Reverse osmosis membrane characteristics for partitioning triglyceride-solvent mixtures

Residual free gossypol in hexane‐extracted cottonseed meal is a frequent concern of the feed industry. It is known that ethanol can efficiently extract the gossypol from cottonseed. However, regeneration of ethanol from ethanol‐rich miscellas by conventional evaporation is costly, due to the high latent heat of ethanol. As an alternative to the evaporative regeneration, reverse osmosis (RO) has been investigated. It was found that commercially available RO membranes which have pore diameter around 20 A‡ (evaluated with deionized water flux) or less perform the necessary partitioning. Among the commercially available RO membranes, cellulose acetate (CA) type membranes with a nominal MWCO (molecular weight cutoff) value between 500 and 1000 were found to be efficient in partitioning the cottonseed triglycerides from the base solvent, but were not chemically compatible with the base solvent. RO membranes made from aromatic polyamide (PA) with MWCO value 1000 were found to have both the chemical stability and the necessary pore characteristics. Experimental results indicated the potential use of RO membranes for the regeneration of ethanol from ethanol miscellas. The required membrane pore characteristics and applicable permeate flux equations are discussed.