A method for resource-based treatment of radioactive wastewater

Abstract

The present application relates to the technical field of wastewater treatment, and specifically discloses a method for resource-based treatment of radioactive wastewater. A method for resource-based treatment of radioactive wastewater comprises the following steps: S1: pretreatment: separation of suspended matter; S2: multi-stage adsorption material treatment: sequentially using thiourea-based molecular sieve-copper loaded montmorillonite treatment, lanthanum-doped hydroxyapatite treatment, and nano-zero-valent iron-copper loaded activated carbon treatment; S3: adsorption material desorption and waste liquid concentration and solidification. The resource-based treatment method for radioactive wastewater adopted in this application can effectively purify nuclear medicine wastewater. 131 I ‑ 、 18 F ‑ as well as 99m TcO4 ‑ .

Description

Technical Field

[0001] The present application relates to the technical field of wastewater treatment, and more specifically, to a method for resource-based treatment of radioactive wastewater. Background Art

[0002] In recent years, the application of nuclear medicine in the field of disease diagnosis and treatment has continued to expand, and the increase in the use of radioactive drugs has led to an increase in wastewater volume year by year. This type of wastewater mainly comes from the preparation of radioactive drugs, patient metabolic excretions, and cleaning of diagnostic and treatment equipment, and contains 131 I. 18 F. 99 mTc and other radioactive nuclides. Among them, radioactive iodine ion ( 131 I - ) poses a significant threat to the ecological environment and human health due to its long half-life (about 8.02 days) and easy accumulation through the food chain.

[0003] At present, the mainstream treatment technology for radioactive wastewater is still based on the decay pool storage method. This method relies on the natural decay of nuclides to reduce radioactivity, but it requires a large area to build multi-stage decay pools. The treatment cycle usually takes more than 80 days, which is difficult to adapt to the "small batch, high frequency" characteristics of nuclear medicine wastewater. In addition, when the wastewater contains excessive iohexol (>20mg / L), its interference effect is particularly significant: on the one hand, traditional adsorption technologies (such as activated carbon and silver-based materials) are significantly interfered with by iohexol, which makes 131 On the other hand, iohexol is easy to carry weakly adsorbed 131 I - Penetrating the membrane pores causes the radioactivity of the permeate to increase, resulting in the effluent not meeting the standards.

[0004] The patent application document with publication number CN103170301A discloses a method for treating nuclear wastewater 131 I -The invention discloses a method for preparing a high-efficiency adsorbent, which comprises the following steps: 1) mixing concentrated NaOH solution with TiO2 particles, stirring and uniformly dispersing by ultrasonication; the concentration of the NaOH solution is 10M and the mass ratio of the NaOH solution to the TiO2 particles is 55-60:3; 2) using a polytetrafluoroethylene liner in a hydrothermal reactor to pack the mixture in step 1) and perform a hydrothermal reaction; 3) washing the precipitate after the reaction in step 2) with distilled water, cleaning it and then drying it to obtain sodium titanate nanofibers or nanotubes as the matrix of the nanoadsorbent; 4) dispersing the product of step 3) with water, adjusting the pH value of the dispersion to 11 by dropwise adding a dilute NaOH aqueous solution, and collecting the alkalized matrix by centrifugation; the concentration of the dilute NaOH aqueous solution is 1mM-1M; 5) soaking the alkalized matrix in step 4) with a silver nitrate aqueous solution and vigorously stirring it; 6) centrifuging the product after treatment in step 5), collecting the precipitate, washing it with water, and drying it to obtain a nano-adsorbent in nuclear waste water. 131 I - Highly efficient adsorbent.

[0005] In this scheme, sodium titanate nanofibers / nanotubes 131 I - The adsorption of ions relies on the dual effects of physical adsorption and chemical adsorption: on the one hand, its porous structure captures ions through physical interception. 131 I - On the other hand, the loaded Ag + Through with 131 I - AgI precipitation is formed to enhance adsorption. However, in neutral solution (nuclear wastewater is usually pH 6-8), due to OH - The concentration is low, and the Na + The binding force with the skeleton is weakened, resulting in Na + Continuous desorption and loss cause the collapse or reorganization of the titanium oxide skeleton, which directly leads to a sharp drop in the porosity of the material and a significant reduction in the specific surface area. Although some 131 I - It is fixed in the adsorption material, but it also causes a sharp decrease in the physical adsorption sites, which reduces the purification ability of the adsorbent. Summary of the Invention

[0006] In order to improve the purification capacity of radioactive wastewater, the present application provides a method for resource recovery treatment of radioactive wastewater.

[0007] The resource recovery treatment method of radioactive wastewater in this application adopts the following technical solutions:

[0008] A method for recycling radioactive wastewater comprises the following steps:

[0009] S1: Pretreatment: Suspended matter separation;

[0010] S2: Multi-stage adsorption material treatment: thiourea-based molecular sieve-copper-loaded montmorillonite treatment, lanthanum-doped hydroxyapatite treatment, and nano-zero-valent iron-copper-loaded activated carbon treatment were used in sequence;

[0011] S3: Desorption of adsorption materials and concentration and solidification of waste liquid.

[0012] In this solution, the pretreatment stage separates suspended solids to create favorable conditions for subsequent adsorption. Within the multi-stage adsorption material, thiourea-based molecular sieves and copper-loaded montmorillonite preferentially capture iodine-related radionuclides, lanthanum-doped hydroxyapatite specifically adsorbs fluorine-related radionuclides, and nano-zero-valent iron-copper-loaded activated carbon synergistically removes residual radionuclides such as technetium through reduction and adsorption. The three-stage materials act sequentially according to their radionuclide characteristics, forming a complementary and enhanced capture system. The adsorbent materials undergo specific desorption, and the desorbed wastewater is concentrated and solidified to ensure safe disposal.

[0013] Preferably, in step S1, the suspended matter is filtered by using an alumina ceramic membrane with a pore size of 0.1-0.3 μm in series.

[0014] Preferably, the membrane flux of the alumina ceramic membrane is 55~65L / (m 2 ·h), the operating pressure is 0.2~0.25MPa.

[0015] Preferably, in step S2, the thiourea-based molecular sieve-copper-loaded montmorillonite treatment is specifically: introducing a thiourea-based molecular sieve-copper-loaded montmorillonite fixed bed and controlling the empty bed flow rate to 0.8-1.0 BV / h.

[0016] Preferably, the thiourea-based molecular sieve-copper-loaded montmorillonite is prepared using thiourea-modified molecular sieve and copper-loaded montmorillonite as raw materials in a mass ratio of (2.5-3.5):1.

[0017] Preferably, the preparation method of the thiourea-modified molecular sieve comprises the following steps:

[0018] The molecular sieve is dispersed in anhydrous ethanol, and the hydrolyzate of 3-isothiocyanatopropyltriethoxysilane is added, and the pH is adjusted to 5.5-6.0. The temperature is raised to 60-75°C and the reaction is carried out for 2-4 hours. Thiourea is then added, and the pH is maintained at 5.5-6.0. The reaction is continued for 12-15 hours. The solid-liquid separation is performed, and the reaction is carried out after washing and drying to obtain the thiourea-modified molecular sieve.

[0019] Preferably, the mass ratio of the molecular sieve, thiourea and 3-isothiocyanatopropyltriethoxysilane is 6: (0.45-0.55): (0.9-1.1).

[0020] Preferably, the preparation method of the hydrolyzate comprises the following steps:

[0021] Mix 3-isothiocyanatopropyltriethoxysilane and ethanol aqueous solution evenly, adjust the pH to 4.5-5.0, heat to 45-50°C, react for 60-90 minutes, and cool to obtain a hydrolyzate.

[0022] Preferably, the method for preparing the copper-loaded montmorillonite comprises the following steps:

[0023] The montmorillonite is dispersed in a copper nitrate solution, heated to 35-45°C, mixed for 5-7 hours, solid-liquid separation, washed, and dried to obtain copper-loaded montmorillonite.

[0024] Preferably, the mass molar ratio of the montmorillonite to copper nitrate is 10g:(0.01-0.015)mol.

[0025] Preferably, the preparation method of the thiourea-based molecular sieve-copper-loaded montmorillonite comprises the following steps:

[0026] The thiourea-modified molecular sieve and copper-loaded montmorillonite are uniformly mixed in a mass ratio of (2.5-3.5):1, a binder is added, pressed into shape, and dried to obtain the product.

[0027] Preferably, the binder is a polyvinyl alcohol aqueous solution with a mass concentration of 6% to 8%.

[0028] In this scheme, the molecular sieve is modified with a silane coupling agent to introduce thiourea groups. The thiourea groups are protonated in a weakly acidic environment and capture I by electrostatic attraction. - ; Cu loaded at the same time 2+ Coordinated with the sulfur atom of the thiourea group, the complex specifically binds to I through soft acid-soft base interaction - The two are compounded in a specific ratio, which not only retains the porous structure of the molecular sieve to ensure mass transfer efficiency, but also improves the overall adsorption capacity and stability through the synergistic effect of copper-loaded montmorillonite.

[0029] Preferably, in step S2, the lanthanum-doped hydroxyapatite treatment is specifically: introducing a lanthanum-doped hydroxyapatite fixed bed and controlling the empty bed flow rate to 0.6-0.7 BV / h.

[0030] Preferably, the lanthanum-doped hydroxyapatite is prepared from calcium nitrate tetrahydrate, diammonium hydrogen phosphate and lanthanum nitrate hexahydrate in a mass ratio of 3:1:(0.05-0.07) as raw materials.

[0031] Preferably, the method for preparing lanthanum-doped hydroxyapatite comprises the following steps:

[0032] Mix the calcium nitrate solution and the lanthanum nitrate solution evenly, then add the diammonium hydrogen phosphate solution while stabilizing the pH at 10-11, raise the temperature to 90-120°C, react for 24-48 hours, cool, separate the solid and liquid, wash, and freeze-dry to obtain the product.

[0033] In this scheme, lanthanum doping increases the interlayer spacing of hydroxyapatite by lattice distortion, thereby increasing the F - The diffusion rate of lanthanum ions is reduced; at the same time, lanthanum ions are hydrolyzed in aqueous solution to form colloids, which adsorb F - , enhance the capture capacity.

[0034] Preferably, in step S2, the nano zero-valent iron-copper loaded activated carbon treatment is specifically: introducing the nano zero-valent iron-copper loaded activated carbon fixed bed and controlling the empty bed flow rate to 0.7~0.9BV / h.

[0035] Preferably, the nano zero-valent iron-copper loaded activated carbon is prepared from oxidized activated carbon, ferric nitrate nonahydrate, and copper nitrate trihydrate in a mass ratio of 1: (0.3-0.4): (0.05-0.07) and is reduced with sodium borohydride.

[0036] Preferably, the method for preparing the oxidized activated carbon comprises the following steps:

[0037] Mix activated carbon with 15% to 20% nitric acid by mass, heat to 60 to 80°C, mix for 3 to 5 hours, cool, separate the solid and liquid, wash, and dry to obtain oxidized activated carbon.

[0038] Preferably, the preparation method of the nano zero-valent iron-copper loaded activated carbon comprises the following steps:

[0039] The ferric nitrate solution is mixed with the oxidized activated carbon for 1.5 to 2.5 hours, during which the pH is maintained at 2.0 to 3.0, and then the copper nitrate solution is added and mixed for 2.5 to 3.5 hours, during which the pH is maintained at 3.0 to 4.0. Thereafter, the pH is adjusted to 8 to 9, and under an inert atmosphere, the sodium borohydride solution is added and mixed for 30 to 50 minutes, followed by solid-liquid separation, washing, and freeze-drying to obtain the product.

[0040] Preferably, the amount of sodium borohydride in the sodium borohydride solution is 45% to 55% of the total mass of ferric nitrate nonahydrate and copper nitrate trihydrate.

[0041] In this protocol, activated carbon is oxidized with nitric acid to introduce oxygen-containing functional groups (such as carboxyl and hydroxyl) onto its surface, enhancing its adsorption capacity for metal ions and providing anchoring sites for subsequent loading. Iron and copper sources are mixed with the oxidized activated carbon in appropriate proportions. The pH of the system is manipulated to ensure uniform adsorption of iron and copper ions on the activated carbon surface. Reduction with sodium borohydride then forms a nanoscale composite structure of zero-valent iron and copper. The nanoscale zero-valent iron reduces Tc(VII) to insoluble Tc(IV) through surface electron transfer. The copper loading forms an Fe-Cu alloy, slowing the oxidative passivation of the iron surface and enhancing its long-term reduction capacity. The activated carbon pores physically trap the reduction products.

[0042] Preferably, the regeneration of the thiourea-based molecular sieve-copper-loaded montmorillonite is performed by desorption using an NH4Cl-NH3·H2O buffer solution having a pH of 10-10.5 and a concentration of 2.0-2.2 mol / L, and collecting waste liquid A.

[0043] Preferably, the regeneration of the lanthanum-doped hydroxyapatite is performed by desorption using nitric acid with a concentration of 0.15 to 0.25 mol / L, and the waste liquid B is collected.

[0044] Preferably, the regeneration of the nano zero-valent iron-copper loaded activated carbon is performed by desorption using a sodium thiosulfate solution with a concentration of 0.08-0.12 mol / L, followed by sintering at 300-350° C. under an inert atmosphere for 1.2-1.5 h, cooling, and collecting the waste liquid C.

[0045] Preferably, in step S3, the solidification is specifically as follows: after the waste liquid is concentrated, it is mixed with the geopolymer at a mass ratio of 1: (4.5-5.5), and sealed and cured at room temperature to obtain a solidified body.

[0046] Preferably, after the waste liquid A is concentrated, AgNO3 with a concentration of 0.1-0.12 mol / L is added, the precipitate is separated from the solid and liquid, and then mixed with the geopolymer at a mass ratio of 1: (4.5-5.5), and sealed and cured at room temperature to obtain a solidified body.

[0047] Preferably, after the waste liquid B is concentrated, the pH is adjusted to 10-11, and then mixed with the geopolymer at a mass ratio of 1: (4.5-5.5), and sealed and cured at room temperature to obtain a solidified body.

[0048] Preferably, the method for preparing the geopolymer comprises the following steps:

[0049] Mix metakaolin and montmorillonite in a mass ratio of (8~8.5): (1.5~2), add sodium silicate solution, mix evenly, pour into a mold, cure at 20~25℃ for 24~26h, demold, and then cure at 75~80℃ for 24~26h to obtain the finished product.

[0050] Preferably, the amount of the sodium silicate solution is 30% to 35% of the total mass of the metakaolin and montmorillonite.

[0051] Preferably, in the sodium silicate solution, the mass concentration of silicon dioxide is 18.5% to 22%, and the mass fraction of sodium oxide is 17.5% to 18%.

[0052] In summary, this application has the following beneficial effects:

[0053] 1. This application uses the synergistic effect of three-stage targeted adsorption materials, thiourea-based molecular sieve-copper-loaded montmorillonite treatment, lanthanum-doped hydroxyapatite treatment, and nano-zero-valent iron-copper-loaded activated carbon treatment to achieve specific capture of iodine-based, fluorine-based, and technetium-based nuclides, respectively, to form a full-process purification system.

[0054] 2. In this application, three adsorption materials are preferred: lanthanum-doped hydroxyapatite, nano-zero-valent iron-copper loaded activated carbon, and thiourea-based molecular sieve-copper loaded montmorillonite. Thiourea-based modification enhances iodine affinity, lanthanum doping improves fluorine selectivity, and bimetallic loading enhances reduction and adsorption synergy. The fixed bed flow rate control is matched with the material properties to ensure full contact between the wastewater and the material, thereby improving treatment efficiency.

[0055] 3. The adsorption material of the present application can achieve the reduction and safe disposal of radioactive waste by specific desorption, and the waste liquid is concentrated and solidified, and combined with the geopolymer to form a low-leaching rate solid body, taking into account both environmental protection and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is the infrared spectrum of the thiourea-based molecular sieve-copper-loaded montmorillonite in Preparation Example 1 of this application. DETAILED DESCRIPTION

[0057] The present application is further described in detail below with reference to the embodiments.

[0058] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0059] Treatment object: Wastewater detection at the entrance of a wastewater treatment station in the nuclear medicine department of a hospital

[0060] Table 1 Composition of wastewater at the inlet of wastewater treatment station

[0061]

[0062] Preparation Examples 1-3 Thiourea-based molecular sieve-copper-loaded montmorillonite

[0063] Preparation Example 1

[0064] The preparation method of the thiourea-based molecular sieve-copper-loaded montmorillonite of this preparation example comprises the following steps:

[0065] S31: 10 g of 3-isothiocyanatopropyltriethoxysilane and 30 mL of aqueous ethanol (ethanol and deionized water in a volume ratio of 1:1) were mixed uniformly, the pH was adjusted to 5.0 with 5% sodium acetate solution, the temperature was raised to 50°C, and pre-hydrolyzed for 60 min. The mixture was cooled to room temperature to obtain a hydrolyzed solution.

[0066] Under a nitrogen atmosphere, 60 g of molecular sieve was added to 400 mL of anhydrous ethanol, and the mixture was transferred to an ultrasonic device. After ultrasonic treatment at a power of 200 W and a frequency of 40 kHz for 30 min, the hydrolyzate was added and stirred to mix evenly. The pH was adjusted to 5.8 with a 5% mass fraction of sodium acetate solution, the temperature was raised to 70°C, and the reaction was continued for 3 h. 5 g of thiourea was added and stirred to mix evenly, while maintaining the pH at 5.8. The reaction was continued for 13 h, cooled, centrifuged, and washed with anhydrous ethanol three times. The mixture was vacuum dried at 60°C to constant weight to obtain a thiourea-modified molecular sieve.

[0067] S32: 20 g of sodium montmorillonite was added to 200 mL of 0.12 mol / L copper nitrate solution, and the mixture was ultrasonically treated at a power of 200 W and a frequency of 40 kHz for 10 min. The mixture was then stirred at 40° C. and a stirring speed of 200 rpm for 6 h. The mixture was then resuspended in 100 mL of deionized water, centrifuged, and dried in vacuo at 60° C. to constant weight to obtain copper-loaded montmorillonite.

[0068] S33: Mix the thiourea-modified molecular sieve and copper-loaded montmorillonite in a mass ratio of 3:1, add an 8% mass concentration of polyvinyl alcohol aqueous solution (the amount is about 25% of the powder mass and can be fine-tuned appropriately), stir until a uniform paste is formed, press into spherical particles with a diameter of 1.5 mm, and vacuum dry at 60°C to constant weight.

[0069] Among them, the molecular sieve is SBA-15, with a specific surface area of ​​about 600m 2 / g, pore size 6~11nm, dried at 150℃ for 2h before use; the specific surface area of ​​sodium montmorillonite is about 730m 2 / g, the interlayer spacing is about 1.3nm; in the polyvinyl alcohol aqueous solution, the average molecular weight of polyvinyl alcohol is about 75,000.

[0070] Preparation Example 2

[0071] The preparation method of the thiourea-based molecular sieve-copper-loaded montmorillonite of this preparation example comprises the following steps:

[0072] S31: 9 g of 3-isothiocyanatopropyltriethoxysilane and 30 mL of aqueous ethanol (ethanol and deionized water in a volume ratio of 1:1) were mixed uniformly, the pH was adjusted to 5.0 with 5% sodium acetate solution, the temperature was raised to 45°C, and pre-hydrolyzed for 70 min. The mixture was cooled to room temperature to obtain a hydrolyzed solution.

[0073] Under a nitrogen atmosphere, 60 g of molecular sieve was added to 400 mL of anhydrous ethanol, and the mixture was transferred to an ultrasonic device. After ultrasonic treatment at a power of 200 W and a frequency of 40 kHz for 30 min, the hydrolyzate was added and stirred to mix evenly. The pH was adjusted to 5.5 with a 5% mass fraction of sodium acetate solution, the temperature was raised to 60°C, and the reaction was continued for 4 h. 4.5 g of thiourea was added and stirred to mix evenly, and the pH was maintained at 5.5. The reaction was continued for 15 h, cooled, centrifuged, and washed with anhydrous ethanol three times. The mixture was vacuum dried at 60°C to constant weight to obtain a thiourea-modified molecular sieve.

[0074] S32: 20 g of sodium montmorillonite was added to 200 mL of 0.1 mol / L copper nitrate solution, and the mixture was ultrasonically treated at a power of 200 W and a frequency of 40 kHz for 10 min. The mixture was then stirred at 35° C. and a stirring speed of 200 rpm for 7 h. After centrifugation, the mixture was resuspended in 100 mL of deionized water, centrifuged, and dried in vacuo at 60° C. to constant weight to obtain copper-loaded montmorillonite.

[0075] S33: Mix the thiourea-modified molecular sieve and copper-loaded montmorillonite in a mass ratio of 2.5:1, add an 8% mass concentration of polyvinyl alcohol aqueous solution (the amount is about 25% of the powder mass and can be fine-tuned appropriately), stir to a uniform paste, press into spherical particles with a diameter of 1.5 mm, and vacuum dry at 60°C to constant weight.

[0076] Among them, the molecular sieve is SBA-15, with a specific surface area of ​​about 600m 2 / g, pore size 6~11nm, particle size distribution 1~50μm, before use, dried at 150℃ for 2h; the specific surface area of ​​sodium montmorillonite is about 730m 2 / g, the interlayer spacing is about 1.3nm, and the particle size distribution is 1~10μm; in the polyvinyl alcohol aqueous solution, the average molecular weight of polyvinyl alcohol is about 75,000.

[0077] Preparation Example 3

[0078] The preparation method of the thiourea-based molecular sieve-copper-loaded montmorillonite of this preparation example comprises the following steps:

[0079] S31: 11 g of 3-isothiocyanatopropyltriethoxysilane and 35 mL of aqueous ethanol (ethanol and deionized water in a volume ratio of 1:1) were mixed uniformly, the pH was adjusted to 4.5 with 5% sodium acetate solution, the temperature was raised to 50°C, and pre-hydrolyzed for 90 min. The mixture was cooled to room temperature to obtain a hydrolyzed solution.

[0080] Under a nitrogen atmosphere, 60 g of molecular sieve was added to 400 mL of anhydrous ethanol, and the mixture was transferred to an ultrasonic device. After ultrasonic treatment at a power of 200 W and a frequency of 40 kHz for 30 min, the hydrolyzate was added and stirred to mix evenly. The pH was adjusted to 6.0 with a 5% mass fraction of sodium acetate solution, the temperature was raised to 75°C, and the reaction was continued for 2 h. 5.5 g of thiourea was added and stirred to mix evenly, and the pH was maintained at 6.0. The reaction was continued for 12 h, cooled, centrifuged, and washed with anhydrous ethanol three times. The mixture was vacuum dried at 60°C to constant weight to obtain a thiourea-modified molecular sieve.

[0081] S32: 20 g of sodium montmorillonite was added to 200 mL of 0.15 mol / L copper nitrate solution, and the mixture was ultrasonically treated at a power of 200 W and a frequency of 40 kHz for 10 min. The mixture was then stirred at 45° C. and a stirring speed of 200 rpm for 5 h. After centrifugation, the mixture was resuspended in 100 mL of deionized water, centrifuged, and dried in vacuo at 60° C. to constant weight to obtain copper-loaded montmorillonite.

[0082] S33: Mix the thiourea-modified molecular sieve and copper-loaded montmorillonite in a mass ratio of 3.5:1, add a 6% mass concentration of polyvinyl alcohol aqueous solution (the amount is about 35% of the powder mass and can be fine-tuned appropriately), stir to a uniform paste, press into spherical particles with a diameter of 1.5 mm, and vacuum dry at 60°C to constant weight.

[0083] Among them, the molecular sieve is SBA-15, with a specific surface area of ​​about 600m 2 / g, pore size 6~11nm, particle size distribution 1~50μm, before use, dried at 150℃ for 2h; the specific surface area of ​​sodium montmorillonite is about 730m 2 / g, the interlayer spacing is about 1.3nm, and the particle size distribution is 1~10μm; in the polyvinyl alcohol aqueous solution, the average molecular weight of polyvinyl alcohol is about 75,000.

[0084] Preparation Examples 4-6 Lanthanum-doped Hydroxyapatite

[0085] Preparation Example 4

[0086] The preparation method of lanthanum-doped hydroxyapatite of this preparation example comprises the following steps:

[0087] S11: Dissolve 170 g of calcium nitrate tetrahydrate in 500 mL of deionized water and stir until completely dissolved to obtain solution A;

[0088] S12: Dissolve 56.7 g of diammonium hydrogen phosphate in 300 mL of deionized water to obtain solution B;

[0089] S13: Dissolve 3.4 g of lanthanum nitrate hexahydrate in 100 mL of deionized water, slowly drip into solution A, continue stirring at a speed of 200 r / min for 30 min, adjust the stirring speed to 500 r / min, slowly drip into solution B, and simultaneously adjust the pH to 10.5 with 5% ammonia water. Transfer to a high-pressure reactor, react at 110°C for 36 h, naturally cool to room temperature, centrifuge, wash with deionized water until neutral, wash twice with anhydrous ethanol, and freeze-dry at -40°C in a vacuum oven to constant weight.

[0090] Preparation Example 5

[0091] The preparation method of lanthanum-doped hydroxyapatite of this preparation example comprises the following steps:

[0092] S11: Dissolve 160 g of calcium nitrate tetrahydrate in 500 mL of deionized water and stir until completely dissolved to obtain solution A;

[0093] S12: Dissolve 53.3 g of diammonium hydrogen phosphate in 300 mL of deionized water to obtain solution B;

[0094] S13: Dissolve 2.7 g of lanthanum nitrate hexahydrate in 100 mL of deionized water, slowly drip into solution A, continue stirring at a speed of 200 r / min for 30 min, adjust the stirring speed to 500 r / min, slowly drip into solution B, and at the same time adjust the pH to 10 with 5% ammonia water. Transfer to a high-pressure reactor, react at 90°C for 48 hours, naturally cool to room temperature, centrifuge, wash with deionized water until neutral, wash twice with anhydrous ethanol, and freeze-dry at -40°C in a vacuum oven to constant weight.

[0095] Preparation Example 6

[0096] The preparation method of lanthanum-doped hydroxyapatite of this preparation example comprises the following steps:

[0097] S11: Dissolve 180 g of calcium nitrate tetrahydrate in 500 mL of deionized water and stir until completely dissolved to obtain solution A;

[0098] S12: Dissolve 60 g of diammonium hydrogen phosphate in 300 mL of deionized water to obtain solution B;

[0099] S13: Dissolve 4.2 g of lanthanum nitrate hexahydrate in 100 mL of deionized water, slowly drip into solution A, continue stirring at a speed of 200 r / min for 30 min, adjust the stirring speed to 500 r / min, slowly drip into solution B, and at the same time adjust the pH to 11 with 5% ammonia water. Transfer to a high-pressure reactor, react at 120°C for 24 h, naturally cool to room temperature, centrifuge, wash with deionized water until neutral, wash twice with anhydrous ethanol, and freeze-dry at -40°C in a vacuum oven to constant weight.

[0100] Preparation Example 7~9 Nano-Zerovalent Iron-Copper Loaded Activated Carbon

[0101] Preparation Example 7

[0102] The preparation method of the nano zero-valent iron-copper loaded activated carbon of this preparation example comprises the following steps:

[0103] S21: Place 60 g of activated carbon in a 500 mL beaker, add 250 mL of 18% nitric acid solution, heat in a 70 °C water bath with stirring for 4 h, cool, filter, wash until neutral, dry in a vacuum at 60 °C to constant weight, and grind through a 100 mesh sieve to obtain oxidized activated carbon;

[0104] S22: 17.5 g of ferric nitrate nonahydrate was added to 150 mL of deionized water, and the mixture was stirred and mixed evenly. 50 g of oxidized activated carbon was added, and the mixture was transferred to an ultrasonic device. After ultrasonic treatment for 15 min at a power of 200 W and a frequency of 40 kHz, the pH was adjusted to 2.5 with 5% nitric acid by mass. After stirring at 200 r / min for 2 h at 20°C, a copper nitrate solution (mixed with 3 g of copper nitrate trihydrate and 20 mL of deionized water) was slowly added dropwise, and the pH was adjusted to 3.5 with 5% nitric acid by mass, and the mixture was continuously stirred at 300 r / min. After the addition was completed, the stirring was continued for 3 h. The pH was adjusted to 8.5 with 5% ammonia water by mass to obtain a suspension;

[0105] S23: Add 10.25 g of NaBH4 to 100 mL of deionized water, stir and mix thoroughly, then add sodium hydroxide to adjust the pH to 12. Cool to 5°C in an ice bath, and add dropwise to the suspension under a nitrogen atmosphere while stirring continuously. After the addition is complete, continue stirring and mixing for 40 min. Centrifuge, wash 3 times with deionized water, then wash 2 times with anhydrous ethanol, and freeze-dry in a vacuum at -40°C to constant weight.

[0106] Among them, the specific surface area of ​​activated carbon is 1200m 2 / g, 20~40 mesh, ash content ≤5%.

[0107] Preparation Example 8

[0108] The preparation method of the nano zero-valent iron-copper loaded activated carbon of this preparation example comprises the following steps:

[0109] S21: Place 60 g of activated carbon in a 500 mL beaker, add 250 mL of 15% nitric acid solution, heat in a 60 °C water bath with stirring for 5 h, cool, filter, wash until neutral, dry in a vacuum at 60 °C to constant weight, and grind through a 100 mesh sieve to obtain oxidized activated carbon;

[0110] S22: Add 15 g of ferric nitrate nonahydrate to 150 mL of deionized water, stir and mix evenly, add 50 g of oxidized activated carbon, transfer to an ultrasonic device, and ultrasonicate for 12 min at a power of 200 W and a frequency of 40 kHz. Then, adjust the pH to 3 with 5% nitric acid by mass. At 25°C, stir at 200 r / min for 1.5 h, and then slowly dropwise add copper nitrate solution (mixed with 3.5 g of copper nitrate trihydrate and 20 mL of deionized water). Adjust the pH to 4.0 with 5% nitric acid by mass and continue stirring at 300 r / min. After the addition is completed, continue stirring for 3.5 h. Adjust the pH to 8.0 with 5% ammonia water by mass to obtain a suspension.

[0111] S23: Add 10.18 g of NaBH4 to 100 mL of deionized water, stir and mix thoroughly, then add sodium hydroxide to adjust the pH to 12.5. Cool to 3°C in an ice bath, and add dropwise to the suspension under a nitrogen atmosphere while stirring continuously. After the addition is complete, continue stirring and mixing for 30 minutes. Centrifuge, wash 3 times with deionized water, then wash 2 times with anhydrous ethanol, and freeze-dry in a vacuum at -40°C to constant weight.

[0112] Among them, the specific surface area of ​​activated carbon is 1200m 2 / g, 20~40 mesh, ash content ≤5%.

[0113] Preparation Example 9

[0114] The preparation method of the nano zero-valent iron-copper loaded activated carbon of this preparation example comprises the following steps:

[0115] S21: Place 60 g of activated carbon in a 500 mL beaker, add 250 mL of 20% nitric acid solution, heat in an 80 °C water bath with stirring for 3 h, cool, filter, wash until neutral, dry in a vacuum at 60 °C to constant weight, and grind through a 100 mesh sieve to obtain oxidized activated carbon;

[0116] S22: Add 20 g of ferric nitrate nonahydrate to 150 mL of deionized water, stir and mix evenly, add 50 g of oxidized activated carbon, transfer to an ultrasonic device, and ultrasonicate for 18 min at a power of 200 W and a frequency of 40 kHz. Then, adjust the pH to 2.0 with 5% nitric acid by mass. At 25°C, stir at 200 r / min for 2.5 h, and then slowly dropwise add copper nitrate solution (mixed with 2.5 g of copper nitrate trihydrate and 20 mL of deionized water). Adjust the pH to 3.0 with 5% nitric acid by mass and continue stirring at 300 r / min. After the addition is completed, continue stirring for 2.5 h. Adjust the pH to 9.0 with 5% ammonia water by mass to obtain a suspension.

[0117] S23: Add 10.13 g of NaBH4 to 100 mL of deionized water, stir and mix thoroughly, then add sodium hydroxide to adjust the pH to 12. Cool to 4°C in an ice bath, and add dropwise to the suspension under a nitrogen atmosphere while stirring continuously. After the addition is complete, continue stirring and mixing for 50 min. Centrifuge, wash 3 times with deionized water, then wash 2 times with anhydrous ethanol, and freeze-dry in a vacuum at -40°C to constant weight.

[0118] Among them, the specific surface area of ​​activated carbon is 1200m 2 / g, 20~40 mesh, ash content ≤5%.

[0119] Preparation Examples 10-11 Geopolymers

[0120] Preparation Example 10

[0121] The preparation method of the geopolymer of this preparation example comprises the following steps:

[0122] Add 80g of metakaolin and 20g of sodium montmorillonite into a ball mill, ball-mill and mix for 10 minutes, transfer to a stirring kettle, slowly add sodium silicate solution dropwise while stirring at 500rpm, continue stirring for 10 minutes after the addition is completed, add deionized water, 2g each time, until the slurry is in the form of a continuous linear flow, then inject into the mold, vibrate at a frequency of 50Hz to remove bubbles, first cure at 25℃ for 24h, then cure at 80℃ for 24h, demold to obtain the finished product.

[0123] Before use, the finished product is crushed and passed through a 100-mesh standard sieve to obtain geopolymer powder for later use.

[0124] In the sodium silicate solution, the mass concentration of silicon dioxide is 18.5%, and the mass fraction of sodium oxide is 18.0%.

[0125] The amount of sodium silicate solution used is 35% of the total mass of metakaolin and montmorillonite.

[0126] Preparation Example 11

[0127] Add 85g of metakaolin and 15g of sodium montmorillonite into a ball mill, ball-mill and mix for 15 minutes, transfer to a stirring kettle, slowly add sodium silicate solution dropwise while stirring at 500rpm, continue stirring for 10 minutes after the addition is completed, add deionized water, 2g each time, until the slurry is in the form of a continuous linear flow, then inject into the mold, vibrate at a frequency of 50Hz to remove bubbles, first cure at 20℃ for 26h, then cure at 75℃ for 26h, demold to obtain the finished product.

[0128] Before use, the finished product is crushed and passed through a 100-mesh standard sieve to obtain geopolymer powder for later use.

[0129] In the sodium silicate solution, the mass concentration of silicon dioxide is 22% and the mass fraction of sodium oxide is 17.5%.

[0130] The amount of sodium silicate solution used is 30% of the total mass of metakaolin and montmorillonite.

[0131] Example 1

[0132] In the resource recovery treatment method of radioactive wastewater in this embodiment, 2L of nuclear medicine wastewater is taken and treated according to the following steps:

[0133] S1: Pretreatment system

[0134] S11: Deep removal of suspended solids: Alumina ceramic membranes with pore sizes of 0.2 μm and 0.1 μm are used for series filtration, and the membrane flux is controlled at 60 L / (m 2 h), operating pressure 0.2 MPa, circulating filtration until the turbidity of the permeate is less than 0.5 NTU, and collecting the permeate;

[0135] S2: Multi-stage adsorption material treatment

[0136] The pretreatment liquid was passed into a thiourea-based molecular sieve-copper-loaded montmorillonite fixed bed (316 stainless steel column, inner diameter 28 mm, column height 300 mm, filling height 220 mm) at an empty bed flow rate of 0.8 BV / h and an operating pressure of 0.05 MPa to obtain a first treatment liquid;

[0137] The first treatment liquid was passed into a lanthanum-doped hydroxyapatite fixed bed (organic glass column, inner diameter 30 mm, column height 300 mm, filling height 200 mm) at an empty bed flow rate of 0.6 BV / h to obtain a second treatment liquid;

[0138] The second treatment liquid was passed into a fixed bed of nano-zero-valent iron-copper loaded activated carbon (organic glass column, inner diameter 25 mm, column height 300 mm, filling height 200 mm) at an empty bed flow rate of 0.9 BV / h to obtain a water solution;

[0139] S3: Desorption of adsorption materials and concentration and solidification of wastewater

[0140] Thiourea-based molecular sieve-copper-loaded montmorillonite fixed bed: desorption was performed using NH4Cl-NH3·H2O buffer with a pH of 10.0 and a concentration of 2.0 mol / L at a flow rate of 0.8 BV / h for 112 min, and waste liquid A was collected;

[0141] Lanthanum-doped hydroxyapatite fixed bed: desorb with 0.15 mol / L nitric acid solution at a flow rate of 0.5 BV / h for 180 min, and collect waste liquid B;

[0142] Nano-zero-valent iron-copper loaded activated carbon fixed bed: Desorb with 0.08 mol / L sodium thiosulfate solution at a flow rate of 1 BV / h for 90 min. After drying, transfer to a tube furnace and sinter at 300°C for 1.5 h under nitrogen protection. Collect waste liquid C.

[0143] Waste liquid A was rotary evaporated at 30°C and vacuum degree -0.06MPa to concentrate to 5% of the original volume, and 0.1mol / L AgNO3 was slowly added dropwise until no precipitate was precipitated. The precipitate was separated and mixed with geopolymer at a mass ratio of 1:4.5. After stirring evenly, the mixture was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body A.

[0144] Waste liquid B was rotary evaporated at 30°C and vacuum degree -0.06MPa to concentrate to 5% of the original volume, calcium hydroxide was added, the pH was adjusted to 10.0, and then mixed with geopolymer powder at a mass ratio of 1:4.5. After stirring evenly, it was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body B;

[0145] The waste liquid C was rotary evaporated at 30°C and vacuum degree of -0.06MPa to concentrate to 5% of the original volume, and then mixed with geopolymer powder at a mass ratio of 1:4.5. After stirring evenly, it was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body C.

[0146] Among them, the thiourea-based molecular sieve-copper-loaded montmorillonite comes from Preparation Example 1; the lanthanum-doped hydroxyapatite comes from Preparation Example 4; the nano-zero-valent iron-copper-loaded activated carbon comes from Preparation Example 7; and the geopolymer powder comes from Preparation Example 10.

[0147] Test results: The total radioactivity of the effluent is 313.3Bq / L, of which: 18 F is 10.4Bq / L, 99m Tc is 54.5Bq / L, 131 I is 248.4Bq / L.

[0148] 28-day leaching rate of solidified body: 131 I is 2.3×10 -5 Bq / (cm 2 d), 18 F is 3.5×10 -7 Bq / (cm 2 d), 99m Tc is 6.5×10 -7 Bq / (cm 2 ·d).

[0149] Example 2

[0150] In the resource recovery treatment method of radioactive wastewater in this embodiment, 2L of nuclear medicine wastewater is taken and treated according to the following steps:

[0151] S1: Pretreatment system

[0152] S11: Deep removal of suspended solids: Alumina ceramic membranes with pore sizes of 0.3μm, 0.2μm, and 0.1μm are used for series filtration, and the membrane flux is controlled at 55L / (m 2 h), operating pressure 0.25 MPa, circulating filtration until the turbidity of the permeate is less than 0.5 NTU, and collecting the permeate;

[0153] S2: Multi-stage adsorption material treatment

[0154] The pretreatment liquid was passed into a thiourea-based molecular sieve-copper-loaded montmorillonite fixed bed (316 stainless steel column, inner diameter 28 mm, column height 300 mm, filling height 220 mm) at an empty bed flow rate of 1.0 BV / h and an operating pressure of 0.05 MPa to obtain a first treatment liquid;

[0155] The first treatment liquid was passed into a lanthanum-doped hydroxyapatite fixed bed (organic glass column, inner diameter 30 mm, column height 300 mm, filling height 200 mm) at an empty bed flow rate of 0.7 BV / h to obtain a second treatment liquid;

[0156] The second treatment liquid was passed into a fixed bed of nano-zero-valent iron-copper loaded activated carbon (organic glass column, inner diameter 25 mm, column height 300 mm, filling height 200 mm) at an empty bed flow rate of 0.9 BV / h to obtain a water solution;

[0157] S3: Desorption of adsorption materials and concentration and solidification of wastewater

[0158] Thiourea-based molecular sieve-copper-loaded montmorillonite fixed bed: desorption was performed using NH4Cl-NH3·H2O buffer with a pH of 10.5 and a concentration of 2.2 mol / L at a flow rate of 0.8 BV / h for 112 min, and waste liquid A was collected;

[0159] Lanthanum-doped hydroxyapatite fixed bed: desorption was performed using 0.25 mol / L nitric acid solution at a flow rate of 0.5 BV / h for 180 min, and waste liquid B was collected;

[0160] Nano-zero-valent iron-copper loaded activated carbon fixed bed: Desorb with 0.12 mol / L sodium thiosulfate solution at a flow rate of 1 BV / h for 90 min. After drying, transfer to a tube furnace and sinter at 350°C for 1.2 h under nitrogen protection. Collect waste liquid C.

[0161] Waste liquid A was rotary evaporated at 30°C and vacuum degree -0.06MPa to concentrate to 5% of the original volume, and 0.1mol / L AgNO3 was slowly added dropwise until no precipitate was precipitated. The precipitate was separated and mixed with geopolymer at a mass ratio of 1:5.5. After stirring evenly, the mixture was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body A.

[0162] Waste liquid B was rotary evaporated at 30°C and vacuum degree -0.06MPa to concentrate to 5% of the original volume, calcium hydroxide was added, the pH was adjusted to 11.0, and then mixed with geopolymer powder at a mass ratio of 1:5.5. After stirring evenly, it was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body B;

[0163] The waste liquid C was rotary evaporated at 30°C and vacuum degree of -0.06MPa to concentrate to 5% of the original volume, and then mixed with geopolymer powder at a mass ratio of 1:5.5. After stirring evenly, it was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body C.

[0164] Among them, the thiourea-based molecular sieve-copper-loaded montmorillonite comes from Preparation Example 2; the lanthanum-doped hydroxyapatite comes from Preparation Example 5; the nano-zero-valent iron-copper-loaded activated carbon comes from Preparation Example 8; and the geopolymer powder comes from Preparation Example 11.

[0165] Test results: The total radioactivity of the effluent is 349Bq / L, of which: 18 F is 11.7Bq / L, 99m Tc is 61.3Bq / L, 131 I is 276Bq / L.

[0166] 28-day leaching rate of solidified body: 131 I is 2.1×10 -5 Bq / (cm 2 d), 18 F is 3.2×10 -7 Bq / (cm 2 d), 99m Tc is 6.2×10 -7 Bq / (cm 2 ·d).

[0167] Example 3

[0168] In the resource recovery treatment method of radioactive wastewater in this embodiment, 2L of nuclear medicine wastewater is taken and treated according to the following steps:

[0169] S1: Pretreatment system

[0170] S11: Deep removal of suspended solids: Alumina ceramic membranes with pore sizes of 0.3μm, 0.2μm, and 0.1μm are used for series filtration, and the membrane flux is controlled at 65L / (m 2 h), operating pressure 0.2 MPa, circulating filtration until the turbidity of the permeate is less than 0.5 NTU, and collecting the permeate;

[0171] S2: Multi-stage adsorption material treatment

[0172] The pretreatment liquid was passed into a thiourea-based molecular sieve-copper-loaded montmorillonite fixed bed (316 stainless steel column, inner diameter 28 mm, column height 300 mm, filling height 220 mm) at an empty bed flow rate of 0.9 BV / h and an operating pressure of 0.05 MPa to obtain a first treatment liquid;

[0173] The first treatment liquid was passed into a lanthanum-doped hydroxyapatite fixed bed (organic glass column, inner diameter 30 mm, column height 300 mm, filling height 200 mm) at an empty bed flow rate of 0.7 BV / h to obtain a second treatment liquid;

[0174] The second treatment liquid was passed into a fixed bed of nano-zero-valent iron-copper loaded activated carbon (organic glass column, inner diameter 25 mm, column height 300 mm, filling height 200 mm) at an empty bed flow rate of 0.8 BV / h to obtain a water solution;

[0175] S3: Desorption of adsorption materials and concentration and solidification of waste liquid

[0176] Thiourea-based molecular sieve-copper-loaded montmorillonite fixed bed: desorption was performed using NH4Cl-NH3·H2O buffer with a pH of 10.5 and a concentration of 2.2 mol / L at a flow rate of 0.8 BV / h for 112 min, and waste liquid A was collected;

[0177] Lanthanum-doped hydroxyapatite fixed bed: desorption was performed using 0.2 mol / L nitric acid solution at a flow rate of 0.5 BV / h for 180 min, and waste liquid B was collected;

[0178] Nano-zero-valent iron-copper loaded activated carbon fixed bed: Desorb with 0.1 mol / L sodium thiosulfate solution at a flow rate of 1 BV / h for 90 min. After drying, transfer to a tube furnace and sinter at 350°C for 1.2 h under nitrogen protection. Collect waste liquid C.

[0179] Waste liquid A was rotary evaporated at 30°C and vacuum degree -0.06MPa to concentrate to 5% of the original volume. AgNO3 with a concentration of 0.1mol / L was slowly added dropwise until no precipitate was precipitated. The precipitate was separated and mixed with geopolymer in a mass ratio of 1:5. After stirring evenly, the mixture was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body A.

[0180] Waste liquid B was rotary evaporated at 30°C and vacuum degree -0.06MPa to concentrate to 5% of the original volume, calcium hydroxide was added, the pH was adjusted to 10.5, and then mixed with geopolymer powder at a mass ratio of 1:5. After stirring evenly, it was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body B;

[0181] The waste liquid C was rotary evaporated at 30°C and vacuum degree -0.06MPa to concentrate to 5% of the original volume, and then mixed with geopolymer powder at a mass ratio of 1:5. After stirring evenly, it was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body C.

[0182] Among them, the thiourea-based molecular sieve-copper-loaded montmorillonite comes from Preparation Example 3; the lanthanum-doped hydroxyapatite comes from Preparation Example 6; the nano-zero-valent iron-copper-loaded activated carbon comes from Preparation Example 9; and the geopolymer powder comes from Preparation Example 11.

[0183] Test results: The total radioactivity of the effluent is 240.7Bq / L, of which: 18 F is 6.5Bq / L, 99m Tc is 40.9Bq / L, 131 I is 193.3Bq / L.

[0184] 28-day leaching rate of solidified body: 131 I is 2.5×10 -5 Bq / (cm 2 d), 18 F is 3.8×10 -7 Bq / (cm 2 d), 99m Tc is 6.8×10 -7 Bq / (cm 2 ·d).

[0185] Example 4

[0186] In the resource recovery treatment method of radioactive wastewater in this embodiment, 2L of nuclear medicine wastewater is taken and treated according to the following steps:

[0187] S1: Pretreatment system

[0188] S11: Deep removal of suspended solids: Alumina ceramic membranes with pore sizes of 0.2 μm and 0.1 μm are used for series filtration, and the membrane flux is controlled at 60 L / (m 2 h), operating pressure 0.2 MPa, circulating filtration until the turbidity of the permeate is less than 0.5 NTU, and collecting the permeate;

[0189] S2: Multi-stage adsorption material treatment

[0190] The pretreatment liquid was passed into a thiourea-based molecular sieve-copper-loaded montmorillonite fixed bed (316 stainless steel column, inner diameter 28 mm, column height 300 mm, filling height 220 mm) at an empty bed flow rate of 0.8 BV / h and an operating pressure of 0.05 MPa to obtain a first treatment liquid;

[0191] The first treatment liquid was passed into a lanthanum-doped hydroxyapatite fixed bed (plexiglass column, inner diameter 30 mm, column height 300 mm, filling height 200 mm) at an empty bed flow rate of 0.6 BV / h to obtain a second treatment liquid;

[0192] The second treatment liquid was passed into a fixed bed of nano-zero-valent iron-copper loaded activated carbon (organic glass column, inner diameter 25 mm, column height 300 mm, filling height 200 mm) at an empty bed flow rate of 0.7 BV / h to obtain a water solution;

[0193] S3: Desorption of adsorption materials and concentration and solidification of waste liquid

[0194] Thiourea molecular sieve-copper-loaded montmorillonite fixed bed: desorption was performed using NH4Cl-NH3·H2O buffer with a pH of 10.0 and a concentration of 2.2 mol / L at a flow rate of 0.8 BV / h for 112 min, and waste liquid A was collected;

[0195] Lanthanum-doped hydroxyapatite fixed bed: desorption was performed using 0.2 mol / L nitric acid solution at a flow rate of 0.5 BV / h for 180 min, and waste liquid B was collected;

[0196] Nano-zero-valent iron-copper loaded activated carbon fixed bed: Desorb with 0.1 mol / L sodium thiosulfate solution at a flow rate of 1 BV / h for 90 min. After drying, transfer to a tube furnace and sinter at 300°C for 1.5 h under nitrogen protection. Collect waste liquid C.

[0197] Waste liquid A was rotary evaporated at 30°C and vacuum degree -0.06MPa to concentrate to 5% of the original volume. AgNO3 with a concentration of 0.12mol / L was slowly added dropwise until no precipitate was precipitated. The precipitate was separated and mixed with geopolymer in a mass ratio of 1:5. After stirring evenly, the mixture was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body A.

[0198] Waste liquid B was rotary evaporated at 30°C and vacuum degree -0.06MPa to concentrate to 5% of the original volume, calcium hydroxide was added, the pH was adjusted to 10.5, and then mixed with geopolymer powder at a mass ratio of 1:5. After stirring evenly, it was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body B;

[0199] The waste liquid C was rotary evaporated at 30°C and vacuum degree -0.06MPa to concentrate to 5% of the original volume, and then mixed with geopolymer powder at a mass ratio of 1:5. After stirring evenly, it was poured into a mold and sealed and cured at 25°C for 28 days to obtain solidified body C.

[0200] Among them, the thiourea-based molecular sieve-copper-loaded montmorillonite comes from Preparation Example 3; the lanthanum-doped hydroxyapatite comes from Preparation Example 6; the nano-zero-valent iron-copper-loaded activated carbon comes from Preparation Example 9; and the geopolymer powder comes from Preparation Example 11.

[0201] Test results: The total radioactivity of the effluent is 177.4Bq / L, of which: 18 F is 5.2Bq / L, 99m Tc is 34.1Bq / L, 131 I is 138.1Bq / L.

[0202] 28-day leaching rate of solidified body: 131 I is 2.8×10 -5 Bq / (cm 2 d), 18 F is 4.0×10 -7 Bq / (cm 2 d), 99m Tc is 7.0×10 -7 Bq / (cm 2 ·d).

[0203] Comparative Example 1

[0204] The difference between this comparative example and Example 1 is:

[0205] S2: Multi-stage adsorption material treatment

[0206] The pretreatment liquid was passed into a thiourea-based molecular sieve-montmorillonite fixed bed (316 stainless steel column, inner diameter 28 mm, column height 300 mm, filling height 220 mm) with an empty bed flow rate of 0.8 BV / h and an operating pressure of 0.05 MPa to obtain a first treatment liquid;

[0207] The preparation method of the thiourea-based molecular sieve-montmorillonite of this comparative example comprises the following steps:

[0208] S31: 10 g of 3-isothiocyanatopropyltriethoxysilane and 30 mL of aqueous ethanol (ethanol and deionized water in a volume ratio of 1:1) were mixed uniformly, the pH was adjusted to 5.0 with 5% sodium acetate solution, the temperature was raised to 50°C, and pre-hydrolyzed for 60 min. The mixture was cooled to room temperature to obtain a hydrolyzed solution.

[0209] Under a nitrogen atmosphere, 60 g of molecular sieve was added to 400 mL of anhydrous ethanol, and the mixture was transferred to an ultrasonic device. After ultrasonic treatment at a power of 200 W and a frequency of 40 kHz for 30 min, the hydrolyzate was added and stirred to mix evenly. The pH was adjusted to 5.8 with a 5% mass fraction of sodium acetate solution, the temperature was raised to 70°C, and the reaction was continued for 3 h. 5 g of thiourea was added and stirred to mix evenly, while maintaining the pH at 5.8. The reaction was continued for 13 h, cooled, centrifuged, and washed with anhydrous ethanol three times. The mixture was vacuum dried at 60°C to constant weight to obtain a thiourea-modified molecular sieve.

[0210] S32: Mix the thiourea-modified molecular sieve and sodium-montmorillonite in a mass ratio of 3:1, add 8% polyvinyl alcohol aqueous solution (the amount is about 25% of the powder mass and can be fine-tuned appropriately), stir to a uniform paste, press into spherical particles with a diameter of 1.5 mm, and vacuum dry at 60°C to constant weight.

[0211] Among them, the molecular sieve is SBA-15, with a specific surface area of ​​about 600m 2 / g, pore size 6~11nm, dried at 150℃ for 2h before use; the specific surface area of ​​sodium montmorillonite is about 730m 2 / g, the interlayer spacing is about 1.3nm; in the polyvinyl alcohol aqueous solution, the average molecular weight of polyvinyl alcohol is about 75,000.

[0212] Other details are the same as in Example 1.

[0213] Test results: The total radioactivity of the effluent is 481.5Bq / L, of which: 18 F is 12.2Bq / L, 99m Tc is 86.7Bq / L, 131 I is 382.6Bq / L.

[0214] 28-day leaching rate of solidified body: 131 I is 4.0×10 -5 Bq / (cm 2 d), 18 F is 3.4×10 -7 Bq / (cm 2 d), 99m Tc is 6.4×10 -7 Bq / (cm 2 ·d).

[0215] Comparative Example 2

[0216] S2: Multi-stage adsorption material treatment

[0217] The pretreatment liquid was passed into a molecular sieve-copper-loaded montmorillonite fixed bed (316 stainless steel column, inner diameter 28 mm, column height 300 mm, filling height 220 mm) at an empty bed flow rate of 0.8 BV / h and an operating pressure of 0.05 MPa to obtain a first treatment liquid;

[0218] The difference between this comparative example and Example 1 is:

[0219] The preparation method of the molecular sieve-copper loaded montmorillonite of this preparation example comprises the following steps:

[0220] S31: 20 g of sodium montmorillonite was added to 200 mL of 0.12 mol / L copper nitrate solution, and the mixture was ultrasonically treated at a power of 200 W and a frequency of 40 kHz for 10 min. The mixture was then stirred at 40° C. and a stirring speed of 200 rpm for 6 h. After centrifugation, the mixture was resuspended in 100 mL of deionized water, centrifuged, and dried in vacuo at 60° C. to constant weight to obtain copper-loaded montmorillonite.

[0221] S32: Mix the molecular sieve and copper-loaded montmorillonite in a mass ratio of 3:1, add an 8% mass concentration of polyvinyl alcohol aqueous solution (the amount is about 25% of the powder mass and can be fine-tuned appropriately), stir until a uniform paste is formed, press into spherical particles with a diameter of 1.5 mm, and vacuum dry at 60°C to constant weight.

[0222] Among them, the molecular sieve is SBA-15, with a specific surface area of ​​about 600m 2 / g, pore size 6~11nm, dried at 150℃ for 2h before use; the specific surface area of ​​sodium montmorillonite is about 730m 2 / g, the interlayer spacing is about 1.3nm; in the polyvinyl alcohol aqueous solution, the average molecular weight of polyvinyl alcohol is about 75,000.

[0223] Other details are the same as in Example 1.

[0224] Test results: The total radioactivity of the effluent was 1.6×10 4 Bq / L, where 18 F is 19.5Bq / L, 99m Tc is 115.9Bq / L, 131 I is 1.59×10 4 Bq / L.

[0225] 28-day leaching rate of solidified body: 131 I is 4.8×10 -5 Bq / (cm 2 d), 18 F is 3.2×10 -7 Bq / (cm 2 d), 99mTc is 6.3×10 -7 Bq / (cm 2 ·d).

[0226] Combined with the analysis of the test results, we can know that:

[0227] Depend on Figure 1 It can be seen that: 1500cm -1 The strong absorption peak near 3000~3500cm corresponds to the stretching vibration of thiourea group, indicating that the thiourea group modification is successful; -1 The broadened absorption band corresponds to NH stretching vibration, and its peak broadening indicates the presence of intermolecular hydrogen bonds, 1000~1200cm -1 The broadened Si-O peak reflects the composite interface effect between molecular sieve and montmorillonite; 500~800cm -1 The complex absorption includes the bending vibration of silicon-oxygen bonds and the coordination vibration of copper, indicating that copper is loaded in the material in a coordinated form.

[0228] From Comparative Examples 1 and 2 and Example 1, it can be seen that in thiourea-based molecular sieve-copper-loaded montmorillonite, the synergistic effect of thiourea-based modification and copper loading is the efficient removal of 131 I - The core of the thiourea group is achieved through specific coordination 131 I - The copper loading enhances the adsorption activity of the thiourea group by forming a complex, further improving the capture efficiency and stability.

[0229] From Examples 1 to 4, it can be seen that: by using multi-stage adsorption materials, the activity of each nuclide is at an extremely low level, and the thiourea-based molecular sieve-copper-loaded montmorillonite is mainly targeted for removal. 131 I - Lanthanum-doped hydroxyapatite efficiently captures 18 F - and part 99m TcO4 - Nano-zero-valent iron-copper loaded activated carbon further removes residual 99m TcO4 - The three work together to achieve 131 I - 、 18 F - 、 99m TcO4 - Comprehensive and efficient removal.

[0230] For different adsorption materials, the adsorbed nuclides are desorbed and concentrated before solidification with geopolymers. With the help of the dense structure and chemical stability of geopolymers, the nuclide leaching rate is significantly reduced to meet the requirements of long-term safe disposal.

[0231] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for recycling radioactive wastewater, characterized in that: The steps include: S1: Pretreatment: Suspended matter separation; S2: Multi-stage adsorption material treatment: thiourea-based molecular sieve-copper-loaded montmorillonite treatment, lanthanum-doped hydroxyapatite treatment, and nano-zero-valent iron-copper-loaded activated carbon treatment were used in sequence; S3: desorption of adsorption materials and concentration and solidification of waste liquid; The thiourea-based molecular sieve-copper-loaded montmorillonite is prepared from thiourea-modified molecular sieve and copper-loaded montmorillonite in a mass ratio of (2.5-3.5):1 as raw materials; The lanthanum-doped hydroxyapatite is prepared from calcium nitrate tetrahydrate, diammonium hydrogen phosphate and lanthanum nitrate hexahydrate in a mass ratio of 3:1:(0.05-0.07). The nano zero-valent iron-copper loaded activated carbon is prepared from oxidized activated carbon, ferric nitrate nonahydrate, and copper nitrate trihydrate in a mass ratio of 1:(0.3-0.4):(0.05-0.07) and is reduced with sodium borohydride.

2. The method for recycling radioactive wastewater according to claim 1, characterized in that: The preparation method of the thiourea-modified molecular sieve comprises the following steps: The molecular sieve is dispersed in anhydrous ethanol, and the hydrolyzate of 3-isothiocyanatopropyltriethoxysilane is added, and the pH is adjusted to 5.5-6.

0. The temperature is raised to 60-75°C and the reaction is carried out for 2-4 hours. Thiourea is then added, and the pH is maintained at 5.5-6.

0. The reaction is continued for 12-15 hours. The solid-liquid separation is performed, and the reaction is carried out after washing and drying to obtain the thiourea-modified molecular sieve.

3. The method for recycling radioactive wastewater according to claim 1, characterized in that: The preparation method of the copper-loaded montmorillonite comprises the following steps: The montmorillonite is dispersed in a copper nitrate solution, heated to 35-45°C, mixed for 5-7 hours, solid-liquid separation, washed, and dried to obtain copper-loaded montmorillonite.

4. The method for recycling radioactive wastewater according to claim 1, wherein: The preparation method of the thiourea-based molecular sieve-copper-loaded montmorillonite comprises the following steps: The thiourea-modified molecular sieve and copper-loaded montmorillonite are uniformly mixed in a mass ratio of (2.5-3.5):1, a binder is added, pressed into shape, and dried to obtain the product.

5. The method for recycling radioactive wastewater according to claim 1, wherein: The preparation method of the lanthanum-doped hydroxyapatite comprises the following steps: Mix the calcium nitrate solution and the lanthanum nitrate solution evenly, then add the diammonium hydrogen phosphate solution while stabilizing the pH at 10-11, raise the temperature to 90-120°C, react for 24-48 hours, cool, separate the solid and liquid, wash, and freeze-dry to obtain the product.

6. The method for recycling radioactive wastewater according to claim 1, wherein: The preparation method of the oxidized activated carbon comprises the following steps: Mix activated carbon with 15% to 20% nitric acid by mass, heat to 60 to 80°C, mix for 3 to 5 hours, cool, separate the solid and liquid, wash, and dry to obtain oxidized activated carbon.

7. The method for recycling radioactive wastewater according to claim 1, wherein: The preparation method of the nano zero-valent iron-copper loaded activated carbon comprises the following steps: The ferric nitrate solution is mixed with the oxidized activated carbon for 1.5 to 2.5 hours, during which the pH is maintained at 2.0 to 3.0, and then the copper nitrate solution is added and mixed for 2.5 to 3.5 hours, during which the pH is maintained at 3.0 to 4.

0. Thereafter, the pH is adjusted to 8 to 9, and under an inert atmosphere, the sodium borohydride solution is added and mixed for 30 to 50 minutes, followed by solid-liquid separation, washing, and freeze-drying to obtain the product.

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