A method of removing a polar solvent from a fluid volume contaminated with at least one polar impurity, such as a free fatty acid, is provided. The method comprises providing a fluid volume that includes at least one polar impurity dissolved in at least one solvent. The fluid volume is contacted with an expanding gas to remove the at least one solvent. The expanding gas may be dissolved into the at least one solvent in the fluid volume to form a gas-expanded solvent. The immiscibility of the polar impurities in the gas-expanded solvent enables separation of the polar impurities from the gas-expanded solvent. After separation of the polar impurities, at least one of the temperature and pressure may be reduced to separate the solvent from the expanding gas such that the clean solvent may be reused.
This invention was made with government support under Contract Number DE-AC07-05ID 14517 awarded by the United States Department of Energy. The government has certain rights in the invention.