A method for recovering sponge cadmium from a zinc hydrometallurgy purification residue

Abstract

The present application relates to a kind of methods for recovering sponge cadmium from zinc purification residue in wet process, belong to the technical field of cadmium resource recovery in wet process, the present application includes the following steps: purification residue is mixed with water according to liquid-solid ratio 2:1 slurry, obtain slurry liquid;The obtained slurry liquid and acid liquor are acid leaching according to volume ratio 1:1.9~1:2.5, after solid-liquid separation, obtain cadmium-rich liquid, wherein the acid leaching uses the concentration of acid liquor 120~160g / L, control end point pH value is 3.0~3.5;The obtained cadmium-rich liquid is replaced once, control temperature 40~70℃, add metal zinc powder and react 0.5~1 hour, stand for 5~10 minutes, after solid-liquid separation, obtain sponge cadmium and clear liquid;The obtained clear liquid is replaced twice, control temperature 40~65℃, add metal zinc powder and react 0.5~1 hour, after solid-liquid separation, obtain cadmium-poor residue and cadmium-poor liquid, cadmium-poor residue returns acid leaching process and is acid leached again, cadmium-poor liquid returns acid leaching process and is reused.The present application is suitable for high-impurity cadmium raw material, and high-grade sponge cadmium product is output.

Description

Technical Field

[0001] This invention relates to the field of cadmium resource recovery technology in hydrometallurgical processes, and particularly to a method for recovering sponge cadmium from the purification slag of hydrometallurgical zinc smelting. Background Technology

[0002] In the hydrometallurgical zinc refining process, zinc powder displacement is often used to remove impurities such as copper, cadmium, and cobalt from the zinc sulfate solution, generating a large amount of purification slag. This slag is rich in valuable metals such as zinc and cadmium and has high recovery value. Currently, the mainstream process for recovering sponge cadmium from the purification slag is the acid leaching-displacement method. This involves first leaching with sulfuric acid to introduce cadmium and zinc into the solution, then adding zinc powder to displace the cadmium, resulting in sponge cadmium. Related studies have explored process parameters such as displacement temperature, zinc powder dosage, and stirring intensity. However, when using a conventional single-stage displacement process, the sponge cadmium grade can usually only be maintained at around 78%, and the product is prone to contain unreacted zinc powder, leading to a high zinc content. Furthermore, in existing industrial practice, excessive zinc powder can easily form a dense coating layer (such as basic zinc sulfate) on the surface of the sponge cadmium during the displacement process, hindering the continued participation of internal zinc powder in the reaction, resulting in low zinc powder utilization, cadmium redissolution, and zinc inclusions in the product.

[0003] For example, Chinese patent CN110195160A discloses a comprehensive recovery method for the slag from a wet zinc smelting process. This method recovers copper, removes iron and arsenic, and recovers cobalt through low-acid leaching to obtain a cobalt-free leachate. Then, zinc powder and sulfuric acid are added to conduct a displacement reaction to obtain sponge cadmium and a zinc-rich leachate. However, this method has poor displacement efficiency in solutions with low cadmium content, resulting in poor quality sponge cadmium, lack of clumping, and high zinc powder consumption. In contrast, Chinese patent CN112176186A discloses a method for cadmium recovery through displacement in a comprehensive slag recovery process. This method includes three steps: a primary displacement reaction, a secondary displacement reaction, and acid leaching of cadmium. In the primary displacement reaction, the amount of zinc powder added (g) = cadmium content (g / L) × volume of liquid in the primary displacement tank (L) × 0.8, and the reaction temperature is 60-70°C. Sulfuric acid is added to adjust the pH to 1.5-2.0, and the reaction time is 0.8-1.2 hours. This method features simple procedures, saves zinc powder, and produces high-quality sponge cadmium. However, this does not address the issue of raw materials containing a high level of impurities. When the impurity content in the raw materials is high, existing processes generally face the problems of loose cadmium clusters, severe zinc inclusions, and large fluctuations in grade of the replacement sponge, resulting in poor production stability.

[0004] Therefore, it is necessary to provide a method for recovering sponge cadmium from the purification slag of wet zinc smelting, which can adapt to high-impurity cadmium raw materials and produce high-grade sponge cadmium products. Summary of the Invention

[0005] In order to overcome the problems existing in the background technology, the present invention provides a method for recovering sponge cadmium from the purification slag of wet zinc smelting, which can adapt to high-impurity cadmium raw materials and produce high-grade sponge cadmium products.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention provides a method for recovering sponge cadmium from the purification slag of hydrometallurgical zinc smelting, comprising the following steps: (1) Mix the purified residue with water at a liquid-solid ratio of 2:1 to form a slurry, and obtain the slurry liquid; (2) The obtained pulping liquid and acid solution are acid leached at a volume ratio of 1:1.9 to 1:2.5. After solid-liquid separation, cadmium-rich solution is obtained. The concentration of acid solution used for acid leaching is 120 to 160 g / L, and the final pH value is controlled to be 3.0 to 3.5. (3) The obtained cadmium-rich solution is replaced once, the temperature is controlled at 40-70℃, zinc powder is added and reacted for 0.5-1 hour, and then left to stand for 5-10 minutes. After solid-liquid separation, sponge cadmium and clear liquid are obtained. (4) The obtained clear liquid is replaced twice, the temperature is controlled at 40-65℃, zinc powder is added and reacted for 0.5-1 hour. After solid-liquid separation, cadmium-poor slag and cadmium-poor liquid are obtained. The cadmium-poor slag is returned to the acid leaching process for acid leaching again, and the cadmium-poor liquid is returned to the acid leaching process for reuse.

[0007] In the above technical solution, the acid leaching time in step (2) is ≥6 hours.

[0008] In the above technical solution, the amount of zinc powder added in the primary replacement is 0.72-0.88 times the theoretical value, and the amount of zinc powder added in the secondary replacement is 0.18-0.22 times the theoretical value. In the above technical solution, the acid solution used in step (2) is a mixture of waste electrolyte, cadmium-poor solution and concentrated sulfuric acid from the wet zinc smelting system. The waste electrolyte has a zinc content of 35~45g / L and an H2SO4 content of 120-150g / L. The cadmium-poor solution has a cadmium content of ≤1000 mg / L and a cobalt content of ≤100mg / L. The concentrated sulfuric acid has a concentration of ≥98%.

[0009] In the above technical solution, the zinc powder contains ≥97% total zinc, ≥96% metallic zinc, and 70-90% of the material passing through a 120-mesh standard sieve.

[0010] In the above technical solution, the cadmium content of the sponge is ≥85%, and the zinc content is ≤4%.

[0011] In the above technical solution, the purified residue contains 15-30% cadmium and 30-40% zinc. The main reaction process of acid leaching is as follows: The main reaction process of the displacement is as follows: In the ionic formula, Me 2+ Represents impurity metal ions.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention, by precisely controlling the pH value at the endpoint of acid leaching within the range of 3.0 to 3.5, and using an acid concentration of 120 to 160 g / L, can effectively inhibit the leaching of impurity ions such as iron and cobalt, reduce the interference of impurities on subsequent replacement reactions, and produce cadmium-rich solutions with a higher cadmium-zinc ratio and lower impurity content, laying the foundation for the production of high-grade sponge cadmium.

[0013] 2. This invention returns the waste electrolyte and the cadmium-poor solution obtained from the secondary replacement to the acid leaching process for reuse, thereby realizing the recycling of process liquids and reducing waste liquid discharge.

[0014] 3. The process of this invention is simple and stable, and it has good adaptability to purification slag raw materials with high impurity content. The cadmium content of the obtained sponge cadmium product can be stably reached above 85%, and the zinc content can be controlled below 4%, and the product quality is stable and reliable. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0017] In the description of this invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] Example 1 A liquid preparation plant processed 9.6 tons of purification residue, which contained 26.09% cadmium and 33.14% zinc.

[0020] (1) Pulping: The purification residue and water are mixed at a liquid-solid ratio of 2:1 to produce a slurry. The purification residue is a first-stage purification residue produced in the wet zinc smelting purification process, which mainly contains valuable metals such as zinc, cadmium, and copper.

[0021] (2) Acid leaching: The waste electrolyte, cadmium-poor solution, and concentrated sulfuric acid are mixed to prepare an acid solution with a concentration of 140 g / L. The waste electrolyte contains 40 g / L zinc and 135 g / L H2SO4; the cadmium-poor solution contains 800 mg / L cadmium and 80 mg / L cobalt; and the concentrated sulfuric acid concentration is ≥98%. 38m 3 Slurry and 76m 3 The acid solution was mixed and leached, with the final pH value controlled at 3.2 and the leaching time at 6.5 hours. After solid-liquid separation, a cadmium-rich solution was obtained.

[0022] (3) First displacement: The obtained cadmium-rich solution was subjected to a first displacement, the temperature was controlled at 55℃, 1.16t of zinc powder was added and reacted for 0.8 hours, and then allowed to stand for 8 minutes. After solid-liquid separation, sponge cadmium and clear liquid were obtained. The zinc powder contained ≥98% total zinc and ≥97% zinc, and 80% of the material was sieved through a 120-mesh standard sieve.

[0023] (4) Secondary replacement: The clear liquid is replaced twice, the temperature is controlled at 50℃, 0.29t of zinc powder is added and reacted for 0.8 hours. After solid-liquid separation, cadmium-poor slag and cadmium-poor liquid are obtained. The cadmium-poor slag is returned to the acid leaching process for acid leaching again, and the cadmium-poor liquid is returned to the acid leaching process for reuse.

[0024] Testing revealed that the cadmium content in the sponge obtained in this embodiment was 87.3%, and the zinc content was 3.2%, meeting the Cd-85 grade requirements.

[0025] Example 2 A liquid preparation plant processed 13.2 tons of purification residue, which contained 18.72% cadmium and 38.15% zinc.

[0026] (1) Pulping: The purification residue and water are mixed at a liquid-solid ratio of 2:1 to produce a slurry. The purification residue is a first-stage purification residue produced in the wet zinc smelting purification process, which mainly contains valuable metals such as zinc, cadmium, and copper.

[0027] (2) Acid leaching: Mix the waste electrolyte, cadmium-poor solution, and concentrated sulfuric acid to prepare an acid solution with a concentration of 120 g / L. The waste electrolyte contains 35 g / L zinc and 120 g / L H2SO4; the cadmium-poor solution contains 600 mg / L cadmium and 60 mg / L cobalt; the concentrated sulfuric acid concentration is ≥98%. Pour 40 m... 3 Slurry and 79m 3 The acid solution was mixed and leached, with the final pH value controlled at 3.0 and the leaching time being 7 hours. After solid-liquid separation, a cadmium-rich solution was obtained.

[0028] (3) First displacement: The obtained cadmium-rich solution was subjected to a first displacement, the temperature was controlled at 40℃, 1.15t of zinc powder was added and reacted for 0.5 hours, and then allowed to stand for 5 minutes. After solid-liquid separation, sponge cadmium and clear liquid were obtained. The zinc powder contained ≥98% total zinc and ≥97% zinc, and 80% of the material was sieved through a 120-mesh standard sieve.

[0029] (4) Secondary replacement: The clear liquid is replaced twice, the temperature is controlled at 40℃, 0.28t of zinc powder is added and reacted for 0.5 hours. After solid-liquid separation, cadmium-poor slag and cadmium-poor liquid are obtained. The cadmium-poor slag is returned to the acid leaching process for acid leaching again, and the cadmium-poor liquid is returned to the acid leaching process for reuse.

[0030] Testing revealed that the cadmium content in the sponge obtained in this embodiment was 85.6%, and the zinc content was 3.8%, meeting the Cd-85 grade requirements.

[0031] Example 3 A liquid preparation plant processed 8.9 tons of purification residue, which contained 28.01% cadmium and 33.90% zinc.

[0032] (1) Pulping: The purification residue and water are mixed at a liquid-solid ratio of 2:1 to produce a slurry. The purification residue is a first-stage purification residue produced in the wet zinc smelting purification process, which mainly contains valuable metals such as zinc, cadmium, and copper.

[0033] (2) Acid leaching: The waste electrolyte, cadmium-poor solution, and concentrated sulfuric acid are mixed to prepare an acid solution with a concentration of 160 g / L. The waste electrolyte contains 45 g / L zinc and 150 g / L H2SO4; the cadmium-poor solution contains 1000 mg / L cadmium and 100 mg / L cobalt; and the concentrated sulfuric acid concentration is ≥98%. 27 m 3 Slurry and 55m 3 The acid solution was mixed and leached, with the final pH value controlled at 3.5 and the leaching time at 6 hours. After solid-liquid separation, a cadmium-rich solution was obtained.

[0034] (3) First displacement: The obtained cadmium-rich solution was subjected to a first displacement, the temperature was controlled at 70℃, 1.16t of zinc powder was added and reacted for 1 hour, and then allowed to stand for 10 minutes. After solid-liquid separation, sponge cadmium and clear liquid were obtained. The zinc powder contained ≥98% total zinc and ≥97% zinc, and 80% of the material was sieved through a 120-mesh standard sieve.

[0035] (4) Secondary replacement: The clear liquid is replaced twice, the temperature is controlled at 65℃, 0.29t of zinc powder is added and reacted for 1 hour. After solid-liquid separation, cadmium-poor slag and cadmium-poor liquid are obtained. The cadmium-poor slag is returned to the acid leaching process for acid leaching again, and the cadmium-poor liquid is returned to the acid leaching process for reuse.

[0036] Testing revealed that the cadmium content in the sponge obtained in this embodiment was 86.8%, and the zinc content was 3.5%, meeting the Cd-85 grade requirements.

[0037] 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 recovering sponge cadmium from the purification slag of wet zinc smelting, characterized in that: Specifically, the following steps are included: (1) Mix the purified residue with water at a liquid-solid ratio of 2:1 to form a slurry, and obtain the slurry liquid; (2) The obtained pulping liquid and acid solution are acid leached at a volume ratio of 1:9 to 1:2.

5. After solid-liquid separation, cadmium-rich solution is obtained. The concentration of acid solution used for acid leaching is 120 to 160 g / L, and the final pH value is controlled to be 3.0 to 3.

5. (3) The obtained cadmium-rich solution is replaced once, the temperature is controlled at 40-70℃, zinc powder is added and reacted for 0.5-1 hour, and then left to stand for 5-10 minutes. After solid-liquid separation, sponge cadmium and clear liquid are obtained. (4) The obtained clear liquid is replaced twice, the temperature is controlled at 40-65℃, zinc powder is added and reacted for 0.5-1 hour. After solid-liquid separation, cadmium-poor slag and cadmium-poor liquid are obtained. The cadmium-poor slag is returned to the acid leaching process for acid leaching again, and the cadmium-poor liquid is returned to the acid leaching process for reuse.

2. The method for recovering sponge cadmium from the purification slag of hydrometallurgical zinc smelting according to claim 1, characterized in that: The acid leaching time in step (2) is ≥6 hours.

3. The method for recovering sponge cadmium from the purification slag of hydrometallurgical zinc smelting according to claim 1, characterized in that: The amount of zinc powder added in the first replacement is 0.72-0.88 times the theoretical value, and the amount of zinc powder added in the second replacement is 0.18-0.22 times the theoretical value.

4. The method for recovering sponge cadmium from the purification slag of hydrometallurgical zinc smelting according to claim 1, characterized in that: The acid solution used in step (2) is a mixture of waste electrolyte, cadmium-poor solution and concentrated sulfuric acid from the hydrometallurgical zinc smelting system. The waste electrolyte has a zinc content of 35-45 g / L and an H2SO4 content of 120-150 g / L. The cadmium-poor solution has a cadmium content of ≤1000 mg / L and a cobalt content of ≤100 mg / L. The concentrated sulfuric acid has a concentration of ≥98%.

5. A method for recovering sponge cadmium from hydrometallurgical zinc refining slag according to any one of claims 1 or 3, characterized in that: The zinc powder contains ≥97% total zinc and ≥96% metallic zinc, with 70-90% of the material passing through a 120-mesh standard sieve.

6. The method for recovering sponge cadmium from the purification slag of hydrometallurgical zinc smelting according to claim 1, characterized in that: The cadmium content of the sponge is ≥85%, and the zinc content is ≤4%.

7. The method for recovering sponge cadmium from the purification slag of hydrometallurgical zinc smelting according to claim 1, characterized in that: The purified residue contains 15-30% cadmium and 30-40% zinc.

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