Efficient copper removal and cyclic utilization process for copper-cyanogen complex wastewater

Abstract

The invention relates to an efficient copper removal and recycling process for copper-cyanogen complex wastewater, which comprises the following steps: (1) critical acidification-selective crystallization of the copper-cyanogen complex wastewater: directionally recombining a copper-cyanogen complex to generate insoluble CuCN crystals by accurately regulating and controlling the pH value of the wastewater; (2) rotational flow enhanced crystallization: separating CuCN crystals from overflow liquid through a hydrocyclone; (3) gradient activation of a composite vulcanizing agent for deep copper removal: enabling the fine CuCN particles and the dissolved-state low-coordination copper-cyanogen complex to react to generate insoluble CuS crystals by adjusting the pH value and adding the composite vulcanizing agent; and (4) magnetic seed enhanced separation: carrying out magnetic separation by adopting modified magnetic seeds and a low-intensity magnetic separator, separating CuS magnetic flocs from the wastewater, and finally obtaining purified tail liquid. According to the closed-loop process, copper in the copper-cyanogen complex wastewater can be efficiently removed and recovered, the purified tail liquid can be reused for cyanidation leaching operation, the unit consumption of sodium cyanide is remarkably reduced, the leaching rate of gold and silver is increased, and zero discharge of wastewater and full recovery of copper resources are truly achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mine wastewater resource utilization, and particularly relates to a copper cyanide complex wastewater efficient copper removal and recycling process. BACKGROUND

[0002] In the cyanide leaching process of gold-silver-containing oxide ore, because the copper content in the raw ore is 0.2% to 0.3%, a large amount of copper cyanide complexes (Cu(CN)3 2- / Cu(CN)4 3- ) are generated by the reaction of copper and sodium cyanide and remain in the tail liquid, which leads to the enrichment of copper concentration in the tail liquid to more than 2000 mg / L through water recycling. The reuse of such high-concentration copper cyanide complex wastewater will cause the following problems: the copper cyanide complex will consume sodium cyanide, which will increase the consumption of sodium cyanide by 2 to 3 times, and the copper cyanide complex will form an adsorption layer on the surface of gold and silver, which will reduce the leaching rate of gold and silver by 5% to 10%, and will also cause the accumulation of salt concentration in the system and the corrosion of equipment.

[0003] However, the traditional acidification method, sodium sulfide precipitation method and iron salt co-precipitation method all have many defects in treating high-cyanide high-copper wastewater. The acidification method needs to reduce the pH to below 2, which will release toxic HCN gas, has extremely high safety risk and causes serious equipment corrosion. The sodium sulfide precipitation method is prone to produce colloidal copper sulfide sludge, which is difficult to separate, and the excessive sulfur ions remaining will cause sulfur accumulation in the water recycling system. The use of the iron salt co-precipitation method will produce a large amount of hazardous waste, and the disposal cost of the hazardous waste is high.

[0004] In view of the above problems, the application provides a new copper cyanide complex wastewater efficient copper removal and recycling process, which aims to solve the recycling and reuse problems of high-concentration copper cyanide complex wastewater, realize the recycling of copper and the recycling of wastewater, and promote clean production and near-zero emission in mines. SUMMARY

[0005] The copper cyanide complex wastewater efficient copper removal and recycling process provided by the application mainly converts the copper cyanide complex in the solution into CuCN crystals by using critical acidification-selective crystallization technology according to the properties of the copper cyanide complex, recovers CuCN copper concentrate through cyclone separation, further uses a composite sulfidation agent for gradient activation deep copper removal, and separates high-density CuS particles by using magnetic seed intensification separation technology, so as to efficiently remove copper in the solution, reduce the enrichment of sulfur S, and convert the high-concentration copper cyanide complex wastewater into recyclable water, thereby solving the recycling and reuse problems of high-concentration copper cyanide complex wastewater.

[0006] A copper cyanide complex wastewater efficient copper removal and recycling process comprises the following steps: (1) Critical acidification-selective crystallization of copper-cyanide complex wastewater: Dilute sulfuric acid was added to the copper-cyanide complex wastewater to adjust the pH of the solution to 4.0-4.5, and the solution was heated to 40°C and reacted for 2 hours to allow the copper-cyanide complex to recombine in a directional manner to generate insoluble CuCN crystals; Based on the synergistic effect of the stepwise dissociation characteristics of copper-cyanide complexes and the thermodynamic stability of cuprous cyanide (CuCN), when the solution pH drops to 4.0–4.5, low CN... - Concentration disrupts the stability of high-coordination copper-cyanide complexes, prompting them to dissociate towards lower coordination numbers. When low-coordination complexes dominate, the extremely low solubility of CuCN becomes the core driving force for directional crystallization, i.e., the copper-cyanide complex ([Cu(CN)3)). 2- [Cu(CN)4] 3- The copper-cyanide complex undergoes directional recombination, forming insoluble crystals CuCN·xH2O (white powder). When the pH of the solution is greater than 5, the copper-cyanide complex does not dissolve; when the pH of the solution is less than 3.5, a large amount of HCN volatilizes, and the dissolution of CuCN intensifies.

[0007] Therefore, this step precisely controls the pH value of the wastewater and utilizes the critical point dissociation characteristics of the copper-cyanide complex at pH 4.0–4.5 to induce directional dissociation of the copper-cyanide complex. At the same time, it maintains the HCN volatilization rate below the nucleation rate to avoid gaseous loss, thereby driving the selective crystallization of thermodynamically stable CuCN.

[0008] (2) Cyclone-enhanced crystallization: The solution from step (1) is transferred into a hydrocyclone at a feed pressure of 0.3 to 0.5 MPa. Solid-liquid separation is performed to obtain CuCN crystals and overflow. After drying, CuCN copper concentrate is obtained. Because CuCN crystals are prone to deformation under pressure, easy to clog filter cloth pores, and have a limited residence time, and given that the separation efficiency of the conical hydrocyclone is well-matched with the crystal properties, and that the equipment has advantages such as corrosion resistance, strong wear resistance, and low operating costs, this application selects a conical hydrocyclone (operating pressure 0.3–0.5 MPa) to separate the CuCN crystals generated after weak acidification.

[0009] (3) Gradient activation of composite sulfide agent for deep copper removal: Add 10% NaOH to the overflow liquid in step (2), adjust the pH value to 8.5-9.0, stir and mix well, then add composite sulfide agent. After stirring and reacting for 2 hours, the fine CuCN particles and dissolved low-coordinated copper cyanide complex in the overflow liquid react to generate insoluble CuS crystals, achieving the dual purpose of deep copper removal and reducing sulfur enrichment. Since residual copper still exists in the overflow liquid after weak acidification and crystallization separation of copper-cyanide complex wastewater, mainly fine CuCN particles that were not captured by the hydrocyclone and dissolved low-coordination copper-cyanide complexes, in order to further remove copper from this part of the solution, this step carried out deep copper removal by gradient activation of composite sulfiding agent on the overflow liquid.

[0010] Its main principle is to use a composite sulfiding agent to convert fine CuCN and dissolved low-coordination copper-cyanide complexes in the solution into CuS, achieving the dual purpose of deep copper removal and reducing sulfur enrichment. In contrast, the traditional sodium sulfide precipitation method, which directly adds excessive sodium sulfide, leads to colloidal contamination, forming colloidal suspensions that are difficult to settle, and excessive sulfur... 2- The inflow into the recycled water causes sulfur accumulation (forming SCN). - (or H2S). To avoid this problem, this application prepares a 10% composite vulcanizing agent by mixing sodium sulfide and triethanolamine at a molar ratio of 1:0.05. Then, a gradient vulcanization control mechanism is employed, namely S... 2- The concentration is controlled at 50–100 mg / L to limit the nucleation rate of CuS and promote crystal growth. At the same time, the steric hindrance layer formed on the surface of CuS crystal nuclei is activated and adsorbed by triethanolamine to prevent the aggregation of fine particles. The pH of the solution is maintained at 8.5–9.0 to avoid the generation of H2S and optimize the crystallinity of CuS.

[0011] (4) Magnetic seed enhanced separation: Add modified magnetic seed Fe3O4@SiO2-CH3 to the solution in step (3), stir and react for 2 hours, then introduce the solution into a weak magnetic separator. Under the action of a weak magnetic field, the modified magnetic seeds attract each other and form chain aggregates. These chain aggregates trap and wrap CuS particles to form CuS magnetic flocs. The CuS magnetic flocs are adsorbed on the surface of the magnetic cylinder and discharged from the concentrate end. After drying, CuS magnetic floc concentrate is obtained, and the separated purified tailings can be recycled.

[0012] To better separate and recover crystalline CuS from the solution and solve the problem of difficult filtration of copper sulfide particles, this step uses modified magnetite powder Fe3O4@SiO2-CH3 as a magnetic seed. This magnetic seed achieves efficient separation and recovery of CuS through the following mechanism: Fe3O4@SiO2-CH3 is a core-shell structured material where Fe3O4 acts as the core providing magnetism, SiO2 acts as the shell providing stability, and the -CH3 groups on the surface endow the magnetic seeds with hydrophobicity. In solution, the hydrophobic groups on the modified magnetic seed surface enable the magnetic seeds to stably bind with CuS particles in the solution through hydrophobic interactions. Subsequently, under the influence of a weak magnetic field, the magnetic seed particles attract each other, forming chain-like aggregates. These chain-like aggregates can trap and encapsulate CuS particles, forming magnetic flocs. These magnetic flocs exhibit good magnetic responsiveness under a weak magnetic field and can be efficiently separated by a weak magnetic separator, thereby achieving the separation and efficient recovery of CuS. Simultaneously, during the adsorption of CuS particles, the magnetic seeds can also adsorb residual S²⁺ in the solution. - To prevent its accumulation in the solution and further reduce the S² of the solution. - To reduce moisture content and avoid secondary pollution, the formation of magnetic flocs and the magnetic separation process effectively remove excess moisture, reduce the moisture content of CuS magnetic flocs, and improve recovery efficiency and product quality.

[0013] Furthermore, the concentration of dilute sulfuric acid in step (1) is 5%.

[0014] Furthermore, in step (1), the pH value of the solution is adjusted to 4.25.

[0015] Furthermore, the feed pressure of the solution in step (2) is 0.42 MPa.

[0016] Furthermore, in step (3), the composite vulcanizing agent is prepared by mixing sodium sulfide and triethanolamine in a molar ratio of 1:0.05.

[0017] Furthermore, the consumption of the composite vulcanizing agent added in step (3) is 75 mg / L.

[0018] Furthermore, in step (3), the pH of the solution is adjusted to 8.5.

[0019] Furthermore, in step (4), the addition consumption of the modified magnetic seed Fe3O4@SiO2-CH3 is 1.5 kg / m³.

[0020] Furthermore, in step (4), the magnetic field strength of the weak magnetic separator is controlled to be 0.5T.

[0021] The beneficial effects of this invention are as follows: This invention constructs a closed-loop process of "critical acidification selective crystallization – cyclone-enhanced crystallization – composite sulfide agent gradient activation – magnetic seed-enhanced separation". It uses precise control of key parameters such as pH, temperature, and pressure as a breakthrough to precisely trigger the directional dissociation of copper-cyanide complexes, inducing highly selective nucleation and growth of CuCN crystals. Subsequently, cyclone fractionation achieves rapid crystal separation, and then composite sulfide agent gradient activation combined with magnetic seed coupling technology further transforms residual copper into easily magnetically separated dense CuS particles, while simultaneously achieving deep desulfurization. The entire closed-loop process can efficiently remove and recover copper from copper-cyanide complex wastewater. After treatment, the wastewater can be reused in cyanide leaching operations, significantly reducing sodium cyanide consumption and increasing the leaching rate of gold and silver. It truly achieves zero wastewater discharge and full copper resource recovery, meeting the green goals of "low sulfur, low slag, and high recovery," with outstanding economic, environmental, and social benefits.

[0022] Furthermore, compared to traditional acidification methods, this invention utilizes critical acidification for selective crystallization, avoiding the need to lower the pH value below 2. This prevents the release of highly toxic hydrogen cyanide (HCN) gas and severe equipment corrosion, significantly improving safety. Compared to conventional sulfide precipitation, this invention employs a "composite sulfide agent gradient activation-magnetic seed enhanced separation" technology, completely solving industry problems such as the difficulty in settling and filtering copper sulfide colloids, uncontrollable sulfur pollution, and the lack of value in sludge. Simultaneously, it avoids excessive sulfur dioxide (S²). - The inflow of wastewater triggers the accumulation of sulfur, leading to the formation of SCN. - Or H2S. Attached Figure Description

[0023] Figure 1 This is a flowchart of a process for efficient copper removal and recycling of copper-cyanide complexed wastewater according to the present invention. Detailed Implementation

[0024] To make the technical problems and solutions solved by the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0025] Taking the copper-cyanide complex wastewater (copper content 2000 mg / L) generated from the cyanidation leaching process of a gold and silver oxide ore as an example, the copper-cyanide complexation high-efficiency copper removal and recycling process described in this invention is used for treatment. The specific implementation is as follows: (1) Critical acidification-selective crystallization of copper-cyanide complex wastewater: Add 5% dilute sulfuric acid to the copper-cyanide complex wastewater to adjust the pH of the solution to about 4.25, and heat the solution to about 40°C for 2 hours to allow the copper-cyanide complex to recombine in a directional manner to generate insoluble CuCN crystals; (2) Cyclone-enhanced crystallization: The solution from step (1) is transferred into a hydrocyclone at a feed pressure of 0.42 MPa. Solid-liquid separation is performed to obtain CuCN crystals and overflow. After drying, CuCN copper concentrate is obtained. (3) Gradient activation of composite sulfide for deep copper removal: Add 10% NaOH to the overflow liquid in step (2) to adjust the pH of the solution to 8.5-9.0. After stirring and mixing, add the composite sulfide. After stirring and reacting for 2 hours, the fine CuCN particles and dissolved low-coordinated copper cyanide complexes in the overflow liquid react to generate insoluble CuS crystals, achieving the dual purpose of deep copper removal and reducing sulfur enrichment. The composite sulfide is prepared by mixing sodium sulfide and triethanolamine in a molar ratio of 1:0.05, and its addition consumption is 75 mg / L.

[0026] (4) Magnetic seed enhanced separation: Add modified magnetic seed Fe3O4@SiO2-CH3 (addition consumption is 1.5kg / m³) to the solution in step (3). After stirring and reacting for 2 hours, introduce the solution into a weak magnetic separator. The magnetic field strength is controlled at 0.5T. Under the action of the weak magnetic field, the modified magnetic seeds attract each other and form chain aggregates. These chain aggregates trap and wrap CuS particles to form CuS magnetic flocs. The CuS magnetic flocs are adsorbed on the surface of the magnetic cylinder and discharged from the concentrate end. After drying, CuS magnetic floc concentrate is obtained, and the separated purified tailings can be recycled.

[0027] After the above treatment, the copper content in the solution decreased from 2000 mg / L to 18 mg / L, with a copper removal rate as high as 99.1%, and a yield of 1.82 kg / m³ was obtained. 3 A CuCN copper concentrate with a copper grade of 61.5% and a yield of 2.1 kg / m³. 3 CuS magnetic flocculent copper concentrate with a copper grade of 43%.

[0028] To further verify the effectiveness of reusing the purified tailings in the cyanide leaching process, compared with cyanide leaching of untreated high-concentration copper-cyanide complex wastewater, the sodium cyanide consumption decreased from 2.6 kg / t to 1.25 kg / t, and the gold leaching rate increased from 88.1% to 94.5% when using the purified tailings for ore cyanide leaching. This demonstrates that the wastewater reuse process described in this invention significantly reduces the amount of sodium cyanide used and improves the gold leaching rate.

[0029] The present invention has been described in detail above through specific and preferred embodiments. However, those skilled in the art should understand that the present invention is not limited to the embodiments described above. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A highly efficient copper removal and recycling process for copper-cyanide complexed wastewater, characterized in that, Includes the following steps: (1) Critical acidification-selective crystallization of copper-cyanide complex wastewater: Dilute sulfuric acid was added to the copper-cyanide complex wastewater to adjust the pH of the solution to 4.0-4.5, and the solution was heated to 40°C and reacted for 2 hours to allow the copper-cyanide complex to recombine in a directional manner to generate insoluble CuCN crystals; (2) Cyclone-enhanced crystallization: The solution from step (1) is transferred into a hydrocyclone at a feed pressure of 0.3 to 0.5 MPa. Solid-liquid separation is performed to obtain CuCN crystals and overflow. After drying, CuCN copper concentrate is obtained. (3) Gradient activation of composite sulfide agent for deep copper removal: Add 10% NaOH to the overflow liquid in step (2), adjust the pH value to 8.5-9.0, stir and mix well, then add composite sulfide agent. After stirring and reacting for 2 hours, the fine CuCN particles and dissolved low-coordinated copper cyanide complex in the overflow liquid react to generate insoluble CuS crystals, achieving the dual purpose of deep copper removal and reducing sulfur enrichment. (4) Magnetic seed enhanced separation: Add modified magnetic seed Fe3O4@SiO2-CH3 to the solution in step (3), stir and react for 2 hours, then introduce the solution into a weak magnetic separator. Under the action of a weak magnetic field, the modified magnetic seeds attract each other and form chain aggregates. These chain aggregates trap and wrap CuS particles to form CuS magnetic flocs. The CuS magnetic flocs are adsorbed on the surface of the magnetic cylinder and discharged from the concentrate end. After drying, CuS magnetic floc concentrate is obtained, and the separated purified tailings can be recycled.

2. The efficient copper removal and recycling process for copper-cyanide complexed wastewater according to claim 1, characterized in that, The concentration of dilute sulfuric acid in step (1) is 5%.

3. The efficient copper removal and recycling process for copper-cyanide complexed wastewater according to claim 1, characterized in that, In step (1), the pH value of the solution is adjusted to 4.

25.

4. The efficient copper removal and recycling process for copper-cyanide complexed wastewater according to claim 1, characterized in that, The feed pressure of the solution in step (2) is 0.42 MPa.

5. The efficient copper removal and recycling process for copper-cyanide complexed wastewater according to claim 1, characterized in that, In step (3), the composite vulcanizing agent is prepared by mixing sodium sulfide and triethanolamine in a molar ratio of 1:0.

05.

6. The efficient copper removal and recycling process for copper-cyanide complexed wastewater according to claim 5, characterized in that, In step (3), the consumption of the composite vulcanizing agent is 75 mg / L.

7. The efficient copper removal and recycling process for copper-cyanide complexed wastewater according to claim 1, characterized in that, In step (3), the pH of the solution is adjusted to 8.

5.

8. The efficient copper removal and recycling process for copper-cyanide complexed wastewater according to claim 1, characterized in that, The addition of modified magnetic seed Fe3O4@SiO2-CH3 in step (4) has a unit consumption of 1.5 kg / m³.

9. A high-efficiency copper removal and recycling process for copper-cyanide complex wastewater according to claim 1 or 8, characterized in that, In step (4), the magnetic field strength of the weak magnetic separator is controlled to be 0.5T.

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