Preparation method of phosphonate-modified acylhydrazone covalent organic polymer and application of the phosphonate-modified acylhydrazone covalent organic polymer in adsorbing and separating heavy rare earth ions

Abstract

The application discloses a preparation method of phosphonate-modified acylhydrazone covalent organic polymer and application of the phosphonate-modified acylhydrazone covalent organic polymer in adsorbing and separating heavy rare earth ions, and belongs to the field of environmental protection. 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and tetraethyl((2,5-di(hydrazine carbonyl)-1,4-phenylene)bis(oxy)bis(ethane-2,1-diyl))bis(phosphonate) are prepared into phosphonate-modified acylhydrazone covalent organic polymer through Schiff base reaction. The acylhydrazone covalent organic polymer is modified with phosphonate functional groups on a skeleton, and can be used for efficient adsorption and separation of heavy rare earth ions in water phase. The preparation method of the phosphonate-modified acylhydrazone covalent organic polymer is simple, has superior adsorption and separation performance for heavy rare earth ions, and is expected to be used as an efficient adsorbent for low-concentration wastewater of ion adsorption type rare earth ore in the south.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental protection, and particularly relates to a preparation method of a phosphonate-modified acylhydrazone covalent organic polymer and application of the covalent organic polymer to adsorption and separation of heavy rare earth ions. BACKGROUND

[0002] South ion-adsorption type rare earth ore is the main source of medium and heavy rare earth in China, and is affected by rainwater leaching and the like. A large amount of low-concentration rare earth wastewater is generated in such a mine area. The content of rare earth ions in the low-concentration wastewater can reach 50 mg / L. If the low-concentration wastewater is directly discharged into the environment without treatment, not only the valuable rare earth resources will be wasted, but also the surrounding ecological environment will be seriously harmed. The current common low-concentration rare earth wastewater treatment methods mainly include solvent extraction, ion exchange, chemical precipitation, membrane separation, microbial method, and adsorption method. Among them, the adsorption method is a very promising treatment method due to its low cost, simple and convenient operation, and high efficiency.

[0003] Covalent organic polymers (COPs) are organic polymers composed of carbon and other heteroatoms such as boron, oxygen, nitrogen, sulfur, phosphorus, etc. connected by strong covalent bonds. The unique physical and chemical properties of COPs make them widely used in many fields. At the same time, the coordination ability of functional groups in the material to target metal ions has always been a key characteristic in the application of nanomaterials in metal ion adsorption. According to the HSAB theory, the phosphonate functional group has a higher affinity and selectivity to heavy rare earth ions than carboxyl, amino, hydroxyl, and sulfonic acid groups.

[0004] Therefore, in this study, the phosphonate functional group is introduced into the COPs material to prepare a phosphonate-modified acylhydrazone covalent organic polymer for adsorption and separation of rare earth ions. The experimental results prove that the prepared covalent organic polymer has a very high distribution coefficient for heavy rare earth ions, and is expected to be used as a high-efficiency adsorbent for low-concentration wastewater of south ion-adsorption type rare earth ore. SUMMARY

[0005] The present application aims to provide a preparation method of phosphonate-modified acylhydrazone covalent organic polymer and its application in adsorbing and separating heavy rare earth ions. The present application prepares a phosphonate-modified acylhydrazone covalent organic polymer through Schiff base reaction between 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and tetraethyl((2,5-bis(hydrazylcarbonyl)-1,4-phenylene)bis(oxy)bis(ethane-2,1-diyl))bis(phosphonate). The acylhydrazone covalent organic polymer has phosphonate functional groups modified on the skeleton, and can be used for efficient adsorption and separation of heavy rare earth ions in water phase. The acylhydrazone covalent organic polymer prepared by the present application has simple preparation method and superior adsorption and separation performance for heavy rare earth ions, and can be used as an efficient adsorbent for low-concentration tail water of southern ionic rare earth ore.

[0006] The present application provides a preparation method of phosphonate-modified acylhydrazone covalent organic polymer, comprising the following steps:

[0007] 1) 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and tetraethyl((2,5-bis(hydrazylcarbonyl)-1,4-phenylene)bis(oxy)bis(ethane-2,1-diyl))bis(phosphonate) are used as raw materials, a solvent is added, and ultrasonic treatment is performed to obtain a reaction mixture;

[0008] 2) The container containing the reaction mixture is degassed through freeze-thaw cycle, sealed by flame, heated at 100-200℃ for 3-7 days, cooled, filtered to collect the precipitate, and dried and washed to obtain the phosphonate-modified acylhydrazone covalent organic polymer.

[0009] Further, the mass ratio of tetraethyl((2,5-bis(hydrazylcarbonyl)-1,4-phenylene)bis(oxy)bis(ethane-2,1-diyl))bis(phosphonate) to 2,4,6-tris(4-formylphenyl)-1,3,5-triazine in step 1) is (1-2):1.

[0010] Further, the solvent in step 1) comprises 1,4-dioxane, 1,3,5-trimethylbenzene and acetic acid, and the volume ratio of the three is (1-5):(5-15):1; the concentration of the acetic acid is 6 M.

[0011] The present application also provides the application of the phosphonate-modified acylhydrazone covalent organic polymer obtained by the above preparation method in adsorbing and separating heavy rare earth ions.

[0012] Further, the heavy rare earth ions are at least one of Ho 3+ , Er 3+ , Tm 3+ , Yb 3+ , Lu 3+ , Y 3+ .

[0013] Further, the phosphonate-modified acylhydrazone covalent organic polymer has the highest distribution coefficient for lutetium ions in the process of adsorbing and separating heavy rare earth ions.

[0014] Compared with the prior art, the present application has the beneficial effects of:

[0015] 1. The phosphonate-modified acylhydrazone covalent organic polymer is synthesized by a one-step method, and the preparation method is simple, and the prepared product can be used for adsorbing and separating rare earth ions without post-treatment.

[0016] 2. The acylhydrazone covalent organic polymer prepared by the present application first introduces a phosphonate functional group in COPs materials.

[0017] 3. The acylhydrazone covalent organic polymer prepared by the present application introduces a phosphonate functional group with high affinity for rare earth ions through monomers, thereby improving the affinity for rare earth ions.

[0018] 4. The acylhydrazone covalent organic polymer prepared by the present application has a very high distribution coefficient for heavy rare earth ions in the process of adsorbing and separating rare earth ions.

[0019] 5. The acylhydrazone covalent organic polymer prepared by the present application realizes efficient adsorption and separation of rare earth ions, and can be used as an efficient adsorbent for low-concentration tail water of southern ionic rare earth ore. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a preparation process schematic diagram of COP-TFPT-TBBP.

[0021] Figure 2 is an infrared spectrum diagram of TFPT, TBBP and COP-TFPT-TBBP.

[0022] Figure 3 is an XPS full spectrum diagram of COP-TFPT-TBBP.

[0023] Figure 4 is a distribution coefficient diagram of COP-TFPT-TBBP for heavy rare earth ions.

[0024] Figure 5 is an XPS full spectrum diagram of COP-TFPT-TBBP after adsorbing lutetium ions. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with embodiments. If specific conditions are not indicated in the embodiments, conventional conditions or conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, they are all conventional products that can be purchased on the market.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0027] Example 1: Preparation and characterization of phosphonate-modified acylhydrazone covalent organic polymer

[0028] A pyrex tube was charged with tetraethyl ((2,5-di(hydrazinocarbonyl)-1,4- phenylene)bis(oxy)bis(ethane-2,1-diyl))bis(phosphonate) (TBBP, 41.5 mg), 2,4,6- tris(4-formylphenyl)-1,3,5-triazine (TFPT, 8 mg), 1,4-dioxane (0.5 mL) and 1,3,5- trimethylbenzene (1.5 mL), and sonicated for 10 min, then 6 M acetic acid solution (0.2 mL) was added to obtain a reaction mixture; the pyrex tube containing the reaction mixture was degassed by three freeze-pump-thaw cycles, then flame-sealed and heated in an oven at 120 ℃ for 3 days, after cooling, the obtained light yellow solid product was washed with N,N-dimethylformamide (DMF), 1,4-dioxane (Diox), acetone (Acetone) for three times, and the solid was collected and dried at 80 ℃ under vacuum for 12 hours to obtain the phosphonate-modified acylhydrazone covalent organic polymer (COP-TFPT-TBBP).

[0029] Figure 1 is a schematic diagram of the preparation process of the phosphonate-modified acylhydrazone covalent organic polymer COP-TFPT-TBBP.

[0030] Figure 2 is the infrared spectrum of TFPT, TBBP and COP-TFPT-TBBP, wherein Figure 2 It can be seen that the aldehyde group HC=O in TFPT is located at 1702 cm -1 , the carbonyl group C=O in TBBP is located at 1682 cm -1 , and the newly generated C=N double bond after the Schiff base reaction is located at 1658 cm -1 , proving the successful preparation of COP-TFPT-TBBP.

[0031] Figure 3 is the XPS full spectrum of COP-TFPT-TBBP, which is Figure 3 It can be seen that the C 1s, N 1s, O 1s, P 2s, P 2p peaks in the XPS full spectrum are clear, which further proves the successful preparation of COP-TFPT-TBBP.

[0032] Example 2: High-efficiency adsorption and separation of phosphonate-modified acylhydrazone covalent organic polymers for heavy rare earth ions

[0033] The adsorption and separation performance of COP-TFPT-TBBP as an adsorbent for heavy rare earth ions (Ho 3+ , Er 3+ , Tm 3+ , Yb 3+ , Lu 3+ , Y 3+ ) was investigated. In 5 mL of a mixed solution of heavy rare earth ions, 5 mg of COP-TFPT-TBBP was added, stirred for 12 h, filtered with a 0.22 μm microporous filter, and the content of rare earth ions in the filtrate was measured by inductively coupled plasma emission spectrometry. The distribution coefficient of COP-TFPT-TBBP for rare earth ions was calculated, and the affinity of the material for rare earth ions was studied. Figure 4 is the distribution coefficient diagram of COP-TFPT-TBBP for heavy rare earth ions. From Figure 4 it can be seen that COP-TFPT-TBBP has a high distribution coefficient for heavy rare earth ions (Ho 3+ , Er 3+ , Tm 3+ , Yb 3+ , Lu 3+ , Y 3+ ), and COP-TFPT-TBBP has the highest affinity for Lu 3+ .

[0034] Example 3: High-efficiency adsorption of phosphonate-modified acylhydrazone covalent organic polymers for lutetium ions

[0035] Figure 5 is the XPS full spectrum of COP-TFPT-TBBP after adsorbing lutetium ions. From Figure 5 it can be seen that COP-TFPT-TBBP has a Lu 4d peak after adsorbing lutetium ions. This is mainly due to the introduction of phosphonate functional groups with high selectivity for heavy rare earth ions in COP-TFPT-TBBP, which can construct efficient heavy rare earth ion capture nanochannels in the material, greatly improving the adsorption performance of the material for heavy rare earth ions.

[0036] The above described embodiments only express several preferred embodiments of the present application, which are described in a more specific and detailed manner, but are not used to limit the present application. It should be noted that the present application can also have various changes and modifications for those skilled in the art, and any modification, equivalent replacement, improvement, etc. made within the concept and principle of the present application shall be included in the protection scope of the present application.

Claims

1. The application of a phosphonate-modified acylhydrazone covalent organic polymer in the adsorption and separation of heavy rare earth ions; The preparation method of the phosphonate-modified acylhydrazone covalent organic polymer includes the following steps: 1) Using 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and tetraethyl((2,5-di(hydrazylcarbonyl)-1,4-phenylene)bis(oxy)bis(ethane-2,1-diethylene))bis(phosphonate) as reactants, a solvent was added and the mixture was ultrasonically treated to obtain a reaction mixture; 2) The container containing the reaction mixture was degassed by a freeze-thaw cycle, sealed with a flame, heated at 100-200℃ for 3-7 days, cooled, filtered, and the precipitate was collected. After drying and washing, the phosphonate-modified acylhydrazone covalent organic polymer was obtained. The heavy rare earth ion is Ho. 3+ Er 3+ Tm 3+ Yb 3+ Lu 3+ Y 3+ At least one of them.

2. The application according to claim 1, characterized in that, In step 1), the molar ratio of tetraethyl((2,5-di(hydrazylcarbonyl)-1,4-phenylene)bis(oxy)bis(ethane-2,1-diethylene))bis(phosphonate) to 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine is (1-2):

1.

3. The application according to claim 1, characterized in that, Step 1) The solvent includes 1,4-dioxane, 1,3,5-trimethylbenzene and acetic acid, with a volume ratio of (1-5):(5-15):1; the concentration of the acetic acid is 6 M.

4. The application according to claim 1, characterized in that, The phosphonate-modified acylhydrazone covalent organic polymer exhibits the highest partition coefficient for lutetium ions during the adsorption and separation of heavy rare earth ions.

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