Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to a hydrometallur~ical
process for the treatmen-t of metal sulphides containing lead.
It relates more specifically to a process for selective
solubilisation of lead as compared to ot:her non-ferrous
metals and iron contained in such sulphides.
It is known that galena, or lead sulphide, is
frequently found in the natural state in other sulphides such
as pyrites, blende, copper sulphide and the sulphides of
non-ferrous metals.
According to the conventional metallurgical processes,
the different sulphides forming part of the ore are separated
by differential flotation, and then treated by conventional
pyrometallurgical processes. Nevertheless, differential
flotation does not always give a perfect separation; the
concentrates obtained may then be either concentrates as
such, or mixed concentrates, or concentrates of very impure
lead whereof the proportion of lead is no more than 40 or 50%
instead of the more usual 60 to 80~.
The above concentrates are very difficult to process
in accordance with the techniques developed in conventional
metallurgy; we have recently made some improvements in the
processing of complex ores and flotation concentrates.
Our British Patent Specification No. 1,478,571
issued May 4, 1977 describes a process for the solubilisation
of all the non-ferrous metals contained in a sulphide
compound by means of cupric chloride regenerated by means of
air and of a regenerating agent which may ke hydrochloric
acid or ferrous chloride.
The processing of the solutions thus obtained, if
they contain zinc, is described in our Specification No.
1,502,404 issued July 12, 1978, namely
- 2 -
~.
lead may be separated :Erom the other non-ferrous metals by pre-
clpitating its chloride by cooling the solution. The ]ead
c~loride thus obtained is very pure; in particular, it contains
no more than small quantities of bismuth whereof the separation
from lead is always difficult. The lead chloride may then be
cemented by more reducing metals than itself, such as zinc or
iron, for example. ~lowever, depsite numerous advantages, this
technique is sometimes costly and is not very appropriate for
the efficient working of deposits of lead sulphide. Also, this
method requires the presence of a plant for precipitation of
lead chloride and has a heat balance which is not always favour-
able.
This is why it is an object of the present invention to
provide a method of treating sulphides containing lead by means
of copper chloride wh:ich renders it possible to obtain a solution
of lead chloride free of copper and a method which is as selective
as possible with respect to the other non-ferrous metals.
Another object of the present invention is to provide a method
of processing the solu-tion obtained from this selective action.
The invention provides a hydrometallurgical process for
the treatment of one or more metal sulphides containing at least
lead as a non-ferrous metal, wherein the said sulphides are con-
tacted with an aqueous solution containing at least one chloride
selected from the chlorides of copper, bismuth, antimony, arsenic
and silver, the quantity of the chlorides used being not more
than 1~0% of that which is stoichiometrically required for the
total dissolution of the lead contained in the sulphide compound;
100 or 110% may often be adequate.
One of the principle uses of the present invention consis-ts
in the selective lixiviation of the lead contained in a
-~ -3-
-
sulphide compound; cuprous and cupric chlorides are preferably
used. (The term "lixiviation" means the leaching o~ the lead
from the ore ~y the chloride solution.)
The lixiviation is performed at a higher temperature than
ambient temperature, preferably between 60C and the boiling
point of the reaction mixture. By virtue of the presence o~ the
copper in limited quantity during this l:ixiviation, the dissolu-
tion of the lead results not only from the action on its sulphide
by cupric chloride to give plumbous chlo:ride and cuprous
chloride, but also an exchange between the cuprous cations of
the solution and the lead of the sulphidised compound. If the
lixiviation is performed solely by means of copper chlorides, two
reactions occur, shown as follows:
~ 1 ti + Pb ore ~ > Pb solution solution
and
2 cu~ -~ Pb ore ~ Pb++ + 2 Cu
solution solution ore, and
the limitation on the quantity of cupric chloride used may con-
sequently be expressed as:
20lCu ~ -~ 2 ~Cu _ ~ 5~ ~ Pb++ ~
the three expressions refer to the respective molar amounts of
cupric copper and cuprous copper present initially and of the
lead present initially in the sulphide compound and able to pass
into solution.
The lixiviation may be carried out in a single reactor or
in a moving bed or in several consecutive reactors in which the
sulphide compound(s) is displaced in counterflow to the attacking
solution.
I'he cupric chloride may be regenerated partially ln situ
or concomitantly with the dissolu-tion by the method claimed in
our British Patent Specification No. 1,478,571. This regeneration,
~1
-- 4 --
, ,d~ 7
which may be performed ln situ or in a separate reactor, con-
sists in oxidising the cuprous ions in the presence of hydro-
chloric acid and~or of ferrous chloride; the reactions involved
in this regeneration are the following:
2 CuCl + 2 HCl + 1/2 2 ~ ~ 2 CuC12 -~ ~2
4 CuCl ~ 2 FeC12 + 3/2 2 ~ ~I2O ----~ 4 CUC12 + 2 Fe(O) OH
In the regeneration, the condition applicable to the quantity
of chlorides placed in operation may be expressed in the
following manner: the quantity of chloride ions present initial-
ly in the form of a chloride o~ copper, bismuth, antimony, arsenic,
si.lver, ferrous iron and/or o~ hydrogen, shoul.d not be more than
that which would be in the form of lead chloride if all. the lead
present in the sulphide compound were in the ~orm of plumbous
chloride.
The selective lixiviation may be used to give either a
sulphide compound containing practically no lead, or else to
directly give as pure a lead chloride solution as possible. In
the first case, it is preferable to lixiviate with as great a
quantity of copper chloride as possible, e.g. 120% of the stoi-
chiometric amount, although even when complete dissolution o~
lead is desired, it is better to use an amount as close as pos-
sible to the stoichiometric amount o~ copper chloride to obtain
the best selectivity. In the second case (to gi~e a solution)
it is preferable to lixiviate with less than the stoichiometric
quantity of chloride (preferably cupric).
Depending on the dissolving capacity of the aqueous lixivia-
tion solution, the lead chloride may be obtained in the Eorm of a
-- 5 --
solution or of a pulp.
In the first case, to ensure the retention in solution of
the lead, the concentration of chloride ions in the aqueous phase
is preferably at least 2 gram-equivalents per litre of chloride
ions, more pre~erably greater than 4 gram-equivalents per litre
disregarding the chlorides used for the lixiviation.
These chloride ions may be added in the aqueous phase in
the ~orm of ammonium chloride or a chloride of a water-soluble
metal chloride, especially of an alkali or alkaline earth metal.
In the second case, recovery in the form of pulp is suffici-
ent for the quantity of lead to be lixiviated per unit of volume
to be greater than the dissolution capacity of the lixiviating
solution.
The products of the lixiviation are (a) a saturated lead
chloride solution possibly containing a small quantity of ginc
chloride, (b) crystalline lead chloride and tc) a solid mixture
of copper sulphides, mainly cupric sulphide, and also sulphides
of the metal(s) whereof the chloride was used to treat the lead
sulphide, and metal sulphides which had not reacted with that
solution.
We have surprisingly found that the presence of the crystal-
lised lead chloride phase does not in any way impede the li~ivi-
ation reaction, desp.ite the fact that the crystals of plumbous
chloride are dispersed and are .intimately mixed with the sulphides,
and tend to cover the particles of ore or of concentrate.
One of the principle advantages in this second embodiment
is that it allows the use of concentrated copper chloride
solutions, having a copper concentration of at least 30 g/l, or
0.5 M. To avoid increasing the solubility of the lead chloride,
the concentration of free chloride ions, excluding the chlorides
~1
-- 6 --
needed for the lixiviation, it preferably not greater than 2
and more preferably between 0~5 and 1.5 gram equivalents per
litre. The chloride ions may be supplied in the form of
wholly or partially dissociated chlorides; only wholly dissociated
chloride is considered in the determination of the quantity of
chlorides to be added.
The solid mixture resulting from the reaction should be
treated, during which the pH value is preferably kept at not
greater than 3 r to separate the lead chloride from the residual
sulphides. Examples of suitable physical treatments currently
used in metallurgy during the production of concentrates from
ores axe flotation, separation in a dense medium and elutriation.
Another separation method consists in cementing into a pulp
the solid mixture by means of a metal more electropositive than
lead, such as iron or zinc, thus obtaining metallic lead which
can easily be separated from the sulphide phase by use of one
o~ the physical separation techniques described above; tha pulp
may be either the reactive mixture after being attacked by the
chloride solution, or may originate from the conversion into
pulp of the cake obtained after filtering and optional washing
of the reaction mixture.
A third separation method consists in dissolving the cake
of lead chloride and sulphide obtained after filtering and
optional washing of the reaction mixture in a solution of dis-
sociated metal chloride, to dissolve the lead chloride and separate
it from the other solids.
The preliminary contacting of the sulphide compound with
cupric or ferric chloride activates the ore, that is to say
distinctly increases the selectivity and speed of the lixivia-
tion. In a first stage, this contac-t modifies the surface condi-
~ - 7 -
~ir,~8~
tion, and in a second stage modifies the sulphur concentration
of the sulphide compound by dissolving a part of the lead.
This favourable modification may equally be obtained whilst
having sulphur in the residual mixture. Since cupric chloride
forms part of the chlorides able to lixiv:iate lead selectively,
its use is preferred to ferric chloride; treatment with cupric
chloride makes it possible to simultaneously activate the ore and
to perform the selective lixiviation.
The selectivity obtained by the present invention is the more
remarkable in that it is applied with respect to less reducing
metals than lead, such as bismuth, more reducing metals such as
zinc, and to metalloids such as arsenic.
Bismuth, arsenic and even copper and silver are among the
most difficult impurities Oe lead an~ should be eliminated from
a lead solution if it is wished to perform a direct cementation.
The process of the present application thus makes it possible to
selectively lixiviate the lead contained in the sulphide compound
by means of its own impurities; the process may equally be applied
to eliminate particular impurities such as silver, bismuth, arsenic
or copper from the lead chloride solutions.
The ease of absorption of these impurities by the ore varies
with the concentration of copper ions of the solution which is to
be purified. The purities obtai.ned are remarkable. The lead con
tained in the ore should be in greater quantity than that which is
required stoichiometrically to precipitate these impurities in the
form of sulphides. This purifying technique is well suited to
lead chloride solutions obtained from treatment with ferric chloride.
The lead present as chloride in the solution thus obtained may
be recovered by methods, for example, as disclosed in our British
Patent Specification No. 1,502,404. ~ecovery techniques which make
~ - 8 -
it possible to obtain the cupric chloride regeneration agents
directly or indirectly, that is to say hydrochloric acld and/or
ferrous chloride are however preferable.
One recovery method is cementation by means of iron (which
yields ferrous chloride), or of zinc (which yields zinc chloride
which may be at least partially pyrohydrolysed into zi.nc oxide
and hydrochloric acid). Iron preferably in the form of pre-
reduced iron, is preferred for performing the cementation; the
term "cementation" is used herein to incl~lde its technical equi-
valents such as (a) soluble anode electrolysis (the metal forming
the anode being different from that to be recovered) and (b) use
of cells of the "Daniell cell" type, which may be considered as
a cementation of copper by means of zinc. In these two cases,
the electrodes may be separated by a partition permeable to chlor-
ide ions.
Another recovery method is reduction of lead chloride by
hydrogen; this may be performed in accordance with the general
technique for reduction of metal chlorides by means of hydrogen
known under the name "van Arkel process". Another method is
described as follows: the lead chloride obtainecl after -the
attacking action is recovered in crystallised form, for example
by cooling the solutions charged with lead chloride. The lead
chloride is then melted and then reduced by means of hydrogen,
used either pu.re or diluted in an inert gas, such as nitrogen
or a rare gas.
Reduction of the molten lead chloride is preferably carried
out at a temperature between 700 and 950C~ and more preferably
between 850C and 950C; the pressure is most conveniently at-
mospheric pressure.
One of the preferred and surprising methods of carrying out
this reducti.on consists in melting the lead chloride in a bath
_ g _
. :
' ' '
6~
and blowing hydrogen into the bath by means of lances. The
hourly rate of flow of hydrogen is preferably at least twice
the stoichiometrical quantity required to reduce all o~ the lead
chloride, the stoichiometry corresponds to the following reduc-
tion:
Pb Cl2 + H2_____ ~ Pb + 2 HCl.
The gases emerging from the reduction thus contain both the
unreacted fraction of the hydrogen and the hydrochloric acid
formed during the reaction. The hydrogen may be burnt to heat
the lead chloride; the hydrochloric acid mixed with the hydrogen
can be separated either before or after the combustion.
The hydrogen may also be recycled to the reduction of lead
chloride after having been separated from hydrochloric acid in
accordance with a conventional technique such as gaseous diffusion
or cooling followed by an absorption in water.
The use o~ this reaction is surprising because thermo-
dynamic calculations demonstrate that the reduction reaction
is very difficult; the standard free enthalpy variations (~ G)
are greater than or equal to nought at the different temperatures
contemplated, as shown in the following table:
Temperature ~ G
gilocalories/mole
900C O
827C ~
527C +ll
These calculations of enthalpy variations were made on the basis
of the tables and graphs published in "The thermochemical pro-
perties of the oxides, fluorides and chlorides to 2500K", by
Alvin Glassner - Report ANL (Argonne National Laboratory) -
5107.
The sulphide residue originating from the purification or
-- 10 --
'
from the lixiviation may be p.rocessed so as to recover the non-
ferrous metals present, e.g., by one of the techniques described
in our British Patent Specifications Nos. 1,47~,571 and 1,502,404
and U.S. Patent Nos. 4,016,056 lssued April 5, 1977 and 4,023,964
issued May 17, 1977.
The application of the process in accordance with the
present application renders it possible to improve and~or extend
the sphere of application of the processes described in these
applications. These processes may make use of the ferrous
chloride produced during the cementation of the lead for -the
regeneration of cupric chloride, and may provide the solution
of chloride required for lixiviation.
The invention will now be described with reference to the
accompanying drawing, the single f:igure of which is a Elow
sheet of an embodiment o:E the process of the invention includlng
reyenerat.ion of the chloride solu-tion.
In this figure, the paths of the solids are illustrated by
means o~ a double line and those of the liquids by means of a
single line.
The lead-containing sulphide to be treated is fed into a
selective action reactor 1 in which it is contacted with a solu-
tion of copper chloride, the origin which is described subsequently.
The lead chloride solution thus obtained is passed into a
cementation plant 2, whilst the residual sulphide is passed into
another reactor 4 in which it is placed in contact with a solu-
tion of cupric chloride and in which all the non-ferrous metals
present are dissolved.
In the cementa-tion plant 2, the lead chloride solution is
placed in contact with metallic lead or with a more reducing
metal than lead, the residual impurities nobler than lead then
~ being precipitated in metallic form.
~L~ i7
~, .
The lead chloride solution emerging from the plant 2 is
passed into another cementation plant 3 in which it is placed
in contact with a more reducing metal than lead, preferably iron.
The lead then precipitates in metallic form and the redwcing
metal (e.g. iron) passes into solution in the form of ferrous
chloride.
The ferrous chloriae solution emerging from the plant 3 is
mixed with the solution of chlorides of non-ferrous metals emerg-
ing from 4 and is conveyed into a plant 5 ~or regeneration of
the cupric chloride by bubbling of air or of a gas containing
oxygen, the ferrous chloride being precipitated in the form of
goethite according to the reaction:
4 Cu ~ 2 FeC12 + M2O ~ 3/202 --> 4 Cu ~ 2FeO(OH) + 4 Cl
~ b
Supplementary quantities of ferrous chloride and possibly of
hydrochloric acid may also be fed into the plant during the
process.
The recovered solution of cupric chloride is separated into
two parts by means of a valve 6: one part is used as the
cupric solution in the reactor 1 in such quantity that the
dissolution of the lead is selective and the remainder is passed
into the reactor 4.
Arsenic, as well as a part of the bismuth and of the
antimony which are possibly put into solution, are eliminated
during the stage of precipitation of goethite, arsenic in the
form of ferric arsenate and bismuth and antimony in the form
of oxychlorides.
One may incorporate a procedure of this kind in one of the
processes described in our British Patent Specification Nos.
1,478,571 and 1,5Q2r404 and U.S. Patent ~05. 3,998,628
issued December 21, 1976, 4,016,056 and 4,023,964 and thereby
~ ~:?,~p
- 12 -
6~7
.,
improve such process. If reference is made to the graphs
of some of these applications, the plants bearing the
references 4 and 5 in the present application correspond
respectively to the plants 2 and 6 of Figure 1 of the U.S.
Patent No. 4,023,964 and to the plants A and E of the British
Patent Specification No. 1,502,404.
The following examples illustrate the invention.
Percentages are by weight unless otherwise specified.
- 12a -
36~
EXAMPLE 1 Lixiviation o~ a lead concentrate by means of cupric
chloride (CuC12) with dissolution of the lead and
precipitation of the copper.
A volume of 6.00 litres of a solution containing 250 g/l of sodium
chloride and 9.76 g/l of copper in the form of cupric chloride
is maintained at the temperature of 80C in a spherical flask
equipped with a heating system and topped by a reflux condenser
428.2 g of a finely crushed lead concentrate, containing
45.1~ of lead and 5.83% o~ zinc in the form of sulphides, is
then added to the above solution. The solid and liquid aggregate
is shaken vigorously for two hours and then filtered, giving
the following analysis:
Description Weight (g) Zn Total Cu Total Ph Total
or volume g/l Zn g g/l- Cu g g/l- Pb g
(ml) -~ % %
initial lead
concentrate428.2 g 5.83% 25.0 1.42% 6.1 45.1%193.1
lnitial less than
solution 6000 ml 0.06g/1 0.36 9.76g/1 58.6 0.02g/1 0
total of the
materials 25.36 64.7 193.1
final 5800 ml 0.72g/1 4.18 1.82g/1 ]0.6 31.lg/1 180.4
final solid270.7 g 7.95% 21.5 20.6% 55.8 3.0%8.1
total of the
emergent
materials 25.68 66.4 188.5
yield of
dissolution % 14.0 95.7
This example clearly shows that almost all the lead goes into
solution, together with the precipitation of the copper.
EXAMPLE 2. Exhaustion of the attack residue 1 and recovery of
the precipitated copper.
Two litres of a solution of cupric chloride containing 9.08 g/l
o~ copper is kept at 80C in a glass reac-tor topped with a reflux
- 13 -
~$~7
condenser. 27.2 gra~nes of -the final solid obtained at the end
of the preceding experiment is then added to this solution
and is stirred ln a homogeneous manner for -two hours followed
by filtration; the cupric ion concentration reaches 6.35 g/l
during this period~
I~he analysis is as follows:
Description Weight (g) Zn Total Cu Total Total Pb
or volume g/1-% Zn g g/l-% Cu g g/1-% g
(ml)
initial less than
solution 2000 ml 0.06g/1 0.12 9.08g/1 18.16 0.01g/1 0
incoming
solia 27.2 g 7.95% 2.16 20.6% 5.6 3.0% 0.82
TOTAL INPUT 2.28 23.76 0.82
final
solution 2000 ml 0.72g/1 1.44 11.54g/1 23.1 0.54 1~08
final solid 17.3 g 4.$2~ 0.78g 1.92% 0.33g 0.35% 0.06
I'OTAL OUTPUT 2.22 23.41 1.14
This experiment shows that the second attack allows the recovery
of the copper precipitated during the first attack and the dis-
solution of a large proportion of the zinc and of the lead which
were not dissolved during the first (selective) attack. If the
chemical composition of the residue from the second attack is
compared to the initial composition of the ore, it is seen that
the overall yield of dissolution of the metals for the two
attacks is:
zinc : 68.9%
lead : 99.7%
copper: 46.3%
The recovery of close to half of the copper ini-tially present in
the concentra-te is thus added to the total re-dissolution of the
copper precipitated during the selective attack.
- 14 -
~!a~67
EXAMPLE 3. Purification of a lead chloride solution by precipi-
tation of the impurities.
This experiment is performed on an aliquote part of the solution
obtained in the experiment of Example 1. 4 grammes of lead pow
der is added in one batch to 500 ml of this solution kept at 80C
and stirred vigorously. The stirring is continued for 70 minutes,
followed by a solid-liquid separation by filtering giving an an-
alysis as ~ollows:
Weight (g) Zn Cu Pb As Bi Ag Sb
volume (ml~ g/l- g/l- g/l- g/l- g/l- g/l- g/l-
% % % % % % %
initial
solution500 0.721.82 31.1 0.118 0.01 t).045 0.01
initial lead
powder 4 100
final
solution500 0.590.026 32.0 0.032 0.005 0.002 0.01
It is observed that at the end of this operation, the solution is
freed of the principal impurities, particular of copper and bismuth
and partially of arsenic, liable to be entrained into a subsequent
cementation of the lead; these impurities accumulate in the previous
cement.
EXAMPLE 4. Cementation of the lead by means of iron sponge,
from a solution of plumbous chloride (PbC12) in a
brine.
The solution oriyinating from the pre-cementation shown in
Example 3 above is taken again for this experiment.
4.3 grams of iron sponge containing 72.4% of metallic iron
crushed beforehand to a grain size of between 80 and 200 microns
is added to 420 ml of this solution. The operation is performed
whilst stirring vigorously at the tempera.ure of 80C for 100
minutes.
..~
- 15 -
At the end of the operation, a solid-liquid separation is
performed, giving an analysis as follows:
Description weight (g) Zn Cu Pb Fe As Bi Ag Sb
volume %- %- %- %- %- %- %- %-
(ml) g/l ~/1 g/l ~/l ~/1 g/l g/l ~/1
precemented
solution 450 ml 0.59 0.03 32.0 0.032 0.01 0~005 0.005
iron sponge 4.3 g 97.0%
final
solution 400 ml 0,58 0.04 9.76 5.94 0~003 0.01 0.001 0.01
final not
cement 11.6 y 0.014 0.11 79.5 11.0 deter-0.02 0.0025 0.005
mined
EXAMPLE 5. Dissolution of lead by means of cuprous chloride
brine ICUCl).
Two litres of a solution containing 16.5 g/l of cuprous i.ons
and 22.:L g/l of copper are fed into a cylindrical reactor.
This solution being kept at 80C, consecutive fractions of lead
concentrate are fed in.
After each addition of concentrate, the stabilisation of
the concentration of cuprous ions is awaited before proceeding
wi-th another addition of ore. This procedure is followed until
the complete disappearance of the cuprous ions. The results
are summarised in the following table.
~1
- 16 -
o o o o o o ~
E~ .
r~
m
E~ o ~ o ~ ~
O o O C.~ ~,
r4 rl
.,1.~ ~
m ~ O
.o
~ ~ ~ O o ~ ~
E~ ~ u~ rq
o\O 0~0 ~IJID O
~O ~ ~, .c
U~ ~, 0~O ~ ,
~ . I I I . I I ~ ~
--~ o 0 4~ o
~ ~ ~ ~ CO ~' ~ ~O ~ ~ ~
~ P~ u) o In o u~ ~ ~o ~ O a~
co ~ ~ 3 ~ ~
,,
o ~ ~) 1 0
O ~ o\
~ ~ ~ O I U~
r~ ~o
00 ~ O Ln ~O
. . . . ~ o~ tn ~1
E~ u7 ~ o ~1 ~ ~ I ,1 0 ,~
r-l r-l
o\ ~ \ Op rl ~ ~
,_ ~ ~ n ~ a) o
~ ~ ~r ~ Ic
C~ ~0\o . ~ .
~ tn ~ r~
rl
O
~1 ~O ~~ f~l r-l O 'rl
o ~ ~1In 00 ~ ~ S O 1
. . .. . . . O t~
O ~ o ~Lr~ r
E~ ~ ~ ,~
~ ~ r~
o\
I ~ O In 4
F. ~1 ~o o 1~ ~ O
0 I I I rl
_ ~ U~ o ~ ~ ~ U~ U~
~ a~ ~ o
~ _~ ~rl
_ IY) ~ rl
~ a~
. o 1~o ~ I I S~
~rl ~ O O O ~ ~ rl rc~ (d
O r-l O O
3 ~ ~r ~ ) r
E~
~ ~ O
r~ ~) r l Orl O a) ~) o\
~I F tl~ rl rl
rl a) rl ~ ~Ir-J ~)r~ Ql r-
rl ~; (d Ql u~ r
~r~ ~ ~rl ~1 ~) ~ r-l tl~ d ~ ~) u~ a)
F O ~ O Orl Oal ~ O ~ r~ rl
~r~ ~ ~ rd
-- 17 --
EXAMPLE 6. Influence of temperature; attack of the ore by the
cuprous chloride (CuCl) at boiling polnt.
The reduced solution is heated to boillng point before the addi-
tion of the ore; boiling is maintained for 5 hours~
The following table gives the results of this operation:
weight (g) (Zn) Total (Cu) Total (Pb) Total
vol. (ml) Zn g Cu g Pb g
initial less
solution 500 ml0.04g/1 0.02 17.9g/1 8.95 than 0
0.02
fresh
concentrate 32.3 g 5.83% 1.58 1.42% 0.46 45.10% 14~57
total input - - 1.90 - 9.41 - 14.57
final
solution 500 ml1.12g/1 0.56 12.88g/1 6.44 10.52g/1 5.26
residue (esti-
mated weight) 26 g 5.15~ 1.3~ 12.7% 3.30 30.~% 7.90
total output 1.90 9.74 13.16
dissolution
yield % 29.5 40.0
EXAMPLE 7. Tests for activation of the ore by means of cuprous
chloride (CuC12).
The ore i5 initially exposed to an activation at 80C, by means
of a solution o~ cuprous chloride titered at approximately 18 g/l
o~ copper, for 15 minutes. The quantity of cuprous chloride
placed in operation is equal to 31.7% of the stoichiometrical
quantity (QS) required to place the lead is solu-tion.
A solution of CuCl is then fed into the reactor in such
volume that the lead initially added exceeds 1.1 QS with respect
to the quantity of C1~3 ions linked to the copper, which are
introduced into the reactor.
~.~
- 18 -
67
weight (g~ (~n) Total TotalTotal
vol. (ml) Zn (Cu) Cu(Pb) Pb
( CJ ) ( g )__ _
activating
solution90 ml - - 18.5g/1 1.67 ~ -
attacking
solution410 ml 0.12g/1 0.05 22.3g/1 9.14 0.02g/1 0
fresh
concentrate 38 g5.83% 2.22 lo 42% 0.54 45.10% 17.12
- total
input - - 2_27 _ 11.35 - 17.12
final
solution480 ml 0~82g/1 0.39 8.6g/1 4.13 18O9g/1 9.07
residue30.2 g 5.85%1.77 16.4% 4.95 24,9% 7.52
total - - 2.16 - 9.08 - 16.59
output
yield (%) - - 18.1 - -- 54.7
The improvement of the yie"d and of the selectivity with respect
to zinc are evident from this data.
E ~PLE 8. Attack within a pulp of a lead concentrate origin-
ating from Aznallcollar (Spain).
1762 grams of lead concentrate is fed into 4 litres of cuprous
chloride solution containing 54 grams of copper per litre,
which corresponds to 85% of the stoichiometrical quantity re-
quired to convert all of the lead present in the ore into plumbous
chloride. After one and a half hours of reaction, the reaction
mixture is filtered to yield a filtrate and a cake, giving
the following analysis:
element ore cakefiltrate
lead 47% 33.4%11.1 g/l
zinc 4.9% 3.98%1.38 g/l
copper 0.96% 9.10% C 0.02 g/l
iron 13.4% not deter-1.46 g/l
mined
.~
.
,
element ore cake filtrate
silver 768 g/T not deter~ not deter-
mined mined
chloridenot deter- 11.2% not deter~
mined mined
(g/T = grams per metric ton).
The lead chloride yield amounts to 80% with respect co the ore,
and 95% with respect to the copper chloride initially placed in
operation at the beginning, and tha-t the rate of zlnc dissolution
amounts to no greater than 6% and demonstrates the great selectivity
of the attack.
This experiment illustrates the possibility of chlorinating
a lead concentrate whilst operating with a high proportion of
solid and with a short residence -time.
EXAMPLE 9. Dissolution of lead chloride contained in a
chlorination concentrate.
20 litres of a brine from previous experiments and containing the
following elements:
NaC1 256 g/l
Pb 4.5 g/l
Zn 0.22 g/l
Cu 0.24 g/l
are kept at 90C in a 20-litre reactor.
2,000 g of a homogenised solid originating from a variety
of chlorination experiments is added in one batch. The composi-
tion of this product is as follows:
Pb 33.5%
Cl 8.73 g/T
Zn 3.24%
Fe 9.94%
Cu 9.24%
- 20 -
H2O 10.0%
The dissolution of lead chloride over a period of time is shown
in the following table:
Time (h. min.) Zn g/l Cu g/l Pb g/l
0.00 0.22 0.24 4~5
0.05 0.26 l.0 19.9
0.10 0.~6 1.0 23.1
0.20 0.30 1.0 26.3
0.40 o.28 l.0 26.6
1.30 0.30 0.94 26.0
This experiment shows that it is possible to observe the speed of
dissolution of lead chloride, since a balance is reached at the
end of 20 minutes, and that 70% oE the balance is reached after
5 minutes. The copper which had been precipitated during the
previous attacks remains practically insoluble.
EXAMPLE lO. Recovery of HCl ~ air from a chlorination residue.
This experiment was performed in a 20 litre cylindrical reactor
equipped with a special stirring system. This stirring system
is a flotation impeller normally designed to perform ore enrich
ments and has the feature of assuring an intimate contact between
the gas and the mixture, thanks to a satisfactory dispersion of
the gas, and to a substantial recircula-tion of the volume of gas
present above the level of the liquid.
20 litres of solution having the following composition:
Pb C0.2 g/l
Cu 16.6 g/l
Zn 41.6 g/l -
Fe 0.2 g/l
are heated to 80C in the above.
.~
- 21 -
~3~67
1,100 g of a solid, obtained from an ore which had been
chlorinated r the lead chIoride formed redissolve~ and the liquor
decanted, is added in one batch. This solid has the composition:
Pb2.61 %
Cu18.7 %
Zn6.84 %
Fe19.2 %
H2010 %
Compressed air is fed into the mixture at a flow rate of
1240 l/h. A solid-liquid separation is made at the end of 10 1/2
hours. After washing with distilled water, the residual solid
weighs 764 g, and its chemical composition is:
Pb 0.45 %
Cu 0.99 %
Zn 1.75 ~
H2O 16.6 %
Based on this analysis, the rate oE dissolution of the
elements present initially in the solid was calculated as
follows:
Pb 88.0 %
Cu 96.3 %
Zn 82.2 %
It is thus shown that it is possible to recover the copper
precipitated during the chlorination stage with a satisfactory
yield, whilst assuring the recovery of the residual Pb and Zn.
EXAMPLE 11. Elimination of the impurities accompanying lead
by crystallisation of lead chloride.
This Example shows the degree of purity which may be reached by
lead chloride obtained by crystallisation.
An impure solution of lead chloride s fil-tered and then
- 22 -
allowed to stand for ~8 hours. The initial and final temperatures
of the solution are 85C and 16C, respectively. The crystals
ob-tained are separated by filtration.
The analyses of the initial solution and of the crystals ob-
tained are specified in the following table:
Description weight Pb Cu Fe Zn Bi Ag Sb As Sn
or % % % % % % % % %
volume g/l g/l g/l g/l g/l g/l g/l g/l g~l
initial
solution 850 1 23.2 2.02 0.22 1.32 0.028 0.044 0.0340.02 0.003
crystals 13.5 kg 74.4 0.015 0.07 0.005 0.009 0.002 0.02 0.01 0.012
The puri-ty obtained is of the order of 99.9%.
Operating method of Examples 12~ 13 and 14:
80g of slightly damp lead chloride (corresponding to 56 g
of metallic lead) are melted in a ~uartz tube. Hydrogen is
bubbled into the molten chloride bath through a quartz pipe.
The height of the molten chloride amounts to S cms,
prior to reduction. The operating parameters and the results
of the different examples are summarised in the following tables:
EXAMPLE 12.
temperature 800C
period 1 hr.
hydrogen flow rate 30 l/hr
weight of the residual
slag (PbC12) g
weight of the recluced
lead 56 g
yield 100 %
The same result is obtained if the hydrogen is replaced by
a hydrogen-nitrogen mixture containing 50% of hydrogen, the
rate of 1Ow of the gaseous mixture being equal to 30 l/hr, the
reaction period being increased to two hours and the other
conditions remaining unchanged.
- 23 -
EXAMPLE 13.
~ temperature 800C
: perîod 1 hr.
hydrogen flow rate 15 l/h
weight of the residual
slag (PbC12) 31 g
weight of the reduced
lead 35 g
yield 64 %
EXAMPLE 14.
temperature 700C
period 1 hr.
hydrogen flow rate 30 l/hr
weight of the residual
slag (PhC12) 36 g
weight o:E the reduced
lead 28 g
yield 52 ~
The lead purity obtained exceeds 99.99%: the proportion
of diEferent impurities in the lead is summarised in the
following table~
Impurity proportion in g/T
arsenic (As) 60
antimony (Sb) 30
copper (Cu) 2
tin (Sn) 2
; silver (Ag)traces (limits of detection)
bismuth (Bi) " " " "
zinc (Zn) " " " "
EXAMPLE 15. Purification of lead chloride solution.
:' 30
The impure lead chloride solution is continuously contacted
.
.. . ' ~ ~
.
.
with fresh lead concentrate in two twenty litre reactors working
co-curren-tly. The operating conditions are as follows:
- Average size of the concentrate granules : 200 ~m
~ Concentrate flow rate : 788 g/h
- Lead chloride solution flow rate : 20 l/h
- Ph : 1.7
- Temperature : 90 C
- Residence time : 2 hours.
The results of this purification are given in the following
Table:
Composition Composition Composition of Composition of
of the of the impure the purified the emergent
concentrate solutionsolution solid
(%) ,, ~1) (q/l) (~)
lead (Pb) 64.3 13.7 28.3 25.2
~lnc (Zn) 4O48 6.3 6.9 6.4
copper (Cu) 0.42 0.00153 97.8
iron (Fe) 4.83 1.0 3.1 6.8
silver (Ag) 0.0919 0.04 less than
0.002 0.34
sulphur (S) 18.0 - ~ 27.0
bismuth (Bi) 0.030 0.02 less than
0.006 0.14
arsenic (As) 0.090 0.034 less than
0.002 0014
antimony (Sb) 0.31 0.018 less -than
0.002 0.52
sodium
chloride - 250 250
This Exam~le shows that it is possible to obtain a very
good purification by contacting impure lead chloride solution
with ore or concentrate containing galena. Such a purity allows
.~ - 25 -
direct electrolysis (with a soluble or insoluble anode) of the
purified lead chloride solution to recover metallic lead.
Ferrous chloride does not impede the purification of lead chloride
dissolved in concentrate chloride solution (more than 2N) by
contacting fresh galena.
_ 26 -
