Equilibrium Study on the Extraction of Levulinic Acid from Aqueous Solution with Aliquat 336 Dissolved in Different Diluents: Solvent's Polarity Effect and Column Design

In the present study, the reactive extraction of levulinic acid (4-oxopentanoic acid) was investigated by using Aliquat 336 in various organic solvents [benzene, dichloromethane (DCM), dodecane, methyl isobutyl ketone (MIBK), 1-octanol] from dilute aqueous solution. Equilibrium data obtained at 298 K and 101.325 kPa were used to determine the values of distribution coefficient (K-D), degree of extraction (E%); loading factor (Z), and complexation constants (K-E). Among the diluents tested, DCM gave the highest extraction efficiency. Using 0;5454 mol.kg(-1) of Aliquat 336 in DCM, KD and E% were obtained as 2.082 and 67.55%, respectively, at 0.2795 mol.kg(-1) initial acid:concentration in the aqueous solution. Z values were found to be between 0.033 and 1.628, depending on the nature of the diluent-used and Aliquat 336 concentration in the organic phase. Using mass action law modeling, the stoichiometry of the extraction reaction was determined, It was observed that mostly, 1:1, 2:1, and 3: types of complexes were formed. The results inferred that the polarity and the molecular size of the solvent were the important critical factors which decide the solubilization of the solvates in the organic phase: DCM was found to be the most appropriate solvent among tested ones for the reactive extraction of levulinic acid. The feasibility of the extraction process was also assessed by calculating the minimum solvent (extractant + diluent) to feed ratio and the number of theoretical stages required for the recovery of levulinic acid in the extraction column.