A mixed alkali metal titanate of composition A x Ti 2-x/3 Li x/3 O 4 (A ) K, Rb, Cs) has been prepared and its ion-exchange/intercalation properties have been explored. Solid-state calcination of appropriate mixtures of TiO 2 and alkali metal carbonates produced the titanate at a stoichiometry of x ) 0.80 for A ) K, 0.75 for Rb, and 0.70 for Cs. Rietveld refinement on neutron diffraction data confirmed that the orthorhombic structure is comprised of lepidocrocite-related host layers of Ti 2-x/3 Li x/3 O 4 and charge-balancing A ions in the interlayer domain. Complete extraction of both alkali metal ions was achieved by acid-leaching, producing a new protonic titanate of H 4x/3 Ti 2-x/3 O 4 ‚H 2 O. This phase is distinguished from isomorphous related compounds in terms of high proton content as a consequence of exchangeable Li ions located in the host framework. The material took up alkali metal ions and organoammonium ions from aqueous media. These ion-exchange and intercalation reactions brought about expansion/contraction of the gallery height and lateral displacement of the layers. The resulting various types of layer sequence can be understood in terms of the nature of the interlayer species.

The influence of layer charge on the intercalation of terephthalate and benzoate anions in MgAl layered double hydroxides has been studied. It is found that, under the synthesis conditions used here, incorporation of the anion is dependent upon the Mg:Al ratio of the host sheets. Pure terephthalate and benzoate intercalates are formed for a ratio of 2 or less from both chloride and nitrate solutions. At higher values of layer charge competitive incorporation of the counteranion present in the solution (i.e., chloride or nitrate) occurs with decreased incorporation of organic anions at ratio 3 or higher. Two extreme orientations are observed for the organic anion within the galleryeither vertical (i.e., perpendicular to the layers) or horizontal. In the case of terephthalate a monolayer arrangement exists, whereas for benzoate the vertical arrangement is a bilayer and the horizontal a monolayer. Whether a vertical or horizontal orientation is adopted depends upon the charge on the layers, the temperature, and the degree of hydration of the sample.

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Abstract--Rehydration is shown to be straightforward for the reconstruction of polyoxometallate-pillared layered double hydroxides. Zn-A1 hydrotalcite-like minerals were prepared with Zn/A1 ratios of 1 to 5 by coprecipitation at pH 7. Good crystallinity was obtained for samples with Zn/Al ratios above 2. Thermal decomposition was achieved by calcining the samples at 300 to 900 ~ The calcined samples were exposed to decarbonated water, with or without hydrothermal treatment to evaluate reconstruction of the hydrotalcite-like minerals by rehydration. Restoration of the hydrotalcite-like structure was found to be independent of the Zn/A1 ratios for samples calcined between 300 and 400 ~ however, a second phase, aluminum hydroxide or zinc oxide, was generally detected. A spinel phase, formed during the calcination of samples at temperatures above 600 ~ inhibited reconstruction of the hydrotalcite-like phase. The rehydrated hydrotalcite-like minerals had Zn/A1 ratios close to 2, irrespective of the chemistry of the starting material.