A rare earth extractant and method for separating yttrium and heavy rare earth

Abstract

The present invention belongs to the field of rare earth separation, and specifically relates to an ionic liquid extractant and a method for separating yttrium and heavy rare earth. The extractant comprises [A] + Cations and [B] ‑ An ionic liquid composed of anions, wherein the [A] + is a methyl trioctyl ammonium cation having a structure as shown in formula (a), wherein [B] ‑ It has a structure as shown in formula (b), wherein R is selected from a C1-C15 straight chain or branched chain alkyl, preferably a C1-C10 straight chain or branched chain alkyl. The extractant of the present invention has a wide source of raw materials, is non-toxic, has fast equilibrium when extracting rare earths, is easy to strip, has high extraction selectivity, is stable in nature, can be recycled, and has a high extraction rate. #imgabs0#

Description

Technical Field

[0001] The invention belongs to the field of rare earth separation, and in particular relates to an ionic liquid extractant and a method for separating yttrium and heavy rare earth. Background Art

[0002] As one of the heavy rare earths, yttrium has been widely used in the fields of metallurgy, electronic devices, laser components, ceramic materials and nuclear energy. With the development of science and technology, the demand for high-purity yttrium products has increased rapidly. For example, the content of impurities in RE needs to be reduced to 1×10 -4 However, since yttrium has similar physical and chemical properties to heavy rare earths, it is difficult to separate and purify yttrium from other heavy rare earth impurities.

[0003] Acids are widely used as extractants in industry to extract and separate yttrium. However, traditional acidic extractants need to be saponified with ammonia or sodium hydroxide before extraction, which will produce a large amount of saponification wastewater and cause environmental pollution. Summary of the invention

[0004] In order to improve the above technical problems, the present invention provides an extractant comprising [A] + Cations and [B] - An ionic liquid composed of anions, wherein the [A] + The cation is a methyltrioctylammonium cation having a structure as shown in formula (a):

[0005]

[0006] Said [B] - The anion has a structure as shown in formula (b):

[0007]

[0008] In formula (b), R is selected from a C1-C15 straight chain or branched chain alkyl group, preferably a C1-C10 straight chain or branched chain alkyl group, for example, a tert-nonyl group.

[0009] According to an embodiment of the present invention, the ionic liquid [B] - Anion and [A] + The molar ratio of the cations may be 1:10 to 10:1, preferably 1:5 to 5:1, and exemplarily 1:1.

[0010] According to an embodiment of the present invention, the ionic liquid is [N1888] + [NDA] - Ionic liquids, [N1888] + With [NDA] - The molar ratio is 1:1, [N1888]+ [NDA] - The structural formula of ionic liquid is as follows:

[0011]

[0012] According to an embodiment of the present invention, the extractant includes at least one of the above-mentioned ionic liquids, for example, includes one, two or more of the above-mentioned ionic liquids.

[0013] According to an embodiment of the present invention, the extractant also includes a solvent, and the solvent is preferably an organic solvent. The organic solvent can be one or more of aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, alcohols and kerosene, etc. Preferably, the aliphatic hydrocarbons include one or more of pentane, heptane, octane and hexadecane, preferably the aromatic hydrocarbons include one or more of benzene, toluene and xylene, preferably the halogenated hydrocarbons include one or more of ethyl chloride, carbon tetrachloride and monochlorotoluene, and preferably the alcohol includes one or more of methanol, ethanol and propanol; the organic solvent is, for example, kerosene.

[0014] The present invention provides a method comprising the above-mentioned [A] + Cations and [B] - The use of the ionic liquid composed of anions as a rare earth extractant is preferably used to separate yttrium from other heavy rare earth elements.

[0015] According to an embodiment of the present invention, the other heavy rare earth elements include but are not limited to holmium, erbium, thulium, ytterbium, and lutetium.

[0016] The present invention provides application of the extractant in separation of yttrium and other heavy rare earth elements.

[0017] According to an embodiment of the present invention, the other heavy rare earth elements are selected as shown above.

[0018] The present invention provides a method for separating yttrium and heavy rare earth elements, comprising the following steps:

[0019] (1) The above-mentioned ionic liquid or extractant is mixed with rare earth feed solution and selectively separated so that heavy rare earth is extracted into the organic phase and yttrium remains in the aqueous phase.

[0020] According to an embodiment of the present invention, after step (1), the method further comprises step (2): stripping the organic phase of the heavy rare earth to obtain a heavy rare earth enriched solution.

[0021] According to an embodiment of the present invention, in step (1), the mixing temperature may be 40 to 80°C, preferably 40 to 50°C, and exemplarily 40°C.

[0022] According to an embodiment of the present invention, the rare earth solution in step (1) can be a rare earth enriched solution containing heavy rare earths or an acid leaching solution containing heavy rare earths; the rare earth enriched solution is, for example, a yttrium-rich rare earth enriched solution; the acid solution can be one, two or three of hydrochloric acid, nitric acid or sulfuric acid.

[0023] According to an embodiment of the present invention, the pH value of the rare earth solution in step (1) may be 2 to 6, preferably 4 to 6, and exemplarily 5.

[0024] According to an embodiment of the present invention, the molar ratio of the ionic liquid to all rare earth elements in the rare earth solution in step (1) is (2-5):1, for example, 2:1 or 3:1.

[0025] According to an embodiment of the present invention, the concentration of the ionic liquid or extractant in step (1) is 0.10 mol / L to 1.00 mol / L, preferably 0.3 to 0.7 mol / L, for example 0.40 mol / L.

[0026] According to an embodiment of the present invention, the concentration of the rare earth solution in step (1) is 0.05 mol / L to 0.50 mol / L, preferably 0.1 to 0.4 mol / L, for example 0.20 mol / L.

[0027] According to an embodiment of the present invention, in step (1), the volume ratio of the ionic liquid or the extractant to the rare earth solution is 10:1 to 1:10, preferably 8:1 to 1:2, for example 1:1.

[0028] According to an embodiment of the present invention, the separation method in step (1) can be extraction, and the extraction can be multi-stage extraction, for example, not less than three-stage extraction, exemplarily 11-stage extraction. Further, the extraction temperature can be 20-50°C, preferably 25-30°C, exemplarily 25°C.

[0029] According to an embodiment of the present invention, the stripping in step (2) may be performed using an acid solution; the acid may be selected from one, two or more of hydrochloric acid, nitric acid, formic acid, acetic acid and lactic acid.

[0030] According to an embodiment of the present invention, the concentration of the acid solution used for stripping in step (2) may be 0.5 to 12 mol / L, preferably 0.5 to 6 mol / L, and exemplarily 0.5 mol / L.

[0031] According to an embodiment of the present invention, the stripping temperature in step (2) may be 20 to 70°C, preferably 25 to 50°C, and exemplarily 25°C.

[0032] The present invention also provides a method for recovering the above-mentioned ionic liquid or extractant, which comprises recovering the ionic liquid after stripping in step (2).

[0033] Beneficial Effects

[0034] The ionic liquid raw materials synthesized by the present invention are widely available and non-toxic. The method of the present invention does not require saponification during the extraction process, which can avoid the generation of saponification wastewater. The rare earth is extracted quickly, the stripping is easy, the extraction selectivity is high, the properties are stable, and it can be recycled. After the cycle, a high extraction rate can still be maintained. The one-time extraction rate can reach more than 80%, and the purity of the obtained yttrium solution is high. The purity of the yttrium solution can be increased to more than 99% through a cascade process. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of a cascade process in Example 1 of the present invention;

[0036] Figure 2 This is a graph of extraction efficiency after 5 cycles using the regenerated ionic liquid as an extractant in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The following will further describe the extractant of the present invention and its application in detail in conjunction with specific examples. It should be understood that the following examples are only for exemplary description and explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies realized based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0038] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0039] Example 1

[0040] (1) Preparation of extractant [methyl trioctyl ammonium] [neodecanoic acid] ([N1888] + [NDA] - )

[0041] Preparation of ionic liquids by acid-base neutralization [N1888] + [NDA] - .

[0042] 16.16 g (0.04 mol) [N1888] + Cl -Dissolve in 40 mL of n-heptane solution and pour it into a 250 mL round-bottom flask. First, add 7.104 g (0.04 mol) of neodecanoic acid to the flask, and then add 40 mL of n-heptane to dilute. Then, dissolve 2.0 g (0.05 mol) of sodium hydroxide in 40 mL of deionized water and add it dropwise to the round-bottom flask to mix. Stir the resulting mixture at room temperature for 4 hours. Add 10 ml of methanol to the resulting product and wash with deionized water until the Cl in the organic phase is completely removed. - Finally, the solvent was removed by a rotary evaporator at 50°C, and the product after the solvent removal was dried in a vacuum drying oven at 80°C for 12 hours to obtain the target product viscous [N1888] + [NDA] - Ionic liquid, with a structural formula as shown in formula (I).

[0043]

[0044] As shown in Table 1, at room temperature, the actual rare earth feed solution (adjusting the pH value to 5) with a total rare earth concentration of 0.2 mol / L was extracted by extracting the aqueous phase, and the concentration of 0.4 mol / L [N1888] + [NDA] - The distribution ratio and separation coefficient of ionic liquid and 100% saponified neodecanoic acid with a concentration of 0.4 mol / L for rare earth elements. [N1888] + [NDA] - Compared with the traditional saponified neodecanoic acid extractant, ionic liquids have a higher separation effect.

[0045] Table 1 [N1888] + [NDA] - Distribution ratio and separation factor of ionic liquid and 100% saponified neodecanoic acid

[0046]

[0047]

[0048] (2) Extraction and separation of yttrium

[0049] Yttrium-containing rare earth enriched solution is from an ionic rare earth mine in Ganzhou, Jiangxi Province. The total rare earth concentration is directly diluted to 0.20 mol / L without treatment, and the pH value is adjusted to 5. The content of each element in the yttrium-containing rare earth enriched solution is shown in Table 2. + [NDA] - The ionic liquid was prepared into a 0.40 mol / L oil phase solution using kerosene.

[0050] The cascade experiment was carried out with a ratio of 2:2:1 for oil phase: liquid phase: washing phase. The washing phase was a 0.28 mol / L hydrochloric acid solution. Figure 1 The cascade process shown in the figure, through 11 stages of extraction and 4 stages of washing, wherein the extraction and washing temperature is 25°C, the time for each stage of extraction to reach equilibrium is 15 minutes, and the time for each stage of washing to reach equilibrium is 15 minutes, to obtain a yttrium chloride product with a purity of 99.03%, after washing and regeneration [N1888] + [NDA] - Ionic liquids are stable.

[0051] The regenerated [N1888] + [NDA] - Ionic liquid is used as an extractant and then added Figure 1 The extraction was carried out in the cascade process shown in the figure, and after 5 cycles, the extraction efficiency was still above 80% (as shown in FIG. Figure 2 shown).

[0052] Table 2 Composition of rare earth elements in yttrium-containing enriched solution

[0053] Metallic elements La~Tb Dy Ho Er Tm Yb Lu Y Molar ratio (%) 0.65 0.93 2.49 4.98 0.55 3.10 0.36 87.88

[0054] 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 rare earth extractant, characterized in that: It is [A] + Cations and [B] - The ionic liquid structured by the anion is composed of [N1888] + [NDA] - Ionic liquids, [N1888] + With [NDA] - The molar ratio is 1:1, [N1888] + [NDA] - The structural formula of ionic liquid is as follows: Formula (I).

2. The rare earth extractant according to claim 1, characterized in that The rare earth extractant consists of an organic solvent and the ionic liquid. The organic solvent is one or more of aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, alcohols and kerosene.

3. The rare earth extractant according to claim 2, characterized in that: The aliphatic hydrocarbons include one or more of pentane, heptane, octane and hexadecane, the aromatic hydrocarbons include one or more of benzene, toluene and xylene, the halogenated hydrocarbons include one or more of ethyl chloride, carbon tetrachloride and monochlorotoluene, and the alcohols include one or more of methanol, ethanol and propanol.

4. A method for separating yttrium and heavy rare earth elements, characterized in that: The following steps are involved: (1) The rare earth extractant according to any one of claims 1 to 3 is mixed with a rare earth feed solution and subjected to selective separation so that the heavy rare earth is extracted into the organic phase and the yttrium remains in the aqueous phase.

5. The method for separating yttrium and heavy rare earth elements according to claim 4, characterized in that: The heavy rare earths include holmium, erbium, thulium, ytterbium and lutetium.

6. The method for separating yttrium and heavy rare earth elements according to claim 4, characterized in that: After step (1), the method further comprises step (2): stripping the organic phase of the heavy rare earth to obtain a heavy rare earth enriched solution.

7. The method for separating yttrium and heavy rare earth elements according to claim 4, characterized in that: In step (1), the mixing temperature is 40-80°C.

8. The method for separating yttrium and heavy rare earth elements according to claim 4, characterized in that: The rare earth liquid in step (1) is a rare earth enriched liquid containing heavy rare earth or an acid leaching liquid containing heavy rare earth; the rare earth enriched liquid is a rare earth enriched liquid rich in yttrium; the acid is one, two or three of hydrochloric acid, nitric acid or sulfuric acid.

9. The method for separating yttrium and heavy rare earth elements according to claim 4, characterized in that: The pH value of the rare earth solution in step (1) is 2-6.

10. The method for separating yttrium and heavy rare earth elements according to any one of claims 4 to 9, characterized in that: In step (1), the molar ratio of the ionic liquid to all rare earth elements in the rare earth solution is (2-5):

1.

11. The method for separating yttrium and heavy rare earth elements according to any one of claims 4 to 9, characterized in that: The concentration of the ionic liquid in step (1) is 0.10 mol / L to 1.00 mol / L.

12. The method for separating yttrium and heavy rare earth elements according to any one of claims 4 to 9, characterized in that: The concentration of the rare earth solution in step (1) is 0.05 mol / L to 0.50 mol / L.

13. The method for separating yttrium and heavy rare earth elements according to any one of claims 4 to 9, characterized in that: In step (1), the volume ratio of the rare earth extractant to the rare earth feed solution is 10:1 to 1:

10.

14. The method for separating yttrium and heavy rare earth elements according to claim 13, characterized in that: In step (1), the volume ratio of the rare earth extractant to the rare earth feed solution is 8:1 to 1:

2.

15. The method for separating yttrium and heavy rare earth elements according to any one of claims 4 to 9, characterized in that: The separation method in step (1) is extraction, and the extraction is multi-stage extraction.

16. The method for separating yttrium and heavy rare earth elements according to claim 15, characterized in that: The multi-stage extraction refers to no less than three-stage extraction.

17. The method for separating yttrium and heavy rare earth elements according to claim 15, characterized in that: The extraction temperature is 20-50°C.

18. The method for separating yttrium and heavy rare earth elements according to claim 6, characterized in that: The stripping in step (2) is carried out using an acid solution; the acid is selected from one, two or more of hydrochloric acid, nitric acid, formic acid, acetic acid and lactic acid.

19. The method for separating yttrium and heavy rare earth elements according to claim 18, characterized in that: The concentration of the acid solution used for stripping in step (2) is 0.5-12 mol / L.

20. The method for separating yttrium and heavy rare earth elements according to claim 6, characterized in that: The stripping temperature in step (2) is 20-70°C.

21. The method for separating yttrium and heavy rare earth elements according to claim 6, characterized in that: After the stripping in step (2), the method further comprises the following steps: recovering the stripped ionic liquid.

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