A method for recovering indium from indium-containing lead fumes

Abstract

The present application relates to a kind of indium-containing lead fume recycling indium method, the method includes (1) indium-containing lead fume is mixed with acid liquor and auxiliary agent, then roasting treatment is carried out, obtains roasting slag and roasting gas;The auxiliary agent includes ammonium salt pyrolysis;(2) the roasting slag of step (1) is treated with acid leaching, obtains filtrate and filter residue;(3) the roasting gas of step (1) is introduced into the filtrate of step (2), then electrochemical reduction is carried out and post-processing is handled, and indium product is obtained.The method of the present application introduces auxiliary agent to assist roasting process, promotes local disturbance and particle structure breakage of leaching system, enhances the exposure and diffusion of indium phase, so that indium and leaching agent are in full contact, thereby improving the leaching efficiency of indium;And through electrochemical reduction arsenic removal treatment, the efficient removal of arsenic is realized, and the arsenic removal efficiency can reach more than 95%, and the stability of the treated waste liquid is high.

Description

Technical Field

[0001] This invention relates to the field of solid waste disposal technology, and in particular to a method for recovering indium from lead-containing dust. Background Technology

[0002] Indium is a typical rare and dispersed metal, with an average abundance of only about 1 × 10⁻⁶ in the Earth's crust. -5 Indium has no independent exploitable deposits and is mainly obtained as a byproduct of lead and zinc smelting. Currently, the mainstream processes for recovering indium from indium-containing lead dust can be roughly divided into three categories: First, leaching with concentrated hydrochloric acid, dissolving indium with ≥30% HCl at room temperature or 50-80℃. Although the leaching rate is relatively high, Cl⁻ causes severe corrosion to equipment and HCl is highly volatile. Second, sulfation roasting—mixing the dust with concentrated sulfuric acid and roasting at 300-500℃, followed by leaching with dilute sulfuric acid. Although this can improve the decomposition efficiency of some impurities, it also generates PbSO₄ and Sb₂(SO₄) with Pb and Sb. 3. Insoluble precipitates form a passivation layer on the particle surface, reducing indium release; 3. Sulfuric acid + oxidant composite leaching—adding H2O2, KMnO4, MnO2, KClO3 and other auxiliaries to a sulfuric acid system at 80-120℃. Among them, H2O2 and KMnO4 react violently with sulfuric acid, posing safety hazards and creating a poor on-site working environment; MnO2 cannot effectively break the PbSO4 passivation layer; KClO3 can oxidize impurities, but it produces a large amount of Cl2 gas, which severely corrodes the equipment.

[0003] Currently, the recovery of indium from indium-containing lead-containing flue dust mainly relies on hydrochloric acid (HCl) or sulfuric acid (H2SO4) leaching processes. While hydrochloric acid systems offer high leaching rates for indium, Cl⁻ ions are highly corrosive to equipment, posing a challenge to the lifespan and operational safety of plant facilities.

[0004] If a sulfuric acid system is used, insoluble precipitates such as PbSO4 and Sb2(SO4)3 will be formed with lead and antimony during the leaching process. These precipitates form a passivation layer on the surface of lead dust particles, which hinders the contact between the leaching solution and the indium phase, resulting in a low indium leaching rate, with a single leaching rate of only about 40%.

[0005] Indium-lead dust commonly contains 3% to 25% arsenic, mostly in the form of As₂O₅ or its derivatives, which is a hazardous element. Current mainstream arsenic removal processes often use lime (CaO) to combine with As to form Ca₃(AsO₄)₂ precipitate. Although the reaction is simple, calcium arsenate has poor stability and is classified as hazardous waste, making it difficult to utilize or safely dispose of. Another arsenic removal method uses SO₂ to reduce As(V) to As₂O₃ (arsenic trioxide), which is easier to volatilize. However, this method often results in large amounts of SO₂ escaping, which is difficult to control and recover, posing environmental pollution and safety hazards.

[0006] CN115612865A discloses a method for recovering indium from lead-containing flue dust. The method involves mixing lead-containing flue dust with concentrated sulfuric acid and then calcining it to obtain calcined sand. The calcined sand is then ground and subjected to multi-stage countercurrent leaching to obtain an indium-containing leachate. The indium-containing leachate is then subjected to sulfur dioxide reduction to remove arsenic, followed by solid-liquid separation to obtain an arsenic-removed liquid. This arsenic-removed liquid is then purified to obtain an indium-rich indium-containing liquid, which is then extracted to obtain an indium-rich loaded organic phase and raffinate. However, the method of mixing lead-containing flue dust with concentrated sulfuric acid and then calcining it fails to break down the coating of lead flue dust formed by the sulfuric acid (either lead sulfate or antimony sulfate), resulting in a relatively low overall indium leaching rate.

[0007] CN113265544A discloses a fully wet process for recovering indium from high-lead, high-indium flue dust. The process involves low-acid leaching of indium-containing flue dust, in which concentrated sulfuric acid and concentrated hydrochloric acid are added to the indium-containing flue dust. After the reaction is complete, the low-acid leaching residue and indium-rich low-acid leaching solution are separated. However, the leaching reaction is carried out using concentrated sulfuric acid and concentrated hydrochloric acid. Concentrated hydrochloric acid is highly volatile and can easily volatilize into chlorine gas, which can cause equipment corrosion and a poor operating environment.

[0008] CN108998677A discloses a wet process for treating indium-containing high-arsenic flue dust. Using high-arsenic flue dust as raw material, water, caustic soda, and an oxidant are added for alkaline leaching, yielding a leachate containing arsenates and a leaching residue containing valuable metals such as antimony, lead, zinc, and silver. The leachate is then subjected to lime precipitation to remove arsenic. Arsenate ions in the solution combine with calcium ions to form water-insoluble calcium salts, which are added to the residue, resulting in a post-precipitation solution and calcium arsenate. While this method of removing arsenic by combining lime with arsenic to form calcium arsenate precipitate is simple, calcium arsenate has poor stability and is classified as hazardous waste, making it difficult to utilize or safely dispose of.

[0009] In summary, existing technologies mostly use sulfuric acid or hydrochloric acid leaching to recover indium, which cannot effectively remove arsenic from indium-lead dust. Furthermore, existing arsenic removal methods often pose secondary pollution or safety hazards. Therefore, there is an urgent need for a new method to recover indium from indium-lead dust that can improve the leaching rate of indium, efficiently remove arsenic, and avoid secondary pollution. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides a method for recovering indium from indium-lead-containing dust. The method involves roasting, acid leaching, electrochemical reduction for arsenic removal, purification, and extraction to obtain a high-purity indium product. By using an auxiliary agent to assist the roasting process, the passivation layer on the surface of the indium-lead-containing dust particles can be removed, thereby increasing the indium leaching rate. Furthermore, the electrochemical reduction for arsenic removal avoids the production of calcium arsenate, achieving highly efficient arsenic reduction and removal. This method is green and pollution-free, does not generate secondary pollution, and has high indium leaching efficiency, making it suitable for industrial applications.

[0011] To achieve this objective, the present invention adopts the following technical solution:

[0012] This invention provides a method for recovering indium from indium-containing lead-containing dust, the method comprising the following steps:

[0013] (1) After mixing indium-lead dust with acid and auxiliary agents, the mixture is roasted to obtain roasting residue and roasting gas; the auxiliary agents include ammonium salt pyrolytes;

[0014] (2) The roasted residue described in step (1) is subjected to acid leaching to obtain filtrate and filter residue;

[0015] (3) The roasting gas from step (1) is introduced into the filtrate from step (2), followed by electrochemical reduction to remove arsenic, purification and extraction to obtain indium product.

[0016] The method of this invention obtains high-purity indium products through roasting, acid leaching, electrochemical reduction for arsenic removal, purification, and extraction. An auxiliary agent is introduced to assist the roasting process. The ammonium salt pyrolysis auxiliary agent reacts at high temperatures to produce reducing gas and ammonia. The reducing gas breaks down the passivation layer on the surface of indium-lead dust particles, and through a synergistic effect, improves the chemical state of harmful elements, prevents passivation deposition, and promotes indium release, thereby increasing indium leaching efficiency. Ammonia helps improve indium migration and dispersion, promoting full contact between indium and the leaching agent. Furthermore, the reducing gas and ammonia generated during the roasting process can be used in subsequent electrochemical reduction for arsenic removal, realizing the resource utilization of by-product gases and reducing emission pressure.

[0017] The specific reactions of ammonium salt pyrolysis products at high temperatures to produce reducing gas and ammonia are as follows:

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] During roasting, concentrated sulfuric acid loses water to produce SO3 gas. SO3 is unstable and decomposes into SO2 and O2, thus producing a large amount of SO2 gas.

[0024] As a preferred technical solution of the present invention, the auxiliary agent in step (1) includes any one or a combination of at least two of ammonium sulfate, ammonium sulfite, ammonium bisulfate, and urea. Typical but non-limiting examples of such combinations include: ammonium sulfate and ammonium sulfite, ammonium sulfite and ammonium bisulfate, ammonium bisulfate and urea, etc.

[0025] In this invention, the auxiliary agent can react to produce sulfur dioxide and ammonia during high-temperature calcination. The gas generation process can promote local disturbance and particle structure rupture in the leaching system, enhance the exposure and diffusion of the indium phase, and enable indium to fully contact the leaching agent.

[0026] Preferably, the acid solution includes concentrated sulfuric acid.

[0027] In this invention, hot concentrated sulfuric acid has strong oxidizing properties and can convert low-valence indium into a high-valence state.

[0028] Preferably, the mass ratio of the indium-lead-containing fume, acid, and auxiliary agent is 1:(1~1.5):(0.005~0.025), such as 1:1:0.005, 1:1.5:0.001, 1:1:0.015, 1:1:0.02, 1:1:0.025, 1:1.5:0.025, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0029] Preferably, the calcination temperature is 300~400℃, such as 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0030] Preferably, the roasting gas comprises a mixture of sulfur dioxide and ammonia.

[0031] As a preferred technical solution of the present invention, the acid solution used in the acid leaching treatment in step (2) includes dilute sulfuric acid; the concentration of the acid solution is 1~3 mol / L, for example 1 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3 mol / L, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0032] Preferably, the temperature of the acid leaching treatment is 20~40℃, such as 20℃, 25℃, 30℃, 35℃, 40℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0033] The acid leaching time is 2 to 4 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0034] Preferably, the filter residue is subjected to lead recovery treatment.

[0035] As a preferred technical solution of the present invention, the roasting gas introduced in step (3) includes a mixture of sulfur dioxide and ammonia; the gas flow rate of sulfur dioxide is 1~5 kg / h, for example 1 kg / h, 2 kg / h, 3 kg / h, 4 kg / h, 5 kg / h, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0036] The ammonia gas flow rate is 0.05~0.15 kg / h, for example 0.05 kg / h, 0.07 kg / h, 0.09 kg / h, 0.11 kg / h, 0.13 kg / h, 0.15 kg / h, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] In this invention, the sulfur dioxide and ammonia produced during the roasting process can be collected and directly injected into the electrochemical reduction arsenic removal reaction system for use, thus realizing the reuse of sulfur dioxide, preventing it from escaping into the atmosphere, and improving environmental safety; and ammonia has a positive effect on H2O. + It has a buffering and neutralizing effect, and can adjust the pH value of the reaction system to 1.5~3.0, creating ideal conditions for electrochemical arsenic removal.

[0038] As a preferred technical solution of the present invention, the electrochemical reduction arsenic removal treatment in step (3) is carried out under stirring; the stirring rate is 300~500r / min, for example 300r / min, 350r / min, 400r / min, 450r / min, 500r / min, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] Preferably, the cathode for the electrochemical reduction arsenic removal treatment comprises any one of porous graphite plate, stainless steel, titanium coated with precious metal, nickel foam, and electrode felt.

[0040] Preferably, the cathode potential of the electrochemical reduction arsenic removal treatment is -0.2 to -0.4V, such as -0.2V, -0.25V, -0.3V, -0.35V, -0.4V, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] In this invention, the cathode potential is controlled to be -0.2 to -0.4V, within this defined range, As can be... 5+ Highly selective reduction to As 3+ It can be transferred to volatile or precipitated forms, but the concentration is lower than that of H. + The starting potential of the hydrogen evolution reaction can effectively suppress the large-scale generation of hydrogen gas and avoid the formation of an explosive atmosphere in the reaction system. The cathode potential range defined in this invention can prevent the evolution of large amounts of hydrogen gas and prevent foam interference.

[0042] The current density of the electrochemical reduction arsenic removal treatment is 5~20 mA / cm². 2 For example, 5mA / cm 2 10mA / cm 2 15mA / cm 2 20mA / cm 2 This applies to, but is not limited to, the listed values; other unlisted values ​​within the above range also apply.

[0043] In this invention, the current density is maintained at 5~20 mA / cm². 2 This ensures the efficiency of the reduction reaction while avoiding side reactions, thus achieving an arsenic removal efficiency of over 95%, and the treated waste liquid has high stability.

[0044] Preferably, the temperature of the electrochemical reduction arsenic removal treatment is 20~40℃, such as 20℃, 25℃, 30℃, 35℃, 40℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0045] The electrochemical reduction arsenic removal treatment time is 1.5 to 3 hours, such as 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0046] Preferably, the pH of the solution for the electrochemical reduction arsenic removal treatment is 1.5 to 3.0, such as 1.5, 2, 2.5, 3, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0047] In this invention, the hydrogen ions in the electrochemical reduction arsenic removal system are regulated by the ammonia gas generated during the roasting process, and the pH of the system is maintained at 1.5~3.0, which is beneficial to the stability of the system and the improvement of arsenic removal efficiency.

[0048] As a preferred technical solution of the present invention, the post-processing in step (3) includes purification treatment, extraction treatment, regeneration treatment, back-extraction treatment and displacement treatment.

[0049] Preferably, the purifying agent used in the purification process includes zinc powder and / or iron powder.

[0050] Preferably, the temperature of the purification treatment is 30~50℃, such as 30℃, 35℃, 40℃, 45℃, 50℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0051] The purification process takes 2 to 3 hours, such as 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0052] Preferably, the purification process yields purified residue.

[0053] Preferably, the purified residue is subjected to separation and recycling treatment.

[0054] As a preferred technical solution of the present invention, the purified liquid obtained after the purification treatment is subjected to extraction treatment.

[0055] Preferably, the extractant used in the extraction process includes a mixed solution of P2O4 and kerosene; the volume fraction of P2O4 in the mixed solution is 15-30%, for example, 15%, 20%, 25%, 30%, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0056] Preferably, the volume ratio of the extractant to the purified liquid in the extraction process is 1:(5~15), such as 1:5, 1:7, 1:9, 1:11, 1:13, 1:15, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0057] Preferably, the extraction temperature is 20~60℃, such as 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0058] The extraction time is 4 to 6 hours, such as 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0059] As a preferred embodiment of the present invention, the extraction process yields an organic phase and a raffinate; the organic phase is regenerated and back-extracted and reused in the extraction process; the raffinate is subjected to zinc recovery treatment.

[0060] As a preferred technical solution of the present invention, the organic phase obtained after the extraction treatment is further subjected to acid washing and impurity removal treatment before regeneration treatment; the acid solution used for acid washing and impurity removal treatment includes dilute sulfuric acid; the concentration of the acid solution is 1~3 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0061] Preferably, the regeneration process specifically includes: back-extraction of the organic phase after acid washing and impurity removal using a regenerating agent.

[0062] Preferably, the regenerant includes ammonium fluoride or hydrogen fluoride; the concentration of the regenerant is 0.5~1 mol / L, for example 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0063] Preferably, the regeneration process takes 0.5 to 1 hour, such as 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0064] As a preferred technical solution of the present invention, the regenerated organic phase is subjected to back-extraction treatment; the back-extraction treatment yields a back-extraction solution; the back-extraction solution is subjected to displacement treatment to obtain the indium product.

[0065] Preferably, the displacement treatment specifically includes: adding zinc powder to the back-extraction solution for displacement treatment.

[0066] Preferably, the temperature of the displacement treatment is 40~60℃, such as 40℃, 45℃, 50℃, 55℃, 60℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0067] The replacement process takes 3 to 6 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0068] Compared with the prior art, the present invention has at least the following beneficial effects:

[0069] (1) This invention introduces an auxiliary agent during the roasting process. Under high-temperature roasting conditions, the auxiliary agent decomposes to produce sulfur dioxide and ammonia. Sulfur dioxide can break the passivation layer of indium-lead dust and promote the release of indium. Ammonia can help improve the migration and dispersion of indium and promote full contact between indium and leaching agent. At the same time, the sulfur dioxide and ammonia produced by roasting can be used in the subsequent arsenic removal process to realize the resource utilization of by-product gas and reduce emission pressure.

[0070] (2) An electrochemical reduction arsenic removal process was adopted, and a low-potential electrochemical arsenic removal system was designed. The cathode potential was controlled at -0.2V to -0.4V. Combined with a mixture of sulfur dioxide and ammonia, efficient arsenic reduction and removal were achieved. By precisely controlling the cathode potential, As 5+Highly selective reduction to As 3+ It can be transferred to volatile or precipitated forms, avoiding the release of large amounts of hydrogen and preventing foam interference; the presence of ammonia can neutralize some of the H in the system. + Maintaining the pH at 1.5-3 is beneficial for system stability and improving arsenic removal efficiency. Attached Figure Description

[0071] Figure 1 This is a process flow diagram of a method for recovering indium from indium-containing lead-containing dust provided by the present invention. Detailed Implementation

[0072] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0073] Example 1

[0074] This embodiment provides a method for recovering indium from indium-containing lead-containing dust, the method comprising the following steps:

[0075] (1) Indium-lead dust, concentrated sulfuric acid and ammonium sulfate are mixed evenly in a mass ratio of 1:1:0.005 and then roasted at 300°C to obtain roasting residue and roasting gas; the roasting gas includes a mixture of sulfur dioxide and ammonia.

[0076] (2) The roasted residue from step (1) is acid-leached with 1 mol / L dilute sulfuric acid at 20°C for 4 hours to obtain filtrate and filter residue; the filter residue is then subjected to lead recovery treatment.

[0077] (3) A mixture of sulfur dioxide and ammonia is introduced into the filter residue from step (2). The flow rate of sulfur dioxide is 1 kg / h and the flow rate of ammonia is 0.05 kg / h. Electrochemical reduction treatment for arsenic removal is carried out at a stirring rate of 300 r / min and a temperature of 20°C for 3 h. The cathode for the electrochemical reduction treatment is a porous graphite plate with a cathode potential of -0.2 V and a current density of 5 mA / cm². 2 And control the pH to be between 1.5 and 3.0;

[0078] Zinc powder was then added to the solution after electrochemical reduction and arsenic removal, and the solution was purified at 30°C for 3 hours. The purified solution and the purified residue were then separated and recycled.

[0079] The purified liquid is subjected to extraction treatment at 20°C for 6 hours; the extractant used in the extraction treatment includes a mixed solution of P2O4 and kerosene; the volume fraction of P2O4 in the mixed solution is 15%; the volume ratio of the extractant to the purified liquid is 1:5.

[0080] The extraction process yields an organic phase and a raffinate; the organic phase is regenerated and back-extracted for reuse in the extraction process; the raffinate undergoes zinc recovery treatment.

[0081] The organic phase was acid-washed and impurities removed using 1 mol / L dilute sulfuric acid, and then regenerated using 0.5 mol / L ammonium fluoride for 1 h. The regenerated organic phase was then back-extracted, and a back-extraction solution was obtained. Zinc powder was added to the back-extraction solution, and a displacement treatment was performed at 40 °C for 6 h to obtain the indium product.

[0082] Example 2

[0083] This embodiment provides a method for recovering indium from indium-containing lead-containing dust, the method comprising the following steps:

[0084] (1) Indium-lead dust, concentrated sulfuric acid and ammonium sulfate are mixed evenly in a mass ratio of 1:1.5:0.025 and then roasted at 400°C to obtain roasting residue and roasting gas; the roasting gas includes a mixture of sulfur dioxide and ammonia.

[0085] (2) The roasted residue from step (1) is treated with 3 mol / L dilute sulfuric acid at 40°C for 2 hours to obtain filtrate and filter residue; the filter residue is then subjected to lead recovery treatment.

[0086] (3) A mixture of sulfur dioxide and ammonia is introduced into the filter residue from step (2). The flow rate of sulfur dioxide is 5 kg / h, and the flow rate of ammonia is 0.15 kg / h. Electrochemical reduction treatment for arsenic removal is carried out at a stirring rate of 500 r / min and a temperature of 40°C for 1.5 h. The cathode for the electrochemical reduction treatment is an electrode felt with a cathode potential of -0.4 V and a current density of 20 mA / cm². 2 And control the pH to be between 1.5 and 3.0;

[0087] Iron powder was then added to the solution after electrochemical reduction and arsenic removal, and the solution was purified at 50°C for 2 hours. The purified solution and purified residue were obtained after the purification treatment. The purified residue was then separated and recycled.

[0088] The purified liquid is subjected to extraction treatment at 60°C for 4 hours; the extractant used in the extraction treatment includes a mixed solution of P2O4 and kerosene; the volume fraction of P2O4 in the mixed solution is 30%; the volume ratio of the extractant to the purified liquid is 1:15.

[0089] The extraction process yields an organic phase and a raffinate; the organic phase is regenerated and back-extracted for reuse in the extraction process; the raffinate undergoes zinc recovery treatment.

[0090] After the organic phase is acid-washed and impurities are removed using 3 mol / L dilute sulfuric acid, it is regenerated using 1 mol / L ammonium fluoride for 0.5 h; the regenerated organic phase is then back-extracted; the back-extraction process yields a back-extraction solution; zinc powder is added to the back-extraction solution, and a displacement treatment is performed at 60 °C for 3 h to obtain the indium product.

[0091] Example 3

[0092] This embodiment provides a method for recovering indium from indium-lead dust. The only difference from Embodiment 1 is that the mass ratio of indium-lead dust, acid and auxiliary agent in step (1) is adjusted to 1:1:0.001. All other steps and conditions are the same as in Embodiment 1.

[0093] Example 4

[0094] This embodiment provides a method for recovering indium from indium-lead dust. The only difference from Embodiment 1 is that the mass ratio of indium-lead dust, acid and auxiliary agent in step (1) is adjusted to 1:1:0.03. All other steps and conditions are the same as in Embodiment 1.

[0095] Example 5

[0096] This embodiment provides a method for recovering indium from lead-containing flue dust. The only difference from Embodiment 1 is that the gas flow rate of sulfur dioxide in step (3) is adjusted to 0.5 kg / h. All other steps and condition parameters are the same as in Embodiment 1.

[0097] Example 6

[0098] This embodiment provides a method for recovering indium from indium-lead flue dust. The only difference from Embodiment 1 is that the gas flow rate of sulfur dioxide in step (3) is adjusted to 6 kg / h. All other steps and condition parameters are the same as in Embodiment 1.

[0099] Example 7

[0100] This embodiment provides a method for recovering indium from indium-lead flue dust. The only difference from Embodiment 1 is that the gas flow rate of ammonia in step (3) is adjusted to 0.01 kg / h. All other steps and conditions are the same as in Embodiment 1.

[0101] Example 8

[0102] This embodiment provides a method for recovering indium from indium-lead flue dust. The only difference from Embodiment 1 is that the gas flow rate of ammonia in step (3) is adjusted to 0.2 kg / h. All other steps and conditions are the same as in Embodiment 1.

[0103] Example 9

[0104] This embodiment provides a method for recovering indium from lead-containing dust. The only difference from Embodiment 1 is that the cathode potential in step (3) is adjusted to -0.1V. All other steps and condition parameters are the same as in Embodiment 1.

[0105] Example 10

[0106] This embodiment provides a method for recovering indium from indium-lead dust. The only difference from Embodiment 1 is that the cathode potential in step (3) is adjusted to -0.5V. All other steps and condition parameters are the same as in Embodiment 1.

[0107] Example 11

[0108] This embodiment provides a method for recovering indium from indium-lead-containing dust. The only difference from Embodiment 1 is that the current density in step (3) is adjusted to 3 mA / cm². 2 The other steps and conditions are the same as in Example 1.

[0109] Example 12

[0110] This embodiment provides a method for recovering indium from indium-lead-containing dust. The only difference from Embodiment 1 is that the current density in step (3) is adjusted to 22 mA / cm². 2 The other steps and conditions are the same as in Example 1.

[0111] Comparative Example 1

[0112] This comparative example provides a method for recovering indium from lead-containing dust containing indium. The only difference from Example 1 is that no auxiliary agent is added in step (1), and ammonia is used to adjust the pH of the system in the electrochemical reduction arsenic removal process in step (3). All other steps and conditions are the same as in Example 1.

[0113] Comparative Example 2

[0114] This comparative example provides a method for recovering indium from lead-containing dust. The only difference from Example 1 is that sodium persulfate is added in step (1), and ammonia is used to adjust the pH of the system in the electrochemical reduction arsenic removal process in step (3). All other steps and conditions are the same as in Example 1.

[0115] Comparative Example 3

[0116] This comparative example provides a method for recovering indium from lead-containing dust. The only difference from Example 1 is that the electrochemical reduction arsenic removal treatment in step (3) is replaced by adding lime for reduction arsenic removal treatment. All other steps and conditions are the same as in Example 1.

[0117] Comparative Example 4

[0118] This comparative example provides a method for recovering indium from lead-containing flue dust. The only difference from Example 1 is that the electrochemical reduction arsenic removal treatment in step (3) is replaced by the introduction of sulfur dioxide for reduction arsenic removal treatment. All other steps and conditions are the same as in Example 1.

[0119] Performance testing

[0120] The single leaching rate of indium and the arsenic removal efficiency in Examples 1-12 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1.

[0121] Table 1

[0122]

[0123] Performance Analysis

[0124] (1) As can be seen from Examples 1-2, the method for recovering indium from lead-containing dust of the present invention can improve the single leaching rate of indium and enhance the arsenic removal efficiency. The single leaching rate of indium can reach up to 72%, and the arsenic removal efficiency can reach more than 95%.

[0125] (2) As can be seen from Examples 1 and 3-4, the present invention helps to improve the single leaching rate of indium and enhance the arsenic removal efficiency by limiting the amount of auxiliary agent added;

[0126] (3) As can be seen from Examples 1 and 5-8, both reducing or increasing the gas flow rate of sulfur dioxide or ammonia will reduce the arsenic removal efficiency. The gas flow rates of sulfur dioxide and ammonia specified in this invention help to improve the arsenic removal efficiency.

[0127] (4) As can be seen from Examples 1 and 9-12, exceeding the range of cathode potential and current density defined by the present invention will lead to a decrease in arsenic removal efficiency and will also generate a large amount of hydrogen, posing a safety hazard.

[0128] (5) By comparing Example 1 and Comparative Examples 1-2, it can be seen that Comparative Example 1 does not add an auxiliary agent, so it cannot remove the passivation layer generated on the surface of indium-lead dust particles, resulting in a low single leaching rate of indium; while Comparative Example 2 uses sodium persulfate, which can also generate gas during the roasting process, but the generated gas cannot participate in the subsequent electrochemical reduction arsenic removal process, resulting in the incomplete utilization of resources.

[0129] (6) By comparing Example 1 and Comparative Examples 3-4, it can be seen that Comparative Examples 3 and 4 use lime precipitation and sulfur dioxide reduction methods to remove arsenic, respectively. Lime precipitation will produce calcium arsenate precipitate, which has poor stability and is a hazardous waste that is difficult to utilize or dispose of safely. Sulfur dioxide reduction will cause a large amount of sulfur dioxide to escape, which is difficult to control and recover, and poses environmental pollution and safety hazards.

[0130] In summary, this invention provides a method for recovering indium from indium-containing lead-containing dust. Through roasting, acid leaching, electrochemical reduction for arsenic removal, purification, and extraction, indium recovery from indium-containing lead-containing dust is achieved. By adding an auxiliary agent during the roasting process, the passivation layer on the surface of the indium-containing lead-containing dust can be broken, promoting indium release and thus increasing the indium leaching rate. The roasting gas generated during the roasting process can also be used in the subsequent electrochemical reduction for arsenic removal, realizing the resource utilization of by-product gas and reducing emission pressure. The method for recovering indium from indium-containing lead-containing dust of this invention is highly safe, the overall process is cleaner and more environmentally friendly, and it is suitable for widespread industrial applications.

[0131] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for recovering indium from indium-containing lead-containing dust, characterized in that, The method includes the following: (1) After mixing indium-lead dust with acid and auxiliary agents, the mixture is roasted to obtain roasting residue and roasting gas; the auxiliary agents include ammonium salt pyrolytes; the roasting gas includes a mixture of sulfur dioxide and ammonia. (2) The roasted residue described in step (1) is subjected to acid leaching to obtain filtrate and filter residue; (3) The roasting gas of step (1) is introduced into the filtrate of step (2), followed by electrochemical reduction arsenic removal treatment and post-treatment to obtain indium product; the cathode potential of the electrochemical reduction arsenic removal treatment is -0.2~-0.4V; The solution subjected to the electrochemical reduction arsenic removal treatment has a pH of 1.5 to 3.

0.

2. The method according to claim 1, characterized in that, The auxiliary agent in step (1) includes any one or a combination of at least two of ammonium sulfate, ammonium sulfite, ammonium bisulfate, and urea.

3. The method according to claim 1, characterized in that, The acid solution includes concentrated sulfuric acid.

4. The method according to claim 1, characterized in that, The mass ratio of the indium-lead-containing fume, acid, and auxiliary agent is 1:(1~1.5):(0.005~0.025).

5. The method according to claim 1, characterized in that, The calcination temperature is 300~400℃.

6. The method according to claim 1, characterized in that, The acid solution used in step (2) for acid leaching includes dilute sulfuric acid; the concentration of the acid solution is 1~3 mol / L.

7. The method according to claim 1, characterized in that, The acid leaching treatment is performed at a temperature of 20-40°C for 2-4 hours.

8. The method according to claim 1, characterized in that, The filter residue is subjected to lead recovery treatment.

9. The method according to claim 1, characterized in that, The roasting gas introduced in step (3) includes a mixture of sulfur dioxide and ammonia; the flow rate of sulfur dioxide is 1~5 kg / h; and the flow rate of ammonia is 0.05~0.15 kg / h.

10. The method according to claim 1, characterized in that, The electrochemical reduction arsenic removal process in step (3) is carried out under stirring; the stirring rate is 300~500 r / min.

11. The method according to claim 1, characterized in that, The cathode for the electrochemical reduction arsenic removal treatment includes any one of the following: porous graphite plate, stainless steel, titanium coated with precious metals, nickel foam, and electrode felt.

12. The method according to claim 1, characterized in that, The current density of the electrochemical reduction arsenic removal treatment is 5~20 mA / cm². 2 .

13. The method according to claim 1, characterized in that, The temperature for the electrochemical reduction arsenic removal treatment is 20~40℃; the time for the electrochemical reduction arsenic removal treatment is 1.5~3h.

14. The method according to claim 1, characterized in that, The post-processing in step (3) includes purification, extraction, regeneration, back-extraction, and displacement.

15. The method according to claim 14, characterized in that, The purifying agent used in the purification process includes zinc powder and / or iron powder.

16. The method according to claim 14, characterized in that, The purification process is carried out at a temperature of 30-50°C for 2-3 hours.

17. The method according to claim 14, characterized in that, The purification process yields purified residue.

18. The method according to claim 17, characterized in that, The purified residue is then separated and recycled.

19. The method according to claim 14, characterized in that, The purified liquid obtained after the purification process is then subjected to extraction.

20. The method according to claim 19, characterized in that, The extractant used in the extraction process includes a mixed solution of P2O4 and kerosene; the volume fraction of P2O4 in the mixed solution is 15-30%.

21. The method according to claim 20, characterized in that, In the extraction process, the volume ratio of the extractant to the purified liquid is 1:(5~15).

22. The method according to claim 14, characterized in that, The extraction temperature is 20~60℃; the extraction time is 4~6h.

23. The method according to claim 14, characterized in that, The extraction process yields an organic phase and a raffinate; the organic phase is regenerated and back-extracted and reused in the extraction process; the raffinate is subjected to zinc recovery treatment.

24. The method according to claim 23, characterized in that, Before the organic phase obtained after the extraction process is regenerated, it is subjected to acid washing to remove impurities; the acid used for acid washing to remove impurities includes dilute sulfuric acid; the concentration of the acid is 1~3 mol / L.

25. The method according to claim 24, characterized in that, The regeneration process specifically includes: back-extraction of the organic phase after acid washing and impurity removal using a regenerating agent.

26. The method according to claim 25, characterized in that, The regenerant includes ammonium fluoride or hydrogen fluoride; the concentration of the regenerant is 0.5~1 mol / L.

27. The method according to claim 25, characterized in that, The regeneration process takes 0.5 to 1 hour.

28. The method according to claim 23, characterized in that, The regenerated organic phase is subjected to back-extraction; the back-extraction process yields a back-extraction solution; the back-extraction solution is then subjected to displacement treatment to obtain the indium product.

29. The method according to claim 28, characterized in that, The displacement treatment specifically includes adding zinc powder to the back-extraction solution for displacement treatment.

30. The method according to claim 28, characterized in that, The temperature of the displacement treatment is 40~60℃; the time of the displacement treatment is 3~6h.

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