ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 9, pp. 1428!1431. + Pleiades Publishing, Inc., 2006.
Original Russian Text + V.V. Sidorchuk, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 9, pp. 1444 !1447.
AND ION-EXCHANGE PROCESSES
Specific Features of Modification of Activated Carbons
with Steam and Hydrogen Peroxide Vapor
at High Temperatures and Pressures
V. V. Sidorchuk
Institute of Sorption and Endoecological Problems, National Academy of Sciences of Ukraine, Kiev, Ukraine
Received February 14, 2006
Abstract-The effect of high-temperature treatment of activated carbons with water and hydrogen peroxide
solutions on their pore structure, surface structure, and adsorption properties was studied.
It is known that steam treatment at 7003950oCis
frequently used in the activation stage in preparing
carbons from various raw materials . Also, there
is published evidence that the adsorption capacity of
some carbon materials increases upon their modifica-
tion in a flow of steam or as a result of treatment in
an autoclave [43 6]. This apparently occurs both via
development of a porous structure in these materials
and because of an increase in the concentration of sur-
face oxygen-containing functional groups [6, 7].
At the same time, no systematics studies concerned
with this issue have been reported. Here we report cer-
tain results of autoclave modification of two carbons
of different origins.
Two kinds of carbons were subjected to vapor-
phase treatment in a 45-ml autoclave: A2PS fruit-
kernel carbon manufactured in Poland and SKN
carbon prepared from an organic polymer. Distilled
water, 10330% aqueous solutions of hydrogen per-
oxide, and 10% aqueous ammonia served as modify-
ing media. The treatment temperature was 2503
350oC, and treatment duration, 3 h.
To calculate the pore structure parameters, nitrogen
adsorption isotherms were measured with a Sorptomat
instrument. These isotherms were used to determine
by the methods described in  the following param-
eters: BET specific surface area, S
; surface area of
, found by the de Boer method from
t-plots; surface area of mesopores, S
, determined by
the Dollimore3Hill method; and volumes of micro-
and mesopores, V
. Also, isotherms of ad-
sorption of benzene and water vapor were obtained by
gravimetry and used to calculate by the BET tech-
nique the specific surface area for benzene, S
the limiting-sorption pore volume for benzene, V
to find the geometric surface area for water, S
The adsorption of water vapor was also used to calcu-
late the concentration of primary adsorption centers
(PAC) . The same installation served to measure
adsorption isotherms of gaseous NH
order to characterize the adsorption capacity of car-
bons in relation to the nature and concentration of
functional groups on their surface.
Table 1 lists parameters of the porous structure of
A2PS carbon upon its treatment at 2503350oC. It can
be seen that, depending on the modification tempera-
ture and medium, a rather intricate pattern is observed
and it is difficult to reveal any fundamental aspects.
However, certain trends can be traced.
First, the specific surface area somewhat grows as
the temperature and hydrogen peroxide concentration
are made higher, because of the appearance of an addi-
tional microporosity, which is indicated by an increase
both in the surface area of micropores by 1203
and in their volume by 0.053 0.07 ml g
This is also indicated by the simultaneous steady rise
in the combustion loss by the modified carbons to
10312%. The micropore width was estimated [11, 12]
to be 0.831.1 nm, and the mesopore size varied within
the range 353 45 nm.
Second, the mesoporous component of the porosity
) remains virtually unchanged
under the conditions studied, whence follows the con-