Vermiculites modified

Kalcher K, Grabec I, Raber G, Cai XH, Tavcar G, Ogorevc B (1995) The vermiculite-modified carbon paste electrode as a model system for preconcentrating mono- and divalent cations. J Electroanal Chem 386 149-156... 

Svegl IG, Ogorevc B, Hudnik V (1996) A methodological approach to the application of a vermiculite-modified carbon paste electrode in interaction studies influence of some pesticides on the uptake of Cu(II) from a solution to the solid phase. Fresenius J Anal Chem... 

Fig. 4. Spatial distribution of (a) relative elemental elongation rate (longitudinal growth rate) and (p) osmotic potential in the apical 10 mm of maize primary roots growing at various vermiculite water contents (see Fig. 3). Growth distributions were obtained by time-lapse photographic analysis of the growth of marked roots points are means from 5 or 6 roots. Osmotic potentials were measured on bulked samples from 30-50 roots points are means s.d. (n = 3-7). Root elongation rates (a, inset) were constant when the measurements were made. Modified from Sharp et al. (1988, 1989).

Growth of Seedlings. Cucumber (Cucumis sativus L., cv. Wisconsin SMR-IS) and soybean (Glycine max L. Merr., cv. Wayne) were grown in vermiculite and watered daily in a controlled environment chamber (26 2 C day, 21 2 C night) on a 12 hr photoperiod (eight 30-W cool-white fluorescent tubes plus four 25-W incandescent bulbs 200+foot-candles). The balanced nutrient solution of Frick and Mohr (H9), modified to include 1 g/1 Ca(N03)2 but without sucrose, succinic acid and kinetin, was applied on alternate days. 

Preparation of Modified Soy Proteins from Germinating Soybeans. Soybean seeds (12 g dry weight) were germinated on wet Vermiculite in a metal pan covered with aluminum foil. Water was added to the tray as needed during the course of germination. To collect products, the germinated seeds were washed and then ground with mortar... 

Experimental. A Parr model 1221 oxygen bomb calorimeter was modified for isothermal operation and to ensure solution of nitrogen oxides (2). The space between the water jacket and the case was filled with vermiculite (exploded mica) to improve insulation. A flexible 1000-watt heater (Cenco No. 16565-3) was bent in the form of a circle to fit just within the jacket about 1 cm. above the bottom. Heater ends were soldered through the orifices left by removing the hot and cold water valves. A copper-constantan thermocouple and a precision platinum resistance thermometer (Minco model S37-2) were calibrated by comparison with a National Bureau of Standards-calibrated Leeds and Northrup model 8164 platinum resistance thermometer. The thermometer was used to sense the temperature within the calorimeter bucket the thermocouple sensed the jacket temperature. A mercury-in-glass thermoregulator (Philadelphia Scientific Glass model CE-712) was used to control the jacket temperature. 

Examples of other property modifiers are silicone powder and liquids, fiuoropolymer powders, Pro-maxon (processed calcium silicate), mica, vermiculite, and waxes. 

In the case of vermiculite, the short-chain organic cations do not penetrate into the interlayer space, and are adsorbed only on the external surface of the mineral. This is clearly seen from the analytical measurements, showing that only 0.06 meq/g of Na" " ions is substituted when Na-vermiculite is treated with tetramethylammonium salt solution, the total exchange capacity being equal to 1.5 meq/g. Therefore, the values of specific surface area obtained from water and hexane adsorption isotherms for the initial and [(CH3)4N] modified vermiculite are virtually the same (Table 3). Such a pronounced difference in the... 

A rather different behaviour is observed [32] for modified montmorillonite, possessing more labile and disordered structure as compared with fluorohectorite and vermiculite. 

Most methods can be modified to suit applications, but for specific applications and to accoimt for long-term efficiency, near faithful conditions may be afforded by humidity chamber techniques, such as soil burial or vermiculite bed. Often a combination of tests is worthwhile in order to reflect performance imder actual climatic and environmental conditions. 

G. Abate, L.B.O. Santos, S.M. Colombo, J.C. Masini, Sequential injection analysis as a tool for on-line monitoring the sorption of fulvic acid onto modified vermiculite, J. Braz. Chem. Soc. 17 (2006) 491. 

Despite the unlikelihood of secondary mineral formation by ion substitution into or movement within an existing solid, some secondary 2 1 layer silicates apparently are formed by solid-phase changes of mica fragments inherited from the parent material. Hydrous mica, for example, is a product of chemical weathering as well as mechanical breakdown of mica. Hydrous mica, in turn, can be modified directly to vermiculite, montmorillonite, or chlorite. The process is not completely understood, but seemingly involves the outward diffusion of K+ from between the layer lattices and a subsequent or simultaneous reduction of charge within the layer lattice. 

Figure 20. A HRTEM image of hydrobiotite. The interlayer regions indicated by arrows have a continuous white line contrast compared to adjacent biotite interlayer regions, snggesting that potassium is depleted in these interlayer regions. They are considered to be formed by the collapse of vermiculite layers (modified from Kognre and Mnrakami 1996).

Vermiculite Surface Modified with Carnauba Wax for Oil Cleaning... 

Since water molecules can adsorb on the clay surface, water can be considered as a modifier. To investigate the hydration process of vermiculite, a calorimetric study was performed with the main results as shovm in this section. The vermicuhte sample used was the same as described in the previous section. 

The safest and probably the most satisfactory equipment for measurements above 350 K is the solid block furnace. A modified version of the aluminium block furnace described by Powell et al. is illustrated in Figure 1. The furnace consists of an aluminium cylinder 300 mm long and 160 mm in diameter. The sample tubes can be inserted into a vertical hole drilled down the axis of the aluminium cylinder and are viewed through a small horizontal hole. The tubes are illuminated from behind by a small focused light. The aluminium block is insulated by a layer of vermiculite (about 100 mm thick) and the whole enclosed in a large asbestos cylinder. The original version was heated by externally wound Nichrome wire. It has been found, however, that electric elements cast in the aluminium block are more convenient, particularly when the furnace is to be operated above 600 K for long periods. 

The study of the polymeric nanocomposites on the basis of the modified layered silicates (broadly distributed and well-known as various clays) is of much interest. The natural layered inorganic structures used in producing the polymeric nanocomposites are the montmorillonite [10-12], hectorite [13], vermiculite [14], kaohn, saponine [15], and others. The sizes of inorganic layers are about 220 and 1 nanometers in length and width, respectively [16,17],... 

Ravichandran, J. and Sivasankar, B. (1997). Properties and catalytic activity of acid-modified montinorillonite and vermiculite. Clays and Clay Minerals, 45 854— 858. 

Table 1.1 Basal plane spacing values of various surface-modified montmorillonites and vermiculites [8-13].

The required amounts of modified montmoriUonite or vermiculite and epoxy resin were calculated by following these relations [13, 14] ... 

Table 8.3 Density of modified vermiculite as well as composites containing 3.5 vol% inorganic filler fraction.

Figure 8.10 X-ray diffractograms of (a) (I) BzC16 modified vermiculite and (II) the filler in epoxy composite and (b) (I) BzCISOH modified vermiculite and (II) the filler in epoxy composite. Reproduced from Ref. [14] with permission from Sage Publishers.

---