【作者】 杜琳；

【导师】 胡常伟；

【作者基本信息】 四川大学 ， 物理化学， 2007， 硕士

【摘要】 染料及印染工业的单位产品耗水量很高,该行业废水具有水量大、色度高、成分复杂、对环境的危害大等特征,因此染料及印染废水的降解脱色处理一直是主要的环境热点之一。电催化氧化和光电催化氧化都是近年发展起来的高级氧化技术,由于具有处理效率高、操作简便、应用灵活、易于自动化、环境友好等优点,因而在染料及印染废水处理的研究中受到广泛的关注。本文分别进行了光电催化和电催化降解染料的实验。在光电催化研究中,以TiO₂为阳极,钛网为阴极,研究了活性艳红K-2BP在NaCl和Na₂SO₄电介质中的降解情况,深入探讨了两种电解质在光电催化降解染料中的作用,研究了电解质浓度,溶液pH值的影响,并探讨了在混合盐电解质存在下,活性艳红K-2BP的降解行为。研究表明,以NaCl为电解质时,Cl^-会转化为氧化性很强的活性氯,活性氯及光电的共同作用,加速了染料的降解。以Na₂SO₄为电解质时,SO₄^2-在光电的作用下将发生两类反应,一部分SO₄^2-捕获光生空穴和HO·,对光电催化降解染料起抑制作用;另一部分SO₄^2-将发生反应生成H₂O₂,对染料降解起促进作用。在进行电催化降解实验时,我们用自制的钛基RuOx-PdO为电极,以常见的一种染料甲基橙为底物,浓度为100mg/L,以0.1mol/L NaCl为电解质,进行了电催化氧化降解的研究,通过多种分析手段,对甲基橙降解的中间产物进行了检测。研究表明,电解过程中能够产生小分子量物质,氯取代物,苯衍生物,长链烷烃,及无机阴离子等物种。氯代物的产生表明电解过程中生成的活性氯攻击甲基橙分子,使其发生断键,参与降解反应。长链烷烃的出现表明氮与甲基相连的C-N键能够在反应中断裂,生成含有甲基的自由基。含有两个苯环的有机物的出现表明,在反应中生成的一些有机物除了可以被继续降解外,还可以发生聚合反应,生成较复杂的有机物。然后再进一步被降解掉。综合各种数据,我们推测了甲基橙的电降解机理。其降解机理大致如下所述,分三个步骤:首先,电氧化过程中产生的活性氯、羟基等活性物种,进攻甲基橙分子,从而产生断键。活性氯可以进攻偶氮与苯环相连的C-N键,形成氯取代物;磺酸基也受到攻击,而从分子上脱去,形成SO₄^2-;偶氮基团可能转化为N2,或其他含氮阴离子;氮与甲基相连的C-N键也发生断裂,形成甲基自由基。然后,第一步形成的物质进行聚合或再分解,其中含甲基的自由基发生聚合反应从而生成了饱和长链烷烃,同时也可以相结合而生成小分子化合物;第一步生成的氯取代物及其他可能存在的有机物,进一步被活性物质攻击,发生断键,并可能与生成的羟基,含甲基的自由基等相结合,近而生成其他苯的衍生物,同时这些物质也可能发生聚合而生成含两个苯环的化合物,及其他可能的复杂有机物。最后,以上生成的物质进一步被降解,最终矿化而转化为CO₂,H₂O及无机离子。更多还原

【Abstract】 The highly coloured waste water of texitile industy contains many complex componds and is harmful to environment. So the discoloration of dye waste water is paid great concern by both governments and reaserchers. Photochemical and photoelectrochemical treatments are two advanced oxidation processes which are widely used because of characters such as high efficiency, simple operation and being benign to environment.In this work, Photochemical and photoelectrochemical treatments are investigated to treat the dye waste water. In the photoelectrochemical experiment, The effect of Cl^- and SO₄^2- ions on the photoelectrocatalytic degradation of the reactive brilliant K-2BP using TiO₂/Ti as anode is investigated, since Cl^- and SO₄^2- are the most common inorganic ions in dye polluted water. It is found that the concentration of the electrolyte, the acidity of the solution and the use of mixed electrolytes alter the degradation process. When NaCl is used as the electrolyte, active chlorine is formed during the process, and is found to be responsible in combination with photo- and electro-effects for the degradation of dye; while Na₂SO₄ is used as electrolyte, two categories of reactions will occur. SO₄^2- may trap HO·and h+, thus the efficiency of degradation is reduced. Under the conditions investigated, SO₄^2- ion may also catalyze the formation of hydrogen peroxide, which is active for the degradation, and then the degradation is favored.In the electrochemical degradation, the mechanism of Methyl Orange degradation with electrochemical method has been studied in 0.1M NaCl solution with RuOx-PdO/Ti as anode. Chemical oxygen demand （COD）, ion chromatography（IC）, FTIR and GC-MS analyses were employed to obtain the details of electrochemical degradation. During the reaction, inorganic ions (SO₄^2-, NO₃^–), low molecular weight compounds, chlorinated compound, benzene derives and long chain alkenes could be formed. The formation of chlorinated compound provided strong evidence that during electrochemical process with NaCl as electrolyte, Cl^– was involved in the degradation reaction to form chlorine-substituted byproduct. Formation of long-chain alkenes radicals demonstrated that CH₃·radicals could be formed in the process. The thorough mechanism of the Methyl Orange is proposed in this study.更多还原