The analysis of the results indicated that, in general, tested mathematical model adequately fitted the experimental data (R2 > 0.90); the model goodness of fit to experimental data is presented in Fig. 4.
The poorest fit for the second phase was observed for case E (Table 1), presented in Fig. 2d; this sample has the largest moisture content and largest particle size, and as described in Table 2 it also corresponds to the larger variability data for k2.