A process for the selective extraction of uranium from a high concentration sulphuric acid medium

Abstract

The application belongs to the field of hydrometallurgy, and an embodiment provides a method for selectively extracting uranium from a high-concentration sulfuric acid medium. The method comprises the following steps: providing an extraction organic phase, wherein the extraction organic phase comprises a compound and a diluent; mixing and extracting the extraction organic phase and a solution, wherein the solution comprises uranium and acid, and the sulfuric acid concentration of the solution is at least 1 g / L, wherein the compound has a structure shown in formula I; formula I, R1, R2 and R3 are independently selected from any one of C3-C18 linear, branched or cyclic aliphatic hydrocarbon groups and C6-C18 aromatic groups; and the diluent comprises at least one of sulfonated kerosene, aviation kerosene, n-hexane and cyclohexane. The method of the embodiment of the application is simple and easy to implement, and can efficiently separate uranium from coexisting impurity metal ions.

Description

Technical Field

[0001] This application relates to the field of hydrometallurgical technology, and in particular to a method for selectively extracting uranium from a high-concentration sulfuric acid medium. Background Technology

[0002] Uranium is an important strategic resource and a fundamental raw material for the nuclear industry. Currently, with strong demand for uranium resources and a tightening supply of high-quality resources, the development and utilization of complex low-grade uranium polymetallic ores (such as those containing niobium, titanium, rare earth elements, and iron) has become an important direction for ensuring uranium resource supply. The uranium-bearing leachate obtained after treating such ores with sulfation roasting-water leaching or acid leaching processes has a complex composition, often containing multiple elements such as niobium, titanium, iron, and rare earth elements, and exhibits extremely high acidity.

[0003] Existing technologies for extracting uranium from uranium-containing solutions mainly include amine extraction and acidic phosphoric acid extractants. Amine extractants have a certain extraction capacity for uranium, but they suffer from significant acid extraction problems during the process, with large amounts of sulfuric acid being extracted into the organic phase. This not only consumes extraction capacity and reduces extraction efficiency but also creates difficulties for subsequent processing. Phosphoric acid extractants (such as P204 and P507) have a certain extraction capacity for uranium under low to medium acidity conditions, but their extraction efficiency decreases significantly under high acidity conditions, and the co-extraction problem for impurity ions such as iron and titanium is quite prominent. Furthermore, the selectivity of the above extraction systems is often insufficient when processing complex solutions containing elements such as niobium, iron, titanium, and rare earth elements.

[0004] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of protection of this application. Summary of the Invention

[0005] This application provides a method for selectively extracting uranium from a high-concentration sulfuric acid medium to solve or alleviate one or more of the technical problems mentioned above.

[0006] The method of this application embodiment includes the following steps: providing an extractable organic phase, the extractable organic phase comprising a compound and a diluent; mixing and extracting the extractable organic phase and a solution, the solution comprising uranium and an acid, the sulfuric acid concentration of the solution being at least 1 g / L, wherein the compound has the structure shown in Formula I; Formula I, R1, R2, and R3 are each independently selected from any one of straight-chain, branched, or cyclic aliphatic hydrocarbon groups (C3-C18) or aromatic groups (C6-C18); the diluent includes at least one of sulfonated kerosene, aviation kerosene, n-hexane, and cyclohexane.

[0007] The method described in this application is simple to operate. No pretreatment such as neutralization or precipitation conversion of the solution is required during extraction; direct extraction and separation are possible, significantly shortening the extraction process, production cycle, and reducing equipment operating and investment costs. It can be used for uranium extraction in harsh chemical environments with high sulfuric acid concentrations, and is particularly suitable for treating complex uranium polymetallic leachates obtained from sulfation roasting-water leaching processes. This is because the carboxyl and carbonyl groups in the compound can form stable chelate structures with uranyl ions, thereby achieving highly selective separation of uranium.

[0008] According to embodiments of this application, the solution further includes coexisting metal ions, including at least one selected from niobium, titanium, iron, and rare earth elements. Thus, the extraction organic phase can also be used for solutions containing uranium and coexisting metal ions.

[0009] According to embodiments of this application, the ratio of the extracted organic phase to the solution is 1:5 to 5:1.

[0010] According to embodiments of this application, the extraction is a single-stage extraction or a multi-stage countercurrent extraction.

[0011] According to embodiments of this application, the number of stages in the multi-stage countercurrent extraction is 2 to 5.

[0012] According to embodiments of this application, the sulfuric acid concentration of the solution is 50 g / L to 400 g / L.

[0013] According to the embodiments of this application, the extraction temperature is 10℃~40℃ and the time is 1min~30min.

[0014] According to embodiments of this application, the extracted organic phase further includes a modifier, which includes one or more of tributyl phosphate, 2-octanol, tert-butanol, P204, P507, N1923, and N235.

[0015] According to embodiments of this application, the volume percentage of the modifier is 1% to 30% based on the total volume of the extracted organic phase.

[0016] According to the embodiments of this application, R1 is selected from any one of straight-chain, branched, or cyclic aliphatic hydrocarbon groups of C3 to C6, and R2 and R3 are each independently selected from any one of straight-chain, branched, or cyclic aliphatic hydrocarbon groups of C3 to C10.

[0017] According to embodiments of this application, the compound has one of the following structures: , .

[0018] According to embodiments of this application, the volume percentage of the compound is 10% to 40% based on the total volume of the extracted organic phase. Detailed Implementation

[0019] The embodiments of this application are described in detail below. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0020] In this application, when numerical intervals (i.e., numerical ranges) are involved, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0021] This application provides a method for extracting uranium. The method includes the following steps: An extractable organic phase is provided, the extractable organic phase comprising a compound and a diluent; The organic phase and solution are mixed and extracted, wherein the solution comprises uranium and an acid, and the sulfuric acid concentration of the solution is at least 1 g / L. The compound has the structure shown in Formula I; Formula I, R1, R2, and R3 are each independently selected from any one of the following: straight-chain, branched, or cyclic aliphatic hydrocarbon groups (C3-C18) and aromatic groups (C6-C18). The method described in this application is simple to operate. No pretreatment such as neutralization or precipitation conversion of the solution is required during extraction; direct extraction and separation are possible, significantly shortening the extraction process, production cycle, and reducing equipment operating and investment costs. It can be used for uranium extraction in harsh chemical environments with high sulfuric acid concentrations, and is particularly suitable for treating complex uranium polymetallic leachates obtained from sulfation roasting-water leaching processes. This is because the carboxyl and carbonyl groups in the compound can form stable chelate structures with uranyl ions, thereby achieving highly selective separation of uranium.

[0022] According to embodiments of this application, an extractable organic phase is provided. The extractable organic phase includes a compound and a diluent. The diluent includes at least one selected from sulfonated kerosene, aviation kerosene, n-hexane, and cyclohexane.

[0023] It is understandable that sulfonated kerosene refers to kerosene that has undergone sulfonation treatment, with unsaturated hydrocarbons <0.2%, making it less likely to react with compounds; aviation kerosene contains a certain amount of olefins and aromatics.

[0024] Further, preferably, the diluent is selected from sulfonated kerosene. Sulfonated kerosene has good compatibility with the extracted organic phase and low volatility, which can ensure the stability of the extracted organic phase.

[0025] In some embodiments, the extracted organic phase further includes a modifier, which is used to adjust the interfacial tension of the extracted organic phase, increase the solubility of the extracted organic phase and the extract in the diluent, improve the phase separation performance of the organic phase, and avoid the formation of a third phase.

[0026] Optionally, the modifier includes one or more of the following: tributyl phosphate, 2-octanol, tert-butanol, P204, P507, N1923, and N235.

[0027] Optionally, based on the total volume of the extracted organic phase, the volume percentage of the modifier is 1% to 30%, for example, 1%, 5%, 10%, 15%, 20%, 25%, 30%, etc. Thus, while maintaining the high selectivity of the compound for uranium, the phase separation performance between the extracted organic phase and the aqueous phase to be extracted is significantly improved, the formation of a third phase is suppressed, and the anti-emulsification ability is enhanced.

[0028] Furthermore, when the content of the modifier is 10%~20%, the optimal balance between extraction selectivity and process stability can be achieved; when the content of the modifier is 25%~30%, it can cope with complex liquid systems with extreme phase separation difficulties.

[0029] In some embodiments, R1 in the compound is selected from any one of straight-chain, branched, or cyclic aliphatic hydrocarbon groups of C3 to C6; R2 and R3 are each independently selected from any one of straight-chain, branched, or cyclic aliphatic hydrocarbon groups of C3 to C10.

[0030] Furthermore, the compound has the following structure: (Compound 1) (Compound 2).

[0031] In some embodiments, the volume percentage of the compound is 10%-40% based on the total volume of the extracted organic phase, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc. When the compound percentage is within the aforementioned range, excellent separation selectivity and good phase separation performance can be maintained while ensuring uranium extraction efficiency. This balances uranium extraction rate and extraction selectivity, avoiding increased organic phase viscosity and slower phase separation due to excessively high concentrations.

[0032] It is understandable that the volume percentage of the diluent in the extracted organic phase is the total volume percentage of the extracted organic phase minus the percentage of other components. These other components can be compounds, or a combination of compounds and modifiers.

[0033] According to embodiments of this application, the extractable organic phase and the solution are mixed and extracted. In this step, the extractable organic phase can be directly used for the extraction of the solution.

[0034] In some embodiments, the solution further includes coexisting metal ions, including at least one selected from niobium, titanium, iron, and rare earth elements. During the extraction process, the carboxyl and carbonyl groups in the compound form chelate coordination structures with uranyl ions, while steric hindrance inhibits the binding of metal ions to the compound, thereby enabling the selective separation of uranium.

[0035] Specifically, carboxyl and carbonyl groups can form stable chelate structures with uranyl ions, while polynuclear sulfate complexes such as niobium and titanium are difficult to coordinate due to steric hindrance and cannot form stable coordination structures with metal elements such as iron and rare earth elements, thus achieving selective separation of uranium.

[0036] In some embodiments, the sulfuric acid concentration of the solution is 50 g / L to 400 g / L, for example, 50 g / L, 100 g / L, 150 g / L, 200 g / L, 300 g / L, 333 g / L, 350 g / L, 400 g / L, etc. This extractive organic phase can extract acidic solutions and is particularly suitable for uranium extraction from solutions with high sulfuric acid concentrations.

[0037] Furthermore, the sulfuric acid concentration of the solution is 100 g / L to 400 g / L. Thus, the extractable organic phase can be used for the separation and extraction of uranium from solutions with higher sulfuric acid concentrations.

[0038] In some embodiments, the ratio of the extractable organic phase to the solution is 1:5 to 5:1, for example, 1:5, 1:1, 2:1, 3:1, 4:1, 5:1, etc. This allows for an optimized match between extraction efficiency and process economy under different feed conditions.

[0039] Understandably, the concentration of uranium in the feed solution can be flexibly adjusted according to the separation requirements.

[0040] In some embodiments, the extraction is a single-stage extraction or a multi-stage countercurrent extraction. Optionally, the extraction is a multi-stage countercurrent extraction. The number of stages in the multi-stage countercurrent extraction can be determined according to the actual process.

[0041] Optionally, the multi-stage countercurrent extraction has 2 to 5 stages. This further improves the uranium extraction rate and the separation effect between uranium and metal ions.

[0042] In some embodiments, the extraction process can separate uranium and metal ions. The extraction reaction conditions include temperatures ranging from 10°C to 40°C, such as 10°C, 20°C, 25°C, 30°C, 35°C, and 40°C. It is evident that when using an extractant to separate and extract uranium, efficient extraction can be achieved at room temperature, eliminating the need for additional heating or cooling equipment and reducing industrial energy consumption.

[0043] In some embodiments, the extraction time is 1 min to 30 min, such as 1 min, 5 min, 10 min, 15 min, 20 min, 30 min, etc. It can be seen that the extraction can be completed in a short time, that is, the extraction reaction rate of uranium using this extraction organic phase is relatively fast.

[0044] In some embodiments, when the extractable organic phase is used to extract uranium, it can be recycled. Specifically, the uranium-loaded organic phase can be back-extracted using an ammonium fluoride solution, with a back-extraction rate of over 95%. The regenerated organic phase can then be returned to the extraction section for recycling. This improved recycling stability of the extractable organic phase significantly reduces its consumption and operating costs, meeting the needs of continuous industrial production.

[0045] Exemplary embodiments according to this application will now be described in more detail. It should be understood that these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0046] The sources of the substances in the examples are as follows: 4-(di(2-ethylhexyl)amino)-2-oxononanoic acid was prepared as follows: diisooctylamine and hexanal were added to ethanol solvent at a molar ratio of 1:1 at room temperature and reacted at 50°C. Pyruvic acid was added at a molar ratio of 1:1.5. The mixture was refluxed at 85°C for 1 hour. After the reaction was completed, the solvent was removed by rotary evaporation to obtain the crude product. The crude product was extracted with MTBE, acid-washed three times, and after phase separation, the organic phase was dried with anhydrous sodium sulfate and the product was obtained by rotary evaporation.

[0047] CAS number for sulfonated kerosene: 64742-82-1; TBP's CAS number is 126-73-8; N235's CAS number is 68814-95-9; CAS number for P204: 298-07-7.

[0048] Example 1 In this embodiment, the carbonyl acid extractant used is 4-(di(2-ethylhexyl)amino)-2-oxononanoic acid (compound 1). 20 vol% of compound 1 was mixed with 80 vol% sulfonated kerosene to obtain the organic phase (extracted organic phase). The aqueous phase was a complex uranium-niobium sulfuric acid leaching solution with the following composition: U 0.166 g / L, Nb 8.13 g / L, Fe 17.5 g / L, Ti 12.9 g / L, RE 3.62 g / L, Be 0.149 g / L, and the sulfuric acid concentration in the aqueous phase was 3.39 mol / L.

[0049] The two phases were mixed and extracted at room temperature (25°C) with a ratio of O / A = 2:1. The mixture was stirred for 15 min and then allowed to stand to separate the phases.

[0050] After phase separation, the raffinate was collected, and the concentrations of each element were determined by ICP-OES.

[0051] Extraction results: Uranium extraction rate was 81.27%, niobium extraction rate was 0.65%, iron extraction rate was 0.71%, titanium extraction rate was 0.43%, and rare earth extraction rate was 0.13%. It is evident that this extraction method has extremely low extraction rates for organic phases and impurities such as niobium, iron, titanium, and rare earths. It can achieve selective separation of uranium and impurities, with fast phase separation speed, clear phase interfaces, and no emulsification phenomenon.

[0052] Example 2 The organic phase composition was 20 vol% compound 1 + 20 vol% TBP + 60 vol% sulfonated kerosene. The aqueous phase composition was the same as in Example 1.

[0053] The two phases were mixed and extracted at room temperature (25°C) with a phase ratio of O / A = 2:1. The mixture was stirred for 15 min and then allowed to stand for phase separation. The extract was collected after phase separation, and the concentrations of each element were determined by ICP-OES.

[0054] Extraction results: Uranium extraction rate was 55.84%, niobium extraction rate was 0.90%, iron extraction rate was 0.71%, titanium extraction rate was 0.10%, and rare earth extraction rate was 1.26%. Compared with Example 1, the addition of TBP showed an antagonistic effect on CAE extraction of uranium, and the uranium extraction rate decreased, but the phase separation performance was further improved, the extraction rate of impurity elements remained at a low level, and the selectivity remained good.

[0055] Example 3 The organic phase composition was 20 vol% compound 1 + 20 vol% N235 + 60 vol% sulfonated kerosene. The aqueous phase composition was the same as in Example 1.

[0056] The two phases were mixed and extracted at room temperature (25°C) with a phase ratio of O / A = 2:1. The mixture was stirred for 15 min and then allowed to stand for phase separation. After phase separation, the raffinate was collected, and the concentrations of each element were determined by ICP-OES.

[0057] Extraction results: Uranium extraction rate reached 88.43%, niobium extraction rate was 1.18%, iron extraction rate was 0.86%, and titanium extraction rate was 1.10%. This composite system showed good uranium extraction capability, indicating that the introduction of N235 exhibited a certain synergistic effect, increasing the uranium extraction rate.

[0058] Comparative Example 1 The organic phase composition was 20 vol% P2O4 + 80 vol% sulfonated kerosene. Water was the same as in Example 1.

[0059] The two phases were mixed and extracted at room temperature (25°C) with a phase ratio of O / A = 2:1. The mixture was stirred for 15 min and then allowed to stand for phase separation. The extract was collected after phase separation, and the concentrations of each element were determined by ICP-OES.

[0060] Extraction results: Uranium extraction rate 18.07%, niobium extraction rate 8.61%, iron extraction rate 8.00%, titanium extraction rate 10.85%, and rare earth extraction rate 1.41%. The organic phase was turbid, and flocculent matter was present at the interface between the two phases. The phase separation was slow, indicating poor adaptability in high-concentration sulfuric acid media.

[0061] Comparative Example 2 The organic phase composition was 30 vol% TBP + 70 vol% sulfonated kerosene. Water was the same as in Example 1.

[0062] The two phases were mixed and extracted at room temperature (25°C) with a phase ratio of O / A = 2:1. The mixture was stirred for 15 min and then allowed to stand for phase separation. The extract was collected after phase separation, and the concentrations of each element were determined by ICP-OES.

[0063] Extraction results: Uranium extraction rate 22.29%, niobium extraction rate 3.32%, iron extraction rate 5.14%, titanium extraction rate 3.88%, and rare earth extraction rate 1.35%. The phase separation rate is fast and the phase interface is clear, but the uranium extraction rate is low, and there is some co-extraction of iron and titanium. The selectivity cannot meet the separation requirements of complex systems.

[0064] Comparative Example 3 The organic phase composition was 20 vol% N235 + 80 vol% sulfonated kerosene. Water was the same as in Example 1.

[0065] The two phases were mixed and extracted at room temperature (25°C) with a phase ratio of O / A = 2:1. The mixture was stirred for 15 min and then allowed to stand for phase separation. The extract was collected after phase separation, and the concentrations of each element were determined by ICP-OES.

[0066] Extraction results: uranium extraction rate 48.43%, niobium extraction rate 4.18%, iron extraction rate 2.86%, titanium extraction rate 3.10%, and rare earth extraction rate 0.37%. The phase separation rate was fast, but the organic phase showed stratification, with some iron and titanium being entrained. At the same time, a large amount of sulfuric acid was extracted, and the concentration of sulfuric acid in the aqueous phase decreased from 3.3 mol / L to 2.68 mol / L.

[0067] A comparison of the above examples and comparative examples shows that the extractive organic phase of this application can achieve highly efficient and selective extraction of uranium in complex high-acid sulfuric acid media, with extremely low extraction rates for impurities such as niobium, iron, and titanium, and excellent phase separation performance. Although the uranium extraction rate is reduced when combined with TBP (Example 2), the selectivity is maintained, the phase separation is better, and the uranium extraction rate is still significantly higher than that of the comparative example. The extractive organic phase composed of N235, Compound 1, and sulfonated kerosene has a significantly higher uranium extraction rate than that of the comparative example, and can separate uranium and impurity metal ions.

[0068] For the same extraction solution, conventional extractants such as P204, TBP, and N235 suffer from problems such as low extraction rate, poor selectivity, or difficulty in phase separation. Therefore, the extraction organic phase of this application provides a highly efficient and selective technical solution for the separation of uranium from complex uranium-containing polymetallic leachates.

[0069] It should also be noted that the terms "some embodiments," "other embodiments," and "embodiments" used in this application refer to specific features, structures, or characteristics described in connection with those embodiments, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0070] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0071] It should also be noted that the above are merely preferred embodiments of this application and do not limit the scope of protection of this application. Any equivalent structural or procedural transformations made using the content of this application specification, or direct or indirect applications in other related technical fields, are similarly included within the scope of protection of this application.

Claims

1. A method for selectively extracting uranium from a high-concentration sulfuric acid medium, characterized in that, Includes the following steps: An extractable organic phase is provided, the extractable organic phase comprising a compound and a diluent; The organic phase and solution are mixed and extracted, wherein the solution comprises uranium and an acid, and the sulfuric acid concentration of the solution is at least 1 g / L. The compound has the structure shown in Formula I; Formula I, R1, R2, and R3 are each independently selected from any one of the following: straight-chain, branched, or cyclic aliphatic hydrocarbon groups (C3-C18) and aromatic groups (C6-C18). The diluent includes at least one of sulfonated kerosene, aviation kerosene, n-hexane, and cyclohexane.

2. The method according to claim 1, characterized in that, The solution also includes coexisting metal ions, which include at least one of niobium, titanium, iron, and rare earth elements.

3. The method according to claim 1, characterized in that, The ratio of the extracted organic phase to the solution is 1:5 to 5:1; And / or, the extraction is a single-stage extraction or a multi-stage countercurrent extraction.

4. The method according to claim 3, characterized in that, The number of stages in the multi-stage countercurrent extraction is 2 to 5.

5. The method according to claim 1, characterized in that, The sulfuric acid concentration of the solution is 50 g / L to 400 g / L.

6. The method according to claim 1, characterized in that, The extraction temperature is 10℃~40℃, and the time is 1min~30min.

7. The method according to claim 1, characterized in that, The extracted organic phase also includes a modifier, which includes one or more of the following: tributyl phosphate, 2-octanol, tert-butanol, P204, P507, N1923, and N235. And / or, based on the total volume of the extracted organic phase, the volume percentage of the modifier is 1% to 30%.

8. The method according to claim 1 or 7, characterized in that, R1 is selected from any one of straight-chain, branched, or cyclic aliphatic hydrocarbon groups from C3 to C6. R2 and R3 are each independently selected from any one of the straight-chain, branched, or cyclic aliphatic hydrocarbon groups from C3 to C10.

9. The method according to claim 1 or 7, characterized in that, The compound has one of the following structures: 、 。 10. The method according to claim 1 or 7, characterized in that, Based on the total volume of the extracted organic phase, the volume percentage of the compound is 10% to 40%.

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