Supercritical fluid extraction
Kristiina Kreek
POKE
2013 Tallinn
Supercritical fluid
Density of carbon dioxide
Properties of supercritical fluids
Properties
High solvating power (ability of a solvent to dissolve a solute): is a good solvent due to it`s near liquid density
High diffusivity – due to it`s gas like properties
Because of lower density then liquids, they have more space for particles to move
High temperatures – particles move faster
Viscosity: 10-100 times smaller then for liquids, particles are far apart
No surface tension (no liquid/gas phase boundary)
Polarity: most supercritical fluids behave like non-polar solvents.
Possible to tune their properties by adding a polar co-solvent
Advantages of SCF-s
Combination of useful propertis of liquids and gases
Good solvents
Penetrate materials easily
Properties can be altered by varying pressure and temperature
Easy solvent removal
Recyclability
Critical parameters of solvents
CO2 as an extrahent
Adventages
Non toxic
Not Flammable
Cheap
Obtained as a byproduct of industriaal processes
Critical point can be „easily“ achieved
Disadvantages
Can`t be used for extracting polar molecules
Expesive equipment
High pressures
The system used for extraction
Advantages of SFE
Low temperature extraction results in minimal degradation of volatile compounds
Faster
High product yields
Spent material is left undamaged
Solvent is easily removed
Somewhat selective
Using CO2 for extraction is cheap and safe
Disadvantages – expensive equipment, not suitable for extracting wet materials.
Applications of SCF-s
Extraction
Decaffinated coffee and tea, hop extract, extraction of lipids, vitamins, preparation of essential oils, pesticide removal, laboratory test methods
Cleaning
Impregnation
Solvent in chemical reactions
Materials synthesis
Formation of nanoparticles
Drying
Supercritical drying
Surface tensions do not exist in supercritical state.
Can be used for making aerogels
Conclusion
Supercritical fluids are the link between liquid and gas, giving the possibility to fine-tune the properties of the solvent.
SCF-s can be used for many diferent applications, from extraction to synthesis.