ISSN 1070-4272, Russian Journal of Applied Chemistry, 2016, Vol. 89, No. 8, pp. 1341−1346. © Pleiades Publishing, Ltd., 2016.
The most common methods for the removal of
Fe(III) from waste process solutions are iron hydroxide
precipitation [1–3] and obtaining MeFe
jarosite, where Me = Na, K, OH [4–8]. In both cases, the
generated sludge is waste product and it is deposited in
a special stores. In addition to these methods “Geothite”
[4, 9–11] and “Hematite” [4, 11–13] processes are applied
for removal of ferric ions from waste solutions. Both
processes allow deep puriﬁ cation of the solutions from
iron (Fe < 1 g L
According to C.K. Gupta , the main advantage of
“Hematite” process is the possibility of obtaining an iron
rich sludge with low content of impurities, which can be
used like feedstock for the ferrous metals production.
The wide use of “Hematite” in the practice is limited
by the need to conduct the process in autoclave at high
temperature (>473.15 K) and pressure.
In case of autoclave pressure oxidation of pyrite
concentrate at high temperature a sulfuric acid (up
to 60 g L
) solution with high ferric ions
concentration (up to 60 g L
) was obtained. From a
practical standpoint, the area of interest here is the
utilization of ferric(III) ions contained in those solutions,
for example, for preparation of AFS or crystalline salts of
iron(III), which ﬁ nds wide practical applications.
The formation of AFS is conducted according to the
following chemical reaction :
O = 2NH
Ammonium sulfate (NH
is used as a reagent.
The super saturation of the solution and precipitation
of AFS was obtained by the salting out, as the required
conditions were created by increasing the concentration
of sulfate and ammonium ions into the solution, which
lowered the solubility of the crystallizing salt.
No data were found in the literature for direct use of
sulfuric acid ferric solutions for preparation of ammonium
Treatment of Ferric Sulfate Waste Solutions
for the Production of Ammonium Ferric
L. Stamenov*, V. Stefanova, K. Petkov, and P. Iliev
University of Chemical Technology and Metallurgy, 1756 Soﬁ a, 359883582150 Bulgaria
Received July 12, 2016
Abstract—The process of precipitation of ammonium ferric sulfate dodecahydrate (NH
waste solutions, obtained during autoclave oxidation of pyrite concentrate has been studied. A special feature
of these solutions is the high concentration of Fe(III) ions (>60 g L
) and sulfuric acid (> 61 g L
). Based on
comprehensive laboratory tests, the study determined the optimal conditions for the precipitation process of am-
monium ferric sulfate dodecahydrate (AFS) by salting out with ammonium sulfate: reagent excess (100% over
stoichiometric, temperature 276 K, time 1 h). The process should be conducted under continuous slow stirring
which would not allow forming of large crystals that are difﬁ cult to remove from the reactor. The test work
conﬁ rmed that high quality crystals can be produced by prior oxidation of Fe(II) to Fe(III) ions using hydrogen
peroxide and copper removal from the solution.