Method for removing cobalt and nickel in P507 raffinate and washing liquor

Abstract

The invention discloses a method for removing cobalt and nickel in P507 raffinate and washing liquor, and belongs to the technical field of metal refining. The method comprises the following steps: (1) adding a sodium sulfide aqueous solution into a mixed solution of P507 raffinate and washing liquor, adjusting the pH to be alkaline, and reacting; after the reaction is finished, filtering to obtain a first filtrate and a first filter residue; (2) adding a polyaluminum chloride aqueous solution and sulfuric acid into the first filtrate, adjusting the pH to be acidic, and reacting; transferring into a precipitation tank after the reaction is finished, and adding caustic soda liquid to adjust the pH for precipitation reaction; after the precipitation reaction is finished, carrying out filter pressing to obtain a second filtrate and a second filter residue; the method has the advantages of simple and convenient steps, good treatment effect and low magnesium content in the filter residues, reduces the difficulty of subsequent treatment of the cobalt-nickel slag in downstream industries, and has a good application prospect in industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of metal refining, in particular to a method for removing cobalt and nickel from P507 raffinate and washing liquid. Background Art

[0002] P507 is an organic phosphorus extractant, its chemical name is 2-ethylhexyl phosphate mono-2-ethylhexyl ester, its molecular formula is C 16 H 35 O3P, molecular weight is 306.4. P507 is mainly used for extraction and separation of cobalt and nickel, as well as deep impurity removal and synergistic extraction in the cobalt-nickel hydrometallurgical process. It is a very important extractant.

[0003] P507 raffinate refers to the solution remaining after extraction in cobalt-nickel hydrometallurgy. P507 raffinate contains unextracted metal ions, such as nickel, cobalt, etc., as well as other impurities. The raffinate usually needs further treatment to recover the valuable metals therein or to carry out environmental protection treatment. Washing liquid refers to the liquid used to wash the loaded organic phase in the above-mentioned extraction process. The function of the washing liquid is to remove the impurities remaining in the organic phase and improve the purity of the organic phase. The washing liquid is usually an acidic solution, such as sulfuric acid solution, etc., which is used to wash metal ions such as nickel and cobalt in the loaded organic phase, which also contains nickel, cobalt, etc. to be recovered or treated for environmental protection. Removing cobalt and nickel from the P507 raffinate and washing liquid, and extracting cobalt and nickel from the cobalt-nickel slag obtained after solid-liquid separation, has a positive effect both for environmental protection and economic purposes.

[0004] For example, the Chinese invention patent with publication number CN116730561A discloses a method for degrading COD in high-salt P507 raffinate wastewater, comprising the following steps: (1) adding activated carbon to the high-salt P507 raffinate wastewater, wherein the activated carbon accounts for 1.5‰-2‰ of the mass of the high-salt P507 raffinate wastewater, stirring and separating to obtain a primary treatment liquid; (2) sending the primary treatment liquid in step (1) to an ozone catalytic oxidation tower for ozone catalytic oxidation treatment to obtain a secondary treatment liquid; (3) adding the secondary treatment liquid in step (2) to an electrocatalytic oxidation tank for electrocatalytic oxidation treatment. This scheme uses a large amount of activated carbon, which is formed by high-temperature calcination and requires a high cost; at the same time, the ozone catalytic oxidation tower requires ozone gas, which is a hazardous chemical with strong oxidizing properties, can react chemically with a variety of substances, has combustion-supporting properties, and is harmful to the human body at high concentrations.

[0005] For another example, the applicant's R&D team provided a method for reducing COD and total phosphorus in nickel-cobalt raffinate in the Chinese invention with publication number CN115321706A, so that the soluble soap salt in the aqueous phase of the raffinate is converted back into a water-insoluble extractant, thereby separating it from the aqueous phase. The separated organic phase can be returned to the P507 extraction production process for continued use, and the COD and total P of the aqueous phase are greatly reduced. However, whether it is this method or the scheme using ozone catalytic oxidation, the magnesium content of the cobalt-nickel slag obtained after treatment is relatively high. In the subsequent recovery or treatment steps, the cobalt-nickel slag needs to be dissolved to extract the cobalt and nickel therein. When the magnesium content of the cobalt-nickel slag is high, it is often accompanied by a very low cobalt-nickel content. This is because the precipitation order and selectivity of different metal ions are greatly affected by the pH value and other chemical conditions of the solution. Magnesium ions are easily converted into precipitates (such as magnesium hydroxide) under certain chemical environments (such as alkaline environments with high pH values), which results in the inability to effectively precipitate cobalt and nickel under the same conditions, and they remain in the solution and fail to be enriched in the slag, which brings great difficulties to subsequent treatment. Summary of the invention

[0006] In view of the above-mentioned defects of the prior art, in a first aspect of the present invention, a method for removing cobalt and nickel from P507 raffinate and washing liquid is provided, which has simple steps, good treatment effect and low magnesium content in the filter residue, and comprises the following steps: (1) adding a sodium sulfide aqueous solution to a combined solution of a P507 raffinate and a washing solution, adjusting the pH to be alkaline, and reacting; after the reaction is completed, filtering to obtain a first filtrate and a first filter residue; (2) Adding polyaluminium chloride aqueous solution and sulfuric acid to the first filtrate, adjusting the pH to be acidic and reacting; after the reaction is completed, transferring the filtrate to a precipitation tank, adding liquid alkali to adjust the pH to carry out precipitation reaction; after the precipitation reaction is completed, performing filter pressing to obtain a second filtrate and a second filter residue.

[0007] Preferably, in step (1), the source of the P507 raffinate and washing liquid is cobalt-nickel hydrometallurgy.

[0008] The concentration of sodium sulfide needs to be controlled within an appropriate range to ensure the effectiveness of precipitation and improve the efficiency of the precipitation process. Controlling the reasonable range of sodium sulfide concentration can ensure that the precipitation reaction can proceed fully, while avoiding excessive use that causes organic matter and heavy metal substances in the wastewater to fail to be completely precipitated.

[0009] Preferably, in step (1), the concentration of the sodium sulfide aqueous solution is 15.0 wt.%-23.0 wt.%.

[0010] Appropriate pH and temperature control can help improve the efficiency, product purity and yield of the precipitation reaction, ensuring that the experiment can be carried out accurately and efficiently, thereby achieving the desired separation and purification effects.

[0011] Preferably, in step (1), the pH is adjusted to 9.5-10.5 and the reaction is carried out at a temperature of 40-50°C.

[0012] The appropriate concentration of polyaluminium chloride can effectively cause the suspended particles and colloids in the solution to condense into larger flocs, thereby accelerating the precipitation process. The polymer chains in polyaluminium chloride can form bridges between particles, connecting multiple small particles to form large flocs, thereby further promoting the precipitation of suspended matter and improving the effect.

[0013] Preferably, in step (2), the concentration of the polyaluminium chloride aqueous solution is 6 wt.%-8 wt.%; and the volume ratio of the first filtrate to the polyaluminium chloride aqueous solution is 4:7.

[0014] The use of 80 wt.% sulfuric acid has the advantages of low cost and readily available raw materials in industrial production.

[0015] Preferably, in step (2), the concentration of sulfuric acid is 80 wt.%.

[0016] Preferably, in step (2), the pH is adjusted to 3.0-4.0 and the reaction is carried out at a temperature of 40-50°C.

[0017] Preferably, in step (2), the concentration of the liquid caustic soda is 30 wt.%-34 wt.%.

[0018] Preferably, in step (2), liquid alkali is added to adjust the pH to 6.0-6.5 for precipitation reaction, and the temperature of the precipitation reaction is 40-50°C.

[0019] The reaction is considered complete when no further precipitation is generated in the reaction system. Those skilled in the art can select an appropriate duration according to the actual scale of the reaction.

[0020] In the process of the present invention, sodium sulfide is used to precipitate cobalt, nickel, copper, manganese and zinc in the P507 raffinate and washing liquid, and the priority order of precipitation in this method is Cu>Zn>Co≈Ni>Mn. In this way, heavy metal ions and oil in the P507 raffinate and washing liquid can be removed. Since MgS can undergo a hydrolysis reaction in water to make it water-soluble, it is not easy to precipitate with other metal ions. Therefore, the cobalt-nickel slag will contain less magnesium, which reduces the magnesium content in the cobalt-nickel slag and reduces the difficulty of subsequent treatment of the cobalt-nickel slag by downstream industries.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention provides a method for removing cobalt and nickel from P507 raffinate and washing liquid, which has the advantages of simple steps, good treatment effect and low magnesium content in the filter residue, reduces the difficulty of subsequent treatment of cobalt and nickel slag by downstream industries, and has good application prospects in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the process flow of the embodiment. DETAILED DESCRIPTION

[0023] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0024] Example 1 A method for removing cobalt and nickel from P507 raffinate and washing liquid, such as Figure 1 As shown, the steps are as follows: (1) adding a sodium sulfide aqueous solution (20 wt.%) to the combined solution of the P507 raffinate and the washing solution, adjusting the pH to 9.5 and reacting (40 °C); after the reaction is completed, filtering to obtain a first filtrate and a first filter residue; (2) Add polyaluminium chloride aqueous solution (6 wt.%) to the first filtrate at a volume ratio of 4:7, adjust the pH to 3.0 with sulfuric acid (80 wt.%), and after the reaction (40 °C) is completed, transfer to a tertiary precipitation tank, add liquid alkali (30 wt.%) to adjust the pH to 6.0, and after the reaction (40 °C) is completed, filter press to obtain a second filtrate and a second filter residue.

[0025] Example 2 A method for removing cobalt and nickel from P507 raffinate and washing liquid, such as Figure 1 As shown, the steps are as follows: (1) adding a sodium sulfide aqueous solution (15 wt.%) to the combined solution of the P507 raffinate and the washing solution, adjusting the pH to 10.5 and reacting (50 °C); after the reaction is completed, filtering to obtain a first filtrate and a first filter residue; (2) Add polyaluminium chloride aqueous solution (8 wt.%) to the first filtrate at a volume ratio of 4:7, adjust the pH to 4.0 with sulfuric acid (80 wt.%), and after the reaction (50 °C) is completed, transfer to a tertiary precipitation tank, add liquid alkali (34 wt.%) to adjust the pH to 6.5, and after the reaction (50 °C) is completed, filter press to obtain a second filtrate and a second filter residue.

[0026] Example 3 A method for removing cobalt and nickel from P507 raffinate and washing liquid, such as Figure 1As shown, the steps are as follows: (1) adding a sodium sulfide aqueous solution (23 wt.%) to the combined solution of the P507 raffinate and the washing solution, adjusting the pH to 9.5 and reacting (40 °C); after the reaction is completed, filtering to obtain a first filtrate and a first filter residue; (2) Add polyaluminium chloride aqueous solution (6 wt.%) to the first filtrate at a volume ratio of 4:7, adjust the pH to 3.0 with sulfuric acid (80 wt.%), and after the reaction (40 °C) is completed, transfer to a tertiary precipitation tank, add liquid alkali (30 wt.%) to adjust the pH to 6.0, and after the reaction (40 °C) is completed, filter press to obtain a second filtrate and a second filter residue.

[0027] Comparative Example 1 In this comparative example, liquid alkali is used instead of sodium sulfide aqueous solution for precipitation, which is used to compare the difference between the process of the present invention and the existing process. The operation is as follows: (1) adding liquid alkali (30 wt.%) to the combined solution of P507 raffinate and washing solution, adjusting the pH to 9.5 and reacting (40 °C); after the reaction is completed, filtering to obtain a first filtrate and a first filter residue; (2) Add polyaluminium chloride aqueous solution (6 wt.%) to the first filtrate at a volume ratio of 4:7, adjust the pH to 3.0 with sulfuric acid (80 wt.%), and after the reaction (40 °C) is completed, transfer to a tertiary precipitation tank, add liquid alkali (30 wt.%) to adjust the pH to 6.0, and after the reaction (40 °C) is completed, filter press to obtain a second filtrate and a second filter residue.

[0028] The metal elements and COD contents of the combined liquid raw water of Example 1 and the second filtrate obtained after treatment were tested and recorded by atomic absorption spectroscopy. The results are shown in Table 1.

[0029] Table 1: Test data of the combined liquid raw water and the second filtrate

[0030] In the table, “ND” stands for not detected.

[0031] The same method was used to test and record the content of metal elements in the first filter residue when the two methods of sodium sulfide precipitation were used in Example 1 and liquid alkali precipitation were used in Comparative Example 1. The test results are shown in Table 2.

[0032] Table 2: Detection data of metal element content in the first filter residue during sodium sulfide precipitation and liquid alkali precipitation

[0033] It can be seen from the above test results that the method of removing cobalt and nickel from P507 raffinate and washing liquid of the present invention has the advantages of simple steps, good treatment effect, and low magnesium content in the filter residue. This method uses sodium sulfide to precipitate cobalt, nickel, copper, manganese, and zinc in P507 raffinate and washing liquid. The priority order of precipitation in this way is Cu>Zn>Co≈Ni>Mn. In this way, heavy metal ions and oil in P507 raffinate and washing liquid can be removed. Since MgS can undergo a hydrolysis reaction in water to make it have a certain water solubility, it is not easy to precipitate with other metal ions. Therefore, the cobalt-nickel slag will contain less magnesium, which reduces the magnesium content in the cobalt-nickel slag and reduces the difficulty of subsequent treatment of the cobalt-nickel slag by downstream industries. It has good application prospects in industrial production.

[0034] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for removing cobalt and nickel from P507 raffinate and washing liquid, characterized in that: The steps include: (1) adding a sodium sulfide aqueous solution to a combined solution of a P507 raffinate and a washing solution, adjusting the pH to be alkaline, and reacting; after the reaction is completed, filtering to obtain a first filtrate and a first filter residue; (2) adding a polyaluminium chloride aqueous solution and sulfuric acid to the first filtrate to adjust the pH to be acidic and react; After the reaction is completed, the mixture is transferred to a precipitation tank, and liquid alkali is added to adjust the pH to carry out precipitation reaction; After the precipitation reaction is completed, pressure filtration is performed to obtain a second filtrate and a second filter residue.

2. The method for removing cobalt and nickel from P507 raffinate and washing liquid according to claim 1, characterized in that: In the step (1), the source of the P507 raffinate and washing liquid is cobalt-nickel hydrometallurgy.

3. The method for removing cobalt and nickel from P507 raffinate and washing liquid according to claim 1, characterized in that: In the step (1), the concentration of the sodium sulfide aqueous solution is 15.0 wt.%-23.0 wt.%.

4. The method for removing cobalt and nickel from P507 raffinate and washing liquid according to claim 1, characterized in that: In the step (1), the pH is adjusted to 9.5-10.5 and the reaction is carried out at a temperature of 40-50°C.

5. The method for removing cobalt and nickel from P507 raffinate and washing liquid according to claim 1, characterized in that: In the step (2), the concentration of the polyaluminium chloride aqueous solution is 6 wt.%-8 wt.%; and the volume ratio of the first filtrate to the polyaluminium chloride aqueous solution is 4:

7.

6. The method for removing cobalt and nickel from P507 raffinate and washing liquid according to claim 1, characterized in that: In the step (2), the concentration of sulfuric acid is 80 wt.%.

7. The method for removing cobalt and nickel from P507 raffinate and washing liquid according to claim 1, characterized in that: In the step (2), the pH is adjusted to 3.0-4.0 and the reaction is carried out at a temperature of 40-50°C.

8. The method for removing cobalt and nickel from P507 raffinate and washing liquid according to claim 1, characterized in that: In the step (2), the concentration of the liquid alkali is 30 wt.%-34 wt.%.

9. The method for removing cobalt and nickel from P507 raffinate and washing liquid according to claim 1, characterized in that: In the step (2), liquid alkali is added to adjust the pH to 6.0-6.5 for precipitation reaction, and the temperature of the precipitation reaction is 40-50°C.

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