Adsorption of As on hydroxy-Fe-montmorillonite complexes

DOI: 10.1360/03yd0553 Arsenic, a toxic element, is ubiquitous in the earth’s crust and may lead to health risks for humans. This may come about as a result of oxidative weathering and dissolution of As-containing minerals, use of ar-senical pesticides, excess use of some fertilizers and from mine drainage, smelter wastes and agricultural drainage water from certain arid regions. The dis-solved inorganic arsenic is transported in surface or2156 Science in China Ser. D Earth Sciences groun…     

Catalysis of aluminosilicate clay minerals to the formation of the transitional zone gas

It has been shown that the major clay minerals of the biothermocatalytic transitional zone source rock are montmorillonite, illite/montmorillonite (I/M) interlayer mineral, illite, kaolinite and chlorite. Within the depth of the transitional zone, montmorillonite could convert to the I/M ordered interlayer mineral via the I/M disordered one, i.e. in the intercrystalline layer of montmorillonite, A1³⁺replaces Si⁴⁺abundantly, resulting in a surface charge imbalance and the occurrenec of a surface acidity. By means of the pyridine analytic method, the surface acidity of these aluminosilicate clay minerals is measured. The catalysis of aluminosilicate clay minerals, such as montmorillonite, illite and kaolinite to the thermo-degraded gas formation of the transitional zone is simulated in the differential thermal analysis-gas chromatography system and the alcohol dehydration catalyzed by clay minerals is employed to discuss this catalytic mechanism. Experiments have shown that montmorillonite is the major catalyst in the formation of the transitional zone gas and it lowers the thermo-degraded temperature of organic matter by 50°C.     

Study of nanocrystals in the dynamic slip zone

Mineral composition is studied and a search to detect nanocrystals is conducted in the surface layers of slickensides formed due to dynamic slip in arkose sandstone. The infrared and Raman spectroscopy show that the slickensided layer is composed of nanocrystals of montmorillonite and anatase measuring ??15 nm and 3 nm, respectively. The crystalline lattice of the nanocrystals of montmorillonite is stretched by ??2.5% while the lattice of the nanocrystals of anatase is compressed by ??0.12%. Deeper than 3 mm below the slickenside surface, the sandstone contains nanocrystals of montmorillonite, beidellite and nontronite, quartz, plagioclase, and anatase. The nanocrystals of anatase have a linear size of ??8 nm. Their crystalline lattice is compressed by ??0.03%. It is supposed that montmorillonite in the slickensides was formed due to hydrolytic decomposition of silicates under friction of the fault planes sliding past each other.     

高温高压下蒙脱石显微变形与力学性质的研究

通过研究高温高压条件下蒙脱石的变形特征和机制,着重阐述了蒙脱石的显微变形特征与温度压力之间的关系,以及对应力-应变的影响。研究表明,在围压为200M Pa条件下,温度升高将导致蒙脱石的变形增大。对相同应变量所需的差异应力则随温度上升而下降。但是,当温度>500℃时,相同应变量所需差异应力较300℃时显著增大,其屈服强度和变形模量在T≥500℃,σ≥300MPa时均因脱水明显增大。蒙脱石在高温高压下均为渐进失稳     

Electrical properties of montmorillonite studied together with the processes occurring under thermal activation

The results of laboratory experiments on studying the electrical conductivity σ of a clay mineral montmorillonite from different sedimentary mineral deposits of Dagestan in the temperature interval from 100 to 1000°C are presented. The general regularities in the dependence of the electrical conductivity σ of the studied samples on the absolute temperature T are accounted for by the existence of the associated complexes of elementary defects of the crystal lattice. These complexes play important role in a variety of kinetic processes under the conditions of the Earth’s interior, and their existence is demonstrated by the experiments. The activation energy of the electrical conductivity and the preexponential factors are determined for all the temperature zones. The relationship between the pattern of temperature variations in electrical conductivity and the processes of releasing interlayer water and hydroxyls from different energy sites is established. It is concluded that the anomalous change in electrical conductivity in some samples reflects the postsedimentation changes of montmorillonite manifesting themselves by the emergence of a hydromuscovite component.     

Oxygen isotope geothermometry and origin of smectites in the Atlantis II Deep,Red Sea

The sediments underlying the hot brine pool of the Atlantis II Deep, a localised area of geothermal activity in the Red Sea, comprise a diversity of facies characterised by combinations of one or more of five species assemblages, sulphide, sulphate, silicate, oxide and carbonate, each including several mineral phases. The silicate mineral assemblage is dominated by geothermal authigenic smectites. Previous studies of these smectites have reported iron-rich varieties only, nontronite in particular, and only one environment of formation. In three cores from the Southwest Basin of the Atlantis II Deep, of the present study, three smectites comprising two species have been distinguished [10,21] evidently from three different environments of formation. Two of these smectites are nontronites, one from sulphide/silicate/amorphous facies, the other from silicate/carbonate/oxide facies. The third is a montmorillonite/beidellite from sulphate/sulphide/silicate/oxide facies.The oxygen isotopic compositions of samples of the three smectites have been determined from which formation temperatures have been calculated. Six samples of the “anoxic” nontronite have formation temperatures in the range 90–140°C. A single sample of the “oxic” nontronite has a formation temperature of about 80°C. Four samples of the montmorillonite/beidellite have formation temperatures in the range 160–200°C.The formation temperature range of the two nontronites is intermediate between the temperature of the brine at or prior to discharge (up to 250°C [12]) and the temperature of the brine pool in the Deep (about 50–60°C [13,14]). The nontronite formation temperature range reflects genesis by combination of isotopically light silica supplied by the incoming brine and isotopically heavier iron oxyhydroxide settling from the upper layers of the brine pool. Evidently, the “anoxic” nontronite forms at greater depth (hotter) in the brine pool than the “oxic” nontronite resulting in a relatively greater contribution from silica but diminished contribution from iron oxyhydroxide in the former compared to the latter. The wide range of the formation temperatures for the “anoxic” nontronite is related to the different actual locations of the samples in the sulphide/silicate/amorphous facies.The formation temperature range of the montmorillonite/beidellite is approaching the estimated temperature of the brine at or prior to discharge. The montmorillonite/beidellite formation temperature range reflects genesis by combination of isotopically light silica and aluminium, both supplied by the incoming brine, at the site of an active discharge vent. The wide range of the formation temperatures for the montmorillonite/beidellite may in part reflect a possible thermal event at the brine source, likely to have occurred during deposition of the sulphate/sulphide/silicate/oxide facies and which, it appears, has contributed to the formation of this facies [10,20].     

Climatic control of the assemblages of secondary clay minerals in the A-horizon of United States soils

The concentrations (per cent) of secondary clay minerals (mica, vermiculite, montmorillonite, chlorite and kaolinite) in the A-horizon of 99 soil sample sites were entered into a cluster program to determine the common clay mineral assemblages found in U.S. soils. Five major assemblages were identified with the most common assemblage consisting of mica, montmorillonite and kaolinite. A suite of climatic variables was determined for each of the 99 sites, including the water balance variables and Arkley's leaching index. A discriminant analysis was then used to predict the occurrence of a clay assemblage from the climate data. Sixty per cent of the sites could be correctly predicted, although not all assemblages could be predicted equally well; two assemblages could be predicted with 88 and 82 per cent accuracy. The precipitation of the wettest month and Arkley's leaching index accounted for most of the predictive power. Thus this study supports theoretical models which suggest that seasonal moisture supply is an important control of clay genesis and persistence. A residuals analysis indicated that many of the palaeosols in the data set and many of the soils from glacial parent materials possessed clay mineral assemblages not expected on the basis of modern climate.     

Element geochemistry and cleaning potential of the No. 11 coal seam from Antaibao mining district

It has aroused great attention that the mobilization of potential toxic substance during coal mining, pro- cessing and using has serious negative influence on environment. Clearly, the coal cleaning can be prop-erly applied to removing hazardous elements or re-ducing their concentrations prior to combustion, which also is considered as an economical and effective technique in minimizing some of these problems[1]. Unfortunately, there are fairly few studies on the parti-tioning behavior of trac…     

Study of swelling-shrinkage regularity of montmorillonite crystal and its relation with matric suction

The swell-shrinking mineral of saturated and unsaturated expansive soil has important effect on engineering mechanical behavior. Based on the swelling-shrinkage change regularity of montmorillonite crystal in this paper, the actions between various interlayers of montmorillonite crystal are generally summarized as two kinds of action potentials-shrinkage potential and swelling potential. Moreover, through the experimental research and analysis, the expression formula for variations of the swelling potential and shrinkage potential with interlayer distance is presented, and the regularity of matric suction variations with interlayer distance is also obtained for unsaturated expansive soil. It may provide a new theoretical basis and research path for further research on the swelling-shrinkage mechanism of expansive soil and matric suction potential of unsaturated soil.     

Neoformation of montmorillonite by post-depositional subsurface weathering in a slope deposit in central France

Observations on an Early Quaternary slope deposit in the Massif Central indicated that the texture and mineralogy of this deposit have been seriously altered by post-depositional subsurface weathering. Analyses of clay fractions and water samples show that the montmorillonite present is a stable mineral in this environment and is, and has been, newly formed. As shown by water analyses from nearby sites, the chemical environment is strongly dependent on local factors. Consequently it can be seen that great care should be taken firstly in correlating different slope deposits on the basis of texture and clay mineralogy and secondly in using these parameters as (paleo) climatic indicators.     

Mineralogical and geomicrobial examination of soil contamination by radioactive Cs due to 2011 Fukushima Daiichi Nuclear Power Plant accident

Soil contamination by radioactive Cs from Fukushima Daiichi Nuclear Power Plant accident was investigated. Absorption and desorption experiments of Cs were conducted for several phyllosillicates (kaolinite, sericite, montmorillonite, vermiculite, chrysotile and biotite), zeolite and solid organic matter (dead and green leaves). The results confirmed the characteristic sorption and desorption of Cs by these materials. The 2:1 type phyllosilicate, especially, vermiculite and montmorillonite absorbed Cs well. Heated vermiculite for agricultural use and weathered montmorillonite also adsorbed Cs. Leaves also absorbed Cs considerably but easily desorbed it. In summary, the relative capacity and strength of different materials for sorption of Cs followed the order: zeolite (clinoptilolite) > 2:1 type clay mineral > 1:1 type clay mineral > dead and green leaves. Culture experiments using bacteria of both naturally living on dead leaves in Iitate village, Fukushima Pref. and bacterial strains of Bacillus subtillis, Rhodococus erythropolis, Streptomyces aomiensis and Actinomycetospora chlora were carried out. Non-radioactive 1% Cs solution (CsCl) was added to the culture media. Two types of strong or considerable bacterial uptakes of Cs were found in bacterial cells. One is that Cs was contained mainly as globules inside bacteria and the other is that Cs was absorbed in the whole bacterial cells. The globules consisted mainly of Cs and P. Based on all these results, future diffusion and re-circulation behavior of Cs in the surface environment was discussed.     

Mineralogy and physical nature of clay gouge

Fault gouges have been observed in the surface outcrops, in shallow excavations, and in deep (300 meters below the surface) tunnels and mines in fault zones. The 2-microns fractions in these fault gouges may compose a few percent to more than fifty percent of the total mass in the outcrops, and the mineralogy of the 2-microns fractions consists of a variety of clays (the common ones are montmorillonite, illite, kaolinite, chlorite, vermiculite and mixed-layer clays) and some quartz, feldspars, etc.Although we cannot yet conclude directly from the studies of gouges that similar gouges exist at depths where many large shallow earthquakes are generated, there is a strong possibility that they do, based on (1) available equilibrium data on various clays — for example, kaolinite has been found to exist at 4 kb and 375°C (±15°C) (Thompson, 1970) and montmorillonite + kaolite has been found to exist at 450°C and 4 kb (Velde, 1969); (2) the compatibility of laboratory velocity data in gouge (Wang et al., 1977) with those in a model for central California (Healy andPeake, 1975); (3) the capability of clays to undergo sudden earthquake-like displacements (Summers andByerlee, 1977); (4) the petrology of intrafault cataclastic rocks in old fault zones (Kasza, 1977); and (5) the compatibility of gouge mineralogy with the mineralogy of hydrothermal clay deposits.If clay gouges are indeed significant components of the fault zone at depth, then the mechanical properties of clays under confining pressures up to 4 kb are important in the behavior of faults. Very few experiments have been performed under such high pressures. But from the physical makeup of clays, we can infer that (1) the range of possible behavior includes stable sliding with vermiculite and montmorillonite (asByerlee andSummers, 1977, have proven) to stick-slip-like behavior with kaolinite, chlorite, etc.; (2) the absence or presence of water will greatly affect the strengths of gouges — it is possible that water may reduce the strength of gouge to a fairly small value.     

Evaluation of reservoir temperatures and local utilization of geothermal waters of the Konkan Coast, India

Geochemical studies on fifteen geothermal manifestations (38–70°C) from the Konkan coast geothermal province of India have been used to evaluate the reservoir temperatures. Activity studies of the minerals and the waters present in the reservoirs suggest that the thermal waters are in equilibrium with montmorillonite, kaolinite and quartz at about 100°C. Reservoir temperatures of these geothermal systems as estimated by geochemical thermometers, are 88 to 128°C, and thus too low for economic electricity production.     

A Comparative Study of the Use of Organoclay‐Based Formulations and Organic Amendment to Reduce the Leaching of the Herbicide MCPA in Soil

MCPA (4‐chloro‐2‐methylphenoxyacetic acid) is an acidic herbicide widely used on olive crops in Spain. Due to its anionic form at natural soil pH, there is high risk of leaching and groundwater contamination by the use of this herbicide. The aim of this work was to study the effects of organoclay‐based formulations of MCPA and olive oil waste amendment on MCPA leaching in a sandy loam soil. For this purpose, batch adsorption and column leaching studies were performed. The organoclays used to prepare the clay‐based formulations of MCPA were obtained by treating Wyoming montmorillonite (SWy‐2) and Arizona montmorillonite (SAz‐1) with an amount of hexadecyltrimethylammonium (HDTMA) cation equal to 100% of the CEC of the montmorillonites. The organic residue used in this study was a solid waste from olive oil production (olive oil waste, OOW). The soil was amended with the organic residue at the rate of 10% (w/w). Batch release and column leaching studies indicated that organoclay‐based formulations of MCPA reduced the release rate and the leaching of the herbicide as compared to the use of a conventional formulation containing the herbicide in an immediately available form. The increase in soil organic matter of the soil upon amendment with the organic residue also resulted in greater adsorption and reduced leaching of MCPA in the soil. Accordingly, both the use of organoclay‐based formulations and the amendment of soil with OOW are proposed as efficient strategies to reduce extensive leaching losses associated with the application of MCPA in high‐risk scenarios, such as Mediterranean olive groves.     

The influence of weathering on the geotechnical properties and slope angles of mudstone in the Mineoka earth-slide area,Japan

Three active earth-slide slopes of Tertiary mudstone were investigated: Slope 1 has an angle of 17 ?4°, Slope 2 of 12.9°, and Slope 3 of 11.6°. Infinite slope analysis indicated that the instability of these three slopes can be well explained by using the residual strength parameters of earth-slide soils near the sliding surface in conjunction with the highest ground water table. The residual angle of shearing resistance, ø'_r, plays an important role in the determination of slope angle because it differs greatly among slopes. Mineralogical studies and X-ray diffraction analyses were performed for the clay minerals included in the slope material. The results showed that illite and chlorite were found in Slope 1, and also in Slopes 2 and 3 together with interstratified illite/montmorillonite and montmorillonite. The degree of weathering is progressive in order of Slopes 1, 2 and 3. The alteration of clay minerals by weathering causes the reduction in ø'_r -values, i.e., 19.4° in Slope 1 (steep, less weathered) and 12.1-9.2° in Slopes 2 and 3 (gentle, much more weathered). This result indicates that the degree of weathering has a great influence on the value of ø'_r, which in turn determines the slope angle.     

A study of the depth of weathering and its relationship to the mechanical properties of near-surface rocks in the Mojave Desert

Weathered granite extends 70 m deep at Hi Vista in the arid central Mojave Desert of southern California. The low strength of this granite is due to the alteration of biotite and chlorite montmorillonite. Deep weathering probably occurs in most granites, although we cannot rule out some anomalous mechanisms at Hi Vista. Geophysical instruments set in these slightly altered rocks are limited by the unstable behavior of the rocks. Thus, tectonic signals from instruments placed in shallow boreholes give vague results. Geophysical measurements of these weathered rocks resemble measurements of granitic rocks near major faults. The rheology of the rocks in which instruments are placed limits the useful sensitivity of the instruments.     

江西省广丰县李家膨润土矿床成因及找矿标志

广丰县李家膨润土矿床赋存于白垩系上统南雄组第二岩性段酸性火山岩的顶底部。膨润土的主要矿物成分为蒙脱石,矿石结构构造与成矿原岩有关。矿石化学成分与酸性熔岩相近,矿体形态及空间分布受酸性熔岩流相带的控制。因此认为,膨润土矿床成矿原岩为酸性玻质熔岩,矿床是由酸性玻璃质熔岩经水解脱玻化而形成,其成因类型为风化淋滤蚀变岩型矿床。膨润土可自然改型,由原来的钠基膨润土改型成钙基膨润土和偏镁的钙基膨润土。对时代较新的酸性火山岩,在玻质熔岩发育处都有可能找到有利用价值的膨润土矿。由于膨润土常由珍珠岩、沸石脱玻化形成,三者常共生出现,是很好的找矿标志。     

Permselective Membrane Fouling During Azo Dye Wastewater Treatment

A Na‐montmorillonite membrane wastewater renovation prototype system was developed to specifically treat an ionic azo dye. Efficiency of this prototype system was limited to membrane fouling. Fouling rates were not consistently uniform owing to steric effects and competition for exchange sites. The decrease in solute rejection with time can be attributed to the decrease in the relative permeability of the compacted Na‐montmorillonite membrane to the dye with time due to fouling. This decrease occurs probably as a two‐step nucleation–growth mechanism with the nucleation part dependent in part on solvent flux, number of nucleation sites on the membrane, and sorbed mass part that controls solute flux and organic polymerization. The effect of concentration polarization was significant since the flux was higher than the mass‐transfer coefficient. The low diffusion coefficient of the ionic azo dye resulted in low mass transfer coefficients. The most important macromolecular solution properties to be considered for pilot systems may include high concentration‐dependent viscosity, possible non‐Newtonian fluid behavior, and low and concentration‐dependent self‐diffusivity amongst other factors. For pilot systems, the greater the quantity of large macromolecules in the ambient water, the greater the necessity of reducing the permselectivity of the membrane to prevent significant polarization.     

Ion concentration caused by an external solution into the porewater of compacted bentonite

The concentrations caused by the external solution into the porewater were studied with compacted bentonite (MX-80), from which easily dissolving components had been removed in order to ensure that the ions in the porewater came from the external solution. The dry densities of the samples varied from 700 to 1700 kg/m³ and NaCl solutions of 0.1–3 M were used as the external solution for saturation. The concentrations in the porewater were determined by the direct analysis of the squeezed porewaters and by dispersing the sample in deionized water.At high concentrations, the Donnan model can predict the concentrations in the porewater rather well. At low concentrations, where the ion exclusion is stronger, the measured concentrations are clearly higher than the modelled values. One possible explanation for this discrepancy is the microstructure of the bentonite, and an attempt to couple the effects of the microstructure and the Donnan model was made. It was assumed that there are two pore types, interlamellar pores in the montmorillonite stacks and large pores in the gel between the stacks. The dimensions of the microstructure were obtained from SAXS and BET(N₂) measurements. In this case, the fitting is much better, which supports the assumption of different pore types in bentonite.