Intensive-radiation-resistant nuclear-grade cation exchange resin as well as preparation method and application thereof

Abstract

The invention belongs to the field of nuclear wastewater treatment, and particularly relates to intense-radiation-resistant nuclear-grade cation exchange resin as well as a preparation method and application thereof. The nuclear-grade cation exchange resin is a nuclear-grade structure compound, a nuclear layer material is porous titanium-lanthanum oxide particles and is obtained by pyrolyzing a titanium-lanthanum binary metal organic framework material, an organic ligand of the titanium-lanthanum binary metal organic framework material is an amino organic phosphonic acid compound, and an organic ligand of the titanium-lanthanum binary metal organic framework material is an organic phosphonic acid compound. And the material of the shell layer is in-situ sulfonated nuclear-grade strong-acid cation exchange resin. The nuclear-grade cation exchange resin has high exchange capacity and good intense radiation resistance, and compared with an existing method, the obtained resin is high in strength and low in TOC content.

Description

Technical Field

[0001] This invention belongs to the field of nuclear wastewater treatment, specifically relating to a nuclear-grade cation exchange resin resistant to strong radiation, its preparation method, and its application. Background Technology

[0002] Nuclear power plant operation and other nuclear industry activities generate large amounts of nuclear wastewater, which contains various radionuclides and heavy metal ions, posing a serious threat to the environment and human health. Traditional nuclear wastewater treatment methods suffer from low efficiency, poor selectivity, complex operation, and high cost. Ion exchange technology is one of the important methods for nuclear wastewater treatment, with advantages such as simple operation, high efficiency, and good selectivity. Nuclear-grade ion exchange resin is a key material in nuclear wastewater treatment, and its performance directly affects treatment efficiency and safety.

[0003] Currently, commonly used nuclear-grade ion exchange resins are mainly sulfonated styrene-based cation exchange resins. However, these resins suffer from drawbacks such as low mechanical strength, poor chemical stability, and low adsorption selectivity. To improve resin performance, researchers have begun exploring core-shell structured ion exchange resins. This structure combines the advantages of different materials by using a core material to provide mechanical strength and chemical stability, and a shell material to provide ion exchange functionality.

[0004] In recent years, some studies have used inorganic materials as the core layer and polymer materials as the shell layer to prepare core-shell structured ion exchange resins. For example, Chinese patent application CN201710998181.5 discloses a core-shell structured anion exchange resin with rare earth oxides as the core and styrene-based resins as the shell. However, this method uses a high amount of rare earth oxides, significantly increasing manufacturing costs. To obtain cation exchange resins, existing technologies typically employ traditional post-sulfonation methods, which suffer from low efficiency and uneven distribution of sulfonic acid groups, as well as resin degradation. Furthermore, the inorganic core materials used in these studies have low surface activity and poor adhesion to the polymer shell, making core-shell separation a common problem.

[0005] Therefore, developing a nuclear-grade cation exchange resin with high mechanical strength, high chemical stability, high selectivity, and high ion exchange capacity, and adopting an efficient and environmentally friendly preparation method, is an urgent problem to be solved in the field of nuclear chemical materials. Summary of the Invention

[0006] This invention provides a nuclear-grade cation exchange resin resistant to strong radiation, its preparation method, and its application. The nuclear-grade cation exchange resin has high exchange capacity and good resistance to strong radiation. Compared with existing methods, the resin obtained has high strength and low TOC content.

[0007] To solve the above-mentioned technical problems, the first aspect of the present invention adopts the following technical solution:

[0008] A radiation-resistant nuclear-grade cation exchange resin is disclosed. This nuclear-grade cation exchange resin is a nuclear-grade structural composite. The core layer material is porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles, which are obtained by pyrolysis of titanium lanthanum binary metal-organic framework material. The organic ligand of the titanium lanthanum binary metal-organic framework material is an amino organophosphonic acid compound, and the shell material is an in-situ sulfonated nuclear-grade strong acid cation exchange resin.

[0009] In a preferred embodiment, the in-situ sulfonated nucleograde strong acid cation exchange resin is prepared by suspension polymerization of styrene, divinylbenzene, trivinylbenzene, sulfonic acid-containing monomers, porogens and initiators, and the organic ligand of the amino organophosphonic acid compound is one of 4-(dimethylamino)triphenylphosphine, aminotrimethylenephosphonic acid or ethylenediaminetetramethylenephosphonic acid.

[0010] Furthermore, the titanium-lanthanum binary metal-organic framework material is prepared by hydrothermal reaction of lanthanum nitrate, titanium nitrate, and an amino organophosphonic acid compound at 120–180 °C. The mass ratio of lanthanum nitrate to titanium nitrate is (2–20):0.2, and the mass ratio of lanthanum nitrate to the amino organophosphonic acid compound is (2–5):1. When calculating the mass ratio, lanthanum nitrate is based on lanthanum nitrate hexahydrate.

[0011] The sulfonic acid-containing monomer is selected from sodium styrene sulfonate or sodium allyl sulfonate.

[0012] The mass ratio of the raw material mixture for preparing the in-situ sulfonated nucleograde strong acid cation exchange resin to the porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles is 100:0.1-1.5.

[0013] At the microscale, titanium exerts a regulatory effect on lanthanum oxide crystallites. Through the spacer effect of titanium, smaller lanthanum oxide crystallites are obtained, increasing the specific surface area of ​​lanthanum oxide and thus enhancing the material's ability to handle radiation elements. Simultaneously, titanium doping into the lanthanum oxide lattice generates more lattice defects. Since titanium has more valence electrons than lanthanum, these defects increase the density of free electrons within the material, thereby improving its resistance to radiation oxidation.

[0014] The mass ratio of lanthanum nitrate to titanium nitrate is (2-20): 0.2. If too much titanium nitrate is used, it will destroy the crystal structure of the lanthanum oxide obtained after calcination and produce a large amount of amorphous lanthanum oxide, which is not conducive to the radiation resistance effect of lanthanum oxide nanoparticles.

[0015] The mass ratio of the raw material mixture to porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles in the preparation of in-situ sulfonated nuclear-grade strong acid cation exchange resin is 100:0.1–1.5. If the amount of porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles is too high, it will lead to the adsorption of too many polymer monomers onto the nanoparticles, resulting in an excessively small polystyrene shell size, a large pressure drop in the resin bed, and easy resin breakage, which is detrimental to the resin's application in nuclear wastewater treatment.

[0016] Amino-organophosphonic acid compounds act as a link between lanthanum and titanium ions, constructing the MOF (Metal-Oxide-Foil) framework. Insufficient amounts of amino-organophosphonic acid compounds can lead to ineffective complexation of lanthanum and titanium ions, preventing the formation of a complete MOF structure. Excessive amounts result in hydrogen bonds between the amino groups and phosphonic acids, separating the structural units of the titanium-lanthanum MOFs and reducing their order. This significantly impacts the uniformity, order, and continuity of the titanium-lanthanum oxide obtained after subsequent oxidation, thus significantly reducing its radiation resistance.

[0017] Amino organophosphonic acid compounds form specific coordination structures with titanium lanthanum ions, promoting the tight binding and uniform and orderly distribution of titanium lanthanum ions, thereby improving radiation resistance and mechanical properties.

[0018] The raw material mixture for the in-situ sulfonated nucleograde strong acid cation exchange resin consists of styrene, divinylbenzene, trivinylbenzene, sulfonic acid-containing monomers, porogens, and initiators. In this invention, the amount of porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles in the resin is extremely small.

[0019] The preparation steps for the radiation-resistant nuclear-grade cation exchange resin are as follows:

[0020] (1) Prepare a mixed aqueous solution of lanthanum nitrate and titanium nitrate, add an amino organophosphonic acid compound to obtain a metal-organic framework precursor solution, react at 120-180℃ for 12-24h, cool, wash and dry to obtain titanium-lanthanum binary metal-organic framework material.

[0021] (2) The titanium-lanthanum binary metal-organic framework material was calcined in an oxidizing atmosphere to obtain porous phosphorus-doped carbon-supported titanium-lanthanum oxide nanoparticles.

[0022] (3) Styrene, divinylbenzene, trivinylbenzene, sulfonic acid-containing monomers, pore-forming agents and initiators are thoroughly mixed to obtain an oil phase mixture, and porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles are added to obtain a composite oil phase mixture;

[0023] (4) Prepare an aqueous solution of dispersant and methylene blue, add the composite oil phase mixture, gradually heat to 90-100℃, react, cool and filter, and wash the resin with organic solvent and deionized water in sequence to obtain a nuclear-grade cation exchange resin resistant to strong radiation.

[0024] Preferably, in step (2), the calcination conditions are: heating to 350-550°C at a heating rate of 2-5°C / min under air or oxygen, and calcining for 2-4 hours.

[0025] Using a calcination temperature of 350-550℃ can effectively remove the organic ligands—amino organophosphonic acid compounds—from MOFs, forming a porous structure. Porous phosphorus-doped carbon is retained, thereby improving the material's adsorption performance and synergistically enhancing radiation resistance with titanium lanthanum oxide. Temperatures above 550℃, without a support (organic ligands, porous phosphorus-doped carbon), easily lead to the aggregation of titanium lanthanum oxide, disrupting the continuous distribution of atomic clusters and reducing activity. Furthermore, the complete decomposition of organic groups in the porous phosphorus-doped carbon structure prevents the effective coupling of these groups, hindering the orderly and homogeneous polymerization of the resin's polymer monomers. This is detrimental to constructing core-shell composites and easily leads to core-shell separation during use.

[0026] The in-situ sulfonation of this invention utilizes specific sulfonic acid monomers. After the polymer monomers are adsorbed by a porous phosphorus-doped carbon material, the compatibility between polymer monomers such as styrene and sulfonic acid monomers such as sodium styrene sulfonate or sodium allyl sulfonate ensures that the sulfonic acid groups are uniformly introduced into the resin skeleton, while avoiding adverse effects on the polymerization reaction. The sulfonic acid monomer content is controlled at 8.3-23.4 wt% to ensure sufficient ion exchange capacity while avoiding a decrease in the mechanical strength of the resin due to excessively high sulfonic acid content.

[0027] Preferably, in step (3), the composition of the oil phase mixture is: 66.7-78.1 wt% styrene, 8.3-15.6 wt% divinylbenzene, 1.7-7.8 wt% trivinylbenzene, 8.3-23.4 wt% sulfonic acid monomer, 2.5-4.7 wt% porogen, and 0.3-1.6 wt% initiator.

[0028] Preferably, in step (3), the pore-forming agent is selected from one or more of ethanol, butanol, isopropanol, n-heptane, n-octane or mixtures thereof, and the initiator is selected from one of cyclohexanone peroxide, benzoyl peroxide, and diisobutyl peroxide.

[0029] Preferably, in step (4), the dispersant is selected from one of polyvinyl alcohol, polyvinylpyrrolidone, methylcellulose, and gelatin, and the mass fraction of the dispersant in the aqueous solution is 0.1-5 wt%, and the concentration of the methylene blue solution in the aqueous solution is 0.001-0.1 wt%.

[0030] Preferably, in step (4), the temperature is gradually increased to 60-65℃ for 0.5-2h, 75-80℃ for 0.5-2h, and 65-100℃ for 2-12h.

[0031] Preferably, the organic solvent in step (4) is acetone or methanol. After washing with the organic solvent, the organic solvent is removed by vacuum distillation and then the resin is washed with deionized water.

[0032] A second aspect of the present invention is to provide a method for preparing the aforementioned radiation-resistant nuclear-grade cation exchange resin.

[0033] A third aspect of the present invention discloses the application of the aforementioned radiation-resistant nuclear-grade cation exchange resin in nuclear wastewater treatment.

[0034] Beneficial effects

[0035] This invention provides a radiation-resistant nuclear-grade cation exchange resin and its preparation method. The resin is a nuclear-grade structural composite, with a core layer material of porous titanium lanthanum oxide particles and a shell material of in-situ sulfonated nuclear-grade strongly acidic cation exchange resin. Compared with the prior art, this invention has the following significant advantages:

[0036] (1) This invention utilizes amino organophosphonic acid compounds as organic ligands to prepare titanium-lanthanum binary metal-organic framework materials through the complexation between the amino groups and lanthanum metal ions, and between the phosphonic acid groups and titanium metal ions. The ordered distribution and tight bonding of titanium and lanthanum metal ions are achieved through the spatial regulation of the organic groups. Combined with calcination, this results in cluster-level continuous distribution and tight bonding of titanium-lanthanum oxide nanoparticles, improving the uniformity of the resin material particles. Simultaneously, the micro-sized titanium's control over the lanthanum oxide microcrystals enhances the radiation resistance of the resin material.

[0037] (2) This invention, through calcination and oxidation of a titanium-lanthanum binary metal-organic framework material, obtains titanium-lanthanum metal oxide, improving the material's radiation resistance, while simultaneously obtaining porous phosphorus-doped carbon material, enhancing the material's adsorption efficiency and improving the diffusion of the radiation medium within the material's core layer, thus enhancing the radiation resistance of the titanium-lanthanum oxide. Utilizing the electron-withdrawing ability of phosphorus in the phosphorus-doped carbon material, more cation adsorption centers are provided to the resin material, improving its adsorption and processing capacity for cations. The porous and organic group characteristics of the porous phosphorus-doped carbon material adsorb polymer monomers, enabling the polymerization of polymer monomers outside the titanium-lanthanum oxide supported by the porous phosphorus-carbon structure, thereby avoiding core-shell separation.

[0038] (3) In the suspension polymerization process, the present invention adds trivinylbenzene as a crosslinking agent, which can regulate the network structure within the polymer and improve the uniformity of the polymer structure. Compared with traditional resins that only use divinylbenzene as a crosslinking agent, the resin layer prepared by the present invention has a higher degree of crosslinking, thereby significantly improving the mechanical strength, wear resistance and heat resistance of the material, enabling it to maintain good structural integrity under harsh nuclear radiation environment and extending the service life of the resin.

[0039] (4) The present invention adopts an in-situ sulfonation method. During the suspension polymerization process, by adding a monomer containing sulfonic acid group (such as sodium styrene sulfonate), the problems of resin degradation and uneven distribution of sulfonic acid group that may be caused by the traditional post-sulfonation method are avoided. While improving the ion exchange capacity and adsorption rate of the resin material, the resin is prevented from cracking due to the harsh sulfonation conditions, and the TOC of the resin is reduced.

[0040] (5) This invention constructs a resin system with titanium lanthanum oxide nanoparticles as the core and in-situ sulfonated resin as the shell. Through the adsorption and coupling effect of porous phosphorus-doped carbon materials, the resin shell is uniformly coated on the titanium lanthanum oxide nanoparticles, so as to synergistically exert the radiation resistance of titanium lanthanum oxide nanoparticles and the strong ion exchange capacity of in-situ sulfonated resin. With a very small amount of titanium lanthanum oxide nanoparticles, the radiation resistance of nuclear-grade cation exchange resin is significantly improved, and the manufacturing cost of nuclear-grade cation exchange resin is reduced. Detailed Implementation

[0041] The present invention will be described in detail below with reference to specific embodiments.

[0042] Example 1

[0043] 1) Weigh 1.0 g of lanthanum nitrate hexahydrate and 0.5 g of titanium nitrate solution (titanium nitrate content 20 wt%), dissolve in 30 mL of deionized water and stir until the solution is clear and transparent. Then, add 0.5 g of 4-(dimethylamino)triphenylphosphine to the solution, adjust the pH of the mixture to 5.5 by adding 1 M dilute ammonia solution dropwise, and stir the mixture at room temperature for 30 min. Transfer the mixture to an autoclave with a polytetrafluoroethylene liner, heat at 120 °C for 12 h, cool to room temperature and centrifuge. Wash the obtained solid three times with deionized water, wash once with ethanol, and then dry in a vacuum oven at 60 °C for 12 h to obtain the titanium-lanthanum binary metal-organic framework material.

[0044] 2) The titanium-lanthanum binary metal-organic framework material was placed in a ceramic crucible and calcined in air at a rate of 2℃ / min to 400℃ and held at 400℃ for 2h to obtain porous phosphorus-doped carbon-supported titanium-lanthanum oxide nanoparticles.

[0045] 3) In a flask, mix 70.0 g styrene, 12.0 g divinylbenzene, 3.0 g trivinylbenzene, 10.0 g sodium styrene sulfonate, 3.0 g ethanol, and 0.5 g cyclohexanone peroxide. Heat the mixture to 60 °C and stir until all components dissolve to obtain an oil phase mixture. Add 1 g of porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles to the oil phase mixture and sonicate the resulting mixture for 1 h to form a stable dispersion, thus obtaining a composite oil phase reaction solution.

[0046] 4) An aqueous solution was prepared by dissolving 1.0 g of polyvinyl alcohol and 0.005 g of methylene blue in 200 mL of deionized water. Under nitrogen protection, the composite oil phase reaction solution was slowly added to the aqueous solution with stirring. The mixture was then heated to 60 °C and reacted for 1 h, followed by increasing the temperature to 75 °C for 1 h, and finally increasing the temperature to 90 °C for 2 h. The mixture was then maintained at 90 °C for 3 h. The mixture was cooled and filtered to collect the resin beads. The resin beads were washed sequentially with acetone and deionized water until the washings were neutral. The resin beads were then dried in a vacuum oven at 70 °C for 8 h to obtain the nuclear-grade cation exchange resin material.

[0047] Example 2

[0048] 1) Weigh 20.0 g of lanthanum nitrate hexahydrate and 1.0 g of titanium nitrate solution (titanium nitrate content 20 wt%), dissolve in 50 mL of deionized water and stir until the solution is clear and transparent. Then, add 5.0 g of ethylenediaminetetramethylenephosphonic acid to the solution, adjust the pH of the mixture to 6.0 by adding 1 M dilute ammonia solution dropwise, and stir the mixture at room temperature for 60 min. Transfer the mixture to an autoclave with a polytetrafluoroethylene liner, heat at 180 °C for 24 h, cool to room temperature and centrifuge. Wash the obtained solid three times with deionized water, wash once with ethanol, and then dry in a vacuum oven at 70 °C for 14 h to obtain the titanium-lanthanum binary metal-organic framework material.

[0049] 2) The titanium-lanthanum binary metal-organic framework material was placed in a ceramic crucible and calcined and oxidized in oxygen by heating to 550°C at a rate of 5°C / min and holding at 550°C for 4 hours to obtain porous phosphorus-doped carbon-supported titanium-lanthanum oxide nanoparticles.

[0050] 3) In a flask, mix 67.0 g styrene, 15.0 g divinylbenzene, 8.0 g trivinylbenzene, 8.0 g sodium allyl sulfonate, 4.5 g n-octane, and 1.5 g diisobutyl peroxide. Heat the mixture to 60 °C and stir until all components dissolve to obtain an oil phase mixture. Add 0.2 g porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles to the oil phase mixture and sonicate the resulting mixture for 2 h to form a stable dispersion, thus obtaining a composite oil phase reaction solution.

[0051] 4) An aqueous solution was prepared by dissolving 5.0 g of methylcellulose and 0.1 g of methylene blue in 500 mL of deionized water. Under nitrogen protection, the composite oil phase reaction solution was slowly added to the aqueous solution with stirring. The mixture was then heated to 65 °C and reacted for 2 h, followed by increasing the temperature to 80 °C and reacting for another 2 h, and finally increasing the temperature to 100 °C and reacting for 12 h. The mixture was cooled and filtered to collect the resin beads. The resin beads were washed sequentially with acetone and deionized water until the washings were neutral, and then dried in a vacuum oven at 80 °C for 9 h to obtain the nuclear-grade cation exchange resin material.

[0052] Example 3

[0053] 1) Weigh 5.0 g of lanthanum nitrate hexahydrate and 0.6 g of titanium nitrate solution (titanium nitrate content 20 wt%), dissolve in 40 mL of deionized water and stir until the solution is clear and transparent. Then, add 1.0 g of aminotrimethylenephosphonic acid to the solution, adjust the pH of the mixture to 7 by adding 1 M dilute ammonia solution dropwise, and stir the mixture at room temperature for 30 min. Transfer the mixture to an autoclave with a polytetrafluoroethylene liner, heat at 140 °C for 18 h, cool to room temperature and centrifuge. Wash the obtained solid three times with deionized water, wash once with ethanol, and then dry in a vacuum oven at 65 °C for 12 h to obtain the titanium-lanthanum binary metal-organic framework material.

[0054] 2) The titanium-lanthanum binary metal-organic framework material was placed in a ceramic crucible and calcined and oxidized in air by heating to 350°C at a rate of 3°C / min and holding at 350°C for 3 hours to obtain porous phosphorus-doped carbon-supported titanium-lanthanum oxide nanoparticles.

[0055] 3) In a flask, mix 75.0 g styrene, 8.5 g divinylbenzene, 7.0 g trivinylbenzene, 9.0 g sodium styrene sulfonate, 2.5 g butanol, and 0.3 g benzoyl peroxide. Heat the mixture to 60 °C and stir until all components dissolve to obtain an oil phase mixture. Add 0.3 g porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles to the oil phase mixture and sonicate the resulting mixture for 1.5 h to form a stable dispersion, thus obtaining a composite oil phase reaction solution.

[0056] 4) An aqueous solution was prepared by dissolving 0.1 g gelatin and 0.01 g methylene blue in 300 mL of deionized water. Under nitrogen protection, the composite oil phase reaction solution was slowly added to the aqueous solution with stirring. The mixture was then heated to 60 °C and reacted for 0.5 h, followed by increasing the temperature to 75 °C and reacting for another 0.5 h, and finally increasing the temperature to 90 °C and reacting for 6 h. The mixture was then held at 90 °C for 4 h. The mixture was cooled and filtered to collect the resin beads. The resin beads were washed sequentially with acetone and deionized water until the washings were neutral, and then dried in a vacuum oven at 60 °C for 12 h to obtain the nuclear-grade cation exchange resin material.

[0057] Example 4

[0058] 1) Weigh 10.0 g of lanthanum nitrate hexahydrate and 0.7 g of titanium nitrate solution (titanium nitrate content 20 wt%), dissolve in 45 mL of deionized water and stir until the solution is clear and transparent. Then, add 2.5 g of ethylenediaminetetramethylenephosphonic acid to the solution, adjust the pH of the mixture to 6.5 by adding 1 M dilute ammonia solution dropwise, and stir the mixture at room temperature for 45 min. Transfer the mixture to an autoclave with a polytetrafluoroethylene liner, heat at 160 °C for 20 h, cool to room temperature and centrifuge. Wash the obtained solid three times with deionized water, wash once with ethanol, and then dry in a vacuum oven at 70 °C for 12 h to obtain the titanium-lanthanum binary metal-organic framework material.

[0059] 2) The titanium-lanthanum binary metal-organic framework material was placed in a ceramic crucible and calcined and oxidized in air by heating to 480°C at a rate of 4°C / min and holding at 480°C for 3 hours to obtain porous phosphorus-doped carbon-supported titanium-lanthanum oxide nanoparticles.

[0060] 3) In a flask, mix 68.0 g styrene, 9.5 g divinylbenzene, 5.0 g trivinylbenzene, 17.0 g sodium styrene sulfonate, 3.0 g isopropanol, and 0.7 g cyclohexanone peroxide. Heat the mixture to 60 °C and stir until all components dissolve to obtain an oil phase mixture. Add 0.4 g porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles to the oil phase mixture and sonicate the resulting mixture for 2 h to form a stable dispersion, thus obtaining a composite oil phase reaction solution.

[0061] 4) An aqueous solution was prepared by dissolving 2.5 g of polyvinyl alcohol and 0.03 g of methylene blue in 350 mL of deionized water. Under nitrogen protection, the composite oil phase reaction solution was slowly added to the aqueous solution with stirring. The mixture was then heated to 65 °C and reacted for 1 h, followed by increasing the temperature to 80 °C and reacting for 1 h, and finally increasing the temperature to 95 °C and reacting for 5 h. The mixture was then maintained at 95 °C for 4 h. The mixture was cooled and filtered to collect the resin beads. The resin beads were washed sequentially with acetone and deionized water until the washings were neutral, and then dried in a vacuum oven at 75 °C for 12 h to obtain the nuclear-grade cation exchange resin material.

[0062] Example 5

[0063] 1) Weigh 3.0 g of lanthanum nitrate hexahydrate and 0.4 g of titanium nitrate solution (titanium nitrate content 20 wt%), dissolve in 35 mL of deionized water and stir until the solution is clear and transparent. Then, add 0.8 g of 4-(dimethylamino)triphenylphosphine to the solution, adjust the pH of the mixture to 5.8 by adding 1 M dilute ammonia solution dropwise, and stir the mixture at room temperature for 38 min. Transfer the mixture to an autoclave with a polytetrafluoroethylene liner, heat at 130 °C for 22 h, cool to room temperature and centrifuge. Wash the obtained solid three times with deionized water, wash once with ethanol, and then dry in a vacuum oven at 65 °C for 10 h to obtain the titanium-lanthanum binary metal-organic framework material.

[0064] 2) The titanium-lanthanum binary metal-organic framework material was placed in a ceramic crucible and calcined and oxidized in air by heating to 500°C at a rate of 4°C / min and holding at 500°C for 4 hours to obtain porous phosphorus-doped carbon-supported titanium-lanthanum oxide nanoparticles.

[0065] 3) In a flask, mix 77.0 g styrene, 14.0 g divinylbenzene, 3.0 g trivinylbenzene, 11.0 g sodium allyl sulfonate, 4.2 g n-heptane, and 1.3 g diisobutyl peroxide. Heat the mixture to 60 °C and stir until all components dissolve to obtain an oil phase mixture. Add 0.5 g of porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles to the oil phase mixture and sonicate the resulting mixture for 1 h to form a stable dispersion, thus obtaining a composite oil phase reaction solution.

[0066] 4) An aqueous solution was prepared by dissolving 3.0 g of methylcellulose and 0.08 g of methylene blue in 400 mL of deionized water. Under nitrogen protection, the composite oil phase reaction solution was slowly added to the aqueous solution with stirring. The mixture was then heated to 65 °C and reacted for 1.2 h, followed by increasing the temperature to 75 °C and reacting for another 1.2 h, and finally increasing the temperature to 95 °C and reacting for 4 h. The mixture was then held at 95 °C for 3 h. The mixture was cooled and filtered to collect the resin beads. The resin beads were washed sequentially with acetone and deionized water until the washings were neutral, and then dried in a vacuum oven at 65 °C for 12 h to obtain the nuclear-grade cation exchange resin material.

[0067] Comparative Example 1

[0068] Without the titanium lanthanum oxide core layer, steps 1)-2) are omitted. In step 3), porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles are not added. Sulfonated resin is prepared by direct suspension polymerization. Other steps are the same as in Example 4.

[0069] Comparative Example 2

[0070] The post-sulfonation method was adopted, that is, styrene-based resin was first prepared, the shell layer did not contain sulfonic acid monomers, and then sulfonated with concentrated sulfuric acid after polymerization (i.e., sulfonation was carried out by adding 5 times the amount of 98% concentrated sulfuric acid of resin microspheres). Other steps were the same as in Example 4.

[0071] Comparative Example 3

[0072] Step 1) does not include ethylenediaminetetramethylenephosphonic acid and is free of phosphorus doping. The other steps are the same as in Example 4.

[0073] Comparative Example 4

[0074] In step 1), titanium nitrate was not added to prepare a pure lanthanum oxide resin that did not contain titanium. The other steps were the same as in Example 4.

[0075] Comparative Example 5

[0076] In step 1), the organophosphonic acid compound was replaced by hydroxyethylidene diphosphonic acid instead of ethylenediaminetetramethylenephosphonic acid. The other steps of Example 4 remained unchanged.

[0077] Comparative Example 6

[0078] In step 1), the amount of ethylenediaminetetramethylenephosphonic acid was adjusted to 10.0 g, so that the mass ratio of lanthanum nitrate hexahydrate to ethylenediaminetetramethylenephosphonic acid was 1:1. The rest were the same as in Example 4.

[0079] Performance Tests and Results

[0080] The following performance tests were performed on the resins prepared in the above embodiments and comparative examples:

[0081] 1) The exchange capacity of the prepared nuclear-grade cation exchange resin was determined according to the Chinese national standard (GB / T8144-2008).

[0082] 2) The crushing strength of the ion exchange resin was determined using a particle strength tester. The crushing strength of 20 resin particles were measured in the sample and randomly selected, and the average value was used to represent the result.

[0083] 3) The temperature resistance of the resin is in accordance with DL / T 953-2005. The mass exchange capacity is tested after heating in a 95℃ water bath for 100 hours.

[0084] 4) Radiation resistance

[0085] Take a certain amount of resin sample, put it into polyethylene plastic bottles, add sufficient deionized water, and use 100 Gy 60 The patient was irradiated with a Co radioactive source for 2 hours, and the TOC release was measured.

[0086] 5) Uniformity coefficient

[0087] The particle size distribution of resin particles was measured by sieving, and the uniformity coefficient was calculated.

[0088] 6) TOC content

[0089] Measure the total organic carbon content in the resin product.

[0090] Table 1 Performance parameters of the examples and comparative examples

[0091]

[0092]

[0093] Compared to Example 4, Comparative Example 1 omitted the titanium lanthanum oxide core layer and directly prepared the sulfonated resin via suspension polymerization. This demonstrates that the titanium lanthanum oxide core layer can improve the ion exchange capacity, mechanical strength, and radiation resistance of the cation exchange resin. This is because the phosphorus-carbon-supported titanium lanthanum oxide complex can act as a core layer, improving the uniformity of polymer particle size and reducing the uniformity coefficient. Furthermore, the antioxidant properties of titanium lanthanum oxide can improve the resin's temperature resistance. However, Comparative Example 1, lacking the phosphorus-carbon-supported titanium lanthanum oxide complex, lacks radiation resistance and exhibits a high TOC release after radiation.

[0094] Compared with Example 4, Comparative Example 2 uses a post-sulfonation method. Due to the low efficiency and uneven distribution of sulfonic acid group introduction, and the high reaction temperature of post-sulfonation, the resin partially degrades. As a result, the ion exchange capacity, mechanical strength, radiation resistance, and temperature resistance all decrease, while the TOC content increases significantly.

[0095] Compared to Example 4, Comparative Example 3 did not contain ethylenediaminetetramethylenephosphonic acid and lacked phosphorus doping. As a result, it was difficult for carbon phosphide to regulate the adsorption and distribution of polymer monomers. Consequently, the polymer did not homogeneously polymerize outside the titanium lanthanum oxide particles, and most of the resulting resins did not exhibit a core-shell structure. The reinforcing properties of titanium lanthanum oxide were not well utilized, resulting in a decrease in mechanical strength, radiation resistance, and temperature resistance, while the uniformity coefficient and TOC content increased.

[0096] Compared to Example 4, Comparative Example 4 did not add titanium nitrate to prepare pure lanthanum oxide resin without titanium. Because the pure lanthanum oxide particles obtained after calcination have large size and few reducible defect sites, it is difficult to fully exert the effect of oxide particles on resin particle size regulation and antioxidant effect. As a result, the uniformity coefficient of the resin increased significantly, and the radiation resistance and temperature resistance decreased.

[0097] Compared to Example 4, in Comparative Example 5, the organophosphonic acid compound was replaced by hydroxyethylidene diphosphonic acid instead of ethylenediaminetetramethylenephosphonic acid. Due to the weak complexation between hydroxyethylidene diphosphonic acid and lanthanum metal ions, a well-structured metal-organic framework could not be formed. This resulted in uneven distribution of titanium and lanthanum in the titanium lanthanum oxide obtained after calcination, leading to larger oxide particle size and fewer reducible defect sites. Consequently, the uniformity coefficient of the resin increased significantly, while the radiation resistance and temperature resistance decreased.

[0098] Comparative Example 6 adjusted the ratio of organophosphonic acid compound to lanthanum nitrate. Due to the excessive amount of amino organophosphonic acid compound, hydrogen bonds formed between amino groups and phosphonic acids in the molecules separated the structural units of titanium lanthanum MOFs, reducing the order of MOFs, thus significantly decreasing radiation resistance and slightly decreasing mechanical properties. Due to the excessive amount of amino organophosphonic acid compound, the roasting and carbonization were insufficient, and some unconverted amino organophosphonic acid compound remained, resulting in a higher TOC content.

[0099] The above embodiments are only used to illustrate the technical solutions of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A nuclear-grade cation exchange resin resistant to strong radiation, characterized in that, This nuclear-grade cation exchange resin is a nuclear-grade structural composite. The core material is porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles, which are obtained by pyrolysis of titanium lanthanum binary metal-organic framework material. The organic ligand of the titanium lanthanum binary metal-organic framework material is an amino organophosphonic acid compound, and the shell material is an in-situ sulfonated nuclear-grade strong acid cation exchange resin.

2. The radiation-resistant nuclear-grade cation exchange resin according to claim 1, characterized in that, The in-situ sulfonated nucleograde strong acid cation exchange resin is prepared by suspension polymerization of styrene, divinylbenzene, trivinylbenzene, sulfonic acid-containing monomers, porogens and initiators. The organic ligand aminoorganophosphonic acid compound is one of 4-(dimethylamino)triphenylphosphine, aminotrimethylenephosphonic acid or ethylenediaminetetramethylenephosphonic acid.

3. The radiation-resistant nuclear-grade cation exchange resin according to claim 1, characterized in that, The titanium-lanthanum binary metal-organic framework material is prepared by hydrothermal reaction of lanthanum nitrate, titanium nitrate and amino organophosphonic acid compound at 120-180℃. The mass ratio of lanthanum nitrate to titanium nitrate is (2-20):0.2, and the mass ratio of lanthanum nitrate to amino organophosphonic acid compound is (2-5):

1.

4. The radiation-resistant nuclear-grade cation exchange resin according to claim 2, characterized in that, The sulfonic acid-containing monomer is selected from sodium styrene sulfonate or sodium allyl sulfonate.

5. The radiation-resistant nuclear-grade cation exchange resin according to claim 1, characterized in that, The mass ratio of the raw material mixture for preparing the in-situ sulfonated nucleograde strong acid cation exchange resin to porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles is 100:0.1~1.5; the raw material mixture consists of styrene, divinylbenzene, trivinylbenzene, sulfonic acid-containing monomers, porogens and initiators.

6. The radiation-resistant nuclear-grade cation exchange resin according to claim 3, characterized in that, The preparation steps of the radiation-resistant nuclear-grade cation exchange resin are as follows: (1) Prepare a mixed aqueous solution of lanthanum nitrate and titanium nitrate, add an amino organophosphonic acid compound to obtain a metal-organic framework precursor solution, react at 120-180℃ for 12-24 h, cool, wash and dry to obtain titanium-lanthanum binary metal-organic framework material. (2) The titanium-lanthanum binary metal-organic framework material was calcined in an oxidizing atmosphere to obtain porous phosphorus-doped carbon-supported titanium-lanthanum oxide nanoparticles. (3) Styrene, divinylbenzene, trivinylbenzene, sulfonic acid-containing monomers, pore-forming agents and initiators are thoroughly mixed to obtain an oil phase mixture, and porous phosphorus-doped carbon-supported titanium lanthanum oxide nanoparticles are added to obtain a composite oil phase mixture; (4) Prepare an aqueous solution of dispersant and methylene blue, add the composite oil phase mixture, gradually increase the temperature to 90~100℃, react, cool and filter, and wash the resin with organic solvent and deionized water in sequence to obtain a nuclear-grade cation exchange resin resistant to strong radiation.

7. The radiation-resistant nuclear-grade cation exchange resin according to claim 6, characterized in that, In step (2), the calcination conditions are: heating to 350-550 ℃ at a heating rate of 2-5 ℃ / min under air or oxygen, and calcining for 2-4 hours.

8. The radiation-resistant nuclear-grade cation exchange resin according to claim 6, characterized in that, In step (3), the composition of the oil phase mixture is as follows: styrene 66.7-78.1 wt%, divinylbenzene 8.3-15.6 wt%, trivinylbenzene 1.7-7.8 wt%, sulfonic acid-containing monomer 8.3-23.4 wt%, porogen 2.5-4.7 wt%, and initiator 0.3-1.6 wt%.

9. The method for preparing the radiation-resistant nuclear-grade cation exchange resin according to any one of claims 1 to 8.

10. The application of the radiation-resistant nuclear-grade cation exchange resin according to any one of claims 1 to 8 in the treatment of nuclear wastewater.

Images