A method for recovering indium from indium-containing dust of lead-zinc smelting

Abstract

This invention provides a method for recovering indium from indium-containing fumes generated during lead-zinc smelting, comprising the following steps: S1. Collecting indium-containing fumes generated during lead-zinc smelting, placing the indium-containing fumes in an acidic solution for reaction, and simultaneously performing ultrasonic treatment during the reaction to obtain an indium-containing leachate; in the acidic solution, H... + The concentration of indium is 3.0–6.0 mol / L; S2. The pH of the indium-containing leachate is adjusted to 1.5–2.5, and then the indium-containing leachate and the organic extract are fed into a centrifugal extractor for extraction and separation to obtain an indium-containing organic phase; the centrifugal extractor speed is 2500–4500 rpm, and the flow ratio of the organic extract to the indium-containing leachate is 1:2–7; S3. The indium-containing organic phase is back-extracted using a back-extraction agent to obtain an indium-containing solution, which is then post-treated to obtain metallic indium. This method can effectively improve the leaching rate and extraction rate of indium from low-indium-content indium-containing dust, achieving efficient, stable, and clean recovery of indium resources from indium-containing dust in lead-zinc smelting.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgy and rare metal recovery technology, specifically relating to a method for recovering indium from indium-containing flue dust in lead-zinc smelting. Background Technology

[0002] The fumes generated during lead-zinc smelting are an important secondary resource for recovering the rare metal indium. However, the resource utilization of these fumes faces severe challenges. First, conventional acid leaching processes are inefficient, and some indium in the fumes, existing in sparingly soluble forms (such as indium ferrite), is difficult to leach effectively, limiting the overall indium recovery rate. Second, the chemical environment of the leachate obtained after acid leaching is extremely harsh, characterized by low and fluctuating indium concentrations (typically between 50-150 mg / L) and extremely high concentrations of interfering ions, especially zinc ions, which can reach over 50 g / L, along with large amounts of iron and arsenic ions.

[0003] In such a challenging "high zinc, low indium" system, traditional solvent extraction processes (such as using D2EHPA (di(2-ethylhexyl) phosphate) extractant alone) face two major bottlenecks: 1) Poor selectivity: Under high zinc conditions, the selectivity of the extractant for indium decreases sharply, resulting in the co-extraction of large amounts of zinc and a significant increase in subsequent back-extraction and purification costs; 2) Significant engineering problems: The D2EHPA system is highly susceptible to severe interfacial emulsification during extraction due to the presence of iron ions, forming a stable "third phase," which makes phase separation extremely difficult, causing equipment blockage and significant material loss. Therefore, existing technologies generally suffer from low indium recovery rates, poor process adaptability, and an inability to stably and efficiently treat actual industrial waste. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for recovering indium from indium-containing flue dust in lead-zinc smelting. This method can effectively improve the leaching rate and extraction rate of indium in indium-containing flue dust with low indium content. In particular, it can perform highly selective extraction of indium during the extraction process, achieving efficient, stable, and clean recovery of indium resources from indium-containing flue dust in lead-zinc smelting.

[0005] This invention provides a method for recovering indium from indium-containing fumes generated during lead-zinc smelting, comprising the following steps: S1. Collecting indium-containing fumes generated during lead-zinc smelting, placing the indium-containing fumes in an acidic solution for reaction, and simultaneously performing ultrasonic treatment during the reaction to obtain an indium-containing leachate; in the acidic solution, H... +The concentration of indium is 3.0-6.0 mol / L; S2. Adjust the pH of the indium-containing leachate to 1.5-2.5, and then send the indium-containing leachate and the organic extract into a centrifugal extractor for extraction and separation to obtain an indium-containing organic phase; the speed of the centrifugal extractor is 2500-4500 rpm, and the flow ratio of the organic extract to the indium-containing leachate is 1:2-7; the organic extract includes a main extractant and a co-extractant, the main extractant is di(2-ethylhexyl)phosphoric acid (D2EHPA), and the co-extractant is a neutral phosphorus extractant, which includes at least one of tributyl phosphate (TBP), trioctylphosphine oxide (TOPO), dimethylheptyl methylphosphonate, dibutyl butyl butyl phosphonate (DBBP), and diisoamyl methylphosphonate (DAMP); S3. Use a back-extraction agent to back-extract the indium-containing organic phase to obtain an indium-containing solution, and then post-process the indium-containing solution to obtain metallic indium.

[0006] First, during the acid leaching process of S1, the present invention simultaneously applies ultrasonic treatment. The powerful cavitation effect and mechanical vibration of ultrasound can effectively break up the agglomerates of dust particles and produce a strong "micro-etching" and stripping effect on the surface of insoluble phases such as indium ferrite, thereby significantly improving their dissolution rate and thus increasing the leaching rate of indium. Simultaneously, in the aforementioned H... + At higher concentrations, when combined with ultrasonic treatment, it is more conducive to the dissolution of metal ions in indium-containing fumes, thus improving the leaching rate of indium.

[0007] Secondly, in the extraction and separation process of S2, the pH of the indium-containing leachate is first adjusted to 1.5-2.5. Then, the indium-containing leachate and a specific organic extract are simultaneously sent into a centrifugal extractor for centrifugal extraction. In this way, the coupling effect of the specific chemical field and the centrifugal field can play a better synergistic effect, which ultimately enhances the extraction and separation effect, optimizes the high-selectivity extraction of indium, and ultimately improves the extraction rate of indium.

[0008] Specifically, firstly, the aforementioned organic extract includes the primary extractant D2EHPA and a co-extractant. The co-extractant is a neutral phosphorus extractant, such as tributyl phosphate, which can interact with the dimer structure of D2EHPA ((HA)2), disrupting its hydrogen bonds and generating a more active monomer-co-extractant complex. This allows for efficient extraction of indium at a lower pH, while significantly inhibiting the co-extraction of ferric iron (iron extraction requires a lower pH), thus achieving highly selective extraction and separation of indium. It should be noted that in traditional single D2EHPA systems (containing only D2EHPA), the hydrogen bonds are not disrupted, therefore a higher pH is required for HA to dissociate sufficiently to release H+. + With In 3+ Exchange, but the pH is too high, In 3+It readily hydrolyzes to form In(OH)3 precipitate, causing metal loss and a decrease in extraction rate. Furthermore, excessively high pH levels increase the saponification of D2EHPA, potentially leading to emulsification or third-phase formation, thus affecting phase separation rate and extraction efficiency. Moreover, within the optimized pH window, the steric hindrance of neutral phosphorus extractants can also hinder Fe... 3+ It forms a stable octahedral complex with D2EHPA, causing the separation coefficient β(In / Fe) to decrease from approximately 10 for pure D2EHPA. 2 Upgraded to 10 3 In terms of magnitude, within this pH range, indium ions are more easily extracted into the organic phase, thus achieving high selectivity.

[0009] Secondly, under the specific high speed of 2500-4500 rpm of the centrifugal extractor and the specific O / A ratio of the indium-containing leaching solution and the organic extract (i.e., the flow ratio of the organic extract and the indium-containing leaching solution, where O is the flow rate of the oil phase, i.e., the organic extract, and A is the flow rate of the aqueous phase, i.e., the indium-containing leaching solution), these three can achieve the best speed and flow matching working condition window. Specifically, on the one hand, the high speed of 2500-4500 rpm has high shear force and strong centrifugal force. (1) The high shear force instantly shears the two phases into micron-sized droplets, forming a huge specific surface area, so that the "phase interface resistance" of the mass transfer process is minimized. This is especially useful for processing low-concentration indium systems (such as indium concentrations of 50-150 rpm). (mg / L) is crucial, as it can increase the total volumetric mass transfer coefficient (KLa) by an order of magnitude. (2) The powerful centrifugal force can instantly and forcibly separate the two mixed phases, effectively overcoming the emulsification problem that easily occurs in the D2EHPA system under iron-containing conditions, shortening the phase separation time from tens of minutes in the traditional mixing and clarifying tank to a few seconds, and ensuring that the phase entrainment loss is controlled below 0.1%. On the other hand, the specific O / A ratio of the above-mentioned indium-containing leaching solution and organic extract combined with the above-mentioned centrifugal speed can ensure that the droplets have enough time to complete mass transfer and be completely removed by centrifugal force. Therefore, under the specific high speed of 2500-4500 rpm of the centrifugal extractor and the specific O / A ratio of the organic extract and indium-containing leaching solution, the dual goals of "fastest extraction" and "cleanest separation" can be achieved, effectively improving the high efficiency and high selectivity of indium extraction and separation. Furthermore, regarding centrifugal speed, if the speed is too low, mass transfer is insufficient, phase separation efficiency decreases, leading to a decline in indium extraction rate; if the speed is too high, emulsification intensifies, co-extracted impurities increase, the indium / zinc separation coefficient decreases, resulting in decreased separation purity and increased equipment wear. Therefore, controlling the centrifugal extractor speed within the aforementioned range is crucial to achieving a balance between mass transfer and separation, avoiding excessive emulsification while ensuring efficient and highly selective indium extraction. Similarly, regarding the O / A ratio of the organic extractant and the indium-containing leachate, excessively high or low ratios cannot achieve a good match with the specific speed mentioned above, ultimately leading to poor indium extraction selectivity and separation efficiency.

[0010] Preferably, in S1, the liquid-to-solid ratio of the acidic solution and indium-containing fume is 5~10:1 (mL / g). Within this liquid-to-solid ratio range, the amount of acid ensures complete reaction without reducing efficiency due to excessive dilution. Therefore, this liquid-to-solid ratio range is a preferred range that balances high leaching rate, low residual indium, and economical acid consumption.

[0011] Preferably, in S1, the acidic solution is a sulfuric acid solution. Using a sulfuric acid solution to prepare the leaching solution has two advantages: first, it dissolves indium-containing dust more quickly, making it easier to leach indium and other metal ions in a short time; second, the generated In... 3+ With SO4 2- Formation of a stable complex ion [In(SO4)2] - Reduce free In 3+ Activity, inhibiting hydrolysis and precipitation, and increasing leaching rate (the leaching rate is usually higher than that of hydrochloric acid); thirdly, SO4 2- with Fe 3+ [Fe(SO4)2] is formed. - Reduce Fe 3+ Competitive extraction improves the indium / iron separation coefficient, while SO4 2- It is beneficial to disrupt colloidal stability, reduce the risk of emulsification during the extraction process, and shorten the phase separation time, thus making it more conducive to the efficient and selective extraction and separation of indium; fourth, sulfuric acid is cheaper than hydrochloric acid, nitric acid, etc., and is also easier to recycle.

[0012] It should also be noted that, from a leaching perspective, the acidic solution can be sulfuric acid, hydrochloric acid, or nitric acid, the purpose of which is to dissolve the indium-containing dust into an ionic solution. However, hydrochloric acid is highly volatile and corrosive; if the dust contains sulfides, it may produce toxic hydrogen sulfide gas. Nitric acid is a strong oxidizing acid, and the reaction process easily produces toxic nitrogen oxides, and it is also costly. Sulfuric acid has a lower overall cost, and the indium-containing dust mainly consists of oxides and sulfides, which readily react with sulfuric acid to form soluble sulfates, facilitating subsequent separation and extraction. Furthermore, sulfuric acid works more efficiently with the extractant in this invention and has lower operational risks; therefore, sulfuric acid is preferred.

[0013] Preferably, in S1, during the ultrasonic treatment, ultrasonic waves with a power density of 30-60 W / L and a frequency of 20-40 kHz are applied. Under the ultrasonic treatment with the above power density and frequency, it can synergistically exert a better metal ion leaching effect with the acidic solution, reduce acid consumption, and achieve efficient leaching of metal ions such as indium with low acid consumption and short time, especially with a more significant effect on the efficient leaching of indium.

[0014] Preferably, in S1, the reaction temperature of the indium-containing fume in the acidic solution is 60-90°C, and the reaction time is 2-4 hours. This invention uses a lower reaction temperature and a shorter reaction time, which, in conjunction with ultrasonic treatment, maximizes the acid leaching effect and improves the leaching efficiency of metal ions such as indium, especially fully leaching indium ions from insoluble indium compounds such as indium ferrite, thereby increasing the indium leaching rate.

[0015] Preferably, in step S1, indium-containing fume is placed in an acidic solution for reaction, and mechanical stirring is performed simultaneously during the reaction at a speed of 150-300 rpm. Furthermore, simultaneous mechanical stirring during acid leaching can further assist ultrasonic treatment, accelerating and fully dissolving indium and other metal ions, providing a stable foundation for subsequent indium extraction and separation.

[0016] Preferably, in step S2, the concentration of indium in the indium-containing leachate is 50-150 mg / L. In particular, the method provided by this invention can significantly improve the separation coefficient of indium from other metal ions such as iron and zinc when processing the aforementioned leachate with a low indium concentration of 50-150 mg / L. Therefore, the method provided by this invention is particularly suitable for efficient extraction and separation of low indium concentrations.

[0017] Preferably, in S2, the volume concentration of di(2-ethylhexyl)phosphoric acid in the organic extract is 15%~25%, and the volume ratio of di(2-ethylhexyl)phosphoric acid to neutral phosphoric acid extractant is 2~5:1. When di(2-ethylhexyl)phosphoric acid is used as the main extractant, if the concentration is too low, the extraction rate is low; if the concentration is too high, the viscosity of the organic phase increases, leading to increased emulsification and difficulty in phase separation. 3+ Co-extraction also increases, In 3+ Selectivity decreases, therefore, excessively high or low concentrations of di(2-ethylhexyl)phosphoric acid are detrimental to the high selectivity and efficient extraction and separation of indium. Simultaneously, it is necessary to control the ratio of di(2-ethylhexyl)phosphoric acid to neutral phosphorus extractant within a specific range. If the volume ratio of di(2-ethylhexyl)phosphoric acid to neutral phosphorus extractant is too low, the system will be dominated by neutral phosphorus extractant, resulting in insufficient acidic extraction sites for In. 3+ Extraction rate decreases; at the same time, Fe 3+ Zn 2+ Impurities are co-extracted due to an excess of "free" co-extractant, causing a sharp drop in the separation coefficient. However, if the volume ratio of di(2-ethylhexyl)phosphoric acid to neutral phosphoric acid extractant is too high, the proportion of D2EHPA dimer increases, viscosity rises, phase separation time is prolonged, the co-extractant is insufficient to break down the dimer, the low pH advantage disappears, and a higher pH is required to extract In. 3+ This leads to Fe 3+ Increased co-extraction of other metal ions reduces In 3+ Highly selective extraction effect.

[0018] Preferably, in S2, the neutral phosphorus extractant in the organic extract includes tributyl phosphate (TBP). Choosing tributyl phosphate as a co-extractant in combination with di(2-ethylhexyl)phosphoric acid results in a better synergistic effect, exhibiting higher extraction rates and higher selectivity for indium.

[0019] Preferably, in S2, the neutral phosphorus extractant in the organic extract is tributyl phosphate (TBP).

[0020] Preferably, in step S2, the organic extract further includes a diluent. Preferably, the diluent includes sulfonated kerosene.

[0021] Preferably, in S2, the flow ratio of the organic extract to the indium-containing leachate is 1:3.

[0022] Preferably, in step S2, a first alkaline solution is used to adjust the pH of the indium-containing leaching solution to 1.5-2.5. Preferably, the first alkaline solution includes at least one of ammonia, lime milk (calcium hydroxide suspension), sodium hydroxide solution, and sodium bicarbonate solution. Preferably, the first alkaline solution includes at least one of ammonia and lime milk (calcium hydroxide suspension). Ammonia and lime milk are low-cost and can avoid introducing new impurities, making subsequent impurity removal easier.

[0023] Preferably, in step S2, the organic extract further includes a diluent, which includes at least one of kerosene, sulfonated kerosene, and aromatic hydrocarbons. Preferably, the volume concentration of the diluent in the organic extract is 62.5% to 82%.

[0024] Preferably, in S2, a certain amount of phase modifier (or modifier) ​​may be introduced into the organic extract according to the actual situation. The phase modifier includes long-chain alcohols, including at least one of n-octanol, 2-ethylhexanol, and nonanol.

[0025] Preferably, in step S2, before the indium-containing leachate and the organic extract are fed into a centrifugal extractor for extraction and separation, the organic extract needs to be saponified and the degree of saponification is controlled to be 30-50%.

[0026] In extraction processes, saponification generally refers to the reaction of an alkaline solution (e.g., NaOH) with an acidic extractant (e.g., D₂EHPA) in a predetermined ratio. This reaction converts some or all of the exchangeable protons (–PO(OH)₂ or –COOH) in the extractant molecules into their corresponding sodium salts (–PO(ONa)₂ or –COONa), thus generating a "saponified extractant." D₂EHPA is an acidic extractant; without saponification, it releases a large amount of H⁺ during extraction, causing a sharp drop in the pH of the aqueous phase, affecting extraction equilibrium and metal ion selectivity. Therefore, saponification of the organic extract is necessary. The RNa formed after saponification readily reacts with metal ions (e.g., In⁻). 3+ (And other metal ions, etc.) undergo ion exchange reactions, improving extraction efficiency. Controlling the degree of saponification between 30% and 50% achieves a balance between selectivity and extraction capacity. If the saponification is too high, the viscosity of the organic phase increases, and Na... + Excessive exchange capacity can easily lead to co-extraction of other impurities, reducing the effectiveness of In. 3+ Selectivity; if saponification is too low, Na + Insufficient release, extraction still relies on HA and In 3+ The reaction is dominant, leading to H + Accumulation of indium ions leads to a decrease in solution pH, inhibiting subsequent extraction. Simultaneously, at low saponification levels, competition for extraction sites between other metal ions, such as iron and indium, reduces the separation factor, further decreasing the extract selectivity for indium ions.

[0027] Preferably, in step S2, the organic extract is saponified using a second alkaline solution, which includes at least one of NaOH solution, KOH solution, and ammonia solution. Preferably, the second alkaline solution is NaOH solution. KOH is slightly more expensive, and ammonia solution is volatile; therefore, NaOH is the optimal choice.

[0028] Preferably, in S2, the centrifugal extractor is a 3-5 stage countercurrent series centrifugal extractor. Multi-stage countercurrent series operation achieves efficient extraction and separation by connecting multiple centrifugal extractors in series. Specifically, the countercurrent flow mode is as follows: the aqueous phase enters from the first stage and flows sequentially backward; the organic phase enters from the last stage in the opposite direction, contacting the aqueous phase in the opposite direction, allowing for sufficient mass transfer between the organic phase (oil phase) and the water phase. This countercurrent design significantly improves the mass transfer driving force, resulting in a larger concentration gradient of solute between the two phases, thereby improving extraction efficiency. After each stage of extraction, the raffinate phase (aqueous phase containing a small amount of solute) enters the next stage for further extraction, while the extracted phase (organic phase containing a high concentration of solute) enters the previous stage for further enrichment. Through multi-stage series connection, the solute gradually accumulates in each stage, ultimately reaching a high concentration in the final stage extracted phase. Therefore, the multi-stage countercurrent series design significantly improves the extraction rate and is suitable for low-concentration or complex systems, such as the complex composition and low indium concentration in the indium-containing dust system of this invention. A 3-5 stage countercurrent series centrifugal extractor can significantly improve the extraction efficiency of indium while minimizing equipment costs, achieving a good balance between extraction efficiency and cost.

[0029] Preferably, in S2, the centrifugal extractor is a 3-5 stage countercurrent series annular centrifugal extractor.

[0030] Furthermore, the centrifugal extractor used in this invention is preferably an annular gap centrifugal extractor, which mainly consists of a motor, a rotating drum (rotor), and a shell (stator). It achieves mixing, mass transfer, and rapid separation of two-phase liquids through centrifugal force generated by high-speed rotation. The working process includes two key steps: mixing and mass transfer, and centrifugal separation. During mixing and mass transfer, two immiscible liquid phases (such as an aqueous phase and an organic phase) enter the annular gap between the rotating drum and the shell through two feed inlets. Under the shear force of the high-speed rotating drum, the two liquid phases are fully mixed, forming tiny droplets, thereby achieving mass transfer. During centrifugal separation, under the action of centrifugal force, the denser heavier phase is thrown towards the drum wall, while the less dense lighter phase approaches the center of the drum. The two liquid phases eventually flow into the collection chamber through their respective weirs and are discharged. Therefore, a 3-5 stage countercurrent series annular gap centrifugal extractor is preferred for extraction, which is more conducive to achieving a highly efficient and energy-saving extraction and separation process. Furthermore, the 3-5 stage configuration effectively improves extraction efficiency and saves equipment costs.

[0031] Preferably, in step S3, the stripping agent includes a hydrochloric acid solution. The choice of hydrochloric acid as the stripping agent is determined by the chemical equilibrium principle of extraction and stripping, the binding characteristics of indium and D₂EHPA, and the chemical properties of the stripping agent. Other reagents, such as sulfuric acid, pure water, or other acids, have limited stripping effects or are unsuitable due to their chemical properties.

[0032] Preferably, the stripping agent is hydrochloric acid.

[0033] Preferably, the concentration of the back-extraction agent is 6-8 mol / L.

[0034] Preferably, in S3, the post-processing includes displacement and electrolytic refining, and the metallic indium obtained after electrolytic refining exists in the form of metallic indium ingots.

[0035] Preferably, according to the mass ratio, the indium-containing dust in this invention includes the following components: (1) major metals (content > 1%), (2) rare and dispersed metals (usually content between 0.01% and 1%), (3) harmful impurities, and (4) other semi-finished elements;

[0036] Major metals include zinc (10-40%), lead (5-25%), and iron (5-20%); rare and dispersed metals include indium (0.02-0.2%), gallium (0.001-0.05%), germanium (0.005-0.1%), and thallium (0.01-0.5%); harmful impurities include arsenic (0.5-8%), cadmium (0.1-2%), and fluorine and / or chlorine (0.5-5%); other semi-precious elements include silver, calcium, and silicon.

[0037] It should be noted that the composition of the "indium-containing dust" varies depending on the raw materials and is not fixed. The method provided in this invention is not limited to processing "indium-containing dust" with the above-mentioned composition.

[0038] Meanwhile, the aforementioned indium ions mainly refer to In 3+ Iron ions mainly refer to Fe 3+ Zinc ions mainly refer to Zn 2 ⁺, but the metal ions in the above-mentioned indium-containing leachate include, but are not limited to, the three metal ions mentioned above. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0040] Example 1

[0041] Indium was extracted from indium-containing fumes using the following steps:

[0042] S1. Indium-containing dust was placed in a jacketed reactor equipped with an ultrasonic transducer and a mechanical stirrer. A 2.25 mol / L sulfuric acid solution was added at a liquid-to-solid ratio of 7.5:1 (mL / g) to carry out the reaction. During the reaction, the ultrasonic transducer and mechanical stirrer were activated to accelerate the dissolution of the indium-containing dust. The ultrasonic power density was 45 W / L and the frequency was 30 kHz. The mechanical stirrer speed was 225 rpm. The reaction temperature was controlled at 75℃ and the reaction time (the entire leaching process) was 3 hours. After the reaction (leaching) was completed, solid-liquid separation was carried out by pressure filtration to obtain an indium-containing leachate (i.e., an indium-containing acidic leachate).

[0043] S2. Adjust the pH of the indium-containing leachate obtained in S1 to 2 using ammonia or lime milk. Then, send the indium-containing leachate and the organic extract into a 3-5 stage countercurrent series annular centrifugal extractor for extraction and separation to obtain the indium-containing organic phase and raffinate. The centrifugal extractor speed is 3500 rpm, and the flow ratio of the organic extract to the indium-containing leachate (O / A ratio of organic phase to aqueous phase) is 1:3. The organic extract includes the main extractant di(2-ethylhexyl)phosphoric acid (D2EHPA), the co-extractant tributyl phosphate (neutral phosphorus extractant), and the diluent sulfonated kerosene. The volume ratio of the main extractant di(2-ethylhexyl)phosphoric acid (D2EHPA), the co-extractant tributyl phosphate (neutral phosphorus extractant), and the diluent sulfonated kerosene is 20:8:72. The volume concentration of the main extractant di(2-ethylhexyl)phosphoric acid (D2EHPA) in the organic extract is 20%. The volume concentration is calculated as (V... 主萃取剂体积 / V 有机萃取液体积 ) × 100%;

[0044] Before the indium-containing leachate and the organic extract are fed into a centrifugal extractor for extraction and separation, the organic extract needs to be saponified. Specifically, the organic extract is saponified using sodium hydroxide solution, with the degree of saponification controlled at 40%.

[0045] S3. Using a 7 mol / L hydrochloric acid solution as the back-extraction agent, the indium-containing organic phase obtained in S2 is back-extracted in another set of centrifugal extractors (a 2-3 stage countercurrent series annular centrifugal extractor, with a centrifugation speed of 3500 rpm and an O / A ratio generally set to 3:1-5:1). The high-purity indium is transferred back to the aqueous phase in the form of a chloride complex, resulting in a high-purity, high-concentration indium trichloride solution. The obtained indium trichloride solution is then subjected to subsequent steps such as displacement and electrolytic refining to finally obtain metallic indium ingots (after displacement and electrolytic refining, the purity of metallic indium ingots and other products reaches over 99.9%).

[0046] The specific operation of the substitution is as follows:

[0047] (1) Pretreatment of the solution before replacement: adjust the pH value to 1.0~2.0 by passing ammonia water to precipitate impurities such as iron, lead, and cadmium, and then filter to obtain the indium-containing solution to be replaced;

[0048] (2) Displacement reaction: Add zinc powder with a purity of 99.5%, stir at a speed of 150~200 rpm, keep warm at 40~60℃ for 1~2 hours.

[0049] (3) Solid-liquid separation: After the displacement reaction is completed, let it stand for 30 minutes, and then filter it through a plate and frame filter press to obtain crude indium filter cake.

[0050] (4) Washing and drying: The crude indium filter cake is soaked in hydrochloric acid, washed with water, and dried to obtain crude indium;

[0051] The specific operation of electrolytic refining is as follows (electrolytic refining steps for crude indium):

[0052] (1) Electrolyte preparation: Crude indium is dissolved in dilute sulfuric acid to generate indium sulfate solution;

[0053] (2) Electrode preparation: The anode is made of crude indium into a plate shape and the surface is polished smooth; the cathode is made of high-purity indium sheet with a purity greater than 99.99%;

[0054] (3) Electrolysis with electricity;

[0055] (4) Cathode product stripping;

[0056] (5) The stripped pure indium sheet is soaked and cleaned with nitric acid, and then melted and cooled to obtain high-purity indium.

[0057] In the process of extracting indium from the above-mentioned indium-containing dust, the indium leaching rate of the indium-containing leachate obtained in S1 is calculated as follows: (1) Sample the untreated waste indium-containing dust (raw material), prepare it into a solution, and then use ICP-OES or IPC-MS to determine the indium content, and calculate the mass ratio of indium in the raw material; (2) Sample the indium-containing leachate obtained in S1 directly, and use ICP-OES or IPC-MS to determine the indium content in the indium-containing leachate; (3) Leaching rate η In =Total indium in the leachate / Total indium mass in the raw material × 100%, Total indium in the leachate = Leachate volume (L) × Indium concentration in the leachate (g / L), Total indium mass in the raw material = Mass of indium-containing dust (g) × Indium mass percentage in the raw material (%); The final calculated indium leaching rate is 99.7%;

[0058] The indium / zinc separation coefficient and the indium / zinc separation coefficient were calculated using the above method (specifically, the organic phase and aqueous phase obtained after extraction in S2 were sampled). The calculation formula is: β In / M=D In / D M ; where: D In The indium distribution ratio = indium concentration in the organic phase (g / L) ÷ indium concentration in the aqueous phase (g / L); D M The distribution ratio of the impurity metal (zinc or iron) is calculated as: metal concentration in the organic phase (g / L) ÷ metal concentration in the aqueous phase (g / L). A larger β value indicates better separation of indium from the impurity. The final indium / zinc separation coefficient (β0.05) is then calculated. In / Zn) and indium / iron separation coefficient (β) In / Fe) were 6516 and 1238 respectively;

[0059] The indium recovery rate was calculated using the above method as follows: untreated waste indium-containing dust (raw material) was sampled, prepared into a solution, and then the indium content was determined by ICP-OES or IPC-MS. The mass of indium in the raw material was calculated by reverse calculation, and the indium recovery rate was calculated by using the mass of indium in the final indium ingot and the mass of indium in the raw material. The final calculated indium recovery rate was 99.5%.

[0060] Example 2

[0061] The indium-containing fume components in this embodiment refer to those in Example 1.

[0062] The specific steps for extracting indium from the indium-containing dust in this embodiment differ from those in Example 1 in that, during the centrifugal extraction process in S2, the tributyl phosphate in the organic extract is changed to trioctylphosphine oxide (TOPO); the remaining treatments are the same as in Example 1.

[0063] The indium / zinc separation coefficient and the indium / iron separation coefficient were calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient were 5086 and 1054, respectively.

[0064] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 98.9%.

[0065] Example 3

[0066] The indium-containing fume components in this embodiment refer to those in Example 1.

[0067] The specific steps for extracting indium from the indium-containing dust in this embodiment differ from those in Example 1 in that, during the centrifugal extraction process in S2, the tributyl phosphate in the organic extract is changed to dimethylheptyl methylphosphonate; the remaining treatments are the same as in Example 1.

[0068] The indium / zinc separation coefficient and the indium / iron separation coefficient were calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient were 5521 and 1197, respectively.

[0069] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 99.1%.

[0070] Example 4

[0071] The indium-containing fume components in this embodiment refer to those in Example 1.

[0072] The specific steps for extracting indium from the indium-containing dust in this embodiment differ from those in Example 1 in that, during the centrifugal extraction process in S2, the tributyl phosphate in the organic extract is changed to dibutyl butyl phosphonate (DBBP); the remaining treatments are the same as in Example 1.

[0073] The indium / zinc separation coefficient and the indium / iron separation coefficient were calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient were 4208 and 550, respectively.

[0074] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 96.4%.

[0075] Example 5

[0076] The indium-containing fume components in this embodiment refer to those in Example 1.

[0077] The specific steps for extracting indium from the indium-containing dust in this embodiment differ from those in Example 1 in that, during the acid leaching reaction in S1, the power density is adjusted to 20 W / L during the ultrasonic treatment; the remaining treatments are the same as in Example 1.

[0078] During the extraction of indium from the indium-containing dust, the indium leaching rate of the indium-containing leachate obtained in S1 was calculated. The specific testing and calculation methods are referred to in Example 1. The final calculated indium leaching rate was 96.1%.

[0079] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 96.0%.

[0080] Example 6

[0081] The indium-containing fume components in this embodiment refer to those in Example 1.

[0082] The specific steps for extracting indium from the indium-containing dust in this embodiment differ from those in Example 1 in that, during the acid leaching reaction in S1, the frequency of the ultrasonic treatment is adjusted to 50 kHz; the remaining treatments are the same as in Example 1.

[0083] During the extraction of indium from the indium-containing dust, the indium leaching rate of the indium-containing leachate obtained in S1 was calculated. The specific testing and calculation methods are described in Example 1. The final calculated indium leaching rate was 96.8%.

[0084] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 96.3%.

[0085] Example 7

[0086] The indium-containing fume components in this embodiment refer to those in Example 1.

[0087] The specific steps for extracting indium from the indium-containing dust in this embodiment differ from those in Example 1 in that the organic extract is not saponified during the centrifugal extraction process in S2; the remaining processes are the same as in Example 1.

[0088] The indium / zinc separation coefficient and the indium / iron separation coefficient were calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient were 8014 and 251, respectively.

[0089] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 95.2%.

[0090] Comparative Example 1

[0091] The indium-containing fume components in this comparative example are referenced in Example 1.

[0092] Indium was extracted from the above-mentioned indium-containing fume according to the following steps:

[0093] S0. The indium-containing fume is dried after being dehydrated and then ground into powder (average particle size is 150 micrometers).

[0094] S1. The pretreated indium-containing powder is added to a reactor, sulfuric acid (20% concentration) is added to the reactor, the liquid-to-solid ratio is 4:1, the reaction temperature is set at 75℃, and the reaction time is 3h (or hydrochloric acid with a concentration of 4.5 mol / L is used as the leaching agent). After the reaction is completed, the indium-containing leachate is obtained by solid-liquid separation by pressure filtration. If the indium-containing powder contains indium sulfide, an appropriate oxidant such as H2O2, MnO2, or NaClO3 (e.g., 2~5 g / L) can be added to promote oxidation and dissolution.

[0095] S2. Add sodium hydroxide or calcium carbonate to the indium-containing leachate obtained in S1 to adjust the pH to 2.5, in order to precipitate Fe. 3+ Al 3+ After solid-liquid separation, zinc powder is added to the resulting filtrate to displace and remove Cu. 2+ Cd 2+ After solid-liquid separation, a purified indium-containing leachate is obtained.

[0096] S3. Adjust the pH of the indium-containing leachate purified in S2 to 2 using ammonia or lime milk. Then, send the indium-containing leachate (aqueous phase) and the extract (organic phase) into a multi-stage countercurrent extraction tank for extraction separation to obtain the indium-containing organic phase and the raffinate. In the extract, the extractant is D2EHPA (20% by volume), and the diluent is sulfonated kerosene (80% by volume). The volume ratio of organic phase to aqueous phase is 1:2, the countercurrent extraction stage is 4 stages, the mixing time is 4 minutes, and the settling time is 15 minutes. Then, wash the indium-containing organic phase with 0.75 mol / L dilute sulfuric acid to remove co-extracted zinc and iron ions.

[0097] S3. The indium-containing organic phase from which co-extracted zinc and iron ions are removed is back-extracted using a 5 mol / L hydrochloric acid solution to obtain an indium trichloride solution; then the indium trichloride solution is subjected to subsequent steps such as displacement and electrolytic refining to obtain indium ingots.

[0098] For specific operations of displacement and electrolytic refining, please refer to Example 1.

[0099] During the extraction of indium from the indium-containing dust, the indium leaching rate of the indium-containing leachate obtained in S1 was calculated. The specific testing and calculation methods are referred to in Example 1. The final calculated indium leaching rate was 88.01%.

[0100] The indium / zinc separation coefficient and the indium / zinc separation coefficient were calculated using the above method (specifically, the organic phase and aqueous phase obtained after extraction in S3 were sampled). The specific testing and calculation methods are referred to in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient were 3015 and 786, respectively.

[0101] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 86.4%.

[0102] Comparative Example 2

[0103] The indium-containing fume components in this comparative example are referenced in Example 1.

[0104] The specific steps for extracting indium from the indium-containing dust in this comparative example differ from those in Example 1 in that, during the reaction of the indium-containing dust in an acidic solution in S1, ultrasonic treatment is not performed; the remaining treatments are the same as in Example 1.

[0105] During the extraction of indium from the indium-containing dust, the indium leaching rate of the indium-containing leachate obtained in S1 was calculated. The specific testing and calculation methods are referred to in Example 1. The final calculated indium leaching rate was 90.06%.

[0106] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 90.0%.

[0107] Comparative Example 3

[0108] The indium-containing fume components in this comparative example are referenced in Example 1.

[0109] The specific steps for extracting indium from the indium-containing dust in this comparative example differ from those in Example 1 in that the centrifugal extraction process in S2 is performed at a centrifugal speed of 2000 rpm; the remaining treatments are the same as in Example 1.

[0110] The indium / zinc separation coefficient and the indium / iron separation coefficient were calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient were 872 and 356, respectively.

[0111] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 92.3%.

[0112] Comparative Example 4

[0113] The indium-containing fume components in this comparative example are referenced in Example 1.

[0114] The specific steps for extracting indium from the indium-containing dust in this comparative example differ from those in Example 1 in that, during the centrifugal extraction process in S2, the flow ratio (O / A ratio of organic phase to aqueous phase) of the organic extract and the indium-containing leachate is 1:1; the remaining treatments are the same as in Example 1.

[0115] The indium / zinc separation coefficient and the indium / iron separation coefficient were calculated using the above method. The specific testing and calculation methods are referred to in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient are 2702 and 643, respectively.

[0116] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 94.1%.

[0117] Comparative Example 5

[0118] The indium-containing fume components in this comparative example are referenced in Example 1.

[0119] The specific steps for extracting indium from the indium-containing dust in this comparative example differ from those in Example 1 in that, during the centrifugal extraction process in S2, the tributyl phosphate in the organic extract was adjusted to trioctylmethylammonium chloride (Aliquat 336-P, phosphonate ammonium salt, weakly alkaline); the remaining treatments were the same as in Example 1.

[0120] The indium / zinc separation coefficient and the indium / iron separation coefficient were calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient were 5268 and 78, respectively.

[0121] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 93.5%.

[0122] Comparative Example 6

[0123] The indium-containing fume components in this comparative example are referenced in Example 1.

[0124] The specific steps for extracting indium from the indium-containing dust in this comparative example differ from those in Example 1 in that, during the centrifugal extraction process in S2, the flow ratio (O / A ratio of organic phase to aqueous phase) of the organic extract and the indium-containing leachate is 1:8; the remaining treatments are the same as in Example 1.

[0125] The indium / zinc separation coefficient and the indium / iron separation coefficient were calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient are 2962 and 157, respectively.

[0126] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 93.2%.

[0127] Comparative Example 7

[0128] The indium-containing fume components in this comparative example are referenced in Example 1.

[0129] The specific steps for extracting indium from the indium-containing dust in this comparative example differ from those in Example 1 in that, in S2, the pH of the indium-containing leachate is adjusted to 3, and then the indium-containing leachate and the organic extract are sent into a centrifugal extractor for extraction and separation; the remaining treatments are the same as in Example 1.

[0130] The indium / zinc separation coefficient and the indium / iron separation coefficient were calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient were 540 and 811, respectively.

[0131] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 94.7%.

[0132] Comparative Example 8

[0133] The indium-containing fume components in this comparative example are referenced in Example 1.

[0134] The specific steps for extracting indium from the indium-containing dust in this comparative example differ from those in Example 1 in that, in S2, the pH of the indium-containing leachate is not adjusted; that is, the indium-containing leachate obtained in S1 and the organic extract are directly fed into a centrifugal extractor for extraction and separation. The remaining treatments are the same as in Example 1.

[0135] The indium / zinc separation coefficient and the indium / iron separation coefficient were calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium / zinc separation coefficient and indium / iron separation coefficient were 5685 and 64, respectively.

[0136] The indium recovery rate was calculated using the above method. The specific testing and calculation methods are described in Example 1. The final calculated indium recovery rate was 94.1%.

[0137] Test results statistics and analysis

[0138] The results of the relevant parameters tested for all the above embodiments and comparative examples are shown in Table 1.

[0139] Table 1. Results of relevant parameters tested in the examples and comparative examples.

[0140]

[0141] As shown in Table 1, the recycling method provided by the present invention can not only effectively improve the leaching rate of indium-containing dust, but also make the indium / zinc separation coefficient and the indium / iron separation coefficient higher, which greatly improves the indium recovery rate from indium-containing dust in lead-zinc smelting. For details, please refer to the data of the embodiments in Table 1 above.

[0142] The conventional recovery method used in Comparative Example 1 is more complicated than the method in this invention, and the leaching rate of indium, the relevant separation coefficient, and the recovery rate are all worse than those in Example 1.

[0143] In Comparative Example 2, the absence of ultrasonic treatment resulted in a significant decrease in the indium leaching rate, ultimately leading to a decrease in the indium recovery rate.

[0144] In Comparative Example 3, the centrifugal speed was low, the mass transfer efficiency was low, and the relevant separation coefficient decreased, resulting in a decrease in the recovery rate of indium.

[0145] The O / A ratios of Comparative Examples 4 and 6 were too high and too low, respectively, which was not conducive to the optimal mass transfer efficiency. As a result, the relevant separation coefficients also decreased to varying degrees, leading to a decrease in the recovery rate of indium.

[0146] In Comparative Example 5, the tributyl phosphate was replaced with trioctylmethylammonium chloride, which resulted in low extraction efficiency, particularly causing a decrease in the indium / iron separation coefficient and a decrease in the indium recovery rate.

[0147] In Comparative Example 7, the pH of the indium-containing leachate was relatively high; in Comparative Example 8, the pH of the indium-containing leachate was not adjusted; all of the above factors resulted in a significant decrease in the indium / zinc separation coefficient and / or the indium / iron separation coefficient, as well as a decrease in the indium recovery rate.

[0148] Furthermore, compared with Examples 2-7, the main extractant in Examples 2-4 was adjusted, resulting in a decrease in the indium-related separation coefficient and recovery rate in Examples 2-4. This indicates that tributyl phosphate is the most effective main extractant. The power density of the ultrasonic treatment in Example 5 was too low, while the frequency of the ultrasonic treatment in Example 6 was too high, resulting in a decrease in the indium leaching rate and the indium recovery rate in Examples 5 and 6. In Example 7, the organic extract was not saponified, which caused a significant decrease in the indium / iron separation coefficient, and therefore the indium recovery rate was also reduced.

[0149] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention, but such modifications or substitutions are all within the scope of protection of the present invention.

Claims

1. A method for recovering indium from indium-containing flue dust in lead-zinc smelting, characterized in that, Includes the following steps: S1. Collect indium-containing fumes generated during lead-zinc smelting, place the indium-containing fumes in an acidic solution for reaction, and simultaneously perform ultrasonic treatment during the reaction to obtain an indium-containing leachate; in the acidic solution, H + The concentration is 3.0-6.0 mol / L; S2. Adjust the pH of the indium-containing leachate to 1.5-2.5, then send the indium-containing leachate and the organic extract into a centrifugal extractor for extraction and separation to obtain an indium-containing organic phase; the centrifugal extractor rotates at 2500-4500 rpm, and the flow ratio of the organic extract to the indium-containing leachate is 1:2-7; the organic extract includes a main extractant and a co-extractant, the main extractant is di(2-ethylhexyl)phosphoric acid, and the co-extractant is a neutral phosphorus extractant, which includes at least one of tributyl phosphate, trioctylphosphine oxide, dimethylheptyl methylphosphonate, dibutyl butylphosphonate, and diisoamyl methylphosphonate; S3. The indium-containing organic phase is back-extracted using a back-extraction agent to obtain an indium-containing solution, and the indium-containing solution is then post-treated to obtain metallic indium.

2. The method for recovering indium from indium-containing flue dust in lead-zinc smelting as described in claim 1, characterized in that, In S1, the liquid-to-solid ratio of the acidic solution and the indium-containing fume is 5-10 mL: 1 g.

3. The method for recovering indium from indium-containing flue dust in lead-zinc smelting as described in claim 1, characterized in that, In S1, the acidic solution is a sulfuric acid solution.

4. The method for recovering indium from indium-containing flue dust in lead-zinc smelting as described in claim 1, characterized in that, In S1, during the ultrasonic treatment, ultrasonic waves with a power density of 30-60 W / L and a frequency of 20-40 kHz are applied.

5. The method for recovering indium from indium-containing flue dust in lead-zinc smelting as described in claim 1, characterized in that, In step S1, the reaction temperature of the indium-containing fume in the acidic solution is 60~90℃, and the reaction time is 2~4h.

6. The method for recovering indium from indium-containing flue dust in lead-zinc smelting as described in claim 1, characterized in that, In S2, the volume concentration of di(2-ethylhexyl)phosphoric acid in the organic extract is 15%~25%, and the volume ratio of di(2-ethylhexyl)phosphoric acid to the neutral phosphoric acid extractant is 2~5:

1.

7. The method for recovering indium from indium-containing flue dust in lead-zinc smelting as described in claim 1, characterized in that, In S2, the neutral phosphorus extractant in the organic extract includes the tributyl phosphate.

8. The method for recovering indium from indium-containing flue dust in lead-zinc smelting as described in claim 1, characterized in that, In step S2, before the indium-containing leachate and the organic extract are fed into a centrifugal extractor for extraction and separation, the organic extract needs to be saponified and the degree of saponification is controlled to be 30-50%.

9. The method for recovering indium from indium-containing flue dust in lead-zinc smelting as described in claim 1, characterized in that, In S2, the centrifugal extractor is a 3-5 stage countercurrent centrifugal extractor connected in series.

10. The method for recovering indium from indium-containing flue dust in lead-zinc smelting as described in claim 1, characterized in that, In S3, the stripping agent comprises a hydrochloric acid solution.

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