Extraction Flashcards
Extraction
◼Extraction = is separation method to separate desired compound from mixture
◼There are 2 types of extraction:
- mechanical extraction
- chemical extraction or solvent extraction
MECHANICAL EXTRACTION
Is apply mechanical force to separate desired compound from raw material/mixture.
Example: chicken fat, fish oil
SOLVENT EXTRACTION
It is often convenient to use a liquid in order to
carry out a separation process.
The liquid is thoroughly mixed with the solids or
other liquid from which the component is to be
removed and then the two streams are separated.
There are:
- liquid-liquid extraction
- solid-liquid extraction
Liquid-liquid Extraction
Separation of one or more component in a mixture by contacting with another phase, which is liquid.
3 stages of Liquid-liquid Extraction
i) bringing the feed mixture and the solvent into
intimate contact
ii) separation of the resulting two phases
iii) removal and recovery of the solvent from each
phase
Solid-Liquid Extraction/Leaching
Many biological, inorganic, and organic substances occur in a mixture or different components in a solid
In order to separate the desired solute or remove the undesirable solute component from the solid, the solid is contacted with a liquid phase.
The two phases are in intimate contact, and the solute can diffuses from the solid to liquid phase
Single Stage Leaching
- Contact of solid and solvent for transfer of solute to solvent
- Separation of resulting solution from the residual solid
- Solution must proceed to distillation process to get pure solute
Examples of animal-based products undergo extraction
1) Collagen
2) Lard
3) Gelatin
4) Casein
5) Fish Sauce
6) Rennet
An ideal solvent should possess the following properties:
◼ Low viscosity.
◼ Low latent heat of evaporation, so that less energy is needed for solvent recovery.
◼ Low specific heat, so that less energy is needed for keeping the solvent warm.
◼ Good solubility of solutes.
◼ The solvent should be chemically inert to solutes
Supercritical Fluid Extraction (SFE)
Process of separating one component (the extractant) from another using supercritical fluids as the extracting solvent.
Supercritical fluid (CO2 at 74 bar and 31oC) has low viscosity, makes it able to penetrate the organic material well and achieve good extraction.
After passing through the material needs to be
extracted, it depressurizes in a solvent or collected
onto an absorbent trap for recovery.
Supercritical Fluid
For every substance, there is a critical temperature (Tc) and pressure (Pc) above which no applied pressure can force the substance into its liquid phase.
If the temperature and pressure of a substance are both higher than the Tc and Pcfor that substance, the substance is defined as a supercritical fluid.
Why CO2 widely used??
• Cheap
• Chemically inert
• Non-toxic
• Non-flammable
• Readily available at high purities
• Low of critical temperature (31oC)
Supercritical Fluid Extraction Process
The oldest typical and most common supercritical fluid extraction from solids is performed as a batch process, with a continuous flow of SCF.
An extraction medium (going to be SCF) stored in the feed tank and liquid SCF is pumped from a reservoir ; it is heated and pressurized to reach the supercritical conditions.
Supercritical SCF enters the extraction chamber where contact with solid particles bed occurs and the more volatile substances are dissolved into the supercritical fluid.
Solute and SCF leave extractor and extract is precipitated in separators, where SCF becomes gaseous.
Gas is recycled by condensation before returning to liquid reservoir.
Advantages of Supercritical Fluid Extraction
◼ SCF is easily recoverable from the extract due to its volatility
◼ Non-toxic solvents leave no harmful residue
◼ High boiling components are extracted at relatively low temperatures
◼ Thermally labile compounds can be extracted with minimal damage as low temperatures can be employed by the extraction
Disadvantages of Supercritical Fluid Extraction
Elevated pressure required
High capital investment for equipment
