重金属在高岭土中对流—弥散参数的测试研究
发布时间：2018-10-19 16:48
【摘要】：近年来现代工业的迅速发展给环境带来了许多负面的影响,各类水土重金属污染事件(如Pb2+、Cd2+等)频频发生,引起了社会各界的高度重视,重金属污染物在水土介质中的扩散、运移问题也引起越来越多的关注。粘土的对流-弥散参数是地下水土重金属污染评估及防治的重要基础数据,而现有的测试方法受到土样前处理方法、土体状态、试验条件等影响存在诸多不确定性。本文系统的研究了重金属污染物在高岭土中的渗透、吸附、扩散、弥散等特性,提出一套测试重金属在低渗透性粘土中对流-弥散参数的方法,并获得了一系列有意义的结论。 (1)三种高岭土渗透系数的对数与其孔隙比均有很好的线性关系,渗透系数随着孔隙比的减小而减小；通过固结压缩,硬质、软质高岭土的饱和渗透系数可降低至1×10-7cm/s,而砂质高岭土的渗透系数比前两者高一个数量级,难以达到1×10-7cm/s;综合考虑三种高岭土的物理性质、渗透性及制样的方便性,推荐采用软质高岭土作为扩散、土柱试验的试验材料。 (2)吸附试验中高岭土对Pb2+、Cd2+的吸附主要发生在0.5小时之内,其对Pb2+、Cd2+的吸附平衡时间分别为6、4小时。随着溶液中Pb2+、Cd2+浓度的增加,高岭土对Pb2+、Cd2+的吸附量逐渐增大并最终趋于饱和,而高岭土对Pb2+、Cd2+的吸附率却逐渐降低；高岭土对Pb2+吸附能力强于对Cd2+的吸附,对Pb2+、Cd2+的饱和吸附量Q0分别为5.190、1.243mg/g。 (3)对于Pb2+、Cd2+污染土,消解法和HCI浸提法的处理率明显比去DW浸提法的处理率高,其中消解法的处理效果最好。DW浸提法测得的污染物的浓度更接近孔隙水中污染物的浓度,而消解法测得的污染物的浓度可以看作污染物的全量；针对被重金属污染的高岭土或重金属在高岭土中扩散、运移后的污染土,建议同时采用DW浸提法和消解法对比分析其孔隙水中重金属的浓度。 (4)Cl-在高岭土中的有效扩散系数与土样的孔隙比有关,孔隙比越大有效扩散系数越大,弯曲因子也就越大；Cl-在高岭土中的弥散系数与流速有关,流速越大弥散系数就越大,弥散度与流速却无明显关系,为0.003m。 (5)扩散试验中DW浸提法测得的Pb2+、Cd2+浓度明显比消解法测得的浓度小,说明采用DW浸提法时,土颗粒上吸附的Pb2+、Cd2+大部分没有解吸；消解法测得的土样对Pb2+、Cd2+的阻滞因子均大于DW浸提法测到的阻滞因子；DW浸提法和消解法得到的土样对Pb2+的阻滞因子均比土样对Cd2+的阻滞因子大,与高岭土对Pb2+、Cd2+吸附能力相对应。 (6)土柱试验中,不同水头(即流速不同)的高岭土对Pb2+、Cd2+的阻滞因子是不同的,水头较高即流速较大时,土样对Pb2+、Cd2+的阻滞因子较小；水头较低即流速较小时,土样对Pb2+、Cd2+的阻滞因子较大。
[Abstract]:In recent years, the rapid development of modern industry has brought a lot of negative effects to the environment. Various kinds of heavy metal pollution events (such as Pb2, Cd2, etc.) have occurred frequently, which has aroused great attention from all walks of life, and the diffusion of heavy metal pollutants in soil and water media. Migration also attracts more and more attention. The convection-dispersion parameter of clay is an important basic data for the assessment and prevention of heavy metal pollution in underground soil and water. However, the existing testing methods are affected by the pre-treatment method of soil sample, the state of soil, the test conditions and so on. In this paper, the permeation, adsorption, diffusion and dispersion of heavy metal pollutants in kaolin are systematically studied, and a set of methods for measuring the convection-dispersion parameters of heavy metals in low permeability clay are proposed. A series of meaningful conclusions are obtained. (1) the logarithm of permeability coefficient of three kaolin has a good linear relationship with its porosity ratio, and the permeability coefficient decreases with the decrease of porosity ratio. The saturated permeability coefficient of soft kaolin can be reduced to 1 脳 10 ~ (-7) cm / s, while the permeability coefficient of sandy kaolin is one order of magnitude higher than that of the former two, so it is difficult to reach 1 脳 10 ~ (-7) cm / s. It is recommended that soft kaolin be used as the experimental material for diffusion and soil column test. (2) the adsorption of Pb2 and Cd2 by kaolin occurs mainly within 0.5 hours in adsorption test, and the equilibrium time of adsorption for Pb2 and Cd2 is 6? 4 hours respectively. With the increase of the concentration of Pb2 and Cd2 in solution, the adsorption capacity of kaolin to Pb2 and Cd2 increases gradually and tends to saturation, while the adsorption rate of Pb2 and Cd2 decreases gradually, and the adsorption ability of kaolin to Pb2 is stronger than to Cd2. The saturated adsorption capacity Q0 for Pb2 and Cd2 were 5.190 ~ 1.243 mg / g 路g / g respectively. (3) for Pb2 and Cd2 contaminated soil, the treatment efficiency of digestion method and HCI extraction method was obviously higher than that of DW extraction method. The concentration of pollutants measured by DW extraction method is closer to the concentration of pollutants in pore water, and the concentration of pollutants measured by digestion method can be regarded as the total amount of pollutants. In view of the heavy metal contaminated kaolin or heavy metal in the spread of kaolin, after the migration of contaminated soil, It is suggested that the concentration of heavy metals in pore water should be analyzed by DW extraction method and digestion method simultaneously. (4) the effective diffusion coefficient of Cl- in kaolin is related to the porosity ratio of soil sample, and the larger the porosity ratio is, the greater the effective diffusion coefficient is. The larger the bending factor is, the larger the dispersion coefficient of Cl- in kaolin is, and the larger the velocity of velocity is, the greater the dispersion coefficient is, but there is no obvious relation between dispersion degree and velocity. (5) the concentration of Pb2 determined by DW extraction method in diffusion test was obviously lower than that by digestion method, which indicated that most of the Pb2 and Cd2 adsorbed on soil particles did not desorb when DW was used. The block factors of Pb2 and Cd2 of soil samples measured by digestion method were higher than those of DW extraction methods, and the blocking factors of soil samples obtained by DW extraction and digestion methods were larger than those of Cd2 by soil samples. The adsorption ability of kaolin to Pb2 and Cd2 is corresponding to that of kaolin. (6) in the experiment of soil column, the retardation factors of kaolin to Pb2 and Cd2 with different water head (i.e. different velocity of flow) are different, and when the water head is higher, that is, the flow rate is higher, The blocking factors of soil samples to Pb2 and Cd2 are smaller, and the water head is lower, that is, the velocity of flow is small, and the blocking factors of soil samples to Pb2 and Cd2 are larger than those of soil samples.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU41;X53
本文编号：2281743
[Abstract]:In recent years, the rapid development of modern industry has brought a lot of negative effects to the environment. Various kinds of heavy metal pollution events (such as Pb2, Cd2, etc.) have occurred frequently, which has aroused great attention from all walks of life, and the diffusion of heavy metal pollutants in soil and water media. Migration also attracts more and more attention. The convection-dispersion parameter of clay is an important basic data for the assessment and prevention of heavy metal pollution in underground soil and water. However, the existing testing methods are affected by the pre-treatment method of soil sample, the state of soil, the test conditions and so on. In this paper, the permeation, adsorption, diffusion and dispersion of heavy metal pollutants in kaolin are systematically studied, and a set of methods for measuring the convection-dispersion parameters of heavy metals in low permeability clay are proposed. A series of meaningful conclusions are obtained. (1) the logarithm of permeability coefficient of three kaolin has a good linear relationship with its porosity ratio, and the permeability coefficient decreases with the decrease of porosity ratio. The saturated permeability coefficient of soft kaolin can be reduced to 1 脳 10 ~ (-7) cm / s, while the permeability coefficient of sandy kaolin is one order of magnitude higher than that of the former two, so it is difficult to reach 1 脳 10 ~ (-7) cm / s. It is recommended that soft kaolin be used as the experimental material for diffusion and soil column test. (2) the adsorption of Pb2 and Cd2 by kaolin occurs mainly within 0.5 hours in adsorption test, and the equilibrium time of adsorption for Pb2 and Cd2 is 6? 4 hours respectively. With the increase of the concentration of Pb2 and Cd2 in solution, the adsorption capacity of kaolin to Pb2 and Cd2 increases gradually and tends to saturation, while the adsorption rate of Pb2 and Cd2 decreases gradually, and the adsorption ability of kaolin to Pb2 is stronger than to Cd2. The saturated adsorption capacity Q0 for Pb2 and Cd2 were 5.190 ~ 1.243 mg / g 路g / g respectively. (3) for Pb2 and Cd2 contaminated soil, the treatment efficiency of digestion method and HCI extraction method was obviously higher than that of DW extraction method. The concentration of pollutants measured by DW extraction method is closer to the concentration of pollutants in pore water, and the concentration of pollutants measured by digestion method can be regarded as the total amount of pollutants. In view of the heavy metal contaminated kaolin or heavy metal in the spread of kaolin, after the migration of contaminated soil, It is suggested that the concentration of heavy metals in pore water should be analyzed by DW extraction method and digestion method simultaneously. (4) the effective diffusion coefficient of Cl- in kaolin is related to the porosity ratio of soil sample, and the larger the porosity ratio is, the greater the effective diffusion coefficient is. The larger the bending factor is, the larger the dispersion coefficient of Cl- in kaolin is, and the larger the velocity of velocity is, the greater the dispersion coefficient is, but there is no obvious relation between dispersion degree and velocity. (5) the concentration of Pb2 determined by DW extraction method in diffusion test was obviously lower than that by digestion method, which indicated that most of the Pb2 and Cd2 adsorbed on soil particles did not desorb when DW was used. The block factors of Pb2 and Cd2 of soil samples measured by digestion method were higher than those of DW extraction methods, and the blocking factors of soil samples obtained by DW extraction and digestion methods were larger than those of Cd2 by soil samples. The adsorption ability of kaolin to Pb2 and Cd2 is corresponding to that of kaolin. (6) in the experiment of soil column, the retardation factors of kaolin to Pb2 and Cd2 with different water head (i.e. different velocity of flow) are different, and when the water head is higher, that is, the flow rate is higher, The blocking factors of soil samples to Pb2 and Cd2 are smaller, and the water head is lower, that is, the velocity of flow is small, and the blocking factors of soil samples to Pb2 and Cd2 are larger than those of soil samples.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU41;X53
【参考文献】
相关期刊论文 前10条
1 卢党军;;我国砂质高岭土资源特点与开发利用现状[J];非金属矿;2009年03期
2 吴宏海,刘佩红,张秋云,何广平;高岭石对重金属离子的吸附机理及其溶液的pH条件[J];高校地质学报;2005年01期
3 李永华,王五一,杨林生,李海蓉;湘西多金属矿区汞铅污染土壤的环境质量[J];环境科学;2005年05期
4 郭伟;赵仁鑫;张君;包玉英;王宏;杨明;孙小丽;金帆;;内蒙古包头铁矿区土壤重金属污染特征及其评价[J];环境科学;2011年10期
5 邵学新;吴明;蒋科毅;;西溪湿地土壤重金属分布特征及其生态风险评价[J];湿地科学;2007年03期
6 李发生,韩梅,熊代群,卢桂兰,刘锋,赵秉强,张夫道;不同浸提剂对几种典型土壤中重金属有效态的浸提效率研究[J];农业环境科学学报;2003年06期
7 息朝庄;戴塔根;张惠军;刘悟辉;;湖南湘潭市土壤重金属污染调查与评价[J];水土保持通报;2008年03期
8 李胤;毛义伟;周立晨;曹丹;刘益宁;王天厚;;上海世博会规划区域城市土壤重金属调查及评价研究[J];土壤通报;2009年04期
9 郭朝晖,朱永官;典型矿冶周边地区土壤重金属污染及有效性含量[J];生态环境;2004年04期
10 乔云峰,沈冰;土壤溶质运移的微观机理模型研究[J];西北水资源与水工程;2001年01期
相关博士学位论文 前1条
1 李振泽;土对重金属离子的吸附解吸特性及其迁移修复机制研究[D];浙江大学;2009年
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