A method for extracting gold by wet process

Abstract

A wet gold extraction method uses high-activity trithiocyanate C3N3S3 generated by hydrolysis of polymeric sodium thiocyanate Na3C3N3S3 in a weak alkaline environment 3‑ Cu is the catalyst and air dissolved oxygen is the oxidant 2+ The alkaline catalytic leaching gold system is composed of the following steps: S1, crushing gold-containing ores to a heap leaching suitable particle size, transporting to a heap leaching site for uniform stacking to form a standardized leaching ore heap; S2, mixing polymeric sodium thiocyanate Na3C3N3S3 with Cu 2+ The catalyst is prepared into a leaching solution at a certain concentration, the pH of the system is adjusted to a weak alkaline range, the leaching solution is uniformly sprayed onto the surface of the ore heap, and the timing is started simultaneously, a continuous or intermittent spraying mode is adopted, and the gold dissolution reaction is completed relying on the oxygen-copper catalytic system; S3, stopping the spraying after reaching the preset leaching time, collecting the ore heap leachate and filtering to obtain a gold-containing leaching solution and a leaching tail liquid, respectively; S4, recovering elemental gold from the gold-containing leaching solution obtained in step S3 3‑ The C3N3S3 generated has high activity in a weak alkaline system, and the reagent hardly hydrolyzes, and the system is stable.

Description

Technical Field

[0001] This invention relates to the field of gold extraction technology in hydrometallurgy, and more particularly to a hydrometallurgical gold extraction method. Background Technology

[0002] Currently, the mainstream heap leaching process for low-grade gold mines both domestically and internationally is still cyanide heap leaching. This process offers stable leaching efficiency, low cost, and suitability for large-scale industrial production. However, its core drawbacks are also extremely prominent. Cyanide is a highly toxic and hazardous chemical, posing significant safety hazards during production, storage, transportation, spraying, and the discharge of waste gas, wastewater, and solid waste. It can easily cause large-scale pollution of soil, groundwater, and surface water. Furthermore, cyanide tailings and liquids require specialized, highly toxic, and harmless treatment, resulting in high operation and maintenance costs and severely hindering the development of green production in the gold mining industry.

[0003] Existing cyanide-free gold extraction technologies mostly focus on acidic leaching systems, thiourea systems, and thiosulfate systems. These suffer from problems such as high reagent consumption, severe equipment corrosion, poor system stability, weak temperature adaptability, and difficulty in adapting to open-system heap leaching production. Among these, acidic cyanide-free systems are highly corrosive to carbon steel equipment, requiring the modification of anti-corrosion equipment and incurring significant investment. Conventional neutral and weakly alkaline cyanide-free systems have drawbacks such as weak complexation stability, low leaching rates, and easy decomposition and inactivation of reagents, making them unable to replace cyanidation processes in industrial applications. Summary of the Invention

[0004] Therefore, the present invention provides a C3N3S3 system in a weakly alkaline environment. 3- This wet gold extraction method features high activity, non-hydrolysis of the reagent, stable system, balanced complexation efficiency and operational safety, and good complexation stability due to the low dissociation and precipitation of the generated gold complex ions, resulting in high leaching recovery rate.

[0005] A wet gold extraction method utilizes highly reactive trithiocyanate (C3N3S3) generated by the hydrolysis of polymerized sodium thiocyanate (Na3C3N3S3) under a weakly alkaline environment. 3- As a complexing agent, dissolved oxygen in the air is an oxidizing agent, Cu 2+ To construct an alkaline catalytic gold leaching system for the catalyst, the following steps are included: S1. Crush the gold-bearing ore to the appropriate particle size for heap leaching, transport it to the heap leaching field, pile it up evenly, compact it, and flatten it to form a standardized leaching heap. S2. Polymeric sodium thiocyanate Na3C3N3S3 and Cu 2+ The catalyst was used to prepare the leachate at a certain concentration, and the pH of the system was adjusted to a slightly alkaline range. The leachate was then sprayed evenly onto the surface of the ore pile, and timing was started simultaneously. The gold dissolution reaction was completed using a continuous or intermittent spraying method, relying on the oxygen-copper catalytic system. The reaction equation is as follows: Anodizing reaction of gold: 4Au-4e - —4Au + Cathode oxygen reduction reaction: O2 + 2H2O + 4e - —4OH - Gold ion stable complexation reaction: Au + +[Cu(C3N3S3)] - —[Au(C3N3S3)] 2- +Cu 2+ 2Au + +[Cu(C3N3S3)] - —[Au2(C3N3S3)] - +Cu 2+ ; S3. After the preset leaching time is reached, the spraying is stopped, the ore pile leachate is collected and filtered to obtain gold-containing leachate and leaching tailings respectively. S4. Use activated carbon adsorption, desorption, or electrolytic deposition processes to recover elemental gold from the gold-containing leachate obtained in step S3.

[0006] Furthermore, the pH range of the system in step S2 is weakly alkaline, which is 9.0–10.0.

[0007] Furthermore, the consumption of the polymeric sodium thiocyanate (Na3C3N3S3) reagent is 0.5–1 kg / t ore.

[0008] Furthermore, the mass concentration of poly(sodium thiocyanate) Na3C3N3S3 in the leachate is 1–3 g / L.

[0009] Furthermore, the total duration of the heap leaching reaction in step S2 is 48–240 h.

[0010] Furthermore, the reaction temperature for the gold dissolution reaction in step S2 is 10–40 °C.

[0011] Furthermore, the leachate obtained in step S2 is subjected to simple processing and recycled for the preparation of leachate.

[0012] Furthermore, the gold-bearing ore is applicable to any of the following: low-grade oxidized gold ore, weathered gold ore, and shallow surface oxidized gold ore.

[0013] Under weakly alkaline conditions, polymerized sodium thiocyanate (Na3C3N3S3) hydrolyzes to generate highly reactive trithiocyanate ions (C3N3S3). 3- After opening the loop, 3 equivalent SCNs are released. - At the complexation site, dissolved oxygen in the air acts as the sole oxidant, resulting in a reduction reaction at the cathode; gold (Au) in the gold-bearing ore undergoes oxidation at the anode to form Au. + Cu 2+ The catalyst first reacts with C3N3S3 3-The reaction generates a Cu-TMT active intermediate to lower the activation energy of the gold dissolution reaction. The active intermediate is [Cu(C3N3S3)]. - Au generated at the anode + A gold ion complexation reaction occurs; this is the C3N3S3 generated in the wet gold extraction method. 3- It exhibits high activity in a weakly alkaline system, while the reagent is almost non-hydrolyzed and the system is stable, balancing complexation efficiency and operational safety. Furthermore, the generated gold complex ions are not easily dissociated and precipitated, exhibiting good complexation stability and high leaching recovery rate. In addition, this wet gold extraction method uses dissolved oxygen in the air as an oxidant, resulting in no violent oxidation reaction, stable reaction throughout the process, and extremely high system stability. Attached Figure Description

[0014] Figure 1 This is a schematic flowchart of a wet gold extraction method according to an embodiment of the present invention. Detailed Implementation

[0015] like Figure 1 As shown, this invention provides a wet gold extraction method using highly active trithiocyanate (C3N3S3) generated by the hydrolysis of sodium thiocyanate (Na3C3N3S3) under a weakly alkaline environment. 3- As a complexing agent, dissolved oxygen in the air is an oxidizing agent, Cu 2+ To construct an alkaline catalytic gold leaching system for the catalyst, the following steps are included: S1. Crush the gold-bearing ore to the appropriate particle size for heap leaching, transport it to the heap leaching field, pile it up evenly, compact it, and flatten it to form a standardized leaching heap. S2. Polymeric sodium thiocyanate Na3C3N3S3 and Cu 2+ The catalyst was used to prepare the leachate at a certain concentration, and the pH of the system was adjusted to a slightly alkaline range. The leachate was then sprayed evenly onto the surface of the ore pile, and timing was started simultaneously. The gold dissolution reaction was completed using a continuous or intermittent spraying method, relying on the oxygen-copper catalytic system. The reaction equation is as follows: Anodizing reaction of gold: 4Au-4e - —4Au + Cathode oxygen reduction reaction: O2 + 2H2O + 4e - —4OH - Gold ion stable complexation reaction: Au + +[Cu(C3N3S3)] - —[Au(C3N3S3)] 2- +Cu 2+ 2Au + +[Cu(C3N3S3)] - —[Au2(C3N3S3)] - +Cu 2+; S3. After the preset leaching time is reached, the spraying is stopped, the ore pile leachate is collected and filtered to obtain gold-containing leachate and leaching tailings respectively. S4. Use activated carbon adsorption, desorption, or electrolytic deposition processes to recover elemental gold from the gold-containing leachate obtained in step S3.

[0016] Under weakly alkaline conditions, polymerized sodium thiocyanate (Na3C3N3S3) hydrolyzes to generate highly reactive trithiocyanate ions (C3N3S3). 3- After opening the loop, 3 equivalent SCNs are released. - At the complexation site, dissolved oxygen in the air acts as the sole oxidant, resulting in a reduction reaction at the cathode; gold (Au) in the gold-bearing ore undergoes oxidation at the anode to form Au. + Cu 2+ The catalyst is also C3N3S3 3- The reaction generates a Cu-TMT active intermediate to lower the activation energy of the gold dissolution reaction. The active intermediate is [Cu(C3N3S3)]. - and the enhancement of Au generated by the anode + A gold ion complexation reaction occurs; this is the C3N3S3 generated in the wet gold extraction method. 3- It exhibits high activity in a weakly alkaline system, while the reagent is almost non-hydrolyzed and the system is stable, balancing complexation efficiency and operational safety. Furthermore, the generated gold complex ions are not easily dissociated and precipitated, exhibiting good complexation stability and high leaching recovery rate. In addition, this wet gold extraction method uses dissolved oxygen in the air as an oxidant, resulting in no violent oxidation reaction, stable reaction throughout the process, and extremely high system stability.

[0017] The pH range of the system in step S2 is weakly alkaline, from 9.0 to 10.0. The generated C3N3S3... 3- It exhibits excellent activity in the weakly alkaline pH range of 9.0–10.0, while showing almost no hydrolysis and system stability, balancing complexation efficiency and operational safety. The consumption of polysodium thiocyanate (Na3C3N3S3) in the weakly alkaline pH range of 9.0–10.0 is 0.5–1 kg / t of ore, lower than conventional cyanide-free gold extraction systems, significantly reducing the production cost of mining reagents.

[0018] The mass concentration of polysodium thiocyanate (Na3C3N3S3) in the leachate is 1–3 g / L. This concentration range is suitable for various low-grade gold ores, meets the complexation requirements, and avoids reagent waste, thus controlling production costs.

[0019] The total reaction time for heap leaching in step S2 is 48–240 hours. This reaction time is sufficient to ensure full leaching of gold from the mine, balancing leaching rate and industrial production efficiency.

[0020] The reaction temperature for the gold dissolution reaction in step S2 is 10–40℃. Stable operation is possible within the 10–40℃ ambient temperature range, without the need for heating or temperature control equipment. Continuous industrial production is possible in all seasons, making it suitable for mining production in different regions and temperature environments.

[0021] Furthermore, the leachate obtained in step S2 is subjected to simple treatment and recycled for the preparation of leachate. The leachate is weakly alkaline and contains OH-. - and C3N3S3 3- It can be reused with simple processing, resulting in low production costs.

[0022] This wet gold extraction method is applicable to any of the following types of gold ore: low-grade oxidized gold ore, weathered gold ore, and shallow surface oxidized gold ore. It has a wide range of applicability to gold ore. Example 1

[0023] Low-grade oxidized gold ore was selected, crushed, and piled into shape. The pH of the leaching system was adjusted to 9.0, and the concentration of polysodium thiocyanate (Na3C3N3S3) was 1 g / L. Continuous spray leaching was carried out for 72 hours. After leaching, the ore was filtered and tested, and the gold leaching rate was calculated to be 83.7%. The leachate was clear and stable, with no reagent decomposition or precipitation. The reagent consumption was 0.5 kg / t of ore. The tailings could be directly recycled after simple treatment. Example 2

[0024] Weathered, low-grade gold ore was selected, crushed, and piled into shape. The leaching system was adjusted to pH 9.5, with a sodium thiocyanate (Na3C3N3S3) concentration of 2 g / L, and intermittent spray leaching was performed for 60 hours. After leaching, the ore was filtered and tested, and the gold leaching rate was calculated to be 85.2%. The leachate was clear and stable, with no reagent decomposition or precipitation, making it suitable for large-scale continuous production. Example 3

[0025] Shallow-surface oxidized gold ore was selected, crushed, and piled into shape. The leaching system was adjusted to pH 10.0, and the concentration of polysodium thiocyanate (Na3C3N3S3) was 3 g / L. Continuous spray leaching was performed for 48 hours, completing the leaching reaction in a short and efficient manner. After leaching, filtration and testing showed a gold leaching rate of 82.5%, significantly improving production efficiency, with controllable reagent consumption, and fully meeting industrial production standards.

[0026] In summary, this invention can stably achieve efficient leaching of low-grade gold ore within a limited alkaline parameter range, with excellent leaching effect, stable operating conditions, low cost, and environmental safety, representing a significant technological advancement compared to existing cyanidation processes.

Claims

1. A wet gold extraction method, characterized in that, Highly active trithiocyanate ions (C3N3S3) generated by hydrolysis of sodium thiocyanate (Na3C3N3S3) under a weakly alkaline environment. 3- As a complexing agent, dissolved oxygen in the air is an oxidizing agent, Cu 2+ To construct an alkaline catalytic gold leaching system for the catalyst, the following steps are included: S1. Crush the gold-bearing ore to the appropriate particle size for heap leaching, transport it to the heap leaching field, pile it up evenly, compact it, and flatten it to form a standardized leaching heap. S2, Mixing sodium thiocyanate Na3C3N3S3 with Cu 2+ The catalyst is used to prepare the leaching solution at a certain concentration, and the pH of the system is adjusted to the weakly alkaline range. The leaching solution is then evenly sprayed onto the surface of the ore pile, and timing is started simultaneously. The gold dissolution reaction is completed using a continuous or intermittent spraying method, relying on the oxygen-copper catalytic system. The reaction equation is as follows: Anodizing reaction of gold: 4Au-4e - —4Au + Cathode oxygen reduction reaction: O2 + 2H2O + 4e - —4OH - Gold ion stable complexation reaction: Au + +[Cu(C3N3S3)] - —[Au(C3N3S3)] 2- +Cu 2+ 2Au + +[Cu(C3N3S3)] - —[Au2(C3N3S3)] - +With 2+ ; S3. After the preset leaching time is reached, the spraying is stopped, the ore pile leachate is collected and filtered to obtain gold-containing leachate and leaching tailings respectively. S4. Use activated carbon adsorption, desorption, or electrolytic deposition processes to recover elemental gold from the gold-containing leachate obtained in step S3.

2. The wet gold extraction method as described in claim 1, characterized in that, The weakly alkaline pH range of the system described in step S2 is 9.0–10.

0.

3. The wet gold extraction method as described in claim 2, characterized in that, The consumption of the polymerized sodium thiocyanate (Na3C3N3S3) reagent is 0.5–1 kg / t ore.

4. The wet gold extraction method as described in claim 1, characterized in that, The mass concentration of the polymeric sodium thiocyanate (Na3C3N3S3) in the leachate is 1–3 g / L.

5. The wet gold extraction method as described in claim 1, characterized in that, The total duration of the heap leaching reaction in step S2 is 48–240 h.

6. The wet gold extraction method as described in claim 1, characterized in that, The reaction temperature for the gold dissolution reaction in step S2 is 10–40℃.

7. The wet gold extraction method as described in claim 1, characterized in that, The leachate obtained in step S2 is further processed and recycled to prepare leachate.

8. The wet gold extraction method as described in claim 1, characterized in that, The gold ore mentioned is applicable to any one of the following: low-grade oxidized gold ore, weathered gold ore, and shallow surface oxidized gold ore.

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