A method for stepwise separation and recovery of niobium and rare earths from niobium-containing rare earth flotation tailings
By employing methods such as wet high-intensity magnetic separation, NaCl–Na2SO4 roasting activation, and high-temperature pressure hydrolysis, the problem of separating niobium and rare earth elements in rare earth flotation tailings has been solved, achieving efficient recovery of niobium and stable recovery of rare earth elements, and significantly improving process stability and efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2026-05-14
- Publication Date
- 2026-06-30
AI Technical Summary
Existing technologies are difficult to effectively recover niobium and rare earth elements from rare earth flotation tailings. Problems include difficulty in capturing niobium minerals, residual reagents affecting flotation stability, complex mineral structures leading to low leaching efficiency, and the co-occurrence of niobium and rare earth elements resulting in long process lengths and high reagent consumption.
Residual reagents were removed by wet strong magnetic separation, minerals were activated by NaCl–Na2SO4 roasting, and niobium and rare earth elements were separated by high-temperature and high-pressure hydrolysis. Combined with the TBP–2-octanol–sulfonated kerosene extraction system and sulfate crystallization treatment, the stepwise separation of niobium and rare earth elements was achieved.
The process improved the recovery rate of niobium and the stability of rare earth elements, with the niobium leaching rate reaching over 90% and the rare earth recovery rate remaining at 92%, thus enhancing process stability and economic efficiency.
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Figure CN122303633A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of secondary resource comprehensive utilization and hydrometallurgical technology, specifically to a method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings. Background Technology
[0002] Niobium, as an important strategic metal, is widely used in high-strength low-alloy steel, superconducting materials, and high-temperature alloys. Rare earth elements are essential resources for new materials and high-end manufacturing. In my country, some rare earth resources are associated with niobium-containing minerals, resulting in the generation of secondary niobium-containing resources during rare earth beneficiation and smelting. Especially when flotation is used in rare earth beneficiation, rare earth flotation tailings are often generated. These tailings, in addition to containing a certain amount of niobium minerals, may also contain residual inhibitory reagents or modifiers used in the rare earth flotation system, thus adversely affecting the re-flotation enrichment of niobium minerals, leading to low niobium recovery rates and difficulty in improving concentrate grades.
[0003] Existing comprehensive utilization routes for niobium-containing solid waste / tailings generally fall into two main categories: physical beneficiation pre-enrichment and hydrometallurgical decomposition leaching.
[0004] (1) In physical mineral processing, magnetic separation, gravity separation, flotation or a combination thereof are often used to pre-enrich niobium-containing minerals. For secondary resources such as rare earth flotation tailings, due to the fine mineral particle size, severe mud formation, and the continuous impact of residual reagents on the surface properties of minerals, direct niobium flotation often suffers from problems such as suppressed collector action, severe gangue entrainment, and poor flotation selectivity. Although single magnetic separation can achieve a certain degree of enrichment, it is difficult to simultaneously solve the adverse effects of residual inhibitors on subsequent niobium flotation, resulting in insufficient overall process stability.
[0005] (2) In terms of decomposition and leaching, common methods include sulfuric acid roasting-acid leaching, alkali fusion / alkali leaching, and fluorination system leaching. Although sulfuric acid roasting-leaching can improve the decomposition degree of some difficult-to-treat niobium minerals, it is often accompanied by corrosion risks and by-product disposal pressure. Iron-containing systems are prone to producing iron-phase hydrolytic colloids or forming complex complexes and adsorption behaviors during acid leaching, which have an adverse effect on the leaching and subsequent separation of niobium and rare earth elements. For niobium-containing minerals of the nepheline type or with complex silicate / oxide structures, the leaching kinetics are slow under conventional acid leaching conditions, and the degree of coexistence between niobium and impurities is high, resulting in long subsequent separation processes, high reagent consumption, and great difficulty in product purification.
[0006] (3) In terms of niobium and rare earth separation, existing processes mostly use methods such as hydrolysis precipitation, solvent extraction, ion exchange and crystallization to separate niobium / rare earth from impurities such as iron and titanium. However, for the acid leaching system of niobium-containing rare earth tailings, there are generally problems such as complex niobium valence state and complexation form, many impurity ions, and high separation selectivity requirements. In addition, rare earth and some impurities make the rare earth recovery process susceptible to fluctuations in acidity and sulfate concentration, making it difficult to achieve both efficient niobium recovery and stable rare earth recovery.
[0007] In summary, it is necessary to provide a cascade separation and recovery method for niobium and rare earth in niobium-containing rare earth flotation tailings, so as to achieve efficient recovery of niobium and further recycling of rare earth while ensuring the industrialization and stable operation of the process. Summary of the Invention
[0008] This invention addresses the following problems existing in the comprehensive utilization of niobium-containing rare earth tailings, such as rare earth flotation tailings: (1) The inhibitory reagents remaining in the tailings used in the rare earth flotation system exhibit a niobium inhibition effect in the subsequent niobium flotation, making it difficult to effectively collect niobium minerals and causing the direct flotation separation index to be unstable. (2) The niobium-bearing minerals in the tailings have complex structures and dispersed occurrence states, which limits the efficiency of conventional acid leaching and decomposition. The leachate contains many impurity ions, making subsequent separation and purification of niobium difficult. (3) The coexistence of niobium and rare earth elements leads to the coexistence of multiple elements in the leachate. If a step-by-step separation strategy is lacking, the process is long, the consumption of reagents is high, and the product quality is difficult to guarantee.
[0009] The purpose of this invention is to provide a cascade separation and recovery method for niobium and rare earth in niobium-containing rare earth flotation tailings, which achieves efficient recovery of niobium and further recovers rare earth while ensuring the feasibility of the process.
[0010] To achieve the above objectives, the present invention adopts the following technical solution: A method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings includes the following steps: (1) After adjusting the slurry of the niobium-containing rare earth flotation tailings, wet high-intensity magnetic separation is carried out. While enriching the niobium-containing magnetic minerals, the magnetic separation medium and the magnetic minerals adsorbed by the washing water are washed, so that the residual flotation reagents in the tailings enter the magnetic separation tailings or are discharged in the overflow with the washing water to obtain magnetic separation rough concentrate; then the magnetic separation rough concentrate is subjected to niobium flotation to obtain niobium-containing concentrate. (2) The niobium-containing concentrate is mixed with NaCl–Na2SO4 binary molten salt and roasted and activated in air atmosphere to obtain roasted product; (3) The roasted product is leached with sulfuric acid to allow niobium and rare earth elements to enter the liquid phase. After solid-liquid separation, a leachate containing niobium and rare earth elements is obtained. (4) Adjust the pH of the leachate to 1.0-2.0 and perform hydrolysis treatment under high temperature and pressure conditions so that the niobium component is preferentially hydrolyzed to form niobium-containing precipitate, while the rare earth is mainly retained in the solution. After solid-liquid separation, the niobium precipitate product and rare earth solution are obtained. (5) The niobium precipitate is leached using a hydrofluoric acid-sulfuric acid mixed acid system. The resulting acid leaching solution is separated by a TBP-2-octanol-sulfonated kerosene extraction system to obtain a niobium-enriched solution. A pH adjuster is added to the niobium-enriched solution to precipitate the niobium-containing substances. The precipitate is washed, dried, or calcined to obtain a niobium oxide-containing product. (6) Add sulfate crystallizing agent to the rare earth solution to crystallize the rare earth in the form of sulfate or ammonium double salt sulfate, thereby realizing rare earth recovery.
[0011] As can be seen from the above technical solution, compared with the prior art, the present invention has the following technical effects: (1) The present invention introduces a washing step in the wet strong magnetic separation process, so that while the niobium-containing magnetic minerals are enriched, the residual flotation reagents in the tailings are discharged with the washing water, reducing the inhibitory effect of the residual reagents on the subsequent niobium flotation, which is conducive to improving the stability of the niobium pre-enrichment process.
[0012] (2) The present invention uses NaCl–Na2SO4 binary molten salt to roast and activate niobium-containing concentrate, which can improve the acid leaching reactivity of niobium-containing minerals. Under preferred conditions, the leaching rates of niobium and rare earth elements can both reach over 90%.
[0013] (3) The present invention adjusts the pH of the leachate and performs high-temperature and high-pressure hydrolysis to make niobium preferentially form niobium-containing precipitate, thereby reducing the impurity load of the subsequent extraction system and achieving the initial separation of niobium and rare earth.
[0014] (4) The present invention uses a TBP-2-octanol-sulfonated kerosene system to extract and separate niobium. Under the preferred system, the niobium extraction rate can reach about 90%.
[0015] (5) The present invention performs sulfate crystallization treatment on the rare earth solution after niobium precipitation, which can further recover rare earth and realize the cascade utilization of niobium and rare earth in the niobium-containing rare earth flotation tailings. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0017] Figure 1This is a process flow diagram of the present invention. Detailed Implementation
[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0019] Characterization of niobium-containing rare earth tailings raw materials in the embodiments of the present invention: This invention deals with rare earth flotation tailings (niobium-containing rare earth tailings), which contain a certain amount of niobium-containing minerals and rare earth minerals, and retain residual inhibitory reagents / modifiers used in the rare earth flotation system (which exhibit a niobium inhibition effect in subsequent niobium flotation). The tailings samples are routinely sampled, mixed, and reduced in size before use. Multi-element chemical composition analysis is performed on the raw materials to determine the occurrence state of niobium and rare earth elements and the characteristics of impurities.
[0020] Table 1. Valuable element content in rare earth flotation tailings
[0021] Niobium-containing rare earth tailings beneficiation in this embodiment of the invention: With a magnetic field strength of 2.4T and a slurry concentration of 30%, the slurry is fed into a wet high-intensity magnetic separator for magnetic separation. During the magnetic separation process, the magnetic minerals are washed to remove residual inhibitory agents from the tailings, thereby obtaining a magnetic rough concentrate with the residual inhibitors removed. The magnetic separation results are shown in Table 2.
[0022] Table 2 Results of Niobium Separation by Strong Magnetic Separation of Rare Earth Flotation Tailings
[0023] Intensive magnetic separation can further improve the niobium grade. The (Nb+Ta)2O5 grade in the niobium concentrate is 2.17%, and the recovery rate is 75.68%.
[0024] The Nb₂O₅ grade in the strong magnetic niobium concentrate obtained from the rare earth flotation tailings was only 2.17%, indicating a low niobium grade. Direct hydrometallurgical production would be costly; therefore, flotation was used to further improve the niobium grade. The collector dosage was 800 g / t, the frother dosage was 20 g / t, the pulp concentration was 30%, the stirring time was 5 min, and the flotation time was 5 min. The flotation results are shown in Table 3.
[0025] Table 3. Flotation Results of Strong Magnetic Niobium Concentrate
[0026] Niobium flotation can yield niobium concentrate with a Nb2O5 grade of 6.85%, with a yield of 22.39% and an Nb2O5 flotation recovery rate of 71.44%.
[0027] In this embodiment of the invention, the NaCl-Na2SO4 binary molten salt was roasted and activated, and sulfuric acid was leached. Niobium-containing concentrate was mixed with a binary molten salt of NaCl and Na₂SO₄ at a ratio of 1:1, wherein the molar fraction of Na₂SO₄ in (Na₂SO₄ + NaCl) was 0.30–0.70. After homogeneous mixing, the mixture was roasted and activated in air at a temperature of 650–950℃ for 30–90 min to obtain the roasted product. The roasted product was leached with 1–4 mol / L sulfuric acid at a liquid-to-solid ratio of 2–4:1 at a leaching temperature of 40–75℃ for 0.5–4 h; preferably, the sulfuric acid concentration was 2 mol / L, the liquid-to-solid ratio was 2:1, and the leaching time was 2 h. After leaching, the solid and liquid were separated to obtain the leachate. The experimental results are shown in Tables 4-6.
[0028] Table 4 Effect of molten salt ratio on leaching (800℃, acid-to-ore ratio 1:2, liquid-to-solid ratio 4:1, room temperature, leaching time 2h)
[0029] Table 5 Effect of roasting temperature on leaching (molten salt ratio 0.8, acid-ore ratio 1:2, liquid-solid ratio 4:1, room temperature, leaching time 2h)
[0030] Table 6. Effects of acid concentration, liquid-to-solid ratio, and leaching time on the leaching of roasted products.
[0031] When the salt ore mass ratio is 0.8, the roasting temperature is 800℃, the sulfuric acid concentration is 2mol / L, the liquid-solid ratio is 2, and the leaching time is 2h, the leaching rates of niobium and rare earth elements are both higher than 90%.
[0032] Niobium high-temperature pressure boiling and niobium precipitation test in the embodiments of the present invention: After adjusting the pH of the leachate to 1.5, it was subjected to high-temperature cooking treatment at a temperature of 150–250℃ for 2 hours with an oxygen partial pressure of 0.5 MPa. This caused the niobium component to form a niobium-containing precipitate, which was then separated to obtain the niobium precipitate product and the rare earth solution. The experimental results are shown in Tables 7-8.
[0033] Table 7 Results of high-pressure niobium immersion tests at different temperatures
[0034] Table 8 Results of the High-Pressure Niobium-Pollution and Oxygenation Condition Test
[0035] Under oxygen-bearing conditions, the recovery rate of niobium is slightly higher, while the precipitation rates of rare earth elements and iron are slightly lower, and the impurity content in the slag sample is also lower.
[0036] Experimental preparation of niobium pentoxide by mixed acid dissolution-extraction and back-extraction in this invention embodiment: The niobium precipitate was leached using a mixed acid system. Under the condition of heating in a water bath at 95°C, a maximum of 650-700g of pressure-cooked niobium precipitate residue could be dissolved in a mixed acid containing 300g / L sulfuric acid and 200g / L hydrofluoric acid.
[0037] After acid leaching, solid-liquid separation was performed to obtain an acid leaching solution. Niobium was then separated from the acid leaching solution by solvent extraction. The organic phase consisted of TBP and 2-octanol, with sulfonated kerosene used as a diluent. The extraction time was 3–8 min. The extraction test results are shown in Tables 9-10.
[0038] Table 9. Extractant Screening Tests
[0039] Table 10 Extraction Time Experimental Data
[0040] Under the determined extraction process conditions, the loaded organic phase was subjected to multi-stage cross-flow extraction and then back-extracted. The back-extractant used was a 0.4 mol / L sulfuric acid solution. After back-extraction for 5 min, the pH value was adjusted with sodium hydroxide until a white precipitate was formed in the solution. The precipitate was washed completely and then analyzed. The precipitate components are shown in Table 11.
[0041] Table 11 X-ray fluorescence analysis of niobium products
[0042] In this embodiment of the invention, a rare earth sulfate precipitation experiment was conducted on the rare earth solution after niobium precipitation: The precipitation rate of rare earth double salts with different sulfate dosages was studied. The experimental conditions were heating and stirring at 95℃ for 1 hour. The specific experimental results are shown in Table 12.
[0043] Table 12 Effect of sulfate dosage on rare earth precipitation
[0044] As shown in Table 12, when the amount of sulfate crystallizing agent is 150-250 g / L, the precipitation recovery rate of rare earth slag remains at around 92%. Further increasing the amount will have limited effect on improving the precipitation recovery rate and will reduce the grade of rare earth slag. Therefore, the preferred amount of sulfate crystallizing agent is 150-250 g / L.
[0045] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.
[0046] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings, characterized in that, Includes the following steps: (1) After adjusting the slurry of the niobium-containing rare earth flotation tailings, wet high-intensity magnetic separation is carried out. During the magnetic separation process, the magnetic separation medium and the magnetic minerals it adsorbs are washed, so that the residual flotation reagents in the tailings are discharged into the magnetic separation tailings with the washing water to obtain magnetic rough concentrate; then the magnetic rough concentrate is floated to obtain niobium-containing concentrate. (2) The niobium-containing concentrate obtained in step (1) is mixed with NaCl-Na2SO4 binary molten salt and then roasted and activated to obtain the roasted product; (3) The roasted product obtained in step (2) is leached with sulfuric acid and the solid and liquid are separated to obtain a leachate containing niobium and rare earth elements; (4) After adjusting the pH of the leachate obtained in step (3), perform high-temperature and high-pressure hydrolysis to form a niobium-containing precipitate and separate it from the rare earth solution to obtain the niobium precipitate product and the rare earth solution. (5) The niobium precipitate obtained in step (4) is acid-leached using a hydrofluoric acid-sulfuric acid mixed acid system, and the acid leaching solution is extracted and separated to obtain a niobium enrichment solution. The pH of the niobium enrichment solution is adjusted to allow niobium-containing substances to precipitate. After washing, drying and calcining, the niobium oxide product is obtained. (6) Add sulfate crystallizing agent to the rare earth solution obtained in step (4) to crystallize the rare earth in the form of sulfate or ammonium double salt sulfate.
2. The method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings according to claim 1, characterized in that, In step (1), the magnetic field strength of wet high-intensity magnetic separation is 1.6-2.4T, the pulp concentration is 15%-30%, the flotation collector is two or more of alkyl hydroxamic acid, benzyl hydroxamic acid, and oxidized paraffin soap, the inhibitor is sodium silicate and sodium fluorosilicate, the foaming agent is pine oil, and the pH range is 8-10.
3. The method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings according to claim 1, characterized in that, The mass ratio of niobium concentrate to binary molten salt in step (2) is 1:1 to 2:1; The binary molten salt comprises NaCl and Na2SO4; the mole fraction of Na2SO4 in the binary molten salt satisfies: Na2SO4 / (Na2SO4+NaCl)=0.30~0.
80.
4. The method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings according to claim 1, characterized in that, In step (2), the roasting atmosphere is air, the roasting temperature is 650–950℃, and the roasting holding time is 30–90 min.
5. The method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings according to claim 1, characterized in that, Step (3) The sulfuric acid concentration is 1~4 mol / L, the liquid-solid ratio is (2-4):1, the leaching temperature is 40~75℃, and the leaching time is 0.5-3h.
6. The method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings according to claim 1, characterized in that, Step (4) Adjust the pH range to 1.0 to 2.0, preferably 1.3 to 1.8, and more preferably 1.
5.
7. The method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings according to claim 1, characterized in that, In step (4), the cooking temperature is 150℃-250℃, the temperature is kept for 1-3 hours, and the oxygen partial pressure is 0.3-0.8MPa.
8. The method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings according to claim 1, characterized in that, The mixed acid system used in step (5) for acid leaching includes sulfuric acid and hydrofluoric acid, wherein the concentration of sulfuric acid is 250~350g / L and the concentration of hydrofluoric acid is 150~250g / L; The extraction system includes TBP, 2-octanol and sulfonated kerosene, wherein the volume fraction of TBP is 20% to 40%, the volume fraction of 2-octanol is 20% to 40%, and the volume fraction of sulfonated kerosene is 20% to 60%; preferably, the volume ratio of TBP, 2-octanol and sulfonated kerosene is 30:30:
40.
9. A method for the cascade separation and recovery of niobium and rare earth elements in niobium-containing rare earth flotation tailings according to claim 1, characterized in that, In step (6), the sulfate crystallizing agent is selected from one or two of sodium sulfate and ammonium sulfate. The amount of sulfate crystallizing agent used is 100-300 g / L, the reaction temperature is 80-100 ℃, and the reaction time is 0.5-2 h. Preferably, the amount used is 150-250 g / L and the reaction temperature is 90-95 ℃.