Extraction by Subcritical and SupercriticalWater, Methanol, Ethanol and Their Mixtures

Hot, subcritical and supercritical water, methanol, ethanol and their binary mixtures have been employed to treat fuels (desulfurize coal and recover liquid fuels from coal and oil shales) and to extract valuable solutes from biomass. The properties of these solvents that are relevant to their extraction abilities are presented. Various extraction methods: accelerated solvent extraction (ASE), pressurized liquid extraction (PLE), supercritical fluid extraction (SFE, but excluding supercritical carbon dioxide) with these solvents, including microwave- and ultrasound-assisted extraction, are dealt with. The extraction systems are extensively illustrated and discussed.