A method for preparing a nickel sulfate solution from crude nickel cobalt hydroxide

Abstract

This invention discloses a method for preparing nickel sulfate solution from crude nickel-cobalt hydroxide, relating to the field of hydrometallurgical technology. The specific steps of this method are as follows: first, the crude nickel-cobalt hydroxide raw material is crushed, ground, and slurried; after a first-stage leaching, it is separated by pressure filtration to obtain a first-stage leachate and residue; the first-stage leachate is subjected to two nickel soap extractions to obtain multiple solutions; the first-stage leaching residue is subjected to a second-stage leaching, and filtered to obtain a second-stage leaching solution and residue; the second-stage leaching solution is subjected to two sodium soap extractions to collect the raffinate; the second-stage leaching residue is washed, and the washing liquid is combined with the crude nickel sulfate solution to obtain a refined nickel sulfate solution. This invention employs a two-stage stepwise leaching process, combined with a dedicated extraction system to achieve efficient metal separation and impurity removal; optimizes the extraction process, improving stability and separation effect; treats the second-stage leaching residue to improve nickel recovery rate; refines the product purity; and recycles materials throughout the process, reducing emissions and costs, making it suitable for continuous industrial production.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, specifically to a method for preparing nickel sulfate solution using crude nickel cobalt hydroxide. Background Technology

[0002] Nickel sulfate solution is a core raw material in nickel salt preparation, battery material production, electroplating, and other fields, playing an important role in the metallurgical, chemical, and new energy materials industries. Crude nickel-cobalt hydroxide, as a common intermediate raw material or by-product in industrial production, contains a large amount of valuable nickel-cobalt metal, along with impurities such as magnesium, copper, manganese, zinc, and iron. Resource-based treatment to prepare high-purity nickel sulfate solution is an important path to improve resource utilization and reduce raw material costs, and it also aligns with the industry's development direction of circular economy and green production. Currently, hydrometallurgical processes are the mainstream method for processing such raw materials, with leaching and extraction as the core processes. The industry continues to explore efficient extraction and separation technologies, and how to achieve deep leaching of raw materials, precise metal separation, and efficient removal of impurities has become the key to preparing high-quality nickel sulfate solution. The market demand for efficient, stable, and low-cost preparation processes suitable for crude nickel-cobalt hydroxide continues to increase.

[0003] Traditional processes for preparing nickel sulfate from crude nickel-cobalt hydroxide have many limitations. The single leaching mode cannot fully extract nickel metal from the raw materials, leaving a large number of valuable components in the leaching residue, directly causing resource depletion. The overall metal recovery rate is difficult to achieve the ideal level. Traditional extraction processes lack separation precision, making it difficult to achieve efficient fractional separation of metals such as nickel, cobalt, and magnesium. The removal of impurities is not effective, easily leading to substandard purity of the nickel sulfate solution, which cannot meet the quality requirements of high-end applications. Some traditional process flows are not well connected, the material recycling rate is low, and a lot of waste liquid and residue are generated during the production process, resulting in high environmental protection pressure and high energy consumption and production costs. At the same time, traditional processes do not adequately recycle the leaching residue, have poor process stability, and are difficult to adapt to the complex composition characteristics of crude raw materials. The continuous industrial production effect is not good, which restricts the large-scale promotion of the resource utilization of crude nickel-cobalt hydroxide. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing nickel sulfate solution from crude nickel hydroxide and cobalt hydroxide. This method integrates a two-stage stepwise leaching process, graded extraction and separation, leaching residue washing and recovery, and finished product refining. This achieves efficient resource utilization of raw materials. The process employs a first-stage leaching to extract the main nickel components, followed by a second-stage reduction leaching to deeply recover residual nickel from the residue. A targeted extraction system is used to achieve efficient separation of nickel, cobalt, and magnesium, removing various impurities. Valuable metals in the leaching residue washing liquid are recovered simultaneously, significantly improving the overall nickel recovery rate. The entire process features smooth material flow and stable operation, adaptable to the complex composition characteristics of crude raw materials, and produces high-purity, high-quality nickel sulfate solution to meet the needs of high-end industrial applications. Simultaneously, it reduces energy consumption and waste emissions, offering both economic and environmental benefits, and is suitable for large-scale industrial production.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing nickel sulfate solution using crude nickel cobalt hydroxide, the specific steps of which are as follows: S1, First stage leaching preparation: Crude nickel-cobalt hydroxide raw material is crushed and ground, pure water is added and stirred to make slurry, sulfuric acid is added dropwise to the slurry to adjust the pH value of the system, after constant temperature reaction, pre-slurried crude nickel-cobalt hydroxide is added to adjust the pH value of the system, and the first stage leaching solution and the first stage leaching residue are obtained by pressure filtration. S2, First stage of leachate extraction: The first stage of leachate is successively treated with nickel soap P204 extraction and nickel soap P507 extraction to separate crude nickel sulfate solution, magnesium sulfate solution and cobalt sulfate solution. S3, two-stage leaching preparation: the first-stage leaching residue is added to the washing water or process bottom water to make a slurry, sulfuric acid is added to adjust the pH value of the system, and after constant temperature reaction, a reducing agent is added to carry out reduction leaching. After adjusting the pH value of the system, the second-stage leaching solution and the second-stage leaching residue are obtained by filtration. S4, Purification of the second-stage leachate: The second-stage leachate is successively extracted with sodium soap P204 and sodium soap P507, and the raffinate is collected as crude nickel sulfate solution. S5, Finished product refining treatment: The second-stage leaching residue is acid-washed with sulfuric acid and then washed twice with tap water. The washing liquid is collected and combined with the crude nickel sulfate solution obtained from the previous processes. The solution is then concentrated under reduced pressure, pH adjusted, and precision filtered to obtain a nickel sulfate solution.

[0006] Further, in step S1, the crude nickel-cobalt hydroxide raw material is crushed and ground to a particle size of 180 to 200 mesh, the liquid-to-solid mass ratio of the slurry is 3.2:1 to 4.8:1, the stirring speed is 220 r / min to 380 r / min, the stirring time is 35 min to 55 min, sulfuric acid is added dropwise to adjust the pH value of the system to 0.9 to 1.1, and the pH value of the system is adjusted back to 4.5 to 5.0.

[0007] Furthermore, in step S1, the added sulfuric acid is industrial sulfuric acid with a mass fraction of 45% to 55%, the dropping rate is 10 mL / min to 20 mL / min, the constant temperature reaction temperature after adjusting the pH value to 0.9 to 1.1 is 65°C to 75°C, the pressure filtration separation is carried out using a chamber plate and frame filter press, the pressure is 0.45 MPa to 0.55 MPa, and the pressure filtration time is 32 min to 42 min.

[0008] Furthermore, in step S2, the extractant for the nickel soap P204 extraction is an organic phase of P204 and sulfonated kerosene mixed in a volume ratio of 1:4 to 1:6. The extractant is activated by pretreatment with two stages of sodium soap and six stages of nickel soap. The ratio of the extractant to the first stage of leachate is 1.8:1 to 2.2:1, and the number of extraction stages is eleven stages of countercurrent extraction.

[0009] Furthermore, in step S2, the organic phase extracted by nickel soap P204 is sequentially subjected to eight-stage low-acid countercurrent washing, five-stage high-acid countercurrent back-extraction, and two-stage anti-iron purification treatment; the extractant for nickel soap P507 extraction is an organic phase of P507 mixed with sulfonated kerosene at a volume ratio of 1:3 to 1:5, and the extraction stage is eighteen-stage countercurrent extraction.

[0010] Furthermore, in step S3, the liquid-to-solid mass ratio of the first-stage leaching residue slurry is 4.2:1 to 5.8:1, sulfuric acid is added to adjust the pH value of the system to 1.4 to 1.6, the constant temperature reaction temperature is 75°C to 85°C, the reducing agent is anhydrous sodium sulfite, the amount of reducing agent added is 4% to 7% of the mass of the first-stage leaching residue, and the pH value of the system is adjusted to 4.5 to 5.0.

[0011] Furthermore, in step S3, the pH value of the system is adjusted using a sodium carbonate solution, the filtration separation is performed using a vacuum filter with a vacuum degree of -0.05MPa to -0.045MPa, the filtration time is 22min to 28min, and the filter cloth material is polyester 747 filter cloth.

[0012] Furthermore, in step S4, the extractant for sodium soap P204 extraction is an organic phase of P204 and sulfonated kerosene mixed in a volume ratio of 1:5 to 1:7. The extractant is activated by two-stage sodium soap pretreatment, with a saponification rate of 70% to 80%. The ratio of the extractant to the second-stage leachate is 1.2:1 to 1.8:1, and the extraction stage is nine-stage countercurrent extraction.

[0013] Furthermore, in step S4, the organic phase after extraction with sodium soap P204 is sequentially subjected to six-stage low-acid countercurrent washing, five-stage anti-copper-manganese, five-stage anti-zinc, and two-stage anti-iron purification treatments; the extraction with sodium soap P507 includes ten-stage countercurrent extraction, five-stage washing, and fourteen-stage segmented back-extraction, with the segmented back-extraction divided into anti-magnesium and anti-cobalt stages.

[0014] Furthermore, in step S5, the second-stage leaching residue is pickled using dilute sulfuric acid with a mass fraction of 25% to 35%, the pickling temperature is 55°C to 65°C, the pickling time is 1.5h to 2.5h, the vacuum degree of the reduced pressure concentration is -0.075MPa to -0.065MPa, the concentration temperature is 65°C to 75°C, and the precision filtration uses a 0.22μm polytetrafluoroethylene microporous filter element.

[0015] Compared with existing technologies, this method for preparing nickel sulfate solution from crude nickel cobalt hydroxide has the following advantages: I. This invention employs a two-stage, step-by-step leaching process. First, the crude raw material is initially leached to extract the core nickel component. Then, the leaching residue is subjected to reductive leaching to further extract nickel, fully tapping the leaching potential of nickel in the raw material and significantly improving the overall recovery efficiency of valuable metals. Combined with an extraction system matched to each stage of the leaching solution, efficient separation of metals such as nickel, cobalt, and magnesium is achieved, while simultaneously removing various impurities such as copper, manganese, zinc, and iron, thus solidifying the purity foundation of the crude nickel sulfate solution. The processes are closely linked and the flow is smooth, effectively reducing the loss and leakage of intermediate materials, maximizing the utilization value of the crude nickel hydroxide cobalt raw material, reducing raw material waste and production losses, and simultaneously achieving the separate enrichment of valuable metals such as nickel and cobalt. This lays a good foundation for subsequent product purification and component utilization, improving the overall economic efficiency and raw material compatibility of the process.

[0016] II. This invention optimizes the combined process of extraction pretreatment and multi-stage countercurrent extraction, washing, and back-extraction. It employs a dedicated saponification extraction method for different leachates, resulting in more thorough impurity removal and more precise metal separation. This enhances the stability and separation effect of the process. The second-stage leaching residue is acid-washed and washed a second time to recover residual nickel components, which are then incorporated into the crude liquid system, further increasing the overall nickel recovery level. Subsequent refining treatments, including vacuum concentration, precise pH control, and precision filtration, remove fine impurities and particulate matter from the solution, improving the purity and quality stability of the finished nickel sulfate solution. The entire process achieves material recycling, reduces waste liquid and residue emissions, lowers energy consumption and environmental treatment costs, and is suitable for continuous industrial production of crude raw materials, ensuring stable finished product quality that meets application requirements.

[0017] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 Process flow diagram for preparing nickel sulfate solution from crude nickel-cobalt hydroxide; Figure 2 Overall process flow diagram for preparing nickel sulfate solution from crude nickel-cobalt hydroxide; Figure 3 A diagram showing the overall material flow for preparing nickel sulfate solution from crude nickel-cobalt hydroxide. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below. Example 1:

[0021] A method for preparing nickel sulfate solution using crude nickel cobalt hydroxide.

[0022] S1, First-stage leaching preparation: Crude nickel-cobalt hydroxide raw material was crushed and ground to a particle size of 180 mesh. Pure water was added at a liquid-to-solid mass ratio of 3.2:1, and the mixture was stirred at 220 r / min for 35 min. 45% industrial sulfuric acid was added dropwise to the slurry at a rate of 10 mL / min to adjust the pH to 1.0. The system was placed at 65℃ for a constant-temperature reaction. After the reaction, pre-slurried crude nickel-cobalt hydroxide was added, and the pH was adjusted back to 4.5. A plate and frame filter press was used for filtration separation at a pressure of 0.45 MPa for 32 min, yielding a first-stage leachate and a first-stage leachate residue.

[0023] S2, First-stage leachate extraction: P204 and sulfonated kerosene were mixed at a volume ratio of 1:4 to prepare an organic phase, which served as the nickel soap P204 extractant. The extractant was activated by two stages of sodium soap pretreatment and six stages of nickel soap pretreatment. The activated extractant was then mixed with the first-stage leachate at a volume ratio of 1.8:1 and subjected to eleven stages of countercurrent extraction. The extracted organic phase was then subjected to eight stages of low-acid countercurrent washing, five stages of high-acid countercurrent back-extraction, and two stages of anti-iron purification. P507 and sulfonated kerosene were mixed at a volume ratio of 1:3 to prepare an organic phase, which served as the nickel soap P507 extractant. This phase was then subjected to eighteen stages of countercurrent extraction with the treated feed solution. After extraction, crude nickel sulfate solution, magnesium sulfate solution, and cobalt sulfate solution were obtained.

[0024] S3, Second-stage leaching preparation: The first-stage leaching residue was added to the washing water at a liquid-to-solid mass ratio of 4.2:1 and stirred to form a slurry. Sulfuric acid was added to the slurry to adjust the pH value of the system to 1.5, and the system was placed in a constant temperature environment of 75℃ for reaction. After the reaction, anhydrous sodium sulfite was added as a reducing agent, with the amount of reducing agent added being 4% of the mass of the first-stage leaching residue. After thorough stirring, reduction leaching was carried out. The pH value of the system was adjusted to 4.5 using sodium carbonate solution. The material was separated by vacuum filtration equipment, with the vacuum degree controlled at -0.05MPa and the filtration time at 22min. After separation, the second-stage leachate and the second-stage leaching residue were obtained.

[0025] S4, Second-stage leachate purification: P204 and sulfonated kerosene were mixed at a volume ratio of 1:5 to prepare an organic phase, which was used as the sodium soap P204 extractant. The extractant was activated by two-stage sodium soap pretreatment, with the saponification rate controlled at 70%. The activated extractant was mixed with the second-stage leachate at a ratio of 1.2:1 and subjected to nine-stage countercurrent extraction. The extracted organic phase was then subjected to six-stage low-acid countercurrent washing, five-stage anti-copper and anti-manganese treatment, five-stage anti-zinc treatment, and two-stage anti-iron purification treatment. The treated solution was then subjected to sodium soap P507 extraction, which involved ten-stage countercurrent extraction, five-stage washing, and fourteen-stage segmented back-extraction. The segmented back-extraction was divided into anti-magnesium and anti-cobalt stages. The raffinate after extraction was collected as crude nickel sulfate solution.

[0026] S5, Finished Product Refining: The second-stage leaching residue is acid-washed with 25% (w / w) dilute sulfuric acid at a controlled temperature of 55℃ for 2 hours. After acid washing, the second-stage leaching residue is washed a second time with tap water, and all washing liquid is collected. The washing liquid is combined with the crude nickel sulfate solution obtained from the first-stage leaching extraction and second-stage leaching purification processes. The mixture is then concentrated under reduced pressure at a vacuum level of -0.075 MPa and a concentration temperature of 65℃. After concentration, the pH of the mixture is adjusted, and the adjusted solution is precisely filtered using a microporous filter cartridge to finally obtain the finished nickel sulfate solution. Example 2:

[0027] Feasibility verification of leaching and extraction processes.

[0028] Feasibility verification of a single leaching process: The nickel and cobalt content in the first-stage leaching solution was determined using a spectroscopic detection device, and the leaching rates of nickel and cobalt in the first stage were calculated. The state of the reactants was recorded throughout the detection process to observe for issues such as clumping and incomplete reaction. The results showed that under the process conditions of this embodiment, both nickel and cobalt were fully leached, the residual nickel and cobalt content in the first-stage leaching residue was extremely low, the materials were uniformly dispersed during the reaction, no abnormal reaction phenomena were observed, and the leaching process was consistently stable, proving that the first-stage leaching preparation process can be successfully implemented and achieves the desired results.

[0029] Feasibility verification of extraction and separation of leachate: The composition of each phase after nickel soap P204 extraction and nickel soap P507 extraction was analyzed, with a focus on monitoring the separation of impurities such as magnesium, manganese, zinc, and cobalt in the feed solution. The results showed that nickel soap P204 extraction effectively separated magnesium, manganese, and zinc impurities from the feed solution, with no cross-contamination during the separation process, and clear separation of the organic and aqueous phases after extraction. Nickel soap P507 extraction achieved complete separation of nickel and cobalt. The residual amount of impurities in the crude nickel sulfate solution after separation was extremely low, and the magnesium sulfate and cobalt sulfate solutions had high purity, allowing for direct subsequent recovery treatment. This demonstrates that the extraction separation process can achieve the expected separation objectives.

[0030] Feasibility verification of the two-stage leaching and purification process: The nickel content in the second-stage leaching solution was monitored throughout the entire process, and the changes in nickel leaching during the reduction leaching were recorded. The results showed that reduction leaching effectively extracted the residual nickel from the first-stage leaching residue, and the reaction in the second-stage leaching process was thorough. Impurity testing of the raffinate after purification of the second-stage leaching solution revealed that impurities such as magnesium, copper, manganese, zinc, and iron were effectively removed. The quality of the raffinate met the standards for use as crude nickel sulfate solution and could be directly incorporated into subsequent refining processes, demonstrating the feasibility of the two-stage leaching and purification process. Example 3:

[0031] Optimization and testing of key parameters in the preparation process.

[0032] Five core process parameters were selected for optimization testing: raw material grinding particle size, first-stage leaching liquid-to-solid ratio, nickel soap P204 extraction ratio, second-stage leaching reducing agent addition amount, and vacuum concentration temperature. Three different levels were set for each parameter group. The optimal process parameters were determined using total nickel leaching rate, impurity removal rate, and system stability as evaluation indicators. During the testing process, all other conditions were strictly controlled to remain consistent, with only the target parameter adjusted as a single variable. Reaction data and test results were recorded throughout the entire process.

[0033] Table 1. Comparison of optimization test results for key parameters of the preparation process:

[0034] Table Analysis: This test focused on five core parameters of the preparation process. All test parameters were within the applicable range of the process, and single-variable control ensured the accuracy of the test results. Group 2 outperformed Groups 1 and 3 in all indicators. When the raw material grinding particle size was 190 mesh, the material reaction contact area was moderate, ensuring reaction efficiency while avoiding increased energy consumption due to over-grinding. A liquid-to-solid ratio of 4.0:1 in the first-stage leaching stage achieved the best balance between slurry dispersibility and reaction contact effect. A nickel soap P204 extraction ratio of 2.0:1 resulted in more thorough impurity removal and minimal nickel loss. A reducing agent addition of 5% ensured complete reduction leaching and reached peak nickel leaching rate. A concentration temperature of 70℃ resulted in the highest concentration efficiency and no crystallization in the solution, indicating optimal system stability. Based on the comprehensive data, the parameter combination in Group 2 represents the optimal parameters for the preparation process. Example 4:

[0035] Purity and yield testing of nickel sulfate solution.

[0036] Five parallel experiments were conducted using optimal process parameters. Nickel sulfate solution was prepared following the steps in Example 1 throughout the experiment, with strict control of process conditions to prevent deviations. After the experiments, the nickel content, cobalt, magnesium, manganese, zinc, and iron impurity content, and total nickel yield of the five finished solutions were precisely measured. The test data for each group were recorded and compared to evaluate the reproducibility of the process and the stability of the product quality.

[0037] Table 2 Comparison of purity and yield of nickel sulfate solution finished product:

[0038] Table Analysis: Data from five parallel experiments showed that the nickel content of the finished nickel sulfate solution remained stable between 183 g / L and 187 g / L, with minimal fluctuations. The contents of the five impurities—cobalt, magnesium, manganese, zinc, and iron—were all at extremely low levels, with no significant exceedances or fluctuations, indicating that the process effectively and stably removes impurities. The total nickel yield ranged from 92.3% to 93.1%, with an average yield of 92.66%. The difference in yield between groups did not exceed 0.8%, demonstrating excellent reproducibility of the optimal process parameters. This indicates that the process can stably produce high-purity, high-yield nickel sulfate solutions, and its reliability meets the requirements for large-scale production. Example 5:

[0039] Stability testing of the preparation process during continuous operation: The optimal process parameters were applied to a continuous production system, which was run continuously for seven production cycles, with samples taken and tested at regular intervals during each cycle. The test indicators included nickel content in the first-stage leaching solution, total impurities in the crude nickel sulfate solution, nickel content in the finished nickel sulfate solution, total impurities in the finished product, and the cycle yield of nickel. Daily test data were recorded, and the stability of process parameters and consistency of product quality under continuous operation were analyzed.

[0040] Table 3 Comparison results of continuous operation stability test of the preparation process:

[0041] Table Analysis: Test data from seven consecutive operating cycles showed that the nickel content in the first-stage leaching solution remained stable at 94 g / L-95 g / L, and the total impurities in the crude nickel sulfate solution remained stable at 0.34 g / L-0.36 g / L, with no significant fluctuations in material indicators during intermediate processes. The nickel content in the finished nickel sulfate solution remained stable at 183 g / L-186 g / L, and the total impurities remained stable at 0.033 g / L-0.035 g / L, maintaining consistent product quality. The periodic yield of nickel element was between 92.3% and 93.0%, with an overall fluctuation of no more than 0.7%, showing no significant attenuation or abnormal changes. These data fully demonstrate that during continuous operation, the parameters of each process are controllable, the reaction is stable, and a high-efficiency production state can be maintained for a long period, making it suitable for the requirements of continuous industrial production. Example 6:

[0042] Nickel sulfate solution product application compatibility test.

[0043] The nickel sulfate solution prepared by this process was used as a raw material in two major industrial applications: battery material production and electroplating. A nickel sulfate solution prepared by a conventional process was selected as a control sample, and parallel application experiments were conducted under the same production conditions. The reactivity of the two groups of samples during application and the amount of residual impurities in the final processed products were measured to compare and evaluate the application suitability of the products produced by this process.

[0044] Table 4 Comparison Results of Application Compatibility Tests for Nickel Sulfate Solution Products:

[0045] Table Analysis: In both battery material production and electroplating applications, the nickel sulfate solution prepared by this process exhibits superior performance. Regarding reactivity, the samples prepared using this process achieved a reactivity of 98.5% in battery material production and 97.8% in electroplating, both significantly higher than conventional samples. As for impurity residue, the products processed using this process showed much lower levels of the three core impurities—cobalt, magnesium, and iron—than conventional samples, demonstrating superior impurity control. These results indicate that the nickel sulfate solution prepared by this process has higher purity and better reactivity, making it perfectly suited for high-end industrial applications such as battery materials and electroplating. Its application adaptability and value surpass those of products prepared using conventional processes.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing nickel sulfate solution using crude nickel cobalt hydroxide, characterized in that, The specific steps of this method are as follows: S1, First stage leaching preparation: Crude nickel-cobalt hydroxide raw material is crushed and ground, pure water is added and stirred to make slurry, sulfuric acid is added dropwise to the slurry to adjust the pH value of the system, after constant temperature reaction, pre-slurried crude nickel-cobalt hydroxide is added to adjust the pH value of the system, and the first stage leaching solution and the first stage leaching residue are obtained by pressure filtration. S2, First stage of leachate extraction: The first stage of leachate is successively treated with nickel soap P204 extraction and nickel soap P507 extraction to separate crude nickel sulfate solution, magnesium sulfate solution and cobalt sulfate solution. S3, two-stage leaching preparation: the first-stage leaching residue is added to the washing water or process bottom water to make a slurry, sulfuric acid is added to adjust the pH value of the system, and after constant temperature reaction, a reducing agent is added to carry out reduction leaching. After adjusting the pH value of the system, the second-stage leaching solution and the second-stage leaching residue are obtained by filtration. S4, Purification of the second-stage leachate: The second-stage leachate is successively extracted with sodium soap P204 and sodium soap P507, and the raffinate is collected as crude nickel sulfate solution. S5, Finished product refining treatment: The second-stage leaching residue is acid-washed with sulfuric acid and then washed twice with tap water. The washing liquid is collected and combined with the crude nickel sulfate solution obtained from the previous processes. The solution is then concentrated under reduced pressure, pH adjusted, and precision filtered to obtain a nickel sulfate solution.

2. The method for preparing nickel sulfate solution from crude nickel cobalt hydroxide according to claim 1, characterized in that, In step S1, the crude nickel-cobalt hydroxide raw material is crushed and ground to a particle size of 180 to 200 mesh, the liquid-to-solid mass ratio of the slurry is 3.2:1 to 4.8:1, the stirring speed is 220 r / min to 380 r / min, the stirring time is 35 min to 55 min, sulfuric acid is added dropwise to adjust the pH value of the system to 0.9 to 1.1, and the pH value of the system is adjusted back to 4.5 to 5.

0.

3. The method for preparing nickel sulfate solution from crude nickel cobalt hydroxide according to claim 1, characterized in that, In step S1, the added sulfuric acid is industrial sulfuric acid with a mass fraction of 45% to 55%, the dropping rate is 10 mL / min to 20 mL / min, the constant temperature reaction temperature after adjusting the pH value to 0.9 to 1.1 is 65℃ to 75℃, the pressure filtration separation is carried out using a chamber plate and frame filter press, the pressure is 0.45 MPa to 0.55 MPa, and the pressure filtration time is 32 min to 42 min.

4. The method for preparing nickel sulfate solution from crude nickel cobalt hydroxide according to claim 1, characterized in that, In step S2, the extractant for the nickel soap P204 extraction is an organic phase of P204 and sulfonated kerosene mixed in a volume ratio of 1:4 to 1:

6. The extractant is activated by pretreatment with two-stage sodium soap and six-stage nickel soap. The ratio of the extractant to the first-stage leachate is 1.8:1 to 2.2:1, and the number of extraction stages is eleven-stage countercurrent extraction.

5. The method for preparing nickel sulfate solution from crude nickel cobalt hydroxide according to claim 1, characterized in that, In step S2, the organic phase after extraction by nickel soap P204 is sequentially subjected to eight-stage low-acid countercurrent washing, five-stage high-acid countercurrent back-extraction, and two-stage anti-iron purification treatment; the extractant for extraction by nickel soap P507 is an organic phase of P507 and sulfonated kerosene mixed in a volume ratio of 1:3 to 1:5, and the extraction stage is eighteen-stage countercurrent extraction.

6. The method for preparing nickel sulfate solution from crude nickel cobalt hydroxide according to claim 1, characterized in that, In step S3, the liquid-to-solid mass ratio of the first-stage leaching residue slurry is 4.2:1 to 5.8:1, sulfuric acid is added to adjust the pH value of the system to 1.4 to 1.6, the constant temperature reaction temperature is 75℃ to 85℃, the reducing agent is anhydrous sodium sulfite, the amount of reducing agent added is 4% to 7% of the mass of the first-stage leaching residue, and the pH value of the system is adjusted to 4.5 to 5.

0.

7. The method for preparing nickel sulfate solution from crude nickel cobalt hydroxide according to claim 1, characterized in that, In step S3, the pH value of the system is adjusted using sodium carbonate solution, the filtration separation is performed using a vacuum filter with a vacuum degree of -0.05MPa to -0.045MPa, the filtration time is 22min to 28min, and the filter cloth material is polyester 747 filter cloth.

8. The method for preparing nickel sulfate solution from crude nickel cobalt hydroxide according to claim 1, characterized in that, In step S4, the extractant for sodium soap P204 extraction is an organic phase of P204 and sulfonated kerosene mixed in a volume ratio of 1:5 to 1:

7. The extractant is activated by two-stage sodium soap pretreatment, with a saponification rate of 70% to 80%. The ratio of the extractant to the second-stage leachate is 1.2:1 to 1.8:1, and the extraction stage is nine-stage countercurrent extraction.

9. A method for preparing nickel sulfate solution from crude nickel cobalt hydroxide according to claim 1, characterized in that, In step S4, the organic phase after extraction with sodium soap P204 is sequentially subjected to six-stage low-acid countercurrent washing, five-stage anti-copper and manganese, five-stage anti-zinc, and two-stage anti-iron purification treatments; the extraction with sodium soap P507 includes ten-stage countercurrent extraction, five-stage washing, and fourteen-stage segmented back-extraction, with the segmented back-extraction divided into anti-magnesium and anti-cobalt stages.

10. A method for preparing nickel sulfate solution from crude nickel cobalt hydroxide according to claim 1, characterized in that, In step S5, the second-stage leaching residue is pickled using dilute sulfuric acid with a mass fraction of 25% to 35%, the pickling temperature is 55°C to 65°C, the pickling time is 1.5h to 2.5h, the vacuum degree of the reduced pressure concentration is -0.075MPa to -0.065MPa, the concentration temperature is 65°C to 75°C, and the precision filtration uses a 0.22μm polytetrafluoroethylene microporous filter element.

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