Method for recycling valuable substances and cyanides in cyanide-containing wastewater

Abstract

The invention provides a method for recycling valuable substances and cyanide in cyanide-containing wastewater, and belongs to the technical field of cyanide-containing wastewater treatment. The method comprises the following steps: firstly, carrying out replacement reaction on a physicochemical material (reducing substance zinc) and a copper-cyanogen complex in the cyanogen-containing wastewater to displace copper, and filtering to obtain filter residues containing zinc and copper, so as to realize copper recovery; in the replacement reaction, the copper-cyanogen complex in the filtrate is converted into a zinc-cyanogen complex with a lower stability constant, and then the zinc in the filtrate is recycled by diaphragm electrolysis. The method specifically comprises the following steps: dividing an electrolytic cell into a cathode region and an anode region by utilizing a membrane material, and enabling electrode reactions to be independently carried out, so that cyanide is prevented from entering the anode region to generate electrochemical oxidation and the decomposition of the cyanide is inhibited, and the cyanide is recycled in a solution for cyclic utilization; and then an alkali-resistant titanium-based coating electrode is used as an anode plate, a porous material is used as a cathode plate, recovery of zinc on the cathode plate is promoted, and recovery of valuable metal zinc and copper and cyclic utilization of cyanide are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of cyanide-containing wastewater treatment, and in particular to a method for recycling valuable substances and cyanide in cyanide-containing wastewater. Background Art

[0002] Cyanide gold extraction has become a mainstream process in today's gold industry due to its ease of operation and high gold recovery rates. However, gold mines are often associated with copper-containing minerals, which significantly interfere with cyanide leaching, slowing the gold dissolution rate and significantly increasing the amount of cyanide used. Furthermore, in the case of complex cyanide tailings containing copper-cyanide complexes, zinc-cyanide complexes, and iron-cyanide complexes, these tailings must undergo multiple recovery and disposal stages before they can be recycled. Previous single disposal processes have significant drawbacks, such as the safety hazard of hydrogen cyanide release during acid recovery, the high water cleanliness requirements of adsorption materials, and the fact that zinc-cyanide and iron-cyanide hinder the recovery of copper from the cyanide tailings during electrolytic recovery, resulting in reduced copper recovery efficiency. Furthermore, the various valuable metals are intermingled, making effective separation difficult, resulting in suboptimal recycling of the individual valuable metals.

[0003] Therefore, there is an urgent need to develop a combined disposal process for the disposal of cyanide tail liquid with complex composition, so as to achieve efficient recovery of metals and cyanide in cyanide-containing wastewater under alkaline environment, thereby achieving the goals of clean production and recycling, and promoting the sustainable development of the gold industry. Summary of the Invention

[0004] In light of the technical problems encountered in the background art, the present application provides a method for recycling valuable substances and cyanide in cyanide-containing wastewater. This method provides a safe and environmentally friendly physicochemical material-diaphragm electrolysis combined treatment process. This application innovatively integrates the replacement reaction of a reducing substance with diaphragm electrolysis. First, a physicochemical material (the reducing substance zinc) undergoes a replacement reaction with the copper-cyanide complex in the cyanide-containing wastewater to displace the copper, which is then filtered to obtain a copper-zinc mixture. During the replacement reaction, the copper-cyanide complex in the cyanide-containing wastewater is converted into a zinc-cyanide complex with a lower stability constant. The wastewater then enters the diaphragm electrolysis treatment process, where a diaphragm separates the electrolytic cell into a cathode and an anode, allowing the electrode reactions to proceed independently. This prevents cyanide from entering the anode and undergoing electrochemical oxidation, inhibiting cyanide decomposition. The cathode region electrolytically breaks down the zinc-cyanide complex in the solution, allowing zinc to be reduced and precipitated on the cathode plate, thereby achieving zinc recovery. The present application provides a method for recycling valuable substances and cyanide in cyanide-containing wastewater, comprising the following steps: S1, adding zinc powder to cyanide-containing wastewater, stirring, carrying out a displacement reaction in an airtight condition for 1-4 hours, filtering to obtain a filter residue containing zinc and copper and a filtrate containing a zinc-cyanide complex; S2, using a diaphragm electrolysis device to perform an electrolysis reaction on the filtrate; the diaphragm electrolysis device includes an electrolytic cell, a diaphragm that separates the electrolytic cell into a cathode area and an anode area, a cathode plate, an anode plate, and a microbubble device arranged in the electrolytic cell; the diaphragm is a cation exchange membrane; the cathode plate is an electrode plate made of a porous material; during the electrolysis reaction, the zinc cyanide complex in the filtrate is broken down by the electrolysis reaction in the cathode area, and zinc is reduced and precipitated on the cathode plate, thereby realizing zinc recovery.

[0005] The cyanide-containing wastewater is wastewater generated by the cyanide gold extraction process and contains cyanide and heavy metals, wherein the heavy metals include valuable substances zinc and copper.

[0006] Furthermore, the particle size of the zinc powder is greater than 500 mesh.

[0007] Furthermore, during the electrolysis reaction, the pH in the electrolytic cell is 9-14.

[0008] Furthermore, the electrolysis reaction was carried out in a constant current mode with a constant current of 0.5~2 A.

[0009] Furthermore, the electrolysis reaction was carried out in a constant voltage mode, with a constant voltage of 3.0~10V.

[0010] Furthermore, the cathode plate is one of graphite felt, activated carbon fiber, carbon felt, foam copper, foam nickel, foam zinc, and foam stainless steel.

[0011] Furthermore, during the electrolysis reaction, the distance between the anode plate and the cathode plate is 3 to 7 cm.

[0012] Furthermore, during the electrolysis reaction, the gas volume of the microbubble device is 1-4 mL / min.

[0013] Furthermore, the anode plate is a titanium-based coated electrode.

[0014] Furthermore, during the electrolysis reaction, the reaction temperature is ambient temperature, ranging from 10-30° C., and the reaction time is 1-4 hours.

[0015] The beneficial effects of this application are: 1. This application proposes a method for recycling valuable substances and cyanide in cyanide-containing wastewater. This method organically integrates a replacement reaction of a reducing substance and diaphragm electrolysis. First, a physicochemical material (a reducing substance, zinc) undergoes a replacement reaction with the copper-cyanide complex in the cyanide-containing wastewater to displace the copper. This is then filtered to produce a filter residue containing zinc and copper, thereby recovering the copper. During the replacement reaction, the copper-cyanide complex in the filtrate is converted into a zinc-cyanide complex with a lower stability constant. The zinc in the filtrate is then recovered using diaphragm electrolysis. The specific recovery principle is as follows: diaphragm electrolysis is used to separate the electrolytic cell into a cathode and an anode using a membrane material, allowing the electrode reactions to proceed independently. This prevents cyanide from entering the anode and undergoing electrochemical oxidation, inhibiting cyanide decomposition. Cyanide is then recovered in solution for recycling. Subsequently, an alkaline-resistant titanium-coated electrode is used as the anode plate, and a porous material with a large specific surface area is used as the cathode plate to facilitate the recovery of zinc at the cathode plate. Ultimately, the valuable metals zinc and copper in cyanide-containing wastewater are recovered and cyanide is recycled.

[0016] 2. The method of the present application can react at room temperature without heating, and achieves efficient recovery of metals and cyanide in cyanide-containing tail liquid in an alkaline environment, thereby realizing clean production and recycling of valuable substances and cyanide.

[0017] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0019] Figure 1 This is the full XPS spectrum of Example 1.

[0020] Figure 2 This is a physical diagram of the reaction process in the physicochemical material stage of Example 1.

[0021] Figure 3 This is a diagram of the physicochemical material reaction products of Example 1.

[0022] Figure 4 This is a physical diagram of the diaphragm electrolysis reaction process of Example 1. DETAILED DESCRIPTION

[0023] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0025] The purpose of this application is to provide a safe and environmentally friendly physicochemical material-diaphragm electrolysis combined treatment process for the complex composition of the cyanide tail liquid produced by the cyanide gold extraction process, so as to achieve efficient recovery of metals and cyanide in cyanide-containing wastewater under alkaline conditions, thereby achieving the goals of clean production and recycling, and promoting the sustainable development of the gold industry.

[0026] The present application provides a method for recovering metals and cyanide by combined treatment of physicochemical materials and diaphragm electrolysis by optimizing physicochemical materials and diaphragm electrolysis parameters.

[0027] The present invention provides a method for recycling valuable substances and cyanide in cyanide-containing wastewater, comprising the following steps: S1, adding zinc powder to cyanide-containing wastewater, stirring, carrying out a displacement reaction for 1-4 hours in an airtight condition, filtering, and obtaining a filter residue containing zinc and copper and a filtrate containing a zinc-cyanide complex.

[0028] Cyanide-containing wastewater is wastewater produced by the cyanide gold extraction process and contains cyanide and heavy metals, among which the heavy metals include valuable substances such as zinc and copper.

[0029] Among them, the particle size of the zinc powder is controlled to be larger than 500 mesh. A smaller particle size can provide more active sites and improve the recovery rate of copper.

[0030] Specifically, the dosage of zinc powder is 1~9 g / L.

[0031] S2, using a diaphragm electrolysis device to electrolyze the filtrate.

[0032] The diaphragm electrolysis device includes an electrolytic cell, a diaphragm that separates the electrolytic cell into a cathode region and an anode region, a cathode plate, an anode plate, and a microbubble device disposed in the electrolytic cell. The diaphragm is a cation exchange membrane.

[0033] The cathode plate is made of porous material, such as graphite felt, activated carbon fiber, carbon felt, foam copper, foam nickel, foam zinc, foam stainless steel, and the like.

[0034] The porous material has high electrical conductivity and can effectively conduct current, reduce electrode resistance, and reduce energy loss. In addition, the unique three-dimensional porous structure of the porous material gives the porous material a large specific surface area, which can increase the contact area between the electrode and the electrolyte, provide more reaction sites for the reduction of cations, and help improve the reduction rate of cations. It also helps to reduce the current density on the electrode surface and reduce the occurrence of side reactions. In addition, the high porosity can increase the rapid diffusion and penetration of the electrolyte inside the electrode, promote the transmission of cations to the electrode surface, improve the material transfer efficiency, help maintain the continuous progress of the electrode reaction, and can accommodate a certain amount of reaction products, reduce the accumulation of products on the electrode surface, maintain the activity and stability of the electrode, and thus improve the efficiency of electrolytic copper recovery.

[0035] The anode plate is a titanium-based coated electrode, which is acid and alkali resistant and has a long service life.

[0036] Aeration was performed using a microbubble device, and the microbubble volume was controlled at 1–4 mL / min.

[0037] The specific surface area of ​​the microbubbles in the microbubble device is much larger than that of conventional bubbles, which can significantly increase the gas-liquid contact area. When the microbubbles rise or burst, they will generate micro-turbulence in the solution, break the boundary layer on the electrode surface, reduce concentration polarization, thereby increasing the ion migration rate and improving the reaction efficiency.

[0038] Preferably, the electrolytic cell is a checkered card type with a stirring function, which can adjust the inter-electrode distance between the anode plate and the cathode plate, and the inter-electrode distance is 3 to 7 cm.

[0039] The electrolysis reaction can be carried out at room temperature, generally 10-30°C.

[0040] The electrolysis reaction is carried out in a constant current mode or a constant voltage mode, and the reaction time is 1.0~4.0 h.

[0041] When the constant current mode is used, the current is a constant current of 0.5~2 A; when the constant voltage mode is used, the voltage is a constant voltage of 3.0~10V.

[0042] During the electrolysis reaction, the pH in the electrolytic cell is 9~14.

[0043] The electrolysis parameters are a constant current of 0.5 to 2 A and a constant voltage of 3.0 to 10 V.

[0044] During the electrolytic reaction, the zinc-cyanide complex in the filtrate is broken down by the electrolytic reaction in the cathode area, and zinc is reduced and precipitated on the cathode plate, thereby realizing zinc recovery.

[0045] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0046] Example 1 The experimental water sample was the cyanide-containing tail liquid from a gold company's cyanidation treatment of copper-gold ore. Its main components are shown in Table 1 below. The unit is mg / L.

[0047] Table 1 Composition of copper-cyanide wastewater This embodiment provides a method for recycling valuable substances and cyanide in cyanide-containing wastewater, which is as follows: S1: Measure 1000 mL of cyanide tail liquid from a gold enterprise and stir it. Add 500-mesh zinc powder at a dosage of 3 g / L and stir to isolate the air for reaction. The replacement reaction time is 4 h. After the reaction is completed, filter to obtain a filter residue containing zinc and copper and a filtrate containing zinc cyanide complex. The reaction process is as follows: Figure 2 shown. Figure 3 This is a physical picture of the obtained filter residue.

[0048] S2, assemble the diaphragm electrolysis device, and the filtrate enters the diaphragm electrolysis device for electrolysis reaction, such as Figure 4 shown.

[0049] The diaphragm electrolysis device comprises a checkered card type electrolytic cell, a cation exchange membrane which divides the electrolytic cell into a cathode area and an anode area, a cathode plate, an anode plate and a micro bubble device arranged in the electrolytic cell.

[0050] A titanium-iridium-tantalum electrode was selected as the anode, and zinc foam was used as the cathode. The cathode and anode electrodes were placed in a cyanide-containing tail solution and aerated using a microbubble aerator. The interelectrode spacing was adjusted to 5 cm. The electrolysis parameters were adjusted to direct current electrolysis, with a constant current mode of 1.5 A and 5.0 V for a reaction time of 4 h.

[0051] After the reaction was completed, filtration was performed and the filtrate was measured.

[0052] Through calculation and analysis, it can be seen that the cyanide recovery rate can reach 93.8%, the copper recovery rate can reach 98.7%, and the zinc recovery rate can reach 70.4%, realizing the recycling of valuable substances and cyanide.

[0053] XPS characterization analysis was performed on the raw water (cyanide-containing tail liquid before treatment) and the filtrate after treatment used in Example 1. The results are as follows: Figure 1 shown.

[0054] It can be seen that after adopting the physicochemical material-diaphragm electrolysis combined process of the present application, the peaks of zinc and copper in the solution disappear, which shows that the content of valuable substances in the solution has dropped significantly, indicating that the valuable substances have been recycled.

[0055] Comparative Example 1 The main difference between Comparative Example 1 and Example 1 is that during the replacement reaction in step S1, no stirring was performed and no air was isolated. Other experimental parameters and conditions were basically the same as those in Example 1 and are not repeated here.

[0056] The experiment shows that in Comparative Example 1, the recovery rate of cyanide is 90.4%, the recovery rate of copper reaches 78.7%, the recovery rate of zinc can reach 32.4%, and the recovery rates of copper and zinc are reduced.

[0057] Comparative Example 2 The main difference between Comparative Example 2 and Example 1 is that stainless steel is used as the cathode plate. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0058] The experiment shows that in Comparative Example 2, the recovery rate of cyanide can reach 89.4%, the recovery rate of copper can reach 72.1%, and the recovery rate of zinc can reach 58.6%, and the recovery rates of copper and zinc are reduced.

[0059] Comparative Example 3 The main difference between Comparative Example 3 and Example 1 is that the microbubble aeration device is replaced by a magnetic stirring device. Other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0060] The experiment shows that in Comparative Example 3, the recovery rate of cyanide can reach 97.3%, the recovery rate of copper is 56.9%, the recovery rate of zinc is 74.8%, and the recovery rate of copper is significantly reduced.

[0061] Comparative Example 4 Comparative Example 4 provides a method for recycling valuable substances and cyanide in cyanide-containing wastewater. Compared with Example 1, the difference is that the particle size of the zinc powder is 325 mesh, as shown in Table 2. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0062] Examples 2-3 and Comparative Example 5 Examples 2-3 and Comparative Example 5 provide a method for recycling valuable substances and cyanide in cyanide-containing wastewater. Compared with Example 1, the difference is that the amount of zinc powder used is different, as shown in Table 2. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0063] Examples 4-5 and Comparative Examples 6-7 Examples 4-5 and Comparative Examples 6-7 provide a method for recycling valuable substances and cyanide in cyanide-containing wastewater. Compared with Example 1, the difference is that the inter-electrode spacing between the cathode plate and the anode plate is different, as shown in Table 2. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0064] Example 6 and Comparative Examples 8-9 Example 6 and Comparative Examples 8-9 provide a method for recycling valuable substances and cyanide in cyanide-containing wastewater. Compared with Example 1, the difference is that the time of the electrolysis reaction is different, as shown in Table 2. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0065] Examples 7-8 and Comparative Examples 10-11 Examples 7-8 and Comparative Examples 10-11 provide a method for recycling valuable substances and cyanide in cyanide-containing wastewater. Compared with Example 1, the difference is that the reaction current is different, as shown in Table 2. Other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0066] Example 9 and Comparative Examples 12-13 Example 9 and Comparative Examples 12-13 provide a method for recycling valuable substances and cyanide in cyanide-containing wastewater. Compared with Example 1, the difference is that the reaction voltage is different, as shown in Table 2. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0067] Comparative Example 14 Comparative Example 14 provides a method for recycling valuable substances and cyanide in cyanide-containing wastewater. Compared with Example 1, the difference is that the cation exchange membrane is replaced by anion exchange membrane, as shown in Table 2. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0068] The electrolysis parameters and test results of the embodiment and comparative example are shown in Table 2.

[0069] The present invention adopts a combined process of physicochemical materials and diaphragm electrolysis to recycle valuable substances and cyanide in cyanide-containing wastewater. As can be seen from the above table, the influence of relevant parameters on the experimental results is as follows: In Comparative Example 4, the zinc powder had a particle size of less than 325 mesh, and the zinc recovery rate was significantly reduced, indicating that smaller particle size and larger mesh size are more conducive to the reaction, and that stirring and oxygen isolation are required during the reaction.

[0070] Comparison of Examples 1-3 and Comparative Example 5 shows that a larger dosage can increase copper recovery, but will reduce zinc powder recovery and increase reagent costs.

[0071] Comparing Examples 1, 4-5 and Comparative Examples 6-7, it can be seen that when the inter-electrode distance is too small, mass transfer will be hindered, and when the inter-electrode distance is too large, resistance will increase, electric energy will be lost, and the experimental effect will be affected.

[0072] Comparison of Examples 1 and 6 with Comparative Examples 8-9 shows that when the electrolysis reaction time is too short, the reaction is insufficient and the effect is poor. Although extending the reaction time can improve the reaction effect to a certain extent, the energy consumption generated increases.

[0073] Comparing Examples 1, 7-9 and Comparative Examples 10-13, it can be seen that when the reaction current and voltage are too small, the effect is not good. When the current and voltage are increased, although the reaction effect will be increased, the power consumption increases, the cost is too high, and the economic cost is not appropriate.

[0074] In Comparative Example 14, the cation exchange membrane was replaced by an anion exchange membrane. Experiments have shown that the use of an anion exchange membrane will lead to obstruction of ion transport and affect the reaction effect.

[0075] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other methods constructed by applying various modifications that can be imagined by those skilled in the art to the embodiments and combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for recycling valuable substances and cyanide in cyanide-containing wastewater, characterized in that: The steps include: S1, adding zinc powder to cyanide-containing wastewater, stirring, carrying out a displacement reaction in an airtight condition for 1-4 hours, filtering to obtain a filter residue containing zinc and copper and a filtrate containing a zinc-cyanide complex; S2, using a diaphragm electrolysis device to perform an electrolysis reaction on the filtrate; the diaphragm electrolysis device includes an electrolytic cell, a diaphragm that separates the electrolytic cell into a cathode area and an anode area, a cathode plate, an anode plate, and a microbubble device arranged in the electrolytic cell; the diaphragm is a cation exchange membrane; the cathode plate is an electrode plate made of a porous material; during the electrolysis reaction, the zinc cyanide complex in the filtrate is broken down by the electrolysis reaction in the cathode area, and zinc is reduced and precipitated on the cathode plate, thereby realizing zinc recovery.

2. The method for recycling valuable substances and cyanide in cyanide-containing wastewater according to claim 1, characterized in that: The particle size of the zinc powder is greater than 500 meshes.

3. The method for recycling valuable substances and cyanide in cyanide-containing wastewater according to claim 1, characterized in that: During the electrolysis reaction, the pH in the electrolytic cell is 9~14.

4. The method for recycling valuable substances and cyanide in cyanide-containing wastewater according to claim 1, characterized in that: The electrolysis reaction was carried out in a constant current mode with a constant current of 0.5~2 A.

5. The method for recycling valuable substances and cyanide in cyanide-containing wastewater according to claim 1, characterized in that: The electrolysis reaction was carried out in a constant voltage mode with a constant voltage of 3.0~10V.

6. The method for recycling valuable substances and cyanide in cyanide-containing wastewater according to claim 1, characterized in that: The cathode plate is one of graphite felt, activated carbon fiber, carbon felt, foam copper, foam nickel, foam zinc, and foam stainless steel.

7. The method for recycling valuable substances and cyanide in cyanide-containing wastewater according to claim 1, characterized in that: During the electrolysis reaction, the distance between the anode plate and the cathode plate is 3 to 7 cm.

8. The method for recycling valuable substances and cyanide in cyanide-containing wastewater according to claim 1, characterized in that: During the electrolysis reaction, the gas volume of the microbubble device is 1-4 mL / min.

9. The method for recycling valuable substances and cyanide in cyanide-containing wastewater according to claim 1, characterized in that: The anode plate is a titanium-based coating electrode.

10. The method for recycling valuable substances and cyanide in cyanide-containing wastewater according to claim 1, characterized in that: During the electrolysis reaction, the reaction temperature is the ambient temperature, ranging from 10-30° C., and the reaction time is 1-4 hours.

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