Improvements in the Treatment of Ores containing Intimately Mixed Copper, Zinc, and Lead.
Year: 1898

page_text: COMPLETE SPECIFICATION.
Improvements in the Treatment of Ores containing Intimately
Mixed Copper, Zinc, and Lead.
I, GUY de BECHI, of Rue de la Chaussée d' Antin, Paris, France, Chemical
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed to be performed, to be particularly described and
ascertained in and by the following statement :-
In nature are to be found considerable quantities of complex mixtures of blend,
galenite and cupreous pyrites which it is impossible to separate by mechanical
treatment.
The metallurgical treatment of this kind of ore has been too expensive for it
hitherto to have been the object of any continued exploitation.
By means of the process or treatment of this invention, nearly the whole of the
copper and the greater portion of the zinc and lead is extracted in a commercially
pure state and in an economical manner.
The ores are treated in the following manner :-
The pulverised ore is mixed with from 20 to 40 per cent. of its weight of ordinary
salt (chloride of sodium) or waste salt rich in alkaline or earthy alkaline chlorides,
and subjected to a chloridising roasting in furnaces such as are usual in metallurgy
in this kind of reactions.
The gaseous products formed in the reaction (hydrochloric acid, sulphurous acid,
chlorine etcetera) as also the metallic salts produced in the volatilisation, or
mechanically, are condensed in suitable towers.
The product of the furnaces then comprises the major portion of the zinc and
copper in the state of salts soluble in water, and a certain quantity of these metals
pass into the state of oxide. They are treated with a solution of chloride of
calcium coming from a preceding operation and the extraction of the metals is
completed by bor waters or acid waters proceeding from the condensing towers.
These waters dissolve the oxides of copper and zinc. Previously the waters of the
condensing towers have added to them such a quantity of chloride of calcium as

page_text: suffices to eliminate in the state of insoluble sulphate of lime the whole of the
sulphuric acid which they contain.
This lixiviation of the roasted ore may be performed cold. It is however
preferable to warm the liquid, for example, by injecting therein warm air or a
mixture of air and steam. The iron is thus transformed for the greater part into a
subsalt at the maximum, insoluble in water.
By the above treatment a solution is obtained which comprises the chlorides of
copper, zinc, sodium, and calcium, as also a certain quantity of free hydrochloric
acid.
Nearly the whole of the lead contained in the ore and of the sulphuric acid
formed in the roasting process remain in the insoluble state with the residue of the
lixiviation.
The liquid of extraction is exactly saturated with the lime so as to give a neutral
liquid of reaction. It is then heated to boiling point and to it is added a quantity
of hydrated oxide of zinc derived from a preceding operation and calculated to
precipitate the copper in the state of hydrated oxide of copper, the zinc dissolving
instead and in the place of the copper in accordance with the equation:-
ZnO2H2, (hydrated oxide of zinc) + CuCl2 (chloride of copper)
(hydrated oxide of copper) + ZnCl2 (chloride of zinc).
-
CuO²H²
This separation of the copper in the state of hydrated oxide may also be effected
by adding to the liquid such a quantity of lime that only the acid united with the
copper is saturated with the alkali. Zinc is not precipitated until all the copper
has been eliminated in the state of hydrated oxide. It is of course understood that
the lime may be replaced by soda, carbonate of soda, etcetera, which equally
determine in the first place the precipitation of the copper before the zinc.
When the whole of the copper has been precipitated, the precipitate of hydrate of
copper is separated, by means of a suitable filter, from the solution and to the
filtered liquid which now only contains zinc, to the exclusion of any other heavy
metal, added the quantity of lime or other alkali necessary for fixing the
acid united with the zinc and precipitating this latter in the state of hydrated oxide
of zinc.
These fractional precipitations are best performed hot but they may be performed
cold in taking care to maintain the liquid in contact with the reagent by means of
an active and prolonged agitation.
The liquid containing the hydrate of zinc in suspension is filtered, the mother.
water then containing only chloride of sodium and chloride of calcium. The
chloride of sodium is regenerated by evaporation and is utilised over again in the
process and a mother water is obtained which is highly charged with chloride of
calcium and which has before stated serves in the extraction process with a fresh
quantity of roasted ore.
The hydrated oxide of copper obtained by the treatment above described may be
transformed into sulphate of copper or into metallic copper by the usual means.
The hydrated oxide of zinc may give metallic zinc by known metallurgical
processes.
Finally the residue of the aqueous extraction which including lead contains all
the impurities of the ore is treated in a cupola furnace in charges suitable to its
composition and thus transformed into metallic lead.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
The treatment by a chloridising roasting of ores containinơ conner
aina

page_text: precipitation of the copper and zinc which are thus obtained in the state of hydrated
oxides commercially pure substantially as described.
Dated this 5th day of January 1898.
CAPITAINE & VON HERTLING,
89, Chancery Lane, London, W.C., Agents for the Applicant.