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Liquid-Liquid Extraction

Some Legacies of Java Island Antique Extraction Products

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Kananga Flower

Extraction Products in Modern Life

Olive Oil

Extraction: Definition

• Liquid/liquid extraction (solvent extraction): a liquid feed

of two or more components is contacted with a second

liquid phase, called the solvent, which is immiscible or only

partly miscible with one or more feed components and

completely or partially miscible with one or more of the

other feed components. Thus, the solvent partially

dissolves certain species of the liquid feed, effecting at least

a partial separation of the feed components

• Solven boleh jadi murni ataupun campuran.

• Biasanya jika umpan (feed) adalah senyawa organik, maka

solvennya adalah air dan sebaliknya bila umpannya larutan

air, maka solvennya adalah senyawa organik kecuali ada

pertimbangan tertentu misalnya adanya incompatibility dll.

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Ref. Seader dkk. (2011)

• Acetic acid is produced

by methanol

carbonylation or

oxidation of

acetaldehyde, or as a

byproduct of cellulose–

acetate manufacture.

• In all cases, a mixture of

acetic acid (n. b.p.118.1

C) and water (n. b.p.

100 C) is separated to

give glacial acetic acid

(99.8 wt% min.).

• When the mixture

contains less than 50%

acetic acid, separation

by distillation is

expensive.

Some Industrial

Extractions

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1.Dissolved or complexed inorganic substances in organic or

aqueous solutions.

2.Removal of a contaminant present in small concentrations,

such as a color former in tallow or hormones in animal oil.

3.A high-boiling component present in relatively small

quantities in an aqueous waste stream, as in the recovery of

acetic acid from cellulose acetate.

4.Recovery of heat-sensitive materials, where extraction may

be less expensive than vacuum distillation.

5.Separation of mixtures according to chemical type rather

than relative volatility.

6.Separation of close-melting or close-boiling liquids, where

solubility differences can be exploited.

7.Separation of mixtures that form azeotropes

Extraction is preferred over distillation for:

Extraction Equipment: Mixer-Settlers

Principles: the two liquid phases are first mixed in a vessel by

one of several types of impellers or impingement and then

separated by gravity-induced settling.

Compartmented mixing vessel

with turbine agitators.

Horizontal gravity-settling

vessel

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Extraction Equipment: Spray Columns

(a) light liquid dispersed,

heavy liquid continuous;

(b) heavy liquid dispersed,

light liquid continuous.

Ref. Seader dkk. (2011)

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Plate Towers

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Skema Langkah Pencampuran Dan Pemisahan Pada

Ekstraksi Solven

Columns with Mechanically Assisted Agitation

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Columns with Mechanically Assisted Agitation

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Solvent Selection

The key to an effective extraction process is a

suitable solvent

Ideal solvents posses characteristics:

1.High selectivity for the solute relative to the carrier to

minimize the need to recover carrier from the solvent

2.High capacity for dissolving the solute to minimize solvent-

to-feed ratio

3. Minimal solubility in the carrier

4. A volatility sufficiently different from the solute that

recovery of the solvent can be achieved by distillation, but

not so high that a high extractor pressure is needed, or so

low that a high temperature is needed if the solvent is

recovered by distillation

5.Stability to maximize the solvent life and minimize the

solvent makeup requirement

6.Inertness to permit use of common materials of

construction

7.Low viscosity to promote phase separation, minimize

pressure drop, and provide a high-solute mass-transfer rate

8.Nontoxic and nonflammable characteristics to facilitate its

safe use

9.Availability at a relatively low cost

10.Moderate interfacial tension to balance the ease of

dispersion and the promotion of phase separation

11.Large difference in density relative to the carrier to achieve

a high capacity in the extractor

Ideal solvent (cont’d)

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12.Compatibility with the solute and carrier to avoid

contamination

13.Lack of tendency to form a stable rag or scum layer at the

phase interface

14.Desirable wetting characteristics with respect to extractor

internals

Ideal solvent (cont’d)

Solute Distribution

Let: A – Solute C – Carrier S - Solvent

Distribution of solute (A) between solvent & carrier:

I : raffinate phase (rich in C)

II: extract phase (rich in S)

Similarly for carrier and solventγI

i is activity coefficient

of component I in

raffinate

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Selectivity of Solvent to Solute Relative to Carrier

• For high selectivity, βAC should be high, so at

equilibrium there is a high concentration 0f A

and a low concentration of C in the solvent.

• Desirable interaction between solvent (S) and

solute (A) is that lowering the activity

coefficient (negative)

• For high solvent capacity, (KA)D should be high

Solute-Solvent Interaction

Chose solvent that lower activity

coefficient (negative interaction)

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Contoh: akan dipungut aseton dari air. Rekomendasikanlah

solvent yang tepat

Jawab: dari tabel terlihat bahwa aseton termasuk

golongan keton. Maka masuk group 3. Dari kolom yang

ada yang memiliki interaksi negativ dengan group 3

adalah group 1 dan group 6.

Pilihan selanjutnya mempertimbangkan harga, faktor

keselamatan dan lingkungan dll

Diskusi GroupAkan dipungut ethylene glycole dari larutan dalam

air dengan proses ekstraksi. Rekomendasikanlah

solvent yang sesuai

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TERNARY LIQUID–LIQUID SYSTEMS

Phase splitting of ternary mixtures: (a) components A

and C mutually insoluble; (b) components A and C

partially soluble.

Case I: Mutually non-soluble solvent and Carrier

Let:

A = rate of carrier A S = flow rate of solvent C

XB= ratio of mass or moles of solute B to mass or

moles of the other component in the feed F,

raffinate (R) or extract (E)

The solute material balance:

Where K’DB = the distribution or partition coefficient

in terms of mass or mole ratios (instead of mass

or mole fractions).

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Bila didefinisikan ekstraction factor untuk solute

B adalah (EB)

Large extraction factors result from large

distribution coefficients or large ratios of solvent to

carrier.

The fraction of B not extracted

Thus, the larger the extraction factor, the smaller

the fraction of B not extracted or the larger the

fraction of B extracted.

Alternatively, the fraction of B extracted is 1 minus

previous equation or EB/(1+EB)

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• Mass (mole) ratios ,X, are related to mass (mole)

fractions, x, by

When values of xi are small, K’D approaches KD.

Ref. Perry’s Handbook

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Ref.: Perry’s Handbook

Liquid-liquid Extraction of Partially Miscible

Liquids

Ternary Diagram

Reference:

J. D. Seader, E. J. Henley, and D. K. Roper, 2011, “Separation

Process Principles: Chemical and Biochemical Operations”,

3rd Edition, John Wiley & Sons.

Baca: Chapter 8 plus Chapter 4

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For Type I, the solute and solvent are miscible in

all proportions, while in Type II they are not.

Both solvent-solute and

carrier-solute solutions are

miscible in all proportion

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Figure 8.11 Effect of solubility on range

of feed composition that can be

extracted.

Only feed solutions in the composition range

from C to F can be separated because,

regardless of how much solvent is added, two

liquid phases are not formed in the feed

composition range of FA (i.e. , FS does not pass

through the two-phase region)

Type II

Transition Type

II into Type I

Type I

Figure 8.12 Effect of temperature on

solubility for the system n-hexane

H)/methylcyclopentane (M)/aniline (A).

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Representasi Lain Ternary System:

Diagram Segitiga Siku

Berbagai Konfigurasi System Ekstraksi

Cair-Cair

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Ekstraksi Stage Tunggal

Neraca massa disusun untuk mendapatkan

persamaan untuk stage tersebut:

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Contoh Kasus: Ekstraksi 1 Stage

Suatu bengkel radiator mobil memiliki limbah air

pendingin yang mengandung ethylene glycole

(EG) dengan konsentrasi 20 % masa. EG akan

dipungut dengan menggunakan pelarut furfural

sehingga konsentrasi tersisa dalam limbah tinggal

10 %. Tentukanlah rasio antara Furfural (murni)

dan air limbah untuk mencapai target di atas

Angka-angka di atas sekedar untuk keperluan ilustrasi (agar titik-

titik mudah dibaca pada diagram) bukan angka yang sebenarnya

F

SR1

E1

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Representasi ekstraktor stage tunggal dalam diagram

segitiga

Jika ekstraksi stage tunggal dinyatakan dalam diagram

x-y atau X-Y bebas solven

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Ekstraksi Multi-stage Cross-flow

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Sistem Ekstraksi Multi Stage: Penentuan Jumlah StageHunter–Nash method

Specification: F, (xi)F,(yi)S, dan T plus

salah satu set berikut,

Bila dipilih set 4 s/d 6, perhitungan

melibatkan trial and error

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Construction 1 (Product Composition Points)

A

S

C

Contoh kasus:

Point M can be put on the ternary diagram based two of the

three values of xiM

Mixing Point M

Andaikan M merupakan pencampuran (mixing) antara F dan S

Bisa dibuktikan secara geometri bahwa titik-titik F, M, dan

S terletak pada satu garis yang sama

(Baca Chapter 4 dari Seader dkk. (2011)

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Ratio S/F is given by the inverse-lever-arm rule as:

• The higher S/F the closer point M to point S.

• Beyond Mmax, there will be no phase separation

Inverse-lever-arm Rule

F

MS

Penentuan Kondisi Terminal yang lain:

• (XA)Rn is on equilibrium curve.

• Titik-titik RN, E1 dan M (sebagai mixing point

dari E1 dan RN) harus terletak pada satu garis

yang sama.

• Dengan menggambar garis dari RN memotong

titik M, maka dapat diperoleh E1 pada curva

setimbang di daerah ekstrak

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The inverse lever-arm rule:

Hasil Lengkap Kondisi Terminal

Construction 2 (Operating Point and Operating Lines)

Referring to Figure 8.13, material balances around groups of

stages from the feed end are:

• P defines a difference point, not a mixing point, M.

• From the same geometric considerations that apply to a

mixing point, a difference point also lies on a line through

the points involved

• P usually lies outside the triangular diagram along an

extrapolation of the line through two points such as F

and E1, RN and S, and so on.

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Construction 3 (Tie Lines and Equilibrium Lines)

• The third type of construction involves the tie lines that

define the equilibrium curve, which is divided into the

two sides (raffinate and extract) by the plait point

• Typically, a diagram will not contain all tie lines needed;

however, they may be added by centering them

between existing tie lines, or by using either of two

interpolation procedures illustrated in Figure 8.16.

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The conjugate line from the plait

point to J is determined from

four tie lines and the plait point.

From tie line DE, lines DG and EF

are drawn parallel to triangle

sides CB and AC, respectively.

The intersection at point H gives

a second point on the conjugate

curve. Subsequent intersections

establish additional points from

which the conjugate curve is

drawn.

Then, using the curve, additional tie

lines are drawn by reversing the

procedure.

Figure 8.16b is used, where

lines are drawn parallel to

triangle sides AB and AC.

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Stepping Off Stages

• Equilibrium stages are stepped off by alternate

use of tie lines and operating lines

• as shown in Figure 8.17, where Constructions 1

and 2 have been employed to locate points F, E, S,

R1, and P.

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Penentuan Minimum Solven/Feed Ratio