ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 5, pp. 889!891. + Pleiades Publishing, Ltd., 2008.
Original Russian Text + L.A. Gladikova, V.V. Teterin, R.G. Freidlina, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 5, pp. 852!
Production of Magnesium Oxide from Solutions
Formed by Acid Processing of Serpentinite
L. A. Gladikova, V. V. Teterin, and R. G. Freidlina
AVISMA Branch, VSMPO!AVISMA Corporation, Open Joint-Stock Company, Berezniki, Perm krai, Russia
Received June 20, 2007
Abstract-Possibility of obtaining magnesium oxide from sulfate, nitrate, and chloride solutions from acid
processing of serpentinite and producing magnesium oxide suitable for manufacture of transformer steel
Recently, recovery of magnesium from silicate
materials, e.g., serpentinite containing up to 383
43 wt % magnesium oxide, has been extensively
studied. Magnesium is recovered from serpentinite
by leaching with mineral acids (H
HCl)  to obtain the corresponding salts. The
salt solutions formed by leaching are contaminated
with impurities present in serpentinite: Fe(II),
Mn(II), Cu(II), Ni(II), Co(II), Al(III), Cr(III), etc.
After a reagent purification, the resulting solutions
can be used to obtain pure salts of magnesium and
magnesium hydroxide or oxide.
The aim of this study was to produce from ser-
pentinite magnesium oxide satisfying the require-
ments to transformer steel production. Solutions
prepared by leaching of serpentinite with mineral
acids at 80390oC for 334 h with a stoichiometric
expenditure of an acid were used in the study.
The compositions of the solutions obtained upon
neutralization with brucite to pH637 are listed in
The technology used to obtain magnesium oxide
from solutions includes the following stages: pre-
cipitation of magnesium hydroxide, filtration, wash-
ing of the Mg(OH)
paste, drying, and calcination
to MgO. Magnesium hydroxide was
precipitated with aqueous ammonia. The results
obtained in precipitation of magnesium hydroxide
solutions are listed in Table 2.
The data obtained show that the filtration
throughput becomes 2.5 times lower and the degree
of magnesium precipitation decreases as the con-
centration of the magnesium sulfate solution in-
creases. The precipitate was washed to remove
ammonium sulfate with water at s : l = 1 : 20.
The filtration throughput in washing was 0.283
. Magnesium hydroxide was dried
at 100oC and calcined at 650oC for 2 h. The result-
ing magnesium oxide contained 83387% MgO and
failed to satisfy the technical requirements to mag-
nesium oxide to be used in manufacture of trans-
former steel. Repeated washing of magnesium
oxide at s : l = 1 : 20, followed by calcination at
650oC, yielded a product of the following composi-
tion (wt %): MgO 96.5, SO
0.42, Ca not found.
The sample did not satisfy the requirements im-
posed by the technical specification, either. Use of
sodium hydroxide to obtain magnesium oxide from
solutions failed to produce positive results.
From a magnesium nitrate solution, magnesium
hydroxide was precipitated with aqueous ammonia
to pH ~9.2. In this case, the degree of magnesium
precipitation was 87.5% After separating the precipi-
tate (paste) of magnesium hydroxide, the solution
contained (g dm
): Mg 10, Ca 4.4, and NH
168.9. The magnesium hydroxide paste was washed
with water on a filter at s : l = 1 : 25, dried, and cal-
cined at 500oC for 2 h. The resulting magnesium
oxide contained (wt %): MgO 98.1, Fe 0.016, Cl
0.12, and CaO 0.12; calcination loss 0.72 wt %; citric
number 40 s. Its properties failed to satisfy the
requirements of the technical specification.
From chloride solutions (350 g dm
magnesium was precipitated with aqueous ammonia
whose expenditure was 1003200% relative to the