Method for recycling cathode powder of waste nickel-cadmium battery

Abstract

The invention relates to the technical field of waste cadmium-nickel battery recycling, in particular to a waste cadmium-nickel battery cathode powder recycling method which comprises the following steps: S1, activating and pretreating cadmium cathode powder to obtain cathode slurry; s2, the cathode slurry is sequentially subjected to leaching treatment and purification treatment, and treated catholyte is obtained; s3, mixing and stirring the treated catholyte and a composite adsorbent, standing, and carrying out solid-liquid separation to obtain an adsorbed catholyte; s4, performing extraction and reverse extraction treatment on the adsorbed catholyte to obtain a cadmium-containing pregnant solution; and S5, adding the cadmium-containing pregnant solution into a water-soluble inorganic salt to obtain a cadmium compound precipitate. According to the technical scheme, efficient recovery of cadmium in the cathode powder of the waste nickel-cadmium battery is achieved, the cadmium extraction rate is higher than 98.5%, the purity of the obtained cadmium carbonate is higher than 99.6%, the technological process is controllable, operation is easy and convenient, and the method is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling of waste nickel-cadmium batteries, and particularly to a method for recycling cathode powder of waste nickel-cadmium batteries. Background Art

[0002] A nickel-cadmium battery is an alkaline storage battery that uses metallic cadmium as the negative active material and nickel hydroxide as the positive active material. Compared with other secondary batteries, nickel-cadmium batteries have better low-temperature cycling performance, stable high-current discharge characteristics, high reliability, long service life, low self-discharge rate, resistance to overcharge and over-discharge, and stable discharge voltage, and are widely used in many fields such as aircraft, ships, transportation, military, and energy storage power grids. With the increasing use of nickel-cadmium batteries, the efficient recycling of waste nickel-cadmium batteries is an indispensable link to achieve resource recycling and avoid environmental pollution. Currently, there are problems in nickel-cadmium battery recycling such as long wet treatment processes and high temperatures and large energy consumption in pyrometallurgical treatment. Conventional wet processes often require strong acid leaching, which not only causes equipment corrosion but also generates a large amount of heavy metal-containing wastewater; while pyrometallurgical treatment has a simple process, but due to the high melting point of the cathode powder, it needs to be carried out at a high temperature above 1200 °C, which not only consumes a huge amount of energy but also has problems of cadmium volatilization loss.

[0003] The existing patent CN201711436821.X discloses a method for recycling cadmium and nickel in waste nickel-cadmium batteries, including: impregnating waste nickel-cadmium battery materials in an HCl solution, adjusting the pH value of the obtained metal ion mixed solution to 4-7, filtering to obtain a pretreatment solution; mixing the pretreatment solution and citric acid, reacting to obtain a reaction solution, adjusting the pH value to 8-11, filtering to obtain cadmium hydroxide and a filtrate; mixing the filtrate and calcium nitrate, adjusting the pH value to 9-12, reacting to obtain a precipitate; reacting the precipitate with an HCl solution, filtering, and adjusting the pH value of the obtained filtrate to 7-12 to obtain nickel hydroxide. However, in the above technical solution, the purity of the recycled cadmium is only 98.65-99.07%, and the recovery rate is also only between 98.21-98.77%. Such a recycling effect may not meet the requirements for high-value-added cadmium products in actual industrial applications. Summary of the Invention

[0004] In view of this, the present invention proposes a method for recycling cathode powder of waste nickel-cadmium batteries to reduce cadmium loss, avoid cadmium pollution, and improve the cadmium recovery rate and the purity of cadmium products.

[0005] The technical solution of the present invention is realized as follows: The present invention provides a method for recycling cathode powder of waste nickel-cadmium batteries, including the following steps:

[0006] S1. Activate and pretreat the cadmium cathode powder to obtain cathode slurry;

[0007] S2. Leach and purify the cathode mud in sequence to obtain the treated cathode solution.

[0008] S3. Mix and stir the treated cathode solution with the composite adsorbent, let it stand, and perform solid-liquid separation to obtain the adsorbed cathode solution.

[0009] S4. Perform extraction and back-extraction on the adsorbed cathode solution to obtain the cadmium-rich solution.

[0010] S5. Add water-soluble inorganic salts to the cadmium-rich solution to obtain cadmium compound precipitates.

[0011] In the present invention, through the six-step linkage process of "activation - leaching - purification - adsorption - extraction - precipitation", the efficient recovery of cadmium is achieved. Among them, wet ball milling is used for activation pretreatment to improve the reaction activity of the materials; a composite leaching agent is used for leaching treatment to achieve the efficient dissolution of cadmium; a purifying agent composed of ammonium persulfate and sodium hydroxide is used to remove impurities; a composite adsorbent combining polyacrylamide and hydroxyapatite is used for deep purification; an organic extractant is used for selective extraction and enrichment; and finally, cadmium is precipitated and recovered through water-soluble inorganic salts (potassium carbonate / sodium sulfide / potassium sulfide). This method significantly improves the recovery rate of cadmium, ensures the product purity, has strong controllability in the process, and uses closed treatment to reduce pollutant emissions. It has the characteristics of reasonable process design, simple operation, and controllable cost, reflecting strong practical value and environmental protection significance.

[0012] Based on the above technical solutions, preferably, in step S1, the activation pretreatment includes: mixing cadmium cathode powder with a ball milling aid and a solvent for wet ball milling treatment, where the solid-liquid ratio of the cadmium cathode powder to the solvent is 1:1 - 3, and the solvent is a mixed solution of water and ethanol with a volume ratio of 100:2 - 10.

[0013] Based on the above technical solutions, preferably, the dosage of the aid is 0.5 - 5% of the mass of the cadmium cathode powder; the ball milling aid is one or several of sodium sulfide, iron sulfide, and ammonium sulfide.

[0014] Through activation pretreatment, the leachability and reaction activity of the cadmium component in the cadmium cathode powder are significantly improved, which is beneficial to the efficient extraction and separation of cadmium in subsequent processes. The use of a ball milling aid can enhance the activation effect of the materials: not only using mechanical force to crush the raw materials into finer particles to increase the reaction surface area, but also, through the local reaction of the chemical aid with the powder, breaking the surface passivation layer and stimulating the potential chemical reaction activity inside the material.

[0015] On the basis of the above technical solutions, preferably, the leaching treatment in step S2 specifically includes: mixing the cathode mud with a leaching agent for leaching treatment, the temperature of the leaching treatment is 80-100 °C, the time is 5-7 h, and after the leaching reaction ends, a leaching solution is obtained through solid-liquid separation; the solid-liquid ratio of the cathode mud to the leaching agent is 1:8-10.

[0016] On the basis of the above technical solutions, preferably, the composition of the leaching agent includes, by mass percentage, 18-22% hydrochloric acid, 8-12% sulfuric acid, 1.5-2.5% ammonium chloride, 0.5-1.5% hydrogen peroxide, and 0.01-0.03% sodium dodecylbenzenesulfonate, and the rest is water.

[0017] Specifically, in the leaching treatment, through the three-in-one effect of acid synergistic dissolution, oxidation and passivation breaking, and complexation strengthening, the synchronous extraction of soluble / insoluble cadmium compounds is completed in a single stage. Among them, the composite acid system of hydrochloric acid and sulfuric acid provides the main dissolution environment, and ammonium chloride enhances the dissolution ability of insoluble cadmium compounds through the complexation of NH4 + The oxidation of hydrogen peroxide can oxidize zero-valent cadmium and cadmium sulfide to soluble Cd 2+ , and sodium dodecylbenzenesulfonate improves the solid-liquid contact effect by reducing the surface tension.

[0018] On the basis of the above technical solutions, preferably, the purification treatment in step S2 includes: mixing the leaching solution with a purifying agent for purification treatment, the temperature of the purification treatment is 75-85 °C, the treatment time is 3-4 h, and after the purification reaction ends, a treated cathode solution is obtained through solid-liquid separation.

[0019] On the basis of the above technical solutions, preferably, the mass ratio of the leaching solution to the purifying agent is 8-10:1, and the purifying agent includes ammonium persulfate and sodium hydroxide, and the mass ratio of ammonium persulfate to sodium hydroxide is 2.5-3.0:1.

[0020] Specifically, this purification treatment scheme realizes the deep purification of the leaching solution through the synergistic effect of ammonium persulfate and sodium hydroxide. Among them, ammonium persulfate can oxidize and decompose residual organic matter and oxidize low-valent impurity metal ions to high-valent states by virtue of its strong oxidizing property, while sodium hydroxide promotes the selective precipitation of impurity ions such as Fe 3+ 、Al 3+ etc. by adjusting the pH value of the system, while the target product Cd 2+ remains in a dissolved state under this condition.

[0021] On the basis of the above technical solutions, preferably, the composite adsorbent includes polyacrylamide and hydroxyapatite, the addition amount of polyacrylamide is 0.1 vol%-0.15 vol% of the first cathode solution, and the addition amount of hydroxyapatite is 0.1 wt%-0.15 wt% of the first cathode solution.

[0022] The function of polyacrylamide can promote the aggregation of small particle impurities, making them form larger flocs, which is convenient for subsequent removal through solid-liquid separation; hydroxyapatite has good adsorption performance and specific chemical affinity, and can selectively adsorb residual heavy metal ions or other impurities in the solution. The compounding of polyacrylamide and hydroxyapatite can more comprehensively cover and adsorb different types of impurities, which is helpful for flocculation and sedimentation, and can also further capture trace ions existing in the solution through chemical adsorption, ensuring that the purity of cadmium ions in the finally purified cathode solution is significantly improved.

[0023] On the basis of the above technical solution, preferably, in step S4, the purified cathode solution is extracted with an extractant, and after the extraction is completed, a cadmium-containing organic solution is obtained, and then a sulfuric acid solution is added thereto for back extraction, that is, a cadmium-rich solution is obtained.

[0024] On the basis of the above technical solution, preferably, the extractant includes one of C272, P204, and P507.

[0025] On the basis of the above technical solution, preferably, the addition amount of the water-soluble inorganic salt is 3-5 wt% of the mass of the cadmium cathode powder, and the water-soluble inorganic salt includes any one of potassium carbonate, sodium sulfide, and potassium sulfide.

[0026] An efficient separation and enrichment of cadmium is achieved by using an organic extraction-back extraction-precipitation three-step method. During the extraction process, a selective organic extractant such as C272, P204, or P507 is selected, and through the active groups in its molecules, it forms a stable complex with Cd 2+ and transfers it to the organic phase to achieve selective extraction of cadmium; then back extraction is carried out using a sulfuric acid solution to transfer the cadmium ions in the organic phase back to the aqueous phase and achieve enrichment. Finally, a water-soluble inorganic salt (potassium carbonate / sodium sulfide / potassium sulfide) is added to the cadmium-rich solution, and a high-purity cadmium compound is obtained through a precipitation reaction.

[0027] The method for recycling the cathode powder of waste cadmium-nickel batteries of the present invention has the following beneficial effects compared with the prior art:

[0028] (1) Through a multi-stage treatment process of "activation-leaching-purification-adsorption-extraction-precipitation", the connection between each process is tight, the parameter setting is reasonable, the efficient recovery of cadmium in the cathode powder of waste cadmium-nickel batteries is realized, the cadmium extraction rate is higher than 98.5%, the purity of the obtained cadmium carbonate is higher than 99.6%, and the process is controllable, the operation is simple, and it is suitable for industrial production;

[0029] (2) In the activation pretreatment stage, a mixed solution of water and ethanol is used as the ball milling solvent, and a sulfide additive is added for activation pretreatment. This combination can effectively destroy the passivation layer on the surface of the cadmium-nickel battery cathode powder, increase the specific surface area, and improve the dissolution efficiency of cadmium in the subsequent leaching process;

[0030] (3) In the leaching stage, the composite leaching agent significantly improves the cadmium leaching rate through the synergistic dissolution effect of hydrochloric acid and sulfuric acid, the complexation effect of ammonium chloride and the oxidation effect of hydrogen peroxide, and the addition of sodium dodecylbenzene sulfonate significantly improves the solid-liquid mass transfer effect; in the purification stage, the purifier compounded with ammonium persulfate and sodium hydroxide can efficiently remove Fe through the synergistic effect of oxidation-precipitation. 3+ 、Al 3+ The purity of the solution is significantly improved after purification.

[0031] (4) In the adsorption treatment stage, a composite adsorbent composed of polyacrylamide and hydroxyapatite is selected. Through the dual effects of flocculation and selective adsorption, heavy metal impurities in the solution can be further removed, thereby improving the subsequent extraction efficiency. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that waste cadmium-nickel batteries come from scrapped energy batteries such as ships and base stations.

[0034] Example 1

[0035] This embodiment provides a method for recycling cathode powder of waste cadmium-nickel batteries, which specifically comprises the following steps:

[0036] S1. Take 10g of cadmium cathode powder, 0.3g of sodium sulfide and 20g of solvent, mix them, place them in a ball mill for ball milling activation treatment, and obtain cathode slurry, wherein the activation liquid is a mixture of water and ethanol in a volume ratio of 100:6.

[0037] S2. Place the cathode mud in the leaching agent, where the leaching agent includes 200 g of hydrochloric acid, 100 g of sulfuric acid, 20 g of ammonium chloride, 10 g of hydrogen peroxide, and 0.2 g of sodium dodecylbenzenesulfonate, and add water to make up 1 L. The solid-liquid ratio of the cathode mud to the leaching agent is 1:9. The temperature of the leaching treatment is 90 °C, and the time is 6 h. After the leaching reaction ends, perform solid-liquid separation to obtain the leaching solution; mix the leaching solution and the purifying agent at a mass ratio of 9:1 for purification treatment. The purifying agent is compounded from ammonium persulfate and sodium hydroxide at a mass ratio of 2.8:1. The temperature of the purification treatment is 80 °C, and the treatment time is 3.5 h. After the purification reaction ends, perform solid-liquid separation to obtain the treated cathode solution.

[0038] S3. Adjust the pH of the treated cathode solution to be less than 10.5 with 0.02 mol / L of ammonium chloride, add polyacrylamide and hydroxyapatite. The addition amount of polyacrylamide is 0.13 vol% of the first cathode solution, and the addition amount of hydroxyapatite is 0.13 wt% of the treated cathode solution. Mix and stir, and after standing for 13 min, perform solid-liquid separation to obtain the purified cathode solution.

[0039] S4. Add the adsorbed cathode solution to the extractant C272 for extraction. After the extraction is completed, obtain the cadmium-containing organic solution, and then add sulfuric acid solution for back-extraction to obtain the cadmium-rich solution.

[0040] S5. Add 0.3 - 0.5 g of potassium carbonate to the cadmium-rich solution to obtain the product cadmium carbonate.

[0041] Example 2

[0042] This example provides a method for recycling the cathode powder of waste cadmium-nickel batteries, which specifically includes the following steps:

[0043] S1. Take 10 g of cadmium cathode powder, 0.05 g of sodium sulfide, and 10 g of solvent and mix them, and place them in a ball mill for ball milling activation treatment to obtain cathode mud. The activation solution is a mixed solution of water and ethanol with a volume ratio of 100:2.

[0044] S2. Place the cathode mud in the leaching agent, where the leaching agent includes 180 g of hydrochloric acid, 80 g of sulfuric acid, 15 g of ammonium chloride, 5 g of hydrogen peroxide, and 0.1 g of sodium dodecylbenzenesulfonate, and add water to make up 1 L. The solid-liquid ratio of the cathode mud to the leaching agent is 1:8. The temperature of the leaching treatment is 80 °C, and the time is 7 h. After the leaching reaction ends, perform solid-liquid separation to obtain the leaching solution; mix the leaching solution and the purifying agent at a mass ratio of 8:1 for purification treatment. The purifying agent is compounded from ammonium persulfate and sodium hydroxide at a mass ratio of 2.5:1. The temperature of the purification treatment is 75 °C, and the treatment time is 4 h. After the purification reaction ends, perform solid-liquid separation to obtain the treated cathode solution.

[0045] S3. Adjust the pH of the treated cathode liquid to less than 10.5 with 0.02 mol / L ammonium chloride, add polyacrylamide and hydroxyapatite. The addition amount of polyacrylamide is 0.1 vol% of the first cathode liquid, and the addition amount of hydroxyapatite is 0.1 wt% of the first cathode liquid. Mix and stir, and after standing for 10 min, perform solid-liquid separation to obtain the adsorbed cathode liquid.

[0046] S4. Add the adsorbed cathode liquid to the extractant C272 for extraction. After the extraction is completed, obtain the cadmium-containing organic liquid, and then add sulfuric acid solution for back-extraction to obtain the cadmium-rich liquid.

[0047] S5. Add potassium carbonate to the cadmium-rich liquid to obtain the product cadmium carbonate.

[0048] Example 3

[0049] This example provides a method for recycling the cathode powder of waste cadmium-nickel batteries, which specifically includes the following steps:

[0050] S1. Take 10 g of cadmium cathode powder, 0.5 g of sodium sulfide and 30 g of solvent and mix them, place them in a ball mill for ball milling activation treatment to obtain cathode slurry. The activation liquid is a mixed liquid of water and ethanol with a volume ratio of 100:10.

[0051] S2. Place the cathode slurry in the leaching agent, where the leaching agent includes 220 g of hydrochloric acid, 120 g of sulfuric acid, 25 g of ammonium chloride, 15 g of hydrogen peroxide and 0.3 g of sodium dodecylbenzenesulfonate, add water to make up 1 L. The solid-liquid ratio of the cathode slurry to the leaching agent is 1:10. The temperature of the leaching treatment is 100 °C and the time is 5 h. After the leaching reaction is completed, perform solid-liquid separation to obtain the leaching solution; mix the leaching solution and the purifying agent at a mass ratio of 10:1 for purification treatment. The purifying agent is compounded by ammonium persulfate and sodium hydroxide with a mass ratio of 3.0:1. The temperature of the purification treatment is 85 °C and the treatment time is 3 h. After the purification reaction is completed, perform solid-liquid separation to obtain the treated cathode liquid.

[0052] S3. Adjust the pH of the treated cathode liquid to less than 10.5 with 0.02 mol / L ammonium chloride, add polyacrylamide and hydroxyapatite. The addition amount of polyacrylamide is 0.15 vol% of the first cathode liquid, and the addition amount of hydroxyapatite is 0.15 wt% of the first cathode liquid. Mix and stir, and after standing for 15 min, perform solid-liquid separation to obtain the adsorbed cathode liquid.

[0053] S4. Add the adsorbed cathode liquid to the extractant C272 for extraction. After the extraction is completed, obtain the cadmium-containing organic liquid, and then add sulfuric acid solution for back-extraction to obtain the cadmium-rich liquid.

[0054] S5. Add potassium carbonate to the cadmium-rich liquid to obtain the product cadmium carbonate.

[0055] Comparative Example 1

[0056] This comparative example provides a method for recycling the cathode powder of waste cadmium-nickel batteries. The difference from Example 1 is that no ball-milling additive was added in the activation pretreatment stage, and it specifically includes the following steps:

[0057] S1. Take 10 g of cadmium cathode powder and 20 g of solvent, mix them, and place them in a ball mill for ball-milling activation treatment to obtain cathode slurry. The activation liquid is a mixed liquid of water and ethanol with a volume ratio of 100:6.

[0058] S2 - S5 are the same as in Example 1.

[0059] Comparative Example 2

[0060] This comparative example provides a method for recycling the cathode powder of waste cadmium-nickel batteries. The difference from Example 1 is the leaching treatment, and it specifically includes the following steps:

[0061] S1. Take 10 g of cadmium cathode powder, 0.3 g of sodium sulfide and 20 g of solvent, mix them, and place them in a ball mill for ball-milling activation treatment to obtain cathode slurry. The activation liquid is a mixed liquid of water and ethanol with a volume ratio of 100:6.

[0062] S2. Place the cathode slurry in a leaching agent, where the leaching agent includes 215 g of hydrochloric acid, 115 g of sulfuric acid and 0.2 g of sodium dodecylbenzenesulfonate, add water to make up 1 L, the solid-liquid ratio of the cathode slurry to the leaching agent is 1:9, the temperature of the leaching treatment is 90 °C, and the time is 6 h. After the leaching reaction ends, perform solid-liquid separation to obtain the leaching solution; mix the leaching solution and the purification agent in a mass ratio of 9:1 for purification treatment. The purification agent is compounded from ammonium persulfate and sodium hydroxide with a mass ratio of 2.8:1. The temperature of the purification treatment is 80 °C, and the treatment time is 3.5 h. After the purification reaction ends, perform solid-liquid separation to obtain the treated cathode solution.

[0063] S3 - S5 are the same as in Example 1.

[0064] Comparative Example 3

[0065] This comparative example provides a method for recycling the cathode powder of waste cadmium-nickel batteries. The difference from Example 1 is the leaching treatment, and it specifically includes the following steps:

[0066] S1. Take 10 g of cadmium cathode powder, 0.3 g of sodium sulfide and 20 g of solvent, mix them, and place them in a ball mill for ball-milling activation treatment to obtain cathode slurry. The activation liquid is a mixed liquid of water and ethanol with a volume ratio of 100:6.

[0067] S2. Place the cathode sludge in the leaching agent, where the leaching agent includes 300 g of hydrochloric acid, 30 g of ammonium chloride, 10 g of hydrogen peroxide, and 0.2 g of sodium dodecylbenzenesulfonate, and add water to make up 1 L. The solid-liquid ratio of the cathode sludge to the leaching agent is 1:9. The temperature of the leaching treatment is 90 °C and the time is 6 h. After the leaching reaction ends, perform solid-liquid separation to obtain the leaching solution; mix the leaching solution and the purifying agent at a mass ratio of 9:1 for purification treatment. The purifying agent is prepared by compounding ammonium persulfate and sodium hydroxide at a mass ratio of 2.8:1. The temperature of the purification treatment is 80 °C and the treatment time is 3.5 h. After the purification reaction ends, perform solid-liquid separation to obtain the treated cathode solution.

[0068] Steps S3 - S5 are the same as those in Example 1.

[0069] Comparative Example 4

[0070] This comparative example provides a method for recycling the cathode powder of waste cadmium-nickel batteries. The difference from Example 1 is the purification treatment, which specifically includes the following steps:

[0071] S1. Take 10 g of cadmium cathode powder, 0.3 g of sodium sulfide, and 20 g of solvent, mix them, and place them in a ball mill for ball milling activation treatment to obtain the cathode sludge. The activation liquid is a mixed liquid of water and ethanol with a volume ratio of 100:6.

[0072] S2. Place the cathode sludge in the leaching agent, where the leaching agent includes 200 g of hydrochloric acid, 100 g of sulfuric acid, 20 g of ammonium chloride, 10 g of hydrogen peroxide, and 0.2 g of sodium dodecylbenzenesulfonate, and add water to make up 1 L. The solid-liquid ratio of the cathode sludge to the leaching agent is 1:9. The temperature of the leaching treatment is 90 °C and the time is 6 h. After the leaching reaction ends, perform solid-liquid separation to obtain the leaching solution; mix the leaching solution and the purifying agent at a mass ratio of 9:1 for purification treatment. The purifying agent is sodium hydroxide. The temperature of the purification treatment is 80 °C and the treatment time is 3.5 h. After the purification reaction ends, perform solid-liquid separation to obtain the treated cathode solution.

[0073] Steps S3 - S5 are the same as those in Example 1.

[0074] Comparative Example 5

[0075] This comparative example provides a method for recycling the cathode powder of waste cadmium-nickel batteries. The difference from Example 1 is the purification treatment, which specifically includes the following steps:

[0076] S1. Take 10 g of cadmium cathode powder, 0.3 g of sodium sulfide, and 20 g of solvent, mix them, and place them in a ball mill for ball milling activation treatment to obtain the cathode sludge. The activation liquid is a mixed liquid of water and ethanol with a volume ratio of 100:6.

[0077] S2. Place the cathode mud in the leaching agent, where the leaching agent includes 200 g of hydrochloric acid, 100 g of sulfuric acid, 20 g of ammonium chloride, 10 g of hydrogen peroxide, and 0.2 g of sodium dodecylbenzenesulfonate, and add water to make up 1 L. The solid-liquid ratio of the cathode mud to the leaching agent is 1:9. The temperature of the leaching treatment is 90 °C and the time is 6 h. After the leaching reaction ends, perform solid-liquid separation to obtain the leaching solution; mix the leaching solution and the purifying agent at a mass ratio of 9:1 for purification treatment. The purifying agent is ammonium persulfate. The temperature of the purification treatment is 80 °C and the treatment time is 3.5 h. After the purification reaction ends, perform solid-liquid separation to obtain the treated cathode solution.

[0078] Steps S3 - S5 are the same as in Example 1.

[0079] Comparative Example 6

[0080] This comparative example provides a method for recovering cathode powder from waste cadmium-nickel batteries. The difference from Example 1 lies in the adsorption treatment, which specifically includes the following steps:

[0081] Steps S1 - S2 are the same as in Example 1.

[0082] S3. Adjust the pH of the treated cathode solution to less than 10.5 with 0.02 mol / L ammonium chloride, add polyacrylamide, and the addition amount of polyacrylamide is 0.26 vol% of the first cathode solution. Mix and stir, and after standing for 13 min, perform solid-liquid separation to obtain the purified cathode solution.

[0083] S4. Add the purified cathode solution to the extractant C272 for extraction. After the extraction is completed, obtain the cadmium-containing organic solution, and then add sulfuric acid solution for back-extraction to obtain the cadmium-rich solution.

[0084] S5. Add potassium carbonate to the cadmium-rich solution to obtain the product cadmium carbonate.

[0085] Comparative Example 7

[0086] This comparative example provides a method for recovering cathode powder from waste cadmium-nickel batteries. The difference from Example 1 lies in the adsorption treatment, which specifically includes the following steps:

[0087] Steps S1 - S2 are the same as in Example 1.

[0088] S3. Adjust the pH of the treated cathode solution to less than 10.5 with 0.02 mol / L ammonium chloride, add hydroxyapatite, and the addition amount of hydroxyapatite is 0.26 vol% of the first cathode solution. Mix and stir, and after standing for 13 min, perform solid-liquid separation to obtain the purified cathode solution.

[0089] S4. Add the purified cathode solution to the extractant C272 for extraction. After the extraction is completed, obtain the cadmium-containing organic solution, and then add sulfuric acid solution for back-extraction to obtain the cadmium-rich solution.

[0090] S5. Potassium carbonate is added to the cadmium-rich solution to obtain cadmium carbonate as the product.

[0091] Performance detection

[0092] The purity and recovery rate of the recycled cadmium in the detection examples and comparative examples are detected. For the purity detection: the cadmium content in the cadmium carbonate samples prepared in the examples and comparative examples is detected by mass spectrometry (ICP-MS), and the purity = the mass of cadmium in the sample / the total mass of the sample × 100%; for the recovery rate: before the recovery treatment, first detect the cadmium content in the cathode powder of waste cadmium-nickel batteries by mass spectrometry (ICP-MS); the cadmium recovery rate = the mass of the actually recycled cadmium in the product / the mass of cadmium in the cathode powder of waste cadmium-nickel batteries × 100%. The results are shown in Table 1.

[0093] Table 1 Recovery rate and recovery purity of cadmium

[0094]

[0095]

[0096] As can be seen from Table 1, the technical solution of the embodiment of the present invention can achieve efficient recovery of cadmium; compared with Example 1, the recovery rate and purity of cadmium in Comparative Example 1 are both reduced. It may be because the activation is insufficient, resulting in poor subsequent treatment effect, thus slightly reducing the recovery efficiency and product purity; compared with Example 1, the recovery rate of cadmium in Comparative Examples 2 and 3 is significantly reduced, indicating that the composition of the leaching agent provided in the example is more conducive to the leaching of cadmium; compared with Example 1, the purity of cadmium in Comparative Examples 4 and 5 is reduced, which may be because simple ammonium persulfate or sodium hydroxide leads to insufficient removal of impurities; compared with Example 1, the recovery rate and purity of cadmium in Comparative Example 6 are both reduced, indicating that only PAM adsorption reduces the ability to selectively remove impurities; compared with Example 1, the recovery rate and purity of cadmium in Comparative Example 7 are both reduced, and only hydroxyapatite adsorption reduces the flocculation and sedimentation effect.

[0097] The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for recycling cathode powder of waste cadmium-nickel batteries, characterized in that: It includes the following steps: S1. Activate and pre-treat the cadmium cathode powder to obtain cathode slurry; S2. Conduct leaching treatment and purification treatment on the cathode slurry in sequence to obtain the treated cathode solution; S3. Mix and stir the treated cathode solution with a composite adsorbent, let it stand, and perform solid-liquid separation to obtain the adsorbed cathode solution; S4. Conduct extraction and stripping treatment on the adsorbed cathode solution to obtain a cadmium-rich solution; S5. Add a water-soluble inorganic salt to the cadmium-rich solution to obtain a cadmium compound precipitate.

2. The method for recycling cathode powder of waste cadmium-nickel batteries according to claim 1, characterized in that: In step S1, the activation pre-treatment includes: mixing the cadmium cathode powder with a ball-milling aid and a solvent for wet ball-milling treatment. The solid-liquid ratio of the cadmium cathode powder to the solvent is 1:1 - 3, and the solvent is a mixed solution of water and ethanol with a volume ratio of 100:2 - 10.

3. The method for recycling cathode powder of waste cadmium-nickel batteries according to claim 2, characterized in that: The dosage of the aid is 0.5 - 5% of the mass of the cadmium cathode powder; the ball-milling aid is one or several of sodium sulfide, iron sulfide, and ammonium sulfide.

4. The method for recycling cathode powder of waste cadmium-nickel batteries according to claim 1, characterized in that: The leaching treatment in step S2 specifically includes: mixing the cathode slurry with a leaching agent for leaching treatment. The temperature of the leaching treatment is 80 - 100 °C, and the time is 5 - 7 h. After the leaching reaction ends, perform solid-liquid separation to obtain the leachate; the solid-liquid ratio of the cathode slurry to the leaching agent is 1:8 - 10.

5. The method for recycling cathode powder of waste cadmium-nickel batteries according to claim 4, characterized in that: The composition of the leaching agent includes, by mass percentage, 18 - 22% hydrochloric acid, 8 - 12% sulfuric acid, 1.5 - 2.5% ammonium chloride, 0.5 - 1.5% hydrogen peroxide, and 0.01 - 0.03% sodium dodecylbenzenesulfonate, and the rest is water.

6. The method for recycling cathode powder of waste cadmium-nickel batteries according to claim 1, characterized in that: The purification treatment in step S2 includes: mixing the leachate with a purifying agent for purification treatment. The temperature of the purification treatment is 75 - 85 °C, and the treatment time is 3 - 4 h. After the purification reaction ends, perform solid-liquid separation to obtain the treated cathode solution.

7. A method for recycling cathode powder of waste nickel-cadmium batteries according to claim 6, characterized in that: The mass ratio of the leachate to the purifying agent is 8 - 10:1, and the purifying agent includes ammonium persulfate and sodium hydroxide, and the mass ratio of ammonium persulfate to sodium hydroxide is 2.5 - 3.0:

1.

8. The method for recycling cathode powder of waste cadmium-nickel batteries according to claim 1, characterized in that: The composite adsorbent includes polyacrylamide and hydroxyapatite. The addition amount of polyacrylamide is 0.1 vol% - 0.15 vol% of the first cathode solution, and the addition amount of hydroxyapatite is 0.1 wt% - 0.15 wt% of the first cathode solution.

9. The method for recycling cathode powder of waste cadmium-nickel batteries according to claim 1, characterized in that: The extractant includes any one of C272, P204, and P507.

10. A method for recycling cathode powder of waste cadmium-nickel batteries according to claim 1, characterized in that: The addition amount of the water-soluble inorganic salt is 3 - 5 wt% of the mass of the cadmium cathode powder, and the water-soluble inorganic salt includes any one of potassium carbonate, sodium sulfide, and potassium sulfide.

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