1070-4272/03/7608-1230 $25.00 C 2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 8, 2003, pp. 1230!1233. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 8, 2003,
Original Russian Text Copyright + 2003 by Yaroshenko, Savos’kin, Magazinskii, Savsunenko.
AND ION-EXCHANGE PROCESSES
Synthesis and Thermal Swelling of Residual Graphite
Hydrosulfates Obtained Using the Na
A. P. Yaroshenko, M. V. Savos’kin, A. N. Magazinskii, and O. B. Savsunenko
Litvinenko Institute of Physicoorganic and Coal Chemistry, Ukrainian National Academy of Sciences, Donetsk, Ukraine
Received August 13, 2002; in final form, March 2003
Abstract-The influence exerted by the conditions of synthesis of residual graphite hydrosulfate in a system
constituted by concentrated sulfuric acid and saturated aqueous solution of sodium dichromate on the prop-
erties of the final product was studied in a wide range of reagent consumptions. The swelling coefficient
and the loss of the product were analyzed as functions of the intercalate content in the product.
Previously, method for preparing high-quality re-
sidual graphite hydrosulfate, including treatment of
natural flaky graphite with a 50-wt % aqueous solu-
tion of CrO
and then with H
, hydrolysis of
the obtained graphite hydrosulfate, and washing and
drying of the final product, has been developed .
The product obtained effectively swells at a relatively
low temperature (500oC) and is used for fire preven-
tion and in metallurgy.
However, this method uses an aqueous solution of
, which is an extremely volatile and toxic com-
pound. In addition, this aqueous solution is highly
corrosive, even with respect to stainless steel.
In this study, we analyzed the possibility of replac-
with less toxic sodium dichromate and the
properties of the residual graphite hydrosulfates ob-
tained in this case.
Natural flaky graphite of GT-1 brand
with ash con-
tent of 5.68 wt % was subjected to oxidation. Mainly
two graphite fractions were present: 0.63030.315 mm
(74.3 wt %) and 0.31530.200 mm (22.1 wt %). We
used a solution in distilled water, containing 67.7 wt %
(r = 1.65 g cm
), as oxidant and chem-
ically pure H
with concentration of 95.8 wt %
(r = 1.835 g cm
The residual graphite hydrosulfate was synthesized
at room temperature by the following procedure. An
The term [residual graphite hydrosulfate] is used in this
study for nonstoichiometric compounds formed upon modi-
fication of graphite hydrosulfate with water.
Graphite from the Zaval’evsk deposit, Ukraine.
aqueous solution of Na
was added to 25 g of
the starting graphite under agitation. After 10 min,
was introduced into the reactor, and the reac-
tion mass was agitated for another 10 min. Then, wa-
ter (500 cm
) was added and the mixture obtained was
agitated and allowed to stay for 24 h to be hydro-
lyzed. During this period, small gas bubbles (CO
probably CO) continuously evolved from the solid-
phase layer. Then, the solid phase was filtered off on
a paper filter in a water-jet-pump vacuum and washed
with 2 l of water. The wet product was dried at 1003
110oC to humidity not exceeding 1.0 wt %. The con-
sumption of the aqueous solution of Na
100 g of graphite was varied within the range
, and that of H
, within 20348 cm
The coefficient of swelling at 500oC in a shock heat-
ing mode, K
), and the mass loss at 500oC
were determined for all the 92 samples synthesized.
The intercalate m
(wt %) in the product was
calculated from the values of the product yield on
the assumption that no phase oxidation of graphite
occurs at room temperature [8, 9], i.e., the whole
amount of carbon is transferred from the graphite
skeleton to the final product.
To determine the swelling coefficient of the prod-
ucts obtained, a weighed portion (m = 0.23 0.3 g) of
the product was introduced into a stainless steel cell,
preliminarily placed in a muffle furnace heated to
500oC, and kept there for 5 min to complete swelling.
The cell with swollen graphite was withdrawn from
the furnace and its contents were carefully transferred
from the cell to a glassy volumetric flask and the vol-
ume V (cm
) occupied by swollen graphite was mea-
sured. The swelling coefficient was determined as