Separation of Butyric Acid from Aqueous Solution by Methyl Isobutyl Ketone with the Introduction of Biological Buffer (EPPS/MOPS) at Elevated Temperatures

The separation and purification of butyric acid from an aqueous solution is of great importance in wide applications. Liquid–liquid extraction is a highly effective technique for the separation of an aqueous mixture with a low concentration of solute. The aim of this study was to isolate butyric acid from an aqueous solution using two biological buffers: 4-(2-hydroxyethyl)-1-piperazine-propanesulfonic acid (EPPS) and 3-(N)-morpholino-propanesulfonic acid (MOPS). Methyl isobutyl ketone (MIBK) was used as an extraction solvent for butyric acid separation. The quaternary liquid–liquid equilibrium (LLE) data for the water-butyric acid-MIBK-EPPS and water-butyric acid-MIBK-MOPS systems were determined under atmospheric pressure (P = 0.1 MPa) at 313.15 and 323.15 K, respectively. The extraction performance was evaluated by calculating the distribution coefficient and the separation factor from the LLE tie lines data. The influence of two types of different buffers on the LLE was studied at elevated temperatures. In this study, the molecule interactions among compounds investigated were assessed by σ-profiles analysis. The universal quasi-chemical (UNIQUAC), the nonrandom two-liquid (NRTL), and the conductor-like screening model for the segment activity coefficient (COSMO-SAC) were able to agree with the experimental LLE data. For the design of the extractor, the improved binary interaction parameters obtained by the improved separation procedure were required.