A method for removing thorium from lutetium-containing liquid

Abstract

The invention belongs to the technical field of hydrometallurgy, and in particular relates to a method for removing thorium from a lutetium-containing liquid. The invention provides a method for removing thorium from a lutetium-containing liquid, comprising the following steps: extracting the lutetium-containing liquid with a metal extract to obtain an organic phase; the volume ratio of the metal extract to the lutetium-containing liquid is 5-10:1; mixing the organic phase with a hydrochloric acid solution for back extraction to obtain an aqueous phase; the molar concentration of the hydrochloric acid solution is 6.3-6.7 mol / L, and the volume ratio of the organic phase to the hydrochloric acid solution is 5-10:1; mixing the aqueous phase with an oxalic acid solution for precipitation to obtain a crude lutetium oxalate product; the mixing is carried out under stirring conditions, the stirring temperature is 58-62°C, and the stirring speed is 100-200 r / min; washing the crude lutetium oxalate product to obtain lutetium oxalate; the washing solvent is a mixed solution of ammonium oxalate solution and ethanol; the mass ratio of the crude lutetium oxalate product to the solvent is 1:3-5; and calcining the lutetium oxalate to obtain lutetium oxide.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a method for removing thorium from a lutetium-containing liquid. Background Art

[0002] Lutetium belongs to heavy rare earths. Trace amounts of radioactive elements thorium and uranium are associated with ionic rare earths. The thorium content ThO2 / REO in rare earth chloride after leaching and enrichment is about 0.001-0.05%. After a series of extraction and separation, thorium is also dispersed in various rare earth components along with rare earths. Among them, ThO2 / Lu2O3 in lutetium chloride solution is greater than 0.003%. Scintillating crystals prepared from high-purity lutetium oxide are often used in positron emission computed tomography systems. Improving the purity of lutetium oxide and reducing spontaneous radiation energy can significantly improve the energy resolution of the system. Therefore, the market has put forward lower requirements for the thorium content in lutetium oxide, among which ThO2 / Lu2O3≤1×10 -6 , or even lower.

[0003] At present, the main thorium removal processes include ion exchange and extraction. For example, Chinese patent CN1394971A discloses a process for extracting and separating thorium and rare earth chloride from a sulfur-phosphorus mixed acid system. Primary amines are added to mixed alcohols as extractants to fractionate and extract thorium from rare earth feed liquid. After separation, ThO2 / REO in the solution is ≤5×10 -6 For example, in Chinese patent CN02144405.6, rare earth concentrate is roasted with concentrated sulfuric acid at low temperature, and the water extract is extracted to remove thorium, and the obtained rare earth product ThO2 / REO≤1×10 -5 For example, in Chinese patent CN101748275A, lutetium chloride solution is subjected to six-stage N235 extraction, and the raffinate lutetium chloride is further subjected to 10-stage cyclohexane acid extraction, and the thorium ion content in the obtained lutetium chloride solution is less than 0.1 μg / ml.

[0004] Although the existing methods can remove part of the thorium in rare earth chloride, it is still difficult to meet the requirement of ThO2 / Lu2O3≤1×10 -6 requirements. Summary of the invention

[0005] In view of this, the present invention provides a method for removing thorium from a lutetium-containing liquid. The thorium content in lutetium oxide can be significantly reduced by treating the lutetium-containing liquid according to the method provided by the present invention, and the ThO2 / Lu2O3 is 0.051×10 -6 ~0.5×10 -6 .

[0006] In order to solve the above technical problems, the present invention provides a method for removing thorium from a lutetium-containing liquid, comprising the following steps:

[0007] The lutetium-containing feed solution is extracted with a metal extract to obtain an organic phase; the volume ratio of the metal extract to the lutetium-containing feed solution is 5 to 10:1;

[0008] The organic phase and the hydrochloric acid solution are mixed for back extraction to obtain an aqueous phase; the molar concentration of the hydrochloric acid solution is 6.3-6.7 mol / L, and the volume ratio of the organic phase to the hydrochloric acid solution is 5-10:1;

[0009] The aqueous phase and the oxalic acid solution are mixed for precipitation to obtain a crude lutetium oxalate product; the mixing is performed under stirring conditions, the stirring temperature is 58 to 62° C., and the stirring speed is 100 to 200 r / min;

[0010] The crude lutetium oxalate is washed to obtain lutetium oxalate; the washing solvent is a mixed solution of ammonium oxalate solution and ethanol; the mass ratio of the crude lutetium oxalate to the solvent is 1:3-5;

[0011] The lutetium oxalate is calcined to obtain lutetium oxide.

[0012] Preferably, the metal extract comprises a P507 extractant diluted with sulfonated kerosene; the molar concentration of the P507 extractant in the metal extract is 1.3 to 1.7 mol / L.

[0013] Preferably, the extraction further comprises: saponifying the extract.

[0014] Preferably, the saponification rate of the saponification is 35-37%.

[0015] Preferably, the mixing of the aqueous phase and the oxalic acid solution comprises the following steps:

[0016] delivering the oxalic acid solution into the aqueous phase;

[0017] The mass concentration of the oxalic acid solution is 18-22%; the flow rate of the oxalic acid solution is 9-15 mL / min; the mass ratio of the oxalic acid solution to the theoretical mass of lutetium oxide is 1.3-1.4:1.

[0018] Preferably, the mass concentration of the ammonium oxalate solution is 1-5%.

[0019] Preferably, the mass percentage of ethanol in the mixed solution of ammonium oxalate solution and ethanol is 0.1-1%.

[0020] Preferably, the pH value of the washing liquid after washing is 6.4-6.6.

[0021] Preferably, before the calcination, the process further comprises: washing the lutetium oxalate with water, filtering and drying in sequence; and the mass ratio of the lutetium oxalate to the washing water is 1:3-5.

[0022] Preferably, the calcination temperature is 900-1000° C., and the calcination time is 3.5-4.5 hours.

[0023] The invention provides a method for removing thorium from a lutetium-containing liquid. The method comprises the following steps: extracting the lutetium-containing liquid with a metal extract to obtain an organic phase; the volume ratio of the metal extract to the lutetium-containing liquid is 5-10:1; mixing the organic phase with a hydrochloric acid solution for back extraction to obtain an aqueous phase; the molar concentration of the hydrochloric acid solution is 6.3-6.7 mol / L, and the volume ratio of the organic phase to the hydrochloric acid solution is 5-10:1; mixing the aqueous phase with an oxalic acid solution for precipitation to obtain a crude lutetium oxalate product; the mixing is carried out under stirring, the stirring temperature is 58-62°C, and the stirring speed is 100-200 r / min; washing the crude lutetium oxalate product to obtain lutetium oxalate; the washing solvent is a mixed solution of ammonium oxalate solution and ethanol; the mass ratio of the crude lutetium oxalate product to the solvent is 1:3-5; and calcining the lutetium oxalate to obtain lutetium oxide. The present invention transfers lutetium in a lutetium-containing liquid to an aqueous phase through extraction and back extraction steps, and at the same time, the purity of lutetium in the aqueous phase is improved by limiting the ratio of the organic phase to the aqueous phase during the extraction and back extraction process. The present invention promotes the growth of lutetium oxalate grains by limiting the temperature and the rotation speed of stirring during the precipitation process, reduces the agglomeration effect, and thus reduces the entrainment of lutetium oxalate grains to improve the purity of lutetium oxalate. The present invention uses a mixed solution of ammonium oxalate solution and ethanol to wash the crude lutetium oxalate product, so as to wash away the thorium oxalate in the crude lutetium oxalate product and improve the purity of lutetium oxalate. Treating the lutetium-containing liquid according to the method provided by the present invention can significantly reduce the thorium content in lutetium oxide, so that ThO2 / Lu2O3 is 0.051×10 -6 ~0.5×10 -6 . BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the process for treating lutetium chloride solution. DETAILED DESCRIPTION

[0025] The present invention provides a method for removing thorium from a lutetium-containing liquid, comprising the following steps:

[0026] The lutetium-containing feed solution is extracted with a metal extract to obtain an organic phase; the volume ratio of the metal extract to the lutetium-containing feed solution is 5 to 10:1;

[0027] The organic phase and the hydrochloric acid solution are mixed for back extraction to obtain an aqueous phase; the molar concentration of the hydrochloric acid solution is 6.3-6.7 mol / L, and the volume ratio of the organic phase to the hydrochloric acid solution is 5-10:1;

[0028] The aqueous phase and the oxalic acid solution are mixed for precipitation to obtain a crude lutetium oxalate product; the mixing is performed under stirring conditions, the stirring temperature is 58 to 62° C., and the stirring speed is 100 to 200 r / min;

[0029] The crude lutetium oxalate is washed to obtain lutetium oxalate; the washing solvent is a mixed solution of ammonium oxalate solution and ethanol; the mass ratio of the crude lutetium oxalate to the solvent is 1:3-5;

[0030] The lutetium oxalate is calcined to obtain lutetium oxide.

[0031] The present invention uses a metal extractant to extract the lutetium-containing solution to obtain an organic phase. In the present invention, the lutetium-containing solution preferably includes lutetium chloride and thorium ions, and the molar concentration of lutetium chloride in the lutetium-containing solution is preferably 1.38 to 1.71 mol / L, more preferably 1.4 to 1.5 mol / L. In the present invention, the mass concentration of thorium ions in the lutetium-containing solution is preferably 5 to 50 μg / mL, more preferably 7 to 41.0 μg / mL.

[0032] In the present invention, the lutetium-containing liquid is preferably prepared by Ganzhou Rare Earth (Longnan) Nonferrous Metals Co., Ltd. In the present invention, the preparation method preferably comprises the following steps:

[0033] Leaching the ore to obtain a mixed rare earth liquid;

[0034] The mixed rare earth solution is subjected to fuzzy linkage extraction to obtain a lutetium-containing solution.

[0035] The present invention has no special limitation on the leaching and fuzzy linkage extraction, and conventional methods in the art may be used.

[0036] In the present invention, the metal extract preferably includes a P507 extractant diluted with sulfonated kerosene; the molar concentration of the P507 extractant in the metal extract is preferably 1.3-1.7 mol / L, more preferably 1.5 mol / L. The present invention preferably further includes: saponifying the extract before the extraction; the saponification solvent is preferably ammonia water, the molar concentration of the ammonia water is preferably 7.8-8.2 mol / L, more preferably 8 mol / L; the saponification rate of the saponification is preferably 35-37%, more preferably 36%.

[0037] In the present invention, the volume ratio of the metal extract and the lutetium-containing feed solution is 5 to 10:1, preferably 8 to 10:1. In the present invention, the extraction is preferably carried out in a separatory funnel; the extraction is preferably carried out by mixing the lutetium-containing feed solution and the metal extract in a separatory funnel and then standing and separating them in sequence. In the present invention, the mixing is preferably carried out under oscillation conditions, and the frequency of the oscillation is preferably 145 to 155 Hz, more preferably 150 Hz; the oscillation time is preferably 4.5 to 5.5 min, more preferably 5 min. In the present invention, the standing time is preferably 13 to 17 min, more preferably 15 min. The content of lutetium element is calculated as lutetium oxide. In the present invention, the lutetium oxide content in the raffinate obtained after the separation is preferably less than 0.01 g / L; the present invention preferably sends the raffinate to a qualified unit for treatment.

[0038] In the present invention, the reaction equation in the extraction process is shown in Formula 1:

[0039] Lu 3+ +3(HA)2=Lu(HA2)3+3H + Formula 4;

[0040] Among them, (HA)2 is a P507 dimer. In the present invention, trivalent lutetium is more likely to react with (HA)2 to exchange cations than tetravalent thorium, and the lutetium content in the organic phase can be increased by extraction.

[0041] The present invention facilitates the separation of lutetium and thorium by limiting the ratio of the metal extract and the lutetium-containing feed solution during the extraction process, while ensuring that lutetium is completely extracted.

[0042] After obtaining the organic phase, the present invention mixes the organic phase and the hydrochloric acid solution for back extraction to obtain an aqueous phase. In the present invention, the molar concentration of the hydrochloric acid solution is preferably 6.3 to 6.7 mol / L, more preferably 6.5 mol / L. In the present invention, the volume ratio of the organic phase to the hydrochloric acid solution is 5 to 10:1, preferably 8 to 10:1.

[0043] In the present invention, the molar concentration of lutetium chloride in the aqueous phase is preferably 0.5 to 1 mol / L, more preferably 0.59 to 0.8 mol / L. In the present invention, the pH value of the aqueous phase is preferably 1.5 to 2.

[0044] In the present invention, the back extraction is preferably carried out in a separatory funnel; the back extraction is preferably carried out by mixing the organic phase and the hydrochloric acid solution in a separatory funnel, and then standing and separating the mixture in sequence. In the present invention, the mixing is preferably carried out under shaking conditions, and the shaking time is preferably 4.5 to 5.5 minutes, more preferably 5 minutes. In the present invention, the standing time is preferably 13 to 17 minutes, more preferably 15 minutes. In the present invention, the organic phase obtained after the back extraction is preferably washed with water, and the washed organic phase can be reused as an extractant for extraction.

[0045] After obtaining the aqueous phase, the present invention mixes the aqueous phase with the oxalic acid solution for precipitation to obtain a crude lutetium oxalate product. In the present invention, the mixing preferably includes the following steps:

[0046] The oxalic acid solution was transferred into the aqueous phase.

[0047] In the present invention, the mass concentration of the oxalic acid solution is preferably 15-22%, more preferably 18-20%. In the present invention, the flow rate of the oxalic acid solution is preferably 9-15 mL / min, more preferably 9-12 mL / min. In the present invention, the mass ratio of the oxalic acid solution to the theoretical mass of lutetium oxide is preferably 1.3-1.4:1, more preferably 1.35:1.

[0048] In the present invention, the mixing of the aqueous phase and the oxalic acid solution is preferably carried out under stirring conditions, the stirring temperature is 58-62°C, preferably 60°C; the stirring speed is 100-200r / min, preferably 150-180r / min. The present invention has no special requirements for the stirring time, and the stirring can be continued for 20 minutes after the precipitation is complete.

[0049] In the present invention, the chemical reactions mainly occurring during the precipitation process are shown in Formulas 2 and 3:

[0050] 2Lu 3+ +3H2C2O4=Lu2(C2O4)3+6H + Formula 2;

[0051] Th 4+ +2H2C2O4=Th(C2O4)2+4H + Formula 3.

[0052] The present invention controls the mixing temperature of the aqueous phase and the oxalic acid solution within the above range, which is beneficial to the growth of lutetium oxalate grains during the nucleation process; the present invention limits the stirring speed within the above range to ensure that the oxalic acid solution and the lutetium chloride solution are evenly dispersed around the nucleated lutetium oxalate grains, thereby promoting the growth of the grains; the present invention limits the mass ratio of the oxalic acid solution to the theoretical mass of lutetium oxide to promote the growth of lutetium oxalate grains, making it more uniform, reducing the agglomeration effect, thereby reducing adhesion and entrainment, and improving the purity of the crude lutetium oxalate product.

[0053] In the present invention, after the precipitation, the process preferably further comprises: filtering the system after the precipitation is complete to obtain a crude lutetium oxalate product. The present invention has no special requirements for the filtration, and a conventional method in the art can be used.

[0054] After obtaining the crude lutetium oxalate, the present invention washes the crude lutetium oxalate to obtain lutetium oxalate. In the present invention, the washing solvent is a mixed solution of ammonium oxalate solution and ethanol; the mass ratio of the crude lutetium oxalate to the solvent is 1:3-5, preferably 1:3.5-4.5. In the present invention, the mass concentration of the ammonium oxalate solution is preferably 1-5%, more preferably 2-4%. In the present invention, the ethanol is preferably anhydrous ethanol. In the present invention, the mass percentage of ethanol in the mixed solution of ammonium oxalate solution and ethanol is preferably 0.1-1%, more preferably 0.5-0.8%. In the present invention, the ammonium oxalate plays a role in dissolving thorium oxalate, and the ethanol plays a role in dispersing. The present invention uses a mixed solution of ammonium oxalate solution and ethanol for washing to reduce the attachment and entrainment of thorium oxalate in lutetium oxalate.

[0055] In the present invention, the washing is preferably agitated washing, and filtering is preferably performed after washing. The present invention has no special requirements on the number of washings, as long as the pH value of the filtrate after filtration is 6.4 to 6.6, more preferably 6.5. The present invention preferably collects the filtrate and sends it to a qualified unit for treatment.

[0056] The present invention takes the pH value of the filtrate of 6.4-6.6 as the end point of washing, and controls the washing end point to ensure that thorium oxalate is dissolved while as little lutetium oxalate as possible is dissolved during the washing process.

[0057] After obtaining lutetium oxalate, the present invention burns the lutetium oxalate to obtain lutetium oxide. In the present invention, the calcination preferably also includes: washing, filtering and drying the lutetium oxalate in sequence. In the present invention, the mass ratio of the lutetium oxalate to the washing water is preferably 1:3 to 5, more preferably 1:4. The present invention has no special requirements for the filtration, and the conventional methods in the art can be used. In the present invention, the drying is preferably oven drying, and the present invention has no special requirements for the drying, as long as the moisture in the filter cake can be removed.

[0058] In the present invention, the calcination temperature is preferably 900-1000° C., more preferably 950-980° C.; the calcination time is preferably 3.5-4.5 h, more preferably 3.8-4.2 h.

[0059] The method provided by the invention is simple and easy to operate, does not introduce new impurities, has low cost, can effectively remove thorium from lutetium oxide, and is easy to realize industrialization.

[0060] Figure 1 The present invention provides a schematic flow diagram of treating lutetium chloride feed liquid, specifically using a P507 extractant saponified with ammonia water to extract the lutetium chloride feed liquid, using hydrochloric acid to back-extract the organic phase obtained by extraction (the organic phase obtained by back-extraction is washed with water and recovered), mixing the back-extracted solution with an oxalic acid solution for precipitation, washing the precipitate with a mixed solution of ammonium oxalate and ethanol, and then washing and calcining to obtain lutetium oxide. The raffinate after extraction and the washing liquid after washing are collected and sent to a qualified unit for treatment.

[0061] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0062] Example 1

[0063] Ganzhou Rare Earth (Longnan) Nonferrous Metals Co., Ltd. leaches the ore to obtain a mixed rare earth solution; the mixed rare earth solution is subjected to fuzzy linkage extraction to obtain a lutetium chloride solution; the concentration of lutetium chloride in the lutetium chloride solution is 1.38 mol / L, and the concentration of thorium ions is 7.48 μg / mL, which is equivalent to a thorium oxide content ThO2 / Lu2O3 in lutetium oxide of 3.1×10 -5 ;

[0064] The sulfonated kerosene and the P507 extractant are mixed to obtain a metal extract having a molar concentration of 1.5 mol / L of the P507 extractant, and the extract is saponified with an ammonia water having a molar concentration of 8 mol / L to obtain a saponification rate of 36%. 1000 mL of the metal extract and 100 mL of the lutetium chloride solution are placed in a separatory funnel, and the separatory funnel is placed on an oscillating instrument and oscillated for 5 minutes at a frequency of 150 Hz, and then allowed to stand for 15 minutes to separate the liquids to obtain an organic phase and a raffinate, respectively. The content of the lutetium element is calculated as lutetium oxide, and the lutetium oxide concentration in the raffinate is less than 0.01 g / L, and the raffinate is sent to a qualified unit for treatment.

[0065] The organic phase was back-extracted with a hydrochloric acid solution having a molar concentration of 6.5 mol / L. During the back-extraction process, the volume ratio of the organic phase to the hydrochloric acid solution was 10:1. The organic phase and the hydrochloric acid solution were mixed in a separatory funnel, and then shaken at 150 Hz for 5 minutes, and then allowed to stand for 15 minutes, and separated to obtain an aqueous phase. The pH value of the aqueous phase was 1.5, the molar concentration of lutetium chloride in the aqueous phase was 0.59 mol / L, and the thorium content was 1.57 μg / mL.

[0066] A 20% oxalic acid aqueous solution at a temperature of 60°C was transported to a water phase at a temperature of 60°C at a flow rate of 9 mL / min, accompanied by stirring at a speed of 150 r / min during the transportation process. The reaction ended after 20 minutes of co-precipitation, and the mixture was kept warm and stirred for 10 minutes.

[0067] The crude lutetium oxalate filter cake obtained by vacuum filtration of the system after precipitation is washed with 500 mL of a mixed solution of ammonium oxalate solution and ethanol; the mass concentration of ammonium oxalate in the mixed solution of ammonium oxalate solution and ethanol is 2%, and the mass percentage of anhydrous ethanol is 0.5%; the crude lutetium oxalate filter cake and the mixed solution of ammonium oxalate solution and ethanol are stirred and washed for 5 minutes and then filtered, and the pH value of the washing solution is detected by pH test paper. The washing process is repeated three times, and the pH value of the washing solution is 6.5, and lutetium oxalate is obtained; the washing solution is sent to a qualified unit for treatment;

[0068] The lutetium oxalate filter cake was stirred and washed with 500 mL of high-purity water for 5 min, and the washing water was filtered off by suction. This process was repeated four times. The filter cake obtained after washing was dried and then placed in a muffle furnace for calcination at 950 ° C for 4 h to obtain lutetium oxide. The lutetium oxide was sent to a testing agency for testing, and the thorium oxide content was ThO2 / Lu2O3=0.051×10 -6 .

[0069] Example 2

[0070] Ganzhou Rare Earth (Longnan) Nonferrous Metals Co., Ltd. leaches the ore to obtain a mixed rare earth solution; the mixed rare earth solution is subjected to fuzzy linkage extraction to obtain a lutetium chloride solution; the concentration of lutetium chloride in the lutetium chloride solution is 1.71 mol / L, the concentration of thorium ions is 41.0 μg / mL, and the thorium oxide content ThO2 / Lu2O3 in lutetium oxide is 1.37×10 -4 ;

[0071] The sulfonated kerosene and the P507 extractant are mixed to obtain a metal extract having a molar concentration of 1.5 mol / L of the P507 extractant, and the extract is saponified with an ammonia water having a molar concentration of 8 mol / L to obtain a saponification rate of 36%. 1000 mL of the metal extract and 100 mL of the lutetium chloride solution are placed in a separatory funnel, and the separatory funnel is placed on an oscillating instrument and oscillated for 5 minutes at a frequency of 150 Hz, and then allowed to stand for 15 minutes to separate the liquids to obtain an organic phase and a raffinate, respectively. The content of the lutetium element is calculated as lutetium oxide, and the lutetium oxide concentration in the raffinate is less than 0.01 g / L, and the raffinate is sent to a qualified unit for treatment.

[0072] The organic phase was back-extracted with a hydrochloric acid solution having a molar concentration of 6.5 mol / L. During the back-extraction process, the volume ratio of the organic phase to the hydrochloric acid solution was 10:1. The organic phase and the hydrochloric acid solution were mixed in a separatory funnel, and then shaken at 150 Hz for 5 minutes, and then allowed to stand for 15 minutes, and separated to obtain an aqueous phase. The pH value of the aqueous phase was 1.5, the molar concentration of lutetium chloride in the aqueous phase was 0.66 mol / L, and the thorium content was 7.94 μg / mL.

[0073] A 20% oxalic acid aqueous solution at a temperature of 60°C was transported to a water phase at a temperature of 60°C at a flow rate of 12 mL / min, accompanied by stirring at a speed of 150 r / min during the transportation process. The reaction ended after 20 minutes of co-precipitation, and the temperature was kept and stirred for 10 minutes;

[0074] The crude lutetium oxalate filter cake obtained by vacuum filtration of the system after precipitation is washed with 500 mL of a mixed solution of ammonium oxalate solution and ethanol; the mass concentration of ammonium oxalate in the mixed solution of ammonium oxalate solution and ethanol is 2%, and the mass percentage of anhydrous ethanol is 0.5%; the crude lutetium oxalate filter cake and the mixed solution of ammonium oxalate solution and ethanol are stirred and washed for 5 minutes and then filtered, and the pH value of the washing solution is detected by pH test paper. The washing process is repeated three times, and the pH value of the washing solution is 6.5, and lutetium oxalate is obtained; the washing solution is sent to a qualified unit for treatment;

[0075] The lutetium oxalate filter cake was stirred and washed with 500 mL of high-purity water for 5 min, and the washing water was filtered off by suction. This process was repeated four times. The filter cake obtained after washing was dried and then placed in a muffle furnace for calcination at 950 ° C for 4 h to obtain lutetium oxide. The lutetium oxide was sent to a testing agency for testing, and the thorium oxide content was ThO2 / Lu2O3=0.5×10 -6 .

[0076] Comparative Example 1

[0077] Ganzhou Rare Earth (Longnan) Nonferrous Metals Co., Ltd. leaches the ore to obtain a mixed rare earth solution; the mixed rare earth solution is subjected to fuzzy linkage extraction to obtain a lutetium chloride solution; the concentration of lutetium chloride in the lutetium chloride solution is 1.38 mol / L, and the concentration of thorium ions is 7.48 μg / mL, which is equivalent to a thorium oxide content ThO2 / Lu2O3 in lutetium oxide of 3.1×10 -5 ;

[0078] The lutetium chloride in the lutetium chloride solution was diluted to a molar concentration of 0.59 mol / L, and the pH was adjusted to 1.5. An oxalic acid aqueous solution with a temperature of 60°C and a mass concentration of 20% was transported to the water phase with a temperature of 60°C at a flow rate of 9 mL / min. During the transportation process, stirring was performed at a speed of 150 r / min. The reaction was completed after 20 minutes of coprecipitation, and the temperature was kept and stirred for 10 minutes.

[0079] The crude lutetium oxalate filter cake obtained by vacuum filtration of the precipitation system was stirred and washed with 500 mL of high-purity water for 5 min, and the washing water was filtered off until the pH of the filtrate was 6.5. The filter cake obtained after washing was dried and placed in a muffle furnace for calcination at 950°C for 4 h to obtain lutetium oxide. The lutetium oxide was sent to a detection agency for testing, and the thorium oxide content was ThO2 / Lu2O3=1.2×10 -5 .

[0080] From the values ​​of ThO2 / Lu2O3 in lutetium oxide obtained by the methods of Examples 1 and 2 and Comparative Example 1, it can be seen that treating the lutetium-containing liquid according to the method provided by the present invention can greatly reduce the content of thorium oxide in lutetium oxide.

[0081] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for removing thorium from a lutetium-containing liquid, comprising the following steps: The lutetium-containing feed liquid is extracted with a metal extract to obtain an organic phase; the volume ratio of the metal extract to the lutetium-containing feed liquid is 5 to 10:1; the metal extract comprises a P507 extractant diluted with sulfonated kerosene; the molar concentration of the P507 extractant in the metal extract is 1.3 to 1.7 mol / L; The organic phase and the hydrochloric acid solution are mixed for back extraction to obtain an aqueous phase; the molar concentration of the hydrochloric acid solution is 6.3-6.7 mol / L, and the volume ratio of the organic phase to the hydrochloric acid solution is 5-10:1; The aqueous phase and the oxalic acid solution are mixed for precipitation to obtain a crude lutetium oxalate product; the mixing is performed under stirring conditions, the stirring temperature is 58-62° C., and the stirring speed is 100-200 r / min; the mass concentration of the oxalic acid solution is 18-22%; the mass ratio of the oxalic acid solution to the theoretical mass of lutetium oxide is 1.3-1.4:1; The crude lutetium oxalate is washed to obtain lutetium oxalate; the washing solvent is a mixed solution of ammonium oxalate solution and ethanol; the mass ratio of the crude lutetium oxalate to the solvent is 1:3-5; The lutetium oxalate is calcined to obtain lutetium oxide.

2. The method according to claim 1, characterized in that: The method also includes saponifying the extract before the extraction.

3. The method according to claim 2, characterized in that: The saponification rate of the saponification is 35 to 37%.

4. The method according to claim 1, characterized in that: The mixing of the aqueous phase and the oxalic acid solution comprises the following steps: delivering the oxalic acid solution into the aqueous phase; The flow rate of the oxalic acid solution is 9-15 mL / min.

5. The method according to claim 1, characterized in that: The mass concentration of the ammonium oxalate solution is 1-5%.

6. The method according to claim 1 or 5, characterized in that: The mass percentage of ethanol in the mixed solution of ammonium oxalate solution and ethanol is 0.1-1%.

7. The method according to claim 1, characterized in that: The pH value of the washing liquid after washing is 6.4-6.

6.

8. The method according to claim 1, characterized in that: Before the calcination, the method further comprises: washing the lutetium oxalate with water, filtering and drying in sequence; the mass ratio of the lutetium oxalate to the washing water is 1:3-5.

9. The method according to claim 1 or 8, characterized in that: The burning temperature is 900-1000° C., and the burning time is 3.5-4.5 hours.

Images