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![Rate of extraction
A mass balance on the solute gives the equation
dw = Vdy
V is the quantity of liquid in the liquid stream.
Vdy/dt = Kl A(ys - y)
which can then be integrated over time t during which time the
concentration goes from an initial value of y0 to a concentration
y, giving
loge [(ys - y0)/ (ys - y)] = tKlA/V.](https://image.slidesharecdn.com/extractionandwashing-210217091727/85/Extraction-and-washing-6-320.jpg)
![• The concentration remaining with the solid
after washing
x1 = x[xw /xw(1 + y)] = x[1/(1 + y)]
after two washings:
x2 = x1[1/(1 + y)] = x[1/(1 + y)]2
and so after n washings:
xn = x[1/(1 + y)]n
Washing](https://image.slidesharecdn.com/extractionandwashing-210217091727/85/Extraction-and-washing-33-320.jpg)
Extraction and washing
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- 2. EXTRACTION • It isdefined as the removal of solid constituents from the solid or liquid or semi solid by means of suitable solvents • Extract- compound contain all the constituents which are soluble in solvent • Menstrum- Solvent used for extraction process • Marc- residue obtained after the extraction process
- 3. PRINCIPLE • The solventused for extraction which diffuse into the compound to dissolve the desired compounds • The solution in compound pass in the opposite direction and mix with the surrounding liquid . • An equilibrium is established between the solute inside the compound and the solvent surrounding
- 5. • Rate ofsolution = driving force/resistance. dw/dt = KlA(ys - y) • dw/dt is the rate of solution • Kl is the mass-transfer coefficient • A is the interfacial area • ys and y are the concentrations of the soluble component in the bulk of the liquid and at the interface. It is usually assumed that a saturated solution is formed at the interface • ys is the concentration of a saturated solution at Rate of extraction
- 6. Rate of extraction Amass balance on the solute gives the equation dw = Vdy V is the quantity of liquid in the liquid stream. Vdy/dt = Kl A(ys - y) which can then be integrated over time t during which time the concentration goes from an initial value of y0 to a concentration y, giving loge [(ys - y0)/ (ys - y)] = tKlA/V.
- 7. Factors influence theextraction process • Nature of compound • Type of Solvent used • Temperature • pH • Size of particle
- 8. THEORIES • Schoenemann’s Diffusiontheory The rate of extraction depends on the rate of diffusion • Soaking theory Not only the rate of diffusion but also the rate of dissolution of the substances in the solvent critically affect the rate of extraction • Karnowsky’s Capillary velocity Theory It represents the rate of extraction as a function of the rate of flow in the capillaries.
- 9. Methods of extraction •Liquid–liquid extraction • Solid-phase extraction • Acid-base extraction • Supercritical fluid extraction • Ultrasound-assisted extraction • Heat reflux extraction • Microwave-assisted extraction
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- 11. Equipments Commercial extractor Phase contactby gravity Phase contact by centrifugal force
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- 16. Advantage reliability, operating flexibility,high capacity, It can handle difficult-to-disperse systems such as those having high interfacial tension and large phase density difference Disadvantage their size and the inventory of material held up in the equipmen Mixer-Settler
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- 18. • Low axialmixing • High extraction efficiency which are due to uniform distribution of energy over a cross- section of the column • Uniform distribution of droplets in the column. Pulse Extractors
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- 21. Mechanically Agitated Extractors Classifiedaccording to mechanical motion patterns • Rotary-agitated columns • Reciprocating or vibrating-plate columns.
- 22. Rotary-agitated columns • Scheibelcolumns • Rotating disk contactor • Oldshue-Rushton Columns • Kuhni columns Reciprocating column • Karr columns. Mechanically Agitated Extractors
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- 32. Washing • Washing isidentical to extraction • Water is used as solvent • Water is cheap and readily available • The washing is designed to remove unwanted residue material
- 33. • The concentrationremaining with the solid after washing x1 = x[xw /xw(1 + y)] = x[1/(1 + y)] after two washings: x2 = x1[1/(1 + y)] = x[1/(1 + y)]2 and so after n washings: xn = x[1/(1 + y)]n Washing