Influence of fermentation by-products on the isolation of ethanol from fermentation broths using pervaporation

摘要

The influence of fermentation by-products on the isolation of ethanol from water using pervaporation was investigated. Two commercial hydrophobic membranes were subjected to experiments with mixtures containing 5 wt. % ethanol in water, in which each individual by-product was added. It was found that by-products influenced the membrane performance significantly. Most severe effects were encountered for the carboxylic acids, which caused an irreversible increase in water flux and decrease in selectivity factor. This was further investigated by contact angle measurements and adsorption characteristics. The adsorption of acids on the membranes was observed to be higher than for ethanol, explaining the lower selectivity. The hydrophobicity degree decreased significantly in the presence of acids, and hence increased the water flux. When the pH of the acid solutions was increased above the dissociation constant, much lower adsorption amounts of acids were observed and no decrease in hydrophobicity.