1. MISS. RAHIMAH BINTI OTHMAN
ERT 313/4 BIOSEPARATION ENGINEERING
MISS. RAHIMAH BINTI OTHMAN (

2. LIST OF CHAPTERS 4 LIQUID-LIQUID EXTRACTION 5
TITLE
WEEK 4
LIQUID-LIQUID EXTRACTION 5
SOLID-LIQUID EXTRACTION (LEACHING) 6
ADSORPTION 8

3. LIST OF CHAPTERS 7 CHROMATOGRAPHY 9 8 ION EXCHANGE 10 CRYSTALLIZATION
TITLE
WEEK 7
CHROMATOGRAPHY 9 8
ION EXCHANGE 10
CRYSTALLIZATION

4. COURSE OUTCOMES CO
APPLY principles of extraction. ANALYZE extraction equipments, Batch Extraction, Continuous Extraction and Aqueous Two Phase Extraction. DEVELOP basic design of extractor.

5. OUTLINES Introduction to extraction. Equipment for extraction.
Principles of Extraction
Operating modes of extraction (Batch Extraction, Continuous Extraction and Aqueous Two Phase Extraction).
Basic design of extractor.

6. INTRODUCTION TO EXTRACTION
Definition of Extraction
Liquid-Liquid extraction is a mass transfer operation in which a liquid solution (the feed) is contacted with an immiscible or nearly immiscible liquid (solvent) that exhibits preferential affinity or selectivity towards one or more of the components in the feed.
Purpose of Extraction
To separate closed-boiling point mixture
Mixture that cannot withstand high temperature of distillation
Example:
- recovery of penicillin from fermentation broth solvent: butyl
acetate
- recovery of acetic acid from dilute aqueous solutions solvent:
ethyl-acetate

7. INTRODUCTION TO EXTRACTION
Advantages of solvent extraction;
Selectivity of extraction directly from fermentation broths or from reaction medium in the case of biotransformations wherein whole cells or enzymes are used for conversion of a substrate into a desired product.
Reduction in product loss due to hydrolytic or metabolic/microbial degradation as the product is transferred to a second phase with different physical and chemical properties.
Suitability over a wide range of scales operation.

8. INTRODUCTION TO EXTRACTION
However, solvent extraction of biological products is beset with several problems. These include;
Compositional complexity of the fermentation broth due to the presence of a variety of dissolved as well as solid substances, which gives rise to phase complexity and influences the extraction of the desired solute (s).
The presence of surface active species influences the mass transfer rate.
The presence of particulate matter and surface active species affects the phase separation
Chemical instability of the desired product due to metabolic or microbial activity and also due to the compositional or pH conditions during extraction affects the overall efficiency in the recovery of the desired product.
The rheological properties of the fermentation broths may show time dependence and may be altered affecting the extraction process.

9. INTRODUCTION TO EXTRACTION

10. EQUIPMENT FOR EXTRACTION
2. Packed extraction towers
3. Perforated-plate towers
1. Mixer-settlers
EQUIPMENT FOR EXTRACTION
6. Centrifugal extractors
4. Agitated tower extractors
7. Auxilary equipment
[stills, evaporators, heaters and condenser]
5. Pulse columns

11. EQUIPMENT FOR EXTRACTION
Batchwise or continuous operation
Feed liquid + solvent (put in agitated vessel) = layers (to be settled and separated)
Extract – the layer of solvent + extracted solute
Raffinate – the layer from which solute has been removed
Extract may be lighter or heavier than raffinate.
Continuous flow – more economical for more than one contact process

12. EQUIPMENT FOR EXTRACTION

13. EQUIPMENT FOR EXTRACTION
2. Packed extraction towers
3. Perforated-plate towers
1. Mixer-settlers
EQUIPMENT FOR EXTRACTION
6. Centrifugal extractors
4. Agitated tower extractors
7. Auxilary equipment
[stills, evaporators, heaters and condenser]
5. Pulse columns

14. MIXER-SETTLERS For Batchwise Extraction:
The mixer and settler may be the same unit.
A tank containing a turbine or propeller agitator is most common.
At the end of mixing cycle the agitator is shut off, the layers are
allowed to separate by gravity.
Extract and raffinate are drawn off to separate receivers through a
bottom drain line carrying a sight glass.
The mixing and settling times required for a given extraction can
be determined only by experiment.
(e.g: 5 min for mixing and 10 min for settling are typical)
- both shorter and much longer times are common.

15. Single Stage Extraction
MIXER-SETTLERS
Single Stage Extraction
Raffinate
Feed
Solvent
Extract
Schematic Diagram Representation of a Single Stage Batch Extraction

16. MIXER-SETTLERS For Continous Extraction:
The mixer and settler are usually separate pieces of equipment.
The mixer; small agitated tank provided with a drawoff line and
baffles to prevent short-circuiting, or it may be motionless mixer
or other flow mixer.
The settler; is often a simple continuous gravity decanter.
In common used; several contact stages are required, a train of
mixer-settlers is operated with countercurrent flow.

17. MIXER-SETTLERS
Note: The raffinate from each settler becomes a feed to the next mixer, where it meets intermediate extract or fresh solvent.

18. EQUIPMENT FOR EXTRACTION
2. Packed extraction towers
3. Perforated-plate towers
1. Mixer-settlers
EQUIPMENT FOR EXTRACTION
6. Centrifugal extractors
4. Agitated tower extractors
7. Auxilary equipment
[stills, evaporators, heaters and condenser]
5. Pulse columns

19. PACKED EXTRACTION TOWERS
Tower extractors give differential contacts, not stage contacts, and mixing and settling proceed continuously sand simultaneously.
Extraction; can be carried out in an open tower, with drops of heavy liquid falling through the rising light liquid or vice versa.
The tower is filled with packings such as rings or saddles, which causes the drops to coalesce and reform, and tends to limit axial dispersion.
In an extraction tower there is continuous transfer of material between phases, and the composition of each phase changes as it flows through the tower.
The design procedure ; is similar to packed absorption towers.

20. PACKED EXTRACTION TOWERS
Tower packings; (a) Raschig rings, (b) metal Pall ring, (c) plastic Pall ring, (d) Berl saddle, (e) ceramic Intalox saddle, (f) plastic Super Intalox saddle, (g) metal Intalox saddle

21. EQUIPMENT FOR EXTRACTION
2. Packed extraction towers
3. Perforated-plate towers
1. Mixer-settlers
EQUIPMENT FOR EXTRACTION
6. Centrifugal extractors
4. Agitated tower extractors
7. Auxilary equipment
[stills, evaporators, heaters and condenser]
5. Pulse columns

22. PERFORATED-PLATE TOWERS
The axial mixing characteristic of an open tower can also be limited by using transverse perforated plate like those in the sieve-plate distillation towers.
The perforations are typically 1 , to 4 mm ( to in.) in diameter.
Plate spacing range from 150 to 600 mm (6 to 24 in.)
Usually, the light liquid is the dispersed phase, and downcomers carry the heavy liquid above.
Extraction takes place in the mixing zone above the perforations, with the light liquid (oil) rising and collecting in a space below the next-higher plate, then following transversely over a weir to the next set of perforations.

23. PERFORATED-PLATE TOWERS

24. EQUIPMENT FOR EXTRACTION
2. Packed extraction towers
3. Perforated-plate towers
1. Mixer-settlers
EQUIPMENT FOR EXTRACTION
6. Centrifugal extractors
4. Agitated tower extractors
7. Auxilary equipment
[stills, evaporators, heaters and condenser]
5. Pulse columns

25. AGITATED TOWER EXTRACTORS
It depends on gravity flow for mixing and for separation.
Mechanical energy is provided by internal turbines or other agitators, mounted on a central rotating shaft.
Fig (a), flat disks disperse the liquids and impel them outward toward the tower wall, where stator rings create quite zones in which the two phases can separate.
In other designs, set of impellers are separated by calming sections to give, in effect, a stack of mixer-settlers one above the other.

26. AGITATED TOWER EXTRACTORS
In the York-Scheibel extractor (Fig. b), the region surrounding the agitators are packed with wire mesh to encounter coalescence and separation of the phases.
Most of the extraction takes place in the mixing sections, but some also occurs in the calming sections.
The efficiency of each mixer-settler unit is sometimes greater than 100 percent.

27. EQUIPMENT FOR EXTRACTION
2. Packed extraction towers
3. Perforated-plate towers
1. Mixer-settlers
EQUIPMENT FOR EXTRACTION
6. Centrifugal extractors
4. Agitated tower extractors
7. Auxilary equipment
[stills, evaporators, heaters and condenser]
5. Pulse columns

28. PRINCIPLES OF EXTRACTION
Most continuous extraction methods use countercurrent contacts between two phases, one a light liquid and the other a heavier one.
Importance measurements; ideal stage, stage efficiency, minimum ratio between the two streams, and size of equipment. (same as distillation column)
Extraction of Dilute Solution
Extraction factor is defined as:
Where:
E = extraction factor
KD = distribution coefficient
V = volume of solvent
L = volume of aqueous

29. PRINCIPLES OF EXTRACTION
For a single-stage extraction with pure solvent;
- the fraction of solute remaining is
- the fraction recovered is

30. PRINCIPLES OF EXTRACTION
BATCH EXTRACTION
EXAMPLE 23.2.
Penicillin F is recovered from a dilute aqueous fermentation broth by extraction with amyl acetate, using 6 volumes of solvent per 100 volumes of the aqueous phase. At pH 3.2 the distribution coefficient KD is 80.
(a) What fraction of the penicillin would be recovered in a single ideal stage?
(b) What would be the recovery with two-stage extraction using fresh solvent in both stages?

33. PRINCIPLES OF EXTRACTION
CONTINUOUS SINGLE STAGE EXTRACTION
EXAMPLE
An inlet water solution of 100 kg/h containing wt fraction nicotine in water is stripped with a kerosene stream of 200 kg/h containing wt fraction nicotine in a single stage extraction unit. It is desired to reduce the concentration of the exit water to wt fraction nicotine. Calculate the flow rate of the nicotine in both of the exit streams.

34. SOLUTION 1. Nicotine in the feed solution = 100 (0
SOLUTION 1. Nicotine in the feed solution = 100 (0.01) = 1 kg/h nicotine Water in feed = 100 ( ) = 99 kg/h water 2. Nicotine in solvent = 200 (0.0005) = 0.1 kg/h nicotine Kerosene = 200 (1 – ) = kg/h kerosene 3. Exit stream of aqueous phase, L1 Water = 99 kg/h = (1 – ) L1 L1 = kg/h (nicotine + water) Nicotine = – 99 = kg/h nicotine in exit stream 4. Exit stream of solvent phase, V1 Solvent = kg/h Nicotine in solvent = (1 – 0.099) = kg/h in exit stream Solvent + Nicotine = = kg/h

35. PRINCIPLES OF EXTRACTION
Extraction of Concentrated Solution
Equilibrium relationship are more complicated – 3 or more components present in each phase.
Equilibrium data are often presented on a triangular diagram such as Fig 23.7 and 23.8.

37. PRINCIPLES OF EXTRACTION
Consider Fig 23.7
Line ACE shows extract phase
Line BDE shows raffinate phase
Point E is the plait point – the composition of extract & raffinate phases approach each other
Tie line – a straight line joining the composition of extract & raffinate phases.
Tie line in Fig 23.7 slope up to the left – extract phase is richer in acetone than the raffinate phase.
This suggest that most of the acetone could be extract from water phase using moderate amount of solvent.

39. PRINCIPLES OF EXTRACTION
Consider Fig 23.8
Line AD shows extract phase
Line BC shows raffinate phase
Tie line in Fig 23.8 slope up to the right – extraction would still be possible
But more solvent would have to use.
The final extract would not be as rich in desired component (MCH)

40. PRINCIPLES OF EXTRACTION
How to obtain the phase composition using the triangular diagram?
- Point M: 0.2 Acetone, 0.3 water, 0.5 MIK
- Draw a new tie line
- Extract phase: acetone, water, MIK
- Raffinate phase: acetone, water, MIK
- Ratio of acetone to water in the product = 0.232/0.043 = 5.4
- Ratio of acetone to water in the raffinate = 0.132/0.845 =0.156
Let’s compare with Fig Which system is more effective?

41. PRINCIPLES OF EXTRACTION
Coordinates Scale
Refer to Treybal, Mass Transfer Operation, 3rd ed., McGraw Hill
The book use different triangular system
The location of solvent (B) is on the right of the triangular diagram (McCabe use on the left)
Coordinate scales of equilateral triangles can be plotted as y versus x as shown in Fig 10.9
Y axis = wt fraction of component C (acetic acid)
X axis = wt fraction of solvent B (ethyl acetate)

42. Coordinates Scale

43. Single-Stage Extraction

44. Single-Stage Extraction
The triangular diagram in Fig (Treybal) is a bit different as compared to Fig (McCabe)
Extract phase – on the left
Raffinate phase - on the right
Fig shows that we want to extract component C from A by using solvent B.
Total material balance:
Material balance on C:

45. Amount of solvent to provide a given location for M1 on the line FS:
The quantities of extract and raffinate:
Minimum amount of solvent is found by locating M1 at D
Maximum amount of solvent is found by locating M1 at K

46. Multistage Crosscurrent Extraction

47. Multistage Crosscurrent Extraction
Continuous or batch processes
Refer to Fig 10.14
Raffinate from the previous stage will be the feed for the next stage
The raffinate is contacted with fresh solvent
The extract can be combined to provide the composited extract
The total balance for any stage n:
Material balance on C:

48. Multistage Crosscurrent Extraction
EXAMPLE
If 100 kg of a solution of acetic acid (C) and water (A) containing 30% acid is to be extracted three times with isopropyl ether (B) at 20°C, using 40 kg of solvent in each stage, determine the quantities and compositions of the various streams. How much solvent would be required if the same final raffinate concentration were to be obtained with one stage?
The equilibrium data at 20°C are listed below [Trans. AIChE, 36, 628 (1940), with permission].

49. Multistage Crosscurrent Extraction

50. Multistage Crosscurrent Extraction
SOLUTION
The horizontal rows give the concentrations in equilibrium solutions. The system is of the type shown in Fig. 10.9, except that the tie lines slope downward toward the B apex. The rectangular coordinates of Fig. l0.9a will be used, but only for acid concentrations up to x = These are plotted in Fig

52. Point M1 is located on line FB
Point M1 is located on line FB. With the help of a distribution curve, the tie line passing through M1 is located as shown, and x1 = 0.258, y1 = wt fraction acetic acid. Eq. (10.8):

54. Stage 3
In a similar manner, B3 = 40, M3 = 130.1, xM3 = ,
x3 = 0.20, y3 = 0.078, E3 = 45.7, and R3 = 84.4.
The acid acetic content of the final raffinate is
= x3 R3 = 0.20(84.4) = kg.
The composited extract is
E1 + E2 + E3 = = kg,
The acid content in the composited extract:
E1y1 + E2y2 + E3y3 = kg.

55. If an extraction to give the same final raffinate concentration, x = 0
were to be done in one stage, the point M would be at the intersection of tie line R3E3 and line BF of Fig ,
XM = 0.12.
The solvent required would then be, by Eq. (10.6),
S1 = 100( )/( ) = 150 kg,
Hence, 150 kg of solvent is required for single stage extraction
120 kg of solvent is required in the three-stage extraction.

56. EXAMPLE 1
A countercurrent system is to be used for the water-acetic acid-isoprophyl ether extraction (see Table 1). Feed is 39 wt % acetic acid and 59 wt % water. Feed flow rate is 1000 kg/hr. Solvent added contains 1 wt % acetic acid but no water. Total flow rate of added solvent is 1500 kg/hr. We desire a raffinate that is 7 wt % acetic acid. What are the weight fractions of EN and R1? What are the flow rates of EN and R1? How many stages are required?

57. EXAMPLE 1
Table 1: Equilibrium data for water-acetic acid-isopropyl ether at 20 oC and 1 atm
Water Layer, wt %
Isopropyl Ether, wt %
Acetic acid xA
Water xD
Isopropyl Ether xS
Acetic Acid yA yD
Isopropyl Ether yS
0.69
98.1
1.2
0.18
0.5
99.3
1.41
97.1
1.5
0.37
0.7
98.9
2.89
95.5
1.6
0.79
0.8
98.4
6.42
91.7
1.9
1.93
1.0
13.30
84.4
2.3
4.82
93.3
25.50
71.1
3.4
11.40
3.9
84.7
36.70
58.9
4.4
21.60
6.9
71.5
44.30
45.1
10.6
31.10
10.8
58.1
46.40
37.1
16.5
36.20
15.1
48.7

58. STEPS Plot equilibrium data and construct conjugate line.
Plot locations of streams Eo = S, RN+1=F, and R1
Find mixing point M on line through points S and F at xA, M value calculated from Equation below;
Line R1M gives pint EN.
Find point as intersection of straight lines EoR1 and ENRN+1
Step off stages, using the procedure shown in Fig To keep the diagram less crowded, the operating lines, EjRj+1, are not shown. You can use straight edge on Fig to check the operating lines.

59. EXAMPLE 2
We wish to remove acetic acid from water using isopropyl ether as solvent. The operation is at 20 oC and 1 atm (See Table 1). The feed is 0.45 wt frac acetic acid, and 0.55 wt frac water. Feed flow rate is 2000 kg/hr. A countercurrent system is used. Pure solvent (no acetic acid and no water) is used. We desire an extract stream that is 0.20 wt frac acetic acid and a raffinate that is 0.20 wt frac acetic acid. (a) How much solvent is required? (b) How many equilibrium stages are needed?

65. Prepared by, MISS RAHIMAH OTHMAN
Thank you
Prepared by,
MISS RAHIMAH OTHMAN