Method for recovering nickel, cobalt and magnesium from resin desorption solution containing nickel, cobalt and magnesium

Abstract

The invention discloses a method for recovering nickel, cobalt and magnesium from a nickel-cobalt-magnesium-containing resin desorption solution, which comprises the following steps: adding ammonium sulfate into the nickel-cobalt-magnesium-containing resin desorption solution, freezing and crystallizing to recover nickel ammonium sulfate, removing nickel and crystallizing mother liquor to be used as washing acid liquor of a P507 cobalt extraction procedure, and extracting and recovering cobalt by using a P507 organic phase. And then the magnesium-containing raffinate is subjected to oil removal and impurity removal and then is subjected to MVR evaporative crystallization to recover magnesium ammonium sulfate. The invention relates to the technical field of nickel-cobalt hydrometallurgy. According to the method for recovering nickel, cobalt and magnesium from the resin desorption solution containing nickel, cobalt and magnesium, freezing crystallization, P507 extraction, MVR evaporation and other unit operations are organically combined, and step-by-step separation and comprehensive recovery of nickel, cobalt and magnesium are achieved. According to the integrated recycling method and the design of the material flow direction, the recycling process is greatly simplified, the recycling efficiency is improved, the original acidity is utilized, consumption of fresh sulfuric acid is reduced, internal circulation of the materials and waste reduction are achieved, and the concepts of green metallurgy and circular economy are met.

Description

Technical Field

[0001] This invention relates to the field of nickel-cobalt hydrometallurgical technology, specifically to a method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent. Background Technology

[0002] The magnesium-containing waste liquid generated during the nickel-cobalt hydrometallurgical process mainly consists of sodium sulfate and magnesium sulfate, characterized by high magnesium content and certain recovery value and significance. In the nickel-cobalt hydrometallurgical process, the raffinate or post-soaping liquid containing low concentrations of nickel and cobalt is generally recovered using resin ion exchange. However, effectively separating and recovering nickel, cobalt, and magnesium from the complex resin eluent is challenging, and existing technologies may face the challenge of balancing product purity, recovery rate, and economic viability.

[0003] Referring to a method for solving the problem of over-extraction of nickel and magnesium in a P507 cobalt extraction system (Chinese Patent Publication No. CN113493871A), this method involves adding P204 raffinate or P507 back-extraction solution to the mixing chamber one stage after the over-extraction stage in the extraction section. After adding the P204 raffinate or P507 back-extraction solution, because the extractant has a stronger binding capacity for cobalt ions than nickel and magnesium ions, the cobalt in the solution is extracted first, while the nickel and magnesium ions that have already been extracted into the organic phase are also replaced by cobalt ions into the aqueous phase, thus quickly and effectively solving the problem of over-extraction in the solution.

[0004] Referring to a washing method and apparatus for a P507 cobalt extraction system disclosed in Chinese Patent Publication No. CN111270070A, based on the different extraction rates of cobalt, magnesium, and nickel, sulfuric acid is added to the organic phase, and the pH value of the solution is controlled between 2.0 and 2.5 to separate most of the nickel from the organic phase, while a portion of magnesium is also separated. Then, hydrochloric acid is added, and the pH value of the solution is controlled between 1.5 and 2.0 to separate the remaining magnesium and residual nickel from the organic phase. The method is simple and easy to operate.

[0005] A comprehensive analysis of the above-mentioned reference patents reveals the following drawbacks: 1) Existing methods for recovering nickel, cobalt, and magnesium from nickel-cobalt-magnesium resin eluent have poor nickel-cobalt separation efficiency, low product purity, and large wastewater volume. For example, the method for solving the over-extraction of nickel and magnesium in the P507 cobalt extraction system (referring to patent CN113493871A) and the washing method and apparatus for the P507 cobalt extraction system (referring to patent CN111270070A) both use the P507 extraction method for recovery. Although the nickel-cobalt separation efficiency is good, the ammonium-containing solution cannot be incorporated into the nickel extraction system for treatment. If a new extraction line is added for treatment, the investment and treatment costs will be significantly higher. 2) Existing recycling technologies still employ ion exchange resin methods, which are unsuitable for eluents with high nickel and cobalt content, have low processing capacity, long cycles, and high resin costs. Another method involves recovering nickel and magnesium using a single freeze-crystallization method, where a solution containing nickel, cobalt, and magnesium is mixed with ammonium sulfate, and different freezing temperatures are controlled to crystallize nickel ammonium sulfate and magnesium ammonium sulfate separately. However, due to the small difference in solubility between nickel ammonium sulfate and magnesium ammonium sulfate, control is difficult, the separation coefficient is low, and cross-contamination of products occurs. Furthermore, current recycling methods easily generate large amounts of waste residue, making it difficult to achieve efficient simultaneous recovery of nickel, cobalt, and magnesium. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention aims to provide a method for the simultaneous and efficient recovery of nickel, cobalt, and magnesium from nickel-cobalt-magnesium resin eluents in an environmentally friendly manner. Specifically, it achieves material recycling and waste reduction through process innovation, solving problems such as poor nickel-cobalt separation, low product purity, large wastewater volume, the unsuitability of ion exchange resin methods for eluents with high nickel-cobalt content, small processing capacity, long cycle time, high resin cost, and the difficulty in controlling and controlling the recovery of nickel and magnesium using a single freeze-crystallization method, resulting in low separation coefficients and cross-contamination of products. Furthermore, current recovery methods tend to generate large amounts of waste residue, making it difficult to achieve efficient and simultaneous recovery of nickel, cobalt, and magnesium.

[0007] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent, specifically comprising the following steps: S1. The pretreated nickel-cobalt-magnesium resin eluent is subjected to a freeze crystallization method. The dissolved nickel-cobalt-magnesium resin eluent is cooled to the metastable zone, nickel ammonium sulfate hexahydrate seed crystals are added, sieved and evenly sprinkled on the surface of the dissolved nickel-cobalt-magnesium resin eluent, and then cooled and kept warm to grow crystals to recover high-purity nickel ammonium sulfate hexahydrate crystals. S2. The nickel removal crystallization mother liquor enters the cobalt P507 line as a cobalt washing solution, and undergoes cobalt washing in the washing section and cobalt back-extraction in the extraction section, as detailed below: a1. The mother liquor for removing nickel crystals is added to the washing section of the cobalt P507 extraction line to wash the loaded organic phase. The flow ratio of the organic phase to the aqueous phase in the washing section is (6-15):1. a2. Then, cobalt is recovered by extraction in the extraction section using P507 organic phase extraction. The flow ratio of organic phase to aqueous phase in the extraction section is (1.5-4):1. S3. After removing oil and impurities from the magnesium-containing ammonium sulfate raffinate produced by P507 extraction in step S2, magnesium ammonium sulfate is recovered by MVR. Specifically, the magnesium-containing ammonium sulfate raffinate after cobalt extraction by P507 is subjected to oil removal, resin adsorption for impurity removal and evaporation crystallization steps in sequence to recover magnesium ammonium sulfate product.

[0008] Preferably, the specific steps for recovering high-purity nickel ammonium sulfate hexahydrate crystals using the freeze-crystallization method in step S1 are as follows: T1. Take a certain volume of the eluent and heat it in a water bath to 65-75℃, stirring at a speed of 450-550 r / min. Then add solid industrial ammonium sulfate and dissolve it completely for 1-1.5 hours. T2. Cool the fully dissolved solution from step T1 and stir it. T3. After the cooling operation in step T2, the fully dissolved eluent in step T1 is cooled to the metastable zone. 0.5%-2% of the expected nickel ammonium sulfate yield is added as nickel ammonium sulfate hexahydrate seed crystals with a particle size of 100-200 mesh. The seed crystals are then lightly and evenly sprinkled on the surface of the fully dissolved eluent in step T1 using a 100-200 mesh sieve. The stirring rate is 100-200 r / min when adding the seed crystals. T4. After the seed crystals are added, slowly restore the stirring rate to 250-350 r / min for 2-3 minutes, and finally cool down to -5 to -10℃. Reduce the stirring rate to 100-200 r / min and continue to keep the temperature warm for 1-2 hours to grow crystals. T5. Centrifugal filtration is carried out using a stepped acceleration method. Under high-speed centrifugation, deionized water at 0-5℃ is used for washing. The washing liquid is sprayed evenly onto the surface of the filter cake in a mist using a sprayer or washing tube. The unloaded material is high-purity nickel ammonium sulfate hexahydrate crystals.

[0009] Preferably, the composition of the eluent in step T1 is: nickel 25-40 g / L, cobalt 3-6 g / L, magnesium 2-4 g / L and total nitrogen 2-5 g / L, and the acidity of the eluent is 0.8-1.2 N.

[0010] Preferably, the amount of solid industrial ammonium sulfate added in step T1 is 0.95-1.05 times the nickel content in the eluent.

[0011] Preferably, in step T2, the cooling rate of the fully dissolved eluent from step T1 is 0.1-0.5℃ / min, and the stirring rate is 250-350r / min.

[0012] Preferably, in step a2, the P507 organic phase extraction is performed using liquid alkali saponification, with a saponification rate of 50%-60%.

[0013] Preferably, in step S3, oil removal is performed using an activated carbon adsorption column, with the oil content at the adsorption endpoint being ≤20ppm.

[0014] Preferably, in step S3, resin adsorption for impurity removal uses nickel-cobalt chelate resin to remove and recover nickel-cobalt impurities, with the flow rate BV controlled at 5-10, and the adsorption endpoint achieved when the cobalt / nickel concentration in the effluent is <1 mg / L.

[0015] Preferably, the evaporation crystallization in step S3 is MVR evaporation crystallization, and the operating temperature is 50-70℃.

[0016] Preferably, the pretreatment in step S1 specifically involves filtering the nickel-cobalt-magnesium resin eluent to remove suspended solid impurities and obtain a clarified liquid.

[0017] (III) Beneficial Effects This invention provides a method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent. Compared with the prior art, it has the following advantages: (1) The method for recovering nickel, cobalt, and magnesium from nickel-cobalt-magnesium resin eluent involves adding ammonium sulfate to the eluent for freeze crystallization to recover nickel ammonium sulfate (nickel recovery). The mother liquor (acidity 0.8-1.2N) is then used as the washing acid in the P507 cobalt extraction process. Cobalt is then recovered through P507 organic phase extraction (cobalt recovery). Afterward, the magnesium-containing extraction residue is degreased and impurity removed before MVR evaporation crystallization to recover magnesium ammonium sulfate (magnesium recovery). By organically combining multiple unit operations such as freeze crystallization, P507 extraction, and MVR evaporation, the stepwise separation and comprehensive recovery of nickel, cobalt, and magnesium are achieved. The integrated recovery method and the design of the material flow direction in this invention greatly improve the recovery efficiency.

[0018] (2) The method for recovering nickel, cobalt and magnesium from the desorption solution of nickel-cobalt-magnesium resin utilizes the resource utilization of the mother liquor for nickel removal crystallization after freezing and crystallizing nickel ammonium sulfate. The mother liquor for nickel removal crystallization after freezing and crystallizing nickel ammonium sulfate is directly used as the washing acid for P507 extraction of cobalt. It utilizes its original acidity (acidity 0.8-1.2N), reduces the consumption of fresh sulfuric acid, realizes the internal circulation of materials and waste reduction, and conforms to the concept of green metallurgy and circular economy.

[0019] (3) The method for recovering nickel, cobalt, and magnesium from the eluent of nickel-cobalt-magnesium resin aims to efficiently and continuously recover all valuable metals (nickel in the form of nickel ammonium sulfate, cobalt in the form of cobalt chloride or cobalt sulfate, and magnesium in the form of magnesium ammonium sulfate), thereby improving resource utilization and reducing the generation of solid waste. Wastewater volume is reduced, the addition of solid ammonium sulfate to the eluent does not increase the volume or reduce the acidity of the eluent, the entire recovery process does not generate new wastewater, reducing wastewater treatment costs, the recovered nickel ammonium sulfate has high purity, and by adding nickel ammonium sulfate seed crystals during freeze crystallization and by controlling the cooling rate and freezing temperature, the precipitation of cobalt and magnesium crystals and the formation of mixed crystals with nickel are controlled. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the recovery of nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent according to the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0022] Please see Figure 1 The present invention provides three technical solutions: a method for recovering nickel, cobalt, and magnesium from nickel-cobalt-magnesium resin eluent, specifically including the following embodiments: Example 1: Take 1L of resin eluent (composition: nickel 25g / l, cobalt 3g / l, magnesium 2g / l, total nitrogen 3g / l, acidity 0.9N), heat it in a water bath to 65℃, and stir at 500r / min; add solid industrial ammonium sulfate (including the ammonium sulfate originally in the eluent, calculated based on nitrogen content) at 0.95 times the theoretically calculated amount of nickel content in the eluent, and allow it to dissolve completely for 1 hour. Then, cool it down at a rate of 0.2℃ / min, while stirring at 350r / min; cool the solution to the metastable zone, add 0.5% of the expected nickel ammonium sulfate yield of nickel ammonium sulfate hexahydrate seed crystals (100 mesh size), and lightly and evenly sprinkle them on the solution surface using a 100-mesh sieve. The stirring rate was 100 r / min. After the seed crystals were added, the stirring rate was slowly restored to 350 r / min after 2.5 min. Finally, the temperature was lowered to -5℃, the stirring rate was reduced to 100 r / min, and the temperature was maintained for another hour to grow the crystals. Centrifugal filtration was carried out using a stepped acceleration method. The filter cake was washed with 5℃ deionized water under high-speed centrifugation. The washing liquid was sprayed evenly onto the surface of the filter cake using a sprayer or washing tube. The unloaded material was nickel ammonium sulfate hexahydrate crystals that met battery-grade standards, with a nickel recovery rate of 99%, a cobalt loss rate of 0.2%, and a magnesium loss rate of 0.4%.

[0023] The mother liquor from the nickel-free crystallization process is added to the washing section of the cobalt extraction line 507 to wash the loaded organic phase. The flow ratio of the organic phase to the aqueous phase in the washing section is 8:1. The P507 extraction uses liquid alkali saponification with a saponification rate of 52%. The flow ratio of the organic phase to the aqueous phase in the extraction section is 2:1. After washing and extraction, the cobalt recovery rate is 99.6%, and the magnesium loss rate is 0.2%.

[0024] The raffinate after cobalt extraction using P507 undergoes a series of steps including oil removal, resin adsorption for impurity removal, and evaporation crystallization to recover magnesium ammonium sulfate, with a magnesium recovery rate of 99.4%. Oil removal is performed using an activated carbon adsorption column, with an adsorption endpoint of 10 ppm oil content. Nickel-cobalt chelating resin is used to remove and recover nickel and cobalt impurities, with a flow rate controlled at 5 BV. The adsorption endpoint is achieved when the cobalt content in the effluent is 0.5 mg / L and the nickel content is 0.8 mg / L. The post-adsorption liquid is then subjected to MVR evaporation crystallization at an operating temperature of 60℃.

[0025] Example 2: Take 1L of resin eluent (composition: nickel 40g / l, cobalt 4g / l, magnesium 3g / l, total nitrogen 2g / l, acidity 1.1N), heat it in a water bath to 75℃, and stir at 550r / min; add solid industrial ammonium sulfate (including the ammonium sulfate originally in the eluent, calculated based on nitrogen content) at 1.02 times the theoretically calculated amount of nickel content in the eluent, and allow it to dissolve completely for 2 hours. Then, cool it down at a rate of 0.3℃ / min, while stirring at 300r / min; cool the solution to the metastable zone, add 0.8% of the expected nickel ammonium sulfate yield of nickel ammonium sulfate hexahydrate seed crystals (200 mesh size), and lightly and evenly sprinkle them on the solution surface using a 200-mesh sieve. The stirring rate was 150 r / min. After the seed crystals were added, the stirring rate was slowly restored to 300 r / min after 2 minutes. Finally, the temperature was lowered to -8℃, the stirring rate was reduced to 200 r / min, and the temperature was maintained for another 2 hours for crystal growth. Centrifugal filtration was carried out using a stepped acceleration method. The filter cake was washed with deionized water at 3℃ under high-speed centrifugation. The washing liquid was sprayed evenly onto the surface of the filter cake using a sprayer or washing tube. The unloaded material was nickel ammonium sulfate hexahydrate crystals that met battery-grade standards, with a nickel recovery rate of 99.4%, a cobalt loss rate of 0.3%, and a magnesium loss rate of 0.2%.

[0026] The mother liquor from the nickel-free crystallization process is added to the washing section of the cobalt extraction line 507 to wash the loaded organic phase. The flow ratio of the organic phase to the aqueous phase in the washing section is 10:1. The P507 extraction uses liquid alkali saponification with a saponification rate of 55%. The flow ratio of the organic phase to the aqueous phase in the extraction section is 3:1. After washing and extraction, the cobalt recovery rate is 99.7%, and the magnesium loss rate is 0.3%.

[0027] The raffinate after cobalt extraction using P507 undergoes a series of steps including oil removal, resin adsorption for impurity removal, and evaporation crystallization to recover magnesium ammonium sulfate, with a magnesium recovery rate of 99.5%. Oil removal is performed using an activated carbon adsorption column, with an adsorption endpoint of 15 ppm oil content. Nickel-cobalt chelating resin is used to remove and recover nickel and cobalt impurities, with a flow rate controlled at 8 BV. The adsorption endpoint is achieved when the cobalt content in the effluent is 0.6 mg / L and the nickel content is 0.9 mg / L. The post-adsorption solution is then subjected to MVR evaporation crystallization at an operating temperature of 70℃.

[0028] Example 3: A method for recovering nickel, cobalt, and magnesium from nickel-cobalt-magnesium resin eluent, specifically including the following steps: S1. The nickel-cobalt-magnesium resin eluent is filtered to remove suspended solid impurities, resulting in a clarified liquid. The pretreated nickel-cobalt-magnesium resin eluent is then subjected to freeze crystallization to recover nickel ammonium sulfate, as detailed below: T1. Take 1L of the eluent (the eluent consists of 31g / L nickel, 4.5g / L cobalt, 3g / L magnesium, and 3.5g / L total nitrogen, and the acidity of the eluent is 1N), heat it in a water bath to 70℃, and stir at 500r / min. Then add solid industrial ammonium sulfate, the amount of which is 1 times the nickel content in the eluent (including the original ammonium sulfate in the eluent, calculated based on the nitrogen content), and dissolve it completely for 1.25h. T2. Cool the fully dissolved eluent from step T1 and stir it. The cooling rate of the fully dissolved eluent from step T1 is 0.3℃ / min and the stirring rate is 300r / min. T3. After the cooling operation in step T2, the fully dissolved eluent in step T1 is cooled to the metastable zone. Nickel ammonium sulfate hexahydrate seed crystals, accounting for 1.25% of the expected nickel ammonium sulfate yield, are added. The seed crystals have a particle size of 150 mesh and are lightly and evenly sprinkled on the surface of the fully dissolved eluent in step T1 using a 150 mesh sieve. The stirring rate is 150 r / min when adding the seed crystals. T4. After the seed crystals are added, slowly restore the stirring rate to 300 r / min for 2.5 min, and finally cool down to -7.5℃. Reduce the stirring rate to 150 r / min and continue to keep warm for 1.5 hours to grow crystals. T5. Centrifugal filtration is performed using a stepped-rate-up method. The filter cake is washed with deionized water at 2.5°C under high-speed centrifugation. The washing liquid is then sprayed evenly onto the filter cake surface using a sprayer or washing tube in a mist form. The discharged product is high-purity nickel ammonium sulfate hexahydrate crystals, with a nickel recovery rate of 99.6%, a cobalt loss rate of 0.2%, and a magnesium loss rate of 0.2%. S2. The nickel removal crystallization mother liquor enters the cobalt P507 line as a cobalt washing solution, and undergoes cobalt washing in the washing section and cobalt back-extraction in the extraction section, as detailed below: a1. The mother liquor for removing nickel crystals is added to the washing section of the cobalt P507 extraction line to wash the loaded organic phase. The flow ratio of the organic phase to the aqueous phase in the washing section is 10:1. a2. Then, in the extraction section, cobalt is recovered through P507 organic phase extraction. The flow ratio of organic phase to aqueous phase in the extraction section is 2.5:1. P507 organic phase extraction uses liquid alkali saponification with a saponification rate of 55%. After washing and extraction, the cobalt recovery rate is 99.8%, and the magnesium loss rate is 0.2%. S3. After removing oil and impurities from the magnesium-containing ammonium sulfate raffinate produced by P507 extraction in step S2, magnesium ammonium sulfate is recovered by MVR. Specifically, the magnesium-containing ammonium sulfate raffinate after cobalt extraction by P507 is subjected to oil removal, resin adsorption for impurity removal, and evaporation crystallization steps in sequence to recover magnesium ammonium sulfate product. Oil removal is performed using an activated carbon adsorption column, with an oil content of 15 ppm at the adsorption endpoint. Resin adsorption for impurity removal uses nickel-cobalt chelate resin to remove and recover nickel-cobalt impurities, with a flow rate BV=7. The adsorption endpoint is achieved when the cobalt concentration in the effluent is 0.8 mg / L and the nickel content is 0.8 mg / L. Evaporation crystallization is performed by MVR evaporation crystallization at an operating temperature of 60℃, and the magnesium recovery rate is 99.7%.

[0029] Comparative Example 1: Take 1L of resin eluent (composition: nickel 25g / L, cobalt 3g / L, magnesium 2g / L, total nitrogen 3g / L). The solution was heated to 65°C in a water bath with a concentration of g / L and an acidity of 0.9N, and stirred at 500 rpm. Solid industrial ammonium sulfate (including the ammonium sulfate already present in the solution, calculated based on nitrogen content) was added at 0.95 times the theoretically calculated amount of nickel content in the eluent. The solution was allowed to dissolve completely for 1 hour, then cooled at a rate of 0.2°C / min, with a stirring rate of 350 rpm. Finally, the solution was cooled to -5°C, and the stirring rate was reduced to 100 rpm. The solution was then kept at this temperature for 1 hour to allow crystal growth. The solution was centrifuged and filtered using a stepped-rate method. The solution was washed with 5°C deionized water under high-speed centrifugation, and the washing liquid was sprayed evenly onto the surface of the filter cake using a sprayer or washing tube. The discharged nickel ammonium sulfate hexahydrate crystals did not meet battery-grade standards, and cobalt-magnesium eutectic precipitates. The nickel recovery rate was 98.4%, the cobalt loss rate was 2.8%, and the magnesium loss rate was 5.6%.

[0030] The mother liquor from the nickel-free crystallization process is added to the washing section of the cobalt extraction line 507 to wash the loaded organic phase. The flow ratio of the organic phase to the aqueous phase in the washing section is 8:1. The P507 extraction uses liquid alkali saponification with a saponification rate of 52%. The flow ratio of the organic phase to the aqueous phase in the extraction section is 2:1. After washing and extraction, the cobalt recovery rate is 97.1%, and the magnesium loss rate is 0.2%.

[0031] The raffinate after cobalt extraction using P507 was subjected to oil removal, resin adsorption for impurity removal, and evaporation crystallization steps to recover magnesium ammonium sulfate product, with a magnesium recovery rate of 94.1%. Oil removal was performed using an activated carbon adsorption column, with an oil content of 10 ppm at the adsorption endpoint. Nickel and cobalt impurities were removed and recovered using nickel-cobalt chelating resin, with a flow rate controlled at 5 BV. At the adsorption endpoint, the cobalt content in the effluent was 0.5 mg / L and the nickel content was 2 mg / L. The liquid after adsorption was subjected to MVR evaporation crystallization at an operating temperature of 60℃.

[0032] Comparative Example 2: The specific method for recovering nickel, cobalt, and magnesium from nickel-cobalt-magnesium resin eluent using existing ion exchange resin adsorption methods is as follows: (1) Pretreatment: The nickel-cobalt-magnesium resin eluent (containing 20 g / L nickel, 15 g / L cobalt and 10 g / L magnesium) was filtered to remove suspended solid impurities and obtain a clear liquid; (2) Impurity removal: Add hydrogen peroxide as an oxidant to the clarified liquid, and filter and remove oil from the treated liquid to make COD≤150mg / L, SS≤150mg / L, and oil content≤30mg / L; (3) Nickel-cobalt separation: The feed solution obtained in step (2) is passed through an LSC-930 ion exchange resin column to separate nickel and cobalt, resulting in an adsorption resin containing nickel and cobalt and a desorption solution containing magnesium (containing 9.5 g / L of magnesium). (4) Nickel-cobalt recovery: The nickel-cobalt adsorption resin obtained in step (3) is desorbed with 7% sulfuric acid solution to obtain nickel-cobalt desorption solution (containing 18 g / L nickel and 13 g / L cobalt) and regenerated resin. The regenerated resin is returned to step (3) for recycling. (5) Magnesium recovery: The magnesium-containing eluent obtained in step (3) (containing 9.5 g / L of magnesium) was added to 5% magnesium hydroxide emulsion, and the pH was adjusted to 9.0 to precipitate magnesium in the form of magnesium hydroxide. The magnesium hydroxide precipitate was obtained by filtration, washed and dried to obtain a high-purity magnesium hydroxide product (containing 8.5 g / L of magnesium). The magnesium recovery rate was 89.3%. (6) Nickel-cobalt desorption solution treatment: The nickel-cobalt desorption solution obtained in step (4) is purified and concentrated to obtain high-purity nickel sulfate and cobalt sulfate products, wherein the recovery rate of nickel is 90.8% and the recovery rate of cobalt is 91.6%.

[0033] Table 1 details the recovery rates of nickel, cobalt, and magnesium from the eluent of nickel-cobalt-magnesium resin in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2.

[0034] Table 1 Recovery rates of nickel, cobalt, and magnesium

[0035] As shown in Table 1, the nickel-cobalt-magnesium recovery rates of Examples 1, 2, and 3, which utilize the freeze-crystallization technology of the present invention to recover nickel-cobalt-magnesium from the eluent of nickel-cobalt-magnesium resin, are significantly higher than those of Comparative Example 1, which only did not employ the freeze-crystallization technology compared to Examples 1, 2, and 3. Furthermore, these rates are also much higher than those of Comparative Example 2, which uses the existing ion exchange resin adsorption method to recover nickel-cobalt-magnesium from the eluent of nickel-cobalt-magnesium resin. Moreover, the nickel-cobalt-magnesium recovery rate of Example 3 is higher than that of Examples 1 and 2. Therefore, the method for recovering nickel-cobalt-magnesium from the eluent of nickel-cobalt-magnesium resin in Example 3 is the optimal one.

[0036] In summary, this invention recovers nickel ammonium sulfate (nickel recovery) by adding ammonium sulfate to the nickel-cobalt-magnesium resin eluent for freeze crystallization, then using the nickel-removing crystallization mother liquor (acidity 0.8-1.2N) as the washing acid for the P507 cobalt extraction process, followed by P507 organic phase extraction to recover cobalt (cobalt recovery), and then the magnesium-containing extraction residue is degreased and impurity removed before MVR evaporation crystallization to recover magnesium ammonium sulfate (magnesium recovery). By organically combining multiple unit operations such as freeze crystallization, P507 extraction, and MVR evaporation, the invention achieves the stepwise separation and comprehensive recovery of nickel, cobalt, and magnesium. The integrated recycling method and material flow design of this invention greatly simplify the recycling process and improve recycling efficiency. By utilizing the mother liquor from the frozen nickel removal crystallization, the mother liquor after frozen crystallization of nickel ammonium sulfate is directly used as the washing acid for P507 cobalt extraction, utilizing its original acidity (0.8-1.2N), reducing the consumption of fresh sulfuric acid, achieving internal material circulation and waste reduction, in line with the concepts of green metallurgy and circular economy. The entire process aims to efficiently and continuously recover all valuable metals (nickel as nickel ammonium sulfate, cobalt as cobalt chloride or cobalt sulfate, and magnesium as magnesium ammonium sulfate), improving resource utilization and reducing solid waste generation. Wastewater volume is reduced; adding solid ammonium sulfate to the eluent does not increase volume or decrease acidity, and the entire recycling process does not generate new wastewater, reducing wastewater treatment costs. The recovered nickel ammonium sulfate has high purity; during frozen crystallization, nickel ammonium sulfate seed crystals are added, and the cooling rate and freezing temperature are controlled to prevent cobalt and magnesium crystal precipitation and the formation of mixed crystals with nickel.

[0037] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent, characterized in that: Specifically, the following steps are included: S1. The pretreated nickel-cobalt-magnesium resin eluent is subjected to a freeze crystallization method. The dissolved nickel-cobalt-magnesium resin eluent is cooled to the metastable zone, nickel ammonium sulfate hexahydrate seed crystals are added, sieved and evenly sprinkled on the surface of the dissolved nickel-cobalt-magnesium resin eluent, and then cooled and kept warm to grow crystals to recover high-purity nickel ammonium sulfate hexahydrate crystals. S2. The nickel removal crystallization mother liquor enters the cobalt P507 line as a cobalt washing solution, and undergoes cobalt washing in the washing section and cobalt back-extraction in the extraction section, as detailed below: a1. The mother liquor for removing nickel crystals is added to the washing section of the cobalt P507 extraction line to wash the loaded organic phase. The flow ratio of the organic phase to the aqueous phase in the washing section is (6-15):

1. a2. Then, cobalt is recovered by extraction in the extraction section using P507 organic phase extraction. The flow ratio of organic phase to aqueous phase in the extraction section is (1.5-4):

1. S3. After removing oil and impurities from the magnesium-containing ammonium sulfate raffinate produced by P507 extraction in step S2, magnesium ammonium sulfate is recovered by MVR. Specifically, the magnesium-containing ammonium sulfate raffinate after cobalt extraction by P507 is subjected to oil removal, resin adsorption for impurity removal and evaporation crystallization steps in sequence to recover magnesium ammonium sulfate product.

2. The method for recovering nickel, cobalt, and magnesium from nickel-cobalt-magnesium resin eluent according to claim 1, characterized in that: The specific steps for recovering high-purity nickel ammonium sulfate hexahydrate crystals using the freeze-crystallization method in step S1 are as follows: T1. Take a certain volume of the eluent and heat it in a water bath to 65-75℃, stirring at a speed of 450-550 r / min. Then add solid industrial ammonium sulfate and dissolve it completely for 1-1.5 hours. T2. Cool the fully dissolved solution from step T1 and stir it. T3. After the cooling operation in step T2, the fully dissolved eluent in step T1 is cooled to the metastable zone. 0.5%-2% of the expected nickel ammonium sulfate yield is added as nickel ammonium sulfate hexahydrate seed crystals with a particle size of 100-200 mesh. The seed crystals are then evenly sprinkled on the surface of the fully dissolved eluent in step T1 using a 100-200 mesh sieve. The stirring rate is 100-200 r / min when adding the seed crystals. T4. After the seed crystals are added, slowly restore the stirring rate to 250-350 r / min for 2-3 minutes, and finally cool down to -5 to -10℃. Reduce the stirring rate to 100-200 r / min and continue to keep the temperature warm for 1-2 hours to grow crystals. T5. Centrifugal filtration is carried out using a stepped acceleration method. Under high-speed centrifugation, deionized water at 0-5℃ is used for washing. The washing liquid is sprayed evenly onto the surface of the filter cake in a mist using a sprayer or washing tube. The unloaded material is high-purity nickel ammonium sulfate hexahydrate crystals.

3. The method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent according to claim 2, characterized in that: The composition of the eluent in step T1 is: nickel 25-40 g / l, cobalt 3-6 g / l, magnesium 2-4 g / l and total nitrogen 2-5 g / l, and the acidity of the eluent is 0.8-1.2 N.

4. The method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent according to claim 2, characterized in that: The amount of solid industrial ammonium sulfate added in step T1 is 0.95-1.05 times the nickel content in the eluent.

5. The method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent according to claim 2, characterized in that: In step T2, the cooling rate of the fully dissolved eluent from step T1 is 0.1-0.5℃ / min, and the stirring rate is 250-350r / min.

6. The method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent according to claim 1, characterized in that: In step a2, the P507 organic phase extraction is performed using liquid alkali saponification, with a saponification rate of 50%-60%.

7. The method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent according to claim 1, characterized in that: In step S3, oil removal is performed using an activated carbon adsorption column, with the oil content at the adsorption endpoint being ≤20ppm.

8. The method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent according to claim 1, characterized in that: In step S3, resin adsorption for impurity removal involves using a nickel-cobalt chelating resin to remove and recover nickel-cobalt impurities, with the flow rate BV controlled at 5-10.

9. The method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent according to claim 1, characterized in that: In step S3, the evaporation crystallization is MVR evaporation crystallization, and the operating temperature is 50-70℃.

10. A method for recovering nickel, cobalt, and magnesium from a nickel-cobalt-magnesium resin eluent according to claim 1, characterized in that: The pretreatment in step S1 specifically involves filtering the nickel-cobalt-magnesium resin eluent to remove suspended solid impurities and obtain a clarified liquid.

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