不同电源及放电形式下低温等离子体降解挥发性有机物的研究进展

介绍了低温等离子体的产生方式,并对几种降解挥发性有机物(VOCs)的工艺及其特点进行阐述。针对电晕放电与介质阻挡放电,重点围绕不同类型电源作用下VOCs的降解特性进行叙述。结合不同电源及放电形式下低温等离子体降解VOCs的表现,对该技术的未来发展进行了展望。     

脉冲电晕放电等离子体降解4-氯酚废水的研究

在废水中进行直接高压脉冲电晕放电产生的非平衡等离子体可以有效地氧化降解水溶液中的有机物.研究表明,在不同的放电条件下废水溶液中4-氯酚的降解过程均符合一级反应,即C=C0e-kt.提高脉冲峰压和放电频率可以提高4-氯酚的降解速率,而增大放电电极与接地电极间的距离将严重降低4-氯酚的降解速率.在一定的放电条件下,4-氯酚降解速率常数k与脉冲峰压Vp、放电频率f和放电距离l的关系符合k=10-8(Vp)4.22、k=4.78×10-6 f 1.81和k=-1.184×10-2lnl+0.02153.     

高压脉冲液相放电降解水中邻氯苯酚

研究了高压脉冲液相放电降解水中邻氯苯酚的特性脉冲峰压的升高、电极距离的缩短、脉冲频率的加大均使邻氯苯酚的降解速率增加.在脉冲峰压为30 kV、电极距离为2 cm、脉冲频率为150 Hz条件下,o-CP的降解率约为98.7%.较高输入电压下,溶液初始离子含量的增加,会使放电形式由火花放电→流柱放电→电晕放电转变.在火花放电和流柱放电条件下,邻氯苯酚降解率无明显变化,但在电晕放电时,降解率有所降低.邻氯苯酚受羟基的攻击,生成2-氯-对苯二酚,并进一步被氧化生成2-氯-1,4-对苯醌,2-氯-1,4-对苯醌开环后,进一步被氧化,自由基最终生成丙酸、草酸、乙酸以及甲酸等低分子有机酸.     

筒电极高度对雾化电晕放电处理采油废水影响的研究

采油废水的成分复杂,较难被直接生化处理。低温等离子法产生的活性物质可以将废水中的难降解有机物氧化为易降解的成分,便于后续处理。利用接地极雾化电晕放电技术提高采油废水的可生化性,并对比了筒电极高度对电流增长的影响,结果表明电流增长受筒电极高度和流量的双重影响,增长率存在一个最佳值;考察了电极高度对BOD和COD的影响,并分析了相关反应机理。结果表明,筒电极的高度与采油废水的处理效果,在一定程度上可成正比。     

电晕放电喷雾荷电特性

静电喷雾广泛应用于工业各个领域,如静电喷涂、静电雾化燃烧、静电雾化除尘等,其应用效果与喷雾荷电特性密切相关。为获得更佳荷电效果,本文探究了电晕荷电过程中感应电流对液滴真实荷电电流的影响,通过改变荷电电压、电极间距、电极环直径及液体流量等,实验研究了各因素变化对喷雾荷质比、电荷衰减及液滴粒径的影响。结果表明：相比于感应荷电,电晕荷电过程不稳定但能获得更佳的荷电效果,液滴荷质比随荷电电压的增加而先减小后增大,随电极环直径的增加而先增大后减小,随电极间距的增大而增大,电极环直径80mm,电极间距40mm能获得最佳荷电效果;荷电液滴带电量会随输运距离增加而泄漏衰减,相同距离下液滴通过电晕放电带有电荷后衰减更快;液滴带电后能够降低液体表面张力,随着液滴荷电量的增加,雾化液滴粒径有所降低。     

Al2O3在脉冲等离子体降解CFC-113中提高转化率的作用机理

催化剂α-Al₂O₃可显著提高脉冲电晕等离子体降解CFC-113的转化率，高达95.5%。着重从物理角度深入研究了催化剂的增效机理：催化剂颗粒表面附近的等离子体鞘层有利于离子和电子的加速；等离子体中的离子、电子、激发态中性分子及亚稳态自由基团等活性粒子与反应器中固体表面的相互作用可促进降解；颗粒孔隙附近产生的局部电晕放电可显著提高附近离子和电子的动能。孔径小、比表面积大的Al₂O₃颗粒能更好地提高CFC-113的转化率，并从脉冲放电粒子荷电等机理出发分析，原因在于局部电晕场较多较强、吸附能力较高。     

185nmUV降解水中4-CP、4-NP和RhB的研究

本文以对氯苯酚（4-cP）、对硝基苯酚（4-NP）和罗丹明B（RhB）为模型有机物（以4-CP和4-NP为小分子模型有机物，以RhB为大分子模型有机物），分别研究了185nmUV对水中这3种模型有机物的降解规律、性能和效果．研究结果表明，185nmUV直接对水中4-CP、4-NP和RhB有很好的降解效果．研究内容包括：185nmUV降解模型有机物的浓度、TOC（Totalorganic carbon）浓度、185nmUV降解模型有机物过程中溶液pH及电导率变化、以及降解模型有机物过程中产生的无机离子等几个方面．     

粉(液)体的带电现象及处理方法(二)——三、电晕放电及电集尘装置

<正> 1.电晕放电 如上所述,粉体在处理过程中会自然带电,反之也可强制地使它带电。促进粉体有效带电的方法主要有接触感应带电如前节所述的感应电荷带电和电晕放电带电。在电集尘装置中可以通过电晕放电使微粒带电从而达到除尘目的。电晕放电的方式大致有二种:扩散带电和电场带电。换句话说,无外界电场时的带电称扩散带电,而有外界电场并忽略离子的扩散作用时称电场带电。 在扩散带电中,离子通过热运动向电位     

铁电极辅助餐厨垃圾高温厌氧消化及微生物的耐盐机理

目前餐厨垃圾中的盐度对其厌氧消化产甲烷有不利影响。为了解决这一问题,本研究通过使用铁-碳微生物电解池来强化高温厌氧消化。本文使用零价铁作为微生物电解池的阳极,提高微生物的耐盐能力,增强了阳极的氧化作用,从而促进产甲烷过程。结果表明,铁-碳微生物电解池的累积产甲烷量最高达到了1110.67mL,比对照组提高了68.18%。随着Na⁺浓度的提高,水解酸化过程受到了抑制,而铁-碳微生物电解池促进了微生物降解有机物的过程,并且促进了丙酸和丁酸转化为乙酸的过程。微生物群落结构分析表明,铁-碳微生物电解池促进了Methanomassiliicoccus的生长,在阳极上占比52%。代谢通路分析表明,铁-碳微生物电解池提高了微生物的耐盐能力,促进了水解酸化过程,并且提高了产甲烷过程中乙酸脱羧和二氧化碳还原过程中相关酶的基因丰度,强化高温厌氧消化。     

铁炭微电解法对处理含盐硝基苯废水的实验研究

对不同的盐分在铁炭微电解降解硝基苯过程中的作用机理进行了研究。在铁炭微电解的条件下,以硝基苯为研究对象,选择盐分为参数,在降解过程中,一定时间下取样检测浓度,并计算硝基苯降解率。铜离子、氯离子能促进硝基苯的去除;钙离子对硝基苯的去除率无明显作用;六价铬离子和磷酸根离子对硝基苯的去除有抑制作用;低浓度的硫酸根离子可促进硝基苯的降解,高浓度的硫酸根离子则会减弱对硝基苯降解的促进作用。铁炭微电解过程中盐分对硝基苯的降解率影响很大。     

High Polymer Content 3,5‐Pyridine‐Polybenzimidazole Copolymer Membranes with Improved Compressive Properties

Three series of polybenzimidazole (PBI) copolymers (3,5‐pyridine‐r‐2OH‐PBI, 3,5‐pyridine‐r‐para‐PBI, and 3,5‐pyridine‐r‐meta‐PBI) were polymerized and cast into membranes by the polyphosphoric acid (PPA) process. Monomer pairs with high and low solubility characteristics were used to define phase stability‐processing windows for preparing membranes with high temperature membrane gel stability. Creep compliance of these membranes (measured in compression at 180 °C) generally decreased with increasing polymer content. Membrane proton conductivities decreased linearly with increasing membrane polymer content. Fuel cell performances of some high‐solids 3,5‐pyridine‐based copolymer membranes (up to 0.66 V at 0.2 A cm^–2 following break‐in) were comparable to para‐PBI (0.68 V at 0.2 A cm^–2) despite lower phosphoric acid (PA) loadings in the high solids membranes. Long‐term steady‐state fuel cell studies showed 3,5‐pyridine‐r‐para‐PBI copolymers maintained a consistent fuel cell voltage of >0.6 V at 0.2 A cm^–2 for over 2,300 h. Phosphoric acid that was continuously collected from the long‐term study demonstrated that acid loss is not a significant mode of degradation for these membranes. The PBI copolymer membranes' reduced high‐temperature creep and long‐term operational stability suggests that they are excellent candidates for use in extended lifetime electrochemical applications.     

Growth of a sulphuric acid droplet exposed to water vapor

The growth of a droplet of concentrated sulphuric acid suddenly exposed to water vapor was investigated. Droplet size and temperature as functions of time were obtained by numerical solution of droplet mass and energy balances. Inclusion of heat effects is thought to be an advance over previous studies of droplets of dilute acid which could be assumed to remain isothermal during the growth process. The results indicate that the growth process is completed in a few milliseconds for micron-size droplets. The solutions presented are applicable to the continuum regime and the results are compared with experimental and calculated results of previous workers.     

Photo‐degradation of hydrophobic esters of pyridinecarboxylic acids as copper extractants from chloride media and their copper complexes

The photo‐stability of hydrophobic esters of pyridine‐3‐carboxylic acid and pyridine‐3,5‐dicarboxylic acid containing 2‐ethylhexyl‐, octyl‐, and dodecyl‐substituents which are model extractants of copper from chloride media were studied together with the photo‐degradation of their copper complexes. The results indicate that UV light degraded the esters of both pyridine‐3,5‐dicarboxylic acid and pyridine‐3‐carboxylic acid. The degree of degradation depended on the structure of the ester, the type of solvent, and the presence of oxygen, water or hydrochloric acid in the solution during exposure to visible or UV‐visible light. Photo‐reactions between the solvent and the esters were also observed. Copper has a considerable influence on the photo‐stability of the esters. Copyright © 2005 Society of Chemical Industry     

Synthesis,Corrosion Inhibition Performance and Biodegradability of Novel Alkyl Hydroxyethyl Imidazoline Salts

New alkyl hydroxyethyl imidazoline salts were synthesized via a high pressure process with imidazoline and dimethyl carbonate, and their chemical structure were confirmed using mass spectral fragmentation and FTIR spectroscopic analysis. In addition, several quaternary ammonium salts with new counterions (formic acid, acetic acid and lactic acid) were also synthesized by ion exchange reaction of methyl carbonate quaternary ammoniums with the corresponding acids. These new compounds reduced the surface tension of water to a minimum value of approximately 27 mN m^?1 at a concentration of 8.72 × 10^?5 mol L^?1. They also show efficient corrosion inhibition performances and could significantly inhibit the corrosion of mild steel in acid solutions. It was also found that the biological degradation of these imidazoline surfactants was greater than 98 % after 7 days.     

Separation characteristics of acetic acid–water mixtures by using poly(vinyl alcohol‐g‐4‐vinyl pyridine) membranes by pervaporation and temperature difference evapomeation techniques

The separation of acetic acid–water mixtures was carried by using pervaporation (PV) and temperature difference evapomeation (TDEV) methods. For the separation process 4‐vinyl pyridine was grafted on poly(vinyl alcohol). Membranes were prepared from the graft‐copolymer by casting method and crosslinked by heat treatment. The effect of feed composition on the separation characteristics was studied and the performances of the separation methods were compared. Permeation rates obtained in PV were found to be high, whereas separation factors were high in TDEV method. Membranes gave permeation rates of 0.1–3.0 kg/(m² h) and separation factors of 2.0–61.0, depending on the composition of the feed mixture and the method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2030–2039, 2006     

The acetylation and enzymatic degradation of starch films

The preparation of films from starch and their degradation by amylase enzymes is described. Starch acetate was prepared by acetylation of starch with a pyridine/acetic anhydride mixture. The resulting polymer was cast into films from solutions of 90% formic acid. A series of films with a range of acetyl content were then exposed to buffered amylase solutions and the retained tensile strength measured. It was found that with a sufficient acetyl content the wet strength of the films was maintained in the aqueous solutions, but that the acetyl content was sufficiently low enough to permit degradation by a mixture of alpha and beta amylases within a period of 1 h. These films could be useful as membranes in bioreactors, which could be degraded at will by the addition of enzymes to the system. © 1993 John Wiley & Sons, Inc.     

Characterization of aluminum and boron containing beta zeolites prepared by solid-state recrystallization of magadiite

A method for the preparation of phase-pure [Al]-BEA and [Al,B]-BEA zeolites based on solid-state recrystallization of synthetic aluminum-containing magadiites is presented. For comparison [B]-BEA was prepared by conventional hydrothermal synthesis. From X-ray diffraction (XRD) measurements conclusions could be drawn in respect to kinetics and mechanism of the recrystallization process. Coordination state and resistance to hydrolysis of framework boron species in as-synthesized and ion-exchanged BEA varieties were investigated by ¹¹B MAS NMR spectroscopy. The acidity of the samples was studied by temperature-programmed ammonia elimination (TPAE) from the NH₄-forms and by IR spectroscopy using pyridine as probe molecule. An effect of framework boron on the acid strength of bridged hydroxyls associated with framework aluminum could not be evidenced. Nevertheless, incorporated boron gives rise to weak acid sites which are involved in ion-exchange processes. The number of strong Brønsted sites can be controlled by the aluminum content of the layer silicate.     

Preparation and properties of poly(benzyl glutamate)–poloxamer–poly(benzyl glutamate) and poly(glutamic acid)–poloxamer–poly(glutamic acid) triblock polymers

The novel block copolymer poly(benzyl glutamate) (PBLG)–polomamer–PBLG were synthesized from glutamic acid and poloxamer in six steps with three different molecular weights, and another new block copolymer, poly(glutamic acid) (PGA)–poloxamer–PGA, was obtained by the benzyl deprotection of PBLG–poloxamer–PBLG. The obtained compounds were characterized by IR spectroscopy, gel permeation chromatography, and ¹H‐NMR. The in vitro biological degradation and water absorption of PBLG showed that a greater proportion of PBLG in the copolymer led to a slower degradation and weaker water absorption, so the speed of degradation and water absorption could be adjusted through adjustment of the ratio of poloxamer. Both PBLG–poloxamer–PBLG and PGA–poloxamer–PGA exhibited lower cytotoxicity and good biocompatibility in the methyl thiazolyl tetrazolium (MTT) assay. The results show that both block polymers are promising as drug‐carrier materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Ionic membranes for water desalination. I. Charge mosaic membranes from blends of random copolymers

The incompatibility of polymers was used in order to prepare films with regular phase separation. The conversion of the separate phases into polyelectrolytes of different charge should lead to the preparation of charge mosaic membranes for piezodialysis. Copolymers of suitable monomers with 20–45 mole-% butadiene content were synthesized which could be cross-linked with sulfur monochloride. The comonomers were: styrene, 2-vinyl pyridine, 4-vinyl pyridine, methacrylic acid, methyl methacrylate and 2-chloroethyl methacrylate. After conversion into the ionic form cross-linked films of these copolymers showed salt rejections in the range of 26–78 % and water permeabilities of 40–43 [1· mm· m^?2· day^?1], respectively. These films can be used as anion and cation exchange membranes for water desalination. Mixtures of poly (2-vinyl pyridine-co-butadiene) and poly (styrene-co-butadiene) yielded films with regular phase separation. After cross-linking and conversion into the ionic form these charge mosaic membranes were porous and had poor mechanical strength. Despite these unfavourable properties a salt enrichment of 4.8 % was found in one case.