Separation of vegetable oil compounds and solvent recovery using commercial organic solvent nanofiltration membranes

Solvent recovery and separation of oil compounds by means of thermal evaporation processes consume a huge amount of energy. Organic solvent nanofiltration (OSN) is an energy-efficient separation technique that can be potentially used for solvent recovery and separation of oil compounds in the vegetable oil industry. However, there are only a few studies on the separation of oil compounds using OSN. Almost no studies have been conducted on membrane fouling and long-term stability using highly concentrated oil/solvent feeds. This study explores the separation of oil compounds such as triglycerides and free fatty acids as well as solvent recovery using a series of Evonik commercial membranes. Under a static testing condition, the permeance of Duramem 500 reduces severely from 1.02 to 0.06 LMH/bar with an increase in oil concentration while its rejection to glyceryl trilinoleate decreases slightly from 86 to 84.8% when the feed concentration increases from 5 to 50 wt %. The severe permeance decline arises from the high viscosity of the permeate and oil layers accumulated on the membrane surface. In contrast, the membrane is able to separate glyceryl trilinoleate from linoleic acid with permeances approximately 3-6 times of those obtained from the static testing mode under 1-week cross-flow tests using a 20 wt% oil/acetone feed.