Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 4, pp. 588−591.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © D.E. Chirkst, O.V. Cheremisina, M.V. Ivanov, I.I. Ivanov, I.T. Zhadovskii, A.A. Chistyakov, 2011, published in Zhurnal Prikladnoi
Khimii, 2011, Vol. 84, No. 4, pp. 552−555.
OF SYSTEMS AND PROCESSES
Sorption Thermodynamics of Cobalt(II) Cations
on Iron-Manganese Concretions
D. E. Chirkst, O. V. Cheremisina, M. V. Ivanov, I. I. Ivanov, I. T. Zhadovskii,
and A. A. Chistyakov
St. Petersburg State Mining Institute, St. Petersburg, Russia
Received May 14, 2009
Abstract—Isotherm of ion exchange of Co
cations on iron-manganese concretions is thermodynamically
described using a modiﬁ ed Langmuir equation. The thermodynamic characteristics of the ion exchange are
It was shown in [1, 2] that iron-manganese concretions
(IMCs) are a promising natural sorbent that can be used
to purify natural and artesian potable water, and also
wastewater and discharged technological solutions.
It is commonly accepted that one the main
mechanisms of accumulation of metals in IMCs is the
chemisorption process, by which considerable amounts
of metals can be recovered from the oceanic medium.
The sorption properties of natural manganese oxides and
hydroxides are poorly understood, whereas synthetic
analogs of these compounds have been the subject of
Quantitatively characterization of the sorbability of
cations on IMCs from model solutions is a topical issue.
In , cations were arranged in order of increasing
sorption capacity on the IMC surface:
Capacity, mequiv g
0.95 1.15 1.46 1.91 2.06 2.07 2.21
However, the capacity depends both on the afﬁ nity
of cations for an ion exchanger and on geometric
factors: “landing area” for cations, speciﬁ c surface
area of the ion exchanger, and concentration of ion-
exchange groups. The displacement capacity of cations,
responsible for the sorption selectivity, is determined
by the chemical afﬁ nity quantitatively characterized
by the Gibbs energy of ion exchange. Therefore,
constructing series of the displacement capacity of
cations (lyotropic series) on the basis of Gibbs energies
of the process is topical for revealing correlations
between cation properties and thermodynamic
functions of ion exchange.
In [4, 5], a method was suggested for determining
the apparent constants and differential Gibbs energies
of ion exchange by mathematical processing of
experimental exchange isotherms by linearization of
a modiﬁ ed Langmuir equation. The limiting sorption and
conditional speciﬁ c surface area of IMCs, found from
the sorption of Methylene blue, were used to calculate
the “landing areas” for cations. The resulting conditional
radii of sorbed cations are intermediate between their
crystallographic radii and Stokes radii. This suggests
that cations are sorbed in a partly dehydrated state. The
degree of dehydration, characterized by the difference
of the Stokes radii of the cations and their radii in
a conditionally sorbed state, grows with decreasing
Gibbs energy of ion exchange.
The exchange isotherm of sodium and cobalt ions was
studied on IMC samples from the Gulf of Finland. The
substance composition of these samples was determined
by X-ray ﬂ uorescence method in .