Structure and Properties of Mg/A1 Layered Double Hydroxides Intercalated with Glutamic Acid： Experimental and Theoretical Studies

采用共沉淀法合成了谷氨酸插层镁铝水滑石（LDHs-Glu）,并使用XRD表征技术以及分子动力学模拟方法对其微观结构与性能进行了研究。结果表明随着LDHs-Glu中水分子数量增加,层间距d003逐渐增大。XRD表征得到其层间距为1.328 nm,与理论模拟得到的当水分子数Nw=7时的水滑石层间距d003=1.323 nm相近。随着层间水分子数量增加,水合能逐渐增大,最终趋于流体水的特征值（-41.8 kJ/mol）。水合过程中,水滑石层板与阴离子间的氢键逐渐减少,而层板与水分子间的氢键逐渐增多,说明水分子与层板间的亲和力更强。实验表征与理论模拟相结合的研究方法,有望成为插层复合材料微观结构研究的重要手段。     

谷氨酸插层水滑石组装、包裹及缓释性能研究

采用共沉淀法和离子交换法实现了谷氨酸与Zn/Al水滑石的插层组装,并采用X射线粉末衍射、差热分析、红外光谱表征了谷氨酸插层水滑石的结构,并在模拟胃液和肠液中测试了复合材料中谷氨酸的缓释性能。结果表明,合成的水滑石前躯体（LDHs-NO3）结构规整、晶相单一,层间距为0.879 nm;2种方法合成的谷氨酸插层水滑石,其层间距分别增加到1.251 nm和1.334 nm,可以推测谷氨酸以垂直方式分布于水滑石层间。插层后水滑石样品在1588 cm-1和1346 cm-1处出现了谷氨酸中羧酸根的不对称伸缩振动和对称伸缩振动峰,也佐证了氨基酸插层成功。谷氨酸插层水滑石后,其热稳定性大大提高,热分解温度由230℃升高至397～434℃。与物理混合法相比,谷氨酸与水滑石复合后增加了谷氨酸的耐酸性,使其具有较好的缓释性能。谷氨酸释放曲线符合Bhaskar方程,表明微粒间的扩散作用是谷氨酸分子释放的限速步骤。LDHs-Glu经海藻酸钠包裹后,在模拟肠液中缓慢释放而在模拟胃液中不释放,起到了肠液定向释放的效果。     

二甲基甲酰胺对高岭石插层的分子动力学模拟

通过对高岭石-二甲基甲酰胺插层复合物随层间域中二甲基甲酰胺分子数逐渐增加的分子动力学模拟,发现高岭石层间距可被小分子的插层大幅度扩增,但需要借助外界条件克服插层能垒。通过对层间距为1.26 nm模型的界面结构和界面作用的计算,发现二甲基甲酰胺在高岭石层间域中呈单层分布。二甲基甲酰胺的分子平面斜交于层间域表面60°左右,其HC=O官能团的O原子作为质子受体与层间域铝氧面的羟基形成较强的氢键,而甲基则与硅氧面以疏水作用相结合。由于高岭石层间域的铝氧面具有反应活性较高的表面羟基,相比于硅氧面表现出对二甲基甲酰胺更强的亲和性。     

甲酰胺在高岭石层间的定向研究

甲酰胺插层作用使高岭石层间距从0．717nm膨胀为1．020nm。其增加值(0．303nm)小于甲酰胺的范得瓦尔分子直径(0．47nm)。DRIFT光谱研究表明插层作用破坏了原高岭石层间氢键，并分别在高岭石Si—O基与甲酰胺NH基和高岭石OH基与甲酰胺C=O基之间形成氢键，甲酰胺HN基还部分嵌入高岭石复三方孔洞。     

高岭土/吡啶插层复合物的制备与表征

以高岭土／甲醇插层复合物作为中间体，用“取代法”制备了高岭土／吡啶插层复合物，产物用X射线粉晶衍射、热分析和傅利叶变换红外光谱进行了表征。在保持吡啶润湿的条件下，高岭土的层间距增加到1．22nm。吡啶的插层率达到了90．20％。高岭土／吡啶插层复合物不稳定，干燥后其层间距减少到0．86nm。高岭土／吡啶插层复合物的红外光谱表明：吡啶分子与高岭土的内表面羟基形成了氢键。吡啶分子在高岭土层间可能以垂直于高岭土层片的方式排列，且氮原子面对八面体层片。     

深层龙马溪组页岩气藏黏土矿物水岩作用微观机制

水岩作用对页岩气藏的地球化学特性和高效开采研究具有重要的意义。为研究我国西南龙马溪组深层页岩气藏水岩作用的微观机制,针对龙马溪组深层页岩组构特征,建立了深层页岩典型黏土矿物(镁蒙脱石、铁蒙脱石和伊利石)水岩作用的分子动力学模型,分析含水量、温度和矿物特征变化对晶胞层间距和水分子扩散系数的影响,通过实验验证水岩作用对典型矿物微观结构的影响程度。研究表明,随着层间水分子数量增加,蒙脱石和伊利石晶胞层间距增大;随着温度增加,蒙脱石和伊利石晶胞层间距变化不明显,层间水分子扩散系数增加;含水量和温度一定,蒙脱石晶胞层间距远大于伊利石,而伊利石的晶胞层间水分子扩散系数远大于蒙脱石,且镁蒙脱石大于铁蒙脱石晶胞层间距,而铁蒙脱石的水分子扩散系数大于镁蒙脱石。上述研究表明,水含量增加会加剧典型黏土矿物晶层破坏的程度,而温度升高会引起典型矿物晶层破坏速度的增快。与浅层页岩相比,温度升高可能导致深部页岩水岩作用更加剧烈。     

CTA~+/蛭石插层复合物在乙醇水溶液中一维结构的变化研究

基于蛭石良好的阳离子交换性和吸附性及层间域的可膨胀性,对新疆尉犁蛭石矿的金云母-蛭石样品采用不同用量的季铵盐进行微波插层处理及插层后样品的乙醇溶液醇洗处理,并对处理后样品一维结构的变化进行了XRD分析,考察了插层剂用量和乙醇溶液浓度对CTA+/蛭石插层复合物最大底面间距的影响。结果表明:蛭石的最大底面间距随着CTAB用量的增加而增大,季铵盐阳离子在蛭石层间的排布模式也随用量的增加,发生由单层倾斜→双层倾斜的规律性转化。插层处理后的样品采用浓度为97%的乙醇溶液醇洗后,蛭石最大底面间距由5.08～4.35 nm减少至4 nm左右,季铵盐阳离子在层间全为单层倾斜排布;采用不同浓度的乙醇溶液对蛭石最大底面间距为4.69 nm的样品进行醇洗,随乙醇溶液浓度的增大,蛭石最大底面间距降低,并在浓度为60%时达到稳定值4.00 nm,随后随乙醇溶液浓度的增大,不再发生变化。季铵盐阳离子在蛭石层间域中以单层倾斜排布,倾斜角为53°±时最稳定。     

1,4-丁二醇插层高岭石的实验研究

以二甲亚砜为前驱物,1,4-丁二醇为插层剂,采用二步插层法制备1,4-丁二醇与高岭石的复合材料。实验研究了温度、时问对插层效果的影响及该复合物在水中的稳定性。采用XRD和IR法对试样进行分析表征。结果表明,在140℃,180℃条件下插层一定时间,均可获得1,4-丁二醇插层高岭石,在180（、条件下反应16h以上,同时高岭石的层间距增大到1．157nm,制备的1,4-丁二醇插层高岭石结构稳定,180℃反应32h可导致高岭石层间1,4-丁二醇转变为其他物质,形成稳定的有机插层高岭石。     

季胺盐阳离子插层蒙脱土对铀吸附性能的研究

通过十六烷基三甲基溴化铵（CTMAB）与钠基蒙脱土离子交换制备出季胺盐阳离子插层蒙脱土（CTMA’-M）,采用小角X射线衍射仪、傅里叶变换红外光谱仪和高分辨透射电镜表征微观结构,研究CTMA’的插层量、溶液的初始pH值、初始浓度和其他共存离子对吸附铀性能的影响,考察了CTMA’-M处理铀矿水）台废水的应用性能。结果表明：CTMA’插层后蒙脱土的层间距由1．21nm增加到4．09nm,但仍保持钠基蒙脱土原有的晶体结构。随CTMAB用量的增加,插层到蒙脱土层间的CTMA’量增加,对铀离子的吸附容量逐渐增大,当CTMAB的用量超过阳离子交换容量的1．4倍时,铀吸附容量基本保持不变。溶液pH和接触时间对铀离子吸附性能影响较大．CTMA’-M最佳吸附pH值为6．0,平衡吸附时间为80min,CTMA’插层能够改善蒙脱土对铀离子的选择性吸附。在1L含有15mg／L铀的废水中加入1．5gCTMA’-M时,铀的去除率达到98％以上。     

醋酸钾/偏高岭石插层复合材料的制备及机理研究

采用机械研磨法,成功制备了醋酸钾/偏高岭石插层复合材料.通过XRD、FTIR和TEM研究了插层前后偏高岭石结构的变化,提出了该复合材料的插层机理和结构模型:首先醋酸钾与水分子以配位键结合,然后通过机械研磨作用进入偏高岭石层间,并将偏高岭石片层撑开.当进行热处理时,水的挥发也会对偏高岭石片层起到撑开作用.最终导致偏高岭石被撑开、剥离.在插层复合材料中,醋酸根与偏高岭石的铝氧层通过水分子桥接方式连接,钾离子水合物为保持电中性,位于带负电的硅氧层附近.     

钠基蒙脱土水合演化机制

为了查明钠基蒙脱土的水合演化过程,以天然钠基蒙脱土为研究对象,开展在相对湿度（ ）为0～0.98区间的水汽等温吸-脱附试验,通过吸附速率曲线、BET曲线界定钠基蒙脱土各水合阶段及相应的水合主控因素;通过测定晶层 值变化规律,从吸附水影响黏土矿物晶层厚度的角度探讨钠基蒙脱土的水合演化特征;基于傅里叶红外光谱,从水分子结构伸缩振动信息角度对钠基蒙脱土水合演化过程进行定性定量验证;通过热重/差热分析,以吸附水相变所需能量与吸附水重量变化的角度解释钠基蒙脱土的吸附水特征与其水合机制的关系。试验结果表明：在较低相对湿度下（0 0.15）,以钠基蒙脱土矿物外表面吸附为主,形成表面吸附水;0.15 0.40为钠基蒙脱土层间阳离子水合阶段;0.40 0.98,为晶层内外表面水合阶段,水分子逐步完整的包裹蒙脱土,形成多层吸附层。钠基蒙脱土的水合演化过程受控于层间钠离子与晶层基面,层间钠离子的水合能影响了钠基蒙脱土水合演化的起始顺序。     

Structure and dynamics of water on muscovite mica surfaces

The structure and dynamics of water on muscovite mica (0 0 1) surfaces have been investigated by molecular dynamics simulations. X-ray reflectivity profiles highly reflecting the interfacial structure are directly calculated and compared with those of experiments. The direct comparison has validated the usefulness of MD simulations to understand the real interfacial structure of the mica−water system. We observed five distinguished peaks in the density profile of oxygen present in water, and these peaks are attributable to the water molecules directly adsorbed on mica, hydrated to the K⁺ ions on the mica surface, and ordered due to hydrogen bonds between hydrated K⁺ ions. The hydrated K⁺ ions make an inner-sphere complex and have an explicit first hydration shell with a radius of 3.6 Å and a hydration number of 2.9. The change of the viscosity of water located above 1 nm apart from the mica surface was not observed. This feature is in good agreement with a recent experimental study in which the shear measurement was conducted using a surface forces apparatus. The increase of the viscosity by a factor of ca. 2-3 relative to that of the bulk water was observed at water located within 1 nm from the isolated mica surface.     

应变率与含水率对冻土单轴压缩特性影响研究

通过对泥浆制样法制备的冻结粉质砂土的单轴压缩试验,系统地研究了冻结砂土在一个宽泛应变率以及含水率范围内的单轴压缩破坏应变特性和线弹模量特性。结果表明：随着应变率的增加,当含水率为12.0%,破坏应变逐渐增大;当含水率在16.7%～24.0%范围内时,破坏应变先增大后减小;当含水率大于等于30.6%时,破坏应变逐渐减小,3种情况下破坏应变最终都逐渐趋于稳定。破坏应变随含水率增加而先急剧增大到一个最大值,然后急剧减小,当含水率超过41.5%时,基本趋于冰的破坏应变。线弹模量先随着应变率的增大而非线性增大到一个最大值,然后应变率的继续增大使线弹模量逐渐减小,线弹模量与应变率的关系满足二次抛物函数规律。在温度为 2.0 ℃,应变率小于4.67×10-3 s-1的条件下,线弹模量随着含水率的增大而非线性增大,直至最后趋于冰的线弹模量;而在大于等于该应变率的条件下,随着含水率的增大,线弹模量先增大到一个最大值,然后减小趋于冰的线弹模量。当温度为 5.0 ℃时,类似的应变率临界值为1.00×10-2 s-1。     

Review on Advances in Chemical Osmosis in Clayey Sediments

Osmotic phenomena refer to water and solute transport processes that occur when transport of solute molecules or ions is restricted by the porous medium relative to that of water molecules. Chemical osmosis and reverse osmosis/ultrafiltration are osmotic phenomena. The studies of “coupled flow” caused by chemical osmosis have been widely applied in many fields, such as earth science, environmental science and civil engineering. This paper provided a review of the considerable advances in the field of chemical osmosis and clay semipermeable membrane since the 1950s. We summarized the research progress of chemical osmosis in clayey sediments into three aspects: theoretical basis, experimental research and numerical model. In particular, the laboratory equipment and measurement methods of the chemico-osmotic efficiency coefficient σ were described,. The existing discontinuous models based on the ‘diffusive double layer’ theory were summerized, as well as the various control factors of σ. It increases with Cation Exchange Capacity (CEC), compaction pressure and decreases by the increasing of porosity and solution concentration. This paper also summerized the contimuum models based on non-equilibrium thermodynamics, which are used to explain and predict anomalies of hydraulic head pressure and salinity in clayey environments. For the future development of this discipline, it is critical to find a reliable method to confirm the σ value. It is also critical to emphasize the research on chemical osmosis in complex conditions and the influence of chemical osmosis on groundwater flow and solute transpotation. China has just stepped into this research area and more efforts should be made if significant progress is desired. This review will be helpful to further research on groundwater numerical simulation integrated with chemical osmosis in China.     

高岭石—聚丙烯腈夹层复合物的制备

作者通过XRD和IR等手段研究了高岭石－聚丙烯腈夹层复合物的形成过程。通过对高岭石／DMSO（二甲亚砜）、高岭石／乙酸铵等中间复合物的置换反应，成功地将丙烯腈单体引入高岭石层间。XRD谱表明高岭石层间被插入有机分子后，其层间距增大；IR谱显示有机分子与高岭石的外羟基可能以氢键的形式相互作用。在有引发剂的存在下，实现了丙烯腈单体在高岭石层间的聚合。     

Experimental study on the swelling behaviour of bentonite/claystone mixture

A mixture of the MX80 bentonite and the Callovo-Oxfordian (COx) claystone were investigated by carrying out a series of experiments including determination of the swelling pressure of compacted samples by constant-volume method, pre-swell method, zero-swell method and swell–consolidation method. Distilled water, synthetic water and humidity controlled vapour were employed for hydration. Results show that upon wetting the swelling pressure increases with decreasing suction; however, there are no obvious effects of synthetic water chemistry and hydration procedure on the swelling behaviour in both short and long terms. For the same initial dry density, the swelling pressure decreases with increasing pre-swell strain; whereas there is a well defined logarithmic relation between the swelling pressure and final dry density of the sample regardless of the initial dry densities and the experimental methods. It was also found that swelling pressure depends on the loading-wetting conditions as a consequence of the different microstructure changes occurred in different conditions. Furthermore, it was attempted to elaborate a general relationship between the swelling pressure and the final dry density for various reference bentonites.     

Effects of substrate structure and composition on the structure, dynamics, and energetics of water at mineral surfaces: A molecular dynamics modeling study

Molecular dynamics computer simulations of the molecular structure, diffusive dynamics and hydration energetics of water adsorbed on (0 0 1) surfaces of brucite Mg(OH)₂, gibbsite Al(OH)₃, hydrotalcite Mg₂Al(OH)₆Cl · 2H₂O, muscovite KAl₂(Si₃Al)O₁₀(OH)₂, and talc Mg₃Si₄O₁₀(OH)₂ provide new insight into the relationships between the substrate structure and composition and the molecular-scale structure and properties of the interfacial water. For the three hydroxide phases studied here, the differences in the structural charge on the octahedral sheet, cation occupancies and distributions, and the orientations of OH groups all affect the surface water structure. The density profiles of water molecules perpendicular to the surface are very similar, due to the prevalent importance of H-bonding between the surface and the water and to their similar layered crystal structures. However, the predominant orientations of the surface water molecules and the detailed two-dimensional near-surface structure are quite different. The atomic density profiles and other structural characteristics of water at the two sheet silicate surfaces are very different, because the talc (0 0 1) surface is hydrophobic whereas the muscovite (0 0 1) surface is hydrophilic. At the hydrophilic and electrostatically neutral brucite and gibbsite (0 0 1) surfaces, both donating and accepting H-bonds from the H₂O molecules are important for the development of a continuous hydrogen bonding network across the interfacial region. For the hydrophilic but charged hydrotalcite and muscovite (0 0 1) surfaces, only accepting or donating H-bonds from the water molecules contribute to the formation of the H-bonding network at the negatively and positively charged interfaces, respectively. For the hydrophobic talc (0 0 1) surface, H-bonds between water molecules and the surface sites are very weak, and the H-bonds among H₂O molecules dominate the interfacial H-bonding network. For all the systems studied, the orientation of the interfacial water molecules in the first few layers is influenced by both the substrate surface charge and the ability by the surfaces to facilitate H-bond formation. The first layer of water molecules at all surfaces is well ordered in the xy plane (parallel to the surface) and the atomic density distributions reflect the substrate crystal structure. The enhanced ordering of water molecules at the interfaces indicates reduced orientational and translational entropy. In thin films, water molecules are more mobile parallel to the surface than perpendicular to it due to spatial constraints. At neutral, hydrophilic substrates, single-monolayer surface coverage stabilizes the adsorbed water molecules and results in a minimum of the surface hydration energy. In contrast, at the charged and hydrophilic muscovite surface, the hydration energy increases monotonically with increasing water coverage over the range of coverages studied. At the neutral and hydrophobic talc surface, the adsorption of H₂O is unfavorable at all surface coverages, and the hydration energy decreases monotonically with increasing coverage.     

Hydration thermodynamics of the SWy-1 montmorillonite saturated with alkali and alkaline-earth cations: A predictive model

The aim of the present work was to study the thermodynamic equilibria between water and a homo-ionic montmorillonite SWy-1 saturated by different cations. The choice of this smectite is justified by the large set of experimental data available from the literature for eight different interlayer cations: Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺. In particular, studies by [Cases et al., 1992], [Cases et al., 1997] and [Bérend et al., 1995] are providing heat of adsorption data, pairs of desorption-adsorption isotherms, and information about the partition of adsorption-desorption water molecules between external surfaces and internal spaces. By calculating the effective amount of hydration water as the difference between the so-called gravimetric water and the surface covering water, a thermodynamic model was then developed, based on the concept of Ransom and Helgeson (1994) considering an asymmetric subregular binary solid solution between a fully hydrated and a anhydrous smectite. A set of six thermodynamic parameters ( and four Margules parameters) was extracted by a least square method from measurements of enthalpies of adsorption and paired adsorption-desorption isotherms for each interlayer cation. These six initial parameters were then used to determine a complete set of standard thermodynamic hydration parameters (, heat capacity, molar volume, and number of interlayer H₂O) and quantify, for each cation, the number of moles of hydration water molecules as a function of relative humidity and temperature. The validation of the standard state thermodynamic properties of hydration for each end member was carried out using three approaches: (1) a comparison with experimental isotherms obtained on hetero-ionic and homo-ionic SWy-1 smectite at different temperatures; (2) a comparison with the experimental integral enthalpy and entropy of hydration of the SWy-1 smectite; and (3) a comparison with experimental isotherms acquired on various smectites (Upton, MX80, Arizona) with different layer charges.Eventually, the present work demonstrates that, from a limited number of measurements, it is possible to provide the hydration thermodynamic parameters for hydrated smectites with different compositions and under different conditions of temperature and relative humidity, using the newly developed predictive model.     

非饱和增湿条件下典型黄土湿陷性研究

利用自制装置,对原状典型黄土试样(柱状)进行不同饱和程度的非饱和增湿,分析增湿过程中土样不同位置处水分的分布规律。对完成增湿过程的试样进行湿陷性测试,并定义非饱和增湿湿陷系数,用以探讨非饱和增湿条件下试样不同位置及总体的湿陷性特征。研究结果表明,低增湿目标含水率时,随着时间增加,原状黄土土柱上层含水率呈速度减缓的下降趋势,下层含水率呈速度减缓的上升趋势,黄土土柱含水率分布不均匀;高增湿目标含水率时,随着时间增加,黄土土柱上层含水率呈速度加快的下降趋势,下层含水率呈速度加快的增长趋势,黄土土柱含水率分布均匀,且趋于均匀的时间缩短。随增湿目标含水率的增加,黄土土柱每层的非饱和增湿湿陷系数增长速度加快,底层与上层系数数值靠拢,黄土土柱整体非饱和增湿湿陷系数增大且随着压力的增加呈速度加快的增长趋势。低增湿目标含水率时,增湿时间越短土柱整体非饱和增湿湿陷系数越大;高增湿目标含水率时,时间越长土柱非饱和增湿湿陷系数越大。成果可为黄土非饱和湿陷性的研究及评价提供一定的参考及依据。