Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 11, pp. 1649−1653.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © I.N. Pyagai, L.A. Pasechnik, A.S. Yatsenko, V.M. Skachkov, S.P. Yatsenko, 2012, published in Zhurnal Prikladnoi Khimii, 2012,
Vol. 85, No. 11, pp. 1736−1740.
AND INDUSTRIAL INORGANIC CHEMISTRY
Recovery of Sludge from Alumina Production
I.N. Pyagai, L. A. Pasechnik, A. S. Yatsenko, V. M. Skachkov, and S. P. Yatsenko
Institute of Solid State Chemistry, Ural Branch, Rusian Academy of Sciences, Yekaterinburg, Russia
Received March 30, 2012
Abstract—The carbonation of the sludge slurry was studied. The main characteristics of the initial and carbonated
red mud were compared. The carbonation of sludge ensures reduction of the toxicity of a sludge ﬁ eld and enables
extraction of some rare metals (scandium, zirconium, titanium), aluminum, and sodium. The possibility of using
the treated sludge as an additive in the manufacture of cement and concrete products was determined.
Existing plants for large-scale alumina production are
characterized by low complexity of bauxite utilization.
More than 1 ton of red mud (RM) as a slurry with pH
12–13 is dumped per each ton of produced alumina.
Sludge reservoirs have accumulated tens of million of
tons of this waste, which is dangerous for the environment
and human health. Weathering and water erosion of
RM cause pollution of nearby soil and surface water. In
October 2010, the dam of reservoir of the alumina plant
in Hungary collapsed, which has raised concerns in other
countries with alumina plants. In the Ural (Sverdlovsk
region) each of the two aluminum plants has three
sludge reservoirs, occupying more than a hundred acres
each. The reclamation of dumped sludge only partially
solves the problem. Covering it with a layer of inert
wastes and soil with the following grass seed takes only
a problem of dust entrainment. In addition, up to the
present, only a small part of the dumped sludge area is
reclaimed. Drilling reclaimed dumped sludge from the
Ural Aluminum Plant (branch of UAP-SUAL Company)
showed that within the waste disposal sites there remains
movable liquid slurry, which continues to penetrate into
the underlying aquifers.
A radical solution is the complete complex process-
ing of RM. Despite the numerous studies of domestic
and foreign research teams are available, the problem of
sludge recovery has not yet been solved. This is primarily
due to the high capital intensity of the proposed solutions.
The RM modiﬁ ed by the preliminary treatment and
the initial RM waste are used in the following industries:
Ferrous metallurgy. Introduction of RM instead of
bentonite in the production of pellets results in harden-
ing of the agglomerate and leads to a 5% increase in
productivity of sintering machines . Cast iron and
self-disintegrated slag with alumina extraction were
obtained by the pyrometallurgical processing of RM .
The resulting slag is treated in acid to obtain gypsum,
fertilizers, and rare-metal concentrates .
Cement industry. As known, nepheline sludge is used
for the production of binders, including Portland cement
. RM of the Bayer process with the addition of minor
amounts of CaO, factory slag, and Portland cement can
be used in the construction of roads and foundations and
in the manufacture of brick and tile .
Other industries. It was proposed to use RM as a co-
agulant of industrial wastewaters, pigments, and sorbents
for a variety of chemical substances .
Scandium is extracted from RM by carbonization in a
ﬂ ow of exhaust gases from the bauxite sintering or calci-
nation furnaces [7, 8]. This technology can reduce green-
house gas emissions. The calcination of 1 million tons of
alumina (approximate performance of a single alumina
plant) causes about 0.5 million tons of carbon dioxide to
release in the atmosphere. Gas emissions from the baux-
ite with soda sintering furnaces make 5 million tons and
contain 17 % CO
, and oxides of sulfur (0.02 %), nitrogen
(0.004 %), and other oxides.