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1.
Sorptive removal of ibuprofen from water using selected soil minerals and activated carbon 总被引：1，自引：1，他引：0
S. K. Behera S. Y. Oh H. S. Park 《International Journal of Environmental Science and Technology》2012,9(1):85-94
Pharmaceuticals have gained significant attention in recent years due to the environmental risks posed by their versatile application and occurrence in the natural aquatic environment. The transportation and distribution of pharmaceuticals in the environmental media mainly depends on their sorption behavior in soils, sediment?Cwater systems and waste water treatment plants, which varies widely across pharmaceuticals. Sorption of ibuprofen, a non-steroidal anti-inflammatory drug, onto various soil minerals, viz., kaolinite, montmorillonite, goethite, and activated carbon, as a function of pH (3?C11), ionic strength (NaCl concentration: 0.001?C0.5?M), and the humic acid concentration (0?C1,000?mg/L) was investigated through batch experiments. Experimental results showed that the sorption of ibuprofen onto all sorbents was highest at pH 3, with highest sorption capacity for activated carbon (28.5?mg/g). Among the minerals, montmorillonite sorbed more ibuprofen than kaolinite and goethite, with sorption capacity increasing in the order goethite (2.2?mg/g)?<?kaolinite (3.1?mg/g)?<?montmorillonite (6.1?mg/g). The sorption capacity of the selected minerals increased with increase in ionic strength of the solution in acidic pH condition indicating that the effect of pH was predominant compared to that of ionic strength. An increase in humic acid concentration from low to high values made the sorption phenomena very complex in the soil minerals. Based on the experimental observations, montmorillonite, among the selected soil minerals, could serve as a good candidate to remove high concentrations of ibuprofen from aqueous solution. 相似文献
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Amin Eisazadeh Khairul Anuar Kassim Hadi Nur 《Geotechnical and Geological Engineering》2012,30(6):1435-1440
Studies on the chemically stabilized soils have shown that the effectiveness of treatment is largely dependent on soil??s natural environment. In this research, the time-dependent changes induced in permanent cation exchange capacity of lime and phosphoric acid treated soils, comprised mainly of montmorillonite and kaolinite minerals, were investigated. Also, in order to study the relationship between the exchange capacity and acidity/alkalinity of pore water, pH measurements were performed on cured samples. Based on the collected data, it was found that the pH of stabilized soils showed a tendency for reaching soil??s natural pH with increasing curing time. In addition, the increase in number of broken bonds around the edges of soil particles and also the formation of cementitious compounds that acquired negative charges contributed to achieving higher CECp values at longer curing periods. Nevertheless, the kaolinite mineral with pH-dependent structural properties, showed a rather limited behavior in the acidic medium. From engineering point of view, the lime treated samples revealed the highest degree of improvement with an approximately ten-fold strength increase in comparison to the natural soil over an 8?months curing period. 相似文献
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盐渍土冻结温度的试验研究 总被引：16，自引：6，他引：10
冻结温度是判别土体是否处于冻结状态的指标,在人工冻结和数值模拟计算中影响冻结壁的厚度和计算精度.通过采用不同土体添加不同的盐分,对不同含水量和含盐量土体进行盐渍土的冻结温度试验,考虑了不同因素对土体冻结温度的影响.实验表明：不论何种土含有何种离子,土体的冻结温度随含盐量的增加而降低,随含水量的增加而增大;土中易溶盐的含... 相似文献
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针对当前水土压力计算中很少考虑土自身性质对其影响的研究现状,以自制试验槽为研究工具,通过使用3种不同渗透性土样进行的支挡结构上水土压力测试研究,对比了水土压力实测值和由水土压力分算、水土压力合算得到的理论计算值,分析了孔隙水压力和土压力的变化规律。由试验结果可以得到,由水土压力合算得到结果偏小,但在一定条件下尚可以接受,在发生主动位移情况下墙后土体会产生负超孔压,渗透系数影响着负超孔压的消散和孔隙水压力的传递程度,并进一步影响支挡结构上水土压力的分布情况。由试验结果推知,当土体渗透系数小到一定程度时,水土压力合算的方法是合理的。 相似文献
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冻结作用对青藏红黏土及兰州粉土微观结构的影响分析 总被引：1，自引：0，他引：1
冻土微观孔隙特征是决定冻土体一系列物理、力学性质的基本参数,冻土中存在的冰晶体其体积受温度影响发生变化会影响到冻土的土体微观结构及孔隙特质发生变化。利用可用于负温冻土观测的新型扫描电镜,通过对青藏红黏土及兰州粉土不同初始条件下的土样冻结前后微观结构进行研究分析。结果表明：冻结作用发生后,冰晶生长对周围土颗粒产生挤压作用,导致周围土颗粒的移动和结构破坏,土中大孔隙的数量增多,加之周围小孔隙补给大孔隙中的冰晶进一步生长,出现局部个别大孔隙体积增大,小孔隙体积缩小的现象,表现在孔隙率上为土体在冻结后孔隙率减小;此外,对于粒径级配不同的土体而言,冻结作用对细颗粒土的土体孔隙的尺寸、形态以及排列方式等方面的影响均大于粗颗粒土;同样,初始含水率决定了冻结作用发生后参与改变土体微观结构的冰晶体生长的"量"的大小,在冻结作用对土体结构性破坏的过程中起重要作用。研究成果定量揭示了冻结作用对不同初始条件下的土体微观结构的影响,为研究冻土宏观力学特性和冻胀机制等提供了理论基础与和试验支撑。 相似文献
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改变边界温度和土样高度,对饱和粉土进行了冻结试验,研究其水分迁移、水分重分布、冻胀和冰透镜体的发展规律。试验结果表明：当温度稳定时,水分持续迁移到冻结锋面附近,含水率急剧增大,易形成冰透镜体。饱和粉土冰透镜体几何形态较为规则,无枝状交叉结构,已冻土为整体状且无网状裂隙。冻结过程中存在起始冻胀时间,在起始冻胀时间之前,土中水分被排出,冻胀发生之后水分补给到冻土中,且补给水分产生的冻胀量和总冻胀量数值接近。土样高度影响水分迁移量和冻胀量,土样越高,冻胀量越小,冻土含水率增量越小,但水分增量分布区域越分散,且起始冻胀时间越长。 相似文献
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红壤中矿物表面对腐殖质吸附萘的影响 总被引：5，自引：1，他引：5
矿物表面可改变土壤腐殖质对疏水性有机污染物的结合能力。采用红壤和高岭石分别与胡敏酸结合制备得到的两种复合体对萘的吸附等温线非线性显著,其n=0.76或0.74,并且有机碳归一化吸附分配系数的实验值Koacds是采用Kow计算得出的理论值Koc的5倍以上,表明红壤、高岭石均对腐殖质吸附萘有强化作用,且红壤较之高岭石对腐殖质吸附萘的影响稍强些。主要原因是,红壤中除了高岭石外,还有与腐殖质结合力很强的铁氧化物,而且很可能是吸附态腐殖质组成结构形态发生了有利于对萘吸附的改变。 相似文献
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土体冻结特征曲线（SFCC）是对冻土中未冻水含量随负温变化关系的数学描述,是研究冻土水热迁移、冻胀、本构关系等问题的重要基础。目前对于SFCC的研究,其经验表达式居多,而物理机制研究相对较少。通过考虑土颗粒与冰界面的吸附作用及冰相尖点的毛细作用,基于冰水相变平衡压力由吸附压力与毛细压力两部分共同组成,从孔隙尺度提出一个新的饱和冻土SFCC模型。模型计算结果表明,当颗粒半径逐渐增大时,相同温度下未冻水含量将不断减小,SFCC也会变得更加陡峭。基于核磁共振设备对单分散SiO2微球冻融过程SFCC进行测试,试验结果与数学模型进行比较验证,结果表明新的SFCC模型与试验结果吻合较好,且具有明确的物理意义,可以为冻土基础研究提供理论依据。 相似文献
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三峡库区重庆段土壤某些重金属污染的矿物学方法评价 总被引：1，自引：0，他引：1
分析了三峡库区重庆段51件土壤样品的矿物组成,结果表明,石英、斜长石和钾长石是土壤中主要矿物,大部分样品中石英的含量高,主要粘土矿物是伊利石,其次是蒙脱石,其他矿物含量较低。同时,参比国家水质标准,根据土壤对金属离子的临界吸附量公式计算了样品重金属污染的阈值,对样品进行了Cd、Hg、Pb、Cu的污染状况评价。结果表明,土壤中污染元素的含量与生态效应评价值并不一致;Cd和Hg的污染尚未达到临界值,危险性较小,但不能因此忽视地球化学定时炸弹的风险;Pb和Cu的污染严重。由于包括母岩在内的样品的评价结果显示污染,可能反映研究区的地球化学背景,需要采取有效措施改善和预防目前和将来的污染危害。 相似文献
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Soil suction is the most relevant soil parameter for characterization of the swell behavior. An attempt was made to predict swell pressures from soil suction measurements. In this study, Na-bentonite was mixed with kaolinite in the ratios of 5, 10, 15, 20 and 25% of dry kaolinite weight to obtain soils in a wide range of plasticity indices (i.e. 30, 50, 68, 84 and 97%). Suction measurements using thermocouple psychrometer technique were made on statically compacted specimens. The dependence of soil suction on water content, dry density and bentonite content was examined. Soil suction was correlated to the soil properties, namely, water content, plasticity index, dry density, cation exchange capacity and specific surface area using multiple regression analyses. The correlations revealed a simple regression equation for a quick prediction of soil suctions from easily determined soil properties. In order to investigate soil suction versus swell pressure behavior, the results of standard constant volume swell tests (ASTM, 1990) performed on statically compacted samples of these clay mixtures were used. A linear relationship was established between the logarithm soil suction and the swell pressure. It was also found that an experimental relationship which would directly relate the initial soil suction to the swell pressure can be established. 相似文献
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The hydrogen isotope fractionation between kaolinite and water 总被引：1，自引：0，他引：1
Hydrogen isotope fractionation factors between kaolinite and water were determined at temperatures between 200° and 352°C. Five-gram samples of kaolinite were heated in contact with 8-mg samples of water in sealed glass reaction tubes. Under these conditions the approach to equilibrium with time will be reflected primarily in the change of the δ D in the water. Also the δ D of the hydrogen in the kaolinite will be relatively constant, subject to minor corrections. About seventy sealed vessels were heated for various times at various temperatures. During four months of heating, ～ 25% of kaolinite hydrogen exchanged with the water at 200°C, whereas 100% exchanged at 352°C. The α-values were estimated assuming equilibrium between exchanged kaolinite and water. The 103lnα-values are estimated to be ?20, ?15, ?6 and +7 for 352°, 300°, 250° and 200°C, respectively, which are in approximate agreement with reported values previously determined at 400°C using conventional methods as well as those estimated from kaolinite in hydrothermally active systems. The curve representing the relationship between the hydrogen isotope fractionation factor for the kaolinite-water system and temperatures between 400° and 25°C is not monotonic but rather has a maximum at 200°C. 相似文献
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Hamid Reza Tabatabaiefar 《Geomechanics and Geoengineering》2017,12(1):28-35
In this study, a synthetic soil mixture has been developed and proposed for experimental soil-structure interaction shaking table tests on building frames with shallow foundations resting on soft soil deposits. The proposed mix provides adequate undrained shear strength to mobilise the required shallow foundation bearing capacity underneath the structural model while meeting both criteria of dynamic similarity between the model and the prototype to model soft soils in shaking table tests. To find the most appropriate mixture, different mixes with different proportions of mix components were examined in the soils laboratory. Performing bender element tests, the shear wave velocity of the soil specimens was acquired at different cure ages and the results were examined and compared. Based on the test results, a synthetic clay mixture consisting of kaolinite clay, bentonite, fly ash, lime and water has been proposed for experimental shaking table tests. 相似文献
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The through-diffusion of HTO, 22Na+ and 36Cl− in kaolinite, homo-ionic Na-illite and homo-ionic Na-montmorillonite was measured at a high degree of compaction as a function of the salt concentration in the ‘external solution’, i.e. in the solution in contact with the clay sample. The clays were chosen for this study because of their differences in the number and nature of ion exchange sites leading to different proportions of interlayer-, inter-particle and free pore water. It was found that the diffusive mass transfer of Na+ in Na-montmorillonite and Na-illite increased with decreasing external salt concentration, while the opposite trend was observed for the diffusion of Cl−. These trends are more pronounced in the case of Na-montmorillonite than in Na-illite, while almost no salt effect was observed for kaolinite. Similarly no salt effect was observed for the diffusion of HTO through all of the clays tested. These observations are in agreement with a conceptual model where it is assumed that cations diffuse preferentially in the interlayer or diffuse double-layer porosity, while anions are almost completely excluded from these regions. In the case of Na+ diffusion, the salt effects can be explained by an influence on the concentration gradient of diffusing cations, while in the case of Cl− the external salt concentration has an effect on the accessible porosity. Effective diffusion coefficients of Cl− fulfil the same relationship to porosity as those of the uncharged HTO, when using accessible porosities for such a comparison. Furthermore it is shown that pore diffusion coefficients for the three tracers are fairly well correlated with the respective diffusion coefficients in bulk water, if the effective diffusion coefficients for Na+ are derived from calculated tracer concentration gradients in the interlayer or diffuse double-layer porosities. 相似文献
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利用测温法和核磁共振法测量了不同浓度典型盐溶液（NaCl、Na2CO3）饱和重塑粉土的冻结温度及冻结特征曲线，并与不同浓度的NaCl、Na2CO3纯溶液作对比分析，研究初始含盐量对冻结温度及未冻水含量的影响。结果表明：土样冻结温度随初始含盐量的增加而逐渐降低；相同浓度NaCl溶液饱和土样的冻结温度低于相应纯溶液的冻结温度，但相同浓度 （<0.6 mol/L）Na2CO3溶液饱和土样的冻结温度却比纯溶液的冻结温度高；同一负温下，土样中未冻水含量随NaCl初始含盐量的增加而增多，但随Na2CO3初始含盐量的变化不明显。通过机制分析，表明盐类型和含盐量对土水势具有不同的影响。基于改进的广义Clapeyron方程，将含盐分土冻结温度表达式引入未冻水含量预测模型，得到了能够考虑不同含盐量影响的土体未冻水含量的定量表达，并与实测数据进行对比，验证了该模型能够较为合理的预测不同温度下含盐土体的未冻水含量。 相似文献
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高岭石和蒙脱石分别是暖湿和冷干气候带内典型土壤的代表性矿物,对二者吸附胡敏酸特点的对比研究可以为探索不同地带土壤中重金属的环境行为提供重要的依据。笔者通过一系列实验研究了pH值、离子强度和胡敏酸初始浓度对胡敏酸在高岭石和蒙脱石上吸附量的影响,重点剖析了引起高岭石和蒙脱石在吸附胡敏酸方面表现出的共性和差异的原因。研究结果表明:1)在pH=5条件下,胡敏酸在高岭石和蒙脱石上的吸附量均随着胡敏酸初始浓度和离子强度的升高而逐渐增加;2)胡敏酸在高岭石和蒙脱石上的吸附量均随着pH值的升高而降低;3)pH<6时,高岭石吸附的胡敏酸量多于蒙脱石,pH>6时则相反。这是由高岭石和蒙脱石在不同pH条件下吸附胡敏酸的机制不同造成的。在pH<6时,高岭石与胡敏酸之间的静电引力起主导作用,其次是配位交换作用和氢键作用。此时,蒙脱石以氢键作用为主要吸附机制。在pH>6时,高岭石和蒙脱石的主要吸附机制分别是疏水性作用和阳离子键桥。 相似文献
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寒区高铁路基中粗颗粒填料水汽迁移可能是路基冻胀变形的来源,直观追踪冻融循环作用下土体水汽迁移过程,有助于研究水分迁移规律,为冻胀机理提供理论依据。基于此,提出采用荧光素示踪和图像处理技术方法,直观观测土体中水汽迁移的规律。首先开展荧光素示踪、蒸发试验及图像处理技术的研究,证明示踪剂可实现冻结锋面及外界液态水迁移的追踪;而后通过改进试样筒,加入液态水隔离装置等实现可视化装置系统的研发;最后通过开放和封闭条件下水汽混合迁移和气态水迁移试验,实现了水汽迁移过程的可视化追踪。验证性试验结果表明：在开放条件下,该试验装置能够有效追踪外界水迁移的时程变化;在封闭条件下,该装置能够实时监测冻结锋面的变化过程。在粗粒土中,气态水迁移是存在的,且水分重分布主要由气态水迁移引起。 相似文献
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Hajer Farroukh T. Mnif F. Kamoun L. Kamoun F. Bennour 《Arabian Journal of Geosciences》2018,11(23):760
Phosphogypsum and cement have been reported to improve the physicochemical properties of clayey soils. The present study aimed to investigate the behavior of various soils with different particle sizes and chemical and mineralogical compositions in the presence of phosphogypsum and cement mixed at various proportions. These hydraulic binders were assayed on three different soil samples, and their effects were examined using a battery of standardized tests, including the Atterberg limit, uniaxial compressive strength, Californian Bearing Rate (CBR) test, thermogravimetric analysis (TGA), microstructure observation (SEM), and X-ray diffraction tests. The results revealed a significant effect associated with the variation of phosphogypsum content in the soils. Keeping the cement content constant in the mixture, the continuous addition of phosphogypsum was noted to allow shifting the domain of plasticity to the highest water contents, which reduces the sensitivity of the soil to water and to increase the strength of soil. An increase of CBR index with the addition of phosphogypsum and cement is obtained. This treatment could have positively influenced the optimum moisture content and the maximal dry density. The mixture of soil-phosphogypsum and cement could give new forms such as ettringite and hydrate indicators of the improvement of the mechanical properties of the soil. This improvement varies from one soil to another, depending on its granularity and its mineralogy. The mineralogical composition of the soil, particularly kaolinite, amount, and size grading, have direct effects on the physical and mechanical properties of the soils under investigation. 相似文献
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Clay minerals can hinder the transport of various contaminants in soil and aquifer, but how clay minerals affect the transport of nanoparticles in aquifers has not been investigated in depth. In this paper, the transport of surfactants dispersed multi-walled carbon nanotubes (MWCNTs) in well-defined quartz sand and mixtures of quartz sand and clay minerals (kaolinite and montmorillonite) with varying ionic strengths was studied. Sodium dodecyl benzenesulfonate (SDBS) and octyl-phenol-ethoxylate (TX100) MWCNT suspensions can migrate through quartz sand easily, but the presence of less than 2% w/w clay minerals in quartz sand can significantly hinder the transport of MWCNT suspensions, especially at high ion strength (0.6 mM CaCl2). The inhibition mechanism of clay minerals for surfactant-dispersed MWCNTs in porous media is the interception of MWCNTs. Kaolinite has stronger inhibition effect for MWCNTs transport than montmorillonite because more kaolinite can be retained in the quartz sand. Adsorption of surfactants by clay minerals does not affect the transport of MWCNTs significantly. This finding is important for the environmental assessment of MWCNT transport risks in soils and aquifers. 相似文献