Analysis of selective extraction of biofuel components from aqueous solution using single-stage membrane solvent extraction (MSE)

The effective separation and purification of biofuel components from dilute aqueous broth is critical for the sustainable production of advanced biofuels, including aviation fuels. This study evaluates the performance of membrane solvent extraction (MSE) using 2,6-dimethyl-4-heptanol (DMHT) as an extraction solvent for key biofuel intermediates: acetone (ACT), ethanol (ET), n-butanol (nB), and isobutanol (IBA). Analysis of the solute concentrations and membrane transfer flux over time and their variability are reported. Initially, all components exhibited the highest flux due to higher concentration driving force, followed by a sharp decline, as the driving force decreases. Among the components, nB and IBA showed better extraction efficiencies, with high initial flux and rapid extraction kinetics, and higher overall mass transfer coefficients owing to their higher Kd, hydrophobicity, and selectivity. ACT and ET, with lower Kd, hydrophobicity and selectivity, exhibited more gradual extraction behavior with lower efficiencies. Novel empirical modeling approach reported here enables us to better analyze the MSE concentration profile data and, hence,accurately determine the membrane transfer flux and the overall mass transfer coefficient. The extraction kinetics reflect a trade-off between partitioning (strongly favoring butanols) and diffusion (favoring ethanol and acetone), with overall transport governed by combined resistance effects. This theoretically expected behavior is consistent with experimental data.