Method for preparing high-grade sponge cadmium from copper ion and ultrasonic enhanced zinc powder

Abstract

The invention relates to a method for preparing high-grade sponge cadmium from copper ions and ultrasonic enhanced zinc powder, and belongs to the technical field of high-value utilization of valuable metals in zinc smelting slag. According to the method, copper sulfate is adopted to regulate and control the concentration of Cu < 2 + > in the copper-cadmium slag leaching solution to 0.83-3.3% of the concentration of Cd < 2 + >; and zinc powder is added into the copper-cadmium slag leaching solution, an ultrasonic enhanced copper ion and zinc powder synergistic replacement reaction is carried out for 10-25 min at the temperature of 20-35 DEG C under the ultrasonic wave condition, and after-replacement liquid and high-grade sponge cadmium are obtained through solid-liquid separation. The high-grade sponge cadmium is prepared by regulating and controlling the concentration of the copper ions and cooperating with ultrasonic strengthening of the zinc powder, the copper ions are preferentially replaced on the surface of the zinc powder and attached to the surface of the zinc powder to form a Zn-Cu microbattery, the negative influence of the zinc-coated cadmium phenomenon on the replacement process can be effectively weakened, the concentration of the copper ions and the reaction time are regulated and controlled, the formation of a Cu-Cd microbattery can be inhibited, and the service life of the sponge cadmium is prolonged. The process of consuming and re-dissolving cadmium as an anode is obviously inhibited; the ultrasonic synergistic dissociation of zinc powder agglomeration accelerates the mass transfer of the solution and promotes the replacement process.

Description

Technical Field

[0001] This invention relates to a method for preparing high-grade sponge cadmium from zinc powder with the synergistic effect of copper ions and ultrasonic enhancement, belonging to the technical field of high-value utilization of valuable metals in zinc smelting slag. Background Technology

[0002] Cadmium does not exist in independent deposits in nature; it often occurs as cadmium sulfate in sphalerite, thus its main source is copper-cadmium slag, a byproduct of hydrometallurgical zinc production. In actual production, to achieve efficient cadmium recovery from copper-cadmium slag, most companies utilize selective leaching-recovery processes. The selective leaching process yields cadmium leachate and copper slag, effectively separating copper and cadmium. The cadmium-containing leachate is purified (removing impurities such as copper, cobalt, and lead) to obtain a cadmium sulfate solution that meets the requirements for cadmium extraction. This solution is then evaporated and concentrated to obtain a high-concentration cadmium sulfate solution for subsequent cadmium recovery.

[0003] The displacement method has become the mainstream approach due to its safety and recyclability. This method recovers cadmium based on the difference in metal activity. However, during the zinc powder displacement process, residual Cu in the solution... 2+ Excessive Cu content has always been considered one of the important factors affecting cadmium purity. 2+ Concentration not only reduces cadmium replacement efficiency but also promotes the formation of Cu-Cd micro-cells, leading to significant cadmium consumption and re-dissolution at the anode, thus inhibiting the overall replacement effect. Therefore, to achieve efficient cadmium extraction, companies remove impurities from the copper-cadmium slag leaching solution, including Cu... 2+ The concentration was reduced to around 1-2 mg / L (to achieve the desired effect without harming the displacement process). At this point, Cu 2+ The content was low, therefore it did not show a promoting effect on the replacement process. Based on the actual production process, Cd 2+ Electron interactions occur on the Zn surface, causing the cadmium product layer to coat zinc powder (the "cadmium-coated zinc" phenomenon). This further induces aggregation of "cadmium-coated zinc" particles based on intermolecular van der Waals forces, significantly reducing the cadmium replacement rate. To overcome these limitations, the actual production process requires adding 3-5 times the theoretical amount of zinc powder. While traditional processes can effectively recover cadmium by adding excessive zinc powder, this results in a large amount of unreacted zinc powder mixed in the product, leading to a low cadmium grade in the sponge. To meet the purity requirements of subsequent refining, repeated acid washing is necessary to dissolve residual zinc, which undoubtedly increases the complexity of the process and replacement costs, severely weakening the economic benefits of cadmium extraction for enterprises. Summary of the Invention

[0004] To address the problems of high zinc powder consumption, low cadmium grade in sponge zinc due to the "cadmium-coated zinc" phenomenon in current replacement processes, as well as cadmium re-dissolution caused by copper ions, this invention proposes a method for preparing high-grade sponge cadmium using copper ions in synergistic ultrasonic enhancement of zinc powder. This invention achieves multiple optimizations in zinc replacement by controlling the copper ion concentration: ensuring a 99.97% replacement rate and a 97.96% sponge cadmium grade, while significantly reducing zinc powder consumption and ultrasonic power, and shortening the production cycle. The reduced ultrasonic power effectively suppresses the hydrogen evolution side reaction of zinc powder induced by high-power ultrasound, thereby reducing the additional zinc powder consumption. Furthermore, low-power ultrasound promotes the escape of dissolved oxygen from the solution due to the cavitation effect, inhibiting further cadmium oxidation and re-dissolution.

[0005] A method for preparing high-grade sponge cadmium using copper ions in conjunction with ultrasonic enhancement of zinc powder, the specific steps of which are as follows: (1) Accurate measurement of Cd in copper-cadmium slag leachate 2+ Content and Cu 2+ The concentration of Cu in the copper-cadmium slag leachate was adjusted using copper sulfate. 2+ Concentration to Cd 2+ Concentrations range from 0.83% to 3.3%; (2) Add zinc powder to copper-cadmium slag leachate and perform ultrasonic-enhanced copper ion synergistic zinc powder replacement reaction at a temperature of 20~35℃ and low power ultrasonic conditions for 10~25 min. After solid-liquid separation, the replacement liquid and high-grade sponge cadmium are obtained.

[0006] Preferably, the pH value of the copper-cadmium slag leachate in step (1) is 2 to 4.

[0007] Preferably, in step (1), the Cd in the copper-cadmium slag leaching solution... 2+ The content is 5000~8000 mg / L.

[0008] Preferably, in step (2), the zinc powder D90 is 14.8~422.2μm, and the amount of zinc powder added is 1.05~1.15 times the theoretical amount.

[0009] Preferably, the ultrasonic power in step (2) is 36~108W and the frequency is 20kHz.

[0010] Preferably, the cadmium content of the sponge in step (2) is 90~99 wt.%.

[0011] The principle of preparing high-grade cadmium sponge by synergistic copper ion and ultrasonic enhancement of zinc powder: (1) Cu 2+ Preferential precipitation occurs on the surface of zinc powder, forming Zn-Cu intermediates. The potential difference between the two constitutes a Zn-Cu micro-cell structure, which can continue to function in areas where ultrasound cannot reach: zinc acts as the anode, consuming and releasing electrons, while Cd...2+ Electrons are gained on the surface of the copper cathode and deposited; by optimizing the copper ion concentration, the formation of Cu-Cd micro batteries can be suppressed, thereby avoiding the back dissolution caused by the consumption of cadmium as the anode, reducing the adverse effects of excessive copper on the cadmium replacement rate and the purity of sponge cadmium, thus achieving more comprehensive deep bonding. (2) The high-frequency vibration generated by low-power ultrasound can effectively dissociate the large zinc powder agglomeration caused by van der Waals forces; at the same time, the micro-jet generated by cavitation effect can timely strip the cadmium product layer on the surface of zinc powder, thereby maintaining the high reactivity of zinc powder.

[0012] The beneficial effects of this invention are: (1) In this invention, zinc is used as a reducing agent and copper ions as an auxiliary agent. The ultrasonic peeling product layer continuously renews the activity of zinc powder and promotes the replacement process. Compared with the traditional replacement method, the preparation of high-grade sponge cadmium by copper ions and ultrasonically enhanced zinc powder can be completed at room temperature. It can also ensure a high replacement rate while producing high-grade sponge cadmium, which can significantly shorten the production cycle and reduce the consumption of zinc powder. (2) The present invention in Cu 2+ In the technique combined with ultrasonic-enhanced zinc powder replacement, Cu-Zn intermediates are generated, forming Cu-Zn micro-batteries. For residual aggregates, the zinc anode can still conduct electrons through the micro-battery system, causing cadmium to deposit on the copper cathode. This allows for efficient replacement with only low-power ultrasound. Therefore, Cu... 2+ The introduction of [a substance] can significantly improve the utilization rate of zinc powder, reduce the zinc content in sponge cadmium, and promote cadmium reduction. Detailed Implementation

[0013] 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.

[0014] Example 1: A method for preparing high-grade sponge cadmium using copper ions in conjunction with ultrasonically enhanced zinc powder, the specific steps of which are as follows: (1) Accurate measurement of Cd in copper-cadmium slag leachate 2+ Content and Cu 2+ Concentration; the pH of the copper-cadmium slag leachate was adjusted to 2 using sulfuric acid; The composition of the copper-cadmium slag leachate in this embodiment is shown in Table 1; Table 1. Composition of copper-cadmium slag leachate ; Copper sulfate was used to regulate the Cu content in the copper-cadmium slag leachate. 2+ Concentration to Cd 2+ The concentration is 0.83%, that is, adjusting Cu 2+ Concentration up to 50 mg / L; (2) Add 1.05 times the theoretical amount of zinc powder (D90 is 422.2μm) to the copper-cadmium slag leachate, and carry out the ultrasonic-enhanced copper ion synergistic zinc powder replacement reaction for 10 min under the conditions of temperature 20℃ and low power ultrasound (power 36W, frequency 20kHz). The solid-liquid separation yields the replacement liquid and high-grade sponge cadmium. The elemental composition and content of cadmium in sponges are shown in Table 2; Table 2 Cadmium content in sponge ; In this embodiment, the high-grade cadmium sponge contains 96.8 wt.% Cd, 2.1 wt.% Zn, and 0.9 wt.% Cu. In this embodiment, the cadmium replacement rate reached 97.44%.

[0015] Example 2: A method for preparing high-grade sponge cadmium using copper ions in conjunction with ultrasonically enhanced zinc powder, the specific steps of which are as follows: (1) Accurate measurement of Cd in copper-cadmium slag leachate 2+ Content and Cu 2+ Concentration; the pH of the copper-cadmium slag leachate was adjusted to 2.5 using sulfuric acid; The composition of the copper-cadmium slag leachate in this embodiment is the same as that in Table 1; Copper sulfate was used to regulate the Cu content in the copper-cadmium slag leachate. 2+ Concentration to Cd 2+ The concentration is 1.7%, that is, adjusting Cu 2+ Concentration up to 100 mg / L; (2) Add 1.10 times the theoretical amount of zinc powder (D90 is 59.7μm) to the copper-cadmium slag leachate, and carry out the ultrasonic-enhanced copper ion synergistic zinc powder replacement reaction for 15 min under the conditions of temperature 30℃ and low power ultrasound (power 60W, frequency 20kHz). The solid-liquid separation yields the replacement liquid and high-grade sponge cadmium. The elemental composition and content of cadmium in sponges are shown in Table 3; Table 3. Cadmium content in sponge ; In this embodiment, the high-grade cadmium sponge contains 93.8 wt.% Cd, 4.5 wt.% Zn, and 0.9 wt.% Cu. In this embodiment, the cadmium replacement rate reached 98.21%.

[0016] Example 3: A method for preparing high-grade sponge cadmium using copper ions in conjunction with ultrasonically enhanced zinc powder, the specific steps of which are as follows: (1) Accurate measurement of Cd in copper-cadmium slag leachate 2+ Content and Cu 2+ Concentration; the pH of the copper-cadmium slag leachate was adjusted to 4 using sulfuric acid; The composition of the copper-cadmium slag leachate in this embodiment is the same as that in Table 1; Copper sulfate was used to regulate the Cu content in the copper-cadmium slag leachate. 2+ Concentration to Cd 2+ The concentration is 3.3%, that is, adjusting Cu 2+ Concentration up to 200 mg / L; (2) Add 1.15 times the theoretical amount of zinc powder (D90 is 14.8μm) to the copper-cadmium slag leachate, and carry out the ultrasonic-enhanced copper ion synergistic zinc powder replacement reaction for 25 min under the conditions of temperature 35℃ and low power ultrasound (power 108W, frequency 20kHz). The solid-liquid separation yields the replacement liquid and high-grade sponge cadmium. The elemental composition and content of cadmium in sponges are shown in Table 4; Table 4. Cadmium content in sponge ; In this embodiment, the high-grade cadmium sponge contains 91.2 wt.% Cd, 7.8 wt.% Zn, and 0.7 wt.% Cu. In this embodiment, the cadmium replacement rate reached 99.76%.

[0017] Example 4: A method for preparing high-grade sponge cadmium using copper ions in conjunction with ultrasonically enhanced zinc powder, the specific steps of which are as follows: (1) Accurate measurement of Cd in copper-cadmium slag leachate 2+ Content and Cu 2+ Concentration; the pH of the copper-cadmium slag leachate was adjusted to 3 using sulfuric acid; The composition of the copper-cadmium slag leachate in this embodiment is the same as that in Table 1; Copper sulfate was used to regulate the Cu content in the copper-cadmium slag leachate. 2+ Concentration to Cd 2+ The concentration is 0.83%, that is, adjusting Cu 2+ Concentration up to 50 mg / L; (2) Add 1.10 times the theoretical amount of zinc powder (D90 is 59.7μm) to the copper-cadmium slag leachate, and carry out the ultrasonic-enhanced copper ion synergistic zinc powder replacement reaction for 10 min under the conditions of temperature 25℃ and low power ultrasound (power 84W, frequency 20kHz). The solid-liquid separation yields the replacement liquid and high-grade sponge cadmium. The elemental composition and content of cadmium in sponges are shown in Table 5; Table 5. Cadmium content in sponge ; In this embodiment, the high-grade cadmium sponge contains 98.0 wt.% Cd, 1.2 wt.% Zn, and 0.7 wt.% Cu. In this embodiment, the cadmium replacement rate reached 99.97%.

[0018] Comparative Example 1: The difference between this comparative example and Example 4 is that step (1) is omitted, that is, the Cu in the copper-cadmium slag leaching solution is not adjusted. 2+ Concentration of Cu in copper-cadmium slag leachate 2+ The concentration was maintained at 1.5 mg / L; The elemental composition and content of cadmium in sponges are shown in Table 6; Table 6. Cadmium content in sponge ; In this embodiment, the high-grade cadmium sponge contains 91.4 wt.% Cd, 6.9 wt.% Zn, and 0.02 wt.% Cu. In this embodiment, the cadmium replacement rate reached 94.47%.

[0019] Comparative Example 2: The difference between this comparative example and Example 4 is that the copper-cadmium slag leachate does not contain Cu. 2+ Furthermore, step (1) is omitted, meaning the copper-cadmium slag leachate remains free of Cu. 2+ ; The elemental composition and content of cadmium in sponges are shown in Table 7; Table 7 Cadmium content in sponge ; In this embodiment, the high-grade cadmium sponge contains 90.2 wt.% Cd, 5.2 wt.% Zn, and 0.0 wt.% Cu. In this embodiment, the cadmium replacement rate reached 94.27%.

[0020] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing high-grade sponge cadmium using copper ions in synergistic ultrasonic enhancement of zinc powder, characterized in that, The specific steps are as follows: (1) Accurate measurement of Cd in copper-cadmium slag leachate 2+ Content and Cu 2+ The concentration of Cu in the copper-cadmium slag leachate was adjusted using copper sulfate. 2 + Concentration to Cd 2+ Concentrations range from 0.83% to 3.3%; (2) Add zinc powder to copper-cadmium slag leachate and perform ultrasonic-enhanced copper ion synergistic zinc powder replacement reaction at a temperature of 20~35℃ and low power ultrasonic conditions for 10~25 min. After solid-liquid separation, the replacement liquid and high-grade sponge cadmium are obtained.

2. The method for preparing high-grade sponge cadmium using copper ion-assisted ultrasonic enhancement of zinc powder according to claim 1, characterized in that: Step (1) The pH value of the copper-cadmium slag leachate is 2~4.

3. The method for preparing high-grade sponge cadmium using copper ion-assisted ultrasonic enhancement of zinc powder according to claim 1, characterized in that: Step (1) Cd in copper-cadmium slag leachate 2+ The content is 5000~8000 mg / L.

4. The method for preparing high-grade sponge cadmium using copper ion-assisted ultrasonic enhancement of zinc powder according to claim 1, characterized in that: Step (2) The zinc powder D90 is 14.8~422.2μm, and the amount of zinc powder added is 1.05~1.15 times the theoretical amount.

5. The method for preparing high-grade sponge cadmium using copper ion-assisted ultrasonic enhancement of zinc powder according to claim 1, characterized in that: Step (2) The ultrasonic power is 36~108W and the frequency is 20.0kHz.

6. The method for preparing high-grade sponge cadmium using copper ion-assisted ultrasonic enhancement of zinc powder according to claim 1, characterized in that: Step (2) The cadmium content of the sponge is 90~99 wt.%.