Study of Thermal Decomposition of Layered Double-Magnesium Aluminum Hydroxide

Layered magnesium aluminum hydroxide Mg₄Al₂(OH)₁₂CO₃⋅3.85H₂O with the hydrotalcite structure is obtained by the solid-phase interaction of AlCl₃⋅6H₂O and MgCl₂⋅6H₂O with (NH₄)₂CO₃ at room temperature. The change in the phase composition of the products of its heat treatment in the temperature range 180–600°C is studied. It is determined by DSC/TG that the thermal decomposition occurs in two stages: the first stage occurs in the temperature range 180–215°C; the second, in the range 400–440°C. The apparent activation energies E_a of both stages of thermal decomposition are found by the model-free Kissinger method to be 62.85 and 141.86 kJ/mol, respectively. The obtained E_a values agree well with the literature data and indicate that both stages are single-step kinetic processes.