Associated mine radioactive wastewater uranium deep treatment and resource collaborative recovery method

Abstract

The application relates to the technical field of radioactive wastewater treatment, and specifically discloses a method for deep treatment and resource collaborative recovery of associated mine radioactive wastewater, which comprises the following steps: S1: ammonium metatungstate, glucose, graphene oxide and hydrochloric acid dopamine are subjected to hydrothermal reaction and calcination to obtain a base powder; S2: the base powder is subjected to template pre-assembly and hydrolysis polycondensation with soluble uranium salt, phytic acid, cyanosilane and a silicon source under weak acid conditions to obtain pre-coated powder; S3: after elution by an acid eluent, the cyan group is converted into amidoxime under weak acid microwave conditions to obtain active powder; S4: the active powder, conductive carbon black and a binder containing polyvinylidene fluoride and carboxylated carbon nanotubes are made into a composite electrode; and S5: a three-electrode system is adopted, and uranium products are recovered through cathode reduction enrichment, anode reverse desorption and precipitation calcination. The composite electrode prepared by the application can realize deep purification of uranium-containing wastewater and efficient recovery of uranium, and the recovered uranium products are high in purity.

Description

Technical Field

[0001] This application relates to the technical field of radioactive wastewater treatment, and more specifically, to a method for deep treatment and co-recovery of uranium resources in radioactive wastewater from associated minerals. Background Technology

[0002] The mining and beneficiation processes of associated minerals such as molybdenum-uranium co-existing deposits and rare earth-associated uranium deposits inevitably generate large amounts of uranium-containing radioactive wastewater. The uranium concentration in leachate from low-grade uranium ore and decommissioned mines is only 0.5–50 mg / L, but its toxicity and radioactivity far exceed emission standards. Direct discharge without thorough treatment will cause irreversible radioactive contamination of surrounding groundwater systems and result in a serious loss of uranium, a strategic nuclear resource.

[0003] For low-concentration uranium-containing wastewater, microbial electrochemical reduction and electroadsorption are promising technological approaches. These technologies capture free hexavalent uranium (U(VI)) through active groups on the electrode surface, then reduce it to insoluble tetravalent uranium (UO2) via cathode bias or extracellular electron transfer from microorganisms, depositing it on the electrode surface. This achieves deep uranium removal and avoids the drawbacks of traditional ion exchange resins, which require extensive acid and alkali regeneration and generate large amounts of radioactive secondary wastewater. However, a core bottleneck remains insurmountable for industrial application: the wastewater quality in actual mining areas is complex, with concentrations of coexisting heavy metal ions such as iron and molybdenum reaching tens to thousands of times higher than those of uranium ions. Based on the theory of hard and soft acids and bases, the active groups on the electrode surface have a strong coordination affinity for both U(VI) and iron ions, which belong to the "hard acid" category. During the cathode reduction process, a large number of adsorbed iron ions are easily reduced and hydrolyzed into iron oxide colloids, which undergo severe co-precipitation and physical coating with UO2 nanoparticles. The purity of the recovered uranium (calculated as U3O8) is usually not higher than 70%, and it carries a large number of iron, molybdenum and other impurity oxides. It cannot be directly used as feed for the refining process and still requires complex chemical purification treatment.

[0004] Patent application CN117800448A discloses a method for preparing an electrochemical uranium extraction electrode material, comprising the following steps: Step 1, cleaning iron foil in an ultrasonic cleaner; Step 2, drying the cleaned iron foil in a vacuum dryer, then placing the dried iron foil in an alumina crucible and annealing it in air to generate Fe3O4 foil; Step 3, immersing the Fe3O4 foil obtained in Step 2 in a Co(NO3)2·6H2O solution, drying it in a vacuum dryer after immersion, and then annealing the dried Fe3O4 foil in air to complete the first cobalt loading, obtaining Co3O4@Fe3O4-1; Step 4, repeating Step 3 on the Co3O4@Fe3O4-1 obtained in Step 3 to obtain Co3O4@Fe3O4-2, and repeating Step 3 multiple times to obtain a Co3O4@Fe3O4 nanosheet array, i.e., an electrochemical electrode uranium extraction material.

[0005] In this technical solution, only Co3O4@Fe3O4 metal oxide is used as the active material, with iron foil as the substrate. However, this electrode lacks selective recognition capability for U(VI) and coexisting competing ions. In the presence of high concentrations of interfering ions such as iron and molybdenum in actual associated mineral wastewater, the active sites are largely occupied non-specifically, leading to a rapid decline in uranium extraction performance. More critically, in the cyclic process of "cathodic adsorption-reduction-anodic polarity reversal desorption," the iron foil substrate undergoes electrochemical corrosion and dissolution when acting as the anode, continuously introducing exogenous iron ions into the system. This exacerbates the co-precipitation problem of iron oxide colloids and UO2, further reducing the purity of the recovered uranium. Summary of the Invention

[0006] In order to improve the purity of recovered uranium (calculated as U3O8), this application provides a method for deep treatment of uranium and co-recovery of resources in associated mineral radioactive wastewater.

[0007] A method for deep treatment and co-recovery of uranium from associated mineral radioactive wastewater includes the following steps:

[0008] S1: Ammonium metatungstate, glucose, graphene oxide, dopamine hydrochloride and water are mixed and then hydrothermally reacted at 150~160℃ for 12~16h. After cooling, solid-liquid separation is performed, followed by washing and drying. Then, the mixture is calcined at 450~500℃ for 2.5~3.5h under an inert atmosphere, heated to 600~620℃ and calcined for 30~40min. After cooling, the base powder is obtained.

[0009] S2: Add the base powder to an ethanol-water solution, mix well, adjust the pH to 4.5-5.0, add soluble uranium salt, phytic acid and cyanosilane, pre-hydrolyze, add silicon source, heat to 40-50℃, hydrolyze for 6-8 hours, separate solid and liquid, wash, dry, and obtain pre-coated powder.

[0010] S3: The pre-coated powder is eluted with acidic elution solution, dried, and then uniformly dispersed in an ethanol aqueous solution. Hydroxylamine hydrochloride is added to adjust the pH to 6.0~6.5. The mixture is then microwaved at 70~80℃ for 2~3 hours. After cooling, solid-liquid separation is performed, followed by washing and drying to obtain the active powder.

[0011] S4: Mix the binder and organic solvent evenly, add active powder and conductive carbon black, ball mill evenly, coat the substrate surface, dry and cure to obtain the composite electrode;

[0012] S5: A three-electrode electrochemical system was constructed using a composite electrode as the working electrode, a graphite plate as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode. After enrichment and reverse desorption treatment, the resulting uranium solution was precipitated and calcined to obtain the target uranium product.

[0013] In this technical solution, under high hydrothermal temperature and long duration, dopamine hydrochloride undergoes directional self-polymerization into polydopamine, which anchors and assists in the reduction of graphene oxide. Simultaneously, it achieves uniform dispersion of the tungsten precursor in the system, providing a uniform precursor environment for subsequent crystal growth. Through hydrothermal reaction and high-temperature calcination in an inert atmosphere, glucose generates reduced carbon species during pyrolysis, leading to the in-situ formation of oxygen-vacancy-rich tungsten oxide nanocrystalline phases on the surface of the reduced graphene oxide. Simultaneously, polydopamine carbonizes into a nitrogen-doped carbon layer, ultimately constructing a substrate powder with high conductivity, high specific surface area, and abundant nucleation anchor sites.

[0014] In a weakly acidic environment, soluble uranium salts induce phosphate groups provided by phytic acid and cyano groups provided by cyanosilanes to complete directional supramolecular pre-coordination. Then, a rigid Si-O-Si inorganic network formed by silicon source hydrolysis co-condensation solidifies and locks the geometric conformation formed by the pre-coordination. After elution with an acidic eluent to remove template uranyl ions, a specific imprinted cavity matching the size and coordination configuration of uranyl ions is released from the rigid silicon-oxygen network. In a weakly acidic microwave environment with a pH of 6.0~6.5, hydroxylamine hydrochloride, in a partially deprotonated form, undergoes a nucleophilic addition reaction with the cyano groups in the cavity, converting them into a meramine oxime group with a strong coordination affinity for uranyl ions, thus obtaining a core active powder with uranyl-specific recognition ability.

[0015] The active powder, conductive carbon black, and binder synergistically construct a stable electrode structure, ensuring full exposure of active sites and achieving efficient electron conduction between the current collector and the active powder. In the three-electrode electrochemical system, under constant cathode potential, the imprinted cavity specifically captures uranyl ions in wastewater. Simultaneously, electrons transferred through the electrode reduce these ions in situ to insoluble UO2, which is deposited on the electrode surface, achieving deep enrichment of uranium and purification of wastewater. After reverse desorption treatment, the resulting high-concentration uranium solution undergoes precipitation and calcination to ultimately produce a high-uranium-content product.

[0016] Furthermore, the mass ratio of ammonium metatungstate, glucose, graphene oxide and dopamine hydrochloride is 15:(1.5~3):(4.5~7.5):(4~6).

[0017] Further, the mass-volume ratio of the substrate powder, soluble uranium salt, phytic acid, cyanosilane, silicon source and hydroxylamine hydrochloride is 5g:(1.5~2.5)g:(0.7~0.8)g:(2.5~3.5)mL:(4~6)mL:(18~22)g.

[0018] Furthermore, the mass-volume ratio of the active powder, conductive carbon black, binder and organic solvent is (7~9) g:(0.9~1.1) g:(1.2~1.6) g:(150~180) mL.

[0019] Furthermore, the binder comprises polyvinylidene fluoride and carboxylated carbon nanotubes, wherein the mass ratio of polyvinylidene fluoride to carboxylated carbon nanotubes is 1:(0.2~0.3).

[0020] Furthermore, the organic solvent is N-methylpyrrolidone.

[0021] In this technical solution, polyvinylidene fluoride provides the electrode coating with excellent chemical stability against acids, alkalis, and high-potential oxidation, preventing the coating from swelling and peeling off during cycling. Carboxylated carbon nanotubes, on the one hand, help to construct a continuous conductive network, reduce the internal resistance of the electrode, and improve the electronic conduction efficiency; on the other hand, they introduce hydrophilic carboxyl groups to improve the wettability of the electrode surface, reduce the mass transfer resistance of hydrated uranyl ions, and improve the adsorption and enrichment efficiency of low-concentration uranium. N-methylpyrrolidone can achieve uniform dispersion of active materials, conductive agents, and binders, ensuring the stability of the slurry and the uniformity of coating.

[0022] Furthermore, the acidic eluent is prepared by first preparing a sodium bicarbonate solution with a molar concentration of 0.5~0.7 mol / L, and then adjusting the pH to 2.5~3.0 with dilute nitric acid with a molar concentration of 0.1~0.15 mol / L.

[0023] In this technical solution, the acidic elution system can break the coordination bonds between uranyl ions and phosphate and cyano groups through protonation. At the same time, bicarbonate ions can form stable water-soluble complexes with the dissociated uranyl ions, continuously promoting the positive shift of the desorption equilibrium, avoiding uranyl re-adsorption, and achieving efficient elution of template uranyl ions. The buffer system formed by sodium bicarbonate and nitric acid can accurately lock the pH of the system, avoiding problems such as silicon shell corrosion and substrate dissolution caused by excessive local acidity, and completely preserving the core structure of the material.

[0024] Furthermore, the soluble uranium salt is uranyl nitrate hexahydrate.

[0025] Furthermore, the cyanosilane is 3-cyanopropyltriethoxysilane.

[0026] Furthermore, the silicon source is tetraethyl orthosilicate.

[0027] Further, step S5 specifically involves: constructing a three-electrode electrochemical system using a composite electrode as the working electrode, a graphite plate as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode; applying a constant potential of -0.3 to -0.5 V relative to the saturated Ag / AgCl electrode to the composite electrode; enriching for 96 to 120 hours; switching the polarization direction; applying a constant potential of +0.8 to +1.2 V relative to the saturated Ag / AgCl electrode to the composite electrode; energizing for 50 to 70 minutes; adjusting the pH to 8.0 to 8.5; allowing to stand; separating the solid and liquid phases; calcining at 700 to 800℃ for 1.5 to 2.5 hours; and cooling to obtain the target uranium product.

[0028] In this technical solution, the cathode potential range of -0.3 to -0.5V can efficiently achieve the reduction and fixation of uranyl ions to tetravalent uranium, while completely avoiding the hydrogen evolution side reaction. The anode potential range of +0.8 to +1.2V can achieve efficient oxidative desorption of deposited uranium, while avoiding passivation of the titanium felt substrate and oxidative degradation of active groups. In a weakly alkaline environment with a pH of 8.0 to 8.5, uranyl ions can be quantitatively converted into ammonium diuranate precipitate. Calcination in air at 700 to 800℃ can convert ammonium diuranate into U3O8.

[0029] Furthermore, the substrate is a titanium felt substrate.

[0030] Furthermore, before use, the titanium felt substrate is sequentially ultrasonically cleaned in acetone, anhydrous ethanol, and 1~1.5mol / L hydrochloric acid solution, then washed, dried, and ready for use.

[0031] In this technical solution, the pretreatment step can effectively remove oil stains and natural dense oxide layer from the surface of titanium felt, roughen the surface of titanium felt, improve the bonding force between slurry and titanium felt substrate, prevent the active coating from falling off during the cycle, and at the same time reduce the contact resistance between current collector and active material, and improve electron conduction efficiency.

[0032] Furthermore, in step S2, after adding the phytic acid, the step of adding acryloyloxypropyl cage-type polysilsesquioxane is also included.

[0033] Furthermore, the acryloyloxypropyl cage-type polysilsesquioxane is 1% to 2% of the mass of the base powder.

[0034] In this technical solution, acryloyloxypropyl cage-type polysilsesquioxane can be covalently embedded in the silica-imprinted silicon shell framework through hydrolytic co-condensation of siloxane groups; its rigid cage structure can enhance the mechanical strength and resistance to potential shock of the silicon shell, and avoid the silicon shell cracking and imprint cavity collapse during cycling; at the same time, it can construct continuous and interconnected mass transfer channels in the silicon shell, reducing the mass transfer resistance of uranyl ions; its acryloyloxy group can preferentially capture the active oxygen generated during anodic desorption, protect the amylopyroxime group in the cavity from being oxidized and degraded, and improve the cycling stability of the electrode.

[0035] Furthermore, in step S4, when adding the binder, the step of adding nano-cerium oxide is also included.

[0036] Furthermore, the amount of nano-cerium oxide used is 1% to 3% of the mass of the active powder.

[0037] Furthermore, the particle size of the nano-cerium oxide is 5~20nm.

[0038] In this technical solution, nano-cerium oxide with a particle size of 5-20 nm is added simultaneously with the binder during the electrode preparation stage: its reversible Ce 3+ / Ce 4+ The electrode couple can cyclically quench hydroxyl radicals generated during anodic desorption and, in conjunction with acryloyloxypropyl cage-type polysilsesquioxane, protect the active groups of the amylopyroxime group in the imprinted cavity. This maintains the imprinted cavity's specific recognition ability for uranyl ions in the long term, reduces the non-specific adsorption and co-deposition of impurity ions, reduces impurity entrainment at the source, and improves the purity of the final uranium product. Its abundant hydroxyl sites on the surface can improve the water wettability of the electrode interface, reduce the mass transfer resistance of uranyl ions, and improve the enrichment efficiency of low-concentration uranium.

[0039] In summary, this application has the following beneficial effects:

[0040] This application constructs a nitrogen-doped carbon-coated oxygen-vacancy-rich tungsten oxide / reduced graphene oxide three-dimensional conductive substrate through synergistic modification with glucose and dopamine hydrochloride. Using a uranyl ion-imprinted rigid silicon shell design, a specific recognition cavity matching the size and coordination configuration of uranyl ions is constructed. Combined with a polyvinylidene fluoride-carboxylated carbon nanotube composite binder system, the resulting composite electrode has a high selective recognition capability for uranyl ions, enabling deep purification of uranium-containing wastewater and efficient uranium recovery. The recovered uranium product has high purity and can be directly used as a refining feedstock for nuclear fuel precursors. Detailed Implementation

[0041] The present application will be further described in detail below with reference to the embodiments.

[0042] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0043] Wastewater from a simulated uranium-containing mining area: uranium concentration 80 mg / L, total iron concentration (as Fe) 2+ (Total concentration) 480 mg / L, total molybdenum concentration 90 mg / L, sulfate 2000 mg / L, pH 6.0.

[0044] Example 1

[0045] The method for deep treatment of uranium and co-recovery of associated mineral radioactive wastewater in this embodiment includes the following steps:

[0046] S1: Dissolve 1.5g ammonium metatungstate and 0.2g glucose in 100mL deionized water, then add 120.0mL of graphene oxide aqueous dispersion (concentration 5mg / mL, monolayer ratio ≥80%), and place on a magnetic stirrer. Stir at 200rpm for 30min, then add 0.50g dopamine hydrochloride at once. Continue magnetic stirring at 25℃ for 2h, transfer to a high-pressure reactor, seal, and keep at 155℃ for 14h. Allow to cool naturally to room temperature, collect the bottom precipitate, and wash three times with deionized water by centrifugation. Dry in a vacuum drying oven at 60℃ for 2h, then place in a tube furnace. Under the protection of flowing argon at a flow rate of 100mL / min, heat to 450℃ at a rate of 5℃ / min and calcine for 2.5h. Continue heating to 600℃ at a rate of 5℃ / min and calcine for 30min. Allow to cool naturally to room temperature to obtain the substrate powder.

[0047] S2: Add 0.5g of base powder to 100mL of ethanol-water solution (volume ratio of anhydrous ethanol to deionized water is 4:1), and ultrasonically disperse evenly at 300W power, 20kHz frequency, and 20min. Adjust the pH of the system to 4.5 with 0.1mol / L dilute nitric acid. Then slowly add 0.20g of uranyl nitrate hexahydrate, 0.15g of phytic acid solution (mass fraction of 50%), and 0.30mL of 3-cyanopropyltriethoxysilane. Then, pre-hydrolyze at 25℃ and 200rpm magnetic stirring for 1h. Dynamically adjust the pH of the system to 4.5 and continue stirring for 10min. Then, add 0.50mL of tetraethyl orthosilicate dropwise at a rate of 0.05mL / min. After the addition is complete, raise the temperature to 40℃ and continue stirring for 8h. Centrifuge and wash three times with anhydrous ethanol to obtain the pre-coated powder.

[0048] S3: Place the pre-coated powder in 200 mL of eluent (prepared with a 0.5 mol / L sodium bicarbonate solution, and slowly adjust the pH to 3.0 with 0.1 mol / L dilute nitric acid; CO2 bubbles will be generated during the addition, which is normal; the pH will stabilize after the bubbles dissipate). Sonicate at 25°C for 2 hours at 300 W and 20 kHz, then centrifuge. Repeat this elution process three times. Detect the absence of uranyl ions in the eluent using the azoarsine III colorimetric method to confirm complete template elution. Use deionized water... The solid product was washed until neutral, dried under vacuum at 60°C for 12 hours, and then added to an ethanol-water solution (anhydrous ethanol and deionized water in a volume ratio of 1:1). It was ultrasonically dispersed evenly at 300W power, 20kHz frequency, and 20min time. 2.0g of hydroxylamine hydrochloride was added, and the pH of the system was adjusted to 6.5 simultaneously with 0.5mol / L sodium carbonate solution. The mixture was then transferred to a microwave reactor and reacted at 75°C and 300W power for 2.5 hours. After naturally cooling to room temperature, the mixture was centrifuged, washed three times with anhydrous ethanol, and dried under vacuum at 60°C to constant weight to obtain the active powder.

[0049] S4: Add 0.02g of carboxylated carbon nanotubes to 15mL of N-methylpyrrolidone, and ultrasonically disperse in an ice bath for 30min at 300W and 20kHz. Then add 0.1g of polyvinylidene fluoride, heat to 60℃, and stir for 60min. Add 0.8g of active powder and 0.1g of conductive carbon black, and transfer to a planetary ball mill for high-speed ball milling at 300rpm for 2h to prepare a uniform and viscous slurry. Then uniformly coat the slurry onto the surface of a titanium felt substrate, with a single-sided coating amount of 8mg / cm². 2 (dry weight), after coating, place in an 80℃ forced-air drying oven for 2 hours, then heat to 120℃ and vacuum dry for 5 hours to obtain the composite electrode;

[0050] Before use, the titanium felt substrate undergoes the following pretreatment steps: it is placed in acetone, anhydrous ethanol, and 1 mol / L hydrochloric acid solution for ultrasonic cleaning for 15 min each, then washed with deionized water until neutral, and vacuum dried at 60℃ for later use.

[0051] S5: A composite electrode was used as the working electrode, a graphite plate as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode. The reactor was placed in a two-chamber electrochemical reactor separated by a proton exchange membrane (Nafion N117 membrane). The effective volume of the cathode chamber was 300 mL, and the effective volume of the anode chamber was 200 mL. 200 mL of uranium-containing simulated mining wastewater was injected into the cathode chamber. High-purity nitrogen was purged for 30 min to remove oxygen, and the reactor was then sealed to maintain an anaerobic environment. A 100 mmol / L phosphate buffer solution (pH=7.0) was injected into the anode chamber. A three-electrode constant potential mode was used, applying a constant potential of -0.4 V (relative to the saturated Ag / AgCl electrode) to the cathode. The reactor was continuously operated at 25℃ under constant temperature and light-proof conditions for 96 h. After the operation was completed, the wastewater in the cathode chamber was drained, and 200 mL of 0.20 mol / L sodium bicarbonate solution was injected as the eluent. The polarization direction was switched, and a constant potential of +1.0 V (relative to the saturated Ag / AgCl electrode) was applied to the composite electrode. The electrode was energized for 60 min to achieve uranium elution. The high-concentration uranium eluent was collected, and the pH was adjusted to 8.5 with 25% ammonia water. After stirring for 30 min, the solution was allowed to stand, and the yellow precipitate (ammonium diuranate) was collected by centrifugation. The precipitate was calcined in a muffle furnace at 750 °C for 2 h and then naturally cooled to room temperature to obtain the target uranium product.

[0052] Example 2

[0053] The method for deep treatment of uranium and co-recovery of associated mineral radioactive wastewater in this embodiment includes the following steps:

[0054] S1: Dissolve 1.5g ammonium metatungstate and 0.15g glucose in 100mL deionized water, then add 90.0mL of graphene oxide aqueous dispersion (concentration 5mg / mL, monolayer ratio ≥80%), and place on a magnetic stirrer. Stir at 200rpm for 30min, then add 0.40g dopamine hydrochloride at once. Continue magnetic stirring at 25℃ for 2h, transfer to a high-pressure reactor, seal, and keep at 150℃ for 16h. Allow to cool naturally to room temperature, collect the bottom precipitate, and wash three times with deionized water by centrifugation. Dry in a vacuum drying oven at 60℃ for 2h, then place in a tube furnace. Under the protection of flowing argon at a flow rate of 100mL / min, heat to 500℃ at a rate of 5℃ / min and calcine for 3h. Continue heating to 620℃ at a rate of 5℃ / min and calcine for 30min. Allow to cool naturally to room temperature to obtain the substrate powder.

[0055] S2: Add 0.5g of base powder to 100mL of ethanol-water solution (volume ratio of anhydrous ethanol to deionized water is 4:1), and ultrasonically disperse evenly at 300W power, 20kHz frequency, and 20min. Adjust the pH of the system to 5.0 with 0.1mol / L dilute nitric acid. Then slowly add 0.15g of uranyl nitrate hexahydrate, 0.14g of phytic acid solution (mass fraction of 50%), and 0.25mL of 3-cyanopropyltriethoxysilane. Then, pre-hydrolyze at 25℃ and 200rpm magnetic stirring for 1h. Dynamically adjust the pH of the system to 5.0 and continue stirring for 10min. Then, add 0.40mL of tetraethyl orthosilicate dropwise at a rate of 0.05mL / min. After the addition is complete, raise the temperature to 50℃ and continue stirring for 6h. Centrifuge and wash three times with anhydrous ethanol to obtain the pre-coated powder.

[0056] S3: Place the pre-coated powder in 200 mL of eluent (prepared with a 0.5 mol / L sodium bicarbonate solution, and slowly adjust the pH to 3.0 with 0.1 mol / L dilute nitric acid; CO2 bubbles will be generated during the addition, which is normal; the pH will stabilize after the bubbles dissipate). Sonicate at 25°C, 300 W, and 20 kHz for 2 hours, then centrifuge. Repeat this elution process three times. Use the arsene III colorimetric method to detect the absence of uranyl ions in the eluent, confirming complete template elution. Then, use deionization... The solid product was washed with water until neutral, dried under vacuum at 60°C for 12 hours, and then added to an ethanol-water solution (anhydrous ethanol and deionized water in a volume ratio of 1:1). It was ultrasonically dispersed evenly at 300W power, 20kHz frequency, and 20min time. 1.8g of hydroxylamine hydrochloride was added, and the pH of the system was adjusted to 6.5 simultaneously with 0.5mol / L sodium carbonate solution. The mixture was then transferred to a microwave reactor and reacted at 70°C and 300W power for 3 hours. After naturally cooling to room temperature, the mixture was centrifuged, washed three times with anhydrous ethanol, and dried under vacuum at 60°C to constant weight to obtain the active powder.

[0057] S4: Add 0.02g of carboxylated carbon nanotubes to 15mL of N-methylpyrrolidone, and ultrasonically disperse in an ice bath for 30min at 300W and 20kHz. Then add 0.1g of polyvinylidene fluoride, heat to 60℃, and stir for 60min. Add 0.7g of active powder and 0.09g of conductive carbon black, and transfer to a planetary ball mill for high-speed ball milling at 300rpm for 2h to prepare a uniform and viscous slurry. Then uniformly coat the slurry onto the surface of a titanium felt substrate with a single-sided coating amount of 8mg / cm². 2 (dry weight), after coating, place in an 80℃ forced-air drying oven for 2 hours, then heat to 120℃ and vacuum dry for 5 hours to obtain the composite electrode;

[0058] Before use, the titanium felt substrate undergoes the following pretreatment steps: it is placed in acetone, anhydrous ethanol, and 1 mol / L hydrochloric acid solution for ultrasonic cleaning for 15 min each, then washed with deionized water until neutral, and vacuum dried at 60℃ for later use.

[0059] S5: Using a composite electrode as the working electrode, a graphite plate as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode, a two-chamber electrochemical reactor separated by a proton exchange membrane (Nafion N117 membrane) was placed. The effective volume of the cathode chamber was 300 mL, and the effective volume of the anode chamber was 200 mL. 200 mL of uranium-containing simulated mining wastewater was injected into the cathode chamber, and high-purity nitrogen was purged for 30 min to remove oxygen before sealing to maintain an anaerobic environment. A 100 mmol / L phosphate buffer solution (pH=7.0) was injected into the anode chamber. A three-electrode constant potential mode was used, applying a constant potential of -0.3 V (relative to the saturated Ag / AgCl electrode) to the cathode. The reactor was continuously operated for 120 h at a constant temperature of 25℃ in the dark. After the process was completed, the wastewater in the cathode chamber was drained, and 200 mL of 0.20 mol / L sodium bicarbonate solution was injected as the eluent. The polarization direction was switched, and a constant potential of +0.8 V (relative to the saturated Ag / AgCl electrode) was applied to the composite electrode. The electrode was energized for 70 min to achieve uranium elution. The high-concentration uranium eluent was collected, and the pH was adjusted to 8.0 with 25% ammonia water. After stirring for 30 min, the solution was allowed to stand, and the yellow precipitate (ammonium diuranate) was collected by centrifugation. The precipitate was calcined in a muffle furnace at 700 °C for 2.5 h and then naturally cooled to room temperature to obtain the target uranium product.

[0060] Example 3

[0061] The method for deep treatment of uranium and co-recovery of associated mineral radioactive wastewater in this embodiment includes the following steps:

[0062] S1: Dissolve 1.5g ammonium metatungstate and 0.3g glucose in 100mL deionized water, then add 120.0mL of graphene oxide aqueous dispersion (concentration 5mg / mL, monolayer ratio ≥80%), and place on a magnetic stirrer. Stir at 200rpm for 30min, then add 0.60g dopamine hydrochloride at once. Continue magnetic stirring at 25℃ for 2h, transfer to a high-pressure reactor, seal, and keep at 160℃ for 15h. Allow to cool naturally to room temperature, collect the bottom precipitate, and wash three times with deionized water by centrifugation. Dry in a vacuum drying oven at 60℃ for 2h, then place in a tube furnace. Under the protection of flowing argon at a flow rate of 100mL / min, heat to 500℃ at a rate of 5℃ / min and calcine for 3.5h. Continue heating to 610℃ at a rate of 5℃ / min and calcine for 40min. Allow to cool naturally to room temperature to obtain the substrate powder.

[0063] S2: Add 0.5g of base powder to 100mL of ethanol-water solution (volume ratio of anhydrous ethanol to deionized water is 4:1), and ultrasonically disperse evenly at 300W power, 20kHz frequency, and 20min. Adjust the pH of the system to 4.5 with 0.1mol / L dilute nitric acid. Then slowly add 0.25g of uranyl nitrate hexahydrate, 0.16g of phytic acid solution (mass fraction of 50%), and 0.35mL of 3-cyanopropyltriethoxysilane. Then, pre-hydrolyze at 25℃ and 200rpm magnetic stirring for 1h. Dynamically adjust the pH of the system to 4.5 and continue stirring for 10min. Then, add 0.60mL of tetraethyl orthosilicate dropwise at a rate of 0.05mL / min. After the addition is complete, raise the temperature to 45℃ and continue stirring for 8h. Centrifuge and wash three times with anhydrous ethanol to obtain the pre-coated powder.

[0064] S3: Place the pre-coated powder in 200 mL of eluent (prepared with a 0.7 mol / L sodium bicarbonate solution, and slowly adjust the pH to 2.5 with 0.15 mol / L dilute nitric acid; CO2 bubbles will be generated during the addition, which is normal; the pH will stabilize after the bubbles dissipate). Sonicate at 25°C for 2 hours at 300 W and 20 kHz, then centrifuge. Repeat this elution process three times. Detect the absence of uranyl ions in the eluent using the azoarsine III colorimetric method to confirm complete template elution. Then, use a deionization method... The solid product was washed with water until neutral, dried under vacuum at 60°C for 12 hours, and then added to an ethanol-water solution (anhydrous ethanol and deionized water in a volume ratio of 1:1). It was ultrasonically dispersed evenly at 300W power, 20kHz frequency, and 20min. 2.2g of hydroxylamine hydrochloride was added, and the pH of the system was adjusted to 6.0 simultaneously with 0.5mol / L sodium carbonate solution. The mixture was then transferred to a microwave reactor and reacted at 80°C and 300W power for 2 hours. After naturally cooling to room temperature, it was centrifuged, washed three times with anhydrous ethanol, and dried under vacuum at 60°C to constant weight to obtain the active powder.

[0065] S4: Add 0.036g of carboxylated carbon nanotubes to 18mL of N-methylpyrrolidone, and ultrasonically disperse in an ice bath for 30min at 300W and 20kHz. Then add 0.12g of polyvinylidene fluoride, heat to 60℃, and stir for 60min. Add 0.9g of active powder and 0.11g of conductive carbon black, and transfer to a planetary ball mill for high-speed ball milling at 300rpm for 2h to prepare a uniform and viscous slurry. Then uniformly coat the slurry onto the surface of a titanium felt substrate with a single-sided coating amount of 8mg / cm². 2 (dry weight), after coating, place in an 80℃ forced-air drying oven for 2 hours, then heat to 120℃ and vacuum dry for 6 hours to obtain the composite electrode;

[0066] Before use, the titanium felt substrate undergoes the following pretreatment steps: it is placed in acetone, anhydrous ethanol, and 1 mol / L hydrochloric acid solution for ultrasonic cleaning for 15 min each, then washed with deionized water until neutral, and vacuum dried at 60℃ for later use.

[0067] S5: Using a composite electrode as the working electrode, a graphite plate as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode, a two-chamber electrochemical reactor separated by a proton exchange membrane (Nafion N117 membrane) was placed. The effective volume of the cathode chamber was 300 mL, and the effective volume of the anode chamber was 200 mL. 200 mL of uranium-containing simulated mining wastewater was injected into the cathode chamber, and high-purity nitrogen was purged for 30 min to remove oxygen before sealing to maintain an anaerobic environment. A 100 mmol / L phosphate buffer solution (pH=7.0) was injected into the anode chamber. A three-electrode constant potential mode was used, applying a constant potential of -0.3 V (relative to the saturated Ag / AgCl electrode) to the cathode. The reactor was continuously operated for 120 h at a constant temperature of 25℃ in the dark. After the process was completed, the wastewater in the cathode chamber was drained, and 200 mL of 0.20 mol / L sodium bicarbonate solution was injected as the eluent. The polarization direction was switched, and a constant potential of +0.8 V (relative to the saturated Ag / AgCl electrode) was applied to the composite electrode. The electrode was energized for 70 min to achieve uranium elution. The high-concentration uranium eluent was collected, and the pH was adjusted to 8.0 with 25% ammonia water. After stirring for 30 min, the solution was allowed to stand, and the yellow precipitate (ammonium diuranate) was collected by centrifugation. The precipitate was calcined in a muffle furnace at 800℃ for 1.5 h and then naturally cooled to room temperature to obtain the target uranium product.

[0068] Example 4

[0069] The difference between this embodiment and embodiment 3 is as follows:

[0070] S2: Add 0.5g of base powder to 100mL of ethanol-water solution (volume ratio of anhydrous ethanol to deionized water is 4:1), and ultrasonically disperse evenly at 300W power, 20kHz frequency, and 20min. Adjust the pH of the system to 4.5 with 0.1mol / L dilute nitric acid. Then slowly add 0.25g of uranyl nitrate hexahydrate, 0.16g of phytic acid solution (mass fraction of 50%), 0.005g of acryloyloxypropyl cage-type polysilsesquioxane, and 0.35mL of 3-cyanopropyltriethoxysilane. Then, at 25℃, pre-hydrolyze the mixture with magnetic stirring at 200rpm for 1h. Dynamically adjust the pH of the system to 4.5 and continue stirring for 10min. Then, add 0.60mL of tetraethyl orthosilicate dropwise at a rate of 0.05mL / min. After the addition is complete, raise the temperature to 45℃ and continue stirring for 8h. Centrifuge and wash three times with anhydrous ethanol to obtain the pre-coated powder.

[0071] Everything else is the same as in Example 3.

[0072] Example 5

[0073] The difference between this embodiment and embodiment 4 is that:

[0074] S4: Add 0.009g of nano-cerium oxide (particle size 5~20nm) and 0.036g of carboxylated carbon nanotubes to 15mL of N-methylpyrrolidone, and ultrasonically disperse in an ice bath for 30min at 300W and 20kHz. Then add 0.12g of polyvinylidene fluoride, heat to 60℃, and stir for 60min. Add 0.9g of active powder and 0.11g of conductive carbon black, and transfer to a planetary ball mill for high-speed ball milling at 300rpm for 2h to prepare a uniform and viscous slurry. Then uniformly coat the slurry onto the surface of a titanium felt substrate with a single-sided coating amount of 8mg / cm². 2 (dry weight), after coating, place in an 80℃ forced-air drying oven for 2 hours, then heat to 120℃ and vacuum dry for 6 hours to obtain the composite electrode;

[0075] Before use, the titanium felt substrate undergoes the following pretreatment steps: it is placed in acetone, anhydrous ethanol, and 1 mol / L hydrochloric acid solution for ultrasonic cleaning for 15 min each, then washed with deionized water until neutral, and vacuum dried at 60℃ for later use.

[0076] The rest is the same as in Example 4.

[0077] Example 6

[0078] The difference between this embodiment and embodiment 5 is as follows:

[0079] In step S2, the amount of acryloyloxypropyl cage-type polysilsesquioxane used is 0.01g;

[0080] In step S4, the amount of nano-cerium oxide used is 0.03g;

[0081] Performance testing

[0082] The wastewater and target uranium product (calculated as U3O8) treated in Examples 1-6 were subjected to the following performance tests, as detailed in Table 1.

[0083] Table 1. Wastewater parameters and target U3O8 product purity after treatment in Examples 1-6

[0084]

[0085] Based on the performance test data in Table 1, it can be seen that for radioactive wastewater with high impurities and associated minerals, the uranium concentration in the effluent can be stably met to meet the environmental protection emission standards for uranium mining and metallurgy, with a high total uranium removal rate. At the same time, it can achieve synergistic removal of associated heavy metals such as molybdenum, resulting in high wastewater purification depth and strong resistance to impurity interference.

[0086] Examples 1-3, by optimizing the hydrothermal reaction temperature, calcination conditions, and electrochemical process parameters, gradually improved the substrate conductivity, specific surface area, and uranium enrichment rate, resulting in a gradient increase in uranium removal rate, recovery rate, and product purity. Examples 4-6 introduced acryloyloxypropyl cage-type polysilsesquioxane and / or nano-cerium oxide, further improving the electrode selectivity for uranyl, the synergistic removal efficiency of associated metals, the overall uranium recovery rate, and product purity, achieving a dual synergistic effect of deep purification of uranium-containing wastewater and high-value recovery of uranium resources.

[0087] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for deep treatment and co-recovery of uranium resources in radioactive wastewater from associated minerals, characterized in that, Includes the following steps: S1: Ammonium metatungstate, glucose, graphene oxide, dopamine hydrochloride and water are mixed and then hydrothermally reacted at 150~160℃ for 12~16h. After cooling, solid-liquid separation is performed, followed by washing and drying. Then, the mixture is calcined at 450~500℃ for 2.5~3.5h under an inert atmosphere, heated to 600~620℃ and calcined for 30~40min. After cooling, the base powder is obtained. S2: Add the base powder to an ethanol-water solution, mix well, adjust the pH to 4.5-5.0, add soluble uranium salt, phytic acid and cyanosilane, pre-hydrolyze, add silicon source, heat to 40-50℃, hydrolyze for 6-8 hours, separate solid and liquid, wash, dry, and obtain pre-coated powder. S3: The pre-coated powder is eluted with acidic elution solution, dried, and then uniformly dispersed in an ethanol aqueous solution. Hydroxylamine hydrochloride is added to adjust the pH to 6.0~6.

5. The mixture is then microwaved at 70~80℃ for 2~3 hours. After cooling, solid-liquid separation is performed, followed by washing and drying to obtain the active powder. S4: Mix the binder and organic solvent evenly, add active powder and conductive carbon black, ball mill evenly, coat the substrate surface, dry and cure to obtain the composite electrode; S5: A three-electrode electrochemical system was constructed using a composite electrode as the working electrode, a graphite plate as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode. After enrichment and reverse desorption treatment, the resulting uranium solution was precipitated and calcined to obtain the target uranium product.

2. The method for deep treatment and co-recovery of uranium resources in associated mineral radioactive wastewater according to claim 1, characterized in that, The mass ratio of ammonium metatungstate, glucose, graphene oxide and dopamine hydrochloride is 15:(1.5~3):(4.5~7.5):(4~6).

3. The method for deep treatment and co-recovery of uranium resources in associated mineral radioactive wastewater according to claim 2, characterized in that, The mass-to-volume ratio of the substrate powder, soluble uranium salt, phytic acid, cyanosilane, silicon source, and hydroxylamine hydrochloride is 5g:(1.5~2.5)g:(0.7~0.8)g:(2.5~3.5)mL:(4~6)mL:(18~22)g.

4. The method for deep treatment and co-recovery of uranium resources in associated mineral radioactive wastewater according to claim 3, characterized in that, The mass-volume ratio of the active powder, conductive carbon black, binder and organic solvent is (7~9) g:(0.9~1.1) g:(1.2~1.6) g:(150~180) mL.

5. The method for deep treatment and co-recovery of uranium resources in associated mineral radioactive wastewater according to claim 1, characterized in that, The binder comprises polyvinylidene fluoride and carboxylated carbon nanotubes, wherein the mass ratio of polyvinylidene fluoride to carboxylated carbon nanotubes is 1:(0.2~0.3).

6. The method for deep treatment and co-recovery of uranium resources in associated mineral radioactive wastewater according to claim 1, characterized in that, The acidic eluent is prepared by first preparing a sodium bicarbonate solution with a molar concentration of 0.5~0.7 mol / L, and then adjusting the pH to 2.5~3.0 with dilute nitric acid with a molar concentration of 0.1~0.15 mol / L.

7. The method for deep treatment and co-recovery of uranium resources in associated mineral radioactive wastewater according to claim 1, characterized in that, Step S5 is as follows: Using a composite electrode as the working electrode, a graphite plate as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode, a three-electrode electrochemical system is constructed. A constant potential of -0.3 to -0.5 V relative to the saturated Ag / AgCl electrode is applied to the composite electrode, and enrichment is carried out for 96 to 120 hours. The polarization direction is switched, and a constant potential of +0.8 to +1.2 V relative to the saturated Ag / AgCl electrode is applied to the composite electrode. Electrolysis is carried out for 50 to 70 minutes, and the pH is adjusted to 8.0 to 8.

5. The mixture is allowed to stand, and solid-liquid separation is performed. The mixture is then calcined at 700 to 800 °C for 1.5 to 2.5 hours and cooled to obtain the target uranium product.

8. The method for deep treatment and co-recovery of uranium resources in associated mineral radioactive wastewater according to claim 1, characterized in that, In step S2, after adding the phytic acid, the step of adding acryloyloxypropyl cage-type polysilsesquioxane is also included.

9. The method for deep treatment and co-recovery of uranium resources in associated mineral radioactive wastewater according to claim 8, characterized in that, The acryloyloxypropyl cage-type polysilsesquioxane is 1% to 2% of the mass of the base powder.

10. The method for deep treatment and co-recovery of uranium resources in associated mineral radioactive wastewater according to claim 1, characterized in that, In step S4, when adding the binder, the step of adding nano-cerium oxide is also included.

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