CA1108867A

CA1108867A - Hydrometallurgical process for the treatment of sulphidized compounds containing lead

Info

Publication number: CA1108867A
Application number: CA282,906A
Authority: CA
Inventors: Jean-Michel Demarthe; Andre Georgeaux; Bernard Lambert
Original assignee: Societe Miniere et Metallurgique de Penarroya
Current assignee: Societe Miniere et Metallurgique de Penarroya
Priority date: 1976-07-20
Filing date: 1977-07-18
Publication date: 1981-09-15
Also published as: MX146692A; IT1081027B; PL199743A1; IE45861L; DE2732817C2; DE2732817A1; AU2717377A; ZA774362B; GR66043B; IE45861B1; PT66825A; GB1560053A; JPS5314613A; PT66825B; AU516246B2; BE856829A; JPS602371B2; ES460890A1; YU179977A; PH17756A

Abstract

ABSTRACT
The specification describes a hydrometallurgical process for treating a mixture of metal sulphides containing lead sulphide, wherein the sulphide mixture is treated with an aqueous lixiviating solution containing at least one chloride selected from the chlorides of copper, bismuth, antimony, arsenic and silver, the quantity of the said chlorides used being not more than 120% of that which is stoichiometrically required for the complete dissolution of the lead contained in the sulphides.

Description

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 , ,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 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 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 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 ' 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 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 ~$~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.

~!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.
..~

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 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 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.

~.~

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%

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.

.~

~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 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.

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 -

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A hydrometallurgical process for treating a mixture of metal sulphides containing lead sulphide, wherein the sulphide mixture is treated with an aqueous lixiviating solution containing at least one chloride selected from the chlorides of copper, bismuth, antimony, arsenic and silver, the quantity of said chlorides used being not more than 120%
of that which is stoichiometrically required for the complete dissolution of the lead contained in the sulphides.

2. A process as claimed in Claim 1, wherein the said aqueous solution contains at least 4 gram-equivalents of chloride ions per litre.

3. A process as claimed in Claim 1, wherein the quantity of chloride in said aqueous solution is not greater than that which is stoichiometrically required for the complete dissolution of the lead contained in the sulphide.

4. A process as claimed in Claim 2, wherein the quantity of chloride in said aqueous solution is not greater than that which is stoichiometrically required for the complete dissolution of the lead contained in the sulphide.

5. A process as claimed in Claim 1, 2 or 3, wherein the temperature of the aqueous solution is between 60°C and the boiling point of the reaction mixture.

6. A process as claimed in Claim 1, 2 or 3, wherein the pH value of the aqueous solution is not greater than 3.

7. A process as claimed in Claim 1, 2 or 3, wherein the aqueous solution also contains at least one chloride selected from ammonium chloride, the chlorides of the alkaline metals and the chlorides of the alkaline earth metals.

8. A process as claimed in Claim 1, 2 or 3, wherein the sulphide is activated, before said treatment, by means of ferric chloride and/or cupric chloride.

9. A process as claimed in Claim 1, 2 or 3, wherein the lead chloride solution resulting from the treatment is purified by being contacted with metallic lead.

10. A process as claimed in Claim 1, 2 or 3, wherein the lead of the lead chloride solution resulting from the treatment is recovered by cementation by means of a more reducing metal than lead.

11. A process as claimed in Claim 1, 2 or 3, wherein the lead of the lead chloride solution resulting from the treatment is recovered by cementation by means of a more reducing metal than lead, and wherein the cementation is an electrolysis in which the anode is a soluble anode of a more reducing metal than lead.

12. A process as claimed in Claim 1, 2 or 3, wherein the lead of the lead chloride solution resulting from the treatment is recovered by cementation by means of a more reducing metal than lead, and wherein the cementation is an electrolysis in which the anode is a soluble anode of zinc or iron metal.

13. A process as claimed in Claim 1, 2 or 3, wherein the aqueous solution contains cupric chloride and the cupric chloride is subsequently regenerated by means of a regenerating agent and air.

14. A process as claimed in Claim 1, 2 or 3, wherein the aqueous solution contains cupric chloride and the cupric chloride is subsequently regenerated by means of a regenerating agent and air, and wherein the said regenerating agent is ferrous chloride produced by the cementation of lead by means of iron.

15. A process as claimed in Claim 1, wherein the quantity of lead present per unit of volume of said compound is greater than the dissolving capacity for lead of the aqueous lixiviating solution used.

16. A hydrometallurigcal process for treating a mixture of metal sulphides containing lead sulphide, wherein the sulphide mixture is treated with an aqueous lixiviating solution containing at least one chloride selected from the chlorides of copper, bismuth, antimony, arsenic and silver, the quantity of the said chlorides used being not more than 120% of that which is stoichiometrically required for the complete dissolution of the lead contained in the sulphides, wherein the temperature of the aqueous solution is between 60°C and the boiling point of the reaction mixture, and wherein the quantity of lead present per unit of volume of said compound is greater than the dissolving capacity for lead of the aqueous lixiviating solution used.

17. A process as claimed in Claim 16, wherein the concentration of the copper in the aqueous solution is not less than 30 grams per litre.

18. A process as claimed in Claim 15, 16 or 17, wherein the concentration of free chloride ions is not greater than 2 grams equivalents per litre.

19. A process as claimed in Claim 15, 16 or 17, wherein the solid mixture of lead chloride and of sulphides obtained after filtration of the reaction mixture is subjected to a physical separation technique, so as to separate the lead chloride from the sulphides.

20. A process as claimed in Claim 15, 16 or 17, wherein the pulp obtained after the contacting with the aqueous lixiviating solution is exposed to a cementation by means of iron or zinc.

21. A process as claimed in Claim 15, 16 or 17, wherein the mixture of lead chloride and sulphides obtained after filtration of the reactive mixture is returned to the state of pulp and cemented by means of iron or zinc.

22. A process as claimed in Claim 15, 16 or 17, wherein the pulp obtained after the contacting with the aqueous lixiviating solution is exposed to a cementation by means or iron or zinc, and wherein the metallic lead obtained after cementation is separated from the sulphides by a physical separation technique.

23. A process as claimed in Claim 15, 16 or 17, wherein the mixture of lead chloride and sulphides obtained after filtration of the reactive mixture is returned to the state of pulp and cemented by means of iron or zinc, and wherein the metallic lead obtained after cementation is separated from the sulphides by a physical separation technique.

24. A process as claimed in Claim 15, 16 or 17, wherein the solid mixture obtained after filtration of the reaction mixture is redissolved in a solution of dissociated metal chlorides to yield a solution of lead chloride and a solid phase consisting of sulphides.

25. A process as claimed in Claim 1, wherein the lead placed in solution is recovered in the form of crystallised lead chloride, the lead chloride being melted and then reduced by means of hydrogen to metallic lead.

26. A process as claimed in Claim 1, wherein the lead placed in solution is recovered in the form of crystallised lead chloride, the lead chloride being melted and then reduced by means of hydrogen to metallic lead, and wherein the reduction is performed at a temperature of between 850°
and 950°C.

27. A process as claimed in Claim 1, wherein the lead placed in solution is recovered in the form of crystallised lead chloride, the lead chloride being melted and then reduced by means of hydrogen to metallic lead, and wherein the reduction is performed at a temperature of between 850° and 950°C, wherein the hydrogen is diluted in an inert gas.

28. A process as in Claim 25 or 26, wherein the hydrogen is diluted in an inert gas.

29. A process as claimed in Claim 25 or 26, wherein hydrogen is blown into the molten lead chloride.

30. A process as claimed in Claim 25 or 26, wherein hydrogen is blown into the molten lead chloride, and wherein the hourly flow rate of hydrogen is not less than twice the stoichiometrical quantity required for the total reduction of the lead chloride.

31. A process as claimed in Claim 25 or 26, wherein the hydrogen contained in the gases emerging from the reduction is separated from hydrochloric acid formed during the reaction of the lead chloride and hydrogen and is recycled to the lead chloride reduction, the hydrochloric acid being recycled to the dissolution of the lead.

32. A process as claimed in Claim 3, wherein impure lead chloride solution is purified by contacting it with fresh lead sulphide ore.

33. A process as claimed in Claim 32, wherein lead is recovered from the purified lead chloride solution by electrolyzing the same using an insoluble anode.