Solvent separation and concentration from acetone-butanol fermentation broth by the pervaporation process

Abstract

Solvent separation and concentration from water-acetone-butanol-ethanol-acetic acid-butyric acid mixtures and acetone-butanol fermentation broth by the pervaporation process with silicone rubber hollow fiber membrane, were carried out at varied feed temperature between 40-80 ℃, permeation pressure between 2-30 torr and membrane thickness between 0.25-1.0 mm. Concentrations of butanol, acetone, ethanol, acetic acid and butyric acid of feed solution were 0.7, 0.6, 0.25, 0.5 and 0.2 g/L, respectively. The optimum operating conditions for this process were at a feed temperature of 60℃, permeation pressure of 2 torr and membrane thickness of 0.25 mm. The permeation flux, permeation concentration membrane selectivity and mass recovery of butanol in water-acetone-butanol-acetic acid-butyric mixtures were 11.29 g/m2 .h, 24.99%wt., 47.26, and 9.11 %wt., respectively and those in acetone-butanol fermentation broth were 8.76 g/m2 .h, 23.02%wt., 43.86 and 7.01%wt., respectively. The permeation flux was increased with increasing feed temperature. Decreasing permeation pressure and decreasing membrane thickness. Permeation concentration and membrane selectivity were irrelevant to the change in feed temperature and permeation pressure. Thick membrane will provide high permeation concentration and membrane selectivity. Results obtained from the solution-diffusion model indicated that permeability increased as molecular weight increased, whereas the opposite was found for diffusivity.