ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2018, Vol. 92, No. 11, pp. 2348–2350. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © G.K. Aibolova, E.Zh. Tuleshova, 2018, published in Zhurnal Fizicheskoi Khimii, 2018, Vol. 92, No. 11, pp. 1817–1819.
SHORT
COMMUNICATIONS
Kinetics and Mechanism of Cathodic Reduction
of Nitrate Ions in a Sulfuric Acid Solution
a
a,
G. K. Aibolova and E. Zh. Tuleshova *
a
Akhmed Yassawi International Kazakh-Turkish University, Turkestan, 161200 Kazakhstan
*
е-mail: elmira.tuleshova@ayu.edu.kz, t.elmira@mail.ru
Received March 1, 2018
Abstract—The cathodic reduction of nitrate ions in aqueous solutions of sulfuric acid in the presence of chro-
mium(III) ions is studied via potentiometry. It is shown for the first time that nitrate ions are reduced to nitro-
gen in nitrate-containing solutions in the presence of chromium(III) ions.
Keywords: potentiodynamic polarization curves, electrochemical behavior, nitric oxide, sulfuric acid, elec-
trode
DOI: 10.1134/S003602441811002X
INTRODUCTION
RESULTS AND DISCUSSION
Electrochemical processes are of great importance
in developing technologies for neutralizing gases con-
taining nitrogen(II) oxide, and in the production of
elemental nitrogen and nitrogen compounds. Reduc-
It is known from the literature [2] that the electro-
chemical reduction of nitrate ions proceeds according
to the reaction
tion of nitrogen oxide and dioxide to N is the effective
−
3
+
2
2
NO + 10e + 12H = N + 6H O,
2
2
means of their removal [1].
(1)
0
E = +1.25 V.
However, there is virtually no data in the literature
on the electrochemical reduction of nitrate ions on a
titanium electrode in the presence of Cr(III) ions cat-
alyst in acidic solutions. In order to fully understand
the electrode processes in the reduction of nitrate ions
in a solution of sulfuric acid, we measured the
cathodic potentiodynamic polarization curves in these
solutions.
However, our electrolysis results showed that
nitrate ions were reduced to nitrogen(II) oxide in a
solution of sulfuric acid:
−
3
+
NO + 3e + 4H → NO + 2H O,
2
(2)
0
E = +0.96 V.
The cathodic reduction of nitrate ions was studied
in a 0.5 M solution of sulfuric acid. The hydrogen
EXPERIMENTAL
To clarify the mechanism behind the reduction reduction currents can be seen on the cathodic polar-
reactions, we studied the cathodic reduction of nitrate ization curve in the potential range of −1.25 V…
ions via potentiometry on an IPC Pro potentiostat. −1.5 V (Fig. 1, curve 1). No other reduction currents
The voltammetric curves were registered at a potential were observed on the polarogram.
sweep rate of 10 mV/s using an H 301/1 flatbed two-
When nitrate ions were added to a sulfuric acid
coordinate potentiometer. Bulk titanium electrodes
solution, the maximum reduction current of nitrate
1
/5 mm in diameter and 3.0 mm long were used as the
ions was observed in the potential range of
cathode, and graphite plates were used as the anode.
‒
0.50 V…‒0.75 V (Fig. 1, curve 2). When we per-
A YaSE-2 special electrochemical cell mounted in
an IТZh-0-03 thermostat was used to conduct our
studies at a constant temperature.
Electrolysis was performed in galvanostatistic con- nitrate ions are reduced to nitrogen by reaction (1), but
ditions in a 100 mL cell. In all experiments, the dura- this process in fact proceeds with high overpotential
tion of electrolysis was 0.5 h.
formed electrolysis under galvanostatic conditions,
the final product was nitrogen oxide(II) according to
reaction (2). From the viewpoint of thermodynamics,
and does not occur.
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