Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 2, pp. 200−203.
Pleiades Publishing, Ltd., 2010.
Original Russian Text
L.A. Zemnukhova, T.A. Babushkina, T.P. Klimova, A.N. Kholomeidik, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83,
No. 2, pp. 203−206.
INORGANIC SYNTHESIS AND INDUSTRIAL
Pore Structure of Samples of Amorphous Silica
of Various Origins by Data on
L. A. Zemnukhova, T. A. Babushkina, T. P. Klimova, and A. N. Kholomeidik
of Chemistry, Far East Branch, Russian Academy of Sciences, Vladivostok, Russia
Nesmeyanov Institute of Elementoorganic Compounds, Russian Academy of Sciences, Moscow, Russia
Received January 28, 2009
Abstract—Pore structure of amorphous silica obtained from biogenic and mineral raw materials was studied by
the nuclear magnetic resonance (
H NMR) at 200–298 K . As biogenic raw materials were used fruit shells, rice
and oats straw, larch needles, horsetail pedicels, and diatomic algae. The pore size distribution in silica samples
of various origins was determined.
Rice manufacturing waste products, straw and shell
(husks, peelings), concentrating from 6 to 20% of amor-
phous silicon dioxide are a promising source of silica
for industrial needs. Silicon dioxide of various qualities
may be obtained by burning of organic components [1, 2]
and by acid precipitation from alkaline solutions formed
upon desilication of rice straw or husk [3, 4]. Application
of silica depends on its properties, which are, in turn,
determined by starting raw material and conditions of
Previously , the pore size distribution in moistened
rice husk and amorphous samples of carbonized and pure
silica obtained from it, containing 46.5% and 97.4% SiO
respectively, was studied by the pulsed
H NMR method
from 200 to 298 K. Experimental data were analyzed
by the Gibbs–Thomson equation relating the melting
point depression of a small object (water in pores) with
a decrease in its size.
ΔТ = K/d, (1)
where ΔТ is the difference in melting temperatures of
water in a volume and in a small pore, d is pore diameter,
K is the thermodynamic coefﬁ cient for a liquid (for water
K = 583 deg Å
Note, the NMR cryoporosimetry, nitrogen vapor diffu-
sion, mercury porosimetry, and differential scanning calo-
rimetry yield close values for pore sizes in silica .
In this work, the pore structure of amorphous silica
samples obtained by different methods from silicophilous
plants (rice and oats straw and husk, larch needles, and
horsetail pedicels) and from diatomic algae were studied
and compared with the commercial silicon dioxide sam-
ples produced from mineral raw material in industry.
We studied samples of amorphous silica obtained
from rice husk and straw (Oryza sativa L., collected in
Krasnodar krai in 2004 and Primorsk krai in 2005, respec-
tively), oats husk and straw (Avene sativa L., collected
in Primorsk krai in 2000), daurian larch needles (Larix
duheri-ca Turcz., collected in Primorsk krai in 2005) and
horsetail pedicels (E. Sylvaticum. L., collected in Primorsk
krai in 2003). The husk was sieved, no less than 2-mm
fraction was sampled, straw and horsetail pedicels were
disintegrated onto 10-mm pieces, rinsed with water, and
dried in air.
Silicon dioxide was separated by two procedures:
two-stage oxidative burning of mineral raw material [1,
2, 8] or precipitation with hydrochloric acid (pH 4) 
from alkaline solutions formed after treatment of the raw
material in a 1 N solution of sodium hydroxide.
To compare pore properties, we studied diatomite