A Short-Process Treatment Method for Silver Electrolysis Anode Sludge

Abstract

This invention belongs to the field of hydrometallurgical technology for precious metals in non-ferrous metallurgy, specifically relating to a short-process treatment method for silver anode sludge in silver electrolysis. The method includes adding an alcohol medium to the silver anode sludge and subjecting it to ultrasonic vibration to disperse the elemental and compound elements present in the silver anode. The undersize material undergoes solid-liquid separation to obtain filter residue and filtrate. The filtrate is returned for further vibration dispersion. The oversize material is then melted and cast into silver anode plates using a reflow method. The obtained filter residue undergoes chlorination leaching to convert rare and precious metals such as gold, platinum, palladium, and rhodium into a chlorinated aqueous solution. The elemental silver and its silver compounds in the filter residue are converted into chlorinated slag containing silver chloride. The chlorinated solution is returned to the gold extraction process for gold separation or precipitation to obtain crude gold powder rich in platinum, palladium, and rhodium, which is used for refining to obtain gold ingots. The chlorinated slag is directly returned to the silver extraction process for reduction or silver separation to obtain high-quality crude silver powder for electrolysis. This invention features a simple process, a short flow, and achieves the recycling of material resources.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical precious metals technology, specifically relating to a short-process treatment method for silver electrolysis silver anode slime. Background Technology

[0002] Silver electrolytic anode slime is a byproduct of the silver electrolytic refining process. The silver anode slime content is typically 0.7-3%. Traditional anode slime composition mainly consists of: silver 30-40%, gold 6-10%, platinum 0.2-1.0%, palladium 0.5-1.0%, copper 0.5-1.5%, lead 0.4-1.0%, and bismuth 2.0-5.0%. However, with the application of high-current-density silver electrolysis technology, the quality of silver anode plates is improved, resulting in silver anode slime with a higher silver content than that produced by traditional low-current-density silver electrolysis. Current methods for treating silver anode slime mainly include nitric acid leaching-chlorination gold separation-gold-palladium purification, and nitric acid leaching-aqua regia gold dissolution-gold powder reduction.

[0003] A search of Chinese patent ZL202010209687.5 reveals a method for efficiently separating silver, platinum, and palladium from silver anode mud. This method uses nitric acid and an oxidant to control the oxidation leaching of the anode mud, recovering silver, platinum, and palladium from the leachate, and then recovering gold from the silver separation residue. Chinese patent ZL201510563937.4 discloses a comprehensive recovery method for platinum and palladium from silver anode mud. Addressing the problem of platinum and palladium dispersion, this method recovers platinum and palladium separately from the silver separation solution and the leaching residue, improving the recovery rate. Chinese patent ZL201010621176.0 discloses a silver anode mud treatment process. By optimizing the nitric acid silver separation process parameters, silver and palladium are leached from the silver anode mud, while gold and platinum enter the leaching residue, avoiding the dispersion of platinum and palladium. Chinese patent CN202310761435.7 discloses a method for recovering gold and silver from silver anode mud. The method involves detection, washing, drying, melting, ash blowing refining, gold separation, and casting. During pyrometallurgical smelting, gold and silver are incorporated into the alloy. Then, silver is separated by nitric acid to obtain a silver nitrate solution, which is then electrolyzed to obtain silver-separated slag, which is then used for gold recovery. This technology can recover gold and silver, but the process is lengthy. It is suitable for processing high-gold and high-silver materials using silver anode mud as an auxiliary material, but not for processing silver anode mud alone.

[0004] However, the existing process has drawbacks such as a long processing time, low gold and silver leaching rates, and easy loss of rare and precious metals during the process; the nitric acid silver separation process does not completely separate platinum and palladium in silver anode mud, resulting in low recovery rates; at the same time, the nitric acid-containing wastewater produced by the nitric acid production process is difficult to treat and the generated nitrogen oxides are difficult to control.

[0005] Therefore, developing a silver electrolytic anode mud treatment method that is simple in process, low in processing cost, high in rare and precious metal recovery rate, and more environmentally friendly is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, in order to solve the problems existing in the prior art, the present invention provides a short-process treatment method for silver electrolytic silver anode mud. This method is designed for high-silver anode mud and can be easily integrated into the existing anode mud treatment process to achieve recycling and avoid the loss of rare and precious metals in the treatment process.

[0007] To achieve the above objectives, the present invention aims to provide a short-process treatment method for silver electrolysis silver anode mud.

[0008] A short-process treatment method for silver electrolysis silver anode slime, comprising the following steps:

[0009] (1) Ultrasonic vibration dispersion-screening treatment: After adding alcohol medium to the silver anode mud, ultrasonic vibration is performed to disperse the elements and compounds present in the silver anode; after vibration for 10 to 50 minutes, the slurry is screened; the undersize is subjected to solid-liquid separation to obtain filter residue and filtrate, and the filtrate is returned to vibration dispersion; the oversize is reheated and cast into silver anode plates.

[0010] (2) Chlorination leaching: Add hydrochloric acid and oxidant to the filter residue obtained in step (1), heat and stir to leach, separate solid and liquid, and obtain chlorination liquid 1 and chlorination residue;

[0011] (3) Return the chlorinated liquid 1 obtained in step (2) to the copper anode mud chlorination and gold separation or gold immersion process to recover rare and precious metals such as gold, platinum, palladium and rhodium;

[0012] (4) After the chlorinated slag obtained in step (2) is purified by chlorination and removed from impurities, it is returned to the reduction and precipitation section of the silver extraction process to obtain crude silver powder, which is then used for the next stage of refining.

[0013] This invention employs a physical grading and screening method using ultrasonic vibration and sieving. This method allows for the direct and easy recovery of high-silver-content particles with larger particle sizes from the silver anode. The returned silver anode is then cast into silver anode plates for direct electrolysis, avoiding its entry into the process and improving silver recovery rate. Furthermore, the chlorination leaching process converts the undersize material (a small amount of elemental silver or silver compounds) into silver chloride, which is then added to the sludge. Gold, platinum, palladium, rhodium, and impurities are converted into chlorinated liquid, which enters the liquid phase. Even small amounts of elemental silver with low conversion rates may enter silver chloride and can be directly added to the precipitated silver process. Small amounts of gold, platinum, palladium, rhodium, and impurities that cannot be converted into the liquid phase can be compensated for through subsequent chlorination purification. The resulting chlorinated liquid is returned to the chlorination leaching process for acid replenishment, concentrating gold, platinum, palladium, and rhodium in the liquid phase, which can then be returned to the existing gold separation or precipitated gold process for centralized recovery of rare and precious metals. This solves the problem of low recovery rates for dispersed platinum and palladium. The chlorinated sludge, after purification, is reduced to produce high-quality silver powder, avoiding the problem of poor-quality silver powder produced by silver chloride reduction in existing processes. Therefore, this invention develops a simple, low-cost, high-rare-precious-metal recovery method for treating silver electrolytic anode sludge, which is also more environmentally friendly.

[0014] Furthermore, by weight percentage, the silver anode mud comprises: 60-85% silver, 2-6% gold, 0.2-1.0% platinum, 0.5-1.0% palladium, 0.05-0.2% rhodium, 0.5-1.5% copper, 0.4-1.0% lead, and 2.0-5.0% bismuth.

[0015] It is worth noting that this invention uses a combination of physical sieving and chemical dissolution followed by solid-liquid separation to quickly separate silver, lead, gold, platinum, palladium, rhodium, and other rare and precious metals from silver anode mud, achieving the raw material requirements for returning them to the silver extraction and gold extraction systems respectively. This invention realizes a short-process treatment of high-silver anode mud and comprehensive recovery of valuable metals, and has advantages such as short process, single reagent consumption, and low operating costs.

[0016] Furthermore, in step (1), the ultrasonic transducer is distributed at the bottom of the material, and the mesh size of the sieve used for screening is 0 to 100 mesh, and the liquid-solid ratio of alcohol to silver anode mud is 2-3:1.

[0017] It is worth noting that the cavitation effect generated by the ultrasonic vibration device at the bottom of the material can quickly vibrate the elemental silver in the silver anode mud, as well as the fine impurity particles or silver compounds adsorbed on the surface of the elemental silver. In the alcohol solution, the fine particles adsorbed on the surface of the elemental silver are easily detached and separated from the elemental silver particles. After sieving in the alcohol medium, the larger elemental silver particles are retained in the oversize material during the 0-100 mesh sieving process, resulting in a higher silver content in the oversize material. If the sieving mesh is too high, the oversize material will have a lower silver content, which is not suitable for direct silver refining; if the sieving mesh is too low, the oversize material will have a higher silver content, but the direct silver recovery rate will be low. When sieving in the alcohol medium, fine particles (impurities or fine elemental silver) or silver compounds easily enter the mixture of undersize material and alcohol. During the sieving process, fine particles or silver compounds will not chemically react with or adhere to the alcohol, which facilitates thorough liquid-solid separation and subsequent operation.

[0018] Furthermore, in step (2), the oxidant is one or two of sodium chlorate, hydrogen peroxide, and hypochlorous acid, the hydrochloric acid concentration is 3-5 mol / L, the solid-liquid ratio of chlorination leaching is 4:1, the reaction time is 3-4 hours, and the endpoint pH potential is greater than 1200mV.

[0019] It is worth noting that through chlorination leaching, fine particles (impurities such as lead, bismuth, copper, or fine elemental silver) react with hydrochloric acid under the action of the oxidizing agent at an oxidation potential of 1200mV. This causes elements such as gold, copper, platinum, palladium, lead, and bismuth in the material to be chlorinated in aqueous solutions of chloroauric acid, cuprous chloride, chloroplatinic acid, chloropalladic acid, lead chloride, and bismuth chloride, respectively. Meanwhile, elemental silver or silver compounds with a particle size of 0-100 mesh are easily reacted and converted into silver chloride slag, thus achieving the separation of silver from other metals. After cooling, lead chloride crystallizes out as supersaturated crystals and is separated from the aqueous solutions of gold, platinum, palladium, and rhodium.

[0020] Furthermore, in step (4), the concentration of hydrochloric acid used for chlorination purification is 3-5 mol / L, the reaction temperature is 80-85℃, the reaction time is 1-3 hours, and the aging time is 2-5 hours.

[0021] It is worth noting that the hydrochloric acid concentration used for chlorination purification is 3-5 mol / L, which further ensures that the impurity metals in the silver chloride slag are more thoroughly converted into a chlorinated aqueous solution and separated from the silver chloride. Simultaneously, after the reaction, aging for 2-5 hours allows the silver chloride slag crystals to grow, preventing the adsorption and entrainment of impurity ions by silver chloride during liquid-solid separation. This ensures that the silver chloride meets the quality requirements for downstream silver refining raw materials, shortens the silver extraction process, and reduces silver loss during the process.

[0022] Furthermore, the chlorinated liquid 2 obtained after chlorination purification and filtration in step (4) is returned to step (2) for chlorination leaching and acid replenishment.

[0023] In other words, by returning the residual gold, platinum, palladium, rhodium, and impurities in the chlorination residue to step (2) in step (4), the present invention can make comprehensive use of the hydrochloric acid in the chlorination solution, which facilitates the control of the hydrochloric acid concentration in step (2). At the same time, the gold, platinum, palladium, and rhodium in the chlorination solution can be recovered by returning them to step (2), thereby improving the recovery efficiency of precious metals and the removal rate of impurities.

[0024] Compared with existing technologies, this invention utilizes ultrasonic vibration-sieving in an alcohol medium to rapidly separate and classify elemental silver particles from fine impurities or silver compounds adsorbed on the surface of elemental silver in silver anode mud, and recovers them separately. The elemental silver particles on the sieve are directly processed into silver anode plates in the reaction process, reducing the recovery rate loss caused by the return of this portion of silver for reprocessing. After solid-liquid separation, the liquid screening agent of the undersize material can be recycled, and the filter residue is chlorinated to bring the rare and precious metals such as gold, platinum, palladium, and rhodium contained in the material into the liquid phase. Its composition meets the conditions for direct return to gold precipitation or gold separation and acid replenishment, so that all rare and precious metals are enriched and enter the gold extraction process for comprehensive recovery. The gold extraction process is a conventional technology. The entire process is short, simple to operate, and environmentally friendly. At the same time, it enriches and recovers valuable elements such as silver, gold, platinum, palladium, and rhodium in silver anode mud with a high recovery rate. It is suitable for simple integration into existing anode mud treatment processes to achieve recycling and avoid the loss of rare and precious metals in the treatment process. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figure 1 This is a process flow diagram of the short-process treatment method for silver electrolytic silver anode slime of the present invention. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0029] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0030] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0031] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0032] This invention belongs to the field of hydrometallurgical precious metals processing technology, specifically relating to a short-process treatment method for silver anode slime in silver electrolysis. The method includes adding an alcohol medium to the silver anode slime and subjecting it to ultrasonic vibration to disperse the elemental metals and compounds present in the silver anode. The undersize material undergoes solid-liquid separation to obtain filter residue and filtrate. The filtrate is returned for further vibration dispersion. The oversize material is then melted and cast into silver anode plates using a reflow method. The resulting filter residue undergoes chlorination leaching to convert rare and precious metals such as gold, platinum, palladium, and rhodium into a chlorinated aqueous solution. The elemental silver and its compounds in the filter residue are converted into chlorinated slag containing silver chloride. The chlorinated solution is returned to the gold extraction process for gold separation or precipitation to obtain crude gold powder rich in platinum, palladium, and rhodium, which is used for refining to obtain gold ingots. The chlorinated slag is directly returned to the silver extraction process for reduction or silver separation to obtain high-quality crude silver powder for electrolysis. This invention features a simple process and a short flow rate, making it suitable for simple integration into existing anode slime treatment processes to achieve recycling and avoid the loss of rare and precious metals during the treatment process.

[0033] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0034] Example 1

[0035] A short-process treatment method for silver electrolysis anode sludge:

[0036] (1) Take 1 kg of silver anode mud, add alcohol to the silver anode mud for slurrying, the amount of alcohol added is 2L, use a 50 mesh sieve to sieve, and obtain the larger particles on the sieve and the smaller particles on the sieve. The weight of the sieve is 450g, and the mass percentage of silver content is 95% by chemical analysis. It is directly mixed with 2000kg of coarse silver powder to cast silver anode plates, and the silver content is 99.3% by direct reading spectrometer analysis.

[0037] Table 1 Composition of silver anode mud in step (1)

[0038] element Ag Au Cu Pb Bi Pd Pt content 72.2％ 3.54％ 0.55％ 0.44％ 2.1％ 0.51％ 0.35％

[0039] (2) The undersize obtained in step (1) is subjected to solid-liquid separation to obtain a filter residue containing 53.5% silver (weighing 540g after drying) and a filtered liquid.

[0040] (3) Add 3 mol / L hydrochloric acid and 40 g sodium chlorate to the filter residue obtained in step (2), with a liquid-to-solid ratio of 4:1. Heat to 80-85℃ and stir for 3.5 hours. After the reaction is complete, age for 4 hours and perform liquid-solid separation to obtain silver chloride and chlorinated liquid. The silver chloride is dried and weighed 388 g. The silver content is determined to be 74.2% by chemical titration. The silver chloride is sent to the silver extraction system and reduced with hydrazine hydrate to obtain crude silver powder. The silver content is 99.95% by direct reading spectrometer analysis.

[0041] (4) Return 3950 mL of the chlorination solution obtained in step (3) to the gold extraction process to produce 233 g of crude gold powder (dry basis). The chemical titration test showed that the gold content was 15.01%, palladium content was 2.10%, and platinum content was 1.48%. The crude gold powder was directly returned to the gold refining system.

[0042] Example 2

[0043] A short-process treatment method for silver electrolysis anode sludge:

[0044] (1) Take 10 kg of silver anode mud, add alcohol to the silver anode mud for slurrying, the amount of alcohol added is 25L, use an 80 mesh sieve to sieve, and obtain the larger particles on the sieve and the smaller particles on the sieve; the weight of the sieve is 5150g, the mass percentage of silver content is 91% by chemical analysis, and it is directly mixed with 2000kg of coarse silver powder to cast silver anode plates, and the silver content is 99.1% by direct reading spectrometer analysis.

[0045] (2) The undersize obtained in step (1) is subjected to solid-liquid separation to obtain filter residue containing 52.2% silver (weighing 4850g after drying) and filtration liquid;

[0046] (3) Add 3 mol / L hydrochloric acid and 440 g sodium chlorate to the filter residue obtained in step (2), with a liquid-to-solid ratio of 4:1. Heat to 80-85℃ and stir for 3.5 hours. After the reaction is complete, age for 4 hours and perform liquid-solid separation to obtain silver chloride and chlorinated liquid. The silver chloride is dried and weighed 3320 g. The silver content is determined to be 74.5% by chemical titration. The silver chloride is sent to the silver extraction system and reduced with hydrazine hydrate to obtain crude silver powder. The silver content is 99.95% by direct reading spectrometer analysis.

[0047] (4) Return the 5650L chlorination solution obtained in step (3) to the crude gold powder for chlorination and gold separation, and comprehensively recover rare and precious metal elements such as gold, platinum, palladium and rhodium in the chlorination solution.

[0048] Example 3

[0049] A short-process treatment method for silver electrolysis anode sludge:

[0050] Take 15 kg of silver anode mud, add 30 L of alcohol to the silver anode mud for slurrying, and sieve it using a 100-mesh sieve to obtain larger particles on the sieve and smaller particles on the sieve. The weight of the sieve material is 8.6 kg, and the silver content is 88% by chemical analysis. It is directly mixed with 2000 kg of coarse silver powder to cast silver anode plates, and the silver content is 99.1% by direct-reading spectrometer analysis.

[0051] The slurry of the sieved material was filtered to obtain a filter residue containing 50.9% silver, with a dry weight of 6.4 kg. 3 mol / L hydrochloric acid and 550 g sodium chlorate were added at a liquid-to-solid ratio of 4:1. The mixture was heated to 80-85℃ and leached with stirring for 3.5 hours. After the reaction was complete, the residue was aged for 4 hours, followed by liquid-solid separation to obtain 4.3 kg of silver chloride, which, according to chemical titration, contained 74.5% silver. This silver chloride was dissolved in a sodium sulfite solution with a concentration of 220 g / L, and then reduced with 3.5 kg of formaldehyde to obtain crude silver powder containing 99.5% silver, which was used as a raw material for silver electrolysis.

[0052] Therefore, this invention uses a physical method of alcohol-sieving to easily separate particulate elemental silver from silver anode slime, quickly returning it to the silver electrolysis system and reducing silver smelting turnover. Fine-particle silver and its compounds are converted into a silver chloride slag phase through the recycling of hydrochloric acid and an oxidant. Aqueous solutions of rare and precious metals such as gold, platinum, palladium, and rhodium, as well as impurities such as lead and bismuth, are converted into chlorides and introduced into the liquid phase, thus separating them from the silver. The resulting silver chloride is purified by chlorination and returned to the silver roughing system, while the chlorinated aqueous solution is returned to the gold roughing system to recover rare and precious metals. This method has a concise overall process flow and can be used to treat silver anode slime independently or integrated into gold and silver hydrometallurgical processes. It is particularly suitable for silver electrolysis anode slime treatment schemes based on copper anode slime treatment processes.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A short process for the treatment of silver electrolytic silver anode slime, characterized in that, The specific steps include: (1) ultrasonic vibration dispersion-screening treatment: after adding alcohol medium in silver anode slime, ultrasonic vibration is carried out to disperse the single substance and compound existing in the silver anode slime; after vibration for 10-50 min, the slurry is screened; the undersize is subjected to solid-liquid separation to obtain filter residue and filtrate, and the filtrate is returned to vibration dispersion; the oversize is returned to fire method silver anode plate casting; the screen mesh size used in screening is 50-100 mesh; (2) chlorination leaching: the filter residue obtained in step (1) is added with hydrochloric acid and oxidizing agent, and is subjected to heating stirring leaching, solid-liquid separation, to obtain chlorination liquid 1 and chlorination residue; the terminal pH potential is greater than 1200 mV; (3) the chlorination liquid 1 obtained in step (2) is returned to copper anode slime chlorination gold separation or gold precipitation process to recover gold, platinum, palladium and rhodium; (4) after the chlorination residue obtained in step (2) is subjected to chlorination purification and impurity removal, it is returned to the reduction silver precipitation section of the silver extraction process to obtain crude silver powder, which enters the next section for refining; The silver anode slime includes, in mass percentage, silver 60-85%, gold 2-6%, platinum 0.2-1.0%, palladium 0.5-1.0%, rhodium 0.05-0.2%, copper 0.5-1.5%, lead 0.4-1.0% and bismuth 2.0-5.0%.

2. The method of claim 1, wherein, In step (1), the ultrasonic vibrator is distributed at the bottom of the material, and the liquid-solid ratio of alcohol to silver anode slime is 2-3:

1.

3. The method of claim 1, wherein, In step (2), the oxidizing agent is one or two of sodium chlorate, hydrogen peroxide and hypochlorous acid, the concentration of hydrochloric acid is 3-5 mol / L, the liquid-solid ratio of chlorination leaching is 4:1, and the reaction time is 3-4 hours.

4. The method of claim 1, wherein, In step (4), the concentration of hydrochloric acid used in chlorination purification is 3-5 mol / L, the reaction temperature is 80-85 ℃, the reaction time is 1-3 hours, and the aging time is 2-5 hours.

5. The method of claim 4, wherein, The chlorination liquid 2 obtained after chlorination purification in step (4) is returned to step (2) for chlorination leaching and acid supplement.

Images