JP2009097076A - Method for recovering valuable material from metal sulfide containing noble metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for effectively recovering valuable components from nickel-copper mats containing noble metals by utilizing existing copper refining facilities without using special facilities. <P>SOLUTION: In the method for recovering the valuable materials from metal sulfides containing the noble metal, nickel is selectively leached and separated in a range where the redox potential of a liquid is not higher than the value where the leaching of copper proceeds, the noble metals are condensed together with the copper sulfide in the leaching residual, while oxidizing the metal sulfide mats containing the sulfides of nickel and copper containing the noble metal as main components by air under atmosphere using sulfuric acid of two times to three times of the equivalent quantity to the nickel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for easily recovering Ni, Cu and noble metals as main components from a noble metal-containing nickel-copper mat (Ni-Cu mat) in a copper smelting process. The present invention relates to a valuable material recovery method in which nickel is selectively leached under normal pressure as a pretreatment when a nickel-copper mat containing metal is processed in a copper smelting process, and copper and noble metals are concentrated in a high yield.

As one of the main platinum group element resources, sulfide ore associated with nickel is known.
This type of ore is separated from the gangue as copper or nickel sulfide ore, and after separating the noble metal such as gold and platinum group together with the base metal, the noble metal is concentrated and separated. In this processing step, various intermediate products containing noble metals are generated. Of particular importance are metal sulfide mats based on nickel sulfide and copper sulfide. When processing ores with high precious metal grades, the desulfurization conditions of the mat are adjusted to separate the metal component having a high precious metal concentration, and then the nickel-copper mat containing a small amount of precious metal is separated. Since this mat has high value as a nickel raw material, it is sent to a nickel smelting process, and leached nickel and refractory copper are leached, and the precious metal is concentrated and recovered in the leaching residue.

In the nickel smelting process, for the leaching of nickel and copper from the nickel copper mat, as a treatment system that can obtain a sufficient leaching rate and reaction rate,
There are two methods: (1) using a chloride-based leachate and using chlorine gas generated by nickel electrolysis for leaching; (2) using a sulfuric acid-based leachate and leaching at high temperature and oxygen pressure in an autoclave. Used mainly.
For example, regarding the former chloride leaching, Patent Document 1 describes a method in which nickel and copper sulfide mats containing cobalt are oxidized with chlorine gas and oxygen and leached at 110 ° C. under atmospheric pressure. Yes. Also, in Patent Document 2, a slurry leached with chlorine under atmospheric pressure is treated at 110 ° C. or higher and pH 4 or lower in an autoclave to fix copper as a sulfide and recover a nickel-enriched liquid. .
On the other hand, although the sulfuric acid pressure leaching is inferior to the chloride solution as the system, the nickel is selectively leached by leaching in stages by selecting the conditions, and then leaching is performed for copper. The leachate as the main component can be collected separately. For example, in Patent Document 3, a nickel-copper sulfide mat is subjected to an acidic sulfate aqueous solution at a temperature of about 100 ° C. or higher under an oxygen pressure of 0.7 kg / cm ² (10 psig, 0.07 MPa) or higher in the first leaching process. Copper is electrolyzed from the sulfuric acid solution obtained by leaching most of nickel and leaching a small amount of nickel and copper remaining at a pressure of 1.05 kg / cm ² (15 psig, 0.105 MPa) at a temperature of about 100 ° C or higher in the second leaching process. A treatment method that uses the collected liquid for the first leaching process is introduced.
In the above treatment, the noble metal contained in the nickel-copper mat is concentrated to the leaching residue together with unreacted sulfur.
In these treatments, it is inevitable that a small amount of PGM is dissolved in the liquid together with copper, particularly under conditions of strong immersion power in which copper leaching proceeds. For this reason, in nickel-copper mat processing including noble metals, it is necessary to devise measures such as collecting the eluted PGM by adding the raw material before leaching to the leaching solution.
JP 7-91599 “Separation of valuable metals” Sumitomo Metal Mining Patent No. 2552136 “Method of separating nickel from copper in autoclave” and US Patent No. 4,828,809 “Separation of nickel from copper inautoclave” Falconbridge JP-B 55-1973 "Processing of copper-nickel sulfide mat" Sherritt-Gordon CFBrugman, DGKerfoot; Proc.Nickel Metallurgy 1986, Vol.1, p.512-531 “Treatment of nickel-copper matte at Western Platinum by Sherritt acidleach process”

On the other hand, in order to treat such precious metal-containing mats in a copper smelting process for metallic copper without using nickel as the main product, it is processed in a converter together with a mat of copper smelting process made of copper sulfide of similar shape. Is simple. In the converter, sulfur is removed as SOx among the components in the noble metal-containing mat. Copper and noble metal are distributed to crude copper, and copper can be separated and recovered as electrolytic copper and noble metal as a porridge in a subsequent electrolysis step. In addition, although the residence time until noble metal collection | recovery increases, nickel copper mat | matte can also be thrown into a flash smelting furnace of a copper smelting process with a sulfide ore, and can be processed.

However, there is a problem in the separation and recovery of nickel in the converter process. A considerable amount of nickel is oxidized during the can-making stage and moves to slag together with iron, so the nickel recovery rate decreases. On the other hand, nickel taken into the crude copper is dissolved and accumulated in the electrolytic solution by electrolytic purification. Nickel accumulated in the electrolytic solution can be finally recovered as nickel sulfate by purifying and concentrating the electrolytic solution. However, in this case, nickel accumulates in the electrolytic solution and the concentration increases, which causes problems such as a reduction in the quality of electrolytic copper and an increase in the load of removing nickel from the electrolytic solution. These problems are also the same when they are put into a flash furnace. Due to the above-mentioned problems, the copper smelting process alone can process only a limited amount of the above-mentioned noble metal-containing nickel-copper mat, and is not commercially viable in terms of wasting expensive nickel. It was an issue.

Since nickel sulfide is more reactive than copper sulfide or the like, a portion of nickel can be leached using sulfuric acid at normal pressure without using an autoclave.
For example, in Non-Patent Document 1, as a pretreatment of sulfuric acid pressure leaching, the result of a 42% Ni leaching rate was obtained by atmospheric pressure leaching using sulfuric acid having a concentration of 50 g / L in the first stage. However, the recovery rate of nickel is insufficient, and in order to completely leach out the nickel remaining in the residue, it is necessary to dissolve it together with copper by using pressure leaching in the subsequent stage. This is because Ni3S2, which is the main form of nickel in the nickel-copper mat, is changed to NiS, which is inferior in reactivity, and a part of S forms a simple sulfur to cover the surface of the matte particle and the reaction proceeds to the center. It is thought that the cause is to inhibit.
(Non-Patent Document 1)

The present invention provides a simple treatment of precious metal-containing nickel-copper mats by using the equipment of the copper smelting process alone, without using nickel smelting equipment such as an autoclave, an electrolytic cell using chlorine gas, and a leaching device. A processing method for recovering all valuable materials with high yield, specifically, without using an autoclave, nickel is selectively leached and separated from the mat by sulfuric acid leaching under air oxidation conditions under normal pressure. At the same time, the present inventors propose an appropriate technique for controlling the oxidation-reduction potential at the time of leaching to prevent leaching loss of the precious metal and condense the total amount of the precious metal into a residue and then processing it in the copper smelting process.

That is, the present invention
(1) A metal sulfide mat mainly composed of nickel and copper sulfides containing precious metals is oxidized in air using atmospheric acid at atmospheric pressure using sulfuric acid of 2 to 3 equivalents of nickel. A method for recovering valuable materials from a noble metal-containing metal sulfide in which nickel is selectively leached and separated in a range where the oxidation-reduction potential of the copper is not more than a value at which copper leaching proceeds, and the noble metal is concentrated together with the copper sulfide in the leaching residue.
(2) Valuation from the noble metal-containing metal sulfide obtained in (1) above, wherein the leaching residue obtained in the copper smelting process converter and / or flash smelting furnace is transferred to crude copper and recovered in the copper electrolysis process. Collection method.
(3) In any of the above (1) or (2), the leaching from the mat is performed in a range where the oxidation-reduction potential of the liquid is +300 mV (Ag-AgCl standard electrode standard) or less. A method for recovering valuable materials from metal sulfides.
(4) A method for recovering valuable materials from a noble metal-containing metal sulfide, wherein the leaching from the mat is performed at 60 ° C. or higher, preferably 80 ° C. or higher in any one of (1) to (3).
(5) In any one of the above (1) to (4), a noble metal-containing metal that is leached by selecting the original solution composition and the pulp concentration so that the nickel concentration of the leached mat leachate is in the range of 45 g / L or less. A method for recovering valuable materials from sulfides.
It is.

According to the present invention, only a sulfuric acid-based liquid regularly used in a copper smelting process without using a chloride-based nickel leaching-electrolytic extraction process with harmful chlorine generation and an expensive autoclave equipment. By handling the above, each valuable component can be separated and recovered with high yield from a nickel-copper mat containing a noble metal such as PGM.

In the present invention, an excess amount of sulfuric acid is used to efficiently leach nickel from the nickel-copper mat with sulfuric acid at atmospheric pressure. The amount and concentration of sulfuric acid are adjusted according to the composition of the mat to be treated and the pulp concentration during leaching. As the free acid concentration decreases, the leaching rate decreases. Also, when the sulfuric acid is in a small excess, after leaching progresses and the nickel quality in the residue decreases, copper and some precious metals begin to melt before the leaching of nickel is completed. Moreover, when the nickel concentration of a liquid becomes high, there exists a tendency for the nickel dissolution from a residue to be suppressed. For this reason, the raw material pulp density | concentration at the time of leaching receives restrictions. If the mat has a standard composition (Ni grade of about 40%), the pulp concentration is in the range of 100 to 200 g / L, preferably about 100 g / L. If the pulp concentration is further reduced, a leachate having a low nickel concentration is treated in a large amount when nickel is recovered in a subsequent step, which is not preferable.
When the pulp concentration is 100 g / L, about 70 g / L of sulfuric acid is required as an equivalent to nickel to dissolve nickel (and components that are preferentially leached with nickel such as iron and cobalt). In order to leach nickel in the raw material to a leaching rate of 90% or more, it is necessary to make sulfuric acid act twice or more. With this pulp concentration, if the sulfuric acid concentration is 200 g / L or more (about 3 times equivalent), favorable results can be obtained for both the reaction rate and the leaching rate.
On the other hand, when recovering nickel from the leachate, it is not preferable that a large excess of acid is contained.
Nickel cannot be electrolyzed at low pH, and separation methods such as solvent extraction and ion exchange cannot be used effectively unless the pH is higher than neutral. An extremely high sulfuric acid concentration during mat leaching increases the amount of alkali consumed when neutralization is performed in a subsequent step. Therefore, even if the sulfuric acid concentration at the time of leaching is extremely increased from the above-mentioned 2-fold equivalent, the cost of the whole treatment is increased, so it is preferable to keep it at most 3-fold equivalent. However, there is no restriction on the upper limit of the sulfuric acid concentration when the nickel sulfate crystal is recovered by concentrating and freezing the nickel sulfate solution as in the case of recovering nickel sulfate from the copper electrolyte in the copper smelting process.

The leaching rate is faster as the temperature is higher. Since the reaction proceeds only partially at room temperature, in order to ensure a practical leaching rate, the temperature is at least 60 ° C. or higher and the boiling point is 100 ° C. or lower, preferably 80 ° C. or higher.

When leaching using an excessive amount of sulfuric acid, as described above, nickel and readily soluble components such as iron and cobalt are preferentially dissolved, and elution of copper starts when the nickel quality in the residue is lowered. If enough time is taken, copper will also leach out under atmospheric pressure, but at this time the oxidation-reduction potential of the liquid will rise. In the state where excess free acid coexists, the ORP of the leachate reaches 300mV (Ag-AgCl electrode standard) when a small amount (0.1g / L or more) of copper elutes in the solution. As copper leaching proceeds further, palladium, rhodium and ruthenium out of the noble metals are dissolved in the liquid.
For this reason, if the leaching of nickel is almost finished by controlling the oxidation-reduction potential at the time of leaching and leaching is finished at a lower potential than the melting of copper begins, loss of precious metal elution into the liquid is prevented, and The noble metal can be concentrated while completely fixed to the residue. In addition, it is possible to prevent a large amount of copper from being mixed into the nickel leaching solution, which becomes a burden in the cleaning process in recovering nickel from the solution.

The leaching rate is also affected by the nickel concentration during leaching. As described above, when the nickel concentration of the liquid is increased, nickel sulfide leaching at normal pressure tends to be suppressed, so that the upper limit of the pulp concentration is restricted. Although affected by other conditions, the leaching peaked out when the Ni concentration exceeded 45g / L. For this reason, for example, even if sulfuric acid is added to the leaching solution containing nickel and the raw material mat is leached again, the leaching rate decreases. On the other hand, the nickel in the residue can be dissolved more efficiently by replacing the leaching solution even after the leaching residue once nickel leaching has stopped, and adding new sulfuric acid not containing nickel and repeating the leaching. However, in this case, elution of copper or the like starts early, and selective leaching separation is difficult.
For these reasons, when leaching nickel copper matte, leaching is performed within a range where the nickel concentration of the leachate does not exceed 45 g / L.

Thus, the liquid in which nickel is selectively leached contains iron and cobalt contained in the raw material, but copper remains at a low concentration. This leachate is neutralized and then separated from impurities by a known method to recover nickel.
On the other hand, the leaching residue mainly consists of copper sulfide and elemental sulfur, and the nickel quality is sufficiently lowered, so if it is put into a converter or flash smelting furnace in the copper smelting process, copper remaining in the residue only with existing equipment and Precious metals can be recovered with good yield.
As described above, according to the present invention, all valuable materials can be removed from nickel-copper mats by utilizing sulfuric acid-based atmospheric leaching and existing copper smelting equipment without using autoclaves or chlorine-based electrowinning equipment. Can be separated and recovered. A processing flow of the method of the present invention is shown in FIG.

(Example 1) When leached under ORP management under standard conditions
Table 1 shows the composition of precious metal-containing nickel-copper mat (crushed powder with an average particle size of 18 microns, containing 8.7% water) added to sulfuric acid with a concentration of 100-200 g / L to make 1 L of slurry with a pulp concentration of 100 g / L. .
Leaching was performed by blowing air at a speed of 2 L / min in a standard state while stirring vigorously at a temperature of 80 ° C. Hydrogen sulfide was generated at the start of leaching, and the oxidation-reduction potential (ORP) was extremely low but gradually increased. The reaction was completed before and after ORP reached 300 mV (Ag-AgCl standard electrode reference, hereinafter the same), and the slurry was filtered. The results of analyzing the leachate are shown in No. 1 to 13 of Table 2. In either case, copper was not found in the leachate, or it remained at a low concentration of about 1 g / L at most. Noble metals were eluted at both Au and PGM concentrations of less than 0.01 mg / L.
Fig. 2 shows an example of the temporal change in the leaching ORP and each component leaching rate (No. 3 in Table 2). When the leaching time exceeded 15h and Cu began to dissolve in the solution, the ORP reached 300mV. In order to keep the Cu leaching rate in the solution below 1% in this reaction system, it is necessary to stop the reaction at the stage where the ORP is 300 mV or less as shown in No. 5 in Table 2 at the same acid concentration.
As shown in Table 2, when the sulfuric acid concentration used is 100 g / L (sulfuric acid / Ni molar ratio in raw material = 1.4), even when ORP rises to 300 mV or higher, the Ni leaching rate is still low at the 70% level and the acid concentration is high. The time to increase the ORP (that is, the reaction rate) became faster and the Ni leaching rate increased. At sulfuric acid concentration 150-200g / L (sulfuric acid / Ni molar ratio in raw material = 2.1-2.9), Ni leaching rate reached 95% or more as shown in No. 6-13 in Table 2.
Thus, in order to stop the leaching before the leaching of Cu and increase the Ni leaching rate to 95% or more, leaching is carried out in an excess of sulfuric acid using 2.1 to 2.9 equivalents of sulfuric acid with respect to nickel dissolved from the raw material. There is a need.

(Comparative Example 1) ... When increasing pulp concentration and changing sulfuric acid / nickel molar ratio
The leaching was performed in the same manner as in Example 1 with the sulfuric acid concentration increased, the pulp concentration during leaching was increased, and the sulfuric acid / nickel molar ratio was small. In order to prevent elution of Cu, leaching was finished before ORP reached 300mV. The results are shown in No. 14-16 of Table 2 above. Even when the sulfuric acid concentration was high, when the molar ratio of sulfuric acid to nickel was less than 2, the Ni leaching rate when reaching the copper elution potential remained below 80% as shown in Table 3. It can be seen that the nickel concentration after leaching is 47 to 59 g / L, and increasing the pulp concentration of the mat to increase the nickel concentration further restricts the leaching rate.

(Comparative Example 2) ... Leaching continues for a long time, ORP rises as Cu leaching progresses, and PGM elution starts
Leaching was carried out for a long time over 60-78 h under the same method and conditions as in Example 1, and leaching was carried out while maintaining a state where ORP continued to rise. The results are shown in No. 17-19 of Table 2.
In addition, Fig. 3 shows the time change of ORP and leaching rate during leaching. All ORPs exceeded 300 mV and reached a maximum of 400 mV. If enough time is taken, as shown in No. 17 of Table 2, even if the initial sulfuric acid concentration is as low as 100 g / L, the Ni leaching rate continues to increase more than the result of Example 1, but as the ORP increases, a large amount of Cu increases. Dissolve in the liquid. Further, in these long-term leaching conditions, Pd, Rh, and Ru were leached out of the noble metals in the liquid.
In this way, it is possible to increase the Ni leaching rate by continuing leaching for a long time even under conditions with a small excess of sulfuric acid, but at this time Cu begins to leach and, as the Cu leaching progresses, it is relatively reactive among precious metals. High Pd, Rh and Ru were found to dissolve simultaneously. Therefore, in order to prevent the dissolution of precious metals, Cu leaching progresses in the oxidizing condition of P350mV-420mV in the range of sulfuric acid concentration 50-200g / L where nitric acid leaching proceeds (sulfuric acid / Ni molar ratio in raw material = 2.1-2.9). It can be seen that the reaction must be stopped before reaching the ORP of 300 mV in order to prevent Cu elution before reaching the above range of sulfuric acid concentration.

(Example 2):
Effect of Temperature Table 3 shows the results of comparing the leaching rates at temperatures of 25 ° C., 60 ° C., and 80 ° C. in the same manner as in Example 1. The higher the temperature, the faster the leaching reaction. Even at room temperature, under conditions of excess sulfuric acid, nickel dissolution occurs initially with hydrogen sulfide generation, but the reaction remains partially. At 60 ℃, Ni leaching proceeds and it takes time until ORP rises. In all the examples shown in the table, ORP was lower than the copper leaching start potential, and PGM was not dissolved at all.

(Comparative Example 3) ...
When leaching by repeatedly using a solution containing nickel, sulfuric acid is added to the leached nickel solution with a sulfuric acid concentration of 200 g / L and a pulp concentration of 100 g / L to return the acid concentration to 200 g / L. The process of obtaining a leachate having a high nickel concentration by repeated use was performed. The results are shown in Table 4. As a result of repeating the leaching three times, PGM was not dissolved at all when ORP was controlled. However, although the concentration of nickel increased slightly when repeated leaching, the nickel leaching rate from the raw material decreased rapidly as shown in Table 4 after the second time. Thus, even if the acid concentration at the time of leaching was used at a predetermined excess concentration relative to the raw material, leaching was suppressed when the nickel concentration of the liquid was increased. When leaching up to a concentration of about 40 g / L in the first stage, the Ni concentration exceeds 45 g / L in the second stage, but it is understood that leaching is rapidly suppressed under this condition.

  As described above, to separate nickel from the noble metal-containing nickel copper mat, sulfuric acid is leached by air oxidation at 60 ° C or higher, preferably 80 ° C or higher, using sulfuric acid 2 to 3 times the nickel in the raw material mat. Nickel can be selectively leached by a reaction under atmospheric pressure without using an expensive autoclave. If the nickel concentration of the liquid is increased, the nickel leaching rate is reduced, so the pulp concentration is limited, and it is preferable to treat the nickel concentration in a range not exceeding 45 g / L. In addition, by managing the ORP at the time of leaching, all the copper and noble metals in the raw material mat can be concentrated and recovered in the leaching residue. This residue is mainly composed of copper sulfide and sulfur, and valuable materials contained therein can be efficiently recovered in existing facilities and processes by putting them in a converter for a copper smelting process.

It is an example of the valuables collection | recovery flow in this invention. 2 shows time changes in oxidation-reduction potential and leaching rate of each component in Example 1. FIG. 4 shows time changes in oxidation-reduction potential and each component leaching rate in Comparative Example 1. FIG.

Claims (5)

Redox reduction of liquid while oxidizing metal sulfide mats mainly composed of nickel and copper sulfides containing noble metals using sulfuric acid of 2 to 3 equivalents of nickel at atmospheric pressure under atmospheric pressure A method for recovering valuable materials from a noble metal-containing metal sulfide, wherein nickel is selectively leached and separated in a range where the potential is not more than a value at which copper leaching proceeds, and the noble metal is concentrated together with the copper sulfide to the leaching residue. From the noble metal-containing metal sulfide, characterized in that the leaching residue obtained in claim 1 is put into a converter and / or a flash smelting furnace of a copper smelting process, and the noble metal is transferred to crude copper and recovered in a copper electrolysis process. Valuable resources recovery method. 3. From a noble metal-containing metal sulfide according to claim 1, wherein leaching from the mat is performed in a range where the oxidation-reduction potential of the liquid is +300 mV (Ag-AgCl standard electrode standard) or less. Valuable resources recovery method. 4. The method for recovering a valuable material from a noble metal-containing metal sulfide according to claim 1, wherein leaching from the mat is performed at 60 ° C. or higher, preferably 80 ° C. or higher. 5. A precious metal-containing composition according to claim 1, wherein the leaching of the matte leachate after leaching is carried out by selecting the original solution composition and the pulp concentration so that the nickel concentration is in a range of 45 g / L or less. A method for recovering valuable materials from metal sulfides.