Improved Method or Process for the Extraction and Recovery of Zinc from Sulphide Ores.
Year: 1899

page_text: Date of Application, 4th Dec., 1899-Accepted, 6th Jan.,
1900
COMPLETE SPECIFICATION.
Improved Method or Process for the Extraction and Recovery of
Zinc from Sulphide Ores.
I, JAMES GITSHAM, of 445, Punt Road, Richmond, in the Colony of Victoria,
Australia, Metallurgist, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement:-
This invention has been devised to provide an economical and efficient method
or process to be applied to or for the purpose of extracting and recovering zinc
contained in sulphide ores, so as to permit of a facile recovery of gold, silver and
other valuable metallic contents of such ores. At the present time the elimina-
tion of zinc from such ores involves considerable expense, combined with un-
reliability as to result, but by my process not only is the zinc cheaply and easily
extracted or removed from the ores but such zinc is secured in a fairly puro
state for commercial purposes.
I shall now describe the operation of the method or process for carrying out the
objects above referred to:-
The sulphide ore to be treated is finely crushed in a dry condition and roasted
in any approved furnace at such a degree of heat as will convert most, or all,
of the sulphides into sulphates, but insufficient in temperature to produce
volatilization of the zine; that is to say, at a temperature preferably not exceeding
six hundred degrees Fahrenheit. By experiment I have found that about six
hours exposure at the degree of heat last mentioned is sufficient for this portion
of the process. During the roasting process the pulverised ore should be
occasionally ravelled either by mechanical power or by a suitable hand rake.
After the roasting of the ore is completed and it is cooled down to a slightly
warm condition it is then mixed with a proportion of powdered metallic zinc.
the proportions of the latter varying according to the local requirements and
conditions of the ore. By experiments I have found that about one per centum.
by weight of metallic zinc should be added to the crushed roasted ore and I have
found zinc "
to be suitable and efficient for this purpose.
grey or dross
Care must be exercised in order that the powdered metallic zine be thoroughly
disseminated throughout the pulverised ore.
"
"
29
The whole mixture is then leached with water in order that such water may
dissolve out and win any soluble acid, salts, or free zinc from the mixture. This
water may be used more than once in some cases and, after being separated from
the ore, the latter is leached with one or more solutions of sulphuric acid and
water. The strength of the sulphuric acid solution must be determined by the
amount of zinc contained in the ore, but should not exceed ten per centum by
weight of sulphuric acid to each one hundred pounds of water, but I desire it
to be understood that by preference I employ from two to two and a half per
centum solution.
About one hundred pounds weight of solution is applied to each hundred
pounds of dry pulverised prepared ore and, in accordance with the amount of

page_text: zine in the ore, I repeat the leaching in solutions of the same or lesser strength,
until the whole or greater portion of the zine has been dissolved and held by such
solution or solutions. By experiment I have found that one leaching operation
in the acidulated water will be generally found to be sufficient but in some
cases as many as four of such operations may be required before the whole of
the required quantity of the zinc has been abstracted from the ore.
During the process of leaching, in both the water and the acidulated solutions,
steam is applied in the vat or vats wherein such operation is carried on for the
purpose of raising the temperature of the solution to a heat of, preferably, about
one hundred and fifty degrees Fahr. but not exceeding two hundred degrees
Fahr. in order to increase the solvent action of the acidified solution, and at the
same time to create agitation of the mixture and thus better effect the leaching.
The vats, and all pipes and cocks, connected with the acid solution are pre-
ferably constructed of wood or lead, or a combination of both these materials,
the reason for employing these special materials being to obviate the corrosion
of, (or chemical action brought about by) other substances more freely affected
by sulphuric acid.
The solution containing the zine having been run off into another vat, the ore
is again treated with one or more washings of weak solutions of sulphuric acid,
and finally with water, or in some cases with water alone; the wash water or
weak acidified solution may then be run in with and form part of the solution
in the first instance herein before referred to, or may be used over again for
washing until such time as it becomes sufficiently acidulated, (in some cases with
the slight addition of acid) as to be strong enough for use in the first instance.
With reference to the whole of the acidulated solutions I would say that I
aim at economizing the employment of sulphuric acid so far as possible by
re-using in a cycle system any of the solutions until they become sufficiently
charged with zinc to justify their neutralization in order to win the zinc there-
from.
When the solution has absorbed, dissolved, suspended or taken to itself what
may be deemed a sufficient supply of zinc, the liquid is run into a separate vat
and neutralized by the administration of caustic soda, or analogous alkali: this
will cause the separation of the zinc from the solution in the form of an oxide by
precipitation. The precipitate is from time to time removed, any liquid remain-
ing therewith exaporated and the product (oxide of zinc) disposed of for com-
mercial purposes.
The remaining ore, (wholly or in most part robbed of the zinc as above set
forth) may then be treated for the recovery of the precious metals contained
therein such as gold and silver, and also for the recovery of lead or other metals;
the refractory or obstructive element, (viz. zinc) being removed, the treatment
for the other metals is rendered comparatively easy.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed I declare that what I
claim is:
1. My hereinbefore described process for the extraction and recovery of zinc
from sulphide ores consisting essentially in pulverising and roasting the ore at
a temperature insufficient to volatilize the zine contained therein adding metallic
zine thereto leaching firstly with water and afterwards with one or more weak
solutions of sulphuric acid applying steam into such solutions to increase the
temperature of and agitate same, and lastly the application of an alkali to pro-
duce neutralization of the acid and precipitate the zinc contents from the solution
substantially as and for the purposes set forth.
2. My hereinbefore described method or process consisting in first pulverising
and secondly roasting the ore at a temperature of about six hundred degrees Fahr.;
thirdly adding powdered metallic zinc in the proportion of one per centum by
weight to the ore; fourthly by leaching such mixture with water; fifthly by

page_text: leaching the mixture with one or more solutions composed of from two to ten
per centum of sulphuric acid by weight with water; sixthly applying steam to
the solutions so as to raise them to a heat not exceeding two hundred degrees
Fahr. and to agitate them; seventhly by the application of sodium or analogous
alkali in sufficient qauntity to the acid solution to neutralize same and-to cause
precipitation of the zine from the solution and removing the precipitate from
ibe solution substantially as and for the purposes set forth.
3. In the method or process as claimed in Claims One and Two, the cyclic
operation of the solution, with or without fortification, from the first to the last
step twice or oftener until such solutions become sufficiently charged with zinc to
economically justify neutralization by an alkali.
300
•
MARKS & CLERK,
18, Southampton Buildings, London, W.C.,
13, Temple Street, Birmingham, and
25, Cross Street, Manchester, Agents.
Dated this 4un ay
MARKS & CLERK,
18, Southampton Buildings, London, W.C.,
13, Temple Street, Birmingham, and
25, Cross Street, Manchester, Agents.