Fig. 15: Comparison between experimental and models’ oil yield
at different particles sizes and time at 55 °C.
Furthermore, Table 1 shows the results of the IGK oil yields obtained at
different temperatures and particle size diameter at 150 min, and
compared with the calculated models’ oil yields values. The compared
results of the experimental and calculated models’ oil yields data
indicate good agreement of the models with the experimental data, as
evident from the low error analysis values (Table 1).
Thermodynamic parameters
The values of the equilibrium constant and other thermodynamic
parameters of IGK oil extraction are presented in Table 2. Similarly,
the plots of In K verses 1/T for different particles sizes of 0.5, 1.0,
1.5, 2.0 and 2.5 mm, that were used in the determination of
thermodynamics parameters (∆H, ∆S and ∆G) values are shown in Fig. 16.
For the thermodynamics of IGK oil extraction, the enthalpy values for
the process were in the ranges of 251.81 – 569.28 kJ/mol, for the
various particle sizes considered. The enthalpy values for the IGK oil
extraction in the present study, were within the ranges (266.18 –
435.87 kJ/mol) and (182.81 – 598.74 kJ/mol) for Colocynthis
vugaris Shrad seed and Terminalia catappa kernel oil
extractions, reported by Agu et al. [56] and Menkiti et al [59],
respectively. However, the enthalpy result in this work was higher than
(4 – 13.5 kJ/mol) reported by Meziane and kadi [61], for olive cake
oil. This difference in the enthalpy values was due to seeds morphology,
as their morphology often affects oil extraction [56]. The positive
values of the enthalpy change are an indication that IGK oil extraction
process was endothermic [59]. Similarly, as could be seen in Table
2, the entropy change of the process was also positive. The entropy
values for IGK oil extraction ranged between 1.08 – 1.99 kJ/mol, with
larger IGK particle sizes having higher entropy change values. The
implication of this positive entropy values is that the process was
irreversible in nature [26,61]. For the Gibbs free energy change
values of the process, the entire values were negative. Hence, this is
an indication of the feasibility and spontaneous nature of the process.
From Table 2, it could be seen that the ∆G values were highly negative
and in the range of -43.22 to -105.49 kJ/mol. This relatively high
negative value(s) of ∆G is an indication that the extraction process was
highly spontaneous [26,56].
[CHART]
Fig. 16: Plot of In K (equilibrium constant) vs. 1/T
(temperature, \(\mathbf{K}^{\mathbf{-1}}\mathbf{)}\) for the
five different particle sizes.