Facile synthesis of hydrotalcite and its thermal decomposition kinetics mechanism study with masterplots method

The hydrotalcite, Mg4Al2(OH)(12)CO3 center dot 3H(2)O, was synthesized via low-heating solid-state reaction at 80 degrees C. The thermal decomposition of Mg4Al2(OH)(12)CO3 center dot 3H(2)O experienced two stages. The apparent activation energy E-a was estimated with Vyazovkin procedure. The average values of E-a associated with the two stages were determined to be 110.9 +/- 10.3, 140.3 +/- 4.2 kJ mol(-1), respectively, which the two stages are single-step kinetic processes. Masterplots and nonlinear methods were used to define the most probable reaction mechanisms of the two stages. The results show that the reaction mechanism functions of the two stages are as follows: (i) g(alpha)=(1-alpha)(-2)-1, (ii) g(alpha)=(1-alpha)(-1/2)-1, respectively. The values of pre-exponential factor A for the two stages were obtained on the basis of E-a and g(alpha). Besides, some thermodynamic functions (Delta S-#, Delta H-# and Delta G(#)) of the transition state complexes for the two stages were also calculated. (C) 2014 Elsevier B.V. All rights reserved.