(643d) Separation of Biofuel Components from Aqueous Mixtures Using Membrane Solvent Extraction

The production of biofuels, encompassing acetone, butanol, and ethanol derived from both primary and secondary feedstock sources, represents a substantial endeavor aimed at advancing sustainability objectives in the United States. Although biofuels offer advantages as additives in gasoline blends, opportunities persist for enhancing cost-effectiveness, energy efficiency, water utilization, and environmental footprint reduction within the biofuels manufacturing sector.

One of the prominent contributors to energy consumption in biofuel production is distillation; however, researchers have explored various alternative separation methods, including absorption, liquid-liquid extraction, membrane separation, and membrane solvent extraction (MSE). Among these methods, MSE stands out for its notable advantages over traditional liquid-liquid extraction approaches. These advantages include the prevention of emulsion formation, the ability to use solvents potentially harmful to microorganisms at higher concentrations, and easy separation facilitated by high-boiling solvents. The extraction of desired solute components from fermentation broth using selected solvent constituents is a crucial aspect of MSE. It also offers an advantage to be integrated with bioprocessing recirculating the extracted broth gaining additional advantages. A crucial initial step in the advancement of separation technologies, such as membrane solvent extraction, involves comprehending the equilibrium extraction characteristics and partition coefficients of biofuel components.

In this study, we present an experimental investigation aimed at analyzing the performance characteristics of MSE utilizing aqueous and broth mixtures with a selected solvent. The experiments were conducted using a specialized experimental setup, encompassing membrane cartridge, reservoirs, and provisions for recirculation at controlled flow rates. Analytical characterization of components within the aqueous and organic phases over time was conducted using Gas Chromatography (GC) and High-Performance Liquid Chromatography (HPLC). The performance metrics assessed include the concentration of biofuel component in both aqueous and organic phases over time, the biofuel component’s membrane transfer flux rate as a function of time, and the overall mass transfer coefficient. A novel method to determine the membrane transfer flux rate more accurately as function of time and, hence, the membrane transfer kinetics has been developed. Additionally, a comparison was made between the concentrations at equilibrium and theoretical predictions obtained using ASPEN plus. The method presented here can be used in the development of effective separation processes in biorefineries.