WO2013030449A1

WO2013030449A1 - Method for recovering metals from sulphidic concentrate

Info

Publication number: WO2013030449A1
Application number: PCT/FI2012/050820
Authority: WO
Inventors: Tuula MÄKINEN; Kari Hietala; Karoliina LAHTINEN
Original assignee: Outotec Oyj
Priority date: 2011-08-29
Filing date: 2012-08-28
Publication date: 2013-03-07
Also published as: FI20110278A0

Abstract

The invention relates to a method for processing a sulphidic bulk concentrate, in which the concentrate is processed in a smelting furnace into matte and slag phases, and the slag from the smelting furnace is processed in a slag cleaning furnace. The smelting furnace matte and slag cleaning furnace matte are processed hydrometallurgically in leaching, after which the recovery of leached valuable metals (Ni, Cu, Co) takes place in a common step.

Description

METHOD FOR RECOVERING METALS FROM SULPHIDIC CONCENTRATE

FIELD OF THE INVENTION

[0001 ] The invention relates to a method for recovering metals from sulphidic concentrate. BACKGROUND OF THE INVENTION

[0002] A conventional pyrometallurgical processing method of a nickel sulphidic concentrate is to process the concentrate in a smelting furnace to nickel matte and further in a converter into high-grade nickel matte. The oxidation degree of the input concentrate, that is, the amount of input oxygen, determines the iron content of the matte created at the bottom of the furnace, as well as the nickel and copper content of the slag. The optimal ratio between the iron in the matte and the nickel and copper content in the slag can be adjusted in relation to the concentrate and oxygen fed into the furnace (Nm3 02/ t cone).

[0003] Published US patent 5 332 414 describes a method with which high-grade nickel matte and a long-oxidized slag is directly produced in a flash smelting furnace, in which case a converter need not be used. The high-grade nickel matte is then directed on to hydrometallurgical processing. The slag from the flash smelting furnace is directed to an electric furnace treatment that produces metallized matte that is also directed to a hydrometallurgical treatment for the recovery of nickel. The slag from the electric furnace is disposable slag. The publication does not describe the hydrometallurgical processing in detail.

[0004] A sulphidic nickel concentrate and, therefore, also the high- grade nickel matte usually always contains copper, and the recovery of nickel from the matte is always also separation of nickel from copper. The hydrometallurgical processing of nickel-copper matte has been described in several patent publications, such as US 4 323 541 and US 5 628 817.

[0005] When processing a bulk concentrate with a high content of copper and possibly cobalt, it should be decided in detail how the different metals can be recovered in an as simple and economic manner as possible.

[0006] Published US patent 5 628 817 describes a method for recovering nickel and copper from high-grade nickel matte, the method comprising first a two-step atmospheric leaching and then a two-step pressure leach- ing. The final recovery of copper and nickel takes place in a corresponding electrolysis. In the first atmospheric leaching step, the Ni-Cu matte is leached using oxygen and a copper sulphate solution, whereby nickel leaches and the leaching copper precipitates. The precipitate of the first leaching step is led to a second atmospheric leaching, in which the leaching is done using a sulphuric acid-containing anolyte of nickel electrolysis in oxidizing conditions. Not only nickel, but also copper leaches, and the solution is led back to the first leaching step. The precipitate of the second atmospheric leaching is led to a first pressure leaching step, in which the remaining nickel is leached using copper sulphate. The obtained solution is led through iron removal to a second atmos- pheric leaching and the precipitate to a second pressure leaching. The precipitate now contains mainly secondary sulphides of copper that are leached using an anolyte of copper electrolysis. The precipitate of the second pressure leaching contains any possible precious metals. The solution from the second pressure leaching contains copper sulphate and impurities that are removed before copper electrolysis.

[0007] However, the nickel-copper matte leaching methods described above are directed to processes, in which only one type of matte is leached and processed.

[0008] Published US patent 6 039 790 describes a method, in which nickel is recovered from two different nickel mattes, that of the smelting furnace and that of the electrical furnace, in one and the same process. The iron content of the electrical furnace matte is clearly higher than that of the smelting furnace matte which is high-grade nickel matte. The leaching of the finely ground nickel-copper matte obtained from the smelting furnace is done in two atmospheric steps and one pressure leaching step, and the leaching of the electrical furnace matte in one atmospheric leaching step. The smelting furnace matte is leached in the first atmospheric leaching step by using the copper sulphate-containing nickel sulphate solution from the second atmospheric leaching. The produced nickel sulphate solution is led to nickel electrolysis af- ter solution purification (cobalt removal). The precipitate from the first leaching step is led to a second leaching step, in which leaching is done using the nickel sulphate solution from the leaching of the electrical furnace matte and a nickel electrolysis anolyte. The precipitate of the second leaching step is led to a pressure leaching step, in which the leaching is done using a nickel electrolysis anolyte. In the pressure leaching step, the secondary nickel sulphide created in the earlier steps leaches and copper precipitates. The copper precipitate that also contains precious metals is led to a pyrometallurgical treatment, for example. The nickel sulphate solution formed in pressure leaching that also contains ferrosulphate is led to the leaching of the electrical furnace matte. A neutralizing agent is also led to the leaching step to precipitate iron as jarosite. OBJECT OF THE INVENTION

[0009] The object of the invention is to provide a novel manner of processing a sulphidic bulk concentrate, from which any valuable metals, such as nickel, cobalt, and copper, are advantageously recovered. According to the invention, the precipitate is processed in a smelting furnace into matte and slag, after which the slag is processed in a slag treating furnace. The smelting furnace matte and slag treating furnace matte are processed either in a separate leaching process or a common leaching process, after which the valuable metals are recovered in a common solution purification step by hydrometallur- gy- SUMMARY OF THE INVENTION

[0010] The invention relates to a method, with which it is possible to recover both the valuable metals nickel, copper and cobalt and possible precious metals from a sulphidic bulk concentrate containing them. According to the method, the sulphidic concentrate is first led to smelting furnace, in which matte and slag phases are formed. Slag treating is continued in a slag cleaning furnace to form a second matte and waste slag. Both the smelting furnace matte and the slag cleaning furnace matte are processed hydrometallurgically initially in their own leaching steps or in a common leaching step, but the final recovery of different valuable metals takes place in a common step.

[0011] The invention relates to a method for a processing sulphidic bulk concentrate by processing the concentrate in a smelting furnace into matte and slag phases, and processing the slag in a slag cleaning furnace, wherein the smelting furnace matte and slag cleaning furnace matte are processed hydrometallurgically in leaching, after which the recovery of the valua- ble metals (Ni, Cu, Co) leached in the leaching steps takes place in a common step. The method of the invention provides an efficient and economical way of recovering desired metals.

[0012] One way of processing a concentrate in accordance with the invention is to process the smelting furnace matte and slag cleaning furnace matte in separate leaching steps, whereby the smelting furnace matte and slag cleaning furnace matte are processed separately in a sulphate-based atmospheric leaching and pressure leaching. The leached valuable metals Cu and Co are then separated by solvent extraction from the product solution and recovered electrolytically. Nickel is also recovered electrolytically from the prod- uct solution that is now poor in copper and cobalt.

[0013] An embodiment of the invention is to process the smelting furnace matte and slag cleaning furnace matte in a common leaching step, wherein they are processed in a common sulphate-based atmospheric leaching and pressure leaching and then led to a common solution purification pro- cess. The leached valuable metals Cu and Co are then extracted by solvent extraction from the product solution and recovered electrolytically. The valuable metal Ni is also recovered electrolytically from the product solution that is now poor in copper and cobalt.

[0014] One way of the invention is to process the smelting furnace matte and slag cleaning furnace matte in a common chloride leaching. The valuable metal-bearing product solution is led to solution purification, in which copper, cobalt, and nickel are extracted from the product solution in consecutive extraction steps, and the aqueous solution of the stripping of each metal is sulphate-based. Copper, cobalt, and nickel are recovered from the sulphate solutions electrolytically, and the anolyte of each electrolysis is used as the aqueous solution in the stripping of the extraction of the corresponding metal. After the valuable metals have been separated, the chloride solution poor in metals is at least partly regenerated and led back to the leaching of the smelting furnace matte and slag cleaning furnace matte. According to an embodi- ment of the invention, the chloride solution contains alkali metal chloride. According to a second embodiment of the invention, the chloride solution contains calcium chloride.

[0015] According to an embodiment of the invention, the sulphidic bulk concentrate also contains PGM metals that remain in the leaching resi- due, and may be recovered from it.

LIST OF FIGURES

[0016] Figure 1 is a diagram of a method according to the invention;

[0017] Figure 2 is a diagram of a second embodiment according to the invention; [0018] Figure 3 is a diagram of a third embodiment according to the invention; and

[0019] Figure 4 is a diagram of a fourth embodiment according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] A sulphidic bulk concentrate containing nickel and other valuable metals, such as copper and cobalt, is melted in a smelting furnace, such as a flash smelting furnace, and matte and slag phases are formed. It should be noted that even though the text refers to a flash smelting furnace matte (FSF matte), the matte may also be from another smelting furnace. The slag from the flash smelting furnace is taken on for processing in a slag cleaning furnace, in which a slag cleaning furnace matte phase is formed, and the matte phase is then ground. The slag cleaning furnace is usually an electric furnace, and later, for the sake of simplicity, the text refers to electric furnace matte (EF matte), but the processing may also take place in another type of furnace, if necessary. A bulk concentrate is a concentrate which contains not only the principal valuable metal, such as nickel, but also other valuable metals, such as copper and/or cobalt.

[0021] The amount of matte formed in an electric furnace is in the range of 1/3 to 1/5 of the amount of flash smelting furnace matte. A typical analysis of the mattes obtained from the flash smelting furnace and electric furnace can be as follows, for example:

FSF matte

Analysis % Mineralogy %

Cu 29.2 Cu₂S 36.5

Fe 4.0 FeS 4.4

Fe₃0₄ 1.6

S 21 .4

Ni 42.7 Ni₃S₂ 45.7

Ni 3.7

NiO 7.0

Co 0.4 C0₉S₈ 0.6 EF matte

Analysis % Mineralogy %

Cu 18.2 Cu₂S 7.7

Cu 12.0

Fe 30.7 FeS 6.8

Fe₃0₄ 0.3

Fe 26.2

S 7.0

Ni 41 .1 Ni₃S₂ 10.8

Ni 33.2

Co 2.7 C0₉S₈ 0.1

Co 2.7

[0022] Figure 1 shows a process diagram according to the invention, in which the flash smelting furnace matte and electric furnace matte are processed in partly separate leaching processes, but in a common solution purification step.

[0023] The matte ground in the leaching circuit of the EF matte is led to a first leaching step that takes place at atmospheric pressure in oxidizing conditions at a temperature of 80°C to 103°C for leaching the metallic components (Ni, Cu, Fe, Co) of the matte. It is clear that the different leaching steps often comprise more than one reactor and that the reactors are mixing reactors. The purpose of atmospheric leaching is to minimize the formation of hydrogen in the subsequent pressure leaching step, because hydrogen may be formed in an autoclave if metallic components are leached in conditions where the amount of oxygen is below the stoichiometric amount. The atmospheric leaching takes place in a sulphate environment, wherein the solution from a later EF matte pressure leaching step, solution from the FSF matte nickel pressure leaching step, and a nickel electrolysis anolyte, that is, a nickel sulphate solution containing sulphuric acid, are used as the leaching solution.

[0024] The sludge from the EF matte atmospheric leaching is sub- jected to solids-liquid separation. The solids are led to an EF matte pressure leaching step that is done in an autoclave in oxidizing conditions. In pressure leaching, the pressure is in the range of 16 to 40 bar and the temperature is 150°C to 250°C. In pressure leaching conditions, the nickel and copper in the EF matte leach and mainly gypsum and a little iron remain in the leaching resi- due. The cake formed after the solids-liquid separation is waste, and the solution is returned to the EF matte atmospheric leaching. The solution from the solids-liquid separation after the EF matte atmospheric leaching is led to iron removal by pressure leaching, wherein iron is precipitated from the solution as hematite or goethite. The solids from the solids-liquid separation are waste, and the valuable metal-bearing solution is led to the FSF matte leaching circuit. In this invention, oxidizing conditions refer to the fact that in the leaching step, oxidizing gas, such as air, oxygen-enriched air or oxygen, is supplied to the leaching step.

[0025] First an atmospheric leaching step, in which the matte is leached in mixing reactors at a temperature of 80°C to 103°C in oxidizing conditions, is performed on the FSF matte. A nickel anolyte and the solution from a second atmospheric FSF matte leaching step are used as the leaching solution. After the first atmospheric leaching step, solids-liquid separation is per- formed and the formed filtrate cake is led to a second atmospheric leaching step. The purpose of the atmospheric leaching steps is to leach the metallic components and some of the sulphides from the matte. The leaching solution is a nickel anolyte from nickel electrolysis. The valuable metal-bearing solution formed in EF matte leaching is also led to the second FSF matte atmospheric leaching step, so it is a common leaching step for both mattes.

[0026] After the common leaching step of the mattes, solids-liquid separation is performed, from which the obtained solution is led to a first FSF matte leaching step and the solids to a first pressure leaching step, which is actually a nickel leaching step. The pressure of the first pressure leaching step is adjusted to the range of 15 to 18 bar and the temperature to 120 to 180°C, and oxygenous gas is supplied to the leaching step. After solids-liquid separation, the solution is led to an EF matte atmospheric leaching step and the solids to a second pressure leaching step that is a copper leaching step. In the copper pressure leaching step, all the remaining undissolved valuable metal components and especially copper sulphides are leached. The leaching residue formed in the solids-liquid separation contains possible PGM (Platina Group Metals) metals and gold of the concentrate, and the leaching residue can be processed further to recover these metals. Iron may be separated before the recovery of PGM metals. The solution formed in the copper pressure leaching step is recirculated to the nickel pressure leaching step. [0027] The solution from the first FSF matte atmospheric leaching step after the solids-liquid separation is a product solution (PLS) of the leaching steps of both the EF matte and FSF matte, and it is led to iron removal and then on to solids-liquid separation. After cooling the product solution poor in iron but containing valuable metals, the solution is purified, during which copper and cobalt are separated from the product solution by solvent extraction and recovered electrolytically (by electrowinning). Nickel is also recovered electrolytically from the solution that is now poor in copper and cobalt.

[0028] In the solution purification done by solvent extraction, copper is first extracted from the product solution by using hydroxy oxime, for example, as the organic extraction agent. The organic phase rich in copper is preferably washed in acidic sulphate solution before stripping. A copper electrolysis anolyte is used as the aqueous solution of copper stripping, and the anolyte is after stripping led to the electrolytic recovery of copper to produce pure cathode copper.

[0029] The product solution poor in copper is led to cobalt extraction, which is preferably done using a dialkyl phosphonic acid-containing extraction reagent, for example. Possible impurities extracted with the cobalt are washed from the extraction solution. The pH of the product solution is made suitable for cobalt extraction by neutralizing the solution at a suitable stage. A cobalt electrolysis anolyte, which is a sulphuric acid-containing solution with cobalt sulphate, is used as the aqueous solution in cobalt stripping. The anolyte enriched in cobalt is led to electrolytic recovery of cobalt to produce pure cobalt.

[0030] The product solution poor in copper and cobalt is led to electrolytic recovery of nickel. A nickel electrolysis anolyte, which is a sulphuric acid-containing solution poor in nickel, is used as the leaching solution of both FSF matte and EF matte.

[0031] Figure 2 shows a second way according to the invention to process flash smelting furnace matte and electric furnace matte, wherein the leaching of both mattes takes place in common leaching steps. Both mattes are ground in the same circuit and a common feed material is produced that is called mixed matte. The mixed matte is first led to the atmospheric leaching step done using a nickel anolyte for leaching the metallic components, such as nickel, copper, iron, and cobalt from the matte, whereby it is possible to avoid the formation of hydrogen in the autoclave. Leaching is done in oxidizing con- ditions. Some of the sulphides in the matte also leach already in this step. The conditions of atmospheric leaching are the same as described in connection with Figure 1 .

[0032] After atmospheric leaching, solids-liquid separation is per- formed, and the undissolved solids are led to pressure leaching that also uses a nickel anolyte as the leaching solution. Pressure leaching is done in oxidizing conditions in an autoclave, whereby nickel and other metals and sulphur leach almost completely at a temperature of 150 to 250 degrees and with the pressure in the range of 16 to 40 bar. After pressure leaching, solids-liquid separa- tion is performed. The leaching residue contains mainly precipitated gypsum and iron oxides as well as possible PGM metals that may be recovered from it. The solution from the pressure leaching is led back to the atmospheric leaching.

[0033] The product solution that comprises leached valuable metals (Ni, Cu, Co) and is obtained from the solids-liquid separation after atmospheric leaching is first subjected to gypsum precipitation by cooling the solution. After this, gypsum is removed by means of solids-liquid separation. The product solution is next led to extraction and electrolytic recover of copper that is performed in the same manner as described in connection with Figure 1 . For the acid balance of the process, the removal of iron from the product solution is preferably done only after copper extraction by neutralizing the solution with a lime compound.

[0034] After neutralization, the product solution is subjected to solids-liquid separation to remove iron compounds and the remaining gypsum, after which selenium may be separated from the product solution, if it is present therein. To remove selenium, it is possible to use sulphur dioxide, for instance, that is added to the solution in a mixing reactor.

[0035] After copper, iron and selenium have been removed, the product solution is led to the cobalt extraction and electrolytic recovery. The nickel remaining in the product solution is also recovered electrolytically and the nickel electrolysis anolyte is led to be used as the leaching solution for mixed matte. The recovery of cobalt and nickel takes place in the same manner as described in connection with Figure 1 . In Figures 1 and 2, the copper and cobalt recovery takes place electrolytically but, according to the invention, the recovery of these metals after the extraction may also take place by crystallization or chemical precipitation. [0036] In Figures 1 and 2, the recovery of valuable metals from matte is done using a sulphate-based leaching solution. Figure 3 shows a third way of processing in accordance with the invention in common leaching step ground mixed matte formed of flash smelting furnace matte and electric fur- nace matte. According to this alternative, the atmospheric leaching step is done using a chloride-based solution in the presence of oxygen, and the chloride solution contains a significant amount of alkali metal chloride, such as sodium chloride. Valuable metals nickel, copper and cobalt are leached according to the method. Bivalent copper leached from mixed matte participates in the leaching reactions and is reduced to univalent copper. Part of the iron oxidizes and precipitates as iron oxide. After leaching, solids-liquid separation is done, after which the solids contain not only precipitated iron, but also PGM metals and sulphur. Iron may be leached from the precipitate, and similarly sulphur may be removed in some known manner, such as by vaporization, whereby a PGM concentrate (not shown in detail in the figure) is obtained.

[0037] Part of the iron remains in the product solution and is precipitated from the solution by using a sodium or lime compound, for instance, prior to the solution purification of the valuable metal-bearing product solution. The solids-liquid separation produces an iron-bearing precipitation waste cake and a valuable metal-bearing product solution that is led to gypsum removal performed by cooling, for instance. After the solids-liquid separation, the copper-, nickel-, and cobalt-rich chloride-based product solution formed in the leaching step is led to solvent extraction steps to separate metals from the solution. Copper extraction is first performed on the product solution by using hydroxy oxime, for instance, as the extraction reagent, and the solution is neutralized with sodium hydroxide, for instance, before or during the extraction. The significance of neutralization is higher in a chloride circuit than in a sulphate circuit, because the ability of a chloride solution to buffer pH alteration is low. After extraction, the copper-rich organic solution is led to washing steps to remove impurities and chlorides. A sulphuric acid-bearing sulphate solution is used as the aqueous solution in stripping. The copper-rich sulphate solution is led to the electrolytic recovery of copper, and the anolyte of this electrolysis is used as the aqueous solution for stripping of copper. Next, cobalt is separated from the product solution by means of extraction, washing of extraction solution, stripping and electrolysis in the same manner as described in connection with Figure 1 . Finally, nickel is separated from the product solution with extraction by using as the extraction reagent for instance a branched C-10 tertiary car- boxylic acid, such as Versatic 10. The product solution is neutralized either before or during extraction to adjust the pH value to a preferred range for nickel extraction. The nickel-rich extraction solution is led to washing to remove impurities and chlorides. A sulphate-based anolyte obtained from nickel electrolysis is used as the aqueous solution of the stripping.

[0038] After nickel separation, the chloride-based solution poor in metal is regenerated. The solution contains small amounts of magnesium that are removed from the solution by precipitation, for instance, with sodium hy- droxide. The solids-liquid separation produces a disposable magnesium precipitate and solution from which small amounts of impurities may be removed with ion exchange (IX), for example. After this, the solution is evaporated to concentrate sodium chloride, and then the solution is fed into chlor-alkali electrolysis (CAE) that produces sodium hydroxide usable in different steps and hydrogen and chlorine that may be burned into hydrochloric acid that is led to a mixed matte leaching step.

[0039] Figure 4 describes yet another embodiment of the invention, in which ground mixed matte formed of FSF matte and EF matte is led to atmospheric chloride-based and oxidizing leaching. In this alternative, the solu- tion does not contain significant amounts of alkali metal chloride, but instead calcium chloride. However, the leaching reactions take place as described in connection with Figure 3, that is, by means of an effect that oxidizes bivalent copper sulphides. During leaching, iron oxidizes and precipitates as hematite or goethite. A solids-liquid separation produces iron precipitate that also con- tains PGM metals and can be processed as described in connection with Figure 3. The valuable metal-containing product solution obtained from leaching is led to solution purification done by solvent extraction, i.e. liquid-liquid extraction and performed in the same manner as described in connection with Figure 3, but in this case calcium hydroxide, for example, is used instead of sodium hy- droxide in the neutralization before and during extractions.

[0040] After the extraction steps, magnesium may be removed from the chloride solution poor in valuable metals, and the slurry is led to solids- liquid separation that produces disposable magnesium precipitate, and the solution is led back to mixed matte leaching. Most of the chloride solution poor in valuable metals, which is mainly a calcium chloride solution, is led either back to leaching or regenerated by means of sulphuric acid into hydrochloric acid, in which case the solids-liquid separation produces a gypsum precipitate and hydrochloric acid solution. Hydrochloric acid may also be used to prepare calcium chloride.

[0041] It is clear that to facilitate the operation of different process alternatives, the process needs to be controlled by an advanced process control system. It will be apparent to a person skilled in the art that as technology advances, the basic idea of the invention may be implemented in many different ways. The invention and its embodiments are thus not restricted to the exemplary modes of operation described above but may vary within the scope of the claims.

Claims

1. A method for processing sulphidic bulk concentrate by processing the concentrate in a smelting furnace into matte and slag phases, and processing the slag in a slag cleaning furnace, characterized by pro- cessing the smelting furnace matte and slag cleaning furnace matte hydromet- allurgically in leaching, after which the recovery of the valuable metals (Ni, Cu, Co) leached in the leaching step takes place in a common step.

2. The method as claimed in claim 1, characterized by processing the smelting furnace matte and slag cleaning furnace matte in sepa- rate leaching steps, after which the solutions are combined and led to solution purification by solvent extraction and to the recovery of valuable metals.

3. The method as claimed in claim 1 or 2, characterized by processing the smelting furnace matte and slag cleaning furnace matte in a sulphate-based atmospheric leaching and pressure leaching.

4. The method as claimed in claim 1, 2, or 3, characterized by separating the leached valuable metals Cu and Co by solvent extraction from the product solution and recovering them electrolytically.

5. The method as claimed in any one of claims 1 to 4, characterized by recovering the valuable metal Ni electrolytically from the product solution that is poor in copper and cobalt.

6. The method as claimed in claim 1, characterized by processing the smelting furnace matte and slag cleaning furnace matte in common leaching steps.

7. The method as claimed in claim 6, characterized by pro- cessing the smelting furnace matte and slag cleaning furnace matte in a common sulphate-based atmospheric and pressure leaching.

8. The method as claimed in claim 6 or 7, characterized by separating the leached valuable metals Cu and Co by solvent extraction from the product solution and recovering them electrolytically.

9. The method as claimed in any one of claims 7 and 8, characterized by recovering the valuable metal Ni electrolytically from the product solution that is poor in copper and cobalt.

10. The method as claimed in claim 6, characterized by processing the smelting furnace matte and slag cleaning furnace matte in a com- mon chloride leaching step.

11. The method as claimed in claim 10, characterized in that the chloride solution contains alkali metal chloride.

12. The method as claimed in claim 10 or 11, characterized in that the chloride solution contains calcium chloride.

13. The method as claimed in any one of claims 10 to 12, characterized by leading the valuable metal-bearing product solution formed in chloride leaching to solution purification, in which copper, cobalt, and nickel are extracted from the product solution in consecutive extraction steps, and the aqueous solution of the stripping of each metal is sulphate-based.

14. The method as claimed in claim 13, c h a r a c t e r i z e d by recovering copper, cobalt, and nickel from sulphate solutions electrolytically, and using the anolyte of each electrolysis as the aqueous solution in the stripping of the corresponding extraction.

15. The method as claimed in any one of claims 10 to 14, char- acterized by leading the chloride solution poor in metals after valuable metals separation and after at least a partial regeneration back to the leaching of the smelting furnace matte and slag cleaning furnace matte.

16. The method of any one of claims 1 to 15, characterized in that the sulphidic bulk concentrate contains PGM metals that remain in the leaching solution.