Niobium composite extracting agent and method for extracting niobium from niobium-tantalum iron ore

Abstract

The invention belongs to the field of selective extraction of niobium, and relates to a niobium composite extracting agent and a method for extracting niobium from niobium-tantalum iron ore. According to the method, ammonium fluoride and ammonium sulfate are added into niobium-tantalum iron ore powder for roasting; after cooling to room temperature, dissolving the roasted product by using a mixed solution of hydrofluoric acid and sulfuric acid to form a mixed solution of fluoroniobic acid and fluotantalic acid; extracting and separating niobium from the mixed solution of the fluoroniobic acid and the fluotantalic acid by using a composite extracting agent; the composite extracting agent comprises the following components: methyl isobutyl ketone, an amine compound, a fluorine-free sulfonyl ionic liquid, a stabilizer tributyl phosphate, di (2-ethylhexyl) phosphate and isodecyl alcohol. The method disclosed by the invention has the advantages of high total niobium extraction rate, low roasting temperature, high yield of niobium extracted by the extracting agent, stability and difficulty in emulsification, and can be repeatedly used.

Description

Technical Field

[0001] The present invention belongs to the field of selective extraction of niobium, and particularly relates to a niobium composite extractant and a method for extracting niobium from columbite-tantalite ore. Background Art

[0002] As a strategic emerging rare metal mineral for the development of high-tech in the 21st century, niobium is widely used in industrial fields such as steel, aerospace, and superconducting materials, and is the alloy noble among rare metals. The niobium element often coexists closely with the tantalum element to form a columbite-tantalite deposit. Therefore, the extraction of niobium from columbite-tantalite ore is of great significance for the development of China's niobium resources and related industries and for ensuring the safety of China's niobium resources. For refractory and polymetallic associated niobium ores, the roasting-acid leaching process provides a new idea for the extraction of niobium. Utilizing the combined process flow to innovate the beneficiation and metallurgy technology and combining different beneficiation methods is conducive to the comprehensive utilization of niobium. The realization of clean and efficient comprehensive utilization of resources through multiple process routes will become the research focus of scientific researchers and the future development trend. At present, there is still a need to seek more innovative and environmentally friendly methods for extracting niobium and realizing the comprehensive utilization of niobium resources.

[0003] CN115109948B discloses a method for extracting and separating tantalum and niobium. The material containing metallic tantalum and niobium is successively subjected to oxidative roasting, alkaline roasting and leaching to obtain a leaching solution containing potassium hexatantalate and potassium hexaniobate; after the leaching solution is extracted with xylene and methyltrioctylammonium chloride, the organic phase is then back-extracted with oxalic acid and nitric acid. This method has good leaching and separation effects of tantalum and niobium, the obtained tantalum and niobium leaching solution has a high purity, and the leaching rate reaches more than 99% under better conditions, and the tantalum-niobium separation ratio reaches 41.74 after back-extraction.

[0004] CN113388745B discloses a method for extracting valuable components from niobium-bearing ilmenorutile without fluorine. The method includes: (1) successively subjecting niobium-bearing ilmenorutile to a first roasting and a second roasting to obtain a roasted material; (2) successively subjecting the roasted material obtained in step (1) to water treatment and acid treatment to obtain an acid treatment solution, and then performing extraction and back-extraction to obtain a niobium-containing feed solution.

[0005] During the roasting process of columbite-tantalite ore, in order to reduce the temperature required for mineral decomposition, decrease energy consumption, and avoid the Ta / Nb encapsulation phenomenon caused by high-temperature sintering, additives need to be added. Additionally, during the extraction process of tantalum and niobium, the selection of extractant is crucial. Methyl isobutyl ketone, tributyl phosphate, cyclohexanone, etc. are commonly used extractants in industry. These extractants have their own characteristics. For example, methyl isobutyl ketone has good selectivity and a large extraction capacity for tantalum and niobium. However, the selectivity of methyl isobutyl ketone for tantalum is higher than that for niobium, resulting in a lower extraction efficiency of niobium. Therefore, other components such as tributyl phosphate need to be added to improve the extraction efficiency of niobium. In a high-concentration metal ion or strong acid system, tributyl phosphate is prone to form a third-phase emulsion, and a modifier needs to be added to inhibit it. The distribution ratio of cyclohexanone for niobium is lower than that of methyl isobutyl ketone and tributyl phosphate, and more extraction stages are required to achieve an ideal recovery rate, increasing equipment investment and energy consumption. Therefore, it is necessary to develop an extraction system and extraction method with excellent niobium extraction performance, stable and not easily forming emulsions, and capable of being recycled and reused multiple times. Summary of the Invention

[0006] Since the chemical properties of tantalum and niobium are very similar and their atomic radii are almost the same, it is very difficult to extract niobium from columbite-tantalite ore. Aiming at the problems of low overall efficiency of extracting niobium from ore, low extraction efficiency of the niobium extraction system, easy formation of emulsions, and being not conducive to multiple recycling and reuse in the prior art, the present invention provides a new niobium composite extractant and a method for extracting niobium from columbite-tantalite ore. The method of the present invention has the advantages of high total extraction rate of niobium, low roasting temperature, high extraction yield of niobium by the extractant, stable and not easily emulsified, and can be recycled and reused multiple times, which is very suitable for industrialization.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] A niobium composite extractant, comprising the following components: methyl isobutyl ketone, amine compound, fluorine-free sulfonyl ionic liquid, stabilizer tributyl phosphate TBP, bis(2-ethylhexyl) phosphate, and isodecanol.

[0009] Furthermore, the volume ratio of each component in the niobium composite extractant is: methyl isobutyl ketone 60 - 85%, preferably 60 - 80%; amine compound 5 - 25%, preferably 8 - 20%; fluorine-free sulfonyl ionic liquid 5 - 15%, preferably 5 - 8%; stabilizer tributyl phosphate 2 - 15%, preferably 5 - 8%; bis(2-ethylhexyl) phosphate 1 - 15%, preferably 2 - 5%; isodecanol 1 - 10%, preferably 2 - 3%.

[0010] Further, the amine compound is trioctylamine; the fluorine-free sulfonyl ionic liquid is a pyridine-based ionic liquid or an imidazole-based ionic liquid, and is selected from at least one of [HSO3-pPy]HSO4, [HSO3-pMIM]HSO4, [HSO3-pPy]pTSA, and [HSO3-pMIM]pTSA. The structural formula is as follows:

[0011]

[0012] The technical solution of the present invention also includes a method for extracting niobium from columbite-tantalite, which is to extract niobium using the aforementioned niobium composite extractant.

[0013] Further, the above method includes the following steps:

[0014] Step 1: Crush the columbite-tantalite ore powder, add a roasting aid and roast to obtain a roasted product. The roasting aid is a compound of ammonium fluoride and ammonium sulfate; place the roasted product in a mixed solution of hydrofluoric acid and sulfuric acid for reaction to form a mixed solution of niobic acid fluoride and tantalic acid fluoride.

[0015] Step 2: Use a composite extractant to extract and back-extract the mixed solution of niobic acid fluoride and tantalic acid fluoride to obtain a precipitate, and the precipitate is calcined to obtain pure Nb2O5.

[0016] Further, in Step 1, the roasting aid is a compound of ammonium fluoride and ammonium sulfate in a mass ratio of 2:1 - 1:2, preferably 2:1 - 1:1; the roasting aid accounts for 3 - 10 wt% of the columbite-tantalite ore powder.

[0017] Further, in Step 1, the crushing is to crush to D50 = 2 ± 0.3 microns; the roasting conditions are: first keep warm at 200 - 300 °C for 1 - 3 h, and then keep warm at 800 - 1000 °C for 3 - 5 h; the mixed solution of hydrofluoric acid and sulfuric acid is a mixed solution of hydrofluoric acid with a molar concentration of 40 - 60% and sulfuric acid with a molar concentration of 80 - 98% in a volume ratio of 1:1 - 1:5; the reaction conditions are: keep the temperature constant at 80 - 95 °C for 4 - 8 hours under the protection of an inert atmosphere.

[0018] Further, in Step 2, the extraction method is: use the niobium composite extractant as the organic phase to extract the mixed solution of niobic acid fluoride and tantalic acid fluoride, and the aqueous phase is sulfuric acid with a concentration of 3 - 8 mol / L, preferably 3 - 5 mol / L; the back-extraction method is: after extraction, separate the organic phase, add deionized water, adjust the sulfuric acid concentration of the aqueous phase to 1 - 2.5 mol / L, preferably 1 - 2 mol / L, separate the aqueous phase for niobium extraction; add the niobium composite extractant to the separated aqueous phase again to extract impurities other than niobic acid fluoride in the aqueous phase, repeat this step three to five times, combine the aqueous phases, and adjust the pH to 8.5 - 9.5 by introducing ammonia water to obtain a precipitate.

[0019] Further, in Step 2, the extraction method is as follows: The mixed solution of niobic acid fluoride and tantalum acid fluoride is extracted with a niobium composite extractant as the organic phase for 5 - 25 minutes, the organic phase / water phase volume ratio is 1:1 - 1:5, the temperature is controlled at 20 - 40°C, and the water phase is sulfuric acid with a concentration of 3 - 5 mol / L; the organic phase is separated, deionized water is added, the sulfuric acid concentration in the water phase of the solution is adjusted to 1 - 2 mol / L, the water phase is separated for niobium back - extraction, and the niobium composite extractant is added to the separated water phase again. This step is repeated three times, and the niobium back - extraction rate > 99%. The combined water phase is passed through ammonia water to adjust the pH to 8.5 - 9.5 to obtain a precipitate.

[0020] Further, in Step 2, the calcination conditions are: calcination at 800 - 1000°C for 3 - 10 h.

[0021] In the roasting process of columbite - tantalite in the present invention, the addition of ammonium fluoride and ammonium sulfate can help decompose the mineral, reduce the roasting temperature, reduce the usage amount of HF acid and improve the niobium extraction efficiency. The reason is that ammonium fluoride decomposes into HF and NH3 during roasting. HF reacts with Ta / Nb oxides in the mineral to form soluble tantalum acid fluoride (H2TaF7) and niobic acid fluoride (H2NbF7), destroying the lattice structure and making the subsequent acid leaching more efficient; while the decomposition products of ammonium fluoride form insoluble fluorides with impurity elements such as iron, manganese, and titanium, thus reducing the dissolution of impurities during subsequent acid leaching and reducing the separation burden in the extraction stage.

[0022] Nb2O5 + 14HF → 2H2[NbF7] + 5H2O

[0023] Ta2O5 + 14HF → 2H2[TaF7] + 5H2O

[0024] To solve the problem of HF volatilization caused by the decomposition of ammonium fluoride and promote mineral decomposition, ammonium sulfate is added for synergistic effect. Ammonium sulfate decomposes into SO3 and NH3. SO3 can promote mineral decomposition, and at the same time NH3 inhibits the volatilization of HF, helping to improve the yield of fluorides. The addition of ammonium fluoride and ammonium sulfate can significantly reduce the temperature required for mineral decomposition, reduce energy consumption and avoid the phenomenon of Ta / Nb encapsulation caused by high - temperature sintering.

[0025] In the extraction process of the present invention, a composite extractant composed of methyl isobutyl ketone, trioctylamine, ionic liquid, stabilizing agent tributyl phosphate, bis(2-ethylhexyl) phosphate, and isodecanol is used. The extraction rate of niobium by this extractant reaches over 99%, and in the preferred embodiment, it reaches 99.9%. Moreover, it has good stability and is not easily emulsified, and can be recycled. Trioctylamine has a synergistic extraction effect. The fluorosulfonyl-free ionic liquid can adjust the polarity and solubility of the system, enhance the extraction ability of niobium and the stability of the system. Tributyl phosphate and bis(2-ethylhexyl) phosphate can enhance the stability and selectivity of the system, form stable complexes with niobium, improve the extraction efficiency, and reduce the interference of other metal ions such as iron ions at the same time. Isodecanol adjusts the viscosity and polarity of the system, improves the dispersibility and stability of the extractant, and can reduce the surface tension of the system, promoting the uniform distribution of the extractant. The fluorosulfonyl-free ionic liquid has better extraction effect than the fluorosulfonyl-containing ionic liquid during extraction. The sulfonyl group has lone pair electrons, which can form strong coordination bonds with niobium ions, enhancing the affinity of the ionic liquid for niobium. This coordination effect and spatial structure combined with specific acidity and other conditions make it have better electrostatic interaction than the fluorosulfonyl group. Therefore, the niobium extraction effect of this type of ionic liquid is better than that of the fluorosulfonyl-containing ionic liquid and other ionic liquids. The niobium composite extractant provided by the present invention can also be used for the efficient and rapid extraction of niobium in the scenario of extracting niobium from niobium-tantalum leaching solution obtained under other conditions.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The method for extracting niobium of the present invention has the advantages of high niobium extraction rate, low roasting temperature, high selectivity of the extractant, stable and not easily emulsified, and can be recycled repeatedly, which is very suitable for industrialization.

[0028] During roasting of the present invention, ammonium fluoride and ammonium sulfate are added to help decompose the minerals, reduce the roasting temperature, reduce the usage amount of HF acid, and improve the extraction efficiency of niobium; during extraction, the extractant is a composite extractant composed of methyl isobutyl ketone, trioctylamine, ionic liquid, stabilizing agent tributyl phosphate, bis(2-ethylhexyl) phosphate, and isodecanol. The extraction rate of niobium by this extractant reaches over 99%, it has good stability and is not easily emulsified, and can be recycled. Specific Embodiments

[0029] The technical solutions of the present invention will be further described below through specific embodiments, but are not limited to the content in the specification. All reagents used are commercially available reagents in the art.

[0030] Example 1

[0031] Step 1: Crush the columbite-tantalite ore powder to D50 = 2 ± 0.3 μm. Take 20 g of the crushed columbite-tantalite ore powder and place it in a closed nickel-based superalloy roasting furnace. Add roasting aids (1 g of ammonium fluoride and 1 g of ammonium sulfate), and heat it up to 400 °C at a rate of 5 °C / min and hold for 1 h. Then continue to heat it up to 800 °C at a rate of 10 °C / min and roast for 3 h, and then cool it down to room temperature to obtain the roasted product. Dissolve the roasted product with 160 mL of a mixed solution of hydrofluoric acid (40% molar concentration) and sulfuric acid (98% molar concentration) with a volume ratio of 1:1. React at a constant temperature of 90 °C for 6 h under nitrogen protection, and filter to remove insoluble substances to obtain a mixed solution of niobic acid fluoride and tantalic acid fluoride;

[0032] Step 2: Use a niobium composite extractant as the organic phase to perform liquid-liquid extraction on the mixed solution of niobic acid fluoride and tantalic acid fluoride for 10 minutes. The niobium composite extractant is composed of methyl isobutyl ketone (accounting for 68% volume content of the total extractant), trioctylamine (accounting for 15% volume content of the total extractant), ionic liquid [HSO3-pPy]HSO4 (accounting for 5% volume content of the total extractant), stabilizing agent tributyl phosphate (accounting for 8% volume content of the total extractant), bis(2-ethylhexyl) phosphate (accounting for 2% volume content of the total extractant), and isodecanol (accounting for 2% volume content of the total extractant). The organic phase / water phase volume ratio is 1:3, the temperature is 35 ± 2 °C, and the water phase is sulfuric acid with a concentration of 4 mol / L. Separate the organic phase to obtain the extracted niobium-tantalum mixed solution, add deionized water, adjust the sulfuric acid concentration in the water phase of the solution to 1.5 mol / L, separate the water phase containing niobium for niobium back extraction, and add a composite extractant with a volume ratio of 1:1 to the separated water phase again. After extracting for 5 minutes, separate the water phase, and repeat this step three times. Finally, the niobium back extraction rate > 99%. Combine the water phases and introduce ammonia water to adjust the pH = 9 to obtain a precipitate; the precipitate is calcined at 900 °C for 5 h to obtain pure Nb2O5. For tantalum back extraction, use a mixed solution of 0.5 mol / L sulfuric acid and 0.1 mol / L NH4F, and the back extraction rate > 99.5%. The ionic liquid is recycled.

[0033] Example 2

[0034] Other conditions are the same as in Example 1, and the difference is the change in the compounding ratio of ammonium fluoride and ammonium sulfate in Step 1. Specifically:

[0035] Step 1: Crush the columbite-tantalite ore powder to D50 = 2 ± 0.3 μm. Take 20 g of the crushed columbite-tantalite ore powder and place it in a closed nickel-based superalloy roasting furnace. Add roasting aids (2 g of ammonium fluoride and 1 g of ammonium sulfate). Heat it at a rate of 5 °C / min to 400 °C and hold for 1 h, then continue to heat at a rate of 10 °C / min to 900 °C and roast for 3 h. Cool it to room temperature to obtain the roasted product. Dissolve the roasted product with 160 mL of a mixed solution of hydrofluoric acid (40% molar concentration) and sulfuric acid (98% molar concentration) with a volume ratio of 1:1. React at a constant temperature of 90 °C for 6 h under nitrogen protection, and filter to remove insoluble substances to obtain a mixed solution of niobic acid fluoride and tantalic acid fluoride;

[0036] Step 2: Use a niobium composite extractant as the organic phase to perform liquid-liquid extraction on the mixed solution of niobic acid fluoride and tantalic acid fluoride for 10 minutes. The niobium composite extractant is composed of methyl isobutyl ketone (accounting for 68% volume content of the total extractant), trioctylamine (accounting for 15% volume content of the total extractant), ionic liquid [HSO3-pPy]HSO4 (accounting for 5% volume content of the total extractant), stabilizing agent tributyl phosphate (accounting for 8% volume content of the total extractant), bis(2-ethylhexyl) phosphate (accounting for 2% volume content of the total extractant), and isodecanol (accounting for 2% volume content of the total extractant). The organic phase / water phase volume ratio is 1:3, the temperature is 35 ± 2 °C, and the water phase is sulfuric acid with a concentration of 4 mol / L. Separate the organic phase to obtain the extracted niobium-tantalum mixed solution, add deionized water, adjust the sulfuric acid concentration in the water phase of the solution to 1.5 mol / L, separate the water phase containing niobium for niobium back-extraction, and add a composite extractant with a volume ratio of 1:1 to the separated water phase again. After extracting for 5 minutes, separate the water phase, and repeat this step three times. Finally, the back-extraction rate of niobium > 99%, and the water phases are combined and ammonia water is introduced to adjust the pH = 9 to obtain a precipitate; the precipitate is calcined at 900 °C for 5 h to obtain pure Nb2O5. For tantalum back-extraction, use a mixed solution of 0.5 mol / L sulfuric acid and 0.1 mol / L NH4F, and the back-extraction rate > 99.5%. The ionic liquid is recovered and recycled.

[0037] Example 3

[0038] Other conditions are the same as those in Example 1, and the difference is that in Step 2, the ionic liquid [HSO3-pMIM]HSO4 is used to replace [HSO3-pPy]HSO4. Specifically:

[0039] Step 1: The same as in Example 1.

[0040] Step 2: Use a niobium composite extractant as the organic phase to perform liquid-liquid extraction on the mixed solution of niobic acid and tantalic acid for 10 minutes. The niobium composite extractant is composed of methyl isobutyl ketone (accounting for 68% volume content of the total extractant), trioctylamine (accounting for 15% volume content of the total extractant), ionic liquid [HSO3-pPy]HSO4 (accounting for 5% volume content of the total extractant), stabilizer tributyl phosphate (accounting for 8% volume content of the total extractant), bis(2-ethylhexyl) phosphate (accounting for 2% volume content of the total extractant), and isodecanol (accounting for 2% volume content of the total extractant). The organic phase / water phase volume ratio is 1:3, the temperature is 35±2°C, and the water phase is sulfuric acid with a concentration of 4 mol / L; separate the organic phase to obtain the extracted niobium-tantalum mixed solution, add deionized water, adjust the sulfuric acid concentration in the water phase of the solution to 1.5 mol / L, separate the water phase containing niobium for niobium back-extraction, add a composite extractant with a volume ratio of 1:1 to the water phase again, separate the water phase after extraction for 5 minutes, and repeat this step three times. Finally, the back-extraction rate of niobium > 99%, combine the water phases, and adjust the pH = 9 with ammonia water to obtain a precipitate; calcine the precipitate at 900°C for 5 h to obtain pure Nb2O5. For tantalum back-extraction, use a mixed solution of 0.5 mol / L sulfuric acid and 0.1 mol / L NH4F, and the back-extraction rate > 99.5%. The ionic liquid is recycled.

[0041] Example 4

[0042] Other conditions are the same as those in Example 1, and the difference is that in Step 2, the ionic liquid [HSO3-pPy]pTSA is used to replace [HSO3-pPy]HSO4. Specifically:

[0043] Step 1: The same as in Example 1;

[0044] Step 2: Use a niobium composite extractant as the organic phase to perform liquid-liquid extraction on the mixed solution of niobic acid and tantalic acid for 10 minutes. The niobium composite extractant is composed of methyl isobutyl ketone (accounting for 68% volume content of the total extractant), trioctylamine (accounting for 15% volume content of the total extractant), ionic liquid [HSO3-pPy]pTSA (accounting for 5% volume content of the total extractant), stabilizing agent tributyl phosphate (accounting for 8% volume content of the total extractant), bis(2-ethylhexyl) phosphate (accounting for 2% volume content of the total extractant), and isodecanol (accounting for 2% volume content of the total extractant). The organic phase / water phase volume ratio is 1:3, the temperature is 35±2°C, and the water phase is sulfuric acid with a concentration of 4 mol / L; separate the organic phase to obtain the extracted niobium-tantalum mixed solution, add deionized water, adjust the sulfuric acid concentration in the water phase of the solution to 1.5 mol / L, separate the water phase containing niobium for niobium back extraction, add the composite extractant with a volume ratio of 1:1 to the water phase again, separate the water phase after extraction for 5 minutes, and repeat this step three times. Finally, the back extraction rate of niobium > 99%, combine the water phases and adjust the pH = 9 by introducing ammonia water to obtain a precipitate; calcine the precipitate at 900°C for 5 h to obtain pure Nb2O5. For tantalum back extraction, use a mixed solution of 0.5 mol / L sulfuric acid and 0.1 mol / L NH4F, and the back extraction rate > 99.5%. The ionic liquid is recycled.

[0045] Example 5

[0046] Other conditions are the same as in Example 1, the difference is that in Step 2, the ionic liquid [HSO3-pMIM]pTSA is used to replace [HSO3-pPy]HSO4, specifically:

[0047] Step 1: The same as in Example 1;

[0048] Step 2: Use a niobium composite extractant as the organic phase to perform liquid-liquid extraction on the mixed solution of niobic acid and tantalic acid for 10 minutes. The niobium composite extractant is composed of methyl isobutyl ketone (accounting for 68% volume content of the total extractant), trioctylamine (accounting for 15% volume content of the total extractant), ionic liquid [HSO3-pMIM]pTSA (accounting for 5% volume content of the total extractant), stabilizer tributyl phosphate (accounting for 8% volume content of the total extractant), bis(2-ethylhexyl) phosphate (accounting for 2% volume content of the total extractant), and isodecanol (accounting for 2% volume content of the total extractant). The organic phase / water phase volume ratio is 1:3, the temperature is 35 ± 2 °C, and the water phase is sulfuric acid with a concentration of 4 mol / L; separate the organic phase to obtain the extracted niobium-tantalum mixed solution, add deionized water, adjust the sulfuric acid concentration in the water phase of the solution to 1.5 mol / L, separate the water phase containing niobium for niobium back-extraction, add a composite extractant with a volume ratio of 1:1 to the water phase to the separated water phase again, separate the water phase after extraction for 5 minutes, and repeat this step three times. Finally, the back-extraction rate of niobium > 99%, combine the water phases and adjust the pH = 9 with ammonia water to obtain a precipitate; calcine the precipitate at 900 °C for 5 h to obtain pure Nb2O5. For tantalum back-extraction, use a mixed solution of 0.5 mol / L sulfuric acid and 0.1 mol / L NH4F, and the back-extraction rate > 99.5%. The ionic liquid is recycled.

[0049] Example 6

[0050] Other conditions are the same as in Example 5, the difference is that the dosages of methyl isobutyl ketone and ionic liquid in Step 2 are increased, specifically:

[0051] Step 1: The same as in Example 1;

[0052] Step 2: Use a niobium composite extractant as the organic phase to perform liquid-liquid extraction on the mixed solution of niobic acid and tantalic acid for 10 minutes. The niobium composite extractant is composed of methyl isobutyl ketone (accounting for 75% by volume of the total extractant), trioctylamine (accounting for 8% by volume of the total extractant), ionic liquid [HSO3-pMIM]pTSA (accounting for 8% by volume of the total extractant), stabilizing agent tributyl phosphate (accounting for 5% by volume of the total extractant), bis(2-ethylhexyl) phosphate (accounting for 2% by volume of the total extractant), and isodecanol (accounting for 2% by volume of the total extractant). The organic phase / water phase volume ratio is 1:3, the temperature is 35±2°C, and the water phase is sulfuric acid with a concentration of 4 mol / L; separate the organic phase to obtain the extracted niobium-tantalum mixed solution, add deionized water, adjust the sulfuric acid concentration in the water phase of the solution to 1.5 mol / L, separate the water phase containing niobium for niobium back-extraction, add the composite extractant with a volume ratio of 1:1 to the separated water phase again, separate the water phase after extraction for 5 minutes, and repeat this step three times. Finally, the back-extraction rate of niobium > 99%, combine the water phases and adjust the pH = 9 with ammonia water to obtain a precipitate; calcine the precipitate at 900°C for 5 h to obtain pure Nb2O5. For tantalum back-extraction, use a mixed solution of 0.5 mol / L sulfuric acid and 0.1 mol / L NH4F, and the back-extraction rate > 99.5%. The ionic liquid is recycled.

[0053] Comparative Example 1

[0054] Other conditions are the same as in Example 1, the difference is that ammonium fluoride and ammonium sulfate were not added during the roasting in Step 1, specifically:

[0055] Step 1: Crush the columbite-tantalite ore powder to D50 = 2±0.3 microns, take 20 g of the crushed columbite-tantalite ore powder, place it in a closed nickel-based superalloy roasting furnace, heat it up to 400°C at a rate of 5°C / min and hold for 1 h, continue to heat it up to 800°C at a rate of 10°C / min and roast for 3 h, and cool it down to room temperature at a rate of 5°C / min; dissolve the roasted product with 160 mL of a mixed solution of hydrofluoric acid (40% molar concentration) and sulfuric acid (98% molar concentration) with a volume ratio of 1:1, react at a constant temperature of 90°C for 6 hours under nitrogen protection, and filter to remove insoluble substances to obtain a mixed solution of niobic acid and tantalic acid;

[0056] Step 2: The same as in Example 1.

[0057] Comparative Example 2

[0058] Other conditions are the same as in Example 1, the difference is that only ammonium fluoride was added during the roasting in Step 1.

[0059] Step 1: Crush the columbite-tantalite ore powder to D50 = 2 ± 0.3 μm. Take 20 g of the crushed columbite-tantalite ore powder and place it in a closed nickel-based superalloy roasting furnace. Add a roasting aid (1 g of ammonium fluoride), heat it up to 400 °C at a rate of 5 °C / min and hold for 1 h, then continue to heat it up to 800 °C at a rate of 10 °C / min and roast for 3 h, and then cool it down to room temperature at a rate of 5 °C / min. Dissolve the roasted product with 160 mL of a mixed solution of hydrofluoric acid (40% molar concentration) and sulfuric acid (98% molar concentration) with a volume ratio of 1:1, and react at a constant temperature of 90 °C for 6 h under nitrogen protection. Filter to remove insoluble substances to obtain a mixed solution of niobic acid fluoride and tantalic acid fluoride;

[0060] Step 2: The same as in Example 1.

[0061] Comparative Example 3

[0062] Other conditions are the same as in Example 1, and the difference is that the organic phase extractant in Step 2 is methyl isobutyl ketone. Specifically:

[0063] Step 1: The same as in Example 1;

[0064] Step 2: Use methyl isobutyl ketone as the organic phase of the extractant to perform liquid-liquid extraction on the mixed solution of niobic acid fluoride and tantalic acid fluoride for 10 minutes. The volume ratio of the organic phase to the aqueous phase is 1:3, the temperature is 35 ± 2 °C, and the aqueous phase is sulfuric acid with a concentration of 4 mol / L. Separate the organic phase to obtain an extracted niobium-tantalum mixed solution, add deionized water to adjust the sulfuric acid concentration in the aqueous phase of the solution to 1.5 mol / L, separate the aqueous phase containing niobium for niobium back-extraction, and add an extractant with a volume ratio of 1:1 to the separated aqueous phase again. After extracting for 5 minutes, separate the aqueous phase, and repeat this step three times. Finally, the back-extraction rate of niobium > 99%, combine the aqueous phases and adjust the pH = 9 by introducing ammonia water to obtain a precipitate; The precipitate is calcined at 900 °C for 5 h to obtain pure Nb2O5. The back-extraction of tantalum uses a mixed solution of 0.5 mol / L sulfuric acid and 0.1 mol / L NH4F, and the back-extraction rate > 99.5%. The ionic liquid is recycled.

[0065] Evaluate the effects of the above examples and comparative examples, and the results are shown in Table 1 below.

[0066] The total extraction rate of niobium = the weight of niobium in the extracted niobium oxide / the weight of niobium in the ore * 100% (using GB / T 17415.2-2010 Methods for chemical analysis of tantalum ores and niobium ores - Part 2: Determination of niobium content, the content and weight of niobium in the ore are determined).

[0067] The extraction rate of niobium = the weight of niobium extracted and separated in the example / the weight of niobium in the original extraction solution * 100% (excluding the step of dissolving the ore, and the determination of other niobium amounts is the same as above, GB / T 17415.2-2010).

[0068] Table 1 Total extraction rate of niobium and performance test of composite extraction system

[0069]

[0070]

[0071] As can be seen from Table 1, in the examples of the present invention, both the total extraction rate and the extraction rate of niobium are relatively high. The total extraction rate of niobium reaches over 91%, and the extraction rate of niobium reaches over 99%. Moreover, the niobium composite extractant is stable and not easily emulsified, and can be recycled multiple times. In Comparative Example 1, ammonium fluoride or ammonium sulfate was not added during the roasting of columbite-tantalite ore, and the extraction rate of niobium was relatively low, only 72.91%. In Comparative Example 2, only ammonium fluoride was added during the roasting of columbite-tantalite ore, and the extraction rate of niobium was also relatively low. In Comparative Example 3, the niobium composite extractant was not used during extraction. The extraction rate of niobium was lower than that of the examples, and the extractant in Comparative Example 3 was easily emulsified, with poor recycling performance.

Claims

1. A niobium composite extractant, comprising the following components: methyl isobutyl ketone, amine compound, fluorine-free sulfonyl ionic liquid, stabilizer tributyl phosphate (TBP), bis(2-ethylhexyl) phosphate, and isodecanol.

2. The niobium composite extractant according to claim 1, wherein the volume percentages of the components in the niobium composite extractant are as follows: methyl isobutyl ketone 60 - 85%, preferably 60 - 80%; amine compound 5 - 25%, preferably 8 - 20%; fluorine-free sulfonyl ionic liquid 5 - 15%, preferably 5 - 8%; stabilizer tributyl phosphate 2 - 15%, preferably 5 - 8%; bis(2-ethylhexyl) phosphate 1 - 15%, preferably 2 - 5%; isodecanol 1 - 10%, preferably 2 - 3%.

3. The niobium composite extractant according to claim 1 or 2, wherein the amine compound is trioctylamine; the fluorine-free sulfonyl ionic liquid is a pyridine-based ionic liquid or an imidazole-based ionic liquid, selected from at least one of [HSO3-pPy]HSO4, [HSO3-pMIM]HSO4, [HSO3-pPy]pTSA, and [HSO3-pMIM]pTSA.

4. A method for extracting niobium from columbite-tantalite, characterized in that, It is the extraction of niobium using the niobium composite extractant described in claim 1.

5. The method according to claim 4, wherein It includes the following steps: Step 1: Crush the columbite-tantalite ore powder, add a roasting aid and roast to obtain a roasted product. The roasting aid is a compound of ammonium fluoride and ammonium sulfate; place the roasted product in a mixed solution of hydrofluoric acid and sulfuric acid for reaction to form a mixed solution of niobic acid fluoride and tantalic acid fluoride. Step 2: Use the composite extractant to extract and back-extract the mixed solution of niobic acid fluoride and tantalic acid fluoride to obtain a precipitate, and calcine the precipitate to obtain pure Nb2O5.

6. The method according to claim 5, characterized in that, In step 1, the roasting aid is a compound of ammonium fluoride and ammonium sulfate in a mass ratio of 2:1 - 1:2, preferably 2:1 - 1:1; the roasting aid accounts for 3 - 10 wt% of the columbite-tantalite ore powder.

7. The method according to claim 5, characterized in that, In step 1, the crushing is to crush to D50 = 2 ± 0.3 microns; the roasting conditions are: first keep warm at 200 - 300 °C for 1 - 3 h, and then keep warm at 800 - 1000 °C for 3 - 5 h; the mixed solution of hydrofluoric acid and sulfuric acid is a mixed solution of 40 - 60% molar concentration of hydrofluoric acid and 80 - 98% molar concentration of sulfuric acid in a volume ratio of 1:1 - 1:5; the reaction conditions are: keep the temperature constant at 80 - 95 °C for 4 - 8 hours under the protection of an inert atmosphere.

8. The method according to claim 5, wherein In step 2, the extraction method is: use the niobium composite extractant as the organic phase to extract the mixed solution of niobic acid fluoride and tantalic acid fluoride, and the aqueous phase is sulfuric acid with a concentration of 3 - 8 mol / L, preferably 3 - 5 mol / L; the back-extraction method is: after extraction, separate the organic phase, add deionized water, adjust the sulfuric acid concentration of the aqueous phase to 1 - 2.5 mol / L, preferably 1 - 2 mol / L, separate the aqueous phase for the extraction of niobium; add the niobium composite extractant again to extract the impurities other than niobic acid fluoride in the aqueous phase, repeat this step three to five times, combine the aqueous phases and introduce ammonia water to adjust the pH to 8.5 - 9.5 to obtain a precipitate.

9. The method according to claim 8, characterized in that, In Step 2, the extraction method is as follows: Use a niobium composite extractant as the organic phase to extract the mixed solution of niobic acid and tantalic acid for 5 - 25 minutes, with the organic phase / aqueous phase volume ratio being 1:1 - 1:5, temperature control: 20 - 40°C, and the aqueous phase being sulfuric acid with a concentration of 3 - 5 mol / L; Separate the organic phase, add deionized water, adjust the sulfuric acid concentration in the aqueous phase of the solution to 1 - 2 mol / L, separate the aqueous phase for niobium back extraction, add the niobium composite extractant to the separated aqueous phase again, repeat this step three times, with the niobium back extraction rate > 99%, combine the aqueous phases and introduce ammonia water to adjust the pH to 8.5 - 9.5 to obtain a precipitate.

10. The method according to claim 5, wherein In Step 2, the calcination conditions are: calcination at 800 - 1000°C for 3 - 10 h.

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