PERSPECTIVES OF APPLICATION OF
CARBON ACID HYDRAZIDES AS MULTIFUNCTIONAL
REAGENTS IN HYDROMETALLURGY
A.V. Radushev, V.Yu. Gusev, L.G. Chekanova
Institute of Technical Chemistry of Ural Division of RAS,
3, Korolev Street, Perm, Russia, 614013
E-mail: avradu@mail.ru
Hydrazides include a vast group of organic derivatives of
hydrazine containing the functional-active group of C(O)NHN atoms
(here in after referred to as FAGA). First representatives, namely
hydrazides of formic and acetic acids, were produced as far back as in
1895 by Kurzius [1]. The great interest in the chemistry of hydrazine and
of its derivatives is explained by diversity and at times by originality of
their properties. Hydrazides find wide application as drugs, chemical
preservers for plants; in industry – for manufacturing polymers, glues
etc.; in analytical chemistry of organic and inorganic substances and for
many other purposes [2].
Hydrazides are rather reactive substances; they are bidentate as
ligands. Depending on medium acidity, reagents form complexes in
either amide (type I) or imide (type II) forms [3].
n+
O
R
O
M
Xn
C
NH
NH 2
R
C
N
m
«type I»
M
NH 2
n
(1)
«type II»
Since 1970-s and until now, the complexation of a number of
carbonic acid hydrazides with ions of non-ferrous and other metals was
studied, significant quantity of papers was published, dozens of
complexes were obtained. However, hydrazides were not used for
separation and concentration of elements for a long time. Obviously, the
first attempt of such using was the extraction of Cu (II) from ammoniac
108
mediums with 2-hydroxybenzoic acid hydrazides as per the general
formula (2) [4]:
OH
1
CONHNH2
2
R
R
R
4
R3
(2)
A feature of the hydrazide FAGA is the selectivity to Cu (II) ions.
However, disadvantages of reagents (2) are bad solubility in organic
solvents, difficulties in their syntheses, small Cu (II) capacity of organic
phase (no more than 1,5 g/l).
In 1994, we proposed hydrazides as per the following formula (3)
as extractants [5]. Apart from being easier synthesized, these reagents
are better dissoluble in kerosene and have better Cu (II) capacity (up to 4
g/l).
4
3
R
O
R-C
NHNH2
(3)
, where R = í -CnH2n+1 ;
n = 10-25
(3а)
R
2
R
R
1
CH 2(CH 2 ) n
(3b)
Carbonic acids with radicals of normal and α-branched structures
(3a) as well as acyclic (naphthenic) acids with radicals (3b) were used
for synthesis of hydrazides (3).
Patent [5] actually initiated investigations in organic derivatives of
hydrazine intended for separation and concentration of non-ferrous
metals. This work was started in the laboratory №4 of the Institute of
Technical Chemistry of Ural Division of the Russian Academy of
Sciences.
109
Hydrazides
Investigations in hydrazides (3) are summarized in theses [6, 7].
Physicochemical properties [8]. Hydrazides of carbonic acids (3)
are amphoteric compounds (4):
–Н+, Ka2
–Н+, Ka1
+
H2L
HL
L–
(4)
A number of hydrazides of carbonic acids with C5H11 - C15H31
were studied. Hydrazides of carbonic acids (hereinafter referred to as
HCA) are white crystals well soluble in alcohols, mildly soluble in HCl
solutions. Only HCAs with RC6H13 are soluble in water. Solubility of
HCAs in all solvents rapidly decreases with the lengthening of their
radical; they are not soluble in hydrocarbons (for example, in heptane).
Hydrazides of naphthenic acids (HNA) are well dissoluble in kerosene.
NCA and HNA are mildly stable to hydrolysis in acid mediums:
hydrolysis degree in 2,15 mol/l solution of H2SO4 for 4 hours is equal to
40%; in 0,01 mol/l solution of H2SO4 ≈ 19%.
HNA are viscous yellowish liquids. Their acid-base properties
slightly differ from the same of HCA. For example, the pK a1 value of
HCA in MeOH is 3,6 – 3,7; for HNA with molecular mass 272 this
value equals to 3,9.
Hydrazides as extractants. It can be seen from Fig.1 that the
reagent with molecular mass 272 most effectively extracts Cu (II) and Ni
(II); at pH 3 the extraction degree for copper ≈ 95%, for nickel ≈ 75%. A
complex with [Cu] : [HNA]= 1:3 is the most characteristic and stable in
acid mediums. The extraction of Cu (II) with hydrazides from acid
mediums (pH 2) can be described by the following equation (5):
Cu2+(aq) + 3H2L+(о)
[Cu(HL)32+](о) + 3Н+(aq)
(5)
Table 1 shows distribution coefficients for Cu – Zn and Cu – Fe
(III) pairs. It is obvious from the Table 1 that the increase in pH leads to
the increase in β. The increase in molecular mass from 243 to 309 at pH
1 leads to the increase of βCu (II)/Fe(III) from 556 to 5298.
110
E,%
100
1
2
степень извлечения, %
80
3
60
4
5
40
6
20
0
2
4
6
8
рН
Fig.1. Extraction degree of metals (E) from sulfuric mediums with 4,7% HNA
(molecular mass 272) in the mixture kerosene/2-ethylhexanol = 3:1 versus pH.
Vorganic phase/Vaqueous phase = 1:10. Curves: 1 – 0,437 Cu (II); 2 – 0,296 Fe (III); 3 –
0,15 Ni (II); 4 – 0,26 Zn (II); 5 – 0,244 Co (II); 6 – 0,35 Fe (II)
Table 1
Extraction degree, distribution and separation (β) coefficients of metal ions with
HNA with molecular mass 243
рН
0,4
1,0
1,4
Extraction degree (%)/separation coefficient
Cu(II)
Fe(III)
Zn(II)
83,2/4,9
4,5/0,05
12,8/0,15
97,8/44,5
7,1/0,08
12,9/0,15
99,2/124
8,0/0,09
16,0/0,19
Cu/Zn
Cu/Fe(III)
33
297
653
98
556
1378
Many mine waters contain copper against a background of a great
deal of Fe (III). Table 2 reflects results of investigations in copper
extraction with HNA in the presence of a big quantity of Fe (III).
111
Table 2
Extraction of Cu (II) in the presence of Fe (III).
Cu (II) content: 0,50 g/l; extractants: 5% solution of HNA (molecular mass 272)
in kerosene/2-ethylhexanol mixture (1:1); Vorganic phase/Vaqueous phase = 1:10
Fe
(III)
рН
content; g/l
9,90
9,90
20,14
20,48
20,55
40,46
0,73
2,02
1,09
1,65
2,07
1,14
Cu (II) content, g/l
Aqueous Organic
phase
phase
0,24
2,59
0,12
3,72
0,31
1,86
0,28
2,11
0,23
2,67
0,29
2,07
Fe (III) content, g/l ßCu/Fe
Aqueous Organic
phase phase
9,90
–
–
9,62
2,79
106
20,14
marks
–
20,48
marks
–
20,34
2,08
114
40,46
marks
–
It can be seen from Table 2 that HNA extracts copper and
practically does not extract Fe (III) in the pH 1 – 1,5 range. In order to
re-extract copper from organic phase, H2SO4 solutions with
concentration 200-250 g/l are used.
Hydrazides as reagents for ion flotation [10, 11]. The availability
of strong surfactant and simultaneously complexing properties of HCA
made it possible to use them for removal of metals from solution with
ion flotation (IF). Data reflecting the influence of pH index on the metal
removal degree into froth fraction with C7H15CONHNH2 are shown on
Fig.2.
Probably, the introduction of HCA leads to ion-dipole interaction
of positively charged particles of metal hydroxide sols with a polar
molecule of the collector resulting in hydrophobization of particles
accompanied by formation of flotation-active sublate, for example, for
bivalent metals as per micellar formula (6):
{[M(OH)2]m . nM2+. (2-x)OH–} . 2xOH– . (m+n)RCONHNH2 (6)
where k, m, n, x are stoichiometric coefficients, k = 1,4 – 2,3
112
S,%
100
Степень извлечения, S, %
80
3
4
2
1
60
40
20
0
2
4
6
8
10
рНрН
Величина
Fig.2. Flotation degree (S) of metals with Hydrazex-79M technical blend versus
pH of the solution. Τflot = 10 min; concentration of metals, mol/l104: 1 – Zn (II)
(2,75); 2 – Ni (II) (4,6); 3 – Cu (II) (4,4); 4 – Fe (III) (3,9); Hydrazex-79M, ,
mol/l104: 1 – 0,625; 2,4 – 1,25; 3 – 1,9
The use of hydrazides as collectors for IF enables to reach
residual concentrations of Cu (II), Fe (III), Ni (II), Zn (II), respectively:
0,08; 0,05; 0,08; 0,12 mg/l [10].
Hydrazides as reagents in the flotation extraction of KCl from
potassium ores [12, 13]. The hydrazide functional-active group is
strongly polar. HCA exhibit surfactant properties at a certain length of
their radical. On addition of acids, cationic surfactants
[RCONHNH3]+X– are formed. It appeared to be interesting to compare
properties of HCA as surfactants with aliphatic amines forming
113
[RNH3]+Cl salts in acid mediums, which are, in particular, for flotation
of KCl. Values of critical concentrations of micellar formation (CCMF)
of HCA hydrochlorides are shown in Table 3. CCMF of hexadecyl- and
octadecylamine solutions in water at 30C are equal, respectively, to
5,210-5 and 8,610-6 mol/l. The increase of HCl concentration and the
decrease in pH from 5,5 to 3,0 and lower lead to the increase of CCMF
values for example for the hydrazide with R=C8H17 from 3,110-5 up to
9,210-5 and 13,610-5 mol/l (30C), respectively. Hydrazides, as
compared with amines, are less disposed to the salting-out.
Table 3
CCMF values of RCONHNH2 in water and in solution saturated with KCl/NaCl
(HCA : HCl = 1:2; t=30C)
Liquid phase composition
Distilled water
КСl – NaCl – Н2О
CCMF, mol/l10-5, depending on the R length
C5H11
C6H13 C7H15 C8H17
C9H19
87
33
1,4
3,1
0,55
55
22
0,7
1,3
0,20
Hydrochloric salts of hydrazides with R= C5H11 – C7H15 have
foam–forming properties, salts with R=C8H17 and C9H19 are defoamers
at concentrations over 0,5 mg/dm3. On application of HCA, dispersion
ability of air bubbles is approximately 2-fold higher than with amines;
this circumstance also confirms better flotation activity of hydrazides.
Resulting from experimental data on flotation activity of
hydrazides, one can suppose that there is an analogy in the action
mechanism of amines and of HCA as collectors. Hydrazides are also
active only in protonated form [RCONHNH3]+. But HCA are more weak
bases as compared with amines; hydrazides are completely protonated in
more acid mediums with pH2.
Experimental-industrial tests of hydrazides were conducted in
«Uralkali» JSC. Data on flotation of KCl with HCA are given in the
Table 4. Hydrazides Nb.3-5 are not inferior to amines in flotation of KCl
but KCl content in concentrates is lower than on flotation with amines.
HCA with R=C8H17 proved to be optimal in flotation activity.
114
Table 4
Hydrazides RCONHNH2 as collectors in flotation process of KCl
Ratios: HCA : HCl = 1:2; RNH2 : HCl = 1:1
№*
1
2
3
4
5
6
7
8
R
Reagent
Product
consump.
produced
(g/t of ore)
С5Н11
300
Concentrate
Tails
С6Н13
400
Concentrate
Tails
С7Н15
200
Concentrate
Tails
С8Н17
200
Concentrate
Tails
С9Н19
200
Concentrate
Tails
Amines, R=
100
Concentrate
С16 – С20
Tails
С7Н15
200
Concentrate
Tails
Amines, R=
100
Concentrate
С16 – С20
Tails
KCl mass KCl flotation
fraction, %
degree, %
75,9
29,6
74,5
18,8
75,2
2,5
66,7
2,5
63,2
2,1
74,5
3,3
66,8
1,0
74,0
1,4
30,0
70,0
65,3
34,7
95,0
5,0
96,6
3,4
97,2
2,8
94,9
5,1
98,0
2,0
96,4
3,6
* Note: Tests 1-6 were conducted on deslimed ores with % wt contents: KCl –
33,9; insoluble residue – 1,12; tests 7,8 – on original ores (KCl – 26,9, insoluble residue – 1,83).
1,2-Diacylhydrazines (DAH)
Physicochemical properties.
following general formula (6):
1,2-diacylhydrazines
have
the
O
R1 C NH
NH
C
O
115
R2
(6)
To
date,
physicochemical
properties
of
symmetric
1,2-diacylhydrazines (R1=R2) of lower carbonic and benzoic acids are
studied in detail [14, 15].
DAH (H2L) are weak dibasic acids characterized by acid
dissociation constants Ka1 and Ka2 (equation 7):
R-C-NH-NH-C-R
O
O
(H2L)
K a1
R-C=N-NH-C-R
OO
-
(HL )
Ka2
R-C=N-N=C-R
OO-
(7)
2-
(L )
pKa1 and pKa2 were determined with spectrophotometric method among
DAH of aliphatic acids [14] and 1,2-dibenzoylhydrazine [15]. DAH are
weak acids; pKa1 and pKa2 values slightly increase with the increase in
the length of the radical: pKa1 – from 10,9 up to 11,2; pKa2 – from 12,1
up to 12,5. Introduction of phenyl radicals into the DAH molecule
strengthens 100-fold acidic properties of the reagents [15].
Symmetric DAH are tetradentate ligands on the account of the
C(O)NHNHC(O) functional group and form stable flotation-active
complexes with ions of Cu (II) and of other non-ferrous metals in
ammoniac/alkali medium [16,17]. Symmetric DAH proved to be
effective in the removal of non-ferrous metal ions from waste waters
with ion flotation [18], of copper ions – with precipitation [19].
1,2-Diacylhydrazines as collectors of ions of Cu (II), Ni (II), Fe
(III), Co (II) from alkali mediums with flotation [18]. Interaction of
metal ions with DAH in alkali mediums occurs practically instantly and
is accompanied by formation of hardly soluble precipitates. These
precipitates are flotation-active, especially on addition of small
quantities of a foaming agent, for example of sulphanole (5-10 mg/l).
Flotation of metal cations with 1,2-dipentanoylhydrazine (DPH)
proceeds in the most high degree at such pH index when hydroxides of
metals are formed (Fig.3). Ions of Cu (II) are flotated with DAG having
C2H5 – C4H9 radicals in a most high degree and in the more wide range
of pH.
116
S,% 100
Co
Сu
Fe
80
Ni
60
40
20
0
0
4
8
12
pH
16
рНравн.
Fig.3. Flotation degree of metals with 1,2-dipentanoylhydrazine (DPH) into
foam-floated product versus pH.
Concentrations (mg/l): Cu (II) – 20,1; Ni (II) – 39,2; Co (II) – 21,4; Fe (III) –
32,2. Flotation time – 10 min; M : DPH = 2 : 1
Complex formation of non-ferrous metal ions in the above mentioned
conditions can be represented by the equation (8):
2(МОН)+ + Н2DAН  [(MOH)2L]  + 2Н+
(8)
A green color precipitate of a copper complex with 1,2dibutanoylhydrazine was obtained from alkali mediums at pH 8 and at
the ratio Cu (II):H2L = 2 : 1. According to data of elemental and thermal
analysis and of infrared spectroscopy, the precipitate corresponds to the
formula [(CuOH)2C3H7CONNCOC3H7(Н2О)2]. Values of solubility
117
product (SP) of non-ferrous metal complexes
dipentanoylhydrazine as an example are given in Table 5.
with
1,2-
Table 5
–lg SP values of (MOH)2L complexes with 1,2-dipentanoylhydrazine
M(II)
Cu(II)
CM
mol/l
104
СН2L,
mol/l
104
Si,
%
3,10
1,55
99,6
[M]eq. рН.
mol/l
106
1,20
8,0
[L2–]
mol/l
[M2+]
mol/l
·108
–lg
SP
3,110-
10,00
40,5
0,70
0,44
32,4
35,0
15
Co(II)
Ni(II)
3,56
6,64
1,78
3,32
99,7
99,8
1,10
1,33
10,5
10,9
1,010-9
810-9
Precipitates of M(II) complexes with H2L are hardly soluble; this
circumstance explains the high flotation degree of non-ferrous metal
ions into foam-floated product. The method (with the use of DPH) was
tested on galvanic sewage of «Telta» JSC (City of Perm) by pressure
flotation (see Table 6). The sewage treatment which meets MPC level
for requirements was achieved by one–stage method.
Table 6
Treatment of galvanic sewage («Теltа» JSC, Perm) with pressure flotation with
the 1,2-dipentanoylydrazine
Sewage
Concentration of metal ions, mg/l
Ni(II) Fe(III) Cu(II) Cr(III) Zn(II)
Before treatment
0,13
18,0
4,40
1,13
2,00
After treatment
0,05
1,20
0,42
0,05
0,30
MPC norms for sewage in 0,09
1,23
1,36
0,19
0,22
city sewer
1,2-diacylhydrazines as precipitators of Cu (II) from ammoniac
solutions. Ammoniac mediums are wide used in plating plants.
Opportunity of application of symmetric diacylhydrazines with R=C3H7
(dibutanoylhydrazine),
C4H9
(dipentanoylhydrazine),
C6H5
(dibenzoylhydrazine) for precipitation of Cu (II) ions was investigated.
Influence of reagent concentrations, of the length and structure of
the DAH radical on the completeness of Cu (II) precipitation was
118
studied [16]. Ratios Cu (II) : DAH = 1:1 and 1:2 in complexes formed at
the precipitation from ammoniac solutions, were obtained by the
equilibrium shift methods and conductometric titration. However,
complexes obtained at ratios mentioned above proved to be identical;
this was confirmed by results of derivatography and of elemental
analyses, as well as by electronic paramagnetic resonance specter and
infrared specter. Thus, only one complex (1:1) is obtained at the
precipitation from ammoniac solutions. Its formation can be represented
by equation (9)
[Cu(NH3)4]2+ +RCONHNHCOR
[Cu(NH3)2RCONNCOR] +2NH4+ (9)
The precipitate obtained is mixed-ligand complex. Its structure may be
represented by the following graphical formula (10):
O
C
N
N
O
Cu
R
NH3
R C
n
NH3
(10)
Values of solubility product (SP) of copper complex precipitates and for
Kequilibr. of reactions (9) are represented in Table 7.
Table 7
–lg SP values and equilibrium constants of the complexation reaction of Cu (II)
ions with 1,2-diacylhydrazines in ammoniac medium
R
СCu,
СН2L,
mol/l
mol/l
103
С3Н7
С4Н9
С5Н11
1,6
1,6
1,6
103
1,6
1,6
1,6
Si,
%
[Cu]equilibr.
mol/l
рН
Кequilibr
10
7,36
3,52
1,12
–lg
SP
9,8
9,8
10,1
23,9
24,8
25,8
8,3·1011
5,8·1012
5,7·1013
5
95,4
97,8
99,3
119
There is problem of using foam-floated products and precipitates
obtained in processes of ion flotation and precipitation. As a rule, they
are dried and ashed. It turned out that Cu (II) – DAH complexes are
easily degraded during their treatment by mineral acids, at that, DAH are
regenerated and Cu (II) ions pass into a filtrate.
An opportunity of treatment of solutions modeling rinsing water
from etching processes and containing 102 mg/l Cu (II) against a
background of 0,25 mol/l NH3 and 0,125 mol/l (NH4)2SO4 was studied.
DAH with R=C3H7 - C5H11 and DAH obtained from a technical fraction
of C5, C6 were used as precipitators. The level of cleaning from Cu (II)
ions with the use of individual DAH amounted to 0,07 mg/l; with a
reagent obtained from acid technical fraction – 0,08 mg/l. The chemical
oxygen demand amounted to 190 mg O2/l; this value corresponds to the
norms for water to be drained into the city sewer.
Thus, hydrazides are of interest as extractants of Cu (II) ions, inter
alia from solutions containing up to 40 g/l Fe (III); as reagents for ion
flotation of non-ferrous metals from the sewage; as collectors in the
mineral resource industry. 1,2-diacylhydrazines can find an application
for the in-depth one-stage treatment of non-ferrous metal ions from
sewages.
References
1. P.A.S. Smith. Organic Reactions. Vol.3, Foreign Literature Publishers, Moscow, 1951, pp.322-426
2. A.P. Grekov. Organic Chemistry of Hydrazine. Technika Publishers,
Kiev, 1966, p. 23.
3. R.I. Machkhoshvili. Coordinative compounds of metals with hydrazines. Doctoral Thesis. M., 1983, p.457
4. Patent of France 2213271. Cl.C 22 B 3/00//C 22 B5/0. Les sels de
hydrazides, leurs obtention et application/ Ciba-Geigi AG (Suisse)
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Metals from Acid or Alkali Solutions.
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from solutions by means of hydrazides of aliphatic naphthene acids.
PhD Thesis. Perm, Institute of Technical Chemistry of Ural Division
of RAS, 1998, p.114.
120
7. A.V. Radushev. Theory and techniques of extraction of copper and
associated metals from solutions by means of hydrazides. Doctoral
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Chemistry, vol.68, 1998, pp.1674-1677.
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Extraction), M., 2001, p.199.
121