ABSTRACT
The extraction of Cobalt (II) ions from various buffered aqueous solutions was studied using chloroform solutions of 4-Propionyl-2, 4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one (HPrP) Schiff base. The complexing agent and concentration effect of 4-propionyl-2, 4-dihydro5-methyl-2-phenyl-3H-pyrazol-3-one (HPrP) in these extractions were also studied and optimized. The effects of certain mineral acids were examined alongside metal ions under a suitable extraction condition. From the mineral acids studied, cobalt didn’t form non extractable complex. Increase in pH above 10.0 resulted to a decrease in cobalt extraction. Increase in the concentration of various acids above 2.0 pushed the percentage extraction to zero (0).
TABLE OF CONTENTS
Page
Cover
page i
Title
page ii
Declaration
iii
Certification
iv
Dedication v
Acknowledgments vi
Table
of contents vii
List
of Tables ix
List
of Figures x
Abstracts
xi
CHAPTER 1: Introduction 1
1.1 Statement of
Problems 5
1.2 Objectives of
the Study 6
1.3 Justification
of the Study 6
1.4 Scope of the
Study 7
CHAPTER
2: Literature Review 8
2.1.1
Sources of Cobalt 8
2.1.2 Compounds of
Cobalt 9
2.2 Origins and use of Heavy
Metals 9
2.3 Factors
Affecting Liquid-Liquid Extraction of Metal Ions 10
2.4 Buffer 14
2.4.1 Types of buffer solution 15
2.4.2 Mechanism of buffering action 16
2.4.3
Preparation of buffer solution 16
2.4.4
Preparation of acid buffer 18
2.5
Schiff Base 19
2.5.1 Synthesis of schiff base 19
2.5.2 Application of schiff base 20
CHAPTER 3: Material and Methods 27
3.1
Materials and Apparatus 27
3.2.
Methods 29
3.2.1
Synthesis of 4-propionyl-2,4-dihydro-5-methyl-2-phenyl-
3h-pyrazol-3-one (HprP) 29
3.2.3 Preparation of stock solutions of ligand. 31
3.2.4 Preparation of stock solutions of mineral
acids 31
3.2.5 Preparation of stock solutions of salts and
base 31
3.2.6 Preparation of buffer solutions for
calibration of pH meter 32
3.2.7 Preparation of buffer solutions 33
3.2.8 Preparation of metal stock solutions 34
3.2.9 Preparation
of stock solutions for anions and complexing agents 34
3.2.10
Extraction of metal ions from aqueous phase at different pH values 34
3.2.11
Extractions with various metal concentrations with ligand 35
3.2.12 Extractions with various ligand
concentrations 35
3.2.13 Extraction in the presence of some
mineral acids 36
3.2.14 Extraction in the presence of some anions 36
3.2.15 Extractions with various metal concentrations
with ligand only 36
CHAPTER 4: Result and
Discussion 37
CHAPTER 5:
Conclusion 43
5.2 Recommendation 43
Reference 44
LIST
OF TABLES
Standard
for cobalt (II) calibration curve 37
Data
for 50mg/L Co (II) in buffered solution into 0.05M HPrP 38
Data
for Effect of H3PO4 in Co (II) Extractions with HPrP 39
Data
for Effect of H2SO4 in Co (II) Extractions with HPrP 40
Data
for effect of NO3- in Co (II) extraction with (HPrP) 41
Data
for effect of PO42- in Co (II) extraction with (HPrP) 42
LIST OF FIGURES
Standard for Cobalt (II) Calibration curve 37
Effect of pH on extraction of Co (II) ions into
0.05M HPrP in chloroform solution 38
Effect
of H3PO4 in Co (II) extraction with (HPrP) 39
Effect
of H2SO4 in Co (II) Extractions with HPrP 40
Effect
of NO3- in Co (II) extraction with (HPrP) 41
Effects
of PO42- in Co (II) extraction with HPrP 42
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Liquid–liquid extraction (LLE),
also known as solvent extraction and partitioning, is a method to separate
compounds or metal complexes, based on their relative solubility in two different
immiscible liquids, usually water (polar) and an organic solvent (non-polar).
There is a net transfer of one or more species from one liquid into another
liquid phase, generally from aqueous to organic. The transfer is driven by
chemical potential, i.e. once the transfer is complete, the overall system of
chemical components that make up the solutes and the solvents are in a more
stable configuration (lower free energy) (Reyes-Labarta & Grossmann, 2015). The solvent that is
enriched in solute(s) is called extract. The feed solution that is depleted in
solute(s) is called the raffinate. LLE is a basic
technique in chemical laboratories, where it is performed using a variety of
apparatus, from separatory funnels to countercurrent
distribution equipment called as mixer
settlers. This type of process is commonly performed after a chemical
reaction as part of the work-up,
often including an acidic work-up (Reyes-Labarta
et al., 2013).
Solvent extraction is an
old, established process and together with distillation constitute the two most
important industrial separation procedures. The first commercially-successful
liquid-liquid extraction operation was developed for the petroleum industry in
1909 when Edeleanu’s process was employed for the removal of aromatic
hydrocarbons from kerosene, using liquid sulfur dioxide as solvent. Since then
many other processes have been developed by the petroleum, chemical,
metallurgical, nuclear, pharmaceutical and food processing industries (Mackenzie & Murdoch 2012).
From a hydrometallurgical perspective,
solvent extraction is exclusively used in separation and purification of
uranium and plutonium, zirconium and hafnium, separation of cobalt and nickel,
separation and purification of rare earth elements etc., its greatest advantage
being its ability to selectively separate out even very similar metals.
One
obtains high-purity single metal streams on 'stripping' out the metal value
from the 'loaded' organic wherein one can precipitate or deposit the metal
value. Stripping is the opposite of extraction: Transfer of mass from organic
to aqueous phase (Marcilla et al., 2011)
The term partittioning is
commonly used to refer to the underlying chemical and physical processes
involved in liquid-liquid
extractuion, but on another reading may be fully synonymous with it. The
term solvent extraction can
also refer to the separation of a substance from a mixture by preferentially
dissolving that substance in a suitable solvent. In that case, a soluble
compound is separated from an insoluble compound or a complex matrix (Reyes-Labarta, et al., 2012).
Whereas distillation
affects a separation by utilizing the differing volatilities of the components
of a mixture, liquid-liquid extraction makes use of the different extent to which
the components can partition into a second immiscible solvent. This property is
frequently characteristic of the chemical type so that entire classes of
compounds may be extracted if desired. The petroleum industry takes advantage
of this characteristic of the process and has used extraction to separate, for
example, aromatic hydrocarbons from paraffin hydrocarbons of the same boiling
range using solvents such as liquified sulfur dioxide, furfural and diethylene
glycol (Filiz et al., 2014).
In general, extraction is applied when the materials to be extracted are
heat-sensitive or nonvolatile and when distillation would be inappropriate
because components are close-boiling, have poor relative volatilities or form
azeotropes (Sanchez et al., 2012).
The simplest extraction
operation is single-contact batch extraction in which the initial feed solution
is agitated with a suitable solvent, allowed to separate into two phases after
which the solvent containing the extracted solute is decanted. This is analagous
to the laboratory procedure employing a separating funnel. On an industrial
scale, the extraction operation more usually involves more than one extraction
stage and is normally carried out on a continuous basis. The equipment may be
comprised of either discrete mixers or settlers or some form of column
contactor in which the feed and solvent phases flow counter currently by virtue
of the density difference between the phases (Lee, 2014)
Although heavy metals are naturally occurring elements that are
found throughout the earth’s
crust, most environmental contamination and
human exposure result
from anthropogenic activities
such as mining and smelting operations, industrial production and
use, and
domestic and agricultural
use of metals and metal-containing compounds (Sanchez et al.,
2003). Environmental contamination can
also occur through
metal corrosion, atmospheric deposition, soil erosion of
metal ions and leaching of heavy metals, sediment re-suspension and metal
evaporation from water resources to soil and ground water. Natural phenomena
such as weathering and volcanic eruptions have also been reported to
significantly contribute to heavy metal pollution (Giridhar
et al., 2016).
Some solutes such as noble gases can be extracted
from one phase to another without the need for a chemical reaction (see absorption).
This is the simplest type of solvent extraction. When a solvent is extracted,
two immiscible liquids are shaken together (Takeshitaet et al., 2018). The more polar solutes dissolve preferentially in
the more polar solvent, and the less polar solutes in the less polar solvent.
Some solutes that do not at first sight appear to undergo a reaction during the
extraction process do not have distribution ratio that is independent of
concentration. A classic example is the extraction of carboxylic acids (HA) into nonpolar media such as benzene. Here, it is often the
case that the carboxylic acid will form a dimer in the organic layer so the
distribution ratio will change as a function of the acid concentration
(measured in either phase).
Using solvent extraction it is possible to extract uranium, plutonium, thorium and many rare earth
elements from acid solutions in a selective way by using the right choice of
organic extracting solvent and diluent. One solvent used for this purpose is
the organophosphate tributylphosphate (TBP).
The PUREX process
that is commonly used in nuclear reprocessing uses
a mixture of tri-n-butyl phosphate and an inert hydrocarbon (kerosene), the uranium(VI) are
extracted from strong nitric acid and are
back-extracted (stripped) using weak nitric acid. An organic soluble
uranium complex [UO2(TBP)2(NO3)2]
is formed, then the organic layer bearing the uranium is brought into contact
with a dilute nitric
acid solution; the equilibrium is shifted away from the organic soluble uranium
complex and towards the free TBP and uranyl nitrate in dilute
nitric acid. The plutonium (IV) forms a similar complex to the uranium VI), but
it is possible to strip the plutonium in more than one way; a reducing agent that
converts the plutonium to the trivalent oxidation state can be added
(Alloway, 2016). This oxidation state does not form a stable complex with TBP
and nitrate unless
the nitrate concentration is very high (circa 10 mol/L nitrate is required
in the aqueous phase). Another method is to simply use dilute nitric acid as a
stripping agent for the plutonium. This PUREX chemistry is a classic example of
a solvation extraction.
Liquid-liquid (or solvent) extraction is a countercurrent separation process for isolating
the constituents of a liquid mixture. In its simplest form, this involves the
extraction of a solute from a binary solution by bringing it into contact with
a second immiscible solvent in which the solute is soluble. In practical terms,
however, many solutes may be present in the iCotial solution and die extracting
‘solvent’ may be a mixture of solvents designed to be selective for one or more
solutes, depending upon their chemical type (Adamo et al., 2013).
Liquid–liquid extraction is possible in non-aqueous systems: In a system
consisting of a molten metal in contact with molten salts, metals can be
extracted from one phase to the other. This is related to a mercury electrode where a metal can
be reduced, the metal will often then dissolve in the mercury to form an amalgam that
modifies its electrochemistry greatly. For example, it is possible for sodium cations to be reduced at a
mercury cathode to
form sodium amalgam,
while at an inert electrode (such as platinum) the sodium cations are not
reduced. Instead, water is reduced to hydrogen. A detergent or fine solid can be used to
stabilize an emulsion,
or third phase (Marcilla et al., 2017).
The
use of new Schiff bases
in liquid-liquid extraction of metals is one area which has generated lots of
interesting and positive research results in the past couple of years.
Pyrazolone is 5-membered
heterocycle containing two adjacent Nitrogen atoms. It can be viewed as a
derivative of pyrazole possessing an additional carbonyl (C=O) group. Compounds
containing this functional group are useful commercially in analgesics and dyes
Pyrazolones are
prominent analytical reagents, potent drugs or pharmaceutical agents,
inhibitors of emzymes and intermediates in the biosynthesis of Nitrogen oxides.
In continuation of our work on the synthesis, characterization of
1-phenyl-3-methyl-4-acylpyrazolone-5 derivatives and their application in the
extraction of transition metal ion such as Co(II) we are reporting the use of
the Schiff base
N,N’-ethylenbis(4-propionyl-2,4-dihydro-5methyl-2-phenyl-3H-pyrazol-3-oneimine)
as a potential extractant for Cobalt (II) ions. In studying the solvent
extraction of Cobalt (II) ions from aqueous media using N, N’-ethylenbis
(4-propionyl-2, 4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-oneimine)
4-propionyl-2, 4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one (HPrP).
1.1
STATEMENT OF PROBLEMS
One of the problems in liquid-liquid metal extract is devising an
extraction procedure that would be allowed to perform bulk separation of
different metals ions. Distribution coefficient represents the equilibrium constant for this
process. If the main goal is to extract a solute from the aqueous phase into
the organic phase, the problem relates to the relative volumes of the phases
which is another problem in liquid liquid extraction. One major problem is that an aqueous sample contains a
complex mixture of organic compounds, all of which are at trace concentrations.
1.2 OBJECTIVES OF THE
STUDY
The main objective
of this study focus on liquid-liquid extraction of heavy metal ions and
complexation of ligands. While the specific objectives are to;
i.
To determine the effect
of the complexing agent
ii.
To determine the effect
of concentration
iii.
To determine the mineral
acids of H3PO4 and H2SO4 on the
extraction of Cobalt (II)
iv.
To determine the effect
of Nitrate ion and Phosphate ion on the extraction of Cobalt (II)
1.3
JUSTIFICATION OF THE STUDY
Liquid-liquid extraction should
be considered as a desirable route for product recovery and purification along
with fractional crystallization and distillation (Feng et al., 2020). The ability to make separations according to
chemical type, rather than according to physical properties such as freezing
point or vapor pressure, is one of extraction’s major attractions. The liquid–liquid extraction process offers
several advantages such
as high capacity of the extractant and high selectivity of separation. Liquid–liquid extraction was successfully used for the recovery of
2, 3-butanediol during fermentation (Birajdar et al., 2015). Liquid-liquid
extraction can be envisaged to play a central role in the future of
the hydrometallurgical exploitation of low-grade ores, the reclamation of scrap
metal, the processing of industrial waste products, and the elimination of
environmental pollution, specifically the removal of heavy
metal ions from muCocipal and industrial
wastewater. Energy frequently can be saved in the recovery of valuable products
from dilute broth solution since a small quantity of a selective solvent can be
used, and recovery from the concentrated extract is then facilitated. Selectivity of potentially attractive solvents
can frequently be determined from simple shake-outs over the desired
concentration range. From these distribution data, the combinations of amount
of solvent and number of theoretical stages can be calculated (Cocola et al., 2020). Today
there exist only a few commercial metal ion specific reagents suitable for
liquid-liquid extraction.
1.4
SCOPE OF THE STUDY
The study is limited
to extraction of inorganic metals from synthesized ligands and the effect of
concentration and complexing agent.
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