Method for recovering cobalt from co-precipitation waste liquid of aluminum-doped cobalt carbonate

Abstract

The invention provides a method for recovering cobalt from co-precipitation waste liquid of aluminum-doped cobalt carbonate. The method comprises the following steps: providing co-precipitation waste liquid of aluminum-doped cobalt carbonate, wherein the co-precipitation waste liquid contains complex cobalt and free cobalt; mixing the coprecipitation waste liquid with a composite precipitator, carrying out cobalt precipitation treatment, and carrying out solid-liquid separation to obtain an enriched cobalt compound and a treatment liquid with the cobalt content reaching the standard; the composite precipitant comprises a complex cobalt precipitant and a free cobalt precipitant. According to the method, the cobalt precipitation process of synergistic precipitation of the complexing cobalt precipitant and the free cobalt precipitant is adopted, efficient and synergistic recovery of the free cobalt and the complexing cobalt in the waste liquid can be achieved, the technological process is simple, operation is convenient, cost is low, complex breaking in advance is not needed, extra energy consumption is effectively avoided, and the method is suitable for industrial production. And the problem of ammonia gas pollution possibly generated in the complex breaking process is also prevented. According to the process, resources are recycled thoroughly, the enrichment degree and purity of cobalt compounds are high, and the treatment liquid meets the environment-friendly discharge standard.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to a method for recovering cobalt from coprecipitation waste liquid of aluminum-doped cobalt carbonate. Background Technology

[0002] With the increasing demands on the voltage (up to 4.5V) and cycle life of lithium cobalt oxide in 3C digital products, aluminum-doped lithium cobalt oxide needs to be prepared. The production of its precursor, cobalt tetroxide, requires liquid-phase synthesis to achieve the co-precipitation of aluminum and cobalt. However, due to the large difference in solubility products between aluminum and cobalt, in order to avoid segregation and uneven distribution of aluminum during co-precipitation, washing, and calcination, the industrial process requires controlling the low-temperature environment and reacting under high pH conditions with ammonium bicarbonate saturation (excess ammonium bicarbonate). Although this can balance the precipitation rate of cobalt and aluminum, it results in a cobalt content of over 500 mg / L in the co-precipitation waste liquid of aluminum-doped cobalt carbonate, which not only causes a significant decrease in the recovery rate of metallic cobalt but also leads to serious environmental pollution problems.

[0003] To address the issue of cobalt loss, current methods employ limestone or liquid alkali recovery. However, these methods have significant drawbacks: they can only recover a portion of the unreacted free cobalt ions, cannot handle complexed cobalt, and the complexed cobalt is easily oxidized in air to trivalent cobalt complexes [Co(NH3)6]. 3+ (It is grayish-black in color), and even after treatment, it still does not meet the discharge standards, thus failing to fundamentally solve the dual problems of environmental protection and resource recycling.

[0004] Therefore, how to efficiently and synergistically recover complexed cobalt and free cobalt from the co-precipitated waste liquid of aluminum-doped cobalt carbonate, while improving the cobalt resource recovery rate and ensuring that the treated liquid meets environmental discharge standards, is an urgent technical problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for recovering cobalt from co-precipitated waste liquid containing aluminum-doped cobalt carbonate. This invention employs a co-precipitation process using a complexed cobalt precipitant and a free cobalt precipitant, achieving not only efficient co-recovery of both free and complexed cobalt from the waste liquid, but also a simple process flow, convenient operation, and low cost. In particular, this invention eliminates the need for pre-complex breaking, effectively avoiding additional energy consumption and preventing ammonia pollution that may occur during the complex breaking process. Therefore, this process achieves thorough resource recovery, high enrichment and purity of cobalt compounds, facilitating subsequent resource utilization, and reducing the total cobalt concentration in the treated liquid to below 10 mg / L, meeting environmental discharge standards. This fundamentally solves the pollution and resource waste problems caused by traditional methods that only recover free cobalt while leaving complexed cobalt residues.

[0006] To achieve this objective, the present invention employs the following technical solution:

[0007] This invention provides a method for recovering cobalt from aluminum-doped cobalt carbonate coprecipitation waste liquid, the method comprising the following steps:

[0008] A coprecipitation waste liquid containing aluminum-doped cobalt carbonate is provided, wherein the coprecipitation waste liquid contains complexed cobalt and free cobalt.

[0009] The co-precipitated waste liquid and the composite precipitant are mixed and subjected to cobalt precipitation treatment. After solid-liquid separation, enriched cobalt compounds and a treated liquid with a cobalt content meeting the standard are obtained. The composite precipitant includes a complexed cobalt precipitant and a free cobalt precipitant.

[0010] The cobalt precipitation process provided by this invention not only achieves efficient and synergistic recovery of free and complexed cobalt from waste liquid, but also features a simple process flow, convenient operation, and low cost. In particular, this invention eliminates the need for pre-complex breaking, effectively avoiding additional energy consumption and preventing ammonia pollution that may occur during the complex breaking process. Therefore, this process achieves thorough resource recovery, high enrichment and purity of cobalt compounds, facilitating subsequent resource utilization. Furthermore, the total cobalt concentration in the treated liquid can be reduced to below 10 mg / L, meeting environmental discharge standards. This fundamentally solves the pollution and resource waste problems caused by traditional methods that only recover free cobalt while leaving complexed cobalt residues.

[0011] It should be noted that the source of the co-precipitation waste liquid of aluminum-doped cobalt carbonate is not limited. For example, it can be the waste liquid remaining after low-aluminum doping cobalt carbonate synthesis (pH 7.1-7.2), the waste liquid remaining after high-aluminum doping cobalt carbonate synthesis (pH 7.2-7.4), or a mixed solution of waste liquid from undoped cobalt carbonate synthesis (pH 7.0-7.1), low-doped cobalt carbonate synthesis (pH 7.1-7.2), and high-doped cobalt carbonate synthesis (pH 7.2-7.4). The different pH values ​​represent different contents of ammonium, bicarbonate, and total cobalt.

[0012] It should be noted that complexed cobalt refers to cobalt in coprecipitation waste liquid where cobalt ions combine with excess ammonia in the solution (such as ammonia that may remain from the preparation process) through coordination bonds to form stable complex ions or complex molecules. The form in which they exist can be, for example, [Co(NH3)6]. 3+ Or [Co(CO3)3] 3- Etc. Free cobalt refers to cobalt that has not formed coordination bonds with other ligands in the coprecipitated waste liquid, existing in a simple ionic form (mainly Co). 2+ Depending on the pH value and redox environment of the waste liquid, a small amount of Co may be present. 3+ Cobalt is freely dispersed in the solution.

[0013] Preferably, the chemical composition of the aluminum-doped cobalt carbonate coprecipitation waste liquid includes, according to mass concentration:

[0014] Aluminum ions 1-1.5 g / L, for example, 1 g / L, 1.1 g / L, 1.2 g / L, 1.3 g / L, 1.4 g / L or 1.5 g / L, etc.; ammonium ions 10-35 g / L, for example, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, etc.; bicarbonate ions 5-15 g / L, for example, 5 g / L, 10 g / L, 15 g / L, etc.; total cobalt 80-550 mg / L, for example, 80 mg / L, 150 mg / L, 300 mg / L, 500 mg / L or 550 mg / L, etc., of which the proportion of complexed cobalt is 60-80%, for example, 60%, 70% or 80%, etc.

[0015] It should be noted that the meaning of 60-80% complexed cobalt is that 60-80% of the total cobalt mass concentration in the co-precipitated waste liquid of aluminum-doped cobalt carbonate exists in the form of complexed cobalt.

[0016] Preferably, the pH of the co-precipitated waste liquid of aluminum-doped cobalt carbonate is 7-7.5, for example, it can be 7.0, 7.1, 7.2, 7.3, 7.4 or 7.5.

[0017] Preferably, the cobalt complexing precipitant comprises sodium sulfide and / or hydrogen sulfide.

[0018] In this invention, sulfides are used as cobalt complex precipitants. On the one hand, this rapidly disrupts the complex structure of cobalt complexes, forcibly releasing cobalt ions. On the other hand, the released cobalt ions can readily react with sulfur. 2- The reaction produces cobalt sulfide precipitate, avoiding the "secondary complexation" problem of cobalt ions recombining with the original ligands to form complexes, and achieving "complex breaking-precipitation" in one step.

[0019] Preferably, the free cobalt precipitant comprises any one or a combination of at least two of calcium hydroxide, magnesium hydroxide, or sodium hydroxide.

[0020] Preferably, the molar ratio of the cobalt complex in the coprecipitated waste liquid to the cobalt complex precipitant is 1:(1.1-1.5), for example, it can be 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5, etc.

[0021] In this invention, the appropriate molar ratio described above can both efficiently break the coordination bonds of the cobalt complex structure and ensure that all released cobalt ions react with S. 2- This process combines the formation of cobalt sulfide precipitate, avoiding residual complexed cobalt due to insufficient precipitant; precise proportions can prevent S 2- Excessive amounts may cause side reactions (such as the formation of other sulfide precipitates with trace impurities in the waste liquid), ensuring the high purity of the generated cobalt sulfide precipitate.

[0022] Preferably, the molar ratio of free cobalt in the coprecipitated waste liquid to the free cobalt precipitant is 1:(1.2-2), for example, it can be 1:1.2, 1:1.4, 1:1.6, 1:1.8 or 1:2, etc., and preferably 1:(1.5-2).

[0023] In this invention, free cobalt exists in a simple ionic form, which has high reactivity. However, the high concentrations of ammonium salts and carbonate ions in the waste liquid may slightly inhibit the precipitation reaction. Therefore, the aforementioned suitable molar ratio can effectively counteract this inhibitory effect, ensuring rapid and complete precipitation even if the concentration of free cobalt in the waste liquid fluctuates slightly, thus ensuring that the total cobalt content in the treated liquid consistently meets the standards.

[0024] Preferably, during the cobalt precipitation process, the pH of the system is controlled at 7-7.5, for example, it can be 7, 7.2, 7.4 or 7.5.

[0025] Preferably, the mixing step includes:

[0026] (a) The co-precipitated waste liquid of aluminum-doped cobalt carbonate and the free cobalt precipitant are mixed to carry out primary cobalt precipitation.

[0027] (b) Add a cobalt complexing precipitant to the solution after step (a) to perform secondary cobalt precipitation.

[0028] In this invention, adding a free cobalt precipitant first separates the free cobalt from the waste liquid in advance, avoiding competition between the free cobalt and the complexed cobalt for sulfur when a complexed cobalt precipitant is added subsequently. 2- Ensure S 2- It can focus on breaking down and precipitating cobalt complexes, improving the processing efficiency of cobalt complexes. Furthermore, the cobalt compound particles generated from the free cobalt precipitation can serve as heterogeneous nucleation seeds for subsequent cobalt complex precipitation, providing attachment sites for the growth of cobalt sulfide precipitates, promoting the agglomeration and growth of cobalt sulfide particles, and preventing the formation of fine, dispersed colloidal particles, thus reducing the difficulty of subsequent solid-liquid separation processes. In addition, the subsequent addition of the cobalt complex precipitant avoids the formation of S... 2- The instantaneous reaction with a large amount of free cobalt generates excessive fine CoS particles, thereby reducing the risk of poor particle aggregation or adsorption of impurities in the waste liquid (such as aluminum compounds), and further improving the purity of the enriched cobalt compounds. In summary, this mixing method can achieve precise fractional recovery of cobalt, improve the overall cobalt recovery rate, and produce precipitated particles with larger particle sizes and excellent filtration performance, which helps to improve the efficiency and effect of subsequent solid-liquid separation and reduce energy consumption and time costs in industrial production.

[0029] Preferably, the temperature of the primary cobalt deposition is 20-30°C, for example, 20°C, 25°C, or 30°C.

[0030] Preferably, the temperature of the secondary cobalt deposition is 25-35°C, for example, it can be 25°C, 30°C or 35°C.

[0031] Preferably, the primary cobalt precipitation process is accompanied by stirring, and the stirring rate is 200-300 rpm, for example, 200 rpm, 250 rpm or 300 rpm.

[0032] Preferably, the secondary cobalt precipitation process is accompanied by stirring, and the stirring rate is 300-400 rpm, for example, 300 rpm, 350 rpm or 400 rpm.

[0033] Preferably, the method includes the following steps:

[0034] (1) Provide a coprecipitation waste liquid of aluminum-doped cobalt carbonate with a pH of 7-7.5, wherein the coprecipitation waste liquid contains complexed cobalt and free cobalt; the chemical composition of the coprecipitation waste liquid, according to mass concentration, includes:

[0035] Aluminum ions 1-1.5 g / L, ammonium ions 10-35 g / L, bicarbonate ions 5-15 g / L, total cobalt 80-550 mg / L, of which complexed cobalt accounts for 60-80%.

[0036] (2) At a speed of 200-300 rpm, the co-precipitated waste liquid and free cobalt precipitant are stirred and mixed, and the pH of the system is controlled at 7-7.5 (e.g., 7.0, 7.1, 7.2, 7.3, 7.4 or 7.5, etc.) and the temperature is controlled at 20-30℃ for primary cobalt precipitation. Then, complexed cobalt precipitant is added and stirred and mixed at a speed of 300-400 rpm, and the pH of the system is controlled at 7.2-7.5 (e.g., 7.2, 7.3, 7.4 or 7.5, etc.) and the temperature is controlled at 25-35℃ for secondary cobalt precipitation. After the cobalt precipitation treatment is completed, the mixture is filtered to obtain a treatment liquid with enriched cobalt compounds and a total cobalt concentration <10 mg / L (e.g., 9.5 mg / L, 9 mg / L, 8.5 mg / L, 8 mg / L, 7.5 mg / L or 7 mg / L, etc.). The pH of the system during the secondary cobalt precipitation process is greater than the pH of the system during the primary cobalt precipitation process.

[0037] In this invention, the pH range set for the primary cobalt precipitation allows the free cobalt precipitant to react efficiently while preventing the precipitation of aluminum ions; the pH set for the secondary cobalt precipitation is higher than that set for the primary cobalt precipitation. The slightly higher pH can slightly weaken the stability of cobalt-ammonia complex bonds, promote the dissociation of complex cobalt, and improve the precipitant's capture efficiency of cobalt ions.

[0038] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) This invention employs a cobalt precipitation process using a combination of complexed cobalt precipitant and free cobalt precipitant. This process not only achieves efficient and synergistic recovery of both free and complexed cobalt from waste liquid, but also features a simple process flow, convenient operation, and low cost. In particular, this invention eliminates the need for pre-complex breaking, effectively avoiding additional energy consumption and preventing ammonia pollution that may occur during the complex breaking process. Therefore, this process achieves thorough resource recovery, high enrichment and purity of cobalt compounds, facilitating subsequent resource utilization. Furthermore, the total cobalt concentration in the treated liquid can be reduced to below 10 mg / L, meeting environmental discharge standards. This fundamentally solves the pollution and resource waste problems caused by traditional methods that can only recover free cobalt while leaving complexed cobalt residues.

[0041] (2) The cobalt precipitation process provided by the present invention takes into account both the need for efficient resource recovery and environmental compliance. It is simple to operate, cost controllable, suitable for large-scale industrial application, and has significant economic and environmental benefits. Attached Figure Description

[0042] Figure 1 This is a process flow diagram provided in Embodiment 1 of the present invention. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] Example 1

[0045] This embodiment provides a method for recovering cobalt from aluminum-doped cobalt carbonate coprecipitation waste liquid, and its process flow diagram is shown below. Figure 1 As shown, the method includes the following steps:

[0046] (1) Provide a coprecipitation waste liquid of aluminum-doped cobalt carbonate with a pH of 7.2, wherein the coprecipitation waste liquid contains cobalt complex ([Co(NH3)6]). 3+ ) and free cobalt (Co) 2+ The chemical components in the coprecipitated waste liquid, according to their mass concentration, include:

[0047] Aluminum ions 1.5 g / L, bicarbonate ions 20 g / L, ammonium ions 10 g / L, total cobalt 500 mg / L, of which complexed cobalt accounted for 70%.

[0048] (2) At a speed of 250 rpm, the co-precipitated waste liquid and free cobalt precipitant are stirred and mixed, and the pH of the system is controlled at 7.2 and the temperature at 30°C for primary cobalt precipitation. Then, complexed cobalt precipitant is added and stirred and mixed at a speed of 350 rpm, and the pH of the system is controlled at 7.3 and the temperature at 30°C for secondary cobalt precipitation. After the cobalt precipitation treatment is completed, the mixture is filtered to obtain enriched cobalt compounds and treatment liquid.

[0049] Wherein, the free cobalt precipitant is calcium hydroxide; the molar ratio of free cobalt in the coprecipitation waste liquid to the free cobalt precipitant is 1:1.6; the complexed cobalt precipitant is sodium sulfide; the molar ratio of complexed cobalt in the coprecipitation waste liquid to the complexed cobalt precipitant is 1:1.3.

[0050] Example 2

[0051] This embodiment provides a method for recovering cobalt from aluminum-doped cobalt carbonate coprecipitation waste liquid, the method comprising the following steps:

[0052] (1) Provide a coprecipitation waste liquid of aluminum-doped cobalt carbonate with a pH of 7.2, wherein the coprecipitation waste liquid contains cobalt complex ([Co(NH3)6]). 3+ ) and free cobalt (Co) 2+ The chemical components in the coprecipitated waste liquid, according to their mass concentration, include:

[0053] Aluminum ions 1.5 g / L, bicarbonate ions 20 g / L, ammonium ions 10 g / L, total cobalt 420 mg / L, of which complexed cobalt accounted for 70%.

[0054] (2) At a speed of 200 rpm, the co-precipitated waste liquid and free cobalt precipitant are stirred and mixed, and the pH of the system is controlled at 7 and the temperature at 25°C for primary cobalt precipitation. Then, complexed cobalt precipitant is added and stirred and mixed at a speed of 300 rpm, and the pH of the system is controlled at 7.2 and the temperature at 25°C. After the cobalt precipitation treatment is completed, the mixture is filtered to obtain enriched cobalt compounds and treatment liquid.

[0055] Wherein, the free cobalt precipitant is magnesium hydroxide; the molar ratio of free cobalt in the coprecipitation waste liquid to the free cobalt precipitant is 1:1.5; the complexed cobalt precipitant is sodium sulfide; the molar ratio of complexed cobalt in the coprecipitation waste liquid to the complexed cobalt precipitant is 1:1.1.

[0056] Example 3

[0057] This embodiment provides a method for recovering cobalt from aluminum-doped cobalt carbonate coprecipitation waste liquid, the method comprising the following steps:

[0058] (1) Provide a coprecipitation waste liquid of aluminum-doped cobalt carbonate with a pH of 7.2, wherein the coprecipitation waste liquid contains cobalt complex ([Co(NH3)6]). 3+ ) and free cobalt (Co) 2+ The chemical components in the coprecipitated waste liquid, according to their mass concentration, include:

[0059] Aluminum ions 1.5 g / L, bicarbonate ions 20 g / L, ammonium ions 10 g / L, total cobalt 480 mg / L, of which complexed cobalt accounted for 70%.

[0060] (2) At a speed of 300 rpm, the co-precipitated waste liquid and free cobalt precipitant are stirred and mixed, and the pH of the system is controlled at 7.4 and the temperature at 20°C for primary cobalt precipitation. Then, complexed cobalt precipitant is added and stirred and mixed at a speed of 400 rpm, and the pH of the system is controlled at 7.5 and the temperature at 25°C. After the cobalt precipitation treatment is completed, the mixture is filtered to obtain enriched cobalt compounds and treatment liquid.

[0061] Wherein, the free cobalt precipitant is sodium hydroxide; the molar ratio of free cobalt in the coprecipitation waste liquid to the free cobalt precipitant is 1:2; the complexed cobalt precipitant is sodium sulfide; and the molar ratio of complexed cobalt in the coprecipitation waste liquid to the complexed cobalt precipitant is 1:1.5.

[0062] Example 4

[0063] The difference between this embodiment and embodiment 1 is that in step (2), the free cobalt precipitant and the complexed cobalt precipitant are added to the co-precipitation waste liquid at the same time for stirring and mixing, and the pH of the system is controlled at 7.2 and the temperature at 25°C.

[0064] The remaining methods and parameters are consistent with those in Example 1.

[0065] Example 5

[0066] The difference between this embodiment and embodiment 1 is that the molar ratio of the complexed cobalt in the co-precipitated waste liquid in step (2) to the complexed cobalt precipitant is 1:2.

[0067] The remaining methods and parameters are consistent with those in Example 1.

[0068] Example 6

[0069] The difference between this embodiment and embodiment 1 is that the molar ratio of the complexed cobalt in the co-precipitated waste liquid in step (2) to the complexed cobalt precipitant is 1:0.8.

[0070] The remaining methods and parameters are consistent with those in Example 1.

[0071] Example 7

[0072] The difference between this embodiment and embodiment 1 is that the molar ratio of free cobalt in the co-precipitated waste liquid and the free cobalt precipitant in step (2) is 1:2.2.

[0073] The remaining methods and parameters are consistent with those in Example 1.

[0074] Example 8

[0075] The difference between this embodiment and embodiment 1 is that the molar ratio of free cobalt in the co-precipitated waste liquid and the free cobalt precipitant in step (2) is 1:1.

[0076] The remaining methods and parameters are consistent with those in Example 1.

[0077] Comparative Example 1

[0078] The difference between this comparative example and Example 1 is that no cobalt complex precipitant is added in step (2).

[0079] The remaining methods and parameters are consistent with those in Example 1.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that no free cobalt precipitant is added in step (2).

[0082] The remaining methods and parameters are consistent with those in Example 1.

[0083] Performance testing

[0084] The purity of the cobalt compounds enriched in the above examples and comparative examples was tested using inductively coupled plasma optical emission spectrometry (ICP-OES), and the cobalt concentration of the treatment solutions prepared in the above examples and comparative examples was tested.

[0085] The test results are shown in Table 1.

[0086] Table 1

[0087]

[0088] analyze:

[0089] As shown in Table 1, the cobalt precipitation process of this invention, employing a synergistic precipitation of complexed cobalt precipitant and free cobalt precipitant, not only achieves efficient synergistic recovery of both free and complexed cobalt from waste liquid, but also features a simple process flow, convenient operation, and low cost. In particular, this invention eliminates the need for pre-complex breaking, effectively avoiding additional energy consumption and preventing ammonia pollution that may occur during the complex breaking process. Therefore, this process achieves thorough resource recovery, high enrichment and purity of cobalt compounds, facilitating subsequent resource utilization, and reduces the total cobalt concentration in the treated liquid to below 10 mg / L, meeting environmental discharge standards. This fundamentally solves the pollution and resource waste problems caused by traditional methods that only recover free cobalt while leaving complexed cobalt residues.

[0090] As can be seen from the comparison between Example 1 and Example 4, compared with the mixed method of adding free cobalt precipitant first and then adding complexed cobalt precipitant, the simultaneous addition of free cobalt precipitant and complexed cobalt precipitant will cause a competitive reaction, reduce the treatment efficiency of complexed cobalt, and the rapid reaction of excessive free cobalt with sodium sulfide may generate a large number of fine CoS colloidal particles, which is not conducive to subsequent filtration and other processes, and reduces the concentration of cobalt compounds.

[0091] A comparison of Examples 1 and 5-6 shows that if the molar ratio of cobalt complex to cobalt complex precipitant in the coprecipitated waste liquid is too small, then excessive S... 2- This will increase the pH value of the waste liquid, potentially causing aluminum ions in the waste liquid to form aluminum hydroxide precipitate, which mixes with cobalt compounds and reduces the purity of the cobalt product. If the molar ratio of complexed cobalt to the complexed cobalt precipitant in the co-precipitated waste liquid is too high, the provided S... 2- It is impossible to completely destroy the coordination structure of all complexed cobalt in the waste liquid, and some complexed cobalt will remain in the treatment liquid, resulting in a significant decrease in cobalt recovery rate, which cannot meet the efficiency requirements of resource recovery; at the same time, unreacted complexed cobalt will cause the cobalt content in the treatment liquid to exceed the standard, which does not meet the environmental emission standards.

[0092] A comparison of Examples 1 and 7-8 shows that if the molar ratio of free cobalt to free cobalt precipitant in the coprecipitation waste liquid is too small, excessive free cobalt precipitant will cause a sharp change in the pH value of the waste liquid, affecting the purity of the cobalt compound and the cobalt content in the treatment liquid; if the molar ratio of free cobalt to free cobalt precipitant in the coprecipitation waste liquid is too large, the free cobalt cannot be completely precipitated, and a large amount of free cobalt remains in the treatment liquid, resulting in a decrease in the total cobalt recovery rate and difficulty in meeting the cobalt content standard in the treatment liquid.

[0093] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, when only free cobalt precipitant is used, a large amount of complexed cobalt will remain in the treatment liquid, resulting in an extremely low total cobalt recovery rate and making it impossible to achieve efficient recovery of cobalt from the waste liquid. When only complexed cobalt precipitant is used, although sodium sulfide can treat both free cobalt and complexed cobalt at the same time, the use of high-cost sodium sulfide when treating free cobalt will result in reagent waste and significantly increase the economic cost of the process. Furthermore, excessive sodium sulfide reacts rapidly with free cobalt, easily generating fine colloidal precipitates that adsorb impurities and increase the difficulty of separation.

[0094] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recovering cobalt from aluminum-doped cobalt carbonate coprecipitation waste liquid, characterized in that, The method includes the following steps: A coprecipitation waste liquid containing aluminum-doped cobalt carbonate is provided, wherein the coprecipitation waste liquid contains complexed cobalt and free cobalt; The co-precipitated waste liquid and the composite precipitant are mixed and subjected to cobalt precipitation treatment. After solid-liquid separation, enriched cobalt compounds and a treated liquid with a cobalt content meeting the standard are obtained. The composite precipitant includes a complexed cobalt precipitant and a free cobalt precipitant.

2. The method according to claim 1, characterized in that, The chemical composition of the aluminum-doped cobalt carbonate coprecipitation waste liquid, according to mass concentration, includes: Aluminum ions 1-1.5 g / L, ammonium ions 10-35 g / L, bicarbonate ions 5-15 g / L, total cobalt 80-550 mg / L, of which complexed cobalt accounts for 60-80%; Preferably, the pH of the co-precipitated waste liquid of aluminum-doped cobalt carbonate is 7-7.

5.

3. The method according to claim 1 or 2, characterized in that, The cobalt complexing precipitant includes sodium sulfide and / or hydrogen sulfide; Preferably, the free cobalt precipitant comprises any one or a combination of at least two of calcium hydroxide, magnesium hydroxide, or sodium hydroxide.

4. The method according to any one of claims 1-3, characterized in that, The molar ratio of the cobalt complex in the coprecipitated waste liquid to the cobalt complex precipitant is 1:(1.1-1.5).

5. The method according to any one of claims 1-4, characterized in that, The molar ratio of free cobalt in the coprecipitated waste liquid to the free cobalt precipitant is 1:(1.2-2), preferably 1:(1.5-2).

6. The method according to any one of claims 1-5, characterized in that, During the cobalt precipitation process, the pH of the system is controlled at 7-7.

5.

7. The method according to any one of claims 1-6, characterized in that, The mixing step includes: (a) The co-precipitated waste liquid of aluminum-doped cobalt carbonate and the free cobalt precipitant are mixed for primary cobalt precipitation; (b) Add a cobalt complexing precipitant to the solution after step (a) to perform secondary cobalt precipitation.

8. The method according to claim 7, characterized in that, The temperature for primary cobalt deposition is 20-30℃; Preferably, the temperature of the secondary cobalt deposition is 25-35°C.

9. The method according to claim 7, characterized in that, The primary cobalt precipitation process is accompanied by stirring at a speed of 200-300 rpm. Preferably, the secondary cobalt precipitation process is accompanied by stirring, and the stirring rate is 300-400 rpm.

10. The method according to any one of claims 1-9, characterized in that, The method includes the following steps: (1) Provide a coprecipitation waste liquid of aluminum-doped cobalt carbonate with a pH of 7-7.5, wherein the coprecipitation waste liquid contains complexed cobalt and free cobalt; the chemical composition of the coprecipitation waste liquid, according to mass concentration, includes: Aluminum ions 1-1.5 g / L, ammonium ions 10-35 g / L, bicarbonate ions 5-15 g / L, total cobalt 80-550 mg / L, of which complexed cobalt accounts for 60-80%; (2) At a speed of 200-300 rpm, the co-precipitated waste liquid and free cobalt precipitant are stirred and mixed, and the pH of the system is controlled at 7-7.5 and the temperature at 20-30℃ for primary cobalt precipitation. Then, complexed cobalt precipitant is added and stirred and mixed at a speed of 300-400 rpm, and the pH of the system is controlled at 7.2-7.5 and the temperature at 25-35℃ for secondary cobalt precipitation. After the cobalt precipitation treatment is completed, the mixture is filtered to obtain enriched cobalt compounds and a treatment liquid with a total cobalt concentration of <10 mg / L. The pH of the system during the secondary cobalt precipitation process is greater than the pH of the system during the primary cobalt precipitation process.

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