Arsenic-containing anode mud treatment method
By using carbon powder and metallic Bi reducing agent to reduce arsenic-containing anode mud at low temperatures, and combining it with vacuum distillation and staged condensation technology, the problem of arsenic oxide volatilization was solved, and efficient and environmentally friendly recycling of metals from anode mud was achieved.
Patent Information
- Application Number
- CN202511540728.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-27
- Publication Date
- 2026-02-13
AI Technical Summary
In existing technologies, arsenic enters the flue dust in the form of As2O3 during the treatment of lead and copper anode sludge, which has no effective treatment, leading to environmental pollution and health threats, and the separation process is complex.
A mixture of carbon powder and metallic Bi was used as a reducing agent for solid arsenic smelting. Arsenic-containing anode mud was reduced at 400℃~500℃. Subsequently, elemental arsenic, lead-antimony-bismuth alloy, silver-copper-gold alloy and other metals were extracted by vacuum distillation and staged condensation separation. The low melting point and reducing properties of Bi were used for synergistic reduction and capture.
This method enables the effective reduction of arsenic oxides to elemental arsenic at low temperatures, avoiding arsenic volatilization, simplifying the separation process, and improving metal recovery rate and environmental friendliness.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of anode mud resource recovery, and more specifically, to a method for treating arsenic-containing anode mud. Background Technology
[0002] Lead and copper anode mud is a byproduct of lead and copper electrolytic refining. It is rich in precious metals (Au, Ag, Pt, Pd), rare and dispersed metals (mainly Se and Te), harmful elements (As, Sb, Bi), and base metals (Cu, Pb, Ni, etc.), all existing in the form of metals, sulfides, selenium / tellurium compounds, oxides, elemental sulfur, and complex basic salts.
[0003] Currently, both domestically and internationally, the main process for extracting precious metals such as silver and gold from lead and copper anode mud is "high-temperature smelting - multi-stage oxidation blowing - multi-step electrolytic refining". During the smelting stage, most of the arsenic enters the flue dust as As2O3 (commonly known as "arsenic trioxide"), and there are currently no effective disposal measures; it is mainly stored, posing a serious threat to human health and ecological safety. During the blowing stage, multiple repeated blowing processes are required to separate base metals such as lead, antimony, bismuth, and arsenic from precious metals such as silver and gold, making the separation process complex. Summary of the Invention
[0004] In view of the shortcomings of the prior art, one of the objectives of this invention is to solve one or more problems existing in the prior art. For example, one objective of this invention is to provide a method for processing arsenic-containing anode mud at low temperatures.
[0005] This invention provides a method for treating arsenic-containing anode mud, which may include the following steps: drying and sieving the arsenic-containing anode mud to obtain anode mud powder; mixing the anode mud powder with a reducing arsenic smelting agent, reducing and smelting it under an inert atmosphere at 400℃~500℃ until the reaction is completed, and cooling it to room temperature to obtain a product containing elemental arsenic, wherein the reducing arsenic smelting agent is a mixture of carbon powder and metallic Bi.
[0006] Furthermore, the reduction smelting time can be 2 to 3 hours.
[0007] Furthermore, the mass of carbon powder can be 7% to 15% of the mass of arsenic-containing anode mud, and the mass of metallic Bi can be 30% to 40% of the mass of arsenic-containing anode mud.
[0008] Furthermore, the arsenic-containing anode mud can be lead anode mud or copper anode mud.
[0009] Furthermore, the process may include the separation and extraction of products containing elemental arsenic. The separation and extraction may include: a single vacuum distillation at a vacuum degree of 20 Pa to 50 Pa and a temperature of 1000 °C to 1100 °C, followed by fractional condensation to obtain elemental arsenic, a lead-antimony-bismuth alloy, and a silver-copper-gold alloy, respectively; a second vacuum distillation of the silver-copper-gold alloy at a vacuum degree of 5 Pa to 10 Pa and a temperature of 1200 °C to 1300 °C to obtain elemental silver and a gold-copper alloy, respectively; and electrolysis of the elemental silver and the gold-copper alloy to enrich the gold and silver.
[0010] Furthermore, the time for a single vacuum distillation can be 2 to 3 hours, and the time for a second vacuum distillation can be 2 to 3 hours.
[0011] Furthermore, the reducing arsenic smelting agent may also include iron filings.
[0012] Furthermore, the mass of iron filings can be 7% to 15% of the mass of arsenic-containing anode mud.
[0013] Compared with the prior art, the beneficial effects of the present invention include at least the following: The method of the present invention uses Bi melt to coat the anode mud and works with carbon powder to reduce and smelt arsenic, which can further reduce the reduction and smelting temperature of arsenic, make the reaction more complete, ensure that all oxides in the anode mud are reduced, and facilitate the formation of intermetallic compounds between elemental arsenic and other reduced metals to fix it. This can prevent the oxides of metals such as arsenic and antimony from volatilizing into the flue gas, thereby achieving the environmentally friendly recycling of metals. Detailed Implementation
[0014] In the following, a method for treating arsenic-containing anode mud according to the present invention will be described in detail with reference to exemplary embodiments.
[0015] Specifically, on the one hand, this invention utilizes the low melting point of Bi (bismuth) and the characteristic that the reduction reaction is more complete in the molten environment of bismuth. The molten Bi encapsulates the anode mud for reduction smelting and arsenic fixation, further reducing the reduction smelting and arsenic fixation temperature to 400℃~500℃ and ensuring a more complete reaction, guaranteeing that all oxides in the anode mud are reduced. Furthermore, bismuth is an effective trapping agent for precious metals, and its use can effectively trap gold and silver. On the other hand, this invention uses carbon as a reducing agent, which can reduce the arsenic oxides in the anode mud to non-toxic elemental arsenic. Elemental arsenic forms intermetallic compounds with other reduced metals and is fixed, preventing the oxides of metals such as arsenic and antimony from volatilizing into the flue gas. Subsequent vacuum distillation and staged condensation can separate the various metals contained in the anode mud, achieving effective metal recovery and utilization.
[0016] This invention provides a method for treating arsenic-containing anode mud. In some embodiments, the method may include the following steps: S01, After drying the arsenic-containing anode mud, it is sieved to obtain anode mud powder; S02, anode mud powder is mixed with reducing arsenic smelting agent, and reduced and smelted in an inert atmosphere at 400℃~500℃ until the reaction is completed, and then cooled to room temperature to obtain a product containing elemental arsenic, wherein the reducing arsenic smelting agent is a mixture of carbon powder and metallic Bi.
[0017] In some implementation schemes, the arsenic-containing anode mud can be lead anode mud produced after lead electrolytic refining, or copper anode mud produced after copper electrolytic refining.
[0018] In some embodiments, reduction smelting under an inert atmosphere may include uniformly mixing anode mud powder with a sufficient amount of reducing arsenic-fixing smelting agent, using a crucible as the reaction vessel, covering the crucible, and placing it in a furnace such as a muffle furnace. The furnace is then purged with gas, and after purging, inert gas is introduced. When the pressure gauge shows positive pressure (one atmosphere), the temperature is raised to 400°C to 500°C. The oxides in the anode mud are reduced until the reaction is complete, yielding a product containing elemental arsenic. For example, the heating temperature can be a combination of 420°C to 490°C, 435°C to 470°C, 450°C to 465°C, or higher. In some embodiments, to better coat the anode mud with bismuth, a thicker layer of bismuth granules can be placed at the bottom of the crucible, followed by the mixture of anode mud powder and reducing arsenic-fixing smelting agent, and then another layer of bismuth granules can be placed on top of the mixture.
[0019] In some implementations, the reduction melting time can be 2 to 3 hours. For example, the reduction melting time can be a combination of 2.2 to 2.8 hours, 2.4 to 2.6 hours, or more.
[0020] In some implementations, the mass of carbon powder used can be 7% to 15% of the mass of arsenic-containing anode mud, and the mass of metallic Bi can be 30% to 40% of the mass of arsenic-containing anode mud. At these amounts of bismuth, the anode mud can be completely coated with bismuth, placing it in a molten environment to lower the temperature for arsenic reduction. At these amounts of carbon powder, it can be ensured that all oxides in the anode mud are reduced to elemental form, laying the foundation for subsequent separation and extraction. Through the synergistic effect of carbon powder and bismuth, the reduction and solidification of arsenic can be achieved by reduction smelting at 400℃ to 500℃ for 2 to 3 hours. For example, the mass of carbon powder can be 8% to 13% of the mass of arsenic-containing anode mud, and the mass of metallic Bi can be 32% to 38% of the mass of arsenic-containing anode mud. Another example is that the mass of carbon powder can be 10% to 12% of the mass of arsenic-containing anode mud, and the mass of metallic Bi can be 34% to 36% of the mass of arsenic-containing anode mud.
[0021] In some implementations, the product containing elemental arsenic after reduction smelting can be subjected to vacuum distillation-fractional condensation to separate the contained metals, specifically including: S100 is subjected to a single vacuum distillation at a vacuum level of 20 Pa to 50 Pa and a temperature of 1000 °C to 1100 °C. After staged condensation, elemental arsenic, lead-antimony-bismuth alloy, and silver-copper-gold alloy are obtained, respectively. For example, a single vacuum distillation can be performed at a vacuum level of 25 Pa to 45 Pa and a temperature of 1050 °C to 1080 °C.
[0022] S200 is used to perform a second vacuum distillation on a silver-copper-gold alloy at a vacuum level of 5 Pa to 10 Pa and a temperature of 1200 °C to 1300 °C, yielding elemental silver and a gold-copper alloy, respectively. For example, a second vacuum distillation of the silver-copper-gold alloy can be performed at a vacuum level of 6 Pa to 8 Pa and a temperature of 1220 °C to 1260 °C. S300 is used to electrolyze elemental silver and gold-copper alloys to enrich gold and silver.
[0023] In some implementations, vacuum distillation-stage condensation of the product after reduction smelting may include: placing the product containing elemental arsenic in a graphite crucible; placing a multi-stage condenser on top of the graphite crucible and placing it inside a furnace; and achieving staged condensation of pure arsenic by changing the stacking method of the condenser. The furnace lid is then closed. A vacuum pump is started, and the changes in the vacuum gauge are observed. When the vacuum level inside the furnace is lower than 10 Pa, the test temperature is set to 1000℃~1100℃, and the holding time is 2h~3h. The heating device is started, and the temperature is slowly heated to 1000℃~1100℃ and held. Throughout the process, the vacuum pump remains operational to maintain the furnace pressure at 20Pa~50Pa. By continuously changing the stacking method of the condenser, arsenic with a purity of over 99% is finally obtained on the first-stage condenser (the topmost condenser), a lead-antimony-bismuth alloy on the second-stage condenser, and a silver-copper-gold alloy as the residue. The silver-copper-gold alloy residue from vacuum distillation-stage condensation is subjected to a second vacuum distillation at a temperature of 1200℃~1300℃ for 2h~3h while maintaining a vacuum of 5Pa~10Pa in the furnace. This yields silver with 99% volatiles and a gold-copper alloy residue. The residue and volatiles are then simultaneously electrolyzed to rapidly enrich the silver and gold.
[0024] In some implementations, the mixture of carbon powder and metallic Bi may also include iron filings. The elemental iron and ferrous oxide in the scrap iron filings can act as reducing agents, synergistically reducing arsenic oxides in the anode slime with the added carbon powder, converting them into non-toxic elemental arsenic. The iron source in the scrap iron filings can also act as a fixative for arsenic, fixing it in place. Furthermore, during the reduction smelting process, iron reacts with sulfides in the anode slime to produce FeS, which floats to the surface and forms a very thin layer of matte. This matte layer can trap metals such as Cu, Se, and Te, achieving copper removal from the anode slime and avoiding the traditional wet copper removal process. The iron source in the scrap iron filings not only acts as a reducing agent but also as an arsenic fixative and copper removal agent, achieving the goal of treating waste with waste.
[0025] In some implementations, the iron filings can be 7% to 15% of the mass of the arsenic-containing anode mud. The addition of iron filings can synergistically reduce and fix arsenic with carbon powder, further reducing the smelting time to less than 2 hours. For example, the smelting time can be 1.2 to 1.8 hours.
[0026] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.
[0027] The composition of the anode mud raw materials used in the following examples and comparative examples is shown in Table 1.
[0028] Table 1 Composition of lead anode mud raw materials
[0029] Example 1 A method for treating arsenic-containing anode mud may include the following steps: Step 1: Weigh 50g of dried anode mud. Mix 4g of carbon powder and 5g of Bi particles into the dried anode mud. Place 10g of Bi particles (crucible diameter Ф50 mm) at the bottom of an alumina crucible, place the mixed material on top of the Bi particles, and then cover the material with another 5g of Bi particles. Cover the crucible and place it in the reactor.
[0030] Step 2: Place the reactor in a muffle furnace and purge it with gas. Then, purge the reactor with nitrogen until the pressure gauge reads one atmosphere, at which point stop purging. Set the heating program to 420℃ and the reduction time to 2 hours, and start the heating program. After the furnace temperature cools to room temperature, remove the reactor and collect the product. Perform ICP analysis on the product; the results are shown in Table 2 below.
[0031] Table 2 ICP Detection and Analysis of Products
[0032] Table 2 shows that As exists in the product in elemental form, without any arsenic oxides, indicating that all arsenic oxides in the anode mud were reduced to elemental arsenic. Calculations show that the arsenic fixation rate is over 95%, the direct silver recovery rate is 100%, and silver did not enter the smelting slag.
[0033] Step 3 involves vacuum distillation and fractional condensation of the product obtained in Step 2, specifically including: The product was placed in a graphite crucible, and a condenser was placed on top of the crucible. The furnace lid was closed. A vacuum pump was turned on to evacuate the furnace until the pressure inside the furnace dropped below 30 Pa. A heating program was set, and the temperature was increased to 1000 °C at a heating rate of 10 °C / min, and held for 3 hours for a single vacuum distillation. After the reaction was completed, the furnace was allowed to cool. The furnace was then opened, and the primary volatiles, secondary volatiles, and residue were removed. The residue was subjected to a second vacuum distillation, with a vacuum of 5 Pa, a temperature of 1250 °C, and a holding time of 3 hours. The resulting volatiles contained 99.9 wt% silver, and the residue contained 75 wt% gold.
[0034] ICP analysis was performed on the primary volatiles, secondary volatiles, and residues after a single vacuum distillation. The mass fractions of substances contained in the primary volatiles are shown in Table 3, the mass fractions of substances contained in the secondary volatiles are shown in Table 4, and the mass fractions of substances contained in the residues are shown in Table 5.
[0035] Table 3. Mass percentage of each substance in primary volatiles
[0036] Table 4. Mass percentage of each substance in secondary volatiles
[0037] Table 5. Mass percentage of each substance in secondary volatiles
[0038] Example 2 A method for treating arsenic-containing anode mud may include the following steps: Step 1: Weigh 50g of dried anode mud. Mix 7g of carbon powder and 10g of Bi particles into the dried anode mud. Place 3g of Bi particles at the bottom of the alumina crucible (crucible diameter Ф50 mm), place the mixed raw material on top of the Bi particles, and then cover the material with another 5g of Bi particles. Cover the crucible and place it in the reactor.
[0039] Step 2: Place the reactor in a muffle furnace and purge it with gas. Then, purge the reactor with nitrogen until the pressure gauge reads one atmosphere, at which point stop purging. Set the heating program to 480℃ and the reduction time to 2.6h, and start the heating program. After the furnace temperature cools to room temperature, remove the reactor and collect the product. Perform ICP analysis on the product; the results are shown in Table 6 below.
[0040] Table 6 ICP Detection and Analysis of Products
[0041] Example 3 A method for treating arsenic-containing anode mud may include the following steps: Step 1: Weigh 50g of dried anode mud. Mix 7g of carbon powder, 10g of Bi particles, and 5g of iron filings into the dried anode mud. Place 3g of Bi particles at the bottom of an alumina crucible (crucible diameter Ф50 mm), place the mixed material on top of the Bi particles, and then cover the material with another 5g of Bi particles. Cover the crucible and place it in the reactor.
[0042] Step 2: Place the reactor in a muffle furnace and perform a gas purging operation. Then, purge the reactor with nitrogen gas until the pressure gauge reads one atmosphere, at which point the purging is stopped. Set the heating program to 480℃ and the reduction time to 1.2h, and start the heating program. After the furnace temperature cools to room temperature, remove the reactor and collect the product. Perform ICP analysis on the product; the results are shown in Table 7 below.
[0043] Table 7 ICP Detection and Analysis of Products
[0044] Comparing Example 3 with Example 2 shows that, at the same reduction smelting temperature, adding iron filings will accelerate the rate of arsenic reduction and reduce the reduction smelting time.
[0045] Although the invention has been described above in conjunction with exemplary embodiments, those skilled in the art will understand that various modifications and changes can be made to the exemplary embodiments of the invention without departing from the spirit and scope defined by the claims.
Claims
1. A method for treating arsenic-containing anode mud, characterized in that, Includes the following steps: The arsenic-containing anode mud was dried and then sieved to obtain anode mud powder. Anode mud powder was mixed with a reducing arsenic smelting agent and reduced and smelted under an inert atmosphere at 400℃~500℃ until the reaction was complete. After cooling to room temperature, a product containing elemental arsenic was obtained. The reducing solid arsenic smelting agent is a mixture of carbon powder and metallic Bi.
2. The method for treating arsenic-containing anode mud according to claim 1, characterized in that, The reduction smelting time is 2 to 3 hours.
3. The method for treating arsenic-containing anode mud according to claim 1 or 2, characterized in that, The carbon powder content is 7% to 15% of the arsenic-containing anode mud content, and the metallic Bi content is 30% to 40% of the arsenic-containing anode mud content.
4. The method for treating arsenic-containing anode mud according to claim 1 or 2, characterized in that, Arsenic-containing anode mud is either lead anode mud or copper anode mud.
5. The method for treating arsenic-containing anode mud according to claim 4, characterized in that, It also includes the separation and extraction of products containing elemental arsenic, the separation and extraction of which includes: A vacuum distillation was carried out at a vacuum degree of 20 Pa to 50 Pa and a temperature of 1000 ° C to 1100 ° C, and after staged condensation, elemental arsenic, lead-antimony-bismuth alloy and silver-copper-gold alloy were obtained respectively. The silver-copper-gold alloy was subjected to a second vacuum distillation at a vacuum degree of 5 Pa to 10 Pa and a temperature of 1200 °C to 1300 °C to obtain elemental silver and gold-copper alloy, respectively. Electrolysis is performed on elemental silver and gold-copper alloys to enrich gold and silver.
6. The method for treating arsenic-containing anode mud according to claim 5, characterized in that, The time for the first vacuum distillation is 2 to 3 hours, and the time for the second vacuum distillation is 2 to 3 hours.
7. The method for treating arsenic-containing anode mud according to claim 1, 2, 5 or 6, characterized in that, Iron filings are also included in the reducing arsenic smelting agent.
8. The method for treating arsenic-containing anode mud according to claim 7, characterized in that, The weight of the iron filings is 7% to 15% of the weight of the arsenic-containing anode mud.