The effect of synthetic conditions on tailoring the size of hydrotalcite particles

The hydrotalcite particles of Mg2Al(OH)6(CO3)1/2·0.1H2O have been prepared by two different methods: (1) direct coprecipitation of aqueous solution of Mg(NO3)2·6H2O, Al(NO3)3·9H2O upon hydrolysis of urea, and (2) hydrothermal aging of the same nitrate solution after NaOH titration. In order to control the particle size and morphology of hydrotalcite, various parameters such as metal ion concentration, aging time, reaction temperature are systematically studied. According to the powder X-ray diffraction, all the samples turn out to be well crystallized with an average basal spacing of 7.6 Å corresponding to the hydrotalcite crystal. From the SEM images, the coprecipitates are found to be hexagonal in shape and are controlled in the particle size range of 0.9–2.2 and 1.2–4.5 μm depending on aging time (6–69 h) and metal ion concentration (0.87–0.065 M), respectively. However, the particle size of the hydrothermally prepared samples increase in proportion to aging time (12–72 h ; 85–120 nm) and reaction temperature (100–180 °C; 115–340 nm). The effect of such parameters upon the particle size was rationalized on the basis of crystal growth mechanism.