煤系高岭石的原始晶粒尺寸及结晶度对插层作用的影响

采用SEM、XRF、XRD和IR研究了大同、平朔和淮北煤系高岭石的结构、粒度及其特性,探讨了粒度大小对高岭石插层作用的影响及其机理。研究发现:粒度中等且结晶有序的平朔煤系高岭石插层率最高,其次为晶体粗大但结晶有序的大同高岭石,粒度最小且结晶无序的淮北高岭石插层率最低。研究认为高岭石原始晶粒粒度对高岭石插层作用有重要影响,中等粒度最有利于高岭石插层作用的进行,粒度过大或过小均不利于高岭石插层作用的进行,其原因是由于不同粒度的高岭石插层作用过程中导致的差异弹性变形引起的。结晶有序度对高岭石插层作用也有重要影响,结构无序不利于插层作用的进行。     

Sorption of lanthanides on smectite and kaolinite

Experiments were carried out to investigate the sorption of the complete lanthanide series (Ln or rare earth elements, REE) on a kaolinite and an a Na-montmorillonite at 22°C over a wide range of pH (3-9). Experiments were conducted at two ionic strengths, 0.025 and 0.5 M, using two different background electrolytes (NaNO₃ or NaClO₄) under atmospheric conditions or N₂ flow (glove box). The REE sorption does not depend on the background electrolyte or the presence of dissolved CO₂, but is controlled by the nature of the clay minerals, the pH and the ionic strength. At 0.5 M, both clay minerals exhibit the same pH dependence for the Ln sorption edge, with a large increase in the sorption coefficient (K_D) above pH 5.5. At 0.025 M, the measured K_D is influenced by the Cation Exchange Capacity (CEC) of the minerals. Two different behaviours are observed for smectite: between pH 3 and 6, the K_D is weakly pH-dependent, while above pH 6, there is a slight decrease in log K_D. This can be explained by a particular arrangement of the particles. For kaolinite, the sorption coefficient exhibits a linear increase with increasing pH over the studied pH range. A fractionation is observed that due to the selective sorption between the HREEs and the LREEs at high ionic strength, the heavy REE is being more sorbed than the light REE. These results can be interpreted in terms of the surface chemistry of clay minerals, where two types of surface charge are able to coexist: the permanent structural charge and the variable pH-dependent charge. The fractionation due to sorption observed at high ionic strength can be interpreted either because of a competition with sodium or because of the formation of inner-sphere complexes. Both processes could favour the sorption of HREEs according to the lanthanide contraction.     

铅在高岭石表面的吸附模式

采用表面络合模式,研究了高岭石表面的酸碱性质以及高岭石表面对铅的吸附行为。结果表明,高岭石表面在不同ｐＨ条件下对质子和铅离子的吸附反应可以用单一表面基团、无静电表面络合模式来描述。高岭石表面酸度常数拟合值分别为ｐＫａ１＝２．７５和ｐＫａ２＝５．５２,电荷零点ｐＨｚｐｃ＝４．１铅在高岭石表面的吸附量随ｐＨ值的升高而增加,吸附铅的两种表面化合态〉ＳＯＰｂ＾＋和〉ＳＯＰｂＯＨ的浓度也随ｐＨ值的变化而变化     

松辽盆地F油层高岭石、伊利石对储层物性、敏感性影响的实验研究

松辽盆地F油层砂泥岩互层发育,高岭石、伊利石为其主要粘土矿物,对研究储层物性及该油层的有效开发具有重要意义。本文通过对F油层90块天然岩心的室内研究发现,F油层渗透率、孔隙度随着高岭石相对含量的增加而增加,随着伊利石相对含量的增加而减小。砂岩层渗透性较好,高岭石相对含量较高,次生石英很少就地沉积,大量长石溶蚀孔隙得以保存;泥岩层渗透性差,伊利石相对含量较高。而且伊利石纤维状赋存和高岭石书页状赋存使砂岩层孔渗性更好,而使泥岩层孔渗性更差。该层开发过程中,高岭石、伊利石对储层物性的影响由室内岩心流动实验可知,F油层为中等强度偏弱速敏、中等强度偏强碱敏,速敏指数随着高岭石、伊利石绝对含量的增加而增加;储层的碱敏指数随高岭石绝对含量的增加而增加,而与伊利石含量无关。由于在所有粘土矿物中,高岭石相对含量接近一半,所以在F油层的开发过程要注重防范高岭石的碱敏、速敏损害。     

Structure of sediments of kaolinite

In an assembly of clay particles placed in a fluid, each particle is typically subjected to: (1) double-layer repulsive forces; (2) van der Waals attractive forces; and (3) contact mechanical forces. The study presented here concerns an approximate, quantitative analysis of clay suspensions, with considerations to the first two - the physico-chemical forces. Using recent theories to calculate the physico-chemical forces between two clay particles in an approximate model of an assembly, the equilibrium void ratio of a clay suspension is computed. The mechanical forces are ignored in the analysis. The results serve to verify the validity of physico-chemical theories employed and help interpret experimental data more fundamentally in terms of the system variables.     

Intercalation of kaolinite with acetamide

Upon intercalation of both ordered (low defect) and disordered (high defect) kaolinites with acetamide, two types of interaction are observed. Firstly, hydrogen bonding between the NH₂ groups of the acetamide with the siloxane oxygens is formed, as evidenced by the formation of two new bands at 3400 and 3509 cm^–1. Secondly, the appearance of additional bands at ∼3600 cm^–1 in both the infrared and Raman spectra of the acetamide intercalates is attributed to a second type of hydrogen bonding by the interaction of the C=O group and the inner surface hydroxyls. Changes in the intensity of the hydroxyl deformation modes in the 895 to 940 cm^–1 region are attributed to the changes in the hydrogen bonding of the kaolinite surfaces. It is proposed that the hydrogen bonding between the adjacent kaolinite layers is replaced with hydrogen bonding between both kaolinite surfaces and the acetamide molecule. Changes in the molecular structure of acetamide are observed upon intercalation. The amide 1 band is lost and replaced with a well-defined NH₂ deformation vibration. The loss of the amide 1 band is attributed the hydrogen bond formation between the amide hydrogens and the siloxane surface. The bands of the C=O group at 1680 and 1740 cm^–1 become a single band at 1680 cm^–1. The amide 2 band remains unchanged. The lack of intensity of the 1740 cm^–1 band is attributed to the formation of hydrogen bonding between the inner surface hydroxyl groups and the carbonyl group. Received: 4 February 1998/ Revised, accepted: 30 June 1998     

不同形态洛美沙星在高岭土上的吸附特性

本研究采用批实验方法探究了不同形态洛美沙星(LOM)在高岭土上的吸附特性。LOM吸附动力学结果符合准二级反应动力学方程,吸附等温数据可用Langmuir方程很好地拟合。随着溶液pH值增大,洛美沙星吸附量先增大后减小,且pH值在洛美沙星pKa1与pKa2间吸附量达到最大。不同形态LOM在高岭土上的吸附量排序为LOM^±>LOM^+>LOM^-。溶液离子强度和无机阳离子种类对LOM^+在高岭土上的吸附影响十分微弱,但均明显抑制了LOM^±的吸附,且离子强度越大,抑制作用越明显。不同无机阳离子抑制程度排序为Mg^2+>Ca^2+>K^+>Na^+。LOM^+在高岭土上的吸附机理主要是内层络合和阳离子交换;LOM^±在高岭土上的吸附机理主要是阳离子交换、氢键作用和静电引力作用;LOM^-与高岭土表面存在较大静电斥力,导致吸附量很小,可能是外层表面络合引起少量的吸附。     

Characterization of dehydration-induced luminescence of kaolinite

Dehydration-induced luminescence (DIL), the emission of light from a clay paste upon dehydration, was characterized experimentally for a colloidal kaolinite. The relationship between total photon count of the emitted light and film thickness is linear up to a thickness of 30 micrometers. The photon emission was obtained over a critical range of water contents (25-60%) of the oven-dry clay, and the kinetics of photon emission was presumed to be closely associated with the kinetics of film dehydration. Whether drying proceeded throughout the bulk or via a moving front was undetermined, but in either mode it was preceded by the formation of a thin dry film at the interface with the atmosphere. Grinding of the kaolinite for several minutes by mortar and pestle before paste preparations resulted in an overall increase of photon emission compared to unground kaolinite and in the formation of more than one emission peak, as well as a prolongation of the light emission. This effect on the kinetics of light emittance was observed for about two months after the application of the mechanical stress and suggests a means of detecting the mechanical stress history of a clay. An estimate was made of the spectral characteristics of the emitted light using optical filters and by incorporating tryptophan and salicylic acid into the kaolinite paste where they acted as fluorescent probes. The latter technique shifted the frequency of the light emitted by the kaolinite from the ultraviolet to the visible range where it was less effectively reabsorbed. The first method showed that the wavelengths of 97% of the emitted light was <460 nm and that 75% of the light had wavelengths < 410 nm. The second method showed that the total intensity of DIL increased in the presence of fluorescence molecules, suggesting that the emittance was in the ultraviolet range.     

Interactions of uranium with bacteria and kaolinite clay

We assessed the accumulation of uranium (VI) by a bacterium, Bacillus subtilis, suspended in a slurry of kaolinite clay, to elucidate the role of microbes on the mobility of U(VI). Various mixtures of bacteria and the koalinite were exposed to solutions of 8 × 10^− 6 M- and 4 × 10^− 4 M-U(VI) in 0.01 M NaCl at pH 4.7. After 48 h, the mixtures were separated from the solutions by centrifugation, and treated with a 1 M CH₃COOK for 24 h to determine the associations of U within the mixture. The mixture exposed to 4 × 10^− 4 M U was analyzed by transmission electron microscope (TEM) equipped with EDS. The accumulation of U by the mixture increased with an increase in the amount of B. subtilis cells present at both U concentrations. Treatment of kaolinite with CH₃COOK, removed approximately 80% of the associated uranium. However, in the presence of B. subtilis the amount of U removed was much less. TEM–EDS analysis confirmed that most of the U removed from solution was associated with B. subtilis. XANES analysis of the oxidation state of uranium associated with B. subtilis, kaolinite, and with the mixture containing both revealed that it was present as U(VI). These results suggest that the bacteria have a higher affinity for U than the kaolinite clay mineral under the experimental conditions tested, and that they can immobilize significant amount of uranium.     

Sorption of phenanthrene on the complexes of kaolinite and different organic component

Sorption of hydrophobic organic chemicals by various components influences their behavior and fate in environment. In the natural environment, mineral components, organic matter and microorganism didn＇t exist alone. They combined or reacted one another and formed the mineral-humic, mineral-microorganic and mineral- humic- microorganic complexes. A clear understanding of the sorption of organic chemicals by the complexes of mineral and humic acid and/or microorganism will help to determine their sorptive mechanisms in environment. In this paper, the sorption patterns of phenanthrene on the complexes of kaolinite and different organic component （humic acid and microorganism） have been carried on. The results show that the combination of HA and kaolinite not only changed the structure of HA, but also modified the surface chemistry of clay mineral. Interaction between HA and kaolinite is presumably ascribable to coulombic interactions and ligand exchange between the -COOH groups of HA and OH groups at the kaolinite surface. During the sorption on mineral surface, aliphatic fractions of HA were preferentially sored by kaolinite while aromatic fractions were left in the solution. More linear isotherms and higher Koc values were observed for kaolinite-HA complex in comparison of the pure HA. The sorption capacity of kaolinite-HA complex increased with increasing ionic strength and pH, and showed more nonlinear character. Kaolinite, microorganism and kaolinite-microorganism complex can all sorb phenanthrene, but the sorption capacity significantly differed. Bacterial cell sorbed more phenanthrene than kaolinite. The biofllm coating of kaolinite affected its sorption to phenanthrene. Kaolinite with biolfilm coating sorbed more phenanthrene than that without biofilm coating. The sorption capacity of kaolinite-microorganism complex decreased with increasing ionic strength and decreasing pH, but showed more nonlinear character. Both HA and microorganism can alter the nature of kaolinite sorbing phenanthrene respectively.     

Long-term behavior of lime-stabilized kaolinite clay

Clay soils create many problems for highway construction and they have to be replaced or improved by stabilization for satisfactory performance. Lime stabilization is a well-established technique to improve the performance of clays. Cementitious minerals form upon mixing of clay with lime causing an improvement in strength and durability. In the study, the changes in the microfabric of long-term cured lime-stabilized kaolinite clay using X-ray diffraction pattern, scanning electron microscope and unconfined compressive strength (UCS) is presented. Unconfined compression test samples at two different lime contents (4 and 12% by weight) were prepared and cured in a humidity room for long time curing. The UCS of pure kaolinite was originally 125 kPa, which increased to 1,015 kPa after 1 month and to 2,640 kPa (21 times the initial value) after 10 years for cured lime-stabilized kaolinite samples. Similar long-term strength increases were also observed for stabilized kaolinite with 12% lime. Calcium aluminate silicate hydrate minerals were detected in the structure of the kaolinite. This suggests pozzolanic reactions with lime stabilization may continue in the long-term for up to 10 years.     

Antimony adsorption on kaolinite in the presence of competitive anions

Antimony (Sb) emissions to the environment are increasing, and there is a dearth of knowledge regarding Sb fate and behavior in natural systems. In natural systems, the presence of competitive anions may compete with Sb for adsorption sites on mineral surfaces, hence increasing its potential bioavailability. Accordingly, the adsorption of Sb(III) on kaolinite was investigated in the presence of competitive anions. Kinetic studies suggest that adsorption reaction of Sb(III) on kaolinite is rapid initially and becoming slow after 12 h both in binary Sb(III)–kaolinite system and in ternary Sb(III)-competitive anion–kaolinite system. The presence of PO₄ ^3? has a much stronger and more obvious promotive effect on the adsorption of Sb(III) on kaolinite compared with the other two anions. The adsorption data of Sb(III) on kaolinite in the absence and presence of competitive anions at three temperatures were successfully modeled using Langmuir (r ² > 0.95) and Freundlich (r ² > 0.95) isotherms. Accompanied the adsorption of Sb(III) on kaolinite, significant oxidation of Sb(III) to Sb(V) had occurred under the experimental conditions used in this study. The presence of kaolinite which has a larger specific surface area could increase the contact area between the adsorbed Sb(III) and oxygen in the bulk solution, which promoted the oxidation rate of Sb(III) to Sb(V).     

Effect of heavy metal and alkali contamination on the swelling properties of kaolinite

One of the most important factors that determine engineering properties of soils are the type and the amount of clay present in soil. Kaolinite being a very common and non-swelling clay mineral in soil was chosen as the medium, and significance of the change in swelling property of kaolinite due to contaminant-clay interaction was investigated. The amount of change in swelling percentages of the kaolinite due to contamination with 10,000 ppm solutions of Pb(NO₃)₂ and Zn(NO₃)₂ was determined using oedometers. For uncontaminated kaolinite, the amount of swell was determined as 2.2%. For Pb-contaminated and Zn-contaminated kaolinite, these values reached to 5.8 and 5.3%, respectively. Besides heavy metals, kaolinite was also contaminated with 4 N NaOH. The biggest change in the amount of swelling was obtained from NaOH-contaminated kaolinite which is 13.9%. In addition to swelling percentages, swelling pressures were also determined. The swelling pressure of the uncontaminated kaolinite was found as 1.06 N/cm². For Zn and Pb-contaminated kaolinite, this value reached up to 2.0 and 2.6 N/cm². The NaOH-contaminated kaolinite has the greatest swelling pressure which was 230 N/cm².     

Shear wave velocity anisotropy of salt- and polymer-amended kaolinite

Shear wave velocity (V_s) anisotropy of kaolinite mixed with sodium chloride (NaCl) and organic polymer (polyethylene oxide, xanthan gum, and chitosan) solutions was investigated using a custom-made floating wall consolidometer-type bender element testing system. The addition of salt and polymers influenced the microfabric anisoopy of platy kaolinite particles, thus resulted in the increment or decrement in the V_s anisotropy. The V_s of kaolinite in all three orthogonal directions increased as the NaCl concentration increased; however, the V_s anisotropy decreased. PEO and chitosan increased the V_s of kaolinite, while xanthan gum exhibited counter-effects. V_s anisotropy (V_s?hh/V_s?vh and V_s?hv/V_s?vh) of polymer amended kaolinite was found to decrease. In addition, both salt- and polymer-modified kaolinite did not show V_s cross-anisotropy.

     

The hydrogen isotope fractionation between kaolinite and water

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.     

Hydrogen isotope fractionation between kaolinite and water revisited

The equilibrium hydrogen isotope fractionation factor (α) between kaolinite and water in the temperature range 330 to 0°C is 1000 In α_kaol-water = −2.2 × 10⁶T⁻² − 7.7. This monotonic expression is based on a combination of experimental data with >75% of exchange and empirical calibrations. The previously proposed and widely accepted complex fractionation expression is considered to reflect the role of surface and intersite fractionation effects in the low percent of exchange experiments(Liu and Epstein, 1984), and incorrect δD water values for the empirical values (Lambert and Epstein, 1980). There is no measurable fractionation between dickite and kaolinite. The temperature dependence of the kaolinite-water hydrogen isotope fractionation factor can probably be used as a model for other phyllosilicate-water systems below 350°C.     

Impact of pore water conductivity and porosity on the electrical conductivity of kaolinite

The purpose of this study is to quantify the magnitudes of surface conduction and pore water conduction from the measured electrical conductivity of kaolinite, with the ultimate goal of estimating the electrical conductivity of kaolinite with a wide range of pore water conductivities (σ _w = 0.013–3.356 S/m) and porosities (n = 0.368–1.0). Therefore, the theoretical background of the electrical conductivity in soils was reviewed, and electrical conductivity measurements on kaolinite were performed using both slurry and consolidation tests in this study. The results of this study demonstrate that the variations of measured electrical conductivity (σ _mix) with n are debatable according to the values of σ _w, because a decrease in n results in both an increase in surface conduction (K _s) and a decrease in pore water conduction (K _w); this causes the relative magnitude of K _s compared to that of K _w to vary with σ _w and n. Consequently, this study develops the relation between the porosity-normalized K _s/K _w and 1/σ _w. Additionally, the surface conductivity of the tested kaolinite is back-calculated and compared with the previous relationship between K _s and zeta potential of kaolinite. The measured and estimated σ _mix values are compared with the varying pore water conductivity and porosity values.     

Influence of vibration grinding and calcination on the physico-chemical properties of Egyptian kaolinite

Summary The effects of vibratory grinding and calcination on the structure and reactivity of Kalabsha kaolinite were studied by means of XRD, IR, DTA and surface area determination. Leaching experiments on ground and calcined samples were carried out using 20% HCl for aluminum extraction. At the early stages of grinding, partial destruction of stacked kaolinite layers occurred. These changes were associated with an increase in surface area due to formation of fine grains with numerous boundaries. Further grinding, as well as calcination, led to deterioration of the kaolinite structure. A significant increase of surface area was observed, starting from 18 m²/g for the original sample to a maximum of 42 m²/g after 120 minutes of grinding and 30 m²/g after calcination at 300°C. The extraction of aluminum after 30 minutes leaching time was about 97% for kaolinite ground for 240 minutes, and about 93% for kaolinite calcined at 550°C.

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Der Einfluß von Aufmahlen und Kalzinierung auf die physiko-chemischen Eigenschaften von ägyptischem Kaolinit

Zusammenfassung Die Effekte von Vibrations-Mahlung und Kalzinierung auf die Struktur und die Reaktivität von Kalolinit aus Kalabsha wurden mit XRD, IR, DTA und Methoden zur Bestimmung der Oberfläche untersucht. Auslaugungsexperimente zur Extraktion des Aluminiums erfolgten an gemahlenen und kalzinierten Proben unter Verwendung 20% er Salzsäure. In den Frühstadien des Mahlprozesses tritt eine teilweise Zerstörung der Kaolinitschichtstruktur auf. Diese Änderungen gehen mit einer Zunahme der Oberfläche, infolge der Neubildung von Körnern mit zahlreichen Korngrenzen, einher. Weiteres Aufmahlen und Kalzinieren führt zu zusätzlicher Zerstörung der Kaolinitstruktur. Eine signifikante Zunahme der Oberfläche von 18 m²/g für das Ausgangsmaterial auf 42m²/g nach 120 min Aufmahlen, bzw. auf 30 m²/ g nach Kalzinierung bei 300°C ist zu beobachten. Die Extraktion von Aluminium nach 30 minütiger Auslaugung liegt bei 97% für gemahlenen Kaolinit (240 min) und bei 93% für bei 550°C kalzinierten Kaolinit.