Layered double hydroxides (LDHs), shown as the general formula of [M2+1-xM3+x(OH)2]x+(An-)x/n∙yH2O, are useful for various applications such as anion exchangers/adsorbents, catalysts and catalysts' supports, and drug/gene carriers due to their structural, compositional and morphological characteristics and their variation. The x value (M3+/(M2+ + M3+) ratio) in layered double hydroxides (LDHs), corresponding to the layer charge density, is one of the important parameters for controlling the properties of LDHs. The x values in commonly available LDHs are limited (0.2 < x < 0.3). In order to obtain LDHs with x < 0.2, Mg2+ Ga3+-LDHs with interlayer iodide were examined. The linear correlation between lattice parameter a and x value in the products with x of 0.06-0.24 was seen, suggesting the successful substitution of Mg2+ in the brucite-like sheet with Ga3+. Carbonate and dodecyl sulfate types MgGa-LDH were prepared by ion exchange with carbonate anion and reconstruction in aqueous solution of sodium dodecyl sulfate. The products with x of 0.06 were dispersed in water and hexanol better than those with x of 0.24 for MgGa-LDHs containing carbonate and dodecyl sulfate, respectively, suggesting effects of the lower layer charge density on the dispersion.
Keywords: layer charge density; layered double hydroxides.