Dodecylammonium vermiculite

Figure 14. The adsorption excess isotherm (a) and the interlameUar expansion (b) for system dodecylammonium-vermiculite in benzene(l)- -n-heptane(2) mixtures. Dotted lines calculated excess isotherms with non-swelling (I) and swelling (II) system.

The structure and the sorption properties of partially hydrophobized silicates (do-decylammonium and dodecyldiammonium vermiculites) were investigated in aqueous solutions of n-butanol. The alcohol is preferentially adsorbed on the surface. The interlayer composition is calculated from adsorption and X-ray diffraction data. In the air-dried state the organic cations lie flat on the interlamellar surface. In aqueous n-butanol solutions, the basal spacing of dodecylammonium vermiculite gradually increases with the extent of n-butanol adsorption because the chains increasingly point away from the surface. The basal spacing of dodecyldiammonium vermicuiite is virtually independent of the interlayer composition, because the expansion of the interlayer space is sterically restricted and a... 

FIG. 27 Basal spacings of ( ) dodecylammonium vermiculite and ( ) dodecyldiam-monium vermiculite in n-butanol-water solutions. 

FIG. 26 Adsorption excess isotherms in n-butanol-water solutions on (O) dodecylammonium vermiculite and on ( ) dodecyldiammonium vermiculite. (From Ref 38.)... 

The surface excess isotherms for dodecylammonium, dodecyldiammonivim vermiculite (Fig. 26), reveal that the amount of butanol adsorbed increases with Because the mole fraction of butanol is very small,... 

If H-vermiculite is immersed in neutral alkylamine, the corresponding alkylammonium-vermiculite is formed, although considerable amounts of Mg, Al, and other inorganic cations may also be present in the interlayer positions because of the instability of H-vermiculite (cf Section BIV5). Moreover, if an alkylammonium-vermiculite such as dodecylammonium is immersed in excess neutral alkylamine such as ethylamine, an interchange occurs within the lattice and ethylammonium-vermiculite, and free dodecylamine are produced (Walker and Bennett [1965]). 

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