Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 7, pp. 1011−1016.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © L.A. Zemnukhova, T.A. Babushkina, A.M. Ziatdinov, A.N. Kholomeidik, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85,
No. 7, pp. 1042−1047.
AND INDUSTRIAL INORGANIC CHEMISTRY
Impurity Paramagnetic Fe(III) and Mn(II) Centers
in Samples of Amorphous Silica of Different Origin
L. A. Zemnukhova, T. A. Babushkina, A. M. Ziatdinov,
and A. N. Kholomeidik
Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russia
Nesmeyanov Institute of Elementoorganic Compounds, Russian Academy of Sciences, Moscow, Russia
Received July 27, 2011
Abstract—Some important magnetic and local structural properties of amorphous silica separated from biogenic
(fruit shell of rice and oats, larch and Korean spruce needles, horsetail pedicels, and diatomic algae) and mineral
raw were determined by the method of electron paramagnetic resonance. The data obtained can be useful when
selecting raw materials and for development of processing scheme of its treatment to separate silicon(IV) oxide
with required characteristics.
Amorphous silicon(IV) dioxide (silica) has a wide
range of applications, depending on its properties,
which are in turn determined by the type of raw material
and processing conditions. Previously, some charac-
teristics of amorphous silica obtained from plant raw
materials, rice and oat production wastes [2–8] have
been determined by the chemical and X-ray analyses
and IR, NMR, and XPS spectroscopies. Qualitative and
quantitative determination of the impurities present in
silica is important to characterize its quality and outline
prospects of use. In the literature, paramagnetic centers
in silicon(IV) dioxide crystalline modiﬁ cation, quartz,
contrary to its amorphous modiﬁ cation, have been ex-
tensively studied .
This work continues the study of the properties of
amorphous silica. The presence and origin of the impu-
rity paramagnetic centers in samples of amorphous silica
obtained by different methods from silicophilous plants
(rice and oats straw and husk, larch and spruce needles,
horsetail pedicels, and diatomic algae) were determined
by the method of electron paramagnetic resonance (EPR)
and compared with the commercial samples produced
from mineral raw material in industry.
We studied samples of amorphous silica obtained
from silicophilous plants: fruit shells (husk) of rice
(Oryza sativa L., collected in Krasnodar and Primorsk
krai), oat husk (Avene sativa L.), daurian larch needles
(Larix duherica Turcz.), Korean spruce needles (Picea
koraiensis) and horsetail pedicels (E. Sylvaticum. L.),
which were collected in Primorsk krai.
Silicon(IV) oxide was separated from plants by two
procedures: two-stage oxidative burning of raw material
(with or without pretreatment with hydrochloric acid) [2,
3] or precipitation with hydrochloric acid (pH 4) from
alkaline solutions formed after treatment of the raw mate-
rial in a solution of sodium hydroxide .
For comparison, we studied diatomite sample col-
lected in Australian deposit, silica samples separated
from Kamchatka thermal waters , sample obtained
from ferroalloy production wastes , commercial re-
agents “Silicic acid, SiO
O” [GOST (State Standard)
4214-78), “Silica for thin-layer chromatography” (TLC)
produced at a Krasnyi Proletarii plant, Russia, and product
“Polysorb MP” produced at a Polysorb Closed Joint-
Stock Company, Russia. Several samples of crystalline