Physico-Chemical Properties of Synthetic Hydrotalcites in Relation to Composition

Shigeo Miyata
Kyowa Chemical industry Co., Ltd., Yashimanishi-machi, Takamatsu-shi, Japan

Abstract: Hydrotalcite solid solutions were prepared by coprecipitation followed by hydrothermal treatment between 150° and 250°C. Based on the structural formula [Mg1−xAlx(OH)2]X+[(CO3)x/2⋅mH2O]x−, pure solid solutions were formed in the range Al/(Al + Mg) = 0.2 to 0.33, where m = (1 − 3x/2). Maximum crystallite size was achieved by hydrothermal treatment between 180 ° and 200°C with x = 0.337 to 0.429. Crystal strain was also minimized at these values of x. The adsorption capacity for Naphthol Yellow S increased as x increased and reached a maximum (1.56 × 10−6 moles/m2) when x = 0.287, a value eight times larger than that of Mg(OH)2. A weak endothermic DTA peak at about 350°C is probably due to the loss of structural water in the main layer of the structure. On calcination between 400° and 700°C only periclase was detected, probably containing Al in solid solution. Hydration of the calcined product resulted in the reconstruction of the original hydrotalcite structure.

Key Words: Crystal strain • Hydrotalcite • Solid solution • Synthesis • Thermal stability

Clays and Clay Minerals; February 1980 v. 28; no. 1; p. 50-56; DOI: 10.1346/CCMN.1980.0280107
© 1980, The Clay Minerals Society
Clay Minerals Society (www.clays.org)