Organic dye removal from aqueous solution by pulsed discharge on the pinhole

Various active chemical species such as hydroxyl radicals, oxygen radical, hydrogen peroxide and ozone etc. can be produced by pulsed discharge. These active species can remove organic pollutants from the aqueous phase effectively. In present work pulsed discharge was formed on the pinhole of an insulating plate which was inserted between two plate electrodes. The characteristic of methyl orange decoloration by the discharge was investigated. The results of experimentation showed that peak voltage, pulsed frequency, initial solution conductivity and gas species impact the decoloration rate of the methyl orange (MO) significantly. The decoloration rate of MO solution is increased with increasing of the peak voltage, pulsed frequency, and decreasing initial solution conductivity. When the MO solution was treated with different gases bubbling, different decoloration rate was obtained and the order of decoloration rate is: oxygen > air > nitrogen.     

纳秒脉冲放电处理有机染料废水的实验研究

随着印染行业的快速发展,印染废水的排放与日俱增。由于废水中的有机物具有成分复杂、难以降解的特点,若未经有效处理直接排放,会对生态环境造成严重的污染和危害。试验设计了一种多针-网式反应器循环处理有机组分为酸性红73(AR73)的模拟废水,其采用自行设计的基于TLT(Transmission Line Transformer)的高压重频纳秒脉冲电源驱动。电源可以产生峰值电压为50 kV,脉宽40 ns,上升沿20 ns的纳秒脉冲信号,工作频率可达500 Hz。试验考察了峰值电压、放电频率、染料初始质量浓度及作用时间等因素对AR73降解效果的影响。为评价处理效果,采用紫外分光光度法分别测量了废水中剩余染料浓度、过氧化氢浓度等指标。结果表明,在初始浓度30 mg/L,循环流量3.4 L/min,放电间距30 mm,峰值电压44.26 kV,放电频率200 Hz条件下处理30 min,AR73降解率可以达到83.20%,单次脉冲注入能量为11.73 mJ,过氧化氢浓度为47.36μmol/L,反应器脱色能效(G50)可以达到31.07 g·kW^-1·h^-1。增大放电电压可以进一步提高AR73降解率,溶液中活性物质浓度提高,但是能量效率有所下降。     

氧氢氧化铁对偶氮染料脱色作用的红外光谱研究

采用傅里叶变换显微红外光谱仪(FTIR),研究了两种纳米氧氢氧化铁矿(α-FeOOH),正方纤铁矿(β-FeOOH)对偶氮染料分子甲基橙和酸性红G的脱色作用.结果表明,(1)甲基橙和酸性红G在氧氢氧化铁表面位＞(＞为α或β)FeOH易形成配合物,尤其是具有两个-SO3 Na基团双齿结构的酸性红G易与纳米氧氢氧化铁发生配合反应被化学吸附,而具有较高的脱色率.(2)吸附脱色2 h后氧氢氧化铁的红外光谱中出现了1 033和1 030 cm-1的-SO3Na基团的特征波数,而1 450～1 400 cm-1的偶氮双键的振动吸收峰减弱或者消失,表明偶氮染料分子是通过带负电的-SO3 Na基团吸附到氧氢氧化铁表面,有机还原性配体与氧氢氧化铁表面Fe3 原子中心电荷转移的过程能一定程度上使偶氮键断裂而使染料发生氧化还原脱色.由以上结果推论:两种偶氮染料的脱色是选择性的化学吸附与氧氢氧化铁界面的氧化还原降解共同作用的结果.     

Simulation and Experimental Study for Degradation of Organic Dyes Using Dual pin‐to‐plate Corona Discharge Plasma reactors for Industrial Wastewater Treatment

This work researches the possibility of increasing the dye removal efficiency from wastewater using nonthermal plasma. A study for the optimal air gap distance between dual pin and surface of Acid Blue 25 dye solution and thickness of ground plate is carried out using 3D‐EM simulator to find maximum electric field intensity at the tip of both pins. The consequences display that the best gap for corona discharge is approximately 5 mm using 15 kV source. In addition, the optimum plate thickness is 0.1 mm. These distance and thickness were mentioned are constant during the study of other factors. Dual pin‐to‐plate high‐voltage corona discharge plasma system is presented to investigation experimentally the gap distance, thickness of ground plate, initial dye concentration, pH solution and conductivity on the amount of Acid Blue 25 dye color removal efficiency from wastewater. There is a large consensus among the simulation and experimental work in the air gap and thickness of ground plate. Where the decolorization for air gap 5 mm is 95.74 at time 35 min compared with 91% and 17% for 1 mm and 20 mm gap distance respectively. Also, the discharge energy at each air gap are calculated. Measurement results for the impact of thickness of an Aluminum ground plate on color removal competence showed color removal efficiencies of 86.3%, 90.78% and 98.06%, after treatment time 15 min for thicknesses of 2, 0.5 and 0.1 mm respectively. The decolorization behavior utilizing dual pin‐to‐plate corona discharge plasma system display 82% pigment evacuation proficiency inside 11min. The complete decolorization was accomplished within 28min for distinctive examined introductory color focuses 5 ppm up to 100 ppm. Likewise, the impacts of conductivity by utilizing diverse salts as AlCl3, CaCl2, KCl and NaCl and with distinctive focuses have been explored. The rising of the solution conductivity leads to the reduction of decolorization efficiency. The decolorization efficiency and discharge energy are calculated at different concentration molarity for AlCl3, CaCl2, KCl and NaCl. It was observed that the presence of salts at the same concentration level substantially decreased the rate and the extent of decolorization. The results indicate that the optimum pH for the decolorization of Acid Blue 25 dye is in the range between 3 and 6. Furthermore the conductivity and discharge energy were measurement at each value of pH. Energy yield for decolorization and Electrical Energy per Order (EE/O) under different initial pH value were calculated. A kinetic model is used to define the performance of corona discharge system under different value of pH. The model of pseudo ‐zero, pseudo‐first order, and pseudo‐second order reactions kinetic are utilized to investigate the decolorization of Acid Blue 25 dye. The rate of degradation of Acid Blue 25 dye follows the pseudo‐first order kinetics in the dye concentration. Energy consumption requirements for decolorization was considered. The outcomes will be useful for designing the plasma treatment systems suitable for industrial wastewaters. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Time-resolved processes in a pulsed electrical discharge in argon bubbles in water

A phenomenological picture of a pulsed electrical discharge in gas bubbles in water is produced by combining electrical, spectroscopic, and imaging characterization methods. The discharge is generated by applying 1 m\mu s pulses of 5 to 20 kV between a needle and a disk electrode submerged in water. An Ar gas bubble surrounds the tip of the needle electrode. Imaging, electrical characteristics, and time-resolved optical emission spectroscopic data suggest a fast streamer propagation mechanism and the formation of a plasma channel in the bubble. Comparing the electrical and imaging data for consecutive pulses applied to the bubble at a frequency of 1 Hz indicates that each discharge proceeds as an entirely new process with no memory of the previous discharge aside from the presence of long-lived chemical species, such as ozone and oxygen. Imaging and electrical data show the presence of two discharge events during each applied voltage pulse, a forward discharge near the beginning of the applied pulse depositing charge on the surface of the bubble and a reverse discharge removing the accumulated charge from the water/gas interface when the applied voltage is turned off. The pd value of ~ 300–500 torr cm, the 1 μs long pulse duration, low repetition rate, and unidirectional character of the applied voltage pulses make the discharge process here unique compared to the traditional corona or dielectric barrier discharges.     

Combined effect of acoustic cavitation and pulsed discharge plasma on wastewater treatment efficiency in a circulating reactor: A case study of Rhodamine B

The present study investigates the wastewater treatment performance of an acoustic cavitation assisted plasma (ACAP) process in a circulating reactor using Rhodamine B (RhB) as a model water pollution. The concept of this process was proposed by the authors recently for a batch type rector. The measurements revealed that combining the ultrasound irradiation with pulsed discharge plasma allows the RhB degradation efficiency to be drastically increased as compared with the plasma-alone case. This effect is especially significant at higher values of solution electrical conductivity examined in a range of 20 ~ 400 μS/cm. Acidic conditions and larger flow rates of solution were found to be favorable for the degradation efficiency. The effect of flow rate was also analyzed through numerical simulation. The results indicated that the mass transfer of RhB to the plasma-cavitation zone is one of the controlling parameters influencing the degradation performance. Behavior of bubbles and pulse discharge frequency were examined using a high-speed video camera. Relatively large bubbles were found to favor the plasma pulse generation and propagation when move near the high-voltage electrode. On the whole, the results of this study suggest that the ACAP process has the potential to synergistically extend the application area of underwater plasma in both research and industry.     

脉冲放电射流辅助射频辉光放电研究

通过实验研究了脉冲放电射流辅助下大气压氦气射频辉光放电的电学和光学特性。采用组合电极结构,在射频放电前段增加脉冲电极,脉冲放电产生的射流以等离子体子弹形式注入射频放电区域,主要研究脉冲射流辅助射频放电的电流电压曲线、最低放电维持电压、放电强度和空间结构时空分布。研究结果表明:等离子体子弹经过射频放电区域后,由于等离子体子弹引入的活性粒子,会使射频放电区域等离子体强度增强;而射频放电最低维持电压也从0.93 kV降低至0.43 kV。     

Multipoint barrier discharge process for removal of NOxfrom diesel engine exhaust

We investigated the application of the dielectric barrier discharge process to the removal of NO_x from exhaust gas of a 20-kVA diesel engine generator. A multipoint-to-plane geometry was used as an electrode for low-voltage operation. A pyrex glass plate with a 2-mm thickness was put on the plane electrode as the dielectric barrier. The reactor consists of six discharge cells, with each cell consisting of five stacked multipoint-to-plane electrodes where the exhaust gas flows with a high flow rate. The exhaust gas was successfully treated at a flow rate of 1.2 m³/min, In order to produce repetitive high-voltage pulse, we made two switching electronic devices, an insulated gate bipolar transistor (IGBT), and a pulse transformer. This pulse modulator supplied the voltage with peak value of 10 kV and repetition rate of 2.5 kp/s (pulses per second) to the reactor. The energy transfer efficiency of the pulse modulator is 65% at 300 W of the power consumed in the reactor, The NO_x (NO+NO₂) in the exhaust gas was reduced by 35 ppm with an electrical efficiency of 32 g/kWh     

The Effect of Sphere Size on Bipolar Pulsed Discharges in Glass-Sphere/Water/Air Columns

Bipolar pulsed discharges were investigated in columns containing glass spheres and water, and with air bubbling through, using a coaxial electrode configuration. The effect of sphere size on the discharge characteristics was studied, and results showed that the diameter of the glass spheres had a significant effect on the electrical discharges in the three-phase mixture. As the sphere size increased from 2 to 12 mm, no significant changes occurred in the peak voltage and rise time of the load voltage, but a clear maximum in the tail voltage, and a minimum in the injected power per pulse, occurred in the sphere diameter range from 5 to 8 mm. The greatest electric field in the interstices between the spheres, and the rate at which a dye could be removed from the water, both exhibited a maximum in the sphere diameter range from 5 to 8 mm.      

Experimental research of diffuse bi-directional pulsed dielectric barrier discharge plasma

A bi-directional nanosecond pulsed power supply is employed to generate diffuse dielectric barrier discharge in N₂ using needle-plate electrode configuration at atmospheric pressure. Both discharge images and optical emission spectra of diffuse bi-directional nanosecond high-voltage pulsed dielectric barrier discharge are successfully recorded under severe electromagnetic interference. The diffuse performance of the discharge at different electrode gap distances is observed. The effects of pulse peak voltage, pulse repetition rate, electrode gap distance, He addition, and O₂ addition on the optical emission spectra are investigated. The main physicochemical processes involved are discussed.     

LaB6在低压强氮气和氦气中的放电特性

 研究了LaB₆在1~10 Pa氮气和氦气中的直流和脉冲放电特性以及放电过程对电极的影响。结果表明，电极直径为5 mm的LaB6氦气放电管在脉冲工作状态下可以长期稳定放电。在脉冲电压为2.2 kV、脉冲宽度10 ms、频率13.3 Hz下，脉冲峰值放电电流超过120 A。氦气放电管在放电过程中，阴极表面有离子的清洗和活化作用，可以使电极的表面逸出功降低，提高放电管的发射能力和稳定性。LaB₆作为气体放电电极具有寿命长、延迟时间短、放电电流大等优点，可用于重复强流脉冲气体放电的高压高速开关器件。     

大气压氦气多路低温等离子体射流

为了研究大气压低温等离子体多路射流阵列的放电特性,设计一个实现7路低温等离子体射流的放电装置,采用单电极放电结构,在开放的大气环境下通入氦气。采用高压窄脉冲重复频率电源激励驱动该放电装置,电源脉冲宽度约230 ns,脉冲上升沿约为120 ns。在重复频率为500 Hz的条件下,通过高速摄影初步发现放电电流脉宽约为110 ns,且无反向放电。试验结果表明:平均射流长度随电压幅值增加而增加,在一定电压幅值时射流长度有达到饱和的趋势,这是由于射流通道尾部有空气进入,电压幅值已不再是主要原因;只有在合适的气体流量值时,才能够获得较长的平均射流长度,这是由于气体流量过大或过小时射流均不足以维持形成的放电通道;此外,中心电极放电射流长度受气体流量影响较大,气体流量在一定值时可以观察到中心电极有较长的射流,射流放电强度较弱,气体流量过大或过小时中心电极几乎无放电,这是由于四周电极更易形成放电射流,削弱了中心电极放电。 ,     

多相脉冲放电体系中羟基自由基的光谱诊断

采用多针-板电极形式的气液混合脉冲放电系统,在其中加入玻璃珠负载的TiO₂膜光催化剂形成了一个气-液-固多相脉冲放电体系,研究中利用脉冲放电过程中产生的紫外光效应诱导其中的TiO₂的光催化作用,通过对放电体系中羟基自由基(·OH)的光谱诊断考察TiO₂光催化作用与脉冲流光放电的协同作用效果。结果表明,本脉冲放电体系中产生的·OH在306 nm(A2Σ+→X2Π跃迁)、309 nm(A2Σ+(ν′=0)→X2Π(ν″=0)跃迁)和313 nm(A2Σ+(ν′=1)→X2Π(ν″=1)跃迁)处均产生发射光谱,其中313 nm处的·OH的光谱强度最强;脉冲放电协同TiO₂光催化作用系统中·OH的发射光谱强度较单独的脉冲放电体系强,同时,条件实验(不同鼓气种类和水溶液初始pH值)的研究结果表明用氩气作为鼓气源时,多相反应体系中313 nm处·OH的发射光谱强度比以空气和氧气作为鼓气源时的强度高,酸性溶液中313 nm处·OH的发射光谱强度比中性和碱性溶液中高。     

Measurement of OH spatially resolved spectrum in a wire-plate pulsed streamer discharge

In this study, spatially resolved measurements of the emission intensity of OH (A²Σ↦X²Π, 0-0) and the vibrational temperature of N₂ (C) have been performed during a positive pulsed streamer discharge with a wire-plate electrode configuration at atmospheric pressure. The effects of pulse peak voltage, pulse repetition rate and the added O₂ flow rate on the spatial distributions of the emission intensity of OH (A²Σ↦X²Π, 0-0) and the vibrational temperatures of N₂ (C) perpendicular to the wire in the direction towards the plate (in the radial direction) are investigated. It has been found that the emission intensity of OH (A²Σ↦X²Π, 0-0) increases with increasing pulse peak voltage and pulse repetition rate and decreases with increasing the distance from the wire electrode. When the different oxygen flows are added in N₂ and H₂O mixture gas, the emission intensity of OH (A²Σ↦X²Π, 0-0) decreases with increasing the flow rate of oxygen. The vibrational temperature of N₂ (C) is nearly independent of pulsed peak voltage and pulsed repetition rate, but increases with increasing the added O₂ flow rate and keeps almost constant in the radial direction under the present experimental conditions. This measurement plays a crucial role in understanding the discharge characters of pulsed streamer discharge and establishing the molecule reaction dynamics model of pulsed streamer discharge.     

大气压射流等离子体放电特性及其灭菌效果

 介绍了一种同轴电极的射流等离子体发生装置,可以直接在大气中将生成的氦气辉光放电射流等离子体喷出进行杀菌消毒,无需反应容器和真空系统,并从电压、频率、流速等方面讨论了该同轴等离子体发生器的放电特性。在稳定的放电条件下,利用实验装置进行了大气压下的等离子体灭菌实验,验证了本装置在等离子体灭菌应用上的可行性和易操作性。灭菌结果表明：在最初的2 min内,细菌减小趋势明显,3 min后细菌几乎全部消亡。     

纳秒脉冲下聚合物电树枝引发实验方法

 借鉴直流、交流的研究经验,比较了纳秒脉冲条件下几种不同的电树枝老化实验方法。对单针-板电极和多针-板电极在纳秒脉冲下实验结果的一致性进行考察,结果表明,多针-板电极系统可以在提高实验效率的同时保证结果的准确性。采用步进法和累加法进行了不同频率下聚苯乙烯电树枝引发实验,结果表明:两种方法得到的纳秒脉冲下聚苯乙烯电树枝引发电压-频率特性基本一致,在50~500 Hz范围内,引发电压随频率的升高而降低;在500~800 Hz范围内,引发电压随频率的升高而增加。最后讨论了对于不同脉冲功率装置中绝缘材料老化试验设计的方法。     

Degradation of aryl-azo-naphthol dyes by ultrasound, ozone and their combination: effect of alpha-substituents

Lab-scale degradation of azo dyes with ultrasound (300 kHz), ozone and both was investigated using an aryl-azo-naphthol dye-C.I. Acid Orange 8. It was found that in all schemes color decay was faster than UV absorbance, and the rates followed pseudo-first-order kinetics except for the decay of UV-254 band by ozone. Sonication alone was sufficient for decolorization, but not for UV absorption abatement or mineralization. Ozonation was more effective than ultrasound in bleaching, but not as much for the mineralization of the dye. Combined operation of ultrasound and ozone improved the rate of bleaching and UV absorption decay and remarkably enhanced the mineralization of the dye. This was attributed to increased mass transfer of ozone in solution and its decomposition in the gas phase to yield hydroxyl radicals and other oxidative species. The effect of alpha-methyl substituent at the aryl carbon of the dye was found to decelerate the rate of degradation as a result of weakened intramolecular hydrogen bonding.     

Stability and energy efficiency of pulsed corona discharge in treatment of dispersed high-conductivity aqueous solutions

Pulsed corona discharge (PCD) is an energy-efficient method of water treatment, although its instability in treatment of conductive solutions showered onto the electrodes presents a problem. The impact of conductivity and gaseous ozone concentration on the discharge stability and the energy transfer efficiency was established. The discharge was stabilized by adjusting the voltage pulse shape. Energy dissipation increases with the treated solution conductivity due to ohmic losses reaching 30% of the energy delivered to the reactor at 45 mS cm⁻¹. The PCD energy efficiency and safety was improved by the modified electrode system design reducing the losses.     

A compact high-voltage pulse generator using a rotary airhole sparkgap

A pulsed-corona-discharge nonthermal plasma technique offers the advantages of energy efficiency and capability for the simultaneous removal of coexisting pollutants. The key to success in a nonthermal plasma approach is to produce a corona discharge in which the bulk of the electrical energy goes into the production of energetic electrons, rather than into gas molecules heating. By driving the nonthermal plasma reactor with very short pulses of high-voltage, short-lived corona discharge plasmas are created that consist of energetic electrons, which in turn produce the radicals and ozone responsible for the decomposition of the toxic molecules. Because of the short lifetime of the pulsed corona discharge, little electrical power is dissipated in movement of heavy molecule ions in the processing region, thus avoiding heating the gas and providing good electrical energy efficiency.A high-voltage pulse generator with a rotary airhole sparkgap, instead of a conventional rotary ball sparkgap, has been proposed. Its rise and fall time characteristics to be used as a smart pulse generator for pulsed corona discharge-type nonthermal plasma reactor were investigated. Parametric studies showed that the proposed airhole sparkgap had a very fast rise time, very short fall time, very low-and-stable breakdown voltage, and reliable pulse repetition characteristics, compared with the conventional rotary ball sparkgap.     

交流等离子体显示器的红外辐射光谱

为优化交流等离子体显示器(AC PDP)的单元结构和驱动电压,采用光谱测量系统和交流等离子体显示器宏单元对电极结构参量、带有浮动电极的新型单元结构及维持电压脉冲参量对Ne-Xe混合气体放电辐射的红外光谱的影响进行了实验研究。结果表明,随着维持电极宽度增加,单元放电辐射的828 nm红外光谱的强度提高,而其辐射效率基本保持不变;随着维持电极间隙增大或在维持电极间加有适当宽度的浮动电极,红外辐射光谱的强度及其辐射效率均提高;提高维持电压脉冲频率或幅度,可增加红外辐射强度,但辐射效率降低。