Efficient copper removal and recycling process for copper cyanide complex wastewater

Abstract

The present application relates to a kind of copper cyanide complex wastewater high-efficiency copper removal and recycling process, comprising the following steps: (1) copper cyanide complex wastewater critical acidification-selective crystallization: by accurately controlling wastewater pH value, make copper cyanide complex directional recombination generate insoluble CuCN crystal;(2) cyclone enhanced crystallization: by water cyclone, CuCN crystal and overflow liquid are separated;(3) composite sulphidizing agent gradient activation deep copper removal: by adjusting pH value and adding composite sulphidizing agent, make micro CuCN particle and dissolved low coordination copper cyanide complex reaction generate insoluble CuS crystal;(4) magnetic seed enhanced separation: using modified magnetic seed and weak magnetic separator magnetic separation, CuS magnetic flocculation is separated from wastewater, and finally purified tail liquid is obtained.The closed-loop process of the present application can efficiently remove and recover copper in copper cyanide complex wastewater, and the purified tail liquid can be used for cyanide leaching operation, significantly reduce the consumption of sodium cyanide and improve gold and silver leaching rate, truly realize wastewater zero discharge and copper resource full recovery.

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 will cause the accumulation of sulfur 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 utilization problems of high-concentration copper cyanide complex wastewater, realize the recycling of copper and the recycling of wastewater, and promote the clean production and near-zero emission of 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 series problems of high-concentration copper cyanide complex wastewater.

[0006] A copper cyanide complex wastewater efficient copper removal and recycling process comprises the following steps:

[0007] (1) Critical acidification-selective crystallization of copper cyanide complex wastewater: Add dilute sulfuric acid to the copper cyanide complex wastewater, adjust the pH value of the solution to 4.0-4.5, and heat the solution to 40°C for 2h, so that the copper cyanide complex directional reorganization generates insoluble CuCN crystals;

[0008] According to the synergistic effect of the step-by-step dissociation characteristics of copper cyanide complex and the thermodynamic stability of cuprous cyanide (CuCN), when the solution pH is reduced to 4.0-4.5, the low CN - concentration destroys the stability of the high coordination copper cyanide complex, prompting it to dissociate into low coordination, and when the low coordination complex is dominant, the extremely low solubility of CuCN becomes the core driving force for directional crystallization, that is, the copper cyanide complex ([Cu(CN)3] 2- , [Cu(CN)4] 3- ) directional reorganization generates insoluble CuCN·xH2O (white powder). When the pH in the solution is >5, the copper cyanide complex will not dissolve; when the pH in the solution is <3.5, HCN is volatilized in large quantities, and CuCN is dissolved intensively.

[0009] Therefore, by precisely controlling the pH value of the wastewater, this step utilizes the critical point dissociation characteristics of copper cyanide complex at pH 4.0-4.5 to cause directional dissociation of copper cyanide complex, while maintaining the HCN volatilization rate lower than the nucleation rate to avoid gaseous loss, thereby driving the selective crystallization of thermodynamically stable CuCN.

[0010] (2) Cyclone enhanced crystallization: The solution of step (1) is transferred into a hydrocyclone at a feed pressure of 0.3-0.5 MPa, and solid-liquid separation is performed to obtain CuCN crystals and overflow liquid, and CuCN copper concentrate is obtained after drying the CuCN crystals;

[0011] Due to the problems of CuCN crystals deforming under pressure, easily blocking filter cloth pores, and not being able to stay for too long, and the fact that the separation efficiency of the conical hydrocyclone is matched with the physical properties of the crystals, and the equipment has the advantages of corrosion resistance, strong wear resistance, and low operating cost, etc., the conical hydrocyclone (operating pressure 0.3-0.5 MPa) is chosen to separate the CuCN crystals generated after weak acidification.

[0012] (3) Gradient activation deep copper removal with composite sulfidizing agent: Add 10% NaOH to the overflow liquid of step (2) to adjust the pH value to 8.5-9.0, mix well, then add a composite sulfidizing agent, and after stirring for 2h, the fine CuCN particles and dissolved low coordination copper cyanide complex in the overflow liquid react to form insoluble CuS crystals, achieving the dual purposes of deep copper removal and reducing sulfur enrichment;

[0013] Since there is residual copper in the overflow solution obtained after the copper cyanide complex wastewater is separated by weak acidification and crystallization, mainly the fine CuCN particles not captured by the cyclone and the dissolved low coordination copper cyanide complexes, in order to further remove the copper in the solution, the step carries out deep copper removal on the overflow solution by gradient activation of a composite sulfidation agent.

[0014] The main principle is to convert the fine CuCN and the dissolved low coordination copper cyanide complexes in the solution into CuS through the action of the composite sulfidation agent, so as to achieve the dual purposes of deep copper removal and reduction of sulfur S enrichment. However, the traditional sodium sulfide precipitation method directly adds excess sodium sulfide, which can cause colloidal pollution, form colloidal suspensions that are difficult to settle, and excessive S 2- into backwater, causing sulfur accumulation (SCN - or H2S) to occur. In order to avoid this problem, the composite sulfidation agent with a concentration of 10% is prepared by mixing sodium sulfide and triethanolamine at a molar ratio of 1:0.05. Then, the gradient sulfidation control mechanism is adopted, that is, the S 2- concentration is controlled to be 50-100 mg / L, so as to limit the nucleation rate of CuS and promote the growth of crystals. At the same time, the triethanolamine activates and adsorbs on the surface of the CuS crystal nucleus to form a steric hindrance layer, preventing fine particle agglomeration, and maintaining the pH value of the solution at 8.5-9.0 to avoid the generation of H2S, while optimizing the crystallinity of CuS.

[0015] (4) Magnetic seed intensification separation: modified magnetic seeds Fe3O4@SiO2-CH3 are added to the solution of step (3), and after stirring for 2 h, the solution is introduced into a low-intensity magnetic separator. Under the action of the low-intensity magnetic field, the modified magnetic seeds attract each other to form chain-like aggregates. These chain-like aggregates entrap and wrap CuS particles to form CuS magnetic flocculation. The CuS magnetic flocculation is adsorbed on the surface of the magnetic cylinder and discharged from the concentrate end. After drying treatment, CuS magnetic flocculation concentrate is obtained, and the separated purified tail liquid can be recycled.

[0016] In order to better separate and recover the crystal CuS in the solution and solve the problem of difficult filtration of copper sulfide particles, the step uses modified magnetite powder Fe3O4@SiO2-CH3 as the magnetic seed. The magnetic seed realizes efficient separation and recovery of CuS through the following mechanisms:

[0017] 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.

[0018] Furthermore, the concentration of dilute sulfuric acid in step (1) is 5%.

[0019] Furthermore, in step (1), the pH value of the solution is adjusted to 4.25.

[0020] Furthermore, the feed pressure of the solution in step (2) is 0.42 MPa.

[0021] Furthermore, in step (3), the composite vulcanizing agent is prepared by mixing sodium sulfide and triethanolamine in a molar ratio of 1:0.05.

[0022] Furthermore, the consumption of the composite vulcanizing agent added in step (3) is 75 mg / L.

[0023] Furthermore, in step (3), the pH of the solution is adjusted to 8.5.

[0024] Furthermore, in step (4), the addition consumption of the modified magnetic seed Fe3O4@SiO2-CH3 is 1.5 kg / m³.

[0025] Furthermore, in step (4), the magnetic field strength of the weak magnetic separator is controlled to be 0.5T.

[0026] The beneficial effects of the present application: the present application constructs a closed-loop process of "critical acidification selective crystallization-cyclone enhanced crystallization-composite sulfurizing agent gradient activation-magnetic seed enhanced separation", which precisely controls key parameters such as pH value, temperature, pressure, etc. as a breakthrough, precisely triggers the directional dissociation of copper cyanide complex, and induces high-selective nucleation and growth of CuCN crystals; then the cyclone classification is used to realize the rapid separation of the crystals, and then the composite sulfurizing agent gradient activation + magnetic seed coupling technology is used to further convert the residual copper into easy magnetic separation CuS dense particles, and simultaneously deep desulfurization. The whole closed-loop process can efficiently remove and recover copper in copper cyanide complex wastewater, and the treated wastewater can continue to be used for cyanide leaching operation, which can significantly reduce the consumption of sodium cyanide and improve the leaching rate of gold and silver, truly realize wastewater zero discharge and copper resource full recovery, meet the green goal of "low sulfur, low slag, high recovery", and have outstanding economic, environmental and social benefits.

[0027] In addition, compared with the traditional acidification method, the present application uses critical acidification method for selective crystallization, avoids reducing the pH value to below 2, thereby avoiding the escape of highly toxic hydrogen cyanide (HCN) gas and the strong corrosion of equipment, and the safety is greatly improved; compared with the conventional sulfurization precipitation, the present application uses the "composite sulfurizing agent gradient activation-magnetic seed enhanced separation" technology, which completely solves the problems of difficult settlement, difficult filtration, uncontrollable sulfur pollution and valueless sludge of copper sulfide colloid in the industry, and avoids the excessive S² - Enter the backwater, and cause sulfur accumulation to generate SCN - Or H2S. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flow chart of a copper cyanide complex wastewater efficient copper removal and recycling process of the present application. DETAILED DESCRIPTION

[0029] In order to make the technical problems and technical solutions solved by the present application clearer, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0030] Taking copper cyanide complex wastewater (copper content of 2000 mg / L) generated in the cyanide leaching process of a certain gold and silver-containing oxide ore as an example, the copper cyanide complex is treated by using the copper cyanide complex efficient copper removal and recycling process described in the present application, and the specific implementation conditions are as follows:

[0031] (1) Critical acidification-selective crystallization of copper cyanide complex wastewater: add dilute sulfuric acid with a concentration of 5% to the copper cyanide complex wastewater, adjust the pH value of the solution to about 4.25, heat the solution to about 40℃, and react for 2h, so that the copper cyanide complex is directionally reorganized to generate insoluble CuCN crystals;

[0032] (2) Cyclone enhanced crystallization: the solution of step (1) is transferred into a hydrocyclone at a feed pressure of 0.42 MPa, and solid-liquid separation is performed to obtain CuCN crystals and overflow liquid, and the CuCN crystals are dried to obtain CuCN copper concentrate;

[0033] (3) Compound sulfurizing agent gradient activation deep copper removal: 10% NaOH is added to the overflow liquid of step (2) to adjust the pH value of the solution to 8.5-9.0, and then a compound sulfurizing agent is added after stirring and mixing, and after stirring and reaction for 2 h, the micro-fine CuCN particles and dissolved low-coordination copper cyanide complexes in the overflow liquid react to form insoluble CuS crystals, achieving the dual purposes of deep copper removal and reducing sulfur enrichment. The compound sulfurizing agent is prepared by mixing sodium sulfide and triethanolamine at a molar ratio of 1:0.05, and the addition rate is 75 mg / L.

[0034] (4) Magnetic seed enhanced separation: modified magnetic seeds Fe3O4@SiO2-CH3 (addition rate of 1.5 kg / m3) are added to the solution of step (3), and after stirring and reaction for 2 h, the solution is introduced into a low-intensity magnetic separator, and the magnetic field strength is controlled at 0.5 T. Under the action of the low-intensity magnetic field, the modified magnetic seeds attract each other to form chain-like aggregates, which capture and wrap CuS particles to form CuS magnetic flocculation. The CuS magnetic flocculation is adsorbed on the surface of the magnetic cylinder and discharged from the concentrate end, and after drying treatment, CuS magnetic flocculation concentrate is obtained, and the separated purified tail liquid can be recycled.

[0035] After the above treatment, the copper content in the solution is reduced from 2000 mg / L to 18 mg / L, and the copper removal rate is as high as 99.1%, and at the same time, CuCN copper concentrate with a yield of 1.82 kg / m 3 and a copper grade of 61.5% is obtained, and CuS magnetic flocculation copper concentrate with a yield of 2.1 kg / m 3 and a copper grade of 43% is obtained.

[0036] In order to further verify the effect of recycling the purified tail liquid to the cyanide leaching process, compared with the untreated high-concentration copper cyanide complex wastewater, when the purified tail liquid is used for ore cyanide leaching, the sodium cyanide consumption is reduced from 2.6 kg / t to 1.25 kg / t, and the gold leaching is increased from 88.1% to 94.5%. It can be seen that the use of wastewater treated by the process of the present application significantly reduces the amount of sodium cyanide used and improves the gold leaching rate.

[0037] The present application is described in detail through specific and preferred embodiments, but those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and any modifications, equivalent replacements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

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 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. 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; the composite sulfide is prepared by mixing sodium sulfide and triethanolamine in a molar ratio of 1:0.

05. (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 consumption of the composite vulcanizing agent is 75 mg / L.

6. 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.

7. 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.

8. The efficient copper removal and recycling process for copper-cyanide complex wastewater according to claim 1 or 7, characterized in that, In step (4), the magnetic field strength of the weak magnetic separator is controlled to be 0.5T.

Images