Fig. 1: Effect of temperature on the oil yield of IGK at different average particle sizes (mm): (a) 0.5, (b) 1.0, (c) 1.5, (d) 2.0, and (e) 2.5 mm
Effect of particle size
Extraction rate increases as the particle size decreases [26,54]. Fig. 2a and b shows the effect of particle size on the extraction of oil from IGK using hexane as solvent. The particle sizes considered in this study were 0.5, 1.0, 1.5, 2.0 and 2.5 mm. It could be seen that their (particles sizes) respective oil yields were 60.08, 42.01, 39.70, 37.18 and 35.4 %, at 35 °C and 150 mins. This shows that highest oil yield was obtained with the smallest particle size of 0.5 mm, and the least with the largest particle size of 2.5 mm. These findings were in line with the works of Sulaiman et al. [26] and Huang et al. [55], for the extractions of solid coconut waste oil and Baizhu, respectively.
The additional oil extracted from smaller particle size was attributed to the larger interfacial area of the solid present in them. Also, the solvent requires minimal distance to penetrate the solid particles in other to extract oil from it. In other words, contributes to increase in pore diffusion between the solute (solid) and the solvent. On the other hand, larger particles have limited contact surface area, which causes more resistance to solvent penetration and oil diffusion. Hence, smaller quantity of oil would be transported from the inside of the larger particles to the surrounding solution [26,53].
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