Process for decomposing low-grade niobium ores rich in calcite

Abstract

The application discloses a decomposition method of low-grade niobium ore rich in epi-dolomite. The decomposition method comprises the following steps: (1) carrying out acid decomposition on the low-grade niobium ore rich in epi-dolomite particles and a first sulfuric acid solution with a concentration of 50-98 wt% at a temperature of 80-320 DEG C for 1-12 h to obtain an acid decomposition product; (2) mixing the acid decomposition product with water and then leaching at 20-50 DEG C to obtain a leaching product; the leaching product is subjected to solid-liquid separation to obtain a leaching residue and a leaching solution; wherein the liquid-solid ratio of the mixture formed by the acid decomposition product and water is (0.5-10) L:1 kg; (3) washing the acid decomposition product with a second sulfuric acid solution with a concentration of 10-50 wt% to obtain a discharge residue and a washing residue solution. The method has a high leaching rate of niobium, titanium, rare earth and iron elements.

Description

Technical Field

[0001] This invention relates to a method for decomposing low-grade niobium ore rich in calcite. Background Technology

[0002] Niobium is an important rare metal element with properties such as high melting point, high boiling point, corrosion resistance, high temperature resistance, superconductivity, and high strength at high temperatures. Niobium is mainly used to produce high-strength low-alloy steel-grade ferroniobium, niobium chemicals, high-purity ferroniobium, niobium alloys, and niobium metal products.

[0003] Niobium ore decomposition processes mainly include chlorination, alkaline decomposition, and acid decomposition. Chlorination utilizes the differences in the thermodynamic properties of chlorination among the components in niobium concentrates, controlling the chlorination reaction conditions to convert the useful components into gaseous or condensed chlorides, thus separating them from other components. This process uses highly corrosive chlorinating agents that easily corrode equipment. Alkaline methods, which often use caustic solutions such as NaOH and KOH to decompose niobium minerals, are now obsolete. Acid decomposition methods mainly include hydrofluoric acid decomposition and sulfuric acid solution decomposition. Hydrofluoric acid decomposition primarily uses high-concentration hydrofluoric acid or a mixture of hydrofluoric acid and concentrated sulfuric acid as the leaching solution. This process requires a large amount of hydrofluoric acid when processing low-grade niobium concentrate, places high demands on equipment, and generates HF-containing fumes during the reaction, polluting the environment.

[0004] CN115852174B discloses a method for recovering rare earth elements and niobium from fluorite concentrate. The method involves preparing fluorite concentrate into granules, mixing the granules with a sulfuric acid solution, and pre-reacting at 100–120°C to obtain a pre-reacted material. The pre-reacted material is then reacted at 220–260°C to obtain a reaction gas and a reaction residue. The reaction residue is leached with water to obtain a leachate containing rare earth elements and niobium, as well as leaching residue. The rare earth minerals in the fluorite concentrate are mainly one or more of bastnaesite, bastnaesite, and Yellow River bastnaesite, while the niobium minerals are mainly one or more of columbite, calcite, and columbite-rutile. This method is used to recover rare earth elements and niobium from fluorite concentrate.

[0005] CN105154659A discloses a method for simultaneously extracting iron and niobium from low-grade niobium ore in Bayan Obo. The method involves pre-treating the low-grade niobium ore to obtain high-temperature granules; melting and reducing the high-temperature granules to obtain niobium-containing molten iron and niobium-containing iron-removing slag; oxidizing and slagging the niobium-containing molten iron to obtain niobium-removing crude iron and niobium-rich slag; mixing and conditioning the iron-removing slag and niobium-rich slag to obtain low-viscosity niobium-containing slag; chlorinating the low-viscosity niobium-containing slag to obtain niobium-removing residue and gaseous polymetallic chlorides; and condensing and separating the gaseous polymetallic chlorides to obtain niobium chlorides. This process uses high-temperature melting and reduction and chlorination separation to treat low-grade niobium ore, resulting in a long process, high energy consumption, and potential environmental pollution risks. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a decomposition method for low-grade niobium ore rich in calcite, which can improve the leaching rate of niobium, titanium, rare earth elements and iron.

[0007] The present invention achieves the above objectives through the following technical solutions.

[0008] This invention provides a method for decomposing low-grade niobium ore rich in calcite, comprising the following steps:

[0009] (1) The low-grade niobium ore particles rich in calcite were subjected to acid decomposition with a first sulfuric acid solution of 50-98 wt% at a temperature of 80-320℃ for 1-12 hours to obtain acid decomposition products.

[0010] The low-grade niobium ore particles in the rich calcite contain more than 90% particles with a particle size of less than 200 mesh; the Nb2O5 content in the low-grade niobium ore particles is 0.1-15 wt%, the TFe content is 6.0-50 wt%, the REO content is 1-15 wt%, and the TiO2 content is 1-15 wt%; the volume-to-mass ratio of the first sulfuric acid solution to the low-grade niobium ore particles is (1-6) L:1 kg.

[0011] (2) The acid decomposition products are mixed with water and leached at 20-50°C to obtain leaching products; the leaching products are separated into solid and liquid to obtain leaching residue and leaching liquid;

[0012] In the mixture formed by acid decomposition products and water, the liquid-to-solid ratio is (0.5-10) L: 1 kg.

[0013] (3) The acid decomposition products are washed with a second sulfuric acid solution with a concentration of 10-50 wt% to obtain external slag and washing liquid.

[0014] According to the decomposition method of the present invention, preferably, it further includes the following steps:

[0015] The low-grade niobium ore of the rich calcite is ground, then filtered and dried in sequence to obtain low-grade niobium ore particles of the rich calcite.

[0016] The slurry concentration is 50–75 wt%, and the grinding time is 5–50 min.

[0017] According to the decomposition method of the present invention, preferably, low-grade niobium ore particles rich in calcite are mixed with a first sulfuric acid solution at a rotation speed of 100-500 r / min and then subjected to acid decomposition.

[0018] According to the decomposition method of the present invention, preferably, in step (2), the concentration of sulfuric acid in the mixture formed by the acid decomposition product and water is 10-50 wt%.

[0019] According to the decomposition method of the present invention, preferably, in step (2), the leaching time is 0.5 to 4 hours.

[0020] According to the decomposition method of the present invention, preferably, the number of washings is 1 to 5, the liquid-solid ratio of the second sulfuric acid solution used in each washing to the leaching residue is (1 to 5) L: 1 kg, and the washing time is 10 to 50 min.

[0021] According to the decomposition method of the present invention, preferably, the leaching residue is washed by stirring the mixture formed by the leaching residue and the second sulfuric acid solution; or the leaching residue is washed by rinsing.

[0022] According to the decomposition method of the present invention, preferably, it further includes the following steps:

[0023] Combine the washing residue and the leachate.

[0024] According to the decomposition method of the present invention, preferably, the leaching rate of niobium is ≥85wt%, the leaching rate of titanium is ≥90wt%, and the leaching rate of rare earth elements is ≥90wt%.

[0025] According to the decomposition method of the present invention, preferably, the iron leaching rate is ≥90 wt%.

[0026] This invention employs an acid decomposition-acid leaching process to leach niobium, titanium, rare earth elements, and iron from low-grade niobium ore rich in calcite, achieving a high leaching rate and improving the comprehensive utilization rate of niobium ore resources. Attached Figure Description

[0027] Figure 1 This is a flowchart of a decomposition method for low-grade niobium ore rich in calcite according to the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0029] The decomposition method for low-grade niobium ore rich in calcite of the present invention includes the following steps: (1) acid decomposition; (2) acid leaching; and (3) washing. Each step is described in detail below.

[0030] Steps of acid decomposition

[0031] Low-grade niobium ore particles rich in calcite are subjected to acid decomposition with a first sulfuric acid solution to obtain acid decomposition products. Preferably, the low-grade niobium ore particles rich in calcite are mixed with the first sulfuric acid solution before acid decomposition. Stirring can be carried out at a speed of 100-500 r / min. Preferably, stirring is carried out at a speed of 200-400 r / min. More preferably, stirring is carried out at a speed of 250-300 r / min.

[0032] In the low-grade niobium ore particles of the rich calcite, particles with a size of less than 200 mesh account for more than 90%; preferably, more than 95%; more preferably, more than 98%. This helps the acid decomposition to proceed fully.

[0033] The concentration of the first sulfuric acid solution is 50–98 wt%. In some embodiments, the concentration of the first sulfuric acid solution is 70–80 wt%. In other embodiments, the concentration of the first sulfuric acid solution is 95–98 wt%. This facilitates complete acid decomposition and improves the recovery rate of niobium, titanium, iron, and rare earth elements.

[0034] The acid decomposition temperature is 80–320°C; preferably 130–280°C. In some embodiments, the acid decomposition temperature is 170–190°C. In other embodiments, the acid decomposition temperature is 250–270°C. This helps the acid decomposition to proceed fully, improving the recovery rate of niobium, titanium, iron, and rare earth elements.

[0035] The acid decomposition time is 1–12 h; preferably 2–8 h; more preferably 3–5 h. This helps the acid decomposition to proceed fully and improves the recovery rate of niobium, titanium, iron, and rare earth elements.

[0036] The volume-to-mass ratio of the first sulfuric acid solution to the low-grade niobium ore particles rich in calcite is (1-6) L:1 kg; preferably (2-5) L:1 kg. In some embodiments, the volume-to-mass ratio is (2.5-3) L:1 kg. In other embodiments, the volume-to-mass ratio is (3.5-4) L:1 kg. This facilitates complete acid decomposition and improves the recovery rate of niobium, titanium, iron, and rare earth elements.

[0037] In the low-grade niobium ore particles rich in calcite, the Nb₂O₅ content is 0.1–15 wt%; preferably 1.5–13 wt%. In some embodiments, the Nb₂O₅ content is 11.5–13 wt%. In other embodiments, the Nb₂O₅ content is 3–6 wt%.

[0038] In the low-grade niobium ore particles of rich calcite, the TFe content is 6.0–50 wt%. In some embodiments, the TFe content is 6.5–7.5 wt%. In other embodiments, the TFe content is 45–49 wt%.

[0039] In the low-grade niobium ore particles rich in calcite, the REO content is 1–15 wt%. In some embodiments, the REO content is 2–4 wt%. In other embodiments, the REO content is 5–8 wt%. In still other embodiments, the REO content is 13–15 wt%.

[0040] In the low-grade niobium ore particles of rich calcite, the TiO2 content is 1–15 wt%. In some embodiments, the TiO2 content is 3–6 wt%. In other embodiments, the TiO2 content is 8–12 wt%.

[0041] In some embodiments, the process further includes grinding low-grade niobium ore rich in calcite, followed by filtration and drying to obtain low-grade niobium ore particles. A ball mill can be used for grinding.

[0042] The concentration of the slurry can be 50–75 wt%. In some embodiments, the concentration of the slurry is 55–65 wt%. In other embodiments, the concentration of the slurry is 70–75 wt%.

[0043] The grinding time can be 5 to 50 minutes; preferably 10 to 30 minutes. In some embodiments, the grinding time is 13 to 17 minutes.

[0044] The low-grade niobium ore of the rich calcite can be found in the Bayan Obo mining area.

[0045] Acid leaching steps

[0046] The acid decomposition products are mixed with water and then leached to obtain the leaching product. The leaching product is then separated into solid and liquid components to obtain leaching residue and leaching solution.

[0047] The leaching temperature is 20–50°C; preferably 25–40°C. In some embodiments, the leaching temperature is 30–35°C.

[0048] The leaching time can be 0.5 to 4 hours. In some embodiments, the leaching time is 1 to 2 hours. In other embodiments, the leaching time is 1.5 to 1.7 hours.

[0049] In mixtures formed by acid decomposition products and water, the liquid-to-solid ratio can be (0.5–10) L:1 kg. In some embodiments, the liquid-to-solid ratio is (2–4) L:1 kg. In other embodiments, the liquid-to-solid ratio is (6–8) L:1 kg. The liquid-to-solid ratio refers to the ratio of the volume of the liquid substance to the mass of the solid substance in the mixture.

[0050] In the mixture formed by mixing the acid decomposition products with water, the concentration of sulfuric acid can be 10–50 wt%; preferably 30–45 wt%. In some embodiments, the concentration of sulfuric acid is 38–42 wt%.

[0051] The above reaction conditions help to improve the recovery rates of niobium, titanium, rare earth elements and iron.

[0052] Washing steps

[0053] The leaching residue is washed with a 10-50 wt% second sulfuric acid solution to obtain discharged residue and washing liquid. In some embodiments, the following step is also included: combining the leaching solution and the washing liquid.

[0054] The concentration of the second sulfuric acid solution is 10–50 wt%; preferably 15–30 wt%. In some embodiments, the concentration of the second sulfuric acid is 23–27 wt%.

[0055] The number of washes can be 1 to 5. In some embodiments, the number of washes is 1 to 3. In other embodiments, the number of washes is 2 to 3.

[0056] The volume-to-mass ratio of the second sulfuric acid solution to the leaching residue used in each wash can be (1-5) L:1 kg; preferably (1.5-3) L:1 kg. In some embodiments, the volume-to-mass ratio of the second sulfuric acid solution to the acid decomposition products used in each wash is (2-2.5) L:1 kg.

[0057] The leaching residue can be washed by stirring the mixture formed by the leaching residue and the second sulfuric acid solution. Alternatively, it can be washed by rinsing.

[0058] The leaching rate of niobium is ≥85 wt%; preferably, the leaching rate of niobium is ≥90 wt%; more preferably, the leaching rate of niobium is ≥95 wt%.

[0059] The leaching rate of titanium is ≥90 wt%; preferably, the leaching rate of titanium is ≥93 wt%; more preferably, the leaching rate of titanium is ≥94 wt%.

[0060] The leaching rate of rare earth elements is ≥90 wt%; preferably, the leaching rate is ≥95 wt%; more preferably, the leaching rate is ≥97 wt%.

[0061] The iron leaching rate is ≥90 wt%; preferably, the iron leaching rate is ≥92 wt%; more preferably, the iron leaching rate is ≥95 wt%.

[0062] The testing method is described below:

[0063] Leaching rates of niobium, titanium, iron, and rare earth elements: Target elements in solid and liquid samples were determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The leaching rates were calculated using the following formula:

[0064] Leaching rate = CV / mw

[0065] In the formula, C is the concentration of the element in the acid treatment solution, g / L; V is the volume of the acid treatment solution, L; w is the mass fraction of the element in the rich calcite low-grade niobium ore, %; and m is the mass of the rich calcite low-grade niobium ore, g.

[0066] The source of the raw materials is described below:

[0067] Low-grade niobium ore from the Fuyi calcite mine: provided by Baotou Steel (Group) Co., Ltd. It is obtained by sequentially processing raw ore from the Bayan Obo mine through weak magnetic flotation, strong magnetic flotation, rare earth flotation, mixed flotation, and mixed sand flotation processes.

[0068] Examples 1-3

[0069] (1) The low-grade niobium ore from the Bayan Obo mining area was ground by ball mill, then filtered and dried in sequence to obtain low-grade niobium ore particles.

[0070] Low-grade niobium ore particles made from rich calcite were mixed with a first sulfuric acid solution and then subjected to acid decomposition to obtain acid decomposition products.

[0071] (2) The acid decomposition products are mixed with water and then leached to obtain leaching products. The leaching products are filtered to obtain leaching residue and leaching solution.

[0072] (3) The leaching residue was washed three times with a second sulfuric acid solution, each time for 30 minutes, to obtain the slag discharge and the slag washing liquid. The slag washing liquid and the leaching liquid were combined to obtain the acid treatment solution.

[0073] The elemental contents of the rich calcite low-grade niobium ore are shown in Table 1. The process parameters and leaching rates of each element are shown in Table 2.

[0074] Table 1

[0075]

[0076] Table 2

[0077]

[0078]

[0079] Note: -200 mesh A% indicates that the percentage of ore particles with a diameter of less than 200 mesh in the rich calcite low-grade niobium ore particles is A.

[0080] As shown in Table 2, the decomposition method of the present invention can fully leach niobium, titanium, rare earth elements and iron elements from the low-grade niobium ore of Bayan Obo Fuyi calcite, with a high leaching rate.

[0081] Comparative Example 1

[0082] (1) Low-grade niobium ore from the Bayan Obo mining area (same as in Example 1) was ground using a ball mill, then filtered and dried sequentially to obtain low-grade niobium ore particles. The slurry concentration was 50 wt%, and the grinding time was 15 min. 95% of the low-grade niobium ore particles had a particle size of less than 200 mesh.

[0083] Low-grade niobium ore particles from rich calcite were mixed with 50 wt% hydrochloric acid at a speed of 280 r / min and then decomposed at 110 °C for 4 h to obtain the acid decomposition product. The volume-to-mass ratio of the hydrochloric acid to the low-grade niobium ore particles from rich calcite was 3 L: 1 kg.

[0084] (2) The acid decomposition products were mixed with water and leached at 20°C for 1 hour to obtain the leaching product. The leaching product was filtered to obtain leaching residue and leaching liquid. The liquid-to-solid ratio of the mixture of acid decomposition products and water was 3L:1kg, and the concentration of hydrogen chloride was 15wt%.

[0085] (3) The leaching residue was washed three times with 10wt% hydrochloric acid, each time for 30 minutes, to obtain slag discharge and washing solution. The volume-to-mass ratio of the hydrochloric acid to the leaching residue was 2L:1kg in each wash. The washing solution and leaching solution were combined to obtain an acid-treated solution. The washing method was to stir the mixture formed by the leaching residue and the second sulfuric acid solution to wash the leaching residue.

[0086] The leaching rates were measured to be 32 wt% for niobium, 45 wt% for titanium, 50 wt% for rare earth elements, and 88 wt% for iron.

[0087] The leaching rates of niobium, titanium, rare earth elements, and iron in Comparative Example 1 were much lower than those in Example 1. This may be because hydrochloric acid has a weak ability to decompose titanium niobate and cannot effectively destroy the structure of easily calcified rocks, resulting in low leaching rates of niobium and rare earth elements.

[0088] Comparative Example 2

[0089] (1) Low-grade niobium ore from the Bayan Obo mining area (same as in Example 2) was ground using a ball mill, then filtered and dried sequentially to obtain low-grade niobium ore particles. The slurry concentration was 75 wt%, and the grinding time was 10 min. 98% of the low-grade niobium ore particles had a particle size of less than 200 mesh.

[0090] Low-grade niobium ore particles from rich calcite were mixed with a 75 wt% first sulfuric acid solution at a speed of 280 r / min and then acid-decomposed at 60 °C for 4 h to obtain the acid decomposition product. The volume-to-mass ratio of the first sulfuric acid solution to the low-grade niobium ore particles from rich calcite was 3 L: 1 kg.

[0091] (2) The acid decomposition products were mixed with water and leached at 25°C for 1.5 h to obtain the leaching product. The leaching product was filtered to obtain leaching residue and leaching liquid. In the mixture formed by the acid decomposition products and water, the liquid-to-solid ratio was 5 L:1 kg, and the concentration of sulfuric acid was 40 wt%.

[0092] (3) The leaching residue was rinsed three times with a 25wt% second sulfuric acid solution to obtain slag discharge and slag washing solution. Each rinsing time was 30 min. In each rinsing, the volume-to-mass ratio of the second sulfuric acid solution to the leaching residue was 1.5 L: 1 kg. The slag washing solution and the leaching solution were combined to obtain the acid treatment solution.

[0093] The leaching rates were measured to be 41 wt% for niobium, 52 wt% for titanium, 65 wt% for rare earth elements, and 85 wt% for iron.

[0094] The leaching rates of niobium, titanium, rare earth elements, and iron in Comparative Example 2 were much lower than those in Example 2. This indicates that the acid decomposition temperature has a significant impact on the leaching rate of the above elements. If the acid decomposition temperature is too low, the titanium and niobium oxides will not decompose sufficiently, the mineral lattice will not open, and the leaching efficiency will decrease significantly.

[0095] Comparative Example 3

[0096] (1) Low-grade niobium ore from the Bayan Obo mining area (same as in Example 3) was ground using a ball mill, then filtered and dried sequentially to obtain low-grade niobium ore particles. The slurry concentration was 60 wt%, and the grinding time was 30 min. 98% of the low-grade niobium ore particles had a particle size of less than 200 mesh.

[0097] Low-grade niobium ore particles from rich calcite were mixed with a 98 wt% first sulfuric acid solution at a speed of 400 r / min and then acid-decomposed at 260℃ for 3 h to obtain the acid decomposition product. The volume-to-mass ratio of the first sulfuric acid solution to the low-grade niobium ore particles from rich calcite was 0.5 L: 1 kg.

[0098] (2) The acid decomposition products were mixed with water and leached at 30°C for 0.5 h to obtain the leaching product. The leaching product was filtered to obtain leaching residue and leaching liquid. In the mixture formed by the acid decomposition products and water, the liquid-to-solid ratio was 7 L:1 kg, and the concentration of sulfuric acid was 50 wt%.

[0099] (3) The leaching residue was rinsed three times with a 15wt% second sulfuric acid solution to obtain slag discharge and slag washing solution. In each washing, the volume-to-mass ratio of the second sulfuric acid solution to the leaching residue was 1L:1kg, and the rinsing time was 30min each time. The slag washing solution and the leaching solution were combined to obtain the acid treatment solution.

[0100] The leaching rates of niobium, titanium, and rare earth elements were measured to be 68 wt%, 70 wt%, and 75 wt%, respectively.

[0101] The leaching rates of niobium, titanium, and rare earth elements in Comparative Example 3 were significantly lower than those in Example 3, indicating that the amount of the first sulfuric acid solution and the amount of low-grade niobium ore particles rich in calcite have a significant impact on the leaching rates of these elements. Insufficient amount of the first sulfuric acid solution will result in the mineral surface not being adequately covered by acid, incomplete acid decomposition reaction, and incomplete conversion of niobium oxides into soluble sulfates.

[0102] Comparative Example 4

[0103] (1) Low-grade niobium ore from the Bayan Obo mining area (same as in Example 2) was ground using a ball mill, then filtered and dried sequentially to obtain low-grade niobium ore particles. The slurry concentration was 75 wt%, and the grinding time was 10 min. 98% of the low-grade niobium ore particles had a particle size of less than 200 mesh.

[0104] Low-grade niobium ore particles from rich calcite were mixed with a 75 wt% first sulfuric acid solution at a speed of 280 r / min and then acid-decomposed at 180 °C for 4 h to obtain the acid decomposition product. The volume-to-mass ratio of the first sulfuric acid solution to the low-grade niobium ore particles from rich calcite was 3 L: 1 kg.

[0105] (2) The acid decomposition products were mixed with water and leached at 25°C for 1.5 h to obtain the leaching product. The leaching product was filtered to obtain leaching residue and leaching liquid. In the mixture formed by the acid decomposition products and water, the liquid-to-solid ratio was 5 L:1 kg, and the concentration of sulfuric acid was 40 wt%.

[0106] (3) The leaching residue was rinsed three times with a 5 wt% second sulfuric acid solution to obtain the discharged residue and the leaching solution. In each washing, the volume-to-mass ratio of the second sulfuric acid solution to the leaching residue was 1.5 L: 1 kg, and the rinsing time was 30 min each time. The leaching solution and the leaching solution were combined to obtain the acid treatment solution.

[0107] The leaching rates were measured to be 83 wt% for niobium, 89 wt% for titanium, 93 wt% for rare earth elements, and 90% for iron.

[0108] The leaching rates of niobium and titanium in Comparative Example 4 were significantly lower than those in Example 2, indicating that the concentration of the second sulfuric acid solution has a significant impact on the leaching rates of niobium and titanium. Insufficient concentration of the second sulfuric acid solution will result in the ineffective dissolution of residual niobium in the leaching residue, leading to a decrease in the leaching rate.

[0109] Comparative Example 5

[0110] (1) Low-grade niobium ore from the Bayan Obo mining area (same as in Example 1) was ground using a ball mill, then filtered and dried sequentially to obtain low-grade niobium ore particles. The slurry concentration was 50 wt%, and the grinding time was 15 min. 95% of the low-grade niobium ore particles had a particle size of less than 200 mesh.

[0111] Low-grade niobium ore particles rich in calcite were mixed with a 75 wt% first sulfuric acid solution at a speed of 250 r / min and then acid-decomposed at 140 °C for 0.5 h to obtain the acid decomposition product. The volume-to-mass ratio of the first sulfuric acid solution to the low-grade niobium ore particles rich in calcite was 3 L: 1 kg.

[0112] (2) The acid decomposition products were mixed with water and leached at 20°C for 1 hour to obtain the leaching product. The leaching product was filtered to obtain leaching residue and leaching liquid. In the mixture formed by the acid decomposition products and water, the liquid-to-solid ratio was 3L:1kg, and the concentration of sulfuric acid was 36wt%.

[0113] (3) The leaching residue was washed three times with a 20wt% second sulfuric acid solution to obtain the discharged residue and the washing solution. In each washing, the volume-to-mass ratio of the second sulfuric acid solution to the leaching residue was 2L:1kg, and the washing time was 30min. The washing solution and the leaching solution were combined to obtain the acid treatment solution.

[0114] The leaching rates were measured to be 58 wt% for niobium, 70 wt% for titanium, 75 wt% for rare earth elements, and 88 wt% for iron.

[0115] The leaching rates of niobium, titanium, rare earth elements, and iron in Comparative Example 5 were significantly lower than those in Example 1, indicating that acid decomposition time has a significant impact on the leaching rates of these elements. Insufficient decomposition time resulted in incomplete mineral reaction, with niobium remaining in the slag as undecomposed calcite, niobium-iron rutile, and other undecomposed forms.

[0116] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A method for decomposing low-grade niobium ore rich in calcite, characterized in that, Includes the following steps: (1) The low-grade niobium ore particles of rich calcite are subjected to acid decomposition with a first sulfuric acid solution of 50-98 wt% at a temperature of 80-320℃ for 3-8 hours to obtain acid decomposition products; The low-grade niobium ore particles in the rich calcite contain more than 90% particles with a particle size of less than 200 mesh; the low-grade niobium ore particles in the rich calcite contain 0.1-15 wt% Nb2O5, 6.0-50 wt% TFe, 1-15 wt% REO, and 1-15 wt% TiO2; the volume-to-mass ratio of the first sulfuric acid solution to the low-grade niobium ore particles in the rich calcite is (2.5-5) L:1 kg; (2) The acid decomposition product is mixed with water and leached at 20-50°C to obtain the leaching product; the leaching product is separated into solid and liquid to obtain leaching residue and leaching liquid; In the mixture formed by the acid decomposition products and water, the liquid-to-solid ratio is (2-8) L:1 kg, and the concentration of sulfuric acid is 30-50 wt%. (3) The leaching residue is washed with a second sulfuric acid solution with a concentration of 10-50 wt% to obtain the slag discharge and the slag washing liquid; (4) Combine the washing residue solution and the leachate; The leaching rate of niobium is ≥85wt%, the leaching rate of titanium is ≥90wt%, the leaching rate of rare earth elements is ≥90wt%, and the leaching rate of iron is ≥90wt%.

2. The decomposition method according to claim 1, characterized in that, It also includes the following steps: The low-grade niobium ore of the rich calcite is ground, then filtered and dried in sequence to obtain low-grade niobium ore particles of the rich calcite. The concentration of the slurry used in the grinding operation is 50–75 wt%, and the grinding time is 5–50 min.

3. The decomposition method according to claim 1, characterized in that, Low-grade niobium ore particles rich in calcite were mixed with a first sulfuric acid solution and then subjected to acid decomposition at a rotation speed of 100–500 r / min.

4. The decomposition method according to claim 1, characterized in that, In step (2), the leaching time is 0.5 to 4 hours.

5. The decomposition method according to claim 1, characterized in that, The washing is performed 1 to 5 times. The liquid-solid ratio of the second sulfuric acid solution used in each washing to the leaching residue is (1 to 5) L: 1 kg. The washing time for each washing is 10 to 50 minutes.

6. The decomposition method according to claim 1, characterized in that, The mixture formed by stirring the leaching residue and the second sulfuric acid solution is used to wash the leaching residue; or The leaching residue is washed by rinsing.

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