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Compared with the organic film , an inorganic film having a good heat resistance and chemical stability , high mechanical strength, resistance to microbial attack , long life and other advantages . However , complex the existing inorganic membrane preparation process , the preparation of a long cycle , high cost , industrialized difficult to implement . For example, after the the boehmite gel preparation completed , the a typical sol - gel method , also need to be repeated coating, drying and heat treatment step 5-7 times , from the first coating to the last calcination end the whole process takes 15 to The 21 -step process of 25 to 30 days. In order to simplify the process of the preparation of inorganic nanofiltration membrane , many exploration and experimental studies , found a simple inorganic nanofiltration membrane preparation method - particle filling method . Its specific implementation method , ordinary unglazed ceramic substrate, the superfine ceramic powder as a filler , using a suitable dispersing agent to the ultra - fine ceramic powder is dispersed in water to form a suspension , with the dip coating matrix , and then dried calcined microporous ceramic membrane, then dipping a sol - gel method , you can obtain nanoscale pore size ceramic membrane . Al 2 < / sub> O 3 the nanofiltration membranes example , their preparation process optimization : Al 2 O 3 fine powder of particle diameter of 200 to 500 nm, Al 2 O 3 suspension volume concentration of 1.5% , the immersion time of the supporting body in the suspension 40 ~~ 60s impregnation step room temperature after impregnation , drying, calcination, dust , repeat dipping, drying , calcination , dust , the calcination temperature of 1200 ° C . From the first coating to the film made ??, the whole process needs a 10 -step process , a total of 10 to 12 days , 20 days shorter than the sol - gel method and process control , and less prone to the sol - gel method frequently encountered the membrane rupture . Exclude the optimization the system was Al of under conditions 2 O 3 film characterization by liquid - liquid membrane pore size distribution between 3.2 ~ 6.5nm The average pore size of 4nm. Hydrolysis of corn stover fermentation Ethanol fermentation broth as the medium , the Al 2 O 3 nanofiltration membranes for the separation of the sugar / alcohol mixture , indicating the fermentation broth sugar retention rate of 82% to 86% , ethanol is easy through .
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