Method for extracting gold from refractory iron-sulfur-gold concentrate by wet process

Abstract

The invention belongs to the technical field of metallurgy, and particularly discloses a method for extracting gold from refractory iron-sulfur-gold concentrate by a wet process, which comprises the following steps: smelting the refractory iron-sulfur-gold concentrate by a pyrogenic process to obtain iron matte slag rich in gold and silver; the method comprises the following steps: crushing, ball-milling and slurrying the iron matte slag, introducing rich oxygen, carrying out pressure leaching under an acidic condition, and carrying out liquid-solid separation to obtain oxygen pressure leaching liquid and oxygen pressure leaching slag; cooling and crystallizing the oxygen pressure leachate to recover ferrous sulfate heptahydrate, and periodically vulcanizing, precipitating and recovering other valuable metals through crystallization mother liquor; sulfur, sulfur concentrate slag and gold and silver slag are separated from oxygen pressure leaching slag through conventional flotation, the sulfur concentrate slag is returned to the pyrogenic smelting process, and gold and silver products can be obtained by dissolving the gold and silver slag through aqua regia and selective reduction.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for hydrometallurgical extraction of gold from refractory iron-sulfur gold concentrate. Background Technology

[0002] With the large-scale development of the gold industry, the reserves of high-quality gold ore have been continuously decreasing during mining. Low-grade gold ore resources that are difficult to process have gradually become the core direction of resource development and technological research in the industry. Among them, encapsulated gold ore, as the mainstream type of difficult-to-process gold ore, has gold elements that are mostly tightly encapsulated by sulfide minerals in a fine disseminated form, directly resulting in a low gold recovery rate in cyanide leaching processes. In addition, this type of ore is often associated with elements such as copper, iron, sulfur, and arsenic, which have been treated as waste and pollute the environment in traditional processes. How to comprehensively develop and utilize these elements has always been a key problem restricting the efficient development of the industry.

[0003] Current pretreatment technologies for refractory gold ores include pyrometallurgical treatment, microbial oxidation, atmospheric chemical oxidation, electrochemical oxidation, and ultrafine grinding. The core of all these technologies is to disrupt the mineral encapsulation structure, exposing gold and silver and thus improving the leaching rate in subsequent processes. However, existing pretreatment technologies all have significant limitations: atmospheric chemical oxidation and microbial oxidation require strict control of process conditions, and their slow reaction rates make them unsuitable for large-scale industrial production; electrochemical oxidation technology is currently mainly at the laboratory research level and has not yet achieved practical industrial application; ultrafine grinding technology has excessively high energy consumption. While pyrometallurgical treatment has advantages such as high process maturity and large single-pass capacity, gold and silver inevitably undergo secondary encapsulation. Especially when the iron content is high, this secondary encapsulation significantly hinders subsequent gold extraction processes, greatly reducing the leaching rate.

[0004] After pretreatment, refractory gold ores are typically leached using reagents such as sodium cyanide, thiosulfate, and thiourea. While cyanide leaching remains the mainstream gold extraction process, the highly toxic nature of cyanide makes it unsuitable for increasingly stringent environmental policies and fails to meet the industry's green development needs. Meanwhile, thiourea and thiosulfate leaching technologies generally suffer from high raw material and reagent consumption.

[0005] Based on the aforementioned industry pain points, this invention proposes a method for the comprehensive recovery of metals from refractory iron-sulfur-gold concentrates, aiming to improve the recovery rate of gold and silver in refractory minerals, realize comprehensive resource utilization, and enhance the economic and social benefits of enterprises. Summary of the Invention

[0006] In view of the above-mentioned problems, the present invention provides a method for hydrometallurgical extraction of gold from refractory iron-sulfur gold concentrate. This invention can both break the inclusions of iron-sulfur minerals to improve the leaching rate and ensure the comprehensive recovery of valuable metals.

[0007] To address the aforementioned problems, this invention provides a method for hydrometallurgical gold extraction from refractory iron-sulfur gold concentrate, comprising the following steps:

[0008] S1. A refractory iron-sulfur-gold concentrate is pyrometallurgically smelted to obtain iron matte slag; wherein the iron grade of the iron matte slag is higher than 60%;

[0009] S2. After wet grinding and pulping, the iron matte slag is added to granulated iron matte slag, followed by the addition of SO4-containing... 2- The acidic solution was diluted to a pH of 0.5-1.5 and then subjected to oxygen pressure acid leaching and filtration to obtain leachate A and leaching residue A.

[0010] S3. The leachate A is cooled and crystallized to obtain an upper crystallization mother liquor and a lower crystal slurry; the upper crystallization mother liquor is reused and, after multiple cycles, sodium sulfide is added for reaction and then filtered to obtain leachate B and leachate residue B; the lower crystal slurry is centrifuged to obtain ferrous sulfate heptahydrate crystals.

[0011] S4. The leaching residue A is separated by flotation to obtain sulfur, gold and silver residue and tailings; the gold and silver residue is leached with aqua regia and filtered to obtain leaching solution C and leaching residue C; sodium sulfite is added to the leaching residue C and then filtered to obtain leaching solution D and leaching residue D; the tailings are returned to the pyrometallurgical smelting process.

[0012] This invention involves pyrometallurgically smelting refractory iron-sulfur-gold concentrate to obtain gold and silver-enriched iron matte slag (iron grade higher than 60%). The iron matte slag is then crushed, ball-milled, and slurried. Under acidic conditions and oxygen-enriched conditions, pressure leaching is performed, resulting in liquid-solid separation to obtain an oxygen-pressure leaching solution (iron leaching rate not less than 90%) and oxygen-pressure leaching residue (sulfur conversion rate not less than 80%). The oxygen-pressure leaching solution is cooled and crystallized to recover ferrous sulfate heptahydrate. Other valuable metals are recovered through periodic sulfidation precipitation of the crystallization mother liquor. The oxygen-pressure leaching residue contains a large amount of converted sulfur, which can be separated from the sulfur, sulfur concentrate slag, and gold and silver slag using conventional flotation. The sulfur concentrate slag can be returned to the pyrometallurgical process to increase the recovery rate of valuable metals and sulfur. The gold and silver slag, now free of sulfides, can be dissolved in aqua regia and selectively reduced to obtain gold and silver products. The overall gold and silver recovery rate is not less than 98%.

[0013] It should be noted that the SO4 added in the oxygen pressure acid leaching of this invention 2- The purpose of using an acidic solution is not only to add acid for leaching, but also to prevent the introduction of impurity negative ions. If a zinc smelter is using it to treat gold-containing slag, waste electrolyte can also be used. If there is not much sulfuric acid solution in the system, sulfuric acid can be added directly.

[0014] It should be noted that the granulated iron matte slag of this invention is used as a reducing agent, and granulating the iron matte slag increases the contact area between the reducing agent and the slurry.

[0015] It should be noted that adding SO4 2- The acidic solution or strongly acidic environment with a pH of 0.5-1.5 is used to break the outer coating of the iron matte and release the precious metals inside.

[0016] It should be noted that any pyrometallurgical process that can transform refractory iron-sulfur-gold concentrate into iron matte slag with an iron grade higher than 60% falls within the scope of protection of this invention.

[0017] For example, in step S1, anthracite and limestone are added during the pyrometallurgical process; the temperature of the pyrometallurgical process is 1200-1400℃, and the time is 2-3 hours.

[0018] Preferably, in step S2, the mass concentration of the slurry is 20%, and the amount of granulated iron matte slag added is 0.3-0.5% of the mass of the iron matte slag in the slurry.

[0019] Preferably, in step S2, the oxygen volume percentage concentration in the oxygen pressure acid leaching vessel is 99.5%, the pressure inside the vessel is 0.5-1.5 MPa, the temperature is 100-200℃, the time is 1-2 h, and the stirring rate is 300-500 r / min.

[0020] Preferably, in step S2, the filter can be a thickener or a pressure filter.

[0021] Preferably, in step S3, the molar amount of sodium sulfide is 1.2-1.5 times the molar amount of Cu in the leachate A, the reaction temperature is 55-65℃, and the reaction time is 1-3h.

[0022] Preferably, in step S4, the roughing, cleaning, and scavenging are two-stage roughing, two-stage cleaning, and two-stage scavenging; the gold and silver residue is leached with aqua regia until the solid content is 15-25 wt%.

[0023] Preferably, in step S4, the temperature for leaching aqua regia is 55-65℃, the time is 5-7h, and the stirring rate is 100-200r / min.

[0024] Preferably, in step S4, the molar amount of sodium sulfite is 1.1-1.3 times the molar amount of Au in the leachate C.

[0025] Preferably, in step S4, the reaction temperature is 75-85℃, the time is 5-7h, and the stirring rate is 100-200r / min.

[0026] The principle of this invention:

[0027] (1) Principle of oxygen pressure acid leaching of iron matte slag: Under oxygen pressure conditions, the gold-containing iron matte slag is leached with concentrated sulfuric acid to generate sulfate and elemental sulfur. The reaction formula is shown in (1)-(2). The granulated iron matte slag (mainly FeS) reduces the ferric sulfate generated in formula (2) to ferrous sulfate. The reaction is shown in formula (3), thereby achieving the purpose of iron matte leaching and iron reduction.

[0028] (1)

[0029] (2)

[0030] (3)

[0031] As can be seen from equation (3), granulated iron slag acts as a reducing agent to convert sulfur (ferric sulfate) into elemental sulfur, which is beneficial for the subsequent recovery of sulfur elements and does not affect the acid balance of the system.

[0032] It should be noted that FeSO4 in equation (2) is generated by equation (1). Although the most suitable conditions can be found by adjusting the amount of oxygen to avoid the oxidation of ferrous iron to ferric iron, it is basically impossible to precisely control the generation of FeSO4.

[0033] (2) The principle of leaching gold and silver residue with aqua regia: Gold has a high standard electrode potential and cannot be dissolved by nitric acid alone, but Cl- in aqua regia can react with Au. 3+ A stable complex is formed, as shown in equation (4), which significantly reduces the dissolution potential of gold. Gold is then reduced from the acidic solution using sodium sulfite as a reducing agent, as shown in equation (5).

[0034] (4)

[0035] (5)

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) Short process flow: In the process of smelting iron-sulfur gold concentrate, iron and sulfur have a good capturing effect on gold and silver, forming gold-silver iron matte (slag); during the oxygen pressure acid leaching process of iron matte (slag), iron, copper, arsenic, nickel and other materials are leached, separated and recovered, and sulfur is recovered by sulfur flotation. Iron and sulfur account for more than 60% of the gold-silver iron matte. Therefore, the subsequent gold and silver extraction only requires processing a small amount of material, and the processing scale is greatly reduced.

[0038] (2) Strong process adaptability: This invention is a wet enhanced leaching process, which can process a wide range of raw materials and has low requirements for gold and silver grades. The oxygen pressure leaching process opens the sulfide enclosure, which can not only efficiently separate various impurity elements and enhance subsequent gold extraction, but also realize the comprehensive utilization of iron and sulfur. Therefore, it can be used in conjunction with various mature gold concentrate pretreatment processes in the industry, or it can be used alone to process gold and silver-containing materials or smelting slag.

[0039] (3) Resource conservation: In the process of this invention, sulfur is converted into sulfur, iron is converted into ferrous sulfate heptahydrate crystals, and other valuable metals are also enriched and utilized through sulfide precipitation, which has a higher value than smelting slag and reduces the treatment cost of hazardous waste residue. The entire process produces no waste liquid or waste gas. Moreover, no acid or alkali needs to be added during oxygen pressure leaching, which reduces the process cost.

[0040] (4) High gold and silver recovery rate: During the oxygen pressure leaching process, gold and silver, as stable metals, remain in the slag. The losses during the flotation process are also returned to the production system through pyrometallurgical pretreatment. The direct recovery rate of gold and silver reaches more than 96%, and the comprehensive recovery rate of gold and silver in the process of this invention reaches more than 98%.

[0041] (5) High degree of automation: The process of this invention can be realized using mature smelting equipment. The main oxygen pressure leaching kettle can be monitored and intelligently controlled through automated instruments and DCS system. The other equipment is conventional smelting equipment, which has been automated in the industry. Attached Figure Description

[0042] Figure 1 This is a process flow diagram of a method for hydrometallurgical gold extraction from refractory iron-sulfur-gold concentrate as described in Embodiment 1 of the present invention. Detailed Implementation

[0043] To make the present invention easier to understand, specific embodiments are described below to further illustrate the invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art; unless otherwise specified, the raw materials and reagents involved herein can be purchased commercially or obtained by known methods.

[0044] To address the problems mentioned in the background section, this invention provides a method for hydrometallurgical gold extraction from refractory iron-sulfur gold concentrate. This invention can both break the inclusions of iron-sulfur minerals to improve leaching rates and ensure the comprehensive recovery of valuable metals.

[0045] The following examples and comparative models further illustrate this point.

[0046] Example 1

[0047] A process for hydrometallurgical gold extraction from refractory iron-sulfur gold concentrate, the flowchart of which is shown below. Figure 1 As shown, it includes the following steps:

[0048] (1) Pyrometallurgical smelting: Gold concentrate containing 24.73% sulfur, 19.8 g / t gold, 6.9 g / t silver, and 0.18% copper + antimony + nickel is mixed with anthracite (added at 16 wt% of the gold concentrate mass) and limestone (added at 14 wt% of the gold concentrate mass), and melted in a furnace (temperature 1200-1400℃, time 2-3h) and undergoes a strong physicochemical reaction to obtain iron matte slag containing 65.51% iron, 27.86% sulfur, 0.015% gold, and 0.006% silver. The main elemental composition is shown in Table 1 below:

[0049]

[0050] (2) Oxygen pressure leaching: The above-mentioned iron matte slag is crushed and wet-milled, slurried with water to a solid content of 20 wt%, and sent to an oxygen pressure acid leaching kettle for high-temperature and high-pressure leaching. Granulated iron matte slag is then added (the amount added is 0.5 wt% of the mass of iron matte slag in the slurry). Figure 1 The pH was adjusted to 1 using concentrated sulfuric acid (not shown). During the leaching process, stirring was initiated at 300 rpm, the leaching temperature was 140°C, oxygen was introduced to maintain the pressure inside the vessel (1.0 MPa), and the leaching time was 2 hours. After leaching, hot filtration was performed to obtain leachate A (oxygen-pressure leaching solution) and leaching residue A (oxygen-pressure leaching residue). Analysis showed that leachate A (oxygen-pressure leaching solution) contained 300 g / L iron, 0.76 g / L zinc, 0.32 g / L copper, and 0.3 g / L nickel, with an iron leaching rate of 98%. Leaching residue A contained >50% sulfur (with a sulfuric acid conversion rate of approximately 70%).

[0051] (3) Iron and sulfur recovery: The leachate A (oxygen pressure leachate) obtained in step (2) is sent to a two-stage crystallization tank and gradually cooled to 20°C for cooling crystallization. The crystallization cycle is 8 hours. The crystal slurry accumulated at the bottom of the crystallization tank is sent to a centrifuge through the bottom discharge valve and centrifuged to obtain ferrous sulfate heptahydrate crystals. The upper crystallization mother liquor is reused and sent to the sedimentation tank after five cycles. According to the molar amount of copper in leachate A, 1.5 times the molar amount of sodium sulfide is added. The reaction temperature is 60°C, the reaction time is 2 hours, and the stirring intensity is 150 r / min. After the reaction is completed, the mixture is filtered to obtain leachate B (for water treatment) and leaching residue B (for sale). The leaching residue B is tested and analyzed. It is mainly copper sulfide slag containing 15% copper.

[0052] Leaching residue A (oxygen pressure leaching residue) is separated into sulfur, gold and silver slag, and tailings through flotation (two-stage roughing, two-stage cleaning, and two-stage scavenging). The tailings contain some unreacted concentrate and gold and silver slag, which are returned to the front-end pyrometallurgical smelting system.

[0053] (4) Gold and silver extraction: The gold and silver residue from step (3) was sent to an aqua regia dissolving tank, and concentrated hydrochloric acid and concentrated nitric acid were added in a volume ratio of 3:1 until the solid content reached 20wt% for acidic leaching. The leaching process was started with stirring at 150r / min, the leaching temperature was 60℃, and the leaching time was 6h. After leaching, the residue was centrifuged and filtered to obtain leachate C (aqua regia filtrate) and leaching residue C. The results showed that leachate C (aqua regia filtrate) contained gold >3g / L; and leaching residue C contained silver chloride >1%.

[0054] Leachate C (aqua regia filtrate) was sent to a reduction tank. Sodium sulfite was added in 1.2 molar amounts based on the molar amount of gold in the leachate. The reaction temperature was 80℃, the reaction time was 6 hours, and the stirring intensity was 150 r / min. After the reaction was complete, the mixture was centrifuged and filtered to obtain leachate D (reduction filtrate, which was then treated with water) and leaching residue D. Analysis showed that leaching residue D was gold mud with a gold content >98%.

[0055] Soaking the gold mud in 10% dilute nitric acid for 1 hour, then repeatedly washing until neutral and drying, yields 99.5% gold mud, which can be cast into ingots and sold as gold ingots.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 1 is that oxygen is not introduced during the leaching process in step (2). Other steps and parameters are the same as in Example 1.

[0058] The weight of the ferrous sulfate heptahydrate crystals obtained in this comparative example decreased by 15%, and flotation could not separate the sulfur and gold / silver residue, leading to a significant increase in subsequent reagent consumption. This is because the lack of oxygen catalysis resulted in insufficient sulfur formation conditions, and high-temperature acid leaching could not effectively break down the secondary encapsulation of iron and sulfur.

[0059] Comparative Example 2

[0060] The difference between this comparative example and Example 1 is that the oxygen in step (2) of the leaching process is replaced with compressed air. Other steps and parameters are the same as in Example 1.

[0061] The weight of the ferrous sulfate heptahydrate crystals obtained in this comparative example decreased by 10%, the weight of the oxygen pressure leaching residue increased, and the purity of the gold mud was <90%. This is because the oxygen catalysis was insufficient to effectively break down the elemental sulfur-encapsulated FeS and the gold and silver surface film.

[0062] Comparative Example 3

[0063] The difference between this comparative example and Example 1 is that granulated iron matte slag is not added during the leaching process in step (2). Other steps and parameters are the same as in Example 1.

[0064] The weight of ferrous sulfate heptahydrate crystals obtained in this comparative example decreased by 5%, while the weight of leaching residue B increased, indicating a decrease in iron reduction rate. This is because the iron matte slag (ferrous sulfide) was lacking as a reducing agent, and some Fe... 3+ It exists in oxygen pressure leachate.

[0065] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for hydrometallurgical extraction of gold from refractory iron-sulfur gold concentrate, characterized in that, Includes the following steps: S1. A refractory iron-sulfur-gold concentrate is pyrometallurgically smelted to obtain iron matte slag; wherein the iron grade of the iron matte slag is higher than 60%; S2. After wet grinding and pulping, the iron matte slag is added to granulated iron matte slag, followed by the addition of SO4-containing... 2- The acidic solution was diluted to a pH of 0.5-1.5 and then subjected to oxygen pressure acid leaching and filtration to obtain leachate A and leaching residue A. S3. The leachate A is cooled and crystallized to obtain an upper crystallization mother liquor and a lower crystal slurry; the upper crystallization mother liquor is reused and, after multiple cycles, sodium sulfide is added for reaction and then filtered to obtain leachate B and leachate residue B; the lower crystal slurry is centrifuged to obtain ferrous sulfate heptahydrate crystals. S4. The leaching residue A is separated by flotation to obtain sulfur, gold and silver residue and tailings; the gold and silver residue is leached with aqua regia and filtered to obtain leaching solution C and leaching residue C; sodium sulfite is added to the leaching residue C and then filtered to obtain leaching solution D and leaching residue D; the tailings are returned to the pyrometallurgical smelting process.

2. The method for hydrometallurgical gold extraction from refractory iron-sulfur gold concentrate according to claim 1, characterized in that, In step S1, anthracite and limestone are added to the pyrometallurgical process; the temperature of the pyrometallurgical process is 1150-1300℃ and the time is 1-3 hours.

3. The method for hydrometallurgical gold extraction from refractory iron-sulfur gold concentrate according to claim 1, characterized in that, In step S2, the mass concentration of the slurry is 20%, and the amount of granulated iron matte slag added is 0.3-0.5% of the mass of the iron matte slag in the slurry.

4. The method for hydrometallurgical extraction of gold from refractory iron-sulfur gold concentrate according to claim 1, characterized in that, In step S2, the oxygen volume percentage concentration in the oxygen pressure acid leaching vessel is 99.5%, the pressure inside the vessel is 0.5-1.5 MPa, the temperature is 100-200℃, the time is 1-2 h, and the stirring rate is 300-500 r / min.

5. A method for hydrometallurgical extraction of gold from refractory iron-sulfur gold concentrate according to claim 1, characterized in that, In step S3, the molar amount of sodium sulfide is 1.2-1.5 times the molar amount of Cu in the leachate A, the reaction temperature is 55-65℃, and the reaction time is 1-3h.

6. The method for hydrometallurgical gold extraction from refractory iron-sulfur gold concentrate according to claim 1, characterized in that, In step S4, the flotation consists of two stages of roughing, two stages of cleaning, and two stages of scavenging; the gold and silver residue is leached with aqua regia until the solid content is 15-25 wt%.

7. A method for hydrometallurgical extraction of gold from refractory iron-sulfur gold concentrate according to claim 1, characterized in that, In step S4, the aqua regia leaching temperature is 55-65℃, the leaching time is 5-7h, and the stirring rate is 100-200r / min.

8. A method for hydrometallurgical extraction of gold from refractory iron-sulfur gold concentrate according to claim 1, characterized in that, In step S4, the molar amount of sodium sulfite is 1.1-1.3 times the molar amount of Au in the leachate C.

9. A method for hydrometallurgical extraction of gold from refractory iron-sulfur gold concentrate according to claim 1, characterized in that, In step S4, the reaction temperature is 75-85℃, the time is 5-7h, and the stirring rate is 100-200r / min.

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