Triethylammonium chloride crystals, preparation thereof and use thereof in the recovery of lanthanides

Abstract

The present application relates to the technical field of lanthanide recovery, and particularly relates to a triethylammonium chloride crystal, preparation thereof and application thereof in lanthanide recovery. The triethylammonium chloride crystal is composed of triethylammonium cation and chloride ion, and has a chemical formula of NEt3HCl. Each nitrogen atom is bonded with three ethyl groups to form a typical triethylammonium cation, and the chloride ion occupies a lattice position and participates in N-H...Cl hydrogen bond interaction. In the triethylammonium chloride crystal, the content of chlorine is 44.22%, the content of carbon is 35.80%, the content of hydrogen is 9.99%, and the content of nitrogen is 9.99%. In the triethylammonium chloride crystal, the nitrogen element serves as a coordination site and can directly coordinate with lanthanide ions. Due to the influence of the hydrophobic effect of the ethyl group in triethylamine, lanthanum 98.30%, europium 98.70% and lutetium 98.79% can be efficiently adsorbed and recovered. It is shown that the triethylammonium chloride crystal has good adsorption performance on lanthanide elements and can realize high-capacity adsorption enrichment of lanthanide elements.

Description

Technical Field

[0001] This invention relates to the field of lanthanide element recovery technology, and in particular to a triethylammonium chloride crystal, its preparation, and its application in lanthanide element recovery. Background Technology

[0002] Lanthanides are indispensable elements in semiconductors, permanent magnets, and photonic materials, forming the cornerstone of modern energy and information technology. However, their enrichment and recovery remain challenging problems due to their high chemical similarity, low abundance, and complex matrices. Traditional solvent extraction methods are typically inefficient and generate organic solvent waste, easily causing environmental problems. Chelating coordination adsorbents can enhance the adsorption capacity and selectivity of lanthanides, such as ODA13, binding protein lanmodulin, macrocyclic DO3A chelators, and octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide. However, most existing coordination adsorbents rely on post-modification to introduce coordinating groups, utilizing N / O coordination sites for adsorption. But because the coordinating atoms are confined within the molecule, they cannot adequately meet coordination requirements, resulting in low adsorption capacity and poor separation efficiency.

[0003] Therefore, developing simple and efficient ligands that do not require post-modification to introduce coordinating groups and can well meet the coordination requirements of lanthanides is crucial for improving the enrichment and recovery efficiency of lanthanides. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a triethylammonium chloride crystal, its preparation, and its application in the recovery of lanthanide elements.

[0005] The objective of this invention can be achieved through the following technical solutions: The first object of the present invention is to provide a triethylammonium chloride crystal, the chemical structural formula of which is shown in formula (I): Formula (I) The triethylammonium chloride crystal, abbreviated as cTEA, is composed of triethylammonium cations and chloride ions, with the chemical formula NEt3HCl. Each nitrogen atom is bonded to three ethyl groups to form a typical triethylammonium cation, while the chloride ions occupy lattice positions and participate in NH···Cl hydrogen bond interactions. The triethylammonium chloride crystals contain 44.22% chlorine, 35.80% carbon, 9.99% hydrogen, and 9.99% nitrogen.

[0006] A second objective of this invention is to provide a method for preparing triethylammonium chloride crystals, comprising the following steps: (S1) Dissolve hexachlorocyclotriphosphazene in a solvent and mix well to obtain a mixed solution; (S2) Triethylamine is added to the mixed solution prepared in step (S1), and the mixture is subjected to a solvothermal reaction and post-treatment to obtain triethylammonium chloride crystals.

[0007] In one embodiment of the present invention, in step (S1), the solvent (a highly polar solvent) is selected from one of DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), acetonitrile (MeCN), HcA (hexamethylphosphoric triamine) or DMAc (N,N-dimethylacetamide).

[0008] In one embodiment of the present invention, in step (S1), the ratio of the amount of hexachlorocyclotriphosphazene to the solvent is 80-90 mg: 1 mL; The mixture is homogenized by ultrasound for 30-60 seconds.

[0009] In one embodiment of the present invention, in step (S2), the molar ratio of triethylamine to hexachlorocyclotriphosphazene is 2~6:1.

[0010] In one embodiment of the present invention, in step (S2), triethylamine and the mixed solution are mixed by ultrasound for 1 to 20 seconds.

[0011] In one embodiment of the present invention, in step (S2), the temperature during the solvothermal reaction is 60~120 °C and the time is 8~24 h; The post-processing includes collecting the solid, washing it with tetrahydrofuran, and then drying it to obtain triethylammonium chloride crystals.

[0012] In one embodiment of the present invention, the drying process is carried out at a temperature of 50-80 °C for 6-24 h.

[0013] The third objective of this invention is to provide an application of triethylammonium chloride crystals in the recovery of lanthanide elements.

[0014] A fourth objective of this invention is to provide a method for recovering lanthanide elements, comprising the following steps: Triethylammonium chloride crystals are added to a solution containing lanthanides. By utilizing the hydrophobic effect of nitrogen atoms coordinating with ethyl groups, lanthanides are precipitated, achieving selective enrichment and recovery of lanthanides (lanthanides precipitate, while non-lanthanides do not). When triethylammonium chloride crystals are added to a lanthanide (Ln) ion solution, the triethylammonium chloride crystals undergo deprotonation and coordinate with Ln through a nitrogen donor to form a hydrophobic Ln-(Et3N)x complex, which spontaneously and rapidly precipitates within seconds, achieving the goal of efficient enrichment and recovery of lanthanide elements.

[0015] In one embodiment of the present invention, the ratio of triethylammonium chloride crystals to a solution containing lanthanides is 500-800 mg: 1 L; During the enrichment process, the temperature was 0~30 ℃ and the time was 0~60 min, with the time being >0 min.

[0016] In triethylammonium chloride crystals, nitrogen acts as a coordination site, directly coordinating with lanthanide ions. Due to the hydrophobic effect of the ethyl group in triethylamine, lanthanide (La) ions are achieved. 3+ 98.30%, Europium (Eu) 3+ 98.70%, Lutetium (Lu 3+ The high recovery adsorption rate of 98.79% indicates that triethylammonium chloride crystals achieve efficient coordination of nitrogen with lanthanides. Combined with the hydrophobic effect of ethyl groups, it exhibits excellent adsorption performance and high-capacity adsorption and enrichment of lanthanides without the need for post-modification to introduce coordinating groups.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention utilizes triethylammonium chloride crystals, a small molecule ligand, to achieve lanthanide enrichment, rather than relying on coordinating groups introduced through post-modification. Hexachlorocyclotriphosphazene (HCCP) is selected as the slow-release agent for HCl, and triethylammonium chloride crystals are prepared via a solvothermal method. In application, triethylammonium chloride serves as a dynamic coordination medium, in which nitrogen atoms interact with lanthanide ions (Ln... 3+ Coordination forms hydrophobic complexes and spontaneously and rapidly precipitates within seconds; the coordination process releases chloride and hydrogen ions to promote coordination, and the ethyl chain creates a hydrophobic microenvironment, promoting molecular aggregation and spontaneous phase separation, achieving efficient enrichment and separation of lanthanide ions, and is well compatible with the coordination requirements of lanthanide elements.

[0018] (2) The present invention provides a simple preparation method for triethylammonium chloride crystals, which only requires hexachlorocyclotriphosphazene, DMF and triethylamine to be obtained by solvothermal reaction; triethylammonium chloride crystals are used as entropy-driven coordination-induced phase separation materials to achieve precipitation of lanthanide ion complexes without solvent extraction, thus simplifying the operation.

[0019] (3) Hexachlorocyclotriphosphazene and triethylamine are inexpensive bulk industrial raw materials, facilitating their industrial application. Compared with other lanthanide enrichment and separation strategies, the triethylammonium chloride crystal strategy of this invention has advantages such as high adsorption capacity and fast adsorption rate. The maximum adsorption capacity for europium (Eu) can reach 426.25 mg / g. 3+ At an initial concentration of 100 mg / L, adsorption equilibrium can be reached in just 10 seconds. Attached Figure Description

[0020] Figure 1The image shows a comparison between the triethylammonium chloride crystals prepared in Example 1 and the simulated X-ray diffraction (PXRD).

[0021] Figure 2 The image shows the adsorption isotherms of the triethylammonium chloride crystals prepared in Example 1 for five lanthanide elements.

[0022] Figure 3 The adsorption kinetics of europium (Eu) on triethylammonium chloride crystals prepared in Example 1 and the fitting curve of the kinetic model are shown.

[0023] Figure 4 The partition coefficient K of triethylammonium chloride crystals prepared in Example 1 for europium (Eu) and different competing ions is given. d picture.

[0024] Figure 5 The diagram shows the separation factor (SF) of triethylammonium chloride crystals prepared in Example 1 against europium (Eu) and different competing ions.

[0025] Figure 6 The graph shows the adsorption recovery rate of 200 mg / L europium (Eu) on the triethylammonium chloride crystals prepared in Example 1 under different pH conditions.

[0026] Figure 7 This is a schematic diagram of the coordination structure formed by triethylammonium chloride crystals prepared in Example 1 and europium (Eu). Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0028] In the following examples, hexachlorocyclotriphosphazene (HCCP) was used as a slow-release agent for HCl to prepare triethylammonium chloride crystals via a solvothermal method; the metal solutions of lanthanum (La), neodymium (Nd), europium (Eu), dysprosium (Dy), lutetium (Lu), aluminum (Al), iron (Fe), zinc (Zn), copper (Cu), and nickel (Ni) were all corresponding nitrate metal solutions; unless otherwise specified, all other reagents used were commercially available reagents, and all detection methods and techniques used were conventional detection methods and techniques in the art.

[0029] Example 1 This embodiment provides a method for preparing triethylammonium chloride crystals, as detailed below: (S1) Dissolve hexachlorocyclotriphosphazene (0.25 mmol, 86.9 mg) in 1.5 mL of N,N-dimethylformamide and sonicate for 30 s to obtain a mixed solution; (S2) Add 0.1 mL of triethylamine to the mixed solution prepared in step (S1) and sonicate for 10 s to obtain the reaction mixture; (S3) The reaction mixture obtained in step (S2) is placed in a reaction vessel and heated to 40 °C in an oven for 6 h. After the reaction is complete, the solid is collected, washed 5 times with tetrahydrofuran, and dried under vacuum at 60 °C for 12 h to obtain triethylammonium chloride crystals, the chemical structure of which is shown below: ; The X-ray diffraction and simulated X-ray diffraction comparison images of the triethylammonium chloride crystals prepared in this embodiment are shown below. Figure 1 As shown.

[0030] Figure 1 The results include X-ray diffraction experiments and simulations of triethylammonium chloride crystals. The nearly identical results indicate the successful preparation of triethylammonium chloride crystals.

[0031] Example 2 This embodiment provides a method for preparing triethylammonium chloride crystals, as detailed below: (S1) Dissolve hexachlorocyclotriphosphazene (0.25 mmol, 86.9 mg) in 1.5 mL of N,N-dimethylformamide and sonicate for 30 s to obtain a mixed solution; (S2) Add 0.1 mL of triethylamine to the mixed solution prepared in step (S1) and sonicate for 10 s to obtain the reaction mixture; (S3) The reaction mixture obtained in step (S2) is placed in a reaction vessel and heated to 60 °C in an oven for 12 h. After the reaction is complete, the solid is collected, washed 5 times with tetrahydrofuran, and dried under vacuum at 60 °C for 12 h to obtain triethylammonium chloride crystals.

[0032] Example 3 This embodiment provides a method for preparing triethylammonium chloride crystals, as detailed below: (S1) Dissolve hexachlorocyclotriphosphazene (0.25 mmol, 86.9 mg) in 1.5 mL of N,N-dimethylformamide and sonicate for 30 s to obtain a mixed solution; (S2) Add 0.1 mL of triethylamine to the mixed solution prepared in step (S1) and sonicate for 10 s to obtain the reaction mixture; (S3) The reaction mixture obtained in step (S2) is placed in a reaction vessel and heated to 100 °C in an oven for 24 h. After the reaction is complete, the solid is collected, washed 5 times with tetrahydrofuran, and dried under vacuum at 60 °C for 12 h to obtain triethylammonium chloride crystals.

[0033] Example 4 This embodiment provides a method for preparing triethylammonium chloride crystals, as detailed below: (S1) Dissolve hexachlorocyclotriphosphazene (0.25 mmol, 86.9 mg) in 1.5 mL of N,N-dimethylformamide and sonicate for 30 s to obtain a mixed solution; (S2) Add 0.1 mL of triethylamine to the mixed solution prepared in step (S1) and sonicate for 10 s to obtain the reaction mixture; (S3) The reaction mixture obtained in step (S2) is placed in a reaction vessel and heated to 60 °C in an oven for 12 h. After the reaction is complete, the solid is collected, washed 5 times with tetrahydrofuran, and dried under vacuum at 60 °C for 12 h to obtain triethylammonium chloride crystals.

[0034] Example 5 This embodiment provides the application of triethylammonium chloride crystals in the recovery of lanthanide elements, specifically including the following steps: 10 mg of triethylammonium chloride crystals (prepared in Example 1) were weighed and added to 10 mL of solutions of different concentrations of lanthanides (La, Nd, Eu, Dy, and Lu, respectively). The solutions were then shaken on a constant temperature shaker (25°C, 200 rpm) for 60 minutes. After the reaction, the solutions were centrifuged and filtered through a 0.22 μm nylon membrane. The content of lanthanides in the filtrate was measured by ICP-OES (results are shown in Figure 1). Figure 2 The equilibrium adsorption capacity (Q) is calculated using formula (1). e ): Formula (1); In the formula: V (L) is the volume of the solution, m (g) is the mass of the adsorbent, and C0 (mg / L) is the concentration of metal ions in the solution before adsorption; C e (mg / L) represents the concentration of metal ions in the solution after adsorption.

[0035] Table 1. Triethylammonium chloride crystals prepared in Example 1 and existing adsorbents for Eu 3+ Comparison of ion adsorption capacity and adsorption kinetics pass Figure 2It can be observed that the maximum adsorption capacity of triethylammonium chloride crystals prepared in Example 1 for europium (Eu), a lanthanide element, reaches 426.25 mg / g. Combined with Table 1, it can be seen that the triethylammonium chloride crystals prepared in this example have advantages such as large adsorption capacity and fast adsorption kinetics compared with adsorbents reported in existing literature. In contrast, commercially available triethylammonium chloride powder (CAS: 554-68-7) cannot form a precipitate and therefore cannot recover lanthanide elements. The maximum adsorption capacity of triethylammonium chloride crystals prepared in Example 1 for lanthanum (La) reaches 388.44 mg / g; the maximum adsorption capacity for neodymium (Nd) reaches 409.43 mg / g; the maximum adsorption capacity for dysprosium (Dy) reaches 456.74 mg / g; and the maximum adsorption capacity for lutetium (Lu) reaches 494.16 mg / g.

[0036] Example 6 This embodiment provides the application of triethylammonium chloride crystals in the recovery of lanthanide elements, specifically including the following steps: 10 mg of triethylammonium chloride crystals (prepared in Example 1) were weighed and added to 10 mL solutions of different concentrations of lanthanides (La, Nd, Eu, Dy, and Lu) and different concentrations of non-lanthanides (Al, Fe, Zn, Cu, and Ni). The solutions were then reacted on a constant-temperature shaker (25 °C, 200 rpm) for 60 minutes. After the reaction, the solutions were centrifuged and filtered through a 0.22 μm nylon membrane. The lanthanide content in the filtrate was measured using ICP-OES.

[0037] Table 2 Summary of the results of lanthanide element recovery from triethylammonium chloride crystals Comparative Example 1 This comparative example provides a method for preparing triethylamine hydrochloride using HCl, triethylamine, and DMF, as detailed below: (S1) Add 0.1 mL of triethylamine and 1.5 mL of N,N-dimethylformamide and sonicate for 30 s to obtain a mixed solution; (S2) Add 0.125 mL of 12 mol / L HCl to the mixed solution prepared in step (S1), and react at 120 °C for 12 h to obtain the reactant; (S3) The reactants obtained in step (S2) are filtered and dried to obtain a white solid.

[0038] When the white solid obtained in step (S3) was mixed with a 50 mg / L lanthanum ion solution, it was found that the white solid had no adsorption effect on lanthanum ions.

[0039] Example 7 This embodiment provides the application of triethylammonium chloride crystals in the recovery of lanthanide elements, specifically including the following steps: 50 mg of triethylammonium chloride crystals (prepared in Example 1) were weighed and added to 10 mL of 100 mg / L europium (Eu) solution. The mixture was then shaken on a constant temperature shaker (25 °C, 200 rpm) for 10 s, 30 s, 1 min, 2 min, 3 min, 4 min, 5 min, and 10 min respectively. After the reaction was completed, the mixture was centrifuged and filtered through a 0.22 μm nylon membrane. The lanthanide content in the filtrate was measured using ICP-OES.

[0040] The adsorption kinetics of europium (Eu) on triethylammonium chloride crystals and the fitting curve of the kinetic model are shown in the figure below. Figure 3 As shown, through Figure 3 It can be observed that when Eu 3+ At an initial concentration of 100 mg / L, the triethylammonium chloride crystals prepared in Example 1 achieved the desired effect on Eu in just 10 seconds. 3+ Adsorption equilibrium.

[0041] Example 8 This embodiment provides the application of triethylammonium chloride crystals in the recovery of lanthanide elements, specifically including the following steps: Weigh 50 mg of triethylammonium chloride crystals (prepared in Example 1) and add them to 10 mL of a 1000 mg / L europium (Eu) solution (wherein the Eu solution contains Cs, Sr, K, Ca, Na, and Mg at a final concentration of 100 mg / L). The mixture is then shaken on a constant temperature shaker (25 ℃, 200 rpm) for 60 minutes. After the reaction, the mixture is centrifuged and filtered through a 0.22 μm nylon membrane. The contents of Eu, Cs, Sr, K, Ca, Na, and Mg in the filtrate are measured using ICP-OES, and the distribution coefficients of the triethylammonium chloride crystals for each ion are calculated (e.g., ...). Figure 4 (as shown) and the separation factor of triethylammonium chloride crystals for Eu (e.g.) Figure 5 (As shown).

[0042] Figure 4 This indicates that the distribution coefficient of europium ions is approximately 10. 5 The distribution coefficient of interfering ions is less than 10; Figure 5 This indicates that the distribution coefficient of europium ions to the six interfering ions exceeds 10. 4 . Figure 4 and Figure 5The results demonstrate that triethylammonium chloride crystals exhibit excellent selectivity for europium ions.

[0043] Example 9 This embodiment provides the application of triethylammonium chloride crystals in the recovery of lanthanide elements, specifically including the following steps: 50 mg of triethylammonium chloride crystals (prepared in Example 1) were weighed and added to 10 mL of 200 mg / L europium (Eu) solutions at different pH values ​​(pH 1, 2, 3, 4, 5, and 6). The solutions were then shaken on a constant-temperature shaker (25 °C, 200 rpm) for 60 minutes. After the reaction, the solutions were centrifuged and filtered through a 0.22 μm nylon membrane. The Eu content in the filtrate was measured using ICP-OES, and the recovery rate of triethylammonium chloride crystals under different pH conditions was calculated (e.g., Figure 6 (As shown).

[0044] Figure 6 The results showed that under pH 3–6 conditions, the recovery rate of europium ions by triethylammonium chloride crystals was close to 100%, while under pH 1–2 conditions, europium ions could not be effectively recovered.

[0045] The triethylammonium chloride crystals prepared in Example 1 precipitate a coordination compound formed after the adsorption of europium (Eu). Simulation results for the precipitation are as follows: Figure 7 As shown, through Figure 7 It can be observed that an Eu 3+ It coordinates with 5 triethylamine molecules, thus forming a hydrophobic complex and a precipitate.

[0046] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the interpretation of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A triethylammonium chloride crystal, characterized in that, The chemical structural formula of the triethylammonium chloride crystal is shown in formula (I): Formula (I) The triethylammonium chloride crystal is composed of triethylammonium cations and chloride ions, with the chemical formula NEt3HCl; each nitrogen atom is bonded to three ethyl groups to form a typical triethylammonium cation, while the chloride ions occupy lattice positions and participate in NH···Cl hydrogen bond interactions. The triethylammonium chloride crystals contain 44.22% chlorine, 35.80% carbon, 9.99% hydrogen, and 9.99% nitrogen.

2. A method for preparing triethylammonium chloride crystals as described in claim 1, characterized in that, Includes the following steps: (S1) Dissolve hexachlorocyclotriphosphazene in a solvent and mix well to obtain a mixed solution; (S2) Triethylamine is added to the mixed solution prepared in step (S1), and the mixture is subjected to a solvothermal reaction and post-treatment to obtain triethylammonium chloride crystals.

3. The method for preparing triethylammonium chloride crystals according to claim 2, characterized in that, In step (S1), the solvent is selected from one of N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, hexamethylphosphoric triamine, or N,N-dimethylacetamide.

4. The method for preparing triethylammonium chloride crystals according to claim 2, characterized in that, In step (S1), the ratio of hexachlorocyclotriphosphazene to solvent is 80-90 mg: 1 mL; The mixture is homogenized by ultrasound for 30-60 seconds.

5. The method for preparing triethylammonium chloride crystals according to claim 2, characterized in that, In step (S2), the molar ratio of triethylamine to hexachlorocyclotriphosphazene is 2~6:

1.

6. The method for preparing triethylammonium chloride crystals according to claim 2, characterized in that, In step (S2), the temperature during the solvothermal reaction is 60~120 ℃ and the time is 8~24 h; The post-processing involves centrifuging to collect the solid, then washing it with tetrahydrofuran and drying it.

7. The method for preparing triethylammonium chloride crystals according to claim 6, characterized in that, During the drying process, the temperature is 50~80 ℃ and the time is 6~24 h.

8. An application of the triethylammonium chloride crystal as described in claim 1 in the recovery of lanthanide elements.

9. A method for recovering lanthanide elements, characterized in that, Includes the following steps: The triethylammonium chloride crystals described in claim 1 are mixed with a solution containing lanthanides to spontaneously form a precipitate, thereby achieving selective enrichment and recovery of lanthanides.

10. A method for recovering lanthanide elements according to claim 9, characterized in that, The ratio of triethylammonium chloride crystals to lanthanide-containing composite materials is 500-800 mg: 1 L; During the enrichment process, the temperature was 0~30 ℃ and the time was 0~60 min, with the time being >0 min.

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