Silver electrolyte recycling purification method based on secondary purification of silver residue

Abstract

This invention discloses a silver electrolyte recycling purification method based on secondary purification of silver-removing slag, belonging to the field of non-ferrous metal hydrometallurgical technology. This method addresses the problems of high silver oxide consumption and the generation of silver-containing hazardous waste in traditional silver electrolyte purification processes by innovatively utilizing the silver-removing slag produced from the primary purification. The silver-removing slag from the primary purification of the silver electrolyte is selectively leached with dilute nitric acid, allowing silver in the slag to be efficiently dissolved in the form of silver nitrate. The resulting silver-rich regenerated solution is directly reused as a purifying agent in the next batch of silver electrolyte purification process, utilizing the highly active silver hydroxide colloid generated in situ by silver ions to deeply remove impurities. This invention achieves selective recovery and closed-loop recycling of silver in the purified slag, significantly reducing silver oxide consumption and greatly reducing hazardous waste emissions, and has the advantages of short process and good purification effect.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal hydrometallurgical technology, specifically relating to a silver electrolyte circulation purification method based on secondary purification of silver slag. Background Technology

[0002] During the silver electrolytic refining process, impurity metal ions such as copper, lead, bismuth, and tellurium continuously accumulate in the electrolyte, leading to a decline in the quality of the cathode silver and a reduction in current efficiency. Regular purification is required to ensure the quality of the cathode silver. Traditional purification processes typically involve adding sodium hydroxide or silver oxide to the waste electrolyte to adjust the pH value and cause the impurities to hydrolyze and precipitate, thereby achieving purification. However, this process has the following shortcomings: (1) High consumption of silver oxide: Silver oxide, as the main purification agent, is expensive and is a disposable consumable; (2) Generation of new solid waste: The silver removal slag (mainly composed of silver hydroxide and impurity hydroxides) generated by precipitation is usually treated as hazardous waste, increasing environmental pressure and disposal costs; (3) Incomplete utilization of resources: The silver removal slag still contains a large amount of silver (in the form of silver hydroxide), and direct disposal results in the waste of precious metal resources.

[0003] Existing technologies have explored some aspects of the above-mentioned problems. Patent CN101445952A discloses a method for cleaning and treating silver electrolysis waste liquid, mainly focusing on optimizing the silver ammonia complex ion Ag(NH3). 2+ The preparation and purification reaction pH parameters are discussed in patent CN115404518A, which discloses a method for preparing silver electrolyte using silver-containing waste liquid, but it mainly focuses on the preparation of silver oxide and copper hydroxide and the optimization of reaction parameters. It is evident that existing technologies have not effectively solved the problems of high silver oxide consumption and insufficient resource utilization of silver residue during the purification process of silver electrolyte.

[0004] Therefore, developing a purification method that can reduce silver oxide consumption, simplify the silver slag recovery process, and simultaneously achieve a closed-loop cycle of silver elements is of great significance for cost reduction, efficiency improvement, and green development in the industry. Summary of the Invention

[0005] To overcome the problems existing in the background technology, the present invention provides a silver electrolyte recycling purification method based on secondary purification of silver removal slag. The silver removal slag generated from the primary purification is used as the raw material for secondary purification. It is dissolved and regenerated into a purified liquid rich in silver nitrate by dilute nitric acid and reused in a new round of electrolyte purification process, thereby significantly reducing the consumption of fresh silver oxide and realizing the closed-loop circulation of silver and the resource utilization of waste slag.

[0006] To achieve the above objectives, this application provides a silver electrolyte circulation purification method based on secondary purification of silver slag removal, the specific scheme of which is as follows: (1) Primary purification and generation of silver slag: The silver electrolysis waste liquid is pumped into the reactor, sodium hydroxide is added and stirred to react, and then the silver oxide is obtained by pressure filtration. The pH of the system is adjusted to 5-6 by adding the silver oxide obtained by pressure filtration. After reacting for 30-80 min, solid-liquid separation is carried out to obtain the primary purified liquid and silver slag rich in silver hydroxide. (2) Acid dissolution regeneration of silver-removed slag: The silver-removed slag obtained in step (1) is transferred to a purification vessel, a dilute nitric acid solution is added, and the mixture is stirred and dissolved at 30-80℃ to completely convert the silver hydroxide in the silver-removed slag into silver nitrate. After dissolution, the solution is filtered to obtain a clear regeneration purification liquid rich in silver nitrate. (3) Secondary purification: When purifying the next batch of silver electrolytic waste liquid, the regenerated purification liquid obtained in step (2) is pumped into the purification reactor as a purification agent until the pH of the system reaches 5-6. After the reaction, a slurry is obtained. If the alkali equivalent provided by the regenerated purification liquid is insufficient, silver oxide or sodium hydroxide is added until the pH of the system reaches 5-6. (4) Post-purification treatment: The slurry obtained in step (3) is subjected to solid-liquid separation to obtain filtrate and secondary silver removal slag. The filtrate is returned to the electrolysis system after sedimentation and acid adjustment, and the secondary silver removal slag is returned to step (2) to enter the next cycle.

[0007] Further preferred, in step (1), the main components of the silver electrolytic waste liquid include: Ag 100-150 g / L, HNO3 10-15 g / L, Cu ≥ 20 g / L, Pb ≥ 6 g / L, Bi ≥ 0.1 g / L, and Te ≥ 0.03 g / L.

[0008] Further preferred, in step (1), the amount of silver oxide used is 0.7-0.9 kg of silver oxide added per liter of silver electrolytic waste liquid.

[0009] Further preferred, in step (1), the amount of sodium hydroxide used is 0.07-0.10 kg of sodium hydroxide per liter of silver electrolytic waste liquid.

[0010] Further preferred, in step (1), the stirring speed is 100-200 rpm and the stirring time is 10-30 min.

[0011] Further preferably, in step (2), the concentration of the dilute nitric acid solution is 2-10 wt%.

[0012] Further preferred, in step (2), the stirring speed is 100-300 rpm and the stirring time is 10-30 min.

[0013] Further preferred, in step (2), the filtration method is to use a bag filter press for fine filtration.

[0014] Further preferred, in step (4), the Cu content in the filtrate is 0-5 g / L, the Bi content is 0-0.05 g / L, the Pb content is 0-2.0 g / L, and the Te content is 0-0.01 g / L.

[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application.

[0016] The beneficial effects of this invention are: 1. This application reduces the reliance on external purification reagents. By dissolving the silver-removing slag generated in the first purification process with dilute nitric acid, it converts it into a regenerated purification liquid and reuses it in the next batch of purification process. This achieves a closed-loop circulation of silver elements in the purification system, turning the silver-removing slag, which was originally hazardous waste, into a recyclable intermediate raw material, and significantly reducing the consumption of purification agents such as silver oxide or sodium hydroxide.

[0017] 2. This application reduces the discharge of silver-containing hazardous solid waste. The silver removal slag is directly reused in the purification system after acid dissolution and regeneration, avoiding the treatment of silver removal slag as hazardous waste in traditional processes. This effectively reduces the amount of silver-containing hazardous solid waste that needs to be discharged and reduces environmental risks.

[0018] 3. The purification effect of this application is stable and helps to improve the purification depth. Under the alkaline conditions of the secondary purification step, the silver ions in the regenerated purification liquid can generate highly active fresh silver hydroxide colloids in situ. Compared with the directly added solid silver oxide, it has a stronger adsorption and co-precipitation effect on impurity ions such as lead and tellurium in the waste liquid, which helps to improve the purification depth.

[0019] 4. The process provided in this application is concise. Except for the regeneration of silver slag, only two steps of dilute nitric acid dissolution and filtration are required to directly obtain reusable regenerated purified liquid without the need for complex purification processes. The overall process path is concise, easy to operate, and easy to promote. Attached Figure Description

[0020] Figure 1 This is the process flow diagram of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and beneficial effects of the present invention clearer, the preferred embodiments of the present invention will be described in detail below to facilitate understanding by those skilled in the art.

[0022] Unless otherwise specified, all reagents and materials used in the following examples were purchased from the market.

[0023] Example 1: The main components of the silver electrolytic waste liquid used in this embodiment are: Ag 132 g / L, HNO3 14 g / L, Cu 25 g / L, Pb 6.5 g / L, Bi 0.18 g / L, and Te 0.04 g / L.

[0024] (1) Primary purification and generation of silver slag: 1 L of silver electrolysis waste liquid was pumped into the purification reactor, 0.085 kg of sodium hydroxide was added, and the mixture was stirred at 100 rpm for 10 min to precipitate silver. The solution was then filtered through a filter press to obtain silver oxide. 0.85 kg of the filtered silver oxide was added to adjust the pH of the system to 5.5, so that the impurity metal ions were hydrolyzed and precipitated. At the same time, some silver ions were converted into silver hydroxide precipitate. After reacting for 30 min, the solid and liquid were separated by a filter press to obtain the primary purification liquid and silver slag rich in silver hydroxide (wet weight about 2.3 kg, water content about 35%, dry silver content about 45 wt%). (2) Acid dissolution regeneration of silver-removed slag: The silver-removed slag obtained in step (1) is transferred to a purification vessel, and 4.5 L of 10 wt% dilute nitric acid solution is added. The solution is stirred at 65℃ and 100 rpm for 10 min to dissolve the silver hydroxide in the silver-removed slag into silver nitrate. After dissolution, a bag filter press is used for fine filtration to obtain about 4.8 L of clear regenerated purification liquid rich in silver nitrate. (3) Secondary purification: When purifying the next batch of silver electrolysis waste liquid, the regenerated purified liquid obtained in step (2) is pumped into the purification reactor as a purifying agent, utilizing the Ag it contains. + Highly active silver hydroxide colloids are generated in situ under alkaline conditions to neutralize free acid in waste liquid and co-precipitate impurities. 0.03 kg of sodium hydroxide is added until the pH of the system reaches 5.5. After reacting for 30 min, a slurry is obtained. (4) Post-purification treatment: The slurry obtained in step (3) is subjected to solid-liquid separation to obtain filtrate and secondary silver removal slag. The filtrate is returned to the electrolysis system after sedimentation and acid adjustment. The filtrate contains Cu content of 3.8 g / L, Bi content of 0.03 g / L, Pb content of 0.8 g / L and Te content of 0.004 g / L. The secondary silver removal slag is returned to step (2) and enters the next cycle.

[0025] Example 2: The main components of the silver electrolysis waste liquid used in this embodiment are: Ag 110 g / L, HNO3 10.5 g / L, Cu 22 g / L, Pb 7.2 g / L, Bi 0.19 g / L, and Te 0.039 g / L. (1) Primary purification and generation of silver slag: 1 L of silver electrolysis waste liquid was pumped into the purification reactor, 0.080 kg of sodium hydroxide was added, and the mixture was stirred at 150 rpm for 20 min to precipitate silver. The solution was then filtered through a filter press to obtain silver oxide. 0.78 kg of the filtered silver oxide was added to adjust the pH of the system to 5.8, so that the impurity metal ions were hydrolyzed and precipitated. At the same time, some silver ions were converted into silver hydroxide precipitate. After reacting for 60 min, the solid and liquid were separated by a filter press to obtain the primary purification liquid and silver slag rich in silver hydroxide (wet weight about 2.1 kg, water content about 35%, dry silver content about 42 wt%). (2) Acid dissolution regeneration of silver-removed slag: The silver-removed slag obtained in step (1) is transferred to a purification vessel, and 4.0 L of 8 wt% dilute nitric acid solution is added. The solution is stirred at 70℃ and 200 rpm for 20 min to dissolve the silver hydroxide in the silver-removed slag into silver nitrate. After dissolution, a bag filter press is used for fine filtration to obtain about 4.3 L of clear regenerated purification liquid rich in silver nitrate. (3) Secondary purification: When purifying the next batch of silver electrolysis waste liquid, the regenerated purification liquid obtained in step (2) is pumped into the purification reactor as a purification agent. Since the alkali equivalent provided by the regenerated purification liquid is insufficient, 0.12 kg of silver oxide is added until the pH of the system reaches 5.8. After reacting for 60 min, a slurry is obtained, which utilizes the Ag it contains. + Highly active silver hydroxide colloids are generated in situ under alkaline conditions to neutralize free acids in waste liquid and co-precipitate impurities. (4) Post-purification treatment: The slurry obtained in step (3) is subjected to solid-liquid separation to obtain filtrate and secondary silver removal slag. The filtrate is returned to the electrolysis system after sedimentation and acid adjustment. The filtrate contains Cu content of 3.2 g / L, Bi content of 0.02 g / L, Pb content of 1.1 g / L and Te content of 0.004 g / L. The secondary silver removal slag is returned to step (2) and enters the next cycle.

[0026] Example 3: The main components of the silver electrolysis waste liquid used in this embodiment are: Ag 148 g / L, HNO3 14 g / L, Cu 22 g / L, Pb 6.9 g / L, Bi 0.18 g / L, and Te 0.045 g / L. (1) Primary purification and generation of silver removal slag: 1 L of silver electrolysis waste liquid was pumped into the purification reactor, 0.070 kg of sodium hydroxide was added, and the mixture was stirred at 200 rpm for 30 min to precipitate silver. The solution was then filtered through a filter press to obtain silver oxide. 0.72 kg of the filtered silver oxide was added to adjust the pH of the system to 5.4, so that the impurity metal ions were hydrolyzed and precipitated. At the same time, some silver ions were converted into silver hydroxide precipitate. After reacting for 80 min, solid-liquid separation was performed to obtain the primary purification liquid and silver removal slag rich in silver hydroxide (wet weight about 2.0 kg, water content about 35%, dry silver content about 40 wt%). (2) Acid dissolution regeneration of silver-removed slag: The silver-removed slag obtained in step (1) is transferred to a purification vessel, and 3.5 L of 9 wt% dilute nitric acid solution is added. The solution is stirred at 40℃ and 300 rpm for 30 min to dissolve the silver hydroxide in the silver-removed slag into silver nitrate. After dissolution, a bag filter press is used for fine filtration to obtain about 3.8 L of clear regenerated purification liquid rich in silver nitrate. (3) Secondary purification: When purifying the next batch of silver electrolysis waste liquid, the regenerated purified liquid obtained in step (2) is pumped into the purification reactor as a purifying agent until the pH of the system reaches 5.4. After reacting for 80 min, a slurry is obtained, which is then used to extract Ag. + Highly active silver hydroxide colloids are generated in situ under alkaline conditions to neutralize free acids in waste liquid and co-precipitate impurities. (4) Post-purification treatment: The slurry obtained in step (3) is subjected to solid-liquid separation to obtain filtrate and secondary silver removal slag. The filtrate is returned to the electrolysis system after sedimentation and acid adjustment. The filtrate contains Cu content of 3.6 g / L, Bi content of 0.025 g / L, Pb content of 1.2 g / L and Te content of 0.003 g / L. The secondary silver removal slag is returned to step (2) and enters the next cycle.

[0027] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for circulating purification of silver electrolyte based on secondary purification of silver slag removal, characterized in that, Includes the following steps: (1) Primary purification and generation of silver slag: The silver electrolysis waste liquid is pumped into the reactor, sodium hydroxide is added and stirred to react, and then the silver oxide is obtained by pressure filtration. The pH of the system is adjusted to 5-6 by adding the silver oxide obtained by pressure filtration. After reacting for 30-80 min, solid-liquid separation is carried out to obtain the primary purified liquid and silver slag rich in silver hydroxide. (2) Acid dissolution regeneration of silver-removed slag: The silver-removed slag obtained in step (1) is transferred to a purification vessel, a dilute nitric acid solution is added, and the mixture is stirred and dissolved at 30-80℃ to completely convert the silver hydroxide in the silver-removed slag into silver nitrate. After dissolution, the solution is filtered to obtain a clear regeneration purification liquid rich in silver nitrate. (3) Secondary purification: When purifying the next batch of silver electrolytic waste liquid, the regenerated purification liquid obtained in step (2) is pumped into the purification reactor as a purification agent until the pH of the system reaches 5-6. After the reaction, a slurry is obtained. If the alkali equivalent provided by the regenerated purification liquid is insufficient, silver oxide or sodium hydroxide is added until the pH of the system reaches 5-6. (4) Post-purification treatment: The slurry obtained in step (3) is subjected to solid-liquid separation to obtain filtrate and secondary silver removal slag. The filtrate is returned to the electrolysis system after sedimentation and acid adjustment, and the secondary silver removal slag is returned to step (2) to enter the next cycle.

2. The silver electrolyte circulation purification method based on secondary purification of silver slag removal according to claim 1, characterized in that, In step (1), the main components of the silver electrolytic waste liquid include: Ag 100-150 g / L, HNO3 10-15 g / L, Cu≥20 g / L, Pb≥6 g / L, Bi≥0.1 g / L, and Te≥0.03 g / L.

3. The silver electrolyte circulation purification method based on secondary purification of silver slag removal according to claim 1, characterized in that, In step (1), the amount of silver oxide used is 0.7-0.9 kg of silver oxide per liter of silver electrolytic waste liquid.

4. The silver electrolyte circulation purification method based on secondary purification of silver slag removal according to claim 1, characterized in that, In step (1), the amount of sodium hydroxide used is 0.07-0.10 kg of sodium hydroxide per liter of silver electrolytic waste liquid.

5. The silver electrolyte circulation purification method based on secondary purification of silver slag removal according to claim 1, characterized in that, In step (1), the stirring speed is 100-200 rpm and the stirring time is 10-30 min.

6. The silver electrolyte circulation purification method based on secondary purification of silver slag removal according to claim 1, characterized in that, In step (2), the concentration of the dilute nitric acid solution is 2-10 wt%.

7. The silver electrolyte circulation purification method based on secondary purification of silver slag removal according to claim 1, characterized in that, In step (2), the stirring speed is 100-300 rpm and the stirring time is 10-30 min.

8. The silver electrolyte circulation purification method based on secondary purification of silver slag removal according to claim 1, characterized in that, In step (2), the filtration method is to use a bag filter press for fine filtration.

9. The silver electrolyte circulation purification method based on secondary purification of silver slag removal according to claim 1, characterized in that, In step (4), the Cu content in the filtrate is 0-5 g / L, the Bi content is 0-0.05 g / L, the Pb content is 0-2.0 g / L, and the Te content is 0-0.01 g / L.

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