高岭石-硬脂酸插层复合物的制备及结构模型的提出

以张家口高岭土为原料,通过直接插层与取代相结合的方法制备高岭石-硬脂酸插层复合物。利用X射线粉末衍射、红外光谱、热重及透射电子显微镜对制备产物进行表征。结果表明:硬脂酸插入到高岭石层间,高岭石层间距d001值由0.72 nm增加到4.05~4.37 nm,插层率达到86.9%;反应时间和溶液p H值会对高岭石-硬脂酸插层复合物的层间距及插层率产生影响;甲氧基嫁接在高岭石表面,与硬脂酸分子同时存在于高岭石层间。高岭石经甲醇改性后脱羟基温度明显降低,高岭石羟基活性提高;高岭石-硬脂酸插层复合物的稳定温度在160℃以下。经过硬脂酸插层改性后的高岭石片层,从边缘开始出现卷曲现象,并且部分长条状片层形成类似埃洛石相的纳米卷;对硬脂酸插层高岭石的作用机理进行分析,结合结构计算,提出高岭石-硬脂酸插层复合物的结构模型,该模型可以解释高岭石-硬脂酸插层复合物在不同条件制备产物层间距变化的原因。     

高岭石-硬脂酸插层复合物的制备及结构模型的提出

以张家口高岭土为原料,通过直接插层与取代相结合的方法制备高岭石-硬脂酸插层复合物.利用 X射线粉末衍射、红外光谱、热重及透射电子显微镜对制备产物进行表征.结果表明:硬脂酸插入到高岭石层间,高岭石层间距d₀₀₁值由0.72 nm增加到4.05~4.37 nm,插层率达到86.9%;反应时间和溶液pH值会对高岭石-硬脂酸插层复合物的层间距及插层率产生影响;甲氧基嫁接在高岭石表面,与硬脂酸分子同时存在于高岭石层间.高岭石经甲醇改性后脱羟基温度明显降低,高岭石羟基活性提高;高岭石-硬脂酸插层复合物的稳定温度在160 ℃以下.经过硬脂酸插层改性后的高岭石片层,从边缘开始出现卷曲现象,并且部分长条状片层形成类似埃洛石相的纳米卷;对硬脂酸插层高岭石的作用机理进行分析,结合结构计算,提出高岭石-硬脂酸插层复合物的结构模型,该模型可以解释高岭石-硬脂酸插层复合物在不同条件制备产物层间距变化的原因.     

直接置换插层法0.85 nm水合高岭石的制备

以高岭石/尿素插层复合物作为中间相,利用简单的直接置换插层法制备了d001=0.85 nm的水合高岭石。利用X射线衍射、红外光谱、扫描电镜表征处理前后高岭石结构与形貌的变化。结果表明:尿素插层后的高岭石层间距从d001=0.72 nm增大到d001=1.08 nm,经不同温度酸洗或水洗后,插层复合物转变成层间有水分子的水合高岭石(d001=0.85 nm),且高岭石晶粒厚度明显从约25 nm减小到约10 nm。在高温条件下形成的水合高岭石含量最高,90℃水洗时d001=0.85 nm水合高岭石的转化率接近70%,这种水合高岭石具有进一步的置换插层能力,是一种制备其他高岭石插层复合物很好的前驱体。与乙二醇形成d001=1.10nm乙二醇/高岭石插层复合物,其置换率达到100%。     

PEG在微波诱导下对高岭石插层及剥片的研究

利用微波能量，快速制备了高岭石/DMSO插层复合物，并以其为前驱体，在熔融状态，微波诱导聚乙二醇(PEG)置换出高岭石层间的DMSO，微波继续协同PEG作用，可以实现其对高岭石的剥片。同时提出了微波作用机理和微波条件下插层物对高岭石的剥片机理。采用X-射线衍射、FTIR光谱、TG-DTA、TEM等技术对插层复合物进行了表征。     

高岭石/苯甲酰胺插层复合物的热分解行为及脱嵌反应动力学

以高岭石/二甲基亚砜为前驱体,利用置换法制备了高岭石/苯甲酰胺插层复合物。XRD和FTIR分析表明苯甲酰胺进入高岭石层间并与其形成新的氢键。采用TG、DSC研究了插层复合物的热分解行为。结果表明复合物在加热过程中发生两步分解,第一步是插层复合物的分解,即插层剂分子于231℃发生脱嵌,第二步为高岭石脱羟基的过程。针对第一阶段的脱嵌反应,采用等转化率法改进后的迭代法、Malek法以及Dollimore法等动力学方法计算得到了完整的动力学三因子:活化能Ea=75.4kJ.mol-1,指前因子A的范围为4.9×1010~8.8×1010s-1,动力学方程为:G(α)=[1-(1-α)1-n]/(1-n),f(α)=(1-α)n。     

高岭石插层效率评价

用基于X射线衍射分析(XRD)的插层率、基于热重分析(TGA)的热失重率和基于红外光谱分析(FTIR)的3 600 cm^-1谱带与3 700 cm^-1谱带强度比值对高岭石/二甲基亚砜(DMSO)插层复合物和高岭石/N-甲基甲酰胺(NMF)插层复合物的插层效率进行了综合评价。结果表明,当插层反应进行到1、6和25 d,高岭石/DMSO的插层率分别为5%、52%和89%;而高岭石/NMF的插层率则分别为93%、94%和95%。与此同时,高岭石/DMSO的热失重率分别为1.06%、8.06%和17.46%;而高岭石/NMF的失重率分别为6%、6.5%和14.2%。在红外光谱图中,高岭石/DMSO复合物的3 600与3 700 cm^-1带强度比分别为1.03,1.141和1.628,而高岭石/NMF复合物分别为1.403,1.433和1.612。3种评价方法显示很好的一致性,相对而言,在插层作用的初期,XRD方法比较灵敏,而在插层作用的后期,TGA和FTIR方法则显得更为灵敏和有效。     

水分子在高岭石中插层行为的量子化学研究

采用密度泛函理论B3LYP方法,在B3LYP/6-31G(d)理论水平上,构建高岭石的层间团簇模型Si6Al6O42H42(层间距为0.844 0和1.000 0nm),并对高岭石层间及其与n(n=1～3)个水分子相互作用的团簇的各种性质进行研究,如优化的几何构型、电子密度、氢键、能量、NBO电荷分布、振动频率等.结果表明,随着水分子个数n(n=1～3)的增加,体系的能量逐渐降低.水分子通过多种类型的氢键插层于高岭石层间,其中水分子间的氢键强度最强,其次是水分子与铝氧层之间形成的氢键,再次是水分子与硅氧层之间的氢键;层间距随着插层分子的增多而增大,但高岭石层间的活性位点依然存在,且位置较插层前没有明显变化.     

高岭石/APTES插层复合物的表征及其脱嵌反应动力学

以高岭石/甲醇(K/M)复合物为前驱体,利用置换法制备出了高岭石/γ-氨丙基三乙氧基硅烷插层复合物(K/APTES),并应用XRD、FTIR、TEM、TG-DSC分析等表征手段对复合物进行了分析。结果表明:APTES分子的氨基与前驱体K/M的四面体硅氧烷基、嫁接在铝氧八面体表面上的甲氧基均发生键合作用形成氢键,APTES分子为两层倾斜排列于高岭石层间,倾角大小与温度有关。插层剂APTES破坏了高岭石层间的氢键,加剧了高岭石自身结构中硅氧四面体片层与铝氧八面体片层之间存在的错位,使得K/APTES插层复合物的部分片层卷曲变形。还针对复合物的插层剂APTES的脱嵌反应,采用Satava积分法和AcharBrindley-Sharp-Wendworth微分法相结合的动力学方法计算得到了完整的动力学三因子:活化能E=197.8 k J·mol-1,指前因子的对数lg(A/s-1)=14.60,最概然机理函数为:f(α)=[-ln(1-α)]-1,G(α)=α+(1-α)ln(1-α)。     

水合肼在高岭石层间插层行为的量子化学研究

水合肼以其碱性及吸附性受到越来越多的关注,同时它在粘土中的污染问题也越来越受到重视.本工作构建了高岭石团簇模型为Al6Si6O42H42并在B3LYP/6-31G(d,p),MP2/6-31G(d,p)//B3LYP/6-31G(d,p)和MP2/6-31++G(d,p)//B3LYP/6-31G(d,p)水平下对一水合肼以及二水合肼在高岭石层间的插层性质(如:优化构型、结构参数、结合能、电荷分布、振动光谱、静电势等)进行探究.计算表明,当一水合肼进入层间后,水分子和肼分子之间的相互作用发生了改变.即水与肼分子分别以氢键的形式插层于高岭石层间,且肼与高岭石之间的相互作用要强于肼与水之间的相互作用,同时插层位点多位于高岭石四面体层和八面体层的重叠区域内,这些都是水合肼易进入高岭石层间而难以脱去的重要因素.当二水合肼进入层间后,随着层间距的不断扩大,肼分子与高岭石铝氧层之间的相互作用仍强于肼分子与水分子间的作用.但当层间距超过1.05 nm时,水分子与肼分子之间的作用则强于肼分子与高岭石的作用,这也印证了若要将肼脱附,需将层间距增大以减弱肼分子与高岭石的作用,再用溶剂将其脱附的可行性.     

高岭石/甲酰胺插层的Raman和DRIFT光谱

用Raman和漫反射红外光谱研究高岭石/甲酰胺插层反应机理及插层作用对高岭石微结构的影响.     

One-step exfoliation of kaolinites and their transformation into nanoscrolls

Kaolinite nanoscrolls, rolled kaolinite sheets with a tubular form, were prepared by a one-step route in which intercalation of guest species and swelling with solvent proceed at the same time. A methoxy-modified kaolinite was exfoliated by the intercalation of hexadecyltrimethylammonium chloride. The formation of nanoscrolls by the one-step route proceeded only by several alkyltrimethylammonium salts and 1-hexadecyl-3-methylimidazolium chloride. Intercalation of primary amines caused the formation of nanoscrolls by a two-step route in which the intercalation and swelling proceed separately. The successful one-step route is ascribed to the relatively weak interactions between the head groups of guest species and the interlayer surface of methoxy-modified kaolinite, and the interaction is thought to allow the formation of a flexible array of interlayer guest species for swelling. The tubular structure was mostly retained after the heat treatment at 600 °C to form hierarchically porous aluminosilicates with amorphous frameworks. The nanoscrolls intercalated organic guests species, which are not directly intercalated into methoxy-modified kaolinite, between the scrolled layers. The formation route to nanoscrolls is quite dependent not only on the surface modification of kaolinite but also on the structure of guest species.     

Effect of reaction temperature on intercalation of octyltrimethylammonium chloride into kaolinite

The structural property, thermal behavior, and morphology of octyltrimethylammonium chloride–kaolinite complexes prepared at different reaction temperatures were studied by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry–differential scanning calorimetry, and scanning electron microscope. The present study demonstrated that the arrangement model of octyltrimethylammonium cations (OTAC⁺) within the kaolinite interlayer space was independent of reaction temperature. The alkyl chains adopted a similar rigid paraffin-bilayer arrangement with different tilted angles. Although the intercalation led to an increased number of gauche conformers, the number of nonlinear conformers remained constant with increasing temperature. With increasing temperature, the number of trans conformers continuously augmented and resulted in decreased gauche/trans ratio. Therefore, the molecular environment remained solid like. Simultaneously, the surfactant packing density gradually increased, along with the decreasing water content in the organoclays. This effect improved thermal stability and hydrophobicity. The thermal decomposition processes of the kaolinite–OTAC⁺ complex can be divided into four steps. Furthermore, SEM images showed that the morphology of these complexes was strongly dependent on the given temperature. In general, increasing the temperature within the limited given temperature (≤70 °C) promoted the transformation from platy layers to nanoscrolls. Most of the transformed nanoscrolls were acquired in the products prepared at 70 °C, and further increasing in temperature decreased the nanoscrolls yield. Nevertheless, the packing density increased in the process, thereby demonstrating that the packing density not only promoted nanoscrolls transformation but also prevented the progress.

     

The effect of kaolinite intercalation on the structural arrangements of N-methylformamide and 1-methyl-2-pyrrolidone

N-methylformamide (NMF) and 1-methyl-2-pyrrolidone (NMP) were intercalated with kaolinite, characterized, and deintercalated for analysis (the NMP was intercalated after expansion of the kaolinite layers with NMF). The dynamics of guest molecules within the kaolinite lamellae was studied by means of FT-IR and liquid state (1)H and (13)C NMR on the NMF and NMP before intercalation and also on the deintercalated solutions. Both compounds were deintercalated using water. The FT-IR spectra show no significant differences before and after intercalation, for either NMF or NMP, indicating that there is no change in molecular arrangement as a result of intercalation. (1)H and (13)C NMR investigations supported the findings of the FT-IR and indicated that structural arrangement and orientation of the guest species remain the same after deintercalation. This work provides evidence that intercalation is due to weak physical bonding.     

A DRIFT spectroscopic study of potassium acetate intercalated mechanochemically activated kaolinite

Kaolinite has been mechanochemically activated by dry grinding for periods of time up to 10 h. The kaolinite was then intercalated with potassium acetate and the changes in the structure followed by DRIFT spectroscopy. Intercalation of the kaolinite with potassium acetate is difficult and only the layers, which remain hydrogen bonded, are intercalated. The mechanochemical activation of the kaolinite may be followed by the loss of intensity of the hydroxyl-stretching vibrations. The intensity of the 3695 and 3619 cm(-1) bands reach a minimum after 10 h of grinding. The observation of a band at 3602 cm(-1) is indicative of the intercalation of the kaolinite with potassium acetate. The degree of intercalation decreases with mechanochemical treatment. The effect of exposure of the intercalated mechanochemically activated kaolinite to moist air results in de-intercalation. The effect of the mechanochemical treatment is loss of layer stacking, which prevents the intercalation of the kaolinite.     

高岭土／羧甲基淀粉复合颗粒的制备及其协同电流变效应

通过二次插层取代法，以二甲基亚砜为前驱体，羧甲基淀粉二次插层取代制备 了高岭土/羧甲基淀粉纳米复合材料。结合XRD，FTIR，SEM和EDS等测试手段对复合 材料的结构进行了表征。研究结果发现，羧甲基淀粉经过二次插层取代引起了高岭 土片层之间的剥离，形成剥离型纳米复合材料。该复合材料制备成电流变液出现了 较大的协同效应，具有很好的电流变行为，并发现电流变性能与复合物中羧甲基淀 粉的含量有密切关系。     

The mechanochemical reactions between CsF and kaolinite

The grinding of a mixture containing kaolinite and CsF was carried out by three different techniques, short manual grinding, Fisher mechanical mortar and Retsch ball mill. In addition to different cesium aluminium silicates which were detected by X-ray powder diffraction, a new type of intercalation complex was identified by FTIR spectroscopy. The X-ray diffractogram of this complex did not show any basal spacing, which may characterize the complex but the 0.715 nm characteristic peak of the untreated kaolinite became very weak. The Retsch ball mill led to a slight destruction of the kaolinite and the formation of small amounts of the new intercalation complex. The delamination of book-like kaolinite assemblages was observed after the manual and Fisher mortar grindings. In the latter grinding techniques the kaolin-like layers persisted and served as the framework for the intercalation complexes. Received: 4 February 1998 Accepted: 11 March 1998     

Effect of surfactant counterion and organic modifier on the properties of surfactant vesicles in electrokinetic chromatography

Counterion and organic modifier are two parameters in EKC that can be varied in order to obtain improved solubility, selectivity, and efficiency. The effect of changing surfactant counterion and/or organic modifier on the chromatographic and electrophoretic properties of cetyltrimethylammonium bromide (CTAB)/sodium octyl sulfate (SOS) vesicles is examined in EKC. The vesicles are prepared in a 1:3.66 cationic/ anionic mole ratio for a total surfactant concentration of 69 mM. The cationic CTAB is replaced by cetyltrimethylammonium chloride (CTAC) and the first use of CTAC/SOS vesicles is reported. The mean diameter of the CTAC/SOS vesicles is 96 nm while that of the CTAB/SOS vesicles is 85 nm. A class I modifier (2-amino-1-butanol) and a class II modifier (acetonitrile) have similar effects on the EOF, elution range, methylene selectivity, and the efficiency of the CTAB/SOS vesicles and the CTAC/SOS vesicles. Upon addition of 10% ACN, there is roughly a 10-fold increase in the efficiency of heptanophenone, a model hydrophobic compound, compared to the efficiency using unmodified vesicles. Linear free energy relationship (LFER) analysis using the Abraham solvation model is employed to characterize solute-vesicle interactions. The results suggest that organic modifier-vesicle interactions depend somewhat on the counterion.     

十六烷基三甲基氯化铵与直接蓝199的相互作用

采用吸收光谱法和电导率法,研究了阳离子表面活性剂十六烷基三甲基氯化铵（CTAC）与直接蓝199(DB199)的相互作用。 实验结果表明,当CTAC的浓度低于临界胶束浓度（CMC）时,混合溶液的电导率随CTAC浓度变化曲线与理论计算曲线基本吻合;高于CMC时,CTAC溶液中有80.88%的Cl-吸附在胶束的表面,当加入染料之后数量会降至78.48%。 混合溶液的最大吸收波长（λmax）随着CTAC浓度的增加先发生蓝移后红移。λmax处吸光度随着CTAC的浓度增大先下降后上升。