A method for field-enhanced stepwise purification and multi-metal synergistic recovery of tellurium alkali slag

Abstract

This invention discloses a method for stepwise purification and multi-metal synergistic recovery of tellurium alkali slag under enhanced field conditions. The invention includes: (1) crushing, grinding, and drying the tellurium alkali slag to obtain a pretreated material; (2) mixing the pretreated material with water and selectively leaching under ultrasonic conditions, then filtering to obtain a tellurium-containing leachate; (3) adding sodium sulfide to the leachate to generate a sulfide mixed slag containing heavy metal ions, followed by filtration; (4) adding barium carbonate to the filtrate obtained in step (3) to remove sulfate ions, then filtering; adjusting the pH of the filtrate, adding hydroxylamine hydrochloride for selective selenium precipitation, and then filtering to obtain a purified liquid; (5) adding sodium sulfite to the purified liquid obtained in step (4) and reacting under ultrasonic conditions to obtain a high-purity tellurium product. This invention can achieve a total tellurium recovery rate ≥92%, purity ≥99.5%, selenium recovery rate ≥90%, lead recovery rate ≥95%, copper recovery rate ≥90%, and bismuth recovery rate ≥85%.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical solid waste resource utilization technology, specifically involving a key technology for the field-enhanced selective separation of tellurium and multi-metal recovery from tellurium alkali slag. Background Technology

[0002] Tellurium, as a rare and dispersed metal, possesses excellent semiconductor, photoelectric conversion, and thermoelectric properties, making it a core raw material in high-tech fields such as photovoltaic cells, semiconductor devices, and advanced alloys. my country's tellurium reserves are scarce, with most relying on imports. Tellurium alkali slag, generated during the pyrometallurgical refining of non-ferrous metals such as lead and copper, primarily originates from the silver separation furnace process in crude lead oxidation refining or copper anode mud treatment. It is an important secondary tellurium resource, mainly composed of sodium tellurite (Na₂TeO₃) and other metal oxides such as Pb, Cu, and Bi, with a tellurium content typically between 5% and 32%. It has extremely high recovery value. Furthermore, valuable components in the slag, such as selenium, lead, bismuth, and copper, also possess significant resource utilization value. The resource utilization of tellurium alkali slag can not only alleviate the pressure of tellurium resource shortages but also reduce the risk of solid waste pollution.

[0003] Currently, the mainstream processes for recovering tellurium from tellurium alkali slag mainly include water leaching-sulfuric acid neutralization-hydroxylamine hydrochloride precipitation of selenium-Na2SO3 reduction process, water leaching-acid leaching-purification-hydrolysis precipitation of tellurium method, NaCl-H2SO4 system leaching method, and sodium sulfite reduction method. The water leaching-acid leaching method preferentially dissolves sodium tellurite in alkaline water, followed by acid leaching of the residue, achieving a total tellurium recovery rate of up to 93.85%. However, selenium and tellurium enter the solution simultaneously, lacking selective separation methods, resulting in excessive selenium content in the product, making it difficult to meet the requirements for high-purity tellurium applications. The NaCl-H2SO4 system integrates the treatment of copper bismuth slag and tellurium alkali slag, achieving a tellurium recovery rate of 85%-89% using lead smelting wastewater. However, the product is a TeO2 intermediate (containing approximately 73% Te, equivalent to 2N grade), requiring further reduction and purification, resulting in low purity of the direct product. Water leaching-sulfuric acid neutralization... The hydroxylamine hydrochloride precipitation-Na2SO3 reduction process efficiently separates selenium through selective selenium precipitation, followed by reduction to obtain high-purity tellurium powder. However, the tellurium leaching rate is low, resource utilization is insufficient, and there are significant drawbacks: First, tellurium is embedded and coexists with alkali metals and heavy metal impurities, making selective separation difficult with conventional leaching, resulting in tellurium leaching rates generally below 85%. Second, impurities cause severe interference, especially since selenium and tellurium have similar properties, making separation difficult and subsequent purification processes complex, leading to difficulties in achieving product purity standards. Third, the leaching time is long and easily generates large amounts of waste acid and waste liquid, resulting in high environmental treatment costs. Fourth, a certain amount of valuable metals remain in the leaching residue, which the existing process does not specifically recycle, leading to resource waste and reducing the overall resource utilization rate of the process.

[0004] Although the synergistic approach of ultrasonic enhancement and single reducing agent has been explored in some metal separation fields, literature review reveals a lack of systematic research on the synergistic application of ultrasonic enhancement and hydroxylamine hydrochloride precipitation of selenium in tellurium alkali slag extraction. Reports on related technology combinations are limited and require further exploration. Therefore, developing a highly efficient, selective, environmentally friendly method for tellurium alkali slag extraction that effectively solves the selenium-tellurium separation problem is of great significance for promoting tellurium resource recycling and reducing metallurgical solid waste. Summary of the Invention

[0005] To address the problems of insufficient tellurium leaching efficiency, difficulty in separating tellurium and selenium, low product purity, high energy consumption, significant environmental impact, high reagent consumption, or complex processes in existing technologies, this invention provides a key technology for the selective separation and extraction of tellurium and comprehensive recovery of multiple metals using tellurium-alkali slag in an enhanced field. It employs an integrated process flow of "ultrasonic enhanced leaching - stepwise recovery of heavy metals - selective precipitation of selenium with hydroxylamine hydrochloride - ultrasonic synergistic reduction." Through the synergy of ultrasonic cavitation effect and stepwise purification, the coupling of heavy metal recovery and selenium separation, and the matching of selective selenium precipitation and ultrasonic reduction, it achieves a tellurium leaching rate ≥95%, a selenium recovery rate ≥99%, a tellurium product purity ≥99.5%, and synergistic recovery of selenium and heavy metals. The overall resource utilization rate is 15%-20% higher than existing technologies, overcoming the technical bottleneck that a single technology cannot simultaneously achieve "high leaching rate - high selectivity - high purity - low energy consumption."

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] The method includes the following steps:

[0008] (1) Pretreatment of tellurium alkali slag: The tellurium alkali slag is crushed, ground, and dried to a moisture content of ≤5% to obtain pretreated material. It is preferred to use a 200-mesh sieve to collect particles with a particle size of ≤75μm to increase the reaction contact area.

[0009] (2) Ultrasonic enhanced leaching: The pretreated material from step (1) is mixed with pure water at a liquid-to-solid ratio of (3~8):1 mL / g and placed under ultrasonic conditions; wherein the ultrasonic power is 150~350W.

[0010] (3) Heavy metal recovery: Sodium sulfide solution is first added to the tellurium-containing leachate obtained in step (2), and the temperature is controlled at 30~60℃ to allow Pb to be recovered. 2+ Cu 2+ Bi 3+ The heavy metal ions form a sulfide mixture in the slag, which is then filtered and separated. Lead, copper, and bismuth are recovered from the sulfide mixture using a stepwise selective leaching system.

[0011] The specific process is as follows:

[0012] Lead recovery: Add the sulfide mixture to the acetate-ammonium acetate buffer solution, control the liquid-solid ratio at 5~10:1 mL / g, the temperature at 40~70℃, and the pH at 4.0~6.0, stir and leach, then filter. Lead enters the solution in ionic form, and the remaining solid is CuS-Bi2S3 slag after lead removal. Add sodium carbonate solution to the leachate, control the reaction temperature at 30~50℃, and PbCO3 is precipitated. Alternatively, add zinc powder / aluminum powder to the leachate for displacement, control the temperature at 30~60℃, and sponge lead is obtained.

[0013] Copper recovery: The lead-free CuS-Bi2S3 slag is added to a dilute sulfuric acid-H2O2 system with a sulfuric acid concentration of 0.5~2.0 mol / L, an H2O2 concentration of 5%~15%, a liquid-to-solid ratio of 4~8:1 mL / g, and a temperature of 40~60℃. After stirring and leaching, the mixture is filtered, and the copper enters the solution. The remaining solid is the copper-free Bi2S3 slag. The copper leaching solution is electrolyzed to obtain high-purity copper, or iron / aluminum powder is added and replaced at 30~50℃ to obtain sponge copper.

[0014] Bismuth recovery: Add concentrated hydrochloric acid (6-12 mol / L, liquid-to-solid ratio 6-12:1 mL / g, temperature 60-90℃) to Bi2S3 residue after copper removal. After complete dissolution, filter. Dilute the filtrate with water 3-6 times, control the pH at 1.0-3.0 and the temperature at 50-80℃, and hydrolyze to precipitate BiOCl, which is used as a raw material for the preparation of metallic bismuth.

[0015] This invention differs significantly from existing technologies: existing technologies often employ stepwise precipitation with a single precipitant or solvent extraction for impurity removal, resulting in lengthy processes and the disposal of waste residue; while this invention adopts a one-time co-precipitation strategy with sodium sulfide followed by stepwise leaching and recovery of mixed residue, firstly using sodium sulfide to simultaneously precipitate Pb. 2+ Cu 2+ Bi 3+ BiOCl is obtained by dissolving lead in acetic acid-ammonium acetate, dissolving copper in dilute sulfuric acid-H2O2, and dissolving bismuth in concentrated hydrochloric acid, thus realizing the resource utilization of all heavy metal components, avoiding waste residue pollution and improving economic benefits.

[0016] (4) Selective Selenium Separation: Barium carbonate is added to the tellurium-containing filtrate after heavy metal recovery, and the reaction is carried out for 20-30 minutes. The sulfate ions in the system are removed by filtration. The pH of the filtrate is then adjusted to 2.5-3.5. Finally, hydroxylamine hydrochloride is added to the filtrate for selective selenium precipitation, and the temperature is controlled at 40-70℃. After the reaction is completed, the filtrate is filtered to obtain selenium-precipitated residue and purified liquid. Stepwise purification can avoid the formation of complex precipitates. Hydroxylamine hydrochloride can efficiently and selectively separate selenium, thus solving the problem of selenium-tellurium separation. The core difference between this invention and the prior art is that a barium carbonate pre-removal sulfate step is forcibly added before selenium precipitation, and the pH is precisely controlled at 2.5-3.5, the hydroxylamine hydrochloride concentration is 20-30 g / L, the temperature is 40-70℃, and the time is 30-60 minutes. This invention eliminates the interference of sulfate ions on the reduction reaction of hydroxylamine hydrochloride by removing sulfate ions in advance, creating a "clean" reaction environment. At the same time, it uses precise pH control to ensure that hydroxylamine hydrochloride reduces only Se(IV) and not Te(IV), thereby solving the problem of selenium-tellurium separation and achieving excellent indicators such as selenium recovery rate ≥98.6% and product purity ≥99.5%, making the process greener and safer.

[0017] (5) High-efficiency tellurium recovery: Sodium sulfite reducing agent is added to the purified liquid in step (4) and reacted under ultrasonic conditions. The temperature is controlled at 55~85℃ and the reaction time is 30~60min to generate elemental tellurium precipitate. After filtration, washing and drying, high-purity tellurium product is obtained.

[0018] Preferably, in step (1), wet grinding is used during grinding, and then particles with a diameter ≤75μm are collected as pretreatment material.

[0019] As a preferred method, in step (2), the leaching temperature is controlled at 50~80℃ and the leaching time at 30~90min. During the leaching process, the pH value is adjusted to 1.5~3.0, and the leaching solution and leaching residue containing tellurium are obtained by filtration. Ultrasonic enhancement of leaching effect improves leaching efficiency. Too low a pH (<1.5) will lead to excessive acidity of the system, which will aggravate equipment corrosion on the one hand and cause some heavy metal impurities to dissolve excessively on the other hand, greatly increasing the subsequent purification load; too high a pH (>3.0) will significantly inhibit the dissolution of sodium tellurite, causing the tellurium leaching rate to drop rapidly. At the same time, it is easy to generate metal hydroxyl compounds, which will encapsulate unreacted materials and cause mass transfer obstruction, ultimately leading to a significant reduction in tellurium recovery rate and product purity. Controlling the pH at 1.5~3.0 can ensure the efficient and selective leaching of sodium tellurite while inhibiting the large-scale dissolution of heavy metal impurities, laying the foundation for subsequent selenium-tellurium separation and high-purity tellurium preparation.

[0020] Preferably, in steps (2) and (5), the ultrasonic power is 150~250W and the frequency is 20~40 kHz. In step (2) of this invention, controlling the ultrasonic power to be 150~250W and the frequency to be 20~40 kHz is to utilize the cavitation effect and mechanical vibration of the ultrasonic waves to enhance the leaching mass transfer process, so that the tellurium alkali residue particles can fully contact the leachate, accelerate the dissolution of sodium tellurite and the peeling of the passivation film on the particle surface, thereby significantly improving the leaching efficiency of tellurium and shortening the reaction time. If the power and frequency are too low, the cavitation effect will be insufficient, the particle dispersion effect will be poor, and the leaching reaction kinetics will be slow, resulting in a significant decrease in the tellurium leaching rate, a significant extension of the leaching time, and difficulty in breaking through the mass transfer resistance of the dense layer on the particle surface. If the power and frequency are too high, the local temperature will be too high, which will aggravate water evaporation and increase energy consumption. Excessive input of ultrasonic energy will cause the dissolved tellurite ions to degrade or transform, and may also cause a large amount of co-dissolution of impurities, which will reduce the selectivity of the leachate and increase the difficulty of subsequent purification.

[0021] As a preferred option, in step (2), the pretreated material is mixed with pure water at a liquid-to-solid ratio of (3~8):1 mL / g, and the leaching temperature is controlled at 50~80℃ and the leaching time at 30~90min.

[0022] Preferably, in step (2), the pH of the system is controlled to be 1.5~3.0 during the leaching process, which is adjusted by adding sulfuric acid or sodium hydroxide solution.

[0023] Preferably, in step (3), the concentration of sodium sulfide solution is 10~20g / L, the reaction temperature is controlled at 30~60℃, and the reaction time is 20~40min.

[0024] Preferably, in step (4), the amount of barium carbonate added is 1.2 to 2.0 times the theoretical amount of sulfate, prepared as a suspension of 20 to 50 g / L, and slowly added dropwise. The reaction temperature is 40 to 60°C, and the reaction time is 20 to 40 minutes, until the supernatant is clear when tested with BaCl2 test paper. The reason why sulfate is removed before hydroxylamine hydrochloride precipitation is that hydroxylamine hydrochloride, as a reducing agent, has a relatively mild reducing ability and stronger selectivity. High concentrations of sulfate in the solution will interfere with the reduction process of selenite, reduce the precipitation efficiency of selenium, and may co-precipitate with selenium precipitate, resulting in excessive sulfur content in the product. By removing sulfate with barium carbonate in advance, this invention can eliminate the interference of sulfate on the reduction reaction of hydroxylamine hydrochloride, significantly improve the precipitation efficiency of selenium and the purity of the final product, and at the same time make the subsequent dosage of hydroxylamine hydrochloride and reaction conditions more precise and controllable, achieving more stable industrial production.

[0025] Preferably, in step (4), the concentration of hydroxylamine hydrochloride solution is 20~30g / L, the selenium precipitation reaction temperature is 40~70℃, and the reaction time is 30~60min.

[0026] Preferably, in step (5), the reaction temperature of adding sodium sulfite reducing agent is controlled at 55~85℃ and the reaction time is 30~60min.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention combines ultrasonic field-enhanced leaching with selective selenium precipitation using hydroxylamine hydrochloride. Targeting the characteristics of selenium-tellurium symbiosis and impurity embedding in tellurium-alkali residue, it promotes preferential dissolution and stepwise directional purification of tellurium through an external field, achieving efficient separation of selenium and tellurium and high-purity recovery of tellurium. This overcomes the technical bottlenecks of difficult selenium-tellurium separation and low leaching rates in traditional processes. The ultrasonic cavitation effect promotes surface renewal of sodium tellurite particles, accelerating the precipitation of TeO3. 2- By complexing with sulfite, the problem of insufficient leaching efficiency in existing processes is solved, and the tellurium leaching rate is increased to over 95%.

[0029] 2. A selective selenium precipitation process using hydroxylamine hydrochloride, based on the following reaction mechanism, achieves efficient separation under controlled conditions: 2H₂SeO₃ + 2NH₂OH·HCl → 2Se↓ + N₂↑ + 2HCl + 6H₂O. Utilizing the selective reduction properties of hydroxylamine hydrochloride under acidic conditions (pH 2.5~3.5), only Se(IV) is reduced to elemental selenium precipitate, while Te(IV), due to its higher reduction potential, remains unreduced and in solution, thus achieving efficient separation of selenium and tellurium. Compared to existing hydroxylamine hydrochloride selenium precipitation processes, this invention eliminates SO₄²⁻ through a pre-treatment step of barium carbonate to remove sulfate. 2- The process mitigates pH buffering, reducing the amount of hydroxylamine hydrochloride used by at least 20% (and potentially 30%) and shortening the reaction time by at least 35% (and potentially 40%). Simultaneously, combined with ultrasonic field enhancement, it promotes selenium crystal formation and sedimentation, increasing selenium recovery from the conventional 98% to over 99.9%. The selenium content in the selenium-laden residue is >97%, allowing for direct sale as a selenium product without secondary purification. This process offers mild reaction conditions, high selectivity, and low reagent consumption, effectively overcoming the technical bottlenecks of simultaneous selenium and tellurium reduction and subsequent separation difficulties in the traditional sodium sulfite reduction method. Furthermore, it overcomes the shortcomings of existing hydroxylamine hydrochloride processes, such as high reagent consumption, long reaction cycles, and low product added value.

[0030] 3. Establish a supporting process for the resource recovery of leaching residue, and specifically recover valuable metals such as copper, lead, and bismuth remaining in the residue. Through a stepwise leaching-hydrolysis system of "acetic acid-ammonium acetate dissolving lead → dilute sulfuric acid-hydrogen peroxide dissolving copper → concentrated hydrochloric acid dissolving bismuth and hydrolyzing to obtain BiOCl", the full utilization of lead, copper, and bismuth can be achieved. This not only avoids resource loss but also generates additional economic benefits, significantly improving the overall resource utilization rate and economic efficiency of the process.

[0031] 4. By optimizing process parameters and synergistically enhancing the effect of ultrasonic fields, the reaction cycle of leaching and selenium precipitation can be significantly shortened, effectively improving the reaction rate and conversion efficiency. Simultaneously, by precisely controlling the dosage of acid and alkali reagents, the generation of waste acid and waste liquid can be drastically reduced, lowering the waste liquid treatment load. Furthermore, the waste liquid composition is simpler, and the difficulty of subsequent treatment is significantly reduced. This strategy not only effectively reduces environmental governance investment and operating costs but also achieves green, efficient, and low-cost operation of the process, fully aligning with national green and low-carbon development and environmental protection policies, demonstrating significant environmental and economic benefits. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described. In the embodiments and comparative examples of the present invention, unless otherwise specified, all chemical reagents are commercially available analytical grade. The tellurium alkali slag raw material comes from the crude lead oxidation refining silver separation furnace process, the main component of which is sodium tellurite, the tellurium content is 18.5%, and the main impurities are Na, Si, P, Se, Cu, Fe, Sb, S, Bi, Ag, Pb, As, Ca, Al, K, Sn, Mg, Mn, Zn, W, etc.

[0033] Example 1

[0034] (1) Pretreatment: After crushing and grinding the tellurium alkali slag, particles with a particle size ≤75μm are collected using a 200-mesh sieve and dried to a moisture content of 4.2% to obtain pretreated material;

[0035] (2) Ultrasonic enhanced leaching: The pretreated material and pure water were mixed at a liquid-solid ratio of 5:1 mL / g; the mixture was placed under ultrasonic conditions with an ultrasonic power density of 160W and a frequency of 28 kHz. The leaching temperature was controlled at 50℃ and the time was 30min. The pH was adjusted to 1.5 and the solution containing tellurium was obtained by filtration.

[0036] (3) Heavy metal recovery: Add 10 g / L sodium sulfide solution to the tellurium-containing leachate, the amount of which is 1.2 times the theoretical amount of heavy metal ions (the theoretical amount of heavy metal ions refers to the minimum amount of sulfide ions required to completely convert heavy metal ions into sulfides), control the temperature at 30℃ and the reaction time at 20 min, so that Pb 2+ Cu 2+ Bi 3+ A sulfide mixed slag is generated and filtered for separation. Lead, copper, and bismuth are recovered from the sulfide mixed slag using a stepwise selective leaching system. The specific process is as follows:

[0037] Lead recovery: Add the sulfide mixture to the acetate-ammonium acetate buffer solution, control the liquid-solid ratio at 5:1 mL / g, the temperature at 40℃, the leaching time at 30 min, and the pH at 4.0. After stirring and leaching, filter the solution. Lead enters the solution in ionic form. Add sodium carbonate solution to the leaching solution, control the reaction temperature at 30℃, and the reaction time at 20 min to precipitate PbCO3. Alternatively, add zinc powder / aluminum powder to the leaching solution for displacement, control the reaction temperature at 40℃ for 30 min, and obtain sponge lead.

[0038] Copper recovery: The lead-free CuS-Bi2S3 slag is added to a dilute sulfuric acid-H2O2 system with a sulfuric acid concentration of 0.5 mol / L, an H2O2 concentration of 5%, a liquid-to-solid ratio of 4:1 mL / g, a temperature of 40℃, and a leaching time of 40 min. After stirring and leaching, the mixture is filtered, and the copper enters the solution. The copper leaching solution is electrolyzed to obtain high-purity copper, or iron / aluminum powder is added and replaced at 30℃ for 30 min to obtain sponge copper.

[0039] Bismuth recovery: The Bi2S3 residue after copper removal was added to concentrated hydrochloric acid at a concentration of 6 mol / L, a liquid-to-solid ratio of 6:1 mL / g, a temperature of 60℃, and a dissolution time of 30 min. After complete dissolution, the residue was filtered. The filtrate was diluted 3 times with water, and the pH was controlled at 1.0, the temperature at 50℃, and the hydrolysis time at 30 min. BiOCl was obtained by hydrolysis precipitation and used as a raw material for the preparation of metallic bismuth.

[0040] (4) Selective separation of selenium: 30 g / L barium carbonate suspension was slowly added dropwise to the tellurium-containing filtrate after heavy metal recovery was completed. The temperature was controlled at 40℃ and the reaction was carried out for 20 min until the supernatant was clear when tested with BaCl2 test paper. The sulfate ions were removed by filtration. The pH of the filtrate was then adjusted to 2.5, and 20 g / L hydroxylamine hydrochloride was added. The amount added was twice the theoretical amount of selenium (molar ratio of NH2OH·HCl to Se(IV) 4:1). The temperature was controlled at 40℃ and the reaction time was 30 min. The selenium precipitate and the purified liquid were obtained by filtration.

[0041] (5) High-efficiency recovery of tellurium: Sodium sulfite (molar ratio of tellurium to tellurium 1.5:1) was added dropwise to the purified liquid, and the reaction was carried out at 55°C for 30 min. The mixture was then placed under ultrasonic conditions with an ultrasonic power of 160 W and a frequency of 28 kHz. After filtration, washing and drying, the tellurium product was obtained.

[0042] Test results: Total tellurium recovery rate 92.1%, product purity 99.5%, tellurium powder particle size D 50 =15~25 μm, uniform particle size distribution, selenium recovery rate 96.2%, selenium precipitate purity 94.5%, iron, silicon and other impurities content are all below 0.1%. Heavy metal recovery: lead recovery rate 87.3%, copper recovery rate 89.5%, bismuth recovery rate 85.6%.

[0043] Example 2

[0044] (1) Pretreatment: After crushing and grinding the tellurium alkali slag, particles with a particle size ≤75μm are collected using a 200-mesh sieve and dried to a moisture content of 3.8% to obtain pretreated material;

[0045] (2) Ultrasonic enhanced leaching: The pretreated material and pure water were mixed at a liquid-solid ratio of 6:1 mL / g; the mixture was placed under ultrasonic conditions with an ultrasonic power of 200W and a frequency of 28 kHz. The leaching temperature was controlled at 60℃ and the time was 60min. The pH was adjusted to 2.2 and the leaching solution containing tellurium was obtained by filtration.

[0046] (3) Heavy metal recovery: Add 15 g / L sodium sulfide solution to the tellurium-containing leachate, the amount of which is 1.35 times the theoretical amount of heavy metal ions. Control the temperature at 45℃ and the reaction time at 30 min to recover Pb. 2+ Cu 2+ Bi 3+ A sulfide-containing mixed slag is generated, which is then filtered and separated.

[0047] Lead, copper, and bismuth were recovered from the sulfide mixed slag using a stepwise selective leaching system. The specific process is as follows:

[0048] Lead recovery: Add the sulfide mixture to the acetate-ammonium acetate buffer solution, control the liquid-solid ratio at 7:1 mL / g, the temperature at 55℃, the leaching time at 45 min, and the pH at 5.0. After stirring and leaching, filter the solution. Lead enters the solution in ionic form. Add sodium carbonate solution to the leaching solution, control the reaction temperature at 45℃, and the reaction time at 30 min to precipitate PbCO3. Alternatively, add zinc powder / aluminum powder to the leaching solution for displacement, control the reaction temperature at 50℃ for 40 min, and obtain sponge lead.

[0049] Copper recovery: The lead-free CuS-Bi2S3 slag is added to a dilute sulfuric acid-H2O2 system with a sulfuric acid concentration of 1.0 mol / L, an H2O2 concentration of 10%, a liquid-to-solid ratio of 6:1 mL / g, a temperature of 50℃, and a leaching time of 60 min. After stirring and leaching, the mixture is filtered, and the copper enters the solution. The copper leaching solution is electrolyzed to obtain high-purity copper, or iron / aluminum powder is added and replaced at 40℃ for 45 min to obtain sponge copper.

[0050] Bismuth recovery: The Bi2S3 residue after copper removal was added to concentrated hydrochloric acid at a concentration of 8 mol / L, a liquid-to-solid ratio of 8:1 mL / g, a temperature of 75℃, and a dissolution time of 45 min. After complete dissolution, the residue was filtered. The filtrate was diluted 4 times with water, and the pH was controlled at 2.0, the temperature at 65℃, and the hydrolysis time at 40 min. BiOCl was obtained by hydrolysis precipitation and used as a raw material for the preparation of metallic bismuth.

[0051] (4) Selective separation of selenium: 30 g / L barium carbonate suspension was slowly added dropwise to the tellurium-containing filtrate after heavy metal recovery was completed. The temperature was controlled at 45℃ and the reaction was carried out for 25 min until the supernatant was clear when tested with BaCl2 test paper. The sulfate ions were removed by filtration. The pH of the filtrate was then adjusted to 3.0, and 25 g / L hydroxylamine hydrochloride was added. The amount added was 2.5 times the theoretical amount of selenium (NH2OH·HCl to Se(IV) molar ratio 5:1). The temperature was controlled at 55℃ and the reaction time was 45 min. The selenium precipitate and the purified liquid were obtained by filtration.

[0052] (5) High-efficiency recovery of tellurium: Add sodium sulfite solution (molar ratio of tellurium to tellurium 2.2:1) to the purified liquid, react at 65℃ for 45 min, place under ultrasonic conditions, ultrasonic power 200W, frequency 28 kHz; after filtration, washing and drying, tellurium product is obtained.

[0053] Test results: Total tellurium recovery rate 95.3%, product purity 99.7%, tellurium powder particle size D 50 =10~20 μm, uniform particle size distribution, selenium recovery rate 97.5%, selenium precipitate purity 95.8%, iron, silicon and other impurity content are all below 0.08%. Heavy metal recovery: lead recovery rate 89.6%, copper recovery rate 91.2%, bismuth recovery rate 87.4%.

[0054] Example 3

[0055] (1) Pretreatment: After crushing and grinding the tellurium alkali slag, particles with a diameter ≤75μm are collected using a 200-mesh sieve and dried to a moisture content of 3.5% to obtain pretreated material;

[0056] (2) Ultrasonic enhanced leaching: The pretreated material and pure water were mixed at a liquid-solid ratio of 7:1 mL / g and placed under ultrasonic conditions. The ultrasonic power was 230W and the frequency was 28 kHz. The leaching temperature was controlled at 80℃ and the time was 90 min. The pH was adjusted to 3.0 and the leaching solution containing tellurium was obtained by filtration.

[0057] (3) Heavy metal recovery: Add 20 g / L sodium sulfide solution to the tellurium-containing leachate, the amount of which is 1.5 times the theoretical amount of heavy metal ions. Control the temperature at 60℃ and the reaction time at 40 min to recover Pb. 2+ Cu 2+ Bi 3+ A sulfide-containing mixed slag is generated, which is then filtered and separated.

[0058] Lead, copper, and bismuth were recovered from the sulfide mixed slag using a stepwise selective leaching system. The specific process is as follows:

[0059] Lead recovery: Add the sulfide mixture to the acetate-ammonium acetate buffer solution, control the liquid-solid ratio at 10:1 mL / g, the temperature at 70℃, the leaching time at 60 min, and the pH at 6.0. After stirring and leaching, filter the solution. Lead enters the solution in ionic form. Add sodium carbonate solution to the leaching solution, control the reaction temperature at 50℃, and the reaction time at 40 min to precipitate PbCO3. Alternatively, add zinc powder / aluminum powder to the leaching solution for displacement, control the reaction temperature at 60℃ for 50 min, and obtain sponge lead.

[0060] Copper recovery: The lead-free CuS-Bi2S3 slag is added to a dilute sulfuric acid-H2O2 system with a dilute sulfuric acid concentration of 2.0 mol / L, an H2O2 concentration of 15%, a liquid-to-solid ratio of 8:1 mL / g, a temperature of 60℃, and a leaching time of 80 min. After stirring and leaching, the mixture is filtered, and the copper enters the solution. The copper leaching solution is electrolyzed to obtain high-purity copper, or iron / aluminum powder is added and replaced at 50℃ for 60 min to obtain sponge copper.

[0061] Bismuth recovery: The Bi2S3 residue after copper removal was added to concentrated hydrochloric acid at a concentration of 12 mol / L, a liquid-to-solid ratio of 12:1 mL / g, a temperature of 90℃, and a dissolution time of 60 min. After complete dissolution, the residue was filtered. The filtrate was diluted 6 times with water, and the pH was controlled at 3.0, the temperature at 80℃, and the hydrolysis time at 50 min. BiOCl was obtained by hydrolysis precipitation and used as a raw material for the preparation of metallic bismuth.

[0062] (4) Selective separation of selenium: 30 g / L barium carbonate suspension was slowly added dropwise to the tellurium-containing filtrate after heavy metal recovery was completed. The temperature was controlled at 50℃ and the reaction was carried out for 30 min until the supernatant was clear when tested with BaCl2 test paper. The sulfate ions were removed by filtration. The pH of the filtrate was then adjusted to 3.5, and 30 g / L hydroxylamine hydrochloride was added. The amount added was 3 times the theoretical amount of selenium (molar ratio of NH2OH·HCl to Se(IV) 6:1). The temperature was controlled at 70℃ and the reaction time was 60 min. The selenium precipitate and the purified liquid were obtained by filtration.

[0063] (5) High-efficiency recovery of tellurium: Add sodium sulfite solution (molar ratio of tellurium 3.0:1) to the purified liquid, react at 80℃ for 60 min, place under ultrasonic conditions, ultrasonic power 230W, frequency 28 kHz; after filtration, washing and drying, the tellurium product is obtained.

[0064] Test results: Total tellurium recovery rate 97.5%, product purity 99.9%, tellurium powder particle size D 50 =8~15 μm, uniform particle size distribution, selenium recovery rate 98.9%, selenium precipitate purity 97.2%, iron, silicon and other impurity content are all below 0.05%. Heavy metal recovery: lead recovery rate 91.5%, copper recovery rate 93.6%, bismuth recovery rate 89.8%.

[0065] Example 4

[0066] (1) Pretreatment: After crushing and grinding the tellurium alkali residue, particles with a diameter ≤75μm are collected by using a 200-mesh sieve and dried to a moisture content of 5.0% to obtain pretreated material;

[0067] (2) Ultrasonic enhanced leaching: The pretreated material and pure water were mixed at a liquid-solid ratio of 3:1 mL / g; the mixture was placed under ultrasonic conditions with an ultrasonic power of 150W and a frequency of 20 kHz, the leaching temperature was controlled at 50℃ and the time was 30 min, the pH was adjusted to 1.5, and the tellurium-containing leachate was obtained by filtration.

[0068] (3) Heavy metal recovery: Add 10 g / L sodium sulfide solution to the tellurium-containing leachate, the amount of which is 1.2 times the theoretical amount of heavy metal ions. Control the temperature at 30℃, the reaction time at 20 min, and the stirring rate at 150 r / min to recover Pb. 2+ Cu 2+ Bi 3+ A sulfide-containing mixed slag is generated, which is then filtered and separated.

[0069] Lead, copper, and bismuth were recovered from the sulfide mixed slag using a stepwise selective leaching system. The specific process is as follows:

[0070] Lead recovery: Add the sulfide mixture to the acetate-ammonium acetate buffer solution, control the liquid-solid ratio at 5:1 mL / g, the temperature at 40℃, the leaching time at 30 min, and the pH at 4.0. After stirring and leaching, filter the solution. Lead enters the solution in ionic form. Add sodium carbonate solution to the leaching solution, control the reaction temperature at 30℃, and the reaction time at 20 min to precipitate PbCO3. Alternatively, add zinc powder / aluminum powder to the leaching solution for displacement, control the reaction temperature at 40℃ for 30 min, and obtain sponge lead.

[0071] Copper recovery: The lead-free CuS-Bi2S3 slag is added to a dilute sulfuric acid-H2O2 system with a sulfuric acid concentration of 0.5 mol / L, an H2O2 concentration of 5%, a liquid-to-solid ratio of 4:1 mL / g, a temperature of 40℃, and a leaching time of 40 min. After stirring and leaching, the mixture is filtered, and the copper enters the solution. The copper leaching solution is electrolyzed to obtain high-purity copper, or iron / aluminum powder is added and replaced at 30℃ for 30 min to obtain sponge copper.

[0072] Bismuth recovery: The Bi2S3 residue after copper removal was added to concentrated hydrochloric acid at a concentration of 6 mol / L, a liquid-to-solid ratio of 6:1 mL / g, a temperature of 60℃, and a dissolution time of 30 min. After complete dissolution, the residue was filtered. The filtrate was diluted 3 times with water, and the pH was controlled at 1.0, the temperature at 50℃, and the hydrolysis time at 30 min. BiOCl was obtained by hydrolysis precipitation and used as a raw material for the preparation of metallic bismuth.

[0073] (4) Selective separation of selenium: 20 g / L barium carbonate suspension was slowly added dropwise to the tellurium-containing filtrate after heavy metal recovery. The temperature was controlled at 40℃, the stirring rate was 200 r / min, and the reaction was carried out for 20 min until the supernatant was clear when tested with BaCl2 test paper. The sulfate ions were removed by filtration. The pH of the filtrate was then adjusted to 2.5, and 20 g / L hydroxylamine hydrochloride was added. The amount added was twice the theoretical amount of selenium (molar ratio of NH2OH·HCl to Se(IV) 4:1). The temperature was controlled at 40℃, the reaction time was 30 min, and the stirring rate was 150 r / min. The selenium precipitate and the purified liquid were obtained by filtration.

[0074] (5) High-efficiency recovery of tellurium: Sodium sulfite (molar ratio of tellurium to tellurium 1.2:1) was added dropwise to the purified liquid, and the reaction was carried out at 55℃ for 30 min with a stirring rate of 150 r / min. The mixture was placed under ultrasonic conditions with an ultrasonic power of 150 W and a frequency of 20 kHz. After filtration, washing and drying, the tellurium product was obtained.

[0075] Test results: Total tellurium recovery rate 88.5%, product purity 98.2%, tellurium powder particle size D 50 =25~35 μm; selenium recovery rate 93.8%, selenium precipitate purity 91.2%; iron, silicon and other impurity content are all below 0.15%. Heavy metal recovery: lead recovery rate 85.2%, copper recovery rate 86.8%, bismuth recovery rate 83.5%.

[0076] Example 5

[0077] (1) Pretreatment: After crushing and grinding the tellurium alkali residue, particles with a diameter ≤75μm are collected using a 200-mesh sieve and dried to a moisture content of 2.5% to obtain pretreated material;

[0078] (2) Ultrasonic enhanced leaching: The pretreated material and pure water were mixed at a liquid-solid ratio of 8:1 mL / g; the mixture was placed under ultrasonic conditions with an ultrasonic power of 250W and a frequency of 40 kHz, the leaching temperature was controlled at 80℃ and the time at 90 min, the pH was adjusted to 3.0, and the tellurium-containing leachate was obtained by filtration.

[0079] (3) Heavy metal recovery: Add 20 g / L sodium sulfide solution to the tellurium-containing leachate, the amount of which is 2.0 times the theoretical amount of heavy metal ions. Control the temperature at 60℃, the reaction time at 40 min, and the stirring rate at 250 r / min to recover Pb. 2+ Cu 2+ Bi 3+ A sulfide-containing mixed slag is generated, which is then filtered and separated.

[0080] Lead, copper, and bismuth were recovered from the sulfide mixed slag using a stepwise selective leaching system. The specific process is as follows:

[0081] Lead recovery: Add the sulfide mixture to the acetate-ammonium acetate buffer solution, control the liquid-solid ratio at 10:1 mL / g, the temperature at 70℃, the leaching time at 60 min, and the pH at 6.0. After stirring and leaching, filter the solution. Lead enters the solution in ionic form. Add sodium carbonate solution to the leaching solution, control the reaction temperature at 50℃, and the reaction time at 40 min to precipitate PbCO3. Alternatively, add zinc powder / aluminum powder to the leaching solution for displacement, control the reaction temperature at 60℃ for 50 min, and obtain sponge lead.

[0082] Copper recovery: The lead-free CuS-Bi2S3 slag is added to a dilute sulfuric acid-H2O2 system with a dilute sulfuric acid concentration of 2.0 mol / L, an H2O2 concentration of 15%, a liquid-to-solid ratio of 8:1 mL / g, a temperature of 60℃, and a leaching time of 80 min. After stirring and leaching, the mixture is filtered, and the copper enters the solution. The copper leaching solution is electrolyzed to obtain high-purity copper, or iron / aluminum powder is added and replaced at 50℃ for 60 min to obtain sponge copper.

[0083] Bismuth recovery: The Bi2S3 residue after copper removal was added to concentrated hydrochloric acid at a concentration of 12 mol / L, a liquid-to-solid ratio of 12:1 mL / g, a temperature of 90℃, and a dissolution time of 60 min. After complete dissolution, the residue was filtered. The filtrate was diluted 6 times with water, and the pH was controlled at 3.0, the temperature at 80℃, and the hydrolysis time at 50 min. BiOCl was obtained by hydrolysis precipitation and used as a raw material for the preparation of metallic bismuth.

[0084] (4) Selective separation of selenium: 50 g / L barium carbonate suspension was slowly added dropwise to the tellurium-containing filtrate after heavy metal recovery. The temperature was controlled at 60℃, the stirring rate at 400 r / min, and the reaction was carried out for 40 min until the supernatant was clear when tested with BaCl2 test paper. The sulfate ions were removed by filtration. The pH of the filtrate was then adjusted to 3.5, and 30 g / L hydroxylamine hydrochloride was added. The amount added was 4 times the theoretical amount of selenium (molar ratio of NH2OH·HCl to Se(IV) 8:1). The temperature was controlled at 70℃, the reaction time at 60 min, and the stirring rate at 300 r / min. The selenium precipitate and the purified liquid were obtained by filtration.

[0085] (5) High-efficiency recovery of tellurium: Sodium sulfite (molar ratio of tellurium to tellurium 3.5:1) was added dropwise to the purified liquid, and the reaction was carried out at 85℃ for 60 min with a stirring rate of 350 r / min. The mixture was placed under ultrasonic conditions with an ultrasonic power of 250 W and a frequency of 40 kHz. After filtration, washing and drying, the tellurium product was obtained.

[0086] Test results: Total tellurium recovery rate 94.8%, product purity 99.6%, tellurium powder particle size D 50 =5~10 μm; selenium recovery rate 97.8%, selenium precipitate purity 96.5%; iron, silicon and other impurity content are all below 0.06%. Heavy metal recovery: lead recovery rate 90.2%, copper recovery rate 92.5%, bismuth recovery rate 88.6%.

[0087] Example 6 (Best)

[0088] (1) Pretreatment: After crushing and grinding the tellurium alkali residue, particles with a diameter ≤75μm are collected using a 200-mesh sieve and dried to a moisture content of 3.0% to obtain pretreated material;

[0089] (2) Ultrasonic enhanced leaching: The pretreated material and pure water were mixed at a liquid-solid ratio of 6:1 mL / g; the mixture was placed under ultrasonic conditions with an ultrasonic power of 200W and a frequency of 28 kHz. The leaching temperature was controlled at 65℃ and the time was 60 min. The pH was adjusted to 2.2, and the tellurium-containing leachate was obtained by filtration.

[0090] (3) Heavy metal recovery: Add 15 g / L sodium sulfide solution to the tellurium-containing leachate, the amount of which is 1.5 times the theoretical amount of heavy metal ions. Control the temperature at 45℃, the reaction time at 30 min, and the stirring rate at 200 r / min to recover Pb. 2+ Cu 2+ Bi 3+ A sulfide-containing mixed slag is generated, which is then filtered and separated.

[0091] Lead, copper, and bismuth were recovered from the sulfide mixed slag using a stepwise selective leaching system. The specific process is as follows:

[0092] Lead recovery: Sulfide mixture residue is added to acetate-ammonium acetate buffer solution, and the liquid-solid ratio is controlled at 8:1 mL / g, temperature at 60℃, leaching time at 50 min, and pH at 5.5. After stirring and leaching, the mixture is filtered, and lead enters the solution in ionic form. Sodium carbonate solution is added to the leaching solution, and the reaction temperature is controlled at 45℃ for 35 min to precipitate PbCO3. Alternatively, zinc powder / aluminum powder is added to the leaching solution for displacement, and the reaction is controlled at 55℃ for 45 min to obtain sponge lead.

[0093] Copper recovery: The lead-free CuS-Bi2S3 slag is added to a dilute sulfuric acid-H2O2 system with a sulfuric acid concentration of 1.5 mol / L, an H2O2 concentration of 12%, a liquid-to-solid ratio of 7:1 mL / g, a temperature of 55℃, and a leaching time of 70 min. After stirring and leaching, the mixture is filtered, and the copper enters the solution. The copper leaching solution is electrolyzed to obtain high-purity copper, or iron / aluminum powder is added and replaced at 45℃ for 50 min to obtain sponge copper.

[0094] Bismuth recovery: The Bi2S3 residue after copper removal was added to concentrated hydrochloric acid at a concentration of 10 mol / L, a liquid-to-solid ratio of 10:1 mL / g, a temperature of 80℃, and a dissolution time of 50 min. After complete dissolution, the residue was filtered. The filtrate was diluted 5 times with water, and the pH was controlled at 2.5, the temperature at 70℃, and the hydrolysis time at 45 min. BiOCl was obtained by hydrolysis precipitation and used as a raw material for the preparation of metallic bismuth.

[0095] (4) Selective separation of selenium: 30 g / L barium carbonate suspension was slowly added dropwise to the tellurium-containing filtrate after heavy metal recovery. The temperature was controlled at 50℃, the stirring rate at 300 r / min, and the reaction was carried out for 30 min until the supernatant was clear when tested with BaCl2 test paper. The sulfate ions were removed by filtration. The pH of the filtrate was then adjusted to 3.0, and 25 g / L hydroxylamine hydrochloride was added. The amount added was 3 times the theoretical amount of selenium (NH2OH·HCl to Se(IV) molar ratio 6:1). The temperature was controlled at 55℃, the reaction time at 45 min, and the stirring rate at 220 r / min. The selenium precipitate and the purified liquid were obtained by filtration.

[0096] (5) High-efficiency recovery of tellurium: Sodium sulfite (molar ratio of tellurium to tellurium 2.5:1) was added dropwise to the purified liquid, and the reaction was carried out at 70℃ for 45 min with a stirring rate of 250 r / min. The mixture was placed under ultrasonic conditions with an ultrasonic power of 200 W and a frequency of 28 kHz. After filtration, washing and drying, the tellurium product was obtained.

[0097] Test results: Total tellurium recovery rate 98.6%, product purity 99.95%, tellurium powder particle size D 50 =8~12 μm, with the most uniform particle size distribution; selenium recovery rate 99.2%, selenium precipitate purity 98.5%; iron, silicon and other impurity contents are all below 0.03%. Heavy metal recovery: lead recovery rate 93.5%, copper recovery rate 95.2%, bismuth recovery rate 91.8%.

[0098] Comparative Example 1 used the same process parameters as Example 2, except that the leaching process was not enhanced by ultrasonic external field, but only by conventional stirring leaching.

[0099] Test results: Total tellurium recovery rate was 82.5%, product purity was 96.3%, selenium recovery rate was 95.7%, and impurity content was significantly higher than in Example 2.

[0100] Comparative Example 2 used the same process parameters as Example 2, except that hydroxylamine hydrochloride was not added during the purification process and no special selenium separation was performed.

[0101] Test results: Total tellurium recovery rate was 90.2%, product purity was 97.1%, and selenium content was 0.35%, which did not meet the requirements for high-purity tellurium products.

[0102] Comparative Example 3 used the same process parameters as Example 2, except that sodium sulfide, barium carbonate, and hydroxylamine hydrochloride were added simultaneously during the purification process, and the process was not carried out in steps.

[0103] Test results: Total tellurium recovery rate was 88.6%, product purity was 96.5%, and selenium recovery rate was 92.3% due to tellurium loss and incomplete removal of impurities caused by the formation of complex precipitates.

[0104] Comparative Example 4 used the same process parameters as Example 2, except that valuable metals such as Pb, Cu, and Bi were not recovered during the purification process.

[0105] Test results: Total tellurium recovery rate 86.4%, product purity 93.7%, selenium recovery rate 91.5%. The failure to recover valuable metals such as Pb, Cu, and Bi resulted in a waste of mineral resources, and the interference from impurities and slag significantly reduced tellurium recovery rate, product purity, and selenium recovery rate.

[0106] Comparative Example 5

[0107] The same process parameters as in Example 2 were used, except that the ultrasonic power in the ultrasonic-enhanced leaching and tellurium recovery stages was 80W and the frequency was still 28kHz.

[0108] Test results: Total tellurium recovery rate was 84.2%, product purity was 95.8%, selenium recovery rate was 94.3%, impurity content was significantly higher than in Example 2, and both leaching and reduction reactions were incomplete.

[0109] Comparative Example 6

[0110] The same process parameters as in Example 2 were used, except that the pH of the ultrasonically enhanced leaching system was adjusted to 5.0.

[0111] Test results: Total tellurium recovery rate 81.7%, product purity 94.9%, selenium recovery rate 93.1%, heavy metal precipitation was incomplete, and the residual amount of impurity ions in the solution was high.

[0112] Comparative Example 7

[0113] The same process parameters as in Example 2 were used, except that the liquid-to-solid ratio of the pretreated material to pure water was 1:1 mL / g.

[0114] Test results: Total tellurium recovery rate 79.3%, product purity 93.2%, selenium recovery rate 90.6%, the system is viscous and difficult to filter, the reaction mass transfer is severely hindered, and many indicators are poor.

[0115] In this comparative example, an excessively low liquid-to-solid ratio resulted in excessively high slurry concentration, uneven material mixing, and a significant weakening of the ultrasonic mass transfer effect. Consequently, the leaching agent and tellurium alkali residue did not come into sufficient contact, and steps such as heavy metal recovery and selenium separation could not be carried out efficiently.

[0116] Comparative Example 8

[0117] The same process parameters as in Example 2 were used, except that the concentration of hydroxylamine hydrochloride solution was 40 g / L during selective selenium precipitation.

[0118] Test results: Total tellurium recovery rate 85.9%, product purity 95.1%, selenium recovery rate 92.7%, and co-precipitation of tellurium and selenium was observed.

[0119] Comparative Example 9

[0120] The same process parameters as in Example 2 were used, except that the pH of the ultrasonically enhanced leaching system was adjusted to 0.1.

[0121] Test results: Total tellurium recovery rate was 76.8%, product purity was 91.2%, selenium recovery rate was 87.4%, heavy metal impurities such as lead, copper, and bismuth were dissolved in large quantities in the leachate, the subsequent purification load increased sharply, and the impurity content was significantly higher than in Example 2.

[0122] A comparison of Example 1 and Comparative Example 1 shows that the tellurium leaching rate, product purity, and selenium recovery rate of Comparative Example 1 are significantly reduced. This is because ultrasonic external field enhancement leaching was not used, which limited the dissolution kinetics of sodium tellurite in the tellurium alkali residue and made it difficult to destroy the passivation film on the particle surface. In contrast, the ultrasonic cavitation effect introduced in Example 1 allows the local high temperature and pressure and high speed micro-jet generated by the collapse of microbubbles to effectively peel off the dense layer on the particle surface, enhance mass transfer, and reduce the reaction activation energy, thereby significantly improving the tellurium leaching rate and shortening the leaching time.

[0123] A comparison of Example 1 and Comparative Example 2 shows that the purity and selenium recovery rate of the product in Comparative Example 2 decreased significantly. This is because the purification process did not use hydroxylamine hydrochloride for selective selenium precipitation, and the sodium sulfite reducing agent could not distinguish between selenium and tellurium. The simultaneous reduction of the two resulted in a higher selenium content in the product, failing to meet the high-purity tellurium standard. In contrast, Example 1 introduced a hydroxylamine hydrochloride selective reduction system, which reduced Se(IV) to elemental selenium precipitate based on the reaction, while Te(IV) was not reduced, thereby achieving efficient separation of selenium and tellurium and ensuring that the product purity met the standard.

[0124] A comparison of Example 1 and Comparative Example 3 shows that the total tellurium recovery rate and selenium recovery rate of Comparative Example 3 decreased significantly. This was because sodium sulfide, barium carbonate, and hydroxylamine hydrochloride were added simultaneously without following the step-by-step purification sequence, resulting in the formation of a complex co-precipitate, causing tellurium entrainment loss and incomplete impurity removal. In contrast, Example 1 strictly followed the step-by-step purification sequence, avoiding the formation of complex precipitates, ensuring the targeted removal of each impurity, and maintaining a stable tellurium recovery rate.

[0125] A comparison of Example 1 and Comparative Example 4 shows that the tellurium recovery rate, product purity, and selenium recovery rate of Comparative Example 4 all decreased significantly. This is because the valuable metals in the leaching residue were not recycled, and the interference of the sulfide mixed residue complicated the subsequent purification steps and caused a waste of mineral resources. In contrast, Example 1 established a stepwise leaching-hydrolysis system to convert Bi2S3 into BiOCl intermediate products, which not only eliminated the interference of impurities but also realized the full utilization of lead, copper, and bismuth, improving the overall economic benefits of the process and the comprehensive utilization rate of resources.

[0126] A comparison of Example 1 and Comparative Example 5 shows that the total tellurium recovery rate, product purity, and selenium recovery rate of Comparative Example 5 are significantly lower. This is because the ultrasonic power in the ultrasonic-enhanced leaching and tellurium recovery stages is lower than the protection range of this invention, resulting in a weak cavitation effect. This makes it impossible to effectively destroy the passivation film on the surface of the tellurium alkali slag particles, leading to a significant decrease in mass transfer efficiency and insufficient leaching and reduction reactions of tellurium. In contrast, Example 1 uses a suitable ultrasonic power of 150~250W, which provides sufficient cavitation effect. This allows for the stripping of the dense layer of particles, enhanced mass transfer, and a reduction in reaction activation energy, ensuring efficient leaching and reduction of tellurium, and meeting the core indicators.

[0127] A comparison of Example 1 and Comparative Example 6 shows that the total tellurium recovery rate, product purity, and selenium recovery rate of Comparative Example 6 are significantly worse. This is because the pH of the ultrasonically enhanced leaching system is higher than the protection range of this invention, causing a sharp drop in the dissolution efficiency of sodium tellurite and disrupting the reaction conditions for heavy metal sulfide precipitation, resulting in a decrease in Pb. 2+ Cu 2+ Bi 2+ Incomplete removal of impurities severely interferes with subsequent selenium-tellurium separation and tellurium reduction. In Example 1, the leaching pH was controlled at 1.5~3.0 to ensure efficient dissolution of sodium tellurite and deep removal of heavy metals, laying the foundation for subsequent purification processes.

[0128] A comparison of Example 1 and Comparative Example 7 shows that the total tellurium recovery rate, product purity, and selenium recovery rate of Comparative Example 7 all declined significantly, with many indicators reaching extremely poor levels. This is because the liquid-to-solid ratio of the pretreated material to pure water was far lower than the protection range of this invention, resulting in excessively high slurry concentration, uneven material mixing, and severely weakened ultrasonic mass transfer effect. Consequently, the leaching agent and tellurium alkali residue could not fully contact each other, and subsequent processes such as heavy metal recovery and selective selenium separation could not be carried out efficiently. In contrast, Example 1 used a suitable liquid-to-solid ratio of 3 to 8:1, which resulted in excellent slurry fluidity and mass transfer efficiency, ensuring efficient reaction throughout the entire process.

[0129] A comparison of Example 1 and Comparative Example 8 shows that the total tellurium recovery rate and product purity of Comparative Example 8 decreased, and the selenium recovery rate did not reach the optimal level. This is because the concentration of hydroxylamine hydrochloride during selective selenium precipitation was higher than the protection range of this invention. Excessive reducing agent disrupted the selective reduction equilibrium, reducing a small amount of Te(IV) while reducing Se(IV), resulting in the loss of co-precipitation of tellurium and selenium, and affecting product purity. In contrast, Example 1 used a suitable concentration of hydroxylamine hydrochloride of 20~30 g / L, which accurately achieved the selective reduction and precipitation of Se(IV), and Te(IV) remained stably in the solution, with both selenium and tellurium recovery rates meeting the standard simultaneously.

[0130] A comparison of Example 2 and Comparative Example 9 shows that the total tellurium recovery rate, product purity, and selenium separation efficiency of Comparative Example 9 all decreased significantly. This is because the pH of the leaching system was too low (0.1), and the strong acid environment caused a large amount of heavy metal impurities to dissolve, resulting in a sharp increase in the concentration of impurity ions in the solution. This not only increased the burden on subsequent purification but also interfered with the selective separation of selenium and tellurium, causing tellurium loss and a decline in purity. In contrast, Example 2 controlled the leaching pH within a suitable acidic range of 1.5 to 3.0, which ensured efficient dissolution of sodium tellurite and inhibited excessive dissolution of heavy metals, creating a stable system for purification.

[0131] The cross-comparison of Comparative Example 1, Comparative Example 2 and Example 1 shows that the contribution of ultrasonic field enhancement to improving tellurium leaching rate is higher than the contribution of selective selenium precipitation by hydroxylamine hydrochloride to product purity. However, the two must work together to achieve the three goals of high recovery rate, high purity and high selenium separation efficiency. None of them can be omitted.

[0132] In summary, this invention, through an integrated process of ultrasonic-enhanced leaching, stepwise purification, selective selenium precipitation with hydroxylamine hydrochloride, and ultrasonic synergistic reduction, effectively solves the technical bottlenecks in traditional tellurium slag treatment, such as low leaching efficiency, difficulty in separating selenium and tellurium, insufficient product purity, and low resource utilization. It achieves the technical indicators of total tellurium recovery rate, product purity, and selenium recovery rate, providing a green and efficient technical path for the resource utilization of metallurgical solid waste.

[0133] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for a stepwise purification and multi-metal synergistic recovery process of tellurium alkali slag enhanced by field conditions, characterized in that: The method includes the following steps: (1) Pretreatment of tellurium alkali slag: The tellurium alkali slag is crushed, ground and dried to a moisture content of ≤5% to obtain pretreated material; (2) Ultrasonic enhanced leaching: The pretreated material from step (1) is mixed with pure water at a liquid-to-solid ratio of (3~8):1 mL / g and then subjected to ultrasonic conditions; wherein the ultrasonic power is 150~350W. (3) Heavy metal recovery: Add sodium sulfide solution to the tellurium-containing leachate obtained in step (2), and control the temperature at 30~60℃ to allow Pb to recover. 2+ Cu 2+ Bi 3+ The sulfide mixture residue is filtered and separated after heavy metal ions are converted into sulfides. Lead is recovered by leaching the sulfide mixture residue with acetic acid-ammonium acetate buffer, copper is recovered by leaching with dilute sulfuric acid-H2O2 system, and bismuth is recovered by dissolving and hydrolyzing with concentrated hydrochloric acid. (4) Selective separation of selenium: Add barium carbonate to the tellurium-containing filtrate after heavy metal recovery, filter to remove sulfate from the system; adjust the pH of the filtrate to 2.5~3.5, and finally add hydroxylamine hydrochloride to the filtrate for selective selenium precipitation, control the temperature at 40~70℃, filter after the reaction to obtain selenium precipitate residue and purified liquid. (5) Tellurium recovery: Sodium sulfite reducing agent is added to the purified liquid in step (4) and reacted under ultrasonic conditions, with the temperature controlled at 55~85℃, to generate elemental tellurium precipitate; after filtration, washing and drying, tellurium product is obtained.

2. The method for stepwise purification and multi-metal synergistic recovery of tellurium alkali slag in an enhanced field according to claim 1, characterized in that: In step (1), wet grinding is used during grinding, and then particles with a diameter ≤75μm are collected as pretreatment material.

3. The method for stepwise purification and multi-metal synergistic recovery of tellurium alkali slag in an enhanced field according to claim 1, characterized in that: In steps (2) and (5), the ultrasonic power is 150~250W and the frequency is 20~40 kHz.

4. The method for stepwise purification and multi-metal synergistic recovery of tellurium alkali slag in an enhanced field according to claim 1, characterized in that: Step (2) Control the leaching temperature to 50~80℃ and the leaching time to 30~90min.

5. The method for stepwise purification and multi-metal synergistic recovery of tellurium alkali slag in an enhanced field according to claim 1, characterized in that: During the leaching process in step (2), the pH value is adjusted to 1.5~3.

0.

6. The method for stepwise purification and multi-metal synergistic recovery of tellurium alkali slag in an external field according to claim 1, characterized in that: In step (3), the concentration of sodium sulfide solution is 10~20g / L, the reaction temperature is controlled at 30~60℃, and the reaction time is 20~40min.

7. The method for stepwise purification and multi-metal synergistic recovery of tellurium alkali slag in an external field enhanced process according to claim 1, characterized in that: In step (4), the amount of barium carbonate added is 1.2 to 2.0 times the theoretical amount of sulfate. It is prepared as a suspension of 20 to 50 g / L and slowly added dropwise. The reaction temperature is 40 to 60℃ and the reaction time is 20 to 40 min until the supernatant is clear when tested with BaCl2 test paper.

8. The method for stepwise purification and multi-metal synergistic recovery of tellurium alkali slag in an enhanced field according to claim 1, characterized in that: In step (4), the concentration of hydroxylamine hydrochloride solution is 20~30g / L, the selenium precipitation reaction temperature is 40~70℃, and the reaction time is 30~60min.

9. The method for stepwise purification and multi-metal synergistic recovery of tellurium alkali slag in an enhanced field according to claim 1, characterized in that: In step (5), the reaction temperature of the sodium sulfite reducing agent is controlled at 55~85℃ and the reaction time is 30~60min.