Solvent extraction of copper(II) from sulfate medium with N -(2-hydroxybenzylidene)aniline

Article abstract of DOI:10.1080/00958972.2010.530662

Solvent extraction of copper(II) from sulfate medium with N-(2-hydroxybenzylidene)aniline is studied with the following parameters: pH, concentration of the extractant, nature of diluent, and temperature. The extraction of copper(II) proceeds by a cation

Full text of DOI:10.1080/00958972.2010.530662

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Solvent extraction of copper(II)
from sulfate medium with N -(2-
hydroxybenzylidene)aniline
A. Aidi a & D. Barkat a
a Département de Chimie Industrielle, Faculté des Sciences et de
la Technologie , Université de Biskra , BP 145, Biskra, Algérie
Published online: 20 Nov 2010.
To cite this article: A. Aidi & D. Barkat (2010) Solvent extraction of copper(II) from sulfate medium
with N -(2-hydroxybenzylidene)aniline, Journal of Coordination Chemistry, 63:23, 4136-4144, DOI:
10.1080/00958972.2010.530662
To link to this article: http://dx.doi.org/10.1080/00958972.2010.530662
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Journal of Coordination Chemistry
Vol. 63, No. 23, 10 December 2010, 4136–4144
Solvent extraction of copper(II) from sulfate medium with
N-(2-hydroxybenzylidene)aniline
A. AIDI and D. BARKAT*
De
´
partement de Chimie Industrielle, Faculte
´
des Sciences et de la Technologie,
rie
Universite de Biskra, BP 145, Biskra, Alge
´ ´
(Received 21 July 2010; in final form 10 September 2010)
Solvent extraction of copper(II) from sulfate medium with N-(2-hydroxybenzylidene)aniline is
studied with the following parameters: pH, concentration of the extractant, nature of diluent,
and temperature. The extraction of copper(II) proceeds by a cation exchange mechanism and
the extracted species are CuL2 in cyclohexane and toluene and CuL2 with some CuL2HL in
chloroform. The equilibrium constants have been calculated as well as thermodynamic
parameters DHꢀ, DSꢀ, and DGꢀ. The temperature effect on the solvent extraction of copper(II)
with N-(2-hydroxybenzylidene)aniline in cyclohexane is discussed.
Keywords: Solvent extraction; Copper(II); Sulfate medium; N-(2-hydroxybenzylidene)aniline;
Temperature effect
1. Introduction
Several salicylidene Schiff bases have been reported including electronic spectra [1, 2],
protonation equilibria [3–8], tautomeric properties [9, 10], and liquid–liquid extraction
of various metal cations [11–13].
In previous studies [14, 15], we investigated the extraction of transition metal ions
with N-(2-hydroxybenzylidene)aniline from sulfate and perchlorate media. It has been
shown that the extraction of copper(II) with N-(2-hydroxybenzylidene)aniline from
sulfate medium is less efficient than that in a perchlorate aqueous medium. This arises
from the fact that the perchlorate is noncomplexing and the sulfate is moderately
complexing. N-(2-hydroxybenzylidene)aniline has been found to be a good chelate
extractant for Cu(II), Co(II), and Ni(II).
In a recent paper, we reported [16] the liquid–liquid extraction of copper(II) from
sulfate medium with Schiff bases derived from salicylaldehyde. Their extraction
constants show dependence on the position of substituent present on the aniline ring.
In this work, we study the solvent extraction of copper(II) from sulfate medium
with N-(2-hydroxybenzylidene)aniline to investigate the effect of temperature on the
extraction of copper(II).
*Corresponding author. Email: barkat_djamel@yahoo.fr
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2010 Taylor & Francis
DOI: 10.1080/00958972.2010.530662

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Extraction of copper(II)
4137
2. Experimental
2.1. Reagents and solutions
N-(2-hydroxybenzylidene)aniline (N2HBA) was prepared by refluxing salicylaldehyde
with aniline and purified by recrystallization from ethanol [15]. Salicylaldehyde, aniline,
and all chemicals used in this work were purchased from Merck and used as received.
Chloroform, toluene, and cyclohexane were pre-equilibrated with aqueous solution
which did not contain copper(II). The initial compositions of the phases were as
follows: aqueous phase: [Cu2þ]i ¼ 1.5 ꢁ 10ꢂ3 mol Lꢂ1; [Na2SO4] ¼ 0.33 mol Lꢂ1; organic
phase: [N2HBA]i ¼ 0.01, 0.02, and 0.04 mol Lꢂ1
.
2.2. Extraction and analytical procedure
Extractions were performed on thermostated vessels. Equal volumes, 30 mL each of
aqueous and organic phases, were shaken with a magnetic stirrer for 30 min, a period
found to be adequate to reach equilibrium. After phase separation by gravity, the metal
concentration in the aqueous phases was determined photometrically at 820 nm using
a Shimadzu UV-VIS 1240. The pH of the aqueous phase was measured by a pH-meter
with an accuracy of 0.02 pH unit. The pH was adjusted to the desired level by the
addition of sodium hydroxide. The ionic strength was maintained at 1 with Na2SO4.
3. Results and discussion
3.1. Extractant concentration and pH dependencies
The overall reaction in the extraction of copper(II) with N2HBA (HL) in cyclohexane,
toluene, and chloroform from the sulfate aqueous medium of ionic strength
(I ¼ 1.0 mol kgꢂ1) may be expressed as
Kex
Cu2þ þ ðn þ mÞHLorg Ð CuLnðHLÞmorg þ nHþ
ð1Þ
where org denotes species in the organic phase.
The extraction constant, Kex, is defined as equation (2) and can be rewritten as
equation (3) by using the distribution ratio, DCu, of copper(II).
Â
Ã
Â
Ã
n
CuLnðHLÞm
Hþ
org
Kex
¼
Â
Ã
ð2Þ
nþm
Cu2þ ½HLꢃorg
½Cuꢃorg
½Cuꢃ
log DCu ¼ log
¼ log Kex þ ðn þ mÞ log½HLꢃorg þ n pH
ð3Þ
Plots of log DCu versus pH for various concentrations of N2HBA are linear with a slope
equal to 2, as shown in figures 1–3. Likewise, in all the extraction systems, plots of
log DCu versus log[HL]org at constant pH are also linear with a slope equal to 2 in
cyclohexane and toluene and 2.3 in chloroform, as shown in figures 4–6. These results

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4138
A. Aidi and D. Barkat
0.8
0.6
0.4
0.2
0.0
–0.2
–0.4
–0.6
–0.8
–1
–1
–1
[N2HBA]=0.01 molL
[N2HBA]=0.02 molL
[N2HBA]=0.04 molL
4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 5.6
pH
Figure 1. Effect of pH on the extraction of copper(II) from sulfate medium with N-(2-
hydroxybenzylidene)aniline in chloroform at 25ꢀC.
1.0
0.8
0.6
0.4
0.2
0.0
–0.2
–1
[N2HBA]=0.01molL
–0.4
–1
[N2HBA]=0.02molL
–1
[N2HBA]= 0.04molL
–0.6
–0.8
–1.0
4.2
4.4
4.6
4.8
5.0
5.2
5.4
5.6
pH
Figure 2. Effect of pH on the extraction of copper(II) from sulfate medium with N-(2-
hydroxybenzylidene)aniline in toluene at 25ꢀC.