An extractant and a method for separating scandium from radioactive elements

Abstract

The present application relates to the field of hydrometallurgy, and discloses an extractant and a method for separating and extracting scandium and radioactive elements. An acidic aqueous phase containing scandium and radioactive elements is mixed with an organic phase containing an extractant, and extraction separation is performed to obtain an aqueous phase containing scandium and an organic phase containing radioactive elements; the extractant is any one of the structures shown below; the present application uses a nitrogen-containing heterocyclic extractant, and through solvent extraction, most of the radioactive elements, such as uranium and thorium, can be removed, a high radioactive removal rate is easy to obtain a high-purity scandium oxide product, the loss of scandium is low, the obtained scandium oxide product has a very high added value, the economic benefits of production are improved, the production safety problems caused by possible radioactive accumulation in the production process are reduced, and the production safety is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrometallurgy, in particular to an extractant and a method for separating scandium and radioactive elements by extraction. BACKGROUND

[0002] Scandium element is an important rare earth resource, which is currently widely used in solid fuel cells, high-performance piezoelectric ceramics, electronic information components, new electric light sources, laser materials and medical radioisotopes, etc. The application of these high-tech and high-value-added products benefits from the high purity of scandium raw materials, and the price of commercially available high-purity scandium (>99.999%) is more than 50,000 yuan per kilogram. Therefore, the preparation and separation of high-purity scandium have important industrial significance and economic value.

[0003] Scandium element exhibits different physical and chemical properties from other rare earth elements due to its small ionic radius, and is more likely to be associated with compatible elements (such as Al, Ti, Fe, etc.), which also makes it difficult to enrich scandium alone into ore and distribute very dispersedly. The complex coexistence of elements brings difficulties to the separation and purification of scandium. Currently, the raw materials of scandium products mainly come from mineral residues such as red mud, titanium white, tungsten uranium tailings, etc. Except for special uranium thorium minerals, the content of uranium thorium in natural minerals is very low, but in the process of extracting and processing these minerals, the content of uranium thorium in these residues will reach a concentration that cannot be ignored. The current production of scandium products mainly focuses on the separation of scandium and its compatible elements, but the impurities of uranium and thorium have been ignored, which not only reduces the purity of the product, but also may cause the service life of some electronic components to be greatly reduced or fail due to the radiation generated by the decay of radioactive elements in the product. Therefore, the removal of radioactive elements from scandium products has important research significance.

[0004] CN110961248A discloses a method for separating scandium and uranium from a scandium-containing uranium ore. The mineral is first mechanically crushed to -200 mesh, and then a scandium-containing concentrate is enriched by using a strong magnetic separator, and a uranium-containing tailings is obtained by acid leaching to obtain a uranium-rich acid solution and tailings. This method realizes the combination of selection and smelting by physical-chemical methods, but the purity of the crude scandium and uranium obtained is low, and further purification is still needed to have higher added value.

[0005] CN104263930A discloses a method for extracting and separating uranium / thorium / scandium / zirconium / titanium. The organic phase used in the patent is composed of sulfonated kerosene, tertiary amine N235 and tributyl phosphate (TBP) solution, and the aqueous phase is composed of hydrochloric acid. After one-step extraction, uranium and associated elements thorium, scandium, zirconium and titanium can be separated. This method cannot completely remove radioactive elements because the electronegativity and ionic radius of thorium and scandium are more similar, and the separation is more difficult.

[0006] CN116024443A discloses a method for recovering metallic scandium, which is immersed after treatment of red mud to obtain a scandium-containing solution, and then the scandium in the aqueous phase is extracted with a mixed solution of two extractants P204 and P227, but the content of radioactive uranium and thorium elements is not detected in the method. In the existing reports, P204 also has good extraction effect on uranium and thorium, and the product treated by the method may contain radioactive contamination. SUMMARY

[0007] The present application aims at the problem of incomplete removal of radioactive elements in the preparation process of high-purity scandium, and provides a method for separating and extracting scandium and radioactive elements. The radioactive elements such as uranium and thorium can be almost completely separated from scandium by solvent extraction, so that scandium with higher purity can be obtained.

[0008] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0009] A method for separating and extracting scandium and radioactive elements, which comprises mixing an acidic aqueous phase containing scandium and radioactive elements with an organic phase containing an extractant to obtain an aqueous phase containing scandium and an organic phase containing radioactive elements by extraction and separation; the extractant is any one of the following structures:

[0010]

[0011] wherein R and R' are independently selected from any one of C2-20 straight-chain or branched alkyl, phenyl, tolyl.

[0012] In the present application, the compound containing pyridine amide structure, bipyridine amide structure or phenanthroline amide structure is used as the extractant, which is found to effectively separate scandium from most radioactive elements such as uranium and thorium, has high removal rate of radioactive elements, and has fast separation speed, and can be used for preparing high-purity scandium-containing products. Such nitrogen-containing heterocyclic extractant contains N and O two "soft and hard" coordination sites, has strong selectivity for actinide elements, and makes coordination not too strong, and is easy to be back-extracted and recycled.

[0013] Preferably, R and R' are independently selected from any one of C6-10 straight-chain or branched alkyl, phenyl, tolyl.

[0014] Further preferably, R and R' are independently selected from one or more of n-pentyl, n-hexyl, n-heptyl, n-octyl, phenyl, tolyl, ethylphenyl and cyclohexyl. The active sites of the nitrogen-containing heterocyclic amide extractant involved in coordination are mainly N and O atoms, and the polarity change of the above side chain substituents may affect the extraction effect and the solubility in different solvents, but does not change the extraction rule.

[0015] The radioactive elements include uranium and / or thorium.

[0016] The concentration of scandium element in the acidic aqueous phase is 100 times or more than that of the radioactive element. Preferably, the concentration of scandium element is 100-300 times that of the radioactive element.

[0017] The acidity of the acidic aqueous phase is 0.5-4 M. Preferably, the acidity of the acidic aqueous phase is 1-2.5 M.

[0018] The organic phase is an organic solution containing an extractant, and the organic solvent used includes one or more of F-3, n-octanol, sulfonated kerosene, and n-dodecane.

[0019] Preferably, the molar ratio of the extractant to the uranium and / or thorium element in the organic phase is 10 or more.

[0020] The volume ratio of the acidic aqueous phase to the organic phase is 1:1-5.

[0021] The mixing time is 3 min or more. Preferably, the mixing time is 10-60 min.

[0022] Preferably, oscillation is performed during the mixing, and the oscillation speed is 1500-4000 rpm.

[0023] The method for separating and extracting scandium from radioactive elements further comprises the steps of: mixing the scandium-containing aqueous phase with a new organic phase containing an extractant again for extraction, and repeating the extraction 2-5 times to obtain a scandium-containing aqueous phase. Multiple extractions can remove radioactive elements more completely, and a scandium product with higher purity is obtained.

[0024] The method for separating and extracting scandium from radioactive elements further comprises the steps of: adding oxalic acid or an oxalate to the scandium-containing aqueous phase to adjust the pH to 3-4 to obtain a precipitate, and calcining the precipitate to obtain high-purity scandium oxide.

[0025] The solid-liquid ratio of the oxalic acid or oxalate to the aqueous phase is 1:5-15; after the addition of the oxalic acid or oxalate, heating is performed to 80-90℃; and a common organic or inorganic base such as ammonia is used to adjust the pH.

[0026] The calcination is performed at 800-1000℃ for 2-6 h.

[0027] In the present application, trace radioactive elements such as uranium and thorium can be removed from scandium products, the removal rate of uranium is 99.9-99.99%, and the removal rate of thorium is 99.9-99.99%. The purity of the obtained scandium oxide product is 99.99-99.999%, and the recovery rate of scandium is 90-94%.

[0028] The present application also provides an extractant, which has the following structure:

[0029]

[0030] The application also provides a preparation method of the extractant, comprising the steps of: adding dropwise di-n-octylamine into a solution of 2,6-pyridine dicarboxylic acid chloride under ice bath, and refluxing the reaction after the dropwise addition is completed to obtain the extractant.

[0031] Preferably, the preparation of the extractant is carried out under inert gas protection, the molar ratio of di-n-octylamine to 2,6-pyridine dicarboxylic acid chloride is 1.8-2.2:1, and an acid binding agent is further contained, and the amount of the acid binding agent is a conventional amount.

[0032] The solvent used in the reaction includes dichloromethane, tetrahydrofuran, etc. The reaction is carried out at a solvent reflux temperature for 3-6h. After the product is washed and dried, the product is purified to obtain the product.

[0033] Compared with the prior art, the application has the following beneficial effects:

[0034] The nitrogen-containing heterocyclic extractant is used in the application, and most of the radioactive elements of uranium and thorium can be removed through solvent extraction, the high radioactive removal rate is easy to obtain high-purity scandium oxide product, the loss of scandium is low, the obtained scandium oxide product has high added value, the economic benefit of production is improved, the production safety problem caused by possible radioactive accumulation in the production process is reduced, and the production safety is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The extraction rates of uranium, thorium and scandium under different acidities of the pyridine amide extractant in Example 1. 1 H nuclear magnetic spectrum.

[0036] Figure 2 The extraction rates of uranium, thorium and scandium under different acidities in Example 7. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application. Those skilled in the art can modify or replace the equivalent without departing from the spirit and scope of the application, which should be covered by the protection scope of the application.

[0038] The raw materials used in the following specific embodiments are all purchased from the market, and the aqueous phase used in the examples of the application is a simulated solution of scandium nitrate: uranyl nitrate: thorium nitrate = 100:1:1-300:1:1 (mass ratio). The removal rate and loss are tested and calculated by using the iCAP PRO inductively coupled plasma emission spectrometer of Thermo Fisher Scientific Company. The extraction and separation process is carried out at room temperature.

[0039] Preparation of pyridine amide extractant

[0040] (1) 1 equivalent of 2,6-pyridine acid chloride was dissolved in super dry dichloromethane (DCM) and stirred to dissolve under helium atmosphere and ice water bath;

[0041] (2) 4 equivalents of triethylamine and 2 equivalents of di-n-octylamine (slightly excess) were added dropwise into the mixed solution while stirring;

[0042] (3) After the dropwise addition was completed, the system was warmed to 45°C, refluxed and stirred for 4h;

[0043] (4) After the reaction was completed, the obtained water phase was washed with 100ml dilute hydrochloric acid twice, and then extracted with 50ml dichloromethane twice, and then combined with the organic phase, and dried with anhydrous sodium sulfate for more than 24h;

[0044] (5) The liquid phase was filtered, and the residue was purified by silica gel chromatography column after rotary evaporation, to obtain a pyridine amide extractant product with the following structure, with a yield of 83.5%.

[0045]

[0046] NMR characterization showed that the target structure product was obtained. 1 H NMR as shown in Figure 1 , the target structure product was obtained.

[0047] The simulated feed liquid composition used was 3750ppm Sc 3+ , 40ppm UO2 2+ , 40ppm Th 4+ , 4M perchloric acid, as the water phase to be extracted.

[0048] The pyridine amide extractant was dissolved in F-3 to form a 20mM organic phase, 40mL of the organic phase and 20mL of the water phase were taken and added into a centrifuge tube, and the volume ratio of the organic phase to the water phase in this case was 2:1. The centrifuge tube was placed in a shaker, the shaking speed was 3000rpm, and the shaking time was 20min.

[0049] After the shaking was completed, the water phase was transferred to a new centrifuge tube, and the same organic phase was added again and shaken. The above shaking extraction process was repeated four times.

[0050] The extracted water phase was taken out, 2g of oxalic acid was added and heated to 85°C, and stirred for 4min. After the oxalic acid was completely dissolved, 1M ammonia water was added dropwise, the pH value of the system was adjusted to 3.2, then the heating was turned off, and the precipitation was aged for 24h. The precipitate was filtered, and calcined in a muffle furnace at 900°C for 5h to obtain a high-purity scandium oxide product.

[0051] The removal rate of uranium is 91.92%, the removal rate of thorium is 65.89%, the recovery rate of scandium is 80.3%, and the purity of the obtained scandium oxide product is >92.8%. Among them, the single-stage extraction rate of uranium is about 41.00%, and the single-stage extraction rate of thorium is 19.72%.

[0052] Example 2

[0053] The o-phenanthroline amide extractant used in this example has the structure:

[0054]

[0055] Its source is synthesized according to the preparation method in the literature "Towards understanding the correlation between extraction and substitute groups in 2,9-diamide-1,10-phenanthroline".

[0056] Its preparation process is:

[0057] (1) Under a helium protective atmosphere, dissolve 1 equivalent of 2,9-o-phenanthroline dicarboxylic acid in dichlorosulfide, and continuously stir throughout the process;

[0058] (2) After dissolution is complete, warm to 85°C, continuously stir, reflux, and react for 3h;

[0059] (3) After the reaction is complete, remove excess dichlorosulfide by rotary evaporation under reduced pressure;

[0060] (4) In a helium atmosphere and ice water bath, dissolve the residue in super-dry dichloromethane, and add 4 equivalents of triethylamine and 2 equivalents or more of di-n-octylamine dropwise;

[0061] (5) After the dropwise addition is complete, warm the system to 45°C, reflux, and stir for 4h;

[0062] (6) After the reaction is complete, wash with 100ml of dilute hydrochloric acid twice, extract the obtained aqueous phase with 50ml of dichloromethane twice, and then combine the organic phases, add anhydrous sodium sulfate, and dry for 24h or more;

[0063] (7) Filter to obtain the liquid phase, rotary evaporate, and then purify the residue with a silica gel chromatographic column to obtain the o-phenanthroline amide product, with a yield of 81.2%.

[0064] The simulated feed liquid composition used is 4000ppm Sc 3+ , 40ppm UO2 2+ , 40ppm Th 4+ ​0.5M nitric acid as the aqueous phase to be extracted.

[0065] The phenanthroline amide extractant is dissolved in F-3 to form a 20 mM organic phase. 40 mL of the organic phase and 20 mL of the aqueous phase are added to a centrifuge tube. In this case, the volume ratio of the organic phase to the aqueous phase is 2:1. The centrifuge tube is placed in a shaker, the shaking speed is 2000 rpm, and the shaking time is 20 min.

[0066] After the shaking is completed, the aqueous phase is transferred to a new centrifuge tube, and the same organic phase is added again for shaking. The above shaking extraction process is repeated four times.

[0067] The extracted aqueous phase is removed, 2 g of oxalic acid is added, and heated to 85°C, and stirred for 4 min. After the oxalic acid is completely dissolved, 1M ammonia water is added dropwise, the pH value of the system is adjusted to 3.2, the heating is turned off, and the precipitate is aged for 24 h. The precipitate is filtered and calcined in a muffle furnace at 900°C for 5 h to obtain a high-purity scandium oxide product.

[0068] It is measured that the removal rate of uranium is 99.97%, the removal rate of thorium is 99.93%, the recovery rate of scandium is 90.3%, and the purity of the obtained scandium oxide product is >99.99%. Among them, the single-stage extraction rate of uranium is about 88.53%, and the single-stage extraction rate of thorium is 54.7%.

[0069] Example 3:

[0070] The structure of the phenanthroline amide extractant used in this example is:

[0071]

[0072] Its source is synthesized according to the preparation method in the literature "Towards understanding the correlation between extraction and substitute groups in 2,9-diamide-1,10-phenanthroline".

[0073] Its preparation process is:

[0074] (1) Under a helium protective atmosphere, 1 equivalent of 2,9-phenanthroline dicarboxylic acid is dissolved in dichlorosulfide, and the whole process is continuously stirred;

[0075] (2) After the dissolution is completed, the temperature is raised to 85°C, and the stirring is continued, refluxing, and the reaction is carried out for 3 h;

[0076] (3) After the reaction is completed, the excess dichlorosulfide is removed by rotary evaporation under reduced pressure;

[0077] (4) In a helium atmosphere and ice water bath, the residue was dissolved in super dry dichloromethane, and 4 equivalents of triethylamine and 2 equivalents or more of di-n-octylamine were added dropwise;

[0078] (5) After the dropwise addition was completed, the system was warmed to 45°C, refluxed, and stirred for 4 h;

[0079] (6) After the reaction was completed, the obtained water phase was extracted twice with 50 mL of dichloromethane, and then combined with the organic phase, and anhydrous sodium sulfate was added for drying for 24 h or more;

[0080] (7) The liquid phase was obtained by filtration, and after rotary evaporation, the residue was purified by a silica gel chromatographic column to obtain the phenanthroline amide product, with a yield of 81.2%.

[0081] The simulated feed liquid used was 3000 ppm Sc 3+ , 20 ppm UO2 2+ , 20 ppm Th 4+ , and 2M nitric acid as the water phase to be extracted.

[0082] The phenanthroline amide extractant was dissolved in sulfonated kerosene to form an organic phase of 15 mM, 30 mL of the organic phase and 30 mL of the water phase were taken and added to a centrifuge tube, and in this case, the volume ratio of the organic phase to the water phase was 1:1. The centrifuge tube was placed in a shaker, the shaking speed was 3000 rpm, and the shaking time was 25 min.

[0083] After the shaking was completed, the water phase was transferred to a new centrifuge tube, and the same organic phase was added again and shaken. The above shaking extraction process was repeated four times.

[0084] The extracted water phase was taken out, 2 g of oxalic acid was added and heated to 80°C, and stirred for 5 min. After the oxalic acid was completely dissolved, 1M ammonia water was added dropwise, the pH value of the system was adjusted to 3.5, the heating was turned off, and the precipitate was aged for 24 h. The precipitate was filtered, and calcined in a muffle furnace at 900°C for 5 h to obtain a high-purity scandium oxide product.

[0085] It was measured that in this embodiment, the removal rate of uranium was 99.95%, the removal rate of thorium was 99.91%, the recovery rate of scandium was 92.1%, and the purity of the obtained scandium oxide product was >99.99%. Among them, the single-stage extraction rate of uranium was about 98.62%, and the single-stage extraction rate of thorium was 71.48%.

[0086] Example 4:

[0087] The bipyridine amide extractant used in this embodiment has the following structure:

[0088]

[0089] The source is synthesized according to the preparation method in the literature "Novel diamides of 2,2'-dipyridyl-6,6'-dicarboxylic acid:

[0090] synthesis, coordination properties, and possibilities of use in electrochemical

[0091] sensors and liquid extraction》.

[0092] The preparation process is as follows:

[0093] (1) Under a helium protective atmosphere, 1 equivalent of 2,9-dipyridyl dicarboxylic acid is dissolved in dichlorosulfide, and the whole process is continuously stirred;

[0094] (2) After the dissolution is completed, the temperature is raised to 85°C, continuously stirred, refluxed, and reacted for 3h;

[0095] (3) After the reaction is completed, the excess dichlorosulfide is removed by rotary evaporation under reduced pressure;

[0096] (4) In a helium atmosphere and ice water bath, the residue is dissolved in super-dry dichloromethane, and 4 equivalents of triethylamine and 2 equivalents or more of di-n-octylamine are added dropwise;

[0097] (5) After the dropwise addition is completed, the system is heated to 45°C, refluxed, and stirred for 4h;

[0098] (6) After the reaction is completed, 100ml of dilute hydrochloric acid is washed twice, the obtained aqueous phase is extracted with 50ml of dichloromethane twice, and then combined with the organic phase, and anhydrous sodium sulfate is added and dried for 24h or more;

[0099] (7) The liquid phase is filtered, and after rotary evaporation, the residue is purified by silica gel chromatography column to obtain the dipyridyl amide extractant product, with a yield of 83.4%.

[0100] The simulated feed liquid composition is 3500ppm Sc 3+ , 15ppm UO2 2+ , 15ppm Th 4+ , 3.5M nitric acid, as the aqueous phase to be extracted.

[0101] The dipyridyl amide extractant is dissolved in F-3 to form a 10mM organic phase, 60mL of the organic phase and 15mL of the aqueous phase are taken into a centrifuge tube, and in this case the volume ratio of the organic phase to the aqueous phase is 4:1. The centrifuge tube is placed in a shaker, the shaking speed is 1500rpm, and the shaking time is 15min.

[0102] After the oscillation is completed, the water phase is transferred to a new centrifuge tube, and the same organic phase is added again and oscillated. The above oscillation extraction process is repeated four times.

[0103] The water phase after extraction is taken out, 2 g of oxalic acid is added and heated to 90°C, and stirred for 3 min. After the oxalic acid is completely dissolved, 1M ammonia water is added dropwise, the pH value of the system is adjusted to 3.8, then the heating is turned off, and the precipitate is aged for 24 h. The precipitate is filtered and calcined in a muffle furnace at 900°C for 5 h to obtain a high-purity scandium oxide product.

[0104] The removal rate of uranium is 99.98%, the removal rate of thorium is 99.92%, the recovery rate of scandium is 91.6%, and the purity of the obtained scandium oxide product is >99.99%. Among them, the single-stage extraction rate of uranium is about 94.96%, and the single-stage extraction rate of thorium is 68.58%.

[0105] Example 6:

[0106] The structure of the bipyridylamide extractant used in this example is:

[0107]

[0108] Its source is synthesized according to the preparation method in the literature "Novel diamides of 2,2'-dipyridyl-6,6'-dicarboxylic acid:

[0109] synthesis, coordination properties, and possibilities of use in electrochemical

[0110] sensors and liquid extraction".

[0111] The preparation process is as follows:

[0112] (1) Under a helium protective atmosphere, 1 equivalent of 2,9-bipyridyl dicarboxylic acid is dissolved in dichlorosulfide, and the whole process is continuously stirred;

[0113] (2) After dissolution is completed, the temperature is raised to 85°C, continuously stirred, refluxed, and reacted for 3 h;

[0114] (3) After the reaction is completed, the excess dichlorosulfide is removed by rotary evaporation under reduced pressure;

[0115] (4) In a helium atmosphere and ice water bath, the residue is dissolved in super-dry dichloromethane, and 4 equivalents of triethylamine and 2 equivalents or more of di-n-octylamine are added dropwise;

[0116] (5) After the dropwise addition is completed, the system is warmed to 45°C, refluxed, and stirred for 4 h;

[0117] (6) After the reaction is completed, the resulting aqueous phase is washed twice with 100 ml of dilute hydrochloric acid, extracted twice with 50 ml of dichloromethane, and then combined with the organic phase, and dried with anhydrous sodium sulfate for 24 h or more;

[0118] (7) The liquid phase is filtered, and the residue is purified by silica gel chromatography to obtain the bipyridine amide product, with a yield of 83.4%.

[0119] The simulated feed liquid composition used was 3800 ppm Sc 3+ , 10 ppm UO2 2+ , 10 ppm Th 4+ , and 4M nitric acid as the aqueous phase to be extracted.

[0120] The bipyridine amide extractant is dissolved in F-3 to form a 10 mM organic phase, 60 mL of the organic phase and 12 mL of the aqueous phase are added to a centrifuge tube, and in this case, the volume ratio of the organic phase to the aqueous phase is 5:1. The centrifuge tube is placed in a shaker, the shaking speed is 4000 rpm, and the shaking time is 5 min.

[0121] After the shaking is completed, the aqueous phase is transferred to a new centrifuge tube, and the same organic phase is added again and shaken. The above shaking is repeated four times.

[0122] The extracted aqueous phase is removed, 2 g of oxalic acid is added and heated to 88°C, and stirred for 3 min. After the oxalic acid is completely dissolved, 1M ammonia water is added dropwise, the pH of the system is adjusted to 3.7, the heating is turned off, and the precipitate is aged for 24 h. The precipitate is filtered, and calcined in a muffle furnace at 900°C for 5 h to obtain a high-purity scandium oxide product.

[0123] It is measured that the removal rate of uranium is 99.99%, the removal rate of thorium is 99.94%, the recovery rate of scandium is 90.5%, and the purity of the obtained scandium oxide product is >99.99%. Among them, the single-stage extraction rate of uranium is about 97.63%, and the single-stage extraction rate of thorium is 85.02%.

[0124] Example 7

[0125] According to the extraction and separation process of Example 1, in order to explore the separation conditions of the three, a lower molar ratio is used to explore the separation conditions of the three. In this example, the molar ratio of uranium: thorium: scandium is 1:1:5. The concentration of nitric acid is adjusted to 1M, 1.5M, 2M, and 2.5M, and other conditions remain unchanged. After the extraction is completed, the extraction rates of uranium, thorium, and scandium are calculated, and the extraction rate calculation method is: i - C a / C i * 100%.

[0126] where C i : concentration of metal ions in the aqueous phase before extraction; C a : concentration of metal ions in the aqueous phase after extraction, the concentrations were measured by ICP-OES.

[0127] The results are shown in Table 1. Figure 2 As can be seen from Table 1, the extraction rates of the three elements all show an increasing trend with the increase of acidity in the range of 1-2.5 M. However, the extraction rates and the rising speed of uranium and thorium are significantly higher than that of scandium at low acidity, and the extraction rates of scandium and uranium / thorium differ greatly, which is more conducive to the efficient separation of uranium, thorium and scandium.

Claims

1. A method for separating scandium from radioactive elements by solvent extraction, characterized in that, Mixing the acidic aqueous phase containing scandium and radioactive elements with the organic phase containing extractant, and separating by extraction to obtain the aqueous phase containing scandium and the organic phase containing radioactive elements; the extractant is any one of the following structures: Wherein, R and R' are independently selected from any one of C6-10 straight chain or branched alkyl, phenyl, toluene.

2. The method of separating scandium from radioactive elements according to claim 1, characterized by, The radioactive elements include uranium and / or thorium; And / or, the molar concentration of scandium in the acidic aqueous phase is more than 100 times of the molar concentration of radioactive elements.

3. The method of separating scandium from radioactive elements according to claim 1, characterized by, The acidity of the acidic aqueous phase is 0.5-4M.

4. The method of separating scandium from radioactive elements according to claim 1, wherein The organic phase containing extractant is an organic solution containing extractant, and the organic solvent used includes one or more of F-3, n-octanol, sulfonated kerosene, n-dodecane; And / or, the molar ratio of extractant to uranium and / or thorium in the organic phase containing extractant is more than 10.

5. The method of separating scandium from radioactive elements according to claim 1, wherein The volume ratio of the acidic aqueous phase to the organic phase containing extractant is 1:1-5; And / or, the mixing time is more than 3min.

6. The method of separating scandium from radioactive elements according to claim 1, wherein Further comprising the step of: mixing the aqueous phase containing scandium with new organic phase containing extractant again for extraction, repeating 2-5 times to obtain the aqueous phase containing scandium.

7. The method of separating scandium from radioactive elements according to claim 1, wherein Adding oxalic acid or oxalate to the aqueous phase containing scandium to adjust the pH to 3-4 to obtain a precipitate, and calcining the precipitate to obtain high-purity scandium oxide.

8. An extractant characterized in that, The extractant structure is as follows:

9. The method of claim 8, wherein the extraction agent is prepared by, Comprising the step of: adding di-n-octylamine dropwise to a solution of 2,6-pyridine dicarboxylic chloride under ice bath, and refluxing after the end of dropwise addition to obtain the extractant.

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