介质阻挡放电微等离子体分解二氧化碳研究

二氧化碳既是主要的温室气体之一,也是包含碳和氧的资源,把相对惰性的CO₂转化为易于利用的CO是其利用的方法之一。采用介质阻挡微等离子体反应器通过单变量和正交实验探究了反应器参数(放电区长度、放电间距、介质厚度)和工艺参数(输入功率、放电频率和停留时间)对CO₂分解为CO的转化率和能量效率的影响规律。研究结果表明,影响CO₂转化率的大小顺序依次为：放电间距>放电长度>输入功率≈停留时间>介质厚度>放电频率;输入功率60.0 W、放电频率9.0 kHz和停留时间1.5 s、放电区长度60 mm、放电间距0.5 m、介质厚度1.6 mm时,CO₂的转化率为10.6%,能量效率为4.1%。     

Simultaneous pentachlorophenol decomposition and granular activated carbon regeneration assisted by microwave irradiation

This paper describes an integrated granular activated carbon (GAC) adsorption/microwave (MW) irradiation process used for the treatment of high concentration pentachlorophenol (PCP) wastewater. Firstly, PCP in water was adsorbed onto GAC, then the PCP was decomposed and GAC regenerated by MW irradiation. The liquid and gas produced during irradiation were collected through condensing, and absorbed by a 0.1 mol l⁻¹ NaOH solution, respectively. The determination of the PCP concentrations in the distillate, absorption solution and GAC was accomplished by a HPLC. The results suggested that when irradiated with 850 W MW for 10 min, most of the PCP adsorbed by GAC and whatever fragments formed were decomposed to CO₂, H₂O and HCl or tightly bound to GAC, and less than 2% of PCP was transformed into intermediates in the distillate. Some dechlorination and dehydroxylation products were identified by the GC/MS analysis, and the degradation mechanism was proposed. It was also confirmed that GAC could be reused after several adsorption/MW regeneration cycles and its adsorption capacity could maintain a relatively high level, even higher than that of virgin GAC, as indicated by BET results, iodine values and PCP adsorption isotherms.     

Catalysis assisted plasma decomposition of benzene using dielectric barrier discharge

Atmospheric non‐thermal plasma generated by dielectric barrier discharge was applied to decompose benzene with a sheet type catalyst of platinum supported by alumina. The experimental results indicated that an enhancement of the decomposition by the catalyst was achieved at low concentration of benzene. Ozone produced in the plasma seemed not to contribute to the decomposition. The deactivation of the catalyst was also observed due to decomposition products such as CO and a solid deposit. However a heating treatment could regenerate the catalyst. The results suggested the plasma‐catalyst hybrid reactor was the effective method to solve volatile organic compound (VOCs) problem.     

Continuous flow removal of acid fuchsine by dielectric barrier discharge plasma water bed enhanced by activated carbon adsorption

Continuous processes which allow for large amount of wastewater to be treated to meet drainage standards while reducing treatment time and energy consumption are urgently needed. In this study, a dielectric barrier discharge plasma water bed system was designed and then coupled with granular activated carbon (GAC) adsorption to rapidly remove acid fuchsine (AF) with high efficiency. Effects of feeding gases, treatment time and initial concentration of AF on removal efficiency were investigated. Results showed that compared to the N2 and air plasmas treatments, O2 plasma processing was most effective for AF degradation due to the strong oxidation ability of generated activated species, especially the OH radicals. The addition of GAC significantly enhanced the removal efficiency of AF in aqueous solution and shorten the required time by 50%. The effect was attributed to the ability of porous carbon to trap and concentrate the dye, increasing the time dye molecules were exposed to the plasma discharge zone, and to enhance the production of OH radicals on/in GAC to boost the degradation of dyes by plasma as well as in situ regenerate the exhausted GAC. The study offers a new opportunity for continuous effective remediation of wastewater contaminated with organic dyes using plasma technologies.     

Analysis of the kinetics of regeneration of bidispersed activated granular carbon, by supercritical carbon dioxide

A desorption of m-xylene by supercritical CO₂ under different temperatures (40, 50 and 60 °C) and pressures (80, 100 and 128 bar) has been modelled using the analytical solution expressing the desorption yield for bidisperse granular activated carbon. This solution is in the form of an infinite double series. The coefficients of which were calculated by solving the transcendental equation using the method of Newton-Raphson. Solutions of first and second order of this equation determine the coefficients of the analytical solution. The results of this modelling, including macropore and micropore diffusion, show very good concordancy between experimental and simulated data for all operating conditions, which confirms the appropriateness of this model for this type of adsorbent considered. Only the equilibrium adsorption constant “K_C” was used as adjustable parameter. The values of K_C varied between 13.32 and 121.33 and the maximum average deviation between estimated and fitted values not exceeding 6.54%. On the other hand, it has been particularly highlighted for the experimental conditions studied, that the contribution of resistance due to external transfer and axial dispersion were negligible and that the resistance due to macropore diffusion was consistent and it was possible to reduce the time of desorption by reducing the size of the grain.     

活性炭载体对TiO2/AC光催化降解苯酚影响研究

分别以典型煤基活性炭和椰壳活性炭为载体,采用溶胶-凝胶法制备了TiO2/AC复合光催化剂,采用低温氮气吸附、X射线衍射、扫描电镜等对其性能进行了表征,分析了活性炭载体对复合光催化剂性能的影响.结果表明:TiO2在椰壳活性炭载体上的负载率高于煤基活性炭,TiO2负载使椰壳活性炭的比表面积和微孔容明显减小,TiO2溶胶对微...     

介质阻挡放电技术再生Pd/AC催化剂的机理探讨

利用介质阻挡放电对失活钯炭催化剂(Pd/AC)进行再生,并通过催化臭氧氧化硝基苯反应评价再生后催化剂的活性。运用扫描电镜(SEM)、比表面积测定(BET)、热重分析(TG)等测定手段对Pd/AC进行表征;并对放电过程进行臭氧产量测定和等离子体发射光谱诊断,分析了Pd/AC催化剂再生的机理。结果表明,催化剂经放电处理30 min后再生率为95%;利用在最优条件下再生的Pd/AC进行催化臭氧氧化反应,硝基苯的降解率为87%;再生过程中臭氧贡献率仅为25.6%,表明放电过程中产生的强氧化性自由基是促使催化剂再生的主要因素。     

介质阻挡放电等离子体改性碳基材料研究进展

介质阻挡放电等离子体因其高效、经济和易操作等优点, 使得其在材料表面改性方面得到了广泛的应用, 同时表现出良好的应用前景。碳基材料由于其许多良好的物化性能, 使得其在很多领域都得到了很好的应用。而经DBD改性后的碳基材料表现出更好的物化性能, 应用更加广泛。主要综述了DBD在改性碳基材料方面的研究现状, 包括活性基团的引入, DBD改性对碳基材料界面结合能、吸附性能、物理结构及其对负载组分分散度的影响。指出改性过程中仍然存在的许多不够完善之处, 提出许多需要进一步深入研究的问题, 如DBD改性对碳基材料物化性能影响的机理研究, 并展望了DBD改性碳基材料技术未来的发展前景。     

氢气和氧气介质阻挡放电合成过氧化氢的研究

利用常压介质阻挡放电,在管式等离子体反应器中将氢氧混合气体直接转化合成H2O2.系统地考察了放电电极材质、放电电极直径、氢气和氧气进料总气速和氧气浓度等参数对H2O2生成的影响.在最优的实验条件下,氧的转化率和H2O2的选择性分别为34.42%和37.94%.并结合实验结果讨论了H2O2的生成机理.     

Immobilized titanium dioxide/powdered activated carbon system for the photocatalytic adsorptive removal of phenol

Titanium dioxide (TiO₂) and powdered activated carbon (PAC) were fabricated via a layer by layer arrangement on a glass plate using a dip-coating technique for the photocatalytic-adsorptive removal of phenol. Thinner TiO₂ layer coated on PAC sub-layer has larger surface area and better phenol removal than the thicker TiO₂ layer. The system obeyed the Langmuir isotherm model, which exhibited a homogeneous and monolayer adsorption with a maximum capacity of 27.8 mg g^-1. The intra-particle diffusion was the rate-limiting step as the linear plot crossed the origin, while the adsorption was unfavorable at elevated temperature. Under light irradiation, the TiO₂/PAC system removed phenol two-times more effectively than the TiO₂ monolayer due to the synergistic effect of photocatalysis by TiO₂ top layer and adsorption by PAC sub-layer. The COD removal of phenol was rapid for 10mg L^-1 of concentration and under solar light irradiation. It was shown that the PAC sub-layer plays a significant role in the total removal of phenol by providing the adsorption sites and slowing down the recombination rate of charge carriers to improve the TiO₂ photocatalytic oxidation performance.     

介质阻挡放电协同复合碳材料去除VOCs

挥发性有机物（VOCs）是常见的空气污染物,实验研究低温等离子体催化技术去除以甲苯为代表的VOCs。采用炭粉末、酚醛树脂和致孔有机高分子聚合物的有机溶剂混合物作为前驱物,经过炭化、水汽活化和负载锰催化剂,制备一种基于发泡金属的复合碳材料。采用扫描电子显微镜、XRD、全自动比表面积及微孔孔隙分析仪对材料进行表征。两段式介质阻挡放电反应器结合复合碳材料降解甲苯,前段介质阻挡放电初步降解甲苯,后段复合碳材料利用介质阻挡放电产生的长寿命活性物种和臭氧进一步去除甲苯。输入电压为10 kV时,甲苯去除率约99.4％,CO₂选择性达72.2%,并且有效控制了副产物臭氧。实验结果表明,复合碳材料有望应用于如臭氧和VOCs等的污染控制。     

介质阻挡放电等离子体处理载体对CO甲烷化Ni/SiO2催化剂性能的改进

以经介质阻挡放电等离子体处理的SiO₂为载体,用浸渍法制备了Ni/SiO₂催化剂,并进行了CO甲烷化反应评价。与载体未经处理的常规Ni/SiO₂催化剂相比,载体经处理的催化剂在400℃下的CO与H₂转化率均提高了约6%,且在经700℃烧结6 h后,活性仍高于常规催化剂。XRD、TEM和H₂-TPR结果表明,载体经处理的催化剂,Ni颗粒粒径更小、粒径分布更集中,Ni与SiO₂之间的相互作用更强,证明等离子体处理使SiO₂更有利于促进Ni的分散。     

介质阻挡放电等离子体对PP非织造布的改性

利用常压介质阻挡放电(DBD)设备,研究了工作气体、放电电压、处理时间、试样布置方式等对聚丙烯(PP)熔喷非织造布吸水率和处理效果均匀性的影响。结果表明:PP非织造布试样在90kV下用氩等离子体处理40s,吸水率达672%,在氩气中混入少量氧气(Ar/O2体积比为10/1),吸水率可提高至717%;试样吸水率随处理时间及放电电压的增加均提高,可以通过增大放电电压来有效地降低处理时间;随着DBD等离子体处理强度的增加,PP非织造布整体亲水性和表观均匀性均得到有效提高;试样布满放电区域有利于提高其吸水率和处理效果的均匀性。     

催化剂协同介质阻挡放电去除VOCs的研究概述

综述了近年来催化剂对介质阻挡放电提高VOCs去除率、减少副产物产量的研究进展,讨论了不同类型催化剂与水蒸气对介质阻挡放电过程的影响及反应机理,分析了反应器中常见副产物的分解机理,展望了未来相关催化剂的发展前景。指出改性催化剂在不同反应条件下与不同介质阻挡反应器的结合有助于进一步研究。     

Kinetic modeling of plasma methane conversion in a dielectric barrier discharge

Methane conversion by plasma offers a promising route to produce higher value-added products. As plasma reaction is a relatively complex process, kinetic modeling is necessary to obtain a general pattern of the complex interaction on the basis of chemical reaction and products. In this paper, we present a method to obtain the kinetic rate coefficient (k) from the experimental data. Although plasma reaction was classified as chemically complex interaction, the reactions showed a certain pattern of the mechanism. In pure methane injection, the decomposition of methane by plasma could initiate coupling reactions and produce C₂H₆, C₃H₈, and C₄H₁₀. Dehydrogenation of C₂H₆ into C₂H₄ and then to C₂H₂ could be clearly seen by the higher value of the reaction rate constant of C₂H_n + 2 to C₂H_n − 2. Using the rate constant values (k) obtained by this method, the pathways of the methane conversion by a dielectric barrier discharge can be drawn.     

Fast and clean functionalization of carbon nanotubes by dielectric barrier discharge plasma in air compared to acid treatment

Multi-walled carbon nanotubes (MWCNTs) have been functionalized by a dielectric barrier discharge plasma in air and compared to those functionalized in HNO₃. The MWCNTs were prepared by chemical vapor deposition of xylene using ferrocene as a catalyst at 850 °C. Air oxidation followed by acid treatment was used to purify the MWCNTs, which were then annealed in helium. The MWCNTs were functionalized in air in a plasma reactor at room temperature. Quantitative analyses of gases evolved during the temperature programmed desorption of the functionalized nanotubes were carried out using Fourier transform infrared spectroscopy and gas chromatography. The influence of plasma parameters, including power in the range of 8-90 W and treatment time in the range of 1-9 min, on the number of the functional groups was investigated. It is shown that the extent of functionalization increases with increasing discharge power, provided that the exposure time of the MWCNTs in the plasma atmosphere does not exceed a certain period of time. Compared to acid treatment, plasma functionalization offers the advantages of much shorter treatment time, and produces less damage.     

新型两级介质阻挡放电降解甲基橙的机理研究

采用新型两级介质阻挡放电(DBD)等离子体反应器对甲基橙废水进行降解处理,考察了甲基橙的p H值、电导率、降解率、化学需氧量(COD)随停留时间的变化。采用紫外光谱、红外光谱、液质联用对处理前后的甲基橙废水进行检测,并推测甲基橙降解机理。结果表明:甲基橙废水的p H值随着停留时间的增长而减小,电导率和降解率均随停留时间的增长而增大,甲基橙的COD值随停留时间的增长呈现先减小再升高最后降低趋于平稳的规律;经过表征分析,处理160 min后的甲基橙降废水中含有NO_3~-,HOOCCH_2CH_2CH_2CH_2CH_2SO_3~-,(CH_3)_2NCH_2CH_2CH_2CH_2CH_2COOH等。     

介质阻挡放电低温等离子体灭活铜绿微囊藻的实验研究

采用介质阻挡放电(Dielectric Barrier Discharge, DBD)低温等离子体对铜绿微囊藻进行灭活研究,考察了电气参数、场结构参数及铜绿微囊藻溶液液相体系因素等放电条件对其灭活规律的影响。利用多种分析方法[如丙酮提取分光光度法、电导率测定、扫描电镜(SEM)和高效液相色谱(HPLC)]检验DBD低温等离子体对铜绿微囊藻的灭活效果。实验结果表明,放电条件对铜绿微囊藻灭活率有极大影响,在最佳条件下(放电电压160 V,放电电流0.6 A,介质间距4 mm,溶液初始OD值0.2,pH值为弱碱性)放电时间5 min,铜绿微囊藻的灭活率可达90%以上。经DBD低温等离子体放电处理后,藻液颜色由鲜绿色→淡绿色→浅黄色→无色,藻细胞的Chl-a含量大幅减少,光合作用能力被抑制,藻细胞的生长受阻。扫描电镜结果显示,藻细胞在放电处理前饱满、完整;而放电后的藻细胞细胞结构破坏严重,细胞膜破裂,细胞内容物泄漏,仅存少量细胞残骸。放电处理后的藻细胞电解质渗出率增大,细胞膜结构受到严重的破坏导致其通透性增大,细胞内容物外泄。DBD低温等离子体灭活铜绿微囊藻的过程中,藻毒素的含量随放电时间先增...     

氩气-低温等离子体分解硫化氢动力学模拟

为探索氩气(Ar)气氛下介质阻挡放电低温等离子体(DBD-NTP)分解硫化氢(H2S)的基元反应动力学规律,通过一系列模型假设,采用水力直径为特征尺度的等效模型(Re相似),利用Chemkin软件的Plasma-PFR反应器模型,构建10组分11动力学模型,进行化学动力学模拟得到数值模拟结果,并和实验结果进行了比较。结果表明:低体积分数时(H2S初始体积分数为5%—15%),模拟数据和实验数据相对误差在10%以内,高体积分数时(H2S初始体积分数为20%—25%),相对误差为10%—30%;低体积分数时,DBD-NTP分解H2S主要最终产物体积分数从高到低依次为H2S4SS2,其中φ(S4)∶φ(S)∶φ(S2)≈104∶3∶1,质量平衡基本在90%以上。     

介质阻挡放电低温等离子体脱硫脱硝过程的研究

考察介质阻挡放电低温等离子体反应器两端电压、电源频率、烟气湿度、氧气含量等因素对NO和SO_2脱除率的影响。结果表明,随着反应器两端电压的增加,NO和SO_2的脱除率提高,在电压16 k V后,脱除率提高变缓;随着频率增加,NO和SO_2的脱除率先增加后减小,频率10 k Hz时,NO和SO_2脱除率达到最大;烟气相对湿度的增加,可以大幅提高SO_2的脱除率,氧气含量的增加,却导致NO的脱除率降低。