Effect of hydrothermal conditions on the crystallization of Mg ₃Al-CO₃^2- hydrotalcite

The effect of hydrothermal treatment conditions on Mg-Al hydrotalcite carbonate crystallization, the relative crystal diffraction intensity, CO ₃^2- interlayer anion state and the layered double oxides (LDO) reconstruction was studied by XRD, TEM, TG-DTA and temperature program decomposition (TPD). The results showed that the crystallinity of samples increased with hydrothermal temperature and (003), (006) faces grew preferentially when the hydrothemal temperature was lower than 270°C. The crystallinity of hydrotalcites destroyed when the temperature was higher than 270°C. The decomposition temperature of the hydrotalcite (HT) to LDO was between 300°C and 380°C. The decarbonization process of HT samples treated with higher hydrothermal temperature moved to higher temperature region and the decomposition temperature interval was narrowed down. LDO was easy to reconstruct to hydrotalcite at hydrothermal conditions. MgO in LDO was easier to recover into HT than AlO(OH) and MgAl₂O₄.