Method for comprehensive recovery of nickel, cobalt and manganese from scandium-containing materials

Abstract

This invention discloses a comprehensive recovery method for nickel, cobalt, manganese, and scandium, belonging to the field of metal production or refining technology. The method includes: pretreatment of nickel-cobalt hydroxide by ultrasonic grinding with oxygen / air introduction; selective leaching of the pretreated nickel-cobalt hydroxide with dilute sulfuric acid solution, followed by solid-liquid separation to obtain manganese oxide slag and a first leachate; using a synergistic extraction system formed by a compound of an organophosphate extractant, a neutral phosphorus-oxygen extractant, and an organic diluent as the first extractant; scandium extraction of the first leachate using the first extractant to obtain a scandium-loaded organic phase and raffinate; precipitation of vanadium and removal of iron in the raffinate, followed by solid-liquid separation to obtain iron alum slag and a second leachate; and nickel-cobalt extraction of the second leachate to obtain a nickel-cobalt-loaded organic phase. This invention enables efficient recovery of nickel, cobalt, manganese, and scandium, and effective separation from impurities.

Description

Technical Field

[0001] This invention relates to the field of metal production or refining technology, and in particular to a comprehensive method for the recovery of nickel, cobalt, manganese, and scandium. 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. The hydrometallurgical process for laterite nickel ore consists of acid leaching, impurity removal, and nickel-cobalt precipitation. Nickel-cobalt hydroxide precipitation is a relatively common intermediate product obtained from the hydrometallurgical process of laterite nickel ore. 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. Besides nickel and cobalt, nickel-cobalt hydroxide also contains relative impurity elements such as iron, manganese, scandium, calcium, and magnesium, and the valence states of iron and manganese ions are unstable. These impurity elements enter the acid leaching solution along with the nickel and cobalt during the nickel-cobalt hydroxide acid leaching reaction, requiring a refining and separation process to remove impurities and obtain a pure nickel-cobalt product.

[0003] In practice, the inventors discovered that nickel-cobalt hydroxide contains iron ions with both +3 and +2 valence states, with +3 being the predominant state, and manganese ions with both +2 and +4 valence states, with +2 being the predominant state. However, the valence state transition process is very slow. This uncertainty in the raw material composition during conventional nickel-cobalt hydroxide refining processes causes significant disruption to industrial production, resulting in low purity, low recovery rates, and unstable production system operation. The iron alum process is a commonly used method for iron removal. However, the conventional iron alum process suffers 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.

[0004] Manganese is one of the impurities leached along with nickel and cobalt and treated in subsequent separation processes. Patent CN115094229B describes a method for removing iron from a nickel-cobalt hydroxide slurry using a goethite method after reduction leaching. While this method achieves scandium co-precipitation enrichment during iron removal, the inventors have discovered that reduction leaching renders manganese divalent, resulting in a high manganese content in the nickel-cobalt solution. This affects nickel-cobalt extraction and product purity, increasing the difficulty of nickel-cobalt extraction.

[0005] Furthermore, a significant amount of nickel-cobalt hydroxide produced from laterite nickel ore contains scandium, a harmful impurity in nickel-cobalt smelting and also a rare earth resource. The inventors have noted that due to the low concentration of scandium in the system and its relatively high impurity content, using precipitation methods to remove and enrich scandium presents problems such as low precipitation rates and difficulty in settling at low scandium concentrations. For example, patent CN103468948B achieves scandium removal and recovery by adjusting the pH to 3.0 or higher during iron and aluminum removal, causing scandium and iron / aluminum to precipitate as hydroxides. However, in practice, this process has a problem: during hydroxide co-precipitation, the special properties of aluminum hydroxide and scandium hydroxide dissolving in strong alkalis make it difficult to determine the reaction endpoint and precisely control the endpoint pH. Too low a pH leads to low scandium recovery, while too high a pH results in colloidal precipitation, affecting filtration performance. Moreover, reactions at higher pH levels increase the loss of nickel, cobalt, and manganese in the slag. When using extraction to purify and separate scandium, there are problems such as low extraction and separation efficiency of scandium with impurities such as iron and aluminum, and difficulty in back-extraction. Scandium exists in solution with elements such as iron and aluminum in the +3 oxidation state, while elements such as nickel, cobalt, manganese, calcium, and magnesium exist in solution in the +2 oxidation state. The extraction of scandium is easily affected by elements such as iron, aluminum, nickel, cobalt, manganese, calcium, and magnesium, while the extraction of nickel and cobalt is easily affected by elements such as scandium, iron, aluminum, manganese, calcium, and magnesium.

[0006] Furthermore, for nickel-cobalt extraction, related 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). The inventors recognize that this nickel-cobalt extraction method has problems such as high extraction equilibrium pH, the need for a large amount of neutralizing alkali, low extraction and separation efficiency, and difficulty in back-extraction. Iron, aluminum, manganese, calcium, magnesium, etc., can easily interfere with the extraction, and iron and aluminum need to be removed in advance by precipitation or other methods. The extraction process also generates a large amount of salt and acid waste liquid that cannot be recycled. Moreover, P204 and P507 have a high extraction capacity for calcium. When calcium is co-extracted into the organic phase, calcium sulfate precipitate is easily generated in the sulfuric acid system. Therefore, the extraction system must add a calcium removal process, which reduces the extraction efficiency.

[0007] Based on the above understanding, the present invention provides a more efficient recycling method to achieve efficient recovery of nickel, cobalt, manganese, and scandium, as well as effective separation from other impurities. Summary of the Invention

[0008] According to one embodiment of the present invention, the objective is to provide a more efficient integrated recovery method for nickel, cobalt, manganese, and scandium. This method employs enhanced grinding to oxidize variable valence metal ions, selective leaching to separate and recover manganese, and a synergistic extraction system to extract scandium from the leachate to obtain a scandium-loaded organic phase. The raffinate is then subjected to iron removal using the iron-vanadium method followed by nickel-cobalt extraction. Furthermore, a saponified synergistic extraction system is used for direct nickel-cobalt extraction, in which nickel and cobalt are directly extracted into the organic phase, thereby achieving efficient recovery of nickel, cobalt, manganese, and scandium and their effective separation from impurities.

[0009] The above objective can be achieved through the following technical solutions:

[0010] According to one aspect of the present invention, a comprehensive recovery method for nickel, cobalt, manganese, and scandium is provided, comprising:

[0011] 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.

[0012] Step S2: Selectively leach the pretreated nickel-cobalt hydroxide with dilute sulfuric acid solution, and separate the solid and liquid to obtain manganese oxide slag and the first leachate;

[0013] Step S3: A synergistic extraction system is formed by combining an organophosphate extractant, a neutral phosphorus extractant, and an organic diluent, which serves as the first extractant; the synergistic extraction system is saponified using an alkaline solution to obtain a saponified synergistic extraction system, which serves as the second extractant.

[0014] Step S4: The first extractant is used to perform scandium extraction on the first leachate to obtain a scandium-loaded organic phase and raffinate;

[0015] Step S5: The raffinate is subjected to vanadium precipitation and iron removal, and solid-liquid separation to obtain iron alum slag and a second leachate;

[0016] Step S6: The second extractant is used to extract nickel and cobalt from the second leachate to obtain a nickel-cobalt supported organic phase.

[0017] Preferably, the molar ratio of the organophosphate extractant to the neutral phosphoric acid extractant is (0.1-10):1.

[0018] Preferably, the organophosphate extractant is one or more of P204, P507, and Cyanex272; the neutral phosphorus extractant is one or more of TBP, Cyanex923, and TOPO.

[0019] Preferably, in the synergistic extraction system, the mass concentration of the extractant is 30-60%.

[0020] Preferably, the organic diluent is any one or more selected from n-heptane, n-octane, No. 5 solvent oil, No. 260 solvent oil, and sulfonated kerosene.

[0021] Preferably, in step S4, scandium extraction is performed using multi-stage countercurrent extraction, multi-stage washing, and multi-stage back-extraction.

[0022] Preferably, the number of scandium extraction stages is 4 to 8, the flow ratio of the first extractant to the aqueous phase is 0.05 to 1:1, the temperature of scandium extraction is 20 to 40°C, the time of scandium extraction is 2 to 10 min, and the equilibrium pH of the aqueous phase reaction during scandium extraction is 0.5 to 2.5.

[0023] Preferably, the scandium extraction washing process has 3 to 6 stages, and the washing solution is dilute sulfuric acid with a concentration of 0.01 to 0.3 mol / L.

[0024] Preferably, the scandium extraction back-extraction stage is 2 to 8 stages, the flow ratio of organic phase to aqueous phase is 0.5 to 10:1, the back-extraction temperature is 20 to 80°C, and the back-extraction time is 5 to 10 min.

[0025] Preferably, step S4 further includes: washing and back-extracting the scandium-supported organic phase to obtain a scandium back-extract, adding a precipitant to the scandium back-extract to precipitate a scandium precipitate, and calcining the scandium precipitate to obtain a scandium oxide product.

[0026] Preferably, the precipitant is selected from any one or more of ammonia, ammonium carbonate, oxalic acid, ammonium oxalate, citric acid, ammonium citrate, malic acid, and ammonium malate.

[0027] More preferably, the precipitant is a composite precipitant formed by two or more of the following: ammonia, ammonium carbonate, oxalic acid, ammonium oxalate, citric acid, ammonium citrate, malic acid, and ammonium malate.

[0028] Preferably, the step of calcining the scandium precipitate employs a two-stage calcination process.

[0029] More preferably, the first stage calcination temperature is 300–500℃, and the calcination time is 10–60 min; the second stage calcination temperature is 400–1200℃, and the calcination time is 30–90 min.

[0030] Preferably, in the step of adding a precipitant to the scandium back-extraction solution for precipitation, the precipitation temperature is 40–90°C and the precipitation time is 5–30 min.

[0031] 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).

[0032] Preferably, in step S1, the frequency of the applied ultrasonic wave is 20,000 Hz to 200,000 Hz.

[0033] Preferably, in step S1, oxygen or air is introduced to make the volume fraction of oxygen in the grinding atmosphere 21% to 99%.

[0034] Preferably, in step S1, the temperature during the enhanced grinding is 25℃~75℃ and the time is 5min~30min.

[0035] Preferably, in step S2, the concentration of the dilute sulfuric acid solution is 0.1–3 mol / L.

[0036] Preferably, in step S2, during selective leaching, the pH of the leaching system is 1.0 to 4.5, and the temperature is 20 to 45°C.

[0037] 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.

[0038] Preferably, in step S3, the alkaline solution is selected from any one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, potassium carbonate, and ammonium carbonate.

[0039] Preferably, in step S5, the step of precipitating vanadium and removing iron from the raffinate includes: adding sulfuric acid or an alkaline neutralizing agent to the raffinate to adjust the pH of the raffinate to 0.6-3.0.

[0040] Preferably, in step S5, the step of precipitating vanadium and removing iron from the raffinate includes: adding the saponification waste liquid generated in step S3 to the raffinate for precipitating vanadium and removing iron.

[0041] Preferably, in step S5, the step of precipitating vanadium and removing iron from the raffinate includes controlling the molar ratio of the total amount of added ammonia, sodium, and potassium to the total amount of iron in the raffinate to be 3:1 to 4.5:1.

[0042] Preferably, in step S5, the step of precipitating vanadium and removing iron from the raffinate includes controlling the reaction temperature during vanadium precipitation and iron removal to be 20–90°C and the reaction time to be 20–150 min.

[0043] Preferably, the alkaline neutralizing agent is selected from any one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, potassium carbonate, and ammonium carbonate.

[0044] Preferably, in step S6, when performing nickel-cobalt extraction, a multi-stage countercurrent extraction, washing, and back-extraction process is adopted.

[0045] Preferably, in step S6, the number of nickel-cobalt extraction stages is 3 to 6, the flow ratio of the second extractant to the aqueous phase is 0.2 to 10:1, the extraction temperature for each stage is 20 to 50°C, the extraction time for each stage is 2 to 10 min, and the equilibrium pH of the extraction aqueous phase is 2.0 to 5.0.

[0046] Preferably, in step S6, the nickel-cobalt extraction and washing process consists of 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.

[0047] Preferably, in step S6, the nickel-cobalt extraction back-extraction stage is 3 to 8 stages, and the concentration of the sulfuric acid back-extraction solution used is 0.5 to 5 mol / L.

[0048] Beneficial Effects: According to one embodiment of the present invention, nickel-cobalt hydroxide is pretreated by mechanical activation coupling to accelerate oxidation, rapidly oxidizing divalent manganese to tetravalent manganese to form manganese dioxide, and rapidly oxidizing divalent iron to trivalent iron. After pretreatment, selective leaching occurs, where the manganese dioxide remains insoluble and enters the slag, separating it from other metals entering the leachate, and manganese is recovered. For the leachate after manganese separation, a synergistic extraction system composed of (unsaponified) organophosphate extractant and neutral phosphoric acid extractant is used for scandium extraction, preferentially extracting scandium into the organic phase, achieving separation from nickel, cobalt, iron, aluminum, calcium, and magnesium, while these other metals enter the raffinate. Vanadium is precipitated in the raffinate to remove iron. A saponification synergistic extraction system is used to extract and separate nickel and cobalt from the leachate after alum precipitation and iron removal, where nickel and cobalt are also directly extracted into the organic phase, achieving separation from other metals. In summary, the method of the present invention can achieve efficient recovery of nickel, cobalt, manganese, and scandium, and effective separation from impurities.

[0049] Compared with related technologies, the embodiments of the present invention also have the following advantages:

[0050] 1) Enhanced grinding accelerates the oxidation rate of variable valence metals. Grinding, ultrasonication, and oxygenation increase the reactive surface area, enhance reaction activity, and accelerate the reaction rate, enabling divalent manganese to be rapidly oxidized to tetravalent manganese to form manganese dioxide, which is insoluble in weak acid solutions. This allows for the separation and enrichment of manganese in the leaching step, making full use of the characteristics of nickel-cobalt hydroxide raw materials. This low-cost method enables the enrichment and separation of manganese and is also beneficial for nickel-cobalt extraction.

[0051] 2) Under normal pressure, dilute sulfuric acid is used to selectively leach pretreated nickel-cobalt hydroxide at low pH conditions. The nickel-cobalt hydroxide is dissolved, and scandium and nickel-cobalt are leached out, while manganese dioxide is not dissolved and enters the slag through solid-liquid separation and is recovered, thus achieving the separation of manganese from other metals that enter the leaching solution.

[0052] 3) A novel synergistic extraction system, constructed using unsaponified organophosphate extractant and neutral phosphorus-oxygen extractant, is first used as a scandium synergistic extractant to extract scandium, achieving efficient extraction, separation, and purification of scandium from other elements at low pH. Furthermore, the scandium-supported organic phase is washed and back-extracted to obtain a scandium back-extract, which is then precipitated and calcined to obtain scandium oxide. The use of a composite precipitant results in a high precipitation rate; segmented calcination leads to a high decomposition rate and high product purity.

[0053] 4) Using the (ammonium, sodium, potassium) iron ore formation method to precipitate vanadium and remove iron from the raffinate of scandium extraction results in a precipitate that is easier to precipitate, wash and filter, and the loss rate of nickel and cobalt (the precipitate slag rate) is lower; in addition, the iron and vanadium precipitate can be formed at higher acidity, reducing the amount of alkali used for neutralization.

[0054] 5) The nickel-cobalt extractant is saponified using an alkaline solution containing ammonia, sodium, and potassium. Saponification increases the extraction and separation efficiency of nickel and cobalt. Furthermore, a synergistic extraction system constructed from an organophosphate extractant and a neutral phosphorus-oxygen extractant is used as the nickel-cobalt extractant. By using this synergistic extraction system, the extraction and separation coefficients of nickel and cobalt from iron, aluminum, manganese, calcium, magnesium, etc., are increased. In addition, the saponification wastewater containing ammonia, sodium, and potassium salts can be recycled to the vanadium precipitation and iron removal step, achieving element recycling while removing iron. Attached Figure Description

[0055] Figure 1 This is a schematic flowchart of a comprehensive recovery method for nickel, cobalt, manganese, and scandium in one embodiment of the present invention. Detailed Implementation

[0056] 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.

[0057] As described above, the inventors discovered that nickel-cobalt hydroxide contains other elements such as scandium, manganese, iron, aluminum, calcium, and magnesium. Furthermore, the coexistence of low-valence and high-valence manganese and iron ions affects the extraction and separation of nickel and cobalt, preventing the comprehensive recovery of valuable elements like scandium and manganese. When using extraction methods to purify and separate scandium, problems arise such as low extraction and separation efficiency of scandium from impurities like iron and aluminum, and difficulty in back-extraction. Nickel-cobalt extraction also suffers from high extraction equilibrium pH, requiring large amounts of neutralizing alkali, resulting in low extraction and separation efficiency and difficulty in back-extraction. To achieve better and more efficient comprehensive recovery of nickel, cobalt, manganese, and scandium, this invention improves upon conventional nickel-cobalt hydroxide treatment processes and proposes a more effective method for recovering these elements. This method employs enhanced grinding to oxidize variable-valence metal ions, selective leaching to separate and recover manganese, and a newly constructed synergistic extraction system to extract scandium from the leachate. The raffinate is then treated with an iron-vanadium method to remove iron, followed by saponification of the synergistic extraction system for nickel-cobalt extraction. Through this stepwise separation, efficient recovery of nickel, cobalt, manganese, and scandium, as well as their effective separation from other impurities, are achieved.

[0058] The principles and effects of each processing step of the present invention are explained below:

[0059] First, nickel-cobalt hydroxide undergoes enhanced grinding pretreatment. Enhanced grinding is a method of accelerating oxidation by mechanical activation coupled with ultrasonic enhancement. Based on the mechanical grinding that results 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 performed using the ultrasonic cavitation effect (ultrasonic cavitation can generate a large number of active free radicals, enhance intermolecular collisions, and increase the chemical reaction rate), accelerating the gas / liquid / solid interface reaction kinetics. These mechanical activation treatments enhance the surface reactivity of the solid, making it more readily react with oxygen. This rapidly oxidizes divalent manganese to tetravalent manganese to form manganese dioxide, and rapidly oxidizes divalent iron to trivalent iron to form ferric hydroxide.

[0060] Secondly, the pretreated nickel-cobalt hydroxide is selectively leached with sulfuric acid under normal pressure, so that the generated manganese dioxide does not dissolve while other metals (such as scandium nickel-cobalt) dissolve. Through liquid-solid separation, the manganese dioxide enters the slag, while the other metals enter the leachate, thus realizing manganese recovery and obtaining the leachate for subsequent scandium extraction.

[0061] Next, scandium is preferentially extracted from the leachate after manganese recovery. A newly constructed synergistic extraction system, consisting of unsaponified organic phosphoric acid extractant and neutral phosphorus-oxygen extractant, is used as the first extractant for scandium. On one hand, the addition of the electron-pair-rich neutral phosphorus-oxygen extractant alters the previously strongly interacting scandium ion-extractant complex into a weakly interacting complex, enhancing scandium extraction capacity (at lower pH) and improving its separation performance from other elements. This allows for effective separation of scandium from elements such as iron, aluminum, calcium, magnesium, nickel, and cobalt at higher acidity, reducing the need for alkali neutralization (eliminating the need for precipitation to remove impurities like iron and aluminum from the original extraction solution). On the other hand, scandium back-extraction capacity is enhanced, and back-extraction efficiency is improved. After back-extraction, scandium oxide can be recovered through precipitation and calcination. For the raffinate containing nickel, cobalt, iron, etc. after scandium extraction, the iron is first removed by precipitation of alum using the (ammonium, sodium, potassium) alum formation method. The iron alum precipitates formed are mainly jaundice alum, jaundice sodium alum, and jaundice ammonium alum. Iron and vanadium can be formed at higher acidity, reducing the need for alkali neutralization. It is not necessary to remove iron by co-precipitating iron hydroxide by increasing the pH value in the iron removal stage. Moreover, the precipitate obtained has a higher crystal form and is easier to precipitate, wash, and filter.

[0062] Finally, the saponified synergistic extraction system is used to directly extract nickel and cobalt from the iron-removed leachate. The nickel and cobalt are directly extracted into the organic phase, thus achieving efficient extraction of nickel and cobalt and effective separation from impurities.

[0063] In one embodiment of the present invention, a method for recovering scandium, nickel, cobalt, and manganese is provided, using nickel-cobalt hydroxide derived from laterite nickel ore as raw material, comprising the following steps:

[0064] Step S1 involves ultrasonically grinding nickel cobalt hydroxide produced from laterite nickel ore. The nickel cobalt hydroxide is first moistened with water, then ultrasonically ground and oxygen or air is introduced 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), resulting in pretreated nickel cobalt hydroxide with finer particle size and increased iron and manganese metal valence states.

[0065] Step S2: Add the pretreated nickel-cobalt hydroxide to a sulfuric acid solution, specifically a dilute sulfuric acid solution, for selective leaching treatment. Perform the first solid-liquid separation on the reaction slurry system to obtain manganese oxide slag and a first leaching solution purified by removing manganese.

[0066] The dilute sulfuric acid solution can be prepared using the sulfuric acid-containing organic phase washing liquid produced in the extraction and washing section; manganese products are recovered from manganese oxide slag.

[0067] Step S3: The organophosphate extractant, neutral phosphorus extractant, and organic diluent are compounded in a certain proportion to form a synergistic extraction system, namely the first extractant; and the second extractant is prepared in advance using the first extractant: the synergistic extraction system is added to an alkaline solution saponifying agent to saponify the extractant, forming a saponified synergistic extraction system, namely the second extractant, so as to perform nickel-cobalt extraction and separation, and generate saponified waste liquid containing one or more of ammonia, sodium, and potassium, specifically a waste solution containing the corresponding sulfates;

[0068] Step S4: Scandium is extracted and separated from the first leachate using a first extractant. Scandium is preferentially extracted and loaded onto the organic phase, while other metals enter the raffinate. The scandium-loaded organic phase is washed with dilute sulfuric acid. The washed scandium-loaded organic phase is back-extracted using a back-extractant solution to obtain a scandium back-extract. The scandium back-extract is then added to a precipitant to precipitate scandium, which is then calcined to obtain scandium oxide product.

[0069] In step S5, the raffinate is added to one or more saponification waste liquids from the ammonia, sodium, and potassium salt solution in step S3 for alum precipitation and iron removal, using the alum ore method to remove iron. The reaction forms an alum-type precipitate and a nickel-cobalt-containing solution. The alum precipitate slurry is then subjected to a second solid-liquid separation to obtain iron-vanadium slag and a second leaching solution purified by removing iron and scandium (a purified nickel-cobalt solution to remove manganese, scandium, and iron).

[0070] Step S6: The second leaching solution is extracted with nickel and cobalt using the pre-prepared second extractant, and the nickel and cobalt are extracted into the organic phase. The nickel and cobalt-loaded organic phase is washed and back-extracted to obtain a nickel and cobalt solution, so as to separate and purify the nickel and cobalt product. The washing section uses dilute sulfuric acid solution to wash, and the washing produces an organic phase washing liquid containing sulfuric acid, which can be used to prepare the dilute sulfuric acid solution in step S2.

[0071] In this embodiment, the saponification waste liquid containing ammonia, sodium, and potassium salts generated during the saponification process of the second extractant is used to precipitate ferric ions in the raffinate to remove iron, achieving element recycling while removing iron impurities. During nickel-cobalt extraction and separation, a novel synergistic extraction system using the same type of extractant as scandium extraction, but after saponification, is used as the second extractant for nickel-cobalt extraction and separation, achieving efficient extraction, separation, and purification of nickel and cobalt. Because the organophosphate extractant and the neutral extractant synergistically form a more hydrophobic and spatially stable complex (metal ion-extractant complex) with nickel and cobalt ions, the nickel-cobalt extraction efficiency is enhanced. Separation of nickel and cobalt from iron, aluminum, etc., can be achieved at lower pH, while effectively separating from impurities such as iron, aluminum, calcium, and magnesium, further reducing the need for neutralization alkali. The method described in this invention has advantages such as high impurity separation efficiency, high recovery rates of nickel, cobalt, manganese, and scandium, low raw material consumption, and high element recycling rate.

[0072] 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.

[0073] Based on mechanical activation treatment, ultrasonic enhancement and the introduction of oxygen or air into the grinding system accelerate the conversion of low-valence manganese and iron ions to high-valence states. Further optimization of parameters in the enhanced grinding process makes the iron-manganese metal oxidation reaction more complete and efficient. Specifically, the grinding system is purged with oxygen or air to ensure the complete oxidation of divalent manganese. The volume fraction of oxygen in the grinding atmosphere is preferably controlled to be 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 oxygen flow rate and controlling the reaction conditions. The grinding process utilizes the ultrasonic cavitation effect of ultrasound to accelerate oxidation. 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.

[0074] 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.

[0075] In step S2, dilute sulfuric acid solution is added to the pretreated nickel-cobalt hydroxide to dissolve the nickel-cobalt hydroxide under low pH conditions, 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) of the nickel-cobalt hydroxide are adjusted. By optimizing the leaching environment, manganese dioxide remains undissolved while other metals are more readily leached. 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. To provide a better leaching environment for more efficient selective leaching, the liquid-to-solid ratio of the leaching system is preferably controlled to 10:1–2:1. The concentration of the dilute sulfuric acid solution used for leaching is preferably 0.1–3 mol / L. Furthermore, the leaching time is preferably 5–20 min.

[0076] In step S3, a synergistic extraction system, namely the first extractant, is formed by combining an organophosphate extractant, a neutral phosphorus oxychloride extractant, and an organic diluent for subsequent scandium extraction. The organophosphate extractant is preferably one or more of di(2-ethylhexyl) phosphate (P204), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507), and bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex272). The neutral phosphorus oxychloride extractant is preferably one or more of tributyl phosphate (TBP), trialkylphosphine oxide (Cyanex923), and trioctylphosphine oxide (TOPO).

[0077] To further improve scandium extraction separation and back-extraction capabilities, preferably, the molar ratio of the organophosphate extractant to the neutral phosphoric acid extractant is controlled at 0.1–10:1, more preferably 0.5–5:1. Preferably, the mass concentration of the extractant in the synergistic extraction system is controlled at 30–60%. When diluting, the organic diluent used 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.

[0078] Further, the above-mentioned synergistic extraction system is added to an alkaline solution as a saponifying agent to perform organic phase saponification, i.e., extractant saponification, thus pre-preparing a saponified synergistic extraction system, i.e., a second extractant, for subsequent nickel-cobalt extraction and separation, and generating a saponification waste liquid containing one or more of ammonia, sodium, and potassium sulfate. 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 20-50%, more preferably 30-40%.

[0079] In step S4, a combined scandium extraction-precipitation-calcination process is used to achieve efficient enrichment and recovery of scandium. Specifically, the scandium extraction preferably employs a multi-stage countercurrent extraction, washing, and back-extraction process. The extraction equipment can be a mixing-clarification extraction tank or an annular multi-stage centrifugal extractor.

[0080] To achieve more efficient scandium extraction and separation, the process parameters for each stage were optimized. Specifically, in the scandium extraction stage: the preferred number of extraction stages is 4–8; the preferred flow ratio of the first extractant to the aqueous phase is 0.05–1:1; the preferred extraction temperature is 20–40℃; the preferred extraction time is 2–10 min; and the preferred equilibrium pH of the aqueous phase reaction is 0.5–2.5. In the scandium extraction washing stage: the preferred number of washing stages is 3–6; the washing solution for the extracted organic phase is dilute sulfuric acid with a preferred concentration of 0.01–0.3 mol / L. After washing, a washed scandium-loaded organic phase and a waste dilute sulfuric acid solution are obtained. This waste dilute sulfuric acid solution can be used to prepare the dilute sulfuric acid solution for selective leaching in step S2. Scandium extraction back-extraction stage: The number of stages in the scandium extraction back-extraction stage is preferably 2 to 8; the back-extraction agent solution is preferably an aqueous solution of sodium hydroxide, hydrochloric acid or nitric acid, and the concentration of the back-extraction agent solution is preferably 0.8 to 5 mol / L; the flow rate ratio of the organic phase (i.e., the washed scandium-loaded organic phase) to the aqueous phase is preferably 0.5 to 10:1; the back-extraction temperature is preferably 20 to 80℃, and the back-extraction time is preferably 5 to 10 min, to obtain a scandium-containing back-extraction solution.

[0081] During precipitation, the added precipitant is preferably selected from any one or more of ammonia, ammonium carbonate, oxalic acid, ammonium oxalate, citric acid, ammonium citrate, malic acid, and ammonium malate. More preferably, two or more of these are used to form a composite precipitant for scandium precipitation to enhance the precipitation efficiency. The precipitation temperature is preferably 40–90°C, and the precipitation time is preferably 5–30 min to further improve the scandium precipitation efficiency. In addition, stirring can be used to accelerate precipitation; the stirring speed is preferably 50–500 rpm.

[0082] During calcination, preferably, the scandium precipitate obtained from precipitation undergoes two-stage calcination. Related technologies use single-stage calcination, which consumes more energy and tends to result in a higher loss-on-burn rate of scandium oxide (i.e., low calcination conversion rate). The preferred embodiment employs two-stage calcination. The first stage removes physically adsorbed water, and the second stage removes chemically bonded water through calcination. This reduces energy consumption, improves calcination decomposition efficiency, and increases product purity. Specifically, the preferred calcination temperature for the first stage is 300–500℃, and the preferred calcination time is 10–60 min; the preferred calcination temperature for the second stage is 400–1200℃, and the preferred calcination time is 30–90 min. Further control of the calcination conditions further improves product purity and processing efficiency.

[0083] In step S5, the iron-vanadium ore method is used to precipitate vanadium and remove iron. To facilitate the vanadium precipitation and iron removal process, the pH of the raffinate is first adjusted. Preferably, an alkaline neutralizing agent or sulfuric acid is added to the raffinate to control the pH of the second leachate to 0.6–3.0, more preferably 0.8–1.8. The alkaline neutralizing agent is preferably any one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, potassium carbonate, and ammonium carbonate.

[0084] To achieve more efficient vanadium precipitation and iron removal, the molar ratio of the total amount of added ammonia, sodium, and potassium to the iron in the raffinate is preferably controlled at 3:1 to 4.5:1. To further improve the efficiency of vanadium precipitation and iron removal, the precipitation temperature, i.e., the temperature of the raffinate, is controlled at 20–90°C, preferably 40–70°C; the precipitation time is preferably 20–150 min. Stirring can be used during the precipitation reaction to accelerate the reaction; the stirring intensity is preferably 200–500 r / min.

[0085] In step S6, during nickel-cobalt extraction and separation, a multi-stage countercurrent extraction, washing, and back-extraction process is preferred, using a mixed-clarification extraction tank. To further optimize each stage of the extraction process, the nickel-cobalt extraction stage is as follows: the number of extraction stages is preferably 3–6; the flow rate ratio of the saponification extraction organic phase (i.e., the second extractant) to the aqueous phase is preferably 0.2–10:1; the extraction temperature for each stage is preferably 20–50℃; the extraction time for each stage is preferably 2–10 min; and the equilibrium pH of the aqueous phase is 2.0–5.0. In the nickel-cobalt extraction washing stage, the number of washing stages is preferably 2–4; the washing solution for the extracted organic phase is a dilute sulfuric acid solution with a concentration preferably 0.02–0.8 mol / L. The resulting dilute sulfuric acid waste solution can be used to prepare the dilute sulfuric acid solution for selective leaching in step S2. Nickel-cobalt extraction back-extraction stage: The number of back-extraction stages is preferably 3 to 8, and the concentration of the sulfuric acid back-extraction solution is preferably 0.5 to 5 mol / L; the nickel-cobalt solution obtained by back-extraction is separated, purified and recovered as nickel-cobalt product.

[0086] The implementation methods and effects of the present invention will be described below with reference to specific embodiments and accompanying drawings:

[0087] Example 1

[0088] The raw material, laterite nickel ore, has the following composition: 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 has the following composition: 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%.

[0089] The specific steps include:

[0090] 1) 2000g of nickel cobalt hydroxide (68.8% water content) prepared from laterite nickel ore was added to 200g of water to wet its surface. It was then subjected to ultrasonic-enhanced grinding with an ultrasonic frequency of 20,000 Hz and an oxygen flow rate of 2 L / min. The reaction conditions were controlled so that the volume fraction of oxygen in the grinding atmosphere was 30%, the temperature was 45℃, and the reaction time was 10 min. The particle size D50 of the pretreated nickel cobalt hydroxide was less than 150 micrometers, as measured by a laser particle size analyzer.

[0091] 2) The pretreated nickel-cobalt hydroxide was leached with a 0.2 mol / L dilute sulfuric acid solution (prepared from waste dilute sulfuric acid solution generated in the washing section) 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 first solid-liquid separation yielded manganese oxide slag (from which manganese was recovered) and a purified first leachate. The manganese recovery rate was 86.1%.

[0092] 3) According to the molar ratio of organophosphate extractant Cyanex272 to neutral phosphoric acid extractant Cyanex923 of 1:1, add No. 5 solvent oil and mix mechanically to prepare a No. 5 solvent oil solution with a volume percentage of 35% extractant. The synergistic extraction system formed by the compounding is the first extractant. Add the above synergistic extraction system to sodium hydroxide solution for organic phase saponification to make the saponification rate 35%, forming a saponified synergistic extraction system, i.e. the second extractant, and generate saponification waste liquid containing sodium sulfate.

[0093] 4) Scandium is extracted and separated from the first leachate using an unsaponified synergistic extraction system, i.e., the first extractant. The extraction equipment is a mixed-clarification extraction tank with 6 extraction stages. The flow ratio of the first extractant to the aqueous phase is 0.2:1, the extraction temperature is 20℃, the extraction time is 2 min, and the equilibrium pH of the aqueous phase is 1.0. The scandium extraction washing stage has 3 stages. The washing solution for the organic phase loaded with scandium is dilute sulfuric acid with a concentration of 0.1 mol / L, producing a washed organic phase loaded with scandium and a waste dilute sulfuric acid solution. The scandium extraction back-extraction stage has 4 stages. The back-extraction agent solution is an aqueous solution of hydrochloric acid with a concentration of 5 mol / L. The flow ratio of the organic phase to the aqueous phase is 5:1. The back-extraction temperature is 30℃, and the back-extraction time is 5 min, yielding a scandium-containing back-extraction solution.

[0094] The scandium-containing back-extraction solution was precipitated by adding a precipitant, which was a composite precipitant of oxalic acid and citric acid in a molar ratio of 1:1. The precipitation temperature was 90℃, the precipitation time was 10 min, and the stirring speed was 300 rpm to obtain scandium precipitate. The scandium precipitate was then subjected to two-stage calcination: the first stage calcination temperature was 300℃ and the calcination time was 40 min, and the second stage calcination temperature was 800℃ and the calcination time was 60 min. The calcination decomposition rate reached 99.9%.

[0095] Testing revealed that the purity of the scandium oxide product reached 99.9%; the total recovery rate of scandium through extraction-washing-back-extraction-precipitation-calcination reached 96.1%.

[0096] 5) Add saponification waste liquid containing sodium sulfate to the raffinate for alum precipitation and iron removal, ensuring the molar ratio of added sodium ions to the total iron content in the leachate is 3.5:1. Control the solution temperature at 50℃, the stirring intensity at 200 r / min, and the precipitation time at 20 min. Perform a second solid-liquid separation to obtain iron alum slag and a second leachate (purified nickel-cobalt solution). Testing showed that the iron precipitation removal rate reached 97%.

[0097] 6) A saponification-based synergistic extraction system, i.e., the second extractant, is used to extract and separate nickel and cobalt from the second leachate. The equipment is a multi-stage mixed-clarification extraction tank containing an extraction section, a washing section, and a back-extraction section. The extraction is carried out through 4 stages of countercurrent extraction at a temperature of 40℃, with an organic phase to aqueous phase ratio of 2:1 and an equilibrium pH of 4.5 for the aqueous phase. The washing section has 4 stages, and the washing solution for the organic phase loaded with the extraction is a 0.2 mol / L dilute sulfuric acid solution. During back-extraction, the washed organic phase loaded with the extraction is back-extracted in 4 stages using a 3 mol / L sulfuric acid solution to obtain nickel and cobalt solutions.

[0098] Testing showed that the total recovery rate of nickel reached 98.1% and cobalt reached 98.3% after extraction, washing and back-extraction.

[0099] Furthermore, after separating and purifying the nickel and cobalt solutions to obtain nickel and cobalt products, the purity of the cobalt product reached 99.2%, and the purity of the nickel product reached 99.2%.

[0100] Example 2

[0101] The raw materials are the same as in Example 1.

[0102] The difference is:

[0103] In step 3), a 40% volume percentage solution of solvent oil (No. 5) is prepared, which is the first extractant, according to the molar ratio of organophosphate extractant P507 to neutral phosphoric acid extractant TBP of 3:1.

[0104] In step 4), scandium is extracted using the first extractant, i.e., the unsaponified synergistic extraction system. The extraction stage has 5 stages, the flow ratio of the first extractant to the aqueous phase is 0.1:1, the extraction temperature is 30℃, the extraction time is 4 min, and the equilibrium pH of the aqueous phase is 1.5. Scandium is extracted into the organic phase. The scandium extraction washing stage has 4 stages, and the washing solution for the loaded organic phase is dilute sulfuric acid with a concentration of 0.05 mol / L, producing a washed scandium-loaded organic phase and a dilute sulfuric acid waste solution. The scandium extraction back-extraction stage has 7 stages, and the back-extraction agent solution is an aqueous solution of hydrochloric acid with a concentration of 4 mol / L. The flow ratio of the organic phase to the aqueous phase is 2:1, the back-extraction temperature is 40℃, and the back-extraction time is also 5 min, yielding a scandium-containing back-extraction solution. Scandium oxide product is obtained through precipitation and calcination.

[0105] In step 6), a saponification-based synergistic extraction system is used to extract nickel and cobalt. The extraction is carried out through 6 stages of countercurrent extraction at a temperature of 30°C. The ratio of the organic phase to the aqueous phase is 1:1, and the equilibrium pH of the extraction aqueous phase is 4.0. Nickel and cobalt are directly extracted into the organic phase, achieving effective separation of nickel and cobalt from iron, aluminum, calcium, magnesium, and manganese. The washing stage also has 4 stages, and the washing solution for the extracted organic phase is a 0.2 mol / L dilute sulfuric acid solution. During back-extraction, the washed extracted organic phase is back-extracted in 5 stages using a 3 mol / L sulfuric acid solution to obtain a nickel and cobalt solution.

[0106] Test results:

[0107] The purity of scandium oxide reached 99.9%; the total recovery rate of scandium through extraction-washing-back-extraction-precipitation-calcination reached 97.3%.

[0108] The overall recovery rate of nickel reached 98.2% and that of cobalt reached 98.2% after extraction, washing and back-extraction.

[0109] Example 3

[0110] The raw materials are the same as in Example 1.

[0111] The difference is that,

[0112] In step 3), a 40% volume percentage solution of solvent oil (No. 5) is prepared, which is the first extractant, according to the molar ratio of organophosphate extractant P204 to neutral phosphoric acid extractant Cyanex923 of 3:2.

[0113] In step 4), scandium is extracted using an unsaponified co-extraction system, i.e., the first extractant. The extraction stage consists of 5 stages, with a flow ratio of the first extractant to the aqueous phase of 0.1:1. The extraction temperature is 30℃, the extraction time is 4 min, and the equilibrium pH of the aqueous phase is 1.5. Scandium is extracted into the organic phase. The scandium extraction washing stage consists of 4 stages, with dilute sulfuric acid (0.05 mol / L) as the washing solution for the loaded organic phase. This produces a washed scandium-loaded organic phase and a waste dilute sulfuric acid solution. The scandium extraction back-extraction stage consists of 8 stages, with an aqueous solution of hydrochloric acid (4 mol / L) as the back-extraction agent. The flow ratio of the organic phase to the aqueous phase is 2:1, the back-extraction temperature is 80℃, and the back-extraction time is 5 min, yielding a scandium-containing back-extraction solution. Scandium oxide is obtained through precipitation and calcination.

[0114] In step 6), a saponification-based synergistic extraction system, i.e., the second extractant, is used to extract nickel and cobalt. The extraction is carried out through 6 stages of countercurrent extraction at a temperature of 30°C. The ratio of the organic phase to the aqueous phase is 1:1, and the equilibrium pH of the aqueous phase is 3.5. Nickel and cobalt are directly extracted into the organic phase. The washing stage consists of 4 stages, and the washing solution for the organic phase loaded with extraction is a 0.2 mol / L dilute sulfuric acid solution. During back-extraction, the washed organic phase loaded with extraction is back-extracted in 5 stages using a 3 mol / L sulfuric acid solution.

[0115] Test results:

[0116] The total recovery rate of scandium through extraction, washing, and back-extraction reached 99.5%, and the purity of scandium oxide reached 99.9%.

[0117] The overall recovery rate of cobalt through extraction-washing-back-extraction reached 98.5%, and the purity of cobalt reached 99.2%.

[0118] The total recovery rate of nickel from extraction, washing, and back-extraction reached 99.3%, and the purity of nickel reached 99.1%.

[0119] Example 4

[0120] The raw materials are the same as in Example 1.

[0121] The difference is that,

[0122] In step 1), the frequency of the applied ultrasound is 200,000 Hz, the volume fraction of oxygen in the grinding atmosphere is 50%, the temperature is 60℃, and the reaction time is 15 min.

[0123] In step 2), the liquid-to-solid ratio in the leaching system is 5:1, the pH value is 3.0, the temperature is 40℃, and the leaching time is 15min.

[0124] Test results:

[0125] The recovery rate of manganese was 87.0%.

[0126] The total recovery rate of scandium through extraction, washing, back-extraction, precipitation, and calcination reached 99.2%.

[0127] The iron precipitation removal rate reached 96.9%.

[0128] The overall recovery rate of nickel reached 98.2% and that of cobalt reached 98.3% after extraction, washing and back-extraction.

[0129] Comparative Example 1

[0130] The raw materials are the same as in Example 1.

[0131] The difference is:

[0132] In step 1), nickel-cobalt hydroxide is directly ground for 60 minutes. In step 2, sulfuric acid and water are used to prepare a 2 mol / L dilute sulfuric acid solution, and the leaching time is 50 minutes. All other steps are the same as in Example 1.

[0133] Test results:

[0134] In step 2), most of the manganese did not enter the manganese slag. The manganese precipitation recovery rate in this step was 23.4%, and 73.4% of the manganese ions entered the leachate. The manganese ion concentration in the leachate was 9.2 g / L. The high concentration of manganese ions in the leachate affected the extraction and separation of scandium, nickel, and cobalt in steps 4), 5), and 6).

[0135] The total recovery rate of scandium through extraction, washing, and back-extraction reached 97.5%, and the purity of scandium reached 97.1%.

[0136] The overall recovery rate of cobalt through extraction-washing-back-extraction reached 96.9%, and the purity of cobalt reached 97.2%.

[0137] The total recovery rate of nickel from extraction-washing-back-extraction reached 97.4%, and the purity of nickel reached 97.1%.

[0138] Comparative Example 2

[0139] The raw materials are the same as in Example 1.

[0140] The difference is that step 5 is not included; instead, in step 4, the residual scandium extract is adjusted to pH 5.0 with sodium hydroxide solution to remove iron. All other steps are the same as in Example 1.

[0141] Test results:

[0142] The iron ion concentration in the raffinate after iron removal is still higher than 0.1 g / L, which affects the extraction and separation of nickel and cobalt and the purity of nickel-cobalt products.

[0143] The overall recovery rate of cobalt through extraction-washing-back-extraction reached 97.1%, and the purity of cobalt reached 96.8%.

[0144] The total recovery rate of nickel from extraction, washing, and back-extraction reached 96.5%, and the purity of nickel reached 97.1%.

[0145] Comparative Example 3

[0146] The raw materials are the same as in Example 1.

[0147] The difference is that steps 3) and 4) are not included.

[0148] Instead, conventional acidic organophosphorus extractants, such as P204, were used to extract scandium from the first leachate obtained in step 2). The results showed that using P204 for scandium extraction resulted in poor acid back-extraction, with a back-extraction rate below 80%. Sodium hydroxide back-extraction resulted in poor phase separation and low yield. Testing revealed that the back-extraction rate of scandium was consistently below 80%, and the overall recovery rate of scandium through extraction, washing, and back-extraction was 75.5%, with a scandium purity of 95.8%.

[0149] Comparative Example 4

[0150] The raw materials are the same as in Example 1.

[0151] The difference is that steps 3) and 6) are not included.

[0152] Instead, conventional saponified acidic organophosphorus extractants are used to perform nickel-cobalt extraction and separation on the second leachate obtained in step 3), such as P204 extraction (calcium and manganese extraction), P507 cobalt extraction, and Cyanex 272 deep extraction (magnesium extraction).

[0153] In this comparative example, nickel sulfate extraction in the raffinate is a thermodynamic equilibrium extraction, requiring a high solution pH and the addition of a large amount of neutralizing alkali. The extraction and separation efficiency between nickel and cobalt, and between nickel / cobalt and impurity elements, is low, requiring more than 10 extraction stages. Testing showed that the extraction separation coefficients for cobalt with nickel and manganese were 3.3 and 3.9, respectively, and the extraction separation coefficient for nickel with manganese was 3.1. The total recovery rates of nickel and cobalt were all below 98.0%.

[0154] Comparing the embodiments of the present invention with Comparative Example 4, it can be seen that the extraction system of the present invention is a direct extraction of nickel and cobalt. Due to the synergistic extraction effect of the extractant, the extraction pH is low, and the metal extraction sequence is different from that of a single extractant. In the present invention, nickel and cobalt are directly extracted into the organic phase, and finally, nickel sulfate is in the back-extraction solution obtained by back-extraction, which is different from Comparative Example 4 (where nickel sulfate is in the raffinate). The extraction system and the impurity extraction system of the two are very different or even fundamentally different.

[0155] 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 comprehensive method for the recovery of nickel, cobalt, manganese, and scandium, 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: Selective leaching of the pretreated nickel-cobalt hydroxide with dilute sulfuric acid solution, the pH of the leaching system being 1.0–4.5 and the temperature being 20–45°C, followed by solid-liquid separation to obtain manganese oxide slag and the first leachate; Step S3: A synergistic extraction system is formed by combining an organophosphate extractant, a neutral phosphorus extractant, and an organic diluent, which serves as the first extractant; the synergistic extraction system is saponified using an alkaline solution to obtain a saponified synergistic extraction system, which serves as the second extractant. Step S4: The first extractant is used to perform scandium extraction on the first leachate to obtain a scandium-loaded organic phase and raffinate; Step S5: The raffinate is subjected to vanadium precipitation and iron removal, and solid-liquid separation to obtain iron alum slag and a second leachate; Step S6: The second extractant is used to extract nickel and cobalt from the second leachate to obtain a nickel-cobalt supported organic phase.

2. The comprehensive recovery method for nickel, cobalt, manganese, and scandium according to claim 1, characterized in that, The molar ratio of the organophosphate extractant to the neutral phosphoric acid extractant is (0.1-10):

1.

3. The comprehensive recovery method for nickel, cobalt, manganese, and scandium according to claim 1, characterized in that, The organophosphate extractant is one or more of P204, P507, and Cyanex272; The neutral phosphorus-oxygen extractant is one or more of TBP, Cyanex 923, and TOPO.

4. The comprehensive recovery method for nickel, cobalt, manganese, and scandium according to claim 3, characterized in that, In the synergistic extraction system, the mass concentration of the extractant is 30-60%. The organic diluent is any one or more selected from n-heptane, n-octane, No. 5 solvent oil, No. 260 solvent oil, and sulfonated kerosene.

5. The comprehensive recovery method for nickel, cobalt, manganese, and scandium according to claim 1, characterized in that, In step S4, scandium extraction is performed using multi-stage countercurrent extraction, multi-stage washing, and multi-stage back-extraction; wherein, The number of scandium extraction stages is 4 to 8, the flow ratio of the first extractant to the aqueous phase is 0.05 to 1:1, the temperature of scandium extraction is 20 to 40℃, the time of scandium extraction is 2 to 10 min, and the equilibrium pH of the aqueous phase reaction in scandium extraction is 0.5 to 2.

5. The scandium extraction washing process consists of 3 to 6 stages, with the washing solution being dilute sulfuric acid at a concentration of 0.01 to 0.3 mol / L. The number of stages for scandium extraction and back-extraction is 2 to 8, the flow ratio of organic phase to aqueous phase is 0.5 to 10:1, the back-extraction temperature is 20 to 80℃, and the back-extraction time is 5 to 10 min.

6. The comprehensive recovery method for nickel, cobalt, manganese, and scandium according to claim 1, characterized in that, In step S6, nickel-cobalt extraction is performed using a multi-stage countercurrent extraction, washing, and back-extraction process. The back-extraction yields nickel and cobalt solutions, which are then separated and purified to obtain the nickel-cobalt product. The nickel-cobalt extraction stage is 3 to 6 stages, the flow ratio of the second extractant to the aqueous phase is 0.2 to 10:1, the extraction temperature for each stage is 20 to 50°C, the extraction time for each stage is 2 to 10 min, and the equilibrium pH of the extraction aqueous phase is 2.0 to 5.

0. The nickel-cobalt extraction and washing process 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 number of stages for nickel-cobalt extraction back-extraction is 3 to 8, and the concentration of the sulfuric acid back-extraction solution used is 0.5 to 5 mol / L.

7. The comprehensive recovery method for nickel, cobalt, manganese, and scandium according to claim 1, characterized in that, Step S4 further includes: washing and back-extracting the scandium-supported organic phase to obtain a scandium back-extract; adding a precipitant to the scandium back-extract to precipitate the scandium to obtain a scandium precipitate; and calcining the scandium precipitate to obtain a scandium oxide product. The precipitant is selected from any one or more of ammonia, ammonium carbonate, oxalic acid, ammonium oxalate, citric acid, ammonium citrate, malic acid, and ammonium malate. In the step of calcining the scandium precipitate, a two-stage calcination process is adopted; wherein, the first stage calcination temperature is 300-500℃ and the calcination time is 10-60min; the second stage calcination temperature is 400-1200℃ and the calcination time is 30-90min.

8. The comprehensive recovery method for nickel, cobalt, manganese, and scandium according to claim 7, characterized in that, The precipitant is a composite precipitant formed by selecting two or more of the following: ammonia, ammonium carbonate, oxalic acid, ammonium oxalate, citric acid, ammonium citrate, malic acid, and ammonium malate. In the step of adding a precipitant to the scandium back-extraction solution for precipitation, the precipitation temperature is 40–90°C and the precipitation time is 5–30 min.

9. The comprehensive recovery method for nickel, cobalt, manganese, and scandium 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.

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

11. The comprehensive recovery method for nickel, cobalt, manganese, and scandium according to claim 1, characterized in that, Step S5, the step of precipitating vanadium and removing iron from the raffinate, includes: Add sulfuric acid or an alkaline neutralizing agent to the raffinate to adjust the pH of the raffinate to 0.6–3.0; Add the saponification waste liquid generated in step S3 to the raffinate for vanadium precipitation and iron removal; The molar ratio of the total amount of ammonia, sodium, and potassium added to the total amount of iron in the raffinate should be controlled to be 3:1 to 4.5:

1. The reaction temperature for vanadium precipitation and iron removal is controlled at 20–90℃, and the reaction time is controlled at 20–150 min. The alkaline neutralizing agent and the alkaline solution are respectively selected from any one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, potassium carbonate, and ammonium carbonate.

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