ISSN 1070-4272, Russian Journal of Applied Chemistry, 2014, Vol. 87, No. 9, pp. 1217−1222. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © A.M. Gaydukova, V.A. Brodskiy, V.A. Kolesnikov, 2014, published in Zhurnal Prikladnoi Khimii, 2014, Vol. 87, No. 9, pp. 1221−1226.
INORGANIC SYNTHESIS AND INDUSTRIAL
Puriﬁ cation of Aqueous Solutions To Remove
Variable-Valence Metals with the Use
of Ruthenium–Titanium Oxide Electrodes
A. M. Gaydukova, V. A. Brodskiy, and V. A. Kolesnikov
Mendeleev University of Chemical Technology, Miusskaya pl. 9, Moscow, 125047 Russia
Received October 8, 2014
Abstract—Method for puriﬁ cation of aqueous solutions to remove Fe(II), Ni(II), and Co(II) ions with ruthenium–
titanium oxide electrodes (ORTA) was studied. The method is based on the process in which divalent metals are
oxidized to the trivalent state at the phase boundary between the oxide layer on the electrode surface and the
aqueous solution, followed by recovery of the metals from solution by ﬁ ltration in the form of poorly soluble
. IT was found that technological parameters of the process affect the recovery efﬁ ciency of
variable-valence metal ions from aqueous solutions. IT is shown that the method is promising for application in
water puriﬁ cation and water treatment processes.
One of priority tasks in development of modern
methods for water puriﬁ cation to remove organic and
inorganic contaminants is to minimize the use of chemical
reagents. This diminishes the secondary contamination
of water and the expenditure for purchase of reagents.
In most cases, puriﬁ cation methods of this kind use as
reagents “ecologically clean” oxidizing agents produced
from water components via its physical processing by
exposure to UV radiation and treatment with cavitation
or ultrasound and pulsed high-voltage discharges [1–6].
It is known that redox processes may occur not only
in the solution bulk upon introduction of oxidizing
or reducing agents into solution, but also at the phase
boundary. As an example of processes of this kind can
serve redox processes at the interface between the oxide
of a variable-valence metal and a solution containing
oxidizing or reducing agents. The necessary requirement
to these oxides is the possibility of returning the surface
to its initial valence state on performing a redox process
(surface regeneration). The most accessible and promising
material for performing processes of this kind is the
ruthenium-titanium oxide electrode (ORTA), a titanium
base with a deposited layer of titanium and ruthenium
For redox processes to be the most complete, the oxide
layer should have a large speciﬁ c surface area in order to
provide the required area of contact with a solution .
A topical task of water puriﬁ cation and water treatment
is to remove from aqueous solutions ions of variable-
valence metals, including iron, nickel, cobalt, etc.
Iron(II) is a widely occurring component of natural water,
nickel(II) and cobalt(II)ions are contained in wastewater
from galvanic and metal-processing industries.
The goal of our study was to examine the process
of puriﬁ cation of aqueous solutions to remove ions of
variable-valence metals for the example of Fe(II), Ni(II),
and Co(II) with the use of ORTA electrodes.
The oxidation process of divalent metals (Fe
) at the phase boundary betwen the oxide electrode
and the electrolyte solution occurs by the scheme shown
in Fig. 1.
Upon a contact of the ORTA electrode surface
composed of titanium and ruthenium(IV) oxides with
the electrolyte containing M
ions, there occur two
redox processes: M
+ e and Ru
+ e → Ru
(Fig. 1a). Upon application of an anodic polarization to
the electrode, the already formed ruthenium(II) oxide