A method for extracting niobium from low-grade niobium-containing ore

Abstract

The present invention relates to a method for extracting niobium from a low-grade niobium-containing ore, which belongs to the technical field of mineral recovery metallurgy and solves the problem that the existing method for extracting niobium from a low-grade niobium-containing ore has hydrofluoric acid pollution of the environment and / or low efficiency of extracting niobium. The method comprises: step (1): mixing the low-grade niobium-containing ore with ammonium sulfate and concentrated sulfuric acid, roasting, and leaching niobium for the first time; step (2): mixing the roasted mixture with fluoride salt and water, and leaching niobium for the second time; step (3): separating the mixture obtained in step (2) from solid and liquid, and extracting niobium from the obtained filtrate. The method of the present invention does not use hydrofluoric acid, has less pollution to the environment, and has a high niobium leaching rate.

Description

Technical Field

[0001] The invention relates to the technical field of mineral recovery metallurgy, and in particular to a method for extracting niobium from low-grade niobium-containing ore. Background Art

[0002] The Bayan Obo rare earth tailings are the products of Baotou Iron and Steel Mine after iron selection, rare earth selection and mixed flotation, and are the raw materials for the production of niobium concentrate. The mineral composition of Bayan Obo rare earth tailings is complex, mainly magnetite, pyrite, dolomite, fluorite and quartz, and contains a wide variety of niobium minerals and niobium minerals. Among them, the mass content of iron oxide is 28.464%, the mass content of magnesium oxide is 5.573%, and the mass content of calcium oxide is 13.398%. Excessive iron, magnesium and calcium content affects the extraction of niobium. The mass content of niobium oxide is 0.10%, which exceeds the boundary grade of niobium oxide by 0.05%. The increasing amount of rare earth tailings piled up in the tailings pond has low utilization value, occupies land, pollutes the environment, and too much tailings may also cause the tailings pond to burst, which is very dangerous. The problem of reasonable recycling of tailings remains to be solved.

[0003] Niobium is a rare white precious metal with high melting and boiling points, strong ductility. Due to its excellent properties, niobium is widely used in high-strength steel manufacturing, superconducting materials industry and medical industry. my country's niobium resources are relatively abundant, and my country's niobium resources are mainly distributed in the Bayan Obo area of ​​Baotou City, Inner Mongolia. There are many types of niobium-containing minerals and niobium minerals in my country. The niobium content in niobium-containing minerals is low, the distribution is scattered, the mineral composition is complex, and it is difficult to extract metallic niobium.

[0004] The existing alkaline decomposition method for extracting niobium consumes a large amount of alkali, causes serious damage to equipment, and is costly, so it is rarely used in actual production. At present, niobium is mainly extracted by mixing high-concentration hydrofluoric acid and sulfuric acid to extract low-grade niobium-containing minerals. However, hydrofluoric acid is easily volatile when heated, polluting the environment and endangering human health. Hydrofluoric acid is easy to corrode equipment and increase the cost of extracting niobium. In recent years, some researchers have used sulfuric acid roasting-oxalic acid leaching to extract niobium, but the efficiency of extracting low-grade niobium-containing ores is low. On this basis, researchers proposed an ammonium salt-enhanced sulfuric acid roasting-oxalic acid leaching process, but the efficiency of extracting niobium from Bayan Obo rare earth tailings was limited. Summary of the invention

[0005] In view of the above analysis, the embodiments of the present invention are intended to provide a method for extracting niobium from low-grade niobium-containing ores, so as to solve at least one of the following problems in the existing methods for extracting niobium from low-grade niobium-containing ores: (1) hydrofluoric acid pollutes the environment, harms human health and corrodes equipment; and (2) the efficiency of niobium extraction is low.

[0006] In one aspect, the present invention provides a method for extracting niobium from a low-grade niobium-containing ore, the method comprising:

[0007] Step (1): mixing low-grade niobium-containing ore with ammonium sulfate and concentrated sulfuric acid, roasting, and initially leaching niobium;

[0008] Step (2): mixing the mixture after the primary leaching with fluoride salt and water to perform secondary leaching of niobium;

[0009] Step (3): separating the solid and liquid of the mixture after the secondary leaching, and extracting niobium from the obtained filtrate.

[0010] Preferably, in step (1), the ratio of the mass of the low-grade niobium-containing ore to the mass of ammonium sulfate and the volume of concentrated sulfuric acid is 1 g: 0.15-0.4 g: 1-1.5 mL.

[0011] Preferably, in step (2), the mass ratio of the low-grade niobium-containing ore to the fluoride salt is 1:0.15-0.25.

[0012] Preferably, in step (2), the ratio of the mass of the low-grade niobium-containing ore to the volume of water is 1 g: 20-30 mL.

[0013] Preferably, in step (2), the temperature of the secondary leaching is 50-80°C.

[0014] Preferably, in step (2), the secondary leaching time is 1-2 hours.

[0015] Preferably, in step (2), stirring is performed during the secondary leaching process, and the stirring speed is 300-500 r / min.

[0016] Preferably, in step (2), the fluoride salt is sodium fluoride.

[0017] Preferably, the low-grade niobium-containing ore is Bayan Obo rare earth tailings.

[0018] Preferably, in step (1), before mixing the low-grade niobium-containing ore with ammonium sulfate and concentrated sulfuric acid, carbonate impurities in the low-grade niobium-containing ore are first removed using dilute hydrochloric acid.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0020] 1. The present invention adopts the method of ammonium sulfate enhanced sulfuric acid roasting-fluoride salt two-stage leaching to effectively improve the niobium extraction efficiency in low-grade niobium-containing ores. Sulfuric acid roasting destroys the mineral structure and releases niobium elements. Ammonium sulfate enhanced sulfuric acid roasting makes fluoride ions and niobium easily complex to form NbF6 - and NbO5 2- , so that niobium ions enter the leaching solution, the niobium leaching rate (also called extraction rate, the niobium leaching rate of the preferred implementation method can reach 82%) is increased, thereby improving the niobium extraction efficiency; and the present invention does not use hydrofluoric acid, reducing environmental pollution and the harm caused by hydrofluoric acid.

[0021] 2. The method of the present invention is particularly suitable for the Baiyunebo rare earth tailings. In the Baiyunebo rare earth tailings, the niobium content is low and the silicon oxide content is high. The niobium in the silicon oxide cannot be leached out by sulfuric acid leaching in the existing method, and the existing hydrofluoric acid leaching will pollute the environment. The present invention adds fluoride ions during the water leaching process. On the one hand, the fluoride ions destroy silicates in the acidic solution and release the niobium contained in the silicates. On the other hand, the fluoride ions are easily complexed with niobium to form NbF6 - and NbOF5 2- , so that niobium ions enter the leaching solution, and the leaching rate of niobium is increased. The reason why fluoride salt is not added in step (1) is that fluoride salt reacts easily with strong acid (concentrated sulfuric acid) to generate hydrofluoric acid, which volatilizes under high temperature conditions, which not only fails to destroy the silicate mineral structure, but also causes environmental pollution.

[0022] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0024] Figure 1 The present invention is a flow chart for extracting niobium from low-grade niobium-containing ore. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0026] The present invention provides a method for extracting niobium from low-grade niobium-containing ore, such as Figure 1 As shown, the method includes:

[0027] Step (1): mixing low-grade niobium-containing ore with ammonium sulfate and concentrated sulfuric acid, roasting, and initially leaching niobium;

[0028] Step (2): mixing the mixture after the primary leaching with fluoride salt and water to perform secondary leaching of niobium;

[0029] Step (3): separating the solid and liquid of the secondary leaching mixture, and extracting niobium from the obtained filtrate.

[0030] Compared with the prior art, the present invention adopts the method of ammonium sulfate enhanced sulfuric acid roasting-fluoride salt two-stage leaching to effectively improve the niobium extraction efficiency in low-grade niobium-containing ores. Sulfuric acid roasting destroys the mineral structure and releases niobium elements. Ammonium sulfate enhanced sulfuric acid roasting makes fluoride ions and niobium easily complex to form NbF6 - and NbOF5 2- , so that niobium ions enter the leaching solution, the leaching rate of niobium is increased, thereby improving the efficiency of niobium extraction; and the present invention does not use hydrofluoric acid, reducing environmental pollution and the harm caused by hydrofluoric acid.

[0031] Illustratively, the low-grade niobium-containing ore refers to a niobium oxide ore having a mass content of less than 0.12%.

[0032] Exemplarily, the low-grade niobium-containing ore is the Bayan Obo rare earth tailings. The Bayan Obo rare earth tailings are the products of Baotou Iron and Steel Mine after iron selection, rare earth selection and mixed flotation. Its components include fluorite, quartz, magnetite, dolomite, and the specific chemical composition is shown in Table 1 below.

[0033] The method of the present invention is particularly suitable for the Baiyunebo rare earth tailings. In the Baiyunebo rare earth tailings, the niobium content is low and the silicon oxide content is high. The niobium in the silicon oxide cannot be leached only by sulfuric acid leaching in the existing method, and the existing hydrofluoric acid leaching will pollute the environment. The present invention adds fluoride ions during the water leaching process. On the one hand, the fluoride ions destroy silicates and release niobium contained in silicates. On the other hand, the fluoride ions are easily complexed with niobium to form NbF6 - and NbOF5 2- , so that niobium ions enter the leaching solution and increase the niobium leaching rate.

[0034] In order to avoid the generation of insoluble sulfate during the ammonium sulfate-sulfuric acid roasting process, and to avoid the violent reaction between sulfuric acid and carbonate, which may cause the risk of overflowing the pot, illustratively, in step (1), before mixing the low-grade niobium-containing ore with ammonium sulfate and concentrated sulfuric acid, dilute hydrochloric acid is first used to remove carbonate impurities in the low-grade niobium-containing ore, thereby improving the subsequent niobium leaching efficiency. The carbonate impurities include carbonate forms of iron, calcium, magnesium, aluminum and other ions.

[0035] Exemplarily, the concentration of the dilute hydrochloric acid is 2-2.5 mol / L.

[0036] Exemplarily, the ratio of the volume of dilute hydrochloric acid to the mass of the low-grade niobium-containing ore is 5-10 mL: 1 g.

[0037] Exemplarily, the temperature of the dilute hydrochloric acid pickling is 60-90° C. and the time is 1-1.5 h.

[0038] After pickling with dilute hydrochloric acid, the mixture is separated into solid and liquid, and the residue is dried for subsequent leaching of niobium.

[0039] Furthermore, before pickling the low-grade niobium-containing ore with dilute hydrochloric acid, the low-grade niobium-containing ore is first sieved through an 80-mesh sieve to remove leaves, small stones and other debris in the low-grade niobium-containing ore, and then the sieved material is dried at 100-120° C. for 4-5 hours.

[0040] Exemplarily, in step (1), the ratio of the mass of the low-grade niobium-containing ore to the mass of ammonium sulfate and the volume of concentrated sulfuric acid is 1 g: 0.15-0.4 g: 1-1.5 mL.

[0041] For example, in step (1), ammonium sulfate is first added to the low-grade niobium-containing ore, and after the low-grade niobium-containing ore and ammonium sulfate are mixed, concentrated sulfuric acid is added and mixed evenly. This can promote the consistency of the mineral reaction degree and improve the niobium leaching rate.

[0042] Illustratively, in step (1), the temperature of the initial leaching is 260-300°C, such as 270°C, 280°C, or 290°C.

[0043] Exemplarily, in step (1), the initial leaching time is 2.0-2.5 h, such as 2.1 h, 2.2 h, 2.3 h, 2.4 h.

[0044] Exemplarily, after the initial leaching is completed, the sample is taken out and cooled to room temperature.

[0045] Exemplarily, in step (2), the mass ratio of low-grade niobium-containing ore to fluoride salt is 1:0.15-0.25. If there is too much fluoride salt, sodium fluoride will be wasted and too many fluoride ions will be produced, which are difficult to handle. If there is too little fluoride salt, the niobium extraction rate will be reduced and niobium cannot be fully extracted.

[0046] In the present invention, in step (2), fluoride ions destroy silicates in an acidic solution, thereby releasing niobium contained in the silicates.

[0047] For example, in step (2), after the mixture after the initial leaching is mixed with fluoride salt and water, the pH of the mixture is adjusted to 1.5-1.8, for example, pH 1.5, 1.6, 1.7, 1.8. If the pH value is too low, hydrofluoric acid is easily formed; if the pH value is too high, the leaching rate of niobium is affected.

[0048] Specifically, fluoride salt is first added to the mixture after the primary leaching, water is added after mixing evenly, and then a pH adjuster is added to adjust the pH of the solution.

[0049] Illustratively, the pH of the mixture is adjusted using dilute sulfuric acid and / or sodium hydroxide.

[0050] Exemplarily, in step (2), the ratio of the mass of the low-grade niobium-containing ore to the volume of water is 1 g: 20-30 mL.

[0051] Illustratively, in step (2), the temperature of the secondary leaching is 60-80°C, such as 60°C, 65°C, 70°C, 75°C.

[0052] Exemplarily, in step (2), the secondary leaching time is 1-2 hours.

[0053] Illustratively, in step (2), stirring is performed during the secondary leaching process at a stirring speed of 300-500 r / min.

[0054] Illustratively, in step (2), the fluoride salt is sodium fluoride.

[0055] Illustratively, in step (3), extracting niobium from the obtained filtrate comprises: fixing the volume of the filtrate to 500 mL, concentrating the fixed niobium solution by 50 times, placing the concentrate and MIBK into a separatory funnel, shaking and then standing until an organic phase and an aqueous phase are stably separated in the separatory funnel, and separating the organic phase; back-extracting niobium from the organic phase, taking the organic phase and 0.5 mol / L sulfuric acid and placing them into a separatory funnel, shaking the separatory funnel, and extracting the aqueous phase after the aqueous phase and the organic phase are completely separated, and the aqueous phase is obtained. The aqueous phase is a niobium-containing solution.

[0056] Exemplarily, the volume ratio of the concentrate to MIBK is 1:1-2.

[0057] Exemplarily, the volume ratio of the organic phase to sulfuric acid is 1:4-5.

[0058] The method for extracting niobium from low-grade niobium-containing ore of the present invention is further illustrated below by means of specific examples.

[0059] The main components of the Bayan Obo rare earth tailings in the following examples and comparative examples are shown in Table 1.

[0060] Table 1

[0061] Components <![CDATA[Na2O]]> MgO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> CaO <![CDATA[TiO2]]> MnO <![CDATA[Fe2O3]]> <![CDATA[Nb2O5]]> Wt.% 2.28 5.57 1.74 19.17 13.40 0.78 1.40 28.50 0.10

[0062] Example 1

[0063] This embodiment provides a method for extracting niobium from a low-grade niobium-containing ore, wherein the low-grade niobium-containing ore is Bayan Obo rare earth tailings, and the method comprises:

[0064] (1) Pretreatment: The Bayan Obo rare earth tailings were screened through an 80-mesh sieve to remove leaves, small stones and other debris from the Bayan Obo rare earth tailings, and the screened material was placed in a tray and dried at 100°C for 4 hours.

[0065] (2) Hydrochloric acid pickling: Take the Bayan Obo rare earth tailings and put them into a round-bottom flask. Add 2 mol / L hydrochloric acid at a liquid-to-solid ratio of 7:1. After connecting the round-bottom flask to a condensation reflux device, place it in a water bath at a temperature of 70°C. The rotor speed is 400 r / min and the pickling time is 1.2 h.

[0066] (3) Filtration and separation: Use a vacuum filter to separate the filtrate and filter residue after acid washing, and dry the filter residue at 100°C for 1 hour.

[0067] The removal rates of iron, magnesium, calcium and aluminum in the Bayan Obo rare earth tailings after pickling were detected and calculated by XRF, and they were 29.51%, 64.76%, 66.85% and 49.09% respectively. The recovery rate of niobium was 86.84%, which refers to the ratio of the remaining niobium in the tailings after pickling to the niobium in the tailings before pickling.

[0068] (4) Ammonium sulfate-enhanced sulfuric acid roasting and primary leaching: 2 g of tailings after acid washing are placed in a glass quartz crucible, and 0.6 g of ammonium sulfate and 2.5 mL of 98% concentrated sulfuric acid are added (the ratio of the mass of tailings to the mass of ammonium sulfate and the volume of concentrated sulfuric acid is 1:0.3:1.25). The tailings are first mixed with ammonium sulfate and then with concentrated sulfuric acid. The glass quartz crucible is placed in a muffle furnace at 290°C and roasted for 2 hours. After the roasting is completed, the quartz glass crucible is taken out and cooled to room temperature.

[0069] (5) Secondary leaching of fluoride salt: Add 0.3 g of sodium fluoride (the mass ratio of tailings to sodium fluoride is 1:0.15) to the glass quartz crucible in step (4), add 50 mL of deionized water (the volume of water to the mass of tailings is 25:1), adjust the pH to 1.7, and place the glass quartz crucible in a constant temperature water bath. The water immersion temperature is 80°C, the leaching time is 1 hour, and the rotor speed is 400 r / min.

[0070] (6) Filtration and separation: Use a vacuum filter to separate the filtrate and residue after leaching.

[0071] Detection of niobium extraction rate: The niobium content in the filtrate after the secondary leaching was detected by ICP-MS and the niobium leaching rate (extraction rate) was calculated to be 82%. The leaching rate is the ratio of the niobium content in the filtrate after the secondary leaching to the niobium content in the tailings before the primary leaching.

[0072] (7) Extraction of niobium: The filtrate was fixed to 500 mL, and the niobium solution was concentrated 50 times. The concentrated solution and MIBK (volume ratio of 1:1) were placed in a separatory funnel. The separatory funnel was shaken for 3 minutes. After the shaking, the separatory funnel was left to stand until the organic phase and the aqueous phase were stably separated in the separatory funnel to separate the organic phase. The niobium in the organic phase was extracted by taking the organic phase and 0.5 mol / L sulfuric acid in a volume ratio of 1:4 and placing them in a separatory funnel. The separatory funnel was shaken for 5 minutes until the aqueous phase and the organic phase were completely separated. The aqueous phase was extracted and the niobium content was detected.

[0073] The niobium in the solution was extracted with MIBK, and the extraction rate reached 87.2%. The niobium was stripped with 0.5 mol / L sulfuric acid solution, and the dissolution rate of niobium was almost 100%.

[0074] Example 2

[0075] This example provides the effect of the amount of ammonium sulfate added on the niobium extraction rate, and adopts a method similar to Example 1 for extracting niobium from a low-grade niobium-containing ore, except that the amount of ammonium sulfate added is 0.1g, 0.2g, 0.4g, 0.5g, 0.6g, 0.7g, and 0.8g, respectively.

[0076] Table 2

[0077] The amount of ammonium sulfate 0.1g 0.2g 0.4g 0.5g 0.6g 0.7g 0.8g Niobium leaching rate 70％ 71％ 78％ 78％ 78％ 76％ 78％

[0078] It can be seen from the data in Table 2 and Example 1 that when the amount of ammonium sulfate added is 0.3-0.8 g (that is, the mass ratio of tailings to ammonium sulfate is 1:0.15-0.4), the leaching rate is maintained above 76%.

[0079] Example 3

[0080] This example provides the effect of the amount of concentrated sulfuric acid added on the niobium extraction rate, and uses a method similar to Example 1 to extract niobium from a low-grade niobium-containing ore, except that the solid-liquid ratio (g / mL) of tailings to concentrated sulfuric acid is 1:0.25, 1:0.5, 1:0.75, 1:1, and 1:1.5, respectively. The results are shown in Table 3.

[0081] Table 3

[0082]

[0083] It can be seen from the data in Table 3 and Example 1 that when the solid-liquid ratio of tailings to concentrated sulfuric acid is 1:1-1.5, the final leaching rate of niobium can reach more than 78%.

[0084] Example 4

[0085] This example provides the effect of roasting temperature on niobium extraction rate, using a method similar to that of Example 1 for extracting niobium from a low-grade niobium-containing ore, except that the roasting temperatures are 200°C, 230°C, 260°C, 280°C, 300°C, and 320°C, respectively. The results are shown in Table 4.

[0086] Table 4

[0087] Calcination temperature 200℃ 230℃ 260℃ 280℃ 300℃ 320℃ Niobium leaching rate 67％ 64％ 71％ 82％ 82％ 29％

[0088] It can be seen from the data in Table 4 and Example 1 that when the roasting temperature is between 260 and 300°C, the niobium extraction rate reaches more than 70%, and when the roasting temperature is between 260 and 300°C, the niobium extraction rate reaches more than 71%.

[0089] Example 5

[0090] This example provides the effect of roasting time on niobium extraction rate, using a method similar to Example 1 for extracting niobium from a low-grade niobium-containing ore, except that the roasting times are 0.5 h, 1.0 h, 1.5 h, and 2.5 h, respectively. The results are shown in Table 5.

[0091] Table 5

[0092] Roasting time 0.5h 1.0h 1.5h 2.5h Niobium leaching rate 73％ 72％ 76％ 82％

[0093] It can be seen from the data in Table 5 and Example 1 that when the roasting time exceeds 2 hours, the niobium extraction rate remains substantially unchanged. Therefore, the preferred roasting time of the present invention is 2-2.5 hours.

[0094] Example 6

[0095] This example provides the effect of the amount of sodium fluoride added during water leaching on the niobium extraction rate, using a method similar to Example 1 for extracting niobium from a low-grade niobium-containing ore, except that the amount of sodium fluoride added is 0.1 g, 0.2 g, 0.4 g, and 0.5 g, respectively. The results are shown in Table 6.

[0096] Table 6

[0097] Sodium fluoride dosage 0.1g 0.2g 0.4g 0.5g Niobium leaching rate 13％ 31％ 82％ 82％

[0098] It can be seen from the data in Table 6 and Example 1 that for 2 g of tailings, the niobium leaching rate is highest when the amount of sodium fluoride used is above 0.3 g, and the niobium leaching rate remains basically unchanged when the amount of sodium fluoride used exceeds 0.3 g.

[0099] Example 7

[0100] This example provides the effect of pH value on niobium extraction rate during water leaching, and adopts a method similar to Example 1 for extracting niobium from low-grade niobium-containing ore, except that the pH value is adjusted by dripping sodium hydroxide solution and sulfuric acid solution, and the pH value of the leachate is adjusted to 2.0.

[0101] The niobium leaching rate in this example is 67%.

[0102] Example 8

[0103] This example provides the effect of the secondary leaching temperature on the niobium extraction rate. A method similar to that of Example 1 is used to extract niobium from a low-grade niobium-containing ore, except that the secondary leaching temperature is 50°C.

[0104] The niobium leaching rate in this example is 68%.

[0105] Comparative Example 1

[0106] The comparative example adopts the method of ammonium sulfate and sulfuric acid roasting + water leaching + oxalic acid leaching to extract niobium from the Bayan Obo rare earth tailings. The method is similar to the method in Example 1, except that: after the initial roasting and leaching by ammonium sulfate and concentrated sulfuric acid roasting, water is added to the mixture for water leaching, and then solid-liquid separation is performed to obtain a first filtrate and a first filter residue, the first filter residue is mixed with oxalic acid, and after the oxalic acid leaching is completed, solid-liquid separation is performed to obtain a second filtrate and a second filter residue, and the total content of niobium in the obtained first filtrate and the second filtrate is detected and the extraction rate is calculated to be 54.6%.

[0107] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for extracting niobium from low-grade niobium-containing ore, characterized in that: The method consists of the following steps: Step (1): mixing low-grade niobium-containing ore with ammonium sulfate and concentrated sulfuric acid, roasting, and initially leaching niobium; Step (2): mixing the mixture after the primary leaching with fluoride salt and water to perform secondary leaching of niobium; Step (3): separating the solid and liquid of the mixture after the secondary leaching, and extracting niobium from the obtained filtrate; The low-grade niobium-containing ore is the Bayan Obo rare earth tailings, and the mass content of niobium oxide is less than 0.12%; In the step (1), before mixing the low-grade niobium-containing ore with ammonium sulfate and concentrated sulfuric acid, the process further includes: first sieving the low-grade niobium-containing ore through an 80-mesh sieve, then drying the sieved material at 100-120° C. for 4-5 hours, and then removing carbonate impurities in the low-grade niobium-containing ore using dilute hydrochloric acid; In the step (1), the calcination temperature is 260-300°C; In the step (2), after the mixture after the initial leaching is mixed with fluoride salt and water, the pH of the mixture is 1.5-1.8; The mass ratio of the low-grade niobium-containing ore to the fluoride salt is 1:0.15-0.

25.

2. The method according to claim 1, characterized in that In step (1), the ratio of the mass of the low-grade niobium-containing ore to the mass of ammonium sulfate and the volume of concentrated sulfuric acid is 1 g: 0.15-0.4 g: 1-1.5 mL.

3. The method according to claim 1, characterized in that In step (2), the ratio of the mass of the low-grade niobium-containing ore to the volume of water is 1 g: 20-30 mL.

4. The method according to claim 1, characterized in that In step (2), the temperature of the secondary leaching is 50-80°C.

5. The method according to claim 1, characterized in that In step (2), the secondary leaching time is 1-2 hours.

6. The method according to claim 1, characterized in that In step (2), stirring is performed during the secondary leaching process, and the stirring speed is 300-500 r / min.

7. The method according to claim 1, characterized in that In step (2), the fluoride salt is sodium fluoride.

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