A method for treating nickel-cobalt sulfate-containing wastewater

Abstract

The application discloses a treatment method of nickel-cobalt sulfate-containing wastewater and relates to the technical field of wastewater treatment. Part of nickel-cobalt sulfate-containing wastewater generated in a P507 cobalt extraction stage is used to dilute crude cobalt sulfate liquid from a leaching workshop, so that the consumption of pure water for pulp preparation in the leaching workshop is reduced, the pulp preparation frequency of the leaching workshop is lowered, and the labor cost is greatly reduced. In the HBL116 nickel extraction stage, another part of nickel-cobalt sulfate-containing wastewater generated in the P507 cobalt extraction stage is further extracted by using HBL116 extractant, so that a low-impurity nickel-cobalt binary liquid can be output, and the pain points such as high production cost of high-purity cobalt chloride / cobalt sulfate solution and great environmental protection pressure are solved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a method for treating nickel-cobalt sulfate-containing wastewater. Background Technology

[0002] Cobalt chloride is a precursor for the preparation of ternary cathode materials for lithium-ion batteries and a basic raw material for the preparation of battery-grade high-purity cobalt tetroxide, widely used in the field of new energy batteries. Currently, the most common method for preparing cobalt chloride solution is solvent extraction. Solvent extraction has advantages such as short process, high efficiency, and low energy consumption, and is considered the most promising method for deep removal of impurities such as calcium, copper, and manganese from cobalt sulfate solution. Commonly used extractants include P204 and P507. Based on the extraction sequence of metal ions using P204 and P507, the commonly used method is to leach cobalt hydroxide with sulfuric acid, remove impurities with P204, and finally extract cobalt with P507 followed by back-extraction with hydrochloric acid to obtain a cobalt chloride solution with a high main content.

[0003] However, the solvent extraction method currently has the following drawbacks: During the preparation of cobalt chloride solution using solvent extraction, P507 cobalt extraction generates a large amount of nickel- and cobalt-containing sulfate wastewater. The conventional treatment method is to send this wastewater directly to a wastewater treatment system. This large volume of sulfate wastewater increases the consumption of processing auxiliary materials, leading to high production costs. Furthermore, this sulfate wastewater has a high nickel- and cobalt content, making it difficult to treat and increasing environmental pressure.

[0004] Therefore, in the production process of preparing cobalt chloride solution using crude cobalt sulfate, the treatment of nickel and cobalt sulfate wastewater is a key factor in reducing production costs. If the nickel and cobalt metals in this wastewater can be recovered and the wastewater generation reduced, not only can the recovery rate of valuable metals be improved, but also the production costs and the pressure of downstream wastewater treatment can be greatly reduced, thus promoting the steady development of the new energy industry.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for treating nickel-cobalt sulfate wastewater, which aims to reduce the amount of wastewater generated in the process and at the same time reduce the impurity content in the nickel-cobalt solution product.

[0007] This invention is implemented as follows:

[0008] In a first aspect, the present invention provides a method for treating nickel-cobalt sulfate wastewater, comprising:

[0009] Wastewater reuse stage: Nickel-cobalt sulfate wastewater and crude cobalt sulfate solution are mixed to obtain cobalt sulfate diluted solution;

[0010] P204 extraction stage: The cobalt sulfate dilution solution is extracted and impurities are removed using P204 extractant. The impurities enter the organic phase and are separated to obtain the first raffinate.

[0011] P507 cobalt extraction stage: The first raffinate is extracted using P507 extractant, and the second raffinate obtained after separation is sulfate wastewater containing nickel and cobalt; part of the second raffinate is returned to the wastewater reuse stage, and the other part enters the HBL116 nickel extraction stage;

[0012] HBL116 nickel extraction stage: The second raffinate is extracted using HBL116 extractant, and after separation, a third raffinate and an organic phase containing nickel and cobalt are obtained. The third raffinate is discharged as wastewater.

[0013] In an optional implementation, when the magnesium content in the second raffinate is greater than or equal to 5 g / L, the wastewater reuse stage is stopped; when the magnesium content in the second raffinate is less than or equal to 4 g / L, a portion of the second raffinate is returned to the wastewater reuse stage.

[0014] In an optional embodiment, the ratio of the volume of the second raffinate returned to the wastewater reuse stage to the volume entering the HBL116 nickel extraction stage is 1:(4-6).

[0015] In an optional embodiment, the amount of nickel-cobalt sulfate wastewater added is adjusted so that the cobalt content in the cobalt sulfate dilution is between 60 g / L and 65 g / L.

[0016] And / or, the cobalt content in the crude cobalt sulfate solution is 85g / L-90g / L.

[0017] In an optional embodiment, the P204 extraction stage includes: mixing and saponifying the P204 extractant and the first diluent to obtain the first extractant, and then mixing and extracting the first extractant with a cobalt sulfate dilution solution.

[0018] Preferably, the volume ratio of P204 extractant to the first diluent is 1:(3.5-4.5);

[0019] Preferably, the volume ratio of the first extraction reagent to the cobalt sulfate dilution is 1:(1.0-1.1);

[0020] Preferably, the first diluent is sulfonated kerosene.

[0021] In an optional embodiment, the P507 cobalt extraction stage includes: mixing and saponifying the P507 extractant and the second diluent to obtain a second extractant, and then mixing and extracting the second extractant with the first raffinate.

[0022] Preferably, the volume ratio of P507 extractant to the second diluent is 1:(2.5-3.5);

[0023] Preferably, the volume ratio of the second extraction reagent to the first raffinate is 1:(0.15-0.20);

[0024] Preferably, the second diluent is sulfonated kerosene.

[0025] In an optional embodiment, the HBL116 nickel extraction stage includes: mixing and saponifying the HBL116 extractant and the third diluent to obtain the third extractant, mixing and extracting the third extractant with the second raffinate, and separating to obtain the third raffinate and the nickel-cobalt-containing organic phase.

[0026] In an optional embodiment, the volume ratio of HBL116 extractant to the third diluent is 1:(3.5-4.5);

[0027] And / or, the volume ratio of the third extraction reagent to the second raffinate is 1:(1.8-2.2);

[0028] And / or, the third diluent is sulfonated kerosene.

[0029] In an optional embodiment, the nickel-cobalt-containing organic phase is washed and back-extracted to obtain a nickel-cobalt-containing binary solution;

[0030] And / or, the third raffinate is evaporated.

[0031] In an optional embodiment, back-extraction is performed using a sulfuric acid solution with a concentration of 0.7 mol / L to 0.8 mol / L.

[0032] This invention offers the following advantages: By using a portion of the nickel-cobalt-containing sulfate wastewater generated during the P507 cobalt extraction stage to dilute the crude cobalt sulfate solution from the leaching workshop, not only is the amount of pure water consumed in the leaching workshop reduced, but the frequency of leaching is also decreased, significantly lowering labor costs. During the HBL116 nickel extraction stage, the remaining portion of the nickel-cobalt-containing sulfate wastewater generated during the P507 cobalt extraction stage is further extracted using the HBL116 extractant, resulting in a low-impurity nickel-cobalt binary solution. This addresses the pain points of high production costs and significant environmental pressure associated with high-purity cobalt chloride / cobalt sulfate solutions. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a process flow diagram for treating nickel-cobalt sulfate wastewater. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0036] This invention provides a method for treating nickel-cobalt sulfate wastewater, such as... Figure 1 As shown, a portion of the nickel-cobalt sulfate wastewater generated during the P507 cobalt extraction stage is used to dilute the crude cobalt sulfate solution from the leaching workshop. The remaining portion of the nickel-cobalt sulfate wastewater generated during the P507 cobalt extraction stage is further extracted using HBL116 extractant. This significantly reduces the amount of wastewater generated in the process and effectively lowers production costs. At the same time, it can also output high-purity nickel-cobalt solution products, improving the recovery rate of nickel and cobalt.

[0037] The following is a detailed explanation of each stage:

[0038] S1, Wastewater Reuse Stage

[0039] The nickel-cobalt sulfate wastewater generated during the P507 cobalt extraction stage is mixed with crude cobalt sulfate solution from the leaching workshop to obtain a diluted cobalt sulfate solution. This embodiment of the invention dilutes the crude cobalt sulfate solution produced in the leaching workshop with the nickel-cobalt sulfate wastewater generated during the P507 cobalt extraction stage. This reduces the pressure of wastewater on downstream workshops and the water consumption in the leaching workshop, significantly lowering production costs while ensuring product quality.

[0040] Specifically, the preparation of crude cobalt sulfate solution in the leaching workshop is an existing process, which uses sulfuric acid solution to leach the ore to obtain crude cobalt sulfate solution with a high cobalt content. When implementing the process provided in this embodiment of the invention for the first time, the crude cobalt sulfate solution can be diluted with water.

[0041] In some embodiments, the cobalt content in the crude cobalt sulfate solution before dilution is 85 g / L-90 g / L, such as 85 g / L, 86 g / L, 87 g / L, 88 g / L, 89 g / L, 90 g / L, etc. By adjusting the amount of nickel-cobalt sulfate wastewater added, the cobalt content in the diluted cobalt sulfate solution is made to be 60 g / L-65 g / L, such as 60 g / L, 61 g / L, 62 g / L, 63 g / L, 64 g / L, 65 g / L, etc. A cobalt concentration within the above range after dilution is preferable, as it helps improve the extraction effect and increase the recovery rate of nickel and cobalt.

[0042] S2, P204 extraction stage

[0043] The cobalt sulfate dilution obtained in step S1 is extracted and impurities such as Ca and Mn are removed by using P204 extractant. During the extraction process, the impurities enter the organic phase. The first raffinate obtained after separation is the cobalt sulfate after impurity removal. The first raffinate enters step S3.

[0044] In some embodiments, the steps of the P204 extraction stage include: mixing the P204 extractant and the first diluent to obtain an organic phase, saponifying the organic phase to obtain a first extraction reagent, mixing the first extraction reagent with the cobalt sulfate dilution obtained in step S1 for extraction, and the resulting first raffinate entering the P507 cobalt extraction stage.

[0045] In some embodiments, the first diluent can be sulfonated kerosene, specifically 260# sulfonated kerosene, but not limited thereto. The volume ratio of P204 extractant to the first diluent is 1:(3.5-4.5), such as 1:3.5, 1:3.8, 1:4.0, 1:4.2, 1:4.5, etc. The volume ratio of the first extraction reagent to the cobalt sulfate diluent is 1:(1.0-1.1), such as 1:1.00, 1:1.03, 1:1.05, 1:1.08, 1:1.10, etc. By adjusting the ratio of P204 extractant to the first diluent and the amount of the first extraction reagent, it is beneficial to improve the extraction effect and remove impurities such as Ca and Mn more thoroughly.

[0046] Specifically, the preparation of the first extraction reagent requires saponification of the organic phase using an alkaline substance. The main purpose of this step is to react the acidic extractant with the alkaline substance, thereby enhancing its metal binding ability and selectivity. The alkaline substance used in the saponification process can be ammonia, which is converted into ammonium salt after the saponification reaction.

[0047] S3, P507 cobalt extraction stage

[0048] The first raffinate is extracted using P507 extractant, allowing most of the cobalt to enter the organic phase. The resulting organic phase and second raffinate (also called cobalt extraction raffinate) are separated. The organic phase contains high-purity cobalt and is output as a product for cobalt chloride production. The second raffinate is nickel-cobalt sulfate wastewater, containing a small amount of cobalt. In this embodiment, a portion of the second raffinate is returned to the wastewater reuse stage (step S1), while the other portion enters the HBL116 nickel extraction stage (step S4). In this embodiment, the cobalt extraction raffinate is reused in the leaching workshop, resulting in enrichment of Ni and Co content, facilitating the operation of the HBL116 nickel extraction process and providing easy control.

[0049] In some embodiments, when the magnesium content in the second raffinate is greater than or equal to 5 g / L, the impurity content is relatively high, and the return to the wastewater reuse stage is stopped; at this time, it all proceeds to the HBL116 nickel extraction process. When the magnesium content in the second raffinate is less than or equal to 4 g / L, the normal reuse process is resumed, and a portion of the second raffinate is returned to the wastewater reuse stage.

[0050] Furthermore, when the magnesium content in the second raffinate is less than or equal to 4 g / L, the conditions for wastewater reuse are met. A portion of the second raffinate is returned to the wastewater reuse stage, while the other portion enters the HBL116 nickel extraction stage. Simultaneously, the ratio of the volume of the second raffinate returned to the wastewater reuse stage to the volume entering the HBL116 nickel extraction stage is controlled to be 1:(4-6), such as 1:4.0, 1:4.3, 1:4.5, 1:4.8, 1:5.0, 1:5.3, 1:5.5, 1:5.8, 1:6.0, etc. By controlling the proportion of the second raffinate entering the two different stages, this portion of nickel-cobalt sulfate wastewater is utilized more fully, and the amount of process wastewater generated can be significantly reduced.

[0051] In some embodiments, the P507 cobalt extraction stage includes: mixing the P507 extractant and the second diluent to obtain an organic phase; saponifying the organic phase to obtain a second extractant; and then mixing the second extractant with the first raffinate for extraction. The second diluent can be sulfonated kerosene, specifically 260# sulfonated kerosene, but is not limited thereto. The volume ratio of the P507 extractant to the second diluent is 1:(2.5-3.5), such as 1:2.5, 1:2.8, 1:3.0, 1:3.2, 1:3.5, etc. The volume ratio of the second extractant to the first raffinate is 1:(0.15-0.20), such as 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, 1:0.20, etc. By adjusting the ratio of the P507 extractant to the second diluent and the amount of the second extractant, the extraction effect can be improved, and cobalt can be extracted more fully into the organic phase.

[0052] Specifically, the organic phase needs to be saponified when preparing the second extraction reagent. The main purpose and reagents used in this step are the same as in step S2, and will not be repeated here. Testing showed that the second raffinate output from the cobalt extraction stage of P507 mainly contains nickel and cobalt. The nickel content is approximately 0.9-1.5 g / L (or 1.1 g / L), and the cobalt content is approximately 0.10-0.15 g / L (or 0.12 g / L).

[0053] S4, HBL116 nickel extraction stage

[0054] The second raffinate obtained in step S3 was extracted using HBL116 extractant, allowing nickel to enter the organic phase. After separation, a third raffinate and a nickel-cobalt-containing organic phase were obtained. The third raffinate was discharged as wastewater, and the nickel-cobalt-containing organic phase was back-extracted to obtain a high-purity nickel-cobalt binary solution.

[0055] In some embodiments, the HBL116 nickel extraction stage includes: mixing the HBL116 extractant and a third diluent to obtain an organic phase; saponifying the organic phase to obtain a third extractant; then mixing the third extractant with a second raffinate for extraction; and separating the third raffinate and the nickel-cobalt-containing organic phase. The third diluent can be sulfonated kerosene, specifically 260# sulfonated kerosene, but is not limited thereto. The volume ratio of the HBL116 extractant to the third diluent is 1:(3.5-4.5), such as 1:3.5, 1:3.8, 1:4.0, 1:4.2, 1:4.5, etc. The volume ratio of the third extractant to the second raffinate is 1:(1.8-2.2), such as 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, etc. By adjusting the ratio of HBL116 extractant and the third diluent, as well as the amount of the third extraction reagent, the extraction effect can be improved, and nickel can be extracted more fully into the organic phase.

[0056] Specifically, the organic phase needs to be saponified when preparing the third extraction reagent. The main purpose of this step and the reagents used are the same as in step S2, and will not be repeated here.

[0057] Furthermore, the residue from the third extraction process can be sent to the water treatment workshop for further water treatment through evaporation. This significantly reduces wastewater generation in the HBL116 nickel extraction process, lowering it to 31.5 m³. 3 / Gold ton of cobalt. Specifically, gold ton of cobalt refers to metallic ton of cobalt, representing a weight of 1 ton of cobalt metal. For example, in the cobalt chloride solution produced by the P507 cobalt extraction process in this technology, the cobalt concentration is approximately 143 g / L, so one ton of cobalt metal corresponds to approximately 7 m 3 Cobalt chloride solution, i.e., the production of 7m 3 Cobalt chloride solution will produce 31.5m 3 Wastewater.

[0058] Further, the nickel-cobalt-containing organic phase is washed and back-extracted, allowing the metal ions loaded in the organic phase to be transferred back to the aqueous phase, resulting in a nickel-cobalt binary solution. Specifically, washing with a 0.125 mol / L-0.175 mol / L sulfuric acid solution can be used to wash the Mg in the organic phase into the aqueous phase, avoiding excessive Mg impurities in the nickel-cobalt sulfate binary solution. Back-extraction can be performed using a sulfuric acid solution with a concentration of 0.7 mol / L-0.8 mol / L, such as 0.70 mol / L, 0.73 mol / L, 0.75 mol / L, 0.78 mol / L, or 0.80 mol / L. This concentration range of sulfuric acid is beneficial for the complete back-extraction of nickel and cobalt, improving the recovery rate of nickel and cobalt.

[0059] It should be added that the process provided in this embodiment of the invention has the characteristics of simple operation, high production efficiency, and short process. Compared with other methods for treating cobalt extraction residue (generated in the P507 cobalt extraction stage), it can effectively reduce production costs. The entire process provided in this embodiment of the invention is carried out under normal pressure, without the need for temperature control, which is conducive to industrial production.

[0060] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0061] It should be noted that the crude cobalt sulfate solution processed in the following examples and comparative examples came from the leaching workshop and was obtained by leaching with a mixture of concentrated sulfuric acid solution with a mass fraction of 98% and cobalt hydroxide powder. The composition of the crude cobalt sulfate solution is shown in Table 1.

[0062] Example 1

[0063] This embodiment provides a method for treating nickel-cobalt sulfate-containing wastewater, the steps of which are as follows:

[0064] (1) Wastewater reuse stage: Nickel-cobalt sulfate wastewater (from the cobalt extraction residue in step (3)) is mixed with crude cobalt sulfate solution, and the Co concentration in the cobalt sulfate dilution sent to the extraction workshop is controlled to be 60 g / L. When the Mg in the cobalt extraction residue obtained in step (3) is ≥5 g / L, reuse is temporarily stopped, and reuse continues when Mg is ≤4 g / L.

[0065] (2) P204 extraction stage: P204 extractant is mixed with 260# sulfonated kerosene at a volume ratio of 1:4 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution by mass and saponified. The saponification rate is controlled at 40%. After saponification, the first extraction reagent is obtained. The first extraction reagent and the cobalt sulfate dilution obtained in step (1) are mixed at a volume ratio of 1:1 for extraction. The raffinate is then extracted into the P507 cobalt extraction stage.

[0066] (3) P507 cobalt extraction stage: P507 extractant and 260# sulfonated kerosene are mixed at a volume ratio of 1:3 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution for saponification, and the saponification rate is controlled at 55%. After saponification, a second extraction reagent is obtained. The second extraction reagent is mixed with the raffinate obtained in step (2) after removing Ca and Mn at a volume ratio of 1:0.15 for extraction reaction. The separated cobalt extraction raffinate is a sulfate wastewater containing nickel and cobalt. Part of this wastewater is sent to the subsequent HBL116 nickel extraction process, and part is returned to step (1). The volume ratio of the cobalt extraction raffinate sent to steps (1) and (4) is 1:4.

[0067] (4) HBL116 nickel extraction stage: HBL116 extractant and 260# sulfonated kerosene are mixed at a volume ratio of 1:4 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution for saponification, and the saponification rate is controlled at 50%. After saponification, the third extraction reagent is obtained. The third extraction reagent and the nickel-cobalt sulfate wastewater obtained in step (3) are mixed at a volume ratio of 1:1.8 for extraction reaction to recover nickel-cobalt metal. After the organic phase is extracted with nickel-cobalt, it is washed with 0.15 mol / L sulfuric acid solution. Then, in the back-extraction section, the loaded organic phase is back-extracted with a sulfuric acid solution with a hydrogen ion concentration of 1.5 mol / L (i.e., the concentration of sulfuric acid solution is 0.75 mol / L) to obtain a nickel-cobalt sulfate binary solution (the volume ratio of organic phase to back-extraction acid is controlled at 15:1, the same below). The obtained raffinate is sent to the water treatment workshop for evaporation treatment.

[0068] Tests showed that the nickel and cobalt concentrations in the nickel-cobalt-containing wastewater obtained in step (3) of this embodiment were 1.31 g / L and 0.15 g / L, respectively. The nickel-cobalt sulfate binary solution prepared in step (4) of this embodiment had a Co concentration of 2.17 g / L, a Ni concentration of 42.69 g / L, and a Mg concentration of 0.015 g / L. The raffinate wastewater generated in step (4) was 34.31 m³. 3 / gold ton cobalt, of which the cobalt and nickel contents are 3.94mg / L and 2.81mg / L respectively.

[0069] Example 2

[0070] This embodiment provides a method for treating nickel-cobalt sulfate-containing wastewater, the steps of which are as follows:

[0071] (1) Wastewater reuse stage: Nickel-cobalt sulfate wastewater (from the cobalt extraction residue in step (3)) is mixed with crude cobalt sulfate solution, and the Co concentration in the cobalt sulfate dilution sent to the extraction workshop is controlled to be 60 g / L. When the Mg in the cobalt extraction residue obtained in step (3) is ≥5 g / L, reuse is temporarily stopped, and reuse continues when Mg is ≤4 g / L.

[0072] (2) P204 extraction stage: P204 extractant is mixed with 260# sulfonated kerosene at a volume ratio of 1:4 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution by mass and saponified. The saponification rate is controlled at 40%. After saponification, the first extraction reagent is obtained. The first extraction reagent is mixed with the cobalt sulfate dilution obtained in step (1) at a volume ratio of 1:1 for extraction. The raffinate is then extracted into the P507 cobalt extraction stage.

[0073] (3) P507 cobalt extraction stage: P507 extractant and 260# sulfonated kerosene are mixed at a volume ratio of 1:3 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution by mass and saponified. The saponification rate is controlled at 55%. After saponification, a second extraction reagent is obtained. The second extraction reagent is mixed with the raffinate obtained in step (2) after removing Ca and Mn at a volume ratio of 1:0.15 for extraction reaction. The cobalt extraction residue obtained is a sulfate wastewater containing nickel and cobalt. Part of this wastewater is sent to the subsequent HBL116 nickel extraction process, and part is returned to step (1). The volume ratio of the cobalt extraction residue sent to steps (1) and (4) is 1:5.

[0074] (4) HBL116 nickel extraction stage: HBL116 extractant and 260# sulfonated kerosene are mixed at a volume ratio of 1:4 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution for saponification, and the saponification rate is controlled at 50%. After saponification, the third extraction reagent is obtained. The third extraction reagent and the nickel-cobalt sulfate wastewater obtained in step (3) are mixed at a volume ratio of 1:1.8 for extraction reaction to recover nickel-cobalt metal. After the organic phase is extracted with nickel-cobalt, it is washed with 0.15 mol / L sulfuric acid solution. Then, in the back-extraction section, the loaded organic phase is back-extracted with a sulfuric acid solution with a hydrogen ion concentration of 1.5 mol / L (i.e., the concentration of sulfuric acid solution is 0.75 mol / L) to obtain a nickel-cobalt sulfate binary solution. The obtained raffinate is sent to the water treatment workshop for evaporation treatment.

[0075] Tests showed that the nickel and cobalt content in the nickel-cobalt-containing wastewater obtained in step (3) of this embodiment was 1.21 g / L and 0.11 g / L, respectively. The nickel-cobalt sulfate binary solution prepared in step (4) of this embodiment contained 1.14 g / L Co, 43.85 g / L Ni, and 0.002 g / L Mg. The raffinate wastewater generated in step (4) was 31.10 m³. 3 / gold ton cobalt, of which the cobalt and nickel contents are 2.57mg / L and 2.21mg / L respectively.

[0076] Example 3

[0077] This embodiment provides a method for treating nickel-cobalt sulfate-containing wastewater, the steps of which are as follows:

[0078] (1) Wastewater reuse stage: Nickel-cobalt sulfate wastewater (from the cobalt extraction residue in step (3)) is mixed with crude cobalt sulfate solution, and the Co concentration in the cobalt sulfate dilution sent to the extraction workshop is controlled to be 60 g / L. When the Mg in the cobalt extraction residue obtained in step (3) is ≥5 g / L, reuse is temporarily stopped, and reuse continues when Mg is ≤4 g / L.

[0079] (2) P204 extraction stage: P204 extractant is mixed with 260# sulfonated kerosene at a volume ratio of 1:4 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution by mass and saponified. The saponification rate is controlled at 40%. After saponification, the first extraction reagent is obtained. The first extraction reagent and the cobalt sulfate dilution obtained in step (1) are mixed at a volume ratio of 1:1 for extraction. The raffinate is then extracted into the P507 cobalt extraction stage.

[0080] (3) P507 cobalt extraction stage: P507 extractant and 260# sulfonated kerosene are mixed at a volume ratio of 1:3 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution for saponification, and the saponification rate is controlled at 55%. After saponification, a second extraction reagent is obtained. The second extraction reagent is mixed with the raffinate obtained in step (2) after removing Ca and Mn at a volume ratio of 1:0.15 for extraction reaction. The separated cobalt extraction raffinate is a sulfate wastewater containing nickel and cobalt. Part of this wastewater is sent to the subsequent HBL116 nickel extraction process, and part is returned to step (1). The volume ratio of the cobalt extraction raffinate sent to steps (1) and (4) is 1:6.

[0081] (4) HBL116 nickel extraction stage: HBL116 extractant and 260# sulfonated kerosene are mixed at a volume ratio of 1:4 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution for saponification, and the saponification rate is controlled at 50%. After saponification, the third extraction reagent is obtained. The third extraction reagent and the nickel-cobalt sulfate wastewater obtained in step (3) are mixed at a volume ratio of 1:1.8 for extraction reaction to recover nickel-cobalt metal. After the organic phase is extracted with nickel-cobalt, it is washed with 0.15 mol / L sulfuric acid solution. Then, in the back-extraction section, the loaded organic phase is back-extracted with a sulfuric acid solution with a hydrogen ion concentration of 1.5 mol / L (i.e., the concentration of sulfuric acid solution is 0.75 mol / L) to obtain a nickel-cobalt sulfate binary solution. The obtained raffinate is sent to the water treatment workshop for evaporation treatment.

[0082] Tests showed that the nickel and cobalt concentrations in the nickel-cobalt-containing wastewater obtained in step (3) of this embodiment were 1.38 g / L and 0.16 g / L, respectively. The nickel-cobalt sulfate binary solution prepared in step (4) of this embodiment had a Co concentration of 2.14 g / L, a Ni concentration of 41.59 g / L, and a Mg concentration of 0.004 g / L. The raffinate wastewater generated in step (4) was 34.85 m³. 3 / gold ton cobalt, of which the cobalt and nickel contents are 3.11mg / L and 3.27mg / L respectively.

[0083] Example 4

[0084] The only difference from Example 1 is that the volume ratio of the cobalt extraction residue to processes (1) and (4) in step (3) is 1:3.

[0085] Tests showed that the nickel and cobalt concentrations in the nickel-cobalt-containing wastewater obtained in step (3) of this embodiment were 1.36 g / L and 0.15 g / L, respectively. The nickel-cobalt sulfate binary solution prepared in step (4) of this embodiment had a Co concentration of 2.23 g / L, a Ni concentration of 42.14 g / L, and a Mg concentration of 0.009 g / L. The raffinate wastewater generated in step (4) was 33.55 m³. 3 / gold ton cobalt, of which the cobalt and nickel contents are 3.55mg / L and 3.74mg / L respectively.

[0086] Example 5

[0087] The only difference from Example 1 is that the volume ratio of the cobalt extraction residue to processes (1) and (4) in step (3) is 1:7.

[0088] Tests showed that the nickel and cobalt concentrations in the nickel-cobalt-containing wastewater obtained in step (3) of this embodiment were 1.27 g / L and 0.13 g / L, respectively. The nickel-cobalt sulfate binary solution prepared in step (4) of this embodiment had a Co concentration of 2.19 g / L, a Ni concentration of 41.58 g / L, and a Mg concentration of 0.007 g / L. The raffinate wastewater generated in step (4) was 36.12 m³. 3 / gold ton cobalt, of which the cobalt and nickel content is 3.45mg / L and 3.18mg / L respectively.

[0089] Example 6

[0090] The only difference from Example 1 is that the amount of extractant and the ratio of the extractant to the pre-extraction liquid are different in steps (2)-(4). Specifically, in step (2), P204 extractant is mixed with 260# sulfonated kerosene at a volume ratio of 1:3.5, and the volume ratio of the first extractant to the cobalt sulfate dilution is 1:1.1; in step (3), P507 extractant is mixed with 260# sulfonated kerosene at a volume ratio of 1:2.5, and the second extractant is mixed with the raffinate obtained in step (2) after removing Ca and Mn at a volume ratio of 1:0.20; in step (4), HBL116 extractant is mixed with 260# sulfonated kerosene at a volume ratio of 1:3.5, and the third extractant is mixed with the nickel-cobalt sulfate wastewater obtained in step (3) at a volume ratio of 1:2.2.

[0091] The test showed that the amount of raffinate wastewater generated in step (4) was 33.75 m³. 3 / gold ton cobalt, of which the cobalt and nickel contents are 4.23 mg / L and 3.59 mg / L respectively. Compared with Example 1, Example 6 increases the proportion of extractant in the organic phase, thereby improving the ability of the organic phase to extract the target metal. At the same time, it increases the flow rate of the pre-extraction liquid, resulting in a higher proportion of the target metal in the organic phase and a decrease in wastewater volume compared with Example 1.

[0092] Example 7

[0093] The only difference from Example 1 is that the amount of extractant and the ratio of the extractant to the pre-extraction liquid are different in steps (2)-(4). Specifically, in step (2), P204 extractant is mixed with 260# sulfonated kerosene at a volume ratio of 1:4.5, and the volume ratio of the first extractant to the cobalt sulfate dilution is 1:1.1; in step (3), P507 extractant is mixed with 260# sulfonated kerosene at a volume ratio of 1:3.5, and the second extractant is mixed with the raffinate obtained in step (2) after removing Ca and Mn at a volume ratio of 1:0.2; in step (4), HBL116 extractant is mixed with 260# sulfonated kerosene at a volume ratio of 1:4.5, and the third extractant is mixed with the nickel-cobalt sulfate wastewater obtained in step (3) at a volume ratio of 1:2.2.

[0094] The test showed that the amount of raffinate wastewater generated in step (4) was 34.51 m³. 3 / gold ton cobalt, of which the cobalt and nickel contents are 3.65mg / L and 3.21mg / L respectively. Compared with Example 1, Example 7 reduced the proportion of extractant in the organic phase, resulting in a decrease in the ability of the organic phase to extract the target metal compared with Example 1. At the same time, it increased the flow rate of the pre-extraction liquid, leading to an increase in wastewater volume compared with Example 1.

[0095] Comparative Example 1

[0096] This comparative example provides a method for treating nickel-cobalt sulfate wastewater. The main difference between this method and Example 3 is that step (4) uses a different extractant. The steps are as follows:

[0097] (1) Wastewater reuse stage: Nickel-cobalt sulfate wastewater (from the cobalt extraction residue in step (3)) is mixed with crude cobalt sulfate solution. The Co concentration in the cobalt sulfate dilution sent to the extraction workshop is controlled to be 60 g / L. The crude cobalt sulfate solution and nickel-cobalt wastewater are mixed at a volume ratio of 3.3:1. Reuse is temporarily stopped when Mg ≥ 5 g / L in the cobalt extraction residue obtained in step (3), and reuse continues when Mg ≤ 4 g / L.

[0098] (2) P204 extraction stage: P204 extractant is mixed with 260# sulfonated kerosene at a volume ratio of 1:4 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution by mass and saponified. The saponification rate is controlled at 40%. After saponification, the first extraction reagent is obtained. The first extraction reagent and the cobalt sulfate dilution obtained in step (1) are mixed at a volume ratio of 1:1 for extraction. The raffinate is then extracted into the P507 cobalt extraction stage.

[0099] (3) P507 cobalt extraction stage: P507 extractant and 260# sulfonated kerosene are mixed at a volume ratio of 1:3 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution by mass and saponified. The saponification rate is controlled at 55%. After saponification, a second extraction reagent is obtained. The second extraction reagent is mixed with the raffinate obtained in step (2) after removing Ca and Mn at a volume ratio of 1:0.15 for extraction reaction. The separated cobalt extraction raffinate is a sulfate wastewater containing nickel and cobalt. Part of this wastewater is sent to the subsequent P204 nickel and cobalt extraction stage, and part is returned to step (1). The volume ratio of the cobalt extraction raffinate sent to steps (1) and (4) is 1:6.

[0100] (4) P204 nickel-cobalt extraction stage: P204 extractant and 260# sulfonated kerosene are mixed at a volume ratio of 1:4 to obtain an organic phase. The organic phase is mixed with a 20% ammonia solution for saponification, and the saponification rate is controlled at 50%. After saponification, the third extraction reagent is obtained. The third extraction reagent and the nickel-cobalt-containing sulfate wastewater obtained in step (3) are mixed at a volume ratio of 1:1.8 for extraction reaction to recover nickel-cobalt metal. After the organic phase is extracted with nickel-cobalt, it is washed with 0.25 mol / L sulfuric acid solution. Then, in the back-extraction section, the loaded organic phase is back-extracted with a sulfuric acid solution with a hydrogen ion concentration of 1.5 mol / L (i.e., the concentration of sulfuric acid solution is 0.75 mol / L) to obtain a nickel-cobalt sulfate binary solution. The obtained raffinate is sent to the water treatment workshop for evaporation treatment.

[0101] Tests showed that the nickel and cobalt concentrations in the nickel-cobalt-containing wastewater obtained in step (3) of this comparative example were 1.27 g / L and 0.18 g / L, respectively. The nickel-cobalt sulfate binary solution prepared in step (4) of this embodiment had a Co concentration of 2.06 g / L, a Ni concentration of 37.56 g / L, and a Mg concentration of 0.127 g / L. The raffinate wastewater generated by the P204 nickel-cobalt extraction line was 38.67 m³. 3 / Golden Cobalt, the nickel and cobalt contents in the raffinate were 15.29 mg / L and 14.36 mg / L, respectively.

[0102] It should be noted that in this comparative example, the pH of the cobalt extraction residue from P507 is approximately 4.0. Under these conditions, the extraction rates of Ni, Co, and Mg are similar. The Mg metal content in the organic phase of the extraction section is significantly higher compared to the HBL116 extractant, requiring a large amount of dilute sulfuric acid to remove the Mg metal in the washing section. The volume of the raffinate is the sum of the volume of the pre-extraction liquid and the volume of the acid washing liquid. This results in a significant increase in wastewater volume for the P204 extractant compared to the HBL116 extractant under single-variable conditions. Furthermore, because the extraction rates of Ni, Co, and Mg are similar under the P204 extractant condition, their back-extraction rates are also similar. This means that the Mg removal effect in the washing section cannot reach the level of HBL116, failing to guarantee a low Mg content in the nickel-cobalt sulfate back-extraction solution, and also failing to guarantee low Ni and Co content in the wastewater.

[0103] Table 1. Metal content in crude cobalt sulfate solution before dilution

[0104] Example 1 90.81 3.63 0.598 4.37 9.78 Example 2 89.57 3.53 0.614 4.12 9.16 Example 3 86.15 3.77 0.601 3.98 8.97

[0105] A comparison of Examples 1-3 shows that when the cobalt extraction residue obtained in step (3) is returned to step (1) at a ratio of 1:5 (i.e. Example 2), the amount of ammonium magnesium sulfate wastewater produced to produce 1 ton of cobalt is less than that produced at a ratio of 1:4 (Example 1) and 1:6 (Example 3), and the magnesium metal content in the produced nickel cobalt sulfate solution is also lower.

[0106] Comparing Example 3 and Comparative Example 1, it can be seen that the extraction rates of P204 extractant for magnesium and nickel-cobalt are similar. If P204 extractant is used to treat the cobalt extraction residue, the amount of wastewater produced per ton of cobalt will increase significantly, and the magnesium impurity in the nickel-cobalt sulfate binary solution will be too high.

[0107] As can be seen, the HBL116 extractant in this embodiment of the invention can treat the nickel-cobalt sulfate wastewater generated in the P507 cobalt extraction process. If all the cobalt extraction residue were to enter the HBL116 nickel extraction process, not only would the wastewater volume be large, but it would also increase the pressure on the wastewater treatment system, increase auxiliary material consumption, and raise production costs such as labor costs. This invention, by reusing the nickel-cobalt sulfate wastewater generated in the P507 cobalt extraction process, can efficiently recover the nickel and cobalt metal, ultimately yielding a high-purity nickel-cobalt binary sulfate solution.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating nickel-cobalt sulfate wastewater, characterized in that, include: Wastewater reuse stage: Nickel-cobalt sulfate wastewater and crude cobalt sulfate solution are mixed to obtain cobalt sulfate diluted solution; P204 extraction stage: The cobalt sulfate dilution solution is extracted and impurities are removed using P204 extractant. The impurities enter the organic phase and are separated to obtain the first raffinate. P507 cobalt extraction stage: The first raffinate is extracted using P507 extractant, and the second raffinate obtained after separation is nickel-cobalt sulfate wastewater; part of the second raffinate is returned to the wastewater reuse stage, and the other part enters the HBL116 nickel extraction stage; HBL116 nickel extraction stage: The second raffinate is extracted using HBL116 extractant, and after separation, a third raffinate and a nickel-cobalt-containing organic phase are obtained. The third raffinate is discharged as wastewater. When the magnesium content in the second raffinate is greater than or equal to 5 g / L, the return to the wastewater reuse stage is stopped; when the magnesium content in the second raffinate is less than or equal to 4 g / L, a portion of the second raffinate continues to be returned to the wastewater reuse stage. The ratio of the volume of the second raffinate returned to the wastewater reuse stage to the volume entering the HBL116 nickel extraction stage is 1:(4.3-5.8).

2. The method for treating nickel-cobalt sulfate wastewater according to claim 1, characterized in that, By adjusting the amount of nickel-cobalt sulfate wastewater added, the cobalt content in the cobalt sulfate dilution is made to be between 60 g / L and 65 g / L; And / or, the cobalt content in the crude cobalt sulfate solution is 85g / L-90g / L.

3. The method for treating nickel-cobalt sulfate wastewater according to claim 1, characterized in that, The P204 extraction stage includes: mixing and saponifying the P204 extractant and the first diluent to obtain the first extraction reagent, and then mixing and extracting the first extraction reagent with the cobalt sulfate diluent.

4. The method for treating nickel-cobalt sulfate wastewater according to claim 3, characterized in that, The volume ratio of the P204 extractant to the first diluent is 1:(3.5-4.5).

5. The method for treating nickel-cobalt sulfate wastewater according to claim 3, characterized in that, The volume ratio of the first extraction reagent to the cobalt sulfate dilution is 1:(1.0-1.1).

6. The method for treating nickel-cobalt sulfate wastewater according to claim 3, characterized in that, The first diluent is sulfonated kerosene.

7. The method for treating nickel-cobalt sulfate wastewater according to claim 1, characterized in that, The P507 cobalt extraction stage includes: mixing and saponifying the P507 extractant and the second diluent to obtain the second extractant, and then mixing and extracting the second extractant with the first raffinate.

8. The method for treating nickel-cobalt sulfate wastewater according to claim 7, characterized in that, The volume ratio of the P507 extractant to the second diluent is 1:(2.5-3.5).

9. The method for treating nickel-cobalt sulfate wastewater according to claim 7, characterized in that, The volume ratio of the second extraction reagent to the first raffinate is 1:(0.15-0.20).

10. The method for treating nickel-cobalt sulfate wastewater according to claim 7, characterized in that, The second diluent is sulfonated kerosene.

11. The method for treating nickel-cobalt sulfate wastewater according to claim 1, characterized in that, The HBL116 nickel extraction stage includes: mixing HBL116 extractant and a third diluent and saponifying them to obtain a third extraction reagent; mixing the third extraction reagent with the second raffinate for extraction; and separating the raffinate to obtain a third raffinate and a nickel-cobalt-containing organic phase.

12. The method for treating nickel-cobalt sulfate wastewater according to claim 11, characterized in that, The volume ratio of the HBL116 extractant to the third diluent is 1:(3.5-4.5). And / or, the volume ratio of the third extraction reagent to the second raffinate is 1:(1.8-2.2). And / or, the third diluent is sulfonated kerosene.

13. The method for treating nickel-cobalt sulfate wastewater according to claim 11, characterized in that, The nickel-cobalt-containing organic phase is washed and back-extracted to obtain a nickel-cobalt-containing binary solution; And / or, the third raffinate is subjected to evaporation treatment.

14. The method for treating nickel-cobalt sulfate wastewater according to claim 13, characterized in that, Back-extraction was performed using a sulfuric acid solution with a concentration of 0.7 mol / L to 0.8 mol / L.

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