## 3 Results and Discussion
### Kinetics
On the other hand, the average experimental activation energies for chitin carbonization, as determined using the Friedman, FWO, KAS, and Starink methods, were 158.4, 162.4, 157.1, and 160.3 kJ/mol, respectively. Overall, FWO and KAS models appear to provide the most consistent and accurate predictions for both chitosan and chitin. While the Friedman and Starink models also perform well, they show slightly higher deviations in some cases, indicating potential limitations depending on the material. The small percentage errors suggest that all models can be considered reliable for predicting the behavior of chitosan and chitin, but that KAS and FWO are preferable choices for minimal deviation. Table 4 shows the variation of the pre-exponential factor during the carbonization processes of chitin and chitosan. The significant variation in the pre-exponential factor as a function of the conversion degree reflected intricate reactions occurring during thermal degradation. As the pre-exponential factor represents the frequency of collisions between reactant molecules, variations in its value with changing conversion degrees can be attributed to differences in reaction chemistry and complex formation. A low pre-exponential factor (<10\({}^{9}\) s\({}^{-1}\)) is associated with surface reactions, whereas in reactions independent of surface area, a low value suggests the presence of a tightly bound, closed complex. Conversely, a high pre-exponential factor (\(\geq\)10\({}^{9}\) s\({}^{-1}\)) indicates a loosely bound, junctional complex. Additionally, higher pre-exponential factors reflect greater sensitivity to temperature variations within the reaction range [34]. For chitosan, pre-exponential factor values were found to be higher than 10\({}^{9}\) s\({}^{-1}\), up to a conversion degree of 0.7. This signifies a transition to a loosely bound, high-mobility reaction state and the increased influence of temperature on reaction kinetics. As carbonization progressed, the structure of chitosan has been broken down into smaller, less reactive fragments, leading to a reduction in the frequency of effective molecular collisions, which lowers the pre-exponential factor. The progressive formation of a thermally resistant char matrix may hinder further decomposition, reducing the number of available reaction sites and consequently lowering the pre-exponential factor to approximately 10\({}^{5}\) s\({}^{-1}\) in the final stage of chitosan carbonization. On the other hand, chitin possessed a highly ordered crystalline structure due to extensive hydrogen bonding, which requires a higher frequency of molecular collisions to sustain decomposition reactions, leading to larger pre-exponential values (\(\geq\)10\({}^{10}\) s\({}^{-1}\)) compared with chitosan at the last stage of thermal decomposition. The linear correlation between lnA and Ea, which facilitates the carbonization reactions in terms of compensation effect, is also depicted in Table 4. The regression analysis for both chitin and chitosan carbonization produced high regression coefficients, confirming a strong linear relationship among each other. In other words, the activation energy (Ea) and pre-exponential factor (A) exhibit a near-perfect linear dependence, which can be described using an lnA = aEa + b mathematical model, supporting the concept of energy compensation. The estimated equations with ANN were also closely matched the experimentally obtained expressions with high regression coefficients. This consistency suggests that the ANN models employed in this study demonstrate strong kinetic prediction capability and generalization performance in modeling the relationship between activation energy and the pre-exponential factor for both chitosan and chitin carbonization.