有机螯合剂和生物表面活性剂联合淋洗污染土壤中的Pb、Cd

发布时间：2018-06-03 10:44

本文选题：有机螯合剂 + 生物表面活性剂　；参考：《西南大学》2015年硕士论文

【摘要】：2014年《全国土壤污染状况调查公报》显示,我国耕地土壤点位超标率为19.4%,其中轻微、轻度、中度和重度污染分别占13.7%、2.8%、1.8%和1.1%,主要受到Cd、As、Hg、口Cr等重金属污染,尤以西南和中南地区最为严重；Cd、Hg、As和Pb等4种重金属含量呈现沿西北向东南、东北向西南逐渐升高的态势,工矿业、农业和交通运输业等人类活动是造成土壤重金属污染和超标的主要原因。进入土壤中的Pb、Cd不被微生物降解,不仅能使土壤肥力、作物的产量与品质下降,还能在动植物体内富集积累,最终通过食物链进入人体,影响人体健康。近年来,我国相继出现Pb、Cd污染事件,如陕西凤翔的“血铅事件”、湘和化工厂的“Cd污染事件”、广东和湖南等省的“镉米污染事件”等,引起政府、公众和学术界的广泛关注。因此,发展Pb、Cd污染土壤的修复技术成为环境科学领域的热点研究问题。目前,Pb、Cd污染土壤的修复技术主要有客土法、热处理法、电动修复法、植物修复法、化学固定法和淋洗法等,这些方法存在修复时间长、成本高、效率低或造成二次污染等问题,采用多种技术联合修复重金属污染土壤逐渐受到学术界的青睐。通过淋洗提高土壤中Pb、Cd的生物有效性,结合植物修复治理Pb、Cd污染土壤,具有广阔的发展前景。为此,本研究制备了模拟Pb、Cd的单一和复合污染土壤,设置3个污染水平(轻度、中度和重度污染),采用振荡淋洗实验,考察有机螯合剂(EDTA、EDDS和柠檬酸)和生物表面活性剂(鼠李糖脂)对模拟污染土壤的淋洗效果,筛选出对Pb、Cd具有最佳淋洗效果的螯合剂,研究有机螯合剂、生物表面活性剂淋洗土壤中Pb、Cd的动力学特征；采用土柱淋溶实验,优化EDTA和鼠李糖脂的配比,获得联合淋洗复合污染土壤中Pb、Cd的动力学特征；比较土柱淋溶前后土壤中Pb、Cd形态的变化,揭示EDTA和鼠李糖脂对Pb、Cd的联合淋溶机制,为植物修复Pb、Cd污染土壤提供基础。取得了如下主要研究结果：1.考察了EDTA、EDDS和柠檬酸(CIT)的浓度和初始pH对污染土壤中Pb、Cd的淋洗效果,获得3种污染水平的土壤中Pb、Cd的最佳淋洗条件：淋洗剂浓度为0.025 mol/L,初始pH 7。淋洗剂对Pb、Cd复合污染土壤与单一污染土壤的淋洗率变化趋势相同,均随土壤污染程度的增加而增加；3种螯合剂对单—污染土壤的淋洗率比复合污染土壤高,对Cd的淋洗率大于Pb。准二级动力学方程能够很好地描述3种有机螯合剂对污染土壤中Pb、Cd的淋洗过程。EDTA和EDDS淋洗单一污染土壤是一个慢速过程,Pb、Cd淋洗分别在120和180 min达到平衡；CIT淋洗Pb、Cd相对较快,分别在45和60 min达到淋洗平衡。EDTA对Pb轻度、中度和重度污染土壤的最大淋洗率分别为81.89%、82.91%和84.4%,Cd污染土壤分别为93.16%、93.62%和94.09%；EDTA对Pb、Cd的最大淋洗率比EDDS和CIT高。对于单一和复合污染土壤,3种螯合剂对Pb、Cd的淋洗速率常数均为轻度污染土壤中度污染土壤重度污染土壤,淋洗能力表现为CIT EDDS EDTA, Pb的淋洗速率常数大于Cd。总体来看,单一污染土壤中Pb、Cd的淋洗速率常数大于对应的复合污染土壤,而EDTA和EDDS对重度复合污染土壤中Pb的淋洗速率常数比对应的单一污染土壤高。2.考察了鼠李糖脂的浓度和初始pH对污染土壤中Pb、Cd的淋洗效果,获得3种污染水平的土壤中Pb、Cd的最佳淋洗条件：鼠李糖脂浓度为0.025 mol/L,初始pH 7。鼠李糖脂对Pb、Cd复合污染土壤与单一污染土壤的淋洗率变化趋势相同,均随污染程度的增加而增加；鼠李糖脂对Pb单一污染土壤的淋洗率小于复合污染土壤,而Cd恰好相反。鼠李糖脂淋洗Pb、Cd是一个快速过程,分别在30和25 mmin达到淋洗平衡,且对Cd的淋洗速率常数大于Pb,明显快于3种有机螯合剂。对于单一和复合污染土壤,Pb、Cd的淋洗速率常数均为轻度污染土壤中度污染土壤重度污染土壤；复合污染土壤中Pb、Cd的淋洗速率常数大于对应的单一污染土壤。3.采用土柱淋溶实验,用EDTA和鼠李糖脂联合淋洗复合污染土壤中的Pb、Cd。随着混合淋洗液体积的增加,两种重金属的淋溶率均呈现逐渐升高到趋于平衡的过程；随着EDTA与鼠李糖脂配比的增加,两种重金属的淋溶率呈现先升高、达到最大值、再降低的变化趋势。当EDTA和鼠李糖脂的配比为1.5：1时,Pb、Cd的淋溶率达到最大,轻度、中度和重度污染土壤中Pb的淋溶率分别为82.97%、87.61%和91.45%,Cd分别为85.45%、89.25%和93.88%,以重度污染土壤的淋溶效果最好。准二级动力学方程可以很好地描述EDTA和鼠李糖脂对复合污染土壤中Pb、Cd的联合淋洗过程,获得轻度、重度和重度污染土壤中Pb的淋溶速率常数分别为0.00092、0.00080和0.00072 kg.mg-1.min-1,Cd分别为0.0004、0.00025和0.00021kg.mg-1.min-1,淋溶速率常数均比它们单独淋洗时低。4.研究了联合淋洗前后污染土壤中Pb、Cd的形态变化,发现联合淋洗能够有效去除土壤中可交换态和碳酸盐结合态,其次为有机结合态,对铁锰氧化物结合态的淋洗效果较差,几乎不淋洗残渣态。EDTA与鼠李糖脂联合淋洗污染土壤中Pb、Cd是配位螯合和胶束增溶共同作用的结果。
[Abstract]:The national survey of soil pollution status in 2014 showed that the excess rate of soil point in cultivated land was 19.4%, of which mild, mild, moderate and severe pollution accounted for 13.7%, 2.8%, 1.8% and 1.1% respectively, mainly by heavy metals such as Cd, As, Hg, and mouth Cr, especially in southwest and middle south areas; the contents of 4 heavy metals such as Cd, Hg, As and Pb were along the edge. The main reason for the heavy metal pollution and exceeding the standard in the soil, such as industry, mining, agriculture and transportation, is the main cause of heavy metal pollution and exceeding the standard in the northwest to the southeast and northeast to the southwest. In the soil, Pb, Cd can not be degraded by microorganisms, not only the soil fertility, the yield and quality of the crops, but also the accumulation and accumulation in the plants and animals. In recent years, Pb, Cd pollution events, such as "blood lead events" in Shaanxi Fengxiang, "Cd pollution events" in Hunan and chemical plants, "cadmium pollution events" in Guangdong and Hunan provinces, have aroused widespread concern in the government, the public and the academia. Therefore, the development of Pb and Cd contaminated soil Soil remediation technology has become a hot research issue in the field of environmental science. At present, the remediation techniques of Pb and Cd contaminated soil mainly include soil method, heat treatment, electric repair, phytoremediation, chemical fixation and leaching. These methods have many problems, such as long repair time, high cost, low efficiency or two pollution. The combined remediation of heavy metal contaminated soil has gradually been favored by the academic community. Through leaching to improve the bioavailability of Pb and Cd in soil, combined with phytoremediation and remediation of Pb and Cd contaminated soil, it has broad prospects for development. Therefore, this study has prepared a single and compound contaminated soil of Pb, Cd, and set 3 levels of pollution (mild, moderate and heavy). The leaching effect of organic chelating agent (EDTA, EDDS and citric acid) and bioactive agent (rhamnolipid) on simulated contaminated soil was investigated by oscillatory leaching, and the chelating agent for the best leaching effect of Pb and Cd was screened, the kinetic characteristics of the organic chelating agent and the bioactive agent in the leaching of soil Pb and Cd were studied. The soil column leaching experiment, optimizing the ratio of EDTA and rhamnolipid, obtained the dynamic characteristics of Pb and Cd in the combined leaching soil, compared the changes of Pb and Cd in soil before and after the leaching of soil column, and revealed the joint leaching mechanism of EDTA and rhamnolipid on Pb and Cd, which provided the basis for the plant to repair Pb and Cd contaminated soil. The results were as follows: 1. the concentration of EDTA, EDDS and citric acid (CIT) and the leaching effect of initial pH on Pb and Cd in contaminated soil were investigated. The optimum leaching conditions of Pb and Cd in 3 polluted soils were obtained: the concentration of the leaching agent was 0.025 mol/L, the initial pH 7. leaching agent was to Pb, and the leaching rate of the contaminated soil was the same as that of the single contaminated soil. The leaching rate of 3 kinds of chelating agents to single polluted soil is higher than that of compound contaminated soil. The leaching rate of Cd is more than Pb. quasi two dynamic equation, and the leaching process of 3 organic chelating agents for contaminated soil can be well described by 3 kinds of organic chelating agents in contaminated soil. The leaching process of.EDTA and EDDS in the leaching process of single contaminated soil is a slow speed over the leaching process of contaminated soil. Process, Pb, and Cd leaching are balanced at 120 and 180 min, respectively, and CIT leaching Pb, Cd relatively faster, respectively, in 45 and 60 min to achieve the leaching equilibrium.EDTA to Pb mildly, the maximum leaching rate of moderate and severe contaminated soil is 81.89%, 82.91% and 84.4%, Cd contaminated soil is 93.16%, 93.62% and 94.09%, respectively, EDTA against Pb, the maximum leaching rate of Pb For single and compound contaminated soil, the leaching rate constants of 3 chelating agents for Pb and Cd were all moderately polluted soil in mild contaminated soil, and the leaching ability of the soil was CIT EDDS EDTA, and the leaching rate constant of Pb was larger than Cd., and the leaching rate constant of Cd was greater than that of the corresponding compound pollution in the single contaminated soil. Soil, while the leaching rate constant of EDTA and EDDS for severe compound contaminated soil was higher than that of the corresponding single contaminated soil.2., and the concentration of rhamnolipid and the leaching effect of initial pH on Pb and Cd in contaminated soil were obtained, and the best leaching strips of Pb and Cd in 3 polluted soils were obtained: the concentration of rhamnolipid was 0.025 mol/L, and the initial pH 7. was 7.. The leaching rate of rhamnolipid on Pb, Cd compound contaminated soil and single contaminated soil was the same, which increased with the increase of pollution degree; the leaching rate of rhamnolipid on Pb single contaminated soil was less than that of compound contaminated soil, while Cd was just the opposite. The leaching of rhamnolipid in Pb and Cd was a rapid process, which was washed in 30 and 25 mmin respectively. The leaching rate constant of Cd is greater than Pb, and it is faster than 3 kinds of organic chelating agents. For single and compound contaminated soil, the leaching rate constants of Pb and Cd are mild contaminated soil contaminated soil with moderate pollution, and the leaching rate of Pb and Cd in compound contaminated soil is greater than that of the corresponding single contaminated soil.3. using soil column drenching. EDTA and Shu Li sugar grease were used to rinse the Pb in the contaminated soil, and the leaching rate of the two heavy metals increased gradually to the balance with the increase of the volume of the mixed lotion. With the increase of the ratio of EDTA and Shu Li sugar and fat, the leaching rate of the heavy metals increased first, reached the maximum and then decreased. When the ratio of EDTA and rhamnolipid was 1.5:1, the leaching rate of Pb and Cd reached the maximum. The leaching rates of Pb in the mild, moderate and severe contaminated soils were 82.97%, 87.61% and 91.45%, respectively 85.45%, 89.25% and 93.88%, respectively. The leaching effect of severe contaminated soil was the best. The quasi two kinetics equation could describe EDTA well. The leaching rate of Pb and Cd in soil contaminated with rhamnolipid and rhamnolipid in the mixed contaminated soil was 0.00092,0.00080 and 0.00072 kg.mg-1.min-1 respectively, respectively, and Cd was 0.0004,0.00025 and 0.00021kg.mg-1.min-1 respectively, and the constant number of leaching rates was lower than that of them when they were washed separately. The morphological changes of Pb and Cd in the contaminated soil before and after washing were found. It was found that the joint leaching could effectively remove the exchangeable and carbonate binding states in the soil, followed by the organic binding state, and the leaching effect of the iron and manganese oxide binding state was poor, and the residue state.EDTA was washed with rhamnolipid in the contaminated soil Pb, and Cd was the coordination chelation and micelle. The result of the combination of solubilization.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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