Degradation of Organic Contaminants in Water by Pulsed Corona Discharge

Degradation of organic contaminants in water by high-voltage pulse discharges was investigated. The effects of gas flow rate and liquid conductivity on the degradation of 4-chlorophenol were studied. With the increase of time, the liquid conductivity increases, which have an important effect on discharge. Meanwhile, with the increase of time, the concentration of H₂O₂ increases. Addition of 200 mg/L H₂O₂, the conversion of 4-chlorophenol was greatly enhanced. This may be due to the synergistic effect of high-voltage pulsed discharge and H₂O₂. Also, it was found that the influence of quantity of TiO₂or CuO on degradation of acetophenone is not apparent, maybe the presence of metal oxides hinders the formation of plasma channel due to increase of collusions between metal oxides and oxygen.     

Formations of Active Species and By-Products in Water by Pulsed High-Voltage Discharge

Formations of active species and by-products are different from bubbling different gases in a pulsed high-voltage discharge reactor. The identification of all the products and the formation rate determination of active species are quite important as the process is applied to wastewater disposal. Serials of measurements were conducted to do the identifications and determinations in this paper. Amounts of · OH all increased but that of H₂O₂ all decreased by bubbling gas. The · OH formation rate was 3.49 × 10⁻⁷, 3.56 × 10⁻⁷, 3.21 × 10⁻⁷ and 1.94 × 10⁻⁷ mol l⁻¹ s⁻¹ with bubbling nitrogen, argon, air and oxygen respectively, but it was 1.61 × 10⁻⁷ mol s⁻¹ l⁻¹ without bubbling. Without any bubbling, the H₂O₂ formation rate was up to 6.53 × 10⁻⁶ mol l⁻¹ s⁻¹, while it was 9.97 × 10⁻⁷, 1.663 × 10⁻⁷, 1.73 × 10⁻⁶ and 3.14 × 10⁻⁶ mol l⁻¹ s⁻¹ with bubbling nitrogen, argon, air and oxygen, respectively. NO₂⁻ and NO₃⁻ was detected in discharged water with bubbling nitrogenous gas. Their formation made the pH decreased.     

Pulsed Corona Discharge for Degradation of Methylene Blue in Water

A pulsed corona discharge in multiwire-plate geometry, generated above water was studied for the removal of organic compounds in liquids. The degradation of methylene blue (MB) and the formation of hydrogen peroxide (H₂O₂) were investigated. The MB solution was rapidly decolorized, evidencing the degradation of the dye after approximately 10 min plasma treatment. Nitrate, formate, sulphate and chlorine ions have been detected in the treated solution, explaining partly the change in the solution properties with plasma exposure, i.e. increase of electrical conductivity and decrease of pH. It was found that the concentration of H₂O₂ generated in water increased with plasma exposure time, reaching 200 mg/L after 30 min treatment. In the MB solution less hydrogen peroxide was detected, suggesting reactions with the dye and its degradation products. The addition of FeCl₂ catalyst had a slight favorable effect on methylene blue degradation due to Fenton’s reaction. It was observed that MB and H₂O₂ concentrations continue to decrease after the plasma treatment was stopped, suggesting that active species which accumulate in the solution may react post-plasma with methylene blue and its degradation products.     

Synthesis of Superabsorbent Copolymers by Pulsed Corona Discharges in Water

Pulsed corona discharges have been utilized for plasma polymerization in aqueous solution for the first time. Superabsorbent copolymers, i.e., poly(acrylamide-co-acrylic acid) hydrogels, were synthesized by aqueous solution polymerization using free radicals produced by pulsed corona discharges as initiator and N,N-methylene-bis-acrylamide as cross-linking agent. Acrylic acid contents in the monomers varied from 0% to 50%. The copolymers thus formed adsorbed 30–1100 g H₂O/g of copolymer. The FTIR spectra of the copolymers are comparable with the published FTIR spectra of the corresponding copolymers synthesized by a conventional chemical method and by -ray technique.     

Mechanism of Calcium Ion Precipitation from Hard Water Using Pulsed Spark Discharges

Direct pulsed spark discharge treatment was found to be able to induce the precipitation of calcium ions in supersaturated hard water (Yang et al. in Water Res 44:3659, 2010). The present study investigated possible pathways for the plasma-induced precipitation. Both UV and reactive species were found not the major factors that stimulate the precipitation in present setup. A transient hot-wire method was used to investigate the effect of plasma-induced local micro-heating. Approximately 15% drop in the calcium-ion concentration was observed, indicating that the local micro-heating effect could be the major contributing factor. Additionally, a nanosecond pulsed corona discharge was used to investigate the non-thermal effect of plasma, and a maximum 7% drop in the calcium hardness was observed. Calcite with rhombohedron morphology was observed in both cases, similar to the structure observed in the spark discharge treatment case, indicating that calcium-ion precipitation process could be attributed to both the thermal and non-thermal effects produced by the plasma.     

脉冲流光放电激发解离H2O分子的动力学过程

采用色散荧光光谱、时间分辨光谱和空间分辨光谱方法,在标准大气压(1.013×105 Pa)下,对以N2气为载气的H2O蒸气脉冲流光放电等离子体激发解离反应动力学过程进行了实验研究.将所得色散荧光谱归属于N2(C3∏u→B3∏8)、·OH(A2 ∑=→X2∏)、H(n=3→n=2)的辐射跃迁;并对N2*、·OH*、H*三种活性粒子的指纹灵敏谱线(337.2、308.4、656.5 nm)荧光信号进行了时间分辨测量.结果表明,·OH*和H*荧光信号分别滞后N2*荧光信号7.4 ns和17.6 ns,由此推断H2O分子的激发解离通道为:H2O分子与高能电子发生非弹性碰撞激发,被激发到第一激发电子态的高振动能级,然后自解离成激发态的·OH*自由基和基态的H原子.空间分辨测量结果表明,在距负电极0.5 mm附近,活性荧光粒子浓度最高,正好对应流光放电的负辉区,该区域电子温度和电子浓度最高,更有利于活性粒子的产生.     

Active Species Generated by a Pulsed Arc Electrohydraulic Discharge Plasma Channel in Contaminated Water Treatments

Pulsed arc electrohydraulic discharge (PAED) direct plasma technique was applied for various types of contaminated water treatment. The experimental system consists of a spark-gap switch type pulse power supply (0.5 kJ/pulse) and a 3 L stainless steel reactor with eccentrically configured rod-to-rod electrodes. The current and voltage waveforms are fundamentally different for different conductivity water. Double pulse current discharges were observed for pond water with relatively higher conductivity (637 mS/m) while a single pulse current discharge was observed for lake water with relatively lower conductivity (78 mS/m). From the optical emission spectrum and UV dosimeters, UV-A, UV-B, excited molecules and radicals including N₂*, O, H, OH, O₃ etc. were observed during the discharge period. Both optical emission and UV intensities in pond water are slightly lower than lake water. The decay time of the UV-A, N₂*, OH, H and O radicals were around 0.6 ms, where the discharge period ended around 0.4 ms. The results indicate that the radicals existed longer than the discharge period. The pH, dissolved oxygen and conductivity were changed during the course of PAED treatment. The ions and radicals such as H·, O·, H⁺, OH· etc. generated by PAED may cause alterations density decay time and the active species in water were present for a longer period. The reduction of total organic carbon (TOC) in pond water reached 80% after 5 min of PAED treatment. Based on local thermal plasma equilibrium (LTE) model, LTE thermal plasma chemical composition model for 1 mol water vapour was used to compare to present experiments. PAED discharge in contaminated pond water generated peak concentration of OH = 28% and O₂H = 0.012% mol in gas-phase and migrated to water-phase via gas–liquid interfaces generated by arc and micro-bubbles to form more stable O₃, H₂O₂, H₂ and O₂. The model suggested that the reduction of TOC occurred in gas/plasma phases or liquid-phase side of gas liquid interfaces.     

Effects of the Liquid Conductivity on Pulsed High-voltage Discharge Modes in Water

Spark, stream and corona pulsed high-voltage discharges in water induced by the various initial conductivities have been examined in this paper. The discharge modes changed from spark to corona discharge with the liquid conductivity increasing. The apparent production of OH radical and quantum yield generated by spark discharge in distilled water were 11.57 gmol/L and 0.0978 photon/s, respectively. A preliminary study on acid fuchsine (AF) treatment indicated that higher AF removal efficiency has been achieved by spark discharge. The process of degradation showed that the oxidative effects through OH radical oxidation did not play an important role and did increase with the discharge mode changing to spark discharge.     

Titanium-Containing Mesoporous Materials：Synthesis and Application in Selective Catalytic Oxidation

Titanium-containing mesoporous molecular sieves are of great significance in selective catalytic oxidation processes with bulky molecules. Recent researches and developments on the designing and synthesis of Ti-containing mesoporous materials have been reviewed. Various strategies for the preparation of Ti-containing rnesoporous materials, such as direct synthesis and post-synthesis, are described. Modifications of Ti-containing mesoporous materials by surface-grafting and atom-planting are also discussed. All approaches aimed mainly at the improving of the stability, the hydrophobicity, and mostly the catalytic activity. Structural and mechanistic features of various synthetic systems are discussed. Ti-containing mesoporous materials in liquid phase catalytic oxidation of organic compounds with H2O2 as an oxidant is briefly summarized, showing their broad utilities for green synthesis of fine chemicals by catalytic oxidative reactions.     

Controlled Synthesis of 3D Flower‐like Ni2P Composed of Mesoporous Nanoplates for Overall Water Splitting

Developing efficient non‐noble metal and earth‐abundant electrocatalysts with tunable microstructures for overall water splitting is critical to promote clean energy technologies for a hydrogen economy. Herein, novel three‐dimensional (3D) flower‐like Ni₂P composed of mesoporous nanoplates with controllable morphology and high surface area was prepared by a hydrothermal method and low‐temperature phosphidation as efficient electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Compared with the urchin‐like Ni_x P_y , the 3D flower‐like Ni₂P with a diameter of 5 μm presented an efficient and stable catalytic performance in 0.5 m H₂SO₄, with a small Tafel slope of 79 mV dec⁻¹ and an overpotential of about 240 mV at a current density of 10 mA cm⁻² with a mass loading density of 0.283 mg cm⁻². In addition, the catalyst also exhibited a remarkable performance for the OER in 1.0 m KOH electrolyte, with an overpotential of 320 mV to reach a current density of 10 mA cm⁻² and a small Tafel slope of 72 mV dec⁻¹. The excellent catalytic performance of the as‐prepared Ni₂P may be ascribed to its novel 3D morphology with unique mesoporous structure.     

Plasma-Induced Synthesis of CuO Nanofibers and ZnO Nanoflowers in Water

Fiber-shaped cupric oxide (CuO) nanoparticles and flower-shaped ZnO nanoparticles were facilely synthesized by plasma-induced technique directly from copper and zinc electrode pair in water, respectively. The phase composition, morphologies and optical property of nanoparticles have been investigated by energy dispersive X-ray analysis, X-ray powder diffraction, transmission electron microscopy and UV–vis. The in situ analysis by an optical emission spectroscopy clarified the formation mechanism. Plasma was generated from the discharge between a metal electrode pair in water by a pulse direct current power. CuO and ZnO nanoparticles were synthesized via almost the same formation mechanism, which were prepared via the rapid energetic radicals’ bombardment to electrodes’ surface, atom vapour diffusion, plasma expansion, solution medium condensation, and in situ oxygen reaction and further growth. This novel plasma-induced technique will become a potential application in nanomaterials synthesis.     

Reduction of NO x /SO2 by Wire-plate Type Pulsed Discharge Reactor with Pulsed Corona Radical Shower

Pulsed discharge deNO _x /deSO₂ process has been studied for over 20 years, but how to achieve higher removal rate at lower cost remains one of the crucial issues for realization of its industrial application. This paper presents a novel deNO _x /deSO₂ process that combines a wire-plate type pulsed discharge reactor and a corona radical shower. Our aim is to increase the deNO _x /deSO₂ rate of wire-plate type reactor by enhancing the generation of radicals with pulsed corona radical shower. Effect of a nozzle electrode on the production of OH radical was studied by emissive spectrum, and deNO _x /deSO₂ experiments using a wire-plate reactor with pulsed corona radical shower were conducted. The experimental results demonstrated that corona radical shower could enhance the production of radicals and the deNO _x /SO₂ performance of a wire-plate reactor. This study will play a positive role in the industrial application of wire-plate pulsed discharge deNO _x /deSO₂ reactor.     

脉冲流光放电激发解离H2O分子的动力学过程

采用色散荧光光谱、时间分辨光谱和空间分辨光谱方法, 在标准大气压(1.013×10⁵ Pa)下, 对以N2气为载气的H2O蒸气脉冲流光放电等离子体激发解离反应动力学过程进行了实验研究. 将所得色散荧光谱归属于N2(C3∏u→B3∏g)、·OH(A2∑+→X2∏)、H(n=3→n=2)的辐射跃迁; 并对N2*、·OH*、H*三种活性粒子的指纹灵敏谱线(337.2、308.4、656.5 nm)荧光信号进行了时间分辨测量. 结果表明,·OH*和H*荧光信号分别滞后N2*荧光信号7.4 ns 和17.6 ns, 由此推断H2O分子的激发解离通道为: H2O分子与高能电子发生非弹性碰撞激发, 被激发到第一激发电子态的高振动能级, 然后自解离成激发态的·OH*自由基和基态的H原子. 空间分辨测量结果表明, 在距负电极0.5 mm附近, 活性荧光粒子浓度最高, 正好对应流光放电的负辉区, 该区域电子温度和电子浓度最高, 更有利于活性粒子的产生.     

Effects of Water Vapor and Ammonia on SO2 Removal from Flue Gases Using Pulsed Corona Discharge

Plasma Chemistry and Plasma Processing - In the study of SO2 removal using pulsed corona discharge, there exists a serious confusion, that is, which kind of reactions, the thermal chemical...     

水中脉冲放电产生H2O2的研究

过氧化氢(H2O2)是强氧化剂,在治理污水中有十分重要的意义,对水中脉冲放电中电压对它的影响进行了研究。结果表明,电压越高,时间越长,H2O2的生成速率减小越快;不同气体成分和流量对H2O2生成也有影响。     

Self-assembled Synthesis of 3D CuO Flocculus-like Nanosheet-based Hierarchical Nanostructures

A simple, surfactant-free, and environmentally benign method has been developed to synthesize a novel 3D flocculus-like CuO hierarchical nanostructure self-assembled with 2D nanosheet as building blocks. Detailed proofs demonstrate that the overall synthetic process underwent the dehydration and re-crystallization of precursor Cu(OH)₂ nanowires, and the subsequent two-step oriented attachment. In addition, 3D butterfly-like and flower-like CuO nanostructures consisted of 2D nanosheets could be obtained by adjusting the concentration of NaOH(c_NaOH) in the solution. c_NaOH played a key role in tailoring the thickness of the nanosheets and changing the morphology of the product. This report may be helpful to constructing fine-tune hierarchical CuO nanostructures under basic conditions.     

Decomposition of Gaseous Sulfide Compounds in Air by Pulsed Corona Discharge

The effectiveness of applying a pulsed corona discharge to the destruction of olfactory pollution in air was investigated. This paper presents a comparative study of the decomposition of three representative sulfide compounds in diluted concentrations: hydrogen sulfide (H₂S), dimethyl sulfide (DMS), and ethanethiol (C₂H₅SH), which could be completely removed when a sufficient but reasonable energy density was deposited in the gas. DMS showed the lowest energy cost (around 30 eV/molecules); C₂H₅SH and H₂S had an EC of respectively 45 eV and 115 eV. The efficiency of the non-thermal plasma process increased with decreasing the initial concentration of sulfide compounds, while the energy yield remained almost unchanged. SO₂ was the only identified byproduct of H₂S decomposition, but the sulfur balance suggests the formation of undetected SO₃. The byproducts analyzed during the degradation of DMS and C₂H₅SH enabled to propose a reaction mechanism, starting with radical attack and breaking of C–S bonds.     

火花放电原子发射光谱法测定镍基合金中12种元素

化学元素的含量及其变化影响镍基合金材料的各项性能.因此准确检测镍基合金化学成分并对其严格控制,对提高和保证镍基合金材料性能具有重要意义.通过对仪器分析条件进行优化,采用控制样品法,建立了用火花放电原子发射光谱法测定镍基合金中Al、C、Cr、Co、Cu、Fe、Nb、P、Si、S、W、Mo等12种元素含量的方法.采用优化的...