Method for synergistically extracting and separating neodymium in solution

Abstract

The invention provides a method for extracting Nd by using fatty acid and primary amine N1923 in a synergistic extraction system. The synergistic extraction system has a high synergistic factor when being used as an extraction agent to extract rare earth, has a high separation coefficient for rare earth and transition metal, can effectively recover rare earth and valuable metal in secondary resources, and has good recycling performance.

Description

Technical Field

[0001] The invention belongs to the field of rare earth extraction and separation, and in particular relates to a method for collaborative extraction and separation of neodymium (Nd). Background Art

[0002] At present, the separation and purification technologies of rare earth elements mainly include solvent extraction, ion exchange, precipitation crystallization, membrane separation, etc. Among them, solvent extraction has been widely used in industry due to its advantages such as large processing capacity, good separation selectivity and fast mass transfer rate. The separation and purification technologies of rare earth elements generally include: solvent extraction, ion exchange, precipitation crystallization, membrane separation, etc. Among them, solvent extraction has been widely used in industry due to its advantages such as large processing capacity, good separation selectivity and fast mass transfer rate. As a research direction of solvent extraction technology, synergistic extraction has been rapidly developed with its unique advantages and has become an important direction for the development of solvent extraction. As a research direction of solvent extraction technology, synergistic extraction has been rapidly developed with its unique advantages and has become an important direction for the development of solvent extraction.

[0003] The synergistic extraction system can not only increase the extractability and selectivity of metal ions, but also improve the solubility of the extractant in the organic phase, eliminate emulsification, and reduce the generation of the third phase. 协 >D 加和 The main reason is that more stable complexes are generated in the synergistic extraction system, and the oil solubility of this complex is increased, so the extraction rate can be significantly increased. The synergistic extraction technology can handle more complex metal solution systems and achieve multi-metal separation. Therefore, compared with the single extractant system, the synergistic extraction system may have better performance in basic research and industrial applications and has broader application prospects. Summary of the invention

[0004] The object of the present invention is to provide a method for extracting and separating neodymium (Nd), which has a high extraction rate for rare earth neodymium, good selectivity, and easy back extraction, and saturated fatty acids do not need to be saponified using a saponifier (a synergistic system can achieve their saponification), and the extraction system can be recycled.

[0005] The present invention provides the following technical solutions:

[0006] A method for collaboratively extracting the rare earth element neodymium comprises: extracting a feed liquid containing neodymium using a collaborative extraction system composed of primary amine N1923 and C8-C18 saturated fatty acids.

[0007] According to an embodiment of the present invention, the C8-C18 saturated fatty acid is selected from at least one of lauric acid, capric acid, myristic acid, palmitic acid or stearic acid, preferably lauric acid or capric acid.

[0008] According to an embodiment of the present invention, the molar ratio of primary amine N1923 to C8-C18 saturated fatty acids in the synergistic extraction system is 1:(0.5-5), for example 1:(0.5-2), such as 1:(0.5-1), such as 1:1.

[0009] According to an embodiment of the present invention, the concentration of the primary amine N1923 is 0.1-1 mol / L, such as 0.14-0.5 mol / L, 0.14-0.18 mol / L.

[0010] According to an embodiment of the present invention, the neodymium-containing liquid also contains at least one of cobalt, nickel and manganese. When it contains at least one of cobalt, nickel and manganese, after the extraction is completed, the separation of neodymium and at least one of cobalt, nickel and manganese can be achieved, and the neodymium is extracted into the organic phase, and at least one of cobalt, nickel and manganese remains in the aqueous phase.

[0011] According to an embodiment of the present invention, the neodymium-containing solution also contains at least one of lanthanum, cerium or praseodymium. When it contains at least one of lanthanum, cerium or praseodymium, after the extraction is completed, the extraction of lanthanum, cerium or praseodymium can also be achieved.

[0012] According to an embodiment of the present invention, the neodymium-containing liquid is a leaching solution of waste NiMH battery alloy powder, which contains lanthanum, cerium, praseodymium, neodymium, manganese, cobalt and nickel. After the extraction is completed, lanthanum, cerium, praseodymium, neodymium and manganese, cobalt and nickel can be extracted and separated.

[0013] According to an embodiment of the present invention, the initial pH of the feed solution is 1-6, for example, 1.5-5.1, preferably 2-4.5.

[0014] According to an embodiment of the present invention, a salting-out agent is added during the extraction process to eliminate emulsification, and the salting-out agent is selected from chloride salts, which can be one or a combination of at least two of sodium chloride, ammonium chloride and potassium chloride. The combination can be a combination of sodium chloride and ammonium chloride, a combination of ammonium chloride and potassium chloride, a combination of potassium chloride and sodium chloride, etc.

[0015] According to an embodiment of the present invention, the amount of the salting-out agent used in the extraction process is 0.001-1 mol / L, such as 0.05-0.8 mol / L, 0.3-0.7 mol / L or 0.1-0.6 mol / L.

[0016] According to an embodiment of the present invention, a phase modifier is further added during the extraction process, and the phase modifier is selected from one or a combination of at least two of isooctyl alcohol, ethylene glycol, TBP or glycerol, preferably isooctyl alcohol.

[0017] According to an embodiment of the present invention, the amount of the phase modifier is 1-30%, for example 10%, of the organic phase.

[0018] According to an embodiment of the present invention, a diluent is further added during the extraction process, and the diluent includes alkanes and / or aromatic hydrocarbons.

[0019] According to an embodiment of the present invention, the alkane is selected from one or more of heptane, octane, hexadecane, aviation kerosene and 260# solvent kerosene, and the aromatic hydrocarbon is selected from one or more of benzene, toluene and xylene.

[0020] According to an embodiment of the present invention, after the extraction is completed, the process of stripping neodymium with a stripping agent is also included, and the stripping agent is selected from one or more of water, inorganic acid, oxalate and oxalic acid. Preferably, the inorganic acid is selected from one or more of hydrochloric acid, nitric acid and sulfuric acid, and the oxalate includes but is not limited to sodium oxalate and ammonium oxalate, and more preferably sodium oxalate.

[0021] According to the present invention, the molar concentration of the stripping agent inorganic acid, oxalate and oxalic acid is between 0.01-1.0 mol / L, preferably between 0.05-0.5 mol / L, and more preferably between 0.1-0.3 mol / L.

[0022] According to the present invention, the extraction temperature is 0-40°C.

[0023] The present invention also provides a method for removing impurities from a NiMH battery alloy leachate, comprising contacting a synergistic extraction system consisting of the primary amine N1923 and a C8-C18 saturated fatty acid with the NiMH battery alloy leachate to remove lanthanum, cerium, praseodymium and neodymium therefrom.

[0024] Beneficial Effects

[0025] The present invention provides a method for extracting Nd using a synergistic extraction system of fatty acid + primary amine N1923. The synergistic extraction system has a high synergistic factor when used as an extractant for extracting rare earths, has a high separation coefficient for rare earths and transition metals, can effectively recover rare earths and valuable metals in secondary resources, and has good recycling performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The results show the effect of the pH value of the initial aqueous phase on the extraction efficiency of Nd(III), Co(II) and Ni(II).

[0027] Figure 2 The results show the effect of salting-out agent on the extraction rate of Nd(III), Co(II) and Ni(II).

[0028] Figure 3Comparison of the extraction phenomena of Nd(III), Co(II) and Ni(II) under different isooctyl alcohol concentrations (Note: the volume ratio of isooctyl alcohol in the organic phase is from left to right: 0, 5%, 10%, 15%, 20% and 25%, [Nd(III)] = [Co(II)] = [Ni(II)] = 0.01 mol / L, [LA] = [N1923] = 0.14 mol / L, [NaCl] = 0.4 mol / L, pH = 4.0, O / A = 1, T = 30°C).

[0029] Figure 4 The results show the effect of phase modifiers on the extraction rates of Nd(III), Co(II) and Ni(II).

[0030] Figure 5 The results show the effect of extractant concentration on the extraction rate of Nd(III), Co(II) and Ni(II).

[0031] Figure 6 The effects of temperature (a) and extraction time (b) on the extraction rates of Nd(III), Co(II) and Ni(II).

[0032] Figure 7 This is the effect of Na2C2O4 concentration on Nd(III) stripping rate.

[0033] Figure 8 The infrared spectra of different extraction systems are shown in Figure 1. (a) LA; (b) N1923; (c) LA+N1923 synergistic extractant before extraction; (d) LA+N1923 synergistic extractant loaded with Nd(Ⅲ) after extraction; (e) LA+N1923 synergistic extractant regenerated after stripping.

[0034] Fig. 9 This is the relationship between lgD and lg[N1923+LA] of Nd(III) extracted in a chlorination system.

[0035] Fig.10 It is the nuclear magnetic resonance hydrogen spectrum (CDCl3) (Note: MIX in the figure represents the LA-N1923 mixture).

[0036] Fig.11 Schematic diagram of the extraction and recovery of Nd(III), Co(II) and Ni(II) by the LA-N1923 system (NH 2 R refers to N1923; RCOOH refers to lauric acid).

[0037] Fig.12 These are the stability test results of the LA-N1923 synergistic extraction system in five cycles.

[0038] Fig.13This is the X-ray diffraction pattern of the calcined oxalic acid precipitate sample. DETAILED DESCRIPTION

[0039] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0040] Experimental reagents: Primary amine N1923 and sulfonated kerosene (#260) were purchased from Shanghai Lai Ya Shi Chemical Co., Ltd. The effective concentration of N1923 was 2.98 mol / kg as measured by acid-base titration. NiMH battery alloy powder was purchased from Xinxiang Heluo Lida Power Material Co., Ltd. All experimental water was deionized water with a specific resistance less than or equal to 18.2 MΩ / cm. The remaining reagents were of analytical grade and no further purification was required before use.

[0041] Instruments and equipment: The concentration of metal ions in the aqueous phase was determined by inductively coupled plasma optical emission spectrometry (ICP-OES), and the correlation of the standard curve was ≥99.99%. The concentration of metal ions in the loaded organic phase was calculated by mass balance method. The phase composition of the roasted oxalic acid precipitate sample was characterized by an X-ray diffractometer at a scanning speed of 10° / min. The instruments and equipment used in the following examples and detailed information are shown in Table 1.

[0042] Table 1 Experimental instruments and equipment

[0043]

[0044] Extraction and back-extraction experimental steps: The extraction organic phase was prepared by weighing a certain mass of the extractant, adding a certain proportion of isooctyl alcohol and sulfonated kerosene to prepare the extraction organic phase required for the experiment, and oscillating it at 300 rpm for 15 minutes at room temperature using an air bath constant temperature oscillator to ensure that the two extractants used for synergistic extraction were evenly mixed.

[0045] The extraction experiment was performed by mixing equal volumes (unless otherwise specified) of organic phase and aqueous phase in a centrifuge tube and oscillating the mixture at 300 rpm for 40 min using an air bath constant temperature oscillator (preliminary experiments showed that the time for the extraction reaction to reach equilibrium was less than 10 min). After the oscillation reaction, the mixture was centrifuged at 3000 rpm for 4 minutes to separate the organic phase and the aqueous phase.

[0046] The stripping experiment is to load equal volumes (unless otherwise specified) of organic phase and stripping agent (Na 2 C 2 O 4The mixture was mixed in a centrifuge tube and shaken at 300 rpm for 30 min using an air bath thermostatic oscillator. After the shaking reaction was completed, the organic phase and the aqueous phase were separated by centrifugation at 3000 rpm for 4 min.

[0047] After separation of the organic phase and the aqueous phase, the metal concentration in the aqueous phase was determined by inductively coupled plasma-atomic emission spectrometry (ICP-OES), and the concentration of metal ions in the organic phase was calculated by the mass conservation method. A / B ) and stripping rate (S) were calculated by the following equations:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053] Where, [M] aq,i and [M] aq,e Respectively represent the initial concentration and equilibrium concentration of the extracted metal in the aqueous phase. V aq and V org are the volumes of aqueous phase and organic phase respectively. a It is the distribution ratio of an extractant to the extracted metal; D b is the distribution ratio of another extractant to the extracted metal; D mix It is the distribution ratio of the mixed extraction system to the extracted metal. A and D B are the distribution ratios of the extracted metals A and B, respectively. [M] org,i is the initial concentration of the metal to be extracted in the organic phase before stripping, [M] aq,s It is the equilibrium concentration of the extracted metal in the aqueous phase after stripping. In the examples of the present application, three parallel experiments were performed for all extraction experiments, and the measurement errors of the three parallel samples were all within 5%.

[0054] Regarding the preparation of the infrared spectrum sample of the organic phase-loaded Nd(III) complex, a mixed extractant consisting of 0.14 mol / L LA and 0.14 mol / L N1923 was used to extract an aqueous solution containing 0.01 mol / L Nd(III) in n-heptane. After the organic phase and the aqueous phase were separated, the n-heptane in the organic phase was evaporated by a rotary evaporator, and then placed in a vacuum drying oven for 24 hours to obtain the Nd(III)-loaded complex.

[0055] Example 1

[0056] Effect of aqueous phase pH on extraction: During the extraction process, since hydrogen ions and rare earth ions exhibit similar chemical behaviors and affinities in the aqueous phase, they often undergo competitive extraction reactions, which affects the effective extraction of rare earth ions. To this end, appropriate measures need to be taken to adjust the aqueous phase conditions, such as appropriately adjusting the pH, etc., to reduce the competitive relationship between hydrogen ions and rare earth ions and improve the extraction rate and selectivity of rare earth ions. The selection of the initial pH of the aqueous solution plays a vital role in the extraction and separation of rare earths. In order to investigate the effect of the initial pH value of the aqueous phase on the extraction effect, hydrochloric acid or sodium hydroxide solution was added in this embodiment to adjust the initial pH value of the aqueous phase to keep it between 1.0-5.1. Then, the extraction behavior of Nd(III), Co(II) and Ni(II) under different pH conditions was studied. Figure 1 As shown, when the pH is greater than 2.5, the extraction rate of Nd(III) tends to be stable, while the extraction rates of Co(II) and Ni(II) always fluctuate within a low range. It can be seen from the figure that at low pH, the extraction system can hardly extract Nd(III) from the aqueous phase, which is mainly due to the competitive extraction of Nd(III) and hydrogen ions. In general, the extraction effect of the extraction system on Nd(III) is best when the pH value is 3.0-5.1. Within this pH range, the competitive extraction of hydrogen ions can be minimized, thereby achieving effective separation of Nd(III) and Co(II) and Ni(II) (Note: Figure 1 The extraction system tested was: [Nd(III)] = [Co(II)] = [Ni(II)] = 0.01 mol / L, [LA] = [N1923] = 0.14 mol / L, [NaCl] = 0.4 mol / L, V O / A =1, v% (isooctanol) = 10%, T = 30°C).

[0057] Effect of salting-out agent on extraction: The addition of salting-out agent can not only eliminate emulsification, but also improve the extraction rate. In this example, NaCl was added as a salting-out agent in the simulated liquid to explore the effect of different concentrations of NaCl on the extraction of Nd(III), Co(II) and Ni(II) by the LA-N1923 synergistic system. Figure 2As shown, with the increase of NaCl concentration, the extraction rate of Nd(III) has a significant upward trend, and then tends to be stable, while the extraction rates of Co(II) and Ni(II) remain relatively stable. When the NaCl concentration increases to 0.4mol / L, the extraction of Nd(III) tends to be saturated, while the extraction rates of Co(II) and Ni(II) show a more obvious upward trend. The increase in the extraction rate of Co(II) and Ni(II) will undoubtedly lead to a decrease in the recovery rate of both, and will reduce the purity of Nd(III) in the final product. In order to minimize the co-extraction of Co(II) and Ni(II) and improve the separation coefficient, the optimal dosage of the salting-out agent NaCl in this embodiment is 0.4mol / L (Note: the extraction system is: [Nd(III)] = [Co(II)] = [Ni(II)] = 0.01mol / L, [LA] = [N1923] = 0.14mol / L, pH = 4.0, V O / A＝1 , v% (isooctanol) = 10%, T = 30°C).

[0058] Effect of phase modifiers on extraction: In order to improve the extraction phenomenon in the solvent extraction process, many researchers add phase modifiers to the extraction system, which can not only effectively avoid undesirable extraction phenomena such as emulsification or the third phase, but also improve the stability and selectivity of the extraction system and promote the extraction reaction to reach equilibrium faster. In order to explore whether the addition of phase modifiers will affect the extraction effect of the LA-N1923 synergistic extraction system, this example selects isooctyl alcohol as a phase modifier and compares the extraction effects of adding isooctyl alcohol in different volume ratios. Figure 3 As shown, emulsification occurred during the extraction in the experimental group without the addition of isooctyl alcohol, and the emulsification phenomenon can be avoided by adding a certain proportion of isooctyl alcohol. Figure 4 The changes in the extraction rates of Nd(III), Co(II) and Ni(II) with the increase of isooctyl alcohol concentration. After comprehensive consideration, the volume ratio of isooctyl alcohol added in the subsequent tests of the embodiment is 10% (relative to the organic phase, the same below) (Note: [Nd(III)] = [Co(II)] = [Ni(II)] = 0.01 mol / L, [LA] = [N1923] = 0.14 mol / L, [NaCl] = 0.4 mol / L, pH = 4.0, V O / A =1, T=30°C).

[0059] Effect of synergistic extractant concentration: The effect of synergistic extractant concentration on the extraction of Nd(III), Co(II) and Ni(II) was tested. Figure 5It can be seen that with the increase of the total concentration of the synergistic extractant, the extraction efficiency of Nd(III), Co(II) and Ni(II) generally shows an upward trend. When [LA+N1923] = 0.28 mol / L, the extraction rates of Nd(III), Co(II) and Ni(II) are 96.35%, 5.58% and 3.90% respectively, and the separation coefficients of Nd(III) / Co(II) and Nd(III) / Ni(II) are 1503 and 2762 respectively, which can ensure the effective separation of rare earth Nd and transition metal Co and Ni (Note: The extraction system is: [Nd(III)] = [Co(II)] = [Ni(II)] = 0.01 mol / L, [LA] / [N1923] = 1, [NaCl] = 0.4 mol / L, pH = 4.0, V O / A =1, v% (isooctanol) = 10%, T = 30°C).

[0060] Effects of temperature and time on extraction: Figure 6 It can be seen that when the temperature is in the range of 20-45℃, the change of temperature has no obvious effect on the extraction effect of the LA-N1923 system, which shows that the extraction process of the LA-N1923 system can be carried out directly at room temperature without adding additional costs to adjust the temperature during the extraction process. In subsequent studies, 25℃ was selected as the extraction temperature. The effect of kinetics on the extraction effect was further studied. Figure 6 It can be seen from b that the extraction rate of Nd(III) remains basically unchanged after 10 minutes, and the extraction rates of Co(II) and Ni(II) change slightly and can be ignored. This means that the time required for the extraction system to reach extraction equilibrium is very short, and a high extraction rate can be achieved. The separation effect will not weaken with the increase of the contact time between the two phases, and the extraction system is relatively stable (Note: The extraction system is: (a) [Nd(III)] = [Co(II)] = [Ni(II)] = 0.01 mol / L, [LA] = [N1923] = 0.14 mol / L, [NaCl] = 0.4 mol / L, pH = 4.0, V O / A =1, v% (isooctanol)=10%; (b) [Nd(III)]=[Co(II)]=[Ni(II)]=0.01mol / L, [LA]=[N1923]=0.14mol / L; [NaCl]=0.4mol / L, pH=4.0, V O / A =1, v% (isooctanol) = 10%, T = 25°C).

[0061] Stripping experiment: Stripping technology is very important for metal ion recovery and is also of great significance for the development of sustainable resource utilization strategies. In terms of recycling of extractants, metal ions can be recovered from the organic phase through stripping, and high-purity metal ions can be obtained, thereby achieving effective utilization and recovery of resources and reducing negative impacts on the environment. In this example, Na 2 C 2 O 4 As a stripping agent. The results show that 0.20 mol / L Na 2 C 2 O 4 The stripping rate of Nd(III) can reach 98.26%. Figure 7 It can be seen that deionized water also has a certain stripping effect on Nd(III) in the loaded organic phase (the stripping rate is 52.36%). 2 C 2 O 4 After stripping, the Nd(III) in the loaded organic phase can be completely stripped by washing with deionized water (Note: the extraction system is: [Nd(III)] = 0.01 mol / L, [LA] = [N1923] = 0.14 mol / L, [NaCl] = 0.4 mol / L, pH = 4.0, O / A = 1, v% (isooctanol) = 10%, T = 25°C).

[0062] Example 2

[0063] In order to study the extraction mechanism of Nd(III) by LA-N1923 system, slope analysis and infrared spectrum analysis were performed in this example. The structures of LA, N1923 and their mixture (before and after extraction) were characterized by infrared spectroscopy. Figure 8 As shown, 3000cm -1 -2800cm -1 The absorption peak at 1376cm can be attributed to the stretching vibration absorption peak of CH in the carbon chain of N1923. -1 and 1462cm -1 The absorption peak at 721 cm-1 can be attributed to the symmetric and asymmetric deformation vibration absorption peaks of -CH in the methyl group of N1923. -1 The absorption peaks at 800 cm-1 can be attributed to the characteristic absorption peaks of the N1923 methylene group. These absorption peaks did not change before and after extraction, indicating that there was no obvious interaction between the carbon chain and the extractant. -1 and 1596cm -1 The absorption peaks at 2 When LA and N1923 are mixed in an equal molar ratio, these two absorption peaks disappear, and the peak at 1637 cm-1 and 1560cm -1 Two new absorption peaks appeared at -NH 3 + The symmetric and asymmetric deformation vibration absorption peaks correspond to the -NH 2 To-NH 3 + For LA, when LA is mixed with N1923, the protonation transition at 1695 cm -1 The C=O stretching vibration peak belonging to the carboxyl group in LA disappears at 1637cm -1 and 1560cm -1 COO - It should be noted that the symmetric and antisymmetric stretching vibration peaks of -NH 3 + and COO - The absorption peaks of LA and N1923 inevitably overlap. The above results show that the hydrogen bonding between LA and N1923 forms a synergistic extractant RNH 3 + ·RCOO - After LA and N1923 were mixed to extract Nd(III), 1637cm -1 and 1560cm -1 The peaks at 1632 cm -1 and 1550cm -1 The Nd(III) loaded extractant was treated with Na 2 C 2 O 4 After stripping and regeneration, 1550cm -1 The peak at 1560cm returned to the peak before extraction. -1 The above shifts indicate that C=O has a significant interaction with Nd(III), confirming that RNH 3 + ·RCOO - Participated in the formation of Nd(III) extractants. The peak shapes and positions of the synergistic extractants after regeneration were basically the same as before extraction, which shows that the synergistic extractants have good stability during extraction and stripping and can be recycled.

[0064] This example also calculated the lgD in hydrochloric acid medium Nd Linear relationship with lg[N1923+LA]. Fig. 9 The slope analysis results showed that lgD NdIt is linearly related to lg[N1923+LA], with a slope close to 2 (Note: the extraction system is: [Nd(III)] = 0.01 mol / L, [LA] / [N1923] = 1, [NaCl] = 0.4 mol / L, pH = 3.9, V O / A =1, v% (isooctanol) = 10%, T = 25°C). It can be seen that the synergistic extractant RNH 3 + ·RCOO - The stoichiometric ratio of Nd(Ⅲ) to Nd(Ⅲ) in the extraction reaction is 2:1. On the other hand, according to the principle of electrical neutrality, cations are extracted by neutral extractants, and anions are co-extracted due to their electrical neutrality. - The stoichiometric ratio of is 3:1. Therefore, when the initial pH of the aqueous solution is in the range of 3.0-5.0, the synergistic extractant RNH 3 + ·RCOO - With Nd 3+ The extraction mechanism can be expressed as the following equation (3-6):

[0065]

[0066] This example uses nuclear magnetic resonance spectroscopy to further study the synergistic extraction mechanism of the LA-N1923 system. Fig.10 The characteristic peaks are shown in Table 2. The peak at 11.43 ppm in LA can be attributed to the -COOH group. The peak at 1.06-1.07 ppm in N1923 is assigned to the -NH 2 When LA is mixed with N1923, the spectral peak of -COOH disappears. At the same time, -NH 2 The peak disappeared and a new NH 3 + The above changes are due to the replacement of the H at -COOH in LA by -NH 2 This is also the key reason why the extraction system in this application can extract Sm(III) without saponification. Fig.10 The corresponding characteristic peaks and chemical shifts (ppm) are analyzed as follows:

[0067] Table 2 Characteristic peaks and chemical shifts in H NMR spectra (ppm)

[0068]

[0069] Note: “ / ” in the above table indicates no absorption peak.

[0070] In this application, during the extraction and recovery of Nd(III), Co(II) and Ni(II) by the LA-N1923 system, the distribution changes of the organic phase and the aqueous phase are as follows: Fig.11 shown.

[0071] Example 3

[0072] like Fig.12 As shown, the LA-N1923 synergistic extraction system is 2 C 2 O 4 Good stability is maintained during the regeneration and circulation process. In addition, the synergistic extraction system maintained a high extraction rate (about 95%) for Nd(III) in 5 cycles, and the extraction rates for Co(II) and Ni(II) were less than 5%. The above results show that the extraction system of the present application is effective and recyclable for the separation of Nd / Co and Nd / Ni in chloride media (Note: the extraction system is: [Nd(III)] = [Co(II)] = [Ni(II)] = 0.01 mol / L, [LA] = [N1923] = 0.14 mol / L, [NaCl] = 0.4 mol / L, pH = 4.0, V O / A =1, v% (isooctanol) = 10%, T = 25°C, [Na 2 C 2 O 4 ]=0.20mol / L).

[0073] Example 4

[0074] The organic phase was loaded with Na 2 C 2 O 4 After stripping, oxalic acid precipitate was obtained, and then 4% NH 3 ·H 2 O was washed three times. Then it was calcined in a muffle furnace at 900℃ to obtain Nd with high purity. 2 O 3 . Fig.13 This is the X-ray diffraction diagram of the sample obtained after washing and calcining the oxalic acid precipitate. It can be seen from the figure that the obtained sample is similar to Nd 2 O 3 The physical phase of the standard card is basically the same. In order to obtain the Nd 2 O 3 The relative purity of the sample was determined by dissolving the calcined oxalic acid precipitate with 2 mol / L hydrochloric acid and determining its elemental composition. The results are shown in Table 3. 2 O 3 The purity is greater than 99.9%. Regarding the recovery of Co and Ni, since the contents of Co and Ni in the organic phase are both low, the present application mainly recovers them in the form of chloride in the raffinate.

[0075] Table 3 Composition of oxalic acid precipitate after calcination

[0076]

[0077] Example 5 Selective separation of multi-metal mixtures from nickel-hydrogen batteries

[0078] This embodiment studies the performance of the LA-N1923 synergistic extraction system in selectively separating Nd, Co and Ni from actual NiMH battery alloy leachate. Commercial NiMH battery alloy powder is dissolved with 2 mol / L HCl under heating conditions, then diluted with deionized water and the pH is adjusted with NaOH solution to obtain actual NiMH battery alloy leachate, which is then extracted and separated using the LA-N1923 synergistic extraction system. The composition of the initial feed solution and the metal content in the solution after extraction are shown in Table 4 (a small amount of aluminum, Fe and other metal elements have little effect on the recovery process due to their low content and are not listed here). Ultimately, the recovery rate of rare earths can reach more than 95%.

[0079] Table 4 Metal content in the feed solution before and after extraction separation

[0080]

[0081] In summary, this application studies the synergistic extraction and separation of Nd, Co and Ni by the acidic extractant LA and the primary amine N1923. When LA and N1923 are mixed and extracted in an equimolar ratio, there is a significant synergistic enhancement effect on the extraction of Nd, and the synergistic coefficient can reach 136.85. It can achieve effective separation of Nd, Co and Ni, and the separation coefficients of Nd / Co and Nd / Ni are 1503 and 2762, respectively. Under the optimized extraction conditions, the extraction of Nd with Na 2 C 2 O 4 As a stripping agent, it can achieve complete stripping of the loaded organic phase, and the regeneration of the extractant can be achieved through a simple extraction-stripping-washing process. After washing and roasting, the oxalic acid precipitate can be obtained to obtain Nd with a purity greater than 99.9%. 2 O 3. The performance of the regenerated extractant is stable, and the extraction effect remains basically unchanged after five cycles. The results of slope analysis and infrared spectroscopy show that the mechanism of Nd extraction by the LA-N1923 synergistic system is ion association. The molar ratio of the synergistic extractant to the extracted rare earth ions is 2:1. In this application, the LA-N1923 synergistic system is applied to the actual NiMH battery alloy powder leachate, which can achieve effective separation and recovery of rare earth elements REE (La, Ce, Pr and Nd) and transition rare earths (Co, Ni and Mn). The separation coefficients of REE / Co, REE / Ni and REE / Mn are 418, 290 and 713, respectively, and the total recovery rate of rare earths can reach more than 95%. The above research results of this application demonstrate the application potential of the LA-N1923 synergistic extraction system to achieve rare earth recovery from discarded NiMH batteries.

[0082] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for synergistic extraction of the rare earth element neodymium, It is characterized in that include: The synergistic extraction system consisting of primary amine N1923 and C8-C18 saturated fatty acids is used to extract the neodymium-containing liquid.

2. The method according to claim 1, It is characterized in that The C8-C18 saturated fatty acid is selected from at least one of lauric acid, capric acid, myristic acid, palmitic acid or stearic acid.

3. The method according to claim 1, It is characterized in that The molar ratio of the primary amine N1923 to the C8-C18 saturated fatty acid in the synergistic extraction system is 1:(0.5-5).

4. The method according to claim 1, It is characterized in that The concentration of primary amine N1923 is 0.1-1 mol / L.

5. The method according to any one of claims 1 to 4, It is characterized in that The neodymium-containing liquid further contains at least one of cobalt, nickel and manganese. When the liquid contains at least one of cobalt, nickel and manganese, after the extraction is completed, the neodymium can be separated from at least one of cobalt, nickel and manganese, and the neodymium is extracted into the organic phase, and at least one of cobalt, nickel and manganese remains in the aqueous phase. Alternatively, the neodymium-containing liquid further contains at least one of lanthanum, cerium or praseodymium. When it contains at least one of lanthanum, cerium or praseodymium, after the extraction is completed, the extraction of lanthanum, cerium or praseodymium can also be achieved. Preferably, the neodymium-containing liquid is a leaching solution of waste NiMH battery alloy powder, which contains lanthanum, cerium, praseodymium, neodymium, manganese, cobalt and nickel. After the extraction is completed, lanthanum, cerium, praseodymium, neodymium and manganese, cobalt and nickel can be extracted and separated.

6. The method according to claim 5, It is characterized in that The initial pH of the feed solution is 1-6.

7. The method according to claim 6, It is characterized in that A salting-out agent is added during the extraction process to eliminate emulsification. The salting-out agent is selected from chloride salts, which can be one or a combination of at least two of sodium chloride, ammonium chloride and potassium chloride. The combination can be a combination of sodium chloride and ammonium chloride, a combination of ammonium chloride and potassium chloride, and a combination of potassium chloride and sodium chloride. Preferably, the amount of the salting-out agent used during the extraction process is 0.001-1 mol / L.

8. The method according to claim 7, It is characterized in that A phase modifier is also added during the extraction process. The phase modifier is selected from one or a combination of at least two of isooctyl alcohol, ethylene glycol, TBP or glycerol. Preferably, the phase modifier is used in an amount of 1-30% of the organic phase. Preferably, a diluent is also added during the extraction process, and the diluent includes alkanes and / or aromatic hydrocarbons. Preferably, the alkane is selected from one or more of heptane, octane, hexadecane, aviation kerosene and 260# solvent kerosene, and the aromatic hydrocarbon is selected from one or more of benzene, toluene and xylene.

9. The method according to claim 8, It is characterized in that After the extraction is completed, the method further includes a process of stripping neodymium using a stripping agent, wherein the stripping agent is selected from one or more of water, inorganic acid, oxalate and oxalic acid. Preferably, the inorganic acid is selected from one or more of hydrochloric acid, nitric acid and sulfuric acid, and the oxalate is selected from sodium oxalate or ammonium oxalate. Preferably, the molar concentration of the stripping agent inorganic acid, oxalate or oxalic acid is between 0.01-1.0 mol / L.

10. A method for removing impurities from NiMH battery alloy leachate, It is characterized in that The invention comprises bringing a synergistic extraction system composed of primary amine N1923 and C8-C18 saturated fatty acid into contact with NiMH battery alloy leaching solution to remove lanthanum, cerium, praseodymium and neodymium therein.

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