A pre-magnesium removal wet treatment method of nickel-cobalt mixed hydroxide

Abstract

The application provides a pre-magnesium removal wet treatment method of nickel-cobalt mixed hydroxide, and relates to the field of hydrometallurgy. The pre-magnesium removal wet treatment method of nickel-cobalt mixed hydroxide comprises the following steps: mixing the nickel-cobalt mixed hydroxide with a first washing liquid, and performing first slurry treatment; adding an acidic solution into the slurry after the first slurry treatment, stirring, performing first solid-liquid separation, and obtaining first washing residue and first filtrate; mixing the first washing residue with a second washing liquid, and performing second slurry treatment; adjusting the pH of the slurry after the second slurry treatment to 6.8-7.2, introducing CO2 gas, performing carbonization reaction, and obtaining slurry after carbonization; performing second solid-liquid separation on the slurry after carbonization, and obtaining pre-magnesium removal solid and second filtrate. The application can realize high magnesium removal efficiency under mild conditions, maximally reduce the loss of metals such as nickel and cobalt, and has the advantages of less acid consumption, less water consumption and short process, so that the application has the feasibility of continuous amplification.

Description

Technical Field

[0001] This application relates to the field of hydrometallurgy, and in particular to a pre-demagnesification hydrometallurgical treatment method for nickel-cobalt mixed hydroxides. Background Technology

[0002] In hydrometallurgical processes, nickel-cobalt mixed hydroxides (MHPs) often contain magnesium at a mass fraction of several percent. Magnesium tends to compete with nickel and cobalt for coordination during subsequent acid leaching-extraction, affecting separation efficiency. Therefore, the industry has proposed various pretreatment schemes to reduce the magnesium content. Current practices can be broadly categorized into water washing for magnesium removal, selective acid leaching, lime slurry or soda ash precipitation for magnesium, ion exchange, or membrane separation. These methods have been applied to varying degrees in industry, but still have many shortcomings.

[0003] The water washing demagnesium removal method uses multi-stage countercurrent clean water washing. This method requires a large amount of water for dilution and replacement to reduce the magnesium content. The circulating water load and drainage volume increase significantly with the number of stages. When the equipment is scaled up to high slurry concentration, there are problems such as decreased mass transfer efficiency and large fluctuations in the demagnesium removal endpoint.

[0004] Selective acid leaching involves preparing a slurry of magnesium hydroxide (MHP) in an acidic solution and reacting it under controlled pH and redox potential. Magnesium is readily soluble, while most of the nickel and cobalt remain in the solid phase. A low-magnesium filter cake can then be obtained by pressure filtration and washing the residue. This method suffers from high acid consumption and a relatively high proportion of nickel and cobalt leached out. These issues typically require balancing through washing liquor concentration, acid reversion, or lime neutralization. It is often used in conjunction with an acid recovery tower and gypsum dewatering system, which lengthens the overall process.

[0005] The lime slurry or soda ash settling process involves first completely acid-leaching MHP into the solution system, then adding Ca(OH)₂ or Na₂CO₃ to the solution in stages to slowly raise the pH to 8-9, causing magnesium to precipitate as Mg(OH)₂ or MgCO₃. Nickel and cobalt precipitate out in large quantities at higher pH levels, thus partial separation can be achieved by controlling the alkali addition rate and stirring intensity, combined with a clarification tank or high-efficiency settling tank to complete solid-liquid separation. However, this method produces flocculent slag during the magnesium precipitation stage that easily carries nickel and cobalt, and the slow settling speed and high moisture content in the sludge cake affect the continuous production cycle.

[0006] Ion exchange or membrane separation involves: dissolving MHP in acid to obtain a solution containing nickel, cobalt, and magnesium, which is then fed into a fixed-bed adsorption column packed with chelating resin. Magnesium ions are selectively captured, and the resin is regenerated with a weak acid or brine to recover magnesium ions. 2+ This method suffers from problems such as high cost of resin or membrane materials and complex treatment of regenerated liquid, making it difficult to deploy widely in large-scale smelting.

[0007] In summary, existing pre-demagnesification treatment methods for nickel-cobalt mixed hydroxides cannot simultaneously achieve a balance in terms of demagnesification efficiency, loss of key metals, consumption of reagents and water, and continuous operation. Summary of the Invention

[0008] The purpose of this application is to provide a wet pre-demagnesification treatment method for nickel-cobalt mixed hydroxides to solve the above-mentioned problems.

[0009] To achieve the above objectives, this application adopts the following technical solution: A wet pre-demagnesification treatment method for nickel-cobalt mixed hydroxides includes: The nickel-cobalt mixed hydroxide is mixed with the first washing solution and subjected to the first pulping treatment to obtain the slurry after the first pulping treatment; After the first pulping treatment, the pH of the slurry was adjusted to 7.5-8.5, an acidic solution was added, and low-acid washing was carried out under stirring conditions. Then, the first solid-liquid separation was carried out to obtain the first washing residue and the first filtrate. The first washing residue is mixed with the second washing liquid and subjected to a second pulping treatment. The pH of the pulp after the second pulping treatment is adjusted to 6.8-7.2. CO2 gas is introduced to maintain the pH of the pulp at 6.8-7.2 and carbonization reaction is carried out to obtain carbonized pulp. The carbonized slurry is subjected to a second solid-liquid separation to obtain pre-demagnesized solids and a second filtrate; The first washing liquid and the second washing liquid may be the same or different, and each independently includes any one of water or a mixture of water and recycled washing liquid. The recycled washing liquid includes at least one of the first filtrate and the second filtrate.

[0010] According to embodiments of this application, the water content of the nickel-cobalt mixed hydroxide is 60%-65%; And / or, the pH of the nickel-cobalt mixed hydroxide after mixing with the first washing solution is ≥7.5; And / or, the magnesium content of the nickel-cobalt mixed hydroxide is 2.0 wt%-3.0 wt%.

[0011] According to an embodiment of this application, the liquid-solid mass ratio of the first washing liquid to the nickel-cobalt mixed hydroxide is 2:1-5:1; And / or, the temperature of the first pulping treatment is 20-30°C; And / or, the time for the first pulping treatment is 0.3-1.0 h; And / or, the concentration of the slurry after the first pulping treatment is 15%-25%.

[0012] According to embodiments of this application, the acidic solution includes at least one of dilute sulfuric acid solution and recycled washing solution; The pH of the acidic solution is 1.5-2.5.

[0013] According to an embodiment of this application, the low-acid washing time is 0.3-1.0 h.

[0014] According to an embodiment of this application, before mixing the slurry after the first pulping treatment with the acidic solution, the method further includes: adding a polyacrylamide solution to the slurry after the first pulping treatment, wherein the mass of the polyacrylamide solution accounts for 0.02%-0.05% of the mass of the slurry after the first pulping treatment; The concentration of the polyacrylamide solution is 0.05-0.12 wt%.

[0015] According to an embodiment of this application, the liquid-solid mass ratio of the second washing liquid to the first washing residue is 4:1-6:1.

[0016] According to embodiments of this application, the flow rate of the CO2 gas is 15-50 mL / min. -1 ; And / or, the carbonization reaction is carried out at a temperature of 20-30°C.

[0017] According to an embodiment of this application, the carbonization reaction is carried out in a carbonization reactor with bottom aeration holes, and the CO2 gas is introduced into the bottom aeration holes.

[0018] According to embodiments of this application, during the carbonization reaction, the method further includes: sampling and testing the Mg content in the slurry every 20-40 minutes. 2+ Concentration, when Mg is sampled in two consecutive samples 2+ Concentration difference < 0.5 g·L -1 ·h -1 At that time, stop the flow of CO2 gas.

[0019] Compared with the prior art, the beneficial effects of this application include: The method described in this application can achieve high magnesium removal efficiency under mild conditions, minimize the loss of valuable metals such as nickel and cobalt, and has the advantages of low acid consumption, low water consumption and short process, making this application feasible for continuous scale-up.

[0020] Specifically, the method described in this application can yield pre-demagnesium solids with significantly reduced magnesium content and stable nickel, cobalt, and manganese grades. Compared to existing pure water washing or high-acid leaching processes, this application offers advantages such as a milder process, lower acid consumption, and a shorter process flow. It can minimize the loss of nickel and cobalt while ensuring high demagnesium removal efficiency, and also boasts advantages such as a high proportion of recycled water and ease of continuous industrial scale-up. Moreover, the pre-demagnesium solids obtained using this method also have the advantages of uniform composition and particle size, and can be directly used in subsequent acid leaching-extraction-crystallization hydrometallurgical units to prepare products such as nickel sulfate, cobalt sulfate, manganese sulfate, and high-nickel ternary precursors, showing promising industrial application prospects. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0022] Figure 1 This is a flowchart of the wet pre-demagnesification treatment method for nickel-cobalt mixed hydroxides in this application. Detailed Implementation

[0023] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0024] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0025] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0026] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0027] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0028] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0029] To better illustrate the technical solution provided in this application, the technical solution will be described in its entirety before the embodiments, as follows: A wet pre-demagnesification treatment method for nickel-cobalt mixed hydroxides, referenced Figure 1 ,include: The nickel-cobalt mixed hydroxide is mixed with the first washing solution and subjected to the first pulping treatment to obtain the slurry after the first pulping treatment; After the first pulping treatment, the pH of the slurry was adjusted to 7.5-8.5, an acidic solution was added, and low-acid washing was carried out under stirring conditions. Then, the first solid-liquid separation was carried out to obtain the first washing residue and the first filtrate. The first washing residue is mixed with the second washing liquid and subjected to a second pulping treatment. The pH of the pulp after the second pulping treatment is adjusted to 6.8-7.2. CO2 gas is introduced to maintain the pH of the pulp at 6.8-7.2 and carbonization reaction is carried out to obtain carbonized pulp. The carbonized slurry is subjected to a second solid-liquid separation to obtain pre-demagnesized solids and a second filtrate; The first and second washing solutions may be the same or different, and each independently comprises any one of water or a mixture of water and recycled washing solution. The recycled washing solution includes at least one of the first and second filtrates. For example, the first and second washing solutions can be obtained by mixing 2 / 3 water and 1 / 3 recycled washing solution by volume, which can reduce water consumption and maintain stable ionic strength.

[0030] This application requires maintaining the slurry pH at 6.8-7.2 during the carbonization reaction to facilitate CO2 gas dissolution and the formation of a weakly acidic solution. If the slurry pH is too high during carbonization, the solution will become overly alkaline, hindering CO2 gas dissolution and reducing the efficiency of the carbonization reaction. Conversely, if the slurry pH is too low, the solution will become more acidic, increasing the loss of the main metal in the nickel-cobalt mixed hydroxide and reducing the overall nickel-cobalt recovery rate.

[0031] According to embodiments of this application, the water content of the nickel-cobalt mixed hydroxide is 60%-65%; For example, the water content of nickel-cobalt mixed hydroxides can be any value between 60%, 61%, 62%, 63%, 64%, 65%, or 60%-65%.

[0032] And / or, the pH of the nickel-cobalt mixed hydroxide after mixing with the first washing solution is ≥7.5; For example, the pH of the nickel-cobalt mixed hydroxide can be 7.5, 7.6, 7.7, 7.8, 7.9 or any value greater than or equal to 7.5.

[0033] And / or, the magnesium content of the nickel-cobalt mixed hydroxide is 2.0wt%-3.0wt%.

[0034] For example, the magnesium content of the nickel-cobalt mixed hydroxide is 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, 3.0 wt%, or any value between 2.0 wt% and 3.0 wt%.

[0035] In some embodiments, the nickel-cobalt mixed hydroxide has a nickel content of 37.4 wt%-38.6 wt%, a cobalt content of 3.9 wt%-4.1 wt%, and a manganese content of 4.7 wt%-4.9 wt%.

[0036] According to an embodiment of this application, the liquid-solid mass ratio of the first washing liquid to the nickel-cobalt mixed hydroxide is 2:1-5:1; For example, the liquid-solid mass ratio of the first washing solution to the nickel-cobalt mixed hydroxide can be any value between 2:1, 3:1, 4:1, 5:1, or 2:1-5:1; And / or, the temperature of the first pulping treatment is 20-30°C; For example, the temperature of the first pulping treatment can be any value between 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, or 20-30°C.

[0037] And / or, the time for the first pulping treatment is 0.3-1.0 h; For example, the time for the first pulping treatment can be any value between 0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, or 0.3-1.0 h.

[0038] In some embodiments, the first pulping process is carried out under stirring conditions at a stirring rate of 300-500 r / min. -1 .

[0039] During the first slurry treatment, the inherent hydroxide and carbonate ions in the nickel-cobalt mixed hydroxide buffer ensure that nickel and cobalt remain stable in hydroxide form during subsequent acid titration.

[0040] And / or, the concentration of the slurry after the first pulping treatment (on a dry basis) is 15%-25%.

[0041] For example, the concentration of the slurry after the first pulping treatment is any value between 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or 15%-25%.

[0042] In some embodiments, the method further includes adding 0.5% to 1.5% process water to the slurry system so that the viscosity of the slurry after the first slurry treatment is 300 to 800 mPa•s, which is beneficial for subsequent solid-liquid separation.

[0043] In some embodiments, the method further includes adjusting the pH by adding an acid or an alkali solution to the system. The acid includes dilute sulfuric acid, and the alkali solution includes sodium hydroxide solution.

[0044] According to embodiments of this application, the acidic solution includes at least one of dilute sulfuric acid solution and recycled washing solution; In some embodiments, the acidic solution includes a dilute sulfuric acid solution with a concentration ≤0.5wt%.

[0045] The pH of the acidic solution is 1.5-2.5. For example, the pH of the acidic solution is 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5 or any value between 1.5 and 2.5.

[0046] According to embodiments of this application, the low-acid washing time is 0.3-1.0 h. By using short-path contact-separation rather than long-path countercurrent, readily soluble magnesium salts can be rapidly transferred to the liquid phase.

[0047] For example, the low-acid washing time can be any value between 0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, or 0.3-1.0 h.

[0048] In some embodiments, the first solid-liquid separation method includes plate and frame filtration or continuous centrifugation. If filtration is used, the solid content of the filter cake is preferably 18%-22%; if centrifugation is used, the rotation speed is preferably 2500-3500 r / min. -1 The time is 3 to 5 minutes to ensure that the filtrate is clear and transparent (<30 NTU).

[0049] In some embodiments, Mg in the first filtrate 2+ The mass concentration reached 1.8-2.4 g•L. -1 .

[0050] Through the first solid-liquid separation, Mg-rich materials can be obtained. 2+ For the first filtrate, this application uses low-acid washing, which can achieve a Mg washing rate of 30%±5%, while the total loss rate of Ni and Co is ≤0.02%.

[0051] This application utilizes a synergistic window of three parameters—liquid-solid ratio, pH, and time—between the first washing solution and the nickel-cobalt mixed hydroxide to limit the leaching rate of nickel and cobalt, thereby controlling the overall metal loss to within 1%. Compared with traditional pure water countercurrent or medium-acid leaching processes, the weak-alkali slurry-low-acid rapid washing combination of this application avoids large-scale freshwater replacement and does not produce high-concentration acidic mother liquor, providing a directly recyclable washing solution for the subsequent carbonization stage.

[0052] According to an embodiment of this application, before mixing the slurry after the first pulping treatment with the acidic solution, the method further includes: adding a polyacrylamide solution to the slurry after the first pulping treatment, wherein the mass of the polyacrylamide solution accounts for 0.02%-0.05% of the mass of the slurry after the first pulping treatment; thereby, the metal ion complexation state can be maintained, preventing Ca... 2 + Al 3+ Wait for the impurities to settle back down.

[0053] For example, the mass of the polyacrylamide solution may be any value between 0.02%, 0.03%, 0.04%, 0.05%, or 0.02%-0.05% of the mass of the slurry after the first pulping treatment.

[0054] The concentration of the polyacrylamide solution is 0.05-0.12 wt%. For example, the concentration of the polyacrylamide solution is any value between 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.10 wt%, 0.11 wt%, 0.12 wt%, or 0.05-0.12 wt%.

[0055] This application employs an in-situ magnesium removal method by directly introducing CO2 after re-slurrying the first washing residue. Under the conditions of this step, magnesium ions react with CO3. 2- The reaction directionally generates soluble magnesium bicarbonate without affecting the structure of the main metal hydroxide. Furthermore, the carbonation step simultaneously removes some of the Ca. 2+ .

[0056] According to an embodiment of this application, the liquid-solid mass ratio of the second washing liquid to the first washing residue is 4:1-6:1.

[0057] For example, the liquid-solid mass ratio of the second washing liquid to the first washing residue is 4:1, 5:1, 6:1, or any value between 4:1 and 6:1.

[0058] According to embodiments of this application, the flow rate of the CO2 gas is 15-50 mL / min. -1 When the CO2 gas flow rate is too low, the Mg removal rate will decrease; when the CO2 gas flow rate is too high, it will lead to the side reaction of nickel bicarbonate formation, which will increase the nickel loss rate.

[0059] For example, the flow rate of CO2 gas is 15 mL•min -1 20 mL•min -1 25 mL•min -1 30mL•min -1 35 mL•min -1 40 mL•min -1 45 mL•min -1 50 mL•min -1 Or 15-50 mL•min -1 Any value between; And / or, the carbonization reaction temperature is 20-30°C. If the carbonization reaction temperature is too low, the reaction rate will be too slow and the pre-magnesium removal efficiency will be too low; if the carbonization reaction temperature is too high, the CO2 overflow rate will be increased, which will reduce the amount of CO2 dissolved in the solution and reduce the pre-magnesium removal efficiency.

[0060] For example, the carbonization reaction temperature can be any value between 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, or 20-30°C.

[0061] In some embodiments, the carbonization reaction takes 2-4 hours.

[0062] For example, the carbonization reaction time can be any value between 2h, 3h, 4h, or 2-4h.

[0063] In some embodiments, the carbonization reaction is carried out under stirring conditions. For example, the stirring rate can be 300-5000 r•min. -1 .

[0064] According to an embodiment of this application, the carbonization reaction is carried out in a carbonization reactor with bottom aeration holes, and the CO2 gas is introduced into the bottom aeration holes. Introducing the CO2 gas from the bottom avoids secondary adhesion of magnesium bicarbonate to the surface of the MHP particles.

[0065] In some embodiments, the diameter of the bottom aeration holes is 0.5-1.0 mm, which allows the bubble diameter to be controlled within 0.5-1.0 mm, thereby enhancing mass transfer and facilitating magnesium removal.

[0066] According to embodiments of this application, during the carbonization reaction, the method further includes: sampling and testing the Mg content in the slurry every 20-40 minutes. 2+ Concentration, when Mg is sampled in two consecutive samples 2+ Concentration difference < 0.5 g·L -1 ·h -1 When the CO2 gas flow is stopped, the flow of Mg gas is stopped. 2+ The concentration difference is less than 0.5 g·L. -1 ·h -1 If the amount of magnesium ions dissolved does not change significantly over time, it indicates that the carbonization reaction has been completed, and the CO2 gas flow can be stopped at this point.

[0067] During the carbonization reaction, the method further includes: using a ribbon jacket for cooling to control the exothermic reaction at <2℃, so as to prevent local overheating from causing Ni(OH)2 conversion.

[0068] After the carbonization reaction is completed, the slurry immediately enters a pressure filter or a high-efficiency settling tank for a second solid-liquid separation. The second solid-liquid separation method includes at least one of pressure filtration, natural sedimentation, and vacuum filtration.

[0069] In some embodiments, the method further includes rinsing the filter cake obtained from the second solid-liquid separation with water. The amount of filter cake rinsing water is 0.4-0.6 t / t of the dry basis mass of the raw material MHP. The rinsing is carried out in two countercurrent sprays, which can further reduce the residual soluble salts by 0.3%-0.5%.

[0070] Mg in the second filtrate 2+Mass concentration ≥18 g•L -1 The second filtrate has a pH of around 7, which is neutral. It can be directly incorporated into the first washing solution for recycling.

[0071] In some embodiments, the reuse rate of the first and second filtrates is ≥80%, the CO2 gas can be obtained from the calcination tail gas of battery materials or external pure gas, and the solid-liquid separation adopts belt vacuum filtration or deep cone thickening-pressure filtration series mode to ensure that the moisture content of the filter cake is ≤35wt%. Thus, it can be adapted to continuous scale-up industrial production processes.

[0072] In some embodiments, the obtained filter cake can be conveyed to a vacuum rake dryer in a wet slurry state and dried under reduced pressure at 80-105°C for 4-6 hours until the moisture content drops to <1%, thus obtaining pre-demagnesium solids. The pre-demagnesium solids are then sealed and packaged for use in subsequent acid leaching or reduction roasting processes.

[0073] Preferably, online particle size shaping is performed at the end of drying, using a 300-mesh vibrating screen to remove abnormal coarse particles, ensuring that ≥86% of the material has a particle size <38µm.

[0074] Preferably, the dry material is cooled to <40°C under inert nitrogen and then sealed to avoid secondary fluctuations in the pH of the slurry caused by CO2 and water vapor in the air.

[0075] In some embodiments, the pre-demagnesium solid has a nickel mass fraction ≥35%, a cobalt mass fraction ≥3.8%, a manganese mass fraction ≥4.5wt%, and a particle size D90 ≤38 μm, which can be seamlessly connected to the downstream acid leaching-extraction-crystallization section.

[0076] In some embodiments, the mass fraction of Ni in the pre-demagnesium solid is 35%-41%, the mass fraction of Co is 3.8%-4.3%, the mass fraction of Mn is 4.5%-5.5%, and the mass fraction of Mg is ≤1.0%; ≥86% of the particles in the pre-demagnesium solid have a particle size of less than 38 μm, and the elements are evenly distributed in each particle size.

[0077] In the method of this application, the total Mg washing rate is ≥50%, the Ni loss rate is ≤3%, and the overall Co loss rate is ≤0.05%.

[0078] The pre-demagnesium solid prepared in this application can be used in subsequent processes of hydrometallurgy, such as acid leaching, extraction, back-extraction, crystallization or roasting reduction, to produce nickel sulfate, cobalt sulfate, manganese sulfate or other nickel-cobalt-manganese compounds.

[0079] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0080] Example 1 This embodiment uses wet Ni-Co mixed hydroxide (MHP) discharged from a high-pressure acid leaching and neutralization section as raw material to illustrate the entire process of wet pre-magnesium removal treatment. The wet MHP used has a water content of approximately 62%, containing 38.6% (w) nickel, 4.1% (w) cobalt, 4.9% (w) manganese, and 2.6% (w) magnesium, with an initial pH of approximately 8.3. The supporting washing solution is a mixture of 65% recycled primary filtrate and 35% fresh deionized water, with an initial pH of 7.2; the CO2 gas purity is above 99.5%, precisely controlled by a flow meter; the dispersant is a 0.1% polyacrylamide solution, and dilute sulfuric acid and NaOH solution are used for pH fine-tuning.

[0081] 160 kg of wet MHP (approximately 60 kg dry weight) was metered and added to a stainless steel pretreatment tank, followed by 320 L of washing liquid to achieve a solid-liquid mass ratio of 1:2. The paddle agitator was turned on at 25 ± 3 °C and operated at 400 r / min. -1 The mixture was stirred continuously at a constant speed for 45 minutes; online monitoring showed that the slurry density was 1.28 g·cm³. -3 The corresponding dry solids content was 19.8%, viscosity was 510 mPa·s, and pH was stable at 7.6, requiring no further adjustment. To improve the fine particle dispersion, a polyacrylamide solution accounting for 0.03% (w) of the total slurry volume was then added dropwise to the system, and the mixture was stirred at a constant temperature of 25°C for 30 min to complete the low-acid washing pretreatment.

[0082] Subsequently, a dilute sulfuric acid solution with a pH of 2 was added to the slurry, and the mixture was stirred for 30 minutes for low-acid washing. After the low-acid washing was completed, the slurry was immediately fed into a pump with a rotation speed of 2800 r / min. -1 Centrifugation in a tubular centrifuge for 4 minutes yielded 420 L of clear primary filtrate and 60 kg of primary filter cake containing water. Chemical analysis showed that the primary washing achieved a magnesium removal rate of 29.4%, while the combined loss rate of Ni and Co was only 0.017%. The primary filter cake's basic solids content was 21.3%, meeting the flowability requirements of the subsequent re-pulping process.

[0083] The entire primary filter cake obtained from centrifugation was transferred into a 300L carbonization reactor with bottom aeration holes, and 240L of water was added to adjust the liquid-to-solid ratio after re-slurrying to 4:1. Subsequently, 1.0 mol·L⁻¹ water was used. -1The initial pH was adjusted to 7.0 ± 0.1 using dilute sulfuric acid. The mixture was then heated in a water bath at 25 ± 3°C at a speed of 300 rpm. -1 Stir and introduce CO2 evenly from the bottom, setting the gas flow rate to 25 mL / min. -1 The carbonization reaction lasted for 3 hours, with Mg samples taken every 30 minutes throughout the process. 2+ Concentration; when two consecutive measurements of Mg 2+ The concentration difference is less than 0.5 g·L. -1 ·h -1 At this point, the reaction was considered essentially complete, with the endpoint pH at 7.01. During the experiment, jacket cooling maintained the heat release of the system within 1.6℃, and no crust formation or large particle agglomeration was observed.

[0084] After aeration was stopped, a plate and frame filter press (8µm filter cloth pore size, 0.6MPa filtration pressure) was immediately used for solid-liquid separation. The secondary filtrate volume was 260L, and the filter cake was 58kg. To further reduce residual soluble salts, the filter cake was subjected to two-stage countercurrent spraying, with a total spraying water volume of 35L and a duration of approximately 6 minutes. Sampling analysis after spraying showed that the magnesium content in the wet filter cake decreased to 0.96% (w), while nickel and cobalt increased to 39.1% (w) and 4.2% (w), respectively. The overall Ni loss rate was 2.7%, meeting the expected targets. The resulting filter cake was then sent to a vacuum rake dryer and dried at 90℃ and 0.09MPa absolute pressure for 5 hours, with the final product moisture content controlled at 0.8%. Subsequently, the product was shaped using a 400-mesh vibrating screen. The particle size distribution showed that ≥87% of the material particles were less than 38µm in diameter, with a true specific gravity of 3.23 g·cm³. -3 All physicochemical indicators remained stable.

[0085] The primary and secondary filtrates produced in the process are mixed, and their Mg content is... 2+ The mass concentration reached 19.3 g·L⁻¹ -1 The liquid can be returned to the front end as washing liquid; when the circulating liquid volume exceeds the system's water balance requirement, the excess is sent to the lime milk magnesium precipitation unit, the sludge is used as cement admixture, and the clarified liquid discharge water quality meets the GB8978-1996 Class I standard.

[0086] This embodiment successfully obtained Ni-Co-Mn ternary pre-demagnesium intermediate with a magnesium content ≤1.0% and uniform particle size, providing a stable raw material for subsequent hydrometallurgical processes such as acid leaching, extraction, or reduction roasting.

[0087] Example 2 This embodiment uses Ni-Co-Mn mixed hydroxide (MHP) precipitated in a wet leaching process as raw material to illustrate the entire experimental procedure for obtaining a pre-demagnesized mixed hydroxide intermediate. The raw material, wet MHP, has a moisture content of 64% and mainly contains 37.4% (w) Ni, 3.9% (w) Co, 4.7% (w) Mn, and 2.8% (w) Mg, with an initial pH of 8.1. The production water is softened process water with a total hardness <30 mg·L⁻¹. -1 (Based on CaCO3); CO2 purity ≥ 99.9%, constant gas supply using a mass flow meter; polyacrylamide (PAM) as dispersant, with a 0.08% (w / w) aqueous solution available; dilute sulfuric acid and NaOH solutions are both prepared to 1 mol·L⁻¹. -1 This is to meet the need for fine-tuning pH.

[0088] First, add 200 kg of wet MHP (approximately 72 kg on a dry basis) to an 800 L stainless steel mixing tank, followed by 580 L of washing liquid, to achieve a solid-liquid mass ratio of approximately 1:2.9. Maintain the tank temperature at 24 ± 2 °C and the stirring speed at 380 r / min. -1 The test was conducted over a period of 40 minutes; the density of the slurry obtained was 1.25 g·cm³. -3 The corresponding dry basis solids content is 18.9%, and the viscosity is 540 mPa·s. The online pH measurement is 7.7, and no further adjustment is needed. To ensure the dispersion of fine particles, polyacrylamide solution was added dropwise after 15 min of stirring to make its mass fraction in the slurry 0.025%, and stirring was continued until 40 min was completed.

[0089] A dilute sulfuric acid solution with a pH of 2 was then added to the slurry, and the mixture was stirred for 30 minutes for low-acid washing. After low-acid washing, solid-liquid separation was performed. A centrifuge (drum diameter 450 mm) was used at 3000 r / min. -1 After running at high speed for 4 minutes, 640 L of filtrate and 85 kg of filter cake were obtained. Chemical analysis showed that the first washing removed 31.2% of magnesium ions, the combined loss rate of Ni and Co was 0.018%, and the solid content of the filter cake was 20.7%.

[0090] The primary filter cake was transferred to a 500L fiberglass carbonization reactor, and 340L of process water was added. The liquid-to-solid ratio after re-slurrying was 4.2:1. Mechanical stirring was started (300 rpm). -1 First, adjust the initial pH to 7.0±0.05 with dilute sulfuric acid, then continuously bubble CO2 into the porous diffuser from the bottom, setting the gas flow rate to 30 mL·min. -1 The reaction temperature was 25±3℃. Carbonization lasted 3 hours, with Mg measured every 20 minutes throughout the process. 2+ Record the mass concentration and temperature rise of the system (maximum temperature rise not exceeding 1.8℃). When two consecutive measurements of Mg... 2+Concentration difference < 0.4 g·L -1 ·h -1 Aeration was stopped at this point, at which point the final pH of the slurry was 7.03.

[0091] Immediately after CO2 was stopped, plate and frame filtration (6µm filter cloth pore size, 0.55MPa pressure difference) was used for separation, yielding 370L of secondary filtrate and 82kg of secondary filter cake. The filter cake was then subjected to two-stage countercurrent spraying, with a total spraying water volume of 45L and a front-to-back ratio of 3:2. After spraying, filtration was maintained for 5 minutes to drain free water. The wet filter cake after spraying was rapidly sampled, and its metal composition was: Mg 0.85%(w), Ni 39.6%(w), Co 4.0%(w), Mn 4.6%(w). The Ni loss rate based on the raw material was 2.9%, meeting the pre-magnesium removal criteria.

[0092] The wet filter cake was continuously fed into a vacuum rake dryer by a screw pump and dried for 4.5 hours at an absolute pressure of 0.08 MPa and a temperature of 85-90℃, resulting in a dry material moisture content of 0.9%. Subsequently, it was shaped using a 350-mesh (45µm) vibrating sieve to remove coarse agglomerates generated by mechanical collision. The final product had a particle size D90 of 34µm and a true specific gravity of 3.22 g·cm³. -3 The resulting dry powder is packaged in double-layer aluminum-plastic bags and stored for later use, and can be directly incorporated into subsequent hydrometallurgical processes such as acid leaching and extraction.

[0093] Comparative Example 1 Take 2 kg of the primary filter cake obtained in Example 1 and transfer it into a 10 L carbonization reactor with bottom aeration holes. Add 8 L of water to adjust the liquid-to-solid ratio after re-slurrying to 4:1. Then use 1.0 mol·L⁻¹ water. -1 The initial pH was adjusted to 7.0 ± 0.1 using dilute sulfuric acid. The mixture was then heated in a water bath at 25 ± 3°C at a speed of 300 rpm. -1 Stir and introduce CO2 evenly from the bottom, with the gas flow rate set to 100 mL / min. -1 The carbonization reaction lasted for 3 hours, with Mg samples taken every 30 minutes throughout the process. 2+ Concentration; when two consecutive measurements of Mg 2+ The concentration difference is less than 0.5 g·L. -1 ·h -1 At this point, the reaction was considered essentially complete, with the endpoint pH at 7.1. During the experiment, jacket cooling maintained the heat release of the system within 1.6℃, and no crust formation or large particle agglomeration was observed.

[0094] After aeration was stopped, solid-liquid separation was immediately performed using a vacuum filter. The secondary filtrate volume was 7.5 L, and the filter cake was 1.8 kg. After filtration, samples were taken for analysis: the magnesium content in the wet filter cake decreased to 0.82% (w), the nickel content decreased to 34.13% (w), and the Ni loss rate was 13.03%, which is 10% higher than the nickel loss rate in Example 1, failing to meet the expected targets. The resulting filter cake was then placed in a vacuum drying oven and dried at 90°C and 0.09 MPa absolute pressure for 5 hours, with the final product moisture content controlled at 0.8%.

[0095] The nickel loss rate in Comparative Example 1 was relatively high, which may be due to the excessive CO2 gas flow rate in Comparative Example 1.

[0096] Comparative Example 2 Take 2 kg of the primary filter cake obtained in Example 1 and transfer it into a 10 L carbonization reactor with bottom aeration holes. Add 8 L of washing water and adjust the liquid-to-solid ratio after re-slurrying to 4:1. Then use 1.0 mol·L⁻¹ water. -1 The initial pH was adjusted to 5.0 ± 0.1 using dilute sulfuric acid. The mixture was then heated in a water bath at 25 ± 3°C at a speed of 300 rpm. -1 Stir and introduce CO2 evenly from the bottom, setting the gas flow rate to 25 mL / min. -1 The carbonization reaction lasted for 3 hours, with Mg samples taken every 30 minutes throughout the process. 2+ Concentration; when two consecutive measurements of Mg 2+ The concentration difference is less than 0.5 g·L. -1 ·h -1 At this point, the reaction was considered essentially complete, with the endpoint pH at 5.5. During the experiment, jacket cooling maintained the exothermic reaction within 1.6℃, and no crust formation or large particle agglomeration was observed.

[0097] After aeration was stopped, solid-liquid separation was immediately performed using a vacuum filter. The secondary filtrate volume was 7L, and the filter cake yielded 1.6kg. After filtration, samples were taken for analysis: the magnesium content in the wet filter cake decreased to 1.20% (w), the nickel content decreased to 37.46% (w), and the Ni loss rate was 5.34%, which was 2.6% higher than the nickel loss rate in Example 1, failing to meet the expected targets. The resulting filter cake was then placed in a vacuum drying oven and dried at 90°C and 0.09 MPa absolute pressure for 5 hours, with the final product moisture content controlled at 0.8%.

[0098] The nickel loss rate was relatively high in Comparative Example 2, which may be due to the low pH of the system during the carbonization reaction.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0100] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A wet pre-demagnesification treatment method for nickel-cobalt mixed hydroxides, characterized in that, include: The nickel-cobalt mixed hydroxide is mixed with the first washing solution and subjected to the first pulping treatment to obtain the slurry after the first pulping treatment; After the first pulping treatment, the pH of the slurry was adjusted to 7.5-8.5, an acidic solution was added, and low-acid washing was carried out under stirring conditions. Then, the first solid-liquid separation was carried out to obtain the first washing residue and the first filtrate. The first washing residue is mixed with the second washing liquid and subjected to a second pulping treatment. The pH of the pulp after the second pulping treatment is adjusted to 6.8-7.

2. CO2 gas is introduced to maintain the pH of the pulp at 6.8-7.2 and carbonization reaction is carried out to obtain carbonized pulp. The carbonized slurry is subjected to a second solid-liquid separation to obtain pre-demagnesized solids and a second filtrate; The first and second washing solutions may be the same or different, and each independently comprises any one of water or a mixture of water and recycled washing solution. The recycled washing solution comprises at least one of the first and second filtrates. The pH of the acidic solution is 1.5-2.

5. The flow rate of the CO2 gas is 15-50 mL. min -1 The carbonization reaction is carried out at a temperature of 20-30°C.

2. The pre-demagnesification wet treatment method for nickel-cobalt mixed hydroxide according to claim 1, characterized in that, The moisture content of the nickel-cobalt mixed hydroxide is 60%-65%; And / or, the pH of the nickel-cobalt mixed hydroxide after mixing with the first washing solution is ≥7.5; And / or, the magnesium content of the nickel-cobalt mixed hydroxide is 2.0 wt%-3.0 wt%.

3. The pre-demagnesification wet treatment method for nickel-cobalt mixed hydroxide according to claim 2, characterized in that, The liquid-solid mass ratio of the first washing solution to the nickel-cobalt mixed hydroxide is 2:1-5:1; And / or, the temperature of the first pulping treatment is 20-30°C; And / or, the time for the first pulping treatment is 0.3-1.0 h; And / or, the concentration of the slurry after the first pulping treatment is 15%-25%.

4. The pre-demagnesification wet treatment method for nickel-cobalt mixed hydroxide according to claim 1, characterized in that, The acidic solution includes at least one of dilute sulfuric acid solution and recycled washing solution.

5. The wet pre-demagnesification treatment method for nickel-cobalt mixed hydroxide according to claim 4, characterized in that, The low-acid washing time is 0.3-1.0 h.

6. The pre-demagnesification wet treatment method for nickel-cobalt mixed hydroxide according to claim 1, characterized in that, Before mixing the slurry after the first pulping treatment with the acidic solution, the method further includes: adding a polyacrylamide solution to the slurry after the first pulping treatment, wherein the mass of the polyacrylamide solution accounts for 0.02%-0.05% of the mass of the slurry after the first pulping treatment; The concentration of the polyacrylamide solution is 0.05-0.12 wt%.

7. The pre-demagnesification wet treatment method for nickel-cobalt mixed hydroxide according to claim 1, characterized in that, The liquid-solid mass ratio of the second washing liquid to the first washing residue is 4:1-6:

1.

8. The pre-demagnesification wet treatment method for nickel-cobalt mixed hydroxide according to claim 1, characterized in that, The carbonization reaction is carried out in a carbonization reactor with bottom aeration holes, and the CO2 gas is introduced into the bottom aeration holes.

9. The pre-demagnesification wet treatment method for nickel-cobalt mixed hydroxide according to any one of claims 1-8, characterized in that, During the carbonization reaction, the process also includes sampling and testing the Mg content in the slurry every 20-40 minutes. 2+ Concentration, when Mg is sampled in two consecutive samples 2+ Concentration difference < 0.5 g·L -1 ·h -1 At that time, stop the flow of CO2 gas.

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