Method for recovering valuable metals from magnesium-containing wastewater

Abstract

The application discloses a valuable metal recovery method in magnesium-containing wastewater and belongs to the technical field of metal resource recycling. The method comprises the following steps: mixing the first magnesium-containing wastewater with the first extractant for extraction, and collecting the first raffinate phase; mixing the first raffinate phase with the second extractant for multi-stage extraction, collecting the first extraction phase of the first preset stage number, collecting the second extraction phase of the second preset stage number and a lithium salt solution; performing multi-stage stripping on the second extraction phase, collecting the first stripping solution of the third preset stage number; mixing the first stripping solution with the third extractant for extraction, collecting the second extraction phase and a nickel salt solution; taking the first extraction phase as a cobalt liquid, performing stripping on the cobalt liquid to obtain a cobalt salt solution; performing stripping on the second extraction phase to obtain a second stripping solution, and taking the second stripping solution as a magnesium liquid, performing pH value adjustment on the magnesium liquid to obtain a magnesium salt solution. The application at least partially solves the technical problem that the product quality of valuable metal recovery in magnesium-containing wastewater is poor.

Description

Technical Field

[0001] This application relates to the field of metal resource recycling technology, and in particular to a method for recovering valuable metals from magnesium-containing wastewater. Background Technology

[0002] Magnesium is an important raw material in modern industry with a variety of uses. The metallurgical raw materials used in conventional nickel-cobalt-manganese-lithium hydrometallurgical industries include: waste lithium battery crushed powder, electrode crushed powder, processed nickel-cobalt hydroxide, and waste containing nickel and cobalt. All of these raw materials contain magnesium, and the production of nickel-cobalt-manganese-lithium from these materials will generate magnesium-containing wastewater. This magnesium-containing wastewater may also contain valuable metals such as nickel and cobalt. Due to the high economic value of magnesium, nickel, and cobalt, such magnesium-containing wastewater has high recycling value.

[0003] In conventional technologies, the recovery of valuable metals from wastewater mostly uses the sulfide precipitation method. However, for magnesium-containing wastewater, the sulfide precipitation method easily carries magnesium into the precipitate residue during the formation of nickel sulfide and cobalt sulfide precipitates, resulting in low purity and poor quality of the obtained products.

[0004] The above content is only used to help understand the technical solution of this application and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main objective of this application is to provide a method for recovering valuable metals from magnesium-containing wastewater, aiming to solve the technical problem of poor product quality in conventional magnesium-containing wastewater recovery.

[0006] To achieve the above objectives, this application provides a method for recovering valuable metals from magnesium-containing wastewater, the method comprising the following steps:

[0007] The first magnesium-containing wastewater is mixed with the first extractant for extraction, and the first raffinate is collected.

[0008] The first raffinate phase is mixed with the second extractant for multi-stage extraction. The first extract phase of the first preset stage is collected, and the second extract phase of the second preset stage and the lithium salt solution are collected, wherein the first preset stage is less than the second preset stage.

[0009] The second extraction phase is subjected to multi-stage back-extraction, and the first back-extraction liquid of the third preset stage is collected;

[0010] The first back-extraction solution is mixed with the third extractant for extraction, and the second extraction phase and nickel salt solution are collected.

[0011] The first extraction phase is used as the cobalt solution, and the cobalt solution is back-extracted to obtain a cobalt salt solution;

[0012] The second extraction phase is back-extracted to obtain a second back-extract, which is then used as a magnesium solution. The pH of the magnesium solution is adjusted to obtain a magnesium salt solution.

[0013] Optionally, the method further includes:

[0014] The second magnesium-containing wastewater is mixed with the first extractant for extraction, and the second raffinate phase is collected.

[0015] The second raffinate phase is used as the first solution, and the first solution is mixed with the second extractant to perform multi-stage extraction. The third extract phase of the fourth preset stage is collected, and the fourth extract phase of the fifth preset stage is collected, wherein the fourth preset stage is less than the fifth preset stage.

[0016] The third extraction phase is used as the cobalt solution;

[0017] The fourth extraction phase is back-extracted to obtain a third back-extract, which is then used as the magnesium solution.

[0018] Optionally, after the step of collecting the first back-extraction solution of the third preset stage, the method further includes:

[0019] Collect the fourth back-extraction solution of the sixth preset stage, wherein the sixth preset stage is greater than the third preset stage;

[0020] The fourth back-extraction solution is used as the first solution.

[0021] Optionally, the method further includes:

[0022] The method further includes:

[0023] The third magnesium-containing wastewater was mixed with the first extractant for extraction, and the third raffinate was collected.

[0024] The third raffinate phase is mixed with the second extractant for extraction, and the fifth extract phase and the fourth raffinate phase are collected.

[0025] The fifth extraction phase is back-extracted to obtain a fourth back-extract, and the fourth back-extract is used as the first solution.

[0026] The fourth raffinate phase is mixed with the third extractant and extracted, and the sixth extract phase and nickel salt solution are collected.

[0027] The sixth extraction phase is back-extracted to obtain a fifth back-extract, which is then used as the magnesium solution.

[0028] Optionally, the first magnesium-containing wastewater includes: black powder leachate;

[0029] And / or, the second magnesium-containing wastewater includes: cobalt intermediate leachate;

[0030] And / or, the third magnesium-containing wastewater includes: nickel intermediate leachate.

[0031] Optionally, the first extractant includes: P204;

[0032] And / or, the second extractant includes: P507;

[0033] And / or, the third extractant includes: Cyanex272.

[0034] Optionally, the volume fraction of the first extractant is 20-30%;

[0035] And / or, the volume fraction of the second extractant is 20-30%;

[0036] And / or, the volume fraction of the third extractant is 10-20%.

[0037] Optionally, the first extractant is a saponified extractant, and the saponification rate of the first extractant is 30-60%.

[0038] And / or, the second extractant is a saponified extractant, and the saponification rate of the second extractant is 30-60%;

[0039] And / or, the third extractant is a saponified extractant, and the saponification rate of the third extractant is 20-50%.

[0040] Optionally, the step of adjusting the pH of the magnesium solution includes:

[0041] An alkaline solution is added to the magnesium solution to adjust the pH value, wherein the alkaline solution includes sodium sulfide, sodium carbonate, and sodium hydroxide.

[0042] Optionally, after the step of collecting the second extraction phase and lithium salt solution of the second preset stage, the method further includes:

[0043] The lithium salt solution is subjected to lithium precipitation treatment to obtain lithium salt and lithium precipitation mother liquor;

[0044] The lithium precipitation mother liquor is used as the alkaline solution.

[0045] This application discloses a method for recovering valuable metals from magnesium-containing wastewater. The method involves mixing a first magnesium-containing wastewater with a first extractant for extraction. Utilizing the difference in extraction capabilities of the first extractant for different metals, impurities in the first magnesium-containing wastewater are removed, yielding a first raffinate phase. This first raffinate phase is then mixed with a second extractant for multi-stage extraction. Utilizing the difference in extraction capabilities of the second extractant for different metals, a first-stage extractant phase rich in cobalt is collected, along with a second-stage extractant phase rich in nickel and magnesium, and the corresponding raffinate phase (i.e., lithium salt solution), thus recovering lithium. The second extractant phase is then further processed... The process involves multi-stage back-extraction, collecting the first back-extraction liquid from a third preset stage; then mixing the first back-extraction liquid with a third extractant for extraction, collecting a magnesium-rich second extract phase and a nickel salt solution to recover nickel; subsequently, using the first extract phase as a cobalt solution, back-extracting the cobalt solution to obtain a cobalt salt solution, thus recovering cobalt; then, back-extracting the second extract phase to obtain a second back-extraction liquid, which is then used as a magnesium solution. The pH of the magnesium solution is adjusted to obtain a magnesium salt solution, causing the small amounts of nickel and cobalt contained in the magnesium solution to transform into nickel-cobalt slag precipitate. After solid-liquid separation, a magnesium salt solution is obtained, thus recovering magnesium. By utilizing the differences in the extraction sequence of different metal elements by different extractants, efficient recovery of lithium, nickel, cobalt, and magnesium elements from magnesium-containing wastewater is achieved. The recovery process is simple and can effectively separate each element, effectively improving the purity and quality of the recovered metal products. Attached Figure Description

[0046] Figure 1 This is a schematic flowchart of a method for recovering valuable metals from magnesium-containing wastewater according to an embodiment of this application.

[0047] Figure 2 This is a process flow diagram of the method for recovering valuable metals from magnesium-containing wastewater involved in the embodiments of this application;

[0048] Figure 3 This is a graph showing the relationship between the metal extraction rate and pH value of P507 involved in the embodiments of this application.

[0049] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application 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.

[0051] Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that simultaneously satisfies A and B. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0052] The first aspect of this application provides a method for recovering valuable metals from magnesium-containing wastewater, referring to... Figure 1 and 2 Methods for recovering valuable metals from magnesium-containing wastewater include:

[0053] Step S10: Mix the first magnesium-containing wastewater with the first extractant for extraction, and collect the first raffinate phase;

[0054] In one feasible embodiment, before recovering valuable metals, impurities in the first magnesium-containing wastewater need to be removed. The first magnesium-containing wastewater is then mixed with a first extractant, allowing the impurities in the first magnesium-containing wastewater to enter the organic phase (extract phase) of the first extractant. The first raffinate phase is then collected through separation. The corresponding extract phase contains manganese and other impurities, which, after impurity removal, can be used to further prepare manganese salts.

[0055] Optionally, the first magnesium-containing wastewater includes: black powder leachate. Black powder is waste lithium battery black powder or electrode powder from lithium batteries; that is, a black powder containing metals such as nickel, cobalt, manganese, copper, iron, aluminum, and lithium, as well as carbon powder, obtained after processes such as dismantling, crushing, screening, pyrolysis, and sorting. This powder is typically used for the recovery of valuable metals, such as nickel, cobalt, manganese, and lithium. For example, the black powder is acid-leached to obtain a black powder leachate.

[0056] Optionally, the first extractant includes P204. P204 refers to di(2-ethylhexyl)phosphoric acid, whose extraction order for metal ions is: Fe... 3+ >Zn 2+ >Ca 2+ >Al 3+ >Mn 2+ >Cu 2+ >Co 2+ >Ni 2+ >Mg 2+ Because P204 extracts nickel and cobalt later in the extraction sequence, its separation effect on these two substances is not ideal. However, P204 is effective at extracting Zn. 2+ Ca 2+ Cu2+ Fe 3+ It has a strong ability to remove impurities, so P204 was used as the extraction method for removing impurities before nickel-cobalt separation.

[0057] Optionally, the volume fraction of the first extractant is 20-30%. The first extractant is a mixture of pure extractant and solvent oil, wherein the volume fraction of di(2-ethylhexyl)phosphoric acid in the first extractant is 20-30%; for example, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0058] Optionally, the first extractant is a saponified extractant with a saponification rate of 30-60%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc. Before using the first extractant, it is saponified to stabilize its pH value and enhance its extraction capacity. Since the extractant's extraction capacity for various metals differs at different pH values, the saponification rate of the first extractant is determined to be 30-60% to ensure the purity of valuable metal recovery from magnesium-containing wastewater.

[0059] Optionally, the first magnesium-containing wastewater is mixed with the first extractant and subjected to 8-12 stages of countercurrent extraction and 8-10 stages of countercurrent washing to collect the first raffinate phase.

[0060] Step S20: Mix the first raffinate phase with the second extractant for multi-stage extraction, collect the first extract phase of the first preset stage, collect the second extract phase of the second preset stage and the lithium salt solution, wherein the first preset stage is less than the second preset stage;

[0061] In one feasible embodiment, after impurity removal, it is necessary to continue to recover valuable metals such as lithium, magnesium, nickel, and cobalt contained in the first raffinate phase. Then, the first raffinate phase is mixed with the second extractant for multi-stage extraction, and the first extract phase of the first preset stage rich in cobalt is collected. Then, the second extract phase of the second preset stage rich in nickel and magnesium and the corresponding raffinate phase (i.e., lithium salt solution) are collected. The first preset stage is less than the second preset stage.

[0062] Optionally, the second extractant includes: P507; P507 refers to 2-ethylhexyl phosphate, 2-ethylhexyl ester, see reference. Figure 3 Its extraction order for metal ions is: Fe 3+ >Zn 2+ >Cu 2+ ≈Mn 2+ ≈Ca 2+ >Co 2+ >Mg 2+ >Ni 2+Among them, the extraction curves of nickel and cobalt are far apart. Therefore, P507 has a higher separation coefficient for cobalt and nickel than P204 and can be used to separate cobalt and nickel.

[0063] Optionally, the volume fraction of the second extractant is 20-30%; the second extractant is a mixture of pure extractant and solvent oil, wherein the volume fraction of 2-ethylhexyl phosphate 2-ethylhexyl ester in the second extractant is 20-30%; for example, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0064] Optionally, the second extractant is a saponified extractant with a saponification rate of 30-60%; for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc. Before using the second extractant, it is saponified to stabilize its pH value and enhance its extraction capacity. Since the extractant's extraction capacity for various metals differs at different pH values, the saponification rate of the second extractant is determined to be 30-60% to ensure the purity of valuable metal recovery from magnesium-containing wastewater.

[0065] Optionally, the lithium salt solution can be evaporated and crystallized to obtain the lithium salt.

[0066] Optionally, the number of stages in a multi-stage extraction process can be 16-24.

[0067] In one feasible implementation, after step S20, which involves collecting the second extraction phase and lithium salt solution of the second preset stage, the method further includes:

[0068] Step S23: Perform lithium precipitation treatment on the lithium salt solution to obtain lithium salt and lithium precipitation mother liquor;

[0069] Step S24: Use the lithium precipitation mother liquor as the alkaline solution.

[0070] In one feasible embodiment, soluble carbonates are added to a lithium salt solution for lithium precipitation to obtain lithium salt and lithium precipitation mother liquor. The lithium precipitation mother liquor contains a large amount of unreacted carbonates, such as sodium carbonate. Conventionally, it needs to be acidified before it can be reused. In this application, the lithium precipitation mother liquor is used as an alkaline solution to adjust the pH of magnesium solution, thereby realizing the recycling of resources.

[0071] Step S30: Perform multi-stage back-extraction on the second extraction phase and collect the first back-extraction liquid of the third preset stage;

[0072] In one feasible embodiment, a second extraction phase rich in nickel and magnesium is subjected to multi-stage back-extraction, and a first back-extraction liquid rich in nickel at a third predetermined stage is collected.

[0073] Alternatively, the stripping agent can be sulfuric acid.

[0074] In one feasible embodiment, after step S30, which involves collecting the first back-extraction solution of the third preset stage, the method further includes:

[0075] Step S31: Collect the fourth back-extraction solution of the sixth preset stage, wherein the sixth preset stage is greater than the third preset stage;

[0076] In one feasible embodiment, when the second extraction phase is back-extracted, since the second extraction phase contains cobalt, magnesium and nickel, nickel is preferentially back-extracted to obtain a first back-extracting solution, and further back-extracting is performed until a sixth preset stage to obtain a fourth back-extracting solution rich in cobalt and magnesium.

[0077] Although the use of a second extractant in actual production can achieve complete extraction and separation of cobalt and magnesium, it is necessary to increase the saponification rate of the second extractant, which requires increasing the flow rate of liquid alkali. At this time, some nickel will be extracted, and a large amount of acid washing is required to wash the nickel off, resulting in the consumption of auxiliary materials. Therefore, this application uses a second extractant with a saponification rate of 30-60%, and introduces the cobalt and magnesium extracted simultaneously into the production line of the second magnesium-containing wastewater during extraction to achieve further extraction.

[0078] Step S32: Use the fourth back-extraction solution as the first solution.

[0079] In one feasible embodiment, since the fourth back-extraction solution contains cobalt and magnesium, in order to improve product purity, reduce process equipment, and lower process costs, the fourth back-extraction solution is used as the first solution, and is then extracted together with the second raffinate obtained based on the second magnesium-containing wastewater. This allows different magnesium-containing wastewater recovery processes to be combined to improve treatment efficiency and process costs, thereby achieving cost reduction and efficiency improvement.

[0080] Step S40: Mix the first back-extraction solution with the third extractant for extraction, and collect the second extract phase and the nickel salt solution;

[0081] In one feasible embodiment, the first back-extraction solution, which is rich in nickel, may also contain some magnesium. In order to improve the purity of the product, the first back-extraction solution is mixed with a third extractant for extraction, and the second extract phase and the corresponding raffinate phase (i.e., nickel salt solution) are collected.

[0082] Optionally, the third extractant includes: Cyanex 272; the main component of Cyanex 272 is bis(2,4,4-trimethylpentyl)phosphonic acid; under the same conditions, the separation coefficient of Cyanex 272 for nickel and cobalt is an order of magnitude higher than that of P507, wherein the cis of Cyanex 272 for metal ion extraction is: Fe 3+ >Zn 2+ >Cu 2+ >Mn 2+ >Co 2+ >Mg2+ >Ca 2+ Ni 2+ Under the same extraction conditions, magnesium is extracted preferentially, thus enabling efficient separation of nickel and magnesium. However, Cyanex 272 is more expensive than P204 and P507. Therefore, Cyanex 272 is used in the final nickel and magnesium recovery stage of valuable metal recovery from magnesium-containing wastewater to effectively reduce process costs while ensuring product purity.

[0083] Optionally, the volume fraction of the third extractant is 10-20%. The third extractant is a mixture of pure extractant and solvent oil, wherein the volume fraction of bis(2,4,4-trimethylpentyl)phosphonic acid in the third extractant is 10-20%; for example, 10%, 12%, 14%, 16%, 18%, 20%, etc.

[0084] Optionally, the third extractant is a saponified extractant with a saponification rate of 20-50%. For example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. Before using the third extractant, it is saponified to stabilize its pH value and enhance its extraction capacity. Since the extractant's extraction capacity for various metals differs at different pH values, the saponification rate of the third extractant is determined to be 20-50% to ensure the purity of valuable metal recovery from magnesium-containing wastewater.

[0085] Optionally, the obtained nickel salt solution can be subjected to degreasing, refining, or other treatments to obtain battery-grade nickel salts, such as battery-grade nickel sulfate.

[0086] Optionally, the third extractant is subjected to 4-6 stages of countercurrent soap conversion and then mixed with the first back-extraction solution for 8-10 stages of countercurrent extraction, followed by 4-8 stages of countercurrent washing, to collect the second extract phase and the nickel salt solution. The second extract phase is then back-extracted to obtain the second back-extraction solution, which is used as the magnesium solution.

[0087] Step S50: The first extraction phase is used as the cobalt solution, and the cobalt solution is back-extracted to obtain a cobalt salt solution;

[0088] In one feasible embodiment, the first extraction phase is rich in cobalt, and the first extraction phase is used as a cobalt solution, which is then back-extracted to obtain a cobalt salt solution.

[0089] Alternatively, sulfuric acid can be used for back-extraction.

[0090] Optionally, the obtained cobalt salt solution can be subjected to degreasing, refining, or other treatments to obtain battery-grade cobalt salts, such as battery-grade cobalt sulfate.

[0091] Step S60: The second extraction phase is back-extracted to obtain a second back-extracting solution, and the second back-extracting solution is used as a magnesium solution. The pH value of the magnesium solution is adjusted to obtain a magnesium salt solution.

[0092] In one feasible embodiment, the magnesium-rich second extraction phase is back-extracted to obtain a second back-extract; since the second back-extract is rich in magnesium, it is used as a magnesium solution, and the pH value of the magnesium solution is adjusted so that the small amount of nickel and cobalt elements contained in the magnesium solution are converted into nickel-cobalt slag precipitates. After solid-liquid separation, a magnesium salt solution is obtained, thereby realizing the recovery of magnesium elements.

[0093] Alternatively, sulfuric acid can be used for back-extraction.

[0094] In one feasible embodiment, step S60, the step of adjusting the pH value of the magnesium solution, includes:

[0095] Step S61: Add an alkaline solution to the magnesium solution to adjust the pH value, wherein the alkaline solution includes sodium sulfide, sodium carbonate, and sodium hydroxide.

[0096] In one feasible embodiment, an alkaline solution is added to the magnesium solution to adjust the pH value of the magnesium solution, so that the small amount of nickel and cobalt elements contained in the magnesium solution are converted into nickel-cobalt slag precipitates. After solid-liquid separation, a magnesium salt solution is obtained, thereby realizing the recovery of magnesium elements. The alkaline solution includes sodium sulfide, sodium carbonate, and sodium hydroxide.

[0097] In this embodiment, the first magnesium-containing wastewater is mixed with a first extractant for extraction. Utilizing the difference in extraction capabilities of the first extractant for different metals, impurities in the first magnesium-containing wastewater are removed, yielding a first raffinate phase. Then, the first raffinate phase is mixed with a second extractant for multi-stage extraction. Utilizing the difference in extraction capabilities of the second extractant for different metals, a first-stage extractant phase rich in cobalt is collected, a second-stage extractant phase rich in nickel and magnesium is collected, along with the corresponding raffinate phase (i.e., lithium salt solution), achieving lithium recovery. Finally, the second extractant phase is subjected to multi-stage back-extraction to collect... The first back-extraction liquid of the third preset stage is then mixed with a third extractant for extraction, collecting a magnesium-rich second extract phase and a nickel salt solution to recover nickel. The first extract phase is then used as a cobalt solution, and back-extracted to obtain a cobalt salt solution, recovering cobalt. The second extract phase is then back-extracted to obtain a second back-extraction liquid, which is used as a magnesium solution. The pH of the magnesium solution is adjusted to obtain a magnesium salt solution, causing the small amounts of nickel and cobalt in the magnesium solution to transform into nickel-cobalt slag precipitate. After solid-liquid separation, a magnesium salt solution is obtained, recovering magnesium. By utilizing the differences in the extraction order of different metal elements by different extractants, efficient recovery of lithium, nickel, cobalt, and magnesium elements from the first magnesium-containing wastewater is achieved. The recovery process is simple and can effectively separate each element, effectively improving the purity and quality of the recovered metal products.

[0098] Furthermore, based on the first embodiment described above, a second embodiment of the method for recovering valuable metals from magnesium-containing wastewater is proposed. In this embodiment, the method further includes:

[0099] Step A10: Mix the second magnesium-containing wastewater with the first extractant for extraction, and collect the second raffinate phase;

[0100] In one feasible embodiment, the production of nickel-cobalt-manganese-lithium materials from different raw materials can generate similar but somewhat different magnesium-containing wastewaters. In addition to the first magnesium-containing wastewater, a second magnesium-containing wastewater is also included. Before recovering valuable metals from the second magnesium-containing wastewater, impurities are removed. Then, the second magnesium-containing wastewater is mixed with a first extractant, allowing impurities in the second magnesium-containing wastewater to enter the organic phase (extract phase) of the first extractant. The second raffinate phase is then collected through separation. This extractant phase contains manganese and other impurities, which, after impurity removal, can be used to further prepare manganese salts.

[0101] Optionally, the second magnesium-containing wastewater includes: a cobalt intermediate leachate. Cobalt intermediates are raw materials for producing cobalt-based compounds, i.e., compounds containing cobalt ions, including cobalt salts, crude cobalt hydroxide, etc. For example, the cobalt intermediates are acid-leached to obtain a cobalt intermediate leachate.

[0102] Optionally, the first extractant includes P204. P204 refers to di(2-ethylhexyl)phosphoric acid, whose extraction order for metal ions is: Fe... 3+ >Zn 2+ >Ca 2+ >Al 3+ >Mn 2+ >Cu 2+ >Co 2+ >Ni 2+ >Mg 2+ Because P204 extracts nickel and cobalt later in the extraction sequence, its separation effect on these two substances is not ideal. However, P204 is effective at extracting Zn. 2+ Ca 2+ Cu 2+ Fe 3+ It has a strong ability to remove impurities, so P204 was used as the extraction method for removing impurities before nickel-cobalt separation.

[0103] Optionally, the volume fraction of the first extractant is 20-30%. The first extractant is a mixture of pure extractant and solvent oil, wherein the volume fraction of di(2-ethylhexyl)phosphoric acid in the first extractant is 20-30%; for example, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0104] Optionally, the first extractant is a saponified extractant with a saponification rate of 30-60%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc. Before using the first extractant, it is saponified to stabilize its pH value and enhance its extraction capacity. Since the extractant's extraction capacity for various metals differs at different pH values, the saponification rate of the first extractant is determined to be 30-60% to ensure the purity of valuable metal recovery from magnesium-containing wastewater.

[0105] Optionally, the second magnesium-containing wastewater is mixed with the first extractant and subjected to 8-12 stages of countercurrent extraction and 8-10 stages of countercurrent washing to collect the second raffinate phase.

[0106] Step A20: Use the second raffinate phase as the first solution, and mix the first solution with the second extractant to perform multi-stage extraction, collect the third extract phase of the fourth preset stage, and collect the fourth extract phase of the fifth preset stage, wherein the fourth preset stage is less than the fifth preset stage;

[0107] In one feasible embodiment, the second raffinate phase is used as the first solution. Since the first solution contains cobalt, magnesium and nickel, it is necessary to separate each metal through multi-stage extraction. Then, the first solution is mixed with the second extractant for multi-stage extraction. First, the third extraction phase of the fourth preset stage rich in cobalt is collected, and then the fourth extraction phase of the fifth preset stage rich in magnesium is collected.

[0108] Optionally, the second extractant includes: P507; P507 refers to 2-ethylhexyl phosphate, which can be used to separate cobalt and magnesium.

[0109] Optionally, the volume fraction of the second extractant is 20-30%; the second extractant is a mixture of pure extractant and solvent oil, wherein the volume fraction of 2-ethylhexyl phosphate 2-ethylhexyl ester in the second extractant is 20-30%; for example, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0110] Optionally, the second extractant is a saponified extractant with a saponification rate of 30-60%; for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc. Before using the second extractant, it is saponified to stabilize its pH value and enhance its extraction capacity. Since the extractant's extraction capacity for various metals differs at different pH values, the saponification rate of the second extractant is determined to be 30-60% to ensure the purity of valuable metal recovery from magnesium-containing wastewater.

[0111] Optionally, the number of stages in a multi-stage extraction process can be 16-24.

[0112] Step A30: The third extraction phase is used as the cobalt solution;

[0113] In one feasible embodiment, the third extraction phase is used as the cobalt solution, thereby performing cobalt back-extraction together with the first extraction phase obtained from the first coal-containing wastewater, achieving efficient integration of different recycling lines.

[0114] Step A40: The fourth extraction phase is back-extracted to obtain a third back-extract solution, which is then used as the magnesium solution.

[0115] In one feasible embodiment, the magnesium-rich fourth extraction phase is back-extracted to obtain a third back-extract. Since the third back-extract is rich in magnesium, it is then used together with the second back-extract obtained from the first magnesium-containing wastewater as a magnesium solution to achieve efficient recovery of magnesium.

[0116] In this embodiment, by using the same reagents (extractant and back-extraction agent, etc.) as the first magnesium-containing wastewater, the valuable metals in the second magnesium-containing wastewater are efficiently recovered. At the same time, the recovery production lines for the first and second magnesium-containing wastewaters are cleverly combined, which improves the recovery efficiency and effectively reduces the production cost, thus achieving cost reduction and efficiency improvement.

[0117] Furthermore, based on the first and / or second embodiments described above, a third embodiment of the method for recovering valuable metals from magnesium-containing wastewater is proposed. In this embodiment, the method further includes:

[0118] Step B10: Mix the third magnesium-containing wastewater with the first extractant for extraction, and collect the third raffinate phase;

[0119] In one feasible embodiment, the production of nickel-cobalt-manganese-lithium materials from different raw materials can generate similar but somewhat different magnesium-containing wastewaters. In addition to the first and second magnesium-containing wastewaters, a third magnesium-containing wastewater is also included. Before recovering valuable metals from the third magnesium-containing wastewater, it is treated to remove impurities. Then, the third magnesium-containing wastewater is mixed with a first extractant, allowing impurities in the third magnesium-containing wastewater to enter the organic phase (extract phase) of the first extractant. The third raffinate phase is then collected through separation. This corresponding extract phase contains manganese and other impurities, which, after impurity removal, can be used to further prepare manganese salts.

[0120] Optionally, the first, second, and third magnesium-containing wastewaters are magnesium-containing wastewaters generated from the purification of nickel-cobalt-manganese-lithium materials from different raw materials. The three have similar elemental compositions but also have subtle differences. Therefore, combining the production lines for recovering valuable metals from the above three magnesium-containing wastewaters can reduce the setup of process equipment and lower the overall process cost while ensuring product purity, thus achieving cost reduction and efficiency improvement.

[0121] Optionally, the third magnesium-containing wastewater includes: nickel intermediate leachate. The nickel intermediate is prepared by pressurized or atmospheric-pressure acid leaching of laterite nickel ore followed by precipitation with liquid alkali, lime, and magnesium oxide; its main components are basic sulfates of nickel, cobalt, and manganese. For example, the nickel intermediate is acid-leached to obtain the nickel intermediate leachate.

[0122] Optionally, the first extractant includes P204. P204 refers to di(2-ethylhexyl)phosphoric acid, whose extraction order for metal ions is: Fe... 3+ >Zn 2+ >Ca 2+ >Al 3+ >Mn 2+ >Cu 2+ >Co 2+ >Ni 2+ >Mg 2+Because P204 extracts nickel and cobalt later in the extraction sequence, its separation effect on these two substances is not ideal. However, P204 is effective at extracting Zn. 2+ Ca 2+ Cu 2+ Fe 3+ It has a strong ability to remove impurities, so P204 was used as the extraction method for removing impurities before nickel-cobalt separation.

[0123] Optionally, the volume fraction of the first extractant is 20-30%. The first extractant is a mixture of pure extractant and solvent oil, wherein the volume fraction of di(2-ethylhexyl)phosphoric acid in the first extractant is 20-30%; for example, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0124] Optionally, the first extractant is a saponified extractant with a saponification rate of 30-60%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc. Before using the first extractant, it is saponified to stabilize its pH value and enhance its extraction capacity. Since the extractant's extraction capacity for various metals differs at different pH values, the saponification rate of the first extractant is determined to be 30-60% to ensure the purity of valuable metal recovery from magnesium-containing wastewater.

[0125] Optionally, the first extractant is subjected to 4-6 stages of countercurrent soaping and then mixed with the third magnesium-containing wastewater for 8-12 stages of countercurrent extraction and 8-10 stages of countercurrent washing, and the third raffinate is collected.

[0126] Step B20: Mix the third raffinate phase with the second extractant for extraction, and collect the fifth extract phase and the fourth raffinate phase;

[0127] In one feasible embodiment, the third raffinate phase is mixed with the second extractant for fine extraction, and the fifth extract phase and the fourth raffinate phase, which are rich in cobalt and magnesium, are collected. Since the third magnesium-containing wastewater includes nickel intermediate leachate, it contains a large amount of nickel. Therefore, during extraction, metals other than nickel in the solution are extracted and separated.

[0128] Optionally, the second extractant includes: P507; P507 refers to 2-ethylhexyl phosphate, which can be used to separate cobalt and magnesium.

[0129] Optionally, the volume fraction of the second extractant is 20-30%; the second extractant is a mixture of pure extractant and solvent oil, wherein the volume fraction of 2-ethylhexyl phosphate 2-ethylhexyl ester in the second extractant is 20-30%; for example, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0130] Optionally, the second extractant is a saponified extractant with a saponification rate of 30-60%; for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc. Before using the second extractant, it is saponified to stabilize its pH value and enhance its extraction capacity. Since the extractant's extraction capacity for various metals differs at different pH values, the saponification rate of the second extractant is determined to be 30-60% to ensure the purity of valuable metal recovery from magnesium-containing wastewater.

[0131] Optionally, the second extractant is subjected to 4-6 stages of countercurrent soaping and then mixed with the third raffinate phase for 8-12 stages of countercurrent extraction and 8-10 stages of countercurrent washing, and the fifth extract phase and the fourth raffinate phase are collected.

[0132] Step B30: The fifth extraction phase is back-extracted to obtain a fourth back-extract, and the fourth back-extract is used as the first solution;

[0133] In one feasible embodiment, the fifth extract phase rich in cobalt and magnesium is back-extracted to obtain a fourth back-extract. In order to further separate cobalt and magnesium in the fourth back-extract, the fourth back-extract is used as a first solution, thereby being extracted and separated together with the second raffinate phase generated from the second magnesium-containing wastewater.

[0134] Step B40: Mix the fourth raffinate phase with the third extractant and extract, then collect the sixth extract phase and the nickel salt solution;

[0135] In one feasible embodiment, the fourth raffinate phase is mixed with the third extractant for extraction, thereby collecting the magnesium-rich sixth extract phase and the corresponding raffinate phase (i.e., nickel salt solution).

[0136] Optionally, the third extractant includes: Cyanex 272; the main component of Cyanex 272 is bis(2,4,4-trimethylpentyl)phosphonic acid; under the same conditions, the separation coefficient of Cyanex 272 for nickel and cobalt is an order of magnitude higher than that of P507, wherein the cis of Cyanex 272 for metal ion extraction is: Fe 3+ >Zn 2+ >Cu 2+ >Mn 2+ >Co 2+ >Mg 2+ >Ca 2+ Ni 2+Under the same extraction conditions, magnesium is extracted preferentially, thus enabling efficient separation of nickel and magnesium. However, Cyanex 272 is more expensive than P204 and P507. Therefore, Cyanex 272 is used in the final nickel and magnesium recovery stage of valuable metal recovery from magnesium-containing wastewater to effectively reduce process costs while ensuring product purity.

[0137] Optionally, the volume fraction of the third extractant is 10-20%. The third extractant is a mixture of pure extractant and solvent oil, wherein the volume fraction of bis(2,4,4-trimethylpentyl)phosphonic acid in the third extractant is 10-20%; for example, 10%, 12%, 14%, 16%, 18%, 20%, etc.

[0138] Optionally, the third extractant is a saponified extractant with a saponification rate of 20-50%. For example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. Before using the third extractant, it is saponified to stabilize its pH value and enhance its extraction capacity. Since the extractant's extraction capacity for various metals differs at different pH values, the saponification rate of the third extractant is determined to be 20-50% to ensure the purity of valuable metal recovery from magnesium-containing wastewater.

[0139] Optionally, the third extractant is subjected to 4-6 stages of countercurrent soap conversion and then mixed with the fourth raffinate phase for 8-10 stages of countercurrent extraction, followed by 4-8 stages of countercurrent washing, and the sixth extract phase and nickel salt solution are collected.

[0140] Step B50: The sixth extraction phase is back-extracted to obtain a fifth back-extract, and the fifth back-extract is used as the magnesium solution.

[0141] In one feasible embodiment, the sixth extraction phase is back-extracted to obtain a fifth back-extract, which is then used as a magnesium solution for treatment together with magnesium solutions obtained from other magnesium-containing wastewater, thereby achieving efficient magnesium recovery.

[0142] Alternatively, sulfuric acid can be used for back-extraction.

[0143] In this embodiment, by using the same reagents (extractant and back-extraction agent, etc.) as the first magnesium-containing wastewater, the valuable metals in the third magnesium-containing wastewater are efficiently recovered. At the same time, the recovery production lines of the first, second, and third magnesium-containing wastewaters are cleverly combined, which improves the recovery efficiency and effectively reduces the production cost, thus achieving cost reduction and efficiency improvement.

[0144] To enable those skilled in the art to clearly understand the details and operations of the above embodiments of this application, and to demonstrate the significant improvement in the performance of the method for recovering valuable metals from magnesium-containing wastewater in the embodiments of this application, the above technical solutions are illustrated below through multiple embodiments.

[0145] Example 1

[0146] 1) Obtain black powder leachate as the first magnesium-containing wastewater, the composition of which is: cobalt content 19.27 g / L, nickel content 48.89 g / L, manganese content 23.06 g / L, lithium content 8.04 g / L, and magnesium content 0.38 g / L;

[0147] 2) The first magnesium-containing wastewater was mixed with P204 and subjected to 10 stages of extraction, and the first raffinate was collected; wherein, the volume fraction of P204 was 25% and the saponification rate was 50%;

[0148] 3) The first raffinate phase is mixed with P507 for multi-stage extraction. The first extract phase of the 12th stage is collected, and the second extract phase of the 24th stage and the lithium salt solution are collected. The volume fraction of P507 is 25%, and the saponification rate is 60%.

[0149] 4) Use sulfuric acid to perform multi-stage back-extraction on the second extraction phase, collect the first back-extraction liquid of the 12th stage and the fourth back-extraction liquid of the 24th stage, mix the first back-extraction liquid with Cyanex 272 and perform 6-stage extraction, collect the second extraction phase and nickel sulfate solution, wherein the volume fraction of Cyanex 272 is 15% and the saponification rate is 50%.

[0150] 5) The fourth back-extraction solution is used as the first solution and enters the treatment section of the second magnesium-containing wastewater in Example 2 for treatment;

[0151] 6) Using the first extraction phase as the cobalt solution, the cobalt solution is back-extracted 12 times with sulfuric acid to obtain a cobalt sulfate solution;

[0152] 7) The second extraction phase is subjected to 12-stage back-extraction with sulfuric acid to obtain the second back-extraction solution, which is used as the magnesium solution. The pH value of the magnesium solution is adjusted, and after solid-liquid separation, a magnesium sulfate solution is obtained.

[0153] Example 2

[0154] 1) Obtain cobalt intermediate leachate as the second magnesium-containing wastewater, with the following composition: cobalt content 63.05 g / L, nickel content 1.39 g / L, manganese content 8.19 g / L, and magnesium content 9.16 g / L;

[0155] 2) The second magnesium-containing wastewater was mixed with P204 and subjected to 12-stage extraction. The second raffinate phase was collected, wherein the volume fraction of P204 was 25% and the saponification rate was 50%.

[0156] 3) The second raffinate phase is used as the first solution, and the first solution is mixed with P507 for multi-stage extraction. The third extract phase of the 12th stage is collected, and the fourth extract phase of the 24th stage is collected. The volume fraction of P507 is 25%, and the saponification rate is 60%.

[0157] 4) The third extraction phase is used as the cobalt solution and is fed into the treatment section of the first magnesium-containing wastewater in Example 1 for treatment;

[0158] 5) The fourth extraction phase was back-extracted with sulfuric acid in 12 stages to obtain the third back-extract. The third back-extract was used as magnesium solution and entered the treatment section of the first magnesium-containing wastewater in Example 1 for treatment.

[0159] Example 3

[0160] 1) Obtain nickel intermediate leachate as the third magnesium-containing wastewater, with the following composition: cobalt content 5.39 g / L, nickel content 69.22 g / L, manganese content 4.48 g / L, and magnesium content 5.48 g / L;

[0161] 2) The third magnesium-containing wastewater was mixed with P204 and subjected to 12-stage extraction. The third raffinate was collected, wherein the volume fraction of P204 was 25% and the saponification rate was 50%.

[0162] 3) Mix the third raffinate with P507 and perform 12-stage extraction, then collect the fifth raffinate and the fourth raffinate.

[0163] 4) The fifth extraction phase is subjected to 12-stage back-extraction using sulfuric acid to obtain the fourth back-extraction solution, which is then used as the first solution and fed into the treatment section of the second magnesium-containing wastewater in Example 2 for treatment.

[0164] 5) The fourth raffinate phase was mixed with Cyanex 272 and subjected to 8 stages of extraction. The sixth extract phase and nickel salt solution were collected. The volume fraction of Cyanex 272 was 15% and the saponification rate was 50%.

[0165] 6) The sixth extraction phase was subjected to 12-stage back-extraction with sulfuric acid to obtain the fifth back-extraction solution, which was then used as magnesium solution and entered the treatment section of the first magnesium-containing wastewater in Example 1 for treatment.

[0166] After the above steps, the recovery rates of nickel, magnesium, cobalt, and lithium were 98.62%, 97.31%, 96.33%, and 96.28%, respectively. The purity of nickel sulfate, magnesium sulfate, cobalt sulfate, and lithium carbonate in the resulting products was greater than 99%, respectively. As can be seen from Examples 1-3 above, the method for recovering valuable metals from magnesium-containing wastewater in this application can effectively separate the various valuable metals, improve product purity, and achieve efficient recovery. Furthermore, the recovery process is simple, the cost is low, and it has good economic benefits.

[0167] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the patent protection scope of this application.

Claims

1. A method for recovering valuable metals from magnesium-containing wastewater, characterized in that, The method includes the following steps: The first magnesium-containing wastewater is mixed with the first extractant for extraction, and the first raffinate is collected. The first magnesium-containing wastewater includes black powder leachate, and the first extractant includes P2O4. The first raffinate phase is mixed with the second extractant for multi-stage extraction. The first extract phase of the first preset stage is collected, and the second extract phase of the second preset stage and the lithium salt solution are collected. The first preset stage is less than the second preset stage. The second extractant includes P507. The second extraction phase is subjected to multi-stage back-extraction, and the first back-extraction liquid of the third preset stage is collected, and the fourth back-extraction liquid A of the sixth preset stage is collected, wherein the sixth preset stage is greater than the third preset stage; The first back-extraction solution is mixed with the third extractant for extraction, and the second extraction phase and nickel salt solution are collected. The third extractant includes Cyanex 272. The first extraction phase is used as the cobalt solution, and the cobalt solution is back-extracted to obtain a cobalt salt solution; The second extraction phase is back-extracted to obtain a second back-extract, and the second back-extract is used as a magnesium solution. The pH of the magnesium solution is adjusted to obtain a magnesium salt solution. The second magnesium-containing wastewater is mixed with the first extractant for extraction, and the second raffinate is collected. The second magnesium-containing wastewater includes: cobalt intermediate leachate. The second raffinate and / or the fourth back-extraction solution A are used as the first solution, and the first solution is mixed with the second extractant to perform multi-stage extraction. The third extraction phase of the fourth preset stage is collected, and the fourth extraction phase of the fifth preset stage is collected, wherein the fourth preset stage is less than the fifth preset stage. The third extraction phase is used as the cobalt solution; The fourth extraction phase is back-extracted to obtain a third back-extract, which is then used as the magnesium solution.

2. The method for recovering valuable metals from magnesium-containing wastewater as described in claim 1, characterized in that, The method further includes: The third magnesium-containing wastewater was mixed with the first extractant for extraction, and the third raffinate was collected. The third raffinate phase is mixed with the second extractant for extraction, and the fifth extract phase and the fourth raffinate phase are collected. The fifth extraction phase is back-extracted to obtain a fourth back-extract solution B, and the fourth back-extract solution B is used as the first solution. The fourth raffinate phase is mixed with the third extractant and extracted, and the sixth extract phase and nickel salt solution are collected. The sixth extraction phase is back-extracted to obtain a fifth back-extract, which is then used as the magnesium solution.

3. The method for recovering valuable metals from magnesium-containing wastewater as described in claim 2, characterized in that, The third magnesium-containing wastewater includes: nickel intermediate leachate.

4. The method for recovering valuable metals from magnesium-containing wastewater as described in claim 1 or claim 2, characterized in that, The volume fraction of the first extractant is 20-30%. And / or, the volume fraction of the second extractant is 20-30%; And / or, the volume fraction of the third extractant is 10-20%.

5. The method for recovering valuable metals from magnesium-containing wastewater as described in claim 1 or claim 2, characterized in that, The first extractant is a saponified extractant, and the saponification rate of the first extractant is 30-60%. And / or, the second extractant is a saponified extractant, and the saponification rate of the second extractant is 30-60%; And / or, the third extractant is a saponified extractant, and the saponification rate of the third extractant is 20-50%.

6. The method for recovering valuable metals from magnesium-containing wastewater as described in claim 1 or claim 2, characterized in that, The step of adjusting the pH value of the magnesium solution includes: An alkaline solution is added to the magnesium solution to adjust the pH value, wherein the alkaline solution includes sodium sulfide, sodium carbonate, and sodium hydroxide.

7. The method for recovering valuable metals from magnesium-containing wastewater as described in claim 6, characterized in that, After the step of collecting the second extraction phase and lithium salt solution of the second preset stage, the method further includes: The lithium salt solution is subjected to lithium precipitation treatment to obtain lithium salt and lithium precipitation mother liquor; The lithium precipitation mother liquor is used as the alkaline solution.

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