1070-4272/05/7802-0234 C 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 2, 2005, pp. 234!238. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005,
Original Russian Text Copyright C 2005 by Prokof’ev, Il’in, Basova.
AND ION-EXCHANGE PROCESSES
Influence of Surfactants on Structuring of Molding
Blends Based on ZnO
V. Yu. Prokof’ev, A. P. Il’in, and T. V. Basova
Ivanovo State Chemical-Engineering University, Ivanovo, Russia
Received October 22, 2004
Abstract-The correlation between the surfactant sorption and structural mechanical properties of molding
blends and granulated sorbents was studied.
ZnO is widely used a a chemisorbent foo removing
impurities and, in particular, sulfur compounds ,
from process gases. Zinc oxide almost irreversibly
sorbs hydrogen sulfide to form solid zinc sulfide,
which allows almost complete removal of H
the gas being treated. At the same time [1, 2], granu-
lated sorbent should have not only a strongly devel-
oped microporous structure but also large pores for
penetration of reagents deep into a granule.
Uzugi and Tamia found  that the sorption of
hydrogen sulfide on zinc oxide depends not only on
its specific surface area but also, to a great extent, on
the pore size distribution. Zinc oxide having, along
with micropores, coarse pores with radius larger than
100 nm exhibits the highest sorption activity. As fol-
lows from the stoichiometry of the reaction of ZnO
S, the highest sorption capacity of zinc oxide
for hydrogen sulfide is 39 wt%. The actual sorption
capacity is lower than 20 wt%. Hence, the H
tion strongly depends on its diffusion into the sorbent
matrix. Under the industrial conditions, only the ex-
ternal surface of zinc oxide granules is converted into
the sulfide, and the internal surface does not work.
It is known that pelletized granules have a nano-
porous structure, whereas extruded granules contain
broad transport pores, along with narrow pores. Pre-
paration of extruded sorbents based on ZnO was
examined in our previous study .
Surfactants are widely used to improve the mold-
ability of blends (including those based on ZnO) to
We used ZnO powder with an almost 100% content
of the main compound. The molding blends were
prepared by addition of polyvinyl alcohol (PVA) or
carboxymethyl cellulose (CMC) solutions of different
concentrations to a ZnO powder. The mixture was
stirred to obtain a homogeneous suspension.
The optimal water content in the blend, j
determined on a conical Rebinder plastometer by
the procedure described in . The structural-mechan-
ical constants (ultimate shear stress P
plastic viscosity h
) and parameters (plasticity Ps and
relaxation time Q) were calculated using the Maxwell3
Shvedov and Kelvin model. For this purpose, we used
the time3strain curves measured on a D.M. Tolstoi’s
plastometer . The complete rheological curves
were measured on a Rheotest-2 rotary viscometer in
the range of shear rates 234960 s
. The data obtained
were processed by the procedure described in [6, 7].
We calculated the following rheological parameters:
full power consumed for flow N, power for degrada-
tion of the coagulation structure DN, consistency con-
, and flow index n.
The butt crushing strength of the granules was
measured on a hydraulic press . The BET specific
surface area was determined from low-temperature
sorption of argon .
We studied the sorption of CMC and PVA on ZnO
particles under different conditions. A maximum at
a132 wt % PVA concentration in the solution is ob-
served in all the sorption curves (Fig. 1). The maxima
in the sorption curves are due to structuring of more
concentrated CMC and PVA solutions with the forma-
tion of aggregates. The sorption capacity of the solid
phase in dispersed solutions is higher by a factor of
2 than that in the stirred solutions.
The sorption capacity depends on the hydrophilic
shell on the surface and the size of oxide particles.