A method for deep purification of a nickel chloride solution

Abstract

The application discloses a deep purification method of a nickel chloride solution and belongs to the technical field of hydrometallurgy. 2+ The method comprises the following steps: (1) copper displacement and precipitation: a composite active agent composed of active nickel concentrate and anode slime in a mass ratio of 4:1 is added in a nickel concentrate:Cu =4:1 ratio, and the pH is increased to 2.0-2.5 and the copper is deeply removed after 3-4 hours of reaction at 90 DEG C; (2) P204 impurity removal: P204 organic phase with a saponification rate of 50% is used to remove Ca, Mg, Mn and Zn under the conditions of pH 3.5-4.0 and O / A=1.5:1; (3) N235 separation of nickel and cobalt: an organic phase composed of 20% N235, 14% isooctanol and 66% sulfonated kerosene is used to deeply remove Cu, Fe, Co and Zn and separate nickel and cobalt under the conditions of Cl-≥270 g / L and O / A=1:1, and the crystallization of nickel chloride is inhibited through organic phase pre-acidification or nickel acid reflux technology. The application realizes the natural connection of deep impurity removal and the process, solves the problems of extraction crystallization and zinc poisoning, and has the advantages of short process, continuous stability, low cost and high product purity.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to a method for purifying and separating nickel chloride solution, and in particular a continuous method and system for achieving deep removal of impurities and efficient separation of nickel and cobalt by integrating displacement copper deposition, multi-stage extraction and crystallization control technologies. Background Technology

[0002] High-purity nickel is a key basic material in aerospace, microelectronics, and special alloys. Its preparation hinges on the deep purification of nickel-containing solutions (especially nickel chloride systems) to completely remove various impurity elements such as copper, cobalt, iron, zinc, calcium, and magnesium. Nickel and cobalt have extremely similar properties, making their separation difficult. This makes the deep purification of nickel chloride solutions and the separation of nickel and cobalt a technical bottleneck in hydrometallurgy.

[0003] Currently, this field mainly faces the following technical challenges: 1. Limitations of copper removal methods: For nickel chloride solutions with high copper content, traditional hydrogen sulfide methods are highly toxic and have poor safety; activated nickel sulfide methods suffer from easy deactivation and operational instability; while ion exchange resin methods (such as the IRC-748 resin method described in publication number CN201810490046.4) can achieve deep copper removal, they are more suitable for solutions with low impurity concentrations. When treating high copper concentration solutions, the resin load is fast and regeneration is frequent, resulting in high operating costs and complex operation. Furthermore, it cannot simultaneously address the problem of excessively high solution acidity (low pH value), requiring additional steps to adjust the pH.

[0004] 2. Significant Issues with Extractant Performance and Synergy: Single extractants struggle to handle complex impurity profiles. For example, extractants such as Cyanex 272 (as described in publication CN201510812285.3) can effectively separate nickel and cobalt, but their removal capacity for divalent metal impurities such as calcium, magnesium, and zinc is limited, and they cannot directly process unpurified solutions under high acidity. More critically, tertiary amine extractants (such as N235), widely used in chloride systems for nickel and cobalt separation, are prone to precipitating nickel chloride crystals due to solution supersaturation during operation, leading to pipe and equipment blockages and disrupted production. Furthermore, N235 is sensitive to zinc, easily causing "zinc poisoning" and reducing separation efficiency. Combining acidic phosphorus extractants (such as P204) with N235 presents problems such as large differences in pH conditions between the two extraction stages, requiring repeated adjustments, lengthy processes, and increased metal loss.

[0005] 3. Fragmented process flow and low integration: Existing technologies often treat impurity removal, pH adjustment, and separation as independent unit operations. For example, after copper removal by displacement, alkali needs to be added for neutralization to suit subsequent extraction, and pH adjustment and liquid-solid separation processes need to be set up independently between extraction stages. This fragmentation results in a long process flow, large equipment investment, many control nodes, high reagent consumption (especially alkali consumption), and makes it difficult to achieve efficient and continuous industrial production.

[0006] Therefore, developing an integrated purification and separation method that can efficiently process nickel chloride solutions with high impurity concentrations, achieve deep and synergistic removal of multiple impurities, effectively inhibit crystallization during the extraction process, and has a short process flow and can operate continuously and stably has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of the prior art and provide a method for deep purification of nickel chloride solution. This method can synergistically remove multiple impurities, including copper, cobalt, iron, zinc, calcium, magnesium and manganese, and in particular, block the toxicity of zinc to the subsequent extractant.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for deep purification and nickel-cobalt separation of nickel chloride solution is based on a three-stage synergistic continuous process: "copper displacement deposition → preferential impurity removal with P204 → nickel-cobalt separation and deep purification with N235", integrating crystallization control technology. The specific steps are as follows: Step 1: Replacement copper plating A composite activator composed of activated nickel concentrate and anode slime at a mass ratio of 4:1, and based on the ratio of activated nickel concentrate to Cu in the solution... 2+ The nickel chloride feedstock solution was added at a mass ratio of 4:1. The initial reaction temperature was 65℃, and after addition, the temperature was raised to 90℃ and maintained at this temperature for 3-4 hours. This step utilizes the reducing property of nickel to displace copper, while simultaneously consuming the acid in the solution, naturally raising the pH of the output solution from an initial <0.6 (acidity of the chlorine leaching solution) to 2.0-2.5. This process not only removes copper concentration from approximately 26.55 g / L to <0.01 g / L (removal rate >99.97%), but also simultaneously replenishes 14-20 g / L of nickel ions.

[0009] Step 2: P204 preferential impurity removal The copper-removed solution with a pH of 2.0-2.5 obtained in step one is directly introduced into the P204 extraction stage. The organic phase used is P204 with a saponification rate of 50%, consisting of 20% P204 and 80% sulfonated kerosene by volume. Multi-stage countercurrent extraction is carried out under the conditions of 40-50℃, aqueous phase pH of 3.5-4.0, and organic phase to aqueous phase volume ratio (O / A) of 1.5:1. This step aims to preferentially and thoroughly remove divalent metal impurities such as calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) from the solution, thereby eliminating the risk of "zinc poisoning" from the subsequent N235 extractant and creating pure material conditions for nickel-cobalt separation.

[0010] Step 3: N235 Nickel-Cobalt Separation and Deep Purification The raffinate obtained in step two (pH approximately 4.0) was introduced into the N235 extraction section. The organic phase used consisted of 20% N235 (v / v), 14% isooctanol, and 66% sulfonated kerosene. Extraction was carried out under conditions of controlled Cl⁻ concentration ≥270 g / L in the aqueous phase, temperature 40-50℃, and O / A = 1:1, achieving deep removal of residual trace amounts of copper, iron, cobalt, and zinc, as well as efficient separation of nickel and cobalt.

[0011] To overcome the technical challenge of N235 easily crystallizing and clogging equipment in nickel chloride systems, this invention integrates one or a combination of the following crystallization control technologies: Organic phase pre-acidification: The N235 organic phase was pre-treated with 5 mol / L hydrochloric acid solution at a volume flow ratio of 15:1 to the organic phase. The acidified aqueous phase was then separated and removed to prevent free acid from entering the extraction system.

[0012] Nickel washing reflux: A 2 mol / L hydrochloric acid solution (nickel washing acid) is refluxed into the extraction section at a volume flow ratio of 10:1 to the supported organic phase.

[0013] Compared with the prior art, the present invention has the following significant advantages: 1. Highly integrated process, improved efficiency: The three-stage process is interconnected. The output pH (2.0-2.5) of the copper plating process directly meets the feed requirements (pH 3.5-4.0) for P204 impurity removal. The pH of the P204 raffinate (~4.0) is also within the appropriate range after natural acidification with the N235 system. This eliminates the independent intermediate steps such as pH adjustment and filtration found in traditional processes, shortening the process by approximately 40% and achieving true continuous production.

[0014] 2. Thorough Impurity Removal and Prevention of Toxicity: The P204 pre-process prioritizes the deep removal of impurities such as Zn, Ca, Mg, and Mn, which cause "zinc poisoning" in N235 extraction. This fundamentally protects the core N235 extraction section, ensuring efficient and stable nickel-cobalt separation. The final purified solution contains extremely low levels of impurities (e.g., Cu < 0.0011 g / L, Co < 0.001 g / L), and the nickel-cobalt ratio (ρ(Ni) / ρ(Co)) is greater than 200,000.

[0015] 3. Solving the crystallization problem and ensuring stable operation: The innovative dual control mechanism of organic phase acidification and nickel washing acid reflux effectively inhibits the precipitation of nickel chloride crystals, solves the common industry problem of pipeline and equipment blockage, and ensures that the system can operate in a long-term, stable and continuous manner.

[0016] 4. Economical and environmentally friendly, resource-saving: The copper displacement process utilizes nickel concentrate to replace copper and consumes acid, replacing the traditional external alkali neutralization, saving approximately 30% of alkali consumption. Simultaneously, this process also replenishes nickel ions, improving metal recovery rate. The entire system is a closed loop, consuming minimal reagents and is environmentally friendly. Detailed Implementation

[0017] The present invention will be further explained and described below with reference to specific embodiments.

[0018] The method of this invention uses a nickel chloride solution containing impurities (such as chlorine leaching solution) as raw material, which is sequentially passed through a displacement copper plating reactor, a P204 multi-stage extraction tower, and an N235 extraction-back-extraction integrated box to finally obtain a deeply purified nickel chloride solution. The entire system can achieve continuous or semi-continuous feeding and discharging.

[0019] The specific implementation steps are as follows: 1. Replacement copper plating step Take a certain volume of nickel chloride feed solution (for example, its typical components may include: Ni 2+ Approximately 60-80 g / L, Cu 2+ Approximately 20-30 g / L for Fe, approximately 10-20 g / L for Co, and approximately 1-3 g / L for Co, with an initial pH < 0.6), pumped into a reaction vessel equipped with an organic base stirrer and an electrically heated temperature control.

[0020] Start stirring and preheat the liquid to 65°C. Then, react the active nickel concentrate with the Cu in the solution... 2+ A composite activator, pre-mixed with active nickel concentrate and anode slime at a mass ratio of 4:1, is calculated and added. This composite activator should ideally be freshly prepared and stored for no more than 72 hours.

[0021] After the materials have been added, continue heating to raise the temperature of the reaction system to 90°C and maintain this temperature. Continue stirring the reaction at this temperature for 3-4 hours.

[0022] After the reaction is complete, liquid-solid separation is performed (e.g., sedimentation followed by decantation or filtration) to obtain a copper-removed liquid and a copper-rich slag phase (from which copper can be further recovered). The pH of the copper-removed liquid will naturally rise to 2.0-2.5, and the Cu content will increase. 2+ The concentration can be reduced to below 0.01 g / L, while the Ni in the solution... 2+ The concentration has increased.

[0023] Key control points: reaction temperature (90℃ constant temperature), activator ratio and dosage, and reaction time.

[0024] 2. P204 impurity removal step The copper-removed solution (pH=2.0-2.5) obtained above can be directly pumped into the P204 multi-stage countercurrent extraction tower (or extraction tank) as the aqueous phase without any pH adjustment.

[0025] Organic phase preparation: 20% by volume of P204 extractant was mixed with 80% sulfonated kerosene, and saponification was performed using a 4 mol / L NaOH solution, with the saponification rate controlled at 50%.

[0026] Control the aqueous phase feed temperature at 40-50℃, and fine-tune (if necessary) the pH of the aqueous phase in the extraction section to stabilize within the range of 3.5-4.0. Set the volumetric flow ratio (O / A) of the organic phase to the aqueous phase to be 1.5:1, and perform multi-stage countercurrent extraction.

[0027] After extraction with P204, divalent impurities such as Ca, Mg, Mn, and Zn in the aqueous phase (raffinate) are significantly removed (e.g., reduced to levels of 0.0018 g / L, 0.0011 g / L, 0.0011 g / L, and 0.0001 g / L, respectively), while some residual Cu, Fe, and Co are further purified. The impurity-loaded P204 organic phase is then recycled after regeneration in the back-extraction system.

[0028] Key control points: aqueous phase pH (3.5-4.0), phase ratio (O / A=1.5:1), and saponification rate (50%).

[0029] 3. N235 separation of nickel and cobalt and deep purification steps The raffinate after removing impurities from P204 (pH approximately 4.0, Cl) - (The concentration usually already meets the requirement of ≥270 g / L) and is introduced into the N235 extraction-back-extraction integrated system.

[0030] Organic phase preparation: 20% by volume of N235 extractant, 14% isooctanol (phase modifier) ​​and 66% sulfonated kerosene are mixed to prepare the N235 organic phase used in this invention.

[0031] Implementation of crystallization control technology: To ensure continuous and stable operation of this step and prevent nickel chloride crystallization, one or a combination of the following methods can be used: a. Organic phase pre-acidification: Before entering the extraction section, the organic phase is passed through an acidification mixing and clarifier. In this unit, the N235 organic phase is thoroughly mixed and contacted with a 5 mol / L HCl solution at a volumetric flow ratio of organic phase:acid = 15:1 to complete the acidification. Subsequently, the aqueous phase (acidified aqueous phase, containing a small amount of Ni²⁺, etc.) is separated in the clarifier and treated separately to prevent acid from entering the main extraction section. The acidified organic phase then enters the extraction section.

[0032] b. Nickel wash reflux: In the back-extraction section of the N235 system, the supported organic phase is back-extracted with hydrochloric acid to recover nickel, generating a nickel-containing hydrochloric acid solution (nickel wash). This 2 mol / L nickel-containing hydrochloric acid solution is precisely metered and refluxed into the appropriate stage of the extraction section at a volume flow ratio of 10:1 to the supported organic phase from the extraction section to suppress crystallization.

[0033] Main extraction operation: Multi-stage countercurrent extraction is performed at a temperature of 40-50℃ and an organic-to-aqueous phase volumetric flow ratio (O / A) of 1:1. During this process, trace amounts of residual Cu, Fe, Co, and Zn in the solution are deeply extracted into the organic phase, while high-purity nickel is enriched in the aqueous phase (purified solution). The Ni concentration in the purified solution can reach approximately 200 g / L, while the Co concentration can be reduced to approximately 0.001 g / L, and the nickel-cobalt ratio (ρ(Ni) / ρ(Co)) is greater than 200,000.

[0034] The N235 organic phase loaded with impurities such as cobalt enters the back-extraction section to recover valuable metals such as cobalt, and the regenerated organic phase is recycled.

[0035] Key control points: aqueous phase Cl⁻ concentration (≥270 g / L), phase ratio (O / A=1:1), and effective implementation of crystallization control technology (acidification flow ratio or reflux flow ratio).

[0036] Example 1 Following the specific implementation method described above, a batch of nickel chloride feed solution was continuously processed. The main operating parameters for each step are as described above. Samples were taken from the feed solution, the solution after copper displacement precipitation, the P204 raffinate, and the N235 purification solution for analysis. The changes in the content and removal rate of key impurity elements are shown in Table 1.

[0037] Table 1. Overall purification effect As can be seen from the above specific implementation methods and examples: (1) Smooth process connection: The pH of the replacement solution (2.3) directly enters the P204 extraction (pH controlled 3.8), and the P204 raffinate directly enters the N235 system, eliminating the need for external pH adjustment throughout the process.

[0038] (2) Thorough removal of impurities: The P204 process reduces Zn from 0.0040 g / L to 0.0001 g / L, effectively preventing zinc poisoning by N235; the N235 process ultimately removes Co from 2.24 g / L to 0.001 g / L.

[0039] (3) Crystallization was controlled: In the example of implementing organic phase pre-acidification (15:1) and nickel acid washing reflux (10:1), no pipe or equipment blockage was observed in the N235 extraction system after 120 hours of operation.

[0040] (4) Significant economic benefits: Compared with the traditional process of multiple alkali additions for neutralization, the total sodium hydroxide consumption in this embodiment is estimated to be reduced by about 30%.

[0041] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for deep purification of nickel chloride solution, characterized in that, Includes the following sequential steps: (1) Displacement of copper: A composite activator is added to a nickel chloride solution to carry out a displacement reaction. The composite activator is composed of active nickel concentrate and anode slime in a mass ratio of 4:

1. The amount of active nickel concentrate added is related to the amount of Cu in the solution. 2+ The mass ratio is 4:1, and the reaction is carried out at 90℃ for 3-4 hours to obtain a copper-removed solution with a pH value of 2.0-2.5; (2) P204 impurity removal: The copper-removed liquid obtained in step (1) is subjected to multi-stage extraction with a P204 organic phase with a saponification rate of 50%. The P204 organic phase consists of 20% P204 and 80% sulfonated kerosene by volume. The pH of the aqueous phase is controlled at 3.5-4.0, and the volume ratio of the organic phase to the aqueous phase is 1.5:1, in order to remove calcium, magnesium, manganese and zinc impurities from the solution. (3) Separation of nickel and cobalt by N235: The raffinate obtained in step (2) is extracted with the acidified N235 organic phase, which consists of 20% N235, 14% isooctanol and 66% sulfonated kerosene by volume. The Cl content in the aqueous phase is controlled. - With a concentration ≥270 g / L and an organic phase to aqueous phase volume ratio of 1:1, it is used to deeply remove copper, iron, cobalt, and zinc impurities and separate nickel and cobalt.

2. The method according to claim 1, characterized in that, In step (1), the storage time of the composite activator shall not exceed 72 hours, the reaction start temperature shall be 65℃, and the temperature shall be raised to 90℃ after the composite activator is added.

3. The method according to claim 1, characterized in that, In step (3), the acidification treatment of the N235 organic phase uses a hydrochloric acid solution with a concentration of 5 mol / L. The volume flow ratio of the organic phase to the hydrochloric acid solution in the acidification section is 15:

1. After acidification, the acidified aqueous phase is separated and removed.

4. The method according to claim 1, characterized in that, In step (3), a 2 mol / L hydrochloric acid solution is used as washing nickel acid for reflux operation. The reflux operation is to add the hydrochloric acid solution into the extraction section at a volume flow ratio of 10:1 to the loaded organic phase.

5. A system for implementing the method according to any one of claims 1-4, characterized in that, include: A copper displacement reactor is used to carry out the displacement reaction in step (1) of claim 1, wherein the reactor is equipped with a mechanical stirring and temperature control device; The P204 multi-stage extraction tower is connected to the outlet of the copper displacement reactor and is used for extraction and impurity removal in step (2) of claim 1. The N235 extraction-back-extraction integrated box is connected to the raffinate outlet of the P204 multi-stage extraction tower for extraction separation in step (3) of claim 1. The integrated box has an organic phase acidification unit and / or a nickel acid washing reflux unit built in it.

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