JP2022511183A - A method for preparing amidoxime-functionalized hollow porous polymer microbeads using CO2 as an emulsion template. - Google Patents

Abstract

The present invention belongs to the technical field of adsorption-separation functional materials, and relates to a method for preparing an amidoxime-functionalized hollow porous adsorbent using CO2 as an emulsion template. As the step, first, silicon dioxide nanoparticles and MF-HP are prepared, MF-HP and PEA are added to ethyl alcohol, and MF-NH2 is subjected to ultrasonic treatment, water bath reaction, water washing, ethyl alcohol washing and drying. -HP is obtained and added to a glutaaldehyde aqueous solution, and then MF-CHO-HP is obtained through water bath, water washing, alcohol washing and drying, and then added to an ethyl alcohol solution together with DAMN, and then subjected to water bath, water washing, alcohol washing and drying. MF-CN-HP was obtained, added to a mixed solution of water and ethyl alcohol together with hydroxylamine hydrochloride, and after the reaction, water washing, alcohol washing and drying were performed to obtain MF-AO-HPS. The present invention allows the grafted graft PEA to provide a large number of functional spots in subsequent modifications, which, coupled with the hollow porous structure, not only improve the adsorption capacity for adsorbing U (VI). Further accelerated mass transfer dynamics. [Selection diagram] Fig. 1

Description

The present invention belongs to the technical field of preparing an adsorption / separation functional material, and specifically relates to a method for preparing an amidoxime-functionalized hollow porous adsorbent using CO ₂ as an emulsion template.

Due to its special use in the nuclear industry, natural uranium resources have already become a strategic resource for the nuclear industry. Uranium stocks exist primarily in seawater as hexavalent uranium (U (VI)) and have been shown to be approximately 4.5 billion tonnes, i.e., seawater is a potential source of uranium resources. Extracting large amounts of uranium from seawater is relatively difficult, so its widespread application is very limited. Uranium located in seawater is not only harmful to both humans and the environment, but also extremely dangerous because of its radioactive and chemical toxicity. Therefore, extracting uranium from seawater is not only economically valuable, but also significant in terms of environmental protection and scientific development. As a method for extracting U (VI) from seawater, a plurality of methods are known, and examples thereof include an electrodialysis method, an extraction method, a chemical precipitation method, an organic-inorganic ion exchange method, and an adsorption separation method. As a mature technique, the adsorption method, which has the advantages of high adsorption efficiency, low preparation cost, low amount of secondary pollution, and easy operation, has already been widely applied to the extraction of uranium from seawater. However, uranium extraction from seawater has faced enormous challenges, including low concentrations (about 3.3 ppb), the presence of large amounts of competitive ions, and complex chemical and biological environments. In order to effectively extract U (VI) from seawater, there is an urgent need to develop an environmentally friendly, highly selective and highly efficient adsorbent.

There are a plurality of types of adsorbents used for ion extraction, and among them, the hollow porous adsorbent (HPS) has attracted widespread attention because of its low density, clear structure, and strong loading capacity. The Pickering emulsion template method is one of the most widely used methods for preparing hollow porous adsorbents. Due to its special configuration, the amidoxime group can achieve the effect of selective adsorption by coordinating with U (VI). By utilizing this principle, the surface of the material can be modified with an amidoxime group to impart its ability of U (VI) selective adsorption.

When using traditional Pickering emulsion template methods, the elution process of the internal phase is generally complicated, the use of organic solvents causes severe environmental problems, size control is limited, size is relatively large, etc. There is a shortage. Not only are there a large number of functional spots inside the polymer and the mass transfer rate is slow because the functional monomers are directly involved in the polymerization, but some functional spots cannot participate in the reaction, resulting in more loss than necessary. Will wake up. In order to avoid the above shortage, it is necessary to consider new materials and apply them to the selective extraction of uranium.

In response to the lack of prior art, an object of the present invention is to overcome problems such as difficulty in elution of the internal phase and difficulty in controlling the structure when preparing by the conventional Pickering emulsion template method, and selectively select an amidoxime group. Hollow porous by amdoxime functionalized underwater gas emulsion template method to prepare a hollow porous adsorbent (MF-AO-HPS) with a ligand, a melamine-formaldehyde resin as a matrix, and an amidoxim functional group grafted on the surface. To provide a method of preparing an adsorbent.

The technical means adopted in the present invention in order to achieve the above-mentioned technical object is as follows.

(1) Preparation of silicon dioxide nanoparticles A certain amount of tetraethyl orthosilicate (TEOS) is added to ethyl alcohol, heated in a water bath to raise the temperature, and then a certain amount of a mixed solution of _NH3・_H2O and water is dropped. Then, the formed mixed solution was reacted under magnetic stirring for a certain period of time, and after the reaction was completed, the product was collected by centrifugation, washed three times with deionized water and ethyl alcohol, and dried to dry silicon dioxide nanoparticles. Got

(2) Preparation of Hollow Porous Melamine-Formaldehyde Resin The silicon dioxide nanoparticles obtained in the step (1) are dispersed in deionized water to obtain a silicon dioxide aqueous dispersion, and then melamine is obtained under constant temperature conditions. To the mixed solution of formaldehyde solution and glutaaldehyde solution, adjust the pH of the mixed solution, stir and continue to react for a certain period of time after the solution becomes milky white to clear, and after the reaction, dioxide under stirring conditions. A silicon aqueous dispersion is added to react, and after the reaction, the reaction is cooled to a certain temperature, the pH is adjusted again, and then the reaction is carried out. After the reaction, the polymerization reaction is carried out under water bath conditions, and finally, the product is centrifuged. Collect, wash with deionized water and ethyl alcohol, dry to obtain powder sample, add powder sample to hydrofluoric acid solution for etching, centrifuge to collect product, wash with deionized water and ethyl alcohol The product was collected by centrifugation again and dried to obtain a hollow porous melamine-formaldehyde resin (denoted as MF-HP).

(3) MF-HP and polyethylenepolyamine (PEA) prepared in step (2) are dispersed in ethyl alcohol to obtain a mixed solution A, which is then subjected to ultrasonic treatment, and the mixed solution A is bathed under magnetic stirring conditions. After the reaction, the product was washed with ethyl alcohol and then centrifuged again to collect the product. Hollow porous melamine-formaldehyde resin polymer micro with amino groups grafted on the surface. Beads (denoted as MF-NH ₂ -HP) were obtained, and MF-NH ₂ -HP and glutaaldehyde were added to ethyl alcohol to obtain a mixed solution B, and then the mixed solution B was placed in a water bath condition under magnetic stirring. After the reaction is completed, the products are washed with deionized water and ethyl alcohol, respectively, and collected by centrifugation. Hollow porous melamine-formaldehyde resin polymer microbeads (MF-CHO-HP) grafted with aldehyde groups on the surface. I write).

(4) MF-CHO-HP prepared in step (3) and diaminomalononitrile (DAMN) were suspended in 40 to 60 mL of ethyl alcohol E to obtain a mixed solution C, which was then subjected to ultrasonic treatment. The mixed solution C is placed in a water bath condition under magnetic stirring to react, and after the reaction, it is centrifuged to obtain a hollow porous melamine-formaldehyde resin (denoted as MF-CN-HP) grafted with a nitrile group on the surface, and finally, Ethyl alcohol F is added to deionized water to obtain a mixed solution of ethyl alcohol and water, MF-CN-HP and hydroxylamine hydrochloride are added to the mixed solution, the pH is adjusted, and then the reaction is carried out under water bath conditions. After that, the product was collected by centrifugation, washed with deionized water and ethyl alcohol, and dried to obtain amidoxim functionalized hollow porous melamine-formaldehyde resin microbeads (denoted as MF-AO-HPS).

By the same method as in step (3), MF-HP was used instead of MF-CHO-HP to obtain another adsorbent (denoted as MF-nPEA-AO-HPS) in which PEA was not grafted.

Preferably, the dose ratio of the tetraethyl orthosilicate, ethyl alcohol, _NH3・_H2O and water in the step (1) is 8.0 to 10 g: 170 to 190 mL: 9.0 to 11 mL: 9.0 to 10 g. The reaction temperature is 30 to 40 ° C., and the reaction time is 2.0 to 4.0 h.

Preferably, the constant temperature condition in the step (2) is 80 to 90 ° C.

Preferably, the dose ratio of the melamine, the mixed solution of formaldehyde and glutaraldehyde in the step (2), and the silicon dioxide dispersion is 1.0 to 2.0 g: 2.0 to 4.0 mL: 5.0 to 15 mL. The volume fraction of the formaldehyde solution is 37%, the volume fraction of the glutaraldehyde solution is 25%, and the concentration of the silicon dioxide aqueous dispersion is 10 wt%.

Preferably, adjusting the above-mentioned pH in the step (2) is to adjust the pH to 9.0 to 10.0 with the Na ₂ CO ₃ solution, and the concentration of the above-mentioned Na ₂ CO ₃ solution is 2. It is 0M.

Preferably, the stirring condition in the step (2) is 1200 to 1600 rpm, the continuous reaction period is 3.0 to 5.0 min, and the silicon dioxide aqueous dispersion is added. The reaction time is 10 to 30 min.

Preferably, the constant temperature when cooling to the above-mentioned constant temperature in the step (2) is 30 to 50 ° C., and the above-mentioned operation of adjusting the pH again is carried out by dropping HCl having a concentration of 2.0 M to pH. Is adjusted to 5.0 to 6.0, and the reaction time after adjusting the pH again is 10 to 30 min.

Preferably, the temperature of the water bath in the step (2) is 30 to 50 ° C., the time of the polymerization reaction is 3.0 to 5.0 h, the volume concentration of the hydrofluoric acid solution is 2%, and the above. The drying temperature is 60 to 80 ° C.

Preferably, the dose ratio of the above MF-HP, polyethylene polyamine and ethyl alcohol in the step (3) is 0.3 to 0.5 mg: 3.0 to 5.0 g: 40 to 60 mL.

Preferably, the ultrasonic treatment time in the step (3) is 5.0 to 10 min, the temperature of the water bath of the mixed solution A is 30 to 40 ° C., and the reaction time is 8.0 to 16 h.

Preferably, the dose ratio of the MF-NH ₂ -HP, glutaraldehyde and ethyl alcohol in the step (3) is 0.2 to 0.4 mg: 8.0 to 12 mL: 30 to 50 mL, and the volume of the glutaraldehyde. The fraction is 25%.

Preferably, the temperature of the water bath of the mixed solution B in the step (3) is 20 to 30 ° C., and the reaction time is 8.0 to 16 hours.

Preferably, the dose ratio of the above MF-CHO-HP, diaminomalononitrile and ethyl alcohol E in the step (4) is 0.2 to 0.6 mg: 0.4 to 1.2 mg: 40 to 60 mL.

Preferably, the ultrasonic treatment time of the mixed solution C in the step (4) is 5.0 to 10 min, the temperature of the water bath is 20 to 30 ° C., and the reaction time is 2.0 to 4.0 h. ..

Preferably, the volume ratio of ethyl alcohol F to water in step (4) is 9: 1, and the dose ratio of the above-mentioned MF-CN-HP, hydroxylamine hydrochloride, and the mixed solution of ethyl alcohol F and water is 0.2. ~ 0.6 mg: 2.0 to 6.0 g: 40 to 60 mL.

Preferably, adjusting the above-mentioned pH in step (4) is to adjust the pH to 8.0 to 9.0 with 1.0 M NaOH, and the temperature of the above-mentioned water bath is 70 to 90 ° C. , The water bath reaction time is 4.0 to 8.0 h.

Preferably, the drying temperature in the step (4) is 60 to 80 ° C.

In the above, ethyl alcohol E and ethyl alcohol F are both ethyl alcohols, and the alphabets E and F are merely for distinguishing expression expressions.

(1) In the present invention, an amidoxim group is selected as a selective ligand for U (VI), a hollow porous melamine-formaldehyde resin is used as a matrix, and a hollow porous surface is functionalized by an underwater gas type emulsion template method. A quality adsorbent (MF-AO-HP) was prepared to achieve specific adsorption to U (VI).

(2) The present invention prepares hollow porous melamine-formaldehyde resin polymer microbeads containing a large amount of aldehyde groups on the surface by an underwater gas emulsion template method, shortens the U (VI) diffusion path, and transmits mass. The kinetics was improved, and the aldehyde group contained in itself avoided phenomena such as bond instability due to subsequent modification, and simplified the preparation flow. By grafting PEA, it became possible to modify high-density functional spots. The dense amidoxim spot grafted on the surface of MF-AO-HP was able to interact with a large amount of U (VI), improving the adsorption capacity of the adsorbent. From the results of pH response tests of MF-AO-HPS and MF-nPEA-AO-HPS, under different pH conditions, both MF-AO-HPS have higher adsorption to U (VI) than MF-nPEA-AO-HPS. It was found to have an amount.

a and b are SEM diagrams of MF-HP prepared in Example 1, and c and d are TEM diagrams of MF-HP prepared in Example 1. 11 is an infrared spectrum chart of MF-HP, MF- _NH2 -HP, MF-CHO-HP, MF-CN-HP and MF-AO-HPS prepared in Example 1. 3 is a Zeta potential graph of MF-HP, MF- _NH2 -HP, MF-AO-HPS and MF-nPEA-AO-HPS prepared in Example 1. a is an XPS graph of MF-AO-HPS prepared in Example 1, b is a C1s high analysis graph of MF-AO-HPS prepared in Example 1, and c is a C1s high analysis graph prepared in Example 1. It is an N1s high analysis graph of MF-AO-HPS. 3 is an organic elemental analysis graph of MF-HP, MF- _NH2 -HP, MF-CHO-HP, MF-CN-HP and MF-AO-HPS prepared in Example 1. 6 is a solid-state nuclear magnetic resonance carbon graph of MF-AO-HPS prepared in Example 1. 6 is a thermogravimetric analysis graph of MF-AO-HPS prepared in Example 1. It shows the influence of pH on the adsorption capacity of MF-AO-HPS, MF-nPEA-AO-HPS and MF-HP prepared in Example 1. It is the adsorption dynamics of MF-AO-HPS prepared in Example 1 and the model approximation curve thereof. It is the influence by temperature and the model approximation curve of the adsorption balance of MF-AO-HPS with respect to uranyl ion prepared in Example 1. FIG. It is a figure which shows the selective adsorption capacity of MF-AO-HPS prepared in Example 1. FIG. It is a figure which shows the adsorption regeneration performance of MF-AO-HPS prepared in Example 1. FIG.

The recognition performance evaluation in the specific embodiment of the present invention was performed by a static adsorption test. The adsorption capacity of 2.0 mg of MF-AO-HPS, MF-nPEA-AO-HPS and MF-HP for U (VI) in the range of pH = 3.0 to 9.0, and U (after adsorption). The content of VI) was measured by an inductively coupled plasma emission spectrophotometer, and the optimum adsorption pH was determined based on the results. In order to investigate the maximum adsorption capacity of MF-AO-HPS, the adsorption balance test was performed within the range of U (VI) concentration of 10 to 500 mg / L, and the adsorption data was approximated using the Langmuir model and the Friendrich model. The adsorption capacity was calculated based on the results. After saturated adsorption, some other substances having the same structure as uranyl ion were selected as competitive adsorbents, and were involved in the study of the selective adsorption performance and adsorption regeneration performance of MF-AO-HPS.

Hereinafter, the present invention will be further described with reference to specific examples.

(1) Preparation of Silicon Dioxide Nanoparticles Silicon dioxide nanoparticles were produced by the Stover method. To the flask, 8.735 g TEOS was added to 180 mL ethyl alcohol, heated in a water bath to raise the temperature to 35 ° C., and then a mixed solution of 10 mL _NH3・_H2O and 9.48 g water was added dropwise. Then, the formed mixed solution was reacted under magnetic stirring for 3.0 hours, and after the reaction was completed, the product was collected by centrifugation and washed 3 times with deionized water and ethyl alcohol, respectively. Drying gave silicon dioxide nanoparticles having a diameter of 180 to 200 nm.

(2) Preparation of hollow porous melamine-formaldehyde resin At 85 ° C, 1.26 g melamine is added to a mixed solution of 3.0 mL 37% formaldehyde and 25% glutaraldehyde (v / v, 2: 1), and then 2 The pH was adjusted to 9.5 with a .0 M Na ₂ CO ₃ solution, stirred at 1500 rpm, and reacted continuously for 3.0 min until the solution turned milky white to clear. Then, 10 mL of 10 wt% silicon dioxide aqueous dispersion was added under stirring, and the reaction was continued for 20 minutes. Then, the solution was cooled to 40 ° C., 2.0M HCl was added dropwise to adjust the pH to 5.5, the reaction was continued for 20 minutes, stirring was stopped, and polymerization was carried out for 4.0 hours under a water bath condition of 40 ° C. .. Finally, the product was collected by centrifugation, washed with deionized water and ethyl alcohol and dried to give a powder sample. The resulting powder is added to a 2% HF solution at room temperature and etched, centrifuged to collect the product, washed 3 times each with deionized water and ethyl alcohol, and centrifuged again to collect the product at 60 ° C. To obtain a hollow porous melamine-formaldehyde resin (denoted as MF-HP).

(3) MF-AO-HPS may be obtained by the following method. First, 0.4 g MF-HP powder and 4.0 g PEA were dispersed in 50 mL of ethyl alcohol in a flask and sonicated for 5.0 min. Then, the formed mixture was reacted under magnetic stirring for 12 hours under a water bath condition of 35 ° C. The product was then collected by centrifugation and washed 3 times with ethyl alcohol to give hollow porous melamine-formaldehyde resin polymer microbeads (MF-NH ₂ -HP) with amino groups grafted on the surface. Then, a mixture of 0.4 g MF-NH ₂ -HP, 10 mL 25% GA and 40 mL ethyl alcohol was added to the flask, and the reaction was carried out under magnetic stirring under water bath conditions at 35 ° C. for 12 hours. After completion of the reaction, the product was washed 3 times with water to remove excess GA, then washed twice with ethyl alcohol and centrifuged to graft aldehyde groups on the surface. Hollow porous melamine-formaldehyde resin polymer microbeads. (Denoted as MF-CHO-HP) was collected.

(4) 0.4 g MF-CHO-HP and 0.8 g DAMN were suspended in 50 mL of ethyl alcohol, sonicated for 5.0 min, and reacted at 25 ° C. for 3.0 hours under magnetic stirring. The product was then collected to give a hollow porous melamine-formaldehyde resin (denoted as MF-CN-HP) grafted with nitrile groups on the surface. Finally, 0.4 g MF-CN-HP and 4.0 g NH ₂ OH · HCl are dispersed in a 50 mL H ₂ O / ethyl alcohol mixed solution (v / v, 1: 9) and pH at 1.0 M NaOH. Was adjusted to 8.0, and the formed mixture was continuously reacted in a water bath at 80 ° C. for 6.0 hours. Separated by centrifugation, rinsed with deionized water and ethyl alcohol, and dried at 60 ° C. to give amidoxim functionalized hollow porous melamine-formaldehyde resin microbeads (denoted as MF-AO-HPS).

By the same method as in step (3), MF-HP was used instead of MF-CHO-HP to obtain another adsorbent (denoted as MF-nPEA-AO-HPS) in which PEA was not grafted. ..

FIG. 1 shows SEM and TEM diagrams of MF-HP. As can be seen from the SEM diagram, the microbeads are monodisperse, their diameter is about 2.0 μm, and the surface is porous. As can be seen from the TEM diagram, the microbeads are hollow.

From FT-IR, XPS and OEA, Zeta potential for each compound and CP-MAS ¹³ C NMR spectra, grafting and chemical modification of MF-AO-HPS were investigated. The FT-IR spectra of MF-HP, MF-NH ₂ -HP, MF-CHO-HP, MF-CN-HP and MF-AO-HPS are shown in FIG. In the graph by MF-CN-HP, there was a characteristic adsorption peak of C≡N at 2210 cm _- ¹ , and the successful modification of DAMN was confirmed. The absorption peak disappeared.

As can be seen from FIG. 3, the Zeta potential will change after either reaction, which is shown because the functional groups on the surface of the material will be different after different substances have been modified. Because it became different. This reflected successful modification for each step and successful preparation for each material.

In the XPS graph of MF-AO-HPS, as shown in a in FIG. 4, three strong peaks appear at 284.83, 399.03, and 535.88 eV, and the core energies of C1s, N1s, and O1s, respectively. Corresponds to the level. The C1s high analysis graph is shown in b in FIG. 4, and as can be seen from the figure, the C1s high analysis graph can be divided into three peaks corresponding to CC, CH and C = N. C in FIG. 4 is an N1s high analysis graph of MF-AO-HPS, which can be divided into three feature absorption peaks, and these three peaks are in NO, C = N, and NH, respectively. Attributed.

FIG. 5 shows changes in the contents of carbon atoms and nitrogen atoms for each product. According to the test, the carbon atom content in MF-HP is lower than that of nitrogen atom, and the carbon atom content in PEA is higher than that of nitrogen atom. Therefore, MF-NH ₂ -HP has a carbon content higher than that of MF-HP. Was relatively increased and the nitrogen content was relatively decreased. For the same reason, MF-CHO-HP and MF-CN-HP contain more carbon than nitrogen and MF-AO-HPS contains more carbon than carbon.

FIG. 6 shows a CP-MAS ¹³ C NMR spectral chart of MF-AO-HPS, which contains four main signals of 48.12 ppm, 105.80 ppm, 162.72 ppm, and 219.75 ppm, which are the signals. Corresponds to carbon absorption peaks of -CH ₂ -NH-, -C = C-, C = NOH, and C = O, respectively. From any of the above results, the successful preparation of MF-AO-HPS can be demonstrated. The stability of MF-AO-HPS was then determined by thermogravimetric analysis (TGA).

As shown in FIG. 7, a 1.75% weight loss between 200 ° C. and 360 ° C. was observed on the MF-AO-HPS curve due to the loss of grafted amidoxime groups on the surface, and the loss of grafted PEA. Therefore, the weight between 360 ° C and 600 ° C was reduced by 1.60%. The slight weight reduction of the MF-AO-HPS demonstrated its good stability.

(1) Preparation of Silicon Dioxide Nanoparticles 8.0 g TEOS was added to 170 mL ethyl alcohol in a flask in which silicon dioxide nanoparticles were produced by the Stover method, heated in a water bath to raise the temperature to 30 ° C., and then 9.0 mL. A mixed solution of NH ₃ · H ₂ O and 9.0 g H ₂ O was added dropwise. Then, the formed mixed solution was reacted for 2.0 hours under magnetic stirring. After completion of the reaction, the product was collected by centrifugation, washed with deionized water and ethyl alcohol three times, and dried to obtain silicon dioxide nanoparticles having a diameter of about 200 nm.

(2) Preparation of hollow porous melamine-formaldehyde resin After adding 1.0 g melamine to a mixed solution (v / v, 2: 1) of 2.0 mL 37% formaldehyde and 25% glutaraldehyde under the condition of 80 ° C. The pH was adjusted to 9.0 with a 2.0 M Na ₂ CO ₃ solution, and the mixture was stirred at 1200 rpm, and the reaction was continued for 4.0 min after the solution became clear from milky white. Then, 5.0 mL 10 wt% silicon dioxide aqueous dispersion was added under stirring, and the reaction was continued for 10 minutes. Then, the solution was cooled to 30 ° C., 2M HCl was added dropwise to adjust the pH to 5.0, the reaction was continued for 10 minutes, stirring was stopped, and the mixture was polymerized for 3.0 hours under a water bath condition of 30 ° C. Finally, the product was collected by centrifugation, washed with deionized water and ethyl alcohol and dried to give a powder sample. The resulting powder is added to a 2% HF solution at room temperature and etched, centrifuged to collect the product, washed 3 times each with deionized water and ethyl alcohol, and centrifuged again to collect the product at 60 ° C. To obtain a hollow porous melamine-formaldehyde resin (denoted as MF-HP).

(3) MF-AO-HPS may be obtained by the following method. First, 0.3 g MF-HP powder and 3.0 g PEA were dispersed in 40 mL ethyl alcohol in a flask, and then subjected to 8.0 min sonication. Then, the formed mixture was reacted for 8.0 hours under a water bath condition of 30 ° C. under magnetic stirring. The product was then collected by centrifugation and washed 3 times with ethyl alcohol to give hollow porous melamine-formaldehyde resin polymer microbeads (denoted as MF-NH ₂ -HP) grafted with amino groups on the surface. Then, a mixture of 0.2 g MF-NH ₂ -HP, 8.0 mL 25% GA and 30 mL ethyl alcohol was added to the flask, and the reaction was carried out under magnetic stirring under water bath conditions at 30 ° C. for 8.0 hours. After completion of the reaction, the product was washed 3 times with water to remove excess GA and then washed twice with ethyl alcohol and centrifuged to graft aldehyde groups on the surface. Hollow porous melamine-formaldehyde resin polymer microbeads. (Denoted as MF-CHO-HP) was collected.

(4) 0.2 g MF-CHO-HP and 0.4 g DAMN were suspended in 40 mL ethyl alcohol, sonicated for 8.0 min, and reacted at 20 ° C. for 2.0 hours under magnetic stirring. The product was then collected to give a hollow porous melamine-formaldehyde resin (denoted as MF-CN-HP) grafted with nitrile groups on the surface. Finally, 0.2 g MF-CN-HP and 2.0 g NH ₂ OH · HCl are dispersed in a 40 mL H ₂ O / ethyl alcohol mixed solution (v / v, 1: 9) and pH at 1.0 M NaOH. Was adjusted to 8.5, and the formed mixture was continuously reacted in a 70 ° C. water bath for 4.0 hours. It was separated by centrifugation, rinsed with distilled water and ethyl alcohol, and dried at 70 ° C. to give MF-AO-HPS.

The direct reaction of MF-HP with DAMN and NH ₂ OH · HCl gave another adsorbent (referred to as MF-nPEA-AO-HPS) that PEA could not contact.

(1) Preparation of Silicon Dioxide Nanoparticles Silicon dioxide nanoparticles were produced by the Stover method. To a flask, 10 g TEOS was added to 190 mL ethyl alcohol, heated in a water bath to raise the temperature to 40 ° C., and then a mixed solution of 11 mL _NH3 · H ₂ O and 10 g H ₂ O was added dropwise. Then, the formed mixed solution was reacted for 4.0 hours under magnetic stirring. After completion of the reaction, the product was collected by centrifugation and washed 3 times with deionized water and ethyl alcohol, respectively. Drying gave silicon dioxide nanoparticles having a diameter of about 200 nm.

(2) Preparation of hollow porous melamine-formaldehyde resin After adding 2.0 g melamine at 90 ° C to a mixed solution of 4.0 mL 37% formaldehyde and 25% glutaraldehyde (v / v, 2: 1), 2 The pH was adjusted to 10.0 with a 0.0 M Na ₂ CO ₃ solution, and the mixture was stirred under the condition of 1600 rpm, and the reaction was continued for 5.0 min after the solution became clear from milky white. Then, 15 mL of 10 wt% silicon dioxide aqueous dispersion was added under stirring, and the reaction was continued for 30 min. Then, the mixture was cooled to 50 ° C., 2.0M HCl was added dropwise to adjust the pH to 6.0, the reaction was continued for 30 minutes, stirring was stopped, and polymerization was carried out for 5.0 hours under a water bath condition of 50 ° C. Finally, the product was collected by centrifugation, washed with deionized water and ethyl alcohol and dried to give a powder sample. The resulting powder is added to a 2% HF solution at room temperature and etched, centrifuged to collect the product, washed 3 times each with deionized water and ethyl alcohol, and centrifuged again to collect the product at 60 ° C. To obtain a hollow porous melamine-formaldehyde resin (denoted as MF-HP).

(3) First, 0.5 g MF-HP powder and 5.0 g PEA were dispersed in 60 mL ethyl alcohol in a flask, and then sonicated for 10 min. Then, the formed mixture was reacted under magnetic stirring under a water bath condition of 40 ° C. for 16 hours. The product was then collected by centrifugation and washed 3 times with ethyl alcohol to give hollow porous melamine-formaldehyde resin polymer microbeads (denoted as MF-NH ₂ -HP) grafted with amino groups on the surface. Then, a mixture of 0.4 g MF-NH ₂ -HP, 12 mL 25% GA and 50 mL ethyl alcohol was added to a 100 mL single-necked flask, and the reaction was carried out under magnetic stirring under water bath conditions at 40 ° C. for 16 hours. After completion of the reaction, the product was washed 3 times with water to remove excess GA, then washed twice with ethyl alcohol and centrifuged to graft aldehyde groups on the surface. Hollow porous melamine-formaldehyde resin polymer microbeads ( MF-CHO-HP) was collected.

(4) 0.6 g MF-CHO-HP and 1.2 g DAMN were suspended in 60 mL of ethyl alcohol, sonicated for 10 minutes, and reacted at 30 ° C. for 4.0 hours under magnetic stirring. Then, the product was collected to obtain a hollow porous melamine-formaldehyde resin (denoted as MF-CN-HP) grafted with a nitrile group on the surface. Finally, 0.6 g MF-CN-HP and 6.0 g NH ₂ OH · HCl were dispersed in a 60 mL H ₂ O / ethyl alcohol (v / v, 1: 9) solution and pH 9 with 1.0 M NaOH. The mixture was adjusted to 0.0, and the formed mixture was continuously reacted at 90 ° C. for 8.0 hours. It was separated by centrifugation, washed with deionized water and ethyl alcohol, and dried at 80 ° C. to give MF-AO-HPS.

The direct reaction of MF-HP with DAMN, NH ₂ OH · HCl gave another adsorbent (referred to as MF-nPEA-AO-HPS) in which PEA was not grafted.

Performance measurement The adsorption behavior of metal ions is greatly affected by the environmental pH. Therefore, the effect of the adsorption capacity of MF-AO-HPS, MF-nPEA-AO-HPS, and MF-HP on U (VI) was investigated in the range of pH 3.0 to 9.0. As shown in FIG. 8, when the pH is 7.0 or less, the adsorption capacities of MF-AO-HPS, MF-nPEA-AO-HPS, and MF-HP tend to gradually increase as the pH increases. When the pH is higher than 7.0, the adsorption capacity decreases with increasing pH, and the adsorption capacity of MF-AO-HPS is MF-nPEA-AO under any pH condition. -Higher than the adsorption capacity of HPS and MF-HP.

The adsorption kinetics of MF-AO-HPS for U (VI) is shown in FIG. As can be seen from the figure, the adsorption capacity of MF-AO-HPS increased rapidly within the first 30 min and reached the maximum adsorption capacity within 60 min.

In order to investigate the maximum adsorption capacity of MF-AO-HPS, the adsorption balance test was performed within the range of U (VI) concentration of 10 to 500 mg / L, and the adsorption data was approximated using the Langmuir model and the Friendrich model. The effect of temperature on the adsorption capacity was investigated. As shown in FIG. 10, within the measurement temperature range, the adsorption capacity increased with increasing temperature.

Since the bond between the interfering ion and the amidoxime group may have a huge effect on the adsorption capacity of MF-AO-HPS adsorbing U (VI), VO ^3- , Co ²⁺ , Ni ⁺ , Cu ²⁺ , Zn ²⁺ , Pb ²⁺ , Ca ²⁺ , Mg ²⁺ , and Na ⁺ are selected as competitive ions for U (VI), and the adsorbents VO ^3- , Co ²⁺ , Ni ⁺ , Cu ²⁺ , Zn. The adsorption behavior of ²⁺ , Pb ²⁺ , Ca ²⁺ , Mg ²⁺ , Na ⁺ , and U (VI) in a mixed solution was investigated. As shown in FIG. 11, in the presence of a large amount of interfering ions, MF-AO-HPS also has the maximum adsorption capacity for U (VI), VO ^3- , Co ²⁺ , Ni ⁺ , Cu. It is much larger than the adsorption capacity corresponding to ²⁺ , Zn ²⁺ , Pb ²⁺ , Ca ²⁺ , Mg ²⁺ , and Na ⁺ .

The adsorption reproducibility is an important index for evaluating the stability of the adsorbent in the recycling process, and therefore, the adsorption regeneration performance of MF-AO-HPS was measured by seven continuous adsorption-desorption circulation tests. As shown in FIG. 12, MF-AO-HPS also has a relatively high adsorption capacity after 7 adsorption-desorption circulation tests, which also has relatively good adsorption regeneration performance and in the circulation utilization process. It was stated that it could maintain a good adsorption capacity for U (VI).

The above examples are technical means described without limitation of the present invention but merely for explaining the present invention. Therefore, the present invention will be described in detail with reference to each of the above examples in the present specification. However, as should be understood by those skilled in the art, all technical means and improvements thereof that can still modify or replace the invention and remain within the spirit and scope of the invention are all present. It is included in the claims of the invention.

Claims (10)

(1) The process of preparing silicon dioxide nanoparticles and
(2) After the silicon dioxide nanoparticles obtained in the step (1) are dispersed in deionized water to obtain a silicon dioxide aqueous dispersion, melamine is mixed with a formaldehyde solution and a glutaaldehyde solution under constant temperature conditions. Add to the solution, adjust the pH of the mixed solution, stir and react continuously for a certain period of time after the solution turns milky white to clear, and after the reaction, add silicon dioxide aqueous dispersion under stirring conditions to react. After the reaction, cool to a certain temperature, adjust the pH again and then react, after the reaction, carry out the polymerization reaction under water bath conditions, and finally collect the product by centrifugation, deionized water and ethyl alcohol. Washed with, dried to obtain a powder sample, the powder sample is added to a hydrofluoric acid solution, etched, centrifuged to collect the product, washed with deionized water and ethyl alcohol, and centrifuged again to collect the product. , The process of drying to obtain a hollow porous melamine-formaldehyde resin (denoted as MF-HP), and
(3) MF-HP and polyethylene polyamine prepared in step (2) are dispersed in ethyl alcohol to obtain a mixed solution A, which is then subjected to ultrasonic treatment, and the mixed solution A is placed in a water bath condition under magnetic stirring. The reaction was carried out, and after the reaction, the product was centrifuged, the obtained product was washed with ethyl alcohol, and the product was centrifuged again to collect the product. -NH ₂ -HP is described), MF-NH ₂ -HP and glutaaldehyde are added to ethyl alcohol to obtain a mixed solution B, and then the mixed solution B is placed in a water bath condition under magnetic stirring to react. After completion of the reaction, the product is washed with deionized water and ethyl alcohol, respectively, and centrifuged to obtain hollow porous melamine-formaldehyde resin polymer microbeads (denoted as MF-CHO-HP) grafted with aldehyde groups on the surface. When,
(4) MF-CHO-HP and diaminomalononitrile prepared in step (3) are taken and suspended in ethyl alcohol E to obtain a mixed solution C, which is then subjected to ultrasonic treatment to magnetically stir the mixed solution C. The reaction is carried out under water bath conditions, and after the reaction, centrifugation is performed to obtain a hollow porous melamine-formaldehyde resin (denoted as MF-CN-HP) grafted with a nitrile group on the surface, and finally ethyl alcohol F is deionized. A mixed solution of ethyl alcohol and water is obtained in addition to water, MF-CN-HP and hydroxylamine hydrochloride are further added, the pH is adjusted, the reaction is carried out in a water bath condition, and after the reaction, the product is centrifuged to collect the product. Then, it was washed with deionized water and ethyl alcohol, and dried to obtain amidoxim functionalized hollow porous melamine-formaldehyde resin microbeads (denoted as MF-AO-HPS).
A method for preparing amidoxime-functionalized hollow porous polymer microbeads using CO ₂ as an emulsion template. The constant temperature condition in the step (2) is 80 to 90 ° C., and the dose ratio of the melamine, the mixed solution of formaldehyde and glutaraldehyde, and the silicon dioxide dispersion is 1.0 to 2.0 g: 2.0 to 4 0.0 mL: 5.0 to 15 mL, the volume fraction of the formaldehyde solution is 37%, the volume fraction of the glutaraldehyde solution is 25%, and the concentration of the silicon dioxide aqueous dispersion is 10 wt%. A method for preparing amidoxime-functionalized hollow porous polymer microbeads using CO ₂ as the emulsion template according to claim 1. To adjust the pH in the step (2) is to adjust the pH to 9.0 to 10.0 with the Na ₂ CO ₃ solution, and the concentration of the Na ₂ CO ₃ solution is 2.0 M. The stirring condition is 1200 to 1600 rpm, the continuous reaction period is 3.0 to 5.0 min, and the reaction time by adding the silicon dioxide aqueous dispersion is 10 to 30 min. A method for preparing amidoxime-functionalized hollow porous polymer microbeads using CO ₂ as the emulsion template according to claim 1. The constant temperature when cooling to the above-mentioned constant temperature in the step (2) is 30 to 50 ° C., and in the above-mentioned operation of adjusting the pH again, the pH is adjusted by dropping an HCl having a concentration of 2.0 M. The pH is adjusted to 0 to 6.0, the reaction time after adjusting the pH again is 10 to 30 min, the temperature of the water bath is 30 to 50 ° C., and the polymerization reaction time is 3. As the emulsion template according to claim 1, the pH is 0.0 to 5.0 h, the volume concentration of the hydrofluoric acid solution is 2%, and the drying temperature is 60 to 80 ° C. A method for preparing amidoxime functionalized hollow porous polymer microbeads using CO ₂ . The first aspect of claim 1, wherein the dose ratio of the MF-HP, the polyethylene polyamine and the ethyl alcohol in the step (3) is 0.3 to 0.5 mg: 3.0 to 5.0 g: 40 to 60 mL. A method for preparing amidoxime functionalized hollow porous polymer microbeads using CO ₂ as the described emulsion template. The ultrasonic treatment time in the step (3) is 5.0 to 10 min, the temperature of the water bath of the mixed solution A is 30 to 40 ° C., and the reaction time is 8.0 to 16 hours. The method for preparing amidoxime-functionalized hollow porous polymer microbeads using CO ₂ as the emulsion template according to claim 1. The dose ratio of the MF-NH ₂ -HP, glutaraldehyde and ethyl alcohol in the step (3) is 0.2 to 0.4 mg: 8.0 to 12 mL: 30 to 50 mL, and the volume fraction of the glutaraldehyde is CO ₂ is used as the emulsion template according to claim 1, which is 25%, the temperature of the water bath of the mixed solution B is 20 to 30 ° C., and the reaction time is 8.0 to 16 hours. A method for preparing microbeads of a hollow porous polymer functionalized with amidoxime. The dose ratio of the MF-CHO-HP, diaminomalononitrile and ethyl alcohol E in the step (4) is 0.2 to 0.6 mg: 0.4 to 1.2 mg: 40 to 60 mL, and the mixed solution C has a dose ratio of 0.2 to 0.6 mg: 0.4 to 1.2 mg: 40 to 60 mL. The emulsion according to claim 1, wherein the ultrasonic treatment time is 5.0 to 10 min, the water bath temperature is 20 to 30 ° C., and the reaction time is 2.0 to 4.0 h. A method for preparing amidoxim functionalized hollow porous polymer microbeads using CO ₂ as a template. The volume ratio of ethyl alcohol F to water in step (4) is 9: 1, and the dose ratio of the MF-CN-HP, hydroxylamine hydrochloride, and the mixed solution of ethyl alcohol and water is 0.2 to 0.6 mg. : 2.0 to 6.0 g: 40 to 60 mL, and adjusting the pH described above means adjusting the pH to 8.0 to 9.0 with 1.0 M NaOH, and the temperature of the water bath. Is 70 to 90 ° C., the water bath reaction time is 4.0 to 8.0 h, and the drying temperature is 60 to 80 ° C., as the emulsion template according to claim 1, CO. A method for preparing amidoxime functionalized hollow porous polymer microbeads using ₂ . Utilization of the amidoxim functionalized hollow porous adsorbent prepared by the method according to any one of claims 1 to 9 for the selective adsorption and separation of hexavalent uranium in a solution.

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