为深入分析土-膨润土混合物对重金属离子的吸附特性,文章开展典型尾矿库中Cu^(2+)在土-膨润土混合物中的吸附试验,探讨土-膨润土混合物对Cu^(2+)的吸附特征。结果表明:增大膨润土掺量,土-膨润土混合物对Cu^(2+)最大吸附量和去除率均提升...为深入分析土-膨润土混合物对重金属离子的吸附特性,文章开展典型尾矿库中Cu^(2+)在土-膨润土混合物中的吸附试验,探讨土-膨润土混合物对Cu^(2+)的吸附特征。结果表明:增大膨润土掺量,土-膨润土混合物对Cu^(2+)最大吸附量和去除率均提升;同一膨润土掺量下,初始Cu^(2+)质量浓度越高,去除率越低。吸附等温模型分析表明:3种模型均适用于试验的吸附特征,基于Langmuir模型的最大吸附量在膨润土掺量增加至20%时,Cu^(2+)最大吸附量Q_(m)增加了29.99%,表明膨润土的掺入可显著提升混合物吸附能力;基于Freundlich模型的吸附常数K_(F)随膨润土掺量增大而增大,表明膨润土掺量越大,吸附能力越强;基于D-R模型,当膨润土掺量为0~20%时,混合物吸附特性主要由离子交换吸附所控制,并通过X射线衍射(X-ray diffraction,XRD)、扫描电子显微镜(scanning electron microscope,SEM)等分析,表明土-膨润土的吸附机理主要表现为离子交换吸附。展开更多
A series of centrifuge model tests exploring the effects of different types of slurry on long-trench stability in soft clay were conducted. The influence of groundwater conditions relative to trench stability was exam...A series of centrifuge model tests exploring the effects of different types of slurry on long-trench stability in soft clay were conducted. The influence of groundwater conditions relative to trench stability was examined by constructing long trenches using different slurries. The soil deformation and surface settlement induced by the excavation of the trench are found to be closely related to slurry type and excavation depth of the long trench. Increasing the bentonite concentration of the slurry has beneficial effects on stability: 1) larger particles can improve local and global stability in cases where filter cakes do not form, and 2) larger viscosity can promote filter cake formation on the walls of long trenches excavated in soft clay and enhance their stability.展开更多
Laboratory tests under different constraint conditions were carried out to obtain the soil-water retention curves(SWRCs) of highly-compacted confined/unconfined Gaomiaozi(GMZ) bentonite at 20,40 and 80 ℃,respectively...Laboratory tests under different constraint conditions were carried out to obtain the soil-water retention curves(SWRCs) of highly-compacted confined/unconfined Gaomiaozi(GMZ) bentonite at 20,40 and 80 ℃,respectively. The effect of temperature on the soil-water characteristics of the highly-compacted GMZ bentonite was analyzed. The results show that the water retention capacity of the highly-compacted GMZ bentonite decreases as the temperature increases under unconfined and confined conditions. At a certain temperature,the constraint conditions have little influence on the water retention capacity of the compacted bentonite at high suction,but the water retention capacity of the confined specimen is lower than that of the unconfined specimen at low suction. Under unconfined conditions,the hysteretic behaviour of the compacted bentonite decreases with increasing temperature. At high suction(>4 MPa) ,the hysteretic behaviour of the unconfined bentonite tends to increase with the decrease of the suction. In summary,the hysteretic behaviour of the compacted bentonite is not significant.展开更多
Soil-bentonite （SB） vertical slurry cutoff wall is a useful treatment for urban industrial contaminated sites. Due to the clay-heavy metal interaction, significant changes would occur in the engineering behavior of ...Soil-bentonite （SB） vertical slurry cutoff wall is a useful treatment for urban industrial contaminated sites. Due to the clay-heavy metal interaction, significant changes would occur in the engineering behavior of SB cutoff walls. However, previous study is limited to kaolinitic soils or montmorillonitic soils along using solidum chloride and/or calcium chloride as target contaminant. In this work, a series of oedometer tests were conducted to investigate the effects of lead （Pb） on the compressibility and the permeability of kaolin-bentonite （KB） mixtures, a simplified model of in-situ SB cutoff wall backfills. In addition, sedimentation tests were conducted to interpret the mechanism controlling the change of compressibility and permeability from the perspective of soil fabric. The Pb-contaminated KB mixtures for oedometer tests and sedimentation tests were prepared with bentonite contents of 0, 5%, 10%, and 15% by dry mass, and they were mixed with pre-determined volume of lead nitrate solution based on designed Pb concentration and solid-to-solution ratio. The Pb concentration was controlled as 0, 0.1, 0.5, 1.0, 5.0, 10, and 50 mg/g with a solid-to-solution ratio of approximate 0.5. The prepared KB mixtures with bentonite contents of 0, 5%, and 10% were chosen for the sedimentation tests. They were freeze-dried and mixed with DDI with a solid-to-solution ratio of 10 g/100 mL. The results indicate that pH, compressibility, and permeability of KB mixture changed considerably with respect to Pb concentration. It is concluded that the fabric of KB mixture, depending on the particle-particle interaction subjected to different ranges of pH and Pb concentration, governs the sedimentation behavior and permeability. The results of liquid limit （WE） cannot be explained in terms of the sedimentation behavior since it is only ionic-dependent.展开更多
Bentonite has been proven to be effective in enhancing the membrane property of clay, by which landfill liners can have better barrier performance with regard to the migration of contaminants. In this work, 5% sodium ...Bentonite has been proven to be effective in enhancing the membrane property of clay, by which landfill liners can have better barrier performance with regard to the migration of contaminants. In this work, 5% sodium bentonite amended with locally available Fukakusa clay was utilized to evaluate the membrane behavior toward different kinds of ions： K, Na and Ca. The chemico-osmotic efficiency coefficient, co, was obtained in electrolyte solution with different concentrations of 0.5, 1, 5, 10, and 50 mmol/L. According to the results, solute type and ion valence have a significant effect on membrane behaviors. Additionally, co continually decreased as the Na and Ca concentrations increased, which is consistent with the Gouy-Chapman theory. The membrane behavior toward Na was similar to that toward K, according to the chemico-osmotic efficiency coefficient co. In the case of the divalent ion Ca, the membrane behavior was lower compared to monovalent ions Na and K at the same concentration. The mechanisms of the membrane performance change were discussed with the assistance of XRD patterns, free-swelling results and SEM images.展开更多
文摘为深入分析土-膨润土混合物对重金属离子的吸附特性,文章开展典型尾矿库中Cu^(2+)在土-膨润土混合物中的吸附试验,探讨土-膨润土混合物对Cu^(2+)的吸附特征。结果表明:增大膨润土掺量,土-膨润土混合物对Cu^(2+)最大吸附量和去除率均提升;同一膨润土掺量下,初始Cu^(2+)质量浓度越高,去除率越低。吸附等温模型分析表明:3种模型均适用于试验的吸附特征,基于Langmuir模型的最大吸附量在膨润土掺量增加至20%时,Cu^(2+)最大吸附量Q_(m)增加了29.99%,表明膨润土的掺入可显著提升混合物吸附能力;基于Freundlich模型的吸附常数K_(F)随膨润土掺量增大而增大,表明膨润土掺量越大,吸附能力越强;基于D-R模型,当膨润土掺量为0~20%时,混合物吸附特性主要由离子交换吸附所控制,并通过X射线衍射(X-ray diffraction,XRD)、扫描电子显微镜(scanning electron microscope,SEM)等分析,表明土-膨润土的吸附机理主要表现为离子交换吸附。
文摘通过在膨润土中掺入不同量的CaCO3模拟高放射性核废料(high-level radioactive waste,HLW)处置库周围地下水侵入屏障生成CaCO3后膨润土性状的变化。通过配置4组不同CaCO3掺入量的膨润土进行了有荷膨胀试验、压缩试验和直剪试验,运用太沙基一维固结理论计算了渗透系数,并采用扫描电子显微镜(scanning electron microscopy,SEM)对样本进行了微观分析。结果表明:最终膨胀率与竖向应力、CaCO3含量有关,竖向应力越大,CaCO3含量越高,最终膨胀率越小;压缩指数随CaCO3含量的增大而小幅下降;随着CaCO3含量的增多,膨润土-碳酸钙混合土渗透性变差;非饱和样的抗剪强度随CaCO3含量变化存在一个峰值,黏聚力先增后减,饱和样则相反;电镜扫描图显示,CaCO3的掺入填充了膨润土中的孔隙,使其结构更加致密。
基金Project(41202220)supported by the National Natural Science Foundation of ChinaProject(20120022120003)supported by the Research Fund for the Doctoral Program of Higher Education,ChinaProject(2652012065)supported by the Fundamental Research Funds for the Central Universities and Beijing Higher Education Young Elite Teacher Program,China
文摘A series of centrifuge model tests exploring the effects of different types of slurry on long-trench stability in soft clay were conducted. The influence of groundwater conditions relative to trench stability was examined by constructing long trenches using different slurries. The soil deformation and surface settlement induced by the excavation of the trench are found to be closely related to slurry type and excavation depth of the long trench. Increasing the bentonite concentration of the slurry has beneficial effects on stability: 1) larger particles can improve local and global stability in cases where filter cakes do not form, and 2) larger viscosity can promote filter cake formation on the walls of long trenches excavated in soft clay and enhance their stability.
基金Projects(40772180, 40572161, 40802064) supported by the National Natural Science Foundation of ChinaProject ([2007]831) supported by Commission of Science, Technology and Industry for National Defense of China+3 种基金Project(07JJ4012) supported by Hunan Provincial Natural Science Foundation of ChinaProject(20080430680) supported by China Postdoctoral Science FoundationProject(08R214155) supported by Shanghai Postdoctoral Scientific Program of ChinaProject(B308) supported by Shanghai Leading Academic Discipline Project of China
文摘Laboratory tests under different constraint conditions were carried out to obtain the soil-water retention curves(SWRCs) of highly-compacted confined/unconfined Gaomiaozi(GMZ) bentonite at 20,40 and 80 ℃,respectively. The effect of temperature on the soil-water characteristics of the highly-compacted GMZ bentonite was analyzed. The results show that the water retention capacity of the highly-compacted GMZ bentonite decreases as the temperature increases under unconfined and confined conditions. At a certain temperature,the constraint conditions have little influence on the water retention capacity of the compacted bentonite at high suction,but the water retention capacity of the confined specimen is lower than that of the unconfined specimen at low suction. Under unconfined conditions,the hysteretic behaviour of the compacted bentonite decreases with increasing temperature. At high suction(>4 MPa) ,the hysteretic behaviour of the unconfined bentonite tends to increase with the decrease of the suction. In summary,the hysteretic behaviour of the compacted bentonite is not significant.
基金Project(51278100) supported by the National Natural Science Foundation of ChinaProjects(BK2010060, BK2012022) supported by the Natural Science Foundation of Jiangsu Province, ChinaProject(103) supported by the Scientific Innovation Research of University Graduate Students of Jiangsu Province, China
文摘Soil-bentonite （SB） vertical slurry cutoff wall is a useful treatment for urban industrial contaminated sites. Due to the clay-heavy metal interaction, significant changes would occur in the engineering behavior of SB cutoff walls. However, previous study is limited to kaolinitic soils or montmorillonitic soils along using solidum chloride and/or calcium chloride as target contaminant. In this work, a series of oedometer tests were conducted to investigate the effects of lead （Pb） on the compressibility and the permeability of kaolin-bentonite （KB） mixtures, a simplified model of in-situ SB cutoff wall backfills. In addition, sedimentation tests were conducted to interpret the mechanism controlling the change of compressibility and permeability from the perspective of soil fabric. The Pb-contaminated KB mixtures for oedometer tests and sedimentation tests were prepared with bentonite contents of 0, 5%, 10%, and 15% by dry mass, and they were mixed with pre-determined volume of lead nitrate solution based on designed Pb concentration and solid-to-solution ratio. The Pb concentration was controlled as 0, 0.1, 0.5, 1.0, 5.0, 10, and 50 mg/g with a solid-to-solution ratio of approximate 0.5. The prepared KB mixtures with bentonite contents of 0, 5%, and 10% were chosen for the sedimentation tests. They were freeze-dried and mixed with DDI with a solid-to-solution ratio of 10 g/100 mL. The results indicate that pH, compressibility, and permeability of KB mixture changed considerably with respect to Pb concentration. It is concluded that the fabric of KB mixture, depending on the particle-particle interaction subjected to different ranges of pH and Pb concentration, governs the sedimentation behavior and permeability. The results of liquid limit （WE） cannot be explained in terms of the sedimentation behavior since it is only ionic-dependent.
基金Projects(51179168,51308310)supported by National Natural Science Foundation of ChinaProject(LQ13E080007)supported by Zhejiang Provincial Natural Science Foundation of ChinaProject supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars(Chinese State Education Ministry)
文摘Bentonite has been proven to be effective in enhancing the membrane property of clay, by which landfill liners can have better barrier performance with regard to the migration of contaminants. In this work, 5% sodium bentonite amended with locally available Fukakusa clay was utilized to evaluate the membrane behavior toward different kinds of ions： K, Na and Ca. The chemico-osmotic efficiency coefficient, co, was obtained in electrolyte solution with different concentrations of 0.5, 1, 5, 10, and 50 mmol/L. According to the results, solute type and ion valence have a significant effect on membrane behaviors. Additionally, co continually decreased as the Na and Ca concentrations increased, which is consistent with the Gouy-Chapman theory. The membrane behavior toward Na was similar to that toward K, according to the chemico-osmotic efficiency coefficient co. In the case of the divalent ion Ca, the membrane behavior was lower compared to monovalent ions Na and K at the same concentration. The mechanisms of the membrane performance change were discussed with the assistance of XRD patterns, free-swelling results and SEM images.
