1070-4272/01/7408-1295 $25.00 C 2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 8, 2001, pp. 1295!1300. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 8, 2001,
Original Russian Text Copyright + 2001 by Tikhomolova, Kufman, Urakova.
AND ION-EXCHANGE PROCESSES
Adsorption and Desorption of Ni(II) in Quartz!Aqueous
Solution Systems at Various pHs
K. P. Tikhomolova, Yu. V. Kufman, and I. N. Urakova
St. Petersburg State University, St. Petersburg, Russia
Received October 25, 2000; in final form, May 2001
Abstract-Adsorption of Ni(II) onto quartz from aqueous solution with pH 337 and its subsequent desorption
are studied. The desorption was done by three procedures with different extents of action on adsorbed
This study is one of a series of works on adsorption
of metal cations capable, in principle, of forming
chemical bonds with active sites on the adsorbent sur-
face . Our selection of the subject matter was
determined by the possibility of donor3acceptor bond-
ing, with account of the electronic structure of the ion
and the lability of the resulting adsorption complex.
In this connection, transition metal cations (as pos-
sible acceptors of unshared electron pairs) and oxides
whose surface groups are potential donors of such
pairs are chosen to constitute an adsorbate3adsorbent
pair. The coordination properties of surface groups of
an oxide can be judged from the general concepts of
the coordination chemistry, including those of the
structure of electronic shells and the mutual effect of
the constituents of the complexes formed in the solu-
tion bulk . Therefore, those oxides should be
selected in which an adsorbed metal does not enter
the crystal lattice, i.e., oxides nonisomorphous with
a given metal.
Of course, electrostatic (Coulombic) forces also
contribute to the interaction between the cation and
negatively charged sites on the adsorbent surface.
The range of these forces is much longer than the
length of the donor3acceptor bonds. Adsorption con-
trolled by these forces is totally reversible, and the
adsorption equilibrium (controlled by cation diffusion)
is established rapidly. The role of the Coulombic in-
teraction is restricted to concentration of the cations
in the diffusion layer at the interface; the higher the
surface potential, the higher the metal concentration.
The adsorption of ionic and molecular species is
only one type of possible interactions. At sufficiently
high pH values, hydroxide particles (colloids in many
cases) form a new phase. In this case, the sorption
mechanism changes fundamentally, and adsorption
gives way to interaction of species of varied nature
and size, which will be further be treated in terms of
It is known that in most of actual systems the
species are considerably more tightly associated than
in the case of a simple coagulation contact, when no
chemical interaction between active centers of the
species is realized (this case is treated in the classi-
cal version of the DLFO theory). Our thought is that
the presence of 3O
and 3OH groups on the surfaces
of the hydroxide adsorbate and oxide adsorbent and
the larger size of the colloidal particles as compared
to ionic and molecular species may result in that hy-
drogen bonding plays the determining role in fixation
of the adsorbate species on the adsorbent surface .
Donor-acceptor bonding can contribute to adhesion
also, but, probably, to a lesser extent, as follows from
the known strict steric limitations.
In this work we studied Ni(II) as an adsorbate.
Being a d metal (3d
), Ni can serve as an acceptor of
the electron pair in complexation with oxygen-con-
taining ligands. According to coordination chemical
views, Ni(II) forms more or less stable, depending on
the ligand nature, and relatively inert complexes in
the bulk of aqueous solutions. From the practical
standpoint the selection of Ni is due to the fact that
it is a component of waste of many industries.
In the cases when coagulation in dispersions with species hav-
ing different nature and size is the subject matter, the term het-
eroadagulation is sometimes used. We prefer to use the term
adhesion for the indicated process, as emphasizing the point
of sticking of hydroxide species to the adsorbent surface.