A modified phenolic resin for solidifying radioactive waste oil and its preparation method

Abstract

The invention discloses a modified phenolic resin preparation method for radioactive waste oil solidification, relates to the technical field of nuclear radioactive waste treatment, and the preparation method includes modifying the phenolic resin obtained by base catalysis; preparing a lead-based metal organic framework; adding the prepared lead-based metal organic framework to dimethylformamide to obtain a lead-based metal organic framework suspension; weighing 1 to 5g of modified phenolic resin, adding it to 20-50 mL of methanol to obtain a modified phenolic resin solution; slowly pouring the lead-based metal organic framework suspension into the methanol solution of the modified phenolic resin, stirring the mixed solution with a magnetic stirrer for 30-60min, so that the lead-based metal organic framework is uniformly dispersed in the phenolic resin solution, and obtaining a lead-based metal organic framework-modified phenolic resin solution. The modified phenolic resin material of the present invention can not only solidify waste oil, but also simultaneously adsorb radioactive isotopes, and can effectively prevent leakage of radioactive waste oil.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear radioactive waste treatment, and in particular to a modified phenolic resin for solidifying radioactive waste oil and a preparation method thereof. Background Art

[0002] With the continuous development of my country's nuclear industry, the generation of radioactive waste oil has increased annually during the production and manufacturing of nuclear fuel elements and the application of nuclear military technology. This waste oil refers to radioactive elements (such as 235U, 137Cs, 90Sr, 60Co, etc.) that inevitably enter the insulating oil, lubricating oil, and hydraulic oil used in nuclear facilities during the operation and maintenance of nuclear facilities. When the oil reaches its service life or is replaced due to performance degradation, it becomes radioactive waste oil contaminated with radioactive elements. The treatment and disposal of radioactive waste oil is one of the major challenges facing the nuclear energy industry and the operation of nuclear facilities.

[0003] Currently, common methods for treating radioactive waste oil include incineration and pyrolysis, and absorption and solidification. Incineration and pyrolysis offer advantages for flammable organic waste oils, including high volume reduction coefficients and stable incineration products. It also eliminates the fire hazard of radioactive organic waste liquids and is widely used for the treatment of radioactive gaseous and liquid waste. However, direct incineration and volume reduction of liquids requires high equipment requirements. Therefore, direct incineration and volume reduction of liquids remains challenging. The absorption and solidification method relies on the absorption of radioactive waste oil or certain radionuclides within it into an absorbent, thereby solidifying or purifying the waste oil. This method offers the advantages of simplicity and low cost, reducing the risk of diffuse spillage associated with organic waste liquid storage. Furthermore, this method allows the solution to be solidified, transported, or further incinerated. Cement solidification is a common absorption and solidification method for treating radioactive organic waste liquids. However, cement solidification poses challenges for treating radioactive organic waste liquids, including increased volume after solidification, a porous structure, volatilization, and leakage, which can even pose a fire hazard. Furthermore, the high leaching rate of radionuclides from cement solidified materials when in contact with water compromises the effectiveness of the treatment. In addition, the storage space required for cement solidification is large, which increases the overall processing and disposal costs. Overall, cement solidification methods face a series of technical and economic challenges in dealing with organic waste liquids, especially radioactive organic waste liquids.

[0004] For example, the patent document CN 104464867A, entitled "Method for Preparing a High-Strength Cement Solidified Body of Radioactive Waste Motor Oil," published on March 15, 2017, discloses a cement solidified body for treating radioactive waste motor oil. This patent addresses the current problem of poor compatibility between motor oil and cement, making it difficult to obtain a cement solidified body that meets the requirements of national standard GB 14569.1-2011. The invention involves preparing a homogeneous oil-in-water emulsion, a cement slurry, and a cement solidified body. The invention employs cement solidification after emulsifying motor oil with water. Fly ash, oil-absorbing resin, and wood fiber are added to the cement formula as additives to increase the strength of the cement solidified body and reduce the leaching rate of radionuclides. However, due to the inherent limitations of cement solidification, leaching is still unavoidable. Furthermore, the heavy weight of the cement solidified body, the fragile nature of the cement solidified body, and the inconvenience of transport remain. Summary of the Invention

[0005] One objective of the present invention is to provide a method for preparing a composite resin for the solidification of radioactive waste oil, addressing the shortcomings of existing cement-solidified radioactive waste oil, such as high weight, volatility, and exudation. The phenolic resin obtained by base catalysis is thermosetting, and its molecular structure is a network.

[0006] The present invention is achieved by the following technical solution: a method for preparing a modified phenolic resin for radioactive waste oil solidification, comprising modifying a phenolic resin obtained by base catalysis; preparing a lead-based metal organic framework; adding the prepared lead-based metal organic framework to dimethylformamide and ultrasonically treating it for 30 to 60 minutes at an ultrasonic frequency of 60 kHz to obtain a lead-based metal organic framework suspension; weighing 1 to 5 g of the modified phenolic resin and adding it to 20 to 50 mL of methanol, stirring the solution with a magnetic stirrer until the modified phenolic resin is completely dissolved to obtain a modified phenolic resin solution; slowly pouring the lead-based metal organic framework suspension into the modified phenolic resin solution, and stirring the mixed solution with a magnetic stirrer for 30 to 60 minutes to uniformly disperse the lead-based metal organic framework in the modified phenolic resin solution to obtain a lead-based metal organic framework-modified phenolic resin solution; transferring the lead-based metal organic framework-modified phenolic resin solution to a rotary evaporator to remove dimethylformamide and methanol solvents to obtain a viscous modified phenolic resin for radioactive waste oil solidification.

[0007] Furthermore, the modification treatment includes first grafting the bromoester onto the synthesized phenolic resin through a grafting reaction to form a first modified phenolic resin; and treating the first modified phenolic resin with functionalized graphene to obtain a second modified phenolic resin.

[0008] Furthermore, the first modified phenolic resin is prepared by the following steps: first, obtaining an unmodified phenolic resin through a condensation reaction of phenol and formaldehyde under alkali catalysis; dissolving the prepared unmodified phenolic resin in dimethyl sulfoxide or ethyl acetate to prepare a first mixed solution; slowly adding ethyl 2-bromoacetate to the first mixed solution under an inert atmosphere, and simultaneously adding an alkaline catalyst to prepare a second mixed solution, maintaining the second mixed solution at 40-50° C. and reacting for 4-6 hours; after the reaction is completed, pouring the second mixed solution into pure water at a temperature of 4-10° C. to precipitate and obtain the first modified phenolic resin.

[0009] Furthermore, the inert gas in the inert atmosphere is argon and / or nitrogen, and the alkaline catalyst is sodium hydroxide or potassium hydroxide.

[0010] Furthermore, the method may further include washing and drying the precipitated first modified phenolic resin, wherein the washing process includes washing the first modified phenolic resin 3 to 4 times with methanol or ethanol to remove unreacted halides and by-products; and the drying process includes drying the washed first modified phenolic resin in a vacuum oven at a drying temperature of 40 to 50° C. to prevent decomposition or volatilization of long-chain groups.

[0011] Furthermore, the second modified phenolic resin is prepared by the following steps: dissolving the first modified phenolic resin in ethanol to obtain a modified solution; dispersing functionalized graphene in ethanol to obtain a functionalized graphene dispersion; slowly adding the functionalized graphene dispersion to the modified solution and stirring at a stirring temperature of 35-50°C and a stirring time of 2-3 hours to prepare the second modified phenolic resin; the dispersion is ultrasonic dispersion at an ultrasonic frequency of 40 kHz and an ultrasonic treatment time of 20-40 minutes.

[0012] Furthermore, functionalized graphene is prepared by the following steps: graphene is uniformly dispersed in an ethanol solution by ultrasonic treatment to prepare solution A; a nitrogen-containing heterocyclic compound is dissolved in an ethanol solution by ultrasonic treatment to prepare solution B; solution A and solution B are mixed together, and ultrasonic treatment is used to promote the reaction, the ultrasonic treatment time is 30 to 50 minutes, and the ultrasonic frequency is 50 kHz; in order to further increase the contact area between graphene and aromatic molecules, the mixed solution can be ultrasonically treated to enhance π-π stacking, and after the reaction is completed, the reacted graphene is separated by centrifugation, the centrifuge speed is 10,000 to 12,000 rpm, and the centrifugation time is 20 to 30 minutes; the graphene is washed three times with dimethylformamide solvent, and the washed graphene is placed in a vacuum oven for low-temperature drying, and the drying temperature is 40 to 50°C to prepare functionalized graphene.

[0013] Furthermore, the nitrogen-containing heterocyclic compound is pyrrole or phenothiazine.

[0014] Furthermore, the preparation of lead-based metal-organic frameworks (Pb-MOFs) includes the following steps: mixing 0.5 mmol of terephthalic acid (H2BDC) solution and 10 mL of N,N-dimethylformamide to obtain a mixed solution A; adding lead nitrate to ultrapure water to dissolve to prepare a mixed solution B; pouring the mixed solution A and the mixed solution B into the same beaker and mixing them, and ultrasonically treating the two solutions to fully mix them to prepare a mixed solution C, wherein the ultrasonic treatment time is 5 to 10 minutes and the ultrasonic frequency is 40 to 60 kHz; transferring the mixed solution C to a high-pressure reactor, maintaining the reactor temperature at 120 to 200°C, and heating for 16 to 24 hours; after the reaction is completed, slowly cooling the reactor to room temperature, and using a centrifuge to separate the lead-based metal-organic framework crystals, the centrifuge speed is 10,000 to 11,000 rpm, and the centrifugation time is 30 to 35 min; the separated lead-based metal-organic framework crystals are washed three times with ethanol to remove residual reactants and solvents; the washed lead-based metal-organic framework crystals are immersed in anhydrous ethanol solution for 4 to 6 hours, and then dried in a vacuum oven at a low temperature of 30 to 45°C to prepare the lead-based metal-organic framework.

[0015] Furthermore, the temperature of the rotary evaporator is 40-60°C, the rotation speed is 100-150 rpm, and an appropriate vacuum degree of 0.05-0.1 MPa is applied.

[0016] Another aspect of the present invention provides a modified phenolic resin for solidifying radioactive waste oil. The modified phenolic resin is prepared according to any one of the methods described above.

[0017] In another aspect, the present invention provides a radioactive waste oil-modified phenolic resin solidified body, comprising the following components in weight percentage: 20 to 50 wt% of radioactive waste oil; 35 to 55 wt% of a modified phenolic resin solidified body, wherein the modified phenolic resin is prepared according to the method described above; 2 to 15 wt% of polypropylene fiber; and 5 to 10 wt% of water.

[0018] Furthermore, the water is tap water or water with a radioactivity less than or equal to 2.5×10 9 Bq / L of radioactive wastewater.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] 1. The modified phenolic resin material prepared by the present invention can not only solidify waste oil, but also simultaneously adsorb radioactive isotopes, thereby effectively preventing the leakage of radioactive waste oil and effectively improving the overall effect of radioactive waste oil solidification treatment.

[0021] 2. The present invention provides a lead-based metal-organic framework and successfully applies the lead-based metal-organic framework to the solidification treatment of radioactive waste oil. The modified phenolic resin with the added lead-based metal-organic framework can effectively absorb radioactive ions in radioactive waste oil and effectively reduce the radiation dose.

[0022] 3. The present invention functionalizes graphene and uses the functionalized graphene to perform secondary modification on phenolic resin, so that the final phenolic resin has high oil absorption, while improving the pressure resistance of the final solidified material and effectively preventing secondary leakage of radioactive waste oil after solidification. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0024] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related thereto. In the event of a conflict with any incorporated document, the contents of this specification shall prevail. As used herein, “comprising,” “including,” “having,” “containing,” and the like are open-ended terms, meaning including but not limited to. Unless the context clearly indicates otherwise, the expressions “a,” “an,” and “an” as used herein include plural references. As used herein, the term “about” refers to a range of ±20% of the value that follows. In some embodiments, the term “about” refers to a range of ±10% of the value that follows. In some embodiments, the term “about” refers to a range of ±5% of the value that follows.

[0025] Example 1

[0026] This example provides a method for preparing a modified phenolic resin for solidifying radioactive waste oil. In this example, ethyl 2-bromoacetate, alkaline phenolic resin, and sodium hydroxide were purchased from Aladdin Biochemical Technology Co., Ltd. (Shanghai, China); N,N-dimethylformamide (DMF), ethyl acetate, and ethanol were purchased from Chengdu Kelong Chemical Co., Ltd. (Chengdu, China); graphene and phenothiazine were purchased from MacLean Biochemical Technology Co., Ltd. (Shanghai, China); and lead nitrate and terephthalic acid were purchased from Sinopharm Chemical Reagent Co., Ltd. (Beijing, China). The specific preparation method includes the following steps:

[0027] Step 1: The phenolic resin obtained by base catalysis is modified twice.

[0028] It should be noted that common phenolic resins are typically prepared using either acid-catalyzed or base-catalyzed methods. Base-catalyzed phenolic resins exhibit high thermal stability, allowing them to be used at high temperatures without decomposing easily. Furthermore, base-catalyzed phenolic resins, compared to acid-catalyzed phenolic resins, possess a molecular network structure, making them easier to modify.

[0029] The modification treatment includes two modification treatments. First, a brominated ester is grafted onto a synthesized phenolic resin through a grafting reaction to form a brominated ester-modified phenolic resin. Then, the first modified phenolic resin is treated with functionalized graphene to obtain a final phenolic resin.

[0030] Specifically, grafting a bromoester onto a synthetic phenolic resin to form a bromoester-modified phenolic resin comprises the following sub-steps:

[0031] 1) Dissolve the unmodified phenolic resin prepared using base catalysis in ethyl acetate. Then, slowly add ethyl 2-bromoacetate to the mixed solution of phenolic resin and ethyl acetate under an argon atmosphere. Simultaneously, add sodium hydroxide. Maintain the mixed solution at 40°C and react for 4 hours. The addition of the base catalyst in this step promotes the grafting reaction. The concentration of the mixed solution is 10% (w / v), meaning 10 g of phenolic resin per 100 mL of solvent.

[0032] 2) The mixed solution after the reaction is poured into pure water at a temperature of 4°C to precipitate and obtain a brominated ester-modified phenolic resin.

[0033] It should be noted that in this implementation, the bromoester selected is 2-bromoethyl acetate. Through the optimization of the modification step, the hydrophobicity of the phenolic resin after the 2-bromoethyl acetate grafting is enhanced, and the absorption of moisture is reduced, thereby the easier adsorption of oily substances. The grafting of 2-bromoethyl acetate not only reduces the surface energy of the phenolic resin material, but also makes the modified phenolic resin more likely to interact with oily substances, and also promotes the material to form a porous structure, which can accommodate more oily substances, thereby promoting oil absorption performance. Simultaneously, the grafting of bromoester effectively enhances the thermal stability of the phenolic resin, so that the modified phenolic resin can keep its physical properties at high temperatures, which has great benefits for the processing of radioactive waste oil.

[0034] Then, functionalized graphene is prepared, which specifically includes the following steps:

[0035] 1) First, 0.08 g of graphene was uniformly dispersed in 100 mL of ethanol solution by ultrasonic treatment for 30 min at a frequency of 30 kHz.

[0036] 2) Phenothiazine was dissolved in an ethanol solution by ultrasonication to prepare a nitrogen-containing heterocyclic compound solution. The ultrasonication was performed for 30 minutes at a frequency of 30 kHz. Nitrogen-containing heterocyclic compounds were chosen because they have a rich π-electron structure, which forms a stable π-π stacking when interacting with the graphene surface. This stacking effect allows the nitrogen-containing heterocyclic compound molecules to be firmly adsorbed on the graphene surface, thereby imparting new functionality and dispersibility to the graphene.

[0037] 3) The graphene suspension and the nitrogen-containing heterocyclic compound solution are mixed together and ultrasonic treatment is used to promote the reaction. The ultrasonic treatment time is 50 minutes and the ultrasonic frequency is 50 kHz.

[0038] 4) After the reaction is completed, the graphene is separated by centrifugation at a centrifuge speed of 10,000 rpm for 20 minutes.

[0039] 5) Wash the centrifugally separated graphene three times with dimethylformamide solvent and dry the washed graphene in a vacuum oven at 40°C to obtain functionalized graphene. The purpose of washing is to remove unreacted aromatic molecules and solvent residues.

[0040] By functionalizing graphene with nitrogen-containing heterocyclic compounds like phenothiazine, additional chemically active sites, such as hydroxyl, carboxyl, or other oxygen-containing functional groups, are introduced onto the graphene surface. These functionalized sites can further react with resins or other materials, thereby improving the composite's interfacial compatibility. The functionalized graphene exhibits improved dispersibility in solvents, preventing aggregation of graphene sheets and improving their uniformity in the resin.

[0041] Finally, the prepared functionalized graphene is used to perform a second modification treatment on the brominated ester modified phenolic resin, and the specific steps include:

[0042] 1) Dissolve the brominated ester-modified phenolic resin in ethanol.

[0043] 2) The functionalized graphene is dispersed in ethanol to obtain a functionalized graphene dispersion. To promote the rapid dispersion of the functionalized graphene, ultrasonic dispersion can be used with an ultrasonic frequency of 20 kHz and an ultrasonic treatment time of 10 min.

[0044] 3) Finally, the functionalized graphene dispersion was slowly added dropwise to the brominated ester-modified phenolic resin solution and stirred at 50°C for 3 hours. After the reaction was completed, the final modified phenolic resin was obtained.

[0045] It should be noted that phenothiazine, as a nitrogen-containing heterocyclic compound, possesses a rich π-electron structure. When interacting with the graphene surface, it forms a stable π-π stacking. This stacking effect enables the nitrogen-containing heterocyclic compound molecules to adsorb firmly to the graphene surface, thereby imparting new functionality and dispersibility to the graphene. By functionalizing graphene with nitrogen-containing heterocyclic compounds, additional chemically active sites (such as hydroxyl, carboxyl, or other oxygen-containing functional groups) are introduced onto the graphene surface. These functionalized sites can further react with the bromoester-modified phenolic resin, thereby improving the interfacial compatibility of the composite material. Furthermore, the functionalized graphene exhibits improved dispersibility in solvents, effectively preventing aggregation of graphene sheets and improving its uniformity in the phenolic resin. This reduces the brittleness of the modified phenolic resin and enhances its tensile strength, fracture toughness, and elastic modulus.

[0046] Step 2: Preparation of lead-based metal-organic frameworks.

[0047] Specifically, the preparation of the lead-based metal-organic framework includes the following sub-steps:

[0048] 1) Mix 0.5 mmol of terephthalic acid solution and 10 mL of N,N-dimethylformamide to prepare a mixed solution;

[0049] 2) Dissolve lead nitrate in ultrapure water to prepare a lead nitrate solution.

[0050] 3) Pour the lead nitrate solution and the mixed solution from 1) into the same beaker and mix them thoroughly by ultrasonic treatment for 5 minutes at a frequency of 40 kHz.

[0051] 4) Transfer the thoroughly mixed solution to a high-pressure reactor, maintain the reactor temperature at 120°C, and heat for 24 hours.

[0052] 5) After the reaction is complete, the reactor is slowly cooled to room temperature and the lead-based metal-organic framework crystals are separated using a centrifuge at a speed of 10,000 rpm for 30 minutes.

[0053] 6) The lead-based metal-organic framework crystals obtained by centrifugation were washed three times with ethanol to remove residual reactants and solvents.

[0054] 7) Soaking the washed lead-based metal-organic framework crystals in an anhydrous ethanol solution for 6 hours, and then drying them in a vacuum oven at a low temperature of 45° C. to obtain a lead-based metal-organic framework.

[0055] It should be noted that lead-based metal-organic frameworks (Pb-MOFs) have good stability in a chemical environment, and through the preparation method of the lead-based metal-organic framework in this embodiment, a Pb-MOFs material with an ordered structure and a clear pore structure can be prepared. When added to the modified phenolic resin, it can effectively adsorb radioactive waste oil. At the same time, thanks to the excellent radiation shielding properties of the lead element itself, the bulk radiation of the prepared radioactive waste oil resin solid can be effectively reduced.

[0056] Step 3: The prepared lead-based metal-organic framework was added to dimethylformamide and treated with ultrasound for 60 minutes at an ultrasonic frequency of 60 kHz to obtain a lead-based metal-organic framework suspension.

[0057] Step 4: Weigh 3 g of modified phenolic resin, add it to 50 mL of methanol, and stir the solution using a magnetic stirrer until the phenolic resin is completely dissolved to obtain a transparent and uniform modified phenolic resin solution.

[0058] Step 5: Slowly pour the lead-based metal organic framework suspension into the methanol solution of the modified phenolic resin, and stir the mixture with a magnetic stirrer for 60 minutes to ensure that the lead-based metal organic framework is evenly dispersed in the phenolic resin solution to obtain a lead-based metal organic framework-modified phenolic resin solution.

[0059] Step 6: Transfer the lead-based metal-organic framework-modified phenolic resin solution to a rotary evaporator to remove the dimethylformamide and methanol solvents, yielding a viscous modified phenolic resin for radioactive waste oil solidification. Specifically, the rotary evaporator was maintained at a temperature of 60°C, a rotation speed of 100 rpm, and a vacuum of 0.05 MPa.

[0060] Example 2

[0061] This embodiment discloses a preparation process of a radioactive waste oil-modified phenolic resin solidified body, which specifically includes:

[0062] The modified phenolic resin prepared by the steps described in Example 1 and radioactive waste oil were mixed in a mass ratio of 1:10 and stirred for 30 minutes to obtain a mixture.

[0063] Then, polypropylene fiber and water are added to the mixture and mixed and stirred, wherein the ratio of the mass of water to the mass of the polypropylene fiber is 1:0.5.

[0064] After stirring for 30 minutes, the mixture was placed in an environment of 80° C. for curing treatment to obtain a radioactive waste oil-modified phenolic resin cured body.

[0065] Specifically, the final obtained radioactive waste oil modified phenolic resin solidified body includes the following components in percentage:

[0066] 30wt% radioactive waste oil.

[0067] 45 wt% of the cured modified phenolic resin prepared by the steps described in Example 1.

[0068] 10wt% polypropylene fibers.

[0069] 15wt% water, wherein, in order to solve the problem of radioactive wastewater, radioactivity less than 2.5×10 9 Bq / L of radioactive wastewater instead of tap water.

[0070] Example 3

[0071] This example provides a method for preparing a modified phenolic resin for solidifying radioactive waste oil. Ethyl 2-bromomethylacrylate, alkaline phenolic resin, and sodium hydroxide were purchased from Aladdin Biochemical Technology Co., Ltd. (Shanghai, China). N,N-dimethylformamide (DMF), ethanol, and dimethyl sulfoxide (DMSO) were purchased from Chengdu Kelong Chemical Co., Ltd. (Chengdu, China); graphene and pyrrole were purchased from MacLean Biochemical Technology Co., Ltd. (Shanghai, China); and lead nitrate and terephthalic acid were purchased from Sinopharm Chemical Reagent Co., Ltd. (Beijing, China). The specific preparation process is as follows:

[0072] Step 1: First, the phenolic resin obtained by base catalysis is modified twice.

[0073] The first modification treatment is to graft the brominated ester onto the synthesized phenolic resin to form a brominated ester modified phenolic resin.

[0074] The base-catalyzed phenolic resin was dissolved in dimethyl sulfoxide (DMSO) to a concentration of 10% (w / v), that is, 10 grams of phenolic resin was contained in every 100 mL of dimethyl sulfoxide solvent.

[0075] Then, ethyl 2-bromomethylacrylate was slowly added to the first mixed solution under a nitrogen atmosphere, and sodium hydroxide was added at the same time. The temperature of the mixed solution was then maintained at 40° C. and the reaction was carried out for 5 hours. The alkaline catalyst was added in this step to promote the grafting reaction.

[0076] Finally, the mixed solution after the reaction is completed is poured into pure water at a temperature of 6°C to precipitate to obtain the first modified phenolic resin, which is then placed in an environment of 4~10°C for use.

[0077] It should be noted that, in the above-mentioned process of grafting the bromoester onto the synthetic phenolic resin, 2-bromomethyl ethyl acrylate, as a compound containing bromine atoms, and bromine as a good leaving group, can be grafted onto the phenolic resin through a nucleophilic substitution reaction. During the reaction process, the hydroxyl group of the phenolic resin can react with the bromomethyl moiety in the 2-bromomethyl ethyl acrylate. By promoting the nucleophilic substitution reaction with sodium hydroxide, the phenolic resin is deprotonated, thereby causing the hydroxyl group of the phenolic resin to become a strong nucleophilic state, and then reacting with the bromomethyl moiety of the bromomethyl ethyl acrylate. In this way, the acrylate structure is grafted by the bromomethyl group, completing the graft modification of the phenolic resin-bromoester.

[0078] Next, functionalized graphene was prepared. First, 0.08 g of graphene was uniformly dispersed in 100 mL of ethanol solution by ultrasonic treatment for 30 min at an ultrasonic frequency of 30 kHz.

[0079] Pyrrole was dissolved in an ethanol solution and then subjected to ultrasonic treatment to uniformly disperse the pyrrole. The ultrasonic frequency was 30 kHz and the treatment time was 30 min.

[0080] The graphene suspension and the pyrrole solution were mixed together and ultrasonic treatment was used to fully mix the two to promote the reaction. The ultrasonic treatment was carried out for 45 minutes at an ultrasonic frequency of 50 KHz.

[0081] After the reaction is completed, the graphene is separated by centrifugation at a centrifuge speed of 11000 rpm for 25 minutes.

[0082] Finally, the graphene obtained by centrifugation was washed three times with dimethylformamide solvent and then dried in a vacuum oven at a low temperature of 40°C to obtain functionalized graphene. The purpose of washing is to remove unreacted aromatic molecules and solvent residues.

[0083] Finally, the prepared functionalized graphene is used to perform a second modification on the phenolic resin after the first modification. The specific steps include:

[0084] First, dissolve the bromoester-modified phenolic resin in ethanol. The solution concentration is 30% (w / v), meaning 30-35 grams of phenolic resin per 100 mL of ethanol. In this example, 30 g of bromoester-modified phenolic resin was dissolved in 100 mL of ethanol.

[0085] Then, 0.08 g of functionalized graphene is dispersed in ethanol to obtain a functionalized graphene dispersion. To promote the rapid dispersion of the functionalized graphene, ultrasonic dispersion can be used with an ultrasonic frequency of 20 kHz and an ultrasonic treatment time of 5 min.

[0086] Finally, the functionalized graphene dispersion was slowly added dropwise to the brominated ester modified phenolic resin solution and stirred at a stirring temperature of 40° C. for 2 h. After the reaction was completed, the final modified phenolic resin was obtained.

[0087] Step 2: Preparation of lead-based metal-organic frameworks.

[0088] 0.5 mmol of terephthalic acid solution and 10 mL of N,N-dimethylformamide were mixed to prepare a mixed solution.

[0089] Lead nitrate was dissolved in ultrapure water to prepare a 0.5 mmol lead nitrate solution.

[0090] The two mixed solutions were poured into the same beaker and mixed, and ultrasonic treatment was performed to fully mix the two solutions. The ultrasonic treatment time was 5 min and the ultrasonic frequency was 60 kHz.

[0091] The thoroughly mixed solution was transferred to a high-pressure reactor, and the reactor temperature was maintained at 150° C. for heating for 16 h.

[0092] After the reaction was completed, the reactor was slowly cooled to room temperature, and the lead-based metal-organic framework crystals were separated using a centrifuge with a centrifuge speed of 10,000 rpm and a centrifugation time of 30 min.

[0093] The lead-based metal-organic framework crystals obtained by centrifugation were washed three times with ethanol to remove residual reactants and solvents.

[0094] The washed lead-based metal-organic framework crystals were immersed in anhydrous ethanol solution for 4 hours and then dried in a vacuum oven at low temperature.

[0095] Step 3: The prepared lead-based metal-organic framework was added to dimethylformamide and treated with ultrasound for 40 minutes at an ultrasonic frequency of 60 kHz to obtain a lead-based metal-organic framework suspension.

[0096] Step 4: Weigh 5 g of modified phenolic resin, add it to 50 mL of methanol, and stir the solution using a magnetic stirrer until the phenolic resin is completely dissolved to obtain a transparent and uniform modified phenolic resin solution.

[0097] Step 5: Slowly pour the lead-based metal organic framework suspension into the methanol solution of the modified phenolic resin, and stir the mixture with a magnetic stirrer for 30 minutes to ensure that the lead-based metal organic framework is evenly dispersed in the phenolic resin solution to obtain a lead-based metal organic framework-modified phenolic resin solution.

[0098] Step 6: Transfer the lead-based metal-organic framework-modified phenolic resin solution to a rotary evaporator to remove the dimethylformamide and methanol solvents, yielding a viscous modified phenolic resin for radioactive waste oil solidification. Specifically, the rotary evaporator was maintained at a temperature of 40°C, a rotation speed of 150 rpm, and a vacuum of 0.1 MPa.

[0099] Finally, a resin material for solidifying radioactive waste oil is obtained.

[0100] Example 4

[0101] This example differs from Example 1 in that step 2 is omitted, and a lead-based metal-organic framework is prepared. That is, the phenolic resin prepared in this example does not contain a lead-based metal-organic framework. The phenolic resin modification steps are the same as in Example 1. Thus, a resin material for curing radioactive waste oil is prepared that does not contain a lead-based metal-organic framework.

[0102] Example 5

[0103] The difference between this embodiment and embodiment 2 is that the functionalized graphene is not used to perform a second modification treatment on the brominated ester modified phenolic resin. That is, the modified phenolic resin in this embodiment is only subjected to the brominated ester modification treatment once, and the remaining steps are the same as those in embodiment 2.

[0104] Example 6

[0105] 1) 10 kg of simulated radioactive waste oil was added to a container containing 1 kg of the modified phenolic resin prepared by the method described in Example 1, stirred at a constant speed for 10 minutes at a stirring blade linear speed of 5 m / s, and allowed to stand for 20 minutes to obtain a resin-simulated radioactive waste oil mixture;

[0106] 2) Add 1.25 kg of polypropylene fiber to 2.5 kg of simulated radioactive wastewater and stir uniformly for 10 minutes at a stirring blade speed of 5 m / s to obtain a radioactive wastewater-polypropylene fiber mixture;

[0107] 3) adding the radioactive wastewater-polypropylene fiber mixture to the resin-simulated radioactive waste oil mixture and stirring the mixture at a stirring blade linear speed of 12 m / s for 15 minutes, and curing and solidifying at 65° C. to obtain a resin solidified body of simulated radioactive waste oil.

[0108] Example 7

[0109] 1) 10 kg of simulated radioactive waste oil was added to a container containing 1 kg of the modified phenolic resin prepared by the method described in Example 3, and the mixture was stirred at a constant speed of 5 m / s for 10 minutes, and allowed to stand for 20 minutes to obtain a resin-simulated radioactive waste oil mixture;

[0110] 2) Add 1.25 kg of polypropylene fiber to 2.5 kg of simulated radioactive wastewater and stir uniformly for 10 minutes at a stirring blade speed of 5 m / s to obtain a radioactive wastewater-polypropylene fiber mixture;

[0111] 3) adding the radioactive wastewater-polypropylene fiber mixture to the resin-simulated radioactive waste oil mixture and stirring the mixture at a stirring blade linear speed of 12 m / s for 15 minutes, and curing and solidifying at 70° C. to obtain a resin solidified body of simulated radioactive waste oil.

[0112] Comparative Example 1

[0113] Simulated radioactive waste oil, an emulsifier (compounded from sodium dialkylbenzene sulfonate and octylphenol polyoxyethylene ether), and water were thoroughly stirred in a volume ratio of 1.3:0.1:1 to form a waste oil emulsion. Ordinary Portland cement, zeolite powder, water, kaolin, and wood fiber were mixed uniformly in a mass ratio of 1:0.05:0.1:0.03:0.01 to form a cement slurry. This cement slurry was then mixed uniformly with the waste oil emulsion in a mass ratio of 1:0.4 to form a cement-solidified form of simulated radioactive waste oil.

[0114] Comparative Example 2

[0115] Simulated radioactive waste oil, sodium hydroxide, and water were thoroughly stirred in a volume ratio of 1.3:0.1:1 to form a waste oil saponified liquid. Ordinary Portland cement, stearic acid, water, diatomaceous earth, and wood fiber were mixed uniformly in a mass ratio of 1:0.05:0.1:0.03:0.01 to form a cement slurry. This cement slurry was then mixed uniformly with the waste oil saponified liquid in a mass ratio of 1:0.4 to form a cement-solidified form of simulated radioactive waste oil.

[0116] Comparative Example 3

[0117] The simulated radioactive waste oil and the radioactive waste oil-free lead-based metal organic framework prepared by the steps in Example 4 were solidified into a resin material. A resin solidified body of the simulated radioactive waste oil was prepared according to the method and steps in Example 6.

[0118] Comparative Example 4

[0119] The simulated radioactive waste oil and the resin material for radioactive waste oil solidification that was once modified and prepared by the steps in Example 5 were used. A resin solidified body of the simulated radioactive waste oil was prepared according to the method and steps in Example 6.

[0120] Experimental example,

[0121] In this experimental example, the performance of the solidified radioactive waste oil in Example 6, Example 7, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 was evaluated, including the following:

[0122] Four φ50 mm × 50 mm resin specimens prepared by the methods of Example 6, Example 7, Comparative Example 3, and Comparative Example 4 were cured at 25°C for 30 days, and the performance of the resin solidified bodies was tested according to the standard leaching test method for low- and medium-level radioactive waste solidified bodies in GBT 7023-2011.

[0123] Two φ50 mm × 50 mm cement specimens prepared by the methods of Comparative Examples 1 and 2 were cured at 25°C for 30 days, and the performance of the cement solidified bodies was tested according to the standard leaching test method for cement solidified bodies in accordance with GB14569.1-2011 Performance requirements for low- and intermediate-level radioactive waste solidified bodies - Cement solidified bodies.

[0124] Through testing, the compressive strength of the resin cured body in Example 6 can reach 26.3 MPa after 30 days; among them, the leaching rate of cesium (Cs) ions per unit area per unit time within the 30-day test period is 0.96×10^-5 cm / d, the leaching rate of uranium (U) ions within the 30-day test period is 9.56×10^-10 cm / d, and the leaching rate of cerium (Ce) ions within the 30-day test period is 1.41×10^-9 cm / d.

[0125] The compressive strength of the resin cured body in Example 7 can reach 26.1 MPa after 30 days. Among them, the leaching rate of cesium (Cs) ions per unit area per unit time within the 30-day test period is 0.82×10^-5 cm / d, the leaching rate of uranium (U) ions within the 30-day test period is 8.91×10^-10 cm / d, and the leaching rate of cerium (Ce) ions within the 30-day test period is 1.56×10^-9 cm / d.

[0126] The compressive strength of the resin cured body in Comparative Example 3 can reach 25.3 MPa after 30 days; among them, the leaching rate of cesium (Cs) ions per unit area per unit time within the 30-day test period is 1.62×10^-5 cm / d, the leaching rate of uranium (U) ions within the 30-day test period is 10.87×10^-10 cm / d, and the leaching rate of cerium (Ce) ions within the 30-day test period is 4.87×10^-9 cm / d.

[0127] The compressive strength of the resin cured body in Comparative Example 4 can reach 20.7 MPa after 30 days; among them, the leaching rate of cesium (Cs) ions per unit area per unit time within the 30-day test period is 1.12×10^-5 cm / d, the leaching rate of uranium (U) ions within the 30-day test period is 8.87×10^-10 cm / d, and the leaching rate of cerium (Ce) ions within the 30-day test period is 3.61×10^-9 cm / d.

[0128] From the comparative experiments above, it can be seen that the lead-based metal-organic framework has little effect on compressive strength, but has a greater impact on the leaching rate of radioactive ions. However, in general, its radioactive ion leaching rate is still lower than that of cement-based solids. Graphene modification has a significant effect on compressive strength, which may be because the modified graphene is evenly distributed in the resin, forming more physical connections and network structures. These structures can prevent and delay crack propagation, improving the fracture toughness of the material. At the same time, the evenly dispersed graphene can fill the tiny gaps and defects in the resin matrix, reducing the brittle areas in the material. This makes the composite material less prone to stress concentration when subjected to stress, thereby reducing the material's brittleness. Resins that have not been modified with graphene do not have these characteristics, so their compressive strength is reduced.

[0129] The compressive strength of the cement solidified body in Comparative Example 1 can reach 18.6 MPa after 30 days. Among them, the leaching rate of cesium (Cs) ions per unit area per unit time within the 30-day test period is 1.92×10^-5 cm / d, the leaching rate of uranium (U) ions within the 30-day test period is 12.36×10^-10 cm / d, and the leaching rate of cerium (Ce) ions within the 30-day test period is 4.56×10^-9 cm / d.

[0130] The compressive strength of the cement solidified body in Comparative Example 2 can reach 12.3 MPa after 30 days. Among them, the leaching rate of cesium (Cs) ions per unit area per unit time within the 30-day test period is 1.66×10^-5 cm / d, the leaching rate of uranium (U) ions within the 30-day test period is 13.72×10^-10 cm / d, and the leaching rate of cerium (Ce) ions within the 30-day test period is 5.17×10^-9 cm / d.

[0131] Then, the cured bodies in the six embodiments and comparative examples were subjected to a 30-day oil permeability test, a combustion weight loss ratio test, and a volume expansion rate test.

[0132] The 30-day oil permeability test method is to place the weighed solidified body on filter paper and place it in a sealed glass.

[0133] The container was stored for 30 days and the oil permeation rate was tested by the change in the mass of the filter paper.

[0134] The combustion weight loss ratio test method involves weighing a certain amount of solidified sample, placing it in a crucible, igniting it, observing and recording the combustion state, and weighing the combustion residue to calculate the solidified body's combustion weight loss ratio. Weight loss ratio = m2 / m1, where m1 is the weight of the solidified body before combustion (g) and m2 is the weight of the residue after combustion (g).

[0135] The volume expansion rate test method is to measure the volume V1 of the waste oil to be solidified and the natural accumulation volume V2 after the solidification test is completed. The volume expansion rate = [(V2 - V1) / V1] × 100%. The experimental results of the three experiments are shown in Table 1.

[0136] Table 1. 30-day oil permeability test, weight loss ratio test, and volume expansion rate test results

[0137]

[0138] From the above experimental comparison, it can be seen that the modified phenolic resin prepared in the present invention performs better in various aspects than traditional cement curing. In particular, with respect to oil permeability, the modified phenolic resin of the present invention can effectively prevent the leakage of radioactive waste oil and has a good sealing effect on radioactive waste oil. Furthermore, as can be seen from Comparative Examples 3 and 4, Comparative Example 3, which removes the lead-based metal-organic framework, shows no significant difference in oil permeability, weight loss ratio, and volume expansion ratio from the resin cured products of Examples 6 and 7; whereas Comparative Example 4, which underwent a single modification operation, showed a significant difference in oil permeability test. This may be due to the modification of the phenolic resin with functionalized graphene, which strengthens the interfacial interaction between the functionalized graphene and the phenolic resin, forming stronger chemical bonds. The enhanced interfacial interaction helps reduce pinholes and microcracks in the resin, thereby reducing the oil molecule permeability of the radioactive waste oil. Functionalized graphene also exhibits better dispersion in phenolic resin, meaning the graphene sheets are more evenly distributed within the resin matrix. This uniform distribution contributes to a denser composite structure, further reducing the penetration pathways for oil molecules. Phenolic resin without graphene modification lacks these characteristics, ultimately leading to the difference in 30-day oil permeability.

[0139] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0140] The present invention discloses a method for preparing a modified phenolic resin for solidifying radioactive waste oil, relating to the technical field of nuclear radioactive waste treatment. The preparation method comprises: modifying a phenolic resin obtained by base catalysis; preparing a lead-based metal-organic framework; adding the prepared lead-based metal-organic framework to dimethylformamide to obtain a lead-based metal-organic framework suspension; weighing 1-5g of the modified phenolic resin and adding it to 20-50mL of methanol to obtain a modified phenolic resin solution; slowly pouring the lead-based metal-organic framework suspension into the methanol solution of the modified phenolic resin, and stirring the mixture with a magnetic stirrer for 30-60 minutes to uniformly disperse the lead-based metal-organic framework in the phenolic resin solution, thereby obtaining a lead-based metal-organic framework-modified phenolic resin solution. The modified phenolic resin material of the present invention can not only solidify waste oil but also simultaneously adsorb radioactive isotopes, effectively preventing the leakage of radioactive waste oil.

Claims

1. A method for preparing a modified phenolic resin for solidifying radioactive waste oil, characterized in that: The preparation method comprises: performing modification treatment on the phenolic resin obtained by base catalysis; Preparation of lead-based metal-organic frameworks; The prepared lead-based metal-organic framework was added to dimethylformamide and treated with ultrasound for 30-60 min at an ultrasound frequency of 60 kHz to obtain a lead-based metal-organic framework suspension. Weigh 1-5 g of the modified phenolic resin, add it to 20-50 mL of methanol, and stir the solution with a magnetic stirrer until the modified phenolic resin is completely dissolved to obtain a modified phenolic resin solution; Slowly pouring the lead-based metal-organic framework suspension into the modified phenolic resin solution, and stirring the mixture with a magnetic stirrer for 30 to 60 minutes to uniformly disperse the lead-based metal-organic framework in the modified phenolic resin solution, thereby obtaining a lead-based metal-organic framework-modified phenolic resin solution; The lead-based metal organic framework-modified phenolic resin solution is transferred to a rotary evaporator to remove dimethylformamide and methanol solvents to obtain a modified phenolic resin for radioactive waste oil solidification; The modification process includes first grafting a bromoester onto a synthesized phenolic resin through a grafting reaction to form a first modified phenolic resin; The first modified phenolic resin is treated with functionalized graphene to obtain the second modified phenolic resin. The preparation of the lead-based metal organic framework comprises the following steps: Mix 0.5 mmol of terephthalic acid solution and 10 mL of N,N-dimethylformamide to obtain a mixed solution A; Lead nitrate is added into ultrapure water and dissolved to prepare a mixed solution B; Pour the mixed solution A and the mixed solution B into the same beaker, mix them, and perform ultrasonic treatment to fully mix the two solutions to prepare a mixed solution C. The ultrasonic treatment time is 5 to 10 minutes and the ultrasonic frequency is 40 to 60 kHz; Transfer the C mixed solution into a high-pressure reactor, maintain the reactor temperature at 120-200°C, and heat for 16-24 hours; After the reaction is completed, the reactor is slowly cooled to room temperature and the lead-based metal-organic framework crystals are separated using a centrifuge at a speed of 10,000-11,000 rpm for 30-35 min. The separated lead-based metal-organic framework crystals were washed three times with ethanol to remove residual reactants and solvents; The washed lead-based metal-organic framework crystals are immersed in an anhydrous ethanol solution for 4 to 6 hours, and then dried in a vacuum oven at a low temperature of 30 to 45° C. to prepare a lead-based metal-organic framework.

2. The method for preparing a modified phenolic resin for solidifying radioactive waste oil according to claim 1, wherein: The first modified phenolic resin is prepared by the following steps: First, unmodified phenolic resin is obtained by polycondensation of phenol and formaldehyde under base catalysis; dissolving the prepared unmodified phenolic resin in dimethyl sulfoxide or ethyl acetate to prepare a first mixed solution; Slowly adding the bromoester to the first mixed solution under an inert atmosphere, and simultaneously adding an alkaline catalyst to prepare a second mixed solution, maintaining the second mixed solution at 40-50° C. and reacting for 4-6 hours; After the reaction is completed, the second mixed solution is poured into pure water at a temperature of 4-10° C. to precipitate to obtain the first modified phenolic resin.

3. The method for preparing a modified phenolic resin for solidifying radioactive waste oil according to claim 1, wherein: The second modified phenolic resin is prepared by the following steps: dissolving the first modified phenolic resin in ethanol; dispersing the functionalized graphene in ethanol to obtain a functionalized graphene dispersion; The functionalized graphene dispersion was slowly added dropwise to the solution and stirred at a temperature of 35-50° C. for 2-3 h to prepare a second modified phenolic resin. The dispersion is ultrasonic dispersion, the ultrasonic frequency is 20 kHz, and the ultrasonic treatment time is 5 to 10 minutes.

4. The method for preparing a modified phenolic resin for solidifying radioactive waste oil according to claim 3, wherein: The functionalized graphene is prepared by the following steps: Graphene was uniformly dispersed in an ethanol solution by ultrasonic treatment to prepare solution A; The nitrogen-containing heterocyclic compound is dissolved in an ethanol solution by ultrasonic treatment to prepare a solution B; Mix solution A and solution B together and promote the reaction by ultrasonic treatment. The ultrasonic treatment time is 30-50 minutes and the ultrasonic frequency is 50KHz. After the reaction is completed, the graphene is separated by centrifugation. The centrifuge speed is 10000~12000 rpm and the centrifugation time is 20~30 min. The graphene was washed three times with dimethylformamide solvent, and the washed graphene was placed in a vacuum oven and dried at a low temperature of 40-50°C to prepare functionalized graphene.

5. The method for preparing a modified phenolic resin for solidifying radioactive waste oil according to claim 1, wherein: The temperature of the rotary evaporator is 40-60°C, the rotation speed is 100-150 rpm, and an appropriate vacuum degree of 0.05-0.1 MPa is applied.

6. A modified phenolic resin for solidifying radioactive waste oil, characterized in that: The modified phenolic resin for solidifying radioactive waste oil is prepared by the method according to any one of claims 1 to 5.

7. A radioactive waste oil-modified phenolic resin solidified body, characterized in that: The radioactive waste oil-modified phenolic resin solidified body comprises the following components in percentage by weight: 20-50wt% radioactive waste oil; 35-55 wt% of a cured modified phenolic resin, wherein the modified phenolic resin is prepared according to the method according to any one of claims 1 to 5; 2-10 wt% polypropylene fiber; 5-15wt% water.

8. The radioactive waste oil-modified phenolic resin solidified body according to claim 7, wherein: The water is tap water or has a radioactivity less than 2.5×10 9 Bq / L of radioactive wastewater.

Images