ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 12, pp. 2024!2027. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + I.V. Goshu, Yu.V. Tsarev, V.V. Kostrov, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 12, pp. 1946!1949.
AND INDUSTRIAL INORGANIC CHEMISTRY
Study of Chromium(VI) Reduction in the Presence
of Metal Salt Additives
I. V. Goshu, Yu. V. Tsarev, and V. V. Kostrov
Ivanovo State University of Chemical Engineering, Ivanovo, Russia
Received May 10, 2006; in final form July, 2007
Abstract-Reduction of Cr(VI) to Cr(III) in a model wastewater in the presence of copper, iron, and nickel
nitrates, sulfates, and chlorides was studied. The effect of the process temperature on the final pH values
of the solutions was examined.
Chromium is a hazardous impurity in the environ-
ment, with the form Cr(VI) being the most toxic.
To prevent discharge of this form of chromium into
the environment, it is necessary to reduce Cr(VI) to
Cr(III) and to remove it from wastewater. Beukes and
co-workers studied reduction of Cr(VI) with sulfites in
wastewater . The experiments were carried out in
an aqueous solution of Na
O at various
pH values and contact durations. It was shown that
the rate of Cr(VI) reaction with sulfites strongly de-
pends on the pH of the reaction mixture. As pH in-
creases from 2.0 to 5.0, the rate of Cr(VI) reduction
decreases. This process is in many respects analogous
to Cr(VI) reduction in neutral aqueous media by Fe(II)
ions; however, Fe(II) is effective in a wider pH range.
The catalytic analytical methods used to determine
components in redox reactions and the mechanism of
catalytic action were considered in . This mech-
anism consists in that the oxidized form of the catalyst
vigorously reacts with a reducing agent, and the re-
sulting product is rapidly oxidized under the action of
the oxidizing agent. The reaction of Fe
thiosulfate, which is catalyzed only by copper(II) ions,
was considered as an example.
According to the data of Smirnov and co-workers
, metal-organosiloxanes containing a transition
metal (including copper) that is used in traditional
catalysts, can be chosen for homogeneous catalysis. It
was shown that the activity of copper-containing com-
pounds is rather high.
The reduction of iron(III) to iron(II) with sodium
sulfite was studied in . It was found that the max-
imum yield of iron(II) is observed in the pH range
2.833.0, with the yield of iron(II) decreasing as pH
It was of interest to study the Cr(VI) reduction in
aqueous solutions containing copper, iron, and nickel
nitrates additives. The reason why these additives
are used is due to the necessity for acceleration of
the process of Cr(VI) reduction, because it is rather
slow in neutral media .
The aim of this study was to examine the effect
of the process temperature T and duration t on
the Cr(VI) reduction to Cr(III) in the presence of
, and Ni(NO
We carried out experiments were carried out with
a model wastewater solution based on chromic
) with a Cr(VI) concentration of
100 mg l
solution was used as
a reducing agent. The reduction was carried out in
the presence of 10% aqueous solutions of Cu(NO
, and Ni(NO
introduced into 100 ml of
the model solution in amounts of 2 mg.
The content of Cr(VI) in the presence of Cr(III)
in the model wastewater was determined by photom-
The technique used in the kinetic experiments was
described in . The duration of the Cr(VI) reduction
process was 60 min.
Previously, it has been found that the degree of
Cr(VI) reduction in the model chromic acid solution