• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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  • 法律状态
  • 优先权
    • 专利摘要:
    To enhance the gold-leaching speed from gold ore containing pyrite without using highly toxic cyanide such as thiourea, thiosulfate, halogen gas, or the like, there is provided a method for leaching gold comprising: a pretreatment stage comprising a step 1 of preparing gold ore containing pyrite and a step 2 of subjecting the gold ore to oxidative roasting; and a step 3 of contacting the gold ore from the pretreatment stage with a gold leaching solution containing halide ions, in the presence of oxidant, to leach gold component contained in the ore, and thereafter separating the solution into the post gold-leaching solution and residue containing iron.
    公开号:AU2013204113A1
    申请号:U2013204113
    申请日:2013-04-10
    公开日:2014-08-21
    发明作者:Yuki Aoto；Kazuhiro Hatano；Takeshi Nakamura
    申请人:JX Nippon Mining and Metals Corp；
    IPC主号:C22B3-00
    专利说明:
    I SPECIFICATION [Title of the invention] Method for leaching gold from gold ore containing pyrite [0001] [Technical field] The present invention relates to a method for leaching gold from gold ore which contains pyrite. [Background of the invention] [0002] As a method for recovering gold from sulfide ore containing gold, a technique relying on the hydrometallurgical process is known. Traditionally, the leaching of gold from the sulfide ore into a solution has been conducted by using reagents such as cyanide, thiourea, thiosulfate, halogen gas or the like. Recently, a gold-leaching solution containing chloride ions, iron ions, copper ions and bromide ions has been proposed as a less toxic leaching solution as described in Japanese Patent Application Publication No. 2009-235525 (Patent document 1) and Japanese Patent Application Publication No. 2009-235519 (Patent document 2). [Prior art literatures] [0003] Patent document 1: Japanese Patent Application Publication No. 2009-235525 Patent document 2: Japanese Patent Application Publication No. 2009-235519 [Summary of the invention] [Problem to be solved by the invention] [0004] The methods disclosed in Japanese Patent Application Publication No. 2009-235525 (Patent document 1) and Japanese Patent Application Publication No. 2009-235519 (Patent document 2) facilitate leaching of gold 2 contained in copper sulfide ore without use of highly toxic cyanide, thiourea, thiosulfate, halogen gas, or the like, and, accordingly are highly practical for leaching the gold included in the copper sulfide ore. However, when this method is applied to the pyrite ore, the gold-leaching speed is not sufficient and there is still room for improvement. [0005] Under the situation, the present invention aims at enhancing the gold-leaching speed from gold ore containing pyrite without using these highly toxic cyanide, thiourea, thiosulfate, halogen gas, or the like. [Means for solving the problem] [0006] The present invention, in one aspect, provides a method for leaching gold comprising: a pretreatment stage comprising a step 1 of preparing gold ore containing pyrite and a step 2 of subjecting the gold ore to oxidative roasting; and a step 3 of contacting the gold ore from the pretreatment stage with a gold-leaching solution containing halide ions, while supplying an oxidant, to leach gold component contained in the ore, and thereafter separating the solution into post gold-leaching solution and residue containing iron. [0007] In one embodiment of the gold-leaching method according to the present invention, the gold-leaching solution contains chloride ions and bromide ions. [0008] In another embodiment of the gold-leaching method according to the present invention, the oxidative roasting in the step 2 is carried out under the condition of 400-650'C. [0009] In a further embodiment of the gold leaching method according to the present invention, the content of the pyrite in the gold ore is 5-80 mass%. [0010] In a further embodiment of the gold-leaching method according to the 3 present invention, the gold-leaching is performed while retaining pH of the gold-leaching solution at 2.0 or less. [Effect of the invention] [0011] By conducting the pretreatment according to the present invention on the gold ore containing the pyrite ore and then conducting the iron-leaching and gold-leaching with a specific leaching solution, a remarkably improved gold-leaching speed can be obtained while the generation of noxious sulfur oxide is suppressed. In addition, high separation efficiency of gold from iron can be attained. In other words, the present invention provides a highly practical gold-leaching process which excels in the safety and preservation of the environment. [Brief explanation of the drawings] [0012] Fig. 1 is a flow diagram according to the gold-leaching process of the present invention. Fig. 2 is a graph showing the relationship between the leaching time and pH and oxidation-reduction potential of the leaching solution in Example 1. Fig. 3 is a graph showing the relation between the leaching time and the concentration of Fe ions dissolved in the leaching solution in Example 1. Fig. 4 is a graph showing the relation between the leaching time and gold-leaching ratio in a test conducted in Example 1 and Comparative Example 1. [Mode of practicing the invention] [0013] The present invention will be explained in details in the following. [0014] 1. Pretreatment One embodiment of pretreatment of gold ore according to the present invention includes a step 1 of preparing gold ore containing pyrite and a 4 step 2 of oxidatively roasting the gold ore to pyrolyze the pyrite in the gold ore into iron oxide having an oxidation number of at least 3. [0015] (1) Step 1 In the step 1, gold ore containing pyrite is prepared. This is because the present invention aims at the enhancement of the leaching ratio of gold in the pyrite, which is refractory and low in the gold-leaching ratio. However, the other conditions, such as the concentration of gold in the ore, for example, are not questioned. The gold ore, which is the object of treatment, may be one having been subjected to conventional beneficiation such as floatation or gravity separation. It is also possible to grind the ore to smaller particle sizes so that the contact of gold-leaching solution with gold within the ore is facilitated. The gold concentration of the gold ore is typically in the order of 0.1-100 ppm by mass, and more typically in the order of 1-20 ppm by mass. [0016] Gold ore contains pyrite but may additionally contain chalcopyrite, galena, sphalerite, arsenopyrite, antimonite, pyrrhotite or the like. In a typical example of the present invention, gold ore containing at least 3 mass% of pyrite, more typically at least 30 mass% of pyrite is used. By using such gold ore, the effect of the pretreatment of the present invention is remarkably enhanced. There is no particular upper limit to the content of the pyrite in the gold ore and 100 mass% is allowable but typically the content is 80 mass% or less. [0017] (2) Step 2 In the step 2, the gold ore is oxidatively roasted. The oxidatively roasted gold ore has a remarkably enhanced solubility into the gold leaching solution. In the oxidative roasting step, the pyrite in the gold ore is preferably converted to iron oxide. Here, the iron oxide typically means Fe2O3 (hematite) having an oxidation number 3. The reaction can be expressed by the following equation.
    5 4FeS2+1 102->2Fe2O3+8SO2 When the oxidative roasting is not sufficient, the pyrite can be converted to iron oxide having oxidation number 2 (FeO) and iron (II) sulfide(FeS). In the conventional cyanide method, the gold leaching efficiency became very low because it was difficult to dissolve FeS. Even in such a case, if the gold-leaching solution is adopted as will be explained later, a sufficient gold leaching efficiency can be obtained. However, it should be noted that, in the present invention, the pyrite ore is converted to hematite ore and iron is dissolved while maintaining the oxidation number at 3, and accordingly it is preferable to carry out the oxidative roasting under sufficient oxygen supply so that the oxidation-reduction potential (ORP) of the leaching solution is not lowered and gold can be leached simultaneously with the dissolution of iron. By doing so, iron can be easily precipitated and removed as insoluble iron oxyiron hydroxide (goethite=FeO(OH)), and thus the separation of iron and gold is made easier in the next gold-leaching step. [0018] The oxidative roasting is preferably performed at a temperature of 400-6509C, more preferably 500-6309C, even more preferably 550-6209C, and most preferably about 6009C. Further, the mole fraction of oxygen in the reaction atmosphere is preferably at least 1/5 and use of the air is practical from the economic standpoint. [0019] Although there is no particular restriction to the type of the heating furnace for the oxidative roasting, a tubular furnace or a rotary kiln, for example, may be used. [0020] Since sulfur oxide generated by the oxidative roasting is contained in the exhaust gas, the sulfur oxide is desirably removed with a wet scrubber or the like. If the facility becomes large in scale, the exhausted sulfur oxide should preferably be recovered for reuse by installing a sulfuric acid production system.
    6 [0021] 2. Gold leaching step In one embodiment of the gold-leaching method according to the present invention, the step 3 of contacting the pretreated gold ore with an gold-leaching solution containing halide ions to leach gold component contained in the ore in the presence of oxidant and thereafter subjecting the resulting solution to a solid-liquid separation to obtain a post gold-leaching solution and residue. Since the iron has been converted by the pretreatment into iron oxide having oxidation number 3, the iron can be precipitated by adjusting the pH to at least 1.5 at the time of gold leaching, there is no necessity of removing the iron content during the steps before and after the gold leaching. Also, in the gold leaching method described in the Patent document 2 (Paragraph 0016 of Japanese Patent Public Disclosure No.2009 235519), the iron in the post leaching solution is removed by precipitating it as oxyiron hydroxide for reuse and the acid is regenerated and excess iron is removed. For this purpose it was necessary to air-oxidize the leached iron in the form of Fe 2 . Such treatment becomes unnecessary by performing the above-described pretreatment. [0022] The leaching of gold proceeds as follows. The dissolved gold reacts with halide ions, particularly chloride ions or bromide ions, to form a gold halide complex, particularly chloride complex or bromide complex of gold. Though chloride ions may be singly used as the halide ions in the gold leaching solution, the combined use of chloride and bromide ions allows formation of a complex at a lower oxidation-reduction potential, thereby enhancing the leaching efficiency of gold. Further, iron ions in the form of ferric ions formed under supply of oxidant, or ferric ions from the beginning, function to oxidize the gold. The gold-leaching solution preferably contains copper ions. Although the copper ions do not directly participate in the reaction, the oxidation of the iron ions is accelerated under the presence of the copper ions. [0023] 7 The method for contacting the gold-leaching solution with gold ore includes sprinkling method, immersion method or the like but there is no particular restriction. However, from the standpoint of the reaction efficiency, a method of immersing and agitating the residue in the leaching solution is preferred. [0024] As the source of chloride ions, although there is no particular restriction, hydrogen chloride, hydrochloric acid, metal chloride and chorine gas, etc. may be cited for instance. From the aspects of economy and safety, it is preferable to feed the ions as metal chloride salt. Cited as metal chloride salts are copper chloride (cuprous chloride, cupric chloride), iron chloride (ferrous chloride, ferric chloride), chloride of alkaline metal (lithium, sodium. potassium, rubidium, cesium, francium), chloride of alkaline earth metal (beryllium, magnesium, calcium, strontium, barium. radium) can be cited. Sodium chloride is preferred from the standpoints of the cost and easy availability. It is also preferable to use copper chloride and iron chloride because they are utilized also as sources of copper ions and iron ions. [0025] As the source of the bromide ions, although there is no particular restriction, hydrogen bromide, hydrobromic acid, metal bromide and bromine gas may be mentioned. As metal bromide, copper bromide (cuprous bromide and cupric bromide), iron bromide (ferrous bromide, ferric bromide), bromide of alkaline metal (lithium, sodium. potassium, rubidium, cesium and francium), bromide of alkaline earth metal (beryllium, magnesium, calcium, strontium, barium, radium), and from the economical standpoint and easy availability, sodium bromide is preferred. Also, copper bromide and iron bromide are preferred because they can be also used as sources of copper ions and iron ions. [0026] Copper ions and iron ions are usually supplied in the form of their salts, for example, halide salts. The copper ions are preferably supplied in 8 the form of copper chloride and/or copper bromide, and the iron ions are preferably supplied in the form of iron chloride and/or iron bromide, from the standpoint that they can be also used as sources of chloride ions and/or bromide ions. As the copper chloride and iron chloride, it is preferable to use cupric chloride (CuCl2) and ferric chloride (FeCl3), respectively, but cuprous chloride (CuCl) and ferrous chloride (FeCl2) may also be used without a significant disadvantage because they are respectively oxidized into cupric chloride (CuCl2) and ferric chloride (FeCl3) by supplying oxidant to the leaching solution. [0027] The concentration of the chloride ions in the gold-leaching solution used in the step 3 is preferably 30g/L-125g/L. The concentration of the bromide ions in the gold- leaching solution is preferably lg/L-100g/L from the standpoints of the reaction rate and the solubility, and more preferably 10g/L-40g/L from the economical standpoint. And, the total concentration of the chloride ions and bromide ions is preferably 120g/L-200g/L. Also, from the standpoint of gold-leaching efficiency, the weight ratio of the concentrations of bromide ions to chloride ions in the gold-leaching solution is preferably at least 1. [0028] The oxidation-reduction potential (vs. Ag/AgCl) of the leaching solution at the beginning of the step 3 is preferably at least 550mV, more preferably at least 600mV, from the standpoint of acceleration of the gold leaching. Also, in order to precipitate iron as oxyiron hydroxide (goethite), pH is preferably at least 1.5, but excessively high pH will also precipitate iron and copper that contribute to facilitation of leaching and accordingly the pH of the gold-leaching solution is preferably 2.5 or less, more preferably 1.8-2.0. The temperature of the gold-leaching solution is preferably at least 45'C and more preferably at least 60'C from the standpoint of acceleration of the gold-leaching. However, excessively high temperature will cause evaporation of the leaching solution or increase the costs for heating, and accordingly 95'C or less is preferable and 85'C or less 9 is more preferable. [0029] Accordingly, in a preferred embodiment of the present invention, a mixed solution containing at least one of hydrochloric acid and hydrobromic acid, at least one of the cupric chloride and cupric bromide, at least one of ferric chloride and ferric bromide, and at least one of sodium chloride and sodium bromide may be used as the gold-leaching solution in the step 3, on the condition that both of chloride ions and bromide ions are contained in the leaching solution. [0030] The gold-leaching step 3 is conducted while the oxidation-reduction potential is controlled by supplying an oxidant. If the oxidant is not supplied, the oxidation-reduction potential will be decreased and thus the leaching reaction will not proceed. Although there is no particular restriction to the oxidant, oxygen, air, chlorine, bromine and hydrogen peroxide or the like may be cited. An oxidant having excessively high oxidation-reduction potential is not necessary and the air is sufficient. The air is preferred from the standpoint of the cost and safety. [0031] After the gold-leaching step, the residue containing iron can be removed by solid-liquid separation, such as filtration, squeezing, decantation, centrifugal separation, or other publicly known methods. Although there is no particular restriction, filter press is preferred from the standpoints of easy operation and obtaining residue of low water content. Gold can be recovered from the resulting gold-leaching solution, utilizing, for example, adsorption on activated carbon, electrowinning, solvent extraction, reduction, cementation, ion-exchange or the like. [0032] Further, it is also an effective means to recover gold during the leaching reaction, whereby the concentration of gold in the leaching solution is lowered and as a result the leaching ratio of gold is enhanced. This can be performed, for example, by introducing activated carbon with or 10 without lead nitrate into the gold-leaching solution during the leaching reaction. [Examples] [0033] In the following, the present invention will be further specifically explained by way of working examples. It should be noted that the present invention is not restricted to the examples. The concentration of the metals used in the working examples was determined by the ICP-AES. However, the analysis of the gold used in the examples was conducted according to ICP-AES for quantitative analysis after causing deposition of gold in the specimens by cupellation process. <Example 1> [0034] Pyrite ore concentrate (produced in Papua New Guinea) was prepared. The content of pyrite in this pyrite ore concentrate was determined by XRD and chemical analysis, and 17 mass% of pyrite was confirmed. The pyrite ore (250g) was charged in a tubular furnace and heated up to 600'C for one hour (heating speed of 10 0 C/min) under supply of air at the rate of 2L/min and retained for one hour. After allowing it cool to the room temperature, the XRD analysis was performed. It was confirmed that the peak of FeS2, which had been originally present in the specimen, disappeared and the peak of iron oxide (Fe2O3) appeared. [0035] The leaching treatment was performed using a hydrochloric acidic gold-leaching solution having the composition as listed in Table 1, with pulp concentration of 100 g/L at a temperature of 85'C for 12 hours. Air was blown in (0.1 L/min per IL of the leaching solution) during the leaching operation with continuous agitation and the oxidation-reduction potential (ORP: vs. Ag/AgCl) was maintained at 550mV or higher. Also, during the leaching, the pH of the gold-leaching solution was maintained approximately at 1.5-2.0 by appropriately adding hydrochloric acid. The changes in the pH and the ORP of the gold-leaching solution with lapse of 11 leaching time are shown in Tables 2 and Fig. 2. [0036] [Table 1] Gold-leaching Solution FeCl3-6H20(g/L) 10 CuCl2-2H2O(g/L) 48 NaCl(g/L) 255 NaBr(g/L) 26 Total chloride ions(g/L) 180 Total bromide ions(g/L) 20 OPR(mV) 729 (vs Ag/AgCl) pH 1.64 [0037] [Table 2] Leach.Timep h pHmV BeforeCharge 0 1.64 729 AfterCharge 0 1.84 645 0.25 1.83 612 05 1 .83 597 1 1.90 592 2 1.93 588 3 1.94 589 4 1.95 593 5 1.94 594 6 1.90 595 7 1.96 605 8 1.93 604 9 1.94 603 10 1.93 604 11 1.91 607 12 1.86 610 12 [0038] During the leaching test, samples of the leaching residue were periodically taken and the concentrations of Au ions and Fe ions were measured. The relation between the leaching time versus the Fe concentration is shown in Fig. 3. Further, the relationship between the leaching time versus the leaching ratio of gold is shown in Fig. 4. The Au leaching ratio is defined by Au leaching ratio (%) = (1-residual Au gradex residual ratio/original Au grade) x 100. The iron oxide after roasting was quickly dissolved and precipitated as iron oxyhydroxide (geothite) because the pH was raised to 1.8 or more. Au was leached because the Au particles contained within the ore were exposed to the leaching solution with the progress of dissolution of the iron oxide. The residual ratio (%) is defined by Residual ratio (%) = (concentrate ore weight after leaching/ concentrate ore weight before leaching)x 100. [0039] During the leaching test, the leach residue was periodically sampled and the Au grade in the residue was determined. As a result, although the gold grade in the original ore was 6.0g/t, the grade decreased to 1.6g/t after 6 hours of leaching and 1.4g/t after 12 hours. [0040] <Comparative Example 1> The same pyrite ore (0.5kg) as that of Example 1 was prepared. Then, without oxidative roasting, the ore was subjected to leaching operation with the same gold-leaching solution as used in the Example 1 at 85'C for 12 hours. Air was blown in during the leaching treatment (0.1L/min per IL of the concentrate ore) with continual agitation, and the oxidation-reduction potential (ORP:vs Ag/AgCl) was maintained at 550mV or more. Also, during the leaching treatment, the pH of the gold-leaching solution was maintained at 550mV or more. During the leaching treatment, the pH was maintained at about 1.1 by appropriately adding hydrochloric acid. During the leaching operation, filtration was effected every 6 hours and the residue was treated with a fresh leaching solution.
    13 [0041] As a result, the gold grade in the original ore of 6.0g/t was lowered only to 4.6g/t after leaching period of 12 hours. The relation between the leaching time and the gold leaching ratio is depicted in Fig. 4.
    权利要求:
    Claims (5)
    [1] 1. A method for leaching gold comprising: a pretreatment stage comprising a step 1 of preparing gold ore containing pyrite and a step 2 of subjecting the gold ore to oxidative roasting; and a step 3 of contacting the gold ore from the pretreatment stage with a gold-leaching solution containing halide ions, while supplying an oxidant, to leach gold component contained in the ore, and thereafter separating the solution into the post gold-leaching solution and residue containing iron.
    [2] 2. The method for leaching gold according to claim 1, wherein the gold-leaching solution contains chloride ions and bromide ions.
    [3] 3. The method for leaching gold according to claim 1 or 2, wherein the oxidative roasting in the step 2 is carried out at 400-650'C.
    [4] 4. The method for leaching gold according to any one of claims 1 to 3, wherein the content of the pyrite in the gold ore is 5-80 mass%.
    [5] 5. The method for leaching gold according to any one of claims 1 to 4, wherein the gold-leaching is performed while the pH of the gold-leaching solution is maintained at 2.0 or less.
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    同族专利:
    公开号 | 公开日
    CL2015002159A1|2015-11-27|
    WO2014122803A1|2014-08-14|
    CA2897470C|2017-09-19|
    AU2013204113B2|2015-07-23|
    JPWO2014122803A1|2017-01-26|
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    引用文献:
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    US5364444A|1993-07-08|1994-11-15|North American Pallidium Ltd.|Metal leaching and recovery process|
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    法律状态:
    2015-11-19| FGA| Letters patent sealed or granted (standard patent)|
    2017-11-02| MK14| Patent ceased section 143(a) (annual fees not paid) or expired|
    2018-01-25| NA| Applications received for extensions of time, section 223|Free format text: AN APPLICATION TO EXTEND THE TIME FROM 10 APR 2017 TO 10 DEC 2017 IN WHICH TO PAY A RENEWAL FEE HAS BEEN FILED |
    2018-04-19| NB| Applications allowed - extensions of time section 223(2)|Free format text: THE TIME IN WHICH TO PAY A RENEWAL FEE HAS BEEN EXTENDED TO 10 DEC 2017 |
    优先权:
    申请号 | 申请日 | 专利标题
    JP2013-022683||2013-02-07||
    JP2013022683||2013-02-07||
    PCT/JP2013/060795|WO2014122803A1|2013-02-07|2013-04-10|Method for leaching gold from gold ore containing pyrite|
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