Montmorillonite clay minerals

Methyltins are less likely than the butyl- and octyl-tins to partition to sediments, soils, and organic carbon. Modelled data for K c suggest much lower capacity for binding to organic carbon than do measured values, often by several orders of magnitude. Measured data have been used in preference to model environmental fate of the compounds. The compounds also bind strongly to clay minerals, montmorillonite in particular. 

Bentonite is the name for a hydrous aluminum silicate comprised principally of the clay mineral montmorillonite, notable for its ability to swell in water and to form a very low-permeability seal." It is available as powder, granule (chip), or pellets. Powder and granule sizes are produced by processing after mining. Bentonite powder... 

The clay mineral montmorillonite, which is often used in different prebiotic syntheses, is probably now the most important mineral for experiments on prebiotic chemistry. It has shown its abilities in the area of simulation experiments on the formation of primitive cellular compartments montmorillonite accelerates the spontaneous conversion of fatty acid micelles to vesicles. Clay particles are often incorporated into the vesicle, just as is RNA, which is adsorbed at such clay particles. If the vesicles have been formed, they can continue to grow if fatty acids are fed to them via micelles. If the vesicles are pressed through 100 nm pore filters, they divide without dilution of their contents. 

Figure 4.7 Structure of one of the smectite group of clay minerals montmorillonite, Al2Si40io(OH)2.nH20. (After Evans, 1966 Figure 11.08b, by permission of Cambridge University Press.)...

Windblown Surface Dust Quartz Calcite Oxides of iron Clay minerals Montmorillonite Illite 1-10 pm 30% globally... 

Theories for even earlier forms of mutateable transmission of genetic information have involved clay minerals. Montmorillonite clay particles have been demonstrated to catalyse the condensation of nucleotides and we discussed in Section 8.2.8 the Cairns Smith hypothesis of how crystal dislocations could transmit some form of genetic information. Most hypotheses about clays have yet to be demonstrated experimentally, however. 

Ruggiero et al. (1989) investigated the ability of a natural silt loam soil and the clay minerals, montmorillonite (Mte) and kaolinite (Kte), to immobilize laccase. They compared the catalytic abilities of the soil-enzyme and clay-enzyme complexes to degrade 2,4-dichlorophenol. They found that the immobilized laccase remains active in removing the substrate even after 15 repeated cycles of substrate addition (Figure 2.24). However, Claus and Filip (1988) found that the activity of tyrosinase, laccase, and peroxidase is inhibited by immobilization on bentonite. The type of saturating cations on clay surfaces also substantially influences enzymatic activity (Claus and Filip, 1990). 

Sawhney, B.L.. 1958. Aluminum interlayers in soil clay minerals, montmorillonite and vermiculite. Nature, 182 1595-1596. 

Stoichiometry and Surface Development. Some Aspects of Tobermorite Structure. Prior to the discussion that follows, it is necessary to point out certain features of the tobermorite structure. Tobermorite has a layer structure, like the clay minerals montmorillonite and vermiculite. Megaw and Kelsey (22) found that each layer of the natural mineral tobermorite was actually a triple layer a Ca02 layer in the center, similar to a distorted Ca(OH)2 layer from which all hydrogen atoms have been removed, and on both sides of this layers of metasilicate chains. This 2 1 layer is called one layer in the following discussion. 

The three-layered clay mineral montmorillonite (bentonite) is characterised by a low-hydraulic conductivity and a capacity to bind water molecules and positively charged ions (cations). As such, water-saturated compacted bentonite powder is used as a hydrological barrier in areas such as waste disposal, for example around land-fill sites where the desire is to prevent leakage of contaminants from the land-... 

Similar to Cs-137, minerals can be classified on the basis of kSr(i) values determined by the linear model (Table 3.10). From clay minerals, montmorillonite and... 

In Chapter 2 the interfacial processes are discussed in a model system. A clay mineral, montmorillonite, has been chosen to illustrate important interfacial processes of geological formations. Some transformations initiated by interfacial processes are demonstrated. 

Lotareva, O. V. Prozorov, A. A. (2000). Effect of the clay minerals montmorillonite and kaolinite on the generic transformation of competent Bacillus subtilis cells. Microbiology, 69, 571-4. 

From the point of view of structure, the above minerals belong to the so-called two-layer ones. Another clay mineral, montmorillonite, has a three-layered structure. It has the formula Al2(Si205)2 (OH)2,and exists as finer particles than the previously mentioned minerals (up to 60% below 0.1 pm). The gaps between the individual layers are readily penetrated by water which produces swelling when wetted and shrinkage when dried. Montmorillonitic clay is called bentonite. It has a considerable ion-cxchange capacity as described below. 

FIGURE 22.5 Structure of the clay mineral montmorillonite. Insertion of variable amounts of water causes the distance between layers to swell from 9.6 A to more than 20 A. When 1 AP ion is replaced by an ion, an additional ion such as Na is introduced into the water layers to maintain overall charge neutrality. 

The mineralogy that comprises the clay component of the soil is also critical to contamination of soils by biological and chemical threat agents. For example, ricin was sorbed to four different clay minerals as described above (Figure 4.2). Kaolinite, a 1 1 clay mineral, sorbed very little ricin. Sepiolite, a fibrous clay mineral, sorbed much more ricin. Illite, a tetrahedrally substituted 2 1 clay mineral, sorbed similar amounts of ricin as the sepiolite. The octahedrally substituted clay mineral, montmorillonite, sorbed much greater quantities than all of the other clay minerals. Even with this clay mineral, the cation that was dominantly sorbed to the clay made a difference. The Na-saturated montmorillonite sorbed more than the Ca-saturated montmorillonite. This is thought to be due to the swelling of the interlayers of the clays. Na-saturated clays swell more so than do Ca-saturated ones. Similar results are shown with aflatoxin Bj (Jaynes et al. 2007). 

Hendricks, S.B., Nelson, R.A. and Alexander, L.T., 1940. Hydration mechanism of the clay mineral montmorillonite saturated with various ions. J. Am. Chem. Soc., 62 1457-1464. 

In Figure 6.16, the effect of adding a 2 1 clay mineral (montmorillonite, in this case) to the solubility diagram is shown. Because this clay has Mg in its octahedral sheet, it becomes more stable (that is, less soluble), as the activity of Mg " is increased. It is necessary, then, to fix Mg activity at a reasonable value (pMg " = 3.7). Furthermore, montmorillonite becomes more stable as the solution pH is raised. To incorporate this fact into the solubility diagram (since the j -axis reflects... 

Bentonite is rock composed of the clay mineral montmorillonite, which is an expandable 2 1 aluminosilicate mineral (13-15). Figure 2 shows that the structure of the mineral consists of sheets or platelets that consist of a layer of octahedrally coordinated aluminum hydroxide sandwiched between two sheets of tetrahedrally coordinated silica (13). Although the thickness of the platelets is about 0.9 nm, the length can extend to about 1 pm. The bentonite platelets are therefore colloidal in size. 

The sodium concentration of soils is determined by the geological origin of the rocks. All minerals of the feldspar group (sodium feldspar, potassium feldspar, calcium feldspar), potassium mica and hornblende are rich in sodium. The same applies to the clay minerals montmorillonite and illite. 

Hendricks, St. B. Base exchange of the clay mineral Montmorillonite for... 

The test is based on the adsorption principle of clay minerals using methylene blue dye. During the test, the quantity of methylene blue required to cover all clayey ingredients is measured. The quantity of methylene blue dye adsorbed is related to the specific surface of the clay mineral (montmorillonite, illite and kaolinite). Active clay minerals have a large specific surface in contrast to inactive clay materials. As a result, the required methylene blue quantity will be proportional to the quantity and the type of clay minerals. 

The field of clay-polymer nanocomposite technology is attracting a great amount of attention (169). Among clay minerals, the 2 1 natural clay mineral montmorillonite has been used for clay nanocomposite applications. The structure of nanocomposites, the dynamics of confined polymer clay nanocomposites using NMR and computer simulations, rheology of clay nanocomposites have been... 

Key words Intercalation, clay mineral, montmorillonite, e-caprolactam, 6-polyamide, XRD, DSC, GPC, polymerization, catalysis, swelling. 

Abstract Data are presented to show that the surfaces of a common clay mineral, montmorillonite, modify the properties of the nearhy water to a depth of at least 3.S nm and that the value of every water property depends exponentially on t, the thickness of the films of adsorbed water, but is independent of the character of the surfaces. The viscosity and yield point are among the properties of the water that are modified. A modification of either of these properties has a commensurate effect on the flow of water between adjacent surfaces. Data are also presented to show that the surface-induced... 

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