JP2011105969A - Method for recovering silver from sulfide containing copper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily leaching a silver from a sulfide containing copper consisting essentially of chalcopyrite, at a low cost without needing a special consideration with respect to the safety environment. <P>SOLUTION: Slurry comprising sulfide containing copper and sulfuric acid containing iron by 30-50 g/L, copper by 10 g/L and preptiser by 0.2-1.0 g/L, is charged into a pressurizing vessel, and the slurry is heated to 120-180°C. Then, the copper and the silver are leached by adjusting an oxidation-reduction potential while adjusting the amount of oxygen and/or air supplied in the gaseous phase part so that the pressure of the gaseous phase part in this pressurizing vessel is made higher by 0.5-2.0 MPa than that in the balanced state, and the silver is precipitated as silver-iron alum, and the copper-leached residue containing this silver-iron alum, is treated with sodium thiosulfate solution and the silver is leached, and the silver in the leached finish solution is adsorbed in activated carbon. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for recovering silver from a copper-containing sulfide, and more specifically, when recovering silver from a copper-containing sulfide mainly composed of chalcopyrite, without using sodium cyanide, which is a toxic substance, The present invention relates to a method for recovering silver from a copper-containing sulfide that does not require special consideration in terms of low cost and safe environment.

Generally, chalcopyrite (Cal Kopai Light: CuFeS _2), chalcocite (Cal co Site: _Cu 2 S), bornite _(Bonaito: Cu 5 _FeS 4), and covellite (Koberaito: CuS) a copper sulfide mineral, such as The copper ore containing is usually pulverized, and is processed into copper concentrate, which is used as a raw material for processing. This copper concentrate contains precious metals such as silver, and is the subject of recovery along with copper.

In order to recover silver from such copper concentrate, the copper concentrate is charged into a smelting furnace, melted at a high temperature to separate impurity elements as slag to obtain a mat, and the obtained mat is further converted into a converter. It is common to obtain crude copper by blowing and electrolytically purify the obtained crude copper as an anode to concentrate silver in an electrolytic slime, which is processed and recovered in a silver separation step.
In this dry smelting process, sulfur contained in the copper concentrate becomes sulfurous acid gas, so this must be recovered as sulfuric acid at the sulfuric acid production facility, but since sulfuric acid is a liquid, Large tank facilities are also required, and there is a problem that a large site is required. In addition, since high-temperature melts are handled, advanced considerations are required regarding the environment and work. Therefore, a wet copper smelting method that can alleviate these problems has been studied.

  The wet copper refining methods are roughly classified into those using chloride ions as the leaching solution and those leaching using an aqueous sulfuric acid solution containing sulfate and an oxidizing agent. Copper is extracted and separated by an extraction method, back-extracted to obtain a copper solution, and this is used as an electrolytic solution for electrolytically collecting copper. For this reason, unlike dry smelting, sulfur in the concentrate is not used as sulfurous acid gas, and high temperature melt is not handled.

  Here, the method using a leaching solution containing chloride ions has an advantage that a relatively high leaching rate can be obtained, but on the other hand, in order to prevent equipment corrosion due to chlorine, a large cost is required for equipment investment and equipment maintenance. There is a problem that it takes. Further, in this method, since the leached silver is dissolved in the leachate as chloride complex ions, the silver is precipitated and collected as silver chloride by adjusting the chlorine concentration of the leachate. Therefore, it is difficult to balance the water in the system, increasing the burden of wastewater treatment.

  On the other hand, the method using a sulfuric acid aqueous solution containing a sulfate and an oxidizing agent has the advantage that the leaching rate is relatively low, but the cost for capital investment and maintenance is low. . Also, silver combines with iron in the leachate to form silver iron alum, precipitates and is distributed to the copper leach residue. In order to recover silver from the copper leaching residue, the copper leaching residue is generally charged in a smelting furnace, concentrated in an anode slime as described above, and processed and recovered in a silver separation step. However, this method takes time to recover the silver and increases the in-process interest rate. Moreover, since a process becomes long, there exists a subject that a loss increases and a real recovery rate becomes low.

As another method for recovering silver from copper leaching residue containing silver iron alum, put the copper leaching residue in calcium hydroxide aqueous solution and heat it to near boiling to decompose silver iron alumite in the residue to remove silver. A method is known in which silver oxide is produced and the produced silver oxide is leached and recovered in a solution containing sodium cyanide (see Non-Patent Document 1).
In this method, all of the added calcium hydroxide must eventually be calcium sulfate, and the amount of generated starch increases. In addition, the cost increases due to the need for a large amount of medicine. In addition, since sodium cyanide, which is a toxic substance, is used, there are many problems in application to actual operation, such as special considerations for handling and treatment of waste liquid from both safety and environmental aspects.
In any case, in order to separate and recover silver from a copper-containing sulfide by a hydrometallurgical method, it is first important to leach silver from the copper-containing sulfide by a method that provides a high leaching rate at a low cost. .

Under these circumstances, as a method of leaching copper at a higher leaching rate than copper-containing sulfides, copper was leached from copper-containing sulfides using the oxidation-reduction reaction between ferrous sulfate and ferric sulfate in a sulfuric acid solution. A method has been proposed.
For example, a copper-containing sulfide pulverized to 150 μm or less is used as a raw material, and in an autoclave, the iron ion concentration is set to 10 to 40 g / L, the sulfuric acid concentration is set to 10 to 60 g / L, and trivalent iron ions and divalent iron ions are added. In the raw material, the oxygen partial pressure is set to 0.2 to 0.7 MPa and the temperature is set to 50 to 105 ° C. by using a leaching start solution in which the ratio of iron ions is 2 or more in the concentration ratio of [Fe ³⁺ / Fe ²⁺ ]. A method of leaching copper is proposed (see Patent Document 1).
However, this method has a low leaching temperature, so the leaching rate is slow. In particular, when the leaching temperature is less than 80 ° C., the leaching rate is extremely reduced even if the iron concentration in the leachate is sufficient, and a high leaching rate is obtained. However, there is a problem that it takes a long time.

Further, for example, in a pressurized container, copper ore is used as a raw material, and this is mixed with an aqueous solution containing iron ions or a sulfuric acid solution containing iron ions to form a slurry, which is 220 to 275 ° C., preferably 235 ° C. or higher. A method has been proposed in which copper is leached from copper ore in oxygen and / or air while maintaining the temperature (see Patent Document 2).
According to this method, the entire copper ore is strongly oxidized at a high temperature, so that a high leaching rate and a high leaching rate can be obtained.
However, in this method, since leaching is performed under a high temperature and high pressure exceeding 200 ° C., the equipment such as a pressure vessel and a pump to be used requires the use and structure of a material that can withstand pressure, temperature, and corrosion. There is a problem that a large amount of capital investment, a large amount of repair costs, and a lot of time and effort are required.
Also, in this temperature range, almost all sulfur contained in copper ore is oxidized to sulfate ions and distributed to the leachate. Therefore, excess sulfate ions in the leachate can be separated and removed from the system using gypsum and the like. There is a problem that it is necessary.

As another method, the temperature in the pressure vessel is set to 90 to 220 ° C., preferably 120 while coexisting 3 to 50 kg of coal with a specific composition per 1 ton of copper concentrate as a catalyst in the pressure vessel. A method is proposed in which oxygen gas is fed and leached so as to maintain the pressure of the gas phase portion in the container at a value corresponding to 0.1 to 3 MPa while maintaining in the range of ~ 180 ° C, more preferably in the range of 135 to 175 ° C. (See Patent Document 3).
In this method, copper is leached in a temperature range that is intermediate between the method described in Patent Document 1 and the leaching method described in Patent Document 2, and copper is produced more efficiently and efficiently than the method described in Patent Document 1. There are merits that it can be leached and the capital investment, repair cost and labor can be reduced as compared with the method described in Patent Document 2.

However, in the method described in Patent Document 3, when the copper sulfide mineral in the target copper-containing sulfide is a secondary sulfide mineral such as chalcopyrite, chalcocite, or copper indigo, these minerals and sulfuric acid are used. And oxygen reacts well, and copper can be leached with high efficiency, but the target is the most common, and when the abundance of chalcopyrite becomes high, the reaction efficiency becomes low, and only low copper leaching efficiency can be obtained, Therefore, there is a problem that the silver in the copper-containing sulfide is not sufficiently converted to silver iron alum.
As can be seen from the above description, when recovering silver from a copper-containing sulfide mainly composed of chalcopyrite, which is a large and existing ratio, without using sodium cyanide, which is a toxic substance, simple, low cost, A method for recovering silver from copper-containing sulfides that does not require special consideration in terms of the safety environment has not yet been proposed.

US Pat. No. 6,537,440 US Pat. No. 6,497,745 US Pat. No. 5,730,776

D. Dreisinger, P.M. Taggart, R.A. Banner, D.C. Copeland, D.C. Jennings, “The Hydromagnetic Treatment of Farallon Resources' Campo Morado Bulk Zn—Pb—Cu—Ag—Au Sulfur Concentrate”, Zinc and Lead 2005.

  In view of the above-mentioned problems of the prior art, the object of the present invention is to recover silver from copper-containing sulfides mainly composed of chalcopyrite, without using sodium cyanide, which is a toxic substance, in a simple, low-cost, safe environment. The object of the present invention is to provide a method for recovering silver from copper-containing sulfides that does not require special consideration.

As a result of various studies to solve the above-mentioned problems, the inventors of the present invention have developed a copper leaching residue in which silver is concentrated as silver iron alum at low cost if the copper-containing sulfide is pressure-leached under specific conditions. The present invention was completed by finding that it can be efficiently obtained, and that when an aqueous solution containing a specific compound is used, silver can be easily leached and separated from the silver iron alum and recovered.
That is, according to the first invention of the present invention, in the method for recovering silver from a copper-containing sulfide containing chalcopyrite as a main component, the following treatments (1) to (5) are sequentially performed. A method for recovering silver from copper-containing sulfides is provided.
(1) Mixing a sulfuric acid solution containing 30 to 50 g / L of iron, a peptizer composed of lignin sulfonic acid and / or a salt thereof at a rate of 0.2 to 1.0 g / L, and the copper-containing sulfide. (2) After the slurry is charged into the pressurized container, the pressure of the gas phase in the pressurized container is less than the equilibrium state while maintaining the temperature of the slurry at 120 to 180 ° C. A sufficient amount of oxygen and / or air to increase by 5 to 2.0 MPa is supplied to the gas phase part to adjust the oxidation-reduction potential of the slurry. (3) A leaching solution containing copper by solid-liquid separation (4) The copper leaching residue is mixed with a sodium thiosulfate solution (silver leaching solution) containing sodium thiosulfate at a rate of 5 to 20 g / L in terms of anhydride. After obtaining the slurry, solid-liquid separation is performed to obtain a silver leaching final solution and a silver leaching residue. (5) contacting the silver leachate and charcoal silver is adsorbed on the activated carbon, and recovering

  According to the second invention of the present invention, in the first invention, the slurry in (1) has a slurry concentration of 150 to 300 g / L. A recovery method is provided.

  According to a third invention of the present invention, in the first invention, the sulfuric acid solution in the above (1) contains 10 g / L or less of copper. A collection method is provided.

  According to a fourth invention of the present invention, from the copper-containing sulfide according to the first invention, the sulfuric acid solution in (1) contains 15 to 45 g / L of free sulfuric acid. A method for silver recovery is provided.

  According to a fifth aspect of the present invention, in the first aspect, the oxidation-reduction potential in (2) is 530 to 620 mV on the basis of a silver / silver chloride electrode. A method for recovering silver from a product is provided.

  According to a sixth invention of the present invention, in the first invention, the copper leaching residue slurry in the above (4) has a slurry concentration of 50 to 100 g / L. A method for recovering silver from is provided.

  According to a seventh aspect of the present invention, in the first aspect, the sodium thiosulfate solution in (4) is a sodium thiosulfate solution to which activated carbon is added at a rate of 5 to 20 g / L. A method for leaching silver from a copper-containing sulfide is provided.

  In the present invention, by taking the above-described configuration, the excess of iron leached together with copper is simply combined with a silver iron agate containing silver iron alum (hereinafter referred to as a silver-containing iron agate). In this case, silver-containing iron alum adheres and deposits on the surface of the sulfur particles that are formed during leaching and become droplets by the deflocculant. Cover with silver-containing iron alum. As a result, it is possible to prevent sulfur particles from unreacting or covering the surface of the copper-containing sulfide particles during the reaction, and silver can be leached at a higher leaching rate than the copper-containing sulfide. Further, by covering the surface of the sulfur particles with silver-containing iron alum, sulfur oxidation can be prevented and the sulfuric acid balance in the system can be easily controlled.

In addition, in the present invention, since silver in silver iron agate is leached with a sodium thiosulfate solution, an operation of heating a solution containing a strong alkali such as calcium hydroxide to near boiling is unnecessary, and is generated by the same operation. It is not necessary to use sodium cyanide, which is a poison, in order to dissolve silver oxide. As a result, there is no amount of generated starch due to the calcium hydroxide in waste water treatment, and no special consideration in terms of safety environment by using sodium cyanide is required.
Further, silver ions in a sodium thiosulfate solution are adsorbed on activated carbon, and the obtained activated carbon is burned, whereby metallic silver can be obtained simply, efficiently, and at low cost.

Furthermore, in the present invention, when leaching silver from a copper-containing sulfide and obtaining silver iron alum, leaching is performed using a leaching solution not containing chloride, and the slurry temperature during leaching is 120 to 180 ° C., There is no need to configure the apparatus with a special expensive material, and stainless steel such as SUS304 and SUS316 having general heat resistance and corrosion resistance can be used, so that the equipment cost can be kept low.
Therefore, the method of the present invention is a method for recovering silver from a copper-containing sulfide that is simple, low-cost, and does not require special consideration in terms of a safe environment, and has high industrial value.

Hereinafter, the present invention will be described in detail.
In the present invention, a slurry is formed with a copper-containing sulfide and a sulfuric acid solution containing iron and a peptizer, preferably further copper, and this is supplied into a pressure vessel, and the temperature of the slurry is set to 120 to 180 ° C. In addition, oxygen and / or air is continuously supplied to the gas phase part so that the pressure in the gas phase part is higher by 0.5 to 2.0 MPa than the pressure at which the gas phase part is in equilibrium with the slurry temperature. The reduction potential is adjusted to 530 to 620 mV on the basis of a silver / silver chloride electrode, copper and silver are leached from a copper-containing sulfide, silver is precipitated as silver iron alum, and the obtained copper containing silver iron alum The leaching residue and sodium thiosulfate solution are mixed and stirred to leaching silver, and the silver is adsorbed on activated carbon and recovered.

In the present invention, it is particularly important that when copper and silver are leached from a copper-containing sulfide, (a) a sulfuric acid solution containing iron and a peptizer, preferably further containing copper, is used as the leaching solution. (Ii) adjusting the oxidation-reduction potential of the slurry during leaching to the above range; and (iii) using a sodium thiosulfate solution as a leaching solution when leaching silver from silver-containing iron alum.
With regard to (A), this is because the sulfur produced as a result of leaching is made into droplet-like particles by the peptizer.
As for (b), the iron ions in the leachate are made trivalent, and the leached silver reacts with the trivalent iron ions to precipitate silver as silver iron alum and excess iron. Ions are precipitated as iron alum and deposited and deposited on the surface of the droplet-shaped sulfur particles to cover the surface of the sulfur particles, and the sulfur particles adhere to the surface of the unreacted or reacting copper-containing sulfide. This is to prevent the surface of the sulfide from being covered. This ensures a good leaching reaction between copper and silver, and a high leaching rate is obtained.
Regarding (c), by using sodium thiosulfate which is inexpensive and easy to handle for silver leaching from silver iron alum, water used to obtain silver oxide from silver iron alum The generation of a large amount of calcium sulfate by calcium oxide and the use of sodium cyanide, which is a poison for dissolving silver oxide, are eliminated.

  Hereinafter, regarding the method for leaching silver from the copper-containing sulfide of the present invention, copper-containing sulfide, sulfuric acid solution, oxygen and / or air, copper leaching solution, copper leaching residue, silver leaching solution, silver leaching residue, activated carbon, and leaching It will be explained in detail by dividing it into recovery methods.

1) Copper-containing sulfides As described above, generally, various components are simultaneously contained in copper-containing sulfides such as copper sulfide ores. For example, in copper ores, pyrite and other gangue components coexist with copper sulfide minerals such as chalcopyrite, chalcocite, chalcopyrite, and copper indigo. Of these, chalcopyrite is a primary sulfide mineral, which consists of copper, iron, and sulfur, and is represented by CuFeS2. Contains trace amounts of gold, silver, tin, zinc, etc. Some contain a small amount of nickel or selenium. It is the most important and most common of copper sulfide minerals and is leaching resistant to acids. And chalcopyrite, porphyry and copper indigo are secondary sulfide minerals produced by the natural oxidation of chalcopyrite, which is a primary sulfide mineral. The sulfur grade is lower than that of chalcopyrite, and the solubility in acids is low. It is good.
Note that noble metals such as silver are present in these copper minerals and gangue components such as meteorites.
Industrially, it is difficult to mine each of these minerals individually, and usually, copper ore mined with chalcopyrite as the main component and mixed with other minerals is scoured and beneficiated. Copper concentrate is obtained and used for the recovery of copper and silver. The ratio of chalcopyrite in the copper ore varies depending on the mine where the copper ore is mined.
The copper-containing sulfide of the present invention is mainly composed of chalcopyrite, and the shape thereof may be pulverized to such an extent that it can be slurried, and is preferably as fine as copper concentrate.

2) Sulfuric acid solution In the present invention, the sulfuric acid solution used for leaching copper and silver from a copper-containing sulfide and converting silver into silver iron alum comprises iron, copper and lignin sulfonic acid and / or a salt thereof. It is preferable to contain peptizers at a rate of 30 to 50 g / L, 10 g / L or less, and 0.2 to 1.0 g / L, respectively, and free sulfuric acid at a rate of 15 to 45 g / L. Hereinafter, the sulfuric acid solution will be described in terms of iron concentration, peptizer concentration, and free sulfuric acid concentration.

2) -1 Iron concentration The iron concentration in the sulfuric acid solution is set to 30 to 50 g / L. When the iron concentration falls below 30 g / L, the amount of iron involved in leaching is insufficient, and the amount of iron precipitated as silver-containing iron alum. This is because there is a possibility that the inhibition of leaching due to sulfur generated during leaching cannot be sufficiently prevented. On the other hand, when it exceeds 50 g / L, the solubility of copper in the leachate is lowered and copper cannot be dissolved in the leachate. Furthermore, in the process of extracting and separating copper from the leachate described later, iron separability is deteriorated, which is not preferable. In order to achieve high production efficiency and low cost, it is preferable to repeatedly use an extraction residue obtained by extracting and separating copper from a leachate described later as a sulfuric acid solution. In such a case, about 10 g of copper in the sulfuric acid solution is used. / L or less. Note that if it exceeds 10 g / L, the copper recovery efficiency decreases, which is not preferable.

2) -2 Peptide concentration Also, lignin sulfonic acid or its salt is used as a peptizer, but these surfactants prevent aggregation of copper-containing sulfide particles and generated sulfur in the slurry, and dispersibility. This is because, in addition to the improvement, sulfur produced due to the presence of these causes a spheroidization phenomenon. By covering and covering the surface of the sulfur particles by depositing and depositing silver-containing iron alum on the surface of the spheroidized sulfur, it is possible to better prevent leaching inhibition by sulfur.
The reason why the amount of the peptizer is 0.2 to 1.0 g / L is that if the amount is below this range, the above effect cannot be sufficiently obtained, and if the amount exceeds this range, further improvement in the effect cannot be obtained. It is.

2) -3 Free Sulfuric Acid Concentration Further, the free sulfuric acid is set to 15 to 45 g / L. If it is less than 15 g / L, the free sulfuric acid consumed at the initial stage of leaching is insufficient, and leaching failure is unfavorable. On the other hand, if it exceeds 45 g / L, iron alum is easy to dissolve, and the covering effect of sulfur is lost, resulting in poor leaching. In addition, when the extraction residue is repeatedly used for leaching as a sulfuric acid solution, the concentration of free sulfuric acid usually falls within this range. However, if the sulfuric acid concentration is insufficient, sulfuric acid is added and the sulfuric acid is excessive. In such a case, slaked lime, quick lime, calcium carbonate, and the like are added to fix sulfuric acid as gypsum, and the sulfuric acid concentration is adjusted by discharging it out of the system.

3) Oxygen and / or air In the present invention, oxygen and / or air can be used as an oxygen source. However, when air is used, the heat to be taken away from the exhausted air increases, and the amount of heat applied to maintain the reaction temperature may increase, so oxygen, for example, industrial oxygen in a cylinder or oxygen It is preferable to use oxygen produced in the plant.
In the present invention, oxygen contributes to the leaching reaction between copper and silver by changing the leached Fe ²⁺ to Fe ^3+, and one serves to precipitate excess Fe ³⁺ as silver-containing iron alum. Have. It is also considered that copper and iron are leached by directly oxidizing copper-containing sulfides.
In addition, it is preferable to supply oxygen continuously to the gas phase part of the pressurized container. When the oxygen flow rate is low or when oxygen is supplied intermittently, the production of iron alum in the leachate does not proceed, and leaching inhibition due to sulfur tends to occur.
In addition, it is important that the supply of oxygen to the pressurized container is performed not in the slurry but in the gas phase part of the pressurized container. This is because, when oxygen is blown into the slurry, bubbles formed in the slurry carry chalcopyrite to the vicinity of the liquid surface, and are not uniformly dispersed, resulting in a decrease in the leaching rate.

4) Copper leaching solution The copper leaching solution obtained by the method of the present invention is an extraction residue mainly containing a small amount of copper, iron and sulfuric acid as a result of extraction and separation of copper in a solvent extraction process in which an acidic extractant is used. The obtained and extracted copper is back-extracted and recovered as a back extract liquid in which copper is concentrated. The back extract is then supplied to a copper electrolysis process using an insoluble electrode as the electrolyte, and the copper is recovered as electrolytic copper. The extraction residual liquid is repeatedly used as the leaching sulfuric acid solution after the composition is adjusted.

5) Copper leaching residue The obtained copper leaching residue contains gangue components, unreacted chalcopyrite, sulfur, and silver-containing iron alum. As described above, silver is also contained in unreacted chalcopyrite and gangue components, as a matter of course. The collection target of the present invention is silver-containing iron alum.
Sulfur may be distilled and separated prior to the following silver leaching, but in that case, it is preferable to pulverize the residue to perform silver leaching.

6) Silver leaching residue The silver leaching residue after leaching silver from silver iron alum contains sulfur, undissolved copper-containing sulfide, and gangue components, and precious metals contained in these also exist. Therefore, usually, sulfur in the silver leaching residue is separated by volatilization, for example, and then subjected to a conventional smelting furnace to recover the noble metal. In addition, it is also possible to use for a silver separation process with the quantity of the sulfur contained.

7) Silver effluent (sodium thiosulfate solution)
As a silver leaching solution used for leaching silver in the present invention, a sodium thiosulfate solution is used, which is for sufficiently dissolving silver-containing iron alum.
The sodium thiosulfate concentration is 5 to 20 g / L. This is because when the amount falls below this range, the dissolved silver cannot be reliably held in the form of [Ag (S ₂ O ₃ ) ₂ ] ^{3− in} the leachate.
In the present invention, the reason why the present invention can be leached with a sodium thiosulfate solution is that the present inventors show that silver iron alum contained in a copper leaching residue is expressed by a molecular formula of Ag (Fe) ₃ (SO ₄ ) ₂ (OH) _6. However, it is dissolved in sulfuric acid and reacted with sodium thiosulfate before the silver becomes saturated as low-solubility silver sulfate (solubility 0.85 g / water 100 g) [Ag (S ₂ O ₃ ) ₂ It is presumed that leaching proceeds by forming ^3- and being secured in the silver leachate as complex ions in the leachate.

8) Activated carbon The activated carbon used for this invention is not specifically limited, A general thing may be used. There are various shapes such as powder, lump, and rod, but the shape may be selected according to the collection method to be employed. For example, if silver leaching and adsorption onto activated carbon are performed simultaneously, a predetermined amount of powdered activated carbon may be supplied to the leaching tank. Moreover, if it is made to adsorb | suck to activated carbon and collect | recover by a column system, it is preferable to use granular activated carbon.
Further, in order to recover silver from activated carbon that has adsorbed silver, the activated carbon may be burned in an electric furnace or a tubular furnace. Alternatively, it may be used as an auxiliary fuel for the dissolution process when casting electrosilver collected by electrolysis.

9) Leaching / recovering method In the present invention, a slurry comprising the copper-containing sulfide and the sulfuric acid aqueous solution is formed, charged in a pressure vessel, and the temperature in the pressure vessel is 120 to 180 ° C. While maintaining the value, oxygen is added to the gas phase portion in the container so that the pressure in the gas phase portion in the pressurized vessel is 0.5 to 2 MPa higher than the equilibrium gas phase pressure at that temperature. Then, the oxidation-reduction potential of the slurry is maintained at 530 mV to 620 mV, preferably 550 mV to 620 mV, and copper and silver are leached from the copper-containing sulfide. Then, a copper leaching residue containing a silver-containing iron alum and a copper leaching solution are obtained. The copper leaching solution is treated as described above, but the copper leaching residue containing silver-containing iron alum is treated with a sodium thiosulfate solution as will be described later, leaching silver, adsorbed on activated carbon, and recovered.
Hereinafter, the copper leaching conditions and the silver leaching / recovery conditions will be described separately.

9) -1 Copper Leaching Conditions Copper leaching conditions will be described in terms of slurry concentration, temperature, oxygen and / or air supply method, and oxidation-reduction potential.

9) -1-1 Slurry concentration As described above, in the present invention, a copper-containing sulfide and the sulfuric acid solution described in 2) above are mixed to form a slurry, which is supplied into a pressurized container, Leach copper from copper-containing sulfides. At this time, if the slurry concentration is low, the production efficiency is low. On the other hand, if the slurry concentration is too high, the time required for the reaction becomes too long and the production efficiency is lowered. Therefore, in the present invention, the slurry concentration is preferably 150 to 300 g / L.

9) -1-2 temperature In this invention, the slurry temperature at the time of leaching shall be 120-180 degreeC. This is mainly for obtaining a sufficient leaching rate and at the same time preventing the sulfur produced by the leaching from being oxidized to sulfuric acid. If it is less than 120 ° C., a sufficient leaching rate cannot be obtained, and it takes a long time to obtain a predetermined leaching rate, resulting in poor productivity. On the other hand, when the temperature exceeds 180 ° C., most of the sulfur produced by the leaching reaction is oxidized to become sulfuric acid, which makes it difficult to balance the sulfuric acid when the extraction residue is repeatedly used.

By the way, since the melting point of sulfur is about 107 to 113 ° C., the single sulfur produced at the slurry temperature at the time of leaching is in a molten state and adheres to the surface of the copper-containing sulfide particles that are unreacted or reacting, If left as it is, the entire surface of the copper-containing sulfide particles is covered with sulfur, and the leaching reaction is inhibited. Conventionally, the reason for the low leaching efficiency of chalcopyrite in this temperature range is that the amount of sulfur produced in the leaching reaction is larger than in the case of other copper minerals, and the produced sulfur is unreacted early or contained during the reaction. It seems to cover the surface of copper sulfide particles and inhibit the leaching reaction.
In the present invention, by using a surface active agent such as lignin sulfonic acid as a peptizer, sulfur produced in this temperature range is made into a spherical droplet state, and silver-containing iron produced from Fe ³⁺ which has been leached and becomes excessive Alum is deposited and deposited on the sulfur surface in the form of droplets to effectively prevent sulfur from adhering to and covering the surface of the unreacted or reactive copper-containing sulfide particles.

9) -1-3 Supply Method of Oxygen and / or Air In the present invention, oxygen is used as the oxidizing agent, but oxygen is not directly blown into the slurry in the pressurized container. This is because, when oxygen is blown into the slurry, bubbles formed in the slurry rise and a phenomenon of carrying chalcopyrite to the vicinity of the liquid surface occurs, resulting in a decrease in the leaching rate due to uneven dispersion. Therefore, oxygen is supplied to the gas phase part in the pressurized container. Specifically, while maintaining the slurry in the pressurized container at 120 to 180 ° C., the gas phase pressure in the pressurized container is set to a pressure obtained by adding 0.5 to 2 MPa to the equilibrium gas phase pressure at that temperature. The supply amount of oxygen and / or air is adjusted so that
Oxygen supplied to the gas phase part in the pressurized container dissolves in the slurry and acts as an oxidizing agent, leaching copper, silver, iron, etc. in the copper-containing sulfide, or leaching Fe ²⁺ . and Fe ^3+, the ^{Fe 3+} was contributing to the leaching reactions of the copper and to precipitate the excess of ^{Fe 3+} as silver-containing iron alum. The oxygen consumed by the reaction is replenished from the gas phase into the slurry by keeping the gas phase pressure in the pressurized container constant.
In the present invention, when the pressure applied to the gas phase part in the pressurized container is less than 0.5 MPa, the oxidation-reduction potential of the slurry is lowered from 530 mV, and the leaching rate is extremely lowered. On the other hand, when the pressure is increased beyond 2 MPa, the oxidation-reduction potential exceeds 620 mV, and the oxidation of sulfur increases without further improvement of the copper leaching rate. In addition, the amount of oxygen and / or air to be supplied increases, and the amount of heat taken away from the exhaust gas increases, making it difficult to stably control the temperature in the pressurized container within a predetermined range.

Under the conditions of the present invention, there is a positive correlation between the added pressure of the gas phase portion in the pressurized container and the oxidation-reduction potential of the slurry. In the present invention, by using this positive correlation, the oxidation-reduction potential of the slurry is controlled, and the leaching reaction of the copper-containing sulfide and the formation reaction of silver-containing iron alum are controlled.
Note that the supply of oxygen and / or air is preferably performed at a constant flow rate. If the supply amount varies, if the supply amount becomes excessive, the oxygen utilization efficiency and energy efficiency are deteriorated, for example, the oxygen gas that has been supplied is exhausted without being used for oxidation. On the other hand, when the feeding amount is insufficient, the amount of oxygen gas introduced per unit volume is reduced, and the oxidation-reduction potential of the slurry cannot be increased.
In the present invention, since the positive correlation between the added pressure of the gas phase in the pressurized container and the oxidation-reduction potential of the slurry is used, the oxidation-reduction potential of the slurry in the pressurized container is controlled easily and continuously. it can.

9) -1-4 Redox potential In the present invention, copper, silver, iron and the like are leached from the copper-containing sulfide. Then, the silver leached in the sulfuric acid solution and the excess of iron are precipitated as silver-containing iron alum, and are deposited and deposited on the surface of the sulfur in the droplet state. This creates a state as if the surface of the sulfur was coated with silver-containing iron alum to prevent sulfur from being unreacted or adhering to the surface of the copper sulfide particles during the reaction and covering. This also prevents sulfur from being oxidized. Therefore, when performing the leaching reaction, the oxidation-reduction potential of the slurry in the pressurized container is adjusted to 530 to 620 mV, preferably 550 to 620 mV.
If the oxidation-reduction potential is less than 530 mV, the rate of leaching copper and the like from the copper-containing sulfide is remarkably reduced, and a practical leaching rate cannot be obtained. On the other hand, if it exceeds 620 mV, the leaching rate increases, but the sulfur is excessive. When the extraction residual liquid after being oxidized and distributed as sulfate ions to the leachate and extracting and separating copper from the leachate is used as the sulfuric acid solution, it is difficult to balance the sulfuric acid in the system.
In addition, when the sulfuric acid in the system becomes excessive, as described above, the excessive free sulfuric acid content must be settled as gypsum with slaked lime, quick lime, calcium carbonate, etc., and discharged out of the system, It becomes a factor of cost increase.

9) -2 Silver Leaching / Recovering Method In the present invention, a copper leaching residue containing silver-containing iron alum is treated with a sodium thiosulfate solution to leach silver, and the silver is adsorbed on activated carbon and recovered.
Hereinafter, the silver leaching / recovering method will be described in terms of slurry concentration and leaching time and silver recovery method.

9) -2-1 Slurry concentration and leaching time The slurry concentration during leaching of silver is preferably 50 to 100 g / L. This is because if the slurry concentration is lower than this range, the leaching efficiency is poor, and if the slurry concentration is high, the leaching may be insufficient.
Moreover, the temperature at the time of leaching is not particularly limited, and the leaching can be sufficiently performed as long as it is at room temperature or higher. Moreover, about leaching time, although it does not specifically limit, It is preferable to set it as 2 to 3 hours. If the length is shorter than this, the leaching is not sufficiently performed, and if the length is longer than this, further increase in the leaching rate cannot be expected.

9) -2-2 Silver recovery method As a means for recovering silver from the silver leachate, a method of adsorbing silver on activated carbon is the simplest and inexpensive. This is because the activated carbon that has adsorbed silver can be easily roasted in an electric furnace or a tubular furnace to recover silver. Furthermore, you may use as auxiliary fuel for the melting furnace used when casting electrodeposition gold | metal | money. By doing this, it is possible to reduce the in-process interest rate of silver.
For adsorption of silver on activated carbon, activated carbon may be brought into contact with a silver leaching final solution leached with silver. At the time of silver leaching, sodium thiosulfate solution, activated carbon, and copper leaching residue are simultaneously added to the leaching tank. May be stirred. When the stirring is stopped, the activated carbon gathers near the liquid surface of the leaching tank due to the difference in specific gravity, and the silver leaching residue sinks to the bottom of the leaching tank, so that the activated carbon can be easily separated and recovered.
As described above, the type and shape of the activated carbon that can be used in the present invention are not particularly limited, but a powdery form is preferable because leaching and adsorption can be performed simultaneously. The amount of activated carbon used is 5 to 20 g / L per liter of silver leachate.
Below this range, the contact between the silver iron alumite and the activated carbon becomes insufficient, and a sufficient leaching effect cannot be obtained. On the other hand, when it exceeds the above range, the amount of activated carbon becomes excessive, which is economically undesirable.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded. In addition, the raw material used in the Example, processing conditions, physical property measurement, etc. are as follows.

<Raw materials, processing conditions, etc.>
Copper-containing sulfide: Copper concentrate with chalcopyrite and pyrite steel as main minerals, with Cu at 20.6% by mass, Fe at 25.7% by mass, and S at 24.6% by mass is there.
Copper leaching reaction vessel: A stainless steel autoclave having an internal volume of 3 L was used.
Copper leaching beaker: A stainless steel cylindrical container having an internal volume of 2.5 L was used.
Oxygen gas: An oxygen cylinder manufactured by Iwatani Gas Co., Ltd. was used. The purity is 99.5%.
<Measurement methods, etc.>
Measurement of gas phase pressure: A pressure gauge provided in the autoclave was used.
Measurement of oxidation-reduction potential: Measurement was performed using a silver / silver chloride electrode manufactured by Toa DKK Corporation.
Analysis of metal components: performed using ICP.

Example 1
The copper-containing sulfide was pulverized using a NANO MILL NM-G2M type wet bead mill manufactured by Asada Tekko Co., Ltd., with a slurry concentration of 1000 g / l, a flow rate of 8 L / min, and a number of passes of 5 times, and pulverized to 10 μm or less. The particle size distribution occupies 80% by mass or more. Next, 200 g of the pulverized copper-containing sulfide was collected in terms of dry weight, and a sulfuric acid aqueous solution having a composition of Cu: 0.88 g / L, Fe: 43.0 g / L, and a free sulfuric acid concentration of 30 g / L. A slurry was prepared by mixing with 1 L. To this slurry, 0.5 g / L of sodium lignin sulfonate (product name: sodium lignin sulfonate manufactured by Tokyo Chemical Industry Co., Ltd.) was added and mixed as a peptizer.
Subsequently, the entire amount of the slurry was placed in a copper leaching beaker, and the beaker was placed in a copper leaching reaction vessel, which was sealed and heated with stirring and maintained at 165 ° C. The equilibrium gas phase pressure at 165 ° C. was about 0.7 MPa. Thereafter, while maintaining the temperature constant at 165 ° C., oxygen was blown into the gas phase portion in the pressure vessel from the oxygen cylinder so that the pressure in the gas phase portion became 1.7 MPa (additional portion 1.0 MPa). The oxygen flow rate was adjusted with an automatic flow control device so that the pressure in the phase portion was maintained at about 1.7 MPa, and the reaction was carried out for 7 hours. Note that the temperature was substantially constant during oxygen blowing, and the flow rate of oxygen was substantially constant at 0.5 L / min.
Thereafter, the heating is stopped and the system is cooled to room temperature, then the pressure vessel is opened and the slurry is taken out. The slurry is filtered and separated into a filtrate and a leaching residue, and the oxidation-reduction potential and pH of the obtained filtrate are measured. The metal ion concentration of the filtrate and the metal component of the leach residue obtained by washing and drying were analyzed.
Of the amount of copper contained in the copper sulfide, the proportion of the amount distributed into the filtrate by leaching was determined and used as the copper leaching rate. The obtained results and the leaching conditions are shown together in Table 1.
Next, 50 g of the dried copper leaching residue, 1 L of silver leaching solution having a sodium thiosulfate concentration of 10 g / l as an anhydrous product, and 10 g of activated carbon were placed in a 2 L beaker and stirred for 3 hours.
The stirrer was stopped and allowed to stand for a while to float the activated carbon on the upper part of the silver leaching final solution in the beaker, and it was collected with a net. Thereafter, filtration was performed to obtain a silver leaching final solution and a silver leaching residue.
The amounts of silver in the copper leaching residue, silver leaching residue, activated carbon, and silver leaching final solution were determined and shown in Table 2.

(Example 2)
Except that the additional portion applied to the gas phase portion in the pressure vessel was set to 2.0 MPa, leaching of copper or the like from the copper-containing sulfide was performed in the same manner as in Example 1, and the obtained copper leaching residue was used. Silver was leached and collected in the same manner as in Example 1. The obtained results and the leaching conditions are shown in Tables 1 and 2. Note that the temperature during oxygen blowing was substantially constant, and the flow rate of oxygen was also substantially constant.

(Example 3)
Except for the reaction temperature of 180 ° C., copper and the like were leached from the copper-containing sulfide in the same manner as in Example 1, and silver was leached and recovered in the same manner as in Example 1 using the obtained copper leaching residue. . The obtained results and the leaching conditions are shown in Tables 1 and 2. Note that the temperature was substantially constant during oxygen blowing, and the flow rate of oxygen was substantially constant.

(Examples 4 and 5)
Except for the iron concentration in the sulfuric acid solution used being 30.0 (Example 4) and 50.0 g / L (Example 5), copper and the like were leached from the copper-containing sulfide in the same manner as in Example 1, Using the obtained copper leaching residue, silver was leached and recovered in the same manner as in Example 1. The obtained results and the leaching conditions are shown in Tables 1 and 2. The temperature was substantially constant during copper leaching and blowing, and the oxygen flow rate was also substantially constant.

(Examples 6 and 7)
50 g of the dried copper leaching residue obtained in Example 1 and sodium thiosulfate pentahydrate converted to an anhydrous product so as to be 5 g / L (Example 6) and 20 g / L (Example 7). 1 L of the dissolved silver leachate and 10 g of activated carbon were placed in a 2 L beaker and stirred for 3 hours.
The stirrer was stopped, allowed to stand for a while, and the activated carbon was floated on the top of the beaker, and was collected with a net. Thereafter, filtration was performed to obtain a leachate and a silver leaching residue.
The amounts of silver in the copper leaching residue, silver leaching residue, activated carbon, and silver leaching solution were determined and shown in Table 2.

(Example 8)
100 g of dry copper leaching residue obtained in Example 1, 1 liter of silver leaching solution in which sodium thiosulfate pentahydrate was converted to an anhydrous product to 10 g / l, and 10 g of activated carbon were added to a 2 liter beaker. And stirred for 3 hours.
The stirrer was stopped, allowed to stand for a while, and the activated carbon was floated on the top of the beaker, and was collected with a net. Thereafter, filtration was performed to obtain a silver leaching final solution and a silver leaching residue.
The amounts of silver in the copper leaching residue, silver leaching residue, activated carbon, and silver leaching final solution were determined and shown in Table 2.

(Comparative Examples 1 and 2)
Except for the amount of addition applied to the gas phase portion in the pressure vessel being 0.4 (Comparative Example 1) and 2.2 MPa (Comparative Example 2), the copper content from the copper-containing sulfide was the same as in Example 1. Leaching was performed. The obtained results and the leaching conditions are shown together in Table 1. Note that the temperature was substantially constant during oxygen blowing, and the flow rate of oxygen was substantially constant.

(Comparative Examples 3 and 4)
Copper and the like were leached from the copper-containing sulfide in the same manner as in Example 1 except that the reaction temperature was 110 (Comparative Example 3) and 200 ° C. (Comparative Example 4). The obtained results and the leaching conditions are shown together in Table 1. Note that the temperature was substantially constant during oxygen blowing, and the flow rate of oxygen was substantially constant.

(Comparative Examples 5 and 6)
Copper and the like were leached from the copper-containing sulfide in the same manner as in Example 1 except that the iron concentration in the sulfuric acid solution used was 15 (Comparative Example 5) and 60.0 g / L (Comparative Example 6). The obtained results and the leaching conditions are shown together in Table 1. Note that the temperature was substantially constant during oxygen blowing, and the flow rate of oxygen was substantially constant.

(Comparative Example 7)
Included in the same manner as in Example 1 except that the gas pressure to be added was manually changed to 0.5 to 2 MPa at an arbitrary time interval while observing the change in temperature without changing the flow rate of oxygen gas to a constant flow rate. Copper and the like were leached from the copper sulfide. The obtained results and the leaching conditions are shown together in Table 1.

(Comparative Examples 8 to 10)
Silver was extracted from the copper leaching residue in the same manner as in Example 6 except that a sodium hydroxide solution having a pH of 11 (Comparative Example 8), 12 (Comparative Example 9), and 13 (Comparative Example 10) was used as the silver leaching solution. Leached. The obtained results are shown in Table 2.

(Comparative Example 11)
Silver was leached from the copper leaching residue in the same manner as in Example 6 except that a sodium sulfite solution adjusted to a concentration of 10 g / L was used as the silver leaching solution. The obtained results are shown in Table 2.

From the results shown in Table 1, in the examples according to the conditions of the present invention, the leaching rate was 85% or more, and good results were obtained. On the other hand, the sulfur oxidation rate is found to be as low as 65% or less in spite of leaching under a temperature of 120 to 180 ° C. and under pressurized conditions. On the other hand, in the comparative example out of the scope of the present invention, the leaching rate of copper is as low as less than 85%, or the oxidation rate of sulfur exceeds 65%, and sufficient leaching results are obtained. It turns out that it cannot be said.
Further, from Table 1, in the method of the present invention in which oxygen and / or air is supplied to the gas phase part in the pressurized container so as to be 0.5 to 2 MPa higher than the gas phase pressure that is in equilibrium with the slurry temperature, It is clear that the oxidation-reduction potential of the slurry can be sufficiently controlled, and that the oxygen supply rate is preferably as constant as possible.

Moreover, from the results of Table 2, in the examples according to the conditions of the present invention, the silver-containing iron alum in the copper leaching residue was sufficiently leached, and as a result, the grade in the silver leaching residue was reduced to 97 to 99 ppm. I understand that. In addition, since the activated carbon contains 3 to 5 ppm of silver, and the silver concentration in the silver leaching solution after the silver leaching finally obtained by separation is 1 ppm or less, the silver iron alum in the copper leaching residue It can be seen that all of the silver leached and transferred into the leachate is adsorbed on the activated carbon. In addition, it seems that the silver in a silver leaching residue exists in the copper sulfide mineral unreacted with the gang component in a silver leaching residue.
On the other hand, in Comparative Examples 8 to 11 using sodium hydroxide and sodium sulfite instead of sodium thiosulfate, the silver quality in the silver iron alunite did not change. In addition, as evidenced by this, no silver was detected in the activated carbon or in the silver leachate finally obtained by separation.
In this example, in order to simultaneously perform leaching of silver and adsorption of silver on activated carbon, activated carbon was allowed to coexist in the copper leaching residue slurry during silver leaching, but silver was leached without coexisting activated carbon. The obtained silver leaching final solution and activated carbon are brought into contact with each other so that the silver in the silver leaching final solution is adsorbed on the activated carbon without any problem.

  In the present invention, when leaching silver from a copper-containing sulfide, the leached silver reacts with trivalent iron in the leaching solution to form silver iron alum. In addition, iron that has been leached and becomes excessive in the leachate is called iron alum. Then, silver iron agate and iron agate are produced upon leaching and adhered to and deposited on the surface of the sulfur particles formed into droplets by the peptizer, and the sulfur particles are unreacted by covering the surface of the sulfur particles. Covering the surface of the copper-containing sulfide particles during the reaction is prevented. Thereby, silver can be leached at a high leaching rate from the copper-containing sulfide. And when leaching silver from silver iron alum, a sodium thiosulfate solution is used without using sodium cyanide. Therefore, the method of the present invention is a low-cost method that does not require special consideration in terms of a safe environment, and its industrial value is high.

Claims (7)

A method for recovering silver from a copper-containing sulfide, wherein the following treatments (1) to (5) are sequentially performed in a method for recovering silver from a copper-containing sulfide containing chalcopyrite as a main component.
(1) Mixing a sulfuric acid solution containing 30 to 50 g / L of iron, a peptizer composed of lignin sulfonic acid and / or a salt thereof at a rate of 0.2 to 1.0 g / L, and the copper-containing sulfide. (2) After the slurry is charged into the pressurized container, the pressure of the gas phase in the pressurized container is less than the equilibrium state while maintaining the temperature of the slurry at 120 to 180 ° C. A sufficient amount of oxygen and / or air to increase by 5 to 2.0 MPa is supplied to the gas phase part to adjust the oxidation-reduction potential of the slurry. (3) A leaching solution containing copper by solid-liquid separation (4) The copper leaching residue is mixed with a sodium thiosulfate solution (silver leaching solution) containing sodium thiosulfate at a rate of 5 to 20 g / L in terms of anhydride. After obtaining the slurry, solid-liquid separation is performed to obtain a silver leaching final solution and a silver leaching residue. (5) contacting the silver leachate and charcoal silver is adsorbed on the activated carbon, and recovering   The method for recovering silver from a copper-containing sulfide according to claim 1, wherein the slurry in (1) has a slurry concentration of 150 to 300 g / L.   The said sulfuric acid solution in said (1) contains 10 g / L or less of copper, The recovery method of the silver from the copper containing sulfide of Claim 1 characterized by the above-mentioned.   The method for recovering silver from a copper-containing sulfide according to claim 1, wherein the sulfuric acid solution in (1) contains 15 to 45 g / L of free sulfuric acid.   The method for recovering silver from a copper-containing sulfide according to claim 1, wherein the oxidation-reduction potential in (2) is 530 to 620 mV on a silver / silver chloride electrode basis.   The method for recovering silver from a copper-containing sulfide according to claim 1, wherein the copper leaching residue slurry in (4) has a slurry concentration of 50 to 100 g / L.   The sodium thiosulfate solution in (4) is a sodium thiosulfate solution to which activated carbon is added at a rate of 5 to 20 g / L. Leaching method.