CN108484929A - A kind of metal organic frame synthesis MIL-53 (Al)-AO based on amidoxime2Preparation method - Google Patents

Abstract

The invention discloses a kind of, and the metal organic frame based on amidoxime synthesizes MIL 53 (Al) AO₂Preparation method, one：With 2 amino terephthalic acid (TPA)s and Al (NO₃)₃·9H₂O is dissolved in DMF and deionized water prepares MIL 53 (Al) NH₂Mixture A1；Two：A1 is washed into impurity with DMF and acrylonitrile respectively and obtains solid product A2；Three：By A2 plus acrylonitrile and Al Cl₃Fully dissolve to obtain intermediate product A3；Four：A3 is distributed in ultra-pure water and alcohol mixeding liquid, K is added₂CO₃And NH₂OHHCl reacts to obtain mixture A4；Five：Vacuum drying is MIL 53 (Al) AO after A4 ethyl alcohol and milli-Q water are filtered and detached₂.Advantageous effect of the present invention：There is provided that a kind of yield is big, and equipment is simple, MIL 53 (Al) AO of easily operated control₂Preparation method；Uranium is carried for uranium-bearing water body, and efficient material is provided.

Description

Preparation of MIL-53(Al)-AO2 Based on Metal-Organic Framework Synthesis of Amidoxime method

technical field

The invention relates to the fields of uranium-containing wastewater and seawater extraction of uranium, in particular to a preparation method for synthesizing MIL-53(Al) _-AO2 based on amidoxime-based metal-organic framework.

Background technique

With the rapid development of the nuclear power industry and the peaceful use of nuclear energy, a large amount of radioactive waste is produced, which contains different types of radionuclides. In addition, some uranium is inevitably released into the natural environment during the production and processing of nuclear fuel. Contamination of dispersed uranium(VI) in uranium tailings is a worldwide concern. Free uranium (VI) ions can accumulate through the food chain and eventually enter the human circulatory system. Radioactive uranium (Ⅵ) ions can destroy biological tissues of the human body. Removing radionuclides from wastewater and releasing them into the natural environment is critical for public health and ecosystem stability.

From the perspective of health and safety, uranium is chemically and radioactively toxic, and uranium-containing wastewater has a considerable concentration of uranium that can cause harm to the human body. Therefore, scientific and engineering workers continue to explore new methods to make uranium-containing wastewater recycle and prevent it from harming the human body. The environment wreaks havoc. From the perspective of energy security, uranium is the basic energy for the development of the nuclear industry, which can reduce greenhouse gas emissions while ensuring energy security. Research and synthesis of new stable and efficient adsorbents, by placing the adsorbent in aqueous solution to adsorb uranium in aqueous solution, and study the adsorption capacity, stability, adsorption mechanism, etc. of the adsorbent, so as to provide possible research directions for seawater extraction of uranium.

The main components of dissolved elements in seawater are Cl, Na, Mg, S, Ca, Br, C, Sr, B, and their proportion exceeds 99.9%. Trace amounts of uranium ions are also present in seawater. Depending on the average salt content in seawater (about 3.5%), the total salt concentration is 10 ⁶ -10 ⁷ times the uranium content. Uranium in aqueous media has a long half-life, complex coordination chemistry, and several stable oxidation states. The main dissolved state of uranium in seawater is the uranyl tricarbonate complex of hexavalent uranium (U ⁶⁺ ) [UO ₂ (CO ₃ ) ₃ ] ^4– . The speciation of dissolved uranium species in seawater is mainly affected by _CO2 concentration and pH. Therefore, the HCO ₃ ^– /CO ₃ ^2– buffer in seawater is favorable for the formation of uranyl tricarbonate complex [UO ₂ (CO ₃ ) ₃ ] ^4– . This complex is stable at pH≈8, and easily decomposes into [UO ₂ (CO ₃ ) ₂ ] ^2– and [UO ₂ (CO ₃ )] complexes at pH 6–8 and 5–7, respectively . Although the concentration of uranium in seawater is only 3 ppb (-3 mg uranium per cubic meter of seawater), the vast volume of all oceans (approximately 1.37 billion cubic kilometers) contains about 4.5 billion tons of uranium. If 50% of this resource can be recovered, it will be enough to keep the world's nuclear reactors running for about 6,500 years. Among the various actinides, uranium is the main and common fuel for nuclear reactors. Therefore, there is great interest in extracting uranium from seawater and using it as an alternative sustainable energy source.

The traditional methods mainly include chemical precipitation, ion exchange, evaporation concentration, extraction, membrane separation, electrochemistry, sedimentation crystallization, coagulation flocculation and adsorption. The adsorption method has the characteristics of wide application range, high efficiency and high enrichment efficiency, and is very suitable for the separation of uranium in uranium-containing wastewater and the enrichment of uranium in seawater. However, due to the low selective adsorption capacity of most adsorbents at present, it is not conducive to the extraction and reuse of uranium in wastewater.

The amidoxime functional group contains both an oxime group and an amino group, and its unbonded lone pair of electrons coordinates with uranyl ions to form a chelate. Since the amidoxime group has a strong chelating effect on uranium, it can be applied to modify inorganic nano-materials and polymers to improve the adsorption capacity of the adsorbent for uranium. Because the specific surface area, pore volume, and metal content of metal organic frameworks have considerable advantages, and metal organic frameworks can be modified according to the purpose of the experiment after the synthesis is completed under simple experimental conditions. At the same time, the amidoxime-based compound has a strong complexing ability for uranium, and the amidoxime-based functional group provides a new breakthrough in improving the adsorption capacity of adsorbents for uranium by metal-organic frameworks.

Contents of the invention

Aiming at the problems existing in the existing adsorption, enrichment and separation of uranium metal ions, the present invention provides a high-yield The preparation method of MIL-53(Al)-AO ₂ is simple in equipment, easy to operate and control, and exhibits efficient selective adsorption effect on uranium in water. MIL-53(Al)-AO ₂ is a metal-organic framework material that introduces amidoxime groups.

In order to achieve the above object, the technical solution adopted in the present invention is: a kind of preparation method based on the metal organic framework of amidoxime synthesis MIL-53(Al)-AO , _the steps are as follows:

(1) Dissolve 0.56g of 2-aminoterephthalic acid and 1.125g of Al(NO ₃ ) ₃ ·9H ₂ O in a mixed liquid of 80mL NN dimethylformamide DMF and 20mL deionized water, and stir thoroughly The mixed liquid was placed in a 200mL polytetrafluoroethylene-lined stainless steel reaction kettle, and the reaction kettle was placed in a vacuum drying oven and adjusted to 150°C for 24 hours of reaction. After the reaction was completed, it was naturally cooled to room temperature. A polytetrafluoroethylene microporous membrane with a pore size of μm was suction-filtered and washed repeatedly with DMF solution to obtain a mixture A1 containing MIL-53(Al)-NH ₂ . (2) Place the mixture A1 in the step (1) in a round-bottomed flask, add DMF again to wash the impurities, heat and reflux with a reflux device to remove the residual 2-aminoterephthalic acid in the sample channel, and use a suction filter pump and filter Membrane suction filtration makes its solid-liquid separation, and then washes DMF repeatedly with acrylonitrile suction filtration, puts into vacuum drying oven and obtains MIL-53(Al)-NH ₂ solid product A2; (3) step (2 ) The obtained solid product A2 was placed in a 200mL polytetrafluoroethylene-lined stainless steel reaction kettle, and 100mL acrylonitrile and 0.5g _AlCl were added to fully dissolve and react at a constant temperature of 75°C for 48h, then cooled to room temperature, and filtered with a suction pump and membrane suction filtration to obtain MIL-53(Al)-N(CN) ₂ , which is the intermediate product A3; (4) distribute the intermediate product A3 obtained in step (3) in 10mL ultrapure water and 90mL ethanol mixed solution, and then Add 1.0g K ₂ CO ₃ and 1.0g NH ₂ OH·HCl and stir well to dissolve. Under sealed conditions, stir magnetically and heat to 80°C for 48 hours, then cool to room temperature, and use suction filtration pump and filter membrane to obtain MIL-53( Al)-AO mixture A4; (5) the solid product A4 of step (4), was washed with ethanol and ultrapure water and suction filtered to separate the solid product, and dried in vacuum at 60° _C for 24h to obtain MIL-53 ( Al)-AO ₂ .

The beneficial effect of the present invention is: aiming at the current uranium-containing wastewater treatment and seawater extraction of uranium, the present invention provides a kind of amidoxime with large output, simple equipment and easy operation and control to synthesize MIL-53(Al)- Preparation method of _AO2 . The introduction of the amidoxime group, combined with the fast adsorption speed of the amidoxime group and the properties of high uranium (VI) loading capacity, can also improve the high-efficiency selectivity and retention adsorption capacity for uranium in the case of a smaller specific surface area. The invention provides a high-efficiency material for extracting uranium from uranium-containing water bodies.

Description of drawings

Figure 1 is a synthetic route diagram of MIL-53(Al)-AO ₂ ;

Figure 2 is the SEM images of MIL-53(Al)(A), MIL-53(Al)-NH ₂ (B) and MIL-53(Al)-AO ₂ (C);

Fig. 3 is the _N2 physical adsorption-desorption curve of MIL-53(Al) _-AO2 .

Detailed ways

Below in conjunction with specific embodiment the present invention is described in further detail:

Step S1: Dissolve 0.56g of 2-aminoterephthalic acid and 1.125g of Al(NO ₃ ) ₃ ·9H ₂ O in a mixed liquid of 80mL NN dimethylformamide DMF and 20mL deionized water, and stir thoroughly The mixed liquid was placed in a 200mL polytetrafluoroethylene-lined stainless steel reaction kettle, and the reaction kettle was placed in a vacuum drying oven and adjusted to 150°C for 24 hours of reaction. After the reaction was completed, it was naturally cooled to room temperature. A polytetrafluoroethylene microporous membrane with a pore size of μm was suction-filtered and washed repeatedly with DMF solution to obtain a mixture A1 containing MIL-53(Al)-NH ₂ .

Step S2: Put the mixture A1 in step S1 in a round-bottomed flask, add DMF again to wash the impurities, heat and reflux with a reflux device to remove the residual 2-aminoterephthalic acid in the sample channel, and use a suction filter pump and a filter membrane to pump Filtrate to separate the solid from the liquid, then repeatedly wash with acrylonitrile to remove DMF by suction filtration, and then dry in a vacuum oven to obtain the solid product _A2 of MIL-53(Al)-NH ;

Step S3: Put the solid product A2 obtained in step S2 into a 200mL polytetrafluoroethylene-lined stainless steel reactor, add 100mL acrylonitrile and 0.5g _AlCl3 to fully dissolve and react at a constant temperature of 75°C for 48h, then cool to room temperature , using suction filtration pump and filter membrane to obtain MIL-53(Al)-N(CN) ₂ , which is the intermediate product A3;

Step S4: Distribute the intermediate product A3 obtained in step S3 in 10 mL of ultrapure water and 90 mL of ethanol mixture, then add 1.0 g of K ₂ CO ₃ and 1.0 g of NH ₂ OH·HCl and stir to dissolve, stir magnetically under sealed conditions and heat to React at 80°C for 48h, then cool to room temperature, and filter with a suction filter pump and filter membrane to obtain a mixture A4 containing MIL-53(Al)-AO ₂ ;

Step S5: The solid product A4 in step S4 was washed with ethanol and ultrapure water and filtered to isolate the solid product, and dried in vacuum at 60°C for 24 hours to obtain MIL-53(Al)-AO ₂ .

As shown in Figure 1, the synthesis route of MIL-53(Al)-AO ₂ shows that the amidoxime functional group can be directly grafted on the MIL by using a series of relatively simple and convenient cyanoethylation reaction synthesis methods without harsh experimental conditions. On the benzene ring of -53(Al)-NH ₂ .

As shown in Figure 2, the scanning electron microscope image (SEM) was obtained by an EPMA-8705QH2 scanning electron microscope, and the sample material needs to be sprayed with gold for 60s before the SEM characterization. According to the scanning electron microscope images of MIL-53(Al) and MIL-53(Al)-NH ₂ , the particles are relatively dispersed without agglomeration. At the same time, the scanning electron microscope images show that MIL-53(Al)-NH ₂ and MIL The spatial size of -53(Al)-AO ₂ did not change significantly, indirectly indicating that the crystal shape of the amidoxime group did not change significantly during the process of introducing the amidoxime group into MIL-53(Al)-NH ₂ .

As shown in Figure 3, the nitrogen adsorption and desorption curve is obtained by the American Canta Nova Win pore size analyzer, and the BET specific surface area of MIL-53(Al)-AO2 is calculated to be 179 by using the BET test method to calculate the specific surface area of the adsorbent. ㎡/g, according to literature review, the specific surface area of MIL-53(Al)-NH2 is 1309㎡/g. Generally, the larger the specific surface area of the adsorption material, the greater the adsorption capacity, but the BET specific surface area of MIL-53(Al)-AO2 is smaller than that of MIL-53(Al)-NH2, and the adsorption effect on uranium(Ⅵ) is better. The introduction of the invention amidoxime will have a breakthrough in the adsorption of uranium (Ⅵ).

Claims (3)

1. a kind of metal organic frame based on amidoxime synthesizes MIL-53 (Al)-AO₂Preparation method, include the following steps：

Step S1：With the 2- amino terephthalic acid (TPA) of 0.56g and the Al (NO of 1.125g₃)₃·9H₂O is dissolved in 80mL N-N diformazans In base formamide DMF and 20mL deionized water mixing liquid, mixing liquid is placed in 200mL polytetrafluoroethylene (PTFE) after being sufficiently stirred In the stainless steel cauldron of lining, reaction kettle is placed in temperature regulating in vacuum drying chamber and to 150 DEG C react 24 hours, waits reacting After make its cooled to room temperature, filtered with the polytetrafluoroethylene (PTFE) miillpore filter filter of 0.22 μm of pore size and use DMF solution Washing obtains containing MIL-53 (Al)-NH repeatedly₂Mixture A1；

Step S2：Mixture A1 in step S1 is placed in round-bottomed flask, DMF is added again and washes impurity, with reflux plus Heat reflux removes remaining 2- amino terephthalic acid (TPA) in sample duct, makes its separation of solid and liquid with suction filter pump and filter membrane suction filtration, then With acrylonitrile repeatedly wash suction filtration wash away DMF after, be put into vacuum drying chamber and be dried to obtain MIL-53 (Al)-NH₂Solid product A2；

Step S3：Step S2 obtained solid products A2 is placed in the stainless steel cauldron of 200mL polytetrafluoroethyllining linings, is added 100mL acrylonitrile and 0.5g Al Cl₃Fully dissolving and 48h is reacted at 75 DEG C of constant temperature, postcooling to room temperature, with suction filter pump and Filter membrane filters to obtain MIL-53 (Al)-N (CN)₂, it is intermediate product A3；

Step S4：Intermediate product A3 obtained by step S3 is distributed in 10mL ultra-pure waters and 90mL alcohol mixeding liquids, is added 1.0gK₂CO₃With 1.0g NH₂OHHCl is sufficiently stirred dissolving, and magnetic agitation and 80 DEG C of reaction 48h are heated under air-proof condition, Postcooling filters to obtain containing MIL-53 (Al)-AO to room temperature, with suction filter pump and filter membrane₂Mixture A4；

Step S5：By the solid product A4 of step S4, solid product is filtered and detached with ethyl alcohol and milli-Q water, at 60 DEG C Vacuum drying is for 24 hours to get MIL-53 (Al)-AO₂。

2. a kind of metal organic frame based on amidoxime according to claim 1 synthesizes MIL-53 (Al)-AO₂Preparation Method, it is characterised in that：2- amino terephthalic acid (TPA), Al (NO described in step S1₃)₃·9H₂O, DMF and deionized water ratio are 0.56g：1.125g：80mL：20mL, 150 DEG C of reactions of constant temperature are for 24 hours.

3. the preparation of metal organic frame synthesis MIL-53 (Al)-AO2 based on amidoxime according to claim 1 a kind of Method, it is characterised in that：In step S2,150 DEG C of reflux 8h in 400ml DMF.