A method for treating cobalt chloride raffinate

Abstract

The application discloses a treatment method of cobalt chloride raffinate, which comprises the steps of removing COD by oxidation, removing phosphorus, primary precipitation and secondary precipitation. The treatment method of cobalt chloride raffinate disclosed by the application fully utilizes by-product sodium hypochlorite in the production process, removes COD by using the strong oxidizing property of sodium hypochlorite in an acidic environment, fully recovers cobalt and nickel residues by using step-by-step precipitation, realizes the open circuit of magnesium, and reduces safety and production costs. Moreover, through detection, Co is completely removed after the raffinate is treated by the method disclosed by the application, the removal rate of Ni and Mg is greater than 99%, the removal rate of COD can reach about 80%, the removal rate of TP can reach more than 90%, and the discharge requirements are met.

Description

Technical Field

[0001] This invention belongs to the field of chemical production technology, and specifically relates to a method for treating cobalt chloride raffinate. Background Technology

[0002] The process of extracting cobalt from cobalt hydroxide ore involves leaching, iron removal, and extraction to ultimately obtain a high-purity cobalt chloride solution. In the iron removal process, iron is removed to below 1 mg / L. In the 204 raffinate extraction process, copper, manganese, zinc, and calcium in the raffinate are also removed to below 1 mg / L (magnesium is not extracted in this process). In the 507 cobalt-nickel separation process, cobalt is extracted, while nickel and magnesium enter the raffinate. The raffinate also contains a small amount of cobalt. During phase separation, oil and water cannot be completely separated; therefore, the raffinate also contains 204 extractant (containing phosphorus), 507 extractant (containing phosphorus), solvent oil (sulfonated kerosene, used as an extraction diluent), and a large amount of sodium sulfate. Therefore, the main components of the raffinate are: cobalt, nickel, magnesium, extractant, and solvent oil.

[0003] Because the raffinate contains a large amount of metallic elements, it has recycling value. In existing technologies, many companies use a method of first removing phosphorus, then using a strong alkali + sodium hydroxide oxidation process. In an alkaline or slightly alkaline environment, divalent nickel and cobalt are oxidized to trivalent nickel and cobalt, forming a precipitate. This method can remove COD and remove cobalt, nickel, and magnesium in one step, saving on filter presses. However, this results in a very high magnesium content in the cobalt-nickel slag, and the tailings can only be sold to magnesium manufacturers at a very low price, making it impossible to recover the cobalt and nickel, leading to economic losses. Many companies also use sodium sulfide for precipitation first, followed by phosphorus and COD removal. This method is more effective, allowing for frequent and unpredictable pH adjustments. However, sodium sulfide must be purchased externally, and as a hazardous chemical, it has higher safety and production costs. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a method for treating cobalt chloride extraction residue, specifically including the following:

[0005] A method for treating cobalt chloride raffinate includes the following steps:

[0006] (1) Oxidation to remove COD: Add acid to the cobalt chloride raffinate to adjust the pH to 1-2, and then add sodium hypochlorite accounting for 1%-2% of the total volume of the raffinate to carry out the oxidation to remove COD reaction.

[0007] (2) Phosphorus removal: Add 2‰-4‰ of polyferric sulfate to the raffinate after COD removal, adjust the pH to 4.0-4.5, carry out the phosphorus removal reaction, and then separate the solid and liquid to obtain phosphorus-containing iron slag and the first supernatant.

[0008] (3) Primary precipitation: Add an alkaline solution to the first supernatant to adjust the pH to 9.5-9.8, carry out primary precipitation, and then separate the solid and liquid to obtain nickel-cobalt slag and second supernatant;

[0009] (4) Secondary precipitation: Add alkali to the second supernatant to adjust the pH to 10.5-11, carry out secondary precipitation, and obtain magnesium slag and third supernatant after solid-liquid separation.

[0010] Preferably, the mass concentration of sodium hypochlorite in step (1) is 10%-13%.

[0011] Preferably, the acid added in step (1) is sulfuric acid.

[0012] Preferably, the oxidation reaction in step (1) is carried out at a temperature of 50-60°C for 1-2 hours.

[0013] Preferably, the phosphorus removal reaction in step (2) is carried out at a temperature of 50-60°C for 1-2 hours.

[0014] Preferably, the reaction temperature for the first precipitation in step (3) is 50-60℃.

[0015] Preferably, in step (3): the mass concentration of the alkaline solution is ≤10%; the method for adjusting the pH is to uniformly add the alkaline solution to the first supernatant.

[0016] Preferably, the (Ni+Co) / Mg ratio in the nickel-cobalt slag is greater than 30.

[0017] Preferably, the method further includes step (5): adjusting the pH of the third supernatant back to 7-8, and then evaporating and crystallizing.

[0018] Preferably, the cobalt chloride raffinate comprises: 20-100 mg / L Co, 100-300 mg / L Ni, 1000-3000 mg / L Mg, 1500-2500 mg / L COD, and 50-200 mg / L TP.

[0019] The beneficial effects of this invention are:

[0020] (1) The method for treating cobalt chloride raffinate disclosed in this invention first involves adding acid to the cobalt chloride raffinate to adjust the pH to 1-2, and then adding sodium hypochlorite, accounting for 1%-2% of the total volume of the raffinate, to carry out an oxidation reaction to remove COD. Under acidic conditions, the electrode potential of sodium hypochlorite can reach 1.61V, which can oxidize most of the extractant and solvent oil in the water. This step can reduce the COD in the cobalt chloride raffinate by 80%-95%. Moreover, sodium hypochlorite is obtained by absorbing chlorine gas generated during the production of cobalt flakes using cobalt chloride in our company through liquid alkali absorption. It is a by-product of our company and does not need to be purchased externally. The whole process is low in cost, simple to operate, and has a good COD removal effect.

[0021] (2) The cobalt chloride raffinate treatment method disclosed in this invention involves adding 2‰-4‰ of polyferric sulfate (PFIS) to the raffinate after COD removal, adjusting the pH to 4.0-4.5, and carrying out a phosphorus removal reaction. During this process, PFIS forms iron slag in the form of ferric hydroxide. The iron slag has extremely strong complexing properties and can adsorb and trap the extractant in the water. This process can further reduce COD while removing phosphorus.

[0022] (3) The method for treating cobalt chloride raffinate disclosed in this invention involves adding alkali to the first supernatant, adjusting the pH to 9.5-9.8, and performing a single precipitation. sp [Mg(OH)2] = 1.8 * 10 -11 K sp [Ni(OH)2] = 2.0 * 10 -15 K sp [Co(OH)2] = 5.92 * 10 -15 According to Ksp, during the precipitation process, nickel and cobalt precipitate preferentially, followed by magnesium. When the pH reaches 9.5-9.8, cobalt and nickel precipitation is essentially complete, while the magnesium precipitation rate does not exceed 5%. The theoretical basis for adjusting the pH to 9.5-9.8 is: with a temperature of 50℃ (Ksp at 50℃...),... w =5.5*10 -14 The nickel ion content in the effluent is ≤0.5mg / L. The calculation process is as follows:

[0023] Ni 2+ +2OH - →Ni(OH)2

[0024]

[0025]

[0026]

[0027] pH = -Lg[H] + ] = 8.44

[0028] Because cobalt and magnesium ions are present in the solution, and excess operation needs to be considered in the actual process, the pH is controlled at 9.5-9.8. Simultaneously, a dilute alkali (concentration ≤10%) is used in this step, and the liquid alkali is added evenly to ensure uniform distribution of water in the reaction tank. This avoids localized over-alkali accumulation caused by concentrated alkali or concentrated liquid alkali addition at a single point, which could lead to magnesium precipitation. Using the method disclosed in this invention, cobalt-nickel slag with very low magnesium content can be obtained, wherein the (Ni+Co) / Mg ratio in the cobalt-nickel slag is greater than 30. This cobalt-nickel slag can be returned to the leaching process for re-dissolving the ore.

[0029] (4) The cobalt chloride raffinate treatment method disclosed in this invention involves adding alkali to the second supernatant to adjust the pH to 10.5-11 for secondary precipitation. This completely precipitates magnesium, and at this time, cobalt and nickel are also completely precipitated. The magnesium slag contains a very small amount of cobalt and nickel, and the magnesium slag has high purity and can be sold externally, thereby improving economic benefits.

[0030] (5) The method disclosed in this invention makes full use of sodium hypochlorite, a byproduct of the production process. It utilizes the strong oxidizing properties of sodium hypochlorite in an acidic environment to remove COD, and employs segmented precipitation to fully recover cobalt and nickel slag, achieving open-circuit treatment of magnesium and reducing safety and production costs. Furthermore, testing shows that the raffinate treated by the method disclosed in this invention completely removes Co, achieves a Ni and Mg removal rate of over 99%, a COD removal rate of approximately 80%, and a TP removal rate of over 90%, meeting emission requirements. Attached Figure Description

[0031] Figure 1 This is a process flow diagram of the method disclosed in this invention. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments shown below do not limit the scope of the invention as described in the claims. Furthermore, the complete contents of the configurations illustrated in the following embodiments are not limited to those necessary for the solution of the invention as described in the claims.

[0033] A method for treating cobalt chloride raffinate includes the following steps:

[0034] (1) COD removal by oxidation: Sulfuric acid is added to the cobalt chloride raffinate to adjust the pH to 1-2 (e.g., 1, 1.2, 1.5, 1.8, 2, etc.). Then, sodium hypochlorite with a mass concentration of 8%-12% (e.g., 8%, 9%, 10%, 11%, 12%, etc.) is added, accounting for 1%-2% (e.g., 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, etc.) of the total volume of the raffinate, to carry out the COD removal by oxidation reaction. The temperature is 50-60℃ (e.g., 52℃, 54℃, 56℃, 58℃, 59℃, etc.), and the time is 1-2h (e.g., 1.2h, 1.4h, 1.6h, 1.8h, etc.); the cobalt chloride raffinate contains: 20-100mg / L Co, 100-300mg / L Ni, 1000-3000mg / L Mg, 1500-2500mg / L COD, and 50-200mg / L TP;

[0035] (2) Phosphorus removal: Add 2‰-4‰ (e.g., 2.2‰, 2.5‰, 2.8‰, 3‰, 3.5‰, 3.8‰, etc.) of polyferric sulfate to the raffinate after COD removal, adjust the pH to 4.0-4.5 (e.g., 4.1, 4.2, 4.3, 4.4, etc.), and carry out the phosphorus removal reaction at a temperature of 50-60℃ (e.g., 52℃, 54℃, 56℃, 58℃, 59℃, etc.). After reacting for 1-2 hours (e.g., 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, etc.), separate the solid and liquid to obtain phosphorus-containing iron slag and the first supernatant.

[0036] (3) Primary precipitation: Add an alkaline solution with a mass concentration ≤10% (e.g., 2%, 3%, 4%, 5%, 6%, 8%, 9%, etc.) uniformly to the first supernatant, adjust the pH to 9.5-9.8 (e.g., 9.5, 9.6, 9.7, 9.8, etc.), and carry out primary precipitation at a temperature of 50-60℃ (e.g., 52℃, 54℃, 56℃, 58℃, 59℃, etc.). Then, separate the solid and liquid to obtain nickel-cobalt slag and a second supernatant. The nickel-cobalt slag has a (Ni+Co) / Mg ratio >30 (e.g., 35, 40, 45, 50, 80, etc.).

[0037] (4) Secondary precipitation: Add alkali to the second supernatant and adjust the pH to 10.5-11 (e.g., 10.5, 10.6, 10.8, 10.9, 11, etc.) to carry out secondary precipitation. After solid-liquid separation, magnesium slag and third supernatant are obtained.

[0038] (5) Adjust the pH of the third supernatant to 7-8, and then evaporate and crystallize.

[0039] According to the test results, after the raffinate was treated by the method disclosed in this invention, Co was completely removed, the removal rate of Ni and Mg was greater than 99.99%, the removal rate of COD was about 95%, and the removal rate of TP was more than 99.3%.

[0040] Example 1

[0041] A method for treating cobalt chloride raffinate includes the following steps:

[0042] (1) Oxidation to remove COD: Add sulfuric acid to the cobalt chloride raffinate to adjust the pH to 1, and then add sodium hypochlorite with a mass concentration of 8% accounting for 1% of the total volume of the raffinate to carry out the oxidation to remove COD reaction. The oxidation reaction is carried out at a temperature of 50°C for 1 hour. The cobalt chloride raffinate contains: 20 mg / L Co, 100 mg / L Ni, 1000 mg / L Mg, 1500 mg / L COD, and 50 mg / L TP.

[0043] (2) Phosphorus removal: Add 2‰ of the total volume of polyferric sulfate to the raffinate after COD removal, adjust the pH to 4.0, carry out the phosphorus removal reaction at 50℃, and after 1 hour of reaction, separate the solid and liquid to obtain phosphorus-containing iron slag and the first supernatant.

[0044] (3) Primary precipitation: Add a 10% alkaline solution to the first supernatant evenly, adjust the pH to 9.5, carry out primary precipitation at 50°C, and then separate the solid and liquid to obtain nickel-cobalt slag and second supernatant. The nickel-cobalt slag has (Ni+Co) / Mg = 35.

[0045] (4) Secondary precipitation: Add alkali to the second supernatant to adjust the pH to 10.5 and carry out secondary precipitation. After solid-liquid separation, magnesium slag and third supernatant are obtained.

[0046] (5) Adjust the pH of the third supernatant back to 7, and then evaporate and crystallize.

[0047] Example 2

[0048] A method for treating cobalt chloride raffinate includes the following steps:

[0049] (1) Oxidation to remove COD: Add sulfuric acid to the cobalt chloride raffinate to adjust the pH to 2, and then add sodium hypochlorite with a mass concentration of 12% accounting for 2% of the total volume of the raffinate to carry out the oxidation to remove COD reaction. The oxidation reaction is carried out at a temperature of 60°C for 2 hours. The cobalt chloride raffinate contains: 100 mg / L Co, 300 mg / L Ni, 3000 mg / L Mg, 2500 mg / L COD, and 200 mg / L TP.

[0050] (2) Phosphorus removal: Add 4‰ of the total volume of polyferric sulfate to the raffinate after COD removal, adjust the pH to 4.5, carry out the phosphorus removal reaction at 60℃, and after 2 hours of reaction, separate the solid and liquid to obtain phosphorus-containing iron slag and the first supernatant.

[0051] (3) Primary precipitation: Add an 8% (w / w) alkaline solution to the first supernatant, adjust the pH to 9.8, carry out primary precipitation at 60°C, and then separate the solid and liquid to obtain nickel-cobalt slag and second supernatant. The nickel-cobalt slag contains (Ni+Co) / Mg = 50.

[0052] (4) Secondary precipitation: Add alkali to the second supernatant to adjust the pH to 11, and carry out secondary precipitation. After solid-liquid separation, magnesium slag and third supernatant are obtained.

[0053] (5) Adjust the pH of the third supernatant back to 8, and then evaporate and crystallize.

[0054] Example 3

[0055] A method for treating cobalt chloride raffinate includes the following steps:

[0056] (1) Oxidation to remove COD: Sulfuric acid is added to the cobalt chloride raffinate to adjust the pH to 1.5, and then sodium hypochlorite with a mass concentration of 10% (1.6% of the total volume of the raffinate) is added to carry out the oxidation to remove COD reaction. The oxidation reaction is carried out at a temperature of 55°C for 1.3 hours. The cobalt chloride raffinate contains: 65 mg / L Co, 180 mg / L Ni, 2100 mg / L Mg, 1900 mg / L COD, and 110 mg / L TP.

[0057] (2) Phosphorus removal: Add 3‰ of the total volume of polyferric sulfate to the raffinate after COD removal, adjust the pH to 4.2, and carry out the phosphorus removal reaction at 55℃. After the reaction is carried out for 1.3h, the solid and liquid are separated to obtain phosphorus-containing iron slag and the first supernatant.

[0058] (3) Primary precipitation: Add a 5% (w / w) alkaline solution to the first supernatant, adjust the pH to 9.7, carry out primary precipitation at 55°C, and then separate the solid and liquid to obtain nickel-cobalt slag and second supernatant. The nickel-cobalt slag contains (Ni+Co) / Mg = 70.

[0059] (4) Secondary precipitation: Add alkali to the second supernatant to adjust the pH to 10.8 and carry out secondary precipitation. After solid-liquid separation, magnesium slag and third supernatant are obtained.

[0060] (5) Adjust the pH of the third supernatant back to 7.5, and then evaporate and crystallize.

[0061] Example 4

[0062] The method disclosed in this invention was used to process three groups of cobalt chloride raffinates, namely #1, #2, and #3. The composition of the three groups of cobalt chloride raffinates is shown in Table 1.

[0063] The specific processing method includes the following steps:

[0064] (1) Oxidation to remove COD: Add sulfuric acid to the cobalt chloride raffinate to adjust the pH to 1-2, and then add sodium hypochlorite with a mass concentration of 8%-12% accounting for 1%-2% of the total volume of the raffinate to carry out the oxidation to remove COD reaction. The oxidation reaction is carried out at a temperature of 50-60℃ for 1-2 hours.

[0065] (2) Phosphorus removal: Add 2‰-4‰ of polyferric sulfate to the raffinate after COD removal, adjust the pH to 4.0-4.5, carry out the phosphorus removal reaction at 50-60℃, and after 1-2 hours of reaction, separate the solid and liquid to obtain phosphorus-containing iron slag and the first supernatant.

[0066] (3) Primary precipitation: Add an alkaline solution with a mass concentration of ≤10% evenly to the first supernatant, adjust the pH to 9.5-9.8, carry out primary precipitation at a temperature of 50-60℃, and then separate the solid and liquid to obtain nickel-cobalt slag and second supernatant, wherein the ratio of (Ni+Co) / Mg in the nickel-cobalt slag is greater than 30.

[0067] (4) Secondary precipitation: Add alkali to the second supernatant to adjust the pH to 10.5-11, carry out secondary precipitation, and obtain magnesium slag and third supernatant after solid-liquid separation.

[0068] (5) Adjust the pH of the third supernatant to 7-8, and then evaporate and crystallize.

[0069] Table 1 Composition of Cobalt Chloride Raffinate

[0070]

[0071] The composition comparison of the cobalt chloride raffinate after treatment by the method disclosed in this invention is shown in Table 1. Calculations show that after treatment by the method disclosed in this invention, Co is completely removed, the removal rates of Ni and Mg are greater than 99%, the COD removal rate can reach approximately 80%, and the TP removal rate can reach over 90%.

[0072] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for treating cobalt chloride raffinate, characterized in that, Includes the following steps: (1) Oxidation to remove COD: Add acid to the cobalt chloride raffinate to adjust the pH to 1-2, and then add sodium hypochlorite accounting for 1%-2% of the total volume of the raffinate to carry out the oxidation to remove COD reaction; (2) Phosphorus removal: Add 2‰-4‰ of polyferric sulfate to the raffinate after COD removal, adjust the pH to 4.0-4.5, carry out the phosphorus removal reaction, and then separate the solid and liquid to obtain phosphorus-containing iron slag and the first supernatant. (3) Primary precipitation: Add an alkaline solution with a mass concentration of ≤10% evenly to the first supernatant, adjust the pH to 9.5-9.8, carry out primary precipitation, and then separate the solid and liquid to obtain nickel-cobalt slag and second supernatant; the nickel-cobalt slag has (Ni+Co) / Mg>30; (4) Secondary precipitation: Add alkali to the second supernatant to adjust the pH to 10.5-11, carry out secondary precipitation, and obtain magnesium slag and third supernatant after solid-liquid separation.

2. The method for treating cobalt chloride raffinate according to claim 1, characterized in that, The mass concentration of sodium hypochlorite in step (1) is 10%-13%.

3. The method for treating cobalt chloride raffinate according to claim 1, characterized in that, The acid added in step (1) is sulfuric acid.

4. The method for treating cobalt chloride raffinate according to claim 1, characterized in that, The oxidation reaction in step (1) is carried out at a temperature of 50-60℃ for 1-2 hours.

5. The method for treating cobalt chloride raffinate according to claim 1, characterized in that, The phosphorus removal reaction in step (2) is carried out at a temperature of 50-60℃ for 1-2 hours.

6. The method for treating cobalt chloride raffinate according to claim 1, characterized in that, The reaction temperature for the first precipitation in step (3) is 50-60℃.

7. The method for treating cobalt chloride raffinate according to claim 1, characterized in that, It also includes step (5): adjusting the pH of the third supernatant back to 7-8, and then evaporating and crystallizing.

8. A method for treating cobalt chloride raffinate according to any one of claims 1-7, characterized in that, The cobalt chloride raffinate contains: 20-100 mg / L Co, 100-300 mg / L Ni, 1000-3000 mg / L Mg, 1500-2500 mg / L COD, and 50-200 mg / L TP.

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