Kinetics and thermodynamics of oil extraction from sunflower seeds in the presence of aqueous acidic hexane solutions

Oil extraction was performed in aqueous HCl, H2SO4 and H3PO4 solutions with n-hexane (C6H14) at 30, 40, 50 and 60 degreesC 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 H2SO4. 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% H2SO4 was found to be E-alpha = 4.2 kJmol(-1), and the activation thermodynamic parameters at 60 degreesC were DeltaH(not equal)=1.43 kJmol(-1), DeltaS(not equal)=-309.3 Jmol(-1)K(-1) and DeltaG(not equal)=104.4 kJmol(-1). The enthalpy value was DeltaH=11.2 kJmol(-1), and the other thermodynamic parameters at 60 degreesC were DeltaS=36.75 Jmol(-1)K(-1) and DeltaG=-1.07 kJmol(-1).