A method for preparing microporous carbon material without activator and application thereof in nano-confined uranium extraction

Abstract

The application provides a method for preparing microporous carbon material without activator and application thereof in nano-limited uranium extraction, belongs to the field of environmental radiochemistry water pollution control and resource recovery, and aims at the problems of slow kinetics and strong interference of competitive ions existing in the existing uranium extraction technology, and provides a new method for uranium extraction based on microporous carbon material regulation and control of nano-limited effect.The method has the characteristics of fast removal rate, strong anti-interference ability and waste resource utilization, and is suitable for efficient resource extraction of uranium-containing wastewater in a strong acid environment and a seawater system.

Description

Technical Field

[0001] This invention relates to the field of environmental radiochemical water pollution control and resource recovery, and more specifically, to a method for preparing microporous carbon materials without activators and its application in nano-confined uranium extraction. Background Technology

[0002] The ocean contains abundant dissolved uranium resources, totaling approximately 4.5 billion tons, far exceeding the proven uranium reserves on land, and is considered a highly promising unconventional uranium resource source. Therefore, efficient uranium extraction from seawater is of significant strategic importance for expanding uranium resource supply channels, ensuring the secure supply of nuclear fuel, and supporting the sustainable development of nuclear energy. However, the real seawater system has a complex composition, extremely low uranium concentration (typically only about 3 ppb), and contains a large number of coexisting ions and competing components, posing significant challenges to seawater uranium extraction. In existing seawater uranium extraction processes, the interfacial enrichment and selective separation of uranyl ions (UO22+) mainly suffer from the following two technical problems: First, slow mass transfer and coordination reaction kinetics. The migration of uranyl ions from the bulk seawater to the adsorption interface and their binding typically involves multiple steps, including bulk diffusion, interfacial transport, desolvation, and coordination complexation. The overall process rate is low, and reaching adsorption equilibrium often takes a long time, resulting in insufficient utilization of active sites and limited uranium enrichment efficiency. Second, insufficient selective separation capability. Seawater contains competing ions such as vanadium, which have similar coordination chemistry to uranyl ions. These ions can compete with active sites in adsorption materials for binding, causing non-target ions to preferentially occupy or occupy a large number of adsorption sites, thus significantly reducing the actual adsorption capacity and selective separation effect of the material for uranium.

[0003] To address the need for enrichment and separation of trace uranyl ions in real seawater systems, it is necessary to develop a seawater uranium extraction material and method that combines rapid mass transfer, efficient coordination, and excellent resistance to competing ion interference, thereby improving uranium enrichment efficiency, selectivity, and practical application performance. Therefore, a method for preparing microporous carbon materials without activators and its application in nano-confined uranium extraction are proposed. Summary of the Invention

[0004] The purpose of this invention is to address the problems of slow adsorption kinetics and strong interference from competing ions in the enrichment of trace uranium [U(VI)] in real seawater, and to provide a confined complexation adsorption system based on a biomass-derived hierarchical porous carbon framework. This system constructs nano-confined reaction microdomains within the framework pores and / or at the pore openings. By synergistically controlling the pore size geometry, pore wall electrical and hydrophilic / hydrophobic properties, and the chemical environment of the localized ligands, it enhances the desolvation, local enrichment, and coordination complexation processes of uranyl ions within the confined space. This achieves rapid and highly selective enrichment of uranium in seawater, improving the kinetic performance and resistance to competing ion interference in the seawater uranium extraction process.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: a method for preparing microporous carbon materials without activators, wherein biochar is placed in a sealed container, and under the condition of carbon dioxide activation atmosphere, the temperature is raised to 500-900℃, activated for 1-3 h, cooled to room temperature, removed, washed with hydrochloric acid and water until neutral, and dried to obtain microporous carbon materials.

[0006] As a preferred embodiment of the present invention, the activation atmosphere is carbon dioxide gas.

[0007] As a preferred embodiment of the present invention, the concentration of the hydrochloric acid is 1 mol / L.

[0008] As a preferred embodiment of the present invention, the activation temperature is 900°C, and more preferably, the activation time is 2 hours.

[0009] As a preferred embodiment of the present invention, the heating rate is 5°C / min.

[0010] A method for preparing porous carbon materials based on carbon dioxide activation, and a method for preparing microporous carbon materials without activators.

[0011] As a preferred technical solution of the present invention, the preparation process is green and environmentally friendly, without secondary pollution, and the material has excellent microporous structure and adsorption performance. The microporous carbon material drives the nano-confinement effect to achieve efficient extraction of uranium-containing wastewater. The surface of the microporous carbon material exhibits a rough and porous morphology, with a rich and uniform pore structure. The pore size is mainly concentrated in the microporous region, and the specific surface area of ​​the material gradually increases with the increase of carbonization temperature, and the pore structure also continuously develops and improves.

[0012] As a preferred technical solution of the present invention, the microporous carbon material can drive the nano-confinement effect through its unique pore structure to construct an efficient reaction microenvironment, thereby enabling efficient and rapid extraction of uranium ions from uranium-containing wastewater.

[0013] As a preferred technical solution of the present invention, ligands containing oxygen- and / or nitrogen-containing coordination units are introduced into the microporous carbon material to construct a stable confined reaction microenvironment; under the reaction conditions of n(ligand):n(U)=4:1, the system achieves a removal rate of not less than 95% for hexavalent uranium in wastewater; in a spiked actual Yellow Sea seawater system simulating a real application scenario, the system achieves a removal rate of more than 95.5% for hexavalent uranium within 2 hours.

[0014] Compared with existing technologies, the present invention offers the following advantages: Using biomass-derived hierarchical porous carbon as a framework, the present invention constructs nano-confined reaction microdomains within and / or at the pore openings of the carbon, forming a confined complex adsorption system. Through the synergistic effect of pore structure, surface physicochemical properties, and localized ligand chemical fields, this system promotes the desolvation, local enrichment, and selective coordination complexation of uranyl ions, significantly enhancing the adsorption rate, adsorption capacity, and selective separation performance of trace uranium in real seawater. Simultaneously, it reduces the adverse effects of competing ions such as vanadium on the adsorption process, thus demonstrating high application prospects and promotional value in the field of uranium extraction from seawater. Attached Figure Description

[0015] Figure 1 These are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of microporous carbon materials prepared without activators.

[0016] Figure 2 These are nitrogen adsorption-desorption isotherms and pore size distribution diagrams for carbon materials with different pore sizes.

[0017] Figure 3 This is a graph showing the removal performance of hexavalent uranium by porous carbon materials and different ligands in Example 1.

[0018] Figure 4 This is a graph showing the uranium extraction performance of actual seawater spiked with hexavalent uranium in Implementation 2. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely illustrates some embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. It should be noted that, in the absence of conflict, the embodiments and features and technical solutions in the embodiments of the present invention can be combined with each other. It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0021] Example 1 Material Characterization: Compared with existing methods for preparing microporous carbon materials using activators, this invention can prepare microporous carbon materials in one step using a carbon dioxide atmosphere. The preparation process does not require the introduction of large amounts of chemical activators, and has advantages such as green process, simple operation, low post-treatment requirements, and no secondary pollution. Figure 1The scanning electron microscope (SEM) images clearly show that the microporous carbon material prepared in this invention has a relatively rough surface, forming a rich pore structure and exhibiting obvious porous morphological characteristics. Figure 2 The specific surface area and pore size distribution test results show that as the carbonization temperature increases, the specific surface area of ​​the obtained material gradually increases and the pore structure continues to develop and improve. At the same time, the pore size of the material is mainly distributed in the micropore region, indicating that this method can effectively regulate the formation and evolution of the micropore structure of the material, thereby improving the adsorption performance and practical application value of the material.

[0022] Example 2: Effect of different ligands on uranium extraction performance: Weigh 0.1g of carbon material B CO2 In a reaction vessel, the molar ratio of uranium to different ligands was set to 1:4. 90 mL of water was added and stirred. Then, hexavalent uranium (10 mg / L) was added to bring the total volume to 100 mL. The reaction was initiated, and samples were taken at regular intervals. The samples were then filtered through a 0.22 µm filter and analyzed using the azoarsine III colorimetric method. The absorbance of the samples was measured at 652 nm using a UV-Vis spectrophotometer. The U(VI) concentration was calculated based on the absorbance, and a time-removal rate curve was plotted based on the U(VI) concentration (see [reference]). Figure 3 Removal rate = Ct / C0), where Ct is the concentration at the time of sampling and C0 is the initial concentration. Figure 3 This diagram illustrates the influence of different ligands on uranium extraction performance. The invention demonstrates that by selecting representative ligand systems containing oxygen and / or nitrogen-containing coordination units, such as PDA-26 and HDP, and introducing them into carbon materials with different pore structures, porous carbon B with a pore size of approximately 1 nm can achieve optimal uranium extraction performance. CO2 The confined reaction microenvironment constructed by -900 significantly enhances the reaction and removal efficiency between ligands and U(VI). Compared to unconfined systems composed of low-porosity or non-porosity carbon materials, under the same conditions, the confined support can significantly improve the uranium removal rate of various ligand systems; under the condition of n(ligand):n(U) = 4:1, the uranium removal rates of PDA-26, HDP, and other systems all reach over 95%. These results indicate that the enhanced effect of the confined microenvironment constructed in this invention has good universality and can provide reliable support for efficient and highly selective uranium reaction and extraction.

[0023] Example 3: Uranium Extraction Performance Test in Actual Seawater: To further verify the applicability of the confinement system constructed in this invention in real and complex seawater environments, a spiked actual Yellow Sea seawater system was used to investigate its anti-interference ability and kinetic response. Actual seawater is characterized by high salinity, multiple ion coexistence, and high ion strength, which can more realistically reflect the application conditions of the material in the seawater uranium extraction process. Experimental results show that under spiked actual Yellow Sea seawater conditions, the PDA-26 confinement system still exhibits excellent uranium removal performance, achieving a 95.5% U(VI) removal rate within 2 hours (see Example 3). Figure 4 The above results demonstrate that the confined reaction microenvironment constructed in this invention can maintain efficient reaction / removal capabilities in complex systems with high salt content and multiple competing ions, exhibiting good anti-interference performance and rapid kinetic response, further proving the application potential of this system in real seawater uranium extraction.

[0024] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described herein. Although the present invention has been described in detail with reference to the above embodiments, the present invention is not limited to the specific embodiments described above. Therefore, any modifications or equivalent substitutions to the present invention, as well as all technical solutions and improvements that do not depart from the spirit and scope of the invention, are covered within the scope of the claims of the present invention.

Claims

1. A method for preparing microporous carbon materials without activators, characterized in that, Biochar was placed in a sealed container and activated at 500-900℃ for 1-3 hours under a carbon dioxide activation atmosphere. After cooling to room temperature, the material was removed, washed with hydrochloric acid and water until neutral, and dried to obtain microporous carbon material.

2. The method for preparing microporous carbon materials without activators according to claim 1, characterized in that, The activation atmosphere is carbon dioxide gas.

3. The method for preparing microporous carbon materials without activators according to claim 1, characterized in that, Cattail powder is obtained by washing, drying, pulverizing, and passing through a 200-sieve.

4. The method for preparing microporous carbon materials without activators according to claim 1, characterized in that, The concentration of the hydrochloric acid is 1 mol / L.

5. The method for preparing microporous carbon materials without activators according to claim 1, characterized in that, The activation temperature is 900℃, and more preferably, the activation time is 2h.

6. The method for preparing microporous carbon materials without activators according to claim 1, characterized in that, The heating rate is 5°C / min.

7. A method for preparing porous carbon materials based on carbon dioxide activation, characterized in that, It is prepared by any one of the preparation methods according to claims 1-6.

8. The method for preparing porous carbon materials based on carbon dioxide activation according to claim 7, characterized in that, The preparation process is green and environmentally friendly, with no secondary pollution. The material has excellent microporous structure and adsorption performance. The microporous carbon material drives the nano-confinement effect to achieve efficient extraction of uranium-containing wastewater. The surface of the microporous carbon material exhibits a rough and porous morphology with a rich and uniform pore structure. The pore size is mainly concentrated in the microporous region. The specific surface area of ​​the material gradually increases with the increase of carbonization temperature, and the pore structure also continuously develops and improves.

9. The application of the microporous carbon material according to claim 8 in the extraction of uranium-containing wastewater, characterized in that, The microporous carbon material can drive a nano-confinence effect through its unique pore structure, thereby constructing an efficient reaction microenvironment for the efficient and rapid extraction of uranium ions from uranium-containing wastewater.

10. The application of the microporous carbon material according to claim 9 in the extraction of uranium-containing wastewater, characterized in that, Ligands containing oxygen- and / or nitrogen-containing coordination units are introduced into the microporous carbon material to construct a stable confined reaction microenvironment. Under the reaction conditions of n(ligand):n(U) = 4:1, the system achieves a removal rate of no less than 95% for hexavalent uranium in wastewater. In a spiked actual Yellow Sea seawater system simulating a real application scenario, the system achieves a removal rate of over 95.5% for hexavalent uranium within 2 hours.

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