Effect of Ca2+, Mg2+, Fe3+, and Al 3+ ions on the deposition of electrolytic manganese dioxide from chloride solutions

Article abstract of DOI:10.1007/s11167-005-0382-0

The effect of Ca²⁺, Mg²⁺, Fe³⁺, and Al³⁺ ions on the deposition of electrolytic manganese dioxide from chloride solutions was studied.

Full text of DOI:10.1007/s11167-005-0382-0

Russian Journal of Applied Chemistry, Vol. 78, No. 5, 2005, pp. 737 740. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5,
005, pp. 751 754.
Original Russian Text Copyright
2
2005 by Kolosnitsyn, Minnikhanova, Karaseva, Dmitriev, Muratov.
APPLIED ELECTROCHEMISTRY
AND CORROSION PROTECTION OF METALS
2
+
2+
3+
3+
Effect of Ca , Mg , Fe , and Al Ions on the Deposition
of Electrolytic Manganese Dioxide from Chloride Solutions
V. S. Kolosnitsyn, E. A. Minnikhanova, E. V. Karaseva,
Yu. K. Dmitriev, and M. M. Muratov
Institute of Organic Chemistry, Ufa Scientific Center, Russian Academy of Sciences, Ufa,
Bashkortostan, Russia
Kaustik Private Company, Sterlitamak, Bashkortostan, Russia
Received September 1, 2004; in final form, February 2005
2
+
2+
3+
3+
Abstract The effect of Ca , Mg , Fe , and Al ions on the deposition of electrolytic manganese dioxide
from chloride solutions was studied.
In the world practice, the raw materials for produc-
tion of electrolytic manganese dioxide (EMD) and
electrolytic manganese metal (EMM) are rich man-
ganese ores, which are virtually lacking in Russia.
Therefore, it is of specific interest to use lean man-
ganese ores, e.g., manganese limestones, for the pro-
duction of manganese compounds. The largest deposit
of manganese limestone ores is the Ulu-Telyak depos-
it (Bashkortostan). Manganese limestones have the
following average chemical composition (wt %):
Mn 9 15, SiO 5 10, Al O 3 5, Fe 1.2 1.5, CaO
leaching solutions to remove undesirable impurities.
As a rule, the processing solutions of hydrochloric
acid leaching contain, apart from MnCl , also CaCl ,
2
2
MgCl , FeCl , and AlCl as main impurities. Prior to
2
3
3
use for the electrolysis, they should be treated to re-
move the impurities that adversely affect the electrol-
ysis and the composition and properties of the prod-
ucts. A common treatment method is the hydrolytic
purification [1], which allows the content of readily
hydrolyzable compounds, Fe3 and Al chlorides, to
be decreased to the acceptable value. However, pre-
sumably, these compounds would not adversely affect
+
3+
2
2 3
3
0 40, S 0.04 0.06, P 0.02 0.04, MgO 3 5, and
H O 1.0 1.5.
the electrodeposition of MnO and its properties.
2
2
In hydrometallurgical reprocessing of lean man-
ganese ores, as leaching agents are used mineral acids,
H SO , HCl, and HNO . The choice of the acid is
mainly determined by its cost and accessibility rather
than by leaching power. For example, a large volume
of a 20 25% hydrochloric acid is formed at chlorine
production plants as waste, which can be utilized for
ore leaching.
Therefore, it was of practical significance to study
the effect exerted by calcium, magnesium, aluminum,
and iron ions on the composition of electrolytic man-
ganese dioxide and the electrolysis parameters.
2
4
3
EXPERIMENTAL
The electrolysis was performed in an electrolyzer
with parallel-plate Plexiglas electrodes. A VT-1-00
titanium was anode and NKh18N10T stainless steel,
a cathode. The electrodes were polarized with a sta-
bilized B5-47 current source. The electrode potentials
were measured relative to a silver chloride reference
electrode.
It should also be noted that leaching of manganese
ores with hydrochloric acid has a number of advant-
ages. For example, in leaching of manganese from
limestone ores with hydrochloric acid, in contrast to
sulfuric acid leaching, no sparingly soluble com-
pounds adversely affecting the process equipment are
formed. Moreover, in reprocessing of ores containing
The change in the acidity of the electrolyte solu-
manganese in higher oxidation states, chlorine can be tions before and after the electrolysis was determined
obtained, which is a valuable chemical raw material.
with a portable microprocessor HI-9025 pH/mV/ C
meter (Portugal).
At the same time, in hydroelectrometallurgical re-
processing of manganese ores, there is also a number
of problems, first of all, the problem of purification of
The experiments were performed at 75 C and a
2
current density of 5 mA cm .
1
070-4272/05/7805-0737 2005 Pleiades Publishing, Inc.

738
KOLOSNITSYN et al.
Current efficiency and degree of recovery of manganese(IV) oxide at various electrolyte compositions (current density
2
5
mA cm , temperature 75 C, MnCl 1 M, and HCl 0.05 M)
2
pH
Degree of Mn
electrodeposi-
tion, %
Apparent den-
Impurity,
CE,
%
U, V
Ea, V
sity of MnO ,
2
M
3
before electrolysis after electrolysis
g cm
CaCl2:
0
0
1
.05
.25
.0
0.65
0.45
0.08
0.30
0.27
0.04
92
93
89
15.5
16.5
14.2
2.58
2.83
3.23
1.62
1.88
2.14
1.55
1.43
1.58
MgCl2:
0
0
1
.05
.25
.0
0.68
0.58
0.31
0.53
0.37
0.12
92
95
90
15.8
17.0
15.3
2.40
2.45
2.85
1.47
1.57
1.69
1.62
1.49
1.55
AlCl3:
0
0
1
.05
.25
.0
0.52
0.42
0.10
0.33
0.22
0.08
80
75
13.0
11.0
2.34
2.43
1.48
1.52
1.55
1.56
Solution after electrolysis is turbid. Breakdown of anode surface.
Voltage across the electrolyzer increased from 2.43 to 6 V
FeCl3:
0
0
.05
.25
0.35
0.08
0.13
0.02
64
8.0
2.82
1.84
1.33
Solution after electrolysis is turbid. Breakdown of anode surface.
Voltage across the electrolyzer increased from 2.43 to 6 V.
The time of all the experiments was 60 min. Under
the given conditions, the current efficiency was 95
Irrespective of the Ca2+ concentration in the elec-
trolyte, MnO is deposited onto the anode in the form
2
97% and the degree of manganese electrodeposition,
8 20%. To retain the relatively constant composition
of a black lustrous flaky film easily exfoliating from
1
the electrode. The weight fraction of MnO in the
2
of the components in the electrolytes, the process was
not performed to greater extents of manganese elec-
trodeposition. The electrolytes were prepared from
chemically pure and analytically pure grade chemicals.
product obtained was 99.7% and the calcium concen-
tration, less than 0.01%.
In magnesium-containing electrolytes, the current
efficiency was 90 95% (see table). The behavior of
the anode and the cathode potentials and of the volt-
age across the electrolyzer was similar to that in cal-
cium-containing electrolytes (Fig. 1b), with the anode
potential and voltage across the electrolyzer being
somewhat lower. For example, the voltage across the
electrolyzer was 2.4 and 2.85 V at 0.05 and 1 M Mg.
At any concentration of Mg2+ in the electrolyte,
The product obtained was analyzed for the content
of MnO and of calcium, magnesium, iron, and alu-
2
minum impurity ions. The manganese content was
determined by Volhard’s method [2]. The microim-
purities of calcium, magnesium, aluminum, and iron
ions were determined by emission spectroscopy on
an ISP-30 spectrometer. The apparent density was
determined by the volumetric-gravimetric method [3].
MnO was deposited onto the anode in the form of
2
2+
In Ca -containing electrolytes, the current effi-
ciency (CE) is 75 93%, and it decreases with growing
a black flaky film easily exfoliating from the surface.
The deposited film contained 99.7% MnO and no
2
2+
Ca concentration (see table). As the concentration of
the calcium ions in the electrolyte increases, the volt-
age across the electrolyzer and the anode potentials
increase. For example, in the electrolyte containing
more than 0.01% magnesium.
When the electrolysis was performed in the pres-
ence of aluminum ions, the current efficiency was 75
3+
8
0%, and it decreased as the Al concentration was
2
+
0
2
.05 M Ca , the voltage across the electrolyzer is
3+
increased (see table). For example, at an Al concen-
tration of 0.05 M, the current efficiency was 80% and
at 0.25 M, 75%. In an electrolyte containing 1 M
2+
.6 V, whereas in that containing 1 M Ca it is 3.2 V.
In the course of the electrolysis, the anode potential
first decreases and then increases, whereas the cathode Al , the anode was damaged and the electrolyte
3+
potential always decreases (Fig. 1a).
became turbid.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 5 2005

2
+
2+
3+
3+
EFFECT OF Ca , Mg , Fe , AND Al IONS ON THE DEPOSITION
739
E, V
(a)
E, V
(b)
,
min
c)
E, V
, min
(d)
(
E, V
,
min
, min
2
+
2+
3+
3+
Fig. 1. Influence of the concentrations of (a) Ca , (b) Mg , (c) Al , and (d) Fe ions on variations of the anode potential
E with time . Electrolyte (M): 1.0 MnCl and 0.05 HCl. (a) CaCl concentration (M): (1) 0.05, (2) 0.25, (3) 1.0, (4) 2.0, and
2
2
(
(
5) 0.0. (b) MgCl concentration (M): (1) 0.05, (2) 0.25, and (3) 1.0. (c) AlCl concentration (M): (1) 0.05, (2) 0.25, and (3) 1.0.
d) FeCl concentration (M): (1) 0.05 and (2) 0.25.
2
3
3
In electrolytes with a low concentration of Al3+
surface. The deposited film contained 99 wt % MnO2
and no more than 0.03 0.1 wt % iron.
ions (0.05 M), variations of the anode potential and
voltage across the electrolyzer in the course of the
The electrolysis of chloride solutions yields man-
ganese tetrachloride, which hydrolyzes to form man-
ganese dioxide [4, 5]:
2+
electrolysis were similar to those in the Ca - and
2+
3+
Mg -containing electrolytes. With the Al concen-
tration increased from 0.25 to 1 M, the anode poten-
tial (Fig. 1c) and voltage across the electrolyzer in-
creased.
MnCl4 + 2H O
MnO2 + 4HCl.
(1)
2
The manganese dioxide film deposited onto the
anode was dense and difficult-to-detach from the sur-
The study showed that the effects exerted by cal-
cium, magnesium, iron, and aluminum salts on the
electrolysis of manganese chloride solutions differ
essentially. The Ca and Mg ions do not noticeably
affect the voltage across the electrolyzer, current effi-
face. The film contained 99.5 wt % MnO and no
2
more than 0.03 wt % aluminum.
2+
2+
3+
In the electrolytes containing Fe , the current ef-
ficiency by MnO was only 64% even at small iron
ciency, and chemical composition of MnO . On the
2
2
3+
contrary, the Fe3 and Al ions exert a very strong
effect on both the electrolysis parameters and the
chemical composition of the forming products. Prob-
ably, this is due to their different acid base properties.
The Al3+ and Fe3+ ions are strong Lewis acids.
+
3+
concentrations (0.05 M Fe ) (see table). With in-
creasing iron concentration, the voltage across the
electrolyzer and the anode potential sharply increased
(
Fig. 1d).
The electrolyte containing 0.25 M FeCl became
3
turbid after the electrolysis. In the course of the elec-
trolysis, the damage of the anode was observed, with
In acid solutions, they form metallic acids:
its small areas coated with a fine MnO deposit.
2
FeCl3 + HCl
AlCl3 + HCl
HFeCl4,
HAlCl4.
(2)
(3)
Manganese dioxide was deposited onto the anode
as a dense dull black film difficult-to-detach from the
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 5 2005

740
KOLOSNITSYN et al.
Therefore, in electrolyte solutions they compete
with Mn4+ ions for chloride ions. The binding of
creased to a required value by adding sulfuric acid.
Calcium sulfate formed in the process can be used in
building industry.
3+
3+
chloride ions with Al and Fe ions can accelerate
the MnCl hydrolysis. Therefore, MnO is formed
4
2
Thus, our results show that electrolytic MnO with
2
both in the bulk of the solution and on the anode sur-
face, forming strong films with a poorly developed
crystal structure.
a low concentration of impurities can be prepared
directly from processing solutions of hydrochloric
acid leaching of manganese ores without their exhaus-
tive purification.
The fact that CE considerably decreases in the pres-
ence of Fe3+ ions can be accounted for as follows.
The iron ions in electrolytes are reduced on the cath-
ode and oxidized on the anode in the course of elec-
trolysis [6]. This results, on the one hand, in a de-
CONCLUSION
Calcium and magnesium ions do not affect ad-
versely the electrolysis of manganese chloride electro-
lytes and the quality of manganese dioxide being
formed. The presence of iron and aluminum ions in
the electrolyte solutions markedly deteriorates elec-
crease in the current efficiency of the MnO electro-
2
deposition owing to Fe2+ oxidation on the anode and,
4+
on the other hand, in a decrease in the Mn concen-
tration owing to the redox reactions
trolysis process and the quality of the MnO deposit.
2
Fe2+ + Mn4+
Fe2+ + Mn4+
Mn3+ + Fe3+,
Mn2+ + 2Fe3+.
(4)
(5)
REFERENCES
2
1
2
. USSR Inventor’s Certificate no. 1497252.
. Charlot, G., Quantitative Inorganic Analysis, London:
Wiley, 1957.
. Pisarenko, V.V., and Zakharov, L.S., Tekhnicheskii
analiz (Technical Analysis), Moscow: Vysshaya Shko-
la, 1972.
A fast increase in the anode potential and, con-
sequently, in the voltage across the electrolyzer may
be due to formation on the anode of a dense passiva-
tion film with a low electrical conductivity. On the
damaged areas of this film, the current densities in-
crease, which results in the damage of the anodes by
electroerosion.
3
4
. Lisov, V.N., in Gidroelektrometallurgiya khloridov
(
Hydroelectrometallurgy of Chlorides), Kiev: Naukova
Continuous electrolysis of electrolytes containing
calcium and magnesium compounds will result in the
formation of spent electrolytes with relatively high
concentrations of Ca2+ and Mg ions and hydro-
chloric acid. The results of this study showed that
spent electrolytes can be used for leaching manganese
compounds. In the process, a part of Ca2+ and Mg
ions passes into the leaching sludge by an ion-ex-
change reaction. The leaching of manganese com-
pounds from ores with calcium chloride solutions has
been described in [7, 8]. Moreover, the concentration
of calcium ions in the spent electrolyte can be de-
Dumka, 1964, pp. 76 98.
5. Stender, V.V., and Lisov, V.N., Zh. Prikl. Khim., 1967,
vol. 40, no. 3, pp. 570 576.
2+
6
. Antropov, L.I., Teoreticheskaya elektrokhimiya (Theo-
retical Electrochemistry), Moscow: Vysshaya Shkola,
1975, vol. 1.
7. Pozin, M.S., Tekhnologiya mineral’nykh solei (Tech-
nology of Mineral Salts), Moscow: Khimiya, 1975,
vol. 1.
8. Lavrukhina, A.K., and Yukina, L.V., Analiticheskaya
khimiya margantsa (Analytical Chemistry of Man-
ganese), Moscow: Nauka, 1974.
2+
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