A method for efficiently and stably enriching actinides by regulating nucleation and growth during colloidal crystallization

Abstract

The present invention relates to the technical field of sewage treatment and resource enrichment. The present invention provides a method for regulating nucleation and growth in the colloidal crystallization process to achieve efficient and stable enrichment of actinide elements. The specific method includes: under acidic conditions, adding the wastewater to be treated containing actinide elements into a filtration column filled with colloid to form a new nanocrystalline phase containing actinide elements, thereby achieving the enrichment of actinide elements; the material of the colloid is a metal-based colloid obtained by heating hydrolysis. The enrichment efficiency of uranium in the present invention is much higher than the U / Fe molar ratio of 10-5 to 0.2 for enriching and fixing uranium by other research methods such as hydrothermal coprecipitation, redox-driven phase transformation, and oriented aggregation of precursor particles.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment and resource enrichment, and in particular to a method for regulating nucleation and growth in the process of colloidal crystallization to achieve efficient and stable enrichment of actinides. Background Art

[0002] Nucleation and crystal growth pathways play a key role in natural mineral growth and artificial material synthesis processes. Polymers regulate the crystallization and organization of inorganic material nanocrystals to form complex morphologies and hierarchical structures. Polymers effectively guide the transformation of amorphous precursors into mineralized products, regulate crystallization by delaying nucleation, control the growth rate, and precisely regulate the morphology, composition, and structure of particles.

[0003] Iron and manganese (oxy) hydroxides are ubiquitous geological substances that have a significant impact on industrial applications and form essential colloidal phases by hydrolyzing ferrous and manganese in natural water. Previous studies have shown the key role of binding actinides such as uranium to iron and manganese (oxy) oxides to achieve effective, stable, and enriched actinides such as uranium. This binding can be achieved through adsorption, coprecipitation, redox-driven transformation, and oriented aggregation of precursor particles. Despite many studies and attempts, these methods can only achieve stabilization at very low U / Fe molar ratios (ranging from 10 -5 to 0.2), and with the crystallization process of (oxy) hydroxides, these incorporated actinides such as uranium often desorb, ultimately failing to effectively stabilize and enrich actinides such as uranium. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method for regulating nucleation and growth in the process of colloidal crystallization to achieve efficient and stable enrichment of actinides. The present invention continuously adds a low-concentration uranyl solution to a simple-to-synthesize and environmentally common colloid, changes the nucleation and growth paths of the colloid, generates a loose new mineral phase composed of a uranium-iron-oxygen nanocrystalline structure, realizes the highly enriched uranyl, and efficiently anchors the uranyl in the new nanocrystalline phase in an acidic environment through a small amount of green, simple-to-synthesize or widely existing colloids in nature. The material synthesis process in the present invention is green and simple to operate, and the material can efficiently and stably hold uranyl for a long time under acidic conditions.

[0005] The purpose of the present invention is to provide a method for regulating nucleation and growth in the process of colloidal crystallization to achieve efficient and stable enrichment of actinides, including the following steps: under acidic conditions, adding the wastewater to be treated containing actinides into a filtration column filled with colloid to form a new nanocrystalline phase containing actinides, thereby achieving the enrichment of actinides; the material of the colloid is a metal-based colloid obtained by heating and hydrolysis.

[0006] In some embodiments of the present invention, the rate at which the wastewater to be treated is added to the filtration column is 5 μL / min to 3 mL / min.

[0007] In some embodiments of the present invention, the types of metals in the metal-based colloid include iron or manganese.

[0008] Furthermore, the metal-based colloid includes iron hydroxide colloid or manganese hydroxide colloid.

[0009] In some embodiments of the present invention, the actinide element is uranium.

[0010] In some embodiments of the present invention, the pH value of the acidic condition is 1 to 3.

[0011] In some embodiments of the present invention, the concentration of the metal in the metal-based colloid is 0.04 to 0.15 M.

[0012] In some embodiments of the present invention, the concentration of the actinide element in the wastewater to be treated is 0.01 to 0.2 mM.

[0013] In some embodiments of the present invention, the pH value of the wastewater to be treated is 2.0 to 5.8.

[0014] In some embodiments of the present invention, the iron source in the iron hydroxide colloid is selected from one or more of iron nitrate, iron chloride, iron sulfate, iron tribromide, iron perchlorate, iron dihydrogen phosphate, iron formate, iron citrate, iron lactate, iron tartrate, iron malate, iron(III) chloride hexahydrate, and iron(III) nitrate nonahydrate.

[0015] In some embodiments of the present invention, the molar concentration ratio of the iron in the metal-based colloid to the actinide element in the wastewater to be treated is (250 to 15000):1.

[0016] The above technical solutions of the present invention have the following advantages compared with the prior art:

[0017] The present invention proposes a groundbreaking method that uses dimers, trimers, and polymeric uranyl formed by actinides (such as uranium), oxygen, and hydrogen to regulate the nucleation and growth of metal colloids. In the present invention, the dimers, trimers, and polymeric uranyl displace a large number of water molecules on the colloid, replace the positions of the water molecules and interact with the colloid to form a uranium-iron-oxygen precursor. By further dehydration strategies, trace uranium is fixed in the nanocrystal structure, and a high ratio and high stability of 2 to 7 moles of actinides (such as uranium) per 1 mole of iron are achieved under low pH conditions. In-situ electron microscopy, freeze-dried atomic resolution scanning / transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electron energy loss spectroscopy reveal significant regulation of the multi-step nucleation pathway at atomic resolution, including separating a uranium-iron-oxygen-rich liquid phase rich in solutes from a relatively poor liquid phase, continuously introducing a low-concentration uranyl solution into the uranium-iron-oxygen-rich liquid phase to form a uranium-iron-oxygen precursor, then forming amorphous uranium-iron-oxygen nanoclusters, and finally stabilizing the uranium in a porous new mineral phase composed of numerous nanocrystals smaller than 5 nanometers to stabilize trace uranium. The size of the final product ranges from a few hundred nanometers to dozens of micrometers, making it easy to enrich and utilize. The present invention not only enhances the understanding of colloid behavior in the natural environment but also proposes a new strategy for enriching uranium from low-pH wastewater, marking a significant advancement in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To make the content of the present invention easier to clearly understand, the following further details the present invention according to specific embodiments of the present invention in combination with the accompanying drawings, where

[0019] Figure 1 are the morphology, element distribution, composition, and corresponding electron energy scattering spectrum of the product generated in Example 1 of the present invention;

[0020] Figure 2 are the morphology, element distribution, composition, electron energy scattering spectrum, and particle size analysis diagram of the product generated in Example 2 of the present invention;

[0021] Figure 3 are the morphology, element distribution, composition, electron energy scattering spectrum, and particle size analysis diagram of the product generated in Example 3 of the present invention;

[0022] Figure 4 is the internal atomic structure diagram of the product generated in Example 2 of the present invention, showing that the product is composed of numerous nanocrystals smaller than 5 nanometers, and the nanocrystals are composed of uranium, iron, and oxygen elements with different contrasts;

[0023] Figure 5 are the high-resolution transmission electron microscopy image of the internal atomic structure of the product generated in Example 2 of the present invention and the Fourier transform diffraction of the nanocrystals, determining that a large number of new mineral phases are contained in the product;

[0024] Figure 6 This is the product formed by the crystallization of the colloid without adding low-concentration uranyl in the blank example of the present invention, and it is determined that the product is common FeOOH;

[0025] Figure 7 This is the uranium / iron molar ratio of the products generated in Examples 1-3 and Comparative Examples I-VIII of the present invention, showing the great advantages and discoveries of the present invention. Detailed implementation manners

[0026] To solve the technical problems pointed out in the background art, the present invention achieves the object of the present invention through the following methods:

[0027] The specific method of the present invention is to continuously and slowly add low-concentration uranyl to the colloid under acidic conditions, thereby changing the nucleation and growth paths of the colloid. Through liquid-liquid phase separation, a metastable uranium-iron-oxygen precursor is formed, and further dehydration condensation forms a new porous and loose aggregated ore phase composed of countless Fe-U-O nanocrystals smaller than 5 nm, thereby realizing the highly efficient enrichment of low-concentration uranyl solution with a U / Fe molar ratio of 2-7 under acidic conditions. The product size is close to the micron level, which is conducive to enrichment. The colloid is a colloid generated by heating hydrolysis and is also a colloid widely existing in nature. The enrichment efficiency of uranium in the present invention is much higher than that of other studies that enrich and fix uranium by means of hydrothermal co-precipitation, redox-driven phase transformation, and oriented aggregation of precursor particles with a U / Fe molar ratio of 10 -5 to 0.2.

[0028] The object of the present invention is to provide a method for regulating nucleation and growth in the process of colloid crystallization to achieve efficient and stable enrichment of actinides, including the following steps: under acidic conditions, adding the wastewater to be treated containing actinides into a filter column filled with colloid to form a new nanocrystal phase containing actinides, thereby realizing the enrichment of actinides; the material of the colloid is a metal-based colloid.

[0029] In a specific embodiment of the present invention, the metal types in the metal-based colloid include iron and / or manganese.

[0030] In a specific embodiment of the present invention, the metal-based colloid includes iron hydroxide colloid and / or manganese hydroxide colloid.

[0031] The iron source in the iron hydroxide colloid in the metal-based colloid is selected from one or more of ferric nitrate, ferric chloride, ferric sulfate, ferric tribromide, ferric perchlorate, ferrous dihydrogen phosphate, iron formate, iron citrate, iron lactate, iron tartrate, iron malate, ferric chloride hexahydrate, and ferric nitrate nonahydrate.

[0032] In a specific embodiment of the present invention, the rate at which the wastewater to be treated is added to the filter column is 5 μL / min to 3 mL / min. Exemplarily, it can be 5 μL / min to 1 mL / min; 1 mL / min to 3 mL / min, etc.

[0033] In a specific embodiment of the present invention, the actinide element is uranium.

[0034] In a specific embodiment of the present invention, the pH value of the acidic condition is 1 to 3. Exemplarily, it can be 1, 2, 3, or 1 to 2, 2 to 3, etc., or any interval value between any two numerical values.

[0035] In a specific embodiment of the present invention, the concentration of the metal in the metal-based colloid is 0.04 to 0.15 M. Exemplarily, it can be 0.04 M, 0.05 M, 0.1 M, 0.12 M, 0.13 M, 0.14 M, 0.15 M, etc., or 0.04 to 0.1 M, 0.04 to 0.11 M, 0.04 to 0.12 M, 0.04 to 0.13 M, 0.04 to 0.14 M, etc.

[0036] In a specific embodiment of the present invention, the concentration of the actinide element in the wastewater to be treated is 0.01 to 0.2 mM. Exemplarily, it can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, etc., or 0.01 to 0.05 mM, 0.01 to 15 mM, 0.1 to 0.2 mM, etc.

[0037] In a specific embodiment of the present invention, the pH value of the wastewater to be treated is 2.0 to 5.8. Exemplarily, it can be 2, 3, 4, 5, 5.5, 5.8, etc., 5 to 5.8, 2 to 5, 3 to 5.8, etc., or 2.0 to 3, 2.0 to 4, 2.0 to 5, etc.

[0038] In a specific embodiment of the present invention, the iron source in the iron hydroxide colloid in the metal-based colloid is selected from one or more of ferric nitrate, ferric chloride, ferric sulfate, ferric tribromide, ferric perchlorate, ferrous dihydrogen phosphate, iron formate, iron citrate, iron lactate, iron tartrate, iron malate, ferric chloride hexahydrate, and ferric nitrate nonahydrate.

[0039] In some embodiments of the present invention, the molar concentration ratio of the metal in the metal-based colloid to the actinide element in the wastewater to be treated is (250~15000):1. The range of the present invention is conducive to the interaction between iron hydroxide colloid and uranyl, stabilizes uranium in the nanocrystal product, and achieves the optimal effect of stabilizing and enriching uranium.

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the specific embodiments cited do not limit the present invention.

[0041] Example 1

[0042] This example provides a method for efficiently and stably enriching actinide elements such as uranium by regulating nucleation and growth during the colloidal crystallization process:

[0043] Provide a silica gel column filled with iron hydroxide colloid with a pH of 1.1 (the concentration of iron in the iron hydroxide colloid is 0.1 M); then use a syringe pump to flow a uranyl solution with a pH of 2.8 and a concentration of 0.04 mM through the silica gel column filled with the colloid at a speed of 0.1 mL / min to obtain a mineral phase with a size of 100~800 nanometers composed of uranium-iron-oxygen nanocrystals enriched with uranium. After the nanocrystals are stacked, micron-sized new minerals are formed, and the uranium / iron molar ratio of the obtained new minerals is 3.8. The new minerals are characterized, and the results are shown in Figure 1 .

[0044] Example 2

[0045] This example provides a method for efficiently and stably enriching actinide elements such as uranium by regulating nucleation and growth during the colloidal crystallization process:

[0046] Provide a silica gel column filled with iron hydroxide colloid with a pH of 1.5 (the concentration of iron in the iron hydroxide colloid is 0.04 M); then use a syringe pump to flow a uranyl solution with a pH of 3.58 and a concentration of 0.05 mM through the silica gel column filled with the colloid at a speed of 0.05 mL / min to obtain a mineral phase with a size of 50~200 nanometers composed of uranium-iron-oxygen nanocrystals enriched with uranium. After the nanocrystals are stacked, micron-sized new minerals are formed, and the uranium / iron molar ratio of the obtained new minerals is 4.1; the new minerals are characterized, and the results are shown in Figure 2 and Figure 4 、 Figure 5 .

[0047] Example 3

[0048] This example provides a method for efficiently and stably enriching actinide elements such as uranium by regulating nucleation and growth during the colloidal crystallization process:

[0049] Provide a silicon nitride column filled with iron hydroxide colloid with a pH of 1.5 (the concentration of iron in the iron hydroxide colloid is 0.04 M); then use a peristaltic pump to flow a uranyl solution with a pH of 5.53 and a concentration of 0.08 mM through the silicon nitride column filled with the colloid at a speed of 0.05 mL / min to obtain a mineral phase with a size of 200 - 1300 nanometers composed of uranium-iron-oxygen nanocrystals enriched with uranium. After the nanocrystals are stacked, micron-sized new minerals are formed. The uranium / iron molar ratio of the obtained new minerals is 4.3. The characterization results are shown in Figure 3 。

[0050] Example 4

[0051] This example provides a method for regulating nucleation and growth during colloid crystallization to achieve efficient and stable enrichment of actinide elements such as uranium:

[0052] Provide a silica column or a silicon nitride column filled with manganese hydroxide colloid with a pH of 1.8 (the concentration of manganese in the manganese hydroxide colloid is 0.04 M); then use an injection pump to flow a uranyl solution with a pH of 4.6 and a concentration of 0.05 M through the silica column filled with the colloid at a speed of 0.05 mL / min to obtain a mineral phase with a size of 160 - 800 nanometers composed of uranium-manganese-oxygen nanocrystals enriched with uranium. After the nanomaterials are stacked, micron-sized new minerals are formed. The uranium / manganese molar ratio of the new minerals is 3.1.

[0053] Blank example

[0054] Similar to Example 1, the difference is that no uranyl solution is introduced into these colloids. The colloids crystallize through the conventional path, and the colloids form products with a structure consistent with FeOOH. The product characterization is shown in Figure 6 。

[0055] Comparative Examples I - VIII

[0056] Comparative Examples I - VIII respectively provide eight situations in the prior art that are the same as the field of the present invention, as shown in Table 1 specifically. The results are shown in Figure 7 and Table 1.

[0057] 1. Structure characterization

[0058] Characterize the structure and elements of the new minerals enriched with uranium finally obtained in Example 1. The characterization results are shown in Figure 1 ,From Figure 1 it can be seen that the final product (new minerals) obtained from the reaction is composed of particles with a size of 100 - 800 nm, and these particles agglomerate together to form micron-sized aggregates; these aggregates are mainly composed of uniformly distributed uranium, iron, and oxygen elements; and the uranium / iron molar ratio is 3.8.

[0059] Characterize the structure and elements of the new minerals enriched with uranium finally obtained in Example 2. The characterization results are shown inFigure 2 , it can be seen from Figure 2 that the product consists of particles with a size of 100 - 800 nm. The size distribution in the statistical area is concentrated in the range of 100 - 200 nm. The product is mainly composed of uranium, iron, and oxygen elements that are evenly distributed in the product; and the uranium / iron molar ratio is 4.1.

[0060] The enriched new mineral containing uranium obtained in Example 3 was characterized in terms of structure and elements. The characterization results are shown in Figure 3 , it can be seen from Figure 3 that the product consists of particles with a size of 200 - 1300 nm. The size distribution in the statistical area is concentrated in the range of 500 - 1000 nm. The product is mainly composed of uranium, iron, and oxygen elements that are evenly distributed in the product; and the uranium / iron molar ratio is 4.3.

[0061] It can be seen from Figure 4 that the high-angle annular dark-field atomic image of the new mineral obtained in Example 2 shows that the product consists of a stacked structure composed of numerous nanocrystals smaller than 5 nm composed of uranium, iron, and oxygen.

[0062] It can be seen from Figure 5 that according to the analysis of the atomic-resolution transmission electron microscope images of the new mineral obtained in Example 2, the structures of these nanocrystals do not match the mineral structures containing two to four elements of uranium, iron, oxygen, and chlorine in the existing structure database, and it is determined that a new mineral phase is formed.

[0063] It can be seen from Figure 6 that in the blank example, when uranyl solution was not introduced into the iron colloid, the colloid crystallized through the conventional path and formed a product with the same structure as FeOOH.

[0064] Table 1

[0065]

[0066] It can be seen from Figure 7 and Table 1 that in the prior art, the U / Fe molar ratio formed by stabilizing uranium with iron oxide is less than 0.2, which is much lower than 3.8 - 4.3 proposed in the examples of the present invention.

[0067] Obviously, the above examples are only for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for regulating nucleation and growth in the process of colloidal crystallization to achieve efficient and stable enrichment of actinide elements, characterized in that: The following steps are involved: Under acidic conditions, wastewater to be treated containing actinides is added to a filter column filled with colloid to form a new nanocrystalline phase containing actinides, thereby achieving enrichment of actinides; the material of the colloid is a metal-based colloid obtained by heating and hydrolysis; the metal-based colloid includes iron hydroxide colloid or manganese hydroxide colloid; the actinide is uranium; and the concentration of the metal in the metal-based colloid is 0.04-0.15 M.

2. The method for regulating nucleation and growth in the colloidal crystallization process to achieve efficient and stable enrichment of actinide elements according to claim 1, characterized in that: The rate at which the wastewater to be treated is added to the filter column is 5 uL / min~3 mL / min.

3. The method for regulating nucleation and growth in the colloidal crystallization process to achieve efficient and stable enrichment of actinide elements according to claim 1, characterized in that: The iron source in the ferric hydroxide colloid is selected from one or more of ferric nitrate, ferric chloride, ferric sulfate, ferric tribromide, ferric perchlorate, ferric dihydrogen phosphate, ferric formate, ferric citrate, ferric lactate, ferric tartrate, ferric malate, ferric chloride hexahydrate, and ferric nitrate nonahydrate.

4. The method for regulating nucleation and growth in the colloidal crystallization process to achieve efficient and stable enrichment of actinide elements according to claim 1, characterized in that: The pH value of acidic conditions is 1~3.

5. The method for regulating nucleation and growth in the colloidal crystallization process to achieve efficient and stable enrichment of actinide elements according to claim 1, characterized in that: The concentration of actinide elements in the wastewater to be treated is 0.01-0.2 mM.

6. The method for regulating nucleation and growth in the colloidal crystallization process to achieve efficient and stable enrichment of actinide elements according to claim 1, characterized in that: The pH value of the wastewater to be treated is 2.0-5.

8.

7. The method for regulating nucleation and growth in the colloidal crystallization process to achieve efficient and stable enrichment of actinide elements according to claim 1, characterized in that: The molar concentration ratio of the metal in the metal-based colloid to the actinide in the wastewater to be treated is (250~15000):1.

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