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a b s t r a c tPervaporation is claimed to be a promising separation technique for the purification of ethanol from fermentation broths during bio-ethanol production. In this study, influence of fermentation by-products on the purification of ethanol from water during hydrophobic pervaporation was investigated.Sugars and salts were found to increase the membrane performance. Reason for this was a change in vapor/liquid equilibrium. 2,3-Butanediol decreased the ethanol flux and selectivity factor, while glycerol exhibited no effect. This was explained by a strong sorption of butanediol into PDMS and no sorption of glycerol. Due to the presence of carboxylic acids, hydrophobicity degree of the Pervap 4060 membrane decreased, which resulted in an irreversible increase in water flux and decrease in separation performance. These observations suggested the presence of silicalite-based fillers in the membrane. When the pH was raised to a value above the dissociation constant, no changes in hydrophobicity degree and membrane performance were found.

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In this work, technical and economical feasibility of bioethanol production from corn with high concentrations of fumonisins is analyzed. Based on data obtained from a limited number of experiments, the cost data of ethanol facilities and conceptual design methods maximum prices for corn contaminated with fumonisins are estimated. The scope of the analysis includes average ethanol concentrations in the fermentor in a range of 6 wt % and 3 wt % for noncontaminated corn and strongly contaminated corn (1400 ppm), respectively. The maximum price for contaminated corn varies from 66% to 33% of the fumonisins-free feedstock cost, according to the level of contamination. The performance of the continuously operated process was also analyzed considering the coupling of the fermentor with a pervaporation unit for continuous ethanol separation. Estimations were made for a volumetric productivity of alcohol of 7.8 kg/(m 3 h) and membrane flux (0.9 kg/(m 2 h)) and selectivity (S = 5) corresponding to a commercial PDMS membrane for a level of 6 wt % ethanol in the stirred-tank fermentor. Results show that an increase of 100% in the membrane flux with a constant value for the selectivity is required to make the continuous alternative attractive.

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The UNIQUAC model is very suitable in describing (liquid + liquid) as well as (vapor + liquid) equilibrium for a wide range of systems. It can be extended to (solvent + polymer) systems for describing sorption equilibria. The original model is expressed in molar-based terms, but requires knowledge of structural parameters and molar masses of all components. Since these cannot always be easily determined for membranes, a conversion to mass-based terms is often performed, which eliminates this issue. Many studies use this model to calculate sorption equilibria in (solvent + polymer) systems. Nevertheless, in this work the conversion from molar to mass-based parameters is postulated to be erroneous. This even leads to an incorrect description of simple (vapor + liquid) equilibrium of pure liquid mixtures and hence it is advised not to use this model for further modeling of sorption equilibrium in (solvent + polymer) systems. In this paper, the errors in the conversion are pinpointed, and the effects it can have on the description of (vapor + liquid) equilibrium, if used improvident, are demonstrated. Furthermore, it is shown that in fact a simple and straightforward conversion can be performed. Finally, in the case when polymers are involved, an adaption and simplification to the model was successfully applied.