Extraction of 1-butanol from aqueous solutions by pervaporation

The extraction of l-butanol from fermentation broths by pervaporation offers potential for use in biotechnology. Various membrane materials have been screened for their suitability for this process. Polydimethylsiloxane (PDMS) membranes gave the best results in terms of flux and selectivity, with large variations depending on their nature and preparation. Selectivity was further increased by including either organophilic adorbents (cyclodextrins, zeolites), or oleyl alcohol in dense PDMS membranes. The predominance of driving force (i.e. activity gradient) on pervaporation extraction performances was shown by a comparative study on different binary aqueous solutions of alcohols. Water flux remained practically constant while the alcohol flux was linearly related to its feed concentration. The conclusions obtained with binary mixtures were consistent with those obtained with two model ternary solutions; the influence of salt on 1-butanol permeability was negligible, whereas ethanol had a strong effect.