Method for realizing efficient and stable enrichment of actinide elements by regulating nucleation and growth in colloidal crystallization process

Abstract

The invention relates to the technical field of sewage treatment and resource enrichment, and provides a method for realizing efficient and stable enrichment of actinide elements by regulating nucleation and growth in a colloidal crystallization process. The method specifically comprises the following steps: under an acidic condition, adding to-be-treated wastewater containing actinide elements into a filter column filled with colloid to form a nanocrystalline new phase containing actinide elements so as to realize enrichment of actinide elements; the material of the colloid is metal-based colloid obtained by heating and hydrolyzing. The uranium enrichment efficiency of the method is far higher than that of uranium enrichment and fixation through hydrothermal coprecipitation, oxidation-reduction driven phase change and precursor particle directional aggregation modes in other researches, and the U / Fe molar ratio is 10 <-5 >-0.2.

Description

Technical Field

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

[0002] Nucleation and crystal growth pathways play a key role in the growth of minerals in nature and the synthesis of artificial materials. Polymers regulate crystallization and organize inorganic 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 growth rate, and precisely regulate the morphology, composition, and structure of particles.

[0003] Iron oxides and manganese (oxy) hydroxides are ubiquitous geological materials with significant impact on industrial applications. They form essential colloidal phases by hydrolyzing ferrous and manganese in natural water. Previous studies have shown that the incorporation of actinides such as uranium into iron and manganese (oxy) oxides plays a key role in effectively stabilizing and enriching actinides such as uranium. This incorporation can be achieved through adsorption, coprecipitation, redox-driven conversion, and directed aggregation of precursor particles. Despite much research and attempts, these methods can only achieve very low U / Fe molar ratios (ranging from 10 -5 To 0.2), and with the crystallization process of (hydroxy) oxides, these incorporated actinides such as uranium often desorb, and ultimately cannot effectively stabilize and enrich uranium and other actinides. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for regulating the nucleation and growth in the process of colloidal crystallization to achieve efficient and stable enrichment of actinide elements. The present invention continuously adds a low-concentration uranyl solution to a colloid that is easy to synthesize and common in the environment, and changes the nucleation and growth path of the colloid to generate a loose new mineral phase composed of a uranium-iron-oxygen nano-polycrystalline structure, thereby achieving high enrichment of uranyl, and efficiently anchoring uranyl in a new nanocrystalline phase in an acidic environment through a small amount of green, simple-to-operate synthesis or widely existing colloid in nature. The material synthesis process in the present invention is green and simple to operate, and the material can efficiently stabilize 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, comprising the following steps: under acidic conditions, adding wastewater to be treated containing actinides into 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.

[0006] In some embodiments of the present invention, the wastewater to be treated is added to the filter column at a rate of 5 uL / min~3 mL / min.

[0007] In some embodiments of the present invention, the metal species 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 1-3.

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

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

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

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

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

[0016] The above technical solution of the present invention has the following advantages compared with the prior art: The present invention proposes a groundbreaking method, using dimers, trimers and polymerized uranyl formed by actinides (such as uranium, etc.), oxygen and hydrogen to regulate the nucleation and growth of metal colloids. The dimers, trimers and polymerized uranyl described in the present invention interact with the colloid by displacing a large number of water molecules on the colloid, replacing the positions of water molecules, and forming a uranium-iron-oxygen precursor. The trace uranium is fixed in the nanocrystalline structure through a further dehydration strategy, and a high ratio and high stability of 1 mole of iron to fix 2 to 7 moles of actinides (such as uranium, etc.) is 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 revealed significant regulation of the multi-step nucleation pathway at atomic resolution, including separation of a solute-rich uranium-iron-oxygen rich liquid phase from a relatively poor liquid phase, continuous introduction of a low-concentration uranyl solution into the uranium-iron-oxygen rich liquid phase to form a uranium-iron-oxygen precursor, and then forming amorphous uranium-iron-oxygen nanoclusters, and finally stabilizing these uraniums in a porous new mineral phase composed of numerous nanocrystals less than five nanometers to stabilize trace uranium. The size of the final product ranges from hundreds of nanometers to tens of microns, which is easy to enrich and utilize. The present invention not only enhances the understanding of colloidal behavior in natural environments, but also proposes a new strategy for enriching uranium from low-pH wastewater, marking a major advance in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 The morphology, element distribution, composition and corresponding electron energy scattering spectrum of the product generated for Example 1 of the present invention; Figure 2 The morphology, element distribution, composition, electron energy scattering spectrum and particle size analysis diagram of the product generated for Example 2 of the present invention; Figure 3 The morphology, element distribution, composition, electron energy scattering spectrum and particle size analysis diagram of the product generated for Example 3 of the present invention; Figure 4 This is a diagram of the internal atomic structure 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; Figure 5 The internal atomic structure high-resolution transmission electron microscopy image and nanocrystal Fourier transform diffraction of the product generated in Example 2 of the present invention confirmed that the product contained a large amount of new mineral phases; Figure 6 The product formed by the colloidal crystals in the blank example of the present invention without adding low concentration uranyl was determined to be common FeOOH; Figure 7The uranium / iron molar ratios of the products generated by Examples 1 to 3 of the present invention and Comparative Examples I to VIII show the great advantages and discoveries of the present invention. DETAILED DESCRIPTION

[0018] In order to solve the technical problems pointed out in the background technology, the present invention achieves the purpose of the present invention by the following method: 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 path of the colloid, and forming a metastable uranium-iron-oxygen precursor through liquid-liquid phase separation, and further dehydration condensation to form a porous loose aggregated new mineral phase composed of countless Fe-UO nanocrystals less than 5 nm, thereby achieving a high enrichment of the low-concentration uranyl solution under acidic conditions with a U / Fe molar ratio of 2 to 7, and the product size is close to the micron level, which is conducive to enrichment. The colloid is a colloid produced by heating and hydrolysis, and is also a colloid widely present in nature. The uranium enrichment efficiency of the present invention is much higher than that of other studies that enrich and fix uranium with a U / Fe molar ratio of 10 by hydrothermal coprecipitation, redox-driven phase change, and directional aggregation of precursor particles. -5 To 0.2.

[0019] The object 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, comprising the following steps: under acidic conditions, adding wastewater to be treated containing actinides into 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.

[0020] In a specific embodiment of the present invention, the metal species in the metal-based colloid include iron and / or manganese.

[0021] In a specific embodiment of the present invention, the metal-based colloid includes iron hydroxide colloid and / or manganese hydroxide colloid.

[0022] 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, ferric dihydrogen phosphate, ferric formate, ferric citrate, ferric lactate, ferric tartrate, ferric malate, ferric chloride hexahydrate, and ferric nitrate nonahydrate.

[0023] In a specific embodiment of the present invention, the speed at which the wastewater to be treated is added to the filter column is 5 uL / min~3 mL / min. For example, it can be 5 uL / min~1 mL / min; 1 mL / min~3 mL / min, etc.

[0024] In a specific embodiment of the present invention, the actinide element is uranium.

[0025] In a specific embodiment of the present invention, the pH value of the acidic condition is 1-3, and illustratively, it can be 1, 2, 3, or 1-2, 2-3, etc., or any interval value between any two values.

[0026] In a specific embodiment of the present invention, the concentration of the metal in the metal-based colloid is 0.04~0.15 M. For example, 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 0.04~0.1 M, 0.04~0.11 M, 0.04~0.12 M, 0.04~0.13 M, 0.04~0.14 M, etc.

[0027] In a specific embodiment of the present invention, the concentration of actinide elements in the wastewater to be treated is 0.01~0.2 mM. For example, 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 0.01~0.05 mM, 0.01~15 mM, 0.1~0.2 mM, etc.

[0028] In a specific embodiment of the present invention, the pH value of the wastewater to be treated is 2.0~5.8. For example, it can be 2, 3, 4, 5, 5.5, 5.8, etc., 5~5.8, 2~5, 3~5.8, etc., or 2.0~3, 2.0~4, 2.0~5, etc.

[0029] 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, ferric dihydrogen phosphate, ferric formate, ferric citrate, ferric lactate, ferric tartrate, ferric malate, ferric chloride hexahydrate, and ferric nitrate nonahydrate.

[0030] In some embodiments of the present invention, 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. The range of the present invention is conducive to the interaction between the iron hydroxide colloid and the uranyl, and stabilizes the uranium in the nanocrystalline product, and achieves the optimal stabilization and enrichment of uranium.

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0032] Example 1 This embodiment provides a method for regulating nucleation and growth in the colloidal crystallization process to achieve efficient and stable enrichment of actinide elements such as uranium: Provide a silica gel column filled with iron hydroxide colloid at pH 1.1 (iron concentration in iron hydroxide colloid is 0.1M); 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 colloid at a speed of 0.1 mL / min, and obtain a mineral phase of 100-800 nanometers composed of uranium-enriched uranium-iron-oxygen nanocrystals. After the nanocrystals are stacked, a new mineral of micrometer size is formed. The uranium / iron molar ratio of the obtained new mineral is 3.8. The new mineral is characterized, and the results are shown in Figure 1 .

[0033] Example 2 This embodiment provides a method for regulating nucleation and growth in the colloidal crystallization process to achieve efficient and stable enrichment of actinide elements such as uranium: A silica gel column filled with iron hydroxide colloid at pH 1.5 (the iron concentration in the iron hydroxide colloid is 0.04M) is provided; then a uranyl solution with a pH of 3.58 and a concentration of 0.05 mM is passed through the silica gel column filled with colloid by a syringe pump at a rate of 0.05 mL / min to obtain a mineral phase of 50 to 200 nanometers in size composed of uranium-enriched uranium-iron-oxygen nanocrystals. After the nanocrystals are stacked, a new mineral of micrometer size is formed. The uranium / iron molar ratio of the obtained new mineral is 4.1; the new mineral is characterized, and the results are shown in Figure 2 and Figure 4 , Figure 5 .

[0034] Example 3 This embodiment provides a method for regulating nucleation and growth in the colloidal crystallization process to achieve efficient and stable enrichment of actinide elements such as uranium: A silicon nitride column filled with iron hydroxide colloid at pH 1.5 (the iron concentration in the iron hydroxide colloid is 0.04M) is provided; then a peristaltic pump is used 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 colloid at a rate of 0.05 mL / min to obtain a mineral phase of 200 to 1300 nanometers composed of uranium-enriched uranium-iron-oxygen nanocrystals. After the nanocrystals are stacked, a new mineral of micrometer size is formed. The uranium / iron molar ratio of the obtained new mineral is 4.3. The characterization results are shown in Figure 3 .

[0035] Example 4 This embodiment provides a method for regulating nucleation and growth in the process of colloidal crystallization to achieve efficient and stable enrichment of actinide elements such as uranium: A silica gel column or a silicon nitride column filled with manganese hydroxide colloid at pH 1.8 (the manganese concentration in the manganese hydroxide colloid is 0.04M) is provided; then a uranyl solution at pH 4.6 and concentration 0.05M is passed through the silica gel column filled with colloid by a syringe pump at a rate of 0.05 mL / min to obtain a mineral phase of 160 to 800 nanometers in size composed of uranium-enriched uranium-manganese-oxygen nanocrystals. After the nanomaterials are stacked, a new mineral of micrometer size is formed, and the uranium / manganese molar ratio of the new mineral is 3.1.

[0036] Blank example Similar to Example 1, except that the uranyl solution was not introduced into the colloids, the colloids were crystallized by conventional routes, and the colloids formed products with the same structure as FeOOH. The product characterization is shown in Figure 6 .

[0037] Comparative Examples I to VIII Comparative Examples I to VIII respectively provide eight situations in the prior art that are the same as those in the present invention, as shown in Table 1. Figure 7 and Table 1.

[0038] 1. Structural characterization The new uranium-enriched mineral finally obtained in Example 1 was characterized in terms of structure and elements. Figure 1 ,Depend on Figure 1 It can be seen that the final product (new mineral) obtained by the reaction is composed of particles of 100~800 nm, which are aggregated together to form micron-sized agglomerates; these agglomerates are mainly composed of evenly distributed uranium, iron and oxygen elements; and the uranium / iron molar ratio is 3.8.

[0039] The new uranium-enriched mineral finally obtained in Example 2 was characterized in terms of structure and elements. The characterization results are shown in Figure 2 ,Depend on Figure 2 It can be seen that the product is composed of particles with a size of 100~800 nm, and the size distribution of the statistical area is concentrated in 100~200 nm. The product is mainly composed of uranium, iron and oxygen elements uniformly distributed in the product; and the uranium / iron molar ratio is 4.1.

[0040] The new uranium-enriched mineral finally obtained in Example 3 was characterized in terms of structure and elements. Figure 3 ,Depend on Figure 3 It can be seen that the product is composed of particles of 200~1300 nm, the size distribution of the statistical area is concentrated in 500~1000nm, and the product is mainly composed of uranium, iron and oxygen elements uniformly distributed in the product; and the uranium / iron molar ratio is 4.3.

[0041] Depend on Figure 4It can be seen that the high-angle annular dark-field atomic image of the new mineral obtained in Example 2 shows that the product is composed of a stacked structure of numerous nanocrystals less than 5 nm composed of uranium, iron and oxygen.

[0042] Depend on Figure 5 It can be seen that according to the atomic-resolution transmission electron microscopy image analysis of the new mineral obtained in Example 2, the structure of these nanocrystals does not match the mineral structure containing two to four elements of uranium, iron, oxygen and chlorine in the existing structural database, and it is determined that a new mineral phase has been formed.

[0043] Depend on Figure 6 It can be seen that in the blank case, when the uranyl solution was not introduced into the iron colloid, the colloid crystallized through the conventional path to form a product with the same structure as FeOOH.

[0044] Table 1

[0045] Depend on Figure 7 As can be seen from Table 1, the U / Fe molar ratio formed by stabilizing uranium with iron oxide in the prior art is less than 0.2, which is much lower than 3.8-4.3 proposed in the embodiments of the present invention.

[0046] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled 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 methods here. The obvious changes or modifications derived from these are still within the protection scope of the 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 containing actinides to be treated 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.

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 metal-based colloid includes iron hydroxide colloid or manganese hydroxide colloid.

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 3, 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.

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 actinide element is uranium.

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 acidic conditions is 1~3.

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 concentration of the metal in the metal-based colloid is 0.04-0.15M.

8. 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.

9. 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.

10. 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.

Images