1070-4272/05/7802-0319 + 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 2, 2005, pp. 319!323. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005,
Original Russian Text Copyright + 2005 by Zemnukhova, Fedorishcheva, Egorov, Sergienko.
AND POLYMERIC MATERIALS
Recovery Conditions, Impurity Composition,
and Characteristics of Amorphous Silicon Dioxide
from Wastes Formed in Rice Production
L. A. Zemnukhova, G. A. Fedorishcheva, A. G. Egorov, and V. I. Sergienko
Institute of Chemistry, Far Eastern Division, Russian Academy of Sciences, Vladivostok, Russia
Received April 12, 2004
Abstract-The conditions of recovery of amorphous and crystalline silicon dioxide from husk and straw of
rice cultivated in various regions were studied. The dependence of the impurity composition and characteris-
tics of amorphous silica on the plant strain, waste type, and procedures of waste processing was established.
The optimum conditions of production of high-purity silicon dioxide were determined, and its characteristics
were compared with those of commercial products.
Amorphous silicon dioxide (silica) has a wide
field of application, depending on its structure, puri-
ty, and physicochemical characteristics. It is used in
food, pharmaceutical, fragrance, paint-and-varnish,
chemical, metallurgical, construction, oil-refining,
rubber-processing, porcelain, glass, textile, plastic,
paper, and other branches of industry. Such forms
of amorphous silicon dioxide as diatomite or diato-
maceous earth, kieselguhr, tripoli powder, carbon
white, Aerosil, and microsilica are used for produc-
tion of modified silica, sorbents for various purposes,
including those for filtration of water, beer, wine,
oils, sugar, and other food substances and solvents
Traditionally, the main sources of silica are min-
eral forms, whose resources in our country and in
the world are rich. A great number of crystalline mod-
ifications of SiO
is known: they differ in the content
of impurities. Impurity metals are incorporated into
the crystal lattice of silica, forming strong bonds.
Production of amorphous silica from crystalline SiO
involves a large expenditure for pretreatment of the
initial raw materials and subsequent removal of con-
comitant impurities [5, 6]. Amorphous SiO
chemically active and, if required, it can be easily
transformed into the crystalline form.
A promising raw material for production of amor-
is the hydrothermal heat carrier used in
regions with operating geothermal power plants 
and large-tonnage wastes from rice production: straw
and fruit shells of corn (husk), in regions of rice cul-
The use of rice husk as a renewable raw material
for production of high-quality amorphous SiO
tremely promising, since the husk is concentrated in
grain-cleaning plants and is a source for additional
production of a number of organic compounds, e.g.,
furfural, xylose, and polysaccharides [8, 9, 12, 13].
However, until now, the main amounts of husk and
straw have not been in industrial use because of the
absence of integrated technologies taking into account
the regional conditions. To develop an integrated
scheme for processing of the waste from rice produc-
tion, it is necessary to know the chemical composition
of raw materials as influenced by the strain and area
of plant vegetation, which have not been studied ad-
This study continues the examination of the in-
tegrated processing of waste from rice production
 and the conditions of production, impurity
composition, and characteristics of amorphous SiO
prepared from rice husk and straw.