1070-4272/01/7408-1392 $25.00 C 2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 8, 2001, pp. 1392!1394. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 8, 2001,
Original Russian Text Copyright + 2001 by Nazarov, Gulakhmadov, Khakdodov, Aminov.
Processing of Aluminum Sulfates into Alumina
Sh. B. Nazarov, Kh. Sh. Gulakhmadov, M. M. Khakdodov, and Sh. G. Aminov
Nikitin Institute of Chemistry, Academy of Sciences of Tajikistan, Dushanbe, Tajikistan
Received June 21, 2000; in final form, May 2001
Abstract-The possibility of processing aluminum sulfates into alumina with the use of calcium carbonate
Production of alumina from aluminum sulfates in
processing of high-silica aluminum ores (alunites,
nephelines, clays, poor-quality bauxites, siallites, etc.)
is of great practical interest. The known methods to
obtain alumina from aluminum sulfates have a number
of shortcomings: cumbersome technological schemes,
difficult deferrization of solutions, necessity for high-
temperature heating of salts containing a great amount
of crystallization water, evaporation of large amounts
of mother liquors, and high energy expenditure for
thermal decomposition of aluminum sulfates.
For example, according to the Kalunit scheme ,
dehydrated alunite ore is leached with reused sulfuric
acid containing potassium sulfate. Fe(III) is removed
from the sulfate solutions with dehydrated alunite ore.
A more thorough removal of iron(III) from solutions
can be achieved in the scheme by recrystallization of
alum calcined at 1000oC. SO
in calcination are used in production of sulfuric acid.
The product of alum decomposition is leached with
water, with sulfates of alkali metals dissolved and
alumina remaining in a sediment.
In another method , clay is treated to remove
Fe(III) with a weak solution of sulfuric acid, calcined,
and decomposed with sulfuric acid. Aluminum and
iron(III) hydroxides isolated from the sulfate solu-
tion by adding Na
are dissolved in alkali, and
is isolated by carbonization. Aluminum hy-
droxide is then used to obtain alumina by calcination.
Much attention has been given by researchers to
processing of alunite ores . Alunites are sulfated
aluminates of alkali metals-MAl
M = Na, K. The sulfate products obtained in ore pro-
cessing are used to obtain alumina by various meth-
ods. However, all of these require improvement and
simplification of their technological schemes.
The present study is concerned with the possibility
of processing of aluminum sulfates with the use of
calcium carbonate to obtain alumina without solution
evaporation or crystallization and thermal decomposi-
tion of salts, which much simplifies the technology.
An aluminum sulfate solution to be used in the
experiments was obtained by processing an alunite
ore of the following chemical composition (wt %):
O 7.2, Na
O 0.15, SO
1.3, CaO 1.08, SiO
24.1, and calcination loss 12.37.
The ore was sintered at 4003650oC and the resulting
mass was treated with 10320% sulfuric acid at 100oC
in the reactor. The resulting suspension (sludge) was
filtered to remove the solid phase (SiO
and its com-
pounds). The filtrate contained sulfates of aluminum,
iron(III), potassium, sodium, etc.
To the filtrate was added calcium carbonate for
aluminum(III) and iron(III) to be precipitated in the
form of their hydroxides by the reactions
2 + 3CaSO
The obtained mass was agitated in the reactor with
a stirrer at 20330oC for 10330 min. Then the liquid
and solid phases of the suspension were separated.
The filtrate was composed of potassium, sodium, and
other sulfates; the residue contained Al(OH)