SEPARATION OF ETHANOL FROM AQUEOUS-SOLUTION BY A METHOD INCORPORATINGSUPERCRITICAL CO2 WITH REVERSE-OSMOSIS

The separation of ethanol from low ethanol-content aqueous solutions b y supercritical CO2 in the presence of a hydrophilic reverse osmosis p olyamine membrane was investigated. The separation was carried out in a membrane module that consisted of two chambers divided by the membra ne. The supercritical CO2 and aqueous solution flowed in parallel into one chamber, while the other chamber was empty and kept at 1 atm. By introduction of supercritical CO2 into the reverse osmosis operation a t a proper time, the ethanol rejection of the present method was signi ficantly enhanced over the reverse osmosis separation and the supercri tical CO2 extraction method. The ethanol rejection could be 70% higher than the best result obtained with reverse osmosis separation at an o perating temperature and pressure near that of the critical point of C O2 and at relatively higher ratios of CO2 flow rate to solution flow r ate. The effects of liquid and CO2 flow rates, ethanol and salt conten ts of the feed solution, as well as pH on ethanol rejection were also examined.