INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 87
Copper (II) Distributions Between Buffered Aqueous Phases and
Organic Phases of 4, 4´-(1E,1E´)-1,1´-(Ethane-1,2-Diylbis (Azan-1-
Yl-1ylidene) Bis (5-Methyl-2-Phenyl-2,3-Dihydro-1h-Pyrazol-3-Ol)
(H
2
BuEtP) in Chloroform
Oguarabau Benson, Jackson Godwin*, Shalom Udochukwu Okanezi and Elijah Ayibamiesintei Napoleon
Department of Chemical Sciences, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria
*Corresponding Author
DOI : https://doi.org/10.51583/IJLTEMAS.2025.14020010
Received: 18 February 2025; Accepted: 22 February 2025; Published: 10 March 2025
Abstract: The distribution of Cu
2+
between buffered aqueous phases and chloroform solutions of 4,4´-(1E,1E´)-1,1´-(ethane-1,2-
diylbis(azan-1-yl1ylidene))bis(5-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-3-ol) (H
2
BuEtP) alone and in the presence of 1-(3-
hydroxy-5-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl) butan-1-one(HBuP) was investigated using solvent-solvent extraction.
200 mgL
-1
Cu
2+
was used for the study with an equilibration time of 60 minutes. Concentration of Cu
2+
in aqueous phases after
equilibration was determined with AAS and calculated by difference between Copper concentration in the aqueous phases and the
organic phases, and distribution ratios(D) and percentage extractions(%E) were determined. Slope analysis from plots of log D
against buffers pHs, ligands concentrations and metal concentrations were used to propose distribution reaction equations and
extracted Cu
2+
complexes as Cu(HBuEtP.X)
(o)
for ligand alone and Cu(HBuEtP.BuP)
(o)
in the presence of HBuP. The extraction
constant log K
ex
, obtained for H
2
BuEtP (-5.11±0.7) was greater than that for H
2
BuEtP/HBuP (-12.94±1.26) which indicated
HBuP did not exert any synergic effects in the distribution of Cu
2+
, even though partition coefficient log D for H
2
BuEtP/HBuP of
2.03 ± 0.81 was > 0.97 ± 0.62 for H
2
BuEtP. Comparing results with those of other studies, showed carbon chain length of
structurally related ligands effects on metal ions distribution is dependent on the particular metal ion. The ligand H
2
BuEtP was a
better extractant for Cu
2+
than Ni
2+
and Fe
2+
only as the results for Pb
2+
, UO
2+
and Cd
2+
were better based on log K
ex
values.
Keywords: Distribution, ligands, buffers, extraction constant and partition coefficient
I. Introduction
Heavy metals pollution and efficient remediation methods have been of serious concern to researchers for many decades. One
method that has shown to be very efficient in extraction of heavy metals from contaminated soils and industrial effluents is the
use of ligands in solvent-solvent extraction (Huang and Keller, 2020: Yu Zhou et al., 2024: Ugwu and Conradie, 2024). The use
of ligands in this extraction studies has been reported to lead to the formation of interesting metal complexes with important
applications in medicine (Kostova and Saso, 2013: Habala and Valentova, 2020: Paderni et al., 2025), agriculture (Dawara et al.,
2011: Jimenez-Falcao and Mendez-Arriaga, 2024) and other industrial uses (Kalyanasundaram and Gra Ètzel 1998: Yu et al.,
2020). Conditions such as optimum pH and oxidation states of the metals from these extraction studies have been used as the
basis for the synthesis of these important metal complexes (Shimazaki, 2013: Rahman, 2024: Rahmati et al., 2024). Recent
studies show that Schiff bases, a class of ligands containing a C=N bond, are excellent metal extractants. 1-Phenyl-3-methyl-4-
acyl-pyrazolone-5 derivatives, such as H
2
BuEtP, have been reported to effectively extract Pb(II), U(VI), Ni(II), Fe(II), Cu(II),
Cd(II), and Zn(II). Similarly, H
2
PrEtP has demonstrated strong extraction properties for U(VI) and Cu(II). In these studies, it is
necessary to determine the equilibration time, the range of pH of quantitative distribution of the metal ions between the two
phases, the pH
1/2
which is the pH at which there is 50% extraction of the metals into the organic phases and the optimum pHs of
distribution of the metal. Slope analysis from plots of log D against pH, log D and log ligand concentrations and log D against
metal concentrations are used to construct reaction equations for the processes from which the structures of the metal complexes
and metal adducts can be proposed. The plots are also used to determine extraction parameters such as log D for the distribution
of the metal between the buffered aqueous phases and the organic phases containing the ligands. Log K
ex
values can be used to
compare the efficiency of ligand/s systems as extractant for a particular metal or different metals as higher values indicate a better
extractant system or conditions. The stabilities of the extracted complexes or adducts can be determined by log K
ex
values that can
be calculated from plots. A higher value of log K
ex
indicates higher stability and formation constant of that complex compared to
one with lower log K
ex
(Uzoukwu, 2009: Muthaiah et al., 2020). In all these studies with 4,4´-(1E,1E´)-1,1´-(ethane-1,2-
diylbis(azan-1-yl1ylidene))bis(5-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-3-ol)(H
2
BuEtP) and N,N`-ethylenebis(4-propionyl-
2,4-dihydro-5methyl-2-phenyl-3H-pyrazol-3-oneimine)(H
2
PrEtP), these extraction parameters pH
1/2,
log D and log K
ex
are well
reported (Godwin and Uzoukwu, 2012a: Godwin et al., 2012: Godwin and Uzoukwu, 2012b: Chukwu and Godwin, 2013:
Godwin et al., 2013: Nwadiri et al., 2016: Godwin and Tella, 2023: Godwin et al., 2024).
Copper, specifically, is vital for modern society, being the third most important metal after iron and aluminium (Sverdrup et al.,
2014). Despite its essential role in technology and infrastructure, the unchecked release of copper into the environment is
problematic. In 2020, global production of copper reached 21 million tonnes, reflecting a 1.9% rise from the previous year,
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 88
though still falling short of projected growth as a result of the COVID-19 pandemic (Mining, 2020). As industrial activities
continue to surge, the release of heavy metals such as copper into the environment often exceeds natural purification capacities,
highlighting the urgent need for improved management and remediation strategies. This has necessitated numerous researches in
the extraction of copper from industrial effluents and soils (Di Palma and Medici, 2002 : Aslam et al, 2004 : Al-Saydeh et al.,
2017 : Napoli et al., 2019).
Nwadire et al. (2016) studied the distribution of Cu(II) ions between buffered aqueous solutions and chloroform solutions of
H
2
PrEtP, both alone and with HPrP. Their findings indicate that the Schiff base effectively extracted Cu(II), with HPrP exhibiting
synergic effects by improving the partition coefficient log D. This study is aimed at evaluating the distribution of Cu(II) between
aqueous solutions and chloroform solutions of 4,4´-(1E,1E´)-1,1´-(ethane-1,2-diylbis(azan-1-yl1ylidene))bis(5-methyl-2-phenyl-
2,3-dihydro-1H-pyrazol-3-ol)(H
2
BuEtP) alone and in the presence 1-(3-hydroxy-5-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-4-
yl) butan-1-one(HBuP). The objectives of this study are; to determine the optimum pH/s for quantitative distribution of Cu(II) to
the organic extractant phases, the pH
1/2
for both organic phases, to determine and compare the extraction parameters log D
(partition coefficients) and log K
ex
(formation constants) for the both organic extractant phases, propose the reaction equations,
structures of the extracted copper complexes using slope analysis, and also determine the effect of carbon chain length of the 1-
Phenyl-3-methyl-4-acyl-pyrazolone-5 derivatives on the distribution of metals.
Experimental
All chemicals used for this study were of analytical grade and supplied by Sigma and Aldrich. The ligand 1-(3-hydroxy-5-methyl-
2-phenyl-2,3-dihydro-1H-pyrazol-4-yl) butan-1-one (HBuP) was synthesized using 5.2 ml of butanoyl chloride
(CH
3
CH
2
CH
2
COCl) introduced into a 25 ml quick-fit dropping funnel. 8.5 g of 1-phenyl-3-methyl-pyrazolone-5 was dissolved in
80 ml of 1,4-dioxane in a 3-necked quick-fit flask carrying a condenser with warming and stirring on a hot plot. When the
pyrazolone-5 was completely dissolved the solution was brought down and cooled to room temperature under tap water, before
10 g of calcium hydroxide was added with stirring to get a suspension of the pyrazolone-5. No heat was applied during drop wise
addition of the acyl chloride from the dropping funnel within a space of 5 minutes with stirring. The reaction is an exothermic
reaction. The reaction between acyl chloride and pyrazolone-5 is in the mole ratio of 1:1 as shown in Figure 1A. Stirring of the
hot reaction mixture was continued for another 40 minutes without heating. At the end of which the reaction mixture was poured
into a chilled 400 ml of 3 M HCl with stirring to decompose the calcium product. This product was stored in a freezer until the 4-
butanoyl-pyrazolone-5 product crystallized. This was filtered and recrystallized from aqueous ethanol to get pure bone white
crystals of HBuP. 10 g of the synthesized HBuP was dissolved in 60 ml of ethanol with stirring in a 250 mL beaker on a hot plate.
1.5 ml of ethylenediamine was introduced into a 25 mL dropping funnel.
The temperature of the ethanol solution obtained above was maintained at about 60
o
C while ethylenediamine was added drop-
wise to the solution of HBuP within a space of 5 minutes with stirring. The reaction between ethylenediamine and HBuP is in the
mole ratio of 1:2 shown in Figure 1B: Stirring was continued for another 30 minutes. At the end the reaction mixture was filtered
and recrystallized from aqueous ethanol to get pure white crystals of the Schiff base H
2
BuEtP with analytical data determined at
the Institut fur Anorganische Chemie, Technische Universitat Dresden, Germany. 70% yield, melting point 235
0
C with molecule
formula C
30
H
36
O
2
N
6
. Slightly soluble in ethanol, methanol, acetone, CH
2
Cl
2
, benzene and very soluble in CHCl
3
[Uzoukwu, et
al., 1998].
The working concentration of Cu (II) in aqueous solutions was 200 mgL
-1
, obtained by taking 0.2 mL from a 2000 mgL-1 stock
solution of copper. This stock solution was prepared by dissolving an appropriate amount of copper(II) sulfate pentahydrate in
distilled water, followed by the addition of 0.2 mL of 2 M HNO
3
to prevent copper hydrolysis. The 2 sets of labelled thirty-one 5
mL extraction bottles containing 0.2 mL Cu(II) solution was made up to 2 mL mark by the addition of 1.8 mL buffers ranging
from pH 1.5 to 9.0. To one set was added 2 mL of chloroform solution of 0.05 M H
2
BuEtP and to the other set of thirty-one
bottles were added 2 mL of chloroform solution of 0.05 M H
2
BuEtP and 0.05 M HBuP in 9:1 volume ratio. The sixty-two bottles
containing the two immiscible phases were agitated with a mechanical shaker for 60 minutes. The 60 minutes in related studies
with same organic ligand phase for the extraction of other metals gave the best time for equilibration to occur (Godwin and
Uzoukwu, 2012a: Godwin et al., 2012: Godwin and Uzoukwu, 2012b: Chukwu and Godwin, 2013: Godwin et al., 2013: Nwadiri
et al., 2016: Godwin and Tella, 2023: Godwin et al., 2024).
The phases were allowed to separate out and 1 mL of aqueous raffinates were then taken with a micropipette and analysed for
copper by difference, using Atomic Absorption Spectrophotometry (AAS) at wavelength of 324.8 nm (Porento et al., 2011).
Absorbance results were used to calculate extraction parameters, Distribution Ratios (D) and Percentage Extraction (%E) using
equations 1 and 2.
D = ---------1
% E = ---------2
The log D is plotted against pH for both organic phases and from these plots the optimum pH/s for the distribution of Cu(II) ions
between the two phases was determined. The two optimum pHs 6.0 and 8.75 were used in the variation of the ligand
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 89
concentration (2.50 × 10
-3
M to 4.00 × 10
-2
M). These pHs were used for the metal distributions at a fixed synergist HBuP
concentration of 5.00 × 10
-3
M while the concentration of ligand H
2
BuEtP varied between 2.50 × 10⁻³ M and 4.00 × 10⁻² M.
Similarly, metal distribution was analyzed with a fixed ligand concentration of 2.50 × 10⁻² M, while the synergist HBuP
concentration was adjusted from 2.50 × 10⁻³ M to 2.25 × 10⁻² M. The Cu(II) concentrations were varied from 100 mgL
-1
to 140
mgL
-1
in the ligand H
2
BuEtP alone and in the presence of HBuP in a 9:1 volume ratio solution and the process was repeated as
earlier described.
Figure 1: Synthetic route for (A) 1-(3-hydroxy-5-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl) butan-1-one (HBuP) and (B)
4,4´-(1E,1E´)-1,1´-(ethane-1,2-diylbis(azan-1-yl1ylidene)) bis (5-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-3-ol) (H
2
BuEtP)
II. Results and Discussion
Figure 2: Plot of log D against pH in the Distribution of 200 mgL
-1
Cu(II) between buffered aqueous phases and chloroform
solutions of 0.05 M H
2
BuEtP
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 90
Figure 3: Plot of log D against pH in the Distribution of 200 mgL
-1
Cu (II) between buffered aqueous phases and chloroform
solutions of 0.05 M H
2
BuEtP/0.05 M HBuP in a 9:1 volume ratio
Figure 4: Plots of log D against log [H
2
BuEtP] in Cu(II) distributions from aqueous solutions
buffered at (a) pH 6.0 and (b) pH 8.75 into chloroform solutions of varied ligand [H
2
BuEtP]
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 91
Figure 5: Plots of log D against log [Cu] from aqueous solutions buffered at (a) pH 6.0 and (b) pH 8.75 into chloroform solution
of ligand [H
2
BuEtP]
Figure 6: Plots of log D against log[H
2
BuEtP] for the extraction of 200 mgL
-1
Cu (II) from aqueous solutions into H
2
BuEtP/HBuP
solutions in chloroform with H
2
BuEtP varied from 2.50 × 10
-3
to 4.00 × 10
-2
M and HBuP kept constant at 5.00 × 10
-3
M in (a)
pH 6.0 and (b) 8.75
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 92
Figure 7: Plots of log D against log [HBuP] for the extraction of 200 mgL
-1
Cu(II) from aqueous solutions into H
2
BuEtP/HBuP
solutions in chloroform with HBuP varied from 2.50 × 10
-3
to 2.25 × 10
-2
M and H
2
BuEtP kept constant at 2.50 × 10
-3
M in (a)
pH 6.0 and (b) 8.75.
Figure 8: Plots of log D against log [Cu] for the extraction of Cu (II) from aqueous solutions into chloroform solutions of 0.05
M H
2
BuEtP /0.05 M HBuP in 9:1 volume ratio at (a) pH 6.0 and (b) pH 8.75.
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 93
Distribution with Ligand H
2
BuEtP alone
Plots of log D against pH for the extraction of 200 mgL
-1
Cu(II) from buffered aqueous phases using ligand H
2
BuEtP as shown in
Table 1 and Figure 2, gave a slope of 0.82 which can be approximated to 1 and indicates that only 1 proton from the ligand
H
2
BuEtP was displaced in the reaction with Cu(II). The expected reaction of Cu(II) with the ligand H
2
BuEtP is shown in equation
3 with displacement of 2 protons.
where H
2
BuEtP is the tetradentate Schiff base with the assumption that the metal : ligand interaction is in the 1:1 mole ratio.
K
ex
=
]][[[
]][)([
)(2
2
2
)(
o
o
BuEtPHCu
HBuEtPCu
---------4
The distribution ratio D is given by D = [Cu(BuEtP)
(o)
]/[Cu
2+
]), which on substitution into equation (4) gives,
Log D = log K
ex
+ log[H
2
BuEtP] + 2pH ---------5
where K
ex
is extraction constant.
Figure 2 also showed that pH 6.0 and 8.75 gave the highest Percentage Extraction (%E) of 99.87 and pH
1/2
at 2.45. The two pHs
(Tables 2 and 3) were used in the other studies of ligand variation and metal variation with plots in Figures 4 and 5. Ligand
H
2
BuEtP concentration variation plots gave approximately slopes of 1 at both pHs, while Cu(II) concentration variation plots
gave slopes of zero. These results confirm the reaction between the ligand H
2
BuEtP and Cu(II) is in 1:1 mole ratio as the reaction
between ligand and metal ion is independent of metal concentrations as shown in Figure 5 with a slope of zero. Thus, the
proposed reaction is slightly different from that expected in equation 3 and is given in equation 6 with the resultant distribution
ratio D given in equation 7.
Where X
-
is anions such as Cl
-
, CH
3
COO
-
etc. from the buffers.
K
ex
=
]][[[
]][)([
)(2
2
)(
o
o
BuEtPHCu
HXHBuEtPCu
---------7
Since [Cu(HBuEtP)X
(o)/[
Cu
2+
] = D
The extraction equation for the distribution is given by equation 8
Log D = log K
ex
+ log [H
2
BuEtP] + pH ---------8
The values for log D and log K
ex
were determined using the slopes and intercepts from plots of log D against log [H
2
BuEtP] in
Figure 4 and equation 8 to be pH 6.0 (log D = 0.35 and log K
ex
= -4.35) and pH 8.75 (log D = 1.59 and log K
ex
= -5.86) and thus,
for the ligand H
2
BuEtP alone, log D
1
= 0.97 ± 0.62 and log K
ex
= -5.11 ± 0.75. In a related study with Cu(II) with the ligand
H
2
PrEtP alone by Nwadiri et al., (2016), they reported the pH
1/2
at 4.57, log D = 1.56 ± 0.01 and log K
ex
= -3.25 ± 0.10.
Comparing the two ligands log D and log K
ex
indicated that the H
2
PrEtP was a slightly better extractant for Cu(II) than H
2
BuEtP
with a higher extraction constant log K
ex
and the partition coefficient log D of the formed Cu(II) complex Cu(HPrEtP.X)
(o)
higher
than that of Cu(HBuEtP.X)
(o)
.
Combining all the results from slope analysis we are proposing the structure of Cu(HBuEtP.X)
(o)
to be that shown in Figure 9.
Figure 9: Proposed Structure of Cu(HBuEtP.X)
Cu
2+
+ H
2
BuEtP
(o)
CuBuEtP
(o)
+ 2H
+
--------- 3
Cu
2+
+ H
2
BuEtP(o) + X
-
Cu(HBuEtP)X + H
+
--------6
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 94
Distribution with Ligand H
2
BuEtP and HBuP
Figure 3 showed that the pH
1/2
for the mixed ligands H
2
BuEtP/HBuP system was established at pH 4.45. The shift in pH
1/2
to a
less acidic media in the presence of the mixed ligands H
2
BuEtP/HBuP was also reported in the distribution of Pb(II) and Cd(II)
(Godwin and Uzoukwu, 2012a: Godwin and Tella, 2023) as against a more acidic media for the mixed ligands H
2
BuEtP/HBuP
system reported for UV(VI), Ni(II), Fe(II) (Godwin et al., 2012: Godwin and Uzoukwu, 2012b: Godwin et al., 2013) and in
Cu(II) study with HPrEtP (Nwadiri et al., 2016). Figure 2 also showed again that pH 6.0 and 8.75 gave the highest Percentage
Extraction (%E) with > 99.8% and the two buffers were used in the other studies.
In the distribution of Cu(II) from the buffered aqueous phases with the mixed ligands H
2
BuEtP/HBuP, plots of log D against pH
as in Figure 3 gave a slope of 1.46 which is approximately 2 indicating that 2 protons were displaced from the ligands. This result
was different from that reported by Nwadire et al., 2016, for the distribution of Cu(II) with H
2
PrEtP/HPrP in which only a proton
was displaced. Results for ligand H
2
BuEtP concentrations varied with HBuP concentration held constant and HBuP
concentrations varied and H
2
BuEtP concentration held constant gave slopes of approximately 2. Also, the plots of log Cu(II)
concentrations varied against log D with the mixed ligands H
2
BuEtP/HBuP at both pH of 6.0 and 8.75 gave slopes of zero and
also confirmed the independence of the metal concentrations in the distribution of the metal ions into the organic phases as shown
in Figure 8. Combining these results, we are proposing the reaction of Cu(II) in the mixed ligands H
2
BuEtP/HBuP organic
extractant system as that shown in equation 9
K
ex
=
]][][[[
]][).([
)(
)(2
2
2
)(
o
o
o
HBuPBuEtPHCu
HBuPHBuEtPCu
---------10
The Distribution ratio (D) which is [Cu(HBuEtP.BuP]/[Cu
2+
] when substituted in equation 10 will give the extraction equation 11
for the distribution of Cu(II) between the aqueous phases and the mixed ligands H
2
BuEtP/HBuP organic extractant system.
Based on slope analysis from Figures 3, 6, 7, 8 and equation 9, we have proposed Figure 10 as the structure of the formed Cu(II)
adduct Cu(HBuEtP.BuP) in the presence of HBuP considering that Figures 3, 6 and 7 are showing that two protons were
displaced from the slopes as against 1 from Figure 2. We are considering the second proton to come from the protonated HBuP in
the agitation process due to keto-enol conversion (Uzoukwu, 2009).
Figure 10: Proposed structure of Cu(HBuEtP.BuP)
The values for log D
2
and log K
ex2
were calculated using slopes and intercepts from Figures 6, 7 and equation 11 to be pH 6.0 (log
D = 2.11 and log K
ex
= -7.30 and pH 8.75 (log D = 1.96 and log K
ex
= -12.05). Overall, log D
2
= 2.03 ± 0.81 and log K
ex2 =
-12.94
± 1.26 were determined for the mixed H
2
BuEtP/HBuP organic extractant system. The extraction constant log K
ex
values are
usually used to access the efficiency of an organic extractant for a particular metal ion (Uzoukwu and Adiukwu, 1996): Uzoukwu,
2009 : Ukoha et al., 2010). The log K
ex
values for pH 6.0 were higher than those at pH 8.75 in both ligand H
2
BuEtP alone and in
the mixed ligands H
2
BuEtP/HBuP organic extractants system and thus, considered the optimum buffer pH for the distribution of
Cu(II) between aqueous phases and the ligand H
2
BuEtP organic phase. Likewise, log K
ex1
(-5.11 ± 0.75) value for ligand
H
2
BuEtP is higher than that of log K
ex2
(log K
ex2 =
-12.94 ± 1.26) for the mixed ligands H
2
BuEtP/HBuP organic system and as
such the presence of HBuP did not exert any synergic effects even though the partition coefficient log D of the mixed ligands
Cu
2+
+ H
2
BuEtP
(o)
+ HBuP
(o)
Cu(HBuEtP.BuP)
(o)
+ 2H
+
---------9
Log D = log K
ex
+ log [H
2
BuEtP] + log [HBuP] + 2pH --------11
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 95
H
2
BuEtP/HBuP was higher than that for ligand H
2
BuEtP alone system (log D
2
= 2.03 ± 0.81 > log D
1
= 0.97 ± 0.62). An
independent t test was performed to compare log D
1
and log K
ex1
of the ligand alone, and log D
2
and log K
ex2
for the ligand mixed
with the synergist, at the 95% confidence level. There was no significant difference observed for the mean value log D
1
(0.97 ±
0.62) and log D
2
(2.03 ± 0.81; t(4) = 1.7999, p = .15). On the contrary, a significant difference was observed for the log K
ex1
(-
5.11 ± 0.75) and log K
ex2
(-12.94 ± 1.26) values with p < .05 and t(4) = 9.245.
Nwadire et al., 2016 in related study with Cu(II) reported a slightly higher value for H
2
PrEtP/HPrP of -3.12 ± 0.10 than for
H
2
PrEtP of -3.25 ± 0.10. However in studies of U(VI) with both H
2
BuEtP and H
2
PrEtP, the H
2
BuEtP system was a better
extractant system than H
2
PrEtP with higher extraction constant log K
ex
(H
2
BuEtP log K
ex
-1.68 ± 0.12 > H
2
PrEtP log K
ex
-5.84 ±
0.18 and H
2
BuEtP/HBuP log K
ex
-0.72 ± 0.13 > H
2
PrEtP/HPrP log K
ex
-8.74 ± 0.50. While a slight synergic effect was exerted by
HBuP, there was no synergic effect in the presence of HPrP (Godwin and Uzoukwu, 2012b: Nwadiri et al., 2016). Thus, the chain
length of related ligands effects in the distribution of metal ions from aqueous phases is related to the type of metal ion. In other
studies with same H
2
BuEtP alone and in the mixed ligands organic extractants system, synergic effect of HBuP was reported for
Ni(II) and Fe(II) (Godwin et al, 2012: Godwin et al, 2013) while no such effects was observed for Pb(II) and Cd(II) (Godwin and
Uzoukwu, 2012a: Godwin and Tella, 2023) as shown in Table 4.
Studies on other metals indicate that the extraction efficiency of the ligand H
2
BuEtP, based on the extraction constant log K
ex
,
follows this order: Pb(II) > U(VI) > Zn(II) > Cd(II) > Cu(II) > Ni(II) > Fe(II) when using H
2
BuEtP alone. In contrast, for the
mixed H
2
BuEtP/HBuP system, the order is U(VI) > Pb(II) > Cd(II) > Ni(II) > Cu(II) > Fe(II) (Godwin and Uzoukwu, 2012a:
Godwin and Uzoukwu, 2012b: Godwin et al., 2012: Chukwu and Godwin, 2013: Godwin et al., 2013: Nwadiri et al., 2016:
Godwin and Tella, 2023: Godwin et al., 2024) from Table 4.
The changes in partition coefficient log D can be attributed to changes in dielectric constants related directly to the solvent
systems with solvents that lead to a more negative enthalpy changes having higher partition coefficients log D and accounts for
the closeness in log D values for the ligands in chloroform system with log D > 1.48 with the exceptions being log D values for
UO
2
2+,
Zn
2+
and Cu
2+
in H
2
BuEtP/chloroform system. Comparatively, the 1-phenyl-3-methyl-4-benzoylpyrazolone (HBP) in
Xylene for the extraction of Pb
2+
and La
3+
gave lower log D values of < 1.39 as shown in Table 4 (Uzoukwu and Adiukwu, 1996
: Housecroft and Sharpe, 2001). On the other hand, the disparities in the formation constants log K
ex
shown in Table 4, is
attributed to the type and energies of bonds formed between the metal ions and the ligands. Those with higher log K
ex
values are
ones in which the formation of the metal complexes have favourable energy factors and results in the ease in their formation of
stronger bonds. A second ligand is expected to result in formation of adducts which are more hydrophobic and thus, expected to
be transferred easily to the organic phases and thus can function as synergists but in some cases, due to energy barriers in their
formation, their addition leads to lower log K
ex
values even though their log D values are high as shown in Table 4 (Housecroft
and Sharpe, 2001 : Uzoukwu, 2009 : Koh et al., 2005 : Imura et al., 2006 : Ukoha et al., 2010)
Table 1: Values of log D against pH in the Distribution of 200 mgL
-1
Cu (II) between buffered aqueous phases and chloroform
solutions of 0.05 M H
2
BuEtP and chloroform solutions of 0.05 M H
2
BuEtP/0.05 M HBuP in a 9:1 volume ratio
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 96
Table 2: Values of log D against log [Cu] from aqueous solutions buffered at (a) pH 6.0 and (b) pH 8.75 into chloroform solution
of ligand [H
2
BuEtP] and into chloroform solutions of 0.05 M H
2
BuEtP /0.05 M HBuP in 9:1 volume ratio at (a) pH 6.0 and (b)
pH 8.75.
Table 3: Values of log D against log[H
2
BuEtP] for the extraction of 200 mgL
-1
Cu(II) from aqueous solutions buffered at pH 6.0
and pH 8.75 into (a) chloroform solutions of varied ligand [H
2
BuEtP] (b) into H
2
BuEtP/HBuP solutions in chloroform with
H
2
BuEtP varied from 2.50×10
-3
to 4.00 × 10
-2
M and HBuP kept constant at 5.00 × 10
-3
M in (c) log D against log [HBuP] for
the extraction of 200 mgL
-1
Cu(II) from aqueous solutions into H
2
BuEtP/HBuP solutions in chloroform with HBuP varied from
2.50 × 10
-3
to 2.25 × 10
-2
M and H
2
BuEtP kept constant at 2.50 × 10
-3
M
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 97
Table 4: H
2
BuEtP and Two other Ligands and their log D and log K
ex
Values for Studied Metal ions
Ligand System
Log D
Log K
ex
H
2
BuEtP in Chloroform
1.92
-32.90
H
2
BuEtP/HBuP in Chloroform
1.82
-9.79
H
2
BuEtP in Chloroform
0.56
-1.68
H
2
BuEtP/HBuP in Chloroform
1.74
-0.72
H
2
BuEtP in Chloroform
1.89
-12.39
H
2
BuEtP/HBuP in Chloroform
1.89
-10.57
H
2
BuEtP in Chloroform
1.5
-13.45
H
2
BuEtP/HBuP in Chloroform
1.68
-13.27
H
2
BuEtP in Chloroform
2.19
-3.01
H
2
BuEtP/HBuP in Chloroform
3.15
-10.09
H
2
BuEtP in Chloroform
-3.05
-2.52
H
2
BuEtP in Chloroform
0.97
-5.11
H
2
BuEtP/HBuP in Chloroform
2.03
-12.94
H
2
PrEtP in Chloroform
1.49
-5.84
H
2
PrEtP/HPrP in Chloroform
2.49
-8.71
H
2
PrEtP in Chloroform
1.56
-3.25
H
2
PrEtP/HPrP in Chloroform
1.70
-3.12
1-phenyl-3-methyl-4-benzoylpyrazolone (HBP) in Xylene
1.00
-0.43
1-phenyl-3-methyl-4-benzoylpyrazolone (HBP) in Xylene
1.38
-0.76
III. Conclusion
From the results presented and from other studies of same extractant systems H
2
BuEtP and HPrEtP for Cu(II) and other metals,
we draw the following conclusions;
The optimal pHs for the extraction of Cu (II) using organic phases of the ligand H
2
BuEtP alone or in the presence of HBuP are
pH 6.0 and 8.75
The presence of HBuP shifted the pH
1/2
from more acidic pH of 2.45 in H
2
BuEtP alone to a less acidic pH 4.50.
The log K
ex
value
for H
2
BuEtP alone (-5.11 ± 0.70) was greater than that for H
2
BuEtP/HBuP (-12.94 ± 1.26) and showed there
was no synergic effect of HBuP in the distribution of Cu(II) between aqueous phases buffered to pH 6.0 and 8.75 and chloroform
solutions of H
2
BuEtP alone and in the presence of HBuP.
Slope analysis from plots proposed the reaction equations and structures of Cu(II) complexes distributed into both organic phases
as Cu(HBuEtP.X) in ligand H
2
BuEtP alone and Cu(HBuEtP.BuP) in H
2
BuEtP/HBuP.
Results from this study and those of U(VI) with H
2
BuEtP alone and in the presence of HBuP compared with those for H
2
PrEtP
alone and in the presence of HPrP showed from the extraction constants log K
ex
, that the carbon chain length effects are
dependent on the type of metal ion.
References
1. Al-Saydeh, S. A., El-Naas, M. H., and Zaidi, S. J. (2017). ‘Copper removal from industrial wastewater: A
comprehensive review’. Journal of Industrial and Engineering Chemistry: 56: 35-44 doi.org/10.1016/j.jiec.2017.07.026
2. Chukwu, U. J., and Godwin, J. (2013). ‘Solvent Extraction Studies of Uranium (VI) from Aqueous Media into
Chloroform Solution of N, N´-ethylenebis(4-propionyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-oneimine)’.
American Chemical Science Journal, 3(4): 479-488 doi: 10.9734/ACSJ/2013/4155
3. Dawara, L., Singh, D. and Singh, R. V. (2011). ‘Antimicrobial and pesticidal activity of some organogermanium (IV)
complexes synthesized under microwave irradiation’. Main Group Metal Chemistry, 34: 3 - 4doi:
10.1515/MGMC.2011.012
4. Di Palma, L. and Medici, F. (2002). ‘Recovery of copper from contaminated soil by flushing’. Waste Management,
22(8): 883-886 doi: 10.1016/S0956-053X(02)00072-7
5. Godwin, J., Benson, O., & Polokeduo, N. R. (2024). ‘Distribution of Zinc (II) Between Buffered Aqueous Phases and
Organic Phase of 4,4´-(1E,1E´)-1,1´-(Ethane-1,2-Diylbis (Azan-1-Yl-1ylidene) Bis(5-Methyl-2-Phenyl-2,3-Dihydro-1h-
Pyrazol-3-Ol) (H2BuEtP) in Chloroform’. European Journal of Applied Sciences, 12(2): 205-
214doi:10.14738/aivp.122.16767
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 98
6. Godwin, J., Chukwu, U. J., and Gad, T. D. (2013). ‘Distribution of Iron(II) between buffered Aqueous Solutions and
Chloroform Solution of N,N’-Ethylenebis(4-butanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-oneimine)’. CIR-
Journal of Advances in Chemistry, 8(2): 1581-1589 doi: 10.24297/jac.v8i2.4039
7. Godwin, J., Nwadire, C. F., and Uzoukwu, B. A. (2012). ‘Extraction of Ni(II) Ions into Chloroform solution of N, N’-
Ethylenebis(4-butanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-oneimine) Schiff base’. European Chemical
Bulletin, 1(7): 269-273
8. Godwin, J., and Tella, L. S. (2023). ‘Distribution of Cd(II) between buffered aqueous solutions and chloroform solution
of 4, 4’-(1E, 1E’)-1, 1’-(Ethane-1,2-Diylbis(Azan-1-yl-1ylidene)Bis(5-Methyl-2-Phenyl-2,3-Dihydro-1H-Pyrazol-3-ol
Schiff Base’. European Journal of Applied Sciences, 11(2): 698-707doi:10.14738/aivp.112.14434
9. Godwin, J., and Uzoukwu, B. A. (2012a). ‘Distribution of Pb (II) ions into chloroform solution of N,N’-Ethylenebis(4-
Butanoyl-2,4-Dihydro-5-Methyl-2-Phenyl-3H-Pyrazol-3-Oneimine) as tris-complex species’. Journal of Applied
Chemistry (IOSRJAC), 1(3): 14-21 doi: 10.9790/5736-0131421
10. Godwin, J., and Uzoukwu, B. A., (2012b). ‘Distribution of U(VI) from aqueous solutions into chloroform solution of
N,N’-Ethylenebis(4-butanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-oneimine) Schiff Base’. International
Journal of Chemistry, 4(4): 105-116 doi:10.5539/ijc.v4n4p105
11. Habala, L., and Valentova, J. (2018). ‘Metal complexes in medicine and pharmacy - the past and the present I’. Česká a
slovenská farmacie, 67(5): 182 – 191doi: 10.36290/csf.2018.026
12. Housecroft, C. E., and Sharpe, A. G. (2001). ‘Non-aqueous Solvent’ Inorganic Chemistry, First Edition, Pearson
Educational Limited, Essex, 188-189.
13. Huang, Y., and Keller, A. A. (2020). ‘Remediation of heavy metal contamination of sediments and soils using ligand-
coated dense nanoparticles’. PloS One 30;15(9):e0239137 doi: 10.1371/journal.pone.0239137
14. Imura, H., Ebisawa, M., Kato, M., and Ohashi, K. (2006). Novel synergism by complex ligands in solvent extraction of
rare earth metals(III) with β-diketones, Journal of Alloys and Compounds, Volumes 408–412, 952-957 doi:
org/10.1016/j.jallcom.2004.12.106.
15. Jimenez-Falcao, S. and Mendez-Arriaga, J. M. (2024). ‘Recent Advances in Metal Complexes Based on Biomimetic and
Biocompatible Organic Ligands against Leishmaniasis Infections: State of the Art and Alternatives’. Inorganics, 12(7):
190 doi.org/10.3390/inorganics12070190
16. Kalyanasundaram, K., and Gra Ètzel, M. (1998). ‘Applications of functionalized transition metal complexes in photonic
and optoelectronic devices’. Coordination Chemistry Reviews, 77: 347-414 doi:10.1016/S0010-8545(98)00189-1
17. Koh, M., Park, K., Yang, D., Kim, H., and Kim, H. (2005),The Synergistic Effect of Organophosphorus and
Dithiocarbamate Ligands on Metal Extraction in Supercritical CO
2
, Bulletin of the Korean Chemical Society, 26(3) doi:
10.5012/bkcs.2005.26.3.423
18. Kostova I, Saso L. (2013). ‘Advances in research of Schiff-base metal complexes as potent antioxidants’. Current
Medicinal Chemistry, 20(36): 4609-4632 doi: 10.2174/09298673113209990149
19. Muthaiah, S., Bhatia, A. and Kannan, M. (2020). ‘Stability of Metal Complexes. Stability and Applications of
Coordination Compounds’. IntechOpen. 1-8 doi.org/10.5772/intechopen.90894
20. Mining (2020). 2020 copper production forecast trimmed to 21mt. Mining.com. https://www.mining.com/2020-copper-
production-forecast-trimmed-to-21mt/ (Retrieved November 12, 2024)
21. Napoli, M., Cecchi, S., Grassi, C. Baldi, A., Zanchi, C. A., and Orlandini, S. (2019). ‘Phytoextraction of copper from a
contaminated soil using arable and vegetable crops’. Chemosphere, 219: 122 – 129
doi.org/10.1016/j.chemosphere.2018.12.017
22. Nwadire, F. C., Ajiwe, V. I. E., Okoye P. A. C. and Godwin, J. (2016). ‘Distribution of Cu(II) between Buffered
Aqueous Phases and Organic Phases Containing N,N’-ethylenebis(4-propionyl-2,4-dihydro-5-methyl-2-phenyl-3H-
pyrazol-3-oneimine (H
2
PrEtP) in chloroform’. International Research Journal of Pure & Applied Chemistry, 13(3):1-9
doi: 10.9734/IRJPAC/2016/30386
23. Paderni, D., Macedi, E., Sordini, E., Amatori, S., Rossi, P., Formica, M., Giorgi, L., Paoli, P., Fanelli, M., and Fusi, V.
(2025). ‘Two bis-maltol-polyamines: Synthesis, characterization and studies of their palladium (II) complexes exploring
their potential anticancer activity’. Journal of Inorganic Biochemistry, 262(112758):1-11;
doi.org/10.1016/j.jinorgbio.2024.112758
24. Panigrahi, S., Parhi, P.K., Sarangi, K., & Nathsarma, K. C. (2009). ‘A study on extraction of copper using LIX 84-I and
LIX 622N’. Separation and Purification Technology, 70(1): 58-62. doi.org/10.1016/j.seppur.2009.08.013
25. Rahman, M. S. (2024). ‘Advancements in solvent extraction of metal ions: Mechanisms, kinetics, and efficiency with
diverse extractants’, International Journal of Science and Research Archive 12(2):2374-
2396doi:10.30574/ijsra.2024.12.2.1493
26. Rahmati, S., Adavodi, R., Hosseini, R.M and Veglio, F.’ (2024). ‘Efficient Metal Extraction from Dilute Solutions: A
Review of Novel Selective Separation Methods and Their Applications’ Metals 2024, 14(6), 605; 1-25
doi.org/10.3390/met14060605
27. Shimazaki, Y. (2013). ‘Oxidation Chemistry of Metal(II) Salen-Type Complexes’. Electrochemistry. InTech. Available
at: http://dx.doi.org/10.5772/48372. (Retrieved November 12, 2024)
INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue II, February 2025
www.ijltemas.in Page 99
28. Sverdrup, H. U., Ragnarsdottir, K. V., & Koca, D. (2014). On modelling the global copper mining rates, market supply,
copper price, and the end of copper reserves. Resources, Conservation and Recycling, 87, 158-174.doi:
10.1016/j.resconrec.2014.03.007
29. Ugwu, I. D and Conradie, J. (2024). ‘The use of bidentate ligands for heavy metal removal from contaminated water’
Environmental Advances, 15(100460): 1-26 doi.org/10.1016/j.envadv.2023.100460.
30. Ukoha, P., Nwabue, F., and Nnamdi, O. (2010)., Solvent Extraction Studies on Copper(II) and Silver(I) Complexes of
Bis(4-hydroxypent-2-ylidene)diaminoethane: Composition of Extracted Copper(II) Species, E-Journal of Chemistry, (8):
1864-1871 Doi: 10.1155/2011/582649
31. Uzoukwu, B. A. (2009). ‘Basic Analytical Chemistry Textbook’, Jenson Service, Rumuomasi PortHarcourt, Millennium
Edition, 2009, 166-196.
32. Uzoukwu, B. A., and Adiukwu, P. U., (1996). ‘Kinetic studies on the recovery of Lead (II0 and Lanthanum (III) from
aqueous solution with xylene solutions of 1-phenyl-3-methyl-4-benzoylpyrazolone’, Indian Journal of Chemistry, 35A:
230 - 232
33. Uzoukwu, B. A., Gloe, K., and Duddeck, H. N. (1998). N‟-Ethylenebis(1-phenyl-3-methyl-4-acylpyrazoloneimine)
derivatives: Synthesis and UV, IR,
1
H and
13
C NMR spectral studies’. Indian Journal of Chemistry, 37B: 1180.
34. Yu, Z., Hagfeldt, A., and Sun, L. (2020). ‘The application of transition metal complexes in hole-transporting layers for
perovskite solar cells: Recent progress and future perspectives’. Coordination Chemistry Reviews, 406:
doi.org/10.1016/j.ccr.2019.213143.
35. Yu, Z., Jiaxing Xiong, Li Wang, Feng Li, Huiping Bai, Shixiong Wang, Xiangjun Yang, (2024). ‘Multi-ligand strategy
for enhanced removal of heavy metal ions by thiol-functionalized defective Zr-MOFs’. Journal of Hazardous Materials,
479: doi.org/10.1016/j.jhazmat.2024.135723.
36. Yudaev, P. and Chistyakov, E. (2022).’Chelating Extractants for Metals’ Metals, 12(8): 1275; 1-60
doi.org/10.3390/met12081275
37. Zoubi, W. A. L. (2013). ‘Solvent extraction of metal ions by use of Schiff bases’, Journal of Coordination
Chemistry 66(13): 2264-2289 doi: 10.1080/00958972.2013.803536
38. Zoubi, W. A. L., Kandil, F., and Chebani, M. K. (2011). ‘Solvent extraction of chromium and copper using Schiff base
derived from terephthaldialdehyde and 5-amino-2-methoxy-phenol’. Arabian Journal of Chemistry, 9(4): 526-531
39. dx.doi.org/10.1016/j.arabjc.2011.06.023