A method for preparing an antibacterial-highly selective graphene oxide composite uranium extraction material

Abstract

This invention discloses a three-dimensional graphene oxide composite foam material with both antibacterial and high uranium selectivity, and its preparation method, belonging to the fields of environmental functional materials and seawater uranium extraction technology. Using graphene oxide (GO) as the matrix, this invention introduces superhydrophilic polyethyleneimine (PEI), highly uranium-selective poly(amine oxime) (PAO), and guanidine phosphate polymer (PGdn) with both antibacterial and uranium coordination capabilities, and prepares the GO-PEI-PAO-PGdn (GPP-PGdn) composite foam material through a one-step covalent cross-linking method. The material prepared by this invention has a three-dimensional interconnected porous structure, superhydrophilic properties, and excellent uranium selectivity. The uranium partition coefficient Kd value in natural seawater reaches as high as 18250 mg / L, and the uranium removal rate reaches 87.65%, achieving highly selective uranium enrichment. Simultaneously, it has significant antibacterial effects against Escherichia coli and Staphylococcus aureus, effectively solving the problem of biofouling during seawater uranium extraction. The material prepared by this invention has a mild and controllable process that can be scaled up and can be widely used in fields such as trace uranium enrichment and uranium-containing radioactive wastewater treatment. It also has excellent adsorption performance, cycle stability and environmental resistance.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional material preparation and radionuclide separation technology, specifically involving a three-dimensional graphene oxide composite foam material with both antibacterial and high uranium selectivity, its preparation method, and its application in seawater uranium extraction and uranium-containing wastewater treatment. Background Technology

[0002] The development and application of nuclear energy technologies generate large amounts of uranium-containing radioactive wastewater. Uranium is highly chemically toxic and radioactive, and direct discharge would seriously endanger the ecological environment and human health. Existing uranium-containing wastewater treatment technologies, such as chemical precipitation, membrane separation, ion exchange, and solvent extraction, generally suffer from drawbacks such as low adsorption capacity, poor selectivity, weak acid-base stability, poor recyclability, and susceptibility to microbial growth and fouling.

[0003] Adsorption is currently the most widely used technology in seawater uranium extraction due to its low cost, simple process, and ease of industrialization. Its core lies in the development of high-performance adsorbents. Graphene oxide (GO) possesses advantages such as ultra-large specific surface area, abundant modifiable oxygen-containing functional groups, and ease of functionalization, showing great application potential in seawater uranium extraction adsorption. Existing research has effectively improved the defects of two-dimensional GO powder, such as easy agglomeration and difficulty in recovery, by constructing three-dimensional GO macrostructures and grafting functional groups. However, in real-world seawater applications, three major technical challenges remain:

[0004] 1. The seawater environment is complex and highly corrosive. Most existing three-dimensional GO materials use inert support frameworks, which do not contribute to uranium adsorption and occupy the internal space of the material, limiting the loading of active components and the exposure density of adsorption sites, thus restricting further improvement of adsorption capacity.

[0005] 2. The concentration of uranyl ions in seawater systems is extremely low (only about 3.3 μg / L), while the concentration of coexisting interfering ions such as sodium, potassium, calcium, and magnesium is extremely high. Existing GO materials have insufficient selectivity for uranium, making it difficult to achieve efficient enrichment of trace uranium in complex matrices.

[0006] 3. A large number of microorganisms in the ocean can easily attach to and reproduce on the surface of materials, forming biofilms that block adsorption channels and shield active sites, leading to a rapid decline in the material's adsorption efficiency. Existing GO-based seawater uranium extraction materials generally lack efficient antibacterial and antifouling capabilities, making it difficult to use them stably in the marine environment for a long time.

[0007] Guanidinyl polymers and their derivatives possess broad-spectrum antibacterial properties, and the guanidinyl group can coordinate with uranyl ions, making them ideal modifying components with both antibacterial and uranium adsorption functions. Poly(amine oxime) (PAO) has a specific chelating ability for uranyl ions, making it a recognized highly selective functional group in seawater uranium extraction. Currently, no research has synergistically introduced these two into a three-dimensional GO foam system to simultaneously improve adsorption capacity, uranium selectivity, and antibacterial properties. Summary of the Invention

[0008] Purpose of the Invention: The purpose of this invention is to overcome the defects of the prior art and solve the problems of existing GO-based seawater uranium extraction materials, such as inert framework limiting active site loading, insufficient uranium selectivity, poor antibacterial and antifouling properties, and weak cycle stability. The invention provides a three-dimensional graphene oxide composite foam material with high adsorption capacity, high uranium selectivity, excellent antibacterial and antifouling properties, and good mechanical and cycle stability. It also provides a mild, controllable, and easily scalable preparation method for the material, as well as its application in seawater uranium extraction and uranium-containing wastewater treatment.

[0009] Technical Solution: This invention provides a three-dimensional graphene oxide composite foam material with both antibacterial and high uranium selectivity. Graphene oxide (GO) is used as the matrix, and a three-dimensional porous foam framework is formed by covalent cross-linking with polyethyleneimine (PEI). The matrix is ​​composited with polyamine oxime (PAO) and guanidine phosphate polymer (PGdn). The material synergistically constructs a multi-active-site uranium coordination adsorption system through the amino groups of PEI, the amylopectin groups of PAO, the guanidine groups of PGdn, and the phosphate groups. Simultaneously, the guanidine groups of PGdn disrupt bacterial cell membranes, endowing the material with broad-spectrum antibacterial and antifouling properties.

[0010] Furthermore, the mass ratio of each component in the material is GO:PEI:PAO:PGdn = 1:(10~25):(5~15):(5~20); the optimal mass ratio is GO:PEI:PAO:PGdn = 1:20:10:15, under which the material achieves an optimal balance between adsorption performance, antibacterial performance, and mechanical properties. Furthermore, the guanidine phosphate polymer PGdn is prepared by melt polycondensation reaction of guanidine hydrochloride, 1,6-hexanediamine, and phytic acid, without the need for organic solvents, making the preparation process green and environmentally friendly. The specific steps are as follows:

[0011] Step 1: Prepare a composite sponge containing PAO and PEI based on graphene oxide. Under a nitrogen protective atmosphere, add guanidine hydrochloride, 1,6-hexanediamine and phytic acid in a molar ratio of 105:86:3 into a reaction vessel and mechanically stir at 90°C for 1 hour until the raw materials are completely melted and mixed. Then raise the temperature to 160°C and continue stirring for 5 hours. The ammonia gas released during the reaction is carried out by the nitrogen flow and absorbed by the dilute hydrochloric acid solution. After the reaction is completed, cool to room temperature, seal and store for later use to obtain the guanidine phosphate polymer PGdn.

[0012] Step 2: Preparation of graphene oxide and poly(gamma-amino)oxime dispersion. Graphene oxide (GO) was weighed and dispersed in NaOH solution, and ultrasonicated at room temperature for 30 min to obtain a uniform GO dispersion. Poly(gamma-amino)oxime (PAO) was also weighed and dispersed in NaOH solution, and ultrasonicated under the same conditions for 30 min to obtain a uniform PAO dispersion.

[0013] Step 3: Crosslinking construction of three-dimensional composite foam. Mix GO dispersion and PAO dispersion, and continue ultrasonic treatment for 30 min until the system is homogeneous. Under continuous stirring at room temperature, slowly add polyethyleneimine (PEI) to the mixture, and simultaneously add PGdn prepared in step 1. After stirring evenly, add glutaraldehyde crosslinking agent. After continuous stirring for 2 h, let it stand at room temperature for 12 h to obtain a gel-like composite.

[0014] Step 4: Post-treatment. The gel-like composite obtained in Step 3 is repeatedly washed with deionized water until the washing solution is neutral. Then, it is placed in a freeze dryer and dried for 48 hours to obtain the three-dimensional graphene oxide composite foam material with both antibacterial and high uranium selectivity, named GPP-PGdn. Simultaneously, this invention provides a guanidine-modified three-dimensional graphene oxide composite foam material, GPP-Gdn, whose preparation method is basically the same as GPP-PGdn, except that phytic acid is not added in Step 1; instead, the guanidine polymer Gdn is obtained only by melt polycondensation of guanidine hydrochloride and 1,6-hexanediamine. The optimal feed amount of Gdn in Step 3 is 0.02 g, and the optimal mass ratio of the components in the final material is GO:PEI:PAO:Gdn = 1:20:10:10.

[0015] This invention provides applications of the aforementioned three-dimensional graphene oxide composite foam material, specifically for the enrichment and extraction of trace uranium from natural seawater, advanced treatment of uranium-containing radioactive wastewater from nuclear power plants, and selective separation and recovery of uranyl ions in high-salt complex systems. Furthermore, the material is applied in a weakly alkaline water body with a pH of 7.0–8.5, which is highly compatible with the pH range of natural seawater; the adsorption equilibrium time is 24 hours, and 0.3 mol / L nitric acid is used as the eluent during recycling, enabling efficient uranium desorption and material regeneration.

[0016] Beneficial effects

[0017] 1. The material of this invention achieves optimal adsorption performance in natural seawater at pH=8, and is highly compatible with the real seawater environment; the theoretical maximum adsorption capacity reaches 480.77 mg / g, and the uranium partition coefficient Kd in natural seawater is as high as 18250 mL / g, which is much higher than other coexisting metal ions in seawater. The uranium removal rate in spiked seawater is stable at over 87%, and it can achieve efficient enrichment of trace uranium in complex environments with high salinity and multiple ion interference.

[0018] 2. Wide pH range of applicability. The material maintains high adsorption activity in the pH range of 3-9 under weakly alkaline conditions. In particular, the adsorption performance is the best under the conditions of pH=7-8 (typical pH of nuclear industry wastewater), with the adsorption capacity increased by more than 40% compared with the unmodified material. There is no need to strictly adjust the pH of the wastewater, which greatly reduces the on-site treatment cost and operation difficulty.

[0019] 3. Excellent antibacterial adhesion performance, solving the problem of biofouling. The polyguanidine component endows the material with broad-spectrum antibacterial activity, which has a strong inhibitory effect on common aquatic bacteria such as Escherichia coli and Staphylococcus aureus. It can effectively prevent microbial adhesion, biofilm formation and material fouling during adsorption, improve long-term operational stability, extend service life, and is suitable for complex actual wastewater systems.

[0020] 4. High desorption efficiency and good recyclability: Using 0.2-0.3 mol / L nitric acid as the eluent, the single desorption rate reaches 92%-95%; after 5 adsorption-desorption cycles, the adsorption capacity retention rate of GPP-PGdn and GPP-Gdn materials is still over 80%, which is much higher than that of unmodified GO-PEI-PAO materials (about 62%), and has good industrial recycling value.

[0021] 5. The material of this invention constructs a three-dimensional network structure through covalent cross-linking, which maintains structural integrity under 80% strain conditions and exhibits excellent mechanical stability; after 5 adsorption-desorption cycles, the desorption efficiency remains above 80%, demonstrating good cyclic regeneration performance, which can meet the engineering requirements for long-term use of uranium extraction from seawater.

[0022] 6. High selectivity: The combined action of polyethyleneimine (PEI), polyamine oxime (PAO), and guanidine phosphate polymer (PGdn) provides specific coordination for uranyl ions, resulting in a uranium partition coefficient Kd value as high as 18250 mg / L in natural seawater and a uranium removal rate of 87.65%.

[0023] 7. The synthesis process is simple, the conditions are mild, and it is easy to scale up. The simple covalent cross-linking method does not require complex equipment or harsh conditions; the raw materials are inexpensive and readily available, environmentally friendly, and free of ammonia pollution, making it suitable for industrial-scale mass production. Attached Figure Description

[0024] Figure 1 The distribution coefficient of Embodiment 5 of the present invention in real seawater.

[0025] Figure 2 The blank bacterial culture of this invention, after co-culturing with the cultures from Examples 3, 4, and 5, exhibits antibacterial activity against Staphylococcus aureus and Escherichia coli. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0027] All raw materials and reagents used in the embodiments of this invention are of analytical grade, and all experimental water used is deionized water. Among them, GO is prepared by the modified Hummers method, and PAO is prepared by the polyacrylonitrile ammonium oxime method. For specific preparation methods, please refer to the corresponding chapters of the paper.

[0028] Example 1: Preparation of guanidine polymer Gdn

[0029] Under a nitrogen atmosphere, 105 mmol of guanidine hydrochloride and 86 mmol of 1,6-hexanediamine were added to a reaction flask and mechanically stirred at 90°C for 1 h until the raw materials were completely melted and mixed. Then the temperature was raised to 160°C and the reaction was stirred continuously for 5 h. The ammonia gas released during the reaction was carried out by the nitrogen flow and absorbed by 0.1 mol / L hydrochloric acid solution. After the reaction was completed, heating was stopped and the mixture was cooled to room temperature to obtain the guanidine polymer Gdn, which was sealed and stored for later use.

[0030] Example 2 Preparation of guanidine phosphate polymer PGdn

[0031] Under a nitrogen atmosphere, 105 mmol of guanidine hydrochloride, 86 mmol of 1,6-hexanediamine, and 3 mmol of phytic acid were added to a reaction flask and mechanically stirred at 90°C for 1 hour until the raw materials were completely melted and mixed. Then, the temperature was raised to 160°C and the reaction was stirred continuously for 5 hours. The ammonia gas released during the reaction was carried out by the nitrogen flow and absorbed by 0.1 mol / L hydrochloric acid solution. After the reaction was completed, heating was stopped and the mixture was cooled to room temperature to obtain the guanidine phosphate polymer PGdn, which was sealed and stored for later use.

[0032] Example 3: Preparation of GO-PEI-PAO Composite Foam

[0033] Weigh 0.02g of GO and disperse it in 5mL of NaOH solution. Sonicate the dispersion at room temperature for 30min to obtain a GO dispersion. Separately weigh 0.2g of PAO and disperse it in 7mL of NaOH solution. Sonicate the dispersion under the same conditions for 30min to obtain a PAO dispersion.

[0034] Mix the GO and PAO dispersions and continue sonicating for 30 min until homogeneous. Slowly add 0.4 g PEI dropwise while stirring at room temperature. After the addition is complete, add 500 μL of 50% wt glutaraldehyde and continue stirring for 2 h. Let it stand at room temperature for 12 h to mature. Wash the product repeatedly with deionized water until neutral and freeze-dry for 48 h to obtain GO-PEI-PAO composite foam.

[0035] Example 4: Preparation of GPP-Gdn Composite Foam

[0036] Gdn was prepared according to the method in Example 1;

[0037] Weigh 0.02g of GO and disperse it in 5mL of NaOH solution. Sonicate the GO solution at room temperature for 30min to obtain a GO dispersion. Separately weigh 0.2g of PAO and disperse it in 7mL of NaOH solution. Sonicate the PAO solution under the same conditions for 30min to obtain a PAO dispersion.

[0038] Mix the GO and PAO dispersions and continue sonicating for 30 min until homogeneous. Slowly add 0.4 g PEI dropwise while stirring at room temperature, and simultaneously add 0.02 g Gdn. After stirring evenly, add 500 μL of 50% wt glutaraldehyde and continue stirring for 2 h. Let it stand at room temperature for 12 h to age.

[0039] The product was repeatedly washed with deionized water until neutral, and then freeze-dried for 48 hours to obtain GPP-Gdn composite foam with a material component mass ratio of GO:PEI:PAO:Gdn=1:20:10:10.

[0040] Example 5: Preparation of GPP-PGdn Composite Foam

[0041] PGdn was prepared according to the method in Example 2;

[0042] Weigh 0.02g of GO and disperse it in 5mL of NaOH solution, then sonicate at room temperature for 30min to obtain a GO dispersion; separately weigh 0.2g of PAO and disperse it in 7mL of NaOH solution, then sonicate under the same conditions for 30min to obtain a PAO dispersion.

[0043] Mix the GO and PAO dispersions and continue sonicating for 30 min until homogeneous. Slowly add 0.4 g PEI dropwise while stirring at room temperature, and simultaneously add 0.03 g PGdn. After stirring evenly, add 500 μL of 50% wt glutaraldehyde and continue stirring for 2 h. Let it stand at room temperature for 12 h to mature.

[0044] The product was repeatedly washed with deionized water until neutral, and then freeze-dried for 48 hours to obtain GPP-PGdn composite foam with a material composition mass ratio of GO:PEI:PAO:PGdn=1:20:10:15.

Claims

1. A three-dimensional graphene oxide composite foam material possessing both antibacterial properties and high uranium selectivity, characterized in that, The material uses graphene oxide (GO) as a matrix and is prepared by covalent cross-linking polyethyleneimine (PEI), polyamine oxime (PAO), and guanidine phosphate polymer (PGdn) to obtain GO-PEI-PAO-PGdn (GPP-PGdn) composite foam material. The material constructs a uranium coordination adsorption system through the synergistic construction of nitrogen-, phosphorus-, and oxygen-containing active groups of PEI, PAO, and PGdn, while the guanidine group of PGdn endows the material with broad-spectrum antibacterial and anti-biofouling properties.

2. The three-dimensional graphene oxide composite foam material according to claim 1, characterized in that, The mass ratio of each component in the material is GO:PEI:PAO:PGdn=1:(10~25):(5~15):(5~20); preferably, the mass ratio of each component is GO:PEI:PAO:PGdn=1:20:10:

15.

3. The three-dimensional graphene oxide composite foam material according to claim 1, characterized in that, The guanidine phosphate polymer PGdn is prepared by melt polycondensation reaction of guanidine hydrochloride, 1,6-hexanediamine and phytic acid.

4. A method for preparing a three-dimensional graphene oxide composite foam material with both antibacterial and high uranium selectivity as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Preparation of guanidine phosphate polymer PGdn: Under a nitrogen protective atmosphere, guanidine hydrochloride, 1,6-hexanediamine and phytic acid are added to a reaction vessel and mechanically stirred at 90°C for 1 hour until the raw materials are completely melted and mixed. The temperature was then raised to 160°C and the reaction was stirred continuously for 5 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain the guanidine phosphate polymer PGdn. Step 2: Preparation of graphene oxide and poly(gamma-amino)oxime dispersion: Graphene oxide (GO) was weighed and dispersed in an aqueous solution, and ultrasonicated at room temperature for 30 min to obtain a uniform GO dispersion; poly(gamma-amino)oxime (PAO) was weighed and dispersed in NaOH solution, and ultrasonicated under the same conditions for 30 min to obtain a uniform PAO dispersion. Step 3: Crosslinking construction of three-dimensional composite foam. Mix GO dispersion and PAO dispersion, and continue ultrasonic treatment for 30 min until the system is homogeneous. Under continuous stirring at room temperature, slowly add polyethyleneimine (PEI) to the mixture, and simultaneously add PGdn prepared in step 1. After stirring evenly, add glutaraldehyde crosslinking agent, and continue stirring for 2 h. Then, let it stand at room temperature for 12 h to obtain a gel-like composite. Step 4: Post-processing. The gel-like composite obtained in Step 3 is repeatedly washed with deionized water until neutral, and then freeze-dried to obtain the three-dimensional graphene oxide composite foam material GPP-PGdn, which has both antibacterial and high uranium selectivity.

5. The preparation method according to claim 4, characterized in that, In step 1, the molar ratio of guanidine hydrochloride, 1,6-hexanediamine, and phytic acid is 105:86:

3.

6. The preparation method according to claim 4, characterized in that, In step 2, the concentration of the GO dispersion was 4 mg / mL, and the concentration of the PAO dispersion was 28.6 mg / mL; the volume ratio of the GO dispersion to the PAO dispersion was 5:

7.

7. The preparation method according to claim 4, characterized in that, In step 3, the mass fraction of glutaraldehyde is 50%, and the feeding volume is 500 μL.

8. A guanidine-modified three-dimensional graphene oxide composite foam material, characterized in that, The material uses graphene oxide (GO) as a matrix and forms a three-dimensional porous foam skeleton through polyethyleneimine (PEI) crosslinking. The matrix is ​​composite with poly(amine oxime) (PAO) and guanidine polymer (Gdn), with the mass ratio of each component being GO:PEI:PAO:Gdn = 1:20:10:

10. The guanidine polymer (Gdn) is prepared by melt polycondensation reaction of guanidine hydrochloride and 1,6-hexanediamine, without the addition of phytic acid in the preparation process.

9. The application of the three-dimensional graphene oxide composite foam material according to any one of claims 1 to 3 and 8 in seawater uranium extraction and uranium-containing radioactive wastewater treatment. The application according to claim 9 is characterized in that, The material selectively enriches uranyl ions in weakly alkaline natural seawater / uranium-containing wastewater with pH=7.0~8.5, with an adsorption equilibrium time of 24h. When recycled, 0.3mol / L nitric acid is used as the eluent.

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