Turkish Journal of Chemistry




Oil extraction was performed in aqueous HCl, H_2SO_4 and H_3PO_4 solutions with n-hexane (C_6H_{14}) at 30, 40, 50 and 60 ^oC using 10 gr of sunflower seeds over 1 h with 10-min. sampling intervals. The optimum acid concentration was wt. 10% for each acid, and the highest oil yield was obtained in the extraction procedure with n-hexane containing H_2SO_4. The extraction process was observed with regard to the percent oil yield versus time, and the reaction order was found to be first-order kinetics by the differential method. The activation energy for the oil extraction kinetics of sunflower seeds with 10% H_2SO_4 was found to be E_a=4.2 kJmol^{-1}, and the activation thermodynamic parameters at 60 ^oC were \DeltaH ^{\neq} =1.43 kJmol^{-1}, \DeltaS ^{\neq}=-309.3 Jmol^{-1}K^{-1} and \DeltaG ^{\neq} =104.4 kJmol^{-1}. The enthalpy value was \DeltaH=11.2 kJmol^{-1}, and the other thermodynamic parameters at 60 ^oC were \DeltaS=36.75 Jmol^{-1}K^{-1} and \DeltaG= -1.07 kJ mol^{-1}.


Hexane, kinetics, oil extraction, sulfuric acid, sunflower seed, thermodynamics.

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