Advanced isoconversional kinetic analysis of lepidolite sulfation products decomposition reactions for selectively extracting lithium

The sulfation and decomposition process has proven effective in selectively extracting lithium from lepidolite. It is essential to clarify the thermochemical behavior and kinetic parameters of decomposition reactions. Accordingly, comprehensive kinetic study by employing thermalgravimetric analysis at various heating rates was presented in this paper. Two main weight loss regions were observed during heating. The initial region corresponded to the dehydration of crystal water, whereas the subsequent region with overlapping peaks involved complex decomposition reactions. The overlapping peaks were separated into two individual reaction peaks and the activation energy of each peak was calculated using isoconversional kinetics methods. The activation energy of Peak 1 exhibited a continual increase as the reaction conversion progressed, while that of Peak 2 steadily decreased. The optimal kinetic models, identified as belonging to the random nucleation and subsequent growth category, provided valuable insights into the mechanism of the decomposition reactions. Furthermore, the adjustment factor was introduced to reconstruct the kinetic mechanism models and the reconstructed models described the kinetic mechanism model more accurately for the decomposition reactions. This study enhanced the understanding of the thermochemical behavior and kinetic parameters of the lepidolite sulfation products decomposition reactions, further providing theoretical basis for promoting the selective extraction of lithium.