JP6038192B2 - Method for leaching gold from gold ore containing pyrite - Google Patents

Description

  The present invention relates to a method for leaching gold from gold ore containing pyrite.

A technique using a wet method is known as a method for recovering gold from a sulfide mineral containing gold. Traditionally, leaching of gold sulfide minerals into solution, cyan, thiourea, has been carried out by the use of chemicals say Chio硫acid. Recently, as a less toxic leachant, chloride ions, iron ions, as described in JP2009-235525A (Patent Document 1) and JP2009-235519A (Patent Document 2), It has also been proposed to use a gold leaching solution utilizing copper ions and bromide ions.

JP 2009-235525 A JP 2009-235519 A

The method described in JP 2009-235525 (Patent Document 1) and JP 2009-235519 (Patent Document 2) is to use highly toxic cyanide, thiourea, the chemicals say Chio硫acid It is extremely practical for leaching gold in copper sulfide ore, but when this is applied to pyrite, the gold leaching rate is not sufficient, leaving room for improvement. Yes.

The present invention has been made in view of the above circumstances, the leaching method of gold from gold ore containing pyrite, highly toxic cyan, thiourea, without the use of chemicals say Chio硫acid, gold It is an object to improve the leaching rate of slag.

In one aspect of the present invention,
A pretreatment including a step 1 of preparing a gold ore containing pyrite and a step 2 of oxidizing and baking the gold ore;
The gold ore after the pretreatment is brought into contact with a gold leaching solution containing halide ions under supply of an oxidant to leach the gold component in the ore, and then the liquid after the gold leaching and a residue containing iron are solid-liquid. Separating step 3;
This is a gold leaching method.

  In one embodiment of the gold leaching method according to the present invention, the gold leaching solution contains chloride ions and bromide ions.

  In another embodiment of the gold leaching method according to the present invention, the oxidation roasting in step 2 is performed under conditions of 400 ° C to 650 ° C.

  In still another embodiment of the gold leaching method according to the present invention, the content of pyrite in the gold ore is 5 to 80% by mass.

  In still another embodiment of the gold leaching method according to the present invention, the gold leaching step is performed while maintaining the pH of the gold leaching solution at 2.0 or lower.

  After applying the pretreatment method according to the present invention to gold ore containing pyrite, leaching while suppressing the generation of harmful sulfur oxides by performing iron leaching and gold leaching using a specific leachate Improved gold leaching rate. Furthermore, high separation efficiency between gold and iron can be achieved. That is, according to the present invention, it is possible to provide a highly practical gold leaching method excellent in safety and environmental conservation.

It is an example of the processing flow according to the gold | metal leaching method which concerns on this invention. It is a graph which shows the relationship of pH of a leaching solution with respect to leaching time and oxidation-reduction potential about Example 1. FIG. It is a graph which shows the relationship between the leaching time and the concentration of Fe ions dissolved in the leachate for Example 1. It is a graph which shows the relationship between the leaching time and the gold leaching rate for Example 1 and Comparative Example 1.

  The present invention will be described in detail below.

1. Pretreatment In one embodiment of the pretreatment method for gold ore according to the present invention, step 1 for preparing gold ore containing pyrite, and oxidation and roasting of the gold ore to convert pyrite in the gold ore into iron And step 2 of changing to an iron oxide having an oxidation number of 3 or more.

(1) Step 1
In step 1, gold ore containing pyrite is prepared. This is because the purpose of the present invention is to increase the gold leaching rate in pyrite, which is hardly soluble and has a low gold leaching rate. However, other requirements such as the concentration of gold in the ore are not important. The gold ore to be treated in the present invention may be subjected to a conventional beneficiation process such as flotation or specific gravity sorting. Grinding can reduce the particle size of the ore so that the gold leachate can easily come into contact with the gold inside the ore. The gold concentration in the gold ore is typically about 0.1 to 100 ppm by mass, and more typically about 1 to 20 ppm by mass.

  In addition to containing pyrite, the gold ore may contain chalcopyrite, galena, sphalerite, arsenite, kyanite, pyrrhotite, etc., but in an exemplary embodiment of the present invention pyrite Is used, and in a more typical embodiment of the present invention, a gold ore containing 30% by mass or more of pyrite is used. By using such gold ore, the effect of the pretreatment according to the present invention is remarkably exhibited. The content of pyrite in the gold ore is not particularly limited, and may be 100% by mass, but typically 80% by mass or less.

(2) Step 2
In step 2, the gold ore is oxidized and roasted. Gold ore after undergoing oxidative roasting has significantly improved solubility in gold leachate. In oxidative roasting, pyrite in the gold ore is preferably converted to iron oxide. The iron oxide is typically Fe ₂ O ₃ (haematite) having an oxidation number of 3. The reaction formula at this time can be expressed by the following formula.
4FeS ₂ + 11O ₂ → 2Fe ₂ O ₃ + 8SO ₂
If oxidative roasting is incomplete, pyrite can be changed to iron oxide (FeO) or iron (II) sulfide (FeS) having an oxidation number of 2. Since it is difficult to dissolve FeS in the conventional cyan method, if the FeS is generated, the gold leaching efficiency is extremely deteriorated. However, by using the gold leaching solution described later, even in such a case, sufficient Gold leaching efficiency is obtained. However, in the present invention, pyrite is changed to hematite, and iron dissolves while its oxidation number is trivalent, so that the ORP of the leachate does not decrease, and gold can be leached simultaneously with iron dissolution. Oxidation roasting is preferably performed under supply of oxygen. This makes it easy to precipitate and remove iron as iron oxyhydroxide (goesite = FeO (OH)), which is hardly soluble in acid, and enables high efficiency separation of iron and gold in gold leaching in the next step. Because it becomes possible.

  The oxidative roasting is preferably performed at a temperature of 400 ° C. to 650 ° C., more preferably 500 to 630 ° C., still more preferably 550 ° C. to 620 ° C., and most preferably 600 ° C. The molar fraction of oxygen in the reaction atmosphere is preferably 1/5 or more, but it is practical to carry out under conditions using air from the viewpoint of economy.

  Although there is no restriction | limiting in particular in the kind of heating furnace for implementing oxidation roasting, For example, a tubular furnace and a rotary kiln can be used.

  Since sulfur oxides generated by oxidative roasting are contained in exhaust gas, it is desirable to recover them with a wet scrubber or the like. When the scale of the facility becomes large, it is preferable to effectively utilize the sulfur oxide discharged by installing a sulfuric acid production facility.

2. Gold leaching step In one embodiment of the gold leaching method according to the present invention, the gold ore after the pretreatment is brought into contact with a gold leaching solution containing halide ions under supply of an oxidizing agent, and the gold component in the ore Next, the step 3 of solid-liquid separation into liquid and residue after gold leaching is performed. Since the iron has been changed to iron oxide having an oxidation number of 3 by pretreatment, iron can be precipitated by setting the pH to 1.5 or more at the time of gold leaching. There is no need to leach and remove. Further, in the gold leaching method described in Patent Document 2 (described in paragraph 0016 of JP2009-235519A), in order to reuse the liquid after leaching, iron is precipitated as iron oxyhydroxide to regenerate the acid. Remove excess iron. Therefore, it is necessary to air-oxidize iron leached as Fe ²⁺ , but it becomes unnecessary by performing the pretreatment described above.

  Gold leaching proceeds by the elution of gold reacting with halide ions, particularly chloride ions or bromide ions, to form gold halide complexes, particularly gold chloride complexes or gold bromide complexes. Chloride ions alone may be used as halide ions in the gold leaching solution. By using chloride ions and bromide ions in combination, a complex is formed at a lower potential, thereby improving gold leaching efficiency. be able to. Further, the iron ions function to oxidize gold by trivalent iron ions oxidized under the supply of an oxidizing agent or trivalent iron ions from the beginning. Therefore, the gold leaching solution preferably contains trivalent iron ions from the beginning. The gold leachate preferably contains copper ions. This is because copper ions are not directly involved in the reaction, but the presence of copper ions increases the oxidation rate of iron ions.

  The contact method between the gold leachate and the gold ore is not particularly limited, and there are methods such as spreading and dipping. From the viewpoint of reaction efficiency, a method of dipping and stirring the residue in the leachate is preferable.

  There are no particular restrictions on the source of chloride ions, but examples include hydrogen chloride, hydrochloric acid, metal chloride, and chlorine gas. In consideration of economy and safety, the supply source is chloride metal salt. preferable. Examples of metal chloride salts include copper chloride (cuprous chloride, cupric chloride), iron chloride (ferrous chloride, ferric chloride), and alkali metals (lithium, sodium, potassium, rubidium, cesium, francium). And chlorides of alkaline earth metals (beryllium, magnesium, calcium, strontium, barium, radium), and sodium chloride is preferred from the viewpoint of economy and availability. Moreover, since it can utilize also as a supply source of copper ion and iron ion, it is also preferable to utilize copper chloride and iron chloride.

  The source of bromide ions is not particularly limited, and examples thereof include hydrogen bromide, hydrobromic acid, metal bromide, bromine gas, and the like. In consideration of economy and safety, the form of metal bromide salt It is preferable to supply by. Examples of metal bromide salts include copper bromide (cuprous bromide, cupric bromide), iron bromide (ferrous bromide, ferric bromide), and alkali metals (lithium, sodium, potassium). , Rubidium, cesium, francium) and alkaline earth metal (beryllium, magnesium, calcium, strontium, barium, radium) bromides, and sodium bromide is preferred from the viewpoints of economy and availability. Moreover, since it can utilize also as a supply source of copper ion and iron ion, it is also preferable to utilize copper bromide and iron bromide.

Copper ions and iron ions are usually supplied in the form of these salts. For example, they can be supplied in the form of halide salts. From the viewpoint that it can also be used as a source of chloride ions and / or bromide ions, copper ions are preferably supplied as copper chloride and / or copper bromide, and iron ions are preferably supplied as iron chloride and / or iron bromide. As copper chloride and iron chloride, it is preferable to use cupric chloride (CuCl ₂ ) and ferric chloride (FeCl ₃ ) from the viewpoint of oxidizing power, respectively, but cuprous chloride (CuCl) and ferric chloride are preferable. Even if (FeCl ₂ ) is used, supplying an oxidizing agent to the leachate will oxidize to cupric chloride (CuCl ₂ ) and ferric chloride (FeCl ₃ ), respectively, so there is no significant difference.

  The concentration of chloride ions in the gold leachate used in step 3 is more preferably 30 g / L to 125 g / L. The concentration of bromide ions in the gold leachate used in step 3 is preferably 1 g / L to 100 g / L from the viewpoint of reaction rate and solubility, and 10 g / L to 40 g / L from the viewpoint of economy. More preferably. The total concentration of chloride ions and bromide ions in the gold leaching solution is preferably 120 g / L to 200 g / L. From the viewpoint of gold leaching efficiency, the weight concentration ratio of bromide ions to chloride ions in the gold leaching solution is preferably 1 or more.

  The oxidation-reduction potential (vs Ag / AgCl) of the leaching solution at the start of step 3 is preferably 550 mV or more, more preferably 600 mV or more from the viewpoint of promoting gold leaching. Moreover, in order to precipitate iron as oxyhydroxide (goethite), the pH is preferably 1.5 or more. However, if the pH is too high, iron and copper that promote leaching are precipitated, and thus the pH of the gold leaching solution is 2. 5 or less is preferable and 1.8 to 2.0 is more preferable. The temperature of the gold leachate is preferably 45 ° C. or higher from the viewpoint of increasing the gold leach rate, and more preferably 60 ° C. or higher. However, if it is too high, the leachate will evaporate and the heating cost will increase. It is preferable to set it as follows, and it is more preferable to set it as 85 degrees C or less.

  Accordingly, in a preferred embodiment of the present invention, at least one of hydrochloric acid and bromic acid, and chloride chloride are selected on the condition that the gold leachate in step 3 is selected to contain both chloride ions and bromide ions. A mixed liquid containing at least one of dicopper and cupric bromide, at least one of ferric chloride and ferric bromide, and at least one of sodium chloride and sodium bromide can be used.

  The gold leaching step of step 3 is performed while supplying an oxidizing agent, thereby managing the oxidation-reduction potential. If an oxidizing agent is not added, the redox potential is lowered in the middle, and the leaching reaction does not proceed. Although there is no restriction | limiting in particular as an oxidizing agent, For example, oxygen, air, chlorine, a bromine, hydrogen peroxide, etc. are mentioned. An oxidant with an extremely high redox potential is not necessary and air is sufficient. Air is also preferable from the viewpoint of economy and safety.

  After the gold leaching reaction, the residue containing iron can be removed by solid-liquid separation. Examples of the solid-liquid separation method include known methods such as filtration, squeezing, decanting, and centrifugation, and are not particularly limited, but a filter press that is easy to operate and can be made into a low water content residue is preferable. Gold can be recovered from the resulting gold solution. Although there is no restriction | limiting in particular as a collection | recovery method of gold | metal | money, Activated carbon adsorption | suction, electrowinning, solvent extraction, reduction | restoration, cementation, ion exchange, etc. can be utilized.

  It is also an effective technique to increase the gold leaching rate by reducing the gold concentration in the leaching reaction solution by collecting gold during the leaching reaction. This can be done, for example, by introducing activated carbon or activated carbon and lead nitrate into the gold leaching solution during the leaching reaction.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these. In addition, the analysis method of the metal used in the Example was performed by ICP-AES. However, in the analysis of gold, gold in the sample was deposited by the ash blowing method, and then quantitative analysis was performed by ICP-AES.

<Example 1>
Pyrite concentrate (Papua New Guinea domestic) was prepared. It was 17 mass% when content of the pyrite in this pyrite concentrate was calculated by XRD and chemical analysis. Pyrite concentrate (250 g) was charged into a tubular furnace, heated to 600 ° C. over 1 hour under a 2 L / min air supply (temperature increase rate = 10 ° C./min), and held for 1 hour. After cooling to room temperature, the XRD analysis before and after the heat treatment confirmed that the FeS ₂ peak contained in the original ore disappeared and the iron oxide (Fe ₂ O ₃ ) peak was generated.

  Next, a leaching treatment was carried out at a liquid temperature of 85 ° C. for 12 hours using a hydrochloric acid acidic gold leachate having the composition shown in Table 1 at a pulp concentration of 100 g / L. During the leaching process, air blowing (0.1 L / min with respect to 1 L of concentrate) and stirring were continued, and the oxidation-reduction potential (ORP: vs Ag / AgCl) was maintained at 550 mV or higher. During the leaching, hydrochloric acid was appropriately added so that the pH of the gold leaching solution was maintained at 2.0 or lower and 1.5 or higher. Changes in pH and ORP of the gold leaching solution as the leaching time elapses are shown in Table 2 and FIG.

During the leaching test, samples of the leaching solution were taken periodically, and the concentrations of Au ions and Fe ions dissolved in the leaching solution were measured. FIG. 3 shows the relationship between the leaching time and the Fe concentration in the leachate obtained from the results of the test. FIG. 4 shows the relationship between the leaching time and the gold leaching rate. The leaching rate of Au was calculated by a formula of (1−residual Au grade × residue rate / original ore Au grade) × 100.
The iron oxide after roasting dissolved immediately and at the same time the pH rose to 1.8 or more, so iron precipitated as iron oxyhydroxide (goethite). Au was leached because the Au particles contained in the ore were exposed to the leachate as the iron oxide was dissolved. The residue rate is defined as residue rate (%) = weight after leaching / weight before leaching × 100.

  In addition, during the leaching test, samples of leaching residue were periodically collected, and the Au quality in the residue was measured. As a result, although the gold grade in the original ore was 6.0 g / t, it decreased to 1.6 g / t after 6 hours of leaching, and 1.4 g / t after 12 hours. It dropped to t.

<Comparative Example 1>
The same pyrite concentrate (0.5 kg) as in Example 1 was prepared. Next, without oxidative roasting, the same gold leachate as in Example 1 was used to obtain a pulp concentration of 100 g / L, and a leaching treatment was performed for 12 hours at a liquid temperature of 85 ° C. During the leaching process, air blowing (0.1 L / min with respect to 1 L of concentrate) and stirring were continued, and the oxidation-reduction potential (ORP: vs Ag / AgCl) was maintained at 550 mV or higher. During the leaching, hydrochloric acid was appropriately added so that the pH of the gold leaching solution was maintained at about 1.1. During the leaching process, filtration was performed every 6 hours, and the residue was treated in fresh leaching solution.

  As a result, although the gold quality in the original ore was 6.0 g / t, it decreased only to 4.6 g / t even after 12 hours had passed. As in Example 1, the relationship between the leaching time and the gold leaching rate is shown in FIG.

Claims (6)

A pretreatment including a step 1 of preparing a gold ore containing pyrite and a step 2 of oxidizing and roasting the gold ore under conditions of a temperature of 550 to 650 ° C ;
Gold ore after pretreatment, by contacting a feed of an oxidizing agent to the gold leaching solution containing halide ions, leach gold component of the gold in the ore, then the solid residue containing liquid iron after the gold leaching Step 3 for liquid separation;
Including gold leaching method.   The gold leaching method according to claim 1, wherein the gold leaching solution contains chloride ions and bromide ions. 3. The gold leaching method according to claim 1 or 2, wherein the oxidation roasting in step 2 changes pyrite in the gold ore into iron oxide .   The gold leaching method according to any one of claims 1 to 3, wherein a content of pyrite in the gold ore is 5 to 80% by mass.   The gold leaching method according to any one of claims 1 to 4, wherein the gold leaching step is performed while maintaining the pH of the gold leaching solution at 2.0 or less. In step 3, the gold ore after the pretreatment is brought into contact with a gold leaching solution containing halide ions and having a pH of 1.5 to 2.5 under supply of an oxidizing agent to oxidize the gold ore. The gold leaching according to any one of claims 1 to 4, wherein the iron is dissolved and precipitated as an iron oxyhydroxide, and the gold component is leached and then separated into a liquid and a residue after gold leaching. Method.

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