Performance of Nanofiltration Membranes in Ethanol

Abstract Several nanofiltration membranes were tested for flux and rejection of selected solutes in ethanol. The membranes were initially conditioned with pure solvent containing increasing concentrations of ethanol. Flux decreased with increase in ethanol concentration and increased at higher temperatures and pressures. The type of solute had an influence on membrane rejection profiles. The DK membrane showed increasing rejection of polyethylene glycols (PEG) dissolved in ethanol from 29% at a molecular weight (MW) of 200 to 80% at MW 1000. However, the MW of sugars and lipids had little or no effect on rejection with the DK membrane; their rejection averaged 87%. In contrast, the TFC‐SR1 membrane showed higher rejections with higher MW compounds: lipid rejection increased from 19% to 71%, sugars from 35% to 85%, and lipids from 77% to 89%. The TFC‐SR2 membrane was much more open and showed the lowest rejections of all these compounds. Flux generally showed opposite trends, with the DK showing the lowest flux and the SR2 the highest.