Anionic clay and hydrotalcite synthesis

Abstract

Anionic clays are becoming more important for their application as catalysts, ion exchangers and adsorbers and for medical applications as well. Anionic clays are also used as stabilizers of dispersive systems of ceramic suspensions and drilling fluids in the oil industry, The anionic clays have an appropriate use in ceramic industry during raw materials activation. This paper presents the results of the hydrotalcite Mg6Al2 (OH)(16)(CO3)(4)H2O synthesis at room temperature of 18 degreesC and pH values of reactant mixtures of pH=12 (synthesis I) and pH=10.5 (synthesis II). The reactants were basic magnesium carbonate (suspended in water) and solutions of AlCl3, Na2CO3 and NaOH. The identification of the synthesized hydrotalcite included the chemical, X-ray, IR, TGA and DTA analyses. The product of the synthesis I is the mixture of the following minerals: hydrotalcite, manasseite, bayerite and brucite. The product of synthesis II is hydrotalcite, together with basic magnesium carbonate that failed to react. The structural formula of synthetic hydrotalcite prepared at room temperature was determined by: [Mg0,64Al0,31(OH)(2)][(CO3)(0,16)0,62H(2)O]. For the synthesized hydrotalcite, the crystal size and morphology, the surface area and hence the catalytic activity varied dramatically with the crystallization temperature. At the crystallization temperature of 60 degreesC only thin, poorly crystallized platelets were obtained and very catalytic activity resulted.