JP2014198886A - Recovery method of gold from gold ore containing iron pyrite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery method of gold from gold ore containing iron pyrite capable of improving leaching speed of gold while suppressing the generation of sulfur dioxide and increasing the adsorption amount of gold to active charcoal, without using toxic chemicals such as cyan, thiourea, thiosulfate and halogen gas.SOLUTION: There is provided a recovery method of gold from gold ore containing iron pyrite comprising a pre-treatment which includes a process 1 of preparing gold ore containing iron pyrite and a process 2 of heating the gold ore under an inactive atmosphere at 450°C or more and thermal decomposing the iron pyrite in the gold ore to iron sulfide (II) and elemental sulfur, but does not include an oxidation roasting process; a process 3 of contacting the gold ore after the pre-treatment process with a gold leaching solution containing chloride iron, bromide iron and iron ion under application of an oxidant and leaching a gold component in the ore; a process 4 of adding the oxidant after adding cuprous chloride to the liquid after leaching the gold component obtained in the process 3, then adjusting the oxidation reduction potential at 520 mV or more to reduce monovalent copper ion in the liquid after leaching gold; and a process 5 of adsorbing gold in the liquid after leaching gold obtained in the process 4 to active charcoal.

Description

  The present invention relates to a method for recovering 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 in sulfide minerals into solutions has been performed by using chemicals such as cyanide, thiourea, thiosulfuric acid, and halogen gas. Recently, a gold leaching solution using chloride ions, iron ions, copper ions, and bromide ions as described in JP-A-2009-235525 (Patent Document 1) is used as a less toxic leachant. It has also been proposed to do.

  Further, as a pretreatment for facilitating leaching of gold from sulfide minerals, a method of oxidizing and roasting sulfide minerals is known, and in recent years, a pretreatment combining oxidation roasting with other processes has also been proposed. . For example, in Japanese Patent Application Laid-Open No. 2010-235999 (Patent Document 2), copper sulfide mineral is leached at a temperature lower than the melting point of sulfur, and sulfur obtained as fine particles from the obtained leaching residue and remains without leaching. Sulfide particles are levitated by utilizing the difference in hydrophobicity from other iron oxides and gangue components, while iron oxide and gangue components are settled or separated as sedimentation to separate them in the leach residue. Concentrate the gold contained in the. After that, the concentrated gold-containing component is oxidized and roasted after removing sulfur to convert the iron component to iron oxide (hematite), and then dissolved using sulfuric acid to recover the gold-enriched residue. Is done.

JP 2009-235525 A JP 2010-235999 A

  Since the method described in JP2009-235525A (Patent Document 1) can easily leach gold without using chemicals such as highly toxic cyanide, thiourea, thiosulfuric acid, and halogen gas, Although it is extremely practical for gold leaching, when it is applied to pyrite, the gold leaching rate is not sufficient, and there remains room for improvement. Therefore, a method of increasing the gold leaching rate by performing pretreatment using oxidation roasting performed by supplying oxygen as described in JP 2010-235999 A (Patent Document 2) is also conceivable.

However, if the method of oxidizing and roasting sulfide minerals including the method described in Patent Document 2 is adopted, 2CuS + 2O ₂ → 2CuO + SO ₂ , 2CuFeS ₂ + 6O ₂ → CuO + 4SO ₂ + Fe ₂ O ₃ , and 4FeS ₂ + 11O ₂ → 2Fe _Since a chemical reaction such as ₂ O ₃ + 8SO ₂ occurs preferentially, the problem that sulfur dioxide (SO ₂ ) known as an environmental pollutant is generated is inevitable. Pretreatment to increase the gold leaching rate is reduced from the viewpoint of safety and environment, sulfur dioxide generated in the mineral treatment process for gold leaching is reduced, safety is increased, and the impact on the environment is low. It is desirable to make it.

  Further, when the pyrite is wet-treated, the accompanying gold is separated and concentrated in advance into a residue and then leached in a halogen bath, or leached in a halogen bath at the same time as the main component ore leaching. A gold complex having a halide as a ligand remains in the liquid. When the gold complex is adsorbed and recovered on activated carbon, the yield increases as the amount of adsorption increases. In particular, when the activated carbon is incinerated, the amount of adsorption per unit activated carbon weight directly affects the production cost and has a great effect. Therefore, development of a method for increasing the unit adsorption amount is desired. However, neither of Patent Documents 1 and 2 has been studied for improving the adsorptivity of gold to activated carbon. There is a problem such as contamination of the liquid after leaching, and an appropriate method is not known.

  The present invention has been made in view of the above circumstances, and in the method for recovering gold from gold ore containing pyrite, without using chemicals such as highly toxic cyanide, thiourea, thiosulfuric acid, halogen gas, and the like. Provides a method for recovering gold from gold ore containing pyrite, which can improve the rate of gold leaching while suppressing the generation of sulfur dioxide and increase the amount of gold adsorbed on activated carbon. To do.

  The present inventors have intensively studied to solve the above-mentioned problems, and after performing a pretreatment for pyrolysis to iron sulfide (II) in an inert atmosphere with respect to pyrite, chloride ions, bromide ions, and It has been found that when gold leaching is performed using a gold leaching solution containing trivalent iron ions, the gold leaching rate is dramatically improved while suppressing the generation of sulfur oxide. Furthermore, when the present inventors adsorbed and recovered the gold-leached solution obtained by gold leaching on activated carbon, the substance that becomes a competitive adsorbent to the activated carbon is a monovalent copper ion in the solution after gold leaching. As a result, it was found that the amount of gold adsorbed on the activated carbon can be significantly improved by performing a treatment for reducing the monovalent copper ions in advance before the gold activated carbon adsorption step. It was.

  The present invention has been completed on the basis of the above knowledge. In one aspect, Step 1 for preparing a gold ore containing pyrite and heating the gold ore to 450 ° C. or higher in an inert atmosphere, Including the step 2 of pyrolysis of pyrite of iron sulfide (II) and elemental sulfur, pretreatment without oxidation roasting, and gold ore after the pretreatment step, chloride ion, bromide ion, and iron ion After adding cuprous chloride to the gold component leaching solution obtained in step 3 and leaching the gold component in the ore by contacting the gold leaching solution containing Step 4 to reduce the monovalent copper ions in the solution after gold leaching by adjusting the redox potential to 520 mV or more by adding an oxidizing agent, and adsorbing the gold in the solution after gold leaching obtained in step 4 to the activated carbon From gold ore containing pyrite, including step 5 It is a method of recovery.

  In one embodiment of the method for recovering gold from gold ore containing pyrite according to the present invention, step 4 adjusts the redox potential (reference electrode, silver / silver chloride) to 520 mV to 570 mV.

  In one embodiment of the method for recovering gold from gold ore containing pyrite according to the present invention, step 4 adjusts the redox potential by blowing air.

  Gold ore containing pyrite is subjected to a pretreatment method according to the present invention and then gold leaching using a specific gold leaching solution, and monovalent copper ions, which are substances that inhibit adsorption to activated carbon, from the gold leaching solution. Contains pyrite, which can dramatically reduce gold leaching rate while suppressing the generation of harmful sulfur oxide and can increase the unit adsorption amount of gold A method for recovering gold from gold ore can be provided.

It is a graph which shows the relationship between leaching time and Au quality in a residue about an Example and a comparative example. It is a TG / DTA curve when the pyrite concentrate after the milling used in Example 1 is subjected to thermal analysis in a nitrogen atmosphere. It is a graph showing the relationship between the oxidation-reduction potential of the solution after gold leaching and the gold concentration in the solution after adsorption. It is a graph showing the relationship between the oxidation-reduction potential and the change in gold concentration when CuCl is added and air is blown when the leachate is continuously supplied to the activated carbon packed column.

  The present invention will be described in detail below.

1. Pretreatment step In one embodiment of the pretreatment method for gold ore according to the present invention, step 1 for preparing gold ore containing pyrite, and heating the gold ore to 450 ° C or higher under an inert atmosphere, Including pyrolysis of pyrite in gold ore into iron sulfide (II) and elemental sulfur, and no oxidation roasting process.

(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.

  Moreover, in this invention, it is one of the characteristics that an oxidation roasting process is not included. In the prior art, oxidation roasting was performed in the presence of oxygen or air, so sulfur in the sulfide mineral was combined with oxygen to produce sulfur oxide. In the present invention, such an oxidation roasting step is not performed.

(2) Step 2
In step 2, the gold ore is heated to 450 ° C. or higher under an inert atmosphere, and pyrite in the gold ore is thermally decomposed into iron sulfide (II) and elemental sulfur. The chemical reaction at this time is represented by the following formula: FeS ₂ → FeS + S. Theoretically there is no generation of sulfur oxide. The gold ore after undergoing the thermal decomposition has a marked improvement in solubility in the gold leachate described below. Compared to the case without thermal decomposition, the gold leaching rate can be increased by about 10 times. Since the pyrolysis method performed in the present invention did not change pyrite (FeS ₂ ) to hematite (Fe ₂ O ₃ ), the gold leaching rate seemed to be insufficient, and thus such a result was obtained. That was extremely surprising.

  Examples of the inert atmosphere when carrying out the thermal decomposition include a rare gas atmosphere such as argon and helium, and a nitrogen atmosphere. Or you may circulate and use the exhaust gas used for thermal decomposition. If oxygen is contained in the atmosphere, the gold ore is oxidized and roasted to generate sulfur dioxide, which is not adopted in the present invention because there is a concern about the influence on the environment.

  It is necessary to keep the temperature of the gold ore at 450 ° C. or higher during pyrolysis. This is because the pyrolysis of pyrite hardly proceeds at less than 450 ° C. Preferably, the thermal decomposition is preferably carried out while maintaining the temperature of the gold ore at 550 ° C. or higher, more preferably at 650 ° C. or higher. The thermal decomposition is preferably continued for 5 minutes or more, and more preferably for 30 minutes or more. This is because the thermal decomposition reaction proceeds sufficiently. However, if the temperature of the gold ore is excessively increased, the energy required for the temperature increase and the treatment time may be increased. Therefore, the holding temperature is preferably 800 ° C. or less, and more preferably 750 ° C. or less. Similarly, the time for maintaining the holding temperature is also preferably 120 minutes or less, and more preferably 60 minutes or less.

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

  Since elemental sulfur generated by pyrolysis is gasified in a high-temperature furnace, it can be separated from gold ore by solid-gas separation. Then, it can be sent to the exhaust system together with the atmospheric gas. However, when single sulfur is sent to the exhaust system, sulfur is deposited with a decrease in temperature to cause problems such as blockage of the gas passage. Therefore, it is desirable to recover with a wet scrubber or the like. Alternatively, the gasified elemental sulfur can be cooled together with the iron (II) sulfide generated in step 2 and recovered together in a solid state and sent together to the gold leaching step. In the gold leaching process, elemental sulfur is separated as a leaching residue without hindering gold leaching. In this case, a wet scrubber is unnecessary, which is economically advantageous.

2. Gold leaching process (1) Process 3
In one embodiment of the gold recovery method according to the present invention, the gold ore after the pretreatment step is brought into contact with a gold leaching solution containing chloride ions, bromide ions, and iron ions under supply of an oxidizing agent, Step 3 of leaching the gold component in the ore is performed.

  Gold leaching proceeds by the elution of gold reacting with chloride ions or bromide ions to form gold chloride complexes or gold bromide complexes. By using bromide ions in combination, a complex is formed at a lower potential, so that the gold leaching efficiency can be improved. 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. 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 method for contacting the leachate with 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 the residue in the leachate and stirring is preferred.

  The supply source of chloride ions is not particularly limited, and examples thereof include hydrogen chloride, hydrochloric acid, metal chloride, and chlorine gas. In consideration of economy and safety, supply in the form of metal chloride is preferable. . Examples of the metal chloride include copper chloride (cuprous chloride, cupric chloride), iron chloride (ferrous chloride, ferric chloride), and alkali metals (lithium, sodium, potassium, rubidium, cesium, francium). Chlorides and chlorides of alkaline earth metals (beryllium, magnesium, calcium, strontium, barium, radium) can be mentioned, and sodium chloride is preferable 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, but examples include hydrogen bromide, hydrobromic acid, metal bromide and bromine gas. In consideration of economy and safety, the form of metal bromide is used. It is preferable to supply. Examples of the metal bromide include copper bromide (cuprous bromide, cupric bromide), iron bromide (ferrous bromide, ferric bromide), alkali metals (lithium, sodium, potassium, Examples thereof include bromides of rubidium, cesium, and francium) and bromides of alkaline earth metals (beryllium, magnesium, calcium, strontium, barium, and radium), and sodium bromide is preferable 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 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. Copper chloride and iron chloride include cupric chloride (CuCl ₂ ), cuprous chloride (CuCl), and ferric chloride (FeCl ₃ ). Ferric chloride (FeCl ₂ ) or the like is used.

  The concentration of chloride ions in the gold leachate used in step 3 is more preferably 40 g / L to 200 g / L. The concentration of bromide ions in the gold leachate used in step 3 is preferably 20 g / L to 100 g / L from the viewpoint of reaction rate and solubility. The iron ions in the gold leachate are preferably 0.01 g / L to 10 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. Further, from the viewpoint of increasing the gold leaching rate, it is preferable to maintain the pH of the gold leaching solution at 2.0 or less. However, the higher the oxidation rate of iron, the higher the pH of the gold leaching solution. More preferably, it is maintained at 5 to 1.9. 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.

  In a preferred embodiment of the present invention, at least one of hydrochloric acid and bromic acid, and cupric chloride are selected on the condition that the gold leachate in step 3 is selected to contain both chloride ions and bromide ions. And at least one of 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.

(2) Step 4
The oxidation-reduction potential of the solution after gold leaching after sufficient gold leaching is about 500 to 520 mV. After the gold leaching, CuCl is further added and stirred, and once the oxidation-reduction potential is lowered to 520 mV or less, more preferably 500 mV or less, an oxidizing agent is added to again adjust the ORP to 520 mV or more. As a result, monovalent copper ions in the solution after gold leaching, which inhibits the adsorption of gold by activated carbon, are oxidized and reduced to divalent copper ions, and there are fewer adsorbing competitors on the activated carbon in the solution after gold leaching. Further, the adsorption rate of gold on activated carbon is further improved.

  The oxidizing agent is not particularly limited, but air is used from the viewpoint of cost. Also, the liquid temperature is not particularly limited, but considering the fact that gold leaching is warm leaching and the aspect of oxidation efficiency, the liquid temperature of the liquid after gold leaching is preferably maintained at 45 ° C. or more, more preferably It is 50 ° C. or higher.

  An increase in ORP indicates a decrease in monovalent copper ions in the solution after gold leaching. Monovalent copper is known as a very soft element, has a high affinity for activated carbon, and competes with the adsorption of gold complexes. By reducing the monovalent copper, the adsorption active sites in the activated carbon are increased in selectivity to gold, thereby achieving efficient recovery of gold.

  By adjusting the ORP to 520 mV or more, it is possible to reduce the monovalent copper concentration in the liquid and improve the adsorption rate of gold on activated carbon. Although there is no restriction | limiting in particular in an upper limit, when the time required for adjustment and the reduction efficiency of monovalent copper are considered, it is preferable to set it as 570 mV or less, More preferably, it is preferable to adjust to 530-560 mV.

3. Gold recovery (process 5)
After the gold leaching reaction, Step 5 of recovering gold by activated carbon adsorption is performed from a gold solution obtained by solid-liquid separation. The contact of gold with activated carbon may be carried out by batch feeding or by continuously passing an acidic leachate through an adsorption tower packed with activated carbon.

  In the case of a batch type, the stirring speed is not specified. The amount of activated carbon added is 50 to 10,000 times the weight of gold.

  In the continuous flow method, the flow rate is not particularly limited (generally, SV1 to 25), but when the gold adsorption amount per unit weight of the activated carbon reaches 20000 to 30000 g / t, the activated carbon does not satisfy the required capacity. . Therefore, gold strips from activated carbon and regeneration are performed based on this amount of adsorption. The method for regenerating activated carbon is carried out with a generally known sulfur compound, nitrogen compound, or acid, and is not particularly limited.

4). Others After performing step 2, it is possible to perform various treatments for removing impurities in the gold ore before performing step 3. For example, elemental sulfur can separate gold and elemental sulfur by heating the gold ore after pretreatment to a temperature sufficient for elemental sulfur to melt and separating it. Iron sulfide (FeS) is made by contacting pre-treated gold ore with various mineral acids such as sulfuric acid and hydrochloric acid, as well as with aqueous solutions of Fe ³⁺ salts such as iron sulfate and iron chloride. It can be removed by liquid separation.

  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.

<Comparative Example 1>
Pyrite concentrate (Papua New Guinea domestic reheel ore) was prepared. It was 17 mass% when content of the pyrite in this pyrite concentrate was calculated by XRD and chemical analysis. Pyrite concentrate (reheel ore) was pulverized and ground with a ball mill, and the particle size (d80) at which the cumulative weight was 80% in the cumulative weight particle size distribution curve was adjusted to 24 μm. d80 is an average value when measured three times with a laser diffraction particle size distribution measuring apparatus (model SALD2100 manufactured by Shimadzu Corporation). Next, the pyrite concentrate (200 g) after milling was subjected to a leaching treatment for 90 hours at a liquid temperature of 85 ° C. with a pulp concentration of 100 g / L using a hydrochloric acid acidic gold leachate having the composition shown in Table 1. It was. 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 500 mV. During the leaching, hydrochloric acid was appropriately added so that the pH of the gold leaching solution was maintained at 1.0 to 1.1.

During the leaching test, samples of the leaching residue were taken periodically, and the Au quality in the residue was measured. FIG. 1 shows the relationship between the leaching time and the Au quality in the residue obtained from the results of the test (see the plot “FeS ₂ no thermal decomposition” in FIG. 1). From this result, it can be seen that it takes 90 hours for the Au quality in the residue, which was initially about 6 g / t, to be reduced to 0.9 g / t.

<Example 1>
The same pyrite concentrate (1.5 kg) after milling as in Comparative Example 1 was charged into a tubular furnace and heated to 700 ° C. (temperature increase rate = 10 ° C./min) over 1 hour in a nitrogen atmosphere. Heated 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 FeS peak was generated. The elemental sulfur produced by the heat treatment was not particularly removed.
Subsequently, the pyrite concentrate after the heat treatment was subjected to a leaching treatment for 18 hours at a liquid temperature of 85 ° C. using a hydrochloric acid acidic gold leaching solution having the same composition as Comparative Example 1 to 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 400 mV or higher. During the leaching, hydrochloric acid was appropriately added so that the pH of the gold leaching solution was maintained at 1.0 to 1.1.

During the leaching test, samples of the leaching residue were taken periodically, and the Au quality in the residue was measured. FIG. 1 shows the relationship between the leaching time and the Au quality in the residue obtained from the results of the test (see the “FeS ₂ thermal decomposition” plot in FIG. 1). From this result, it can be seen that the Au quality in the residue, which was about 6 g / t at the beginning, decreased to 0.6 g / t in just 12 hours.

<Peak changes of FeS ₂ and FeS in XRD given by thermal decomposition conditions>
Diffraction intensity of FeS ₂ and FeS in XRD analysis when holding temperature and holding time are changed as shown in Table 1 for pyrite concentrate (1.5 kg) after milling used in Example 1 The change was investigated. The experiment was performed using a tubular furnace under a nitrogen atmosphere. Elemental sulfur produced by pyrolysis was evaporated and removed by a nitrogen stream. The heating rate was all 10 ° C./min. Cooling was allowed to cool to room temperature. For the XRD analysis, RIG2200 model RINT2200 ultimate was used. FeS ₂ has characteristic peaks at 2θ = 32.98 ° and 56.15 °, and FeS has characteristic peaks at 2θ = 43.67 ° and 33.78 °, so attention was paid to these incident angles. The results are shown in Table 2.

  From the results in Table 2, it can be seen that the pyrite-derived peak disappears reliably when heated to 600 ° C. or higher, which indicates that the crystalline pyrite was thermally decomposed, and the holding temperature and holding time were 650 ° C. and higher, respectively. When the condition is 60 minutes or longer, a clear FeS peak appears, which is most preferable.

<Example 2>
The pyrite concentrate after milling used in Example 1 was examined for weight change and endothermic-exothermic heat at each temperature by thermal analysis in a nitrogen atmosphere (model TG / DTA6300 manufactured by Seiko). The heating rate was 20 ° C. per minute. The results are shown in FIG. The decrease in mass begins at 450 ° C, and at the same time heat generation is seen, indicating that the decomposition of pyrite has started. In a nitrogen atmosphere, pyrolysis of pyrite will not occur unless the temperature is raised to at least 450 ° C. However, from the above-mentioned XRD analysis results, it is considered that the thermal decomposition takes a long time at around 450 ° C., and the heat treatment at 600 ° C. or higher is desirable.

<Example 3>
In a gold leaching solution obtained after the gold leaching step using a gold leaching solution containing 50 g / L chloride ion, 80 g / L bromide ion, 18 g / L copper, and 0.2 g / L iron. Leached gold. The solution after gold leaching contained NaCl: 84 g / L, NaBr: 103 g / L, Cu: 20 g / L, Fe: 2 g / L, Au: 8 mg / L, and pH was 1.2. CuCl was added to adjust the ORP to 510 mV. After leaching, the liquid was heated to 55 ° C. and stirred while blowing 0.4 L of air per minute. This gold leaching solution was passed through a glass column filled with approximately 14 ml of coconut shell-derived activated carbon (Yaikol MC manufactured by Taihei Chemical Sangyo Co., Ltd.) to adsorb gold onto the activated carbon. The column diameter was 11 mm and the height was 150 mm. The liquid supply rate was 11.9 ml / min, and the space velocity was 50 (1 / h). Gold in the discharged solution after adsorption was diluted with hydrochloric acid and quantified by ICP-AES. The relationship between the ORP and the post-adsorption liquid is shown in FIG.

  It can be seen that the gold concentration contained in the post-adsorption liquid is significantly reduced in the liquid in which the ORP is adjusted to 520 mV or more. Although the upper limit of ORP is not set, it is understood that even if the potential is raised excessively, the gold concentration in the solution after adsorption does not drop dramatically, and it is sufficient to oxidize to at least 520 mV, but it does not prevent excessive oxidation. .

<Example 4>
The gold concentration in the post-adsorption liquid was measured by changing the ORP by adding CuCl and blowing air while continuously feeding liquid after the gold leaching used in Example 3 and using the activated carbon packed column. The results are shown in FIG.

  The relationship between adsorption of ORP and gold on activated carbon is clear also from FIG. 2, and gold can be recovered satisfactorily when the solution after gold leaching is ORP 520 mV or higher and contacted with activated carbon. It can also be seen that it is Cu (I) that affects the ORP.

  Cu (I) tends to be oxidized to Cu (II) in an aqueous solution, but exists relatively stably in an aqueous solution containing a high-concentration halide as in this system. Therefore, in addition to air blowing, it is estimated that similar results can be obtained by oxidizing Cu (I) with an oxidizing agent such as hydrogen peroxide or hypochlorous acid. Is preferred.

Claims (3)

Step 1 for preparing gold ore containing pyrite and Step 2 for heating the gold ore to 450 ° C. or higher under an inert atmosphere and thermally decomposing the pyrite in the gold ore into iron (II) sulfide and elemental sulfur. Including pre-treatment that does not include oxidation roasting process;
In step 3 and step 3, the gold ore after the pretreatment step is brought into contact with a gold leaching solution containing chloride ions, bromide ions, and iron ions under supply of an oxidizing agent to leach gold components in the ore. Step 4 of adding cuprous chloride to the obtained gold component leaching solution and then adding an oxidizing agent to adjust the oxidation-reduction potential to 520 mV or more to reduce monovalent copper ions in the gold leaching solution; ,
A method for recovering gold from gold ore containing pyrite, which comprises adsorbing gold in the solution after gold leaching obtained in step 4 to activated carbon.   The method for recovering gold from gold ore containing pyrite according to claim 1, wherein step 4 includes adjusting the redox potential (reference electrode, silver / silver chloride) to 520 mV to 570 mV.   The method for recovering gold from gold ore containing pyrite according to claim 1 or 2, wherein step 4 includes adjusting the oxidation-reduction potential by blowing air.