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Liquid liquid extraction and flocculation

Liquid-liquid extraction and flocculation are separation processes discussed in the document. Liquid-liquid extraction involves using two immiscible liquids to separate components of a mixture based on their relative solubilities in each liquid. Factors like distribution coefficient, selectivity, and physical properties of solvents are considered when choosing extraction solvents. Common equipment used includes mixer-settlers, columns, and centrifuges. Applications include removing products/pollutants from aqueous streams and washing polar compounds from organics. Flocculation involves using chemicals to induce clumping/aggregation of suspended particles in liquids to aid separation.

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Liquid-Liquid Extraction And Flocculation By- Pradip Yadav Ajay kumar Afzal farooque
Contents  Introduction to Extraction  Principle and objective  Types of Liq-liq extraction and Equipments used  Applications  Introduction to Flocculation  Objective  Design of flocculator  Applications .
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 .
Hierarchy of Separation Technologies Physical Separations Decantation, Coalescing, Filtration, Demisting Evaporation Single Effect, Multiple Effect Distillation Simple, Azeotropic, Extractive, Reactive Extraction Simple, Fractional, Reactive Adsorption Pressure Swing, Temperature Swing Crystallization Melt, Solvent Membranes MF, UF, NF, RO Easy Difficult DifficultyDifficulty OfOf SeparationSeparation
Liquid-liquid extraction : It is a useful method to separate components (compounds) of a mixture
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.
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.
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
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.
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)
(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
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
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!
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
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"
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)
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. .
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 .
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. .
Triangular phase diagrams Each apex of triangle represents 100% pure component . B A S P %A%S %B
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. .
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 .
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 .
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. .
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
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
Extraction equipment Batch: mixer-settler column: separatory funnel rotating-disk contacter a. agitator; b. stator disk single-stage: Continuous:
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
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
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
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
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
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
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
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
Removal of Phenol from Wastewater ppb Phenol ExtractionExtraction RaffinateRaffinate StrippingStripping SolventSolvent RecoveryRecovery Wastewater Feed 0.1 – 8 % Phenol Raffinate Recycled Solvent Extract PhenolBiological TreatmentBiological Treatment OrOr Carbon AdsorptionCarbon Adsorption < 1 ppm Phenol
Recovery of Acetic Acid from Water Using a Low Boiling Solvent Aqueous Feed 20 - 40 % Acetic Acid Typical Solvents: Ethyl Acetate Butyl Acetate ExtractionExtraction RaffinateRaffinate StrippingStripping SolventSolvent RecoveryRecovery Raffinate Recycled Solvent Extract Acetic AcidAqueous Raffinate
Recovery of Carboxylic Acids from Wastewater Using a High Boiling Point Solvent ExtractionExtraction DehydrationDehydration SolventSolvent RecoveryRecovery Water Feed 0.1 – 5 % Mixed Acids Acetic Acid 99%+ Purity Recovered SolventRecovered Solvent Clean UpClean Up AcidAcid RecoveryRecovery Formic Acid 99%+ PurityWater Raffinate < 1,000 ppb Mixed Acids
Series Extraction Extractor#1Extractor#1 Extractor#2Extractor#2 Feed A + B Extract B + C Solvent 1 C Solvent 2 D Product B + D Raffinate A Extractor 1 & 2 May Differ By: - Temperature - pH - Solvent
Recovery of Caprolactam Feed From Reaction Section LactamOilExt.LactamOilExt. AQ Waste toAQ Waste to DischargeDischarge Am.SulphateExt.Am.SulphateExt. Am. Sulph.Am. Sulph. Waste toWaste to DischargeDischarge Re-ExtractionRe-Extraction Lactam Oil toLactam Oil to RecoveryRecovery Water Lactam Oil Phase 65 – 70% Caprolactam Ammonium Sulphate Phase 2 – 3% Caprolactam Extract Raffinate Solvent
Phosphoric Acid Purification via Extraction ExtractionExtraction Raffinate toRaffinate to DisposalDisposal ScrubExtractionScrubExtraction Re-ExtractionRe-Extraction PhosphoricPhosphoric Acid toAcid to RecoveryRecovery Water Solvent PhosphatePhosphate Rock DigesterRock DigesterHCLHCL Feed Recycle Scrub Solve.
Extraction of Flavors and Aromas Oil Essential Extract ExtractionExtraction Solvent1Solvent1 DistillationDistillation Aqueous Alcohol Solvent2Solvent2 DistillationDistillation Essential Oil Hydrocarbon Typical Products: Orange Oil Lemon Oil Peppermint Oil Cinnamon Oil
Separation of Structural Isomers Typical Applications: m. p. - Cresol Xylenols 2 , 6 - Lutidine 3 , 4 - Picoline Solvent1Solvent1 DistillationDistillation Solvent2Solvent2 DistillationDistillation ExtractionExtraction Mixed Isomer Feed Isomer 1 ExtractionExtraction Isomer 2 pH Adjust (Optional) Reflux Solvent 1 Recycle Solvent 2 Recycle Aqueous Raffinate Aqueous Recycle pH Adjust (Optional)
Choice of separation process Factors to be considered:  Feasibility  Product value  Cost  Product quality  selectivity .
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 - - - - --- - - - - --- - - - - --- - - - - ---
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.
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.
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.
Coagulation and flocculation aim 04/08/15. 49
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
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
Colloidal interaction 04/08/15water treatment 52
Charge reduction 04/08/15water treatment 53
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
Floc formation with polymers 04/08/15water treatment 55
04/08/15. 56 Cross flow Flocculator (sectional view) Plan (top view) Transversepaddle L H W Mechanical Flocculator
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
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. .
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 .
Paul Ashall 2007

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Liquidliquidextraction 1-171202052711
byPRINCE PATEL
 

Liquid liquid extraction and flocculation

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  • 2.
    Contents  Introduction toExtraction  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 .
  • 4.
    Hierarchy of Separation Technologies PhysicalSeparations Decantation, Coalescing, Filtration, Demisting Evaporation Single Effect, Multiple Effect Distillation Simple, Azeotropic, Extractive, Reactive Extraction Simple, Fractional, Reactive Adsorption Pressure Swing, Temperature Swing Crystallization Melt, Solvent Membranes MF, UF, NF, RO Easy Difficult DifficultyDifficulty OfOf SeparationSeparation
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    Liquid-liquid extraction : Itis a useful method to separate components (compounds) of a mixture
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    Let's see anexample. 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.
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    How about shakingthe 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.
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    By shaking thelayers (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
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    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.
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    Here is theuniversal 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)
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    (1) If thereare 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
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    What happens ifyou 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
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    An additional 67particles 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!
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    If you extracttwice 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
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    Did you getit? .....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"
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    Basic principles In liquid-liquidextraction, 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)
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    Example - PenicillinG 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. .
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    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 .
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    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. .
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    Triangular phase diagrams Eachapex of triangle represents 100% pure component . B A S P %A%S %B
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    Extractants The efficiency ofa 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. .
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    Choice of solvent Factorsto 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 .
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    Selectivity: β = (massfraction 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 .
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    Recoverability of solventand 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. .
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    Types of flowin LLE When both phases are flowing:  Co-current contact  Cross flow Counter-current flow . Stage 1 Stage 2 1 2 1 2
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    Major Types ofExtraction 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
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    Extraction equipment Batch: mixer-settler column: separatory funnel rotating-diskcontacter a. agitator; b. stator disk single-stage: Continuous:
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    Types: Simple Extraction SingleStage 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
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    Cross Flow Extraction A RR11RR22 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
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    Countercurrent Flow Extraction A RR11RR22 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
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    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
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    Dilute fractional extraction Acommon 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
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    Center-cut extraction When thereare 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
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    Typical Applications • Removeproducts 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
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    Extraction is Usedin 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
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    Removal of Phenolfrom Wastewater ppb Phenol ExtractionExtraction RaffinateRaffinate StrippingStripping SolventSolvent RecoveryRecovery Wastewater Feed 0.1 – 8 % Phenol Raffinate Recycled Solvent Extract PhenolBiological TreatmentBiological Treatment OrOr Carbon AdsorptionCarbon Adsorption < 1 ppm Phenol
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    Recovery of AceticAcid from Water Using a Low Boiling Solvent Aqueous Feed 20 - 40 % Acetic Acid Typical Solvents: Ethyl Acetate Butyl Acetate ExtractionExtraction RaffinateRaffinate StrippingStripping SolventSolvent RecoveryRecovery Raffinate Recycled Solvent Extract Acetic AcidAqueous Raffinate
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    Recovery of CarboxylicAcids from Wastewater Using a High Boiling Point Solvent ExtractionExtraction DehydrationDehydration SolventSolvent RecoveryRecovery Water Feed 0.1 – 5 % Mixed Acids Acetic Acid 99%+ Purity Recovered SolventRecovered Solvent Clean UpClean Up AcidAcid RecoveryRecovery Formic Acid 99%+ PurityWater Raffinate < 1,000 ppb Mixed Acids
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    Series Extraction Extractor#1Extractor#1 Extractor#2Extractor#2 Feed A +B Extract B + C Solvent 1 C Solvent 2 D Product B + D Raffinate A Extractor 1 & 2 May Differ By: - Temperature - pH - Solvent
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    Recovery of Caprolactam FeedFrom Reaction Section LactamOilExt.LactamOilExt. AQ Waste toAQ Waste to DischargeDischarge Am.SulphateExt.Am.SulphateExt. Am. Sulph.Am. Sulph. Waste toWaste to DischargeDischarge Re-ExtractionRe-Extraction Lactam Oil toLactam Oil to RecoveryRecovery Water Lactam Oil Phase 65 – 70% Caprolactam Ammonium Sulphate Phase 2 – 3% Caprolactam Extract Raffinate Solvent
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    Phosphoric Acid Purificationvia Extraction ExtractionExtraction Raffinate toRaffinate to DisposalDisposal ScrubExtractionScrubExtraction Re-ExtractionRe-Extraction PhosphoricPhosphoric Acid toAcid to RecoveryRecovery Water Solvent PhosphatePhosphate Rock DigesterRock DigesterHCLHCL Feed Recycle Scrub Solve.
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    Extraction of Flavorsand Aromas Oil Essential Extract ExtractionExtraction Solvent1Solvent1 DistillationDistillation Aqueous Alcohol Solvent2Solvent2 DistillationDistillation Essential Oil Hydrocarbon Typical Products: Orange Oil Lemon Oil Peppermint Oil Cinnamon Oil
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    Separation of Structural Isomers TypicalApplications: m. p. - Cresol Xylenols 2 , 6 - Lutidine 3 , 4 - Picoline Solvent1Solvent1 DistillationDistillation Solvent2Solvent2 DistillationDistillation ExtractionExtraction Mixed Isomer Feed Isomer 1 ExtractionExtraction Isomer 2 pH Adjust (Optional) Reflux Solvent 1 Recycle Solvent 2 Recycle Aqueous Raffinate Aqueous Recycle pH Adjust (Optional)
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    Choice of separationprocess Factors to be considered:  Feasibility  Product value  Cost  Product quality  selectivity .
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    What is Coagulation? 04/08/15watertreatment 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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    What is Flocculation? 04/08/15watertreatment 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.
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    04/08/15water treatment 47 FLOCCULATIONConti… 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.
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    Flocculants should havethe 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.
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    04/08/15.t 50 Why flocculation? Varioussizes 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
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    04/08/15water treatment 51 ColloidStability ------ ------ 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
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    Colloid Destabilization  Colloidscan 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
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    Floc formation withpolymers 04/08/15water treatment 55
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    04/08/15. 56 Cross flowFlocculator (sectional view) Plan (top view) Transversepaddle L H W Mechanical Flocculator
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    04/08/15. 57 Hydraulic Flocculation • Horizontallybaffled 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
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    Applications:  Surface chemistry: In colloidchemistry, 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. .
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    Appli…  Water treatment: Flocculationand 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 .
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Editor's Notes

  • #34 Next year: add a slide on batch L-L extraction