1070-4272/02/7511-1787$27.00C2002 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 75, No. 11, 2002, pp. 1787!1790. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 11,
2002, pp. 1823!1825.
Original Russian Text Copyright + 2002 by Saikova, Panteleeva, Nikolaeva, Pashkov.
AND ION-EXCHANGE PROCESSES
Optimal Conditions of Ion-Exchange Synthesis of Cobalt(II)
Hydroxide with AV-17-8 Anion Exchanger in the OH Form
S. V. Saikova, M. V. Panteleeva, R. B. Nikolaeva, and G. L. Pashkov
Institute of Chemistry and Chemical Technology, Siberian Division, Russian Academy of Sciences,
Krasnoyarsk State University, Krasnoyarsk, Russia
Received Oktober 31, 2001; in final form, April 2002
Abstract-Ion-exchange synthesis of cobalt(II) hydroxide by treatment of aqueous solutions of cobalt salts
with OH form of AV-17-8 anion exchanger was studied. The influence of time, anion of cobalt salt, number
of precipitation stages, and anion exchanger swelling on the degree of cobalt(II) precipitation was examined.
It is convenient to synthesize cobalt-containing
substances (including salts) from cobalt(II) hydroxide,
which readily dissolves in acids and does not partici-
pate in side redox reactions. As a result, pure salts are
formed. Traditional preparation of cobalt(II) hydrox-
ide by exchange of cobalt salts with a small excess of
alkali gives the product contaminated with anions of
the initial cobalt salt and cations of the precipitant,
whose removal requires special separation procedures.
In a strongly alkaline medium, Co(OH)
oxidized into cobalt(II, III) hydroxide whose dissolu-
tion proceeds under more rigid conditions and is ac-
companied by redox reactions, which is unacceptable
in preparation of certain cobalt-containing substances.
Basing on reference data , we assumed that
cobalt(II) hydroxide can be prepared using an anion
exchanger in the OH form. Because of sufficiently
strong binding of anions of cobalt salt with the anion
can be prepared in a weakly
alkaline medium, avoiding noticeable oxidation of
In the case of CoCl
solution, such a process can
be described by the equation
2R!OH + CoCl
$ 2R!Cl + Co(OH)
In , we showed that the use of an anion ex-
changer, indeed, allows the synthesis of cobalt(II)
hydroxide at pH 637.
We also found that, for efficient precipitation of
cobalt(II) hydroxide as a separate phase, it is neces-
sary to use strongly basic anion exchangers, which, in
contrast to weakly basic sorbents, have a high Donnan
potential (the positive surface charge of the anion
exchanger matrix inhibiting penetration of cations).
In addition, the sorbent should have gel-like structure
containing no macropores. This decreases formation
of the Co(OH)
precipitate in the anion exchanger
phase. We found that AV-17-8 anion exchanger ex-
hibits such properties.
The goal of this work is to study the effect of the
process time, anion of the initial cobalt(II) salt, num-
ber of precipitation stages, and degree of anion ex-
changer swelling on Co(OH)
cobalt(II) salt solutions with strongly basic anion
exchanger AV-17-8 in the OH form.
Initially, the AV-17-8 anion exchanger was trans-
formed into the OH form by four 1-h treatments with
2 M NaOH at the volume ratio of the liquid to solid
phase of 3 : 1, followed by 1-day treatment under
similar conditions. Then, the sorbent was washed with
water to pH 637 and dried at 60oC,
and its total ex-
change capacity (TEC) was determined by the reaction
with excess 1 M HCl (TEC 2.72 mg equiv g
mination error <2%).
The anion-exchange precipitation of Co(OH)
performed by the method described in : A threefold
molar excess of the anion exchanger was added to a
0.25 or 0.5 M solution of the cobalt(II) salt. Precipita-
tion proceeded at 20+2oC for the time from 30 min to
In certain experiments, the anion exchanger was not dried; in
these cases TEC was related to 1 ml of the swollen anion ex-