Ternary (Mg-Zn-Al) hydrotalcites synthesis

In this work, synthesis of ternary hydrotalcites Mg-Zn-Al was obtained by chemical coprecipitation method. In the samples the amount of Zn and Mg varied; but molar ratio (Mg+Zn)/Al are kept constant (3.0). A study of species in solution determined that samples with high magnesium content had to be prepared at pH>9.5, while those with greater Zn molar content had to be prepared at pH=7.5. Using XRD, typical structure of hydrotalcites was identified in the samples; additionally, the samples that contain zinc exhibited some differences with respect to Mg-Al hydrotalcite, the differences are: 1) Presence of an adjacent shoulder to 009 plane (2theta=34.7degrees). 2) An additional peak, at 2theta=37degrees. This peak intensity is related with the amount of zinc. Thermal studies (TG, DTA) of the samples were very similar, and registered intervals of temperature in each one of the weight losses are very similar to the ones reported for Mg-Al hydrotalcites.