Membrane assisted processing of acetone, butanol, and ethanol (ABE) aqueous streams

Downstream processing of ABE fermentation broth is challenging issue. In this work, results of the application of both hydrophobic and hydrophilic commercial membranes during the pervaporation of ABE aqueous mixtures were investigated and presented. Hydrophobic pervaporation experiments were performed using ABE-water mixtures containing 0-5 wt% of organics in feed, using commercial membranes: POMS, PEBAX, and PervapTM4060. Separation factor and Pervaporation Separation Index were employed to discuss hydrophobic pervaporation results. PervapTM4060 membrane revealed the best separation performance in the removal of ABE components from diluted aqueous mixtures mimicking the fermentation broth, resulting in two-phase permeate containing ca. 34 wt% of organics. The subsequent liquid-liquid phase separation resulted in the organic phase containing 62 wt% of ABE. Hydrophilic pervaporation experiments were performed in contact with ABE-water system initially comprising 38 wt% of water applying both the PervapTM4100 PVA based polymeric membrane and modified silica ceramic one. Application of hydrophilic membranes allowed for the complete dewatering of ABE-water mixtures. Eventually, the combination of membrane separation processes (microfiltration, hydrophobic pervaporation, hydrophobic thermopervaporation, membrane distillation, and hydrophilic pervaporation) enhanced by the liquid-liquid phase separation was suggested for the recovery and dehydration of ABE aqueous mixture.