Method for enriching scandium and manganese and separating nickel and cobalt by extraction

Abstract

This invention discloses a method for scandium-manganese enrichment and nickel-cobalt extraction and separation, belonging to the field of metal production or refining technology. The method includes: ultrasonic-enhanced grinding pretreatment; selective leaching with dilute sulfuric acid solution; vanadium precipitation and iron removal from the leachate; forming a synergistic extraction system using a carboxylic acid extractant, a hydroxyoxime extractant, and an organic diluent, followed by saponification; and using the saponified synergistic extraction system to perform kinetic extraction and separation of nickel and cobalt from the leachate after vanadium precipitation and iron removal. Using this invention for nickel-cobalt extraction and separation, the synergistic extraction effect of the constructed synergistic extraction system lowers the extraction pH; utilizing its higher extraction rate for cobalt than for nickel, kinetic extraction and separation of cobalt are achieved; the synergistic extraction system constructed in this invention increases the extraction and separation coefficients of nickel and cobalt from iron, aluminum, manganese, etc., and both nickel and cobalt extractions are direct extractions, with nickel and cobalt directly extracted into the organic phase, thus achieving efficient extraction of nickel and cobalt and effective separation from iron, aluminum, manganese, etc.

Description

Technical Field

[0001] This invention relates to the field of metal production or refining technology, and in particular to a method for scandium-manganese enrichment and nickel-cobalt extraction and separation. Background Technology

[0002] Laterite nickel ore has become a major nickel-cobalt resource, also containing associated resources such as scandium and manganese. However, the utilization of laterite nickel ore resources currently faces two major problems: firstly, valuable elements such as scandium and manganese are difficult to recover efficiently and comprehensively; and secondly, the efficiency of nickel-cobalt recovery and separation is low. Nickel-cobalt hydroxide precipitation is a common intermediate product obtained from the hydrometallurgical processing of laterite nickel ore (including acid leaching, impurity removal, and nickel-cobalt precipitation processes). Besides nickel and cobalt, it also contains relative impurities such as iron, manganese, scandium, calcium, and magnesium, and the valence states of iron and manganese ions are unstable. The main purpose of the nickel-cobalt hydroxide refining process is to remove impurities from the system to obtain nickel-cobalt metal or its compounds.

[0003] The technical challenges in separating nickel and cobalt lie not only in separating nickel and cobalt from elements such as scandium, iron, aluminum, manganese, calcium, and magnesium, but also in separating nickel and cobalt themselves. In practice, the inventors discovered that nickel-cobalt hydroxide contains iron ions with both +3 and +2 valence states, predominantly +3, and manganese ions with both +2 and +4 valence states, predominantly +2. However, the valence state transition is extremely slow. This uncertainty in the raw material composition during conventional nickel-cobalt hydroxide refining processes significantly disrupts industrial production, leading to low purity, low recovery rates, and unstable production system operation. Iron ions are a major impurity in the separation and utilization of valuable metals. The iron alum process is a commonly used method for iron removal, but conventional iron alum methods suffer from the problem that the oxidation pH of ferrous iron is much higher than the pH of alum precipitation. Oxidants available within the suitable pH range for alum precipitation have disadvantages such as slow oxidation rates and high costs. Manganese is one of the impurities leached along with nickel and cobalt and treated in subsequent separation processes. Manganese interferes with the extraction of nickel and cobalt, affecting product purity. Moreover, a significant amount of nickel-cobalt hydroxide produced from laterite nickel ore contains scandium, which is a harmful impurity in nickel-cobalt smelting and also a rare earth resource. Because the concentration of scandium in the system is low, when scandium is removed and recovered by the scandium precipitation method alone, the precipitation rate is low and the precipitate is not easy to settle, thus making it difficult to enrich.

[0004] To achieve scandium removal and recovery, the inventors adjusted the pH to 3.0 or higher during the iron and aluminum removal process, thereby precipitating scandium in a co-precipitate form with iron and aluminum. This achieved the removal and recovery of scandium from nickel-cobalt solutions. However, in practice, the inventors found a problem with this process: during the formation of hydroxide co-precipitates, the special properties of aluminum hydroxide and scandium hydroxide dissolving in strong alkalis made it difficult to determine the reaction endpoint and precisely control the endpoint pH. Too low a pH resulted in low scandium recovery, while too high a pH led to colloidal precipitation, affecting filtration performance. Furthermore, the reaction at higher pH values ​​increased the loss of nickel, cobalt, and manganese in the slag. Further, by using the goethite method to remove iron from the leaching solution after the reduction leaching of nickel-cobalt hydroxide slurry, the inventors achieved the effect of vanadium precipitation and iron removal while simultaneously enriching scandium through co-precipitation. However, the inventors found that this reduction leaching method caused manganese to become divalent, resulting in a high manganese content in the nickel-cobalt solution, which affected nickel-cobalt extraction and increased the difficulty of the subsequent nickel-cobalt extraction.

[0005] Furthermore, the inventors have recognized that existing nickel-cobalt extraction technologies use saponified acidic organophosphorus extractants such as P204, P507, and Cyanex 272 for extraction and separation (P204 extraction - P507 cobalt extraction - Cyanex 272 deep extraction). These technologies suffer from problems such as high extraction equilibrium pH, the need for large amounts of neutralizing alkali, and low extraction and separation efficiency. Iron and aluminum need to be removed beforehand through precipitation or other methods. In addition, the extraction process generates a large amount of salt- and acid-containing waste liquid. Moreover, P204 and P507 have a high extraction capacity for calcium. When calcium is co-extracted into the organic phase, calcium sulfate precipitates are easily formed in the sulfuric acid system. Therefore, the extraction system must include a calcium removal process, which reduces the extraction efficiency. Summary of the Invention

[0006] According to one embodiment of the present invention, the objective is to provide a method for the enrichment of scandium and manganese and the extraction and separation of nickel and cobalt. The method involves oxidizing variable-valence metal ions Fe(II) and Mn(II) through solid-state enhanced grinding, selectively leaching to achieve manganese separation and recovery, and using an iron-vanadium process to remove iron and enrich scandium. A synergistic extraction system is constructed using a carboxylic acid extractant and a hydroxime extractant. Based on this newly constructed synergistic extraction system, efficient extraction and separation of nickel and cobalt are achieved. The method of the present invention can achieve comprehensive recovery of metallic nickel, cobalt, manganese, and scandium.

[0007] The above objective can be achieved through the following technical solutions:

[0008] According to one aspect of the present invention, a method for scandium-manganese enrichment and nickel-cobalt extraction separation is provided, comprising:

[0009] Step S1: Wet the nickel-cobalt hydroxide with water, and then perform enhanced grinding using ultrasound and oxygen or air to obtain pretreated nickel-cobalt hydroxide.

[0010] Step S2: The pretreated nickel-cobalt hydroxide is added to a dilute sulfuric acid solution for selective leaching and solid-liquid separation to obtain manganese oxide slag and a first leachate purified by manganese removal.

[0011] Step S3: Add salt solution to the first leachate to precipitate vanadium and remove iron, forming an iron alum-type precipitate with adsorption or doping of scandium. Separate the solid and liquid to obtain scandium-containing iron-vanadium slag and a second leachate purified by removing iron and scandium. The salt solution contains one or more of ammonia, sodium, and potassium ions.

[0012] Step S4: The carboxylic acid extractant, hydroxyoxime extractant and organic diluent are compounded to form a synergistic extraction system. An alkaline solution is added to the synergistic extraction system for saponification to form a saponified synergistic extractant system and generate saponification waste liquid.

[0013] Step S5: The second leachate is subjected to nickel and cobalt kinetic extraction separation using the saponified synergistic extractant system. Specifically, the cobalt extraction rate is higher than that for nickel using the synergistic extractant system, thus preferentially extracting cobalt to obtain a cobalt-loaded organic phase (i.e., cobalt is directly extracted into the organic phase), thereby separating and purifying the cobalt product. The cobalt extraction residue is then subjected to nickel extraction to obtain a nickel-loaded organic phase (i.e., nickel is directly extracted into the organic phase), thereby separating and purifying the nickel product.

[0014] Preferably, the carboxylic acid extractant is one or more of cycloalkanoic acid, isomeric acid Versatic 10, and isomeric acid Versatic 911; the hydroxyoxime extractant is an α-hydroxyoxime extractant containing a long-chain alkyl group. More preferably, the hydroxyoxime extractant is 5,8-diethyl-7-hydroxy-dodecane-6-oxime.

[0015] Preferably, the molar ratio of the carboxylic acid extractant to the hydroxyoxime extractant is (0.1-10):1.

[0016] Preferably, the volume concentration of the extractant in the synergistic extraction system is 10-40%.

[0017] Preferably, the organic diluent is one or more of n-heptane, n-octane, No. 5 solvent oil, No. 260 solvent oil, and sulfonated kerosene.

[0018] Preferably, in step S5, the step of preferentially extracting cobalt employs multi-stage countercurrent extraction. More preferably, the number of cobalt extraction stages is 3 to 6.

[0019] Preferably, in step S5, the extraction time for each cobalt extraction stage is 10 to 150 seconds.

[0020] Preferably, in step S5, during the step of preferentially extracting cobalt, the flow rate ratio of the saponification extraction organic phase to the aqueous phase is (0.2~10):1.

[0021] Preferably, in step S5, the temperature of each cobalt extraction stage is 20–50°C, and the equilibrium pH of the aqueous phase is 2.0–4.0.

[0022] Preferably, in step S5, the nickel extraction of the cobalt extraction residue is performed using multi-stage countercurrent extraction. More preferably, the number of nickel extraction stages is 3 to 6.

[0023] Preferably, in step S5, in the step of further nickel extraction of the cobalt extraction residue, the flow rate ratio of the saponification extraction organic phase to the aqueous phase is (0.2~10):1.

[0024] Preferably, in step S5, the nickel extraction of the cobalt extraction residue is carried out at a temperature of 30–60°C for each nickel extraction stage, for a time of 3–10 minutes for each nickel extraction stage, and the equilibrium pH of the aqueous phase is 2.0–4.5.

[0025] Preferably, step S5 further includes: washing the cobalt-supported organic phase and back-extracting it.

[0026] Preferably, step S5 further includes: washing the nickel-supported organic phase and back-extracting it.

[0027] Preferably, step S5 further includes: combining the sulfuric acid waste liquid generated from the washing section of the cobalt-supported organic phase and the washing section of the nickel-supported organic phase, and preparing the dilute sulfuric acid solution in step S2.

[0028] Preferably, the washing stage of the cobalt-supported organic phase has 2 to 4 stages, and the washing solution is a dilute sulfuric acid solution with a concentration of 0.02 to 0.8 mol / L; the back-extraction stage of the cobalt extraction has 3 to 6 stages, and sulfuric acid back-extraction solution with a concentration of 1 to 4 mol / L is used for back-extraction.

[0029] Preferably, the washing stage of the nickel-supported organic phase has 2 to 4 stages, and the washing solution is a dilute sulfuric acid solution with a concentration of 0.02 to 0.8 mol / L; the back-extraction stage of the nickel extraction has 3 to 8 stages, and the back-extraction solution is sulfuric acid with a concentration of 0.8 to 3 mol / L.

[0030] Preferably, in step S1, the amount of water added is such that the mass ratio of dry-based nickel-cobalt hydroxide to water is 1:0.3-4.

[0031] Preferably, in step S1, the frequency of the applied ultrasonic wave is 20,000 Hz to 200,000 Hz.

[0032] Preferably, in step S1, oxygen or air is introduced to make the volume fraction of oxygen in the grinding atmosphere 21% to 99%.

[0033] Preferably, in step S1, the temperature during the enhanced grinding is 25℃~75℃ and the time is 5min~30min.

[0034] Preferably, in step S2, the pH of the leaching system is 1.0–4.5, and the temperature is 20–45°C.

[0035] Preferably, in step S2, the liquid-to-solid ratio of the leaching system is 10:1 to 2:1, and the leaching time is 5 to 20 minutes.

[0036] Preferably, in step S2, the concentration of the dilute sulfuric acid solution is 0.1–3 mol / L.

[0037] Preferably, step S3 further includes: adding sulfuric acid or an alkaline neutralizing agent to adjust the pH of the first leachate to 0.6–3.5. Preferably, the alkaline neutralizing agent is one or more selected from sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, potassium carbonate, and ammonium carbonate.

[0038] Preferably, in step S3, when adding salt solution to the first leachate for vanadium precipitation and iron removal, the molar ratio of the total amount of added ammonia, sodium, and potassium to the total amount of iron and scandium metal elements in the first leachate is controlled to be (1.2~4.5):1.

[0039] Preferably, in step S3, the reaction temperature during vanadium precipitation and iron removal is controlled to be 20–90°C, and the reaction time is 20–200 min.

[0040] Preferably, the method further includes: using the saponification waste liquid generated in step S4 as the salt solution in step S3, adding it to the first leachate for vanadium precipitation and iron removal, so as to recycle it.

[0041] Beneficial effects:

[0042] According to one embodiment of the present invention, a synergistic extraction system constructed by a carboxylic acid extractant and a hydroxyoxime extractant is used for nickel-cobalt extraction and separation. This synergistic extraction system increases the extraction and separation coefficients of nickel-cobalt from iron, aluminum, manganese, etc. Due to the synergistic extraction effect of the extractants, the extraction pH is low, and the metal extraction sequence is different from that of a single extractant. By fully utilizing the difference in kinetic extraction rates of nickel and cobalt in the constructed synergistic extraction system, i.e., taking advantage of the faster extraction rate of cobalt, the kinetic preferential extraction of cobalt is achieved. Moreover, the synergistic extraction system of the present invention performs direct extraction of both nickel and cobalt (nickel and cobalt are extracted into the organic phase), achieving efficient extraction and separation of nickel and cobalt and their effective separation from iron, aluminum, manganese, etc. Furthermore, pretreatment of nickel-cobalt hydroxide using a mechanical activation coupling accelerated oxidation method enhances its solid-state reactivity, making it more readily react with oxygen. This rapidly oxidizes divalent manganese to tetravalent manganese to form manganese dioxide, and divalent iron to trivalent iron. Following pretreatment, nickel-cobalt hydroxide is dissolved in dilute sulfuric acid solution under low pH conditions to leach scandium and nickel-cobalt. The undissolved manganese dioxide is separated into the slag, thus achieving manganese recovery and separation from other metals entering the leachate. The next step involves precipitating alum and removing iron from the purified leachate after manganese removal, while simultaneously enriching scandium through co-precipitation to generate scandium-rich iron alum. Scandium is recovered while iron is removed, resulting in a purified leachate with removed iron and scandium. Further nickel-cobalt extraction and separation can be achieved by performing nickel-cobalt extraction and separation on this leachate, enabling more efficient extraction and separation.

[0043] Compared with related technologies, the embodiments of the present invention have the following advantages:

[0044] 1) A novel synergistic extraction system was constructed using carboxylic acid extractant and hydroxyoxime extractant. Based on their synergistic extraction effect, extraction can be carried out at a lower pH. The extraction rate of cobalt using this synergistic extraction system is greater than that of nickel, thus achieving the kinetic separation of cobalt. The synergistic extraction system increases the extraction separation coefficient of nickel and cobalt from iron, aluminum, manganese, etc., thus achieving efficient extraction of nickel and cobalt and effective separation from iron, aluminum and manganese.

[0045] 2) The extraction system of this invention is a direct nickel-cobalt extraction, in which both nickel and cobalt are directly extracted into the organic phase. Cobalt is kinetically separated, and nickel sulfate is in the back-extraction solution obtained from the back-extraction. In contrast, the existing extraction process "P204 extraction (calcium and manganese) -- P507 cobalt extraction (cobalt extraction is thermodynamic equilibrium extraction) -- Cyanex 272 deep extraction (magnesium extraction)" involves nickel sulfate in the raffinate, and the entire extraction process is thermodynamic equilibrium extraction, requiring a high solution pH.

[0046] 3) By accelerating the oxidation rate of variable-valence metals through enhanced grinding, manganese dioxide insoluble in weak acid solution is formed, so that manganese can be separated and enriched in the leaching step. The characteristics of nickel-cobalt hydroxide raw material are fully utilized, and manganese enrichment and separation are achieved through low-cost means, which is also beneficial to nickel-cobalt extraction.

[0047] 4) Dilute sulfuric acid is used to dissolve nickel-cobalt hydroxide under low pH conditions to leach scandium and nickel-cobalt, while manganese dioxide remains undissolved and enters the slag through solid-liquid separation and is recovered, thus separating it from other metals that enter the leaching solution.

[0048] 5) After selective leaching, the iron removal of the leaching solution by the (ammonium, sodium, potassium) iron alum formation method forms an iron alum-type precipitate with doped or adsorbed scandium. That is, iron removal is achieved at the same time as scandium enrichment. Moreover, the resulting scandium-rich precipitate has a higher crystal form, is easier to precipitate, wash and filter, has a higher scandium recovery rate, and has a lower loss rate of nickel and cobalt (into the precipitate residue rate). In addition, the precipitate can be formed at a higher acidity, reducing the amount of alkali used for neutralization.

[0049] 6) By saponifying the synergistic extraction system, its efficiency in nickel-cobalt extraction and separation is further increased, achieving efficient nickel-cobalt extraction and separation at low pH.

[0050] 7) Nickel-cobalt extraction, manganese oxide precipitation, and iron-vanadium scandium precipitation can all be carried out at higher acidity, reducing the need for alkali in neutralization.

[0051] 8) In addition, when using the (ammonium, sodium, potassium) alum ore formation method to remove iron and enrich scandium, the saponification waste liquid generated during the saponification process can be added to the leachate to recycle the ammonia, sodium, and potassium elements in the saponification waste liquid. When washing the organic phase loaded with extract after extraction, a dilute sulfuric acid solution can be used as the washing liquid. The sulfuric acid waste liquid generated after washing can be used to prepare the dilute sulfuric acid solution used in selective leaching to achieve recycling. Attached Figure Description

[0052] Figure 1 This is a schematic flowchart of a method for scandium-manganese enrichment and nickel-cobalt extraction and separation in one embodiment of the present invention. Detailed Implementation

[0053] The technical solution of the present invention will be clearly and completely described below with reference to embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0054] As described above, the technical challenges in separating nickel and cobalt lie not only in the separation of nickel and cobalt from elements such as scandium, iron, aluminum, manganese, calcium, and magnesium, but also in the separation of nickel and cobalt elements themselves. The coexistence of low-valence and high-valence manganese and iron ions in nickel-cobalt hydroxide affects the extraction and separation of nickel and cobalt, preventing the comprehensive recovery of valuable elements such as scandium and manganese. The inventors also recognized that using conventional acidic organic extractants to extract nickel and cobalt suffers from problems such as a high extraction equilibrium pH, the need for large amounts of neutralizing alkali, the need for additional calcium removal processes, and low extraction and separation efficiency.

[0055] To achieve better comprehensive recovery of nickel, cobalt, manganese, and scandium, an improved nickel-cobalt hydroxide refining process was proposed, along with a method for scandium-manganese enrichment and nickel-cobalt extraction and separation. Through a stepwise separation process (selective leaching after enhanced grinding to oxidize and enrich manganese-separate manganese-iron removal from the leachate using the iron-vanadium method while simultaneously achieving scandium enrichment-co-nickel extraction and separation), efficient separation and recovery of elements such as nickel, cobalt, scandium, and manganese were achieved.

[0056] First, the nickel-cobalt hydroxide undergoes enhanced grinding pretreatment, a method that combines mechanical activation with ultrasonic enhancement to accelerate oxidation. Based on the mechanical grinding process resulting in finer solid particles and increased surface area, the raw material characteristics of nickel-cobalt hydroxide—alkaline and containing water (35-75% water content)—are utilized. A small amount of water is added to wet the surface and form an alkaline solution. Oxygen or air is then introduced to induce a gas-liquid-solid reaction, oxidizing low-valence iron and manganese ions. Ultrasonic enhancement is then achieved using the ultrasonic cavitation effect (ultrasonic cavitation generates numerous active free radicals, enhancing intermolecular collisions and increasing the chemical reaction rate), accelerating the gas / liquid / solid interface reaction kinetics. This enhances the surface reactivity of the solid, making it more readily react with oxygen, rapidly oxidizing divalent manganese to tetravalent manganese to form manganese dioxide, and rapidly oxidizing divalent iron to trivalent iron to form ferric hydroxide. Under normal pressure, pretreated nickel-cobalt hydroxide is selectively leached with sulfuric acid, resulting in manganese dioxide that does not dissolve while other metals dissolve, achieving liquid-solid separation. This allows manganese dioxide to enter the slag, while other metals (scandium, nickel, cobalt, etc.) enter the leachate, thus achieving manganese recovery and obtaining the leachate. Scandium enrichment is achieved by precipitating alum with ferric ions and co-precipitating trace amounts of scandium ions. Iron is removed from the leachate using a (potassium, sodium, ammonium) alum ore formation method, resulting in a scandium-doped or adsorbed alum-type precipitate (mainly potassium ferric alum, sodium ferric alum, and ammonium ferric alum) and a nickel-cobalt-containing solution. This process removes iron impurities while simultaneously enriching scandium. Furthermore, this iron-vanadium scandium precipitate can form at higher acidity, eliminating the need for conventional methods of removing scandium by increasing pH (which involves co-precipitating iron-aluminum scandium hydroxide to remove scandium during the iron-aluminum removal stage). This reduces the use of alkali for neutralization, and the resulting precipitate has a higher crystal structure, making it easier to precipitate, wash, and filter.

[0057] Then, based on the leachate after vanadium precipitation and iron removal, a synergistic extraction system constructed from carboxylic acid extractant and hydroxyoxime extractant was used for nickel-cobalt extraction and separation. The inventors discovered that the carboxylic acid extractant and hydroxyoxime extractant formed more hydrophobic and spatially stable complexes (metal ion-extractant complexes) with nickel and cobalt ions, enhancing nickel-cobalt extraction efficiency. This allows for separation of nickel and cobalt from iron, aluminum, etc., at lower pH. Simultaneously, by increasing the extraction separation coefficient of nickel and cobalt from iron, aluminum, manganese, etc., effective separation of nickel and cobalt from impurities such as iron, aluminum, calcium, and magnesium is achieved. This eliminates the need for precipitation to remove impurities such as iron and aluminum in the original extraction solution, further reducing the use of alkali for neutralization. Furthermore, by fully utilizing the different kinetic extraction rates of nickel and cobalt, and prioritizing cobalt extraction due to its faster extraction rate, kinetic separation of cobalt is achieved, resulting in highly efficient separation of nickel and cobalt to obtain high-purity nickel and cobalt products.

[0058] One embodiment of the present invention provides a method for scandium-manganese enrichment and nickel-cobalt extraction and separation. The raw material in this embodiment is nickel-cobalt hydroxide produced from laterite nickel ore. The method specifically includes the following steps:

[0059] Step S1 involves strengthening the grinding of nickel cobalt hydroxide produced from laterite nickel ore; this includes: first adding water to wet the surface of the nickel cobalt hydroxide, then using ultrasonic strengthening and introducing oxygen or air for strengthened grinding, in order to accelerate the conversion of low-valence manganese and iron ions into high-valence states (divalent manganese is oxidized to tetravalent manganese, and divalent iron ions are oxidized to trivalent iron ions), to obtain pretreated nickel cobalt hydroxide with finer particle size and increased iron and manganese metal valence states.

[0060] Step S2: The pretreated nickel-cobalt hydroxide is added to a sulfuric acid solution for selective leaching treatment, and the reaction slurry system is subjected to a first solid-liquid separation to obtain manganese oxide slag and a first leaching solution purified by manganese removal.

[0061] This step is based on ultrasonic enhancement and oxygen or air-enhanced grinding to oxidize and selectively leach variable valence metal ions Fe(II) and Mn(II), thereby achieving manganese separation and recovering manganese products.

[0062] Specifically, the sulfuric acid solution is a dilute sulfuric acid solution, which can be prepared using sulfuric acid-containing organic phase washing liquid, i.e., sulfuric acid waste liquid, produced by the nickel-cobalt extraction washing section. For example, it can be prepared by mixing sulfuric acid-containing organic phase washing liquid with water and concentrated sulfuric acid to achieve the recycling of acid reagents.

[0063] Step S3: Add a salt solution containing one or more of ammonia, sodium, and potassium ions to precipitate alum and remove iron. This process utilizes the alum ore method to remove iron from the first leaching solution, forming an alum-type precipitate with adsorption or doping of scandium, thus simultaneously removing iron and enriching scandium through co-precipitation. After the reaction, the alum slurry undergoes a second solid-liquid separation to obtain scandium-enriched iron-vanadium slag and a second leaching solution purified by removing iron and scandium (purified nickel-cobalt solution).

[0064] This step achieves scandium enrichment and recovery by removing iron from the leachate using the iron-vanadium method.

[0065] The salt solution can be, for example, a sulfate solution. In addition, the salt solution can also be recycled from the saponification waste liquid generated in step S4.

[0066] Step S4 involves compounding a carboxylic acid extractant, a hydroxyoxime extractant, and an organic diluent in a specific ratio to form a synergistic extraction system. This synergistic extraction system is then added to an alkaline solution for saponification, resulting in a saponified synergistic extractant system and generating saponification waste liquid. Saponification further increases the extraction and separation efficiency of nickel and cobalt, making it more conducive to the extraction and separation of nickel and cobalt. The saponification waste liquid contains one or more of ammonia, sodium sulfate, and potassium sulfate.

[0067] Step S5: The second leachate is subjected to nickel and cobalt kinetic extraction separation using a saponified synergistic extractant system.

[0068] Specifically, the synergistic extractant system utilizes the different extraction rates of nickel and cobalt, i.e., the extraction rate of cobalt is greater than that of nickel, thus prioritizing the extraction of cobalt to obtain a cobalt-loaded organic phase (i.e., cobalt is extracted into the organic phase) and a cobalt raffinate containing nickel, calcium, and magnesium, to separate and purify the cobalt product; then, nickel extraction is performed on the cobalt raffinate containing nickel, calcium, and magnesium to obtain a nickel-loaded organic phase (i.e., nickel is extracted into the organic phase), to separate and purify the nickel product.

[0069] This step utilizes a synergistic extraction system constructed with carboxylic acid extractant and hydroxyoxime extractant to extract nickel and cobalt from the purified nickel-cobalt solution after iron and vanadium precipitation. By fully leveraging the different kinetic extraction rates of nickel and cobalt, cobalt is extracted preferentially, achieving efficient separation of nickel and cobalt. This synergistic system also increases the extraction and separation coefficients of nickel and cobalt from iron, aluminum, manganese, etc. Furthermore, this synergistic system performs direct extraction of both nickel and cobalt, directly extracting them into the organic phase, thus achieving efficient extraction and effective separation of nickel and cobalt. In addition, the nickel / cobalt-loaded organic phases are washed with dilute sulfuric acid solution as a detergent, producing a sulfuric acid-containing organic phase washing liquid, which can be used to prepare the sulfuric acid solution used in step S2. By recycling the sulfuric acid-containing organic phase washing liquid and the saponification waste liquid generated from saponification, the elements are recycled, reducing raw material consumption.

[0070] In step S1, during the enhanced grinding process, taking advantage of the fact that nickel-cobalt hydroxide is an alkaline raw material containing water (35-75% water content), a small amount of water is first added to the nickel-cobalt hydroxide to wet its surface and form an alkaline solution, which is more conducive to the subsequent reaction. Preferably, the amount of water added can be determined according to the mass ratio of (dry basis) nickel-cobalt hydroxide to water of 1:0.3-4, for example, 1:0.3, 1:0.5, 1:1, 1:2, 1:3, 1:4, etc.

[0071] Based on mechanical activation treatment, ultrasonic enhancement and the introduction of oxygen / air into the grinding system are used for enhanced grinding, which accelerates the conversion of low-valence ions to high-valence ions. By further optimizing the parameters in the enhanced grinding step, the oxidation reaction of iron and manganese metal is made more complete and efficient. Specifically, oxygen or air is introduced into the grinding system to ensure the complete oxidation of divalent manganese. The volume fraction of oxygen in the grinding atmosphere is preferably controlled at 21%–99%, such as 21%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 99%, etc., which can be achieved by adjusting the flow rate of oxygen and controlling the reaction conditions. Ultrasonic enhancement is used to accelerate oxidation during the grinding process. The frequency of the applied ultrasound is preferably 20 kHz to 200 kHz (20 kHz to 200 kHz), such as 20 kHz, 50 kHz, 100 kHz, 150 kHz, 200 kHz, etc.

[0072] Furthermore, in order to achieve sufficient oxidation of low-valence iron and manganese while improving pretreatment efficiency, during enhanced grinding, the temperature is preferably controlled at 25–75°C, for example, 25°C, 35°C, 45°C, 55°C, 65°C, 75°C, etc. Preferably, the reaction time is controlled at 5–30 min, for example, 5 min, 10 min, 20 min, 30 min, etc.

[0073] In step S2, sulfuric acid solution, specifically dilute sulfuric acid solution, is added to the pretreated nickel-cobalt hydroxide under low pH conditions to dissolve the nickel-cobalt hydroxide, thereby leaching scandium and nickel-cobalt, while manganese dioxide remains undissolved, achieving selective leaching. To better achieve leaching selectivity, the pH and temperature of the sulfuric acid leaching solution, i.e., the leaching system, are adjusted. Preferably, the pH of the leaching system is adjusted to 1.0–4.5, more preferably 2.0–3.5; preferably, the leaching temperature is adjusted to 20–45°C, more preferably 25–40°C. By optimizing the leaching system, manganese dioxide remains undissolved while other metals dissolve more easily. Manganese is then separated through liquid-solid separation, and the manganese product is recovered, yielding a purified leaching solution containing scandium, nickel, and cobalt, etc., after manganese removal.

[0074] To provide a better leaching environment, the liquid-to-solid ratio of the leaching system is preferably controlled at 10:1 to 2:1. The concentration of the dilute sulfuric acid solution used for leaching is preferably 0.1 to 3 mol / L. Furthermore, the leaching time is preferably 5 to 20 minutes. To accelerate selective leaching, stirring can be performed at an intensity of 700 to 900 r / min.

[0075] In step S3, a salt solution containing one or more of ammonia, sodium, and potassium ions is added to utilize the (ammonia, sodium, potassium) iron-vanadium ore method for iron precipitation and scandium enrichment. To make the reaction more efficient and achieve scandium product enrichment and recovery, preferably, the molar ratio of the total amount of ammonia, sodium, and potassium added to the total amount of iron and scandium metal elements in the first leaching solution is controlled to be 1.2–4.5:1, for example, 1.2:1, 1.6:1, 2:1, 3:1, 4:1, 4.5:1, etc. The total amount of ammonia, sodium, and potassium added here includes the ammonia, sodium, and potassium contained in the salt solution.

[0076] In some embodiments, prior to the step of vanadium precipitation, iron removal, and scandium enrichment, preferably, the process further includes controlling the pH of the first leaching solution for manganese removal and purification to be 0.6–3.5, more preferably 0.8–1.8. The pH can be adjusted by adding an alkaline neutralizing agent or sulfuric acid to the first leaching solution. The alkaline neutralizing agent is preferably any one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, potassium carbonate, and ammonium carbonate. Adjusting the pH of the first leaching solution is more conducive to vanadium precipitation and iron removal. Since scandium precipitation can be formed at higher acidity, less alkali is needed for neutralization during pH adjustment.

[0077] To further improve the efficiency of vanadium precipitation for iron removal and scandium enrichment, the reaction temperature, i.e., the temperature of the first leaching solution, is preferably controlled at 20–90°C, more preferably at 40–70°C. Furthermore, the precipitation time is preferably 20–200 min. To accelerate the reaction, stirring is performed during the vanadium precipitation process, with a stirring intensity preferably of 200–500 r / min.

[0078] In step S4, a synergistic extraction system is formed by combining a carboxylic acid extractant, a hydroxyoxime extractant, and an organic diluent, which can significantly improve the extraction and separation efficiency of nickel and cobalt. The carboxylic acid extractant is preferably one or more of naphthenic acids, isomeric acids Versatic 10, and Versatic 911. The hydroxyoxime extractant is preferably an α-hydroxyoxime extractant containing a long-chain alkyl group (aliphatic α-hydroxyoxime), and more preferably 5,8-diethyl-7-hydroxy-dodecane-6-oxime (Lix63).

[0079] To further improve the nickel-cobalt extraction and separation efficiency of the synergistic extraction system, the molar ratio of the carboxylic acid extractant to the hydroxyoxime extractant is controlled to be 0.1–10:1, for example, 0.1:1, 0.5:1, 1:1, 2:1, 4:1, 6:1, 8:1, 10:1, etc., preferably 0.5–5:1. Furthermore, the volume concentration of the extractant in the synergistic extraction system is controlled to be 10–40%, for example, 10%, 20%, 30%, 40%, etc. The organic diluent used for dilution is preferably a long-chain alkane, specifically selected from any one or more of n-heptane, n-octane, No. 5 solvent oil, No. 260 solvent oil, and sulfonated kerosene.

[0080] To achieve more efficient nickel-cobalt extraction and separation, the aforementioned synergistic extraction system is added to a saponifying agent solution for organic phase saponification. The saponifying agent is preferably any one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, potassium carbonate, and ammonium carbonate. During saponification, the saponification rate is preferably 30–75%, more preferably 40–60%. The saponification process forms a synergistic extraction agent system that facilitates nickel-cobalt extraction and separation. Furthermore, the saponification waste liquid containing one or more of ammonia, sodium, and potassium sulfates is returned to step S3 for recycling ammonia, sodium, and potassium elements, reducing raw material consumption.

[0081] Based on the different extraction rates of nickel and cobalt in the constructed synergistic extraction system, the extraction rate of cobalt is greater than that of nickel, so cobalt is extracted preferentially and cobalt is extracted into the organic phase, resulting in a cobalt-loaded organic phase and a raffinate containing nickel, calcium and magnesium.

[0082] For optimal cobalt extraction, a multi-stage countercurrent extraction method is employed, using a centrifugal extractor. To further improve the efficiency of cobalt extraction and separation, the preferred number of cobalt extraction stages is 3 to 6. The extraction time for each stage is preferably 10 to 150 seconds, such as 10 seconds, 50 seconds, 80 seconds, 100 seconds, 120 seconds, and 150 seconds. If the cobalt extraction time is too long, exceeding 120 seconds, it affects the kinetic extraction and separation of nickel and cobalt, as prolonged cobalt extraction can lead to nickel being extracted into the organic phase, thus affecting the purity of cobalt. Furthermore, the flow rate ratio of the saponified synergistic extractant (i.e., the extraction organic phase to the aqueous phase) is preferably 0.2 to 10:1; the preferred temperature for each stage of cobalt extraction is 20 to 50°C. The equilibrium pH of the extraction aqueous phase is 2.0 to 4.0. This synergistic extraction system enhances the equilibrium extraction efficiency of nickel and cobalt, enabling extraction and separation at lower pH levels, and further reducing the need for neutralization alkali.

[0083] Further, the cobalt-supported organic phase is subjected to multi-stage washing and back-extraction to separate and purify the cobalt product. Preferably, the extraction and washing stage of the cobalt-supported organic phase has 2 to 4 stages, and the washing solution for extracting the supported organic phase is a dilute sulfuric acid solution with a preferred concentration of 0.02 to 0.8 mol / L, generating sulfuric acid waste liquid. Preferably, the cobalt extraction and back-extraction stage has 3 to 6 stages, and sulfuric acid back-extraction solution with a preferred concentration of 1 to 4 mol / L is used for back-extraction.

[0084] The cobalt raffinate containing nickel, calcium, and magnesium after the initial cobalt extraction is further extracted using the saponification synergistic extraction system, and nickel is also extracted into the organic phase to obtain a nickel-loaded organic phase.

[0085] For nickel extraction, a multi-stage countercurrent extraction method is employed, using a mixing-clarification extraction tank. To further improve the nickel extraction and separation efficiency, the number of extraction stages is preferably 3 to 6. The flow ratio of the saponified synergistic extractant (i.e., the organic phase to the aqueous phase) is preferably 0.2 to 10:1. The extraction temperature for each stage is preferably 30 to 60°C, and the extraction time for each stage is preferably 3 to 10 minutes. The equilibrium pH of the aqueous phase is 2.0 to 4.5.

[0086] Further, the nickel-supported organic phase is subjected to multi-stage washing and back-extraction to separate and purify the nickel product. Preferably, the washing stage of the nickel-supported organic phase has 2 to 4 stages, and the washing solution for extracting the supported organic phase is a dilute sulfuric acid solution with a concentration preferably of 0.02 to 0.8 mol / L. Preferably, the nickel extraction back-extraction stage has 3 to 8 stages, and the concentration of the sulfuric acid back-extraction solution used is 0.8 to 3 mol / L.

[0087] By combining a carboxylic acid extractant and a hydroxime extractant into a synergistic extraction system for nickel-cobalt extraction and separation, the carboxylic acid extractant and the hydroxime extractant form more hydrophobic and spatially stable complexes (metal ion-extractant complexes) with nickel and cobalt ions. This increases the extraction and separation coefficients of nickel and cobalt from iron, aluminum, manganese, etc., and enhances the equilibrium extraction efficiency of nickel and cobalt. This allows for the separation of nickel and cobalt from iron and aluminum at lower pH levels, while also effectively separating them from impurities such as iron, aluminum, calcium, and magnesium. This eliminates the need for precipitation to remove impurities like iron and aluminum from the original extraction feed, and further reduces the need for neutralization with alkali. Furthermore, it fully utilizes the difference in extraction kinetics between nickel and cobalt to achieve efficient separation of nickel and cobalt, yielding high-purity nickel and cobalt products. Moreover, in the synergistic extraction system constructed in this invention, both nickel and cobalt are directly extracted into the organic phase; that is, the nickel-cobalt extraction of this invention is a direct extraction, which constitutes a substantial difference from the extractant extraction technology of the prior art.

[0088] The present invention and its effects will be further described below with reference to specific embodiments and accompanying drawings:

[0089] Example 1

[0090] The raw material, laterite nickel ore, contains the following components: nickel 1.18%, cobalt 0.15%, aluminum 3.5%, manganese 0.55%, iron 40.0%, magnesium 2.0%, calcium 2.0%, and scandium 0.0033%. The nickel-cobalt hydroxide produced from laterite nickel ore contains the following components: nickel 38.6%, cobalt 3.16%, aluminum 2.41%, manganese 5.37%, iron 1.91%, magnesium 2.07%, calcium 0.33%, and scandium 0.035%.

[0091] Includes the following steps:

[0092] 1) 2000g of nickel cobalt hydroxide (68.8% water content) prepared from laterite nickel ore was moistened with 200g of water and subjected to intensive mechanical grinding. The ultrasonic frequency was 20,000 Hz, the oxygen flow rate was 2 L / min, and the reaction conditions were controlled to maintain an oxygen volume fraction of 30%, a temperature of 45℃, and a reaction time of 10 min. The particle size D50 of the ground nickel cobalt hydroxide was measured to be less than 150 micrometers using a laser particle size analyzer.

[0093] 2) Sulfuric acid waste liquid from the extraction and washing section was mixed with sulfuric acid and water to prepare a 0.2 mol / L dilute sulfuric acid solution. This solution was used to leach pretreated nickel-cobalt hydroxide at a liquid-to-solid ratio of 3:1, pH 2.0, temperature 45℃, leaching time 20 min, and stirring intensity 800 r / min. The mixture was then filtered (the first solid-liquid separation) to obtain manganese oxide slag and a purified first leachate. The manganese recovery rate was 86.3%.

[0094] 3) Adjust the pH of the first leachate to 1.0, add sodium-containing waste liquid to the first leachate to precipitate alum and remove iron and scandium, so that the molar ratio of the added sodium ions to the total amount of iron and scandium metal elements in the leachate is 1.5:1, control the temperature of the leachate to 50℃, the stirring intensity to 200 r / min, the precipitation time to 20 min, and filter to obtain scandium-rich sodium iron vanadium and second leachate (purified nickel cobalt solution).

[0095] The scandium enrichment recovery rate reached 95.8% according to the test results.

[0096] 4) According to the molar ratio of carboxylic acid extractant to hydroxyoxime extractant of 0.5:1, measure the organic carboxylic acid extractant naphthenic acid and the hydroxyoxime extractant LIX63, add 5# solvent oil and mix mechanically to prepare a 5# solvent oil solution containing 35% by volume of the composite extractant, which is the synergistic extraction system formed by compounding; add the above synergistic extraction system to sodium hydroxide solution for organic phase saponification, so that the saponification rate is 30%, forming a saponified synergistic extractant system, i.e., saponified organic phase, and generating saponification waste liquid containing sodium sulfate.

[0097] 5) The above-mentioned saponified organic phase was used to perform cobalt kinetic extraction separation in the third leachate. The extraction equipment was a multi-stage centrifugal extractor with 4-stage countercurrent extraction. The flow ratio of the organic phase to the aqueous phase was 0.2:1, the extraction temperature was 30℃, the extraction time for each stage was 20 seconds, and the equilibrium pH of the aqueous phase was 2.0. Cobalt-loaded organic phase and raffinate containing nickel, calcium and magnesium were obtained.

[0098] The cobalt-loaded organic phase was washed in a three-stage extraction washing section. The washing solution for the cobalt-loaded organic phase was a dilute sulfuric acid solution with a concentration of 0.1 mol / L. The flow ratio of the organic phase to the aqueous phase was 5:1, resulting in a washed cobalt-loaded organic phase and sulfuric acid waste liquid. The washed cobalt-loaded organic phase was then back-extracted with a 1 mol / L sulfuric acid solution at a flow ratio of 5:1 to the aqueous phase, yielding a purified cobalt sulfate solution.

[0099] The extraction separation coefficients of cobalt with nickel and manganese reached 12.5 and 17.0, respectively. The total recovery rate of cobalt after extraction, washing and back-extraction reached 99.1%, and the purity of cobalt reached 99.9%.

[0100] For the raffinate containing nickel, calcium, and magnesium, nickel extraction separation was performed using the saponified organic phase from step 4). A multi-stage mixed-clarification extraction tank containing extraction, washing, and back-extraction sections was used. The extraction was performed in three stages of countercurrent extraction at 20°C. The ratio of the organic phase to the aqueous phase was 1:1, and the extraction time for each stage was 5 minutes. The equilibrium pH of the aqueous phase was 3.5, yielding a nickel-loaded organic phase and a raffinate containing calcium and magnesium. The nickel-loaded organic phase was washed in four stages using a 0.2 mol / L dilute sulfuric acid solution. The flow rate ratio of the organic phase to the aqueous phase was 3:1. The washed organic phase was then back-extracted in four stages using a 2 mol / L sulfuric acid solution, with a flow rate ratio of 4:1, yielding a purified nickel sulfate solution.

[0101] The results showed that the extraction separation coefficient of nickel and manganese reached 8.3, the total recovery rate of nickel from extraction to washing to back-extraction reached 98.8%, and the purity of nickel reached 99.5%.

[0102] Example 2

[0103] The raw materials are the same as in Example 1.

[0104] The difference is:

[0105] In step 4), according to the molar ratio of carboxylic acid extractant to hydroxime extractant of 0.5:1, measure out the organic carboxylic acid extractant isomer acid Versatic 10 and hydroxime extractant LIX63, and prepare a No. 5 solvent oil solution containing 38% by volume of the composite extractant.

[0106] In step 5), when extracting cobalt, the preferred flow rate ratio of the organic phase to the aqueous phase is 0.1:1, the extraction temperature is 40℃, the extraction time for each stage is 100 seconds, and the equilibrium pH of the aqueous phase is 3.5.

[0107] All other steps are the same as in Example 1.

[0108] Test results:

[0109] The extraction separation coefficients of cobalt with nickel and manganese reached 14.7 and 18.8, respectively. The total recovery rate of cobalt by extraction-washing-back-extraction reached 99.3%, and the purity of cobalt reached 99.9%.

[0110] The extraction separation coefficient of nickel and manganese reached 8.7, the total recovery rate of nickel from extraction-washing-back-extraction reached 98.9%, and the purity of nickel reached 99.6%.

[0111] Example 3

[0112] The raw materials are the same as in Example 1.

[0113] The difference is:

[0114] In step 1), the frequency of the applied ultrasound is 200,000 Hz, the volume fraction of oxygen in the grinding atmosphere is 35%, the temperature is 50℃, and the reaction time is 12 min.

[0115] In step 2), the concentration of the dilute sulfuric acid solution is 1.5 mol / L, the liquid-to-solid ratio is 5:1, the pH value is 2.5, the temperature is 50℃, and the leaching time is 25 min.

[0116] All other steps are the same as in Example 1.

[0117] Test results:

[0118] The particle size D50 of the ground nickel-cobalt hydroxide is less than 145 micrometers.

[0119] The manganese recovery rate was 86.3%.

[0120] The enrichment and recovery rate of scandium reached 96.0%.

[0121] The extraction separation coefficients of cobalt with nickel and manganese reached 13.4 and 18.5, respectively. The total recovery rate of cobalt by extraction-washing-back-extraction reached 99.2%, and the purity of cobalt reached 99.8%.

[0122] The extraction separation coefficient of nickel and manganese reached 8.6, the total recovery rate of nickel from extraction-washing-back-extraction reached 98.7%, and the purity of nickel reached 99.6%.

[0123] Example 4

[0124] The raw materials are the same as in Example 1.

[0125] The difference is:

[0126] In step 3), sodium-containing waste liquid is added to the first leachate to precipitate alum and remove iron and scandium, so that the molar ratio of the added sodium ions to the total amount of iron and scandium metal elements in the leachate is 3.5:1. The temperature of the leachate is controlled at 60℃, the stirring intensity is 200r / min, the precipitation time is 30min, and the solution is filtered to obtain scandium-rich sodium iron vanadium and the second leachate (purified nickel cobalt solution).

[0127] All other steps are the same as in Example 1.

[0128] After testing,

[0129] The enrichment and recovery rate of scandium reached 96.0%.

[0130] The extraction separation coefficients of cobalt with nickel and manganese reached 15.1 and 17.8, respectively. The total recovery rate of cobalt by extraction-washing-back-extraction reached 99.3%, and the purity of cobalt reached 99.9%.

[0131] The extraction separation coefficient of nickel and manganese reached 8.6, the total recovery rate of nickel from extraction-washing-back-extraction reached 98.9%, and the purity of nickel reached 99.7%.

[0132] Comparative Example 1

[0133] The raw materials are the same as in Example 1.

[0134] The difference is:

[0135] In step 1), nickel-cobalt hydroxide is directly ground for 35 minutes. In step 2), sulfuric acid and water are used to prepare a 1 mol / L dilute sulfuric acid solution. All other steps are the same as in Example 1.

[0136] Testing revealed that most of the manganese in step 2) did not enter the manganese slag. The manganese precipitation recovery rate in this step was 25.4%, and 72.9% of the manganese ions entered the leachate. The concentration of manganese ions in the leachate was 9.7 g / L. The high concentration of manganese ions in the leachate affected the formation of scandium iron alum and the extraction and separation of nickel, cobalt and manganese.

[0137] The enrichment and recovery rate of scandium reached 94.1%.

[0138] The extraction separation coefficients for cobalt with nickel and manganese were 10.1 and 12.3, respectively. The total recovery rate of cobalt through extraction-washing-back-extraction reached 98.9%, and the purity of cobalt reached 98.2%.

[0139] The extraction separation coefficient of nickel and manganese was 7.1, the total recovery rate of nickel from extraction-washing-back-extraction reached 98.6%, and the purity of nickel reached 99.3%.

[0140] Comparative Example 2

[0141] The raw materials are the same as in Example 1.

[0142] The difference is that steps 4) and 5) are not included.

[0143] Instead, conventional saponified acidic organophosphorus extractants were used to extract and separate nickel and cobalt from the second leachate obtained in step 3). Specifically, this included P204 extraction (calcium and manganese), P507 cobalt extraction (cobalt extraction was thermodynamic equilibrium extraction, followed by magnesium extraction after P507 cobalt extraction), and Cyanex 272 deep extraction (magnesium extraction). In this extraction step, nickel sulfate remained in the raffinate, and the entire extraction was thermodynamic equilibrium extraction, requiring a high solution pH. A large amount of neutralizing alkali was added during extraction, resulting in low extraction and separation efficiency between nickel and cobalt, and between nickel / cobalt and impurity elements. The required number of extraction stages was greater than 10. Testing showed that the extraction separation coefficients for cobalt with nickel and manganese were 3.5 and 4.1, respectively, and the extraction separation coefficient for nickel with manganese was 3.6. The total recovery rates of nickel and cobalt were all below 97.0%.

[0144] Comparative Examples 1-2 and Comparative Example 2: The extraction system of the present invention is direct nickel-cobalt extraction. Due to the synergistic extraction effect of the extractant, the extraction pH is low. The metal extraction sequence is different from that of a single extractant. Nickel and cobalt are extracted into the organic phase, where cobalt is kinetically separated, and nickel sulfate is in the back-extraction solution obtained from the back-extraction.

[0145] In summary, by adopting the newly constructed synergistic extraction system of this invention, the extraction pH is reduced, cobalt kinetic separation is achieved, nickel and cobalt are directly extracted into the organic phase, and the extraction separation coefficient of nickel, cobalt and iron, manganese, etc. is increased based on the synergistic extraction system, ultimately achieving efficient extraction and separation of nickel and cobalt. It has the advantages of high impurity separation efficiency, high recovery rate of nickel, cobalt, manganese and scandium, high purity of nickel and cobalt products, low raw material consumption, and the ability to realize element recycling.

[0146] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for scandium-manganese enrichment and nickel-cobalt extraction separation, characterized in that, include: Step S1: Wet the nickel-cobalt hydroxide with water, and then perform enhanced grinding using ultrasound while introducing oxygen or air to obtain pretreated nickel-cobalt hydroxide; wherein the frequency of the applied ultrasound is 20,000 Hz to 200,000 Hz; and the volume fraction of oxygen in the grinding atmosphere is 21% to 99%; Step S2: The pretreated nickel-cobalt hydroxide is added to a dilute sulfuric acid solution for selective leaching. The pH of the leaching system is 1.0 to 4.5, and the temperature is 20 to 45°C. Solid-liquid separation is performed to obtain manganese oxide slag and a first leaching solution purified by manganese removal. Step S3: Add salt solution to the first leachate to precipitate vanadium and remove iron, forming an iron alum-type precipitate with adsorption or doping of scandium. Separate the solid and liquid to obtain scandium-containing iron-vanadium slag and a second leachate purified by removing iron and scandium. The salt solution contains one or more of ammonia, sodium, and potassium ions. Step S4: The carboxylic acid extractant, hydroxyoxime extractant and organic diluent are compounded to form a synergistic extraction system. An alkaline solution is added to the synergistic extraction system for saponification to form a saponified synergistic extractant system and generate saponification waste liquid. Step S5: The second leachate is subjected to nickel and cobalt kinetic extraction separation using the saponified synergistic extractant system; wherein, the extraction rate of cobalt using the synergistic extractant system is greater than that of nickel, and cobalt is extracted preferentially to obtain a cobalt-loaded organic phase, so as to separate and purify the cobalt product; then the cobalt extraction residue is subjected to nickel extraction to obtain a nickel-loaded organic phase, so as to separate and purify the nickel product.

2. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 1, characterized in that, The carboxylic acid extractant is one or more of cycloalkanoic acid, isomeric acid Versatic 10, and isomeric acid Versatic 911. The hydroxyoxime extractant is an α-hydroxyoxime extractant containing a long-chain alkyl group.

3. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 2, characterized in that, The molar ratio of the carboxylic acid extractant to the hydroxyoxime extractant is (0.1-10):1; The hydroxyoxime extractant is 5,8-diethyl-7-hydroxy-dodecane-6-oxime.

4. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 2, characterized in that, The volume concentration of the extractant in the synergistic extraction system is 10–40%. The organic diluent is one or more of the following: n-heptane, n-octane, No. 5 solvent oil, No. 260 solvent oil, and sulfonated kerosene.

5. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 2, characterized in that, In step S5, the step of preferentially extracting cobalt employs multi-stage countercurrent extraction. The cobalt extraction stage is 3 to 6 stages, the flow rate ratio of the saponification extraction organic phase to the aqueous phase is (0.2 to 10): 1, the extraction time for each stage is 10 to 150 seconds, the extraction temperature for each stage is 20 to 50°C, and the equilibrium pH of the extraction aqueous phase is 2.0 to 4.0, thus obtaining the cobalt-loaded organic phase.

6. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 5, characterized in that, In step S5, the nickel extraction of the cobalt extraction residue is carried out using multi-stage countercurrent extraction with 3 to 6 nickel extraction stages. The flow rate ratio of the saponification extraction organic phase to the aqueous phase is (0.2 to 10):

1. The temperature of each nickel extraction stage is 30 to 60°C, the extraction time is 3 to 10 minutes, and the equilibrium pH of the extraction aqueous phase is 2.0 to 4.5, thus obtaining the nickel-loaded organic phase.

7. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 5, characterized in that, Also includes: The cobalt-supported organic phase was washed and back-extracted. The nickel-supported organic phase was washed and back-extracted. Combine the sulfuric acid waste liquids generated from the washing sections of the cobalt-supported organic phase and the nickel-supported organic phase to prepare the dilute sulfuric acid solution in step S2. The washing stage of the cobalt-supported organic phase consists of 2 to 4 stages, with the washing solution being a dilute sulfuric acid solution at a concentration of 0.02 to 0.8 mol / L; the back-extraction stage of the cobalt extraction consists of 3 to 6 stages, with back-extraction using a sulfuric acid back-extraction solution at a concentration of 1 to 4 mol / L. The washing stage of the nickel-supported organic phase has 2 to 4 stages, and the washing solution is a dilute sulfuric acid solution with a concentration of 0.02 to 0.8 mol / L; the back-extraction stage of the nickel extraction has 3 to 8 stages, and the back-extraction solution is sulfuric acid with a concentration of 0.8 to 3 mol / L.

8. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 1, characterized in that, In step S1, The water added should be in a dry weight ratio of nickel-cobalt hydroxide to water of 1:0.3-4. During the enhanced grinding process, the temperature is 25℃~75℃ and the time is 5min~30min.

9. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 1, characterized in that, In step S2, The liquid-to-solid ratio of the leaching system is 10:1 to 2:1, and the leaching time is 5 to 20 minutes. The concentration of the dilute sulfuric acid solution is 0.1–3 mol / L.

10. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 1, characterized in that, Step S3 further includes: adding sulfuric acid or an alkaline neutralizing agent to adjust the pH of the first leachate to 0.6-3.5; wherein the alkaline neutralizing agent is one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, potassium carbonate, and ammonium carbonate.

11. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 1 or 10, characterized in that, In step S3, When adding salt solution to the first leachate for vanadium precipitation and iron removal, the molar ratio of the total amount of added ammonia, sodium, and potassium to the total amount of iron and scandium metal elements in the first leachate is controlled to be (1.2~4.5):

1. The reaction temperature for vanadium precipitation and iron removal is controlled at 20–90℃, and the reaction time is controlled at 20–200 min.

12. The method for scandium-manganese enrichment and nickel-cobalt extraction separation according to claim 1, characterized in that, Also includes: The saponification waste liquid generated in step S4 is used as the salt solution in step S3 and added to the first leachate for vanadium precipitation and iron removal, so as to be recycled.

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