An enhanced leaching and purification method for tellurium in arsenic-antimony-tellurium alkaline residue

Abstract

This invention discloses an enhanced leaching and purification method for tellurium in arsenic-antimony-tellurium alkaline slag, belonging to the field of solid waste resource utilization and rare and dispersed metal extraction in non-ferrous metal smelting. Using high-arsenic-antimony-tellurium alkaline slag as raw material, a mixed leaching method with tellurium-directed leaching agents is employed. Through the synergistic effect of "strong alkali complexation-reduction solubilization-high salt stable solubility," efficient tellurium leaching and directional retention of arsenic and antimony are achieved, resulting in a low-impurity tellurium-containing solution after solid-liquid separation. After pH adjustment, a one-step tellurium purification agent is added for reduction purification, directly preparing high-grade elemental tellurium. This invention overcomes the limitations of traditional step-by-step processes, with high tellurium recovery as the core technical objective, achieving efficient separation and one-step purification of tellurium from arsenic and antimony: tellurium leaching rate ≥95%, reduction purification rate ≥98%, total recovery rate ≥93%, product grade ≥99.5%; arsenic and antimony leaching rates ≤3.5% and ≤5.0%, respectively. The leaching residue and purified liquid can be recycled. The process is short, the reagent consumption is low, it is compatible with conventional equipment, and it is suitable for industrial promotion.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and rare and dispersed metal extraction technology in non-ferrous metal smelting. Specifically, it relates to a method for selective and efficient leaching of tellurium from high-arsenic antimony tellurium alkaline slag produced by antimony smelting, relying on a tellurium-directed leaching agent to achieve selective and efficient leaching of tellurium and a tellurium one-step purification agent to achieve one-step reduction and purification of tellurium. It is applicable to the industrial extraction of the rare and dispersed metal tellurium. Background Technology

[0002] Tellurium, as a rare and dispersed strategic metal, is a core raw material in high-end manufacturing fields such as semiconductors, optoelectronic materials, and new energy batteries. Its natural mineral reserves are scarce, and it is mainly recovered from the comprehensive recycling of by-products of non-ferrous metal smelting such as copper, lead, and antimony. High-arsenic antimony tellurium alkaline slag is a typical hazardous solid waste generated in the arsenic removal and refining process of antimony smelting. It contains 1% to 5% tellurium and is accompanied by high contents of arsenic and antimony. Direct stockpiling not only wastes tellurium resources but also easily causes soil and water pollution due to the leaching of arsenic and antimony, threatening the ecological environment and human health.

[0003] Existing technologies for recovering tellurium from high-arsenic and antimony tellurium slag have a core challenge: the separation efficiency between tellurium and arsenic and antimony is low. Conventional leaching systems struggle to achieve selective dissolution of tellurium, and the large-scale dissolution of arsenic and antimony severely interferes with subsequent tellurium purification. Furthermore, existing tellurium purification processes often employ a single reducing agent, resulting in slow reduction rates, low product grades, and cumbersome purification steps. Multiple impurity removal and electrolysis processes are required to obtain high-grade tellurium, leading to long process flows, high reagent consumption, and high production costs, making it difficult to meet the demands of efficient industrial production.

[0004] Developing a specialized system for selective and efficient leaching of tellurium, and a reduction system for directly purifying tellurium from tellurium-containing leachate in one step, are key to solving the problems of low tellurium recovery efficiency and poor product quality, and are also important research directions in this field, given the characteristics of high-arsenic, antimony, and tellurium alkaline residue. Summary of the Invention

[0005] The purpose of this invention is to provide an enhanced leaching and purification method for tellurium in arsenic-antimony-tellurium alkaline residue. This method utilizes a tellurium-directed leaching agent to achieve efficient and selective separation of tellurium from arsenic and antimony. Then, through the synergistic effect of a tellurium one-step purification agent, high-grade elemental tellurium is directly obtained from the tellurium-containing leachate through a one-step reduction and purification process. This solves the problems of difficult tellurium-arsenic-antimony separation, cumbersome tellurium purification steps, and low product grade in existing technologies. It simplifies the process flow, reduces production costs, and achieves efficient recovery of tellurium resources.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a method for enhanced leaching and purification of tellurium in arsenic-antimony-tellurium alkaline residue, specifically including the following steps: Step a): Selective leaching of tellurium using a tellurium-directed leaching agent. Take high-arsenic antimony tellurium alkali residue and add tellurium directional leaching agent (initial NaOH concentration 2.0~4.0 mol / L, initial NaCl concentration 0.5~2.0 mol / L, initial Na2S concentration 0.05~0.3 mol / L) at a liquid-to-solid ratio of 6~15:1 mL / g. The tellurium directional leaching agent is a composite aqueous solution composed of sodium hydroxide, sodium chloride and sodium sulfide. The temperature is raised to 55~85℃ and leaching is carried out at atmospheric pressure for 1.0~3.0 h. After leaching, the solid and liquid are separated by a plate and frame filter press to obtain tellurium-containing leachate and arsenic-antimony enriched leaching residue. The arsenic-antimony enriched leaching residue is returned to the antimony smelting system for comprehensive recovery of arsenic and antimony. Step b): One-step purification of tellurium using a one-step reduction agent. 1. Acidification and pH adjustment: Slowly add 98% concentrated sulfuric acid or 5-15% dilute sulfuric acid to the tellurium-containing leachate obtained in step a), and stir to adjust the pH of the system to 1.0-3.5 to obtain the acidified tellurium-containing solution; 2. Preparation of tellurium one-step purification agent: Dissolve sodium sulfate and sodium sulfite in deionized water at a mass ratio of 0.3 to 1.0:1, and stir to prepare an aqueous solution of tellurium one-step purification agent with a mass concentration of 10 to 25%, which is used as a one-step reduction purification agent; 3. One-step reduction and purification reaction: According to the total amount of tellurium one-step purification agent added to the molar ratio of tellurium in the leachate of 1.2 to 2.5:1, the mixed reduction and purification agent is added to the acidified tellurium-containing solution, the temperature is raised to 65 to 85℃, and the reaction is carried out at a constant temperature and stirred at 200 to 400 r / min for 1.0 to 2.5 h. Tellurate / tellurite is reduced to elemental tellurium crystals and precipitates. 4. Solid-liquid separation and drying: After the reaction is completed, the mixture is cooled to room temperature and then separated into solid and liquid components by vacuum filtration to obtain elemental tellurium filter cake. The filter cake is repeatedly washed with deionized water until the pH of the washing liquid is 6.0–7.5. The filter cake is then placed in a forced-air drying oven at 75–95℃ and dried for 1.5–4.0 h to obtain high-grade elemental tellurium product. The reduced and purified liquid is then concentrated by evaporation to recover sodium sulfate and sodium sulfite, which are then recycled back to this step.

[0007] Core reaction principle: This invention relies on the complexation and salt effect of the tellurium-directed leaching agent and the synergistic effect of the reduction and purification of the tellurium one-step purifying agent to achieve selective leaching and one-step purification of tellurium. The core chemical reaction and mechanism of action are as follows: 1. Leaching reaction and mechanism of tellurium directional leaching agent (1) Selective leaching and simultaneous impurity removal mechanism of tellurium Tellurium in the raw material mainly exists in the form of tetravalent oxide (TeO2). In the alkaline leaching system, TeO2 undergoes a complexation reaction with sodium hydroxide to generate soluble sodium tellurite, which enters the solution, achieving selective dissolution of tellurium. The main reaction is as follows: TeO2 + 2NaOH = Na2TeO3 + H2O To address the potential presence of hexavalent tellurium in the raw materials, sodium sulfide (Na₂S) in the leaching agent can reduce it to its easily soluble tetravalent form, thereby significantly improving the total tellurium leaching rate. Simultaneously, the S released from Na₂S... 2- It can react with Pb in the leachate 2+ Cu 2+ Heavy metal ions form insoluble sulfide precipitates, achieving effective separation of tellurium from heavy metal impurities during the leaching stage.

[0008] (2) Salt effect enhances dissolution and stabilization mechanism The high concentration of sodium chloride (NaCl) in the system is completely ionized, forming a high ionic strength environment. This salt effect can significantly improve the apparent solubility of products such as sodium tellurite, effectively inhibit their hydrolysis and crystallization, thereby continuously promoting the forward leaching reaction and ensuring that tellurium exists stably in the liquid phase at a high concentration, creating the necessary conditions for subsequent reduction and purification.

[0009] (3) Targeted inhibition and retention mechanisms of arsenic and antimony Under alkaline and high ionic strength conditions, impurities arsenic and antimony are effectively suppressed and retained in the slag phase: antimony is converted into insoluble Sb(OH)3 or Sb2O3·xH2O precipitate; arsenic reacts with Pb in the system. 2+ Fe 3+ The isocation reaction produces Pb3(AsO4)2 and FeAsO4 precipitates with low solubility products. The high ionic strength environment formed by NaCl can accelerate the above precipitation reaction, promote the aggregation of precipitates, and inhibit their redispersion, thereby achieving deep and stable retention of arsenic and antimony.

[0010] This invention constructs a multifunctional synergistic leaching system of strong base complexation, reduction solubilization, and high salt stability, which not only systematically solves the technical problem of efficient and stable leaching of tellurium oxides of different valence states, but also innovatively achieves simultaneous completion of leaching and preliminary purification, laying a solid chemical and process foundation for obtaining high-purity elemental tellurium products through a short process.

[0011] 2. Reduction purification reaction and mechanism of tellurium in one-step purification agent Under acidic conditions, sodium sulfite in the tellurium one-step purification agent acts as the main reducing agent, directionally reducing tellurate / tellurite ions in the solution to elemental tellurium crystals. The core reduction reaction is as follows: TeO3 2- + 2SO3 2- + 4H + = Te↓+ 2SO4 2- +2H2O TeO4 2- + 3SO3 2-+ 6H + = Te↓+ 3SO4 2- + 3H2O Sodium sulfate in the system completely ionizes into Na. + SO4 2- On the one hand, it increases the ionic strength of the reducing system, inhibiting the co-precipitation of trace arsenic and antimony impurities with tellurium in the solution through the salt effect, thus reducing impurity entrainment; on the other hand, SO4 2- It can be adsorbed on the surface of tellurium grains, regulating the precipitation rate and growth morphology of tellurium grains, preventing grain agglomeration, refining grains, and improving the purity and crystal regularity of tellurium products; at the same time, sodium sulfate provides a stable ionic environment for the reduction reaction, promoting the uniform and efficient reduction reaction, eliminating the need for additional impurity removal and electrolysis processes, and achieving one-step efficient reduction and high-grade purification of tellurium.

[0012] Compared with the prior art, the present invention has the following significant advantages: 1. High selective separation efficiency of tellurium and arsenic / antimony: Utilizing the synergistic effect of strong alkali complexation, reduction solubilization, and high salt solubility of the sodium hydroxide-sodium chloride-sodium sulfide composite leaching agent, it simultaneously achieves efficient leaching of tellurium (including tetravalent and hexavalent arsenic) while deeply retaining impurities such as arsenic and antimony. Tellurium leaching rate ≥95%, arsenic and antimony dissolution rates ≤3.5% and ≤5.0% respectively, significantly reducing the interference of impurities on subsequent purification from the source, laying a core foundation for one-step purification; 2. High efficiency and excellent product grade of tellurium in one step: The sodium sulfate-sodium sulfite mixed system synergistically realizes the targeted reduction and purification of tellurium without the need for multiple impurity removal and electrolysis. The tellurium reduction and purification rate is ≥98%, and the elemental tellurium product with a grade of ≥99.5% is obtained directly. The total tellurium recovery rate is ≥93%, which meets the purity requirements of tellurium products in high-end manufacturing. 3. Short process flow and low production cost: High-grade tellurium can be obtained through only two core processes: selective leaching and one-step reduction and purification. No complex pretreatment equipment is required, which reduces production operation links and equipment investment, and reduces the difficulty of production management and production costs. 4. High resource recycling rate and green environmental protection: The arsenic and antimony enrichment leaching residue is returned to the antimony smelting system for comprehensive recovery of arsenic and antimony. After reduction and purification, the liquid is evaporated and concentrated to recover sodium sulfate and sodium sulfite for recycling. The reagent utilization rate is high, and no secondary waste liquid or waste residue is generated, which meets the requirements of green smelting development. Attached Figure Description

[0013] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0014] 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 thereto. Example 1

[0015] An enhanced leaching and purification method for tellurium in arsenic-antimony-tellurium alkaline residue includes the following steps: 1. Tellurium Directional Leaching: 100g of high-arsenic-antimony tellurium alkaline residue (containing 2.5% Te, 16.2% As, and 23.5% Sb) was added to 800mL of tellurium directional leaching agent (the leaching agent was a sodium hydroxide-sodium chloride-sodium sulfide composite aqueous solution, with an initial NaOH concentration of 2.5mol / L, an initial NaCl concentration of 1.0mol / L, and an initial Na2S concentration of 0.1mol / L). The liquid-to-solid ratio was 8:1 mL / g, and the temperature was controlled at 75℃. Leaching was carried out for 2 hours under normal pressure. After leaching, solid-liquid separation was performed to obtain tellurium-containing leachate and arsenic-antimony-enriched leaching residue. The tellurium leaching rate was 95.8%, the As leaching rate was 3.2%, and the Sb leaching rate was 4.5%.

[0016] 2. One-step purification of tellurium: 98% concentrated sulfuric acid was added dropwise to the above tellurium-containing leachate to adjust the pH to 2.0. A one-step tellurium purification agent with a total solute concentration of 20% was prepared according to a sodium sulfate:sodium sulfite mass ratio of 0.5:1. This purification agent was added to the acidified tellurium-containing solution at a molar ratio of 1.5:1. The reaction was carried out at a constant temperature of 75℃ and a stirring rate of 300 r / min for 1.5 h. After the reaction was completed, the mixture was vacuum filtered, and the filter cake was washed with deionized water until the pH reached 7.0. The filter cake was then dried at 85℃ for 2 h to obtain elemental tellurium product. Testing showed that the tellurium reduction and purification rate was 98.2%, the product grade was 99.6%, and the total tellurium recovery rate was 94.1%. Example 2

[0017] An enhanced leaching and purification method for tellurium in arsenic-antimony-tellurium alkaline residue includes the following steps: 1. Tellurium Directional Leaching: Take 100g of high-arsenic antimony tellurium alkaline residue (containing 3.0% Te, 15.1% As, and 22.8% Sb), add 1000mL of tellurium directional leaching agent (the leaching agent is a sodium hydroxide-sodium chloride-sodium sulfide composite aqueous solution, wherein the initial concentration of NaOH is 3.5mol / L, the initial concentration of NaCl is 1.5mol / L, and the initial concentration of Na2S is 0.2mol / L), the liquid-to-solid ratio is 10:1 mL / g, the temperature is controlled at 80℃, and leaching is carried out for 1.5h under normal pressure. After leaching, solid-liquid separation is performed to obtain tellurium-containing leachate and arsenic-antimony enriched leaching residue. The tellurium leaching rate is 97.2%, the As leaching rate is 2.8%, and the Sb leaching rate is 4.2%.

[0018] 2. One-step purification of tellurium: 10% (v / v) dilute sulfuric acid was added dropwise to the above tellurium-containing leachate to adjust the pH to 1.5. A one-step tellurium purification agent with a total solute concentration of 25% was prepared according to a sodium sulfate:sodium sulfite mass ratio of 0.8:1. This purification agent was added to the acidified tellurium-containing solution at a molar ratio of 2.0:1. The reaction was carried out at a constant temperature of 80℃ and a stirring rate of 350 r / min for 1.0 h. After the reaction was completed, the mixture was vacuum filtered, and the filter cake was washed with deionized water until the pH reached 6.5. The filter cake was then dried at 90℃ for 2 h to obtain elemental tellurium product. Testing showed that the tellurium reduction and purification rate was 98.5%, the product grade was 99.8%, and the total tellurium recovery rate was 95.8%. Example 3

[0019] An enhanced leaching and purification method for tellurium in arsenic-antimony-tellurium alkaline residue includes the following steps: 1. Tellurium Directional Leaching: 100g of high-arsenic-antimony tellurium alkaline residue (containing 4.0% Te, 14.5% As, and 21.2% Sb) was added to 1200mL of tellurium directional leaching agent (the leaching agent was a sodium hydroxide-sodium chloride-sodium sulfide composite aqueous solution, with an initial NaOH concentration of 4.0mol / L, an initial NaCl concentration of 2.0mol / L, and an initial Na2S concentration of 0.15mol / L). The liquid-to-solid ratio was 12:1 mL / g, and the temperature was controlled at 85℃. Leaching was carried out for 1.0h under normal pressure. After leaching, solid-liquid separation was performed to obtain tellurium-containing leachate and arsenic-antimony-enriched leaching residue. The tellurium leaching rate was 96.5%, the As leaching rate was 3.0%, and the Sb leaching rate was 4.0%.

[0020] 2. One-step purification of tellurium: 15% (v / v) dilute sulfuric acid was added dropwise to the above tellurium-containing leachate to adjust the pH to 3.0. A one-step tellurium purification agent with a total solute concentration of 15% was prepared according to a sodium sulfate:sodium sulfite mass ratio of 1.0:1. This purification agent was added to the acidified tellurium-containing solution at a molar ratio of 2.5:1. The reaction was carried out at a constant temperature of 65℃ and a stirring rate of 400 r / min for 2.5 h. After the reaction was completed, the mixture was vacuum filtered, and the filter cake was washed with deionized water until the pH reached 7.5. The filter cake was then dried at 75℃ for 4.0 h to obtain elemental tellurium product. Testing showed that the tellurium reduction and purification rate was 98.1%, the product grade was 99.5%, and the total tellurium recovery rate was 93.7%.

[0021] Comparative Example 1: A conventional leaching and purification method for tellurium in arsenic-antimony-tellurium alkaline residue includes the following steps: 1. Conventional Leaching: Take 100g of high-arsenic antimony tellurium alkaline residue (containing 2.5% Te, 16.2% As, and 23.5% Sb), add 800mL of sodium hydroxide leaching agent (initial NaOH concentration 2.5mol / L, no NaCl or Na2S added), control the temperature at 75℃, and leach for 2 hours under normal pressure. After leaching, perform solid-liquid separation to obtain tellurium-containing leachate and leaching residue. The tellurium leaching rate was 78.3%, the As leaching rate was 12.5%, and the Sb leaching rate was 15.8%.

[0022] 2. Conventional purification: 98% concentrated sulfuric acid was added dropwise to the tellurium-containing leachate to adjust the pH to 2.0. A single sodium sulfite purification agent was added (the molar ratio of sodium sulfite to tellurium in the leachate was 1.5:1). The reaction was carried out at 75℃ and a stirring rate of 300 r / min for 1.5 h. After the reaction was complete, the mixture was vacuum filtered, and the filter cake was washed with deionized water until the pH reached 7.0. The filter cake was then dried at 85℃ for 2 h to obtain elemental tellurium. Testing showed that the tellurium reduction and purification rate was 89.5%, the product grade was 95.2%, and the total tellurium recovery rate was 69.9%.

[0023] Effect verification: Compared to the conventional method in Comparative Example 1, Examples 1-3 of this invention achieve the following technical effects by using a sodium hydroxide-sodium chloride-sodium sulfide composite directional leaching agent (exerting a synergistic effect of strong alkali complexation-reduction solubilization-high salt solubility) and a sodium sulfate-sodium sulfite composite purification agent: The tellurium leaching rate increased by 17.5–19.2 percentage points (the NaCl salt effect continuously promoted and stabilized the dissolution of tellurium), the total recovery rate increased by 23.8–25.9 percentage points, and the product grade increased to over 99.5%. At the same time, the leaching rates of arsenic and antimony decreased significantly by 9.3–9.7 and 11.3–11.8 percentage points, respectively, demonstrating the key role of Na2S in reducing solubility and simultaneously inhibiting the dissolution of impurities. This method has a simple process, high recovery rate, and thorough impurity separation, and has excellent prospects for industrial application.

Claims

1. A method for enhanced leaching and purification of tellurium in arsenic-antimony-tellurium alkaline residue, characterized in that, Includes the following steps: a. Selective leaching of tellurium using a tellurium-directed leaching agent: Take high-arsenic and antimony tellurium alkaline residue, add a tellurium-directed leaching agent and leach under normal pressure. The tellurium-directed leaching agent is a composite aqueous solution composed of sodium hydroxide, sodium chloride and sodium sulfide. The liquid-solid ratio of the high-arsenic and antimony tellurium alkaline residue to the tellurium-directed leaching agent is 6-15:1 mL / g. The leaching temperature is 55-85℃ and the leaching time is 1.0-3.0 h. Tellurium is selectively leached while arsenic and antimony are retained. After leaching, solid and liquid are separated to obtain a tellurium-containing leachate and an arsenic and antimony-enriched leaching residue. b. One-step reduction purification of tellurium using a tellurium one-step purifier: Add acid dropwise to the tellurium-containing leachate obtained in step a) to adjust the pH to 1.0–3.5, then add a tellurium one-step purifier, which is a sodium sulfate-sodium sulfite mixed aqueous solution with a total solute mass concentration of 10%–25% and a sodium sulfate to sodium sulfite mass ratio of 0.3–1.0:

1. Control the total amount of tellurium one-step purifier added to the molar ratio of tellurium in the leachate to 1.2–2.5:

1. The reduction purification reaction temperature is 65–85℃, the reaction time is 1.0–2.5 h, and the stirring rate is 200–400 r / min. After stirring to complete the one-step reduction purification reaction, solid-liquid separation, washing, and drying are performed to obtain a high-grade elemental tellurium product. The reduced and purified liquid is then evaporated and concentrated to recover sodium sulfate and sodium sulfite, which are then returned to the reduction purification process for recycling.

2. The enhanced leaching and purification method for tellurium in arsenic-antimony-tellurium alkaline residue according to claim 1, characterized in that... After the leaching agent described in step a) is added to the reaction system, the initial concentration of NaOH in the system is 2.0–4.0 mol / L, the initial concentration of NaCl is 0.5–2.0 mol / L, and the initial concentration of Na2S is 0.05–0.3 mol / L.

3. The enhanced leaching and purification method for tellurium in arsenic-antimony-tellurium alkaline residue according to claim 1 or 2, characterized in that... Step a) After leaching, the tellurium leaching rate is ≥95%, the arsenic leaching rate is ≤3.5%, and the antimony leaching rate is ≤5.0%. The arsenic and antimony enriched leaching residue is returned to the antimony smelting system for comprehensive recovery of arsenic and antimony.

4. The enhanced leaching and purification method for tellurium in arsenic-antimony-tellurium alkaline residue according to claim 1 or 2, characterized in that... Step b) The acid used to adjust the pH of the system is concentrated sulfuric acid with a mass fraction of 98% or dilute sulfuric acid with a volume fraction of 5% to 15%.

5. A method for enhanced leaching and purification of tellurium in arsenic-antimony-tellurium alkaline residue according to claim 1 or 2, characterized in that... The preparation method of the tellurium one-step purification agent in step b) is as follows: first, dissolve sodium sulfate in deionized water, then add sodium sulfite and stir until a homogeneous, clear and stable solution is formed.

6. A method for enhanced leaching and purification of tellurium in arsenic-antimony-tellurium alkaline residue according to claim 1 or 2, characterized in that... After solid-liquid separation in step b), the tellurium filter cake is washed with deionized water until the pH of the washing liquid is 6.0-7.

5. The drying temperature is 75-95℃ and the drying time is 1.5-4.0 h to obtain a high-grade elemental tellurium product.

7. A method for enhanced leaching and purification of tellurium in arsenic-antimony-tellurium alkaline residue according to claim 1 or 2, characterized in that... The grade of the elemental tellurium product obtained in step b) is ≥99.5%, the tellurium reduction and purification rate is ≥98%, and the total tellurium recovery rate is ≥93%.

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