Method for extracting thorium by using a chromotropic acid-bis-water phase system

Abstract

This invention relates to the field of radionuclide pollution control technology, and in particular to a method for extracting thorium using a chromotropic acid-aqueous two-phase system. The method involves adding a ligand, a salting-out agent, and an extractant to thorium-containing wastewater, mixing them thoroughly, adjusting the pH of the mixture to induce phase separation, resulting in a thorium-rich upper organic phase and a lower aqueous phase containing inorganic salts. The thorium-rich upper organic phase is then taken, and the pH is adjusted to induce phase separation again. The upper layer contains recyclable chromotropic acid and the extractant, while the lower layer is a thorium hydroxide precipitate obtained through back-extraction. The thorium hydroxide precipitate is then taken and calcined under nitrogen protection to obtain thorium oxide. The ligand is chromotropic acid; the salting-out agent includes any one or more of sulfates, halide salts, and silicates; and the extractant includes any one or more of ethanol, propanol, chloroform, acetone, and benzene. This invention has broad application prospects in the field of separation, enrichment, recovery, and determination of the long-lived, highly soluble, and biotoxic radionuclide thorium.

Description

Technical Field

[0001] This invention relates to the field of radionuclide pollution control technology, and in particular to a method for extracting thorium using a chromotropic acid-aqueous two-phase system. Background Technology

[0002] Thorium is widely distributed in the Earth's crust, with an abundance three to four times that of uranium. It is a potential nuclear fuel, and its decay releases far more energy than uranium, coal, oil, and other fuels combined. Furthermore, thorium is a safer nuclear fuel than uranium and represents the future direction of nuclear energy development.

[0003] Thorium compounds are lithophile elements, primarily in the +4 valence state. They can hydrolyze into precipitates in aqueous solutions, and precipitation also occurs under low pH conditions. Furthermore, thorium ions can be precipitated by Fe(OH)3 and Al(OH)3. Their chemical properties are similar to those of zirconium (Zr) and hafnium (Hf). Thorium is a radioactive element and exists in nature as a radioactive element. 232 Th has a half-life of approximately 1.4 × 10⁻⁶. 10 In 1948, after being bombarded with neutrons, we obtained... 233 U.

[0004] The development and utilization of rare earth resources has resulted in large-scale waste rock dumps and tailings ponds. The unextracted thorium in these dumps, under the influence of microorganisms and acid rain, will form thorium-rich leachate. As wet firewood, thorium is a potentially valuable energy source that can be recycled to alleviate the environmental pollution crisis caused by fossil fuels. However, due to the large volume, long lifespan, easy migration, and radioactivity of thorium-containing leachate, it poses a significant threat to the ecological environment.

[0005] The thorium-containing acid leaching solution, originating from a uranium mine waste rock dump and tailings in northern Guangdong, contains not only Th but also abundant Sr, Pb, Ba, Ra, Ba, NH3, Na, K, Si, Mg, and Ca. Located in a tropical and subtropical region with abundant rainfall, the mine often contains stagnant water in its ore piles, slag heaps, and open-pit mines, or a mixture of mining water and groundwater. Due to the presence of H2O, O2, and H... + The acidic wastewater participates in the oxidation of sulfide minerals, causing continuous leaching of the ore. This acidic wastewater is a major carrier of toxic heavy metal ion pollutants from uranium mines, leading to the migration of radioactive thorium with rainwater. Thorium concentrations exceed 2 mg / L, 2-3 orders of magnitude higher than industrial emission standards, making it a significant source of radioactive pollution in mines. Therefore, effectively separating thorium from tailings wastewater can reduce tailings pollution, enable the utilization of thorium resources in tailings, and help alleviate the increasingly strained nuclear fuel supply.

[0006] Thorium typically forms ores together with other rare metals; therefore, the key to preparing high-purity thorium products lies in the efficient and selective separation of thorium from thorium-containing mixed ions. In existing technologies, the extraction efficiency of thorium from mine wastewater using reagents such as alcohols, acetone, and benzene is very low, with almost no extraction effect; specific ligands are required in conjunction.

[0007] Existing thorium extraction processes primarily utilize the Thorex process, which involves the non-coordinated electron pairs (P=O) of organophosphine bonds and the protonation of alkylamines ([R3NH)). + Thorium can be combined to form hydrophobic extracts that dissolve in organic phases such as alcohols, chloroform, acetone, and aromatics to improve its extraction performance. While the Thorex process is widely used for extracting thorium from highly radioactive waste, it is susceptible to interference from various coexisting components. Furthermore, the use of polymers easily leads to emulsification or the formation of a three-phase mixture (a second organic phase between the organic and aqueous phases), resulting in a low thorium distribution ratio and separation coefficient between the two phases. Consequently, thorium cannot be completely separated, and its concentration remains at ppm, causing resource waste and threatening ecological security. Therefore, a new challenge arises for ppm-level thorium extraction methods.

[0008] Currently, the academic community has conducted relevant research, mainly including the modification of the structure of organophosphorus and alkylamine extractants, the development of new ligands, and the matching separation process. However, many shortcomings and challenges still exist. For example, some scholars have attempted to improve the phase separation performance of organophosphorus and alkylamine extractants by using their homologues and phosphonamide complexing ligands as thorium coordinating agents. Although this has slightly improved the separation performance of thorium in breeder reactor nuclear fuel, the thorium extraction process still suffers from insufficient selectivity: on the one hand, the steric hindrance effect of the extractant is ignored, leading to a reduction in the matching coordination effect of thorium; on the other hand, it focuses too much on the upper limit of thorium extraction, but the interference of impurity ions limits the thorium extraction to only ppm level. Therefore, due to the steric hindrance effect of ligands, the interference of coexisting media, and the high selectivity requirement for thorium, it is not suitable for the actual situation of thorium separation in complex mine wastewater.

[0009] Furthermore, existing separation methods for thorium separation focus excessively on the steric hindrance effect, structural strength, and active sites of functional ligands. Previous studies on thorium extraction from breeder reactor nuclear fuel used di(2-ethylhexyl)phosphoric acid and tributyl phosphate as complexing agents, and alcohols, acetone, and xylene as extractants. While these methods extracted some thorium from high-level radioactive waste, they were subject to interference from various coexisting components, and the extractants were prone to emulsification, resulting in residual thorium at the ppm level in the raffinate. Other methods for separating scandium and thorium, such as the chloroform method and the P350-sulfonated kerosene method, combined with organic reagents like ethanol, ether, and methanol, transfer scandium and thorium into the organic phase for separation. However, these methods are designed for high-level radioactive waste containing thorium in nitric acid systems, and the raffinate still contains 0.1% thorium after extraction. In the earlier invention patent CN 112939132B, a method was proposed for treating similar thorium-containing wastewater, using citrate as a salting-out agent, halide salts as a coordinating agent, and polyethylene glycol as an extractant. While this effectively improved the extraction efficiency of strontium and thorium, citrate or chlorosalts did not overcome the limitations of strontium extraction. 2+ Pb 2+ Ba 2+ Ra 2+ Ba 2+ and Ca 2+ Interference from coexisting ions, and the fact that the use of high polymer polyethylene glycol is prone to emulsification or the formation of three phases, meant that the early inventions for extracting thorium from mine wastewater still lacked a dynamic matching interface with efficient decontamination, anti-emulsification and acid resistance.

[0010] In view of this, the present invention is proposed. Summary of the Invention

[0011] The purpose of this invention is to provide a method for extracting thorium using a chromotropic acid-aqueous two-phase system. This method enhances the extraction selectivity and extraction capacity of thorium, achieving the goal of efficient and highly selective separation of thorium.

[0012] This invention provides a method for extracting thorium using a chromotropic acid-aqueous two-phase system, comprising the following steps:

[0013] S1. Add a complexing agent, a salting-out agent, and an extractant to the thorium-containing wastewater, mix them evenly, adjust the pH of the mixture to separate the phases, and obtain an upper organic phase rich in thorium and a lower aqueous phase containing inorganic salts.

[0014] S2. Take the thorium-rich upper organic phase, adjust the pH to separate the phases, wherein the upper layer is the recyclable chromotropic acid and extractant, and the lower layer is the thorium hydroxide precipitate obtained by back-extraction.

[0015] S3. Take the thorium hydroxide precipitate and calcine it under nitrogen protection to obtain thorium oxide;

[0016] The ligand is chromotropic acid;

[0017] The salting-out agent includes any one or more of sulfates, halide salts, and silicates;

[0018] The extractant includes any one or more of ethanol, propanol, chloroform, acetone, and benzene.

[0019] This invention utilizes a chromotropic acid ligand capable of accurately identifying thorium ions, a salting-out agent with anti-interference effects on multiple components, and a low-molecular-weight extractant that easily separates into phases to construct a chromotropic acid-aqueous two-phase system involving a low-molecular-weight organic extractant. In this system, Th in wastewater... 4+ With chromotropic acid (C 10 H8O8S2) combines to form Th(C) 10 H6O8S2)2, this associative compound has strong hydrophobicity, and therefore can be easily partitioned to the upper layer by the salting-out agent-extractant aqueous two-phase system. The Th(C) group partitioned to the upper layer... 10 H6O8S2)2 can form thorium hydroxide precipitate under certain acidity. The hydroxide precipitate is then calcined to obtain thorium oxide, which can then be used to recover thorium from wastewater.

[0020] The salting-out agent includes any one or more of sulfates, halide salts, and silicates, which can remove coexisting interfering ions and improve thorium ion selectivity. The extractant includes any one or more of ethanol, propanol, chloroform, acetone, and benzene. The aqueous two-phase carrier composed of inorganic salts and small molecule organic extractants can provide a highly efficient decontamination, anti-emulsification, and anti-acid interface during thorium separation, thereby enhancing the extraction selectivity and extraction capacity of thorium, and thus achieving the goal of efficient and highly selective separation of thorium.

[0021] The thorium-containing wastewater targeted by this invention is complex mine thorium wastewater containing ppm levels, specifically thorium-containing wastewater with a thorium concentration of less than or equal to 10 mg / L.

[0022] Studies have shown that in step S1, when the molar concentration of the ligand is 0.01-0.035 mol / L, the mass fraction of the salting-out agent is 7-15%, and the mass fraction of the extractant is 8-12%, the constructed chromotropic acid-aqueous two-phase system exhibits the highest separation and extraction efficiency for thorium.

[0023] In a preferred embodiment of this technical solution, in step S1, the pH of the mixture is adjusted to 0-3.

[0024] At an acidity level of 0-3, thorium and chromotropic acid in water couple to form Th(C)2. 10 H6O8S2)2, and extracted by a sulfate-low molecular weight organic reagent aqueous two-phase system:

[0025]

[0026] In a preferred embodiment of this technical solution, in step S2, the pH is adjusted to 9-10.

[0027] The extracted thorium (IV) is separated by re-entering the lower aqueous phase at a pH of 9-10, while the extractant remains in the organic phase and can be regenerated.

[0028]

[0029] As a preferred embodiment of this technical solution, hydrochloric acid or ammonia solution is used to adjust the pH value, and the concentration of the saline or ammonia solution is 0.1-1 mol / L.

[0030] As a preferred embodiment of this technical solution, in step S3, the calcination temperature is controlled at 500-600℃ and the time is 3-5h, preferably calcined at 500℃ for 4h.

[0031] Studies have shown that the chromotropic acid-aqueous two-phase system constructed in this invention is fully applicable to thorium-containing wastewater containing organic matter, organic complexes, and coexisting ions. The organic matter includes humic substances, the organic complexes include diethyltriaminepentaacetic acid, citric acid, oxalic acid, and ethylenediaminetetraacetic acid, and the ions include Sr... 2+ Pb 2+ Ba 2+ Ra 2+ Ba 2+ NH4 + Na + K + SiO3 2- Mg 2+ and Ca 2+ The presence of the above substances does not interfere with the phase separation of thorium at all. This is due to the strong coordination properties of thorium ions and chromotropic acid, as well as the anti-interference and strong phase separation capabilities of sulfate and low-molecular-weight organic reagents as aqueous two-phase carriers.

[0032] The method for extracting thorium using the chromotropic acid-aqueous two-phase system of the present invention has at least the following technical effects:

[0033] 1. This invention utilizes the strong coordination properties of thorium ions and chromotropic acids, as well as the anti-interference and strong phase separation capabilities of the aqueous two-phase carrier composed of salting-out agent and extractant, to form a clearly defined interface between a thorium-rich organic phase and an inorganic salt phase. Specifically, Th in wastewater... 4+ and chromotropic acid (C 10 H8O8S2) combines to form Th(C) 10 H6O8S2)2, this associative compound has strong hydrophobicity, and therefore can be easily partitioned to the upper layer by the salting-out agent-extractant aqueous two-phase system. The Th(C) group partitioned to the upper layer... 10H6O8S2)2 can form thorium hydroxide precipitate under certain acidity, thereby realizing the recovery of thorium from wastewater;

[0034] 2. This invention proposes a method to improve thorium ion selectivity by removing coexisting interfering ions using an inorganic salt salting-out agent. Based on this, a highly efficient detergency, deemulsification, and acid-resistant interface is constructed, enhancing the extraction selectivity and extraction capability of thorium, and achieving the goal of efficient and highly selective separation of thorium. Specifically, the salting-out agent of this invention includes any one or more of sulfates, halide salts, and silicates, preferably sulfates, which can effectively remove Sr in the form of sulfate precipitation. 2+ Pb 2+ Ba 2+ Ra 2+ Ba 2+ and Ca 2+ Interference from coexisting ions;

[0035] 3. This invention avoids the use of highly toxic organic solvents or easily emulsified polymers, and has broad application prospects in the field of separation, enrichment, recovery and determination of radionuclides thorium with long lifespan, high solubility and biotoxicity.

[0036] 4. The chromotropic acid, salting-out agent, and extractant used in this invention can all be recycled and reused, which greatly reduces the cost of thorium recovery and the pollution caused by reagent discharge to the environment. It is an environmentally friendly, convenient, low-cost, efficient, and highly selective method for separating and recovering thorium from wastewater, which solves the problems of mine wastewater pollution and thorium resource utilization, and enriches the basic theory of aqueous two-phase extraction for thorium separation and its application in the post-treatment of mine wastewater. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a flowchart of the chromotropic acid-aqueous two-phase system for thorium extraction according to the present invention;

[0039] Figure 2 This is a schematic diagram illustrating the selection of salting-out agents in the aqueous two-phase system of the present invention, wherein a is sodium chloride, b is sodium silicate, and c is sodium sulfate;

[0040] Figure 3 The present invention relates to the ultraviolet-visible spectroscopic analysis of chromotropic acid-thorium ions;

[0041] Figure 4The spectrophotometer of this invention is used to measure Th. 4+ Concentration standard curve;

[0042] Figure 5 This invention illustrates the effect of different amounts of chromotropic acid on the testing of thorium ions.

[0043] Figure 6 The UV-Vis spectra of thorium ions and chromotropic acid mixtures at different pH values ​​are shown in this invention. Detailed Implementation

[0044] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0045] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0046] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Prepare the following simulated thorium-containing wastewater solution for the following experiment:

[0048] Thorium concentration was 10 mg / L, humic substances, diethyltriaminepentaacetic acid, citric acid, oxalic acid, ethylenediaminetetraacetic acid, and coexisting Sr ions. 2+ Pb 2+ Ba 2+ Ra 2+ Ba 2+ NH4 + Na + K + SiO3 2- Mg 2+ and Ca 2+ The concentration of each was 60 mmol / L.

[0049] Example 1

[0050] S11. Add chromotropic acid, sodium sulfate and ethanol to the thorium-containing wastewater, mix well, adjust the pH of the mixture to 0-3, and separate the phases to obtain an upper organic phase rich in thorium and a lower aqueous phase containing inorganic salts.

[0051] S12. Take the thorium-rich upper organic phase, adjust the pH to 9-10, and separate the phases. The upper layer is the recyclable chromotropic acid and extractant, and the lower layer is the thorium hydroxide precipitate obtained by back-extraction.

[0052] S13. Take the thorium hydroxide precipitate and calcine it at 500℃ for 4 hours under nitrogen protection to obtain thorium oxide;

[0053] The concentration of chromotropic acid is 0.02 mol / L, the mass fraction of sodium sulfate is 10%, and the mass fraction of ethanol is 10%.

[0054] Example 2

[0055] S21. Add chromotropic acid, sodium sulfate and ethanol to the thorium-containing wastewater, mix well, adjust the pH of the mixture to 0-3, and separate the phases to obtain an upper organic phase rich in thorium and a lower aqueous phase containing inorganic salts.

[0056] S22. Take the upper organic phase rich in thorium, adjust the pH to 9-10, and separate the phases. The upper layer is the recyclable chromotropic acid and extractant, and the lower layer is the thorium hydroxide precipitate obtained by back-extraction.

[0057] S23. Take the thorium hydroxide precipitate and calcine it at 500℃ for 4 hours under nitrogen protection to obtain thorium oxide;

[0058] The concentration of chromotropic acid is 0.01 mol / L, the mass fraction of sodium sulfate is 7%, and the mass fraction of ethanol is 8%.

[0059] Example 3

[0060] S31. Add chromotropic acid, sodium sulfate and ethanol to thorium-containing wastewater, mix well, adjust the pH of the mixture to 0-3, and separate the phases to obtain an upper organic phase rich in thorium and a lower aqueous phase containing inorganic salts.

[0061] S32. Take the upper organic phase rich in thorium, adjust the pH to 9-10, and separate the phases. The upper layer is the recyclable chromotropic acid and extractant, and the lower layer is the thorium hydroxide precipitate obtained by back-extraction.

[0062] S33. Take the thorium hydroxide precipitate and calcine it at 500℃ for 4 hours under nitrogen protection to obtain thorium oxide;

[0063] The concentration of chromotropic acid is 0.035 mol / L, the mass fraction of sodium sulfate is 15%, and the mass fraction of ethanol is 12%.

[0064] Compare with Example 1

[0065] The ethanol in Example 1 was replaced with polyethylene glycol 1000 / polyethylene glycol 6000, and the rest was basically the same as in Example 1.

[0066] Compare with Example 2

[0067] The sodium sulfate in Example 1 was replaced with sulfuric acid, and everything else was basically the same as in Example 1.

[0068] This invention uses a UV-Vis spectrophotometer to detect the concentration of thorium in different solutions and calculates the extraction rate or back-extraction rate of thorium according to the following formula. The test results are shown in Table 1.

[0069] The extraction rate or back-extraction rate is calculated as follows: E(%) = (C0 - C t )*100 / C0, where C0 is the initial concentration, mg / L; C t The concentration of the lower layer after extraction equilibrium is expressed in mg / L.

[0070] Table 1 shows the extraction rates of thorium in Examples 1-3 and Comparative Examples 1-2.

[0071]

[0072] As shown in Table 1, the method for extracting thorium using the chromotropic acid-aqueous two-phase system of the present invention can efficiently and selectively separate and recover thorium from wastewater, with an extraction rate of 87.26-99.99%.

[0073] In Comparative Example 1, polyethylene glycol is prone to emulsification or the formation of three phases during phase separation, which is detrimental to the separation and extraction of thorium from wastewater. In Comparative Example 2, although the introduction of sulfate ions can also overcome the Sr... 2+ Pb 2+ Ba 2+ Ra 2+ Ba 2+ and Ca 2+ The interference of coexisting ions is mitigated, but because sulfuric acid cannot form an aqueous two-phase extraction system with ethanol, the amount of extractant is insufficient, and only 10 mg / L of thorium can be partially extracted.

[0074] Experimental Example 1

[0075] According to the cloud point method, 10 mL of 10% ethanol was fixed, and its phase separation ability was investigated by adding the same amount of salts (NaCl, Na2SO4, Na2SiO3).

[0076] Depend on Figure 2It can be seen that only Na2SO4 and Na2SiO3 can cause phase separation in an 8% ethanol solution, and under equal conditions, the order of their ability to reach the cloud point is Na2SO4 > Na2SiO3 > NaCl.

[0077] When the amount of Na2SO4 is 7-15%, the solution separates into layers quickly, and the upper phase is relatively clear. This indicates that the required salt concentration for Na2SO4 phase separation is low, and the interface is clear. Since some of the salting-out agent enters the organic phase as the concentration increases, thereby reducing the concentration of the free extractant and hindering extraction, the optimal dosage of Na2SO4 used in this invention is 8%.

[0078] Na+ and SO4 2- It has no interfering effect on the extraction of Th(Ⅳ) in acid leaching solutions, making it suitable as a common salting-out agent in aqueous two-phase extraction systems, and effectively removing Sr. 2+ Pb 2+ Ba 2+ Ra 2+ Ba 2+ and Ca 2+ Interference from plasma. Therefore, sodium sulfate is preferred as the salting-out agent in the aqueous two-phase extraction system of thorium in the acid leaching solution of the present invention.

[0079] Experimental Example 2

[0080] The phase separation capabilities of combinations of ethanol, propanol, chloroform, acetone, benzene, and sodium sulfate were investigated using the cloud point method.

[0081] When the sodium sulfate concentration is fixed, the phase separation ability of the extractant is in the order of ethanol >> propanol > chloroform > acetone > benzene. When the optimal dosage of Na₂SO₄ is 8%, the preferred extractant mass fraction for forming an aqueous two-phase system with ethanol is 8-12%. Furthermore, the optimal extraction system is chromotropic acid-ethanol-sodium sulfate.

[0082] Experimental Example 3

[0083] The concentration of thorium ions was measured by UV-Vis spectrophotometry using azoarsin III as an indicator, and the concentration of chromotropic acid as a thorium ion ligand was investigated.

[0084] like Figure 3 It can be seen that azoarsine III has a characteristic peak at 531 nm, while chromotropic acid does not have an obvious characteristic peak. After thorium ions are coordinated by chromotropic acid, two significant characteristic peaks appear at 531 nm and 662 nm under the action of azoarsine III indicator.

[0085] This invention establishes a standard curve for testing thorium ion concentration using ultraviolet-visible spectroscopy, with a characteristic peak at 662 nm. Figure 4The mixture was thoroughly mixed with ethanol and sodium sulfate (ethanol mass fraction 10%, sodium sulfate mass fraction 8%). Results showed that chromotropic acid concentrations greater than 0.035 mol / L masked the indicator's chromatographic peak; therefore, a chromotropic acid concentration of 0.01–0.035 mol / L was most favorable for thorium ion extraction. Figure 5 ).

[0086] Test Example 4

[0087] Take 30 mL of wastewater into several centrifuge tubes, add ethanol and sodium sulfate to each centrifuge tube respectively, and mix well (wherein, the mass fraction of ethanol in the mixture is 10%, the mass fraction of sodium sulfate is 8%, and the molar concentration of chromotropic acid is 0.01 mol / L), and investigate the effect of acidity on the extraction of thorium ions.

[0088] The results showed that, under the same conditions, pH values ​​from 0 to 8 were favorable for the extraction of thorium ions. However, because thorium ions hydrolyze more rapidly at pH > 3, forming thorium hydroxide complexes or precipitates, the extraction effect is inhibited. Therefore, the preferred pH value for thorium extraction in this invention is 0-3.

[0089] Experimental Example 5

[0090] Based on the above, thorium-containing wastewater (with a thorium concentration below 10 mg / L) from a mining plant in Shaoguan, Guangdong Province, was extracted. The wastewater contained Sr ions. 2+ Pb 2+ Ba 2+ Ra 2+ Ba 2+ NH 4+ Na + K + SiO3 2- Mg 2+ , and Ca 2+ The concentration was 60 mmol / L. 30 mL of wastewater was taken into several centrifuge tubes (pH = 0-3) to investigate the effect of coexisting ions on the extraction of thorium ions. The results are shown in Table 2.

[0091] Table 2. Effects of coexisting ions

[0092]

[0093]

[0094] Table 2 shows that the chromotropic acid-sodium sulfate-ethanol system can enable Th 4+ In coexisting ions such as Sr 2+ Pb 2+ Ba 2+ Ra 2+Ba 2+ NH4 + Na + K + SiO3 2- Mg 2+ and Ca 2+ It was well separated.

[0095] Experimental Example 6

[0096] Based on the above, the effects of coexisting humic acid (HA), diethyltriaminepentaacetic acid (DTPA), citric acid (CA), oxalic acid (OX), and ethylenediaminetetraacetic acid (EDTA) on the extraction of thorium were investigated. The concentrations of the above organic matter and organic complexes were all 60 mmol / L. The results are shown in Table 3.

[0097] Table 3. The Influence of Organic Matter

[0098] Organic matter system <![CDATA[Th 4+ Extraction rate <![CDATA[Th 4+ -HA]]> 96.10 <![CDATA[Th 4+ -DTPA]]> 97.22 <![CDATA[Th 4+ -CA]]> 96.21 <![CDATA[Th 4+ -OX]]> 97.52 <![CDATA[Th 4+ -EDTA]]> 97.61

[0099] Table 3 shows that the chromotropic acid-sodium sulfate-ethanol system can enable Th 4+ It was well separated in humic substances (HA), diethyltriaminepentaacetic acid (DTPA), citric acid (CA), oxalic acid (OX), and ethylenediaminetetraacetic acid (EDTA).

[0100] In summary, this invention utilizes the strong coordination properties of thorium ions and chromotropic acid, as well as the anti-interference and strong phase separation capabilities of the aqueous two-phase carrier composed of salting-out agent and extractant, to construct a highly efficient decontamination, anti-emulsification, and anti-acid interface, thereby enhancing the extraction selectivity and extraction capability of thorium and achieving the goal of efficient and highly selective separation of thorium.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for extracting thorium using a chromotropic acid-aqueous two-phase system, characterized in that, Includes the following steps: S1. Add chromotropic acid, sodium sulfate and ethanol to thorium-containing wastewater containing organic matter, organic complexes and coexisting ions. After mixing evenly, adjust the pH of the mixture to 0-3 to separate the phases and obtain an upper organic phase rich in thorium and a lower aqueous phase containing inorganic salts. S2. Take the thorium-rich upper organic phase, adjust the pH to 9-10 to separate the phases. The upper layer contains recyclable chromotropic acid and extractant, and the lower layer contains thorium hydroxide precipitate obtained by back-extraction. S3. Take the thorium hydroxide precipitate and calcine it under nitrogen protection to obtain thorium oxide; The organic matter in the thorium-containing wastewater includes humic substances, organic complexes including diethyltriaminepentaacetic acid, citric acid, oxalic acid, and ethylenediaminetetraacetic acid, and coexisting ions including Sr. 2+ Pb 2+ Ra 2+ Ba 2+ NH4 + Na + K + SiO3 2- Mg 2+ and Ca 2+ .

2. The method for extracting thorium using a chromotropic acid-aqueous two-phase system according to claim 1, characterized in that, The concentration of thorium in the thorium-containing wastewater is less than or equal to 10 mg / L.

3. The method for extracting thorium using a chromotropic acid-aqueous two-phase system according to claim 1, characterized in that, In step S1, the molar concentration of the chromotropic acid in the mixture is 0.01-0.035 mol / L.

4. The method for extracting thorium using a chromotropic acid-aqueous two-phase system according to claim 1, characterized in that, In step S1, the mass fraction of sodium sulfate in the mixture is 7-15%.

5. The method for extracting thorium using a chromotropic acid-aqueous two-phase system according to claim 1, characterized in that, In step S1, the mass fraction of ethanol in the mixture is 8-12%.

6. The method for extracting thorium using a chromotropic acid-aqueous two-phase system according to claim 1, characterized in that, When adjusting the pH value, use hydrochloric acid or ammonia solution, and the concentration of hydrochloric acid or ammonia solution is 0.1-1 mol / L.

7. The method for extracting thorium using a chromotropic acid-aqueous two-phase system according to claim 1, characterized in that, In step S3, the calcination temperature is controlled at 500-600℃ and the time is 3-5h.

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