Iodine-adsorbing bismuth tungstate, preparation method and application thereof

Abstract

This invention discloses an iodine-adsorbing bismuth tungstate, its preparation method, and its application, belonging to the field of wastewater treatment technology. The iodine-adsorbing bismuth tungstate is a core-shell structured composite material, comprising: an Fe, Mo, and V metal co-doped bismuth tungstate core, a tannic acid-iron metal-phenol intermediate shell, and a polyethyleneimine grafted outer layer. The co-doped bismuth tungstate is prepared by a hydrothermal method; a tannic acid-iron coating is self-assembled in Tris-HCl buffer; and polyethyleneimine is grafted. This invention utilizes Mo… 6+ Fe 3+ V 5+ The combined effect, along with the TA-Fe sacrificial coating, consumes H. + / OH － This achieved a significant improvement in chemical stability over a wide pH range of 2-12; simultaneously, it utilized electrostatic enrichment of the PEI layer and Bi... 3+ It exhibits specific coordination synergy, high selectivity, rapid kinetics, and high adsorption capacity for iodide ions.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to an iodine-adsorbing bismuth tungstate, its preparation method, and its application. Background Technology

[0002] The efficient treatment of radioactive iodine-containing wastewater is one of the core challenges in the field of nuclear energy environmental safety. Iodine-129 (half-life of approximately 15.7 million years) has extremely long environmental persistence and high biomobility, and can accumulate in the thyroid gland, causing long-term radiation damage; Iodine-131 (half-life of approximately 8 days) has high specific activity and poses a major environmental risk in the early stages of a nuclear accident. This type of wastewater is characterized by high salinity, a wide pH range (2-12), and high radiation intensity, with Cl... － NO3 － SO4 2－ The concentration of competing anions is usually higher than that of I. - Two to three orders of magnitude higher.

[0003] Existing adsorption materials have the following limitations: activated carbon mainly relies on physical adsorption, resulting in extremely poor selectivity; anion exchange resins follow the SO42-dioxanone adsorption process. 2－ NO3 －- >I － The selective sequence has poor radiation stability; Ag-zeolite forms AgI (Ksp=8.5×10⁻⁶) －17 It is highly efficient at capturing iodine, but in high Cl... － An AgCl passivation layer (Ksp=1.8×10⁻⁶) is formed on the surface in the environment. －10 ), and Ag at pH < 3 + Severe dissolution. Bismuth tungstate (Bi2WO6) relies on Bi... 3+ to I － Its specific affinity and excellent radiation stability make it a potential alternative material, but [Bi2O2] is problematic at pH < 4. 2+ The Bi-O key in the layer is H + The attack caused Bi 3+ Dissolution of WO4 at pH > 10 2- The leaching of the material in the form of soluble tungstates severely limits its practical applications. Existing doping modifications mostly focus on photocatalysis, and no reports have been found on systematic optimization for structural stability over a wide pH range. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an iodine-adsorbing bismuth tungstate, its preparation method and application, so as to solve the technical problem that the crystal structure of existing bismuth tungstate-based adsorbent materials is irreversibly destroyed in acidic environments with pH < 4 or alkaline environments with pH > 10, resulting in the dissolution of active components, loss of adsorption sites and poor cycle stability.

[0005] To achieve the above objectives, this application adopts the following technical solution: In one aspect, this application provides an iodine-adsorbing bismuth tungstate.

[0006] An iodine-adsorbing bismuth tungstate, characterized in that the iodine-adsorbing bismuth tungstate is a core-shell structured composite material, comprising: (A) Core: Multimetal-doped bismuth tungstate, chemical formula Bi 2-x Fe X W 1-y-z Mo y V z O 6- δ, where 0.02≤x≤0.10, 0.02≤y≤0.12, 0.01≤z≤0.08, δ is the oxygen vacancy concentration, with a value range of 0.01≤δ≤0.10. (x is Fe) 3+ Replace Bi 3+ (molar ratio), 0.02≤y≤0.12 (y is the molar ratio of Mo). 6+ Replace W 6+ (molar ratio), 0.01≤z≤0.08 (z is V) 5+ The molar ratio of cross-site doping), δ is the oxygen vacancy concentration (related to x, y, z); (B) Intermediate shell: Tannic acid-iron metal-phenol network coating, covering the surface of the core; (C) Outer layer: Polyethyleneimine grafted layer, covalently grafted onto the surface of the intermediate shell layer.

[0007] Secondly, this application provides a method for preparing the above-mentioned iodine-adsorbed bismuth tungstate, comprising the following steps: Step 1: Preparation of multi-metal co-doped bismuth tungstate: (1) Preparation of precursor solution A: Dissolve bismuth nitrate pentahydrate and ferric nitrate nonahydrate in 0.2-1.0M dilute nitric acid at a molar ratio of Bi:Fe = 1:0.01~0.05, so that Bi 3+ At a concentration of 0.2-0.5M, polyvinylpyrrolidone (PVPK30, weight average molecular weight 44000-54000) was added. The PVP and Bi... 3+ The mass ratio is 0.01:1 to 0.05:1, and the mixture is stirred until completely dissolved; (2) Preparation of precursor solution B: Dissolve sodium tungstate dihydrate, sodium molybdate dihydrate, and ammonium metavanadate in deionized water at a molar ratio of W:Mo:V = 1:0.02~0.12:0.01~0.08, so that W 6+ The concentration is 0.2-0.5M; stir until completely dissolved. (3) Coprecipitation reaction: Under stirring conditions of 200-500 rpm, the precursor solution B is added dropwise to the precursor solution A at a rate of 2-10 mL / min. After the addition is complete, the pH is adjusted to 4.8-5.2 with 1-2M NaOH solution, and stirring is continued for 0.5-2 hours. (4) Hydrothermal crystallization: The suspension obtained in step (3) is transferred to a hydrothermal reactor and reacted at 170-200℃ for 14-24 hours; (5) Post-treatment: After natural cooling, centrifuge or filter to collect the precipitate, wash it with deionized water and anhydrous ethanol in sequence, dry it at 50-80℃ for 6-24 hours, and grind it to obtain multi-metal doped bismuth tungstate.

[0008] Step 2: Coating with a tannic acid-iron-phenol network coating: (1) Preparation of Tris-HCl buffer: Weigh tris(hydroxymethyl)aminomethane (Tris) and dissolve it in deionized water. Adjust the pH to 8.0-8.8 with hydrochloric acid. The concentration is 0.05-0.2M. (2) Preparation of TA-Fe mixed solution: Dissolve tannic acid and ferric nitrate nonahydrate in Tris-HCl buffer solution at a mass ratio of TA:Fe=2:1~4:1, with the tannic acid concentration being 2-8 g / L, and stir until the solution turns dark purple; (3) Surface modification: Disperse the polymetallic doped bismuth tungstate from step one in a solid-liquid ratio of 1:20~1:100 g / mL in a TA-Fe mixed solution, and stir or shake at 20-40℃ for 2-6 hours; (4) Washing and drying: Centrifuge to collect the product, wash with deionized water, and vacuum dry at 40-60℃ for 4-12 hours to obtain TA-Fe@BWO-MVF.

[0009] Step 3: Grafting of polyethyleneimine: (1) Preparation of PEI grafting solution: Dilute 50% polyethyleneimine aqueous solution with deionized water to a concentration of 2-10 g / L, and adjust the pH to 7.5-8.5 with hydrochloric acid or sodium hydroxide; (2) Grafting reaction: Disperse the TA-Fe@BWO-MVF obtained in step 2 in PEI grafting solution at a solid-liquid ratio of 1:20~1:100 g / mL, and stir or shake at 20-40℃ for 4-12 hours; (3) Post-processing: Centrifuge to collect the product, wash repeatedly with deionized water until the supernatant is no longer purple as detected by the ninhydrin colorimetric method, and dry at 50-70℃ for 4-12 hours to obtain iodine-adsorbed bismuth tungstate.

[0010] Thirdly, this application provides the application of the above-mentioned iodine-adsorbing bismuth tungstate in the treatment of iodine-containing radioactive wastewater.

[0011] The iodine-adsorbing bismuth tungstate is added to iodine-containing wastewater at a dosage of 0.5-2.0 g / L. The mixture is stirred and adsorbed for 1-3 hours at a pH of 4-10 and a temperature of 15-35°C. The iodine removal is completed after solid-liquid separation.

[0012] Compared with the prior art, this application has the following beneficial effects: 1. Significantly improved chemical stability over a wide pH range: The material of this invention exhibits significantly improved chemical stability over a wide pH range of 2-12. 3+ Dissolution rate <1.0%, WO4 2－ Dissolution rate <1.5%, after 5 adsorption-desorption cycles I - Removal rate retention rate >90%.

[0013] 2. Iodide ion adsorption has strong selectivity: in Cl... － NO3 － SO4 2－ Concentration 10 times that of I － Under competitive conditions, the partition coefficient Kd remains above 2000 mL / g.

[0014] 3. High adsorption capacity: Maximum adsorption capacity reaches 126.7 mgI － / g, which is about 123% higher than that of undoped Bi2WO6 (56.8mg / g).

[0015] 4. Strong irradiation tolerance: Adsorption capacity retention rate >88% after 200kGy γ irradiation. Attached Figure Description

[0016] Figure 1 Scanning electron microscope (SEM) images of iodine-adsorbed bismuth tungstate prepared in Example 1 of this invention, wherein (a) is an SEM image of iodine-adsorbed bismuth tungstate at a size of 1 µm and (b) is an SEM image of iodine-adsorbed bismuth tungstate at a size of 200 nm.

[0017] Figure 2 Infrared spectrum of iodine-adsorbed bismuth tungstate prepared in Example 1 of this invention.

[0018] Figure 3 Example 1 of this invention describes the iodine-adsorbing bismuth tungstate prepared under different pH conditions for I... － Removal rate bar chart.

[0019] Figure 4 : Cycle curve of iodine-adsorbed bismuth tungstate prepared in Example 1 of this invention.

[0020] Figure 5 Bismuth tungstate prepared in Example 1 of this invention and Comparative Examples 1-3 － Adsorption capacity comparison chart.

[0021] Figure 6 The Bi of Example 1 and Comparative Examples 1-3 of this invention were soaked in water at pH=2 for 24 hours. 3+ Dissolution rate comparison chart.

[0022] Figure 7 WO4 from Example 1 and Comparative Examples 1-3 of this invention was soaked at pH=12 for 24 hours. 2－ Dissolution rate comparison chart.

[0023] Figure 8 Example 1 of the present invention: Adsorption capacity retention curves under different γ-irradiation doses. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are only for explaining the invention and not for limiting it. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0026] Example 1 Preparation of iodine-adsorbed bismuth tungstate: Step 1: Preparation of multi-metal co-doped bismuth tungstate: (1) Preparation of precursor solution A: Weigh 9.7g (20mmol) Bi(NO3)3·5H2O and 0.404g (1mmol) Fe(NO3)3·9H2O and dissolve them in 50mL of 0.5M dilute nitric acid. Add 0.5g PVPK30 and stir for 30 minutes until completely dissolved.

[0027] (2) Preparation of precursor solution B: Weigh 6.60g (20mmol) Na2WO4·2H2O, 0.484g (2mmol) Na2MoO4·2H2O and 0.117g (1mmol) NH4VO3 and dissolve them in 50mL of deionized water. Stir for 30 minutes until completely dissolved.

[0028] (3) Coprecipitation reaction: Under stirring at 300 rpm, the precursor solution B was added dropwise to the precursor solution A at a rate of 5 mL / min. After the addition was completed, the pH was adjusted to 5.0 with 1M NaOH and stirring was continued for 1 hour.

[0029] (4) Hydrothermal crystallization: Transfer the suspension to a 200mL hydrothermal reactor and react at 190℃ for 18 hours.

[0030] (5) Post-treatment: After natural cooling, centrifuge (8000 rpm, 10 minutes) to collect the precipitate, wash 3 times with deionized water and 1 time with anhydrous ethanol, dry at 60℃ for 12 hours, and grind to obtain BWO-MVF (specifically Bi...). 1.95 Fe 0.05 W 0.85 Mo 0.10 V0.05O 6-δ (δ=0.025)).

[0031] Step 2, TA-Fe coating: (1) Prepare Tris-HCl buffer: Weigh 3.03g Tris and dissolve it in 200mL deionized water, and adjust the pH to 8.5 with 1M HCl.

[0032] (2) Preparation of TA-Fe mixed solution: Weigh 0.85g tannic acid and 0.27g Fe(NO3)3·9H2O and dissolve them in 100mL Tris-HCl buffer solution and stir until deep purple.

[0033] (3) Surface modification: Weigh 2.0g of BWO-MVF and disperse it in the above TA-Fe solution. Shake the reaction at 25℃ and 150rpm for 4 hours.

[0034] (4) Washing and drying: Centrifuge to collect, wash 3 times with deionized water, and vacuum dry at 50℃ for 6 hours to obtain TA-Fe@BWO-MVF.

[0035] Step 3, PEI grafting: (1) Preparation of PEI grafting solution: Dilute 50% PEI aqueous solution with deionized water to 5 g / L, and adjust pH to 8.0 with 0.1 M HCl.

[0036] (2) Grafting reaction: Weigh 1.0g TA-Fe@BWO-MVF and disperse it in 50mL PEI solution, and stir the reaction at 25℃ for 6 hours.

[0037] (3) Post-processing: Centrifuge to collect, wash with deionized water until no purple color is detected by ninhydrin detection, dry at 60℃ for 6 hours to obtain PEI@TA-Fe@BWO-MVF.

[0038] Scanning electron microscopy of iodine-adsorbed bismuth tungstate, as shown in Figure 1 Figure 1 As shown. From Figure 1 (a) It can be seen that iodine-adsorbed bismuth tungstate exhibits a uniform three-dimensional hierarchical microsphere structure, consisting of a "flower-like" hierarchical structure formed by the self-assembly and stacking of numerous ultrathin nanosheets. The thickness of the nanosheets is estimated to be 25-60 nm, and the width is 180-600 nm. Abundant open mesopores and slit-like pores are formed between the nanosheets. From Figure 1(b) It can be seen that the surface of the nanosheets exhibits an amorphous "fluffy" coating.

[0039] The infrared spectrum of iodine-adsorbed bismuth tungstate is as follows: Figure 2 As shown. From Figure 2 The following lattice characteristics of Bi₂WO₆ were observed: WO bond vibrations (800-750 cm⁻¹). －1 ) and Bi-O bond vibration (651 cm) －1 This confirms that the material retains the layered crystal structure of bismuth tungstate. TA-Fe coating characteristics (635 cm⁻¹) －1 The appearance of the characteristic peak of the Fe-O coordination bond confirms that tannic acid and Fe... 3+ Successful coordination led to the formation of a metal-phenol network. Evidence of successful PEI grafting (2900-2750 cm⁻¹) －1 +1680-1540cm －1 ): Methylene stretching bimodal (2900-2750cm) －1 This confirms the existence of long PEI chains, specifically the amide I band (1650-1630 cm). －1 ) and amide II band (1560-1540cm) －1 This confirms that PEI is grafted onto the TA-Fe coating surface via covalent bonds (Schiff base / Michael addition), rather than simple physical adsorption, and the polyphenol hydroxyl characteristics (1250-1000 cm⁻¹) are evident. －1 (Regional multiple absorption): The typical infrared characteristics of TA as a polyphenol compound are clearly presented in this region, confirming the successful coating of TA-Fe. Broad peak at 3400 cm⁻¹. －1 The peaks at this location are characteristic of phenolic hydroxyl and amino groups.

[0040] The specific surface area of ​​the obtained product is 78.6 m². 2 / g, Zeta potential (pH=7) +32.4mV.

[0041] Adsorption performance test: Weigh 0.05g of product and add it to 50mL of solution containing I. － 100mg / L, Cl － 1000mg / L, NO3 － 1000mg / L, SO4 2－ In a simulated wastewater solution of 200 mg / L (pH=7), the mixture was shaken at 25°C and 200 rpm for 2 hours. After adsorption, I... - When the concentration was reduced to 0.85 mg / L, the removal rate was 99.15%, the adsorption capacity was 126.7 mg / g, and Kd = 5835 mL / g.

[0042] Example 2 The difference from Example 1 is as follows: the Fe doping ratio was changed to 2% (0.1616g Fe(NO3)3·9H2O), the Mo doping ratio was changed to 4% (0.1936g Na2MoO4·2H2O), the V doping ratio was changed to 2% (0.0468g NH4VO3), the hydrothermal temperature was 180℃, and the hydrothermal time was 20 hours. The TA-Fe coating time was 3 hours, and the PEI grafting time was 5 hours.

[0043] The specific surface area of ​​the obtained product is 85.2 m². 2 / g, Zeta potential (pH=7) +28.6mV.

[0044] Under the same conditions I － Removal rate 98.2%, Kd=4320mL / g.

[0045] Example 3 The difference from Example 1 is as follows: the Fe doping ratio was changed to 8% (0.6464g Fe(NO3)3·9H2O), the Mo doping ratio was changed to 12% (0.5808g Na2MoO4·2H2O), and the V doping ratio was changed to 7% (0.1638g NH4VO3). The hydrothermal temperature was 200℃, and the hydrothermal time was 16 hours. The TA-Fe coating time was 5 hours, and the PEI grafting time was 8 hours.

[0046] The specific surface area of ​​the obtained product is 62.4 m². 2 / g, Zeta potential (pH=7) +35.1mV.

[0047] Under the same conditions I － Removal rate 98.8%, Kd=5390mL / g.

[0048] Example 4 Take 0.05g of the product from Example 1 and add it to 50ml of L1. - In a 100 mg / L solution, the pH was adjusted to 2, 4, 7, 9, and 11, and the mixture was shaken at 25°C and 200 rpm for 2 hours. I was tested under the same conditions. － Removal rate, such as Figure 3 As shown.

[0049] It can be seen that the iodine-adsorbing bismuth tungstate prepared in Example 1 has chemical stability over a wide pH range.

[0050] Example 5 Take 0.5g of the product from Example 1 and add it to 500ml of water. － Adsorption was performed in simulated wastewater (pH=7) at a concentration of 100 mg / L according to the application method. After adsorption saturation, the product was immersed in 50 mL of 1 M NaOH solution and stirred for 30 minutes. After washing with deionized water until neutral, it was reused.

[0051] After 5 cycles, I － The removal rate decreased from 99.2% to 91.5% (e.g.) Figure 4 As shown in the figure, the regeneration rate reached 92.2%.

[0052] Comparative Example 1 Undoped Bi2WO6 was prepared by synthesizing 9.7g Bi(NO3)3·5H2O and 6.60g Na2WO4·2H2O according to step one of Example 1, without doping or coating treatment.

[0053] Under the same conditions I － Adsorption capacity: 56.8 mg / g.

[0054] Comparative Example 2 Prepared according to the method of Example 1, but without adding Fe and V salts, and only doped with 10% Mo.

[0055] Under the same conditions I － Adsorption capacity: 78.3 mg / g.

[0056] Comparative Example 3 Prepared according to the method of Example 1, but without adding Mo and V salts, only doped with 5% Fe.

[0057] Under the same conditions I － Adsorption capacity: 72.6 mg / g.

[0058] Comparative Example 4 Undoped Bi2WO6 was prepared according to the method of Comparative Example 1, and then TA-Fe coating and PEI grafting were performed according to steps two and three of Example 1.

[0059] Under the same conditions I － Adsorption capacity: 68.2 mg / g.

[0060] from Figure 5 As can be seen from the above, the bismuth tungstate prepared in Example 1 of this invention has I － The adsorption capacity was significantly better than that of Comparative Examples 1-3.

[0061] Stability test results Acid stability: 0.1 g of each of the materials from the examples and comparative examples were immersed in 50 mL of HNO3 solution with pH=2 for 24 hours, and the Bi content in the solution was measured. 3+ Dissolution rate. For example... Figure 6 As shown.

[0062] It can be seen that in Examples 1-3, Bi 3+ The dissolution rate was much lower than that of Comparative Examples 1-4.

[0063] Alkali stability: Each material was immersed in a NaOH solution with pH=12 for 24 hours, and the WO4 content in the solution was measured. 2－ Concentration. For example... Figure 7 As shown.

[0064] It can be seen that WO4 in Examples 1-3 2－ The dissolution rate was much lower than that of Comparative Examples 1-4.

[0065] Irradiation stability: The material from Example 1 was subjected to... 60 I was measured after irradiation with Coγ rays (dose rate 10 kGy / h) at dose rates of 50, 100, and 200 kGy respectively. － Adsorption capacity, calculation of I － Adsorption capacity retention rate, such as Figure 8 As shown.

[0066] It can be seen that the retention rate is 97.8% after irradiation of 50kGy, 94.5% after 100kGy, and no less than 88% after 200kGy, indicating good radiation resistance.

[0067] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A bismuth tungstate with iodine adsorption properties, characterized in that, The iodine-adsorbing bismuth tungstate is a core-shell structured composite material, comprising: (A) Core: multi-metal doped bismuth tungstate, chemical formula represented as Bi 2-x Fe X W 1-y-z Mo y V z O 6- δ, wherein 0.02≤x≤0.10, 0.02≤y≤0.12, 0.01≤z≤0.08, δ is the oxygen vacancy concentration, and the value range is 0.01≤δ≤0.10; (B) Intermediate shell: Tannic acid-iron metal-phenol network coating, covering the surface of the core; (C) Outer layer: Polyethyleneimine grafted layer, covalently grafted onto the surface of the intermediate shell layer.

2. A method for preparing iodine-adsorbing bismuth tungstate as described in claim 1, characterized in that, Includes the following steps: Step 1: Preparation of multi-metal co-doped bismuth tungstate: First, prepare precursor solution A: dissolve bismuth nitrate pentahydrate and ferric nitrate nonahydrate in dilute nitric acid, add polyvinylpyrrolidone, and stir to dissolve; then prepare precursor solution B: dissolve sodium tungstate dihydrate, sodium molybdate dihydrate, and ammonium metavanadate in deionized water, and stir to dissolve; then add precursor solution B dropwise to precursor solution A, adjust the pH to 4.8-5.2, and carry out a co-precipitation reaction; finally, crystallize by hydrothermal reaction to obtain multi-metal-doped bismuth tungstate; Step 2: Coating with a tannic acid-iron-phenol network coating: First, prepare a Tris-HCl buffer solution, then add tannic acid and ferric nitrate nonahydrate to obtain a TA-Fe mixed solution; disperse the multi-metal doped bismuth tungstate from step one in the TA-Fe mixed solution, react at 20-40℃ for 2-6 hours, and then process to obtain a multi-metal doped bismuth tungstate coated with a tannic acid-iron metal-phenol network coating. Step 3: Grafting of polyethyleneimine: First, prepare the PEI grafting solution: dilute the polyethyleneimine aqueous solution with deionized water to a concentration of 2-10 g / L and adjust the pH to 7.5-8.5; disperse the product obtained in step two in the PEI grafting solution, and react and graft at 20-40℃ for 4-12 hours. After post-treatment, iodine-adsorbed bismuth tungstate is obtained.

3. The method for preparing iodine-adsorbing bismuth tungstate according to claim 2, characterized in that, In step one: Bi in the precursor solution A 3+ The concentration is 0.2-0.5M, and the molar ratio of Bi to Fe is 1:0.01-0.05; the precursor solution B contains W 6+ The concentration is 0.2-0.5M, and the molar ratio of W:Mo:V is 1:0.02~0.12:0.01~0.

08.

4. The method for preparing iodine-adsorbing bismuth tungstate according to claim 2, characterized in that, In step one: the polyvinylpyrrolidone has a weight-average molecular weight of 44,000-54,000, and the polyvinylpyrrolidone reacts with Bi... 3+ The mass ratio is 0.01:1 to 0.05:1; the concentration of the dilute nitric acid is 0.2-1.0M; and the pH is adjusted using 1-2M NaOH solution.

5. The method for preparing iodine-adsorbing bismuth tungstate according to claim 2, characterized in that, The hydrothermal reaction temperature is 180-200℃, and the time is 16-20 hours.

6. The method for preparing iodine-adsorbing bismuth tungstate according to claim 2, characterized in that: The concentration of the Tris-HCl buffer solution is 0.05-0.2M; the mass ratio of tannic acid to iron in the TA-Fe mixed solution is 2:1 to 4:1, and the concentration of tannic acid is 2-8 g / L.

7. The method for preparing iodine-adsorbing bismuth tungstate according to claim 2, characterized in that: The molecular weight of the polyethyleneimine is 600-1800; the concentration of the PEI grafting solution is 5 g / L, and the pH is 8.

0.

8. The method for preparing iodine-adsorbing bismuth tungstate according to claim 7, characterized in that: The grafting reaction time is 6 hours.

9. The application of the iodine-adsorbing bismuth tungstate of claim 1 in the treatment of iodine-containing wastewater, characterized in that: The iodine-adsorbing bismuth tungstate is added to iodine-containing wastewater at a dosage of 0.5-2.0 g / L. The mixture is stirred and adsorbed for 1-3 hours at a pH of 4-10 and a temperature of 15-35°C. The iodine removal is completed after solid-liquid separation.

10. The application according to claim 9, characterized in that: The iodine-containing wastewater is radioactive iodine-containing wastewater, in which iodine exists in the form of iodide ions, and the wastewater also contains Cl. － NO3 － SO4 2－ One or more competing anions are present; after the iodine-adsorbing bismuth tungstate is saturated, it is desorbed and regenerated by soaking in 1-2M NaOH solution for 30-60 minutes, and the regenerated material can be reused.

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