1070-4272/03/7607-1179$25.00C 2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 7, 2003, pp. 1179!1181. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 7,
2003, pp. 1213!1215.
Original Russian Text Copyright + 2003 by Savos’kin, Yaroshenko, Shologon, Galushko.
Influence of Pretreatment of Expanded Graphite on Its Sorption
Properties with Respect to Petroleum
M. V. Savos’kin, A. P. Yaroshenko, V. I. Shologon, and L. Ya. Galushko
Litvinenko Institute of Physical Organic Chemistry and Coal Fuel Chemistry,
National Academy of Sciences of Ukraine, Donetsk, Ukraine
Received August 13, 2002
Abstract-Petroleum sorption on expanded graphite prepared from residual graphite hydrosulfate at 3003
900oC was studied as influenced by pretreatment of the sorbent with water.
Expanded graphite is a highly efficient sorbent for
petroleum and its derivatives; its sorption capacity for
petroleum and industrial oil determined by the direct
sorption procedure is about 80  and 70 g g
7], respectively. The sorption capacity for petroleum
and industrial oil form their aqueous emulsion is about
20 g g
[7, 8], i.e., it is lower by a factor of 3.53 4.
This sharp decrease in the sorption capacity cannot
be due to competitive water sorption, since expanded
graphite surface is mainly hydrophobic. Even if water
is sorbed in the first steps, it should be desorbed from
the sorbent by such a hydrophobic liquid as oil or
petroleum. The lowering of the sorption capacity in
an aqueous emulsion as compared to the direct sorp-
tion experiment is likely due to structural transforma-
tions of expanded graphite under the action of water.
To check this assumption, in this work we studied
the influence of pretreatment of expanded graphite
with water on its sorption properties with respect to
We used residual graphite hydrosulfate prepared
from GT-1 natural flake graphite with the ash content
of 5.68 wt % (Zaval’evskoe deposit). The graphite con-
sists of mainly 0.6303 0.315- (74.3 wt %) and 0.3153
0.200-mm fractions (22.1%). The sample was treated
with stirring with a 50% aqueous solution of chromi-
um(VI) oxide (13 cm
/100 g graphite) for 10 min and
then with 95.8% sulfuric acid (42 cm
/100 g graphite)
for 10 min. After that, water (500 cm
per 100 g of
the initial graphite) was added at room temperature
and the reaction mixture was kept for 24 h. The crude
product was filtered off and washed on the filter with
water (8 dm
per 100 g of the initial graphite). The
product was dried at 105oC to constant weight. Two
batches of expanded graphite were prepared from the
resulting graphite hydrosulfate.
The samples of the first batch were prepared by
flash heating of residual graphite hydrosulfate in
a muffle at a temperature ranging from 300 to 900oC.
The samples were kept at 3003500oC for 5 min and
then at 6003900oC for 2 min. The samples of the sec-
ond batch were prepared by keeping samples of the
first batch in water for 30 min. Then the liquid phase
was carefully removed by filtration and drying at
105oC to constant weight.
We measured the specific surface area S
specific volume V
), and specific sorption
of industrial oil W
) for all the samples of
expanded graphite. The latter parameter was deter-
mined by the direct sorption method. The BET specif-
ic surface area was determined by low-temperature
argon adsorption. The specific volume was calculated
as the reciprocal of the bulk density of the sorbent.
We measured the sorption capacity of the expanded
graphites for heavy oil [r = 0.873 g cm
from Lisichansk refinery. To a weighed portion of
expanded graphite (~0.2 g) in a glass vessel, excess
oil (25 g) was carefully added and the system was
kept for 60 min to complete the sorption. Then the
vessel was covered with a perforated metal foil and
nonsorbed oil was allowed to drain down for 1 day.
The oil sorption was determined gravimetrically. The
sorption capacity of each sample was calculated as
arithmetic mean of seven measurements.
When expanded graphite was treated with water,
the following transformations were visually observed.
Expanded graphite nonwetted with water was gradual-
ly saturated with water for 10 min, with its volume
decreasing sharply. However, the vermiculite structure
of graphite particles was retained. After drying, the
black color of the initial expanded graphite changed to