Activated carbon modification method for nuclear power wastewater nuclide purification treatment

Abstract

The invention discloses an activated carbon modification method for nuclear power wastewater nuclide purification treatment, which comprises the following steps: adding activated carbon and potassium hydroxide into deionized water, carrying out ultrasonic dispersion treatment, stirring and dipping at constant temperature, evaporating and drying to remove the deionized water to obtain a mixture; under the protection of nitrogen, the mixture is subjected to heating treatment, acid pickling and water washing are conducted after heating treatment, and then drying is conducted; putting a product obtained in the step 2 into a rotary furnace, performing stage heating, finally cooling to room temperature under the protection of nitrogen, performing acid pickling and water washing again, and finally performing vacuum drying to obtain modified activated carbon; the activated carbon is sequentially subjected to potassium hydroxide modification and hot air oxidation modification, the specific surface area of the activated carbon is increased, sphybrid carbon in a carbon skeleton is oxidized into sphybrid carbon, stable acidic oxygen-containing groups are generated, the polarity and the chemical adsorption capacity are enhanced, the prepared modified activated carbon is better in adsorbability, and the service life of the activated carbon is prolonged. And the adsorption rate of each element in water is improved.

Description

Technical Field

[0001] This invention belongs to the field of adsorbent technology, specifically relating to an activated carbon modification method for the purification of radionuclides in nuclear power plant wastewater. Background Technology

[0002] With the rapid development of the nuclear power industry and the potential demand for the restart of inland nuclear power plants in the future, the safe treatment and discharge of radioactive wastewater has become an important issue for the sustainable development of nuclear energy. In particular, radioactive wastewater from the secondary loop of nuclear power plants has complex sources, high salinity, and increasingly stringent discharge standards (such as a total activity requirement of ≤100 Bq / L for offshore / inland sites), making it difficult for traditional treatment processes to meet actual needs.

[0003] Deep bed filtration, a composite process combining physical interception and biochemical action, effectively removes suspended solids, organic matter, and radionuclides from wastewater through the adsorption, interception, and microbial denitrification of deep filter media (such as quartz sand and activated carbon). The application of deep bed filtration technology in the treatment of radioactive wastewater from nuclear power plants has become a research hotspot in recent years, especially demonstrating significant technological potential in activated carbon filtration and modification. Nuclear power plant wastewater contains radionuclides (such as Cs-137, Co-60, and I-131) and pollutants such as suspended solids and organic matter, making treatment difficult and requiring strict compliance with emission standards. Taking the AP1000 nuclear power plant as an example, its radioactive laundry wastewater treatment system adopts a "two-stage activated carbon deep bed column + zeolite column" process. Through the adsorption and filtration of activated carbon, it can remove 97.1% of suspended solids and 86.5% of COD, while retaining most of the radionuclides such as Fe and Co existing in colloidal or particulate form. The final effluent radioactivity is lower than the national standard. Activated carbon, as a core material for deep-bed filtration, provides ideal conditions for the adsorption of radionuclides due to its porous structure and large specific surface area. Conventional activated carbon can remove radionuclides such as iodine and cesium from wastewater through physical adsorption. However, natural activated carbon has limited selectivity and capacity for adsorption of specific radionuclides, especially for elements such as Rb, Cs, and La, where existing activated carbon has extremely low adsorption capacity. Therefore, modification technology has become the key to improving treatment efficiency. Summary of the Invention

[0004] One object of the present invention is to at least solve the above-mentioned problems or defects and to provide a technical solution whose advantages will be described later.

[0005] To achieve these and other advantages of the present invention, an activated carbon modification method for the radionuclide purification treatment of nuclear power plant wastewater is provided, comprising the following steps: Step 1: Add activated carbon and potassium hydroxide to deionized water, disperse them by ultrasonication, stir and impregnate at a constant temperature, evaporate and dry to remove the deionized water, and obtain a mixture. Step 2: Under nitrogen protection, heat the mixture, then acid wash and water wash, and finally dry it. Step 3: Place the product obtained in Step 2 into a rotary kiln for staged heating, and finally cool it to room temperature under nitrogen protection. Then, perform acid washing and water washing again, and finally vacuum drying to obtain modified activated carbon.

[0006] Optionally, in step one, the activated carbon is coconut shell activated carbon or coal-based activated carbon, the mass ratio of activated carbon, potassium hydroxide and deionized water is 1:1~2:50~10, the ultrasonic dispersion frequency is 20~40kHz, the ultrasonic treatment is 30~60min, and the mixture is stirred and impregnated at 60~70℃ for 12~18h.

[0007] Optionally, in step two, the heating parameters are as follows: under nitrogen protection, the temperature is increased to 800-900℃ at a rate of 5-8℃ / min, and then held for 2-3 hours.

[0008] Optionally, in step two, the pickling process involves soaking in hydrochloric acid with a concentration of 1-2 mol / L for 6-8 hours, washing with deionized water until neutral, and drying in a vacuum drying oven at 80-90°C for 24-36 hours until the moisture content is less than 5%.

[0009] Optionally, in step three, the stage heating parameters are as follows: first, preheat at 100~200℃ in a nitrogen atmosphere for 10~20 min; then, introduce air with an oxygen concentration of 5~21% at a flow rate of 0.5~12 / min and heat to 400~600℃ for oxidative heating for 15~40 min; then, introduce carbon dioxide and raise the temperature to 800~850℃ for 5~10 min.

[0010] Optionally, in step three, the pickling process involves soaking in 0.1-0.2 mol / L hydrochloric acid for 6-8 hours, washing with deionized water until neutral, and drying in a vacuum drying oven at 60-70°C for 12-24 hours.

[0011] Optionally, step two is as follows: under nitrogen protection, the mixture obtained in step one is heated and treated, and after cooling, it is dispersed in water together with sulfur powder, tin powder and alumina, and then transferred to a reaction vessel and the reaction vessel is sealed. The reaction is then heated under vacuum. After the reaction is completed, the mixture is washed with water and then dried to obtain pretreated activated carbon.

[0012] Optionally, the ratio of the mixture, sulfur powder, tin powder, and alumina is 10g:0.001~0.002g:0.008~0.012g:0.001~0.002g, and the ratio of the mixture to water is 10g:18~27g. The mixture is heated to 180~220℃ and reacted for 8~12 hours.

[0013] Optionally, the modified activated carbon obtained in step three can be post-treated by dispersing the modified activated carbon in water, then adding zirconium oxychloride and stirring to dissolve it, then adding sodium pyrophosphate and stirring to react. After the reaction is completed, centrifuge, filter and dry to obtain the post-treated modified activated carbon.

[0014] Optionally, the ratio of modified activated carbon, zirconium oxychloride and sodium pyrophosphate is 10g:0.129g~0.258g:0.106~0.212g, the ratio of precursor to water is 10g:20~30g, and the reaction is stirred for 12~24h.

[0015] This invention offers the following advantages: By sequentially modifying activated carbon with potassium hydroxide and then with hot air oxidation, KOH reacts with carbon at high temperatures to generate K₂CO₃ and K₂O, releasing CO₂ gas to form pores. After melting, KOH penetrates the carbon layer; the residue after pyrolysis serves as a template to form regular pores. Subsequently, oxygen etches the carbon layer, expanding micropores and forming mesopores, increasing the specific surface area. Furthermore, the sp² hybrid carbon in the carbon skeleton is oxidized to sp³ hybrid carbon, generating stable acidic oxygen-containing groups, enhancing polarity and chemisorption capacity. The resulting modified activated carbon exhibits better adsorption properties, with improved adsorption rates for various elements in water. In addition, this invention pre-treats the potassium hydroxide-modified activated carbon, loading it with radioactive nuclide adsorbents to enhance its adsorption capacity for certain radioactive elements. Post-treatment of the modified activated carbon generates layered zirconium hydrogen phosphate on its surface, further increasing the specific surface area and enhancing its adsorption capacity for elements such as Cs, Rb, and La. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0017] Example 1 A method for modifying activated carbon for the purification of radionuclides in nuclear power plant wastewater includes the following steps: Step 1: Add 100g of coconut shell activated carbon and 200g of potassium hydroxide to 500g of deionized water, ultrasonically disperse at 20KHz for 30min, then stir and impregnate at 60℃ for 12h, and then evaporate and dry to remove the deionized water to obtain a mixture. Step 2: Under nitrogen protection, heat the mixture to 800℃ at 5℃ / min for 2 hours. After heating, cool the mixture and soak it in 1mol / L hydrochloric acid for 6 hours for acid washing. After acid washing, wash with deionized water until neutral and then dry until the water content is less than 5%. Step 3: Place the product obtained in Step 2 into a rotary kiln, preheat it to 100℃ for 10 minutes under a nitrogen atmosphere, then heat it to 400℃ and introduce air with an oxygen content of 5% at a flow rate of 0.5L / min, heat and oxidize for 40 minutes, then heat it to 800℃ and introduce carbon dioxide for 10 minutes, finally cool it to room temperature under nitrogen protection, and then soak it in 0.1mol / L hydrochloric acid for 6 hours for acid washing. After acid washing, wash it with deionized water until neutral, and finally dry it in a vacuum drying oven at 60℃ for 12 hours to obtain modified activated carbon.

[0018] Example 2 A method for modifying activated carbon for the purification of radionuclides in nuclear power plant wastewater includes the following steps: Step 1: Add 100g of coconut shell activated carbon and 200g of potassium hydroxide to 500g of deionized water, ultrasonically disperse at 20KHz for 30min, then stir and impregnate at 60℃ for 12h, and then evaporate and dry to remove the deionized water to obtain a mixture. Step 2: Under nitrogen protection, the mixture is heated to 800℃ at 5℃ / min and heated for 2 hours. After heating, it is cooled. Then, the product is dispersed in 180g of water along with 0.02g of sulfur powder, 0.12g of tin powder and 0.02g of alumina. The mixture is then transferred to a reaction vessel and sealed. The reaction vessel is heated under vacuum to 180℃ for 12 hours to obtain pretreated activated carbon. Step 3: Place the activated carbon loaded with radioactive nuclide adsorbent into a rotary kiln. First, preheat it to 100℃ for 10 minutes under a nitrogen atmosphere, then raise the temperature to 400℃ and introduce air with an oxygen content of 5% at a flow rate of 0.5 L / min, and heat for oxidation for 40 minutes. Then, raise the temperature to 800℃ and introduce carbon dioxide for 10 minutes. Finally, cool it to room temperature under nitrogen protection and soak it again in 0.1 mol / L hydrochloric acid for 6 hours for acid washing. After acid washing, wash it with deionized water until neutral, and finally dry it in a vacuum drying oven at 60℃ for 12 hours to obtain modified activated carbon. Then, perform post-treatment on the obtained modified activated carbon, including the following methods: 100g of modified activated carbon was dispersed in 200g of water, then 1.29g of zirconium oxychloride was added and stirred to dissolve, followed by 1.06g of ferrous sulfate and stirred for 12h. After the reaction was completed, the carbon was centrifuged, filtered, and dried to obtain the post-treated modified activated carbon.

[0019] Example 3 A method for modifying activated carbon for the purification of radionuclides in nuclear power plant wastewater includes the following steps: Step 1: Add 100g of coconut shell activated carbon and 200g of potassium hydroxide to 500g of deionized water, ultrasonically disperse at 20KHz for 30min, then stir and impregnate at 60℃ for 12h, and then evaporate and dry to remove the deionized water to obtain a mixture. Step 2: Under nitrogen protection, the mixture is heated to 800℃ at 5℃ / min and heated for 2 hours. After heating, it is cooled. Then, the product is dispersed in 180g of water along with 0.02g of sulfur powder, 0.12g of tin powder and 0.02g of alumina. The mixture is then transferred to a reaction vessel and sealed. The reaction vessel is heated under vacuum to 180℃ for 12 hours to obtain pretreated activated carbon. Step 3: Place the activated carbon loaded with radioactive nuclide adsorbent into a rotary kiln. First, preheat it to 100℃ for 10 minutes under a nitrogen atmosphere. Then, raise the temperature to 400℃ and introduce air with an oxygen content of 5% at a flow rate of 0.5L / min. Heat and oxidize for 40 minutes. Then, raise the temperature to 800℃ and introduce carbon dioxide for 10 minutes. Finally, cool it to room temperature under nitrogen protection. Then, soak it in 0.1mol / L hydrochloric acid for 6 hours for acid washing. After acid washing, wash it with deionized water until neutral. Finally, dry it in a vacuum drying oven at 60℃ for 12 hours to obtain modified activated carbon A.

[0020] Example 4 A method for modifying activated carbon for the purification of radionuclides in nuclear power plant wastewater includes the following steps: Step 1: Add 100g of coconut shell activated carbon and 200g of potassium hydroxide to 500g of deionized water, ultrasonically disperse at 20KHz for 30min, then stir and impregnate at 60℃ for 12h, and then evaporate and dry to remove the deionized water to obtain a mixture. Step 2: Under nitrogen protection, heat the mixture to 800℃ at 5℃ / min for 2 hours. After heating, cool the mixture and soak it in 1mol / L hydrochloric acid for 6 hours for acid washing. After acid washing, wash with deionized water until neutral and then dry until the water content is less than 5%. Step 3: Place the product obtained in Step 2 into a rotary kiln. First, preheat it to 100℃ for 10 minutes under a nitrogen atmosphere. Then, raise the temperature to 400℃ and introduce air with an oxygen content of 5% at a flow rate of 0.5L / min. Heat and oxidize for 40 minutes. Then, raise the temperature to 800℃ and introduce carbon dioxide for 10 minutes. Finally, cool it to room temperature under nitrogen protection. Soak it again in 0.1mol / L hydrochloric acid for 6 hours for acid washing. After acid washing, wash it with deionized water until neutral. Finally, dry it in a vacuum drying oven at 60℃ for 12 hours to obtain modified activated carbon. Then, perform post-treatment on the obtained modified activated carbon. The specific method includes: dispersing 100g of modified activated carbon in 200g of water, then adding 1.29g of zirconium oxychloride and stirring to dissolve it, then adding 1.06g of ferrous sulfate and stirring to react for 12 hours. After the reaction is completed, centrifuge, filter and dry to obtain modified activated carbon B.

[0021] Comparative Example 1 This comparative example uses conventional, unmodified coconut shell activated carbon.

[0022] Comparative Example 2 A method for modifying activated carbon for the purification of radionuclides in nuclear power plant wastewater includes the following steps: Step 1: Add 100g of coconut shell activated carbon and 200g of potassium hydroxide to 500g of deionized water, ultrasonically disperse at 20KHz for 30min, then stir and impregnate at 60℃ for 12h, then evaporate and dry to remove the deionized water to obtain a mixture. Dry the mixture to obtain modified activated carbon C.

[0023] Comparative Example 3 A method for modifying activated carbon for the purification of radionuclides in nuclear power plant wastewater includes the following steps: Step 1: Under nitrogen protection, heat 100g of coconut shell activated carbon to 800℃ at 5℃ / min for 2h. After heating, cool the carbon and soak it in 1mol / L hydrochloric acid for 6h for acid washing. After acid washing, wash it with deionized water until neutral and then dry it until the water content is less than 5% to obtain modified activated carbon D.

[0024] Adsorption experiments were conducted using existing laboratory filtration equipment, with activated carbon from Examples 1-4 and Comparative Examples 1-3 added. The simulated source terms were passed through an activated carbon filter column for continuous filtration. The tail liquid of the stable effluent was collected at 10 min, 20 min, and 30 min, and the ICP-MS of the filtered solution was tested. The simulated source terms were prepared according to Table 1 below.

[0025] Table 1 Pharmaceuticals Amount Pharmaceuticals Amount Deionized water 5 L Na2CrO4 155.8 mg NaCl 50 g MnCl2 180.2 mg NH4CI 382.1 mg FeCl3 145.3 mg [YCl3] 170.7 mg CoCl2 201.9 mg Na2MoO4 126.1 mg AgNO3 78.4 mg [Tc (replaced with NaReO4)] 73.4 mg Na2TeO3 86.9 mg RbCl 70.8 mg BaCl2 95.2 mg [CaCl2] 90.5 mg LaCl3 88.3 mg CsCl 63.3 mg NaI 59.0 mg NaBr 64.4 mg

[0026] Table 2-6 shows the removal rates and tail liquid concentrations of the source term with an influent concentration of 10 mg / L in Examples 1-4.

[0027] Table 2 - Removal rate and tailings concentration of activated carbon prepared in Example 1 Element type Tail liquid concentration (μg / L) Removal rate (%) Element type Tail liquid concentration (μg / L) Removal rate (%) Br 6203.3024 37.97 Cr 6552.3695 34.48 I 20.1214 99.80 Mn 8848.1238 11.52 Y 18.5998 99.81 Fe 3954.2274 60.46 Mo 30.8699 99.69 Co 6453.2189 35.47 Tc(Re) 2.7529 99.97 Ag 5.5721 99.94 Rb 7748.3745 22.52 Te 799.5422 92.00 Sr 2009.1024 79.91 Ba 388.5449 96.11 Cs 6955.2161 30.45 La 6014.2249 39.86 Table 3 - Removal rate and tailings concentration of activated carbon prepared in Example 2 Element type Tail liquid concentration (μg / L) Removal rate (%) Element type Tail liquid concentration (μg / L) Removal rate (%) Br 3512.8735 64.87 Cr 3985.1426 60.15 I 12.6358 99.87 Mn 987.5241 90.12 Y 10.9873 99.89 Fe 102.6358 98.97 Mo 23.5875 99.76 Co 3332.1568 66.68 Tc(Re) 1.8955 99.98 Ag 1.2134 99.99 Rb 3978.5241 60.21 Te 723.5874 92.76 Sr 866.3258 91.34 Ba 225.6876 99.77 Cs 3525.8741 64.74 La 3168.7412 68.31 Table 4 - Removal rate and tailings concentration of activated carbon prepared in Example 3 Element type Tail liquid concentration (μg / L) Removal rate (%) Element type Tail liquid concentration (μg / L) Removal rate (%) Br 4225.3265 57.75 Cr 4102.5625 58.97 I 12.8848 99.87 Mn 1412.2529 85.88 Y 11.5431 99.88 Fe 199.2554 98.01 Mo 24.2254 99.76 Co 4322.9459 56.77 Tc(Re) 2.0152 99.98 Ag 5.7745 99.94 Rb 7516.9953 24.83 Te 777.154 92.23 Sr 1895.4557 81.05 Ba 355.215 96.45 Cs 6425.6623 35.74 La 6577.2154 34.23 Table 5 - Removal rate and tailings concentration of activated carbon prepared in Example 4 Element type Tail liquid concentration (μg / L) Removal rate (%) Element type Tail liquid concentration (μg / L) Removal rate (%) Br 5512.4526 44.88 Cr 4868.5466 51.31 I 13.9863 99.86 Mn 2303.1023 76.97 Y 12.4458 99.88 Fe 2806.3547 71.94 Mo 25.7714 99.74 Co 6121.5548 38.78 Tc(Re) 1.9653 99.98 Ag 5.1472 99.95 Rb 3895.6653 61.04 Te 794.884 92.05 Sr 998.1154 90.02 Ba 375.5469 96.24 Cs 4011.6854 59.88 La 3895.6612 61.04

[0028] Table 6-8 shows the removal rates and tail liquid concentrations of source terms with an influent concentration of 10 mg / L for Comparative Examples 1-3.

[0029] Table 6 - Removal rate of activated carbon and concentration of tail liquid in Comparative Example 1 Element type Tail liquid concentration (μg / L) Removal rate (%) Element type Tail liquid concentration (μg / L) Removal rate (%) Br 9217.1000 7.82 Cr 4864.9976 51.35 I 1336.9428 86.63 Mn 277.4678 97.22 Y 4.8821 99.95 Fe 732.8688 92.67 Mo 6063.7442 39.36 Co 170.3113 98.29 Tc(Re) 321.3953 96.79 Ag 1.3967 99.98 Rb 9075.2334 9.2 Te 24.0039 99.75 Sr 8429.0951 15.71 Ba 478.3500 95.22 Cs 7568.5522 24.31 La 116.5606 98.83 Table 7 - Removal rate and tailings concentration of activated carbon prepared in Comparative Example 2 Element type Tail liquid concentration (μg / L) Removal rate (%) Element type Tail liquid concentration (μg / L) Removal rate (%) Br 7778.9643 22.21 Cr 6091.6537 39.08 I 122.4413 98.78 Mn 9980.0090 2.00 Y 36.7509 99.63 Fe 1802.8127 81.97 Mo 117.1943 98.82 Co 7527.8658 24.72 Tc(Re) 15.8244 99.84 Ag 9.6538 99.90 Rb 8041.5255 19.58 Te 498.5719 95.01 Sr 6959.4756 30.40 Ba 1848.0453 81.52 Cs 5603.4384 43.97 La 5677.2011 43.23 Table 8 - Removal rate and tail liquid concentration of activated carbon prepared in Comparative Example 2 Element type Tail liquid concentration (μg / L) Removal rate (%) Element type Tail liquid concentration (μg / L) Removal rate (%) Br 6698.3411 33.02 Cr 6587.4578 34.13 I 22.7041 99.77 Mn 9414.4876 5.86 Y 19.4306 99.80 Fe 4003.2139 59.96 Mo 31.5274 99.68 Co 7653.1962 23.47 Tc(Re) 2.8724 99.97 Ag 6.3402 99.94 Rb 7961.1289 20.39 Te 805.1503 91.95 Sr 2119.4970 78.80 Ba 409.28 95.91 Cs 6642.2870 33.58 La Element type Tail liquid concentration (μg / L) Removal rate (%) Element type Tail liquid concentration (μg / L) Removal rate (%) 6804.1638 31.9

[0030] As shown in Tables 2-8, this invention modifies activated carbon sequentially using potassium hydroxide and then hot air oxidation. In the latter case, KOH reacts with carbon at high temperature to generate K₂CO₃ and K₂O, releasing CO₂ gas to form pores. After melting, KOH penetrates the carbon layer, and the residue after pyrolysis serves as a template to form regular pores. Then, oxygen etches the carbon layer, expanding micropores and forming mesopores, increasing the specific surface area. Furthermore, the sp² hybrid carbon in the carbon skeleton is oxidized to sp³ hybrid carbon, generating stable acidic oxygen-containing groups, enhancing polarity and chemisorption capacity. The resulting modified activated carbon exhibits better adsorption properties than the original activated carbon and activated carbon modified using only one method, with improved adsorption rates for various elements in water. In addition, this invention further enhances the adsorption capacity of activated carbon for certain radioactive elements by loading radioactive nuclide adsorbents onto the potassium hydroxide-modified activated carbon. Furthermore, by post-treating the modified activated carbon to generate layered zirconium hydrogen phosphate on its surface, the specific surface area of ​​the activated carbon is further increased, while simultaneously enhancing its adsorption capacity for elements such as Cs, Rb, and La.

[0031] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. Other modifications can be easily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A method for modifying activated carbon for the purification of radionuclides in nuclear power plant wastewater, characterized in that, Includes the following steps: Step 1: Add activated carbon and potassium hydroxide to deionized water, disperse them by ultrasonication, stir and impregnate at a constant temperature, evaporate and dry to remove the deionized water, and obtain a mixture. Step 2: Under nitrogen protection, heat the mixture, then acid wash and water wash, and finally dry it. Step 3: Place the product obtained in Step 2 into a rotary kiln for staged heating, and finally cool it to room temperature under nitrogen protection. Then, perform acid washing and water washing again, and finally vacuum drying to obtain modified activated carbon.

2. The activated carbon modification method for radionuclide purification treatment of nuclear power plant wastewater as described in claim 1, characterized in that, In step one, the activated carbon is coconut shell activated carbon or coal-based activated carbon, the mass ratio of activated carbon, potassium hydroxide and deionized water is 1:1~2:50~10, the ultrasonic dispersion frequency is 20~40kHz, the ultrasonic treatment is 30~60min, and the mixture is stirred and impregnated at 60~70℃ for 12~18h.

3. The activated carbon modification method for radionuclide purification treatment of nuclear power plant wastewater as described in claim 1, characterized in that, In step two, the heating parameters are as follows: under nitrogen protection, the temperature is increased to 800-900℃ at a rate of 5-8℃ / min, and then held for 2-3 hours.

4. The activated carbon modification method for radionuclide purification treatment of nuclear power plant wastewater as described in claim 1, characterized in that, In step two, the pickling process involves soaking the sample in hydrochloric acid with a concentration of 1-2 mol / L for 6-8 hours, followed by washing with deionized water until neutral, and then drying the sample in a vacuum drying oven at 80-90°C for 24-36 hours until the moisture content is less than 5%.

5. The activated carbon modification method for radionuclide purification treatment of nuclear power plant wastewater as described in claim 1, characterized in that, In step three, the stage heating parameters are as follows: first, preheat at 100~200℃ in a nitrogen atmosphere for 10~20 minutes; then, introduce air with an oxygen concentration of 5~21% at a flow rate of 0.5~12 / min and heat to 400~600℃ for oxidative heating for 15~40 minutes; then, introduce carbon dioxide and raise the temperature to 800~850℃ for 5~10 minutes.

6. The activated carbon modification method for radionuclide purification treatment of nuclear power plant wastewater as described in claim 1, characterized in that, In step three, the pickling process involves soaking in 0.1-0.2 mol / L hydrochloric acid for 6-8 hours, followed by washing with deionized water until neutral, and drying in a vacuum drying oven at 60-70°C for 12-24 hours.

7. The activated carbon modification method for radionuclide purification treatment of nuclear power plant wastewater as described in claim 1, characterized in that, Step two is as follows: Under nitrogen protection, the mixture obtained in step one is heated and treated. After cooling, it is dispersed in water together with sulfur powder, tin powder and alumina, then transferred to a reaction vessel and sealed. The reaction is carried out under vacuum heating. After the reaction is completed, it is washed with water and then dried to obtain pretreated activated carbon.

8. The activated carbon modification method for radionuclide purification treatment of nuclear power plant wastewater as described in claim 7, characterized in that, The ratio of the mixture, sulfur powder, tin powder, and alumina is 10g:0.001~0.002g:0.008~0.012g:0.001~0.002g, and the ratio of the mixture to water is 10g:18~27g. The mixture is heated to 180~220℃ and reacted for 8~12 hours.

9. The activated carbon modification method for radionuclide purification treatment of nuclear power plant wastewater as described in claim 1, characterized in that, The modified activated carbon obtained in step three is post-treated as follows: the modified activated carbon is dispersed in water, then zirconium oxychloride is added and stirred to dissolve, then sodium pyrophosphate is added and stirred to react. After the reaction is completed, the carbon is centrifuged, filtered, and dried to obtain the post-treated modified activated carbon.

10. The activated carbon modification method for radionuclide purification treatment of nuclear power plant wastewater as described in claim 9, characterized in that, The modified activated carbon, zirconium oxychloride and sodium pyrophosphate were used in a ratio of 10g:0.129g~0.258g:0.106~0.212g, and the precursor and water were used in a ratio of 10g:20~30g. The reaction was carried out by stirring for 12~24h.