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不同黏粒含量土的固结和重金属吸附解吸特性
武亚军, 岳皓凡, 臧学轲, 张旭东, 章长松, 吴金红
raybet体育在线 院报 ›› 2025, Vol. 42 ›› Issue (5) : 88-96.
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不同黏粒含量土的固结和重金属吸附解吸特性
Consolidation and Heavy Metal Adsorption-Desorption Characteristics of Soils with Different Clay Contents
在实际修复工程中,对高黏粒含量的重金属污染土进行淋洗是十分困难的。这既是因为高黏粒含量土渗透性差,也是因为黏粒含量对于污染土淋洗的具体影响规律和机理尚未明晰。通过固结试验和振荡离心试验探究了不同黏粒含量土壤的固结和重金属吸附解吸特性。研究结果显示,不同黏粒含量土壤的物理力学特性存在显著差别,高黏粒含量土壤具有更高的液塑限和更大的压缩性,而土壤的渗透性和孔隙比则更低。并且,黏粒含量的增加显著提高了土壤对重金属离子的吸附能力,同时降低了药剂淋洗的去除效果。黏粒含量从20%增加到50%,重金属吸附量最大可提高50%,去除率最大可降低20%,其中,在20%和30%黏粒含量之间的变化尤为显著,主要原因是大量团聚体的形成。这些物理力学特性和吸附解吸特性的差别将对土壤淋洗技术和参数的选择产生较大影响,研究结果可为重金属污染土淋洗修复技术的优化提供一定的参考依据。
[Objective] In practical remediation projects, leaching heavy metal-contaminated soils with high clay content is highly challenging. This is not only due to the low permeability of high-clay-content soils, but also because of the unclear influencing patterns and mechanisms of clay content on soil leaching. Current studies on the effects of clay content primarily focus on mixtures of sand and fine-grained soils, lacking systematic investigations into clay soils. Moreover, previous studies investigate the physicomechanical properties of soils with different clay contents, without comparing their effects on heavy metal adsorption and desorption. Studies on the correlation between heavy metal and clay content rely on field sampling methods. However, due to varying soil samples and contamination types, along with complex influencing factors, the conclusions are inconsistent. Therefore, this study intends to artificially prepare soil samples with different clay contents to eliminate complex influencing factors, investigate differences in their leaching performance and geotechnical properties, and analyze their correlations. In doing so, the single-factor influencing pattern of clay content can be obtained. [Methods] Based on the principle that soil particles of different sizes had different settling speeds in solution, soil samples with clay contents of 20%, 30%, 40%, and 50% were prepared via sedimentation method. First, the basic physical properties of soil samples were analyzed, followed by consolidation tests to investigate the porosity ratios, compression characteristics, permeability, and consolidation behaviors of soils with different clay contents, as well as their microscopic characteristics under scanning electron microscope (SEM). Through batch oscillation-centrifugation experiments, the adsorption of heavy metals (Cu and Zn) by the soil samples and their desorption characteristics during heavy metal removal using citric acid were studied, with analysis incorporating pH values and particle size variations. [Results] Soils with different clay contents exhibited significant differences in physicomechanical properties. Soils with a high clay content had larger specific surface areas, lower relative densities, more muscovite and chlorite minerals, and fewer quartz and albite minerals. Additionally, these soils had higher liquid-plastic limits and greater compressibility, while showing lower permeability and porosity ratios, with more soil particle aggregates observed microscopically. The increase in clay content significantly enhanced the soil’s adsorption capacity for heavy metal ions, while deteriorating the desorption performance of citric acid during leaching. As the clay content increased from 20% to 50%, the maximum heavy metal adsorption increased by up to 50%, whereas the maximum desorption rate decreased by up to 20%. Notably, pronounced differences were observed between 20% and 30% clay contents, mainly attributed to the formation of numerous aggregates during this stage, which enhanced the adsorption performance of the soil for heavy metals. In addition, the correlations of clay content with Zn and Cu differed. Zn was more difficult to remove than Cu in high-clay-content contaminated soils. [Conclusions] The experimental findings demonstrate that the differences in various physicomechanical and adsorption-desorption characteristics caused by different clay contents significantly influence the selection of technologies and parameters for soil leaching. Therefore, practical remediation projects must integrate relevant research and experimental analyses to fully consider the effects of clay content, so as to better achieve the goals of contaminated soil remediation.
重金属污染 / 土壤淋洗 / 黏粒含量 / 沉降法 / 固结试验 / 吸附-解吸
heavy metal contamination / soil leaching / clay content / sedimentation method / consolidation test / adsorption-desorption
| [1] |
关天霞, 何红波, 张旭东, 等. 土壤中重金属元素形态分析方法及形态分布的影响因素[J]. 土壤通报, 2011, 42(2): 503-512.
(
|
| [2] |
|
| [3] |
Ionic rare earth mining is of strategic importance in China; however, the heavy metal pollution it causes is of great concern, both at home and abroad. Data on Pb speciation at a rare earth mine were used to analyse the migration capacity of Pb during the process of ore leaching. The major factors thought to influence the migration capacity of Pb, including the clay mineral content, soil pH, oxidation-reduction potential, organic matter content, and cation exchange capacity (CEC), were quantified. Entropy and fuzzy clustering methods were used to identify the most predictive factors. The results showed that the clay mineral content of the soil exerts the strongest influence on the migration capacity of Pb in rare earth mines; the other factors demonstrated relatively weak influences on the transport processes. The results obtained from the classification of Pb per the potential migration index (PMI) approximated those obtained from fuzzy clustering, and the results of entropy analyses were consistent with those of fuzzy clustering. Thus, the methods upon which the proposed model is based are suitable for predicting the migration capacity of Pb in ore during the mining of ionic rare earth minerals.Copyright © 2018 Elsevier Inc. All rights reserved.
|
| [4] |
刘雪珠, 陈国兴. 粘粒含量对南京粉细砂液化影响的试验研究[J]. 地震工程与工程振动, 2003, 23(3): 150-155.
(
|
| [5] |
|
| [6] |
崔俊丽, 刘鸿雁, 徐梦, 等. 夜郎湖沿岸表层土壤重金属含量及其影响因素[C]//中国环境科学学会学术年会论文集. 海口: 中国环境科学学会,2016:977-982.
(
|
| [7] |
卢瑛, 龚子同, 张甘霖, 等. 南京城市土壤重金属含量及其影响因素[J]. 应用生态学报, 2004, 15(1): 123-126.
研究了南京城市土壤重金属含量、来源及其与土壤性质的关系.结果表明,南京城市土壤中,Fe、Ni、Co、V污染不明显,但受到了不同程度的Mn、Cr、Cu、Zn、Pb污染,其中Pb污染非常严重;重金属在土壤剖面分布没有规律性;Fe、Ni、Co、V元素主要来源于原土壤物质,Cu、Zn、Pb、Cr元素主要来源于人为输入,Mn可能在不同的土壤中来源不同;Fe、Cr、Ni、Co、V元素含量之间均呈极显著正相关,Cu、Zn、Pb、Cr元素含量之间均呈极显著正相关.Fe、Co、V、Ni含量与粘粒含量、CEC呈极显著正相关;Cu、Zn、Pb含量与粘粒含量呈极显著负相关;Cu、Zn、Pb、Cr含量与有机碳呈极显著正相关,Pb含量与pH呈极显著正相关.
(
The concentration and source of heavy metals in Nanjing urban soils and their relationships with soil properties were studied. The results indicated that the soils in Nanjing urban were not obviously polluted by Fe, Ni, Co and V, but polluted by Mn, Cr, Cu, Zn, and Pb to a certain extent. The heavy metals were irregularly distributed in soil profiles. Fe, Ni, Co, and V were originated from soil materials, but Cu, Zn, Pb, and Cr were anthropogenic input. Probably, Mn had different origins in different soils. There were positive correlations among Fe, Cr, Ni, Co, and V concentration, and among Cu, Zn, Pb, and Cr concentration. The Fe, Co, V, and Ni concentration were positively correlated with soil clay content and CEC, and the Cu, Zn and Pb concentration were negatively correlated with clay content. There were positive correlations between Cu, Zn, Pb and Cr concentration and organic C content, and between Pb concentration and soil pH.
|
| [8] |
赵玉花, 沈日庚. 基于固结试验结果计算渗透系数方法[J]. 工程勘察, 2009, 37(增刊2): 109-113.
(
|
| [9] |
|
| [10] |
Low molecular weight organic acids (LMWOAs) present in soil alter equilibrium pH of soil, and consequently, affect heavy metal sorption and desorption on soil constitutes. This study was conducted to investigate the effects of different concentrations (0.1, 1, 2.5, 5, 10, 30, 40, 50, 70, and 100 mM) of citric, malic, and oxalic acids on sorption and desorption of cadmium (Cd) and copper (Cu) in two calcareous soils. Increasing the concentrations of three LMWOAs decreased the equilibrium pH of soil solutions. The results indicated that increase in organic acids concentrations generally reduced Cd and Cu sorption in soils. Increase concentrations of LMWOAs generally promoted Cd and Cu desorption from soils. A valley-like curve was observed for desorption of Cu after the citric acid concentration increment in soil 2. Increasing the concentrations of three LMWOAs caused a marked decrease in Kd(sorp) values of Cd and Cu in soils. In general, citric acid was the most effective organic acid in reducing sorption and increasing desorption of both metals, and oxalic acid had the minimal impact. The results indicated that LMWOAs had a greater impact on Cu sorption and desorption than Cd, which can be attributed to higher stability constants of organic acids complexes with Cu compared to Cd. It can be concluded that by selecting suitable type and concentration of LMWOAs, mobility, and hence, bioavailability of heavy metals can be changed. So, environmental implications concerning heavy metals mobility might be derived from these findings.
|
| [11] |
|
| [12] |
黄春霞, 黄敏, 蔡伟, 等. 不同黏粒含量粉土的微观结构研究[J]. 岩土工程学报, 2020, 42(4): 758-764.
(
|
| [13] |
付佳佳, 王炼, 尤苏南, 等. 黏-砂混合土压缩特性与微观结构特征关系研究[J]. raybet体育在线
院报, 2021, 38(5): 115-122.
黏-砂混合土在吹填土地基中广泛应用,混合土地基变形与微观结构息息相关。为探讨黏-砂混合土压缩变形的微观机制,以黏土与砂不同配比的混合土为研究对象,利用压缩、扫描电镜(SEM)试验和图像处理技术(IPP)对固结前后试样的颗粒排列、孔隙分布进行定性和定量分析,从微观层面探讨了混合土微观结构随固结压力变化的演变机制。结果表明:随着含砂量的增大,混合土孔隙比呈先减小后增大的趋势,压缩系数不断减小;大、中孔隙随着含砂量增大明显增多,颗粒间接触方式从以边-面、面-面接触为主向点-点、点-面接触过渡;固结作用提高了颗粒排列的密实性和有序性,孔径分布向小孔径范围移动,大孔隙面积占比最大降幅达31.39%,中孔隙面积显著增加,对微、小孔隙影响不明显;土体颗粒的定向概率熵与和含砂量呈正线性相关,与压缩系数a<sub>1-2</sub>呈负线性相关,含砂量越大,混合土颗粒排列越混乱,定向概率熵越大,其压缩性越低。由此可见,固结压力和配比不同引起的颗粒、孔隙微观结构参数变化是导致混合土压缩特性差异的内在原因。
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Clay-sand mixture is widely used in dredger fill. The deformation of mixed soil foundation is closely related to its microstructure. To explore the microscopic mechanism of compression deformation of mixed soils, we analyzed in qualitative and quantitative scales the particle arrangement and pore distribution of clay-sand mixture samples before and after consolidation via compression tests, scanning electron microscopy (SEM) tests and Image-Pro Plus (IPP) image processing. Results revealed that with the increase of sand content, the void ratio of mixed soil reduced at first and then grew, and the compressibility decreased gradually. The sensitivity of each pore group to consolidation pressure is closely related to sand content. With the increase of sand content, the number of large and medium pores increased, and the contact mode between particles transferred from edge-face and face-face contact to point-point and point-face contact. Compression enhanced the compactness and orderliness of particle arrangement. Pore size tended to be smaller. The percentage of large pore area dropped up to 31.39%, which resulted in the expansion of middle pores; however, the impact on micro-and-small pores is not obvious. The directional probability entropy of soil particle is linearly correlated with sand content, while negatively linearly correlated with compressibility coefficient <i>a</i><sub>1-2</sub>. Lager sand content led to the more chaotic arrangement of mixed soil particles, larger directional probability entropy, and smaller compressibility. In conclusion, the change of microstructure parameters of particles and pores caused by different consolidation pressure and sand content ratio is the internal reason for the difference in the compression characteristics of mixed soil.
|
| [14] |
朱学敏, 庞志明, 代佳骏, 等. 黏粒含量对钙质砂渗透特性影响试验研究[J]. 辽宁科技学院学报, 2022, 24(4): 36-39, 46.
(
|
| [15] |
胡其志, 洪昌伟, 刘恒, 等. 黏粒含量对花岗岩残积土渗透与强度特性的影响[J]. raybet体育在线
院报, 2020, 37(9): 64-69.
花岗岩残积土由于强度较高,常常用于高速公路路基的填方,但花岗岩残积土具有较强的渗透性,抗冲刷能力较差,在多雨季节施工,雨水冲刷会对填方质量产生较大的影响。通过对不同红黏土掺量的花岗岩残积土进行渗透试验和无侧限抗压强度试验,研究红黏土掺量对花岗岩残积土的渗透系数和无侧限抗压强度的影响趋势;在室内试验的基础上选取具体工程进行填方对比试验。研究结果认为:花岗岩残积土的渗透系数随着红黏土掺量的增加而减小;无侧限抗压强度随着红黏土掺量的增加而增大;花岗岩残积土中红黏土的最优掺量是40%,具体工程中采取2车花岗岩残积土加1车红黏土的“3+2”混合填料法能达到较好的填方效果。研究结果为花岗岩残积土地区工程建设的基础材料填筑与加固提供参考。
(
|
| [16] |
鞠远江, 胡明鉴, 秦坤坤, 等. 珊瑚礁岛钙质砂细颗粒渗透运移规律研究[J]. 岩土力学, 2021, 42(5): 1245-1252, 1265.
(
|
| [17] |
|
| [18] |
吴炎, 丁姝昱, 赵浩楠, 等. 不同浓度ZnCl2污染粉质黏土强度特性试验[J]. 土木工程与管理学报, 2020, 37(6): 108-112,123.
(
|
| [19] |
Soil washing is an effective technology for the remediation of multi-metal contaminated soils. However, bioavailability of residual heavy metals in soils and soil properties could be changed during washing processes. This study investigated the effects of EDTA, FeCl and mixed chelators (MC) on bioavailability of residual heavy metals in soils and soil biological properties after soil washing. The results showed that soil washing by chelators successfully decreased the total concentration of heavy metals in soils, while it did not effectively decrease the exchangeable fraction of heavy metals, especially for calcareous contaminated soil. The toxic effects of the washed soils seemed to exhibit higher correlations with the changes in the soil properties such as soil pH and nutrient concentrations. As compared with FeCl and EDTA, MC tended to moderately change soil properties (e.g., pH, total N, available N, available P, and exchangeable K, Ca, and Mg). Additionally, MC-washed soil had the least influence on the soil enzymes activities, and had the highest germination and growth of Chinese cabbage. Accordingly, MC is a moderate washing solution in the removal of heavy metals from multi-metal contaminated soils, and had minimal negative effects on soil qualities.Copyright © 2018 Elsevier Ltd. All rights reserved.
|
| [20] |
|
| [21] |
饶为国, 马福荣, 陈日高, 等. 重金属污染对土压实性及抗剪强度影响的试验研究[J]. 工业建筑, 2013, 43(4):92-97.
(
|
| [22] |
方兴斌, 张汝壮. 土壤粒径和参数对重金属淋洗的影响分析[J]. 环保科技, 2022, 28(6):6-10.
(
|
| [23] |
|
| [24] |
|
| [25] |
|
| [26] |
王哲, 黄国和, 安春江, 等. Cu2+、Cd2+、Zn2+在高炉水淬渣上的竞争吸附特性[J]. 化工进展, 2015, 34(11):4071-4078.
利用等温吸附法考察了高炉水淬渣对Cu<sup>2+</sup>、Cd<sup>2+</sup>、Zn<sup>2+</sup>的单组分吸附和竞争吸附性能。结果表明,单一组分吸附时,金属离子吸附等温线属于“H”形等温线,吸附平衡符合Langmuir吸附等温模型,高炉水淬渣吸附的顺序为Cu<sup>2+</sup> >Cd<sup>2+</sup> >Zn<sup>2+</sup>,这与重金属离子电负性、水合离子半径及荷径比等有关。当加入竞争离子后,Cu<sup>2+</sup>的吸附等温线基本维持原来形状,且仍旧与Langmuir吸附等温模型比较相符,而Cd<sup>2+</sup> 和Zn<sup>2+</sup>的吸附无法与现有等温吸附模型很好地拟合,等温线的形状由于竞争作用也与传统的等温线均不相同,同时各金属离子的吸附量都比单组分的吸附量降低了。吸附动力学过程先是一个快速阶段,然后进入慢速阶段。无论是单组分还是竞争条件下,伪二级动力学方程拟合结果较好,说明高炉水淬渣与Cu<sup>2+</sup>、Cd<sup>2+</sup>、Zn<sup>2+</sup>之间的吸附过程主要是以化学吸附为主。
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The single-component and competitive adsorption properties of Cu<sup>2+</sup>、Cd<sup>2+</sup>、Zn<sup>2+</sup> ions on water-quenched blast furnace slag (WBFS) were investigated by isothermal adsorption experiment. The results showed the adsorption process and isotherm curves of the metal ions followed Langmuir isotherm model and “H” type in single-component adsorption, respectively. The order of the adsorption capacities was Cu<sup>2+</sup>> Cd<sup>2+</sup>> Zn<sup>2+</sup>, which determined mainly by the electro negativity, hydrated ionic radius and charge to radius ratio. The adsorption isotherms of Cu<sup>2+</sup> maintained the original shape and still fitted to Langmuir adsorption model in competitive condition, while the other adsorption model could not well represent the competitive adsorption of Cd<sup>2+</sup> and Zn<sup>2+</sup>. The mutual competition and antagonism effect of heavy metals in competitive system resulted in the irregularity of sorption isotherm curves of Cd<sup>2+</sup> and Zn<sup>2+</sup>. The adsorption capacities of the competitive ions on WBFS decreased to some extent compared with those of single ion adsorption. The sorption kinetic processes were rapid first and followed slow in accordance with pseudo-second-order kinetic model, which suggested that the process controlling the rate may be a chemical sorption between WBFS and Cu<sup>2+</sup>、Cd<sup>2+</sup>、Zn<sup>2+</sup>.
|
| [27] |
丁国权, 陈凯. 激光粒度仪在特殊土颗粒分析试验中的应用[J]. raybet体育在线
院报, 2024, 41(9):123-129.
采用激光粒度仪对膨胀土、黄土和红土进行了颗粒分析试验,研究了取样质量和超声波分散时间对试验结果的影响,发现遮光率与取样质量呈现很好的线性正相关,给出了特殊土在激光粒度仪法试验中适宜的遮光率范围(15%~25%)、取样质量(膨胀土取0.1~0.2 g,黄土取0.4~0.8 g,红土取0.2~0.4 g)和超声波分散时间(膨胀土取6 min,黄土和红土取2 min);激光粒度仪法试验结果的离散性,对于黄土和膨胀土较小,但对红土相对较大,红土平行试验中粒组含量极差的最大值为10.1%;与密度计法相比,激光粒度仪法测得的胶粒(0,0.002]mm含量偏小,而黏粒(0.002,0.005]mm或更大粒组的含量则偏大,可能是因为两者试验原理的不同而导致的;2种方法对红土的测试结果差异较大,与红土的特殊性质有一定关系。研究成果为激光粒度仪在特殊土颗粒分析试验中的应用提供了借鉴。
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