A method for recovering Mg from cobalt-nickel intermediates

Abstract

This invention relates to the field of metal recycling technology, and in particular to a method for recovering Mg from cobalt-nickel intermediates. The method comprises the following steps: (A) washing the cobalt-nickel intermediates to obtain a washing liquid and the washed cobalt-nickel intermediates; (B) sequentially subjecting the washed cobalt-nickel intermediates to decomposition, chemical purification, and extraction to obtain a solution containing nickel sulfate and / or cobalt sulfate, and a raffinate; (C) sequentially subjecting the washing liquid to degreasing, ion exchange, and dissolution crystallization to obtain mixed crystals of magnesium sulfate and sodium sulfate; (D) dissolving the mixed crystals of magnesium sulfate and sodium sulfate, then adding sodium hydroxide solution to react and obtain magnesium hydroxide and sodium sulfate solutions. This method can recover Mg from nickel-cobalt intermediates to obtain magnesium hydroxide, with a Mg recovery rate ≥95%. Furthermore, all byproducts of this method can be recycled within the system, reducing the generation of hazardous waste.

Description

Technical Field

[0001] This invention relates to the field of metal recycling technology, and in particular to a method for recovering Mg from cobalt-nickel intermediates. Background Technology

[0002] With the rapid growth in global electric vehicle production, the consumption of battery metals is gradually increasing, leading to a growing demand for nickel and cobalt raw materials, most of which are intermediate products of nickel and cobalt.

[0003] Cobalt and nickel intermediates are primary hydroxide products with high cobalt and nickel content obtained by using cobalt and nickel-containing minerals as raw materials and processing them through leaching, precipitation, and other processes. Types of nickel and cobalt intermediates include nickel hydroxide (Ni(OH)2), cobalt hydroxide (Co(OH)2), and nickel cobalt hydroxide (MHP).

[0004] Most common nickel and cobalt intermediates are precipitated using magnesium oxide, inevitably resulting in the inclusion of some Mg metal ions. Using nickel-cobalt intermediates as raw materials, nickel-cobalt sulfate products are prepared via hydrometallurgical processes. Since the raw materials contain multiple metal elements such as nickel, cobalt, copper, manganese, and magnesium, the recovery of magnesium during actual metal recovery primarily involves the preparation of low-value-added products such as industrial-grade magnesium carbonate or magnesium sulfate.

[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 recovering Mg from cobalt-nickel intermediates, which can recover metallic Mg from the hydrometallurgical process of nickel-cobalt intermediates to obtain magnesium hydroxide, with a Mg recovery rate of ≥95%. Furthermore, all by-products of this method can be recycled within the system, reducing the generation of hazardous waste.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] This invention provides a method for recovering Mg from cobalt-nickel intermediates, comprising the following steps:

[0009] (A) Wash the cobalt-nickel intermediate to obtain the washing liquid and the washed cobalt-nickel intermediate;

[0010] (B) The washed cobalt-nickel intermediate is sequentially decomposed, chemically purified and separated by extraction to obtain a solution containing nickel sulfate and / or cobalt sulfate and raffinate;

[0011] (C) The washing liquid is subjected to degreasing, ion exchange and dissolution crystallization in sequence to obtain mixed crystals of magnesium sulfate and sodium sulfate;

[0012] (D) After the mixed crystals of magnesium sulfate and sodium sulfate are dissolved, sodium hydroxide solution is added to react and magnesium hydroxide and sodium sulfate solution are obtained.

[0013] Further, in step (A), the pH of the detergent used for washing is 5.0 to 6.0.

[0014] Preferably, the detergent used for washing includes the raffinate from step (B).

[0015] Furthermore, in step (A), the washing temperature is 45–60°C; the liquid-to-solid ratio of the washing is 3–5 mL / g; and the washing time is 1–3 h.

[0016] Further, in step (A), the pH of the washing solution is 7.5 to 8.5, and the total concentration of Ni and Co in the washing solution is 0.3 to 0.5 g / L.

[0017] Further, in step (B), the decomposition includes mixing the washed cobalt-nickel intermediate, the acid solution, and the reducing agent.

[0018] Preferably, the acid solution includes sulfuric acid.

[0019] Preferably, the reducing agent includes at least one of sodium sulfite, sodium metabisulfite, and sulfur dioxide.

[0020] Further, in step (C), the degreasing includes adsorbing the washing liquid with an adsorption resin.

[0021] Further, in step (C), the adsorption resin includes one or more of the following: styrene-based polymeric adsorption resin, styrene-divinylbenzene copolymer gel resin, non-polar macroporous adsorption resin, medium-polar macroporous adsorption resin, and weakly polar macroporous adsorption resin.

[0022] Further, in step (C), the ion exchange resin for ion exchange includes one or more of styrene-based chelating resins, free amine-type resins, epoxy-based chelating resins, and iminodiacetic acid-type chelating resins.

[0023] Preferably, the Co content in the washing solution after ion exchange is ≤0.001g / L and the Ni content is ≤0.0005g / L.

[0024] Preferably, the cations in the washing solution after ion exchange include Na. + and Mg 2+ .

[0025] Further, in step (C), the dissolution crystallization includes adding the washing solution after ion exchange to an ethanol solution.

[0026] Further, in step (D), the sodium sulfate solution is subjected to bipolar membrane electrodialysis to obtain a sodium hydroxide solution and a sulfuric acid solution.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The method for recovering Mg from cobalt-nickel intermediates of the present invention can comprehensively recover and utilize metallic Mg from nickel-cobalt intermediates to obtain magnesium hydroxide, with a Mg recovery rate of ≥95%. At the same time, while achieving excellent recovery of metallic Mg from nickel-cobalt intermediates, it also ensures the recovery rates of metallic Co and Ni.

[0029] The method for recovering Mg from cobalt-nickel intermediates of the present invention takes into account the overall slag and water recycling, and has low cost and high recycling rate in the process design. All by-products can be recycled in the system, reducing the generation of hazardous waste. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a flowchart of the method for recovering Mg from cobalt-nickel intermediates in Example 1 of the present invention. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0033] See Figure 1 The following is a detailed description of a method for recovering Mg from cobalt-nickel intermediates according to an embodiment of the present invention.

[0034] In some embodiments of the present invention, a method for recovering Mg from cobalt-nickel intermediates is provided, comprising the following steps:

[0035] (A) Wash the cobalt-nickel intermediate to obtain the washing liquid and the washed cobalt-nickel intermediate;

[0036] (B) The washed cobalt-nickel intermediates are successively subjected to decomposition, chemical purification and extraction to obtain a solution containing nickel sulfate and / or cobalt sulfate and raffinate.

[0037] (C) The washing liquid is successively subjected to degreasing, ion exchange and dissolution crystallization to obtain mixed crystals of magnesium sulfate and sodium sulfate;

[0038] (D) After the mixed crystals of magnesium sulfate and sodium sulfate are dissolved, sodium hydroxide solution is added to react and magnesium hydroxide and sodium sulfate solution are obtained.

[0039] The method for recovering Mg from cobalt-nickel intermediates of the present invention can comprehensively recover and utilize metallic Mg from nickel-cobalt intermediates to obtain magnesium hydroxide, with a Mg recovery rate of ≥95%; at the same time, it also ensures the recovery rates of metallic Co and Ni.

[0040] The method for recovering Mg from cobalt-nickel intermediates of the present invention takes into account the overall slag and water recycling, and has low cost and high recycling rate in the process design. All by-products can be recycled in the system, reducing the generation of hazardous waste.

[0041] This invention separates and recovers magnesium from the raw material stage. More than 30% of Mg can be washed during the raw material washing process, which can reduce the cost of impurity removal during the extraction and purification process. At the same time, high contents of Co and Ni in the feed liquid can be precipitated and recovered during the washing process.

[0042] In some embodiments of the present invention, the cobalt-nickel intermediate includes cobalt intermediate, nickel intermediate, or a mixture of cobalt intermediate and nickel intermediate.

[0043] In some embodiments of the present invention, in step (A), the pH of the detergent used in the washing process is 5.0 to 6.0.

[0044] In some embodiments of the present invention, in step (A), the detergent used in the washing process includes the raffinate from step (B).

[0045] In some embodiments of the present invention, the pH of the raffinate is 5.0 to 6.0; the total concentration of Co and Ni in the raffinate is 3 to 5 g / L, the concentration of Mg is 5 to 10 g / L, and the concentration of Na is 45 to 60 g / L.

[0046] In some embodiments of the present invention, in step (A), the washing temperature is 45–60°C; the liquid-to-solid ratio is 3–5 mL / g; and the washing time is 1–3 h. Typical but not limiting examples include washing temperatures of 45°C, 50°C, 55°C, or 60°C, etc.; liquid-to-solid ratios of 3 mL / g, 4 mL / g, or 5 mL / g, etc.; and washing times of 1 h, 1.5 h, 2 h, 2.5 h, or 3 h, etc.

[0047] In some embodiments of the present invention, in step (A), the pH of the washing solution is 7.5 to 8.5, and the total concentration of Ni and Co in the washing solution is 0.3 to 0.5 g / L.

[0048] In step (A) of the present invention, the Mg content in the washed cobalt-nickel intermediate can be reduced by 30% to 40% compared to the Mg content in the cobalt-nickel intermediate.

[0049] In some embodiments of the present invention, step (B) of the decomposition includes mixing the washed cobalt-nickel intermediate, the acid solution, and the reducing agent.

[0050] In some embodiments of the present invention, in step (B), the acid solution includes sulfuric acid.

[0051] In some embodiments of the present invention, in step (B), the reducing agent includes at least one of sodium sulfite, sodium metabisulfite, and sulfur dioxide.

[0052] In some specific embodiments of the present invention, in step (B), the chemical method for removing impurities includes precipitation and / or displacement methods.

[0053] In some specific embodiments of the present invention, step (B) of the extraction separation includes extraction, washing, and back-extraction processes; preferably, the extraction uses liquid alkaline soap; preferably, the extractant used in the extraction separation process includes at least one of P204, P507, and C272. P204 is used to remove Fe, Al, Zn, Mn, Cr, Cd, Ca, etc.; P507 or C272 is used to separate Co, Ni, and Mg.

[0054] In step (B) of the present invention, the washed cobalt-nickel intermediate can remove most of the Fe, Al, Cr, Cd and other elements by decomposition and chemical purification. The solution after chemical purification is extracted to remove trace amounts of Fe, Al, Cr, Cd, as well as Ca, Zn, Mn and Cu, to obtain a pure cobalt and nickel salt solution (i.e. a solution containing nickel sulfate and / or cobalt sulfate).

[0055] In the method for recovering Mg from cobalt-nickel intermediates of the present invention, the raffinate after extracting Co and Ni metals is used as a detergent in the washing process. While consuming the residual acid present in the raffinate itself, most of the heavy metals Co and Ni in the raffinate are precipitated and returned to the raw material slag, thus ensuring the yield of metals Co and Ni.

[0056] In some embodiments of the present invention, step (C) includes degreasing the washing liquid by adsorption treatment with an adsorption resin.

[0057] In some embodiments of the present invention, in step (C), the adsorption resin includes one or more of the following: styrene-based polymeric adsorption resin, styrene-divinylbenzene copolymer gel resin, nonpolar macroporous adsorption resin, medium-polar macroporous adsorption resin, and weakly polar macroporous adsorption resin.

[0058] In some embodiments of the present invention, in step (C), the ion exchange resin used in the ion exchange process includes one or more of styrene-based chelating resins, free amine-type resins, epoxy-based chelating resins, and iminodiacetic acid-type chelating resins.

[0059] In some embodiments of the present invention, in step (C), the Co content in the washing solution after ion exchange is ≤0.001 g / L and the Ni content is ≤0.0005 g / L.

[0060] In some embodiments of the present invention, in step (C), the cations in the washing solution after ion exchange include Na. + and Mg 2+ .

[0061] Ion exchange is used to remove weight from the solution. Ion exchange resin can separate most of the Co, Ni and Mg in the solution, with good enrichment effect, and obtain a Co and Ni mixed solution with high purity and concentration. Moreover, ion exchange is simple to operate, safe, and ensures relatively low operating costs. This step further improves the yield of Co and Ni.

[0062] In some specific embodiments of the present invention, in step (C), sulfuric acid solution is used to elute the ion exchange resin after ion exchange to obtain an eluent; then, washing is performed to obtain a washing solution.

[0063] In some embodiments of the present invention, the total concentration of Co and Ni in the eluent is 20–40 g / L, the concentration of Mg is ≤0.1 g / L, and the concentration of H is... + The concentration is 1.0–2.0 mol / L.

[0064] The eluent and washing liquid from the above steps are used in the dissolution step in step (B) to achieve closed-loop recycling.

[0065] In some specific embodiments of the present invention, in step (C), the dissolution and crystallization includes adding the washing solution after ion exchange to an ethanol solution.

[0066] After crystallization, the mother liquor is evaporated using distillation equipment to obtain the volatile component ethanol. The ethanol can be recycled back to the crystallization step; the non-volatile components can be directly treated and discharged.

[0067] Taking advantage of the insolubility of sodium sulfate and magnesium sulfate in ethanol, the washing solution after ion exchange is added to a high-purity ethanol solution in a sealed container (to prevent ethanol evaporation), causing sodium sulfate and magnesium sulfate crystals to precipitate. This utilizes the low solubility of magnesium sulfate and sodium sulfate in ethanol to achieve purification and concentration.

[0068] Ethanol is used as the dissolution and crystallization reagent because it is essentially non-toxic, has a higher safety profile than other organic solvents, has a low boiling point (78.3℃), is easy to remove by distillation, has a high recovery rate, can be recycled, and is low in cost.

[0069] In some specific embodiments of the present invention, step (C) further includes drying the mixed crystals of magnesium sulfate and sodium sulfate.

[0070] In some embodiments of the present invention, in step (D), after dissolving the dried mixed crystals of magnesium sulfate and sodium sulfate, sodium hydroxide is added to react and precipitate Mg in the solution to obtain pure magnesium hydroxide precipitate, which is then dried to obtain the magnesium hydroxide product.

[0071] In some embodiments of the present invention, in step (D), the sodium sulfate solution is subjected to bipolar membrane electrodialysis to obtain a sodium hydroxide solution and a sulfuric acid solution.

[0072] The sodium sulfate solution is treated by bipolar membrane electrodialysis, and the resulting sulfuric acid solution can be returned to the decomposition step in step (B). The resulting sodium hydroxide solution is used to mix with the mixed crystals of magnesium sulfate and sodium sulfate to precipitate magnesium hydroxide.

[0073] In some specific embodiments of the present invention, in step (B), the source of the acid solution is divided into three parts: the first part is the eluent and washing liquid, the second part is the sulfuric acid obtained from the bipolar membrane electrodialysis process, and the third part is the concentrated sulfuric acid added when the above-mentioned recovered acid is insufficient.

[0074] Example 1

[0075] See Figure 1 This embodiment provides a method for recovering Mg from cobalt-nickel intermediates, comprising the following steps:

[0076] 1. The cobalt-nickel intermediate was washed with detergent to obtain 480 mL of washing solution and 97.7 g of washed cobalt-nickel intermediate;

[0077] The detergent is the raffinate obtained in step 4; the temperature is controlled at 60℃ during the washing process, the liquid-solid ratio of detergent to cobalt-nickel intermediate is 5mL:1g, and the washing time is 2h.

[0078] 2. Mix the washed cobalt-nickel intermediate from step 1, 500 mL of acid solution, and 7 g of reducing agent to obtain a mixed solution;

[0079] The acid solution is obtained from the eluent and washing solution in step 5, the sulfuric acid solution obtained from the bipolar membrane electrodialysis process in step 7, and the concentrated sulfuric acid added when the consumed acid is insufficient; the reducing agent is sodium metabisulfite.

[0080] 3. Remove most of the Fe, Al, Cr, Cd and other elements from the mixture in step 2 using chemical methods;

[0081] Chemical methods for removing impurities include oxidation and precipitation.

[0082] 4. After chemical purification, the mixture is then separated and removed by extraction to remove trace amounts of Fe, Al, Cr, Cd, as well as Ca, Zn, Mn, and Cu, to obtain a pure nickel and cobalt sulfate solution.

[0083] The extractants used in the extraction separation process are P204, P507 and C272; the extraction separation includes extraction, washing and back-extraction processes.

[0084] 5. The washing solution from step 1 is degreased using a styrene-divinylbenzene copolymer gel resin, and then subjected to ion exchange with a styrene-based chelating resin to remove heavy metals and adsorb Co and Ni. The solution after ion exchange treatment has a Co content ≤0.001 g / L and a Ni content ≤0.0005 g / L. The cations in the solution after ion exchange mainly include Na. + and Mg 2+ ;

[0085] The resin after adsorbing metal ions is desorbed using sulfuric acid solution, and then washed to obtain desorbed solution and washing solution. The desorbed solution and washing solution in this step are returned to step 2 as part of the acid solution source, so as to achieve closed-loop recycling.

[0086] 6. In a sealed container, add 200 mL of the solution obtained after ion exchange to 400 mL of anhydrous ethanol solution (the reactor needs to be a sealed container to prevent ethanol evaporation) to obtain mixed crystals of magnesium sulfate and sodium sulfate and mother liquor; place the mixed crystals of magnesium sulfate and sodium sulfate in a sealed desiccator for drying; evaporate the mother liquor after crystallization using a distillation device to obtain the volatile component ethanol for recycling; the non-volatile component can be directly treated and discharged.

[0087] 7. Add the dried magnesium sulfate and sodium sulfate mixed crystals to pure water, dissolve to obtain a mixed solution, control the sulfate concentration in the mixed solution to 2 mol / L, then add sodium hydroxide solution at 40℃ to adjust the pH to 11-12, precipitate Mg in the solution, filter to obtain pure magnesium hydroxide and sodium sulfate solution; treat the sodium sulfate solution with bipolar membrane electrodialysis to obtain approximately 2 mol / L sulfuric acid solution and approximately 4 mol / L sodium hydroxide solution; the sulfuric acid solution can be returned to step 2 for use, and the sodium hydroxide solution is used to precipitate magnesium hydroxide.

[0088] Example 2

[0089] This embodiment provides a method for recovering Mg from cobalt-nickel intermediates, comprising the following steps:

[0090] 1. The cobalt-nickel intermediate was washed with detergent to obtain 380 mL of washing solution and 98.4 g of washed cobalt-nickel intermediate;

[0091] The detergent is the raffinate obtained in step 4; the temperature is controlled at 70℃ during the washing process, the liquid-solid ratio of the detergent and the cobalt-nickel intermediate is 4mL:1g, and the washing time is 2h.

[0092] 2. Mix the washed cobalt-nickel intermediate from step 1, 400 mL of acid solution, and 8 g of reducing agent to obtain a mixed solution;

[0093] The acid solution is obtained from the eluent and washing solution in step 5, the sulfuric acid solution obtained from the bipolar membrane electrodialysis process in step 7, and the concentrated sulfuric acid added when the consumed acid is insufficient; the reducing agent is sodium metabisulfite.

[0094] 3. Remove most of the Fe, Al, Cr, Cd and other elements from the mixture in step 2 using chemical methods;

[0095] Chemical methods for removing impurities include oxidation and precipitation.

[0096] 4. After chemical purification, the mixture is then separated and removed by extraction to remove trace amounts of Fe, Al, Cr, Cd, as well as Ca, Zn, Mn, and Cu, to obtain a pure nickel and cobalt sulfate solution.

[0097] The extractants used in the extraction separation process are P204, P507 and C272; the extraction separation process includes extraction, washing and back-extraction.

[0098] 5. The washing solution from step 1 is degreased using a styrene-divinylbenzene copolymer gel resin, and then subjected to ion exchange with a styrene-based chelating resin to remove heavy metals and adsorb Co and Ni. The solution after ion exchange treatment has a Co content ≤0.001 g / L and a Ni content ≤0.0005 g / L. The cations in the solution after ion exchange mainly include Na. + and Mg 2+ ;

[0099] The resin after adsorbing metal ions is desorbed using sulfuric acid solution, and then washed to obtain desorbed solution and washing solution. The desorbed solution and washing solution in this step are returned to step 2 as part of the acid solution source, so as to achieve closed-loop recycling.

[0100] 6. In a sealed container, add 300 mL of the solution obtained after ion exchange to 400 mL of anhydrous ethanol solution (the reactor needs to be a sealed container to prevent ethanol evaporation) to obtain mixed crystals of magnesium sulfate and sodium sulfate and mother liquor; place the mixed crystals of magnesium sulfate and sodium sulfate in a sealed desiccator for drying; evaporate the mother liquor after crystallization using a distillation device to obtain the volatile component ethanol for recycling; the non-volatile component can be directly treated and discharged.

[0101] 7. Add the dried magnesium sulfate and sodium sulfate mixed crystals to pure water, dissolve to obtain a mixed solution, control the sulfate concentration in the mixed solution to 2.2 mol / L, then add sodium hydroxide solution at 50℃ to adjust the pH to 11-12, precipitate Mg in the solution, filter to obtain pure magnesium hydroxide and sodium sulfate solution; treat the sodium sulfate solution with bipolar membrane electrodialysis to obtain approximately 2 mol / L sulfuric acid solution and approximately 4 mol / L sodium hydroxide solution; the sulfuric acid solution can be returned to step 2 for use, and the sodium hydroxide solution is used to precipitate magnesium hydroxide.

[0102] Experimental Example 1

[0103] The components and their contents in each solution in each step of Example 1 were tested, and the results are shown in Tables 1, 2, 3 and 4.

[0104] The recovery rates of each step in Example 1 were tested, and the results are shown in Table 5. The recovery rate after ion exchange refers to the recovery rate of each metal in the washing solution after ion exchange. The recovery rate after Mg precipitation refers to the yield of Mg obtained from the cobalt-nickel intermediate.

[0105] Table 1

[0106]

[0107] Table 2

[0108]

[0109] Table 3

[0110]

[0111] Table 4

[0112]

[0113] Table 5

[0114]

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recovering Mg from cobalt-nickel intermediates, characterized in that, Includes the following steps: (A) A cobalt-nickel intermediate is obtained by magnesium oxide precipitation, and the cobalt-nickel intermediate is washed to obtain a washing liquid and the washed cobalt-nickel intermediate. (B) The washed cobalt-nickel intermediate is sequentially decomposed, chemically purified and separated by extraction to obtain a solution containing nickel sulfate and / or cobalt sulfate and a raffinate; (C) The washing liquid is subjected to degreasing, ion exchange and dissolution crystallization in sequence to obtain mixed crystals of magnesium sulfate and sodium sulfate; (D) After the mixed crystals of magnesium sulfate and sodium sulfate are dissolved, sodium hydroxide solution is added to react and magnesium hydroxide and sodium sulfate solution are obtained; In step (A), the pH of the detergent used for washing is 5.0 to 6.0; the detergent used for washing includes the raffinate from step (B); In step (A), the pH of the washing solution is 7.5~8.5, and the total concentration of Ni and Co in the washing solution is 0.3~0.5 g / L; In step (C), the dissolution crystallization includes adding the washing solution after ion exchange to an ethanol solution.

2. The method for recovering Mg from cobalt-nickel intermediates according to claim 1, characterized in that, In step (A), the washing temperature is 45~60℃; the liquid-to-solid ratio of the washing is 3~5mL / g; and the washing time is 1~3h.

3. The method for recovering Mg from cobalt-nickel intermediates according to claim 1, characterized in that, In step (B), the decomposition includes mixing the washed cobalt-nickel intermediate, acid solution, and reducing agent.

4. The method for recovering Mg from cobalt-nickel intermediates according to claim 3, characterized in that, The acid solution includes sulfuric acid.

5. The method for recovering Mg from cobalt-nickel intermediates according to claim 3, characterized in that, The reducing agent includes at least one of sodium sulfite, sodium metabisulfite, and sulfur dioxide.

6. The method for recovering Mg from cobalt-nickel intermediates according to claim 1, characterized in that, In step (C), the degreasing includes using an adsorption resin to adsorb the washing liquid.

7. The method for recovering Mg from cobalt-nickel intermediates according to claim 6, characterized in that, In step (C), the adsorption resin includes one or more of the following: styrene-based polymeric adsorption resin, styrene-divinylbenzene copolymer gel resin, non-polar macroporous adsorption resin, medium-polar macroporous adsorption resin, and weakly polar macroporous adsorption resin.

8. The method for recovering Mg from cobalt-nickel intermediates according to claim 1, characterized in that, In step (C), the ion exchange resin for ion exchange includes one or more of styrene-based chelating resins, free amine-type resins, epoxy-based chelating resins, and iminodiacetic acid-type chelating resins.

9. The method for recovering Mg from cobalt-nickel intermediates according to claim 1, characterized in that, In step (C), the Co content in the washing solution after ion exchange is ≤0.001 g / L and the Ni content is ≤0.0005 g / L.

10. The method for recovering Mg from cobalt-nickel intermediates according to claim 1, characterized in that, In step (C), the cations in the washing solution after ion exchange include Na. + and Mg 2+ .

11. The method for recovering Mg from cobalt-nickel intermediates according to claim 1, characterized in that, In step (D), the sodium sulfate solution is subjected to bipolar membrane electrodialysis to obtain sodium hydroxide solution and sulfuric acid solution.

Images