1070-4272/05/7810-1596 C 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 10, 2005, pp. 1596!1599. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 10, 2005,
Original Russian Text Copyright + 2005 by Shinkareva, Lazareva, Shchurevich, Kurakevich.
AND ION-EXCHANGE PROCESSES
Effect of Synthesis Conditions of Magnetite on Its
Water-Vapor Sorption Capacity
E. V. Shinkareva, T. G. Lazareva, O. A. Shchurevich, and L. A. Kurakevich
Institut Obshchei i Neorganicheskoi Khimii Natsional’noi Akademii Nauk Belorussii (Institute of General and
Inorganic Chemistry, National Academy of Sciences of Belarus) State Research Institution, Minsk, Belarus
Received November 4, 2004; in final form, June 2005
Abstract-The water-vapor sorption capacity of magnetite obtained by precipitation with solutions of NaOH,
O, and urea in a single stage was studied. It was found that the type of a precipitating agent, thermal
treatment temperature, concentration of the starting FeSO
solution, and order in which the reagents are
poured together affect the water-vapor sorption capacity of the magnetite obtained.
Most widely used as a magnetic component in
manufacture of magnetorheological fluids and mag-
netic paints, fibers, and tapes [1, 2] are ferromagnetic
materials based on iron oxides: magnetite (Fe
[3, 4]. Modern ferromagnetic materials
should satisfy a number of requirements: have high
magnetic characteristics, good sorption capacity (in
the cases when the surface is to be modified), and
a certain specific surface area (10350 m
) for dis-
persion in a binder.
Synthesis of magnetite is a rather complicated
task performed in four successive stages: synthesis of
goethite a-FeOOH, thermal decomposition of goethite
to hematite a-Fe
, and reduction of hematite to
It is known that magnetite can be obtained by
single-stage precipitation . However, the character-
istics of such a material strongly depend on synthesis
conditions (type of a precipitating agent and washing
reagent, thermal treatment temperature, concentration
of the starting FeSO
solution, and order in which
the reagents are poured together).
In this study, the influence exerted by conditions
of a single-stage precipitation of magnetite on its
water-vapor sorption capacity is assessed.
The single-stage precipitation of magnetite was
performed from a 0.131.0 M FeSO
a 20% NaOH solution at 85oC and pH 10311 or with
a 25% NH
O solution at pH 839, as well as
with a 10% urea solution at 100oC and pH 536 under
vigorous stirring for 3 h; a 20% solution of the oxi-
dizing agent, NH
, was added at a molar ratio
After the synthesis, the magnetite obtained was
allowed to stand for 1 day under a layer of the mother
liquor for the necessary structure of its crystals to be
formed. Then the precipitate was washed by decanta-
tion with hot distilled water to negative reaction for
ion in the washing water and filtered off.
The washing process was monitored with a 2% BaCl
solution. The precipitate obtained was additionally
washed with ethanol or acetone. Samples dried at
room temperature for 12 h were thermally treated in
nitrogen at temperatures of 100 to 200oC for 3 h.
The samples were stored in quartz weighing bottles
with ground-glass covers.
An X-ray phase analysis was performed on a DRF-
2.0 diffractometer (Fe
The shape and dimensions of particles of magnetic
powders were studied with an LEO 1420 scanning
electron microscope at a magnification of 37000.
A gold layer was deposited onto the surface of
the samples in a VUP-2K vacuum-evaporation instal-
The sorption of water vapor by magnetite was car-
ried out by keeping samples for 20 days (time of the
most intense moisture absorption) in desiccators at