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.