SALT EFFECT ON LIQUID LIQUID EQUILIBRIUM FOR TERNARY SYSTEM

SALT EFFECT ON LIQUID LIQUID EQUILIBRIUM FOR TERNARY SYSTEM
A
Project Report on
SALT EFFECT ON LIQUID LIQUID EQUILIBRIUM
FOR TERNARY SYSTEM
WATER +1-PROPANOL +ETHYL ACETATE
In partial fulfillment of the requirements of
Bachelor of Technology (Chemical Engineering)
Submitted By
Mahendra Kumar Khuntia (Roll No.10400042D)
Jyoti Ranjan Swain (Roll No.10300043)
Session: 2006-07
Department of Chemical Engineering
National Institute of Technology
Rourkela-769008
Orissa
A
Project Report on
SALT EFFECT ON LIQUID LIQUID EQUILIBRIUM
FOR TERNARY SYSTEM
WATER +1-PROPANOL +ETHYL ACETATE
In partial fulfillment of the requirements of
Bachelor of Technology (Chemical Engineering)
Submitted By
Mahendra Kumar Khuntia (Roll No.10400042D)
Jyoti Ranjan Swain (Roll No.10300043)
Session: 2006-07
Under the Guidance of
Dr. Pradip Rath
Department of Chemical Engineering
National Institute of Technology
Rourkela-769008
Orissa
National Institute of Technology
Rourkela
CERTIFICATE
This is to certify that that the work in this thesis report entitled “salt effect on liquid liquid
equilibrium for ternary system water +1-propanol +ethyl acetate” submitted by Mahendra
Kumar Khuntia and Jyoti Ranjan Swain in partial fulfillment of the requirements for the
degree of Bachelor of Technology in Chemical Engineering Session 2003-2007 in the
department of Chemical Engineering, National Institute of Technology Rourkela, Orissa
an authentic work carried out by them under my supervision and guidance.
To the best of my knowledge the matter embodied in the thesis has not been submitted to
any other University /Institute for the award of any degree.
Date:
Prof. (Dr) Pradip Rath
Department of Chemical Engineering
National Institute of Technology
Rourkela - 769008
ACKNOWLEDGEMENT
It is with a feeling of great pleasure that we express our sincere gratitude to Prof.
Pradip Rath for suggesting us the topic and his ready and able guidance, constructive
criticism through out the course of the project. We thank Prof. R.K Singh for acting as
project co-ordinator.
We are thankful to the Department of Chemical Engineering for providing us
necessary instrument. We are also grateful to Prof. Madhushree Kundu for providing us
the necessary guidance for the completion of our project. We also thank the other staff
members of my department for their invaluable help and guidance.
Mahendra Kumar Khuntia
(Roll No. 10400042D)
Jyoti Ranjan Swain
(Roll No. 10300043)
B. Tech Final Year
Chemical Engineering
CONTENTS
Page No
Abstract
List of figures
List of Tables
i
ii
iv
Chapter1
1
1.1
1.2
1.3
Chapter2
2.1
INTRODUCTION
1
Introduction
2
Importance and Application
Liquid-liquid Extraction
Salt effect on liquid-liquid Extraction
3
THEORIES AND THERMODYNAMIC
MODELS
8
Theories of salt effects
2.1.1 Hydration Theory
9
2.1.2
Electrostatic Theory
10
2.1.3
Vanderwaals Theory
11
2.1.4
Internal Pressure Theory
11
4
6
9
2.2
Salting-in and salting-out effect
12
2.3
Thermodynamic Model
14
2.3.1
UNIQUAC MODEL
14
2.3.2
UNIFAC MODEL
15
2.3.3
NRTL MODEL
17
2.3.4 WILSON MODEL
18
2.3.5
18
DEBYE HUCKLE MODEL
PREVIOUS INVESTIGATIONS
20
Previous Investigations
20
3.1.1 Previous Investigations on LLE
20
3.1.2 Investigations of salt effect on LLE
25
EXPERIMENTAL PROCEDURE
29
4.1
Introduction
30
4.2
Experimental Setup
30
4.3
Procedure for the system
31
Chapter3
3.1
Chapter4
4.4
Procedure for system with salt
32
4.5
Method of analysis
32
4.5.1
Titration Method
33
4.5.2
Gas Chromatograph Method
33
4.5.3
Refractive Index Method
33
4.5.4
Specific Gravity Method
33
4.6
Chapter5 5
5.1
Chromatography
34
PRESENTATION OF RESULTS
39
Empirical correlation of salt effect on liquid-liquid
40
equilibrium.
5.2
Solubility data
56
5.3
Equilibrium data
60
5.4
Results and Discussion
85
CONCLUSION
86
6.1
Conclusion
87
6.2
Future scope of work
87
Reference
88
Chapter6
ABSTRACT:Liquid/liquid extraction is a very common method used in the organic laboratory.
Organic reactions often yield a number of by-products, some inorganic, some organic...
Liquid/liquid extraction is often used as the initial step in the work-up of a reaction, before final
purification of the product by recrystallization, distillation or sublimation.
Salting-out effect can be used to improve the extraction of some solutes by modifying
the solute distribution between two liquid phases. Experiments are conducted on the system
Water + 1-propanol + Ethyl acetate with varying salt concentrations and varying temperatures.
The basic objective of this project is to determine the best temperature range and the salt from
NaCl and (NH4)2SO4 which enhances the separation or extraction of the solute by the specified
solvent. The experiments were conducted and the resulting extract and raffinate phase was
analyzed with the help of the gas chromatography. The plots of voltage vs time was obtained
from the gas chromatography, showing the percent volume of the different components present
in both the phases. For each phase a separate plot is obtained.
Here we have considered two salts: NaCl and (NH4)2SO4. We have tried to show the effect of
these two salts on the system at temperatures 27ºC, 32ºC and 37ºC.The solubility data are
tabulated in Table 5.1 and the equilibrium data are tabulated in Table 5.2. Considering these data
the solubility curves and the distribution curves were plotted. All salt containing data are
reported on salt free basis. The experimental tie-line data under no salt condition were
determined and presented in respective tables. It can be seen from the diagrams that the addition
of the salts shifts the distribution in favour of ethyl acetate layer especially at higher salt
concentrations. The presence of the salt decreases the solubility of the system increasing the
heterogeneous zone. Heterogeneous area is an important characteristic. In the present system, the
areas of the solubility curves are more in case of salt addition than that of without salt. At
increasing salt concentrations more 1-propanol is transferred to the ethyl acetate phase. This
process is usually referred to as salting out and is caused by the fact that the presence of high
amounts of hydrated ions reduces the availability of the water molecules in the aqueous phase to
the salvation of other solvents. Presence of salts mainly increase the concentrations of 1-propanol
in organic phase and hence enlargement of the two-phase region occurred.
LIST OF FIGURES
Fig No.
Contents
Page No.
1.
Experimental setup for liquid-liquid extraction.
31
2.
Experimental setup for extracting salt from sample
32
3.
Diagram illustrating the Gas-Liquid Chromatography
34
4.
Steel column installed in Oven
35
5.
Injector
36
6.
Crosssection of a fused silica open tubular column
37
7.
Flame Ionization Detector
38
8.
G. C. Analysis report for 10% NaCl (32ºC) Raffinate Phase 1
42
9.
G. C. Analysis report for 10% NaCl (32ºC) Extract Phase 1
43
10.
G. C. Analysis report for 10% NaCl (32ºC) Raffinate Phase 2
44
11.
G. C. Analysis report for 10% NaCl (32ºC) Extract Phase 2
45
12.
G. C. Analysis report for 10%NaCl (32ºC) Raffinate Phase 3
46
13.
G. C. Analysis report for 10% NaCl(32ºC) Extract Phase 3
47
14.
G. C. Analysis report for 10% Nacl(32ºC) 4
48
15.
G. C. Analysis report for 10%(NH4)2SO4 (32ºC) Raffinate Phase 1
49
16.
G.C. Analysis report for 10 %( NH4)2SO4 (32ºC) Extract Phase 1
50
17.
G. C. Analysis report for 10%(NH4)2SO4 (32ºC) Raffinate Phase 2
51
18.
G. C. Analysis report for 10%(NH4)2SO4 (32ºC) Extract Phase 2
52
19.
G. C. Analysis report for 10%(NH4)2SO4 (32ºC) Raffinate Phase 3
53
20.
G. C. Analysis report for 10 %(NH4)2SO4 (32ºC) Extract Phase 3
54
21.
G. C. Analysis report for 10%(NH4)2SO4 (32ºC) 4
55
22.
Solubility curve for no salt (27ºC)
65
23.
Solubility curve for 5% NaCl (27ºC)
65
24.
Solubility curve for 10%NaCl (27ºC)
66
25.
Solubility curve for 15% NaCl (27ºC)
66
26.
Solubility curve for no salt (32ºC)
67
27.
Solubility curve for 5% salt (32ºC)
67
28.
Solubility Curve for 10% NaCl (32ºC)
68
29.
Solubility Curve for 15% NaCl (32ºC)
68
30.
Solubility Curve for no salt (37ºC)
69
31.
Solubility Curve for 5% NaCl (37ºC)
69
32.
Solubility Curve for 10% NaCl (37ºC)
70
33.
Solubility Curve for 15% NaCl (37ºC)
70
34.
Solubility Curve for 5% (NH4)2SO4 (27ºC)
71
35.
Solubility Curve for 10%(NH4)2SO4 (27ºC)
71
36.
Solubility Curve for 15% (NH4)2SO4 (27ºC)
72
37.
Solubility Curve for 5% (NH4)2SO4 (32ºC)
72
38.
Solubility Curve for 10%(NH4)2SO4(32ºC)
73
39.
Solubility Curve for 15% (NH4)2SO4 (32ºC)
73
40.
Solubility Curve for 5% (NH4)2SO4 (37ºC)
74
41.
Solubility Curve for 10% (NH4)2SO4 (37ºC)
74
42.
Solubility Curve for 15% (NH4)2SO4 (37ºC)
75
43.
Solubility Curve at 27ºC
76
44.
Solubility Curve at 32ºC
77
45.
Solubility Curve at 37ºC
78
46.
Solubility Curve at 27ºC
79
47.
Solubility Curve at 32ºC
80
48.
Solubility Curve at 37ºC
81
49.
Distribution Curve at 27ºC
82
50.
Distribution Curve at 32ºC
82
51.
Distribution Curve at 37ºC
83
52.
Distribution Curve at 27ºC
83
53.
Distribution Curve at 32ºC
84
54.
Distribution Curve at 37ºC
84
LIST OF TABLES
Table No.
Contents
Page No.
1.
List of some previous investigation on LLE
21
2.
List of investigations of salt effect on LLE
25
5.2.1.
Solubility data for No Salt (27ºC).
56
5.2.2.
Solubility data for 5% NaCl (27ºC)
56
5.2.3.
Solubility data for 10%NaCl (27ºC)
56
5.2.4.
Solubility data for 15%NaCl (27ºC)
56
5.2.5.
Solubility data for No Salt (32ºC)
57
5.2.6.
Solubility data for 5%NaCl (32ºC)
57
5.2.7.
Solubility data for 10%NaCl (32ºC)
57
5.2.8.
Solubility data for No Salt(37ºC)
57
5.2.9.
Solubility data for 15% NaCl(32ºC)
57
5.2.10.
Solubility data for 10%NaCl(37ºC)
58
5.2.11.
Solubility data for 15%NaCl(37ºC)
58
5.2.12.
Solubility data for 5% NaCl(37ºC)
58
5.2.13
Solubility data for 5%(NH4)2SO4 (27ºC)
58
5.2.14.
Solubility data for 10% (NH4)2SO4 (27ºC)
58
5.2.15.
Solubility data for 15% (NH4)2SO4 (27ºC)
59
5.2.16
Solubility data for 5% (NH4)2SO4 (32ºC)
59
5.2.17.
Solubility data for 10%(NH4)2SO4 (32ºC)
59
5.2.18.
Solubility data for 15%(NH4)2SO4 (32ºC)
59
5.2.19.
Solubility data for 5% (NH4)2SO4 (37ºC)
59
5.2.20.
Solubility data for 10%(NH4)2SO4 (37ºC)
60
5.2.21.
Solubility data for 15%(NH4)2SO4 (37ºC)
60
5.3.1.
Equilibrium data for No Salt (27ºC)
60
5.3.2.
Equilibrium data for 5% NaCl (27ºC)
60
5.3.3.
Equilibrium data for 10%NaCl (27ºC)
61
5.3.4.
Equilibrium data for 15%NaCl (27ºC)
61
5.3.5.
Equilibrium data for No Salt (32ºC)
61
5.3.6.
Equilibrium data for 5%NaCl (32ºC)
61
5.3.7.
Equilibrium data for 10%NaCl (32ºC)
61
5.3.8.
Equilibrium data for No Salt(37ºC)
62
5.3.9.
Equilibrium data for 15% NaCl(32ºC)
62
5.3.10.
Equilibrium data for 10%NaCl(37ºC)
62
5.3.11.
Equilibrium data for 15%NaCl(37ºC)
62
5.3.12.
Equilibrium data for 5% NaCl(37ºC)
62
5.3.13
Equilibrium data for 5%(NH4)2SO4 (27ºC)
63
5.3.14.
Equilibrium data for 10% (NH4)2SO4 (27ºC)
63
5.3.15.
Equilibrium data for 15% (NH4)2SO4 (27ºC)
63
5.3.16
Equilibrium data for 5% (NH4)2SO4 (32ºC)
63
5.3.17.
Equilibrium data for 10%(NH4)2SO4 (32ºC)
63
5.3.18.
Equilibrium data for 15%(NH4)2SO4 (32ºC)
64
5.3.19.
Equilibrium data for 5% (NH4)2SO4 (37ºC)
64
5.3.20.
Equilibrium data for 10%(NH4)2SO4 (37ºC)
64
5.2.21.
Equilibrium data for 15%(NH4)2SO4 (37ºC)
64
CHAPTER-1
INTRODUCTION
1
1. INTRODUCTION
Separation processes in which two immiscible or partially soluble liquid phases are brought into
contact for the transfer of one or more components are referred to as liquid-liquid extraction or
solvent extraction. The processes taking place are primarily physical, since the solutes being
transferred are ordinarily recovered without chemical change. On the other hand the physical
equilibrium relationships on which such operations are based depends mainly on the chemical
characteristics of the solutes and solvents. Thus, use of a solvent that chemically resembles one
component of a mixture more than the other components will lead to concentration of that
component in the solvent phase, with the exclusion from that phase of dissimilar components.
Liquid-liquid extraction process is based on the transfer of a dissolved component from its
solvent to a second solvent in order to bring about any one of several effects. The second solvent
has to be immiscible with the first solvent and preferably has a higher affinity to the transferred
component. Liquid-liquid extraction can purify a component with respect to dissolved
components that are not soluble in the solvent. The solute distributes between both diluents and
solvent until liquid-liquid equilibrium is reached. Since diluents and solvent are immiscible the
two phases can be separated and the process can be repeated at different condition.
An accurate thermodynamic model is required to calculate the liquid-liquid equilibria and the
distribution of the solute between the liquid phases. Many thermodynamic models are available
that is able to give an accurate description of distribution of product between two liquid phase.
The presence of an electrolyte in a solvent mixture can significantly change its equilibrium
composition. The concentration of a solvent component in a liquid phase increases if component
is salted in and decreases if it is salted out of the liquid phase. This salt effect has been
advantageously used in solvent extraction. Separation by solvent extraction becomes
increasingly more difficult as the tie lines become parallel to the solvent axis as in the case of a
solutropic solution. By adding a suitable salt the tie lines of a liquid-liquid equilibrium mixture
can be significantly changed, even to the extent of eliminating the solutrope.
2
1.1 IMPORTANCE AND APPLICATION
Liquid-liquid extraction is an easy method which is generally preferred over other
methods. Some of the reasons why liquid-liquid extraction is preferred are as follows: When separation by distillation is ineffective or very difficult, liquid-liquid extraction is
one of the main alternatives to consider. Close boiling mixtures or substances that cannot
withstand the temperature of distillation, even under a vacuum, may often be separated
from impurities by extraction, which utilizes chemical differences instead of vapourpressure differences.
It is like a substitute for the chemical methods. Since chemical methods consume
reagents and frequently lead to expensive disposal problems for chemical byproducts. But
liquid extraction has less chemical consumption and also less byproduct formation. Here
in this case also the solvent recovered is utilized as the reflux .Thus this process is less
costly in comparison with the other methods.
In comparison with other methods it is less costly .Other separation methods like
distillation and evaporation heat or steam is required which increases the cost .but liquidliquid extraction is the simple extraction methods using chemicals, thus it is relatively
less costly. Metal separations such as uranium-vanadium, hafnium-zirconium, and
tungsten-molybdenum are more economical by liquid-liquid extraction.
Simple extraction process is a time consuming and a low effectiveness. So salt is added
to increase the effectiveness of separation and less time is required. The addition of an electrolyte
to a solvent mixture modifies the interaction among the various solvent and solute molecules
resulting in shifting their phase equilibrium.
The addition of an electrolyte to a solvent mixture modifies the interaction among the
various solvent and solute molecules resulting in shifting their phase equilibrium even to the
extent of eliminating solutrope in liquid equilibrium. In an aqueous-organic solvent mixture,
addition of an electrolyte generally salts out the organic solvent molecules thus enriching the
organic phase with organic solvent component resulting in considerable reduction of the energy
cost incurred in the recovery and purification of the organic solvent. The simulation and design
3
of industrial extraction process involving electrolytes depends heavily on the availability of
models that can be described in influence of ion on the phase behaviors. The presence of charge
species in a mixed solvent solution appreciably influence of the charge distribution of solute
between the liquid phases.
These types of extraction using salt are used in industrial processes. Some examples are
as follows: Extraction of caprolactum from benzene using nylon-6.
Presence of ammonium sulfate in newer production processes of caprolactum.
Determination of alcohol in wine using sodium chloride salt.
Tantalum and niobium can be separated by liquid extraction of the hydrofluoric acid
solutions with methyl isobutyl ketone.
1.2 LIQUID-LIQUID EXTRACTION
Extraction is the drawing or pulling out of something from something else. Liquidliquid extraction is the separation of the constituents of a liquid solution by contact with another
insoluble liquid. It is also called as solvent extraction. If the substances constituting the original
solution distribute themselves differently between the two liquid phases, a certain degree of
separation will result and this can be enhanced by use of multiple contacts or their equivalent in
the manner of gas absorption and distillation.
Liquid/liquid extraction is a very common method used in the organic laboratory. An
organic reaction often yields a number of by-products, some inorganic, some organic...
Liquid/liquid extraction is often used as the initial step in the work-up of a reaction, before final
purification of the product by recrystallization, distillation or sublimation. A simple example will
indicate the scope of the operation and some of its characteristics. If a solution of acetic acid in
water is agitated with a liquid such as ethyl acetate, some of the acid but relatively little water
will enter the ester phase. Since at equilibrium the densities of the aqueous and ester layers are
different, they will settle when agitation stops and can be decanted from each other. Since now
the ratio of acid to water in the ester layer is different from that in the original solution and also
4
different from that in the residual water solution, a certain degree of separation will have
occurred. This is an example of stage wise contact, and it can be carried out either in batch or in
continuous fashion. The residual water can be repeatedly extracted with more ester to reduce the
acid content still further, or we can arrange a countercurrent cascade of stages. Another
possibility is to use some sort of countercurrent continuous-contact device, where discrete stages
are not involved. The use of reflux, as in distillation, may enhance the ultimate separation still
further.
In all such operations, the solution which is to be extracted is called the feed, and the
liquid with which the feed is contacted is the solvent. The solvent-rich product of the operation is
called the extract, and the residual liquid from which solute has been removed is called as the
raffinate.
Extraction involves the use of systems composed of at least three substances, and
although for the most part the insoluble phases are chemically very different, generally all three
components appear at least to some extent in both phases. Thus liquid-liquid extraction is
generally represented by the tie-lines and the equilateral-triangular coordinates. These are used
extensively in the chemical literature to describe graphically the concentrations in ternary
systems. Triangular diagrams are used for representing three-component systems. Every possible
composition of the ternary mixture corresponds to a point in the diagram.
It is the property of an equilateral triangle that the sum of the perpendicular distances
from any point with in the triangle to the three sides equals the altitude of the triangle. Therefore
the altitude represents 100 percent composition and the distances to the three sides the
percentages or the fractions of the three components. Each corner of the triangle represents a
pure component and its designation is marked at this corner. On the side opposite to this corner
the mass fraction of this component is zero. In these triangular diagrams the left vertex generally
represents the diluents, right vertex as the solvent and the top as the solute. The sides of the
triangle represent the corresponding two-component system.
The mass fraction of each component is given by lines parallel to the side opposite to
the corner which represents the pure component. The numbering can be placed at edges of the
triangle in which case it is advisable to extend the lines. The numbers can also be inserted in the
middle of the lines, this makes the diagram easier to use. Thus the plotting of the values for the
percentages of any two compounds of a ternary system determines a point in the triangle, fixes
the percentages of the third component, and checks the corresponding mass fractions of all the
5
three components. As every point in a triangular diagram corresponds to a composition there is
no coordinate free for another reference variable.
If the ternary system exists in two phases, then the plot of the compositions of the two
individual phases when in equilibrium with each other gives a mutual solubility curve. Only
ternary systems with miscibility gaps are suitable for extractions, and the boundary lines between
the liquid single-phase region and the two phase regions particularly important. This boundary
line is called as the bimodal curve. Every point in the binodial curve is in equilibrium with
another binodial point. The interaction of the diluent and solvent branches of the curve is called
the plait point and has some unique characteristics. It represents simultaneously a solvent and a
diluent phase, and is a point where both phases have the same composition and density. The line
which connects points in equilibrium with one another is called as the tie lines. All mixture,
which corresponds to a point on a tie line separate into two phases. The composition of these
phases is given by the end points of the tie lines and their quantities are given by lever rule. The
equilibrium data have to be determined experimentally in each individual case.
1.3 SALT EFFECT ON LIQUID-LIQUID EXTRACTION
The addition of a salt to an aqueous solution of a volatile non electrolyte has a marked
effect upon the liquid-liquid and vapour-liquid equilibria of the solution. The presence of the salt
may either raise or lower the relative volatility of the nonelectrolyte or in extreme cases cause
the formation of the two liquid phases. The observed effects depend upon the nature and
concentration of both the salt and nonelectrolyte. Generally salt has a considerable effect on the
solvent to which it is added. It changes the general properties or characteristics of the solvent. As
soon as any salt dissolves in the water, the boiling point of the water gets affected when salt is
added are as follows: Lowering of the vapour pressure
Elevation in boiling point
Depression in freezing point
Change in osmotic pressure
6
The addition of non-volatile solute to a solvent mixture modifies the interaction among
the various solvent solute molecules resulting in shifting their phase equilibrium even to the
extent of eliminating the solutrope in liquid-liquid equilibrium. The salt mainly affects the
solubility of organic component in an aqueous-organic solvent mixture. Addition of an
electrolyte generally salts out the organic solvent molecules thus enriching the organic in organic
phase with the organic solvent component resulting in considerable reduction of the energy cost
incurred in the recovery and purification of the organic solvent. The distribution of the solute
between the two liquid phases mainly depends upon the concentration of electrolyte. The
electrolyte will remain in the phase in which it is most soluble and other solute will be
transferred to the phase that is poor in electrolyte. In other cases the addition of salt to a solvent
mixture can cause a phase split in a system that did not show demixing, this treatment is
sometimes used to enable separation by liquid extraction. When salt is added to the liquid
components the structure of the liquid components may be altered by promoting, destroying or
otherwise affecting interaction between the liquid components, there by altering the selectivity
properties of one of the liquid component. The result is then a solvent is added to extract a solute
from a liquid mixture in which a salt is dissolved, the distribution of solute between the two
solvents gets altered. This may be due to the preferential association of the solute molecules with
any one of the solvents in which the salt is dissolved. Thus the separation becomes easier in
presence of the salt.
Addition of the salt to an aqueous solution of the ternary system increases the
heterogeneity significantly. The area of heterogeneity is more as compared to no salt condition. It
also enhances distribution coefficients and selectivity’s. Salt mainly affects the mutual solubility
of solute and water and the distribution coefficient of solute. The selectivity, which is a ratio of
distribution coefficient of solute to that of water, is changed much more by the salt addition than
is the distribution coefficient of the solute alone.
7
CHAPTER-2
THEORIES OF SALT EFFECT
AND
THERMODYNAMIC MODELS
8
2.1 THEORIES OF SALT EFFECT
Generally the salt effects on the phase equilibrium can be explained by different
theories proposed by the well known individuals. The presence of a salt or a non-volatile solute
in a solvent mixture can significantly change its equilibrium composition. The salt effect theories
are generally concerned with the calculations of ion-electrolyte interaction parameters, which is
known as the “salting-out parameter”, and the later is used to indicate the magnitude of the salt
effect. Positive values indicate the salting out and the negative value indicates the salting in
effect. The causes and effect of polar attraction of a dissolved salt for one component of a water
non-electrolyte solution have been explained by various theories. These theories can be
explained with respect to hydration, electrostatic interaction, internal pressure and vanderwaals
forces.
2.1.1 HYDRATION THEORY
According to this theory each salt ion binds a constant number of water molecules as a
shell of oriented water dipoles surrounding the ion, there by decreasing the activity of the water.
This bound water is then unavailable as solvent for the nonelectrolyte. The number of water
molecules so bound by each salt ion is called the hydration number of the ion. Considering the
wide variation in hydration numbers this concept permits only a qualitative estimate of the
magnitude of the salt effect. This theory also doesn’t allow the occurrence of salting in effect.
This theory explains the differences in effects due to solutes and ions by assuming that each ion
orients water molecules in a definite direction. If the orientation is favorable to the nonelectrolyte molecules, salting-in occurs whereas an unfavorable orientation produces salting-out.
Addition of a salt to liquid-liquid equilibrium introduces ionic forces that affect the
equilibrium. When the ions are solvated, part of the water molecules become unavailable for the
solutions and they are salted out from the aqueous phase. This salt effect can be used for
removing organic compounds from water. In other hand when a polar solvent is added to an
aqueous salt solution, it captures the water molecules that were solvated the ions in a salting in
affect. This effect may be used for recovering salt from concentrated aqueous solutions.
9
2.1.2 ELECTROSTATIC THEORY
This theory was proposed by Meranda and Furter in 1974 but later it was developed by
Debye and Mc Auley. It was based on the amount of work necessary to discharge the ions in the
solvent and to recharge them in a solution containing non-electrolyte. This quantity yields the
electrostatic contribution to the chemical potential of the neutral solute. The theory thus takes
into account only electrostatic effects. It does not allow for the influence of dispersion type
forces between the ion and the solute molecules or for the alteration which the ion may produce
in the hydrogen bond interactions between neighboring water molecules.
This theory says that the addition of relatively small amount of salt may exerts large
effects on the relative volatility of components. The salt dissolved in a mixed solvent may affect
the boiling point, the mutual solubility’s of the two liquid components. Generally the particles
(non-dissociated molecules or ions or both) of dissolved salts tend to attract preferentially one
type of solvent molecules more strongly than the other. Usually the molecules of the more polar
components are preferentially attracted by the electrostatic field of the ions and hence the vapour
composition is enriched by the less polar solvent, in which the salt is less soluble. Kirk wood
taking into account the repulsion between the ionic charges and an image charge induced in the
cavity created in the solvent by the electrolyte molecule calculated the ion non-electrolyte
interaction energy. He derived an equation quite similar in form to that of Debye and Mc Auley.
The electrostatic theory basically considers only the action of columbic forces and omits
other factors. Because of simplification and approximations made in its derivation, the DebyeMc Auley equation is a limiting equation only. Butler, using a similarly simplified model,
obtained an equation virtually identical with that of Mc Auley. Later Debye, taking into account
the heterogeneity of the mixture of water and neutral solute, expressed the total free energy of
the system, including the contribution due to the field of ion, as a function of distance from the
ion .These electrostatic theories treats the solvent as a structural continuum, through which the
electrostatic ions are determined solely by their macroscopic electric constants.
10
2.1.3 VANDERWAALS FORCES THEORY
A given non-electrolyte may be salted-in by some electrolyte and salted-out by other
in same solvent. This fact suggested that short range dispersion forces might also be applicable in
determining salt effect especially at finite concentration. Long and Mc.Davit in an attempt to
allow for the trends towards salting-in of the non-electrolyte by large ions, proposed a modified
version of the Kirkwood and Debye equation to account for dispersion and displacement of
forces. They concluded that this theory was included in establishing the note of dispersion forces.
Since the electrostatic interaction between an ion and a neutral molecule is short range
in nature, additional interaction or Vander Waals type must be considered more fully. These
terms involves the polarizability of salt ions, solvent molecules, and non-electrolyte solute
molecules, as higher selectivity in extraction system with salt. The lower distribution coefficient
of water can be means a good attributed to the association of water molecules in unrestricted salt
in the aqueous phase, which impedes a transfer of water to the organic phase. From practical
point of view resulting higher selectivity well as the special force fields originating from any
component dipoles that may be present.
Bergen and Long disused salting-in and salting-out in terms of the effectiveness of the
electrolyte on the degree of order in the solvent structure. Gross indicated that salting-in indicate
a preferential attraction of ion for the non-electrolyte over the solvent. In the presence of the
large ions having weak electrostatic fields or in the presence of relatively un-dissociated salt, the
highly polar water molecule may tend to associate much more strongly with each other than with
the solvent forcing the salt into the vicinity of the less polar non-electrolyte molecules with
which the salt is associated.
2.1.4 INTERNAL PRESSURE THEORY
According to the internal pressure concept proposed by Tammann and applied by Mc.
Davit and Long, the concentration in total volume upon the addition of salt to water can be
thought of as a compression of the solvent. This compression makes the introduction of a
11
molecule of non-electrolyte more difficult, and this result in salting out. An increase in total
volume upon the addition of a salt would produce the counter effect known as salting in. Mc.
Davit and Long, applying the internal pressure concept of Tammann to nonpolar nonelectrolytes, calculated the free energy of the transfer of the latter from pure water to the salt
solution.
2.2 SALTING-IN AND SALTING-OUT EFFECT
The presence of a salt or a non-volatile solute in a solvent mixture can significantly
change its equilibrium composition. Addition of a salt to liquid-liquid equilibrium introduces
ionic forces that affect the equilibrium. If an electrolyte is added to water, it is usually found that
the solubility of a non-electrolyte in the ionic solution thus formed is lower than in pure water. It
means solubility decreases; this is known as salting-out effect. The term salting out is used since
if salt is added to a saturated solution of a non-electrolyte in water, the result is to bring the nonelectrolyte out of the solution. This salting out effect is not restricted to dilute3 solutions or
solutions of non-polar substances. Thus one salt may be salted-out by another and colloidal
substances may be salted out. In general, polar substances tend to be salted out rather less readily
than on-polar substances.
One explanation which has been brought forward to explain the salting-out depends on
the supposition that the water molecules in an ionic solution tend to from compact clusters
around the ions. The formation of such cluster is an energetically favorable process, which will
be preferred at the expenses of the formation of the rather different cage structures, which are
believed to surround a non-electrolytic solute molecule. In other words, the water molecules
which surround the ions are not available for the solution of non-electrolytes. The reason given
for the greater effectiveness of the smaller ions is that these have a greater charge density for a
given volume of ion and that it is this property which dictates the degree of hydration of the ion,
and hence it’s salting-out power. The rule that the salting-out power of an ion decreases as its
size increases is however, only roughly true and there are exceptions, particularly in the cases of
the smallest cat ions.
12
Very large ions produce increased solubility or salting-in. This phenomenon was first
studied by Neuberg and was called by him hydrotropism. The phenomenon has been most
extensively studied in the case of polar non-electrolyte solutes. The concept of ion hydration,
used to explain salting out, does not explain why very large ions should produce an actual
enhancement of the solubility. This effect may be due in part to the large dispersion type
attractive forces, which will exist between the non-polar part of these ions and the solute
molecules. These ion-solute interactions would be expected to increase with the size of the ion
and would tend to produce a congregation of non-electrolyte molecules around the ions at the
expense of the water molecules. A large ion with an unsymmetrical charge distribution and a
prominent non-polar region might be expected to show this effect particularly strongly, and such
ions do in fact cause salting-in in many cases.
Another reason why large ions produce salting-in may be that these ions, when
dissolved in water distort the water structure in their vicinity and create a fluid in which the
degree of hydrogen bonding is less than that of pure water. This would be expected to produce an
enhancement of the solubility of the foreign solute molecule. This aspect of salting in has been
stressed particularly by Long and McDavit. It is probable that both the above mechanisms are in
fact operative. Salting may also occur in cases where a specific chemical reaction takes place
between the solute and salt ions.
It has been calculated by previous experimental findings that the magnitude of the salt
effect in a given system mainly depends on the concentration of the salt present in the solution
which can be expressed in terms of a salt effect parameter. In turn, salt effect parameter is a
function of the factors such as degree of differences of solubility of the salt in the solution, ionic
charges, ionic radii and others.
13
2.3 THERMODYNAMIC MODEL
2.3.1 UNIQUAC MODEL (Universal quasi-chemical model)
At liquid-liquid equilibrium, the composition of the two phases (Raffinate phase &
extract phase) can be determined from the following equations:
(γ i χ i )1 = (γ i χ i )2 ------------------- (1)
∑χ
i1
= ∑ χ i2 = 1 -------------- (2)
Here γ i1 & γ i2 are the corresponding activity coefficient of component i in phase 1(Raffinate phase) and phase -2(extract phase).Equation 1 & 2 are solved for the mole
fraction(x) of component `i` in the two liquid phases. This method of calculation gives a single
tie line. The UNIQUAC model is given by Abrams & Prausnitz.
C
Φ
gE
= ∑ X i Ln i
RT i =1
 Xi
 Z C
Θ
 + ∑ qi X i Ln i
 2 i =1
 Φi
 C

 C
 − ∑ qi X i Ln ∑ Θ jτ ji  ------------- (3)
 i =1
 j =1

Or, Ln γ i = Lnγ iC + Lnγ iR ---------- (4)
Φ
Where, Lnγ iC = Ln i
 Xi
Lnγ iR
 Z
Θ
 + qi Ln i
 2
 Φi

Φ
 + τ i − i
Xi

C
∑X τ
j
j =1




C
C
Θ jτ ij


= q i 1 − Ln ∑ Θ jτ ji  − ∑  C


 j =1
 j =1  Θ τ
∑ k kj

 k =1







j
----------- (5)
------------- (6)
Here γ iC is the combinatorial part of the activity coefficient, γ iR the residual part of the
activity coefficient, τ ij is the adjustable parameter in the UNIQUAC equation, and χ i is the
equilibrium mole fraction of component i, the parameter Φ i & Θ i are given by:Segment fraction
Φi =
χ iτ i
C
∑χ τ
i =1
-------------- (7)
i i
14
Θi =
Area fraction
qi χ i
∑q χ
i =1
τi =
---------------- (8)
C
i
i
Z
(ri − qi ) − (ri − 1) ------ (9)
2
Where, z---lattice coordination number
ri ---number of segments per molecule
q i ---relative surface area per molecule
The extended UNIQUAC model is described by Nicolaisen et al (1993) for aqueous
electrolyte systems. It is derived from the original model (Abrams and Prausnitz ,1975 ;Maurer
and Prausnitz ,1978) by adding a Debye-Huckel term( sander et al,1986 ) to take into account the
presence of the ionic species in the mixture. The only parameters for the extended UNIQUAC
model are the UNIQUAC interaction parameters and volume and surface area parameters.
2.3.2 UNIFAC GROUP CONTRIBUTION METHOD
The UNIFAC group contribution method ( Fredenslund et al, 1975, 1977) is a broadly
used tool for the prediction of liquid phase activity coefficients parameterized for a wide range of
structural groups (Hansen et al ,1991). The empirical modification of the UNIFAC group
contribution is the UNIFAC-Dortmund model, as developed by Gmehling et al (1993).
In UNIFAC model, the activity coefficients of a molecular component i ( γ i ) in a multi
component mixture are expressed as sum of two contributions: a combinatorial part (C),
accounting for size and shape of the molecules and a residual part (R), a result of inter-molecular
interactions.
Lnγ i = Lnγ iC + Lnγ iR ------------------- (1)
The original UNIFAC is modified to Dortmund version by including ¾ exponents in the
calculation of volume fraction.
Lnγ
C
i
 Φ i'
= Ln
 χi

 Φ
Φ'
Φ
 + 1 − i − 0.5qi 1 − i + Ln i
χi
Θi
 Θi

15

 -------------- (2)

Φ i' =
Where,
χ i ri
∑χ
j
Θi =
3
4
3
4
j j
----------------- (3)
r
qi χ i
∑qjχ j
----------------- (4)
j
χ i ri
∑ χ j rj
----------------- (5)
q i = ∑ v ki Qk
----------------- (6)
Φi =
j
k
Where, χ i ----- mole fraction of the component i
v ki -----no. of groups of type K in molecule I .
The residual part is given by the solution of groups concept, expressed by
(
Lnγ iR = ∑ v ki Lnγ k − Lnγ ki
)
------------- (7)
k
Where, γ k ---- Group residual activity coefficient.
γ ki ---- Group residual activity coefficient for reference solution.


Θ mψ km 



Lnv k = Qk 1 − Ln ∑ Θ mψ mk  − ∑
-------------- (8)


m
m ∑ Θ nψ nm




n
The residual part remains unchanged compressing with the original UNIFAC, except the
energy parameters, ψ mn is correlated by a more complex expression for the temperature
dependence.
ψ mn
 Α mn + Β mnT + C mnT 2
= exp −
T

Θm =
Qm χ m
∑ Qn χ n

 ------------------ (9)

----------------- (10)
n
16
The parameters Amn , Bmn andC mn in the above expression have been fitted by Gmehling
et al (1993) using liquid-liquid equilibrium data.
2.3.3 NRTL MODEL( Non-random two liquid Model)
The model NRTL ( non-random two liquid ) by Renon and Prausnitz for the activity
coefficient is based on the local composition concept and it is applicable for partially miscible
systems. In order to take into account the salt effect on liquid-liquid equilibrium, the original
NRTL model has been empirically extended. The extended NRTL model is given by:-
∑τ
Lnγ i =
j
g ij
RT
G ji χ i
∑G
k
τ ij =
ji
ki
χk
= Aij +
k
Bij
T
g ij = exp(− α ijτ ij )
α ij = α ji

∑k τ kj Gkj χ k
χ j Gij 
+∑
τ ij −
j ∑ G kj χ k 
∑ Gkj χ k

k


 -------------- (1)


----------------- (2)
------------------- (3)
------------------- (4)
In equations (1) to (3), g ij represents the energy interactions between compounds i and
j, while α ij is a non-randomness parameter that derives from the local composition assumption.
Thus, there are 5 adjustable parameters for each pair of substances: Aij , A ji , Bij , B ji and α ij .
These parameters can be estimated with experimental data.
A large amount of experimental data was used to determine the NRTL energy
interaction parameters. For the interactions of binary liquid-liquid the experimental data Othmer
et al, Mc Cants et al, Matsumoto and Sone, Raja Rao and Venkata Rao, Venkataratnam et al,
Petritis and Geankoplis, Ababi et al, Smirnova and Morachevskii, Lesteva et al, Krupatkin and
Glagoleva, Iguchi and Fuse, De Santies et al, Kaczmarik and Radecki, Tegtmeier and
Misselhorn, Marangirs et al, Ruiz et al, Letcher et al, Nakayama et al, Spottke et al,Esquivel and
Bernardo-Gil and Letcher and Suswana were used with a total of 57 tie-lines. These data were
available from the Dortmund Data Bank.
The estimation procedure is based on the Simplex method and Maximum Likelihood
principle and consists in the minimization of the objective function S.
17
 T − T m
 jk
jk
S= ∑∑ 

σT jk
K
j 

D NK
2
1
1m
 Ck −1  χ ijk
− χ ijk
 + ∑ 

 σχ ijk
i 


2
11
11, m
  χ ijk
− χ ijk
 +
  σχ
ijk
 




2

  ------------ (5)


Where, D----- the number of data sets.
N k --- the number of data points.
C k --- the number of components in the data set K.
σ ijk -- standard deviation in temperature.
σ xijk , σ 11
xijk -----standard deviations in the composition of both liquid phases
at equilibrium.
2.3.4 WILSON MODEL
Wilson model was proposed by Wilson in 1964 and it was modified by Renon and
Prausnitz, (1969). The Wilson equations are as follows:
Λ 12 X 2
Λ 21 X 2 
Lnγ 1 = C − Ln( X 1 + Λ 12 X 2 ) +
−
 ------------ (1)
X 1 + Λ 12 X 2 X 2 + Λ 21 X 1 


Λ 21 X 1
Λ 12 X 1 
Lnγ 2 = C − Ln( X 2 + Λ 21 X 1 ) +
−
 ------------ (2)
X
+
Λ
X
X
+
Λ
X

2
21 1
1
12
2 
V
 − ∆λ12 
Where, Λ 12 = 2 exp
 ------------- (3)
V1
 RT 
V1
 − ∆λ 21 
exp
 ------------- (4)
V2
 RT 
V1 ,V2 ----molar liquid volumes.
∆λ12 , ∆λ21 ---- adjustable energy parameters.
C--------- adjustable binary parameter, usually set equal to unity.
Λ 21 =
2.3.5
DEBYE-HUCKEL MODEL
The Debye-Huckel model ( Debye and Huckel, 1924 ) was the first model to describe
long-rangeinteractions of the ions and it still is the commen element of many electrolyte models.
The Debye-Huckel model can be derived either from electrostatics (Poisson equation) or from
classical mechanics. In the Debye-Huckel theory the ions are point charges and the solvent is
replaced by a dielectric continuum, according to the Mc Millan Mayer theory. For charged hard
spheres the interaction potential U ij between ion 1 and 2 is given by coulomb interaction.
18
Zi Z j e2
U ij =
∑r
ij
Where , e---charge of one electron.
Z---valence of the ion.
Σ --Dielectric constant.
The Boltzmann`s distribution law is inserted into Poisson`s equation, which is a relation
between the distribution of charges and the electrostatic potential Ψ . The resulting equation is
called Poisson-Boltzmann equation and describes the distribution of charge around an ion by
assuming a Boltzmann distribution.
∇ 2 Ψ (r ) = −
1
∑ Z eρ
ε
i
i
i
 Z eΨ (r ) 
exp i

 KT 
The Debye-Huckel theory further assumes that KT>> Z i eΨ ,so that the exponential term
can be linearized.
∇Ψ (r ) = K 2 Ψ (r )
K2 =
e2
εKT
∑ρ Z
i
i
2
i
=
2I
εKT
Where K-----Debye-Huckel Shielding parameter.
I------Ionic strength.
The expression for activity coefficient is written as
Lnγ i = −
Z i2 e 2κ
8πεKT
2.3.6 Extended Debye-Huckel
The charged density with in a radius `Q` from the centre of the ion is assumed to be 0,
resulting in--Z i2 e 2
κ
Lnγ i = −
8πε KT (1 + κa )
The radius `a` is referred to as the closest approach parameter and is treated as an
empirical constant.
19
CHAPTER-3
PREVIOUS INVESTIGATIONS
20
3.1 PREVIOUS INVESTIGATIONS
Many authors have worked on this liquid-liquid extraction system. But few of them
have worked on the salt effect on liquid-liquid extraction system. It is observed that the use of
salt has proven advantageous. Although a relative few significant advances and developments in
this field is reported at experimental level. In this review developments and trends are outlined
with emphasis on existing correlation. The systems with the results obtained by different authors
are listed below.
3.1.1 LIST OF SOME PREVIOUS INVESTIGATION ON LLE
TABLE—1
Sl
Authors
System studied
Results
No
.
1.
Alberto Arce, Hector Water+Methanol+
The system was studied at different
Rodriguez,
temperatures
Oscar dibutyl ether.
Rodriquez, Ana Soto.
and
correlated
their
experimental data with UNIQUAC
and NRTL model. UNIQUAC model
led to better results. It was found that
this method gives a relatively good
prediction of liquid-liquid equilibrium
of the system, but not good enough for
many practical purposes.
2.
H. Ghanadzadeh, A. Water + 2-ethyl-1- The optimum UNIQUAC inter -action
Ghanadzadeh.
hexanol + Ethanol
parameters between water, ethanol and
2-ethyl-1-hexanol
were
determined
using the experimental data. The
21
average
RMSD
value
observed
and
calculated
between
mole
fractions with a reasonable error was
1.70 % for the UNIQUAC model. The
solubility of water in 2-ethyl-1hexanol increases with amounts of
ethanol added to water + 2-ethylhexanol.
3.
H.
Ghanadzadeh 2, 3-butanediol + 2- The system was studied at different
Gilani, G. Khiati, A. K. ethyl-hexanol
Haghi.
+ temperatures
water.
(300
.2,
305.2,
310.2,315.2K). The UNIQUAC model
was used to correlate the experimental
data.
The
average
RMSD
value
between observed and calculated mole
fraction is 1.38%. The solubility of
water in 2-ethyl hexanol increases with
amounts of 2,3-butanediol added to
water + 2-ethyl hexanol.
4.
Juan C. Asensi , Julia 1-propanol
+
1- The UNIQUAC model was correlated
Molto , Maria del Mar pentanol + water
with the data. For the liquid phases in
Olaya, Francisco Ruiz.
the liquid-liquid equilibrium mean
absolute deviations (MAD) is 0.04
mole fraction. Therefore, a not too
satisfactory
experimental
correlation
of
the
temp-composition
results was obtained with the model.
5.
Mohsen Mohsen-Nia.
Ethanol +toluene + n- The NRTL was used to correlate the
decane + water.
experimental results and to calculate
the phase compositions of studied
mixture. The effect of temperature in
extraction of toluene from n-decane at
lower
temprature.
Selectivity
coefficient is higher but distribution
22
coefficient is lower, therefore in the
practical
extraction
the
optimum
temperature can be considered.
6.
Suheyla Cehreli, Dilek 1-propanol + water + The UNIFAC model gives better
Ozmen, Vmur Dramur.
solvent
(Methyl prediction for (water + 1-propanol +
acetate, ethyl acetate, ethyl acetate) and (water + 1-propanol
n-propyl acetate).
+
n-propyl
acetate)
where
as
UNIQUAC was found more suitable
for (water + 1-propanol + methyl
acetate). It is apparent from the
separation factors and experimental
tie-lines that n-propyl acetate is found
to be preferable solvent for separation
of 1-propanol from aqueous solutions.
7.
S. Ismail Kirbaslar
Butyric
acid
+ The temperature had practically no
dodecanol + water.
effect on the size of immiscibility
region at the different temperatures
studied. The results showed that
butyric acid was more readily soluble
in the solvent-rich phase than in the
water-rich phase.
8.
Suheyla Cehreli, Besir Water
Tatli, Pelin Bagman.
acid
+
+
propionic It was observed that the effect of the
cyclo temperature changes on the shape and
hexanone.
the size of the immiscibility gap were
insignificant over the investigated
range. Experimental tie lines data of
this work were analyzed and predicted
using UNIFAC model. The average
RMSD value between the measured
and calculated mass fraction was 0.08
for UNIFAC model.
23
9.
Hengde Li, Kazuhiro Ethanol + α-pinene + The experimental results were well
Tamura.
water.
correlated by the modified UNIQUAC
model having only binary parameters.
Youn Yong Lee, Youn Water
10.
Woo Lee.
+
alcohol
Ter-butyl They studied the system at different
+
Di- temperatures
Isobutylene.
and
correlated
their
experimental data with NRTL and
UNIQUAC model. They observed
experimentally that as the temperature
is increased, the solubility as well as
area of heterogeneity increased with a
minimum variation.
Joseph
11.
W.Kovach Dibutyl ether + Water They
Warren D. Selder.
+ Sec-Butyl alcohol.
studied
correlated
the
independently
the
system
and
experimental
data
by
using
the
UNIQUAC model.
12.
Suheyla Cehreli, Dilek Water
+
propionic The average RMSD value between the
Ozmen, Besir Talli.
+
diethyl measured and calculated mass fraction
phthalate.
was 0.03. It can be concluded that
acid
diethyl phthalate has high separation
factor, very low solubility in water,
high boiling point may be an adequate
solvent to extract propionic acid from
its dilute solutions.
24
3.1.2 LIST OF INVESTIGATIONS OF SALT EFFECT ON LLE
TABLE-2
Sl
Authors
System
Salt used
Results
Fania S. Santos,
Water+1-
Sodium
The effect of the salt addition on
Saul G.D`Avila,
butanol +
chloride,
the original ternary systems was
Martin Aznar.
Acetone.
Sodium
observed by the increase of the
Acetate.
two-phase region and the changes
No.
1.
in the slopes of the experimental
tie-lines. Both salts have caused
salting-out effect but the effect of
sodium acetate is less than sodium
chloride.
2.
HoracioN.Solimo,
Carlos
Water
+ Sodium
Solubility and tie-line data were
chloride
obtained at 303.2 K. The addition
M.Bonatti, propionic
Monica B. Gramajo acid + 1-
of salt enhanced significantly the
De Doz.
distribution
butanol.
coefficient
and
selectivity’s, while the region of
heterogeneity
increased
as
compared to the salt distribution.
Tie-lines data were correlated by
method of Othmer and Tobias and
their parameters were evaluated.
3.
Kaj Thomsen, Maria Water
C.
Iliuta,
Rasmussen.
Peter alcohol.
+ Sodium
The extended UNIQUAC model
chloride,
has been shown to be a good
KCl,
thermodynamic
model
for
Sodium
describing the complex
phase
sulphate.
behavior of mixed solvent systems
containing one or more salts. The
model
only
interaction
25
requires
binary
parameters.
These
parameters
are
temperature
dependent
but
composition
independent.
4.
Milton A. P. Pereira, Water+2Martin Aznar.
Pota-ssium
In general, both salts caused a
propanol +1 bromide,
salting out effect, but the effect of
butanol.
Magne-sium
magnesium chloride is more than
chloride
of potassium bromide. From the
experimental
data,
activity
coefficient was determined for the
NRTL model. The parameters
were estimated by using the
simplex method.
5.
M. Govindarajan , P. Acetic acid Sodium
The
L. Sabarathinam
modified to fit the data of salt
+
Methyl chloride,
isobutyl
ketone
water.
Sodium
+ nitrate,
Campbell
correlation
is
containing ternary liquid system.
The distribution data of these salts
Sodium
containing
system
sulphate,
correlated through the modified
Zinc
Nernst, Campbell and Eisen-joffe
sulphate.
equations.
Results
have
been
based
on
modified Nernst equation show
following order of salts zinc
sulphate
>sodium
sulphate>
sodium chloride>sodium nitrate.
6.
M.
U.
Pal, Ethyl
Madhusudan Rao.
acetate
ethyl
alcohol
Pota-ssium
Solubility and tie lines data in
+ acetate,
presence and absence of salt at
sodium
30ºC is determined. Potassium
+ acetate.
acetate system is more advantage
water.
over sodium acetate. Data on
effect of same electrolytes on
mutual solubility’s of ethyl acetate
26
and water at salt saturation at 30ºC
also presented.
7.
M. M. Olaya, A. Ethanol
Botella, A. Marcilla.
water
+ Sodium
+1- chloride.
pentanol
The addition of salt to above
system
has
following
consequences; The 2liq quaternary
region
increases
its
size
on
addition of salt. It improves the
distribution coefficient for ethanol
extraction with 1-pentanol and
selectivity
also
increases.
It
improves the ethanol extraction
with 1-pentanol.
8.
T.
C.
Tan,K.K.D. Water+1-
D.S.Kannangara.
Pota-ssium
Solubility and tie line data were
propanol + chloride
obtained at 25ºC. Correlation was
methyl
done by NRTL model. System was
ether.
studied
at
higher
salt
concentration.
9.
Taher A. Al-sahhaf, Water+2-
KI,NaBr,
The salts used have a greater
Emina Kapetanovie butanone,
LiCl.
salting out efficiency on ethyl
Qadria Kadhem.
Water
+
acetate
than
on
2-butanone.
ethyl
Potassium iodide exhibits a salting
acetate.
in effect on 2-butanone and it
appears
that
the
salvation
mechanism for KI is different from
the other salts.
10.
T.C.Tan,
Aravinth.
S. Acetic acid NaCl, KCl
+
1-
They studied the above system at
different
temperatures
and
butanol+
correlated the data using NRTL
water
model method and Eisen-joffe
equation. Both salts show similar
properties.
27
11.
V.Gomis,F.Ruiz,N.B
Water+1-
Lithium
The NRTL model satisfactorily
oluda, M.D. Saquete.
pentanol
chloride
correlates
the
data
with
low
concentrations of LiCl. However
when the concentration of salt
raises, the model is unable to
predict
the
increase
in
concentration of salt in the organic
phase produced by the formation
of solvate alcohol-salts.
12.
Xiaoping
Lu
, Water
+ Pota-ssium
The separation of tertiary butanol
fluoride
from aqueous solution is feasible
Pingfan
Han
, tertiary
Yaming
Zhang
, butanol
by
salting
out
effect.
The
Yanru Wang , Jun
concentration of tertiary butanol
Shi.
increases
slowly
with
an
increasing salt.
13.
Water+
Water+n-
Licl,NaBr,K
Salting out occurs at higher salt
butanol,n-
Br
concentration, more amount of n-
propanol
propanol is transferred to the
butanol phase. Salotropic is not
eliminated completely.
28
CHAPTER-4
EXPERIMENTAL PROCEDURE
29
4. EXPERIMENTAL PROCEDURE
4.1 INTRODUCTION
The experimental measurement of liquid-liquid equilibrium must accomplish two
things. It must locate the position of the solubility curve and it must determine the composition
of the coexisting phases, which locate the ends of the tie lines. In some cases these two
objectives can be accomplished in one measurement, and in the other cases, two sets of
measurements are necessary. In the first case, for a ternary system mixtures of three components
are allowed to separate into its conjugate phases at equilibrium and the equilibria layers are
analyzed for their composition which will give the end points of the tie lines. These endpoints
when connected will give the bimodal curve. This method is called the method of analysis. The
second method involves the estimation of binodal curve and the tie lines in two stages, which is
measured separately.
4.2 EXPERIMENTAL SETUP
The experimental set up used for the determination of solubility data are as follows:A cell of 100ml capacity is taken. Here the temperature of the apparatus and the
experimental fluid is controlled by a water jacket around the cell. The cell has two opening, one
at the top and another at the bottom. Through the top opening the liquids are taken into the cell
and during the experiment a thermometer is placed into it to record the temperature of the
liquids. The bottom opening is the outlet for the liquids. A magnetic stirrer is provided for the
sufficient agitation within the apparatus. The composition of the sample can be analyzed using
the Gas Chromatography apparatus equipped with a thermal conductivity detector.
30
Fig.1 EXPERIMENTAL SETUP FOR LIQUID-LIQUID EXTRACTION
4.3 PROCEDURE FOR THE SYSTEM
The liquid-liquid measurements for the ternary system were made at atmospheric
pressure in the temperature range of 300 to 325K. The preweighed amount of the mixture is
taken in a 100ml jacketed cell. Then the other component is added and simultaneously the
mixture is kept in constant agitation condition with the help of the magnetic stirrer. Water is
continuously supplied to the jacketed cell to maintain the constant temperature. The mixture is
stirred for 1-2 hours and then it is left to settle for 2-3 hours. After 2-3 hours the system gets
separated into two phases. The top phase is taken out with the help of a syringe and the bottom
phase is taken out through the bottom outlet. Then the samples are taken separately and analyzed
in the Gas Chromatography. This procedure is repeated for the different amount of the liquids so
as to cover the entire range of the composition.
31
4.4 PROCEDURE FOR THE SYSTEM WITH SALT
The experimental procedure for the determination of the solubility data of a salt
containing ternary liquid system is similar to the procedure adopted for the salt free solution. The
concentration of the aqueous salt solution is varied from 5% to20% of salt by mass. In this case
the determination of the composition is not possible directly by Gas Chromatography due to the
presence of the salt. So each layer (raffinate and extract) is taken or collected separately and each
layer is boiled separately and condensed to make it salt free and then the composition of the
sample is analyzed by using the Gas Chromatography.
Fig. 2 EXPERIMENTAL SETUP FOR EXTRACTING SALT FROM SAMPLE
4.5 METHOD OF ANALYSIS
The composition of the sample obtained from the liquid-liquid extraction can be
analyzed by the following methods:-
32
4.5.1
TITRATION METHOD
In ternary liquid-liquid system, compositions of the coexisting phases were found by
analyzing the concentration of the consulate component in each of the two phases. Known
amounts of the two components and the dissolved salt corresponding to the points with in the
binodial curve with contained in stoppered flasks, were agitated at constant temperature bath
over a period of 2 hours. At the end of this period the flasks were allowed to remain in the bath
until the phases had completely separated. Then the samples of the separated layers were
withdrawn. Then the analysis is done by the simple titration method.
4.5.2
GAS CHROMATOGRAPH METHOD
Gas chromatograph consists of a flame ionization detector and electronic integrator.
The injector and detector are maintained at constant temperature. A stainless steel with 10%
squalane in chromosorb was used .Helium carrier gas was used with a constant flow rate at room
temperature. Samples are alternatively withdrawn from the two phases with 1-µl
chromatographic syringes and injected into the chromatograph. Calibration analyses are carried
out to convert the peak area ratio to the weight composition of the mixture. In case of dissolved
salts each layer was boiled separately and condensed to make it salt free and then analyses of
each layer was carried out.
4.5.3
REFRACTIVE INDEX METHOD
In this the three components were agitated in a constant temperature bath over a period
of 2 hours. At the end of this period the flasks were allowed to remain in the bath until the phases
had completely separated. Then the samples of the separated layers were withdrawn and their
refractive indexes were measured. The composition of the equilibrium layers were determined by
references to a large scale plot of refractive index against solute concentration for saturated
solution. In case of dissolved salts each layer was boiled separately and condensed to make it salt
free and then refractive index of each layer was measured.
4.5.4
SPECIFIC-GRAVITY METHOD
Here similar procedure is followed as in other case. The separated layers were
withdrawn and their specific gravities were measured. The compositions of the equilibrium
layers were determined by references to a large-scale plot of specific gravity against solute
33
concentration for saturated solutions. In case of dissolved salts each layer is boiled separately
and condensed to make it salt free and then specific gravity of each layer was measured.
4.6 CHROMATOGRAPHY
Chromatography involves a sample (or sample extract) being dissolved in a mobile
phase (which may be a gas, a liquid or a supercritical fluid). The mobile phase is then forced
through an immobile, immiscible stationary phase. The phases are chosen such that components
of the sample have differing solubility’s in each phase. A component which is quite soluble in
the stationary phase will take longer to travel through it than a component which is not very
soluble in the stationary phase but very soluble in the mobile phase. As a result of these
differences in mobility’s, sample components will become separated from each other as they
travel through the stationary phase.
Gas chromatography is the use of a carrier gas to convey the sample through a column
consisting of an inert support and a stationary phase that interacts with sample components. Gas
chromatography especially gas-liquid chromatography involves a sample being vaporized and
injected onto the head of the chromatographic column. The sample is transported through the
column by the flow of the inert, gaseous mobile phase. The column itself contains a liquid
stationary phase which is adsorbed onto the surface of an inert solid.
Fig.3 Diagram illustrating the Gas-Liquid Chromatography
34
4.6.1 Instrumental components
•
Carrier gas
The carrier gas must be chemically inert. Commonly used gases include nitrogen,
helium, argon, and carbon dioxide. The choice of carrier gas is often dependant upon the type of
detector which is used. The carrier gas system also contains a molecular sieve to remove water
and other impurities.
Fig 4 Steel column installed in Oven
•
Sample injection port
For optimum column efficiency, the sample should not be too large, and should be
introduced onto the column as a "plug" of vapour - slow injection of large samples causes band
broadening and loss of resolution. The most common injection method is where a microsyringe
is used to inject sample through a rubber septum into a flash vaporizer port at the head of the
column. The temperature of the sample port is usually about 50°C higher than the boiling point
of the least volatile component of the sample. For packed columns, sample size ranges from
35
tenths of a micro liter up to 20 micro liters. Capillary columns, on the other hand, need much less
sample, typically around 10-3mL. For capillary GC, split/split less injection is used.
The injector can be used in one of two modes; split or split less. The injector contains a
heated chamber containing a glass liner into which the sample is injected through the septum.
The carrier gas enters the chamber and can leave by three routes (when the injector is in split
mode). The sample vaporizes to form a mixture of carrier gas, vaporized solvent and vaporized
solutes. A proportion of this mixture passes onto the column, but most exits through the split
outlet. The septum purge outlet prevents septum bleed components from entering the column.
Here is an illustration of a split/split less injector.
Fig. 5 Injector
•
Columns
There are two general types of column, packed and capillary (also known as open
tubular). Packed columns contain a finely divided, inert, solid support material (commonly based
on diatomaceous earth) coated with liquid stationary phase. Most packed columns are 1.5 - 10m
in length and have an internal diameter of 2 - 4mm.Capillary columns have an internal diameter
36
of a few tenths of a millimeter. They can be one of two types; wall-coated open tubular (WCOT)
or support-coated open tubular (SCOT). Wall-coated columns consist of a capillary tube whose
walls are coated with liquid stationary phase. In support-coated columns, the inner wall of the
capillary is lined with a thin layer of support material such as diatomaceous earth, onto which the
stationary phase has been adsorbed. SCOT columns are generally less efficient than WCOT
columns. Both types of capillary column are more efficient than packed columns. In 1979, a new
type of WCOT column was devised - the Fused Silica Open Tubular (FSOT) column;
•
Column temperature
For precise work, column temperature must be controlled to within tenths of a degree.
The optimum column temperature is dependant upon the boiling point of the sample. As a rule of
thumb, a temperature slightly above the average boiling point of the sample results in an elution
time of 2 - 30 minutes. Minimal temperatures give good resolution, but increase elution times. If
a sample has a wide boiling range, then temperature programming can be useful. The column
temperature is increased (either continuously or in steps) as separation proceeds.
•
Detectors
There are many detectors which can be used in gas chromatography. Different
detectors will give different types of selectivity. A non-selective detector responds to all
compounds except the carrier gas, a selective detector responds to a range of compounds with a
common physical or chemical property and a specific detector responds to a single chemical
compound. Detectors can also be grouped into concentration dependant detectors and mass flow
dependant detectors. The signal from a concentration dependant detector is related to the
concentration of solute in the detector, and does not usually destroy the sample Dilution of with
make-up gas will lower the detectors response. Mass flow dependant detectors usually destroy
37
the sample, and the signal is related to the rate at which solute molecules enter the detector. The
response of a mass flow dependant detector is unaffected by make-up gas.
Fig.7 Flame Ionization Detector
The effluent from the column is mixed with hydrogen and air, and ignited. Organic
compounds burning in the flame produce ions and electrons which can conduct electricity
through the flame. A large electrical potential is applied at the burner tip, and a collector
electrode is located above the flame. The current resulting from the pyrolysis of any organic
compounds is measured. FIDs are mass sensitive rather than concentration sensitive; this gives
the advantage that changes in mobile phase flow rate do not affect the detector's response. The
FID is a useful general detector for the analysis of organic compounds; it has high sensitivity, a
large linear response range, and low noise. It is also robust and easy to use, but unfortunately, it
destroys the sample.
38
CHAPTER-5
PRESENTATION OF RESULTS
39
5. PRESENTATION OF RESULTS
Experiments are conducted on the system Water + 1-propanol + Ethyl acetate with varying salt
concentrations and varying temperatures. The basic objective of this project is to determine the
best temperature range and the salt from NaCl and (NH4)2SO4 which enhances the separation or
extraction of the solute by the specified solvent. The experiments were conducted and the
resulting extract and raffinate phase was analyzed with the help of the gas chromatography. The
plots of voltage vs time was obtained from the gas chromatography, showing the percent volume
of the different components present in both the phases. For each phase a separate plot is
obtained.
Here we have considered two salts: NaCl and (NH4)2SO4. We have tried to show the effect of
these two salts on the system at temperatures 27ºC, 32ºC and 37ºC. Thus considering all these
factors lot of experiments are conducted and lot of plots were obtained from the gas
chromatography. But it is not possible to produce all these plots in this project. Thus we have
attached some of the plots and the other plots are available in the department library. From these
the volume of the different components present in each phase is calculated. These are tabulated
in Table 5.1 and the equilibrium data’s are tabulated in Table 5.2.Considering these data’s the
solubility curves and the equilibrium curves are plotted on the ternary plots. All salt containing
data are reported on salt free basis. The experimental tie-line data under no salt condition were
determined and presented in the respective Tables.
5.1
EMPIRICAL
CORRELATION
OF
SALT
EFFECT
ON
LIQUID-LIQUID
EQUILIBRIUM
The presence of the dissolved salt in a liquid mixture is likely to bring about a change in the
liquid structure by promoting, destroying or bringing about other interactions between the
components. Also the forces involved and any changes caused by salt addition may differ from
system to system and from salt to salt.
40
The effects of salt on liquid-liquid equilibria of a ternary system have been widely studied.
Several theories have advanced to explain the complex effect. However, the mathematical
characterization of the salt effect has been semi-quantitative at best, because of the limitations of
the theories or inadequacy of assumption made in the derivation of those equations. Hand,
Othmer and Tobias have proposed equations to correlate the tie-line data of ternary liquid-liquid
systems under pure /no salt condition. Eisen and Joffe have proposed semi empirical models to
correlate the tie-line data of the ternary liquid-liquid equilibrium under salt dissolved in the
system. But the best method to correlate the tie-line data of the ternary liquid-liquid equilibrium
under salt dissolved is the UNIQUAC Model(Universal quasi-chemical model ) proposed by
Abrams and Prausnitz and the UNIFAC group contribution method proposed by Fredenslund et
al.
41
Fig.8 G. C. Analysis report for 10% NaCl (32ºC) Raffinate Phase 1
42
Fig.9 G. C. Analysis report for 10% NaCl (32ºC) Extract Phase 1
43
Fig.10 G. C. Analysis report for 10% NaCl (32ºC) Raffinate Phase 2
44
Fig.11 G. C. Analysis report for 10% NaCl (32ºC) Extract Phase 2
45
Fig.12 G. C. Analysis report for 10%NaCl (32ºC) Raffinate Phase 3
46
Fig.13 G. C. Analysis report for 10% NaCl(32ºC) Extract Phase 3
47
Fig.14 G. C. Analysis report for 10% Nacl(32ºC) 4
48
Fig.15 G. C. Analysis report for 10%(NH4)2SO4 (32ºC) Raffinate Phase 1
49
Fig.16 G.C. Analysis report for 10 %( NH4)2SO4 (32ºC) Extract Phase 1
50
Fig.17 G. C. Analysis report for 10%(NH4)2SO4 (32ºC) Raffinate Phase 2
51
Fig.18 G. C. Analysis report for 10%(NH4)2SO4 (32ºC) Extract Phase 2
52
Fig.19 G. C. Analysis report for 10%(NH4)2SO4 (32ºC) Raffinate Phase 3
53
Fig.20 G. C. Analysis report for 10 %(NH4)2SO4 (32ºC) Extract Phase 3
54
Fig.21 G. C. Analysis report for 10%(NH4)2SO4 (32ºC) 4
55
5.2 SOLUBILITY DATA
SYSTEM: WATER + 1-PROPANOL + ETHYL ACETATE
Table 5.2.1 No Salt (27ºC)
Water
16.0
14.0
13.0
11.0
8.0
1-Prop
2.2
16.2
42.5
22.5
4.5
EA
15.6
24.5
54.0
28.5
3.2
14.9
18.4
27.1
37.8
RAFFINATE
Water 1-Prop
9.320 0.714
8.953 4.209
8.869 9.700
8.331 14.702
EA
4.843
5.191
8.545
14.775
RAFFINATE
Water 1-Prop
9.428 0.772
7.660 4.448
8.274 8.883
EA
2.200
3.292
4.943
18.9
36.3
82.3
24.2
EXTRACT
Water 1-Prop
6.680 1.399
5.047 11.965
4.131 32.764
2.669 7.785
EA
10.779
19.280
45.434
13.716
24.7
28.8
26.6
EXTRACT
Water 1-Prop
1.372 0.228
2.340 3.052
2.026 6.217
EA
23.100
23.408
18.357
22.6
31.2
36.8
EXTRACT
Water 1-Prop
2.005 7.690
1.821 5.192
2.387 0.591
EA
12.905
24.187
33.822
32.1
32.8
50.3
EXTRACT
Water 1-Prop
1.902 6.269
2.684 10.055
4.813 22.927
EA
23.929
20.061
22.560
Table 5.2.2 5% NaCl (27ºC)
Water
10.8
10.0
10.3
4.2
1-Prop
1.0
7.5
15.1
11.0
EA
25.3
26.7
23.3
10.3
12.4
15.4
22.1
Table 5.2.3 10%NaCl (27ºC)
Water
12.1
10.9
10.0
10.0
1-Prop
8.2
9.8
11.4
24.3
EA
15.2
26.6
38.7
11.4
12.9
16.1
23.3
RAFFINATE
Water 1-Prop
10.095 0.510
9.079 4.608
7.613 10.809
EA
2.295
2.413
4.878
Table 5.2.4 15%NaCl (27ºC)
Water
14.0
13.0
15.0
7.0
1-Prop
6.7
17.6
37.6
20.3
EA
26.6
23.0
25.8
7.4
15.2
20.8
28.1
RAFFINATE
Water 1-Prop
12.098 0.431
10.316 7.545
10.231 14.791
56
EA
2.671
2.939
3.078
Table 5.2.5 No Salt (32ºC)
Water
14.0
14.0
13.0
8.0
1-Prop
0.9
14.6
21.0
17.2
EA
25.8
25.5
22.2
14.3
19.9
25.0
38.3
RAFFINATE
Water 1-Prop
12.800 0.542
11.185 7.086
10.812 12.598
EA
6.558
6.729
4.890
RAFFINATE
Water 1-Prop
12.397 0.474
11.514 8.062
8.165 10.129
EA
4.829
4.324
5.206
RAFFINATE
Water 1-Prop
13.097 0.357
9.543 9.458
8.311 13.368
EA
2.646
3.099
4.821
RAFFINATE
Water 1-Prop
13.019 0.796
11.832 6.831
8.901 13.856
EA
2.285
2.437
3.143
RAFFINATE
Water 1-Prop
11.250 0.576
10.886 6.932
7.282 9.375
EA
8.174
5.182
4.843
20.8
29.1
27.9
EXTRACT
Water 1-Prop
1.200 0.358
2.815 7.514
2.188 8.402
EA
19.242
18.771
17.310
31.9
37.6
36.0
EXTRACT
Water 1-Prop
1.603 0.626
2.486 5.438
3.835 11.571
EA
29.671
29.676
20.594
37.4
31.2
33.5
EXTRACT
Water 1-Prop
0.903 0.743
3.457 5.542
3.689 13.232
EA
35.754
22.201
16.579
43.3
35.4
27.3
EXTRACT
Water 1-Prop
1.981 12.404
2.168 15.069
4.099 14.844
EA
28.915
18.163
8.357
37.3
20.3
27.3
EXTRACT
Water 1-Prop
3.750 0.624
2.114 3.768
3.718 9.825
EA
32.926
14.418
13.757
Table 5.2.6 5%NaCl (32ºC)
Water
14.0
14.0
12.0
9.0
1-Prop
1.1
13.5
21.7
22.3
EA
34.5
34.0
25.8
14.1
17.7
23.9
23.5
Table 5.2.7 10%NaCl (32ºC)
Water
14.0
13.0
12.0
9.0
1-Prop
1.1
15.0
26.6
24.8
EA
38.4
25.3
21.4
20.9
16.1
22.1
26.5
Table 5.2.8 15% NaCl(32ºC)
Water
15.0
14.0
13.0
9.0
1-Prop
13.2
21.9
28.7
23.7
EA
31.2
20.6
11.5
5.0
16.1
21.1
25.9
Table 5.2.9 No Salt(37ºC)
Water
15.0
13.0
11.0
8.0
1-Prop
1.2
10.7
19.2
17.6
EA
41.1
19.6
18.6
11.2
20.0
23.0
21.5
57
Table 5.2.10 5% NaCl(37ºC)
Water
14.0
14.0
12.0
8.0
1-Prop
1.2
13.3
21.8
18.8
EA
28.2
29.5
19.4
8.4
18.3
22.9
24.8
RAFFINATE
Water 1-Prop
12.415 0.533
11.547 6.729
8.250 12.680
EA
5.352
4.624
3.870
RAFFINATE
Water 1-Prop
14.423 1.125
10.342 7.247
7.683 15.982
EA
2.352
2.111
3.935
25.1
33.9
28.4
EXTRACT
Water 1-Prop
1.585 0.667
2.453 6.571
3.750 9.120
EA
22.848
24.876
15.530
28.1
49.8
33.9
EXTRACT
Water 1-Prop
0.577 5.075
3.658 16.453
4.317 15.518
EA
22.448
29.689
14.065
23.8
30.3
35.2
EXTRACT
Water 1-Prop
1.569 6.742
1.233 12.770
3.161 17.776
EA
15.489
16.297
14.262
25.2
28.3
26.6
EXTRACT
Water 1-Prop
0.926 0.571
3.092 4.354
3.698 7.923
EA
23.703
20.854
14.879
21.1
29.8
21.7
EXTRACT
Water 1-Prop
1.051 0.354
1.472 6.066
2.232 6.793
EA
19.695
22.262
12.675
Table 5.2.11 10%NaCl(37ºC)
Water
15.0
14.0
12.0
7.0
1-Prop
6.2
23.7
31.5
26.4
EA
24.8
32.4
18.0
14.4
17.9
20.3
17.6
Table 5.2.12 15%NaCl(37ºC)
Water
14.0
13.0
12.0
7.0
1-Prop
7.3
19.5
36.5
29.5
EA
17.6
19.3
16.7
10.6
15.1
21.5
30.0
RAFFINATE
Water 1-Prop
12.431 0.558
11.767 6.730
8.839 18.723
Table 5.2.13 5%(NH4)2SO4 (27ºC)
RAFFINATE
Water 1-Prop EA
Water 1-Prop
16.0
1.0
27.1
18.9
15.074 0.429
15.0
10.6
28.0
25.3
11.908 6.246
12.0
22.0
23.0
30.5
8.302 14.077
8.0
19.0
16.8
Table 5.2.14 10% (NH4)2SO4 (27ºC)
RAFFINATE
Water 1-Prop EA
Water 1-Prop
15.0
0.9
24.4
19.2
13.949 0.546
14.0
11.3
28.5
24.0
12.528 5.234
12.0
19.1
18.9
28.3
9.768 12.307
8.0
18.7
13.9
58
EA
2.111
3.003
2.438
EA
3.397
7.146
8.121
EA
4.705
6.238
6.225
Table 5.2.15 15% (NH4)2SO4 (27ºC)
RAFFINATE
Water 1-Prop EA
Water 1-Prop
16.0
6.2
27.1
19.1
14.034 0.583
15.0
17.5
29.4
24.4
12.414 6.314
13.0
28.3
19.1
28.4
9.720 13.592
8.0
23.1
11.7
Table 5.2.16 5% (NH4)2SO4 (32ºC)
RAFFINATE
Water 1-Prop EA
Water 1-Prop
15.0
1.0
29.3
19.1
13.500 0.567
14.0
12.1
28.7
24.8
11.490 7.656
13.0
22.2
27.2
35.1
10.404 14.371
8.0
20.9
19.5
Table 5.2.17 10%(NH4)2SO4 (32ºC)
RAFFINATE
Water 1-Prop EA
Water 1-Prop
15.0
1.1
33.2
18.0
13.142 0.496
14.0
12.7
21.0
23.7
12.093 6.599
12.0
21.2
17.2
29.8
9.551 13.907
8.0
18.9
12.3
Table 5.2.18 15%(NH4)2SO4 (32ºC)
RAFFINATE
Water 1-Prop EA
Water 1-Prop
14.0
5.7
16.9
16.3
12.592 0.492
14.0
21.3
24.7
21.4
11.419 6.474
12.0
25.9
18.9
23.4
8.869 10.939
8.0
26.0
13.3
Table 5.2.19 5% (NH4)2SO4 (37ºC)
RAFFINATE
Water 1-Prop EA
Water 1-Prop
15.0
0.9
23.0
18.6
14.039 0.468
14.0
10.7
21.8
23.6
12.048 6.228
12.0
20.5
18.9
28.8
9.657 12.924
8.0
19.0
16.8
59
30.3
37.5
32.0
EXTRACT
Water 1-Prop
1.966 5.617
2.586 11.186
3.280 14.708
EA
22.617
23.728
14.012
EA
5.093 26.2
5.654 30.0
10.325 27.3
EXTRACT
Water 1-Prop
1.500 0.493
2.510 4.443
2.596 7.829
EA
24.207
23.046
16.875
EA
4.362
5.008
6.342
31.3
24.0
20.6
EXTRACT
Water 1-Prop
1.858 0.604
1.907 6.101
2.449 7.293
EA
28.838
15.992
10.858
20.3
38.6
33.4
EXTRACT
Water 1-Prop
1.408 5.208
2.581 14.826
3.131 14.961
EA
13.684
21.193
15.308
20.3
22.9
22.6
EXTRACT
Water 1-Prop
0.961 0.432
1.952 4.472
2.343 7.576
EA
18.907
16.476
12.681
EA
4.483
5.672
5.088
EA
3.216
3.507
3.592
EA
4.093
5.324
6.219
Table 5.2.20 10%(NH4)2SO4 (37ºC)
RAFFINATE
Water 1-Prop EA
Water 1-Prop
15.0
6.5
25.9
17.4
13.035 0.579
15.0
17.7
27.5
24.8
13.141 7.113
12.0
30.1
23.6
30.3
9.103 16.199
8.0
30.8
15.5
Table 5.2.21 15%(NH4)2SO4 (37ºC)
RAFFINATE
Water 1-Prop EA
Water 1-Prop
14.0
8.1
19.4
16.5
12.934 0.592
14.0
30.1
27.2
25.0
12.206 8.696
13.0
45.2
22.1
35.2
10.730 20.861
7.0
35.7
11.9
EA
3.786
4.546
4.998
EA
2.974
4.098
3.609
30.0
35.4
35.4
EXTRACT
Water 1-Prop
1.965 5.921
1.859 10.587
2.897 13.901
EA
22.114
22.954
18.602
25.0
46.3
45.1
EXTRACT
Water 1-Prop
1.066 7.508
1.794 21.404
2.270 24.339
EA
16.426
23.02
18.491
5.3 EQUILIBRIUM DATA
Table 5.3.1 No Salt (27ºC)
RAFFINATE
Water
1-Propanol
0.87
0.02
0.78
0.11
0.64
0.21
0.51
0.27
0.42
0.29
EthylAcetate
0.11
0.11
0.15
0.22
0.29
Table 5.3.2 5% NaCl (27ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.925
0.023
0.052
0.782
0.136
0.082
0.681
0.219
0.100
0.420
0.330
0.250
Water
0.21
0.22
0.28
0.32
EXTRACT
1-Propanol
0.01
0.14
0.24
0.28
Water
0.194
0.261
0.242
EXTRACT
1-Propanol
0.010
0.102
0.223
60
EthylAcetate
0.78
0.64
0.48
0.40
EthylAcetate
0.796
0.637
0.535
Table 5.3.3 10%NaCl (27ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.934
0.014
0.052
0.822
0.125
0.053
0.632
0.269
0.099
0.498
0.363
0.139
Table 5.3.4 15%NaCl (27ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.940
0.010
0.050
0.776
0.170
0.054
0.664
0.288
0.048
0.470
0.409
0.879
Table 5.3.5 No Salt (32ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.879
0.011
0.110
0.748
0.142
0.110
0.685
0.239
0.076
0.481
0.310
0.209
Table 5.3.6 5%NaCl (32ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.904
0.010
0.086
0.768
0.161
0.071
0.655
0.244
0.101
0.471
0.349
0.180
Table 5.3.7 10%NaCl (32ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.946
0.008
0.046
0.727
0.216
0.057
0.616
0.297
0.087
0.418
0.346
0.236
Water
0.269
0.197
0.221
EXTRACT
1-Propanol
0.309
0.168
0.016
EthylAcetate
0.422
0.635
0.763
Water
0.198
0.254
0.280
EXTRACT
1-Propanol
0.196
0.285
0.401
EthylAcetate
0.606
0.461
0.319
Water
0.200
0.292
0.245
EXTRACT
1-Propanol
0.018
0.234
0.283
EthylAcetate
0.782
0.474
0.472
Water
0.178
0.219
0.311
EXTRACT
1-Propanol
0.021
0.144
0.282
EthylAcetate
0.801
0.637
0.407
Water
0.092
0.329
0.316
EXTRACT
1-Propanol
0.023
0.158
0.340
EthylAcetate
0.885
0.513
0.344
61
Table 5.3.8 15%NaCl (32ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.942
0.017
0.041
0.817
0.142
0.041
0.644
0.301
0.055
0.551
0.410
0.039
Table 5.3.9 No Salt (37ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.839
0.013
0.148
0.765
0.146
0.089
0.646
0.249
0.105
0.499
0.329
0.172
Table 5.3.10 5% NaCl(37ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.895
0.012
0.093
0.786
0.137
0.077
0.635
0.293
0.072
0.510
0.359
0.131
Table 5.3.11 10%NaCl(37ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.941
0.022
0.037
0.785
0.165
0.050
0.572
0.357
0.071
0.380
0.430
0.190
Table 5.3.12 15%NaCl(37ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.948
0.013
0.039
0.811
0.139
0.050
0.587
0.374
0.039
0.380
0.480
0.140
Water
0.156
0.195
0.387
EXTRACT
1-Propanol
0.292
0.407
0.421
EthylAcetate
0.552
0.398
0.192
Water
0.314
0.313
0.372
EXTRACT
1-Propanol
0.016
0.167
0.294
EthylAcetate
0.670
0.520
0.334
Water
0.216
0.234
0.365
EXTRACT
1-Propanol
0.027
0.188
0.267
EthylAcetate
0.757
0.578
0.368
Water
0.076
0.231
0.348
EXTRACT
1-Propanol
0.201
0.312
0.375
EthylAcetate
0.723
0.457
0.277
Water
0.213
0.137
0.264
EXTRACT
1-Propanol
0.275
0.424
0.447
EthylAcetate
0.512
0.439
0.289
62
Table 5.3.13 5%(NH4)2SO4 (27ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.941
0.008
0.051
0.767
0.121
0.112
0.573
0.290
0.137
0.450
0.320
0.230
Table 5.3.14 10% (NH4)2SO4 (27ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.914
0.011
0.075
0.802
0.101
0.097
0.652
0.246
0.102
0.471
0.330
0.199
Table 5.3.15 15% (NH4)2SO4 (27ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.917
0.011
0.072
0.791
0.121
0.088
0.646
0.271
0.083
0.450
0.389
0.161
Table 5.3.16 5% (NH4)2SO4 (32ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.907
0.010
0.083
0.758
0.151
0.091
0.604
0.250
0.146
0.421
0.330
0.249
Table 5.3.17 10% (NH4)2SO4 (32ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.916
0.010
0.074
0.791
0.129
0.080
0.626
0.273
0.101
0.480
0.342
0.178
Water
0.135
0.327
0.381
EXTRACT
1-Propanol
0.025
0.138
0.245
EthylAcetate
0.840
0.535
0.374
Water
0.177
0.169
0.304
EXTRACT
1-Propanol
0.018
0.209
0.277
EthylAcetate
0.805
0.622
0.419
Water
0.215
0.221
0.295
EXTRACT
1-Propanol
0.184
0.286
0.397
EthylAcetate
0.601
0.493
0.308
Water
0.199
0.266
0.287
EXTRACT
1-Propanol
0.020
0.141
0.260
EthylAcetate
0.781
0.593
0.453
Water
0.205
0.250
0.336
EXTRACT
1-Propanol
0.020
0.240
0.301
EthylAcetate
0.775
0.510
0.363
63
Table 5.3.18 15% (NH4)2SO4 (32ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.931
0.011
0.058
0.803
0.137
0.060
0.681
0.252
0.067
0.420
0.409
0.171
Table 5.3.19 5% (NH4)2SO4 (37ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.925
0.009
0.066
0.792
0.123
0.085
0.642
0.257
0.101
0.450
0.320
0.230
Table 5.3.20 10% (NH4)2SO4 (37ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0.923
0.012
0.065
0.802
0.130
0.068
0.599
0.320
0.081
0.381
0.440
0.821
Table 5.3.21 15% (NH4)2SO4 (37ºC)
RAFFINATE
Water
1-Propanol EthylAcetate
0;935
0.013
0.052
0.809
0.173
0.018
0.601
0.350
0.049
0.339
0.520
0.141
Water
0.350
0.212
0.276
EXTRACT
1-Propanol
0.248
0.365
0.396
EthylAcetate
0.402
0.423
0.328
Water
0.169
0.267
0.304
EXTRACT
1-Propanol
0.023
0.184
0.295
EthylAcetate
0.808
0.549
0.401
Water
0.215
0.175
0.250
EXTRACT
1-Propanol
0.195
0.299
0.334
EthylAcetate
0.590
0.526
0.416
Water
0.146
0.130
0.161
EXTRACT
1-Propanol
0.308
0.464
0.519
EthylAcetate
0.546
0.406
0.320
64
Fig. 22 Solubility curve for no salt (27ºC)
Fig.23 Solubility curve for 5% NaCl (27ºC)
65
Fig.24 Solubility curve for 10%NaCl (27ºC)
Fig.25 Solubility curve for 15% NaCl (27ºC)
66
Fig.26 Solubility curve for no salt (32ºC)
Fig.27 Solubility curve for 5% salt (32ºC)
67
Fig.28 Solubility Curve for 10% NaCl (32ºC)
Fig.29 Solubility Curve for 15% NaCl (32ºC)
68
Fig.30 Solubility Curve for no salt (37ºC)
Fig. 31 Solubility Curve for 5% NaCl (37ºC)
69
Fig. 32 Solubility Curve for 10% NaCl (37ºC)
Fig. 33 Solubility Curve for 15% NaCl (37ºC)
70
Fig. 34 Solubility Curve for 5% (NH4)2SO4 (27ºC)
Fig. 35 Solubility Curve for 10%(NH4)2SO4 (27ºC)
71
Fig. 36 Solubility Curve for 15% (NH4)2SO4 (27ºC)
Fig. 37 Solubility Curve for 5% (NH4)2SO4 (32ºC)
72
Fig. 38 Solubility Curve for 10%(NH4)2SO4(32ºC)
Fig. 39 Solubility Curve for 15% (NH4)2SO4 (32ºC)
73
Fig. 40 Solubility Curve for 5% (NH4)2SO4 (37ºC)
Fig. 41 Solubility Curve for 10% (NH4)2SO4 (37ºC)
74
Fig. 42 Solubility Curve for 15% (NH4)2SO4 (37ºC)
75
Fig. 43 Solubility Curve at 27ºC
•
•
♦
No Salt
5% NaCl
10% NaCl
15% NaCl
76
Fig. 44 Solubility Curve at 32ºC
•
∇
♦
No Salt
5% NaCl
10% NaCl
15% NaCl
77
Fig. 45 Solubility Curve at 37ºC
•
∇
♦
No Salt
5% NaCl
10% NaCl
15% NaCl
78
Fig. 46 Solubility Curve at 27ºC
•
∇
♦
No Salt
5% (NH4)2SO4
10% (NH4)2SO4
15% (NH4)2SO4
79
Fig. 47 Solubility Curve at 32ºC
•
∇
♦
No Salt
5% (NH4)2SO4
10% (NH4)2SO4
15% (NH4)2SO4
80
Fig. 48 Solubility Curve at 37ºC
•
∇
♦
No Salt
5% (NH4)2SO4
10% (NH4)2SO4
15% (NH4)2SO4
81
6
5
Series1
4
Xcb
Series2
3
Series3
Series4
2
Series5
1
0
0
1
2
3
4
5
6
Xca
Fig.49 Distribution Curve at 27ºC
Series2-----No Salt(27°C)
Series3-----5% NaCl (27°C)
Series4-----10% NaCl (27°C)
Series5-----15% NaCl (27°C)
6
5
Xcb
4
Series1
Series2
3
Series3
Series4
2
1
0
0
1
2
3
4
5
6
Xca
Fig.50 Distribution Curve at 32ºC
Series2-----No Salt(32°C)
Series3-----5% NaCl (32°C)
Series4-----10% NaCl (32°C)
Series5-----15% NaCl (32°C)
82
7
Xcb
6
5
Series1
4
Series2
Series3
3
Series4
Series5
2
1
0
0
2
4
6
8
Xca
Fig.51 Distribution Curve at 37ºC
Series2-----No Salt(37°C)
Series3-----5% NaCl (37°C)
Series4-----10% NaCl (37°C)
Series5-----15% NaCl (37°C)
6
5
Series1
4
Xcb
Series2
3
Series3
Series4
2
Series5
1
0
0
1
2
3
4
5
6
Xca
Fig.52 Distribution Curve at 27ºC
Series2-----No Salt(27°C)
Series3-----5% (NH4)2SO4 (27°C)
Series4-----10% (NH4)2SO4 (27°C)
Series5-----15% (NH4)2SO4 (27°C)
83
6
5
Series1
Series2
Series3
Series4
Xcb
4
3
2
1
0
0
2
4
6
Xca
Fig.53 Distribution Curve at 32ºC
Xcb
Series2-----No Salt(32°C)
Series3-----5% (NH4)2SO4 (32°C)
Series4-----10% (NH4)2SO4 (32°C)
Series5-----15% (NH4)2SO4 (32°C)
8
7
6
5
4
3
2
1
0
Series1
Series2
Series3
Series4
Series5
0
2
4
6
8
Xca
Fig.54 Distribution Curve at 37ºC
Series2-----No Salt(37°C)
Series3-----5% (NH4)2SO4 (37°C)
Series4-----10% (NH4)2SO4 (37°C)
Series5-----15% (NH4)2SO4 (37°C)
84
5.4 RESULTS AND DISCUSSION
The Liquid-liquid equilibrium for ternary system was studied at atmospheric pressure and
temperature of 27ºC, 32ºC and 37ºC. The ternary solubility data and the tie-line data for no salt,
NaCl and (NH4)2SO4 at 5%, 10% and 15% concentrations for the system Water + 1-propanol +
Ethyl Acetate were determined at the above temperatures. It can be seen from the diagrams that
the addition of the salts shifts the distribution in favour of ethyl acetate layer especially at higher
salt concentrations. The presence of the salt decreases the solubility of the system increasing the
heterogeneous zone. Heterogeneous area is an important characteristic. In the present system, the
areas of the solubility curves are more in case of salt addition than that of without salt. At
increasing salt concentrations more 1-propanol is transferred to the ethyl acetate phase. This
process is usually referred to as salting out and is caused by the fact that the presence of high
amounts of hydrated ions reduces the availability of the water molecules in the aqueous phase to
the salvation of other solvents. Presence of salts mainly increase the concentrations of 1-propanol
in organic phase and hence enlargement of the two-phase region occurred. These effects increase
with salt concentrations and are maximum at salt saturation.
From the solubility curve at 27ºC for 5%, 10%, 15% concentrations of NaCl, it is found that the
heterogeneous area is more for the 10% NaCl and the saturation level is obtained. Similarly
considering the solubility curve at 32ºC for 5%, 10%, 15% concentration of NaCl it is found that
10% concentration of NaCl is quite effective in extracting 1-propanol from aqueous phase to
organic phase. Though at 5% concentration of NaCl at 37ºC is also effective but it is less than
10% concentration of NaCl. Thus using the salt NaCl it is found that at 10% concentration of
NaCl the maximum shifting of 1-propanol from aqueous phase to organic phase takes place.
From the solubility curve at 27ºC for 5%, 10%, 15% concentrations of (NH4)2SO4, it is found
that the heterogeneous area is more for the 10% (NH4)2SO4 and the saturation level is obtained.
Similarly considering the solubility curve at 32ºC for 5%, 10%, 15% concentration of (NH4)2SO4
it is found that 10% concentration of (NH4)2SO4 is quite effective in extracting 1-propanol from
aqueous phase to organic phase. Though at 5% concentration of (NH4)2SO4 at 37ºC is also
effective but it is less than 10% concentration of (NH4)2SO4. Thus using the salt (NH4)2SO4 it is
found that at 10% concentration of (NH4)2SO4 the maximum shifting of 1-propanol from
aqueous phase to organic phase takes place.
85
CHAPTER-6
CONCLUSION
86
6.1 CONCLUSION
The equilibrium diagram for ternary system Water + 1-Propanol + Ethyl acetate was determined
at 27ºC, 32ºC and 37ºC. The effect of addition of salts like NaCl and (NH4)2SO4 to the ternary
system at different concentrations were studied at all these temperatures. The solubility data are
tabulated in Table 5.1 and the equilibrium data are tabulated in Table 5.2. Considering these data
the solubility curves and the distribution curves were plotted. All salt containing data are
reported on salt free basis. The experimental tie-line data under no salt condition were
determined and presented in respective tables. The experimental results lead to the conclusion
that a salting out effect exists for all salts under study, increasing for higher salt concentrations.
In conclusion it may be mentioned that concerted efforts on the investigations of the salt effect
on the distribution of a solute between two partially miscible liquids have a potential scope for
engineering applications.
The advantage of using solid inorganic salt in place of liquid separating agent in extraction
processes is that by use of a small amount of solid salt bring about a substantial change in phase
equilibrium in ternary liquid system. This fact is observed in case of ternary system under
investigation. Thus it is concluded that this technique can be used effectively for extraction using
a suitable solid salts.
6.2 FUTURE SCOPE OF WORK
These experimental data obtained further can be correlated with the different thermodynamic
models like UNIQUAC (Universal quasi-chemical model), UNIFAC group contribution model,
NRTL model etc. By correlating with these thermodynamic models the accuracy of the
experimental data can be calculated.
87
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