| ABE toxicity is one of the most critical problems of ABE fermentation which eventually results in low ABE fermentation yield and high production cost. In order to alleviate the problem of ABE toxicity, in situ product recovery techniques have been widely used to improve the fermentation performance. Pervaporation ?PV? have been be integrated with ABE fermentation process. Nevertheless, the fermentation broth directly contacts with the membrane in pervaporation-fermentation coupling process, which lead to serious membrane fouling and limit its industrial application. To solve the problem of serious membrane fouling in the pervaporation process, vapor permeation?VP? is proposed to integrate with ABE fermentation as an ISPR technique in this work. Since the VP technology is put forward, this technology has received extensive attention of people because of its economy. VP is an alternative membrane technique, the feed of VP is clean vapor, not the broth. VP technology not only has the characteristics of pervaporation technology, it also can effectively avoid the concentration polarization and membrane fouling of PV process. Therefore, the performance of VP-fermentation coupling process is better than PV.In this article PDMS/PVDF composite membrane is first prepared and used for VP recovering ABE from dilute simulated solutions. The effect of different operation temperature, concentration of feed, cycling flow of the vapor and V/A ratio on the VP performance is investigated. And the difference of VP and PV separation process is studied in the same membrane setup. The results show that the VP membrane separation technology can effectively remove organic components from ABE fermentation simulated solutions. Butanol, acetone and ethanol are condensed from 1.0wt%,0.5wt% and 0.2wt% to 22.1 wt%,15.5wt% and 1.4wt% at 40? for ABE simulated solutions. The permeation flux of PDMS membrane reaches 330g·m-2·h-1.Secondly, to improve the separation factor of PDMS membrane for ABE, the silica filled PDMS membrane is prepared and used for VP separating ABE from simulated solutions, and compared with no filled PDMS membrane. The difference between silica filled PDMS membranes and PDMS membrane from the perspective of surface structure and internal structure is revealed by some characterization methods, such as AFM, SEM, CA and swelling degree to explore the relationship between membrane structure and VP performance. Furthermore, the effect of silica content, operation temperature and concentration of feed on the VP performance is investigated. Results show that the surface roughness, hydrophobicity and swelling degree of silica filled PDMS membrane are greatly increased than pure PDMS membrane. At the same time, the separation factor of silica filled PDMS membrane for acetone and butanol increases highly. Comparing with pure PDMS membrane, the separation factor of silica filled PDMS membrane increased to 48 and 67 when the silica content reach to 3 wt%. Which are increased by 55% and 24% respectively than pure PDMS membrane. But the permeation flux of membrane drops from 330g·m-*2·h-1 to 143g·m-2·h-1.Finally, silica filled PDMS membrane is applied to ABE fermentation-VP coupling process. Effect of VP for the ABE fermentation is investigated, as well as the impact on ABE fermentation yield and the utilization ratio of sugar. The results show that ABE production of batch fermentation suffers from low yield and productivity due to ABE inhibition. VP is used to overcome the product inhibition effect by continuous removing ABE from broth during the process. Comparing with batch fermentation, solvent production rate increases from 0.15g·L-1h-1 to 0.36g·L-1·h-1, The glucose consumption rate increases from 0.42g·L-1·h-1 to 0.77g·L-1·h-1, The ABE productivity of VP integrated process is higher than that of batch fermentation process. Comparing with batch fermentation, for VP-fed-batch fermentation the total ABE production increased from 13.6g·L-1·h-1 to 37.6 g·L-1·h-1. |
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