 418(1):2129-. DOI:10.1088/1742-6596/418/1/012129
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    ABSTRACT: How to deal with unstable ammonium sulfite, the byproduct of flue gas desulfuration by ammonia absorption methods, has been a difficult problem in recent years. Oxidation of ammonium sulfite in aqueous solutions using ozone produced by a surface discharge system was investigated in the paper. The oxidation efficiency of ammonium sulfite by ozone and traditional air aeration were compared, and the factors including ozone concentration, gas flow rate, initial concentration of ammonium sulfite solution and reaction temperature were discussed. The results show that the oxidation efficiency of ammonium sulfite by ozone technology reached nearly 100% under the optimum conditions, which had a significant increase compared with that by air aeration.
    Journal of Physics Conference Series 03/2013; 418(1):2130-. DOI:10.1088/1742-6596/418/1/012130