Separation of oil constituents in organic solvents using polymeric membranes.

Different types of commercial nonporous (reverse
osmosis and gas separation) polymeric membranes were
screened for their abilities to separate FFA, MG, DG, and TG
from a lipase hydrolysate of high-oleic sunflower oil after diluting
it with organic solvents (ethanol and hexane). Cellulose
acetate (CA) (NTR-1698) membrane gave the largest difference
in rejection between FFA and glycerides and high flux in
oil/ethanol mixtures. In the hexane system, the values of permeate
flux and rejection were generally lower than those in the
ethanol system. The silicone–polyimide composite membrane
(NTGS-2100) gave the highest flux and rejections of solutes
(70.2% for FFA, 94.4% for TG) in oil/hexane mixtures. In the
ethanol system with the CA membrane, TG had the highest rejection
(98%) followed by DG (90%) and MG and FFA
(50–70%) when the oil concentration was varied from 6.3 to
45.8%. A discontinuous diafiltration process (16 batches) using
the CA membrane with ethanol changed the composition of the
oil from 31:28:9:32 TG/DG/MG/FFA to 65:30:1:4. The results
of this study showed that oil constituents can be separated in
suitable solvents using appropriate nonporous membranes.