Submitted to: Separation Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2005
Publication Date: 11/15/2005
Citation: Kwiatkowski, J.R., Cheryan, M. Stability and performance of nanofiltration membranes for ethanol extracts of corn. 2005. Separation Science and Technology. 40(13):p.2651-2662.
Interpretive Summary: The generation and recovery of additional products along with ethanol is one way of increasing the value of a corn kernel using the dry-grind process. Methods have been developed previously to do this by extracting corn oil using ethanol, which is already produced during the process. The corn oil, which typically passes through the process without participating in any reactions, could be recovered and sold to increase the revenue of the process as a whole. The method used here proposes to purify the extracted corn oil using membrane filtration. Separation of the corn oil from the ethanol using synthetic membrane filters generates corn oil as a product while also recovering the ethanol used in extraction. Validation of the method prior to implementation requires testing of the membranes with simpler compounds. The membranes selected for use were fully characterized in terms of their performance in this unique, non-water-based medium. Several membranes were identified to have good performance based on their ability to separate the desired components while still being able to handle a large flow rate of material. This information will be very useful to researchers who are trying to commercialize new, lower cost membrane processes for making commercial corn oil.
Technical Abstract: Several nanofiltration membranes were tested for their stability in pure ethanol solutions, with the objective of finding a membrane suitable for use in purifying oil from ground corn that has been extracted with ethanol. Each of the membranes was conditioned with solutions of ethanol in water (0-100 volume/volume%) and ranked based on their performance. The top three membranes chosen were evaluated further in absolute ethanol, with the molecular weight cut-off (MWCO) of each estimated using polyethylene glycols (PEG), lipids, sugars, and refined corn oil. From this study, it is shown that the type of molecule has an influence on the apparent molecular weight cut-off, since molecules of the same molecular weight exhibited differing rejections in pure ethanol. Characterization of these membranes is the first step in developing a membrane-based separation process for purifying liquid extracts of corn oil in ethanol.