A method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue

Abstract

The present invention relates to the technical field of hydrometallurgy, and specifically to a method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue. The separation method provided by the present invention comprises the following steps: S1. pre-reduction treatment; S3. selective oxidation of leached cobalt and precipitated manganese. The separation method of the present invention selectively leaches cobalt by regulating the synergistic effect of ORP and pH, and selects suitable reducing agents and oxidizing agents, and inhibits the dissolution of manganese in steps, thereby reducing the circulation of manganese into the leaching and extraction system, reducing the operating cost of the leaching and extraction, and at the same time introducing a selective complexing agent to reduce the co-dissolution of impurities and simplify the subsequent purification process. The preparation method is simple to operate, easy to industrialize, and has good application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, in particular to a method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue. Background Art

[0002] With the rapid development of the new energy industry, the demand for efficient recovery and separation technologies for cobalt and manganese, core elements in lithium-ion battery cathode materials, is becoming increasingly urgent. Crude cobalt hydroxide leach residue, a hydrometallurgical intermediate, typically contains cobalt, manganese, and other impurities such as copper, iron, and zinc. Its complex composition and highly similar physicochemical properties make the separation of cobalt and manganese a technical challenge in the industry.

[0003] Common methods include acid atmospheric pressure leaching, ammonia leaching, solvent extraction, high pressure leaching and bioleaching.

[0004] Acid leaching: Using strong acids such as sulfuric acid and hydrochloric acid as leaching agents can effectively dissolve cobalt and manganese, but impurities such as iron and aluminum are easily dissolved, which increases the burden of subsequent purification. In addition, cobalt in crude cobalt hydroxide slag often exists in multiple valence states such as Co(OH)2 and Co(OH)3, which are difficult to dissolve; while manganese exists in the form of Mn²⁺ or Mn 4 ⁺ Direct leaching easily leads to the simultaneous dissolution of cobalt and manganese, resulting in poor selectivity. In industrial applications, all cobalt and manganese are leached and recycled back to the leaching system.

[0005] Ammonia leaching: Cobalt is complexed with ammonia or ammonium carbonate. Although the selectivity is good, manganese tends to remain in the form of oxides, requiring an additional oxidation step (such as sodium hypochlorite) to achieve separation. The process is complicated and ammonia volatilization causes environmental pollution.

[0006] Solvent extraction: Extractants such as Cyanex272 can achieve cobalt and manganese separation, but the extractant is easily depleted and requires frequent regeneration. High concentrations of impurities (such as calcium and zinc) will significantly reduce separation efficiency and increase operating costs.

[0007] High-pressure leaching: Oxygen-pressure acid leaching can improve the leaching rate of cobalt and nickel, but the equipment investment is high, the energy consumption is large, and the selectivity control of manganese is insufficient, making it difficult to adapt to low-grade slag.

[0008] Bioleaching and green reagents: Although environmentally friendly, they have slow reaction rates, poor bacterial adaptability, and are difficult to scale up industrially.

[0009] The above methods all have many disadvantages and are difficult to meet the needs of complex industrial separations. Summary of the Invention

[0010] The object of the present invention is to provide a method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue, comprising the following steps:

[0011] S1. Pre-reduction treatment: Crude cobalt hydroxide leaching residue and pure water are mixed at a liquid-to-solid ratio of (4-6):1 to form a slurry, then sulfuric acid is added to dissolve the mixture, and the pH is adjusted to 2.0-6.0. The mixture is filtered, and the filtrate is heated to 50-60°C, and a reducing agent is added. After reacting for 1-2 hours, the reaction end point ORP is between 100-300 mV, and the mixture is filtered to obtain a reduced leachate and leach residue.

[0012] S2 complexation treatment: the reduction leachate obtained in step S1 was added a complexing agent at a temperature between 30 and 50 ° C, the pH value was adjusted to alkaline, the reaction was carried out for 0.5 to 1.0h, and a complexation reaction was performed to obtain a complexing solution;

[0013] S3. Selective oxidation leaching of cobalt and precipitation of manganese: an oxidant is added dropwise to the complex solution obtained in step S2 for primary oxidation, then the temperature is lowered to 20-30°C, an acid is added to adjust the pH to 2.0-3.0, a manganese oxidant is added for secondary oxidation, the reaction is carried out for 1.0-2.0 hours, and the manganese slag and the cobalt-containing solution are filtered.

[0014] Furthermore, in step S1, the reducing agent is at least one of sodium sulfite or thiourea dioxide, and the added amount is 1 to 8 times the theoretical consumption. The reducing agent can reduce high-valent cobalt, manganese, iron and other ions to low-valent states, making them easier to dissolve.

[0015] Furthermore, in step S2, the complexing agent is at least one of ammonium carbonate and ammonium oxalate. The function of the complexing agent is to form a stable complex with the cobalt ions and manganese ions in the solution to reduce the co-dissolution of impurities. Ammonium oxalate has a better technical effect because oxalate can also be used as a complexing ion for complexation.

[0016] Furthermore, in step S3, the oxidant is a hydrogen peroxide solution, the amount added is 1 to 8 times the theoretical consumption, and the concentration of the hydrogen peroxide solution is 27.5 wt %. The use of hydrogen peroxide as an oxidant can not only oxidize cobalt but also avoid manganese oxidation. At the same time, because commercially available hydrogen peroxide solutions are all acidic, they can also play a role in regulating the pH value.

[0017] Furthermore, in step S3, the manganese oxidant is ammonium persulfate or oxygen, and the amount added is 1 to 9 times the theoretical consumption.

[0018] Furthermore, in step S3, the acid is at least one of sulfuric acid or oxalic acid, and oxalic acid is a better choice because oxalic acid has a complexing effect, which can enhance the complexing effect and achieve a better separation effect.

[0019] Furthermore, in step S2, adjusting the pH value to 8-9 is conducive to the formation of a stable complex between the complexing agent and the cobalt ion, thereby reducing the co-dissolution of impurities.

[0020] Furthermore, in step S3, the ORP at the endpoint of the primary oxidation reaction is controlled between 450 and 550 mV, and the ORP at the endpoint of the secondary oxidation reaction is controlled between 1000 and 1200 mV. Controlling the ORP at the endpoint of the primary oxidation reaction at 450 to 550 mV is to utilize the difference in the solubility of cobalt and manganese to selectively oxidize and leach cobalt and inhibit the dissolution of manganese, thereby keeping the manganese ions relatively stable; controlling the ORP at the endpoint of the secondary oxidation reaction at 1000 to 1200 mV can oxidize the manganese ions into manganese dioxide precipitation to achieve the purpose of separating cobalt and manganese.

[0021] Furthermore, in step S1, the pH value is adjusted to 3.2-4.5. When the pH value is between 3.2-4.5, trivalent iron ions can be converted into ferric hydroxide for precipitation treatment, thereby reducing the iron content in the manganese slag in step S3.

[0022] The separation method of the present invention selectively leaches cobalt by step-by-step oxidation through the synergistic effect of regulating the redox potential (ORP) and pH, and selecting suitable reducing agents and oxidizing agents, and inhibits the dissolution of manganese, thereby reducing the circulation of manganese into the leaching and extraction system, reducing the leaching and extraction operating costs, and at the same time introducing a selective complexing agent to reduce the co-dissolution of impurities and simplify the subsequent purification process. The preparation method is simple to operate, easy to industrialize, and has good application prospects. DETAILED DESCRIPTION

[0023] 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 embodiments described 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 making creative efforts are within the scope of protection of the present invention.

[0024] In the embodiment of the present invention, the crude cobalt hydroxide material is subjected to a normal pressure sulfuric acid leaching process to obtain a leaching residue. The content of each element in the leaching residue is shown in Table 1.

[0025] Table 1

[0026] element Co wt% Mn wt% Fe wt% Cu wt % content 7.55% 4.21% 1.54% 2.01%

[0027] Example 1

[0028] A method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue comprises the following steps:

[0029] S1. Pre-reduction treatment: 1 kg of crude cobalt hydroxide leaching residue and 5 kg of pure water were mixed into a slurry, and then sulfuric acid was added to dissolve it, and then the pH value was adjusted to 2.5, filtered, and then the filtrate was heated to between 50 and 55 ° C, 75 g of sodium sulfite was added, and the reaction was carried out after 1 hour. The reaction end point ORP was between 150 and 200 mV, and filtered to obtain a reduced leachate and leach residue;

[0030] S2 complexation treatment: the reduction leachate obtained in step S1 was added ammonium carbonate at a temperature between 45 and 50 ° C, the pH value was adjusted to 8 to 9, the reaction was carried out for 1h, and a complexation reaction was performed to obtain a complex solution;

[0031] S3. Selective oxidation leaching of cobalt and precipitation of manganese: 27.5wt% hydrogen peroxide solution was added dropwise to the complex solution obtained in step S2 for primary oxidation, and the ORP of the primary oxidation reaction endpoint was controlled to be between 450 and 500mV. The mixture was then cooled to 25-30°C, sulfuric acid was added to adjust the pH to 2.3, oxygen was introduced, and a secondary oxidation was performed, and the ORP of the secondary oxidation reaction endpoint was controlled to be between 1000 and 1050mV. The reaction was carried out for 2.0h, and the manganese slag and the cobalt-containing solution were obtained by filtration.

[0032] The contents of various elements in the cobalt solution were detected, and the results are shown in Table 2.

[0033] Table 2

[0034] element Co g / L Mn g / L Fe mg / L Cu mg / L content 18.31 0.21 19.25 25.12

[0035] The contents of various elements in manganese slag were detected, and the results are shown in Table 3.

[0036] Table 3

[0037] element Co wt% Mn wt% Fe wt% Cu wt% content 0.87 15.87 5.89 7.69

[0038] Example 2

[0039] A method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue comprises the following steps:

[0040] S1. Pre-reduction treatment: 1 kg of crude cobalt hydroxide leaching residue and 5 kg of pure water were mixed into a slurry, and then sulfuric acid was added to dissolve it, and then the pH value was adjusted to 2.3, filtered, and then the filtrate was heated to between 50 and 55 ° C, 70 g of thiourea dioxide was added, and the reaction was carried out after 1 hour. The reaction end point ORP was between 150 and 200 mV, and filtered to obtain a reduced leachate and leach residue;

[0041] S2 complexation treatment: the reduction leachate obtained in step S1 was added ammonium carbonate at a temperature between 45 and 50 ° C, the pH value was adjusted to 8 to 9, the reaction was carried out for 1h, and a complexation reaction was performed to obtain a complex solution;

[0042] S3. Selective oxidation leaching of cobalt and precipitation of manganese: 27.5wt% hydrogen peroxide solution was added dropwise to the complex solution obtained in step S2 for primary oxidation, and the ORP of the primary oxidation reaction endpoint was controlled to be between 450 and 500mV. The mixture was then cooled to 25-30°C, sulfuric acid was added to adjust the pH to 2.3, and ammonium persulfate was added for secondary oxidation, and the ORP of the secondary oxidation reaction endpoint was controlled to be between 1000 and 1050mV. The reaction was carried out for 2.0h, and the manganese slag and the cobalt-containing solution were obtained by filtration.

[0043] The contents of various elements in the cobalt solution were detected, and the results are shown in Table 4.

[0044] Table 4

[0045] element Co g / L Mn g / L Fe mg / L Cu mg / L content 18.41 0.28 20.1 24.15

[0046] The contents of various elements in manganese slag were tested, and the results are shown in Table 5.

[0047] Table 5

[0048] element Co wt% Mn wt% Fe wt% Cu wt% content 0.86 15.94 5.79 7.53

[0049] Example 3

[0050] A method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue comprises the following steps:

[0051] S1. Pre-reduction treatment: 1 kg of crude cobalt hydroxide leaching residue and 5 kg of pure water were mixed into a slurry, and then sulfuric acid was added to dissolve it, and then the pH value was adjusted to 2.3, filtered, and then the filtrate was heated to between 50 and 55 ° C, 70 g of thiourea dioxide was added, and the reaction was carried out after 1 hour. The reaction end point ORP was between 150 and 200 mV, and filtered to obtain a reduced leachate and leach residue;

[0052] S2 complexation treatment: the reduction leachate obtained in step S1 was added ammonium oxalate at a temperature between 45 and 50 ° C, the pH value was adjusted to 8 to 9, the reaction was carried out for 1h, and a complexation reaction was performed to obtain a complex solution;

[0053] S3. Selective oxidation leaching of cobalt and precipitation of manganese: 27.5wt% hydrogen peroxide solution was added dropwise to the complex solution obtained in step S2 for primary oxidation, and the ORP of the primary oxidation reaction endpoint was controlled between 450 and 500mV. The mixture was then cooled to 25-30°C, oxalic acid was added to adjust the pH to 2.3, and ammonium persulfate was added for secondary oxidation, and the ORP of the secondary oxidation reaction endpoint was controlled between 1000 and 1050mV. The reaction was carried out for 2.0h, and the manganese slag and the cobalt-containing solution were obtained by filtration.

[0054] The content of each element in the cobalt solution was detected, and the results are shown in Table 6.

[0055] Table 6

[0056] element Co g / L Mn g / L Fe mg / L Cu mg / L content 18.91 0.22 20.2 24.19

[0057] The contents of various elements in manganese slag were tested, and the results are shown in Table 7.

[0058] Table 7

[0059] element Co wt% Mn wt% Fe wt% Cu wt% content 0.72 16.12 5.79 7.53

[0060] Example 4

[0061] A method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue comprises the following steps:

[0062] S1. Pre-reduction treatment: 1 kg of crude cobalt hydroxide leaching residue and 5 kg of pure water were mixed into a slurry, and then sulfuric acid was added to dissolve it, and then the pH value was adjusted to 3.5, filtered, and then the filtrate was heated to between 50 and 55 ° C, 70 g of thiourea dioxide was added, and the reaction was carried out after 1 hour. The reaction end point ORP was between 150 and 200 mV, and filtered to obtain a reduced leachate and leach residue;

[0063] S2 complexation treatment: the reduction leachate obtained in step S1 was added ammonium oxalate at a temperature between 45 and 50 ° C, the pH value was adjusted to 8 to 9, the reaction was carried out for 1h, and a complexation reaction was performed to obtain a complex solution;

[0064] S3. Selective oxidation leaching of cobalt and precipitation of manganese: 27.5wt% hydrogen peroxide solution was added dropwise to the complex solution obtained in step S2 for primary oxidation, and the ORP of the primary oxidation reaction endpoint was controlled between 450 and 500mV. The mixture was then cooled to 25-30°C, oxalic acid was added to adjust the pH to 2.3, and ammonium persulfate was added for secondary oxidation, and the ORP of the secondary oxidation reaction endpoint was controlled between 1000 and 1050mV. The reaction was carried out for 2.0h, and the manganese slag and the cobalt-containing solution were obtained by filtration.

[0065] The content of each element in the cobalt solution was detected, and the results are shown in Table 8.

[0066] Table 8

[0067] element Co g / L Mn g / L Fe mg / L Cu mg / L content 18.53 0.22 7.2 24.31

[0068] The contents of various elements in manganese slag were tested, and the results are shown in Table 9.

[0069] Table 9

[0070] element Co wt% Mn wt% Fe wt% Cu wt% content 0.70 16.11 1.32 6.54

[0071] From the above data analysis, it can be seen that the separation methods of Examples 1 to 4 all have good technical effects and can achieve high efficiency of cobalt and manganese. Comparison of the data of Example 2 and Example 3 shows that the separation effect of adjusting the pH with oxalic acid and complexing with ammonium oxalate is better. The data of Example 4 shows that by accurately controlling the pH value in step S1, most of the trivalent iron ions can be removed in step S1, effectively reducing the iron content in the final cobalt solution and manganese slag.

Claims

1. A method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue, characterized in that: The following steps are involved: S1. Pre-reduction treatment: Crude cobalt hydroxide leaching residue and pure water are mixed at a liquid-to-solid ratio of (4-6):1 to form a slurry, then sulfuric acid is added to dissolve the mixture, and the pH is adjusted to 2.0-6.

0. The mixture is filtered, and the filtrate is heated to 50-60°C, and a reducing agent is added. After reacting for 1-2 hours, the reaction end point ORP is between 100-300 mV, and the mixture is filtered to obtain a reduced leachate and leach residue. S2 complexation treatment: the reduction leachate obtained in step S1 was added a complexing agent at a temperature between 30 and 50 ° C, the pH value was adjusted to alkaline, the reaction was carried out for 0.5 to 1.0h, and a complexation reaction was performed to obtain a complexing solution; S3. Selective oxidation leaching of cobalt and precipitation of manganese: an oxidant is added dropwise to the complex solution obtained in step S2 for primary oxidation, then the temperature is lowered to 20-30°C, an acid is added to adjust the pH to 2.0-3.0, a manganese oxidant is added for secondary oxidation, the reaction is carried out for 1.0-2.0 hours, and the manganese slag and the cobalt-containing solution are filtered.

2. The method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue according to claim 1, characterized in that: In step S1, the reducing agent is at least one of sodium sulfite and thiourea dioxide, and the amount added is 1 to 8 times the theoretical consumption.

3. The method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue according to claim 1, characterized in that: In step S2, the complexing agent is at least one of ammonium carbonate and ammonium oxalate.

4. The method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue according to claim 1, characterized in that: In step S3, the oxidant is a hydrogen peroxide solution, and the amount added is 1 to 8 times the theoretical consumption.

5. The method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue according to claim 1, characterized in that: In step S3, the manganese oxidant is ammonium persulfate or oxygen, and the amount added is 1 to 9 times the theoretical consumption.

6. The method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue according to claim 1, characterized in that: In step S3, the acid is at least one of sulfuric acid or oxalic acid.

7. The method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue according to claim 1, characterized in that: In step S2, adjusting the pH value to 8-9 is conducive to the formation of a stable complex between the complexing agent and the cobalt ion, thereby reducing the co-dissolution of impurities.

8. The method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue according to claim 1, characterized in that: In step S3, the ORP of the endpoint of the primary oxidation reaction is controlled to be between 450 and 550 mV, and the ORP of the endpoint of the secondary oxidation reaction is controlled to be between 1000 and 1200 mV.

9. The method for selectively leaching and separating cobalt and manganese from crude cobalt hydroxide leaching residue according to claim 1, characterized in that: In step S1, the pH value is adjusted to 3.2-4.5.