Process for Obtaining Ferric Sulphate and Metal Sulphates from Iron. Pyrites and other Sulphide Ores.
Year: 1899

page_text: Date of Application, 27th Nov., 1899
Complete Specification Left, 20th July, 1900-Accepted, 8th Sept., 1900
PROVISIONAL SPECIFICATION.
Process for Obtaining Ferric Sulphate and Metal Sulphates from Iron.
Pyrites and other Sulphide Ores.
I, OTTO MEURER, of 56 Muhlenbach, Köln a/Rhine, Germany, Manufacturer,.
do hereby declare the nature of this invention to be as follows:-
This invention relates to a process for obtaining sulphates of metals from iron
pyrites and analogous ores containing iron disulphide. The product may be
ferric sulphate or metal sulphates free from iron.
For this purpose iron pyrites is heated in a muffle with alkali polysulphide
whereupon the iron bisulphide which it contains is decomposed into a ferroso-
ferric sulphide, free sulphur and ferrous sulphide, of which the last named
is in an easily oxidisable form. The mass is allowed to cool and disintegrate in.
the air, a process which may be aided by sprinkling the mass with water, and
is then leached with water to extract the salts. The solution is separated from
the undissolved portion and the latter is dried and exposed to the air. A spon-
taneous oxidation of the ferrous sulphide ensues without any application of heat
from outside. The oxidation proceeds more rapidly if the heat evolved is able
to raise the temperature of the mass to a red heat, so that this process is aided
if the chamber in which it takes place is heated; but this is not necessary and.
when practised the temperature should not exceed 200° C.
When the iron sulphide in the mass has oxidised in this manner to ferric
sulphate this salt is leached out with water.
The following example illustrates the process:
-
The pyrites may be supposed to contain 42 per cent. of iron, 48 per cent. of
sulphur and 10 per cent, of other matter. The ore is finely ground and mixed
with 12 per cent. of sodium polysulphide. The mixture is heated at a strong red
heat in a muffel from 'which air is excluded. About 150 to 200 kilos. may
be heated at a time, but this depends, obviously, on the size of the muffel. The
duration of the heating may be from 2 to 3 hours. The chemical change may
be represented by the equation
(I) Na+ 6FeS,
=
2FeS + FeS + Na2S, + S₂
The heated mass is drawn from the oven and allowed to cool, whereupon it at
the same time disintegrates, an end which may be hastened by sprinkling the
mass with water. Leaching with water to extract the salts which have formed
now follows, and the residue is dried and exposed to the air, preferably in a
chamber heated to a temperature not exceeding 200° C..
To expose a large surface to the air the mass is spread in a thin layer and
stirred. Presently the mass spontaneously becomes red hot and the ferrous
sulphide is oxidised to ferric sulphate, while the ferroso-ferric sulphide remains
unaltered.

page_text: with salt to produce ferric chloride and sodium sulphate, the latter of which
may be crystallised from the mixture.
Instead of starting with alkali polysulphide as recommended above alkali
monosulphide may be used, when the polysulphide will be formed during the
heating process from the sulphur of the pyrites, thus--
(I) Na S +5Fe, Na₂S + FeS4 Fest
The proportion of the monosulphide mixed with the ore should be the equiva-
lent of the alkali polysulphide recommended.
For the alkali monosulphide. may be substituted its equivalent; a mixture
of carbon and sodium sulphate; sodium sulphide will then be produced during
the process, thus
onional!
(IVa) Na₂SO + C₂ = Na2S+ 2002, or,
(V6) Na2SO4 + C₁ = N₁₂S + 4C)
The proportion of carbon to sodium sulphate may correspond with either
equation, accordingly as carbon monoxide. or dioxide is desired as a by-product.
This substitution of carbon and sodium sulphate for alkali monosulphide
considerably cheapens the process.
In the case of ores which contain sulphide of copper, sulphide of zinc, sulphide
of nickel and, the like and in which there is always more or less iron pyrites, the
ferric sulphate formed by the spontaneous oxidation becomes ferric oxide, sul-
phates of the other metals present being formed at the same time.
The progress of the oxidation of the ferrous sulphide in the presence of the
sulphides of divalent metals such as copper, nickel, zinc and the like, may be
expressed by the following equation in which R stands for such divalent metal:-
(V) 2FeS + FeS
S+RS +14 =3
Fe̱()¸ (S¸)¸ + Fe̱S + RS + SO₂
The ferric sulphate is decomposed at the température of the reaction, sulphuric
anhydride is formed and the sulphides of the other metals become. sulphates,
sulphur dioxide being evolved, thus
5
(VI) Fe₂O (SO3)3 + R₂S + 0 = Fe₂0, +2RO. (SO) + 2S0.
To obtain the sulphates of the divalent metals free from iron it is necessary
that the proportion of iron to the other metals shall be such that the sulphur
combined with the iron is sufficient to convert all the metals into sulphates.
The reaction then proceeds quantitatively, while when too little iron is present
a part of the other metals is not converted into sulphates..
If, therefore, the ore does not contain a sufficient proportion of iron sulphide
an addition of this must be made in the form of a sulphide ore rich in iron.
If on the other hand, the proportion of iron is too large the whole of the iron
sulphate will not be decomposed so that iron sulphate will remain in the final
product of the reaction and will contaminate the other metal sulphates. The
presence of such an excess of iron may be corrected by the addition of sulphide
ores free from iron.
The proportion of iron bisulphide to other metal sulphides should be ten
molecular proportions of the former to two molecular proportions of the latter,
if. the sulphates of the metals are to be free from iron. This follows from the
fact that five molecules of iron bisulphide yield two molecules of iron mono-
sulphide and that for the formation of the sulphates of the other metals two
molecules of iron monosulphide are required for two molecules of the sulphides
of the other metals.
3.
The treatment in the muffel with alkali polysulphide or monosulphide and
the subsequent oxidation are effected in the same manner as that described for the
preparation of ferric sulphate: The metal sulphates are leached by water from
the oxidised mass and are crystallised from the solution.

page_text: :
The addition of other sulphide ores in order to obtain metal sulphates free from
iron is not necessary:.
set wan
The complete decomposition of the ferric sulphate can be achieved, without
adjusting the proportion of iron sulphide to other sulphides by allowing the
oxidation of the mass from the muffel to proceed for a sufficient. time.
By testing a small portion of the heated mass after the oxidation to see whether
iron sulphate can be dissolved from it by water, the progress of the oxidation can
be ascertained; so long as this is the case the oxidation must be allowed to pro-
ceed, until ferric sulphate is no longer dissolved from the test by water. It is
advantageous, however, to follow the prescribed addition of other (sulphide ores.
Dated this 27th day of November 1899.
Process for Obtaining Ferric Sulphate and Metal Sulphates from Iron
Pyrites and other Sulphide Oreser
1, OTTO MEURER, of 56 Muhlenbach, Köln a/Rhine, Germany Manufacturer,
do hereby declare the nature of this invention and in what manner the same, is
to be performed, to be particularly described and ascertained in and by the
following statement: -
This invention relates to a process for obtaining sulphates of metals from iron
pyrites and analogous ores containing iron disulphide. The product may be
ferric sulphate or metal sulphates free from iron.
'1
For this purpose, iron pyrites is heated in a muffle with alkali polysulphide
whereupon the iron bisulphide which it contains is decomposed into, a ferroso-
ferric sulphide, free sulphur and ferrous sulphide, of which the last named
is in an easily oxidisable form. The mass is allowed to cool and disintegrate in
the air, a process which may be aided by sprinkling it, with water, and, is
then leached with water to extract the saits. The solution, is separated from
the undissolved portion and the latter is dried and exposed to the air. A spon-
taneous oxidation of the ferrous sulphide ensues without any application of heat
from outside: The oxidation proceeds more rapidly if the heat evolved is able
to raise the temperature of the mass to a red heat, so that this process is ailed
if the chamber in which it occurs is heated; but this is not necessary and when
practised the temperature of such heating should not exceed 200° C.
When the iron sulphide in the mass has oxidised in this manner to ferric
sulphate this salt is leached out with water.
The following example illustrates the process:-
4
21
gif biza
The pyrites may be supposed to contain 42 per cent. of iron, 48 per cent. of
sulphur and 10 per cent. of other matter. The ore is finely ground and mixed
with 12 per cent. of sodium polysulphide. The mixture is heated at a strong. red
heat in a muffle from which air is excluded. About 150 to 200 kilos. may be
heated at a time, but this depends, obviously, on the size; of
the maffle.. The
duration of the heating may be from 2 to 3 hours. The chemical change may be
represented by the equation
(I) Na,S6FeS, = 2FeS + FeS +N+S
11
maitij (6:

page_text: mass with water. Leaching with water to extract the salts which have formed
now follows, and the residue is dried and exposed to the air, preferably in a
chamber heated to a temperature not exceeding 200° C.
To expose a large surface to the air the mass is spread in a thin layer and
stirred. Presently the mass spontaneously becomes red hot and the ferrous
sulphide is oxidised to ferric sulphate, while the ferroso-ferric sulphide remains
unaltered.
The chemical change is expressed by the equation
The ferric sulphate is leached out with water and the solution is evaporated
and either crystallised to obtain ferric sulphate as the final product or mixed
with salt to produce ferric chloride and sodium sulphate the latter of which
may be crystallised from the mixture.
Instead of starting with alkali polysulphide as recommended above alkali
monosulphide may be used, when the polysulphide will be formed during the
heating process from the sulphur of the pyrites, thus-
II) Na,S+5FeS,
5
NS + FeS + FeS.
The ferric sulphate is decomposed at the temperature of the reaction, sulphuric
anhydride is formed and the sulphides of the other metals becomes sulphates,
sulphur dioxide being evolved, thus-
1
(VI), Fe2O, (SO) + RS + O₁ = Fе₂O + 2RO (SO₂) + 250,
To obtain the sulphates of the divalent metals free from iron it is necessary
that the proportion of iron to the other metals shall be such that the sulphur
combined with the iron is sufficient to convert all the metals into sulphates."
The reaction then proceeds quantitatively, while when too little iron is present
a part of the other metals is not converted into sulphates.
If, therefore, theore does not contain a sufficient proportion of iron sulphide
an addition of this must be made in the form of a sulphide ore rich in iron.
If. on the other hand, the proportion of iron is too large the whole of the iron
sulphate will not be decomposed so that iron sulphate will remain in the final

page_text: product of the reaction and will contaminate the other metal sulphates. The
presence of such an excess of iron may be corrected by the addition of sulphide
ores free from iron.
The proportion of iron bisulphide to other metal sulphides should be ten
molecular proportions of the former to two molecular proportions of the latter,
if the sulphates of the metals are to be free from iron. This follows from the
fact that five molecules of iron bisulphide yield two molecules of iron mono-
sulphide and that for the formation of the sulphates of the other metals two
molecules of iron monosulphide are required for two molecules of the sulphides
of the other metals.
The treatment in the muffle with alkali polysulphide or monosulphide and
the subsequent oxidation are effected in the same manner as that described for
the preparation of ferric sulphate. The metal sulphates are leached by water
from the oxidised mass and are crystallised from the solution.
The addition of other sulphide ores in order to obtain metal sulphates free from
iron is not necessary.
The complete decomposition of the ferric sulphate can be achieved without
adjusting the proportion of iron sulphide to other sulphides by allowing the
oxidation of the mass from the muffle to proceed for a sufficient time.
By testing a small portion of the heated mass after the oxidation to see whether
iron sulphate can be dissolved from it by water, the progress of the oxidation can
be ascertained; so long as this is the case the oxidation must be allowed to pro-
ceed until ferric sulphate is no longer dissolved from the test by water. It is
advantageous, however, to follow the prescribed addition of other sulphide ores.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is: :-
1. A process for obtaining ferric sulphate from iron pyrites by first heating
the pyrites with an alkali polysulphide, air being excluded, so as to convert the
iron disulphide of the pyrites into iron monosulphide, then allowing the mass
to oxidise in the air until the iron monosulphide has become ferric sulphate, and
finally leaching out the ferric sulphate with water, substantially as described.
2. In the process for obtaining ferric sulphate from iron pyrites referred to
in the first claim, heating the pyrites with alkali monosulphide or a mixture
which yields alkali monosulphide, instead of with alkali polysulphide, sub-
stantially as described.
.
3. A process for obtaining metal sulphates from sulphide ores which contain
iron bisulphide as well as the sulphides of other metals, by first heating the said
ores with an alkali polysulphide or an alkali monosulphide, with or without addi-
tion of ores containing iron bisulphide or sulphide ores free from iron, then
allowing the mass to oxidise in the air and finally leaching out the metal sulphates
with water, substantially as described.
ABEL & IMRAY,
Agents for the Applicant.