Method for high-efficiency leaching of zinc, indium and germanium from hard zinc residue

Abstract

This invention discloses a method for efficiently leaching zinc, indium, and germanium from hard zinc slag, belonging to the field of hydrometallurgical technology. A leaching agent with an acid concentration of 125-130 g / L is added to the hard zinc slag at a liquid-to-solid ratio of 4-4.5:1, and the reaction is carried out at 75-85°C for 55-65 min. KMnO4 is then added at a dosage of 15-18 g / L, and the reaction is continued for 8-12 min. A pH adjuster is added to adjust the pH of the system to 4.5-5.0, and the reaction continues for 15-25 min. The leached slurry is then separated into liquid and solid components. The first stage of leaching solution enters the zinc recovery process, and the first stage of leaching residue is used as raw material for the second stage of high-acid enhanced leaching. A leaching agent with an acid concentration of 280–300 g / L is added to the first-stage leaching residue at a liquid-to-solid ratio of 5.5–6:1. The temperature is raised to 85–95℃, and NaClO3 is added at a dosage of 20–25 g / L. The reaction is carried out for 3.5–4.5 hours. The leached slurry is then separated into liquid and solid components. The second-stage leaching solution enters the indium and germanium recovery process, and the second-stage leaching residue is stockpiled. This method can achieve a zinc leaching rate >98%, an indium leaching rate ≥88%, and a germanium leaching rate ≥90% for hard zinc slag. The indicators of the first-stage leaching solution meet the requirements for reuse in zinc smelting production and can be directly reused in the zinc recovery process. The second-stage leaching solution provides qualified raw materials for subsequent indium and germanium recovery processes.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to a method for efficiently leaching zinc, indium, and germanium from hard zinc slag. Background Technology

[0002] Hard zinc slag is a multi-element alloy and compound mainly composed of zinc, produced during the distillation of crude zinc. The yield is about 4-4.5% of the crude zinc processing volume. It is produced by vacuum distillation of hard zinc (also known as indium-rich slag). It contains 1000-2000 g / t of indium and 2000-3000 g / t of germanium. It also has high contents of silver, copper and tin. It has significant comprehensive recovery value and is a high-quality raw material for extracting valuable metals such as zinc, indium and germanium.

[0003] Currently, the extraction of indium and germanium from hard zinc slag mainly employs pyrometallurgical methods, such as indirect flame furnaces-electric furnaces and vacuum furnaces, as well as hydrochloric acid leaching wet processes. However, both types of processes share common technical challenges: low indium and germanium recovery rates, failing to fully utilize these high-grade valuable metal resources; complex process flows and stringent operating conditions; high overall costs, with pyrometallurgical methods consuming enormous amounts of energy, and hydrochloric acid leaching in wet processes causing equipment corrosion and incurring high subsequent treatment costs; and a difficulty in balancing resource utilization with environmental friendliness. Traditional processes not only suffer from severe resource waste but also exhibit significant acid and alkali pollution, while the purity of byproducts is poor, further reducing the overall utilization value of the resources.

[0004] Based on this, the present invention aims to provide a new method that can achieve efficient extraction of zinc, indium and germanium metals from hard zinc slag, and is simple in process, cost-controllable and environmentally friendly, in order to provide a systematic solution to the above-mentioned technical pain points. Summary of the Invention

[0005] The purpose of this invention is to provide a method for efficiently leaching zinc, indium, and germanium from hard zinc slag.

[0006] The objective of this invention is achieved as follows: the method for efficiently leaching zinc, indium, and germanium from the hard zinc slag includes the following steps: Oxidative neutral leaching: Add leaching agent with an acid concentration of 125-130 g / L to the hard zinc slag at a liquid-to-solid ratio of 4-4.5:1, heat to 75-85℃ and react for 55-65 min, then add oxidant KMnO4 at a dosage of 15-18 g / L, and continue the reaction at a constant temperature for 8-12 min.

[0007] Add a pH adjuster to the reaction system to adjust the pH value to 4.5~5.0, and continue the reaction at a constant temperature for 15~25 minutes; perform liquid-solid separation on the leaching slurry, and the resulting first-stage leachate is a zinc-rich solution, which enters the zinc recovery process, while the first-stage leaching residue is used as the raw material for the second-stage high-acid enhanced leaching.

[0008] High-acid enhanced leaching: Add leaching agent with an acid concentration of 280-300 g / L to the first-stage leaching residue at a liquid-to-solid ratio of 5.5-6:1, raise the temperature to 85-95℃, add oxidant NaClO3 at a dosage of 20-25 g / L, maintain constant temperature, and react for 3.5-4.5 h; then perform liquid-solid separation on the leaching slurry, and the resulting second-stage leaching solution is an indium and germanium-rich solution, which enters the indium and germanium recovery process, and the second-stage leaching residue is stockpiled.

[0009] Compared with the prior art, the technical solution described in this invention has the following advantages: The proposed technical solution utilizes relatively mild low-acid and weak-oxidation conditions in the first stage to rapidly dissolve zinc while avoiding the leaching of iron, indium, and germanium. This achieves efficient separation of zinc from in-situ associated elements, creating pure raw material conditions for the subsequent enrichment of indium and germanium.

[0010] After the first leaching stage, a pH adjustment treatment is added, utilizing Fe... 3+ Zn is completely hydrolyzed within this pH range. 2+ The non-hydrolyzable property enables complete separation of iron and zinc, resulting in a pure zinc-rich solution. Under the set pH conditions, indium and germanium have not yet undergone hydrolysis and precipitation, thus remaining entirely in a leaching residue, avoiding dispersion loss of indium and germanium during the impurity removal process.

[0011] The described technical solution utilizes a high-acid environment combined with strong oxidation conditions in the second stage to effectively oxidize and decompose the zinc ferrite or sulfide lattice encapsulating indium and germanium, releasing indium and germanium. The oxidant is added in stages, maintaining the long-term stability of the oxidation potential within the reaction system, thus avoiding ineffective decomposition of the oxidant and ensuring the full exposure and dissolution of the sparingly soluble phases.

[0012] In summary, the technical solution described in this invention can achieve a zinc leaching rate of >98%, an indium leaching rate of ≥88%, and a germanium leaching rate of ≥90% in hard zinc slag; the indicators of the first-stage leaching solution fully meet the requirements for recycling in zinc smelting production and can be directly reused in the zinc recovery process; the second-stage leaching solution provides qualified raw materials for subsequent indium and germanium recovery processes. Attached Figure Description

[0013] Figure 1 This is a process flow diagram of the technical solution described in this invention. Detailed Implementation

[0014] The present invention will be further described below, but this is not intended to limit the invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the scope of protection of the present invention.

[0015] The method for efficiently leaching zinc, indium, and germanium from hard zinc slag includes the following steps: Oxidative neutral leaching: Add leaching agent with an acid concentration of 125-130 g / L to the hard zinc slag at a liquid-to-solid ratio of 4-4.5:1, heat to 75-85℃ and react for 55-65 min, then add oxidant KMnO4 at a dosage of 15-18 g / L, and continue the reaction at a constant temperature for 8-12 min.

[0016] Add a pH adjuster to the reaction system to adjust the pH value to 4.5~5.0, and continue the reaction at a constant temperature for 15~25 minutes; perform liquid-solid separation on the leaching slurry, and the resulting first-stage leachate is a zinc-rich solution, which enters the zinc recovery process, while the first-stage leaching residue is used as the raw material for the second-stage high-acid enhanced leaching.

[0017] High-acid enhanced leaching: Add leaching agent with an acid concentration of 280-300 g / L to the first-stage leaching residue at a liquid-to-solid ratio of 5.5-6:1, raise the temperature to 85-95℃, add oxidant NaClO3 at a dosage of 20-25 g / L, maintain constant temperature, and react for 3.5-4.5 h; then perform liquid-solid separation on the leaching slurry, and the resulting second-stage leaching solution is an indium and germanium-rich solution, which enters the indium and germanium recovery process, and the second-stage leaching residue is stockpiled.

[0018] The chemical composition of the hard zinc slag is as follows:

[0019] In the neutral oxidative leaching process, the leaching reaction temperature is preferably 80°C, and the leaching time is preferably 60 min. The oxidation reaction time is preferably 10 min. The pH adjuster is either zinc calcined sand or zinc oxide dust.

[0020] In the high-acid enhanced leaching process, the NaClO3 is added in stages, with each addition spaced 1 hour apart. Preferably, the NaClO3 is added in four stages. The leaching reaction is preferably carried out at a temperature of 90°C for 4 hours.

[0021] The leaching agent is the waste electrolyte produced in the zinc hydrometallurgical system, or the waste electrolyte is mixed with concentrated sulfuric acid to achieve the required acid concentration.

[0022] Example 1

[0023] Neutral oxidative leaching: At a liquid-to-solid ratio of 4:1, sulfuric acid leaching agent with an acid concentration of 125 g / L was added to 100 g of hard zinc slag to prepare the slurry. The slurry was then transferred to the leaching equipment, heated in a water bath to 80°C, and maintained at this temperature for 60 min. Then, oxidant KMnO4 was added at a dosage of 15 g / L, and the reaction was continued for another 10 min while maintaining the constant temperature. Under these conditions, the zinc leaching rate was 98.2%.

[0024] After the oxidation reaction is completed, zinc calcined sand or zinc oxide dust is added to the slurry to adjust the pH of the system to 4.5. The operation is terminated after the constant temperature reaction is continued for 20 minutes. The leaching slurry is then subjected to liquid-solid separation. The resulting first-stage leaching solution is a zinc-rich solution and enters the zinc recovery process. The first-stage leaching residue is used as the raw material for the second-stage high-acid enhanced leaching. Indium, iron, and germanium are basically not leached.

[0025] High-acid enhanced leaching: At a liquid-to-solid ratio of 5.5:1, sulfuric acid leaching agent with an acid concentration of 280 g / L was added to 100 g of the first-stage leaching residue to prepare the slurry. The mixture was heated in a water bath to 90°C. Oxidizing agent NaClO3 was added in four portions at a total dosage of 20 g / L, with each addition spaced 1 hour apart. Each addition was 1 / 4 of the total dosage, and the reaction was maintained at a constant temperature for 4 hours. After the reaction, the leaching slurry underwent liquid-solid separation. The resulting second-stage leaching solution was rich in indium and germanium and entered the indium and germanium recovery process. The second-stage leaching residue was stockpiled. Under these conditions, the indium leaching rate reached 88.5%, and the germanium leaching rate reached 90.2%.

[0026] Example 2

[0027] Neutral oxidative leaching: At a liquid-to-solid ratio of 4.2:1, sulfuric acid leaching agent with an acid concentration of 128 g / L was added to 100 g of hard zinc slag to prepare the slurry. The slurry was then transferred to the leaching equipment, heated in a water bath to 85°C, and reacted at this temperature for 55 min. Then, oxidant KMnO4 was added at a dosage of 16 g / L, and the reaction was continued at a constant temperature for another 8 min. Under these conditions, the zinc leaching rate was 98.5%.

[0028] After the oxidation reaction is completed, zinc roasted sand or zinc oxide dust is added to the slurry to adjust the pH of the system to 4.8. The operation is terminated after the constant temperature reaction is continued for 15 minutes. The leaching slurry is then subjected to liquid-solid separation. The resulting first-stage leaching solution is a zinc-rich solution and enters the zinc recovery process. The first-stage leaching residue is used as the raw material for the second-stage high-acid enhanced leaching. Indium, iron, and germanium are basically not leached.

[0029] High-acid enhanced leaching: At a liquid-to-solid ratio of 5.7:1, sulfuric acid leaching agent with an acid concentration of 290 g / L was added to 100 g of the first-stage leaching residue to adjust the slurry. The mixture was heated in a water bath to 95°C. Oxidizing agent NaClO3 was added in four portions at a total dosage of 23 g / L, with each addition spaced 1 hour apart. Each addition was 1 / 4 of the total dosage, and the reaction was maintained at a constant temperature for 3.5 hours. After the reaction, the leaching slurry was subjected to liquid-solid separation. The resulting second-stage leaching solution was rich in indium and germanium and entered the indium and germanium recovery process. The second-stage leaching residue was stockpiled. Under these conditions, the indium leaching rate reached 88.8%, and the germanium leaching rate reached 90.7%.

[0030] Example 3

[0031] Neutral oxidative leaching: At a liquid-to-solid ratio of 4.5:1, sulfuric acid leaching agent with an acid concentration of 130 g / L was added to 100 g of hard zinc slag to prepare the slurry. The slurry was then transferred to the leaching equipment, heated in a water bath to 75°C, and maintained at this temperature for 65 min. Then, oxidant KMnO4 was added at a dosage of 18 g / L, and the reaction was continued for another 12 min while maintaining the constant temperature. Under these conditions, the zinc leaching rate was 98.7%.

[0032] After the oxidation reaction is completed, zinc calcined sand or zinc oxide dust is added to the slurry to adjust the pH of the system to 5.0. The operation is terminated after the constant temperature reaction is continued for 25 minutes. The leaching slurry is then subjected to liquid-solid separation. The resulting first-stage leaching solution is a zinc-rich solution and enters the zinc recovery process. The first-stage leaching residue is used as the raw material for the second-stage high-acid enhanced leaching. Indium, iron, and germanium are basically not leached.

[0033] High-acid enhanced leaching: At a liquid-to-solid ratio of 6:1, sulfuric acid leaching agent with a concentration of 300 g / L was added to 100 g of the first-stage leaching residue to prepare the slurry. The mixture was heated in a water bath to 85°C. Oxidizing agent NaClO3 was added in four portions at a total dosage of 25 g / L, with each addition spaced 1 hour apart. Each addition was 1 / 4 of the total dosage, and the reaction was maintained at a constant temperature for 4.5 hours. After the reaction, the leaching slurry underwent liquid-solid separation. The resulting second-stage leaching solution was rich in indium and germanium and entered the indium and germanium recovery process. The second-stage leaching residue was stockpiled. Under these conditions, the indium leaching rate reached 89%, and the germanium leaching rate reached 91%.

Claims

1. A method for efficiently leaching zinc, indium, and germanium from hard zinc slag, characterized in that, The process includes the following steps: Oxidative neutral leaching: Add leaching agent with an acid concentration of 125-130 g / L to the hard zinc slag at a liquid-to-solid ratio of 4-4.5:1, heat to 75-85℃ and react for 55-65 min, then add oxidant KMnO4 at a dosage of 15-18 g / L, and continue to react for 8-12 min while maintaining a constant temperature. Add a pH adjuster to the reaction system to adjust the pH value to 4.5~5.0, and continue the reaction at a constant temperature for 15~25 minutes; perform liquid-solid separation on the leaching slurry, and the resulting first-stage leachate is a zinc-rich solution, which enters the zinc recovery process, while the first-stage leaching residue is used as the raw material for the second-stage high-acid enhanced leaching. High-acid enhanced leaching: Add leaching agent with an acid concentration of 280-300 g / L to the first-stage leaching residue at a liquid-to-solid ratio of 5.5-6:1, raise the temperature to 85-95℃, add oxidant NaClO3 at a dosage of 20-25 g / L, maintain constant temperature, and react for 3.5-4.5 h; then perform liquid-solid separation on the leaching slurry, and the resulting second-stage leaching solution is an indium and germanium-rich solution, which enters the indium and germanium recovery process, and the second-stage leaching residue is stockpiled.

2. The method for efficient leaching of zinc, indium, and germanium from hard zinc slag according to claim 1, characterized in that, The chemical composition of the hard zinc slag is as follows: 。 3. The method for efficiently leaching zinc, indium, and germanium from hard zinc slag according to claim 1, characterized in that, In the oxidative neutral leaching process, the leaching reaction is carried out at a temperature of 80°C for 60 minutes.

4. The method for efficiently leaching zinc, indium, and germanium from hard zinc slag according to claim 1, characterized in that, In the oxidative neutral leaching process, the oxidation reaction takes 10 minutes.

5. The method for efficiently leaching zinc, indium, and germanium from hard zinc slag according to claim 1, characterized in that, In the oxidative neutral leaching process, the pH adjuster is either zinc calcined sand or zinc oxide dust.

6. The method for efficiently leaching zinc, indium, and germanium from hard zinc slag according to claim 1, characterized in that, In the high-acid enhanced leaching process, the NaClO3 is added in stages, with each addition spaced 1 hour apart.

7. The method for efficiently leaching zinc, indium, and germanium from hard zinc slag according to claim 6, characterized in that, In the high-acid enhanced leaching process, the NaClO3 is added in four stages.

8. The method for efficiently leaching zinc, indium, and germanium from hard zinc slag according to claim 1, characterized in that, In the high-acid enhanced leaching process, the leaching reaction temperature is 90°C and the time is 4 hours.

9. The method for efficiently leaching zinc, indium, and germanium from hard zinc slag according to claim 1, characterized in that, The leaching agent is the waste electrolyte produced in the zinc hydrometallurgical system, or the waste electrolyte is mixed with concentrated sulfuric acid to achieve the required acid concentration.

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