Prepared by Guided by
Ms. Juhi Bandre Ms. Neha Raut
M.Pharm 2nd Sem. (2019-2020)
Pharmaceutical Chemistry Department.
Smt.Kishoritai Bhoyar College of Pharmacy, Kamptee.

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INDEX
1.Introduction
2.Liquid-liquid equilibria
3.Extraction with Agitation
4.Counter-current extraction
5.Reference
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• Extraction is a process where one or more solute(s) are removed from one
liquid phase (technically called a diluent) by transferring that/those the solute(s)
to another liquid phase (or a solvent).
• Since this is the operation between the two liquid phases, no vaporisation is
needed; thus, extraction can be performed at low temperatures.
• Accordingly, extraction is suitable for separating materials that may decompose
or denature at elevated temperatures.
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Liquid – Liquid Extraction (LLX)
• Liquid-liquid extraction(LLX) is a mass transfer operation in which a solution
(feed: a mixture of solute and carrier liquid) is brought into intimate contact with
a second immiscible or slightly miscible liquid (solvent) in order to achieve the
transfer of solute (s) from the feed to solvent.
• The solute rich phase is called the extract.
• The residual liquid (feed stream) that may have the little of the left in it is called
the raffinate.
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Liquid-liquid Equilibria(LLE)
• According to the phase rule there are three degrees of freedom (three independent
variables) for a ternary(three-component) system consisting of two liquid phases
at equilibrium.
• At any temperature and pressure, therefore, only one degree of freedom remains.
If the composition of one of the liquid phase is specified or fixed, and the
composition of the second liquid is also fixed and is not an independent variable
provided that equilibrium condition exist.
• Classification of Ternary Systems -
• A liquid-liquid extraction system contains at least three components –Solute (A),
Carrier liquid in the feed (B), Extracting material (C) may be regarded as
composed of three binary system – A and B, B and C, and A and C. 5

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Fig.,Triangular diagram for one pair of partially miscible liquids.
Pyridine –water –chlorobenzene at 25℃.
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Categories-
1. The component A and B are completely miscible.
2. The component A and C are completely miscible.
3. The component B and C are partially miscible.
• In fig. the triangular diagram for the system pyridine-water-chlorobenzene at 25℃.
• Pyridine and water are completely miscible (A and B), Pyridine and chlorobenzene
are completely miscible ( A and C ), while water and chlorobenzene (B and C) are
practically immiscible at this temperature.
• The curve labeled EFG, called the “solubility curve,” separates the two-phase region
from the single-phase region.
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• Any point inside the boundary of the solubility curve, such as point H,
represents the composition of a mixture consisting of two liquid phases.
• If equilibrium is attained, the composition of two liquid phases is represented by
the intersection of the tie line (shown as dotted line) with two branches, I -EF and II –FG
of the solubility curve.
• Any straight lines such as PQ, RS, TV, or EG joining two points on the solubility
curve which represent the composition of liquid phases in equilibrium is called a “tie line.”
• Examination of the tie lines shows that the length of the tie lines decreases and that the
Compositions of the two liquid phases in equilibrium approach each other as the pyridine
concentration increases.
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• Liquid phase having composition on the branch of the solubility curve EF
corresponding to the higher solute compositions are called extract phases, while those
corresponding to compositions on the branch FG are called raffinate phases.
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• Liquid-liquid extraction is an easy method which is generally preferred over other
methods.
• This method is used for heat sensitive materials or when components to be separated
have very close boiling points.
• When there are expensive disposal problems for by products then this method can
be used as a substitute.
• This method has less chemical consumption and also less formation of by products.
• This method is cost effective unlike other methods of separation in which capital is
required for setting up various incentives.
Application of Liquid-liquid Equilibria -
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Extraction With Agitation
• Agitation is the movement of one or more components of a mixture to improve
contact.
• Putting into motion by shaking or stirring often to achieve mixing.
• Rotary-agitated columns
• Reciprocating columns
• Examples of Rotary-agitated columns include:
- Scheibelll columns, Rotating disk contactor (RDC), Oldshue-Rushton Columns,
Kuhni columns, etc.
- An example of the Reciprocating column is the Karr columns.
Mechanically Agitated Extractors
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Scheibel Extractor
• This is probably the oldest of column having agitators. It operates on the mixer-
settler principle.
• There are many versions of this design, an example of which is shown in the
Figure. The agitators are mounted at fixed intervals on a central vertical shaft, and
wire-mesh packings are installed to improve coalescence and separation of the
phases.
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Rotating Disk Contactor (RDC)
• In this system, horizontal disks are used as agitating elements, which are mounted
on a centrally supported shaft.
• Mounted on the column wall and offset against the agitator disks are the stator
rings, whose have aperture is greater than the agitator disk diameter.
• This device uses the shearing action of the rapidly rotating disks to inter-disperse
the phases.
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Asymmetric Rotating Disk (ARD) Contactor
• The column consists of an asymmetrically located mixing zone and a transfer-
settling zone partially separated from each other by means of a vertical baffle.
• The mixing zone contains a number of compartments, each of which is equipped
with a disk-type mixing impeller mounted on a common rotor shaft. The transfer-
settling zone consists of a series of compartments, separated by means of annular
horizontal baffles.
• Its design is aimed at retaining the efficient shearing action of the RDC by using
rotating disks to produce dispersion while using the coalescence re-dispersion
cycle produced in the separated transfer-settling zone to reduce back-mixing.
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Karr Reciprocating-Plate Extractor
• This is a "descendant" of the pulse column with fixed plates. Essentially, the
reciprocating-plate column has sieve plates moving up and down (i.e.
reciprocating motion) driven by an overhead motor. Thus its operation
involves "pulsing" the plates in a steady flow liquid medium.
• The Karr Extractor consists of a stack of perforated plates and baffles which
have a free area of about 58%. The central shaft which supports the plates is
reciprocated by means of a reciprocating drive mechanism located at the top
of the column. The amplitude is adjustable generally from 3 to 50-mm and
the speed is variable up to 1000 stokes/cm.
• Perforated trayes moves up and down.
• More uniform drop size distribution.
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Counter current extraction
1. Counter-current extraction with filter.
2. Continuous counter-current decantation systems.
• Counter-current extraction is a refinement of basic liquid-liquid extraction that
permits separation of substance with very similar portioning behaviour.
• The term counter-current indicates that the two phases move in opposite direction
actually in the CCD procedure it is usually used one phase is stable and other
moves hence the two phases are in relative motion.
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Principle of counter-current extraction
• The distribution of a single solute between two liquids the fraction p distribution
into the upper phase is a function of the partition coefficient k and the U of upper to
lower phase volume
p=KU/KU+1
The fraction of solutes in the lower phase at equilibrium q is given by,
q=1/KU+1
since p+q=1 The greater the value of KU the larger the fraction p of solutes that
passes into the upper phase
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• In these extraction wet raw material is pulverised using toothed disc
disintegrators to produce the fine slurry.
• The material to be extacted is moved in the one direction (generally in the
form of fine slurry) within a cylindrical extractor where it comes in contact
with extraction solvent.
• The further the starting material moves the more concentrated the extract
becomes.
• Finally, sufficiently concentrated extract comes out at one end of the extractor
while the marc falls out the other end.
Procedure -
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Counter – current extraction with filter
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• For.eg., System for the manufacture of caustic soda by the reaction of sodium carbonate
and milk of lime.
• The two reagents in solution are mixed in agitator A, which may be a standard agitator
of any type.
• The volume of agitator A compared to the amount of solution being introduced is such
that time is allowed for the reaction to become complete.
• The agaitator overflows continuously to a thickener B where a preliminary separation is
made, and from the launder of thickener B the clear solution of the same concentration
as that produced in agitator A is taken off as the product of the process.
Process for Counter current extraction
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• The filter cake is washed with a solution so that a calcium carbonate
precipitate,partly washed free from caustic,is obtained.
• The filtrate from this filter is now added to the overflow of thickener B and becomes
the product of the process.
• The cake from filter C is altogether too thick to pump,and therefore it is dropped into
a repulper D.
• The underflow from thickener B, consisting now of calcium carbonate
suspended in a caustic soda without introducing so much wash water that an
undue load is placed on the evaporators for the solution.
• This underflow is pumped by a diphragm pump to a rotatory continuous filter C.
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• Repulper D is merely a half cylinder with paddles, in which a stream of solution
is introduce until the mixture has been reduced to the thickest consistency that
can be pumped with safety. This is then pumped to a second filter E.
• Filter E is washed with fresh water; and, if the process has been properly
designed,the cake leaving filter E contains so little caustic that it may be sent to
waste.
• The filtrate from filter E is the liquid that is used (a) to repulp the cake in
repulper D, and (b) to wash the cake on filter C.
• The systems of more than two filters are not common, but there may be any
conceivable combination of thickeners and filters in series.
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Advantages-
• A much smaller amount of wash water theoretically required for unit quantity
plant material extraction. The same degree of removal of solute as done in
counter- current decantation system without filter but with much more water.
• The filters take much less space than the equivalent thickeners.
• CCE is commonly done at room temperature which spare thermolabile
constitutes from exposure to heat which is employed in most other techniques.
• CCE procedure has been rated to be more effective and efficient than continuous
hot extraction.
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Disadvantage-
• The filter system is that the degree with which the wash water comes into equilibrium with the
solution on the filter is questionable; and it depends to a considerable extent on the care taken in the
maintenance of the filter cloth and the spray nozzles that supply the water.
• If the filters are not properly operated,the cake thickness may be variable,in which case the wash
water to largely through the spots in the cake and will not extract the thicker spots.
• This is not applicable for colloidal or very slow – settling solids.
Application-
• DNA purification.
• Food industry.
• Examples citrus oils unsaturated fatty acids.
• An important application is citrus oils processing.
• An important subject in perfumes and food industry. 25

Theory
A method of multiple liquid-liquid extractions is
counter current extraction, which permits the separation
of substances with different distribution coefficients
(ratios).
A clever design known as Craig apparatus is used for
this purpose (Lyman C. Craig, 1943).
• It consists of 300-400 such chambers.
• The organic solvent and the aqueous solution is
introduced to tube and then it passes to B.
Procedures
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• When the apparatus is again made vertical.
• The liquid passes through D into E in the next chamber of A and then into B.
• The process is repeated till the two liquid gets almost separated.
• It is allowed to attain the equilibrium.Now,the appartus is tilted so that the
upper layer gets decanted through C and is collected in D.
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Application-
• With the help of this method we can have accurate quantitative analysis of a single
as well as the mixture of components.
• In this case, apparatus required are very simple ( separating funnel, burette,
conical flask, etc).
• Time required for analysis is very small.
• The method is very well used for detection of traces quantity of substance where
precipitation method, Gravimetry method not possible.
• Fe+3 ferric ion can be easily extracted by ether from 6 Molar HCL solution of the
ferrous alloy and iron core.
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• In industrial and commercial field extraction by counter current extraction is
frequently applied in the separation of components where the difference in the
distribution coefficient small.
• The phenomenon is widely applied in the drug analysis.
• The solvent extraction is used in clinical laboratory.
• Metal chelates are more soluble in non polar solvent.Thus Ni(ll) in it’s tetra co-
ordinate complex with dimethyl glyoxime can be extracted into chloroform. In
presence of citrate or tartrate the precipitation of Fe(lll) and Cr(lll) can be
avoided.
• The extract can also be used in the extraction of metal as metal chelate has high
solubility in an immiscible solvent such as Chloroform and Benzene.
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Reference –
1.Introduction to chemical engineering TATA MC GRAW HILL Edition by
Walter.Badger & Julius T. Banchero.
2.https://youtu.be/pJ_U359lMD4
3. Pharmaceutical Engeeneering New age international publishers by
K.Sambamurthy.
4. Pharmaceutical analysis, Nirali Prakashan,Volume ll by Dr.A.V. Kasture,
Dr.K.R.Mahadik, Dr.S.G.Wadodkar, Dr.H.N.More.
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Thank
you!!