岩土力学 ›› 2019, Vol. 40 ›› Issue (8): 2989-2996.doi: 10.16285/j.rsm.2018.0766

• 基础理论与实验研究 • 上一篇    下一篇

基于改进滤失试验的重金属污染 膨润土渗透特性试验研究

范日东1, 2，刘松玉1, 2，杜延军1, 2   

  1. 1. 东南大学 岩土工程研究所，江苏 南京 210096；2. 东南大学 江苏省城市地下工程与环境安全重点实验室，江苏 南京 210096
  • 收稿日期:2018-05-04 出版日期:2019-08-12 发布日期:2019-08-25
  • 通讯作者: 杜延军，男，1972年生，博士，教授，博士生导师，主要从事环境岩土工程和特殊土地基处理等方面的研究。E-mail: duyanjun@seu.edu.cn E-mail: fanrd@seu.edu.cn
  • 作者简介:范日东，男，1988年生，博士，主要从事环境岩土工程方面的研究
  • 基金资助:
    国家重点研发计划（No. 2018YFC1803100，No. 2018YFC1802300）；国家自然科学基金（No. 41877248）；江苏省重点研发计划（No. BE2017715）；中国博士后科学基金（No. 2018M642143）；中央高校基本科研业务费专项（No. 2242019R20033）。

Modified fluid loss test for measuring the hydraulic conductivity of heavy metal-contaminated bentonites

FAN Ri-dong1, 2, LIU Song-yu1, 2, DU Yan-jun1, 2   

  1. 1. Institute of Geotechnical Engineering, Southeast University, Nanjing, Jiangsu 210096, China; 2. Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety, Southeast University, Nanjing, Jiangsu 210096, China
  • Received:2018-05-04 Online:2019-08-12 Published:2019-08-25
  • Supported by:
    This work was supported by the National Key Research and Development Program (2018YFC1803100, 2018YFC1802300), the National Natural Science Foundation of China (41877248), the Primary Research & Development Plan of Jiangsu Province (BE2017715), the China Postdoctoral Science Foundation (2018M642143) and the Fundamental Research Funds for the Central Universities (2242019R20033).

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摘要： 通过改进滤失试验研究典型钠化改性钙基和天然钠基膨润土在重金属铅-镉以及铬作用下渗透系数的变化规律。研究发现，膨润土试样渗透系数在重金属铅-镉浓度小于6 mmol/L时增幅较小，为2～3倍；当浓度超过10 mmol/L时呈急剧增大的趋势。铬酸钾溶液作用下，钠化改性钙基膨润土的渗透系数低于未污染试样；天然钠基膨润土的渗透系数则增大2～8倍。两者差异归因于土-液相互作用下铬在不同pH-Eh环境中化学形态的不同。研究中钠化改性钙基膨润土浆液中铬以阴离子络合的六价铬形态存在，使得膨润土颗粒表面负电荷密度趋于增加，因而保持和促进膨润土的分散状态。天然钠基膨润土浆液中铬则出现以阳离子形态存在的三价铬，显著挤压膨润土颗粒双电层，导致膨润土颗粒团聚。综合国内外研究总结无机盐溶液作用下膨润土化学相容性随污染程度变化规律，发现渗透系数比与离子强度关系存在一临界值，当离子强度达到该临界值则渗透系数将呈数量级增大。

关键词: 膨润土, 渗透系数, 重金属, 化学形态

Abstract: A series of modified fluid loss tests was carried out to investigate the hydraulic conductivities (k) of typical sodium treated Ca-bentonite (CaB) and natural Na-bentonite (NaB) contaminated by lead-cadmium (Pb-Cd) and chromium (Cr). The results showed that when the bentonite was exposed to Pb-Cd concentration lower than six mmol/L, its permeability coefficient exhibited a smaller increase by approximately 2 to 3 times, while it increased significantly when Pb-Cd concentration increased to 10 mmol/L. Under the action of potassium chromate, the k of Cr-contaminated sodium-treated CaB sample was slightly lower than that of uncontaminated samples, whereas the k of Cr-contaminated NaB sample was approximately 2 to 8 times higher than that of uncontaminated samples. The results can be attributed to the different forms of chromium existing in bentonite slurry under soil-liquid interaction in different pH-Eh conditions. Since chromium exists in the anionic complex as Cr(VI) in sodium treated CaB slurry, the negatively charged bentonite particles increase, which enhances the dispersed state of the bentonite. In contrast, Cr(III) cation is identified in NaB slurry, which leads to the aggregation of bentonite particles due to the diffuse double layer contraction. A comprehensive analysis was conducted on the variation of chemical compatibility of bentonites under ionic strength obtained from this study associated with those reported in the literature. It is found that a threshold of ionic strength exists, k increases more than an order of magnitude beyond the threshold.

Key words: bentonite, hydraulic conductivity, heavy metal, chemical species

中图分类号: 

  • TU 443
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