Response surface experiment results
Figures 1 present the response surface as a 3-D plot, enabling the prediction of DD% for varying test variable values and the identification of their interaction. The interaction between all variables in the DD% response is found to be statistically significant (Table 4).
In order to optimize and validate the predicted mathematical model, additional Expert Design runs were conducted using the same experimental conditions. The accuracy of the model was significantly enhanced by increasing the desirability function. The optimal parameters, corresponding to a desirability value of 0.99, resulted in a DD% of 93.98% (Fig. 2). Under the specified conditions, the highest achieved DD% was attained with the following parameters: NaOH concentration (1.41 M), demineralization time (15.75 hours), HCL concentration (7.49% vol), deacetylation time (2.01 hours), and deacetylation temperature (81.15 °C). Chitosan samples were prepared using these conditions and subjected to characterization analysis.