【作者】 蔡玉池；

【导师】 黄玉明；

【作者基本信息】 西南大学 ， 分析化学， 2011， 硕士

【摘要】 挥发性烷基硫化物主要包括二甲基硫(DMS)、二甲基二硫(DMDS)和甲硫醇(MT)等,是潜流人工湿地上空臭味的主要来源之一。同时这些硫化物也对全球变暖、酸雨的形成等自然现象有重要的影响。人工湿地作为大陆湿地的重要组成部分,因具有高效、运行费用低廉、操作简单方便等优势被很多国家作为一种独特、新型的污水处理技术广泛应用。目前,人工湿地研究大多集中在湿地设计和处理污水的能力等方面,湿地作为陆地上空烷基硫的重要生产地常被人们忽略,因而也很少有研究关注其内部烷基硫的形成机理及中间降解产物与烷基硫之间的联系。本论文以中试潜流人工湿地为对象,深入研究湿地中烷基硫的产生、转化和降解过程,主要研究内容如下：1.以人工湿地中的淤泥作为底物,模拟人工湿地环境,研究常见有机物降解中间产物醇、醛、酸、酮对DMS的产生和释放的影响以及DMS甲基供体的新探索。2.人工湿地中硫酸盐、硝酸盐等对DMS、DMDS、MT形成以及相互转化的影响和原因分析。3.利用芬顿反应原理寻找一种快速、高效且环境友好的降解DMS的方法。通过研究得到如下主要结果：1.为了探索潜流人工湿地中二甲基硫DMS的来源,本文模拟人工湿地环境,通过假设湿地中含甲基或醛基的可溶性有机物为产生DMS的甲基供体,研究DMS产生的机理。结果表明：人工湿地中的DMS在微生物的作用下通过硫化物的甲基化产生,同时被微生物降解。乙醇、乙酸、丙酮和醛类均能够抑制产甲烷菌对DMS的消耗从而增加DMS产量。在抑制甲烷菌活性的环境中,乙醇、乙酸、丙酮等对DMS的产生并无明显的影响,第48 h、72 h产生的DMS均与相应的对照组浓度接近,说明它们并不是甲基供体；醛类物质对DMS产生影响显著(p<0.001),且两者之间存在较高的线性相关性(R2=0.937-0.984),添加的甲醛40 mmol/L使DMS浓度高达153.05μg/L,影响最为显著。通过含甲基有机物与硫化钠在纯水中的反应实验发现：添加甲醛的反应瓶中有5.32μg/L的DMS产生,其产量远远小于在淤泥底物中,其他有机物与硫化钠均不能产生烷基硫。此结果证明了甲醛确实为DMS的甲基供体,与硫化物合成DMS既可通过生物途径也可通过化学途径,生物途径是最主要的途径。pH值对DMS的产生影响较为显著,酸性条件下DMS浓度较大,碱性条件时DMS的浓度明显降低至消失。2.硝酸盐的存在有利于DMDS和DMS的产生,亚硝酸盐能够促进MT和DMS的产生,硫酸盐能够被还原菌还原为硫化物为DMS的产生提供硫供体,从而促进DMS的产生。金属离子中只有铜离子能够促进DMS产生,其他金属离子均无显著影响,纳米材料对烷基硫生产是否产生作用与自身的性质和粒径均有密切关系,四氧化三铁纳米材料能够显著影响DMS的生产和释放,而碳纳米管则不能。3.芬顿降解反应中,Fe2+浓度小于1mg/L, H2O2浓度小于5mg/L就能使DMS的降解效率达到100%,pH对此氧化反应的影响较小。若仅使用H2O2,则浓度需达到1000 mg/L,温度为60℃时,才能接近完全降解。降解产物为Fe3+和SO42-等,从动力曲线得出此反应的活化能Ea=39.18kJ/mol,通过计算得出Fe2+、H2O2指数(m,n)的值为m=0.4998,n=0.2284,m>n,说明此反应更依赖于Fe2+的浓度,即在此芬顿反应中Fe2+比H2O2发挥的降解作用更大。更多还原

【Abstract】 The dimethyl sulfide (DMS), dimethyl disulfide (DMDS) and methyl mercaptan (MT) are the main volatile alkyl sulfides and the major source of one of odors in the constructed wetlands. These sulfides show significant impact on global warming, acid rain formation.The constructed wetland is an important integral part of the land wetland. As a unique and new sewage treatment technology, it is widely used in the many countries because of its high efficiency, low operating costs and simple operation. However, rescent works on the constructed wetland are focused on the design of wetlands and its performance for treating sewage. The wetlands are often ignored as the source of alkyl sulfur on land, very few studies have dealt with the mechanism of alkyl sulfur formation in the internal of wetland and the linkages between the intermediate degradation products of organic pollutants and the formation of alkyl sulfur. Therefore, the object of this thesis is to evaluate the production, transformatin and degradation of alkyl sulfur in the constructed wetland, and the main contents are as follows:1. Effect of commonly found degradation intermediates of organic pollutants, such as alcohols, aldehydes, acids and ketones, on production and release of DMS was studied by using sludge from the constructed wetlands. On this basis, methyl donor for DMS formation was discussed.2. The effect of sulfate, nitrate on the formation and the transformation of DMS, DMDS, MT in constructed wetlands was studied.3. A fast, efficient and environment-friendly method for degradation of DMS was investigated.The major conclusions through our study are summarized as follows: 1. In order to explore the source of DMS in the subsurface flow constructed wetland, we simulated the constructed wetland environment and studied the mechanism of DMS production by assuming that the soluble organic matter containing methyl are the methyl donor of DMS. The experimental results suggested that DMS was produced by sulfide biomethylation and degradated by microbial at the same time. Ethanol, acetic acid, acetone can inhibit the activity of methanogenic bacteria, leading to increase of DMS production. However, ethanol, acetic acid, and acetone did not significantly affect the production of DMS. The concentration of DMS produced in experiment group at the 48 h, and 72 h were close to control groups, which indicated that they are not real methyl donor. Aldehydes impact on the DMS significantly (p<0.001) and it has higher linear correlation (R2=0.937-0.984) between aldehydes and DMS. DMS production increased with increasing aldehyde concentration from 0-40 mmol/L, up to 153 ppb DMS could be produced at 40 mmol/L aldehyde level. The above results suggested that aldehyde may reaction with sulfide as methyl donor in constructed wetlands. The reaction of DOM and sodium sulfide in water suggested that only 5.32 ppb DMS can be produced when using the same formaldehyde concentration as those in above experiment. This showes DMS production by chemical methylation of sulfide, but biological pathway is the most important way. pH value has more significant on the production of DMS, the DMS production is larger under acidic conditions, but significantly reduced to disappear in alkaline conditions.2. It was found that the presence of nitrate is in favor of the production of DMDS and DMS. Nitrite can promote the production of MT and DMS. Sulfate can be reducted by SRB to sulfide, which is as S-donor for the production of DMS, thus contributing to the production of DMS. Only copper ions can promote the production of DMS, and other metal ions had no significant effect on the production of DMS. The effect of nano-materials on the role of alkyl sulfur is closely related to its nature and size. Iron oxide nano-materials can significantly affect the production and release of DMS, but carbon nanotubes can not.3. In Fenton degradation reaction, when concentration of Fe2+ is less than 1 mg/L, concentration of H2O2 is less than 5 mg/L, DMS degradation efficiency can reach the 100%, pH value has little effect on this oxidation reaction. If H2O2 is used alone, 100% DMS degradation can be reached under conditions of 1000 mg/L of H2O2, temperature of 60℃. The Degradation products are Fe3+ and SO42- and others. The activation energy of the reaction is 39.182 kJ mol/L with index of 0.4998, and 0.2284 for Fe2+, and H2O2, respectively, suggesting that this reaction is more dependent on the concentration of Fe2+.更多还原