2. • Removal of soluble fraction in the form of solution from an
insoluble matrix with which the soluble fraction is associated
with the help of suitable solvent.
3. Mechanism of solid – liquid extraction
• Mechanism of solid – liquid extraction also known as
“leaching”, involve simple physical solution or dissolution
made by chemical reaction.
• diffusion of solvent – dissolution of chemical constituents –
diffusion of solution.
• Extraction enhanced by increased surface area and decreased
radial distance by decreased particle size .
11. • Strained liquid and Expressed liquid are mixed
after clarification of expressed liquid.
• Final volume is not adjusted to initial volume
because dilution occurs.
25. Choice of extraction process
• Depends on physico chemical char. Of raw
material and economic consideration.
• Maceration: - is suitable for unorganised drug, and
whose permeability is low.
• Percolation:- rapid and complete extraction, skill care
and frequent attention is needed
26. Large scale equipment
• Large circular and rectangular towers with
false bottom
• Mechanism of extraction
• In solid - liquid E: “Leaching”
• In Liquid – Liquid E: “Partition”
27. Solid - Liquid Extraction
• Carried in different methods
• A. Simple single contact.
• B. Simple multiple contact.
– Fresh solvent is in contact with CD, after first
extraction, repeated extracts are dilute, recovery
of solute is improved.
• C. Continuous Counter current contact
• Are carried out in different methods
28. • Discontinuous absolute extraction, in which the
extraction solvent and drug are moved against each
other.
• Continuous relative counter current extraction,
solvent is in motion and other phase i.e solid remains
stationary.
• Continuous Absolute counter current extraction
contact involves continual movement of both solvent
and CD.
29.
30. Solid - Liquid Extraction Equipment
• Simple single stage contact
– Mixers
– Vortical extractor
– Ultrasound extractor – Ultra sonic transmitters for accelerating
extraction about 20,000 Hz.
– Electrical discharge extractor.
• Counter current contact
– Diffusion battery
– Rotocel extractor
– Basket extractor
• Continuous absolute extractor
– Screw extractor
– Hilderbrandt Extractor
– Pulsation column extractor
34. Screw Extractor
CD and solvent are in opposite direction, sections are heated or cooled. Factors
affecting working of extractor is - Angle of inclination of cylinder, temp of solvent
speed of rotation feed charge and rise in pressure inside the cylinder.
35. Silver Continuous diffusion battery
• Less labour cost and produce high conc.s
• 20-24 units in two tiers, one above the other.
• Closed trough, helical screw, at the end
consists of wheel consists inclined perforated
buckets- pick CD and drain the liquid, dischare
54. Agitated tower extractor
References: 1. Unit operations of chemical engineering by Warren L. McCabe, Julian C.Smith.
2. Introduction to Pharmaceutical Engineering by Anant Paradkar Pg.No: 190