Improvements in the Separation and Recovery of Zinc from Liquors containing Zinc in Solution with Iron and other Metals.
Year: 1897

page_text: Improvements in the Separation and Recovery of Zinc from Liquors
containing Zinc in Solution with Iron and other Metals.
We, WALTER JOHN WIGG, of The Firs, Chester, in the County of Chester,
Manufacturer, and EDWARD GEORGE BALLARD, of Newton Lane, Chester afore-
said, Chemist, do hereby declare the nature of this invention to be as follows:-
In certain metallurgical operations, as for instance, in the extraction of copper
by what is known as the wet process, there are produced certain residual liquors,
which contain both iron and zinc in solution; and it is the separation and re-
covery of these metals from such liquors, that this invention has for its object
and effect; and also, the carrying out of such separation and recovery in a manner
or by methods which shall render it capable of being performed at a commercially
profitable rate, that is, to render the process or method of recovery a profitable
one.
The process or processes, treatments, or methods, according to this invention,
by which these ends are effected, are as follows, for convenience the invention
being described as applied to the separation and recovery of iron and zinc from
the residual liquors constituting the effluent, of the extraction of copper by the
wet process.
By certain known methods, a large proportion of the iron which is contained
in solution in these liquors, is extracted, but the liquor still contains in solution
a considerable proportion of iron in conjunction with the zinc, in the form of a
chloride or sulphate, or both, and the separation of this residue of iron will be
first described. This is effected by first precipitating it, then oxidizing it, then
rendering the whole slightly acid, and then bringing the zinc back into solution
and keeping the iron oxidized. The zinc being now in solution, and the iron
precipitated, the solution and precipitate are separated in any known suitable
way. The substances employed, and mode of effecting these operations, are
these: The iron is precipitated by a hydrate of lime (or other hydrate of alkali).
The precipitate, viz., the iron, is then oxidized to a sufficient degree, for the
purpose of the process, by air, or other oxidizing agent, and the liquor subjected
to the action of such air or other oxidizing agent which is forced through the
liquor and precipitate until the oxidization has reached the required degree.
The whole is then rendered slightly acid by the addition of sulphuric acid, or
other suitable acid. And then, after this, the zinc is brought back into solution,
and the iron kept in its oxidized state, by again injecting air or other oxidizing
agent into the acid liquor-which also mixes it-and the zinc being now in
solution, and the iron precipitated, they are readily separated.

page_text: The iron, being oxide of iron, is suitable for use as a pigment, and therefore
in itself is valuable; whilst the zinc may, if desired, at this stage, be precipitated
and smelted in the usual manner of zinc smelting.
The zinc resulting from the process thus far described, would be impure, and,
therefore, for the purpose of its application or use as a zinc pigment, it would
be unsuitable, as it still holds a trace of iron, which is sufficient to render the
pigment made from it an impure white. To purify it, and to separate or get
rid of this trace of iron, the liquor is treated thus:-
The liquor is treated with air or other oxidizing agent and a small quantity
of calcium carbonate or other carbonates of the alkaline earths, the liquor being
preferably heated in a suitable vessel during the operation, the effect being that
the residuary iron is oxidized, and precipitated as an oxide. The liquor thus
ridded of all iron, will, nevertheless, in most cases, be still impure, as it may
contain some manganese, the presence of which in the zinc, if it is to be used
as a pigment, is inadmissible. The liquor, therefore, must, under such circum-
stances, be further treated for the separation or removal of this manganese;
and this is effected by the addition of a weak solution of bleaching powder to the
hot solution of zinc. The liquor is then filtered, and is in a condition for pre-
cipitation with a solution of hydrate of lime, or other precipitant suitable for
converting zinc to pigment. After this, the zinc precipitate is filtered and
calcined as usual. The zinc thus produced is in a purified and pure state, suit-
able for use as a pigment of the highest quality, or a lower grade according to
the precipitate used.
411
333
CHF3
day of August 1897.
Improvements in the Separation and Recovery of Zinc from Liquors
containing Zinc in Solution with Iron and other Metals.
We, WALTER JOHN WIGG, of The Firs, Chester, in the County of Chester,
Manufacturer, and EDWARD GEORGE BALLARD, of Newton Lane, Chester afore-
said, Chemist, 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:-
In certain metallurgical operations as for instance in the extraction of copper
by what is known as the wet process, there are produced certain residual liquors,
which contain both iron and zinc and other metals in solution; and it is the
separation and recovery of these metals from such liquors that this invention has
for its object and effect; and also, the carrying out of such separation and
recovery in a manner or by methods which shall render it capable of being per-
formed at a commercially profitable rate, that is, to render the process or method
of recovery a profitable one.
The process or processes, treatments, or methods according to this invention,
by which these ends are effected, are as follows, for convenience, the invention
being described as applied to the separation and recovery of iron and zinc from

page_text: the residual liquors constituting the effluent of the extraction of copper by the
wet process.
By certain known methods, a large proportion of the iron which is contained
in solution in these liquors, is extracted, but the liquor still contains in solution
a considerable proportion of iron in conjunction with the zinc, in the form of a
chloride or sulphate, or both, and the separation of this residue of iron will be
first described. This is effected by first precipitating it, then oxidizing it, then
rendering the whole slightly acid, and then bringing the zinc back into solution
and keeping the iron oxidized. The zinc being now in solution, and the iron
precipitated, the solution and precipitate are separated in any known suitable
way. The substances employed, and mode of effecting these operations, are
these: The iron is precipitated by a hydrate of lime (or other hydrate of alkali).
The precipitate, viz., the iron, is then oxidized to a sufficient degree for the
purpose of the process, by air, or other oxidizing agent, and the liquor subjected
to the action of such air, or other oxidizing agent, which is forced through the
liquor and precipitate until the oxidization has reached the required degree.
The whole is then rendered slightly acid by the addition of sulphuric. acid, or
other suitable acid. And then, after this, the zinc is brought back into solution,
and the iron kept in its oxidized state, by again injecting air or other oxidizing
agent into the acid liquor, which operation also mixes it-and the zinc being
now in solution and the iron precipitated, they are readily separated.
The iron, being now in the state of oxide of iron, is suitable for use as a pig-
ment and therefore in itself is valuable; whilst the zinc may, if desired, at this
stage, be precipitated and smelted in the usual manner of zinc smelting.
The zinc resulting from the process thus far described would be impure, and,
therefore, for the purpose of its application or use as a zinc pigment, it would
be unsuitable as it still holds a trace of iron which is sufficient to render the
pigment made from it an impure white. To purify it and to separate or get
rid of this trace of iron, the liquor is treated thus:
The liquor containing the zinc with impurities is treated with air or other
oxidizing agent and a small quantity of calcium carbonate or other carbonate
of the alkaline earths, in a suitable vessel, the effect being that the residuary
iron is oxidized, and precipitated, all the zinc remaining in solution.
The liquor thus ridded of all iron, will nevertheless, in most cases, be still
impure, as it may contain some manganese nickel or cobalt, the presence of
which substances in the zinc, if it is to be used as a white pigment, is inadmiss-
able. The liquor therefore must, under such circumstances be further treated
for the separation or removal of the manganese nickel and cobalt; and this is
effected by the addition of a solution of chloride of lime or bleaching powder to
the hot neutral solution of zinc; or chlorine gas may be passed through the
heated liquor in a suitable vessel, the liquor being kept neutral during the pro-
cess by the addition of a little calcium carbonate in the form of chalk or broken
limestone or other carbonates of the alkaline earths. The liquor is then filtered
and is in a condition for precipitation with a solution of hydrate of lime or other
precipitant suitable for converting the zinc into a pigment. After this the zinc
precipitate is filtered pressed and calcined as usual. The zinc thus produced is
in a purified & pure state, suitable for use as a pigment of the highest quality,
or a lower grade according to the precipitant employed.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is :-
1. The separation of iron from zinc in solution by precipitating both together,
oxidizing with air re-acidifying and blowing again with air to keep the iron
oxidized and to enable the zinc to be redissolved in the acid added, substantially
as described.

page_text: 2. The removal of the last traces of iron from the zinc liquor produced in the
last mentioned operation by adding some carbonate of lime or other alkaline
earthy carbonate in slight excess, and causing air to pass up through the liquor
substantially as described.
Dated in day or may
WALTER J. WIGG.
EDWARD GEO. BALLARD.
Signed by the said Walter John Wigg and
Edward George Ballard in the presence of:-
.
-
HANNAH PARRY.