Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 7, pp. 1230−1233.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
E.G. Shirinov, Z.G. Gasanly, D.M. Ganbarov, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 7, pp. 1134−1137.
AND CORROSION PROTECTION OF METALS
Reduction of Vanadium from Alkaline Solutions
E. G. Shirinov, Z. G. Gasanly, and D. M. Ganbarov
Nagiev Institute of Chemical Problems, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
Received December 3, 2008
Abstract—Effect of the potential sweep rate and temperature on the reduction kinetics of vanadate ions from
alkaline solutions was studied. The nature of polarization in separate regions of the cathodic process was
The available published data [1, 2] indicate that
vanadium(V) compounds in acid aqueous solutions
can be successively electrochemically reduced to
quadruple-, triple-, and double-charged states. All the
reduction products are soluble and remain in the course
of electrolysis in solution and impart to it blue, green, and
violet coloration. It is difﬁ cult to recover vanadium from
aqueous solutions because of the high negative potential
of the last stage of reaction .
The reduction of vanadium in alkaline solutions is
rather poorly understood, with the exception of results of
, in which a low-concentration (0.05 M NaOH) alkali
solution was used. It should be noted that there have
been nearly no reports in the literature about studies of
the nature of polarization in electroreduction of vanadate
anions, although these studies are of indubitable interest
for development of a technology for recovery of metals
from industrial solutions.
Because of the importance of advances in this area, the
aim of the present study was to examine the electrolytic
reduction of vanadate ions from alkaline solutions.
The kinetics and mechanism of vanadium reduction
from alkaline solutions were studied using an electrolyte
containing 0.0034 M NH
and 6 M NaOH.
The concentrations of vanadium(V) and alkali in this
solution corresponded to the concentrations of industrial
aluminate solutions from Gyandzha alumina plant,
produced by the Bayer method .
The chemical composition of the solution under study,
as regards the main components of the industrial solution,
is as follows (g l
O 186; Al
0.30; and other impurities.
Polarization curves were measured in the potentio-
dynamic mode with a P-5827 M potentiostat and N 307/1
recorder. A platinum wire with a surface area of 0.22 cm
served as the working electrode, and a platinum plate with
a surface area substantially exceeding that of the working
electrode, as the auxiliary electrode. A saturated silver
chloride electrode served as reference.
As can be seen in Fig. 1 (curves 1–5), the cathodic
polarization curves show two portions of reduction of
vanadate anions. This means that, in the reduction of
vanadate ions, the process occurs in two stages. In portion
I of the polarization curves at potentials of 0...0.60 V,
vanadate ions are reduced to V(IV) (V
portion II of the polarization curves at potentials of
–0.750…–0.90 V, V
O is reduced to V(III) (V
It is known that salts of vanadic acid are the most
stable vanadium compounds in alkaline media . In
electrolysis, V(V) anions (VO
) are reduced
to V(IV) and V(III) compounds [7, 8].
Cathode deposits were obtained from a solution of
6 M NaOH + 0.0034 M NH
by the potentiostatic
method at potentials of –0.60 and –0.75 V. The deposits