1,2-Dibenzoyl- and 1-benzoyl-2-acetylhydrazines as reagents for recovering Cu(II) ions from alkaline solutions

Article abstract of DOI:10.1134/S1070427207030056

The conditions of complexation of 1,2-diacylhydrazines (H₂L) C₆H₅C(O)NHNHC(O)R, where R = C₆H₅ or CH₃, with Cu(II) ions in alkaline solutions were studied. The composition of the complexes formed by precipitation of Cu(II) from alkaline solutions, (CuOH)₂L and CuL, was determined. The possibility of afterpurification of solutions with a low Cu(II) content by pneumatic flotation using H₂L was examined.

Full text of DOI:10.1134/S1070427207030056

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 3, pp. 368 371. Pleiades Publishing, Ltd., 2007.
Original Russian Text A.V. Radushev, L.G. Chekanova, Yu.B. El’chishcheva, A.V. Ershova, 2007, published in Zhurnal Prikladnoi Khimii, 2007,
Vol. 80, No. 3, pp. 370 373.
PHYSICOCHEMICAL STUDIES
OF SYSTEMS AND PROCESSES
1
,2-Dibenzoyl- and 1-Benzoyl-2-acetylhydrazines as Reagents
for Recovering Cu(II) Ions from Alkaline Solutions
A. V. Radushev, L. G. Chekanova, Yu. B. El’chishcheva, and A. V. Ershova
Institute of Technical Chemistry, Ural Division, Russian Academy of Sciences, Perm, Russia
Perm State University, Perm, Russia
Received October 12, 2005; in final form, April 2006
Abstract The conditions of complexation of 1,2-diacylhydrazines (H L) C H C(O)NHNHC(O)R, where R =
2
6 5
C H or CH , with Cu(II) ions in alkaline solutions were studied. The composition of the complexes formed
6
5
3
by precipitation of Cu(II) from alkaline solutions, (CuOH) L and CuL, was determined. The possibility of
2
afterpurification of solutions with a low Cu(II) content by pneumatic flotation using H L was examined.
2
DOI: 10.1134/S1070427207030056
1
,2-Diacylhydrazines RC(O)NHNHC(O)R (H L)
and silver chloride electrodes. The IR spectra were
recorded in mineral oil on a Specord M 80 spectro-
photometer. The derivatograms were taken on an
MOM Q-1500D derivatograph (Hungary). The Cu(II)
concentration in solution was determined by an ex-
traction-photometric method with sodium diethyldi-
thiocarbamate [6].
2
are tetradentate ligands and form stable flotation-
active complexes ML with ions of Cu(II) and other
nonferrous metals in ammonia or alkaline solutions
1, 2]. Replacement of alkyl radicals in symmetrical
,2-diacylhydrazine molecules by phenyl radicals
enhances the acid properties of the reagent, so that
poorly soluble complexes of 1,2-dibenzoylhydrazine
DBzH) with Cu(II) are formed in ammonia solutions
[
1
Complexation of reagents with Cu(II) ions was
studied by the precipitation method, because the pre-
cipitates formed are insoluble in water and common
solvents. Figure 1 (curve 4) shows that the maximal
(
at pH 5 8 [3].
The goal of this study was to examine the condi-
tions of complexation of 1,2-diacylhydrazines C H5
6
S, %
C(O)NHNHC(O)R, where R = C H or CH , with
6
5
3
Cu(II) ions in alkaline solutions and the possibility of
using these reagents for afterpurification of waste-
water to remove Cu(II) after precipitation of the major
amount of Cu(II) in the form of Cu(OH)2.
EXPERIMENTAL
1,2-Dibenzoylhydrazine was prepared as described
in [4], by thermal decomposition of 2C H COOH
6
5
N H H O [4]; 1-acetyl-2-benzoylhydrazine (BAH)
2
4
2
was prepared similarly by the reaction of benzhydra-
zide with concentrated acetic acid. The main sub-
stance content in the reagent samples was 97% as
determined by conductometric titration on an OK-
102/1 conductometer (Hungary) with a bell-shaped
Fig. 1. pH dependences of the recovery S of Cu(II) ions
OK-0902P electrode [5]. The optical density of solu-
tions was measured on SF-26 and KFK-2 spectropho-
tometers, and pH, on an EV-74 pH meter with glass
with (1) DBzH, (2) BAH, and (3) DPH, and (4) in the form
1
of Cu(OH) without adding reagents. c
= 63.5 mg l
,
2
Cu(II)
2
c
= 10 M in EtOH; [Cu(II)] : [H L] = 1 : 1, = 5 min.
H L
2
2
368

1,2-DIBENZOYL- AND 1-BENZOYL-2-ACETYLHYDRAZINES
369
degree of precipitation of Cu(II) in the form of
,
S
Cu(OH) under the action of alkali is 99.8% in the
2
pH range 7.0 10.0. The 99.9% precipitation of Cu(II)
in the presence of DBzH was observed at pH 5.5
(
curve 1); in the presence of BAH, at pH 6.3 (curve 2);
and in the presence of dipropionylhydrazine (DPH),
at pH 7 (curve 3). These differences can be accounted
for by considering the dissociation of 1,2-diacylhydra-
zines:
pK
pK
a
a
1
2
L2 .
H2L
HL
(1)
The acid properties of the reagents under considera-
tion increase in the order DPH (pKa1 11.21 0.04,
pKa2 12.5 0.3 [7]) < BAH (pKa1 9.37 0.03, pKa2
V, ml
1
0.9 0.2) < DBzH (pKa1 9.22 0.04, pKa2 10.8 0.3
Fig. 2. Electrical conductivity of a CuSO solution as a
4
[
3]). Therefore, the complexation of Cu(II) with DPH
function of the precipitant (BAH) solution volume V (alka-
occurs in neutral and weakly alkaline solutions,
whereas BAH and DBzH form complexes with Cu(II)
even at pH 4.5 5.
3
3
line medium). c
= 0.9 10 M, c
= 10 M.
BAH
Cu(II)
was added with stirring. The mixture was allowed to
stand for 20 min. The precipitates were filtered off,
washed on the filter with ethanol and hot water, and
dried in air.
+
We calculated the amount of H (moles) released
in complexation of DBzH and BAH with Cu(II) at
varied pHeq and constant concentration ratio Cu(II) :
H L = 1 : 1 by slope analysis in the coordinates log
2
With DBzH and BAH at a Cu(II) : H L concentra-
2
pH , where is the sorption ratio [ = S /(1 Si)].
eq
i
tion ratio of 2 : 1 we obtained green precipitates, and
at the 1 : 1 ratio, brown precipitates insoluble in water
and common organic solvents, which is characteristic
of polymeric compounds.
Equations (2) and (3) wre obtained by the least-
squares method for BAH and DBzH, respectively:
log = 1.8 0.1 (r = 0.9995, n = 4, P = 0.95), (2)
log = 1.7 0.1 (r = 0.9995, n = 4, P = 0.95). (3)
Analysis of the precipitates for Cu(II) gave the fol-
lowing results, wt %: [Cu(II)] : [DBzH] = 1 : 1, 20.75
and 2 : 1, 28.82; [Cu(II)] : [BAH] = 1 : 1, 25.9 and
2 : 1, 33.87. The composition of the complexes corre-
sponds to the following formulas [calculated Cu(II),
wt %]: [Cu(C H OCNNCOC H )], 21.06; [(CuOH)
Hence, Cu(II) ions form with DBzH and BAH the
complexes CuL in which the ligand is double-depro-
tonated.
6
5
6
5
2
(
C H OCNNCOC H ) 2H O], 29.20; [Cu(C H O
The composition of the complexes was confirmed
6 5 6 5 2 6 5
CNNCOCH )], 26.51; and [(CuOH) (C H OCNN
by potentiometric titration. For this purpose, a 100-ml
3
2
6 5
3
COCH ) 2H O], 34.05.
beaker was charged with 5.0 ml of a 0.9 10
M
3
2
solution of CuSO and 60 ml of a 1 : 1 EtOH H O
4
2
To determine the structure of the complexes, we
recorded their IR spectra. As compared to the starting
DBzH and BAH, the IR spectra of the complexes do
not contain stretching vibration bands of the C=O and1
N H bonds, but contain bands at 1395 1404 cm
corresponding to stretching vibrations of C O single
mixture. The resulting solution was titrated with 1
3
1
0
M solutions of potassium salts of the reagents.
The complexation with DBzH and BAH occurred in
steps; the bends in the curve were observed at Cu(II) :
H L concentration ratios of 2 : 1, 1 : 1, and 1 : 2
2
(
Fig. 2).
1
bonds. The bands at 1520 1535 cm , absent in the
Then we isolated complexes at the Cu(II) : H2L
spectra of the starting diacylhydrazines, can be as-
signed to stretching vibrations of the C=N bonds [8].
Thus, the IR spectra confirm that Cu(II) ions form
complexes with the reagent molecules in the double-
deprotonated enol form. The spectra of the 2 : 1 com-
plexes, in contrast to those of the 1 : 1 complexes,
concentration ratios of 1 : 1 and 2 : 1 in alkaline solu-
tions. A 250-ml beaker was charged with 50 ml of a
2
2
1
10 or 2 10 M solution of CuSO , 1.6 ml of
4
a 1 10 1 M KOH solution was added, and 50 ml of
a 1 10 M solution of DBzH or BAH in ethanol
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 3 2007

370
RADUSHEV et al.
Calculated solubility products SP and molar solubilities S of the complexes CuL with reagents C H C(O)NHNHC(O)R
6
5
in alkaline solutions
cCu 104
c
104
c 2 1012 cCu2+ 106
H L
[Cu]b
eq
106,
L
S 109,
2
Si,
%
R
pHeq
logSP
M
M
M
M
CH3
C6H5
8.9
10.0
8.9
10.0
99.8
99.9
1.57
1.26
7.0
6.5
1.8
0.1
1.57
1.26
17.6
18.9
1.70
0.35
also contain absorption bands in the range 3350
520 cm 1 corresponding to stretching vibrations of
of the precipitates of the complexes are lower than
7
3
that of Cu(OH) (1.8 10 M [10]) by two orders of
2
hydroxy groups and water of crystallization. The pres-
ence of water of crystallization is also confirmed by
thermal analysis of the complexes. The DTA curve
exhibits endothermic peaks in the interval 170 210 C
with maxima at 180 C for the Cu BAH (2 : 1) com-
plex and at 190 C for the Cu DBzH (2 : 1) complex,
assignable to the loss of water of crystallization.
magnitude. Therefore, Cu(II) ions are recovered from
alkaline solutions in the form of complexes with the
ligands in question more completely than in the form
of Cu(OH)2.
We found that, at the initial Cu(II) concentration of
7 mg l , precipitation of the complexes at the 1 : 1
1
5
component ratio reduces the residual Cu(II) concentra-
tion to 0.08 mg l 1 with DBzH and 0.1 mg l 1 with
BAH. However, to precipitate Cu(II), large amounts
of the reagent should be added [2.8 mg of BAH per
milligram of Cu(II)], and the reagent is not regener-
ated. Therefore, it was interesting to examine the
possibility of additional recovery of Cu(II) ions from
solutions with their low content [after precipitation of
On the basis of the above facts, the suggested
structures of the 2 : 1 and 1 : 1 complexes can be pre-
sented by formulas (4) and (5), where R = CH or
3
C H .
6
5
The complexation of DBzH and BAH with Cu(II)
ions in alkaline solution at a component ratio of 1 : 1
can be described by Eq. (6).
Cu(II) in the form of Cu(OH) ] by pneumatic flotation
2
with BAH.
O
To a solution containing 3 mg l 1 of Cu(II) [after
precipitation of Cu(OH)2 with NaOH], we added
BAH in 0.1 M KOH or in ethanol at the [Cu(II)] :
Cu
C C H
6
5
,
N N
(4)
[
BAH] ratio of 1 : 1 or 1 : 2; the mixture was stirred
R
C
for 1 2 min. The precipitates, Cu(II) complexes with
the reagents, passed into the foam and were removed
from the solution. The flotation installation and the
experimental conditions were similar to those de-
scribed in [11]. The experiments were performed at
O
n
H2O
O Cu OH,
2
0 2 C. The sample of the purified solution was
taken through a sampler and analyzed for the residual
Cu(II) content by the extraction-photometric method
R
C
(
5)
N
N
[
6]. The degree of additional recovery of Cu(II) at
C C6H5
pH 9 was 83.8 and 95%; the residual concentration of
Cu(II) ions was 0.5 and 0.15 mg l , respectively,
HO Cu O
H2O
1
which is below MPC for household water [12].
Cu2+ + H L + 2OH
CuL + 2H O.
(6)
+
2
2
CONCLUSIONS
To calculate the equilibrium concentrations of Cu2
(
1) Conditions for complexation of Cu(II) with
,2-dibenzoyl- and 1-benzoyl-2-acetylhydrazines in
2
and L , we used data from [9].
1
The solubility products SP and molar solubilities S
of the complexes, calculated from data in Fig. 1, are
given in the table. It is seen that the molar solubilities
the course of precipitation were optimized. The 1 : 1
and 2 : 1 complexes of Cu(II) with H L were isolated
2
from alkaline solutions (pH 9) and identified.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 3 2007

1,2-DIBENZOYL- AND 1-BENZOYL-2-ACETYLHYDRAZINES
371
(
2) Replacement of one phenyl radical in 1,2-di-
5. Radushev, A.V., Chekanova, L.G., Gusev, V.Yu., and
Sazonova, E.A., Zh. Anal. Khim., 2000, vol. 55, no. 5,
pp. 496 499.
benzoylhydrazine by the acetyl radical increases the
solubility of the complex and decreases the degree of
recovery of Cu(II) ions.
6. Podchainova, V.N. and Simonova, L.N., Analitiches-
kaya khimiya elementov: Med’ (Analytical Chemistry
of Elements: Copper), Moscow: Nauka, 1990.
(3) 1-Acetyl-1-benzoylhydrazine is suitable for
afterpurification of wastewater by pneumatic flotation
after precipitation of Cu(II) with alkali in the form of
Cu(OH)2.
7
8
9
. Chekanova, L.G., Radushev, A.V., Lesnov, A.E., and
Sazonova, E.A., Zh. Obshch. Khim., 2002, vol. 72,
no. 8, pp. 1315 1319.
. Machkhoshvili, R.I., Coordination Compounds of
Metals with Hydrazines, Doctoral Dissertation, Mos-
cow, 1983.
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