A Process for the Electrolytic Extraction of Zinc, and other Metals from Ore or Waste containing them.
Year: 1898

page_text: Date of Application, 17th Nov., 1898-Accepted, 13th May, 1899
A Process for the Electrolytic Extraction of Zinc, and other Metals
from Ore or Waste containing them.
A communication from abroad by WILHELM STRZODA, of Zalenze, near Kattowitz,
Silesia, in the German Empire, Chemist.
I, JOHN CORRY FELL, of the Firm of Fell and James, of 1, Queen Victoria Street,
in the City of London, Chartered Patent Agent, 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:-
Hitherto zinc has been extracted from its ores or from waste containing zine, by
first extracting the zine by means of suitable solutions or lyes in a vat, then drawing
off this lye and subjecting it to electrolysis in a separate vat.
This invention consists in electrochemically converting the zinc into a soluble
compound from its ores or from zinc waste in an alkaline bath, and decomposing such
compound in the same vat simultaneously, whereby metallic zinc is deposited on the
cathode.
The pulverised ore or pulverised waste such as zinc-ash containing zinc is piled up
in. an electrolysing vat or box to the height of from 0.1 to 03 metre. This vat is
provided with metallic cathodes, zinc or iron for example. The alkaline solution is
then allowed to enter the vat (this solution may be a lye containing 10% of caustic
soda for instance) and carbon and metal plates arranged vertically at small intervals
apart extend into this solution and other loose cathode plates may be arranged to lie
upon a wooden lining horizontally on the bottom of the vat. If the electric circuit
is closed, the zinc is dissolved at the cathodes from the ores or the waste and at the
same time a metallic separation of the same takes place.
In a few hours all the zinc except 1% which remains in the ore, is deposited on the
cathodes. During the whole operation the solution becomes heated to about 40° to
60°. Rapid separation is assisted by the whole liquid being maintained in constant
agitation owing to liberation of gas on the bottom cathodes, causing a thorough
mixing so that fresh solution of ore is always able to reach the cathodes.
When the process is completed the immersed anode and cathode plates are re-
moved from the solution and the pulpy residue separated from the solution by means
of a filter press.
The solution may be regenerated and be used again.
The foreign metals contained in the zinc ores which consist mainly of lead and
cadinium but which may be of another character, such as copper, silver, gold, or the
like, are separated metallically, at the same time as the zinc, and the zinc may be
separated from other metals deposited with it by distillation in the usual method.
By means of the foregoing process not only zine ores, but also lead and cadmium
ores, for instance lead glance may be converted into metal.
The alkaline solution may contain caustic soda, caustic potash, ammonia or any
ammoniacal salt, either alone or with the addition of a salt of potassium or sodium
and the like.
The reactions in the vats are illustrated by the following examples.

page_text: If, for example, calamine (carbonate of zinc) is used, and as electrolyte a 10% solu-
tion of caustic soda, the following reaction will take place.
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Zn S+ 2 Na OH =Zn (OH), + Na, S.
The dissolution of the hydroxide of zinc in the excess of caustic soda solution and
the further decomposition takes place as in the foregoing example.
As is apparent from the above statements, this invention constitutes an important
technical progress, in that the extraction of the zinc from its ores and the simulta-
neous electrolytic deposition of the metallic zinc takes place in one process. The
production of the zinc is thus rendered much less costly than by the methods
hitherto employed, more especially because even poor zinc ores may be profitably
treated by this process.
The carbonic alkaline solutions occurring in the process are decomposed by means
of caustic lime and the alkali is used again in the process.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
A process for the electrolytic extraction of zinc from their ores or from waste
containing them in which the pulverized ore such as calamine, blende and the like or
waste containing zine such as zinc-ash and so forth is exposed to the action of an
electric current directly in an alkaline bath, without any preliminary chemical
treatment, whereby the zinc and also the other metals present are at once in such
bath metallically separated on the cathode.
Dated this 17th day of November
1909
FELL & JAMES,
Agents for the Applicant.