Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 4, pp. 607−610.
Pleiades Publishing, Ltd., 2010.
Original Russian Text
V.N. Lebedev, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83, No. 4, pp. 555−558.
INORGANIC SYNTHESIS AND INDUSTRIAL
Speciﬁ c Features of Disposal of Sulfuric Acid Solutions
Resulted from Magnesium Silicate Decomposition
V. N. Lebedev
Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials,
Kola Scientiﬁ c Center, Russian Academy of Sciences, Apatity, Karelian Republic, Russia
Received May 7, 2009
Abstract—The photocatalytic activity of crystalline titania nanopowders synthesized in a stream of ultrahigh-
frequency discharge oxygen-containing low-temperature plasma was assessed. To this end, oxidation of an
organic dye was carried out in UV-irradiated aqueous suspensions of ТiO
at different concentrations and varied
Neutralization of sulfuric acid solutions resulted
from magnesium silicate decomposition, in which silica
occurs in a soluble form, was examined. It was suggested
that the magnesium loss by neutralization due to binding
into hydrosilicate be prevented by treating the solution
with calcium carbonates or dolomite.
Magnesium silicates: olivine (MgFeSiO
), and serpentines with the general formula
] are widely distributed in nature,
occur as associated minerals at many deposits under
development, and are dumped in amounts of several
millions of tons, in particular, on Kola Peninsula. These
minerals are fairly easily soluble in acids and can be
converted into magnesium and silicate compounds by acid
decomposition [1–3]. Hydrochloric acid decomposition
poses the major problem in terms of separation of silica;
in the case of concentrated sulfuric acid taken in excess,
silica gives a precipitate which is easily separated with
nondecomposed minerals. Impurities from magnesium
sulfate solutions are precipitated by soda in the presence
of an oxidant or by an alkali; soda solution is also used
for magnesium carbonate precipitation. These processes
yield a sodium sulfate solution in an amount proportional
to that of sulfuric acid spent for decomposition of the
concentrate. The resulting solution needs to be disposed,
for which purpose the preparation of little-demanded
sodium sulfate decahydrate was suggested.
The interest in this topic can be encouraged by the
use for magnesium silicate mineral decomposition of
dilute waste sulfuric acid solutions formed in many
industrial processes. Also, in some cases the selective
decomposition of magnesium silicates with dilute acids
may be helpful in chemical enrichment and treatment
of some concentrates, e.g., baddeleyite concentrate .
Disposal of these solutions can be economically justiﬁ ed
by additional preparation of magnesium compounds.
Such solutions will be characterized by high degree
of dilution and will contain dissolved silica, which is due
to a low acid concentration and its possibly exhaustive
consumption. In sulfuric acid treatment of concentrates,
the precipitation of silica is basically undesirable because
of the need for its separation from the main product.
Here, we examined the speciﬁ c features of disposal
of solutions, resulted from sulfuric acid decomposition
of magnesium silicates that contain soluble silica.
We used solutions prepared by decomposition with
8–12 wt% sulfuric acid of forsterite, an impurity (up to
15 wt%) in baddeleyite concentrate waste and in some
crude concentrates. At high silica content the solutions
can appear as gelled masses from which it is difﬁ cult
to separate the nondecomposed minerals. Formation of