Comparative study of the coprecipitation methods for the preparation of Layered Double Hydroxides

• Main Authors: Crepaldi Eduardo L., Pavan Paulo C., Valim João B.
• Format: Article
• Language: English
• Published: Sociedade Brasileira de Química 2000-01-01
• Series: Journal of the Brazilian Chemical Society
• Subjects: layered double hydroxides; coprecipitation; intercalation; hydrotalcite
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532000000100012

Coprecipitation is the method most frequently applied to prepare Layered Double Hydroxides (LDHs). Two variations of this method can be used, depending on the pH control conditions during the precipitation step. In one case the pH values are allowed to vary while in the other they are kept constant throughout coprecipitation. Although research groups have their preferences, no systematic comparison of the two variations of the coprecipitation method is available in the literature. On this basis, the objective of the present study was to compare the properties of LDHs prepared using the two forms of pH control in the coprecipitation method. The results showed that even though coprecipitation is easier to perform under conditions of variable pH values, materials with more interesting properties, from the point of view of technological applications, are obtained at constant pH. Higher crystallinity, smaller particle size, higher specific surface area and higher average pore diameter were found for materials obtained by coprecipitation at constant pH, when compared to the materials obtained at variable pH.