A bispyridyl extractant, its preparation method and application as a nickel-cobalt extractant

Abstract

This invention discloses a bispyridyl extractant, its preparation method, and its application as a nickel-cobalt extractant. The bispyridyl extractant has the following structure: wherein R is C 12 ~C 25 The alkyl group is prepared by reacting chloromethylpyridine hydrochloride with a primary amine compound via a bimolecular nucleophilic substitution reaction. This bispyridine extractant has stable physicochemical properties, large saturation capacity, good oil solubility of the extract, and good coordination complexing ability for nickel (cobalt) ions. It can be used in combination with DNNSA or P204 to form a synergistic extraction system for selective extraction and separation of nickel and cobalt in complex metal ion solution systems. It can also be used as a single extraction system for efficient extraction and separation of nickel and cobalt in hydrochloric acid systems, showing good prospects for industrial application.

Description

Technical Field

[0001] This invention relates to a bispyridyl extractant, a method for preparing the bispyridyl extractant, and the application of the bispyridyl extractant in the selective extraction and separation of nickel and cobalt, belonging to the field of hydrometallurgical technology. Background Technology

[0002] Lithium-ion batteries play a crucial role in achieving global sustainable development goals, leading to a significant increase in their production and consumption in recent years. As key raw materials for battery cathodes, the demand for high-purity Ni(II) and Co(II) products (>99.99%) is also increasing. Currently, high-purity Ni(II) and Co(II) products are primarily produced through hydrometallurgical processes using laterite nickel ore. However, given the approximately 10-year lifespan of lithium-ion batteries, the number of waste batteries will increase significantly over time. Therefore, recycling waste batteries as secondary resources to avoid environmental pollution and resource waste caused by Ni(II) and Co(II) in waste batteries is crucial. However, the bottlenecks in using laterite nickel ore and secondary resources as raw materials to prepare high-purity Ni(II) and Co(II) products mainly lie in the efficient and low-consumption separation of nickel, cobalt, and metallic impurities, as well as the efficient and low-consumption separation of nickel and cobalt.

[0003] 1. Due to the low grade and complex composition of lateritic nickel ore and secondary resources, hydrometallurgical processes with low energy consumption and high recovery rates are the main methods for extracting Ni(II) from lateritic nickel ore and secondary resources. However, before solvent extraction, neutralization, precipitation, and solid-liquid separation processes are usually used to remove Fe(III) and Al(III) from the lateritic nickel ore leachate and secondary resources, which directly increases acid and alkali consumption and production costs. In addition, the loss rate of Ni(II) and Co(II) is relatively high during neutralization and precipitation. Even after removing Fe(III) and Al(III) from the filtrate, further precipitation, solid-liquid separation, secondary leaching, and multi-stage extraction are still required to separate Ni(II), Co(II), Ca(II), Mg(II), Mn(II), and Zn(II). This leads to problems such as long process flow, high energy consumption, industrial wastewater generation, and high production costs. To overcome these problems, many researchers have been working hard to find extractants and extraction systems that can selectively extract Ni(II) and Co(II) from lateritic nickel ore and secondary resource leachates. Due to the excellent coordination properties of nitrogen atoms with Ni(II) and Co(II), LIX-type solvent extractants and pyridine derivative extractants can form extractables by combining nitrogen atoms with Ni(II) and Co(II). Therefore, various LIX-type and pyridine derivative extractants have been synthesized and tested. Representative extractants include LIX63, DH2,3,4PIA, 3PC10, 3PC-PrCl, and 2,3,4PC. However, these extractants containing oxime groups (-C=NOH) are easily degraded in the presence of organic acids. Therefore, when these extractants are used in synergistic extraction systems with acidic extractants, their decomposition is inevitable, greatly limiting their application. Therefore, pyridine carboxylic acid ester extractants such as 2,3,4PC have attracted widespread attention because they can form synergistic extraction systems with acidic extractants. However, the hydrochloric acid or sulfuric acid widely used in washing and back-extraction processes inevitably damages the ester bonds (-COOR) in the 2,3,4PC molecular structure, leading to 2,3,4PC degradation and significantly reducing its recycling performance. Furthermore, 2,3,4PC's selectivity for Ni(II) and Co(II) is not high enough to achieve deep purification, greatly limiting its industrial application. Therefore, there is an urgent need to design and synthesize a highly efficient and stable nickel and cobalt extractant to solve the bottleneck problems currently faced in the hydrometallurgical processes of laterite nickel ore and secondary resources.

[0004] 2. Due to the similarity in ionic radius, oxidation state, and coordination number between Ni(II) and Co(II), a clean and efficient separation method is not feasible. Currently, solvent extraction is a common method for separating Ni(II) and Co(II). Most previous studies on the extraction and separation of Ni(II) and Co(II) have used organophosphorus extractants in acidic sulfate media and amine extractants in high-concentration hydrochloric acid solutions. Cyanex 272, D2EHPA, and PC-88A are commonly used organophosphorus extractants. However, regardless of whether PC-88A, Cyanex 272, or D2EHPA is used, the separation coefficient between Ni(II) and Co(II) does not exceed 10. Furthermore, organophosphorus extractants require saponification to improve extractant utilization, and a high pH value of the Ni(II)-Co(II) solution must be maintained during extraction. High concentrations of hydrochloric acid or sulfuric acid are also required during back-extraction. Therefore, this extraction system has many disadvantages, such as high consumption of acid and alkali, long extraction process, and difficulty in recovering the extractant due to saponification of the organophosphorus extractant. As for amine extractants, at least 5 mol / L hydrochloric acid is required in the solution to selectively separate Ni(II) and Co(II) because Co(II) forms a negatively charged cobalt chloride complex under high acidity, forming an ion pair with the amine extractant cation at the membrane solution interface. Therefore, the extraction process consumes a large amount of hydrochloric acid, and a large amount of alkaline stripping agent is consumed during the back-extraction process to regenerate the amine extractant. Although this process can effectively separate Ni(II) and Co(II), its application is limited due to the severe corrosive effect of high-concentration hydrochloric acid on the extraction equipment, resulting in harsh production conditions. Furthermore, most lithium-ion batteries contain 15–30% Co(II) and 10% Ni(II), while laterite nickel ore contains 1.5–1.8% Ni(II) and 0.02–0.1% Co(II). Currently, the separation of Co(II) and Ni(II) is mainly achieved through the preferential extraction of Co(II), while Ni(II) remains in the raffinate. While this method is applicable to lateritic nickel ore, it is clearly unsuitable for use in waste batteries, given the extraction cost and efficiency. Furthermore, a single extractant system for the selective extraction of Ni(II) from Ni(II)-Co(II) solutions has not yet been successfully developed.

[0005] Therefore, the separation of Ni(II) and Co(II) from metallic impurities, as well as the separation of Ni(II) and Co(II) itself, cannot currently be achieved in a low-consumption, clean, and efficient manner, especially when using waste batteries and laterite nickel ore as raw materials. Therefore, developing novel extractants and breakthrough methods for the efficient separation of Ni(II) and Co(II) from metallic ion impurities, and achieving efficient separation of Ni(II) and Co(II), is crucial. Summary of the Invention

[0006] Existing hydrometallurgical processes for recovering valuable metals from laterite nickel ore and waste lithium-ion batteries suffer from technical drawbacks such as complex processes, low nickel and cobalt recovery rates, and difficulties in separating nickel and cobalt.

[0007] The first objective of this invention is to provide a bispyridyl extractant that is physicochemically stable, has a large saturation capacity, good oil solubility of the extract, and good coordination complexing ability for nickel (cobalt) ions.

[0008] The second objective of this invention is to provide a method for preparing a bispyridyl extractant, which has the advantages of cheap and readily available raw materials, simple synthesis process, convenient operation, and high yield, and is conducive to large-scale production.

[0009] The third objective of this invention is to provide an application of a bispyridyl extractant, which can be used as a single extraction system or in combination with P204 or DNNSA to form a synergistic extraction system. The synergistic extraction system of the bispyridyl extractant and DNNSA exhibits a strong positive synergistic extraction effect on nickel and cobalt ions in complex metal ion solutions containing nickel, cobalt, iron, aluminum, calcium, magnesium, manganese, and zinc, while showing a significant negative synergistic extraction effect on other metal ions. This significantly improves the separation coefficient between nickel and cobalt and other metal ions, making it highly suitable for the extraction and separation of nickel and cobalt from iron, aluminum, calcium, magnesium, manganese, and zinc in laterite nickel ore acid leaching solutions. It shows great promise for the separation and recovery of valuable metals from laterite nickel ore. Alternatively, a synergistic extraction system combining a bispyridine extractant and P204 can be used. This system exhibits a strong positive synergistic extraction effect on nickel and cobalt ions in complex metal ion solutions containing nickel, cobalt, aluminum, calcium, magnesium, manganese, and zinc, while showing a significant negative synergistic extraction effect on other metal ions. This significantly improves the separation coefficient between nickel and cobalt and other metal ions. After conventional iron removal in laterite nickel ore acid leaching solutions, nickel and cobalt can be separated from aluminum, calcium, magnesium, manganese, and zinc through extraction, showing high application potential for the separation and recovery of valuable metals in laterite nickel ore. Alternatively, the bispyridine extractant can be used as a single extraction system. Based on the strong coordination ability of the bispyridine extractant for nickel and cobalt, and the fact that Ni(II) and Co(II) exist in different easily extractable forms in Ni(II)-Co(II) solutions at different chloride ion concentrations and pH values, the different association forms of nickel and cobalt ions can be used to achieve efficient separation of Ni(II) and Co(II). This method can selectively extract both nickel and cobalt. By selectively extracting nickel or cobalt with low content in the Ni(II)-Co(II) solution, the extraction process can be significantly shortened. Therefore, it has high application prospects for the separation and recovery of nickel and cobalt.

[0010] To achieve the above technical objectives, the present invention provides a bispyridyl extractant having the structure shown in Formula 1:

[0011]

[0012] Where R is C 12 ~C 25 Alkyl groups.

[0013] The bispyridine extractant of this invention has a unique molecular structure, with a tertiary amine as the main molecular component. The tertiary amine has two symmetrical pyridine groups and a long-chain alkyl group. The long-chain alkyl group endows the extractant molecule with good overall oil solubility and hydrophobicity, which can improve its phase separation ability. At the same time, the long-chain alkyl group has flexibility, which can improve its solubility and dispersibility in organic solvents. The pyridine group has a coordination effect on nickel-cobalt metal ions. In particular, when two symmetrical pyridine groups are introduced simultaneously, a pair of chelating groups can be formed, which can form a stable chelate ring structure with nickel-cobalt metal ions, thereby improving its binding ability and selectivity for nickel-cobalt metal ions. Furthermore, the complexing ability of pyridine groups with different substitution positions for nickel-cobalt metal ions varies. In the bispyridine extractant, the pyridine group is introduced in the form of 2-methylpyridine. The 2-position of the pyridine group is an electron-donating group, which can improve the coordination ability of the lone pair electrons of the N atom on the pyridine to nickel-cobalt metal ions. At the same time, there is a torsion methylene group between the two pyridine groups, and the two pyridine groups are symmetrically distributed, which makes it easy to chelate nickel-cobalt metal ions to form a stable chelate ring structure. This greatly improves the selective coordination ability and saturation capacity of the bispyridine extractant for nickel-cobalt metal ions.

[0014] As a preferred option, R in the bispyridyl extractant is C. 12 ~C 25 straight-chain alkyl or C 12 ~C 25 Branched alkanes. Specific examples include straight-chain alkyl groups such as dodecyl, tetradecyl, hexadecyl, and octadecyl, and branched alkyl groups such as isotetradecane and isohexadecane. The length of the alkyl chain affects its lipophilicity and hydrophobicity, thus influencing its extraction and phase separation capabilities. A further preferred option is C14. 14 ~C 18 alkyl.

[0015] The present invention also provides a method for preparing a bispyridyl extractant, wherein chloromethylpyridine hydrochloride is reacted with a primary amine compound of formula 2 via a bimolecular nucleophilic substitution reaction to obtain the bispyridyl extractant.

[0016] RNH2

[0017] Formula 2

[0018] Where R is C 12 ~C25 Alkyl groups.

[0019] This invention uses commercially available 2-chloromethylpyridine hydrochloride and primary amine as raw materials to synthesize a product through a one-step bimolecular nucleophilic substitution reaction. The method is simple, has short steps, mild conditions, and readily available raw materials, which is beneficial for industrial production.

[0020] As a preferred embodiment, the molar ratio of chloromethylpyridine hydrochloride to the primary amine compound is (2–2.2):1.

[0021] As a preferred embodiment, the conditions for the bimolecular nucleophilic substitution reaction are: reaction at 60–90°C for 48–60 h under alkaline conditions. An alkaline, such as potassium carbonate, is used as a neutralizing agent to promote the reaction. At least one of acetonitrile, xylene, and methanol is used as a solvent, with the solvent amount being 100%–300% of the mass of the tertiary amine compound. These preferred reaction conditions ensure a high yield.

[0022] The specific preparation method of the bispyridyl extractant provided by this invention (a typical synthesis method of bispyridyl extractant is described below): First, 2-chloromethylpyridine hydrochloride (2 mol, 328.06 g) and acetonitrile are added to a round-bottom flask and heated with stirring in an oil bath at 80°C. After the 2-(chloromethyl)pyridine hydrochloride is completely dissolved in the acetonitrile solution, potassium carbonate solution (2.4 mol, 331.2 g) is added dropwise, followed by molten tetradecylamine (0.9 mol, 192.02 g). After stirring and refluxing at 90°C for 2 days, the reaction solution is filtered, and the aqueous phase is separated using a separatory funnel. The organic phase is removed by rotary evaporation at 85°C to remove acetonitrile. Then, the oily complex is washed three times with ultrapure water to remove unreacted 2-chloromethylpyridine hydrochloride, and then dried with anhydrous sodium sulfate. The final dark brown oily complex has a yield of 90% and a purity of over 95%.

[0023] The synthesis process of the bispyridyl extractant of the present invention mainly involves a bimolecular nucleophilic substitution reaction, and the specific reaction formula is as follows (using tetradecylamine and 2-chloromethylpyridine hydrochloride as examples for illustration):

[0024]

[0025] This invention also provides an application of a bispyridyl extractant as a nickel and / or cobalt extractant. The bispyridyl extractant exhibits selective coordination or chelation of nickel and cobalt ions and has good solubility and dispersibility in the oil phase, making it particularly suitable for use as a nickel-cobalt extractant.

[0026] As a preferred option, the bispyridyl extractant is used for the separation of nickel and cobalt from other metal ions in complex metal ion solution systems, or for the separation of nickel ions and cobalt ions in nickel-cobalt solution systems.

[0027] As a preferred option, the bispyridyl extractant can be used alone, in combination with DNNSA, or in combination with P204.

[0028] As a preferred method, a bispyridyl extractant is used alone to separate nickel and cobalt ions in a nickel-cobalt solution system. The concentration of the bispyridyl extractant in the organic phase is 0.1–0.4 mol / L, and the extraction conditions are: pH 0–6, temperature 15–40℃, and chloride ion concentration in the nickel-cobalt solution system is 1–4 mol / L. The nickel-cobalt solution system is a hydrochloric acid solution system containing nickel and cobalt ions. Sources of the nickel and cobalt ion solution system include, for example, laterite nickel ore and nickel-cobalt solutions purified by hydrometallurgical processes from waste batteries. Based on the strong coordination ability of the bispyridyl extractant for Ni(II) and Co(II), and the fact that Ni(II) and Co(II) exist in different easily extractable forms in Ni(II)-Co(II) solutions with different chloride ion concentrations and pH values, the bispyridyl extractant is suitable not only for selectively extracting Co(II) but also for selectively extracting Ni(II) from Ni(II)-Co(II) solutions by utilizing the different association forms of nickel and cobalt ions. Experimental results confirmed that the separation coefficients of the bispyridine extractant for Ni(II) and Co(II) were significantly higher than those for organophosphorus and amine extractants. Furthermore, a high back-extraction rate could be achieved using deionized water, and using deionized water during the back-extraction process also avoided the problem of extractant degradation due to contact with acids or alkalis. Therefore, the entire "extraction-back-extraction" process significantly reduced production costs, minimized environmental impact, reduced acid and alkali consumption, and exhibited good recycling performance. Further optimized pH values ​​of 0–2 achieved selective extraction of nickel, and pH values ​​of 5–6 achieved selective extraction of nickel.

[0029] As a preferred embodiment, a bispyridine extractant is synergistically applied with DNNSA for the separation of nickel and cobalt from other metal ions in a complex metal ion solution system, wherein the complex metal ion solution system contains nickel and / or cobalt, and at least one of iron, aluminum, calcium, magnesium, zinc, and manganese; the extraction conditions are: pH 0.25–2.5, temperature 15–40 °C; the concentration of the bispyridine extractant in the organic phase is 0.1–0.4 mol / L; and the molar ratio of the bispyridine extractant to DNNSA is 1:1–4. Based on the strong coordination ability of the bispyridine extractant to Ni(II) and Co(II) and the low extraction ability of DNNSA to Fe(III), using DNNSA-bispyridine extractant as a synergistic extraction system can directly extract Ni(II) and Co(II) from Fe(III), Al(III), Ca(II), Mg(II), Mn(II), and Zn(II). A synergistic extraction system composed of a bispyridyl extractant and DNNSA in an appropriate ratio can significantly improve the complexation selectivity of nickel and cobalt ions, especially nickel ions, in complex metal ion solutions. As the proportion of the bispyridyl extractant in the organic phase increases, the extractant's ability to extract nickel and cobalt ions further increases, while the extraction rates of other metal ions remain essentially unchanged, resulting in increasingly better separation. The molar ratio of the bispyridyl extractant to DNNSA is 1:1 to 4; more preferably 1:2 to 4. Under these preferred conditions, the coordination and chelation effect of the composite extractant on nickel and cobalt ions in complex metal ion solutions can be enhanced, reducing phase separation time and thus improving extraction and separation efficiency. Sources of complex metal ion solutions include, for example, sulfuric acid leaching solutions from laterite nickel ore.

[0030] As a preferred embodiment, a bispyridyl extractant is used in synergy with P204 for the separation of nickel and cobalt from other metal ions in a complex metal ion solution system, wherein the complex metal ion solution system contains nickel and / or cobalt, and at least one of aluminum, calcium, magnesium, zinc, and manganese; the extraction conditions are: pH 0.25–2.5, temperature 15–40°C; the concentration of the bispyridyl extractant in the organic phase is 0.1–0.4 mol / L; and the molar ratio of the bispyridyl extractant to P204 is 1:1–4. The synergistic extraction system composed of bispyridyl extractant and P204 exhibits a strong positive synergistic extraction effect on nickel and cobalt ions in complex metal ion solutions containing nickel, cobalt, aluminum, calcium, magnesium, manganese, and zinc, while showing a significant negative synergistic extraction effect on other metal ions. This significantly improves the separation coefficient between nickel and cobalt and other metal ions. After conventional iron removal in laterite nickel ore acid leaching solutions, nickel and cobalt can be separated from aluminum, calcium, magnesium, manganese, and zinc through extraction methods, showing high application prospects for the separation and recovery of valuable metals in laterite nickel ore.

[0031] The organic phase of the present invention further comprises a polar modifier and a diluent; the polar modifier is at least one selected from isooctanol, TBP, sec-octanol, and n-octanol, and the polar modifier accounts for 5% to 40% of the volume of the organic phase. The diluent in the organic phase is at least one selected from sulfonated kerosene, higher alcohols, and n-heptane.

[0032] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0033] 1) The bispyridyl extractant provided by the technical solution of the present invention is synthesized in one step by using amine compounds and 2-chloromethylpyridine as raw materials through a bimolecular nucleophilic substitution reaction. It has the advantages of short synthesis process, simple operation, green and environmentally friendly, low production cost and high product yield, which is convenient for large-scale production.

[0034] 2) The bispyridyl extractant provided by the technical solution of the present invention uses a long-chain amine compound structure as the molecular body, which can ensure that the extractant has good oil solubility and hydrophobicity. Furthermore, the extractant has stable physicochemical properties under the extraction process conditions and has good metal ion complexing ability, and has good application prospects in organic synthesis, hydrometallurgy and other fields.

[0035] 3) The bispyridyl extractant provided by the present invention has two pyridyl groups attached to the primary amine formed by the bimolecular nucleophilic addition reaction or a pair of chelating groups. By utilizing the selective coordination complexation of the coordinating group or chelating group with nickel ions and cobalt ions, its coordination chelation ability for nickel ions and cobalt ions can be improved.

[0036] 4) The bispyridyl extractant provided by this invention, in synergy with DNNSA, serves as an extractant for transition metals nickel and cobalt, belonging to an acidic-neutral mixed-type synergistic extraction system. The bispyridyl extractant can coordinate or chelate with nickel and cobalt. Since the nitrogen atom in the pyridine functional group that coordinates with the metal ions is a boundary base, according to the hard-soft acid-base rule, the bispyridyl extractant has good complexation with boundary nickel and cobalt ions. Furthermore, the N atom in the carbon chain of the bispyridyl extractant may increase the electron density of the N atom in the pyridine group, thereby enhancing its coordination ability with Ni(II) and Co(II). Therefore, the bispyridyl extractant has a large electrostatic interaction. The position of the N atom on the pyridine ring has a significant impact on the selectivity of the extractant. When the N atom on the pyridine ring is in the ortho position, the steric hindrance of the extractant is greater than when the N atom is in the para position. Therefore, the ortho-position bispyridyl extractant may have greater steric hindrance, thereby improving the selectivity for Ni(II) and Co(II). Furthermore, the two pyridine groups in the bispyridine extractant can form an eight-membered chelate ring with Ni(II) and Co(II). Therefore, due to the chelating effect, the extract formed by the bispyridine extractant is relatively stable. DNNSA, on the other hand, is a sulfonic acid extractant with the structure shown in Formula 3. The main function of DNNSA is to improve the extraction capacity of the synergistic extraction system and reduce the iron extraction rate. Therefore, the synergistic extraction system composed of the bispyridine extractant and DNNSA exhibits excellent selectivity and strong extraction capacity for nickel and cobalt ions.

[0037]

[0038] 5) The bispyridyl extractant provided by the technical solution of the present invention is used in synergy with DNNSA as an extractant for nickel ions and cobalt metal ions. The extraction process is carried out at room temperature. The extraction process has good phase separation performance, clear oil-water interface, and short phase separation time, and can achieve efficient separation of nickel and cobalt from iron, aluminum, calcium, magnesium, manganese and zinc in laterite nickel ore sulfuric acid leaching solution.

[0039] 6) The bispyridyl extractant provided by this invention, in synergy with P204, serves as an extractant for the transition metals nickel and cobalt, belonging to an acidic-neutral mixed-type synergistic extraction system. The bispyridyl extractant can coordinate or chelate with nickel and cobalt ions. P204 is a phosphoric acid extractant, with a structure shown in Formula 4. The main function of P204 is to enhance the extraction capacity of the synergistic extraction system. Therefore, the synergistic extraction system composed of the bispyridyl extractant and P204 exhibits excellent selectivity and strong extraction capacity for nickel and cobalt ions.

[0040]

[0041] 7) The bispyridyl extractant provided by the technical solution of the present invention is used in synergy with P204 as an extractant for nickel and cobalt metal ions. The extraction process is carried out at room temperature. The extraction process has good phase separation performance, clear oil-water interface, and short phase separation time. It can achieve efficient separation of nickel and cobalt from aluminum, calcium, magnesium, manganese and zinc in laterite nickel ore sulfuric acid leaching solution after pre-iron removal.

[0042] 8) The technical solution of this invention is based on the strong coordination ability of pyridine extractant to nickel and cobalt, and the fact that Ni(II) and Co(II) exist in different easily extractable forms in Ni(II)-Co(II) solutions with different chloride ion concentrations and different pH values. The different association forms of nickel and cobalt ions are utilized to achieve efficient separation of Ni(II) and Co(II). This method can selectively extract both nickel and cobalt.

[0043] 9) The bispyridyl extractant provided by the technical solution of the present invention is used as an extractant for separating nickel ions and cobalt ions. The extraction process is carried out at room temperature. The extraction process has good phase separation performance, clear oil-water interface, and short phase separation time, and can achieve efficient separation of nickel and cobalt in sulfuric acid or hydrochloric acid leaching solutions of laterite nickel ore and secondary resources. Attached Figure Description

[0044] 【 Figure 1 [Image caption: High-resolution mass spectrometry (HRMS) image of the bispyridyl extractant in Example 1.]

[0045] 【 Figure 2 The image shows the 1H NMR spectrum of the bispyridyl extractant in Example 1. 1 H-NMR).

[0046] 【 Figure 3 The effect of a 2:1 molar ratio of DNNSA to bispyridyl extractant in Example 2 on the extraction efficiency of Ni(II), Co(II), Fe(III), Al(III), Mg(II), Zn(II) and Mn(II).

[0047] 【 Figure 4 The effect of the DNNSA:bispyridyl extractant molar ratio of 2:1.5 on the extraction efficiency of Ni(II), Co(II), Fe(III), Al(III), Mg(II), Zn(II) and Mn(II) in Example 3 is shown.

[0048] 【 Figure 5 The effect of a 2:2 molar ratio of DNNSA to bispyridyl extractant in Example 4 on the extraction efficiency of Ni(II), Co(II), Fe(III), Al(III), Mg(II), Mg(II), Zn(II) and Mn(II).

[0049] 【 Figure 6 [Image shows the extraction saturation curves of Co(II) and Ni(II) in Example 4 and their McCabe-Thiele plots.]

[0050] 【 Figure 7 (a) Effect of chloride ion concentration on the extraction process in Example 5 (pH=6, temperature=20℃, O / A ratio=1:1, extraction time=10 minutes), (b) Effect of pH value on the extraction process (2mol / L Cl) - (c) [CoCl] (temperature = 20℃, O / A ratio = 1:1, extraction time = 10 minutes) x ] 2-x The relationship between the mole fraction and chloride ion concentration. (c) [CoCl x ] 2-x Mole fraction and chloride concentration ([Co(II)]) T = 9 g / L, logK1 = -1.05, logK2 = -2.69, logK3 = -1.54, log K4 = -1.34. Chloride concentration [Ni(II)] T =9 g / L, log K1 = -0.423), (e) Effect of extraction time on the extraction process of Co(II) (2 mol / L Cl) - (f) Effect of extraction time on Ni(II) extraction process (2mol / L Cl) pH=6, temperature=20℃, O / A ratio=1:1. - (pH=0, temperature=20℃, O / A ratio=1:1).

[0051] 【 Figure 8 [This is a comparison of the extraction behavior of the bispyridine extractant (NNPA) in Example 5 at pH < 2 and pH > 2.]

[0052] 【 Figure 9 [This is a comparison of the separation coefficients of Ni(II) and Co(II) by the bispyridyl extractant (NNPA) and different extraction systems in Example 5.]

[0053] 【 Figure 10 The image shows the extraction saturation curves and McCabe-Thiele plots of Co(II)(a) and Ni(II)(b) in Example 6.

[0054] 【 Figure 11 The effect of a 2:2 molar ratio of P204 to bispyridyl extractant in Example 7 on the extraction efficiency of Ni(II), Co(II), Al(III), Mg(II), Mg(II), Zn(II) and Mn(II). Detailed Implementation

[0055] To better understand the present invention, specific embodiments are described below, but the listed embodiments do not limit the scope of protection of the present invention.

[0056] Example 1

[0057] Preparation of bispyridyl extractant:

[0058] First, 2-chloromethylpyridine hydrochloride (2 mol, 328.06 g) and 300 mL of acetonitrile were added to a round-bottom flask and heated with stirring in an oil bath at 80 °C. After the 2-(chloromethyl)pyridine hydrochloride was completely dissolved in the acetonitrile solution, potassium carbonate solution (2.4 mol, 331.2 g) was added dropwise, followed by molten tetradecylamine (0.9 mol, 192.02 g). The mixture was stirred and refluxed at 90 °C for 2 days. The reaction solution was then filtered, and the aqueous phase was separated using a separatory funnel. The organic phase was removed by rotary evaporation at 85 °C to remove acetonitrile. The oily complex was then washed three times with ultrapure water to remove unreacted 2-chloromethylpyridine hydrochloride, and then dried over anhydrous sodium sulfate. The final dark brown oily complex yielded 90% and had a purity exceeding 95%. The high-resolution mass spectrometry (HRMS) image of the bispyridine extractant is shown below. Figure 1 As shown, the 1H NMR spectrum of the bispyridine extractant ( 1 H-NMR (image) Figure 2 As shown.

[0059] Example 2

[0060] Configuration containing 3g·L -1 Ni(II), 0.3 g·L -1 Co(II), 3g·L -1 Fe(III), 3g·L -1 Al(III), 0.2 g·L -1 Ca(II), 1g·L -1 Mg(II), 0.86 g·L -1 Zn(II), and 0.4 g·L -1 A 20 mL sulfuric acid leaching solution of simulated lateritic nickel ore containing Mn(II) was used as the aqueous phase for extraction. The initial pH of the solution was adjusted by dissolving the solution in 2 mol / L sulfuric acid and 1 mol / L sodium hydroxide. An organic phase was prepared containing 0.2 mol / L DNNSA, 0.1 mol / L bispyridyl extractant, sulfonated kerosene as the diluent, and 30% isooctanol as the polar modifier. The oxygen / acid ratio was 1:1. The extraction equilibrium pH was adjusted by saponifying the organic phase with 10 mol / L sodium hydroxide solution. The aqueous phase was added to the organic phase, and the mixture was shaken in a 25°C water bath for 10 min, followed by standing to separate the phases. After phase separation, the metal ion concentration in the extract was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The metal ion concentration in the organic phase was obtained by subtraction.

[0061] like Figure 3 As shown, with the increase of equilibrium pH, the extraction efficiency of Ni(II) and Co(II) increases slowly, while the extraction efficiency of Fe(III), Al(III), Ca(II), Mg(II), Zn(II) and Mn(II) increases slightly and then decreases significantly. However, at this point, the extraction rate of Co(II) is low, and the aqueous phase still contains a large amount of Co(II), so the aqueous phase needs further extraction treatment.

[0062] Example 3

[0063] Configuration containing 3g·L -1 Ni(II), 0.3 g·L -1 Co(II), 3g·L -1 Fe(III), 3g·L -1 Al(III), 0.2 g·L -1 Ca(II), 1g·L -1 Mg(II), 0.86 g·L -1 Zn(II), and 0.4 g·L -1 A 20 mL sulfuric acid leaching solution of simulated lateritic nickel ore containing Mn(II) was used as the aqueous phase for extraction. The initial pH of the solution was adjusted by dissolving the solution in 2 mol / L sulfuric acid and 1 mol / L sodium hydroxide. An organic phase was prepared containing 0.2 mol / L DNNSA, 0.15 mol / L bispyridyl extractant, sulfonated kerosene as the diluent, and 30% isooctanol as the polar modifier. The oxygen / acid ratio was 1:1. The extraction equilibrium pH was adjusted by saponifying the organic phase with 10 mol / L sodium hydroxide solution. The aqueous phase was added to the organic phase, and the mixture was shaken in a 25°C water bath for 10 min, followed by standing to allow phase separation. After phase separation, the metal ion concentration in the extract was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The metal ion concentration in the organic phase was obtained by subtraction.

[0064] like Figure 4 As shown, with the increase of equilibrium pH, the extraction efficiency of Ni(II), Co(II), and Zn(II) increases slowly, while the extraction efficiency of Fe(III), Al(III), Ca(II), Mg(II), and Mn(II) increases slightly and then decreases significantly. The extraction rate of Ni(II) does not increase significantly compared to Example 2, but the extraction rate of Co(II) is improved. However, the extraction rate of Co(II) is still low, and the aqueous phase still contains a large amount of Co(II), so the aqueous phase needs further extraction treatment.

[0065] Example 4

[0066] Configuration containing 3g·L -1Ni(II), 0.3 g·L -1 Co(II), 3g·L -1 Fe(III), 3g·L -1 Al(III), 0.2 g·L -1 Ca(II), 1g·L -1 Mg(II), 0.86 g·L -1 Zn(II), and 0.4 g·L -1 A 20 mL sulfuric acid leaching solution of simulated lateritic nickel ore containing Mn(II) was used as the aqueous phase for extraction. The initial pH of the solution was adjusted by dissolving the solution in 2 mol / L sulfuric acid and 1 mol / L sodium hydroxide. An organic phase was prepared containing 0.2 mol / L DNNSA, 0.2 mol / L bispyridyl extractant, sulfonated kerosene as the diluent, and 30% isooctanol as the polar modifier. The oxygen / acid ratio was 1:1. The extraction equilibrium pH was adjusted by saponifying the organic phase with 10 mol / L sodium hydroxide solution. The aqueous phase was added to the organic phase, and the mixture was shaken in a 25°C water bath for 10 min, followed by standing to allow phase separation. After phase separation, the metal ion concentration in the extract was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The metal ion concentration in the organic phase was obtained by subtraction.

[0067] like Figure 5 As shown, with increasing equilibrium pH, the extraction efficiencies of Ni(II), Co(II), and Zn(II) increase slowly, while the extraction efficiencies of Fe(III), Al(III), Ca(II), Mg(II), and Mn(II) increase slightly before decreasing significantly. The extraction rate of Ni(II) decreases compared to Examples 1 and 2, while the extraction rate of Co(II) increases significantly. However, the extraction rates of Ni(II) and Co(II) are still low, and the aqueous phase still contains a significant amount of Ni(II) and Co(II), requiring further extraction treatment. Because the bispyridine extractant molecule contains two basic pyridine rings, it reacts with the acidic extractant DNNSA to form a complex, thus reducing the concentration of free DNNSA and resulting in a decrease in metal extraction rate. However, increasing the concentration of the bispyridine extractant shows good impurity suppression ability, which may be due to the competitive effect of excess bispyridine extractant and impurity metals on free DNNSA. Therefore, in high-nickel, low-cobalt systems, a stronger driving force (a higher concentration of bispyridyl extractant) is needed to improve the extraction efficiency of cobalt.

[0068] Therefore, a six-stage cascade extraction process was selected for further extraction and separation of nickel and cobalt ions, such as... Figure 6As shown in Table 1, after six stages of countercurrent cascade extraction, impurities were essentially not extracted, while the extraction rates of nickel and cobalt ions both reached over 99%. This indicates that under similar extraction conditions, the synergistic extraction system of DNNSA-bispyridyl extractant can directly extract Ni(II) and Co(II) from the sulfuric acid leachate of laterite nickel ore.

[0069] Table 1 shows the six-stage countercurrent cascade extraction data for nickel and cobalt using 0.2M DNNSA + 0.1-0.2M bispyridine extractant.

[0070]

[0071] Example 5

[0072] The configuration contains 9g·L -1 Ni(II), 9 g·L -1 A 20 mL solution of sulfuric acid leaching solution of simulated laterite nickel ore purified by hydrometallurgical process and secondary resources was used as the aqueous phase for extraction. The initial pH of the solution was adjusted using 2 mol / L sulfuric acid and 1 mol / L sodium hydroxide, and the chloride ion concentration was adjusted using sodium chloride. An organic phase was prepared, containing 0.3 mol / L bispyridyl extractant, sulfonated kerosene as the diluent, and isooctyl alcohol (30% by volume) as the polar modifier, with an O / A ratio of 1:1. The aqueous phase was added to the organic phase, and the mixture was shaken in a 25°C water bath for 10 min, followed by standing to separate the phases. After phase separation, the metal ion concentration in the extract was determined by inductively coupled plasma optical emission spectrometry (ICP-OES), and the metal ion concentration in the organic phase was obtained by difference method.

[0073] like Figure 7 As shown in (a), Ni(II) and Co(II) exhibit different extraction characteristics as the chloride ion concentration increases because Ni(II) and Co(II) form different complexes. Figure 7 (c) and Figure 7 (d) describes the [CoCl] in the aqueous phase. x ] 2-x and [NiCl x ] 2-x The relationship between the mole fraction and chloride ion concentration. As the chloride ion concentration increases, [Co(H₂O)₆] 2 It mainly forms four complexes with chloride ions, including [CoCl1(H2O)5]. + [CoCl2(H2O)4], [CoCl3(H2O)3] - [CoCl4] 2- And [Ni(H2O)6] 2+ It mainly forms a complex, [NiCl(H2O)5]. +This can be explained by the fact that although both Ni(II) and Co(II) exist as hydrated ions in aqueous solution, the hydrated ions of Ni(II) are more stable than those of Co(II). Specifically, water molecules in the inner coordination spheres of Ni(II) are more difficult to be replaced by chloride ions than those in Co(II). This is because the exchange rate (K) between Ni(II) and water is higher. H2O (s -1 ) = 10 6 The exchange rate of Co(II) with water (K) H2O (s -1 ) = 10 4 ~10 5 The concentration of chloride ions is an order of magnitude larger. Therefore, when the chloride ion concentration exceeds 1 mol / L, Co(II) begins to form a four-coordinate structure instead of a six-coordinate structure, while Ni(II) retains its six-coordinate structure. When the chloride ion concentration in the aqueous solution is 2 mol / L, Co(II) mainly forms a four-coordinate hexahedral coordination structure with four chloride ions ([CoCl4)). 2- Ni(II) mainly has two six-coordinate octahedral coordination structures: [NiCl(H2O)5] + and [Ni(H2O)6] 2+ The different forms of Co(II) and Ni(II) lead to the formation of different extracts. Therefore, in the experiments, Co(II) was observed to be preferentially extracted by NNPA. Furthermore, high concentrations of chloride ions also promoted Ni(II) extraction, so once Co(II) extraction was complete, NNPA began extracting Ni(II). Therefore, to selectively separate Ni(II) and Co(II), a chloride ion concentration of 2 mol / L was chosen as the optimal concentration for subsequent experiments.

[0074] Both pink cobalt sulfate and light green nickel sulfate are present in the solution, causing the solution to appear brown. For example... Figure 7 As shown, the colors of the organic and aqueous phases changed significantly during the extraction process. When Ni(II) or Co(II) was selectively extracted, the colors of the two phases differed markedly. Below pH 2, the organic phase changed from wine red to dark green, while the aqueous phase changed from brown to pink. Above pH 2, the organic phase changed from wine red to dark purple, while the aqueous phase changed from brown to light green. The dark green and dark purple organic phases represent the extracted Ni(II) and Co(II) complexes, respectively. The light green aqueous phase indicates that only nickel sulfate remained in the aqueous phase, while the pink aqueous phase indicates that Ni(II) was completely extracted into the organic phase.

[0075] according to Figure 7(b) shows the data and experimental phenomena. When the concentration of chloride ions in the synthesis solution is 2 mol / L, it can be seen that as the pH value increases from 0 to 6, the extraction efficiency of Co(II) increases rapidly, while the extraction efficiency of Ni(II) decreases sharply. Figure 8 As shown, due to the binding of hydrogen ions to the basic sites of the bispyridyl extractant (hereinafter referred to as NNPA), deprotonation is required before the extraction process when the pH value is below 2. The extraction behavior of NNPA mainly consists of deprotonation and extraction. During deprotonation, Ni(II) replaces hydrogen ions to compete for the lone pair electrons of the nitrogen atom. During extraction, the deprotonated nitrogen atom coordinates with Ni(II). However, Ni(II) can replace hydrogen ions on the pyridyl group, but cannot replace hydrogen ions bonded to the N atom of the tertiary amine. Due to the presence of a large π bond in the pyridyl group, which has an electron-withdrawing effect, and the alkyl group on the tertiary amine having an electron-donating effect, the electron cloud density of the N atom on the tertiary amine is greater than that of the N atom on the pyridyl group. Therefore, the nature of the N atom on the pyridyl group changes from a "strong base" to a "border base," but the nature of the N atom on the tertiary amine remains a "strong base." According to the SHAB theory, Ni(II) and Co(II) belong to the "border acid" category, and are therefore more likely to replace the protons on the pyridyl group than on the tertiary amine. Furthermore, the nitrogen atom on the tertiary amine (pKa = 10.76) is more basic than the nitrogen atom on the pyridyl group (pKa = 5.17), so the nitrogen atom on the tertiary amine binds to hydrogen ions more strongly than the nitrogen atom on the pyridyl group. Therefore, after the deprotonation process, the tertiary amine on NNPA still binds to hydrogen ions ((R)3NH+). NNPA-H + It can react with [NiCl(H2O)5] + Or [Ni(H2O)6] 2+ This forms an electrically neutral and coordination-saturated extractable complex (NNPANiHCl3 and a small portion of NNPANiHCl3H2O). Meanwhile, NNPA-H... + Cannot be used with [CoCl4] 2- A complex ([NNPAHCoCl2]) is formed that is electrically neutral and coordinate-saturated for extraction. + Because only the N atom on the pyridine group can replace the Cl atom in the Co(II) inner coordination sphere. - The tertiary amine on NNPA still interacts with H. + Combine.

[0076] However, at pH values ​​above 2, the hydrogen ion concentration is too low to bind to the basic sites of NNPA, leading to the formation of another extracted Ni(II) complex (NNPANiCl2(H2O)2). Since deprotonation is not required at pH values ​​above 2, NNPA can bind with [CoCl4]. 2-It forms an electrically neutral and coordination-saturated extraction complex ([NNPACoCl2]). Therefore, the extraction selectivity of NNPA changes with increasing pH. This is one reason why NNPA selectively extracts Ni(II) at pH below 2, while selectively extracting Co(II) at pH above 2. Figure 7 (e) and Figure 7 (f) shows the rapid extraction capability of NNPA for Ni(II) and Co(II), with the extraction reaching equilibrium within 10 minutes.

[0077] like Figure 9 As shown, NNPA exhibits superior separation performance for Ni(II) and Co(II) compared to organophosphorus and amine extractants. Furthermore, NNPA can selectively extract Ni(II) from Ni(II)-Co(II) solutions, a capability that organophosphorus and amine extractants cannot achieve. This breakthrough method of separating Ni(II) and Co(II) using NNPA can reduce extractant consumption, shorten the extraction process, improve efficiency, and reduce energy consumption.

[0078] Example 6

[0079] A Ni(II)-Co(II) solution containing 16.8 g / L Ni(II) and 1.2 g / L Co(II) was prepared to simulate a Ni(II)-Co(II) solution leached from laterite nickel ore and purified by hydrometallurgical process. In addition, leaching solutions from actual waste lithium-ion batteries containing 3.5 g / L Li(I), 23.6 g / L Co(II), 1.2 g / L Ni(II), 2.35 g / L Mn(II), and 2.6 g / L Al(III) were also prepared. To verify the extraction performance of NNPA, the Ni(II)-Co(II) solution leached from laterite nickel ore was adjusted to pH=6 to selectively extract Co(II), while the actual waste lithium-ion battery leachate was adjusted to pH=0 to selectively extract Ni(II). The diluent was sulfonated kerosene, and the polarity modifier was isooctanol at 30% by volume. After shaking in a water bath at room temperature (25°C) for 10 min, the mixture was allowed to stand and separate into phases. After phase separation, the concentration of metal ions in the extract was determined by inductively coupled plasma optical emission spectrometry (ICP-OES), and the concentration of metal ions in the organic phase was obtained by difference method. Figure 10 (a) and Figure 10 (b) shows the extraction saturation curves of Co(II) and Ni(II) at 10 vol% NNPA and 3 mol / L chloride concentrations, and their McCabe-Thiele plots, respectively.

[0080] according to Figure 10It was found that a 5-stage countercurrent extraction experiment was conducted with an A / O ratio of 9 / 1. After 5 stages of countercurrent extraction, approximately 98% of Co(II) or Ni(II) was extracted. In the organic phase of the extracted Co(II) or Ni(II), the mass concentration ratios of Co(II) / Ni(II) and Ni(II) / Co(II) reached 836 and 891, respectively. As shown in Table 2, the separation performance of NNPA for Ni(II) and Co(II) is not affected by impurities. According to the SHAB theory, since Li(I), Al(III), and Mn(II) are not "boundary acids," they may not harmonize with pyridine groups. Even if these metallic impurities are present in the Ni(II)-Co(II) solution, they will not affect the separation performance of NNPA for Ni(II) and Co(II). After the back-extraction process with deionized water, CoCl2 or NiCl2 in the raffinate and back-extraction liquid were precipitated by carbonates, while sodium ions remained in the coarse filtrate and stripping liquid. These precipitates are subsequently converted into CoSO4 or NiSO4, and after further purification by hydrometallurgical processes, they can be used as raw materials for battery cathodes.

[0081] Table 2. Raffinate after 5-stage countercurrent extraction

[0082]

[0083] Example 7

[0084] Configuration containing 3g·L -1 Ni(II), 0.3 g·L -1 Co(II), 3g·L -1 Al(III), 0.2 g·L -1 Ca(II), 1 g·L -1 Mg(II), 0.86 g·L -1 Zn(II), and 0.4 g·L -1 A 20 mL sulfuric acid leaching solution of simulated lateritic nickel ore containing Mn(II) was used as the aqueous phase for extraction. The initial pH of the solution was adjusted by dissolving the solution in 2 mol / L sulfuric acid and 1 mol / L sodium hydroxide. An organic phase was prepared, containing 0.2 mol / L P₂O₄, 0.2 mol / L bispyridyl extractant, sulfonated kerosene as the diluent, and 30% isooctanol as the polar modifier. The ratio (O / A) was 1:1. The extraction equilibrium pH was adjusted by saponifying the organic phase with 10 mol / L sodium hydroxide solution. The aqueous phase was added to the organic phase, and the mixture was shaken in a 25°C water bath for 10 min, followed by standing to separate the phases. After phase separation, the metal ion concentration in the extract was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The metal ion concentration in the organic phase was obtained by the difference method.

[0085] like Figure 4As shown, the extraction rates of Ni(II) and Co(II) increase significantly with increasing equilibrium pH, while the extraction rates of Al(III), Ca(II), Mg(II), Mn(II), and Zn(II) increase slightly with increasing equilibrium pH. The extraction trends of Ni(II) and Co(II) are similar to those in Example 4. However, the synergistic extraction system using a bispyridyl extractant and P204 requires the neutralization and removal of Fe(III) from lateritic nickel ore and secondary resource leachate before direct extraction and separation of Ni(II) and Co(II) from Al(III), Ca(II), Mg(II), Mn(II), and Zn(II) can be achieved. However, since DNNSA is relatively expensive and its extraction capacity and saturation capacity are inferior to P204, this example is very suitable for extracting and separating Ni(II) and Co(II) from lateritic nickel ore and secondary resource leachate with low iron content after pre-removal of Fe(III).

Claims

1. The application of a bispyridyl extractant, characterized in that: It is used as a nickel or cobalt extractant for the separation of nickel and cobalt ions in nickel-cobalt solution systems; the bispyridyl extractant has the structure shown in Formula 1: ； Formula 1 Where R is C 12 ~C 25 The alkyl group; the bispyridyl extractant is used alone to separate nickel ions and cobalt ions in a nickel-cobalt solution system, the concentration of the bispyridyl extractant in the organic phase is 0.1-0.4 mol / L, the extraction conditions are: pH 0, 2-6, temperature 15-40℃, and the chloride ion concentration in the nickel-cobalt solution system is 2-4 mol / L.

2. The application of the bispyridyl extractant according to claim 1, characterized in that: R is C 12 ~C 25 straight-chain alkyl or C 12 ~C 25 Branched alkanes.

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