Exchange interlayer

Since the hydrotalcite-like material contains exchangeable interlayer anions, it can be used as a catalyst for reactions for which anion-exchange resins have been used as catalyst. The disproportionation of trimethoxysilane (eq. 2) is... 

Basically, little can be said about the montmorillonite data. The compositional dispersion is quite large. Some of this variation can be explained in part by an overpopulation of octahedral sites due to mis-assignment of magnesium ions as proposed by Foster (1951). In such case, a portion of the magnesium present is exchangeable, interlayer ions which if misassigned to octahedral sites will decrease the apparent interlayer... 

Newman, S. P. and Jones, W. (1999). Comparative study of some layered hydroxide salts containing exchangeable interlayer anions. J. Solid State Chem. 148, 26. 

An important feature of the smectites, vermiculites and other 2 1 layer silicates is that isomorphous substitutions can occur in both the tetrahedral and octahedral sheets. Thus, substitution of Si by A1 occurs in the tetrahedral sheet, together with replacement of A1 by Mg, Fe, Li or other small atoms in the octahedral sheet. The substitutions lead to a deficit of positive charge, which is compensated by the presence of exchangeable, interlayer cations. 

Foldvari, M., P. Kovacs-Palffy, N. M. Nagy, and J. Konya. 1998. Use of the second derivative of TG curves for investigation of the exchanged interlayer cation in montmoril-lonite. J. Therm. Anal. 53 547-558. 

Note Cations listed first in curved brackets for the smectites and vermiculites (Na, Ca, K, and Mg) arc present as exchangeable interlayer ions. All the smectites and vermiculites (and thus interlayer iilite-smectites) have important amounts of interlayer water, the amount of which depends upon the clay and the nature of interlayer cations (cf. Brindley and Brown 1980). As is customary, these waters are left out of the mineral formulae. 

The adsorption and binding of DNA by clay minerals can be affected by many different factors [34, 48, 55] such as for example pH [43, 56], presence of water [57], the clay type [58], the nature of exchangeable interlayer cations [56, 59], and also the DNA structure [44, 51]. However, the obtained results are in conflict with each other and the interactions of DNA with clay minerals have not been clarified yet except the predictions that the adsorption could occur also due to the Coulombic attraction, van der Waals interactions [26] and hydrogen bonding [43]. 

NMR spectrum of o-H2Si205, Figure 9-7a, shows a narrow resonance at 4.05 ppm and a broad resonance centered about 16 ppm indicating the presence of two different non-exchanging interlayer proton environments. 

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