Kinetic Analysis of Illite Dehydroxylation Based on Differential Scanning Calorimetry

TL;DR

This study investigates the dehydroxylation process of illite using differential scanning calorimetry, calculating kinetic parameters and revealing diffusion-controlled mechanisms for both trans- and cis-vacant layer dehydroxylation.

Contribution

It provides detailed kinetic parameters and mechanistic insights into illite dehydroxylation, highlighting diffusion-controlled reactions and nucleation behaviors.

Findings

Activation energies for trans- and cis-vacant layers are approximately 227 kJ/mol and 242 kJ/mol.

Dehydroxylation follows diffusion-controlled mechanisms with specific nucleation characteristics.

Kinetic parameters enable better understanding of illite thermal behavior.

Abstract

The two-step dehydroxylation of illite is studied using the differential scanning calorimetry on powder samples with heating rates from 1 to 10 ${\deg}$C min$^{-1}$ in a dynamic argon atmosphere. The values of apparent activation energy and pre-exponential factor are calculated using the Kissinger method. The determined values of apparent activation energy and pre-exponential factor of trans-vacant layer dehydroxylation are $(227 \pm 6)$ kJ mol$^{-1}$ and $(2.87 \pm 0.09) \times 10^{13}$ min$^{-1}$, respectively. The results also show that this process can be characterized by 1D diffusion controlled reaction with instantaneous nucleation rate. For the cis-vacant layer dehydroxylation, the values of apparent activation energy and pre-exponential factor are $(242 \pm 10)$ kJ mol$^{-1}$ and $(5.37 \pm 0.23) \times 10^{12}$ min$^{-1}$, respectively. The value of Avrami peak factor for this step indicates diffusion controlled growth of the new phase with zero or decreasing nucleation rate.