The liquid-liquid extraction of acetic acid from an aqueous solution with 1-heptanol as an extraction solvent in the extraction column and mixer-decanter at 30°C and atmospheric pressure was simulated using Aspen Plus. A Non-Random Two-Liquid (NRTL) based model was developed by minimizing maximum-likelihood objective function. In the simulation of the extraction column and mixer-decanter, the effect of the number of stages and the flow rate of the solvent on the percent recovery can be seen. In addition, a comparison of the percent recovery value between acetic acid extraction systems using EPPS (4-(2-hydroxyehtyl)-1-piperazine propanesulfonic acid) and HEPES (4-(2-hydroxyethyl)-1 piperazineethanesulfonic acid) buffers was also carried out with systems without buffers. In this study, an economic analysis was also carried out for the acetic acid extraction system using an extraction column and a mixer-decanter. Based on the simulation results, the acetic acid extraction system with the addition of HEPES buffer using extraction column with the number of stages = 8 and solvent to feed mass ratio = 1.6 was the most optimal and efficient extraction process obtained in this study. This system has the capital cost of 180,729,262.67 USD with the percent recovery up to 99.83% and the mass fraction of acetic acid in the raffinate phase is 0.0002 which is also extremely low.

Biological buffer has a significant impact on aqueous organic phase equilibria in extraction processes. This study investigated the effect of biological buffer on the efficacy of butyric acid extraction from aqueous solution utilizing methyl isobutyl ketone (MIBK) as the extraction solvent. The liquid–liquid equilibria (LLE) of quaternary systems of methyl isobutyl ketone (MIBK) + butyric acid + water + biological buffer MOPS [3-(N)-morpholino propane sulfonic acid], HEPES (2-(4-(2-hydroxyethyl)-1-piperazinyl)­ethanesulfonic acid), or EPPS (4-(2-hydroxyethyl)-1-piperazine propanesulfonic acid) were determined at temperature T = 303.15 K (30 °C) and P = 0.1 MPa (atmospheric pressure). The addition of EPPS to the butyric acid aqueous solution resulted in superior extraction efficacy compared to the other biological buffers, as determined by experimental data. Generally, the extraction performance was in the order EPPS > MOPS > HEPES, which represented the buffering-out strength as well. The non-random two-liquid (NRTL) and UNIversal QUAsi Chemical (UNIQUAC) models fit well with the actual LLE data of the quaternary systems. The σ-profile analysis was also evaluated in this study. Additionally, a potential process flow sheet using biological buffer and MIBK solvent was suggested for removing butyric acid from its aqueous solution.