【作者】 莫玉琴；

【导师】 高锦章；

【作者基本信息】 西北师范大学 ， 分析化学， 2005， 硕士

【摘要】 等离子体是物质的第四态,它由中性的原子或分子、激发态的原子和分子、自由基、电子或负离子以及辐射光子组成。从化学的角度看,等离子体空间富集的离子、电子、激发态的原子、分子及自由基,恰恰是极活泼的反应物种。实验室产生等离子体的方法有:热电离法、激波法、光电离法、射线辐照法以及直流、低频、射频、微波气体放电法及辉光放电法等。接触辉光放电等离子体由电极和电解质液面之间的直流辉光放电来维持,它最显著的特征是化学产物与法拉第定律的偏离。 完全辉光放电时,初始反应区包括阳极周围的等离子体和等离子体-阳极液面附近的液相。在阳极周围的等离子体中,水蒸汽分子在放电过程中分解产生H·,·OH等活性组分,另一方面,在等离子体-阳极液界面附近的液相反应区中,液态的水分子被阳极等离子体中产生的H₂O_gas⁺撞击分解为H·,·OH和HO₂（?）这些活性组分的混合物进入本体溶液,它们可以相互反应产生H₂O₂或与溶液中底物发生反应。辉光放电过程中产生的·OH是最强的氧化剂之一,它能将许多有机物氧化为脂肪酸、CO₂或简单无机物。因而,接触辉光放电等离子体可用于水溶液中有机物的降解。 基于以上理论,论文从接触辉光放电等离子体处理有机污染物方面展开了一系列的研究工作,具体分为四部分。 第一部分 文献综述 本章综述了等离子体的应用、产生方法和接触辉光放电等离子体的电极特征以及它在不同介质中的化学效应,并对阳极和阴极辉光放电等离子体产生化学效应的机理进行了讨论,同时简要论述了接触辉光放电等离子体的应用前景。 第二部分 内置式接触辉光放电等离子体诱导氧化降解邻-氯酚 接触辉光放电电解是一种新型的产生等离子体的电化学方法。本文测定了催化剂、pH值对接触辉光放电等离子体降解水体中邻-氯苯酚降解效率的影响。更多还原

【Abstract】 Plasma, the fourth state of matter, consists of a collection of radicals, active atoms and molecules, free-moving electrons, and other species. Some components in plasma are very active species, which can induce novel chemical reactions. Energy is needed to strip electrons from atoms to produce plasma. The energy can be of various origins: thermal, electrical, or light （ultraviolet light or intense visible light from a laser）. Contact glow discharge plasma was sustained by glow discharge between the anode and the surface of the electrolyte. Its remarkable characteristic was the strong deviation of the chemical yields from that expected on the basis of Faraday’s law.In the reaction zone within the plasma around the anode, H₂O vapor molecules was ionized or activated, and then bombard each other to break up by charge transfer. The ultimate result was the production of ·OH radicals and sometimes H· radicals. On the other hand, in the liquid-phase reaction zone near the plasma-acolytes interface, several liquid H₂O molecules broke up into H·, ·OH, HO₂·and H· by being bombarded by each H₂O_gas⁺ from the anodic plasma. As a mixture of the active species ·OH, HO₂·, H· and H₂O_gas⁺ diffused out of the primary zone that was called plasma layer and into the bulk electrolyte, they could interact among themselves and with any active substrate in the solution. Since ·OH is one of the strongest oxidants that could oxidize many organic pollutants into fatty acids, carbon dioxide or simple inorganic compound, contact glow discharge plasma can be applied in the treatment of organic contaminants in aqueous solution.On the basis of above facts and ideas, a series of research work have been carried out, concerning plasma degradation of organic contaminants. All of these researches and the relevant results are reported in the following five parts.Part Ⅰ Review on plasma, its application and chemical effectsThe application and chemical effects of contact glow discharge plasma in different mediums are described in this part. The discharge characteristics and the mechanisms on chemical process about glow discharge plasma are also reviewed.And the perspective of contact glow discharge plasma was discussed to the point.Part II The oxidative degradation of o-chlorophenol in aqueous solution induced by plasma with submersed glow dischargeContact glow discharge electrolysis is a novel type of electrochemical process. Effects of catalyst and pH value on the degradation of o-chlorophenol in aqueous solution with contact glow discharge electrolysis plasma were studied. The experimental data showed that degradation benefits from basic condition, Fe2+ had a remarkable catalytic effect on degradation. The concentration of intermediate products and o-chlorophenol changed by time were analyzed by a high performance liquid chromatograph （HPLC）.PartUI Oxidative degradation of 4-nitrophenol in aqueous solution by plasma with submersed glow discharger electrolysis.The oxidative degradation of 4-nitrophenol, in aqueous solution by plasma with submersed glow discharge has been investigated. The reaction intermediates were determined by high performance chromatography （HPLC）. Various influencing factors such as the initial pH, the concentrate of pollutants and the catalytic action of Fe + ion were examined.The results indicate that the degradation pathways involve two steps. One is that the hydroxyl radicals attack the aromatic ring and open it; the other is the oxidation of the aliphatic compounds. The results also suggested that the reaction was obeyed a pseudo-first order kinetic reaction. It is enough to prove that the proposed method is an efficient way for the nitrophenol degradation.Part IV Degradation of tannin induced by plasma with contact glow discharge electrolysisDegradation of tannin in water induced by plasma with contact glow discharge electrolysis（CGED）was investigated. Some influence factors such as initial concentration, pH and the catalysts were examined. The result suggested that the Fe2+ had a remarkable catalytic effect on the degradation. On the analysis of the intermediate products of the degradation and the kinetic consideration a reaction pathway was proposed which include two steps.更多还原