ADSORPTION PROPERTIES OF THE CORUNDUM SURFACE
IN CORUNDUM-BASED REFRACTORIES
S. I. Borovik,
T. N. Ivanova,
A. I. Soldatov,
A. M. Chuklai,
and O. I. Frolov
Translated from Novye Ogneupory, No. 8, pp. 37 – 40, August, 2005.
Distribution of the adsorption sites in fused corundum is studied depending on the fractional composition of
the material and specific surface of its finely ground fractions. Treatment of the corundum surface with a phe
nolic resin is shown to affect, both quantitatively and qualitatively, the distribution of acid-base adsorption
Corundum-carbon refractories have found wide applica
tion as material for blow-off nozzles in the extra-furnace
steel processing technology owing to the superior qualities of
their constituents: electrofused corundum as filler and phenol
resins as binder. The argon blowdown at different steps of
the steelmaking process is done at a different rate, which
places strict requirements on the operation of blow-off noz-
zles [1, 2].
Adsorption ability of fused corundum plays a major role
in the buildup of a strong refractory material. Most processes
in which the surface of solids is involved, are local in charac-
ter and in many respects are controlled by the energetic pa
rameters of particular active sites.
By construction-and-use regulations, a mixture of
polyfractional composition with the grain size from 2 to
<0.063 mm should be used. Therefore it was thought of in
terest to identify active sites on the surface of a solid filler
that could adsorb the binder molecules and thus to what role
may play a particular fraction in the buildup of the refractory
The reactivity of active aluminum oxide is controlled by
the acid-basic properties of the surface formed. In an acid
medium, the Al
surface develops a positive charge, which
allows ions of opposite sign to adsorb. In this case, Al
acts as an anion adsorbent. In an alkaline medium, Al
velops a negative charge, which results in the adsorption of
Generally, three types of sites involved in adsorption are
distinguished on the surface of solid aluminum oxide: (i)
electron accepting orbitals of metal cations, (ii) electron do
nating orbitals of oxygen ions; (iii) hydroxyl hydrate shell
formed by the different adsorption of water molecules .
The acid-basic properties of a solid surface are controlled
by the concentration and strength of active sites involved —
acidic, basic, and their distribution. In this work, we use an
indicator method to study the acid-basic properties of corun-
dum surface; the method is based on the surficial adsorption
of an indicator and the change of its color which is taken to
be a measure of acidity (basicity) of the surface .
The distribution of acid-base sites over the surface was
studied in the range of –0.29 to 8.8 of the dissociation con-
of the indicator. For this purpose, 100 ml solutions
of each indicator were prepared in water or water/ethanol
mixture. Relevant characteristics are given in Table 1.
The adsorption sites of particular acid strength were
quantified in terms of the
index (mmole/g) using a
spectrophotometric method in the UV and visible range of
the spectrum. The solutions were measured photometrically
on an SF-26 spectrophotometer using cells with l =1cm
against the neat solvent at the wavelength l
ing to a maximum absorption of each indicator.
The concentration of active sites of a particular acid
(equivalent to the amount of indicator adsorbed) was calcu
lated by the formula
are the absorbances (optical densities) of
the indicator solution before and after sorption, respectively;
is the absorbance of a “blank” solution .
Refractories and Industrial Ceramics Vol. 46, No. 4, 2005
1083-4877/05/4604-0287 © 2005 Springer Science+Business Media, Inc.
South Ural State University; Ural Electrode Institute JSC;
Chelyabinsk State University; Terg-K Research and Production
Association, Chelyabinsk, Russia.