2. Contents
Introduction to Extraction
Principle and objective
Types of Liq-liq extraction and Equipments used
Applications
Introduction to Flocculation
Objective
Design of flocculator
Applications
.
3. Separation processes -
general
Mechanical separations e.g. filtration of a solid from a
suspension in a liquid, centrifugation, screening etc
Mass transfer operations e.g. distillation, extraction etc
Mass transfer operations – nature of interface between
phases:
Gas-liquid contact e.g. absorption, evaporation,
distillation etc
Liquid-liquid contact e.g. extraction
Liquid-solid contact e.g. crystallization, adsorption
Gas-solid contact e.g. adsorption, drying etc
.
6. Let's see an example.
Suppose that you have a mixture of sugar in vegetable oil (it tastes sweet!)
and you want to separate the sugar from the oil. You observe that the sugar
particles are too tiny to filter and you suspect that the sugar is partially
dissolved in the vegetable oil.
7. How about shaking the mixture with
water
Will it separate the sugar from the oil?
Sugar is much more soluble in water
than in vegetable oil, and, as you know,
water is immiscible (=not soluble) with
oil.
Did you see the result? The water phase is
the bottom layer and the oil phase is the
top layer, because water is denser than
oil.
*You have not shaken the mixture yet, so
sugar is still in the oil phase.
8. By shaking the layers (phases) well, you
increase the contact area between the
two phases. The sugar will move to the
phase in which it is most soluble: the
water layer
Now the water phase tastes sweet,
because the sugar is moved to the
water phase upon shaking.**You
extracted sugar from the oil with
water.**In this example, water was the
extraction solvent ;the original oil-
sugar mixture was the solution to be
extracted; and sugar was the
compound extracted from one phase to
another. Separating the two layers
accomplishes the separation of the
sugar from the vegetable oil
9. Partition Coefficient Kp (Distribution Coefficient Kd)
When a compound is shaken in a separatory funnel with two immiscible
solvents, the compound will distribute itself between the two solvents.
Normally one solvent is water
and the other solvent is a
water-immiscible organic
solvent.
Most organic compounds are
more soluble in organic solvents,
while some organic compounds
are more soluble in water.
10. Here is the universal rule:
At a certain temperature, the ratio of concentrations of a solute in
each solvent is always constant. And this ratio is called the
distribution coefficient, K.
(when solvent1 and solvent2 are immiscible liquids
For example, Suppose the
compound has a distribution
coefficient K = 2 between
solvent1 and solvent2
By convention the organic
solvent is (1) and water is (2)
11. (1) If there are 30 particles
of compound , these are
distributed between equal
volumes of solvent1 and solvent2..
(2) If there are 300 particles
of compound , the same
distribution ratio is observed
in solvents 1 and 2
(3) When you double the
volume of solvent2 (i.e., 200
mL of solvent2 and 100 mL of
solvent1),the 300 particles of
compound distribute as shown
If you use a larger amount of extraction solvent, more solute is
extracted
12. What happens if you extract twice with 100 mL of solvent2 ?
In this case, the amount of extraction solvent is the same volume as was
used in Figure 3, but the total volume is divided into two portions and you
extract with each.
As seen previously, with 200 mL of
solvent2 you extracted 240
particles of compound . One
extraction with 200 mL gave a
TOTAL of 240 particles
You still have 100 mL of solvent1,
containing 100 particles. Now you
add a second 100 mL volume of
fresh solvent2. According to the
distribution coefficient K=2, you
can extract 67 more particles from
the remaining solution
13. An additional 67 particles are
extracted with the second portion
of extraction solvent (solvent2).The
total number of particles extracted
from the first (200 particles) and
second (67 particles) volumes of
extraction solvent is 267.This is a
greater number of particles than
the single extraction (240
particles) using one 200 mL portion
of solvent2!
It is more efficient to carry out
two extractions with 1/2 volume
of extraction solvent than one
large volume!
14. If you extract twice with 1/2 the volume, the extraction is more
efficient than if you extract once with a full volume. Likewise,
extraction three times with 1/3 the volume is even more efficient….
four times with 1/4 the volume is more efficient….five times with 1/5
the volume is more efficient…ad infinitum
The greater the number of small extractions, the greater the quantity
of solute removed. However for maximum efficiency the rule of
thumb is to extract three times with 1/3 volume
15. Did you get it? .....the concept of liquid-liquid extraction?
Liquid-liquid extraction is based on the transfer of a solute substance
from one liquid phase into another liquid phase according to the
solubility. Extraction becomes a very useful tool if you choose a
suitable extraction solvent.You can use extraction to separate a
substance selectively from a mixture, or to remove unwanted
impurities from a solution. In the practical use, usually one phase is a
water or water-based (aqueous) solution and the other an organic
solvent which is immiscible with water.
The success of this method depends upon the difference in solubility of
a compound in various solvents. For a given compound, solubility
differences between solvents is quantified as the "distribution
coefficient"
16. Basic principles
In liquid-liquid extraction, a soluble component (the solute) moves from
one liquid phase to another. The two liquid phases must be either
immiscible, or partially miscible.
usually isothermal and isobaric
can be done at low temperature (good for thermally fragile
solutes, such as large organic molecules or biomolecules)
can be very difficult to achieve good contact between poorly
miscible liquids (low stage efficiency)
extracting solvent is usually recycled, often by distillation
(expensive and energy-intensive)
can be single stage (mixer-settler) or multistage (cascade)
17. Example - Penicillin G
6-aminopenicillanic acid (6-APA) is
manufactured by GSK in Irvine. It is used to
manufacture amoxicillin and ‘Augmentin’.
Fermentation products (penicillin G broth) are
filtered (microfiltration) and extracted at low
pH with amyl acetate or methyl isobutyl
ketone. The penicillin G is then extracted
further at a higher pH into an aqueous
phosphate buffer.
.
18. Immiscible liquids
e.g. water – chloroform
Consider a feed of water/acetone(solute).
K = mass fraction acetone in chloroform phase
mass fraction acetone in water phase
K = kg acetone/kg chloroform = y/x
kg acetone/kg water
K = 1.72
i.e. acetone is preferentially soluble in the
chloroform phase
.
19. Partially miscible liquids
E.g. water – MIBK
Consider a solute acetone.
Need to use a triangular phase diagram to show equilibrium
compositions of MIBK-acetone-water mixtures.
Characteristics are single phase and two phase regions, tie
lines connecting equilibrium phase compositions in two
phase region.
.
21. Extractants
The efficiency of a liquid liquid extraction can be enhanced
by adding one or more extractants to the solvent phase.
The extractant interacts with component I increasing
the capacity of the solvent for i.To recover the solute
from the extract phase the extractant-solute complex
has to be degraded.
.
22. Choice of solvent
Factors to be considered:
Selectivity
Distribution coefficient
Insolubility of solvent
Recoverability of solute from solvent
Density difference between liquid phases
Interfacial tension
Chemical reactivity
Cost
Viscosity, vapour pressure
Flammability, toxicity
.
23. Selectivity:
β = (mass fraction B in E)/(mass fraction A in E)
(mass fraction B in R)/(mass fraction A in R)
β > 1
Distribution coefficient:
K = y/x
Large values are desirable since less solvent is required for a given degree of
extraction
Physical properties:
Low viscosity
Low vapour pressure
Non-flammable (high flash point)
Non-toxic
.
24. Recoverability of solvent and solute:
No azeotrope formed between solvent and solute
Mixtures should have a high relative volatility
Solvent should have a small latent heat of vaporization
Density:
A density difference is required between the two phases.
Interfacial tension:
The larger the interfacial tension between the two phases the
more readily coalescence of emulsions will occur to give two
distinct liquid phases but the more difficult will be the
dispersion of one liquid in the other to give efficient solute
extraction.
Chemical reactivity:
Solvent should be stable and inert.
.
25. Types of flow in LLE
When both phases are flowing:
Co-current contact
Cross flow
Counter-current flow
.
Stage 1 Stage 2
1 2
1 2
26. Major Types of Extraction Equipment
ColumnColumn
ContactorsContactors
Mixer SettlersMixer Settlers
CentrifugalCentrifugal
Used primarily in the metals
industry due to:
- Large flows
- Intense mixing
- Long Residence time
- Corrosive fluids
- History
Used primarily in the
pharmaceutical industry due to:
- Large flows
- Intense mixing
- Long Residence time
- Corrosive fluids
- History
StaticStatic AgitatedAgitated
SpraySpray PackedPacked TrayTray PulsedPulsed RotaryRotary
ReciprocatingReciprocating
Rarely used Used in:
- Refining
- Petrochemicals
Example:
- Random
- Structured
- SMVPTM
Used in:
- Refining
- Petrochemicals
Example:
- Sieve
Used in:
- Nuclear
- Inorganics
- Chemicals
Example:
- Packed
- Tray
- Disc & Donut
Example:
- RDC
- Scheibel
Example:
- Karr
Used in:
- Chemicals
- Petrochemicals
- Refining
- Pharmaceutical
28. Types:
Simple Extraction Single Stage
A – 99
B – 0
C – 1
100
Feed (F)
A – 0
B – 50
C – 0
50
Solvent (S)
A – 0
B – 50
C – 0.8
50.8
Extract (E)
A – 99.0
B – 0
C – 0.2
99.2
Raffinate (R)
( )( ) ( )( ) 4.07.92
99
50M
F
SE
7.92
99
0.2
50
0.8
RaffinateinSoluteConc.
ExtractinSoluteConc.
M
0.2
1.0
0.2
FeedinSolute
RaffinateinSolute
U
===
===
===Fraction Unextracted
Distribution Coefficient
Extraction Factor
29. Cross Flow Extraction
A
RR11 RR22 RR33 RR44
C C C C
F + S = M1 R1 + S = M2 R2 + S = M3 R3 + S = M4
A + B
F
B + C B + C B + C B + C
E1 E2 E3 E4
R1
R2
R3
R4
E1
E2
E3
E4
M1
M2
M3
M4
B
A C
F
30. Countercurrent Flow Extraction
A
RR11 RR22 RR33 RR44
A + B
F
B + C
C
E1
E2
E3
E4
B + C B + C
B + C
F + S = M
E1 + R4 = M
F + S = E1 + R4
F – E1 = R4 – S = ∆
Equations
C
R1
R2
R3
R4
E1
B
A
F
∆
M E2
E3
E4
S
31. Countercurrent Extraction
B + C
A
C
A + B
Feed (F)
Solvent (S)
Extract (E):
Solute Rich Stream
Raffinate (R):
Solute Lean Stream
Primary Interface
Continuous Phase
Dispersed Phase
32. Dilute fractional extraction
A common situation:
the feed contains two important
solutes (A, B), and we want to
separate them from each other.
Choose two solvents:
A prefers solvent 1 (“extract”)
B prefers solvent 2 (“raffinate”)
Kd,A = yA/xA > 1
Kd,B = yB/xB < 1
1
N
F
zA
zB
solvent 1
yA,N+1 = 0
yB,N+1 = 0
solvent 2
xA,0 = 0
xB,0 = 0
extract
yA,1
yB,1
raffinate
xA,N
xB,N
E R
E R
absorbing
section
stripping
section
33. Center-cut extraction
When there are 3 solutes: A, B and C,
and B is desired
(A and C may be > 1 component each)
solvent 1
solvent 2solvent 1
+ A
solvent 2
+ B + C solvent 3
solvent 2solvent 3
+ B
solvent 2
+ C
F
zA, zB, zC
Requires two columns:
• column 1 separates A from
B+C
• column 2 separates B from C
Requires three extracting
solvents:
A prefers solvent 1 over solvent 2
B, C prefer solvent 2 over solvent
1B prefers solvent 3 over solvent 2
C prefers solvent 2 over solvent 3
34. Typical Applications
• Remove products and pollutants from dilute aqueous streams
• Wash polar compounds or acids/bases from organic streams
• Heat sensitive products
• Non-volatile materials
• Azeotropic and close boiling mixtures
• Alternative to high cost distillations
35. Extraction is Used in a Wide
Variety of Industries
Chemical •Washing of acids/bases, polar compounds from organics
Pharmaceuticals
• Recovery of active materials from fermentation broths
• Purification of vitamin products
Effluent Treatment
• Recovery of phenol, DMF, DMAC
• Recovery of acetic acid from dilute solutions
Polymer Processing
• Recovery of caprolactam for nylon manufacture
• Separation of catalyst from reaction products
Petroleum
• Lube oil quality improvement
• Separation of aromatics/aliphatics (BTX)
Petrochemicals
• Separation of olefins/parafins
• Separation of structural isomers
Food Industry
• Decaffeination of coffee and tea
• Separation of essential oils (flavors and fragrances)
Metals Industry
• Copper production
• Recovery of rare earth elements
Inorganic Chemicals • Purification of phosphoric acid
Nuclear Industry • Purification of uranium
44. Choice of separation process
Factors to be considered:
Feasibility
Product value
Cost
Product quality
selectivity
.
45. What is Coagulation?
04/08/15water treatment 45
Coagulation is the destabilization of colloids by addition of
chemicals that neutralize the negative charges
The chemicals are known as coagulants, usually higher valence
cationic salts (Al3+
, Fe3+
etc.)
Coagulation is essentially a chemical process
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46. What is Flocculation?
04/08/15water treatment 46
Flocculation is the agglomeration of destabilized particles into
a large size particles known as flocs which can be effectively removed
by sedimentation or flotation.
47. 04/08/15water treatment 47
FLOCCULATION Conti…
Flocculation, in the field of chemistry, is a process wherein colloids come
out of suspension in the form of floc or flake; either spontaneously or due
to the addition of a clarifying agent. The action differs
fromprecipitation in that, prior to flocculation, colloids are merely
suspended in a liquid and not actually dissolved in a solution. In the
flocculated system, there is no formation of a cake, since all the flocs are
in the suspension.
Examples - milk, blood, seawater
Mechanisms
1-perikinetic:
collisions from Brownian motion.
Thermal activity or Brownian motion is responsible for colloid collisions in the case of
perikinetic flocculation. Smoluchowski theory can be used to predict rate of reduction
of particle (colloid) number with time.
2-orthokinetic:
induced collisions through stirring.
In this case there is an external mixing source which promotes particle-particle
contact.
48. Flocculants should have the
following properties They must react rapidly with the cells.
They must be non-toxic.
They should not alter the chemical
constituents of the cell.
They should have a minimum cohesive power
in order to allow for effective subsequent
water removal by filtration.
Neither high acidity nor high alkalinity should
result from their addition.
They should be effective in small amounts
and be low in cost.
They should preferably be washable for reuse.
50. 04/08/15.t 50
Why flocculation?
Various sizes of particles in raw water
Particle diameter (mm) Type Settling velocity
10 Pebble 0.73 m/s
1 Course sand 0.23 m/s
0.1 Fine sand 0.6 m/min
0.01 Silt 8.6 m/d
0.00010.0001 (10 micron)(10 micron) Large colloidsLarge colloids 0.3 m/y0.3 m/y
0.000001 (1 nano)0.000001 (1 nano) Small colloidsSmall colloids 3 m/million y3 m/million y
Particle diameter (mm) Type Settling velocity
10 Pebble 0.73 m/s
1 Course sand 0.23 m/s
0.1 Fine sand 0.6 m/min
0.01 Silt 8.6 m/d
0.00010.0001 (10 micron)(10 micron) Large colloidsLarge colloids 0.3 m/y0.3 m/y
0.000001 (1 nano)0.000001 (1 nano) Small colloidsSmall colloids 3 m/million y3 m/million y
Colloids – so small: gravity settling not possible
GravItysettlIng
51. 04/08/15water treatment 51
Colloid Stability
------ ------
Repulsion
Colloid - A Colloid - B
Colloids have a net negative surface charge
Electrostatic force prevents them from agglomeration
Brownian motion keeps the colloids in suspension
H2O
Colloid
Impossible to remove colloids by gravity settling
54. Colloid Destabilization
Colloids can be destabilized by charge
neutralization
Positively charges ions (Na+, Mg2+, Al3+,
Fe3+ etc.) neutralize the colloidal negative
charges and thus destabilize them.
With destabilization, colloids aggregate in
size and start to settle
04/08/15water treatment 54
56. 04/08/15. 56
Cross flow Flocculator (sectional view)
Plan (top view)
Transversepaddle
L
H
W
Mechanical Flocculator
57. 04/08/15.
57
Hydraulic Flocculation
• Horizontally baffled tank
Plan view (horizontal flow)
• Vertically baffled tank
L
Isometric View (vertical flow)
L
W
H
The water flows horizontally.
The baffle walls help to create
turbulence and thus facilitate mixing
The water flows vertically. The baffle
walls help to create turbulence and thus
facilitate mixing
58. Applications:
Surface chemistry:
In colloid chemistry, flocculation refers to the process by which
fine particulates are caused to clump together into a floc. The floc may
then float to the top of the liquid (creaming),settle to the bottom of the
liquid (sedimentation), or be readily filtered from the liquid.
Physical chemistry:
For emulsions, flocculation describes clustering of individual dispersed
droplets together, whereby the individual droplets do not lose their
identity.[5]
Flocculation is thus the initial step leading to further aging of
the emulsion (droplet coalescence and the ultimate separation of the
phases).(1993) Flocculation is used in mineral dressing
Civil engineering/earth sciences:
In civil engineering, and in the earth sciences, flocculation is a condition in
which clays, polymers or other small charged particles become attached
and form a fragile structure, a floc.
.
59. Appli…
Water treatment:
Flocculation and sedimentation are widely employed in
the purification of drinking water as well as sewage
treatment, storm-water treatment and treatment of
other industrial wastewater streams.
Biology:
In biology, flocculation refers to the asexual aggregation of
microorganisms.
Cheese production:
Flocculation is widely employed to measure the progress
of curd formation while in the initial stages of making
many cheeses to determine how long the curds must set
.
