Liquid liquid extraction and flocculation

Liquid-Liquid Extraction And

FlocculationBy- 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 SeparationsDecantation, Coalescing, Filtration, Demisting

EvaporationSingle Effect, Multiple Effect

DistillationSimple, Azeotropic, Extractive, Reactive

ExtractionSimple, Fractional, Reactive

AdsorptionPressure Swing, Temperature Swing

CrystallizationMelt, Solvent

MembranesMF, UF, NF, RO

Easy

Difficult

DifficultyDifficultyOf Of 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 particlesof compound , these aredistributed between equalvolumes 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 waterK = 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

Column Column ContactorsContactors

Mixer SettlersMixer SettlersCentrifugalCentrifugal

Used primarily in the metals industry due to: - Large flows - Intense mixing - Long Residence time - Corrosive fluids - History

Used primarily in thepharmaceutical 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 contactera. 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)

( )( ) ( )( ) 4.07.929950MF

SE

7.92

990.250

0.8

RaffinateinSoluteConc.

ExtractinSoluteConc.M

0.21.0

0.2

FeedinSolute

RaffinateinSoluteU

===

===

===Fraction Unextracted

Distribution Coefficient

Extraction Factor

Cross Flow Extraction

ARR11 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

R1R2

R3

R4

E1E2

E3

E4

M1

M2M3M4

B

A C

F

Countercurrent Flow Extraction

ARR11 RR22 RR33 RR44

A + B

F

B + CC

E1

E2

E3

E4B + C B + C

B + C

F + S = ME1 + R4 = MF + S = E1 + R4

F – E1 = R4 – S = ∆

Equations

C

R1

R2

R3

R4

E1

B

A

F

∆

M E2

E3E4

S

Countercurrent Extraction

B + C

A

C

A + BFeed (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

FzA

zB

solvent 1yA,N+1 = 0yB,N+1 = 0

solvent 2xA,0 = 0xB,0 = 0

extractyA,1

yB,1

raffinatexA,N

xB,N

E R

E

R

abso

rbin

g se

ctio

nst

rippi

ng s

ectio

n

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

FzA, 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 2B, C prefer solvent 2 over solvent

1B prefers solvent 3 over solvent 2C 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

Extra

ction

Extra

ction

Raffin

ate R

affinate

Strip

pin

gS

tripp

ing

So

lvent

So

lvent

Reco

very

Reco

very

Wastewater Feed

0.1 – 8 % Phenol

Raffinate

RecycledSolvent

Extract

PhenolBiological TreatmentBiological Treatment

OrOr

Carbon AdsorptionCarbon Adsorption

< 1 ppm Phenol

Recovery of Acetic Acid from WaterUsing a Low Boiling Solvent

Aqueous Feed

20 - 40 % Acetic Acid

Typical Solvents: Ethyl Acetate Butyl Acetate

Extra

ction

Extra

ction

Raffin

ate R

affinate

Strip

pin

gS

tripp

ing

So

lvent

So

lvent

Reco

very

Reco

very

Raffinate

RecycledSolvent

Extract

Acetic AcidAqueous Raffinate

Recovery of Carboxylic Acids from WastewaterUsing a High Boiling Point Solvent

Extra

ction

Extra

ction

De

hyd

ration

De

hyd

ration

So

lvent

So

lvent

Reco

very

Reco

very

Water Feed

0.1 – 5 % Mixed Acids

Acetic Acid99%+ Purity

Recovered SolventRecovered Solvent

Clean UpClean Up

Acid

A

cid

Reco

very

Reco

very

Formic Acid99%+ PurityWater

Raffinate< 1,000 ppb Mixed Acids

Series Extraction

Extra

ctor #1

Extra

ctor #1

Extra

ctor #2

Extra

ctor #2

Feed

A + B

Extract

B + C

Solvent 1

C Solvent 2

D

ProductB + D

RaffinateA

Extractor 1 & 2 May Differ By: - Temperature - pH - Solvent

Recovery of Caprolactam

Feed From

ReactionSection

Lacta

m O

il Ext.

Lacta

m O

il Ext.

AQ Waste to AQ Waste to DischargeDischarge

Am

. Sulph

ate Ext.

Am

. Sulph

ate Ext.

Am. Sulph. Am. Sulph. Waste to Waste to DischargeDischarge

Re

-Extra

ction

Re

-Extra

ction

Lactam Oil to Lactam Oil to RecoveryRecovery

WaterLactam Oil Phase65 – 70% Caprolactam

Ammonium Sulphate Phase2 – 3% Caprolactam

Extract

RaffinateSolvent

Phosphoric Acid Purification via Extraction

Extra

ction

Extra

ction

Raffinate to Raffinate to DisposalDisposal

Scru

b E

xtractionS

crub

Extraction

Re

-Extra

ction

Re

-Extra

ction

Phosphoric Phosphoric Acid to Acid to RecoveryRecovery

Water

Solvent

Phosphate Phosphate Rock DigesterRock DigesterHCLHCL

Feed

Recycle

Scrub Solve.

Extraction of Flavors andAromas

Oil Essential Extract

Extra

ction

Extra

ction

So

lvent 1

S

olven

t 1

Distilla

tionD

istillation

Aqueous Alcohol

So

lvent 2

S

olven

t 2

Distilla

tionD

istillation

Essential Oil

Hydrocarbon

Typical Products: Orange Oil Lemon Oil Peppermint Oil Cinnamon Oil

Separation of StructuralIsomers

Typical Applications: m. p. - Cresol Xylenols 2 , 6 - Lutidine 3 , 4 - Picoline

So

lvent 1

S

olven

t 1

Distilla

tionD

istillation

So

lvent 2

S

olven

t 2

Distilla

tionD

istillation

Extra

ction

Extra

ction

Mixed

IsomerFeed

Isomer 1

Extra

ction

Extra

ction

Isomer 2

pH Adjust(Optional)

Reflux

Solvent 1 Recycle Solvent 2 Recycle

AqueousRaffinate

AqueousRecycle

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?


Flocculation is the agglomeration of destabilized particles into a large size particles known as flocs which can be effectively removed by sedimentation or flotation.


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.

http://en.wikipedia.org/wiki/Chemistry

http://en.wikipedia.org/wiki/Colloid

http://en.wikipedia.org/wiki/Suspension_(chemistry)

http://en.wikipedia.org/wiki/Clarifying_agent

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

G r

a v

I t

y s

e t

t l I

n g


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


Charge reduction


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


Floc formation with polymers


04/08/15. 56

Cross flow Flocculator (sectional view)

Plan (top view)

Tra

nsv

erse

pad

dle

L

H

W

Mechanical Flocculator

04/08/15.

57

Hydraulic Flocculation

• Horizontally baffled tank

Plan view (horizontal flow)

• Vertically baffled tank

LIsometric 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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Liquid liquid extraction and flocculation