Sepiolite effects

Calcite and sepiolite precipitate in large part because of the effects of the escaping C02. The corresponding reactions are,... 

Substitution and variations in the tetrahedral sites change the manner of side linkages for the ribbons, effecting the octahedral cation and water associations. In addition, different ribbon widths can lead to different numbers of octahedral cations. Variation in the width of chains and substitution of cations and water are easily accomplished, which means that accurate and consistent chemical and crystal structural data on these minerals are difficult or, at best, approximate. However, the minerals do form fibers with a consistent fiber axis repeat of about 0.512 nm (Preisinger, 1959 Rautureau et al., 1972). Sepiolite and palygorskite represent the widest possible structural and chemical diversity among fibrous silicate minerals. 

Figure 5. The effects of vanadium on a cracking catalyst activity before and after addition of a metal scavenger (Spanish sepiolite).

In this paper, XPS and Raman spectroscopy have been used to study the chemical state and location of Ni and V contaminants. The effects of thermal and hydrothermal treatments on catalyst surface properties, and the role of sepiolite in promoting metals tolerance has been observed and reported. 

The relative ease with which VpOr can be reduced to V(III) in aluminosilicates indicate the exiirence of weak metal-surface interactions and the inability of the surface to effectively passivate vanadium. Similarly, V on Kaolin (and metakaolin) exist mostly as the "free oxide and can (in part) be reduced to V(III) species. Therefore, DFCC systems containing metakaolin microspheres (or amorphous aluminosilicates (15)) should not be as effective as sepiolite in passivating metals TTke Ni and V. In fact, DCC mixtures loaded with 5000 ppm Ni-equivalents (that is 0.6% V + 0.38% Ni) are not metals resistant when metakaolin is used as a metals scavenger (1) ... 

DFCC mixtures containing 40% sepiolite and 60% GRZ-1 are equally effective in passivating high (10,000 wtppm) levels of vanadium impurities (1 ). In both cases, metakaolin microspheres do not... 

Choudhury et al. [86] have studied the effect of polymer-solvent and clay-solvent interaction on the mechanical properties of the HNBR/sepiolite nanocomposites. They chose nine different sets of solvent composition and found that chloroform/methyl ethyl ketone (Qi/MEK) (i.e., HNBR dissolved in Ch and sepio-lite dissolved in MEK) is the best solvent combination for improvement in mechanical properties. XRD, AFM, , and UV-vis spectroscopy studies show that the dispersion of clay is best in the Ch/MEK solvent combination and hence polymer-filler interaction is also the highest. images shown in Fig. 14a, b clearly elucidate the aforementioned phenomena. Consequently, the tensile strength and modulus are found to be higher (5.89 MPa and 1.50 MPa, respectively) for the Ch/MEK system due to the minimum difference in interaction parameter of HNBR-solvent (xab) and sepiolite-solvent (Xcd)- Choudhury et al. have also studied the effect of different nanoclays [NA, , 15A, and sepiolite (SP)] and nanosilica (Aerosil 300) on the mechanical properties of HNBR [36]. The tensile... 

Thus the solution always contains Mg in approximately constant abundance, which makes it effectively a perfectly mobile component. The same is true for H+ since pH changes little after precipitation of the sepiolite even though the reaction consumes (OH). The experimental system is then "open" with respect to these two components. A determination of the solubility product constant of a natural iron-calcium-aluminous sepiolite confirms generally the above results (Christ, et al , 1973). 

Borja and Banks studied the kinetics of the anaerobic digestion of fruit processing wastewater (COD = 5.1 g/l). They used several substrata as scaffolds for the development of degrading colonies of bacteria. The kinetics of degradation were compared with the kinetics of a suspended biomass. The first order rate constant was determined and is shown in Figure 5.13. While the rate for the polyurethane was lower than rates for the sepiolite and saponite, some of the improvements we suggested and an improvement in mass transport could improve the rates of reaction. In any case, the paper of Borja and Banks suggests effect on kinetics exerted by the substratum. 

FCC catalyst development to reduce the effect of vanadium has been aimed at reduction of vanadium mobility the application of special ingredients in the catalyst which function as metal scavengers or metal catchers. In the past (2, 10) transport experiments were used to show that during steam-aging, intraparticle transfer of vanadium occurs and that migrating vanadium can be irreversibly sorbed by a metal trap such as sepiolite (2) in the form of a heat stable vanadate. 

The model described in Figure 13.5 takes into account both the physical and chemical effects of the interlayers but the chemical ones, which are reflected, for example, in the ignition time, have not yet been discussed. A number of cone calorimetric investigations reported a decrease of the time to ignition (TTI) in presence of clay nanofillers. Such results can be seen in Table 13.2 for MMT and sepiolite (SEP) clay types. 

Schlitter [4] demonstrated that catalysts of the montmorillonite/saponite group, the kaolin/serpentine group, and the palygorskite/sepiolite group were effective as the THF polymerization agents. 

Effect on rheological properties sepiolite thennal treatment 81... 

Sepiolite was subjected to a thermal treatment which removes crystallization water at 500 C and constitution water at 850°C. When these changes occur, they are accompanied by crystal folding which introduce substantial changes in the structure and interaction capabilities of sepiolite. Treated and untreated sepiolites were used in the preparation of a polyurethane adhesive to determine if the modification impacts the properties of the adhesive such as its interaction with polymer essential for its performance in adhesive. Figure 19.1 shows the effect of treatment... 

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