Method for leaching niobium from low-grade niobium ore containing fluorine by using mixed acid of boric acid and organic acid

Abstract

This invention discloses a method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixed acid solution, belonging to the field of rare metal metallurgy technology. The method includes the following steps: S1, selecting fluorine-containing low-grade niobium ore powder of the target particle size; fluorine-containing low-grade niobium ore exceeding the target particle size is crushed, ground, and sieved to obtain niobium ore powder of the target particle size; S2, adding a mixed acid solution containing boric acid and organic acid to the niobium ore powder, controlling the solid-liquid ratio to obtain a slurry; S3, stirring the slurry under heating and heat preservation conditions to carry out the leaching reaction, followed by filtration and solid-liquid separation to obtain a niobium-containing leachate. This invention cleverly utilizes the fluorine-containing minerals (such as fluorite) inherent in the ore as a fluorine source, generating fluoroborate ions in situ through reaction with boric acid, avoiding the direct use of highly toxic hydrofluoric acid and achieving intrinsic safety; moreover, the implementation conditions are mild, environmentally friendly, and the waste liquid is easy to treat, providing a new technical path for the efficient and green development of low-grade niobium resources.

Description

Technical Field

[0001] This invention belongs to the field of rare metal metallurgy technology, specifically relating to a method for leaching niobium from fluorine-containing low-grade niobium ore using a mixture of boric acid and organic acid. Background Technology

[0002] Niobium is an important rare metal, widely used in core fields such as steel, superconducting materials, and aerospace due to its excellent high-temperature resistance, corrosion resistance, superconductivity, and strong alloying properties. Bayan Obo and other regions are major niobium resource bases in my country. However, these resources generally exhibit low grades, complex mineral compositions, fine-grained niobium mineral distribution, and close association with gangue minerals such as iron, rare earth elements, and fluorides. They are typical low-grade fluorine-containing associated niobium resources. Traditional niobium ore beneficiation techniques are insufficient for efficient dissociation and enrichment of niobium minerals, making it difficult to obtain high-grade niobium concentrate (Nb₂O₅ grade > 5%), and the overall recovery rate is typically less than 30%.

[0003] Currently, niobium ore processing mainly employs traditional processes such as high-temperature alkaline fusion, hydrofluoric acid leaching, and high-pressure sulfuric acid leaching, all of which have insurmountable drawbacks:

[0004] High-temperature alkali fusion method: using NaOH / Na2CO3 as flux, the reaction temperature is usually higher than 600℃. The process is mature but has extremely high energy consumption, large alkali consumption, serious equipment corrosion, and a long process. The treatment cost of alkali residue and wastewater is high, making it difficult to adapt to the efficient and green extraction of low-grade niobium ore.

[0005] Hydrofluoric acid (HF) leaching method: It has a strong ability to destroy the crystal lattice of niobium minerals and has a high decomposition rate for high-grade ores. However, HF is a highly toxic and corrosive reagent that is easy to volatilize and generate fluorine-containing waste gas. The disposal of fluorine-containing wastewater and waste residue is difficult and poses significant safety and environmental risks. At the same time, it has strict requirements for equipment materials, high investment and operating costs, poor adaptability to low-grade ores, and significant interference from impurities.

[0006] Sulfuric acid process: The raw material cost is relatively low, but the conventional process requires high temperature and high pressure conditions above 200°C. The reaction conditions are harsh, the energy consumption is high, the equipment investment is large, the niobium leaching rate is unstable and generally below 80%, and a large amount of impurities such as calcium, magnesium and iron are dissolved, making subsequent separation and purification difficult. It is not economical and safe.

[0007] In recent years, the industry has attempted to conduct low-temperature leaching research using single organic acids (oxalic acid, citric acid, etc.) to enhance leaching efficiency through the complexation of organic acids with niobium. However, due to the dense structure and stable chemical properties of niobium minerals, they are difficult to decompose effectively at low temperatures, resulting in low leaching efficiency, long cycles, and poor results, hindering industrial application. Therefore, developing a new process for efficiently, greenly, and cost-effectively extracting niobium from low-grade niobium ores at low temperature and normal pressure is of great significance. Summary of the Invention

[0008] To address the problems of high energy consumption, severe equipment corrosion, significant environmental pollution risks, and low niobium recovery rates in existing niobium extraction processes, this invention aims to provide a method for leaching niobium from low-grade fluorine-containing niobium ores using a boric acid-organic acid mixture. This method utilizes the fluorides (such as fluorite) naturally present in the ore to react with boric acid in situ to generate fluoroborate ions, providing a stable fluorine source to disrupt the niobium mineral lattice without producing hydrofluoric acid. Simultaneously, the organic acid synergistically complexes niobium ions and inhibits the dissolution of impurities, achieving efficient and green extraction of niobium at low temperature and normal pressure.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0011] S1. Select fluorine-containing low-grade niobium ore powder with the target particle size. For fluorine-containing low-grade niobium ore with a particle size exceeding the target size, crush, grind and screen it to obtain niobium ore powder with the target particle size.

[0012] S2. Add a mixed acid solution containing boric acid and organic acid to niobium ore powder, control the solid-liquid ratio, and obtain a slurry;

[0013] S3. Under heating and heat preservation conditions, the slurry is stirred to carry out the leaching reaction, and then filtered to separate the solid and liquid, thus obtaining a niobium-containing leachate.

[0014] Furthermore, in step S1, the Nb2O5 grade in the fluorine-containing low-grade niobium ore is <5%, the fluorine-containing mineral is mainly fluorite, and other fluorine-containing minerals include one or more of fluorapatite, bastnaesite, Yellow River ore, and bastnaesite calcium cerium.

[0015] Furthermore, in step S1, the target particle size of niobium ore powder is 90% or more below 74 μm.

[0016] Furthermore, in step S2, the mass concentration of boric acid in the mixed acid solution is 6% to 35%, and the mass concentration of organic acid is 1% to 5%.

[0017] Furthermore, the organic acid is selected from oxalic acid and citric acid.

[0018] Furthermore, in step S2, the mixed acid solution also includes inorganic acid, with a volume concentration of 0-10%.

[0019] Furthermore, the inorganic acid is selected from hydrochloric acid and sulfuric acid.

[0020] Furthermore, in step S2, the solid-liquid mass ratio of niobium ore powder to mixed acid solution is 1:5 to 1:10.

[0021] Furthermore, in step S3, the leaching reaction temperature is 90℃~150℃, and the time is 10h~20h.

[0022] Furthermore, in step S3, after obtaining the niobium-containing leachate, an alkaline compound is added to adjust the pH value to ≥6.

[0023] Advantages and effects of the present invention:

[0024] This invention employs a boric acid-organic acid mixed acid method for leaching niobium from fluorine-containing low-grade niobium ore. It cleverly utilizes the fluorine-containing minerals within the ore itself (such as fluorite) as a fluorine source. Through in-situ reaction with boric acid, fluoroborate ions are generated, avoiding the direct use of highly toxic hydrofluoric acid and achieving intrinsic safety. Under low-temperature (≤150℃) and normal-pressure conditions, fluoroborate ions disrupt the niobium mineral lattice, while the organic acid simultaneously complexes niobium ions and inhibits impurity dissolution. This synergistic effect results in a niobium leaching rate exceeding 84.7%. Compared to traditional high-temperature alkaline fusion or strong acid leaching processes, this invention features lower leaching temperatures, lower energy consumption, milder implementation conditions, environmental friendliness, and easier wastewater treatment, providing a novel technological path for the efficient and green development of low-grade niobium resources. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process for leaching niobium from fluorine-containing low-grade niobium ore using a mixture of boric acid and organic acid, as described in this invention. Detailed Implementation

[0026] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0027] A method for leaching niobium from low-grade fluorine-containing niobium ore using a mixture of boric acid and organic acid, such as... Figure 1 As shown, it includes the following steps:

[0028] S1. Directly select fluorine-containing low-grade niobium ore powder with a particle size ≤74μm. For fluorine-containing low-grade niobium ore with a particle size exceeding the target size, crush, grind and screen it so that the proportion of niobium ore powder with a particle size ≤74μm is more than 90%. The Nb2O5 grade in the fluorine-containing low-grade niobium ore is <5%. The main fluorine-containing mineral is fluorite, and other fluorine-containing minerals include one or more of fluorapatite, bastnaesite, Yellow River ore, and bastnaesite calcium cerium.

[0029] S2. Add a mixed acid solution containing boric acid and organic acid to the niobium ore powder. The mass concentration of boric acid in the mixed acid solution is 6% to 35%, and the mass concentration of organic acid is 1% to 5%. The organic acid is selected from oxalic acid and citric acid. An inorganic acid with a volume concentration of 0% to 10% can also be added to the mixed acid solution. The inorganic acid is selected from hydrochloric acid and sulfuric acid. Control the solid-liquid mass ratio of niobium ore powder to mixed acid solution to be 1:5 to 1:10 to obtain a slurry.

[0030] S3. Stir the slurry and leach at 90℃~150℃ for 10h~20h. Then filter and separate the solid and liquid to obtain niobium-containing leachate. Add alkaline compounds (such as NaOH, Na2CO3 or ammonia) to adjust the pH value to ≥6.

[0031] Example 1

[0032] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0033] S1. Niobium-bearing tailings from Bayan Obo were selected as raw materials, with a Nb₂O₅ grade of 0.65% and a particle size ≤74μm accounting for 98%. The main chemical components are shown in Table 1.

[0034] Table 1. Main chemical composition (wt.%) of raw material mineral sample in Example 1

[0035]

[0036] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0037] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0038] Testing showed that the niobium leaching rate in the niobium-containing leachate of Example 1 reached 93.5%. The impurity content in the leachate is shown in Table 2.

[0039] Table 2. Impurity element content (wt.%) in niobium-containing leachate from Example 1

[0040]

[0041] Example 2

[0042] S1. Niobium-bearing tailings from Bayan Obo were selected as raw material, with a Nb₂O₅ grade of 0.217% and a particle size ≤74μm accounting for 91.56%. The main chemical components are shown in Table 3.

[0043] Table 3. Main chemical composition (wt.%) of raw material mineral sample in Example 2

[0044]

[0045] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 5 wt.% citric acid + 3 vol.% H2SO4. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:10 to obtain a slurry.

[0046] S3. Place the slurry in a reaction vessel and stir and leach at 110°C for 15 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add Na2CO3 to adjust the pH value to ≥6.

[0047] The niobium leaching rate in the niobium-containing leachate of Example 2 was found to be 87.2%. The impurity content in the leachate is shown in Table 4.

[0048] Table 4. Impurity element content (wt.%) in niobium-containing leachate from Example 2

[0049]

[0050] Example 3

[0051] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0052] S1. Niobium-bearing tailings from Bayan Obo were selected as raw materials, as in Example 1;

[0053] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid. Mix niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0054] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add ammonia to adjust the pH value to ≥6.

[0055] The niobium leaching rate in the niobium-containing leachate of Example 3 was found to be 84.70% after testing. The impurity content in the leachate is shown in Table 5.

[0056] Table 5. Impurity element content (wt.%) in niobium-containing leachate from Example 3

[0057]

[0058] Example 4

[0059] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0060] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0061] S2. Prepare a mixed acid solution: 6 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0062] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0063] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 4 reached 87.36%.

[0064] Example 5

[0065] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0066] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0067] S2. Prepare a mixed acid solution: 15wt.% boric acid + 2wt.% oxalic acid + 5vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0068] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0069] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 5 reached 93.38%.

[0070] Example 6

[0071] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0072] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0073] S2. Prepare a mixed acid solution: 20 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0074] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0075] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 6 reached 94.22%.

[0076] Example 7

[0077] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0078] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0079] S2. Prepare a mixed acid solution: 25 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0080] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0081] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 7 reached 93.77%.

[0082] Example 8

[0083] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0084] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0085] S2. Prepare a mixed acid solution: 30wt.% boric acid + 2wt.% oxalic acid + 5vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0086] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0087] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 8 reached 95.09%.

[0088] Example 9

[0089] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0090] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0091] S2. Prepare a mixed acid solution: 35wt.% boric acid + 2wt.% oxalic acid + 5vol.% HCl. Mix niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0092] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0093] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 9 reached 94.18%.

[0094] Example 10

[0095] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0096] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0097] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 1 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0098] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0099] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 10 reached 88.82%.

[0100] Example 11

[0101] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0102] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0103] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 3 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0104] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0105] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 11 reached 92.11%.

[0106] Example 12

[0107] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0108] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0109] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 4 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0110] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0111] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 12 reached 93.92%.

[0112] Example 13

[0113] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0114] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0115] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 5 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0116] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0117] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 13 reached 95.06%.

[0118] Example 14

[0119] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0120] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0121] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 0.5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0122] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0123] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 14 reached 89.33%.

[0124] Example 15

[0125] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0126] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0127] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 3 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0128] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0129] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 15 reached 90.08%.

[0130] Example 16

[0131] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0132] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0133] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 7 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0134] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0135] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 16 reached 93.33%.

[0136] Example 17

[0137] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0138] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0139] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 10 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0140] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0141] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 17 reached 94.11%.

[0142] Example 18

[0143] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0144] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0145] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:5 to obtain a slurry.

[0146] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0147] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 18 reached 86.46%.

[0148] Example 19

[0149] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0150] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0151] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:10 to obtain a slurry.

[0152] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0153] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 19 reached 92.94%.

[0154] Example 20

[0155] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0156] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0157] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0158] S3. Place the slurry in a reaction vessel and stir and leach at 120°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0159] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 20 reached 95.37%.

[0160] Example 21

[0161] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0162] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0163] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0164] S3. Place the slurry in a reaction vessel and stir and leach at 125°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0165] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 21 reached 95.66%.

[0166] Example 22

[0167] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0168] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0169] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0170] S3. Place the slurry in a reaction vessel and stir and leach at 150°C for 10 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0171] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 22 reached 90.21%.

[0172] Example 23

[0173] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0174] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0175] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0176] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 15 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0177] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 23 reached 96.07%.

[0178] Example 24

[0179] A method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture includes the following steps:

[0180] S1. The same niobium-bearing tailings from Bayan Obo as in Example 1 were selected as raw materials.

[0181] S2. Prepare a mixed acid solution: 10 wt.% boric acid + 2 wt.% oxalic acid + 5 vol.% HCl. Mix the niobium ore powder with the mixed acid solution at a solid-liquid mass ratio of 1:8 to obtain a slurry.

[0182] S3. Place the slurry in a reaction vessel and stir and leach at 90°C for 20 hours. Then filter and separate the solid and liquid to obtain a niobium-containing leachate. Add NaOH to adjust the pH value to ≥6.

[0183] Tests showed that the niobium leaching rate in the niobium-containing leachate of Example 24 reached 95.84%.

[0184] The above embodiments fully demonstrate that the method of the present invention can achieve efficient and selective leaching of niobium in low-grade niobium ore under mild conditions, and has significant prospects for industrial application.

Claims

1. A method for leaching niobium from fluorine-containing low-grade niobium ore using a mixture of boric acid and organic acid, characterized in that, Includes the following steps: S1. Select fluorine-containing low-grade niobium ore powder with the target particle size. For fluorine-containing low-grade niobium ore with a particle size exceeding the target size, crush, grind and screen it to obtain niobium ore powder with the target particle size. S2. Add a mixed acid solution containing boric acid and organic acid to niobium ore powder, control the solid-liquid ratio, and obtain a slurry; S3. Under heating and heat preservation conditions, the slurry is stirred to carry out the leaching reaction, and then filtered to separate the solid and liquid, thus obtaining a niobium-containing leachate.

2. The method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixed acid as described in claim 1, characterized in that, In step S1, the Nb2O5 grade in the fluorine-containing low-grade niobium ore is <5%, the main fluorine-containing mineral is fluorite, and other fluorine-containing minerals include one or more of fluorapatite, bastnaesite, Yellow River ore, and bastnaesite calcium cerium.

3. The method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture as described in claim 1, characterized in that, In step S1, the target particle size of niobium ore powder is 90% or more below 74 μm.

4. The method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixed acid as described in claim 1, characterized in that, In step S2, the mass concentration of boric acid in the mixed acid solution is 6% to 35%, and the mass concentration of organic acid is 1% to 5%.

5. The method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture as described in claim 4, characterized in that, The organic acid is selected from oxalic acid and citric acid.

6. The method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixed acid as described in claim 1, characterized in that, In step S2, the mixed acid solution also includes inorganic acid, with a volume concentration of 0-10%.

7. The method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixed acid as described in claim 6, characterized in that, The inorganic acid is selected from hydrochloric acid and sulfuric acid.

8. The method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixed acid as described in claim 1, characterized in that, In step S2, the solid-liquid mass ratio of niobium ore powder to mixed acid solution is 1:5 to 1:

10.

9. The method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture as described in claim 1, characterized in that, In step S3, the leaching reaction is carried out at a temperature of 90℃ to 150℃ for 10h to 20h.

10. The method for leaching niobium from fluorine-containing low-grade niobium ore using a boric acid-organic acid mixture as described in claim 1, characterized in that, In step S3, after obtaining the niobium-containing leachate, an alkaline compound is added to adjust the pH value to ≥6.

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