The Optimized Fabrication Of PDMS Pervaporation Membrane And Its Application In Butanol Separation

The exhaustion of fossil fuels has made butanol production using ABE fermentation route received increasing attention.At present,the main problem is that the butanol produced during fermentation will produce toxic inhibitory effect on bacteria.Therefore,fermentation integrated with pervaporation technology was selected to improve the butanol productivity.The core of pervaporation technology is membrane.Improving the separation efficiency of pervaporation membrane can effectively improve the butanol concentration and reduce the separation process cost.In this paper,21 kinds of polydimethylsiloxane(PDMS)pervaporation membranes were prepared to study the impacts of crosslinking conditions including PDMS types(PDMS of different molecular weights),cross-linker contents,crosslinking temperature and crosslinking time on the pervaporation performance of membrane.Firstly,scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FTIR),contact angle,Young's modulus and swelling degree were used to analyze the PDMS membrane with different crosslinking degree.The SEM and FTIR images showed that the PDMS membranes had uniformly dense structure and crosslinking reaction occurred obviously.The contact angles of PDMS membranes were in the range of 109.5°-116.5°indicating that the material was obviously hydrophobic.With the increase of molecular weight of PDMS,the Young's modulus and the swelling selectivity of PDMS membrane increased,indicating a short chain between cross-links points.When the cross-linker content multiplied,the Young's modulus increased at first and then decreased,and the swelling selectivity showed the same trend.Too high or too low crosslinking temperature was adverse to the Young's modulus and the swelling selectivity of PDMS membrane.With the extension of crosslinking time,the Young's modulus and swelling selectivity of PDMS membrane showed the current of increasing at first and then decreasing,proving that the cross-linking time of 8-12 h was the ideal choice.The separation of 15 g/L butanol solution using PDMS membranes prepared under different crosslinking conditions was investigated.When the molecular weight of polymer increased,the permeation flux of PDMS membrane reduced and the separation factor increased.When the cross-linker content was multiplied,the change of permeation flux of PDMS membrane presented an upward parabolic trend.When the mass ratio of TEOS to PDMS was 0.1,the PDMS membrane showed the best pervaporation performance,the total flux and separation factor of which was 68.7 g/m~2/h and 48.4,respectively.With the increase of crosslinking temperature,the separation factor of membrane increased at first and then decreased,while the total flux showed the opposite trend.The PDMS membrane cross-linked with 80?showed the best pervaporation performance.PDMS membrane prepared in the range of 8-12 h had the optimal separation performance,above or below which the separation performance of the membrane was degenerated.The impacts of feed temperature and concentration on the separation properties of PDMS membrane were investigated.When the feed temperature was improved,the separation factor reduced while the total flux increased.When the feed concentration enriched,the separation factor declined while the total flux rose.Finally,ABE fermentation incorporated with pervaporation experiment was carried out.Comparing with batch fermentation,the total solvent and butanol yield increased by 50.6%and 56.5%,respectively.And the total solvent and butanol production rate increased from0.45 g/L/h and 0.29 g/L/h to 0.53 g/L/h and 0.36 g/L/h,respectively.During the fermentation incorporated with pervaporation process,the performance of PDMS membrane was relatively stable.