Method for removing arsenic and recovering copper and zinc from scrap copper smelting smoke dust

Abstract

The invention discloses a method for removing arsenic and recovering copper and zinc from scrap copper smelting smoke dust, which comprises the following steps: carrying out first-stage acid leaching on the scrap copper smelting smoke dust to obtain first-stage leaching liquid and first-stage leaching slag; second-stage acid leaching is conducted on the first-stage leaching residues, second-stage leaching liquid and second-stage leaching residues are obtained, and the second-stage leaching liquid is returned to the first-stage acid leaching; zinc oxide is added into the first-section leaching solution to adjust the first-section leaching solution to a preset pH value, then iron powder is added to replace copper in the mixed leaching solution, and copper sponge and a replaced solution are obtained; zinc oxide is added into the replaced liquid to adjust the replaced liquid to a preset pH value, then ferrous sulfate heptahydrate is added, oxygen is introduced for oxidation arsenic precipitation, and arsenic precipitation residues and arsenic precipitation liquid are obtained; and adding zinc oxide into the arsenic-precipitated liquid to adjust the arsenic-precipitated liquid to a preset pH value for neutralization and purification to obtain neutralized and purified residues and a zinc sulfate solution, and returning the neutralized and purified residues to the second-stage acid leaching. According to the method, the valuable elements of arsenic, copper and zinc can be thoroughly separated, and arsenic precipitation caused in the zinc stannate decomposition process can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of non-ferrous metal smelting and solid waste treatment, and in particular to a method for removing arsenic from scrap copper smelting dust and recovering copper and zinc. The method can achieve efficient arsenic removal from zinc stannate-containing and high-arsenic scrap copper smelting dust, and simultaneously recover valuable metals such as copper and zinc. Background Art

[0002] Copper ore is mined and beneficiated to produce high-copper concentrate, the primary raw material for traditional copper pyrometallurgy. Compared to concentrate pyrometallurgy, scrap copper pyrometallurgy significantly reduces energy consumption, but both processes generate dust. Due to the diverse sources, complex types, and high concentration of impurities of scrap copper, the composition of the dust generated by pyrometallurgy is even more complex. While the dust is rich in various valuable metal elements and holds significant recycling value, it also contains toxic arsenic. The unregulated discharge and storage of arsenic-containing materials poses a serious threat to the environment and human health. After repeated reprocessing, valuable metals accumulate in the dust, hindering effective recovery and placing significant strain on the dust collection system, deteriorating furnace conditions, and impacting product quality. Due to differences in raw material composition and process conditions, the dust generated during pyrometallurgy varies significantly in composition, necessitating distinct treatment methods. Currently, copper smelting dust treatment technologies fall into two main categories: pyrometallurgical treatment and hydrometallurgical treatment.

[0003] Zinc stannate in smoke is not only chemically stable, but also induces arsenic precipitation during decomposition, making traditional processes inefficient in leaching zinc and arsenic. Efficiently leaching, separating, and recovering zinc, arsenic, and copper remains a challenge for companies.

[0004] Reference 1 (Zou Wei, Liu Junchang, Fu Weiqin, et al. Experimental study on leaching zinc and enriching lead and tin from zinc-lead-tin dust using sulfuric acid [J]. Hydrometallurgy, 2020, 39(1): 18-22.) uses zinc-lead-tin dust obtained from pyrometallurgical treatment of electroplating sludge as raw material. A two-stage countercurrent acid leaching process was used. Under the conditions of a liquid-to-solid ratio of 3 / 1, a temperature of 80°C, a leaching time of 1 hour, a sulfuric acid concentration of 30 g / L in the first leaching stage, and a sulfuric acid concentration of 110 g / L in the second leaching stage, the crystal structure of zinc stannate was destroyed, and zinc was completely leached with a leaching rate of 96.44%. Although this method can achieve efficient zinc leaching, the arsenic content in the dust used is only 2.65%, which is low-arsenic dust. Furthermore, no research was conducted on the leaching behavior of arsenic and the effective removal of arsenic from the leachate and the separation and recovery of valuable metals.

[0005] Reference 2 (Shi Shanlin, Lu Wen, Cao Xinyu, et al. Research on the separation and recovery process of tin, zinc, and cadmium from tin smelting dust [J]. Hydrometallurgy, 2024, 43(4): 380-384.) Using tin ore smelting dust as raw material, under the conditions of an initial sulfuric acid concentration of 15%, a liquid-to-solid volume mass ratio of 3:1, a leaching time of 120 min, and a leaching temperature of 90 °C, the leaching rates of Zn and Cd were 93.25% and 89.35%, respectively. Although this method can achieve the leaching of most of the zinc, some zinc stannate still remains in the leaching residue, indicating incomplete zinc leaching. In addition, the arsenic content in the dust used was only 1.56%, which is low-arsenic dust. The arsenic concentration of the leachate was 0.011 g / L, and the arsenic leaching rate was low, which cannot effectively remove arsenic from the dust.

[0006] Chinese patent CN116287759B discloses the leaching of arsenic-containing dust from copper smelting using aqueous sulfuric acid to produce lead-bismuth slag. Arsenic sulfide slag is used to separate copper and arsenic from the leachate, yielding low-arsenic copper sulfide slag. The copper precipitation solution is then cooled to produce high-purity arsenic trioxide crystals. After crystallization, the solution is returned to the copper smelting arsenic-containing dust leaching system for recycling, where zinc is circulated and enriched to produce a high-concentration zinc sulfate solution. This leaching process is only applicable to dust containing copper and zinc primarily as oxides and is not suitable for copper smelting dust with high zinc stannate and arsenic content.

[0007] Chinese patent CN113444886B discloses a pretreatment method in which smoke dust is mixed with concentrated sulfuric acid at a specific acid-to-dust ratio; the smoke dust is leached with dilute sulfuric acid, and the leached residue is sent to a lead smelting system for recovery; an alkaline agent is added to the primary leachate to remove arsenic from the solution as a stable solid arsenate; zinc powder is added to the post-arsenic precipitation solution to precipitate and recover copper from the solution as sponge copper; the post-copper precipitation solution is purified and concentrated and crystallized to obtain zinc sulfate heptahydrate. This method uses temperatures of 25°C to 60°C for both the pretreatment and dilute sulfuric acid leaching steps, which do not allow for the decomposition of zinc stannate, ignoring the decomposition temperature of zinc stannate.

[0008] Chinese patent CN106834708B discloses a method for removing soluble arsenic from flue dust through atmospheric pressure alkaline leaching. After catalytic oxidation of trivalent arsenic in the leachate to pentavalent arsenic, a stable arsenic-containing mineral is synthesized using a combination of controlled growth, distributed crystallization, lime precipitation, and precipitation conversion. This method removes arsenic from the flue dust, but leaves valuable metals in the slag, failing to achieve efficient recovery of these metals.

[0009] Fire leaching offers advantages such as a short process flow, low labor costs, and significant arsenic volatilization efficiency. However, it also suffers from high energy consumption, environmental pollution from the release of toxic and hazardous gases such as arsenic, low purity of the resulting arsenic trioxide, and low overall metal recovery rates. Hydrochloric acid leaching is highly corrosive to equipment. While pressurized leaching achieves high leaching rates for arsenic and valuable metals, it consumes a lot of energy, requires expensive leaching equipment, and is difficult to commercialize. Alkaline leaching allows for selective and efficient arsenic leaching, but suffers from low leaching rates for valuable metals, high alkali consumption, and high costs. Sulfuric acid leaching is relatively inexpensive and can achieve the majority of leaching of arsenic and valuable metals. In an acidic system, it creates favorable conditions for the subsequent separation of valuable metals from arsenic. Therefore, sulfuric acid is generally used to leach dust in industrial production.

[0010] In summary, currently available methods for treating copper smelting dust containing zinc stannate and arsenic all have several shortcomings, primarily manifested in three aspects: 1. They only consider the decomposition of zinc stannate, ignoring the leaching rate of arsenic, resulting in low arsenic leaching rates; 2. The raw material adaptability of the leaching process is low; and 3. The leaching temperature is low, preventing effective decomposition of zinc stannate. Summary of the Invention

[0011] In view of the deficiencies in the prior art, the present invention provides a method for removing arsenic and recovering copper and zinc from waste copper smelting dust containing high contents of zinc stannate and arsenic.

[0012] The present invention discloses a method for removing arsenic and recovering copper and zinc from waste copper smelting dust, wherein the waste copper smelting dust has a high content of zinc stannate and arsenic; the method comprises: Step 1: performing a first-stage acid leaching on the waste copper smelting dust to obtain a first-stage leachate and a first-stage leach residue; Step 2: performing a second-stage acid leaching on the first-stage leaching residue to obtain a second-stage leaching solution and a second-stage leaching residue, and returning the second-stage leaching solution to step 1 for a first-stage acid leaching; Step 3: adding zinc oxide to the first leachate to adjust the pH to a preset value, and then adding iron powder to displace the copper in the mixed leachate to obtain sponge copper and a displaced solution; Step 4: first adding zinc oxide to the replaced solution to adjust the pH to a preset value, then adding ferrous sulfate heptahydrate, and introducing oxygen to oxidize and precipitate arsenic, thereby obtaining arsenic precipitate residue and arsenic precipitate solution; Step 5: Add zinc oxide to the arsenic precipitation solution to adjust to a preset pH for neutralization and purification, thereby obtaining a neutralized and purified slag and a zinc sulfate solution. The neutralized and purified slag is returned to step 2 for secondary acid leaching.

[0013] As a further improvement of the present invention, the step 1 specifically includes: The waste copper smelting dust and the second-stage leachate are slurried with dilute sulfuric acid, and a first-stage acid leaching is carried out at 50-70° C. and a stirring speed of 300-500 r / min for 1-2 hours. After the reaction, solid-liquid separation is carried out to obtain a first-stage leaching residue and a first-stage leachate; wherein, the stirring speed is preferably 400 r / min, and the concentration of the dilute sulfuric acid solution is adjusted according to the acid consumption of different dusts, the liquid-solid ratio and the endpoint sulfuric acid concentration of the first-stage leachate are controlled to control the endpoint sulfuric acid concentration of the first-stage leachate to be not less than 12.6 g / L. The liquid-solid ratio of the waste copper smelting dust, the second-stage leachate and the dilute sulfuric acid is preferably 3-4 mL / g.

[0014] As a further improvement of the present invention, the step 2 specifically includes: The first-stage leaching residue and the neutralization and purification residue are slurried with dilute sulfuric acid, and a second-stage acid leaching is carried out at 90-100° C. and a stirring speed of 300-500 r / min for 1-2 hours. After the reaction, solid-liquid separation is carried out to obtain a second-stage leaching residue and a second-stage leachate. The stirring speed is preferably 400 r / min, and the concentration of the dilute sulfuric acid solution is adjusted according to the content of zinc stannate in the first-stage leaching residue and the neutralization and purification residue, and the liquid-solid ratio and the endpoint sulfuric acid concentration of the second-stage leachate are adjusted to control the endpoint sulfuric acid concentration of the second-stage leachate to be not less than 110 g / L. The liquid-solid ratio of the first-stage leaching residue and the neutralization and purification residue to the dilute sulfuric acid is preferably 3-4 mL / g.

[0015] As a further improvement of the present invention, the method further comprises: feeding the second-stage leaching slag into an electric furnace reduction smelting system.

[0016] As a further improvement of the present invention, the step 3 specifically includes: Zinc oxide is added to a first-stage leachate to adjust the pH to 1-1.5, and then iron powder is added. The mixture is reacted at 50-70° C. and a stirring speed of 300-500 r / min for 40-80 minutes to replace the copper in the mixed leachate. After the reaction, the mixture is filtered while hot to obtain sponge copper and a replaced solution. The iron powder is added at a Fe / Cu molar ratio of 1.2-1.4, the stirring speed is preferably 400 r / min, and the reaction time is preferably 1 hour.

[0017] As a further improvement of the present invention, the method further comprises: feeding the sponge copper into a copper smelting system.

[0018] As a further improvement of the present invention, step 4 specifically includes: Zinc oxide is added to the replaced liquid to adjust the pH to 1-1.5, and then ferrous sulfate heptahydrate is added and oxygen is introduced. The arsenic precipitation reaction is carried out at 90-100° C. and a stirring speed of 300-500 r / min for 1.5-2.5 hours. After the reaction, the arsenic precipitate residue and the arsenic precipitation liquid are obtained by hot filtration. The amount of ferrous sulfate heptahydrate is added according to an Fe / As molar ratio of 1-1.2, the flow rate of the oxygen (purity 99.9%) is 150-250 mL / min, the preferred stirring speed is 400 r / min, and the preferred reaction time is 2 hours.

[0019] As a further improvement of the present invention, the step 5 specifically includes: Zinc oxide is added to the arsenic precipitation solution to adjust the pH to 4-5, and a neutralization purification reaction is carried out at 50-90°C and a stirring speed of 300-500 r / min for 40-80 minutes. After the reaction, the solution is filtered while hot to obtain a neutralization purification residue and a zinc sulfate solution; wherein the preferred stirring speed is 400 r / min, and the preferred reaction time is 1 hour.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention can achieve complete separation of valuable elements such as arsenic, copper and zinc, and can avoid arsenic precipitation caused by the decomposition process of zinc stannate. The obtained lead-tin slag (second-stage leaching slag) has low arsenic content and high lead-tin grade, and can be used as a high-quality lead-tin raw material to be returned to the electric furnace reduction smelting system to smelt lead-tin alloy. The obtained sponge copper has high copper content and low arsenic content, and can be used as a high-quality raw material for copper smelting. The obtained ferric arsenate (arsenic precipitation slag) has high arsenic and iron contents, and can be used as a raw material for arsenic-iron alloy products. The obtained high-concentration zinc sulfate solution does not contain As and Fe, and can be sold directly or used to prepare zinc sulfate heptahydrate products through evaporation and crystallization. No waste liquid or waste gas is discharged during the treatment process, and the entire process is carried out under normal pressure, with low treatment cost, which can improve the economic benefits of copper smelting smoke treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention discloses a flow chart of a method for removing arsenic and recovering copper and zinc from waste copper smelting dust.

[0022] Figure 2 This is the XRD spectrum of smoke from the fuming furnace process.

[0023] Figure 3 This is the XRD pattern of electric furnace dust. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0025] The present invention is described in further detail below with reference to the accompanying drawings: like Figure 1 As shown, the present invention provides a method for removing arsenic and recovering copper and zinc from scrap copper smelting dust, wherein the scrap copper smelting dust has a high content of zinc stannate and arsenic; comprising: Step 1: slurrying the waste copper smelting dust and the second-stage leachate with dilute sulfuric acid, performing a first-stage acid leaching at 50-70° C. and a stirring speed of 400 r / min for 1-2 hours, and performing solid-liquid separation after the reaction to obtain a first-stage leaching residue and a first-stage leachate; wherein the concentration of the dilute sulfuric acid solution is adjusted according to the acid consumption of different dusts, the liquid-solid ratio and the endpoint sulfuric acid concentration of the first-stage leachate are adjusted to control the endpoint sulfuric acid concentration of the first-stage leachate to be not less than 12.6 g / L, and preferably the liquid-solid ratio of the waste copper smelting dust, the second-stage leachate and the dilute sulfuric acid is 3-4 mL / g.

[0026] Step 2, slurrying the first-stage leaching residue and the neutralization and purification residue with dilute sulfuric acid, performing second-stage acid leaching at 90-100° C. and a stirring speed of 400 r / min for 1-2 hours, performing solid-liquid separation after the reaction to obtain second-stage leaching residue and second-stage leachate, sending the second-stage leaching residue to an electric furnace reduction smelting system, and returning the second-stage leachate to step 1; wherein the concentration of the dilute sulfuric acid solution is adjusted according to the content of zinc stannate in the first-stage leaching residue and the neutralization and purification residue, the liquid-solid ratio and the endpoint sulfuric acid concentration of the second-stage leachate are controlled to control the endpoint sulfuric acid concentration of the second-stage leachate to be not less than 110 g / L, and preferably the liquid-solid ratio of the first-stage leaching residue and the neutralization and purification residue to the dilute sulfuric acid is 3-4 mL / g.

[0027] Step 3: Add zinc oxide to the first leachate to adjust the pH to 1-1.5, then add iron powder, react at 50-70° C. and a stirring speed of 400 r / min for 1 hour to replace the copper in the mixed leachate, and filter while hot after the reaction to obtain sponge copper and a replaced liquid; wherein the amount of iron powder is added according to a Fe / Cu molar ratio of 1.2-1.4.

[0028] Step 4: zinc oxide is added to the replaced liquid to adjust the pH to 1-1.5, and then ferrous sulfate heptahydrate is added, and oxygen is introduced. The arsenic precipitation reaction is carried out at 90-100° C. and a stirring speed of 400 r / min for 2 hours. After the reaction, the arsenic precipitate residue and the arsenic precipitation liquid are obtained by hot filtration; wherein, the amount of ferrous sulfate heptahydrate is added according to the Fe / As molar ratio of 1-1.2, and the flow rate of the introduced oxygen (purity 99.9%) is 150-250 mL / min.

[0029] Step 5: Add zinc oxide to the arsenic precipitation solution to adjust the pH to 4-5, carry out neutralization purification reaction at 50-90° C. and a stirring speed of 400 r / min for 1 hour, and filter while hot after the reaction to obtain neutralization purification residue and zinc sulfate solution.

[0030] In order to better understand the present invention, several steps described in the above invention are further described below.

[0031] For leaching scrap copper smelting dust and primary leaching residue, pure dilute sulfuric acid is the best choice. This has the advantage of preventing impurities from entering the zinc sulfate solution. Sodium hydroxide cannot be used to adjust pH, but zinc oxide must be used. This is because the addition of sodium hydroxide introduces sodium ion impurities, which can affect the quality of the subsequent zinc sulfate solution. Using zinc oxide to adjust pH does not introduce new impurities, but rather increases the zinc concentration of the zinc sulfate solution, increasing the valuation factor.

[0032] The first stage of leaching controls the acidity and temperature to dissolve arsenic oxides and metal oxides, preventing zinc stannate from dissolving and entering the first stage of leaching residue. The second stage of leaching uses high acid and high temperature to dissolve zinc stannate, avoiding the problem of arsenic precipitation caused by the decomposition of zinc stannate. The end point of the second stage leaching solution is high in acidity, so it is diluted with water to a certain acid concentration and then returned to the first stage of leaching, avoiding the use of a large amount of neutralizer and saving costs. Arsenic in scrap copper smelting dust mainly exists in the form of lead arsenate, arsenic trioxide and arsenic pentoxide, and zinc exists in the form of zinc stannate. Scrap copper smelting dust contains a large amount of oxides, such as copper oxide, zinc oxide, cadmium oxide, lead oxide and indium oxide. The main reactions that may occur in scrap copper smelting dust in dilute sulfuric acid aqueous solution are as follows: As2O5+ H2O= H3AsO4(1) As2O3+ H2O= H3AsO3 (2) ZnO+H2SO4=ZnSO4+H2O (3) CuO+H2SO4=CuSO4+H2O (4) CdO+H2SO4=CdSO4+H2O (5) Zn2SnO4 + 2H2SO4 = SnO2 + 2ZnSO4 + 2H2O (6) In2O3+3H2SO4=In2 (SO4)3+3H2O (7) Ferrous sulfate heptahydrate is used as an arsenic precipitation agent, and oxygen is used as an oxidant to oxidize trivalent arsenic and ferrous iron, and arsenic is precipitated in the form of ferric arsenate. A large number of experiments have shown that the use of hydrogen peroxide to oxidize ferrous iron and trivalent arsenic has a strong ability to oxidize hydrogen peroxide, resulting in a high concentration of trivalent iron in the solution, difficult liquid-solid separation, and a reduced arsenic precipitation rate. Therefore, using oxygen as an oxidant not only has a lower production cost than hydrogen peroxide, but also facilitates liquid-solid separation and a high arsenic precipitation rate. During the arsenic precipitation process, arsenic and iron precipitation is incomplete, and the impurity elements contained in the liquid after arsenic precipitation can affect the quality of the zinc sulfate solution. Therefore, zinc oxide is used to adjust the pH of the liquid after arsenic precipitation for neutralization and purification.

[0033] The advantages of the present invention are: 1. The effective decomposition of zinc stannate was achieved, and the problem of arsenic precipitation caused by the decomposition of zinc stannate was solved.

[0034] 2. The leaching rate of zinc and arsenic is improved, which not only prevents the circulation and accumulation of zinc and arsenic in the pyrometallurgical smelting system, but also renders the arsenic harmless and resource-based, reducing the threat posed by arsenic to the environment and human health.

[0035] 3. The valuable metals such as copper and zinc enriched in the leachate can be effectively recovered later, which can improve the comprehensive utilization rate of resources, bring certain economic benefits to the enterprise, and enhance the competitiveness of the enterprise.

[0036] 4. Sulfuric acid leaching is not only low-cost but also allows for the leaching of most arsenic and valuable metals. Furthermore, the acidic environment creates favorable conditions for the subsequent separation of valuable metals from arsenic. Example 1

[0037] The soot used in this example is a mixture of process soot, boiler soot, and ring-collected soot from a domestic company, all mixed according to their production ratios. The main components, by mass percentage (%), are: As 8.18%, Cu 0.68%, Zn 12.87%, Pb 19.85%, and Sn 11.92%.

[0038] S11, smoke dust leaching: The initial sulfuric acid concentration in the first stage of leaching was 75 g / L, analytical grade sulfuric acid was used (the same below), the reaction temperature was 70°C, the leaching time was 2 hours, the liquid-to-solid ratio was 3 mL / g, and the stirring speed was 400 r / min. The first stage leaching residue and first stage leachate were obtained by filtration. The results are shown in Table 1.

[0039] Table 1

[0040] S12, Second stage leaching: Under the conditions of an initial sulfuric acid concentration of 150 g / L for the second-stage leaching, a reaction temperature of 90°C, a leaching time of 2 hours, a liquid-to-solid ratio of 3 mL / g, and a stirring speed of 400 r / min, the second-stage leaching residue and second-stage leaching liquid were obtained by filtration. The results are shown in Table 2.

[0041] Table 2

[0042] S13, Iron powder replaces copper: The first-stage leachate was first treated with zinc oxide to adjust the pH to 1.5. Iron powder was then added at a Fe / Cu molar ratio of 1.4. The reaction was carried out at 60°C for one hour with a stirring speed of 400 rpm. The leached residue was filtered and washed to produce the replacement slag and post-replacement solution. The copper content in the replacement slag was 45.18%, and the copper precipitation rate was 81.04%. This can be returned to the copper smelting system as high-quality copper raw material.

[0043] S14, arsenic precipitation by oxidation: The pH of the replacement solution was adjusted to 1.5 by adding zinc oxide. Ferrous sulfate heptahydrate was then added at a Fe / As molar ratio of 1, and oxygen was introduced at a rate of 250 mL / min. The reaction was carried out at 90°C for 2 hours with a stirring rate of 400 rpm. The arsenic precipitate and the precipitate were filtered and washed. The arsenic and iron contents in the precipitate were 31.50% and 17.47%, respectively, and the arsenic precipitation rate was 90.27%.

[0044] S15, Neutralization and purification: Zinc oxide is added to the arsenic precipitation solution to adjust its pH to 5. The reaction is carried out at a temperature of 60°C for one hour with a stirring speed of 400 r / min. The solution is then filtered and washed to obtain a neutralized purified residue and a neutralized purified solution. This produces a highly concentrated zinc sulfate solution with a Zn concentration of 67.84 g / L while simultaneously reducing the Fe and As concentrations to 0 g / L. This zinc sulfate solution can be sold directly or used to produce zinc sulfate heptahydrate through evaporation and crystallization.

[0045] Example 2 The smoke used in this embodiment is the smoke from a domestic enterprise's fuming furnace process, such as Figure 2 As shown, its main components are calculated in mass percentage (%): As 8.99%, Cu 0.56%, Zn 14.24%, Pb 22.51%, and Sn 12.92%.

[0046] S21, smoke dust leaching: The initial sulfuric acid concentration in the first stage of leaching was 50 g / L, analytical grade sulfuric acid was used (the same below), the reaction temperature was 70°C, the leaching time was 2 hours, the liquid-to-solid ratio was 4 mL / g, and the stirring speed was 400 r / min. The first stage leaching residue and first stage leachate were obtained by filtration. The results are shown in Table 3.

[0047] Table 3

[0048] S22, Second stage leaching: Under the conditions of an initial sulfuric acid concentration of 150 g / L for the second-stage leaching, a reaction temperature of 95°C, a leaching time of 2 hours, a liquid-to-solid ratio of 4 mL / g, and a stirring speed of 400 r / min, the second-stage leaching residue and second-stage leaching liquid were obtained by filtration. The results are shown in Table 4.

[0049] Table 4

[0050] S23, Iron powder replaces copper: The first-stage leachate was first treated with zinc oxide to adjust the pH to 1. Iron powder was then added at an Fe / Cu molar ratio of 1.2. The reaction was carried out at 60°C for 1 hour with a stirring speed of 400 rpm. The leached residue was filtered and washed to produce the replacement slag and post-replacement solution. The copper content in the replacement slag was 57.31%, and the copper precipitation rate was 64.27%. This can be returned to the copper smelting system as high-quality copper raw material.

[0051] S24, arsenic oxide precipitation: The pH of the replacement solution was first adjusted to 1.2 by adding zinc oxide. Ferrous sulfate heptahydrate was then added at a Fe / As molar ratio of 1.2, and oxygen was introduced at a flow rate of 200 mL / min. The reaction was carried out at 95°C for 2 hours with a stirring rate of 400 rpm. The arsenic precipitate and the precipitate were filtered and washed. The arsenic and iron contents in the precipitate were 29.32% and 20.40%, respectively, and the arsenic precipitation rate was 84.00%.

[0052] S25, Neutralization and purification: Zinc oxide is added to the arsenic precipitation solution to adjust the pH to 4.5. The reaction is carried out at a temperature of 60°C for one hour and a stirring speed of 400 r / min. The solution is then filtered and washed to obtain a neutralized purified residue and a neutralized purified solution. This produces a highly concentrated zinc sulfate solution with a Zn concentration of 65.12 g / L while simultaneously reducing the Fe and As concentrations to 0 g / L. This zinc sulfate solution can be sold directly or used to produce zinc sulfate heptahydrate through evaporation and crystallization.

[0053] Example 3 The smoke used in this embodiment is the smoke from the electric furnace of a domestic enterprise, such as Figure 3 As shown, the main components are calculated in mass percentage (%): As 5.40%, Cu 0.00%, Zn 42.16%, Pb 11.50%, and Sn 14.22%.

[0054] S31, smoke dust leaching: The initial sulfuric acid concentration in the first stage of leaching was 200 g / L, the sulfuric acid used was analytical grade (the same below), the reaction temperature was 70°C, the leaching time was 2 hours, the liquid-to-solid ratio was 3 mL / g, and the stirring speed was 400 r / min. The first stage leaching residue and the first stage leachate were obtained by filtration. The results are shown in Table 5.

[0055] Table 5

[0056] S32, Second stage leaching: Under the conditions of an initial sulfuric acid concentration of 300 g / L for the second-stage leaching, a reaction temperature of 90°C, a leaching time of 2 hours, a liquid-to-solid ratio of 3 mL / g, and a stirring speed of 400 r / min, the second-stage leaching residue and second-stage leaching liquid were obtained by filtration. The results are shown in Table 6.

[0057] Table 6

[0058] Example 4 The soot used in this embodiment is the soot from a fuming furnace of a domestic enterprise, and its main components are (in mass percentage): As 8.99%, Cu 0.56%, Zn 14.24%, Pb 22.51%, and Sn 12.92%.

[0059] First stage leaching of smoke and dust: The initial sulfuric acid concentration in the first stage of leaching was 250 g / L, analytical grade sulfuric acid was used (the same below), the reaction temperature was 70°C, the leaching time was 2 hours, the liquid-to-solid ratio was 4 mL / g, and the stirring speed was 400 r / min. The first stage leaching residue and first stage leachate were obtained by filtration, as shown in Table 7.

[0060] Table 7

[0061] Example 5 The soot used in this embodiment is the soot from a fuming furnace of a domestic enterprise, and its main components are (in mass percentage): As 8.99%, Cu 0.56%, Zn 14.24%, Pb 22.51%, and Sn 12.92%.

[0062] First stage leaching of smoke and dust: The initial sulfuric acid concentration in the first stage of leaching was 250 g / L, the sulfuric acid used was analytical grade (the same below), the reaction temperature was 95°C, the leaching time was 2 hours, the liquid-to-solid ratio was 4 mL / g, and the stirring speed was 400 r / min. The first stage leaching residue and the first stage leachate were obtained by filtration. The results are shown in Table 8.

[0063] Table 8

[0064] Example 6 The soot used in this embodiment is the soot from a fuming furnace of a domestic enterprise, and its main components are (in mass percentage): As 8.99%, Cu 0.56%, Zn 14.24%, Pb 22.51%, and Sn 12.92%.

[0065] First stage leaching of smoke and dust: The initial sulfuric acid concentration in the first stage of leaching was 300 g / L, the sulfuric acid used was analytical grade (the same below), the reaction temperature was 95°C, the leaching time was 2 hours, the liquid-to-solid ratio was 4 mL / g, and the stirring speed was 400 r / min. The first stage leaching residue and the first stage leachate were obtained by filtration. The results are shown in Table 9.

[0066] Table 9

[0067] in conclusion: Examples 4-6 show that zinc stannate does not decompose at 70°C. When the temperature is raised to 95°C, zinc stannate decomposes, but the arsenic leaching rate decreases. Therefore, the traditional one-stage leaching process cannot achieve efficient leaching of zinc and arsenic.

[0068] Examples 1-3 show that for scrap copper smelting dust with high zinc stannate and arsenic contents, efficient leaching of zinc and arsenic can be achieved by using a two-stage leaching process.

[0069] Effect analysis: This invention achieves efficient separation and recovery of zinc stannate and arsenic through a two-stage countercurrent sulfuric acid leaching process. The first stage dissolves arsenic oxides and metal oxides at relatively low acidity (endpoint sulfuric acid concentration ≥12.6 g / L) and temperature (50-70°C), while simultaneously suppressing the decomposition of the zinc stannate to prevent arsenic precipitation. The second stage utilizes high acidity (endpoint sulfuric acid concentration ≥110 g / L) and high temperature (90-100°C) to forcefully decompose the zinc stannate, ensuring complete zinc leaching. The second-stage leachate is recycled to the first-stage leaching system, reducing the amount of neutralizer used and lowering costs.

[0070] This method uses zinc oxide as the sole pH regulator throughout the entire process, avoiding the introduction of sodium ion impurities and improving the purity and zinc concentration of the zinc sulfate solution. Key pH control points include before copper displacement (pH 1-1.5), before arsenic precipitation (pH 1-1.5), and neutralization purification (pH 4-5). During the copper displacement step, iron powder is added at an Fe / Cu molar ratio of 1.2-1.4 to selectively displace and produce high-purity sponge copper (copper content ≥45%). Arsenic precipitation is then achieved through oxygen oxidation (oxygen purity ≥99.9%, flow rate 150-250 mL / min) combined with ferrous sulfate heptahydrate to oxidize trivalent arsenic to pentavalent arsenic, generating a stable ferric arsenate precipitate (arsenic precipitation rate ≥84%).

[0071] After arsenic precipitation, the solution is neutralized and purified with zinc oxide to produce a high-concentration zinc sulfate solution (Zn ≥ 65 g / L) free of As and Fe. This solution can be directly used to crystallize zinc sulfate heptahydrate. The neutralized and purified residue is then returned to the secondary leaching system, achieving resource recycling. The final products include low-arsenic lead-tin slag (Pb ≥ 28%, Sn ≥ 17%, As ≤ 3.5%), which serves as a raw material for lead-tin alloys; high-purity sponge copper (Cu ≥ 45%, As ≤ 0.5%), which is used for copper smelting; and ferroarsenate slag (As ≥ 29%, Fe ≥ 17%), which is used to prepare ferroarsenic alloys.

[0072] The entire process operates at atmospheric pressure, eliminating waste liquid and gas emissions. The combined recovery rate for zinc, copper, lead, and tin is ≥90%, and the arsenic removal rate is ≥80%. The scope of protection encompasses two-stage leaching process parameters (acidity, temperature, liquid-to-solid ratio), reagent selection (zinc oxide, oxygen), product characteristics (purity, recovery), and recycling design, ensuring robust technical barriers and maximizing economic benefits.

[0073] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for removing arsenic and recovering copper and zinc from scrap copper smelting dust, wherein the scrap copper smelting dust has a high content of zinc stannate and arsenic; characterized in that: include: Step 1: performing a first-stage acid leaching on the waste copper smelting dust to obtain a first-stage leachate and a first-stage leach residue; Step 2: performing a second-stage acid leaching on the first-stage leaching residue to obtain a second-stage leaching solution and a second-stage leaching residue, and returning the second-stage leaching solution to step 1 for a first-stage acid leaching; Step 3: adding zinc oxide to the first leachate to adjust the pH to a preset value, and then adding iron powder to displace the copper in the mixed leachate to obtain sponge copper and a displaced solution; Step 4: first adding zinc oxide to the replaced solution to adjust the pH to a preset value, then adding ferrous sulfate heptahydrate, and introducing oxygen to oxidize and precipitate arsenic, thereby obtaining arsenic precipitate residue and arsenic precipitate solution; Step 5: Add zinc oxide to the arsenic precipitation solution and adjust it to a preset pH value for neutralization and purification to obtain neutralization and purification residue and zinc sulfate solution. The neutralization and purification residue is returned to step 2 for secondary acid leaching.

2. The method for removing arsenic and recovering copper and zinc from scrap copper smelting dust according to claim 1, characterized in that: The step 1 specifically includes: The waste copper smelting fume and the second-stage leaching solution are slurried with dilute sulfuric acid, and a first-stage acid leaching is carried out at 50-70° C. and a stirring speed of 300-500 r / min for 1-2 hours. After the reaction, solid-liquid separation is carried out to obtain a first-stage leaching residue and a first-stage leaching solution; wherein the endpoint sulfuric acid concentration of the first-stage leaching solution is not less than 12.6 g / L, and the liquid-to-solid ratio of the waste copper smelting fume, the second-stage leaching solution and the dilute sulfuric acid is 3-4 mL / g.

3. The method for removing arsenic and recovering copper and zinc from scrap copper smelting dust according to claim 1, characterized in that: The step 2 specifically includes: The first-stage leaching residue and the neutralization and purification residue are slurried with dilute sulfuric acid, and second-stage acid leaching is carried out at 90-100° C. and a stirring speed of 300-500 r / min for 1-2 hours. After the reaction, solid-liquid separation is carried out to obtain second-stage leaching residue and second-stage leachate; wherein the endpoint sulfuric acid concentration of the second-stage leachate is not less than 110 g / L, and the liquid-solid ratio of the first-stage leaching residue and the neutralization and purification residue to the dilute sulfuric acid is 3-4 mL / g.

4. The method for removing arsenic and recovering copper and zinc from waste copper smelting dust according to claim 1 or 3, characterized in that: Also includes: The secondary leaching slag is fed into the electric furnace reduction smelting system.

5. The method for removing arsenic and recovering copper and zinc from scrap copper smelting dust according to claim 1, characterized in that: The step 3 specifically includes: Zinc oxide is added to a first-stage leachate to adjust the pH to 1-1.5, and then iron powder is added. The mixture is reacted at 50-70°C and a stirring speed of 300-500 r / min for 40-80 minutes to replace the copper in the mixed leachate. After the reaction, the sponge copper and the replaced liquid are obtained by hot filtration. The amount of iron powder added is based on a Fe / Cu molar ratio of 1.2-1.

4.

6. The method for removing arsenic and recovering copper and zinc from scrap copper smelting dust according to claim 1 or 5, characterized in that: Also includes: The sponge copper is fed into the copper smelting system.

7. The method for removing arsenic and recovering copper and zinc from scrap copper smelting dust according to claim 1, characterized in that: The step 4 specifically includes: Zinc oxide is added to the replaced liquid to adjust the pH to 1-1.5, and then ferrous sulfate heptahydrate is added and oxygen is introduced. The arsenic precipitation reaction is carried out at 90-100° C. and a stirring speed of 300-500 r / min for 1.5-2.5 hours. After the reaction, the arsenic precipitate residue and the arsenic precipitation liquid are obtained by hot filtration. The amount of ferrous sulfate heptahydrate added is based on an Fe / As molar ratio of 1-1.2, and the flow rate of the introduced oxygen is 150-250 mL / min.

8. The method for removing arsenic and recovering copper and zinc from scrap copper smelting dust according to claim 1, characterized in that: The step 5 specifically includes: Zinc oxide is added to the arsenic precipitation solution to adjust the pH to 4-5, and a neutralization purification reaction is carried out at 50-90° C. and a stirring speed of 300-500 r / min for 40-80 minutes. After the reaction, the solution is filtered while hot to obtain a neutralization purification residue and a zinc sulfate solution.

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