JP2013155416A - Method for leaching copper from copper sulfide ore containing copper pyrite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an efficient method for stably leaching copper from copper sulfide ore containing copper pyrite at a high leaching rate for a long period by enhancing the leaching rate.SOLUTION: When copper is leached from copper sulfide ore containing copper pyrite, an iron sulfate aqueous solution having an iron concentration adjusted to 1-20 g/L and a pH adjusted to 1.0-2.0, preferably 1.5-2.0 is used as a leaching solution, relative to a mixture of the copper sulfide ore and magnetite of a mass 0.1 to 10 times that of the whole mass of copper mineral contained in the copper sulfide ore, and the leaching is performed while maintaining the oxidation/reduction potential of the leaching solution in leaching within a range of 600-700 mV, preferably, 600-650 mV in terms of standard hydrogen electrode.

Description

  The present invention relates to a method for leaching copper from a copper sulfide ore containing chalcopyrite.

  Conventionally, as one method for recovering copper from copper ore, copper is leached with sulfuric acid and the like, and the extracted copper is recovered as a copper cathode by electrowinning using a solution obtained by solvent extraction. ing. When copper contained in copper ore is in the form of oxides or carbonates, even such simple acid leaching can easily leach 40-90% of the contained copper, resulting in high yields of copper. It is possible to collect at a rate.

In addition, when the copper mineral in the copper ore is a secondary sulfide mineral such as chalcocite (Cu ₂ S) or porphyry (Cu ₅ FeS ₄ ), a bacterial leaching method is used. This method makes it possible to efficiently leach copper by using a leachate containing iron sulfate as an oxidizing agent under the conditions in which microorganisms such as iron bacteria coexist. All of these methods are widely used in large-scale copper mines in North America or South America because copper can be recovered economically and efficiently.

  In the bacterial leaching method, the trivalent iron ions contained in the leachate act as an oxidizing agent and promote the dissolution of sulfide minerals. At this time, the trivalent iron ions in the leachate are reduced to divalent iron ions. Therefore, the redox potential of the leachate decreases as the reaction proceeds. However, microorganisms such as iron bacteria that naturally inhabit the deposited ore dumps obtain their own energy by oxidizing these divalent iron ions into trivalent iron ions. The redox potential rises again, and particularly under conditions where microorganisms such as iron bacteria are actively active, the redox potential reaches about 700 to 900 mV (versus the standard hydrogen electrode).

  Thus, when the copper mineral contained in the ore is a secondary sulfide mineral such as chalcocite or porphyry, the higher the redox potential, the easier it is to dissolve, and the above action causes the trivalent in the leachate to be dissolved. Since iron ions increase, the amount of copper eluted and recovered increases.

However, when the copper mineral contained in the copper ore is a primary sulfide mineral such as chalcopyrite (CuFeS ₂ ), a redox potential of 700 to 900 mV (versus standard hydrogen electrode) in which microorganisms such as iron bacteria are actively active. In the region, the copper leaching rate is extremely slow. For this reason, normal bacterial leaching is a suitable condition for leaching of secondary sulfide minerals as described above, but when applied to primary sulfide minerals, the copper leaching rate remains at a few percent to about 20%. End up. Although the leaching can be accelerated by further increasing the oxidation-reduction potential, it is difficult to maintain such a high oxidation-reduction potential only by the oxidizing action of microorganisms such as iron bacteria.

  In general, the majority of copper ore contained in low-grade copper ore, such as the primary sulfide mineral zone below the porphyry deposit, is chalcopyrite. Moreover, copper ores including chalcopyrite are widely distributed throughout the world. However, low-grade copper ores such as chalcopyrite are not suitable for copper recovery by the above-mentioned leaching method, so that copper concentrate is recovered by the economically disadvantageous flotation method. The fact is that it has been disposed of.

  On the other hand, in US Pat. No. 6,277,341, in the reactor, the surface potential of chalcopyrite is maintained in the range of 350 to 450 mV (vs. calomel electrode vs. standard hydrogen electrode, 600 to 700 mV). It has been proposed to promote the leaching of chalcopyrite. However, in the actual heap leaching method, as described above, the oxidation-reduction potential increases beyond this range, so it is difficult to stably promote the leaching of chalcopyrite and improve the leaching rate.

  US Patent Application Publication No. 2007/0042482 and US Patent Application Publication No. 2008/0026450 attempt to promote the leaching of chalcopyrite by using certain bacteria, but are not exposed to the external environment. In heap leaching, it is not easy to maintain the activity and identity of the bacterium which is a living organism for a long time, and it is difficult to stably promote the leaching of chalcopyrite and improve the leaching rate.

  In Japanese Patent Application Laid-Open No. 2004-156123 by the present inventors, 350 to 450 mV, which is a range suitable for the leaching of chalcopyrite, is obtained by mixing naturally occurring pyrite with the reducing power of sulfide. A method of maintaining 550 to 650 mV in terms of silver chloride electrode and standard hydrogen electrode is proposed. However, this method is based on the premise that the target ore contains pyrite. Otherwise, pyrite must be collected from other areas and used, which increases costs. There's a problem.

In addition, in Japanese Patent Laid-Open Nos. 2005-15864 and 2007-204830 by the present inventors, H ₂ S which is a product of a chalcopyrite dissolution reaction is obtained by adding powdery carbon or fixed carbon-containing material. There has been proposed a method for maintaining the oxidation-reduction potential at an appropriate range of 350 to 450 mV (to silver-silver chloride electrode) by adsorbing and removing gas and enhancing the reducing power of chalcopyrite itself by promoting leaching reaction. . However, in this method, it is necessary to use a large amount of sulfuric acid to make the pH about 1.5 or less, or to use a large amount of carbon material to be added in order to enable leaching at a high pH, There is a problem from an economic point of view as well.

  In addition, in JP 2011-84757 A and US Pat. No. 5,730,776, as a method of leaching chalcopyrite at a high speed, a method of leaching copper under high temperature and pressure conditions by adding sulfuric acid and an oxidizing agent, etc. Has been proposed. However, although these methods can achieve a high leaching rate, both methods require a large amount of energy consumption and reagent cost, and are problematic from an economical viewpoint. Moreover, the oxidative pressure leaching is performed under severe conditions such as high temperature and high pressure, and can be said to be fundamentally different from the leaching method under mild conditions such as bacterial leaching.

US Pat. No. 6,277,341 US Patent Application Publication No. 2007/0042482 US Patent Application Publication No. 2008/0026450 JP 2004-156123 A JP 2005-15864 A JP 2007-204830 A JP 2011-84757 A US Pat. No. 5,730,776

  The object of the present invention is to increase the leaching rate from copper sulfide ores containing chalcopyrite and to efficiently leach copper at a high leaching rate and stably over a long period of time in view of the problems of the prior art described above. Is to provide a simple method at low cost.

In order to achieve the above object, the present inventors have conducted extensive research on a method for leaching copper from chalcopyrite containing copper ore, and as a result, mixed a predetermined amount of magnetite (Fe ₃ O ₄ ) with the copper sulfide ore. In addition, the present inventors have found that by leaching under specific conditions, copper leaching rate can be increased and copper can be leached stably at a high leaching rate over a long period of time. .

  The present invention relates to a method for leaching copper from a copper sulfide ore containing chalcopyrite. In particular, in the present invention, magnetite having a mass of 0.1 to 10 times the total mass of the copper mineral contained in the copper sulfide ore is mixed with the copper sulfide ore. Using an aqueous iron sulfate solution having a concentration of 1 to 20 g / L and a pH of 1.0 to 2.0, the redox potential of the leachate during leaching is in the range of 600 to 700 mV (vs. standard hydrogen electrode). And leaching copper. Note that the redox potential of the leaching solution is maintained in the above range over the entire leaching period.

  The redox potential of the leachate is preferably in the range of 600 to 650 mV (vs. standard hydrogen electrode), particularly preferably in the range of 600 to 630 mV (vs. standard hydrogen electrode). For this reason, it is preferable to make pH of the said leaching solution into the range of 1.5-2.0.

  The method of the present invention can be suitably applied to any of the heap leaching method, the bat leaching method, and the column leaching method using the bacterial leaching method.

  The method of leaching copper sulfide ore containing chalcopyrite of the present invention increases the leaching rate of copper from the copper sulfide ore containing chalcopyrite, thereby lowering the cost at a lower cost and stabilizing the copper for a long period of time. It can be said that its industrial value is extremely large.

It is the graph which showed the relationship between the pH when magnetite was suspended in the iron sulfate aqueous solution, and the oxidation-reduction potential (vs. standard hydrogen electrode) of the solution. It is the schematic of the column leaching apparatus used for the present Example. It is a graph showing transition of the copper leaching rate (integration) obtained by the Example and the comparative example. It is a graph showing the oxidation-reduction potential (vs. standard hydrogen electrode) in a column in (a) 42nd day, (b) 56th day, and (c) 69th day of an Example and a comparative example.

  In order to leach copper from copper sulfide ores containing chalcopyrite at a high leach rate, the leachate used in the usual bacterial leaching method is used for the oxidation-reduction potential (vs. standard hydrogen electrode) at the time of leaching. In the range of 600 to 630 mV (vs. standard hydrogen electrode) that promotes the dissolution of chalcopyrite and maintain this redox potential as much as possible, and 600 to 700 mV (vs. standard) over the entire leaching period. Hydrogen electrode), preferably 600 to 650 mV (vs. standard hydrogen electrode), it was necessary to maintain it, and earnestly researched on this point. As a result, the inventors obtained knowledge that the oxidation-reduction potential can be controlled within the above range when copper magnetite is mixed with crystalline magnetite and leached under specific conditions, and the present invention is completed. It has come to be.

First, the present invention leaches copper from copper sulfide ore mixed with crystalline magnetite having a mass of 0.1 to 10 times the total mass of copper mineral contained in the copper sulfide ore. There are features. This magnetite (Fe ₃ O ₄ ) basically acts as a reducing agent for trivalent iron ions contained in the leachate.

  More specifically, first, in the leaching of copper from the copper sulfide ore, the trivalent iron ions contained in the leachate act as an oxidizing agent, so that they themselves are reduced to divalent iron ions. Since it is oxidized again to trivalent iron ions by the action of bacteria and air oxidation, the redox potential of the leachate rises to 700-900 mV (versus standard hydrogen electrode). At this time, if a predetermined amount of magnetite is present in the sulfuric acid aqueous solution, trivalent iron ions present in the solution are reduced to divalent iron ions by the following reaction.

2Fe ₃ O ₄ + 2Fe ³⁺ + H ₂ O = 3Fe ₂ O ₃ + 2Fe ²⁺ + 2H ⁺
If the factors over time are not taken into account by this reduction action, the redox potential of the leachate is reduced to about 600 to 630 mm / V (vs. standard hydrogen electrode), so that the leaching rate of copper in chalcopyrite does not decrease. Leaching with high efficiency. This reduction action by magnetite is effective even when leaching takes place over a long period of time, whereby the redox potential of the leaching solution is maintained in the range of 600 to 650 mm / V (versus standard hydrogen electrode) for a long period of time. Even if the improvement of the redox potential based on the time-dependent factors such as the action of air and air oxidation is considered, the redox potential of the leachate is 600 to 700 mm / V (vs. the standard hydrogen electrode) over the entire leaching period (about 120 days). ) Is maintained within the range.

  Here, magnetite is used as an additive that regulates the redox potential of the leachate. This magnetite is a mineral that is widely contained in rocks and soils, and is basically present all over the world, unlike pyrite. This is because it can be easily recovered by magnetic separation and can be obtained at a very low cost. This natural magnetite is usually rich in crystallinity. Moreover, although the production area of magnetite is not specifically limited, it is preferable to confirm the effect by this invention suitably by a preliminary test etc.

  When magnetite is also included in the ore containing copper sulfide ore to which the present invention is applied, raw materials can be collected simultaneously, and the present invention can be applied more easily. In particular, in the copper deposit, magnetite may be contained more abundantly than pyrite, or pyrite may not be contained and only magnetite may be present. In such a case, the present invention is applied particularly advantageously. It becomes possible.

  The amount of magnetite added is appropriately selected according to the properties of the applied copper sulfide ore and the composition of the leachate. When leaching copper sulfide ore containing general chalcopyrite under normal conditions, it should be 0.1 to 10 times, preferably 1 to 10 times the total mass of copper mineral contained in copper sulfide ore is necessary. If less than 0.1 times the total mass of copper minerals contained in the copper sulfide ore, the effect of lowering the redox potential cannot be expected, and if more than 10 times the amount, when leaching copper from chalcopyrite, This is not preferable because there is a concern that the leaching reaction may be hindered by the galvanic interaction accompanying direct contact between chalcopyrite and magnetite.

  In order to increase the efficiency of the reduction reaction, the magnetite has a 80% passing particle size of preferably 1000 μm or less, more preferably 100 μm or less. When the particle size exceeds 1000 μm, the contact area between the leachate and magnetite is not sufficiently ensured, so that the above reduction reaction does not proceed sufficiently. In addition, when the particle size of the recovered magnetite is out of this range, the particle size is appropriately adjusted by granulation or pulverization. The means for granulation or pulverization is not particularly limited, and known means can be used.

The copper minerals contained in copper sulfide ores are usually chalcopyrite, but those containing secondary sulfide minerals such as chalcocite (Cu ₂ S) and chalcopyrite (Cu ₅ FeS ₄ ) to some extent are also included. The present invention can be applied. Furthermore, the copper concentrate obtained by flotation or the like from this copper sulfide ore and containing the copper mineral is also included in the copper sulfide ore containing chalcopyrite in the present invention.

  In addition, about the copper sulfide ore, what was crushed beforehand is usually used in order to expose most copper minerals. As the crushing method, blasting during mining or various crushers are used. In the present invention, the particle size of the copper sulfide ore after crushing is not particularly limited, and the optimum pulverized particle size may be selected by comprehensively judging the properties and profitability of the raw ore. In addition, when the object is copper concentrate, since it is already fine, pulverization thereof is unnecessary.

  The present invention is characterized in that an iron sulfate aqueous solution having an iron concentration adjusted to 1 to 20 g / L and a pH adjusted to 1.0 to 2.0 is used as the leachate. Among these, the pH of the leachate is restricted to the above range for the following reason.

That is, in the present invention, the redox potential (vs. standard hydrogen electrode) of the leachate at the time of leaching is controlled in the range of 600 to 700 mV, preferably 600 to 650 mV, more preferably 600 to 630 mV suitable for the leaching of chalcopyrite. This is very important. When magnetite is present in an iron sulfate aqueous solution, the relationship shown in FIG. 1 is established between the redox potential of the iron sulfate aqueous solution and the pH, so the pH of the leachate should be maintained at 1.0 to 2.0. Thus, it is understood that the redox potential range suitable for the leaching of chalcopyrite can be adjusted. In addition, since the leaching rate of chalcopyrite becomes maximum when the redox potential of the leachate is 600 to 630 mV, it is more preferable to adjust the pH of the leachate to 1.5 to 2.0. In addition, as long as the oxidation-reduction potential of the leachate is controlled within the above range, in the present invention, H ₂ S gas that is a chalcopyrite dissolution reaction product is not generated, and it is not necessary to take countermeasures.

  In addition, when the pH of the leachate is less than 1.0, not only the acid consumption increases, but also the extraction rate in the solvent extraction process, which is a downstream process, decreases. On the other hand, when the pH exceeds 2.0, the leaching rate of copper decreases, and the problem that the leaching reaction is hindered by precipitation of insoluble iron compounds may occur. The method for adjusting the pH is not particularly limited, and can be performed by adding a general acid such as sulfuric acid or hydrochloric acid. It is preferable to use sulfuric acid from the viewpoint of cost.

  The iron concentration in the aqueous iron sulfate solution is preferably 1 to 20 g / L, more preferably 1 to 10 g / L, and still more preferably 1 to 5 g / L. If the iron concentration is less than 1 g / L, the copper leaching rate decreases, and the recovery efficiency decreases. The higher the concentration of iron, the higher the copper leaching rate. However, when the concentration exceeds 20 g / L, the viscosity of the liquid increases and precipitation of insoluble iron compounds increases, and the leaching is hindered.

  The method for adjusting the iron concentration is not particularly limited, and can be performed by adding ferric sulfate to the leaching solution or replacing the adjusted circulating fluid.

  In the present invention, the leaching step is performed by adding the iron sulfate aqueous solution to copper sulfide ore, but the leaching method is not particularly limited. In addition to the heap leaching method, the present invention can be applied to any of the bat leaching method, the column leaching method, and the stirring leaching method.

  The method for removing the noble liquid containing copper from the leaching step is not particularly limited, and is a method of intermittently collecting the leachate in the reaction tank by replenishing the leachate, and continuously collecting the leaching solution in small portions. Since known means such as a method and a method for collecting all the precious liquids at a time can be used, it is preferable to appropriately select one suitable for the form and ability of the downstream process.

  Moreover, it does not specifically limit about the method of collect | recovering copper from the said noble liquid, A well-known means can be used. For example, the noble liquid recovered in the present invention can be applied to a method of producing electrolytic copper by solvent extraction and electrolytic collection.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited at all by these Examples.

(Example)
In this example, 11 kg of quartz (meteorite) adjusted to a particle size of 2.8 mm or more and 12.5 mm or less was added with 462 g of chalcopyrite so that the overall Cu quality was 1% by mass, and kneaded. The copper sulfide ore containing chalcopyrite (Cu quality: about 1.4% by mass) was used. Note that 150 ml of distilled water was used as the cross-linking liquid during kneading. In addition, as the chalcopyrite, a natural massive chalcopyrite produced in the United States was pulverized and adjusted to 9 μm at an 80% passing particle size.

  As magnetite, natural lump magnetite produced in the United States was crushed and adjusted to 48 μm at 80% passing particle size.

  Table 1 shows chemical analysis values (composition ratios) of chalcopyrite and magnetite used in this example, as measured by an ICP emission analyzer (manufactured by SII Nanotechnology Inc., SPS7800).

  In this example, copper leaching was performed using column leaching, which is widely applied to the heap leaching method simulation test. Specifically, copper was leached from the copper sulfide ore using the column apparatus (1) shown in FIG. The column (2) includes a commercially available vinyl chloride tube (3) having an inner diameter of 10 cm and a length of 100 cm, a joint (4), and a filter (not shown) that is disposed in the column (2) and transmits only the leachate. Made in combination. Further, in order to collect the leachate during the leaching, a total of 11 holes with a diameter of 5 mm were formed in the side surface of the vinyl chloride tube at intervals of 10 cm in the vertical direction to obtain a sample collection port (5). Further, the sampling port was sealed with a tape (6) so that it could be opened only when sampling the leachate.

  At the time of kneading, a sample added with magnetite having a mass (1848 g) four times that of chalcopyrite in the copper sulfide ore was sampled uniformly into the column (2) so as not to collapse.

  As the leachate, a ferric sulfate solution having an iron concentration of 0.1 mol / L (5.6 g / L) and pH 1.5 was used, and this leachate was removed from the leach tank (7) using the pump (8), and the top of the column. To 1.4 mL / min (2 L per day). Then, the leachable noble liquid discharged | emitted from the column lower end was collect | recovered by the discharge tank (10) with the pump (9).

  Column leaching was performed for 112 days. On days 42, 56, and 69, a sponge was inserted from the sample collection port on the side of the column to collect the leachate, and the redox potential of the leachate was measured with an ORP meter using a silver-silver chloride electrode. It converted into the value of the standard hydrogen electrode. FIG. 4 shows the oxidation-reduction potential (versus the standard hydrogen electrode) at each position (0 to 1.0 m) in the height direction of the column. As can be seen from FIG. 4, the redox potential of the leachate decreases from 850 mV at the top of the column to around 600 mV at the bottom of the column. This is because of trivalent iron ions due to oxidation leaching of chalcopyrite. Is consumed and reduced to divalent iron ions.

  Until the 56th day, in most of the height direction, the redox potential (vs. standard hydrogen electrode) of the leachate was maintained in the range of 600 to 650 mV. Even on the 69th day, it was maintained in the range of 650 to 700 mV. Thus, in this example, the oxidation-reduction potential range suitable for dissolution of chalcopyrite is maintained over a long period of time. This can be said to be due to the potential adjusting action of the added magnetite. It is understood that the leaching of chalcopyrite was promoted.

  Moreover, the leaching noble liquid was collected from the tank every 3 to 4 days, mixed well, and then analyzed for its copper concentration using an ICP emission analyzer. FIG. 3 shows the cumulative copper leaching rate obtained from the analysis. In this example, the cumulative copper leaching rate for 112 days is 88%, and an extremely high effect is obtained.

(Comparative example)
Column leaching was carried out under the same conditions as in the Examples, except that magnetite was not added to the copper sulfide ore. As in the example, column leaching was performed for 112 days and the same measurement was performed. As shown in FIG. 3, the cumulative copper leaching rate was higher than that of Example 1 until around 50 days, but after 60 days it was lower than that of Example 1, and the cumulative copper leaching rate for 112 days was only 77%. It was.

  Moreover, the oxidation-reduction potential (vs. standard hydrogen electrode) of the leachate on the 42nd day, the 56th day, and the 69th day, measured for the comparative example, is shown in FIG. On the 42nd day, the redox potential exceeded 700 mV in the range of height of 0.6 m or more, and was in the range of 650 to 700 mV in the range of 0.4 to 0.6 m. Furthermore, after the 56th day, it exceeded 650 mV in most height ranges, and exceeded 700 mV especially in the height range of 0.3 m or more. That is, in the latter half of the leaching period, the oxidation-reduction potential is in a range that is not suitable for the leaching of chalcopyrite, the leaching rate is lowered, and it can be said that the final leaching rate is not sufficient.

  As is clear from the above, the leaching method of copper sulfide ore containing chalcopyrite of the present invention is suitable as a leaching method of copper mineral used in the copper refining field. In particular, it is useful as a method for leaching copper at a high leaching rate stably over a long period of time from a hardly leachable copper ore whose main copper mineral is chalcopyrite.

DESCRIPTION OF SYMBOLS 1 Column leaching device 2 Column 3 Vinyl chloride pipe 4 Joint 5 Sampling port 6 Tape 7 Leaching tank 8 Pump 9 Pump 10 Discharge tank

Claims (3)

  When copper is leached from a copper sulfide ore containing chalcopyrite, with respect to the copper sulfide ore mixed with magnetite having a mass of 0.1 to 10 times the total mass of the copper mineral contained in the copper sulfide ore. As an leaching solution, an iron sulfate aqueous solution with an iron concentration adjusted to 1 to 20 g / L and a pH within a range of 1.0 to 2.0 is used, and the oxidation-reduction potential of the leaching solution during leaching is 600 versus a standard hydrogen electrode. A method of leaching copper from a copper sulfide ore containing chalcopyrite, characterized in that leaching is performed while maintaining a range of ˜700 mV.   The method of leaching copper from copper sulfide containing chalcopyrite according to claim 1, wherein the redox potential of the leachate is maintained in a range of 600 to 650 mV with a standard hydrogen electrode.   The method of leaching copper from a copper sulfide ore containing chalcopyrite according to claim 1, wherein the pH of the leachate is in the range of 1.5 to 2.0.

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