Utilization method of low-grade easily dissolvable stone type niobium concentrate

Abstract

The invention relates to a utilization method of low-grade easily dissolvable stone type niobium concentrate, and belongs to the field of mineral processing and hydrometallurgy. The method solves at least one of the problems of low recovery rate of Fe and Nb elements, complex process flow, high energy consumption and cost, harsh reaction conditions, high environmental pollution risk and the like in the utilization of the low-grade easily dissolvable stone type niobium concentrate in the prior art. The invention relates to a utilization method of low-grade easily dissolvable stone type niobium concentrate, which comprises the following steps: uniformly mixing niobium concentrate with a reducing agent, pelletizing, and reducing and roasting to obtain roasted ore; the roasted ore is smashed and then subjected to magnetic separation, and iron ore concentrate and tailings are obtained; acidizing and roasting to obtain re-roasted ore; circulating grass leaching to obtain grass leaching liquid and grass leaching residues; the grass extract is subjected to extraction and back extraction through extraction resin, and niobium-containing back extraction liquid is obtained. According to the method, the leaching rate of niobium and the recovery rate of the iron element are increased, the technological process is simplified, the energy consumption and the production cost are reduced, and green and environment-friendly production is achieved.

Description

Technical Field

[0001] This invention relates to the fields of mineral processing and hydrometallurgical technology, and in particular to a method for utilizing low-grade easily calcified niobium concentrate. Background Technology

[0002] Niobium (Nb) is a key strategic metal supporting modern steel industry, aerospace, superconducting technology, and the information industry. Although my country is a major niobium resource country, its reserves are highly concentrated in polymetallic symbiotic deposits such as Bayan Obo, where easily calcified niobium minerals, due to their complex composition, similar floatability, and fine particle size, can only yield low-grade easily calcified niobium concentrate (Nb₂O₅ content less than 10%) through conventional beneficiation techniques. This situation of "having resources but difficulty in utilization" has resulted in my country's long-term high dependence on imported niobium resources.

[0003] In existing technologies, the separation and purification processes for easily calcite-type niobium concentrate are still in the laboratory research stage and have not yet been industrialized. The mainstream technical routes mainly include high-purity niobium purification processes based on hydrofluoric acid decomposition-solvent extraction, and alkali fusion-water leaching as efficient pre-impurity removal and enrichment steps. Although these methods can achieve the separation of niobium from major associated elements under laboratory conditions, they all have significant drawbacks: the hydrofluoric acid system is highly toxic, corrosive, and poses serious environmental hazards; while the alkali fusion process is energy-intensive and causes significant equipment wear.

[0004] Current processes do not adequately address the separation and recovery of iron from niobium concentrate. Existing iron removal technologies largely rely on high-temperature reduction (above 1000℃), protective atmospheres, and ultrafine grinding—high-energy-consuming and costly methods that struggle to achieve efficient and selective separation of complex-formed iron deposits. Due to the lack of efficient and economical iron separation methods, iron impurities are only incidentally treated through extreme chemical environments in the main process (such as strong alkali slagging or strong acid extraction), resulting in long overall processes, low efficiency, significant environmental risks, and unstable product quality. These problems severely restrict the comprehensive industrial utilization of easily calcite resources. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a method for utilizing low-grade easily calcified niobium concentrate, in order to solve at least one of the problems existing in the prior art for utilizing low-grade easily calcified niobium concentrate, such as low Fe and Nb element recovery rates, complex process flow, high energy consumption and cost, harsh reaction conditions, and high environmental pollution risk.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention provides a method for utilizing low-grade easily calcified niobium concentrate, comprising the following steps: (1) Niobium concentrate and reducing agent are mixed at a mass ratio of 10: (5.0~3.0), pelletized, and then reduced and roasted at 450~600℃ to obtain roasted ore; (2) The roasted ore is crushed and then subjected to magnetic separation to obtain iron concentrate and tailings; (3) The tailings are mixed with sulfuric acid and leaching aid and then acidified and roasted to obtain re-roasted ore. The acidification and roasting temperature is 300~400℃. (4) The re-roasted ore is mixed with oxalic acid solution for cyclic oxalic leaching, and oxalic leaching solution and oxalic leaching residue are obtained after solid-liquid separation; (5) The herb extract is extracted and back-extracted using a leaching resin, and the leaching resin is acidified before extraction to obtain a niobium-containing back-extract.

[0008] Further, the particle size of the extraction resin in step (5) is 60-80 mesh; and / or, The acidification treatment is carried out using a sulfuric acid solution with a concentration of 0.10~0.50 mol / L.

[0009] Furthermore, in step (1), the holding time for the reduction calcination is 60~180min.

[0010] Furthermore, in step (4), the cyclic grass leaching refers to the process where, after the first grass leaching and solid-liquid separation, the leachate continues to leach the next re-roasted ore until the Nb2O5 content in the leachate is greater than 25 g / L.

[0011] Further, in step (5), the solid-liquid volume ratio during extraction is 1:1 to 8:1; and / or, The back-extraction uses a mixed solution of 0.1~0.5 mol / L nitric acid and 2.0~3.0 mol / L ammonium nitrate as the back-extraction agent, and the solid-liquid volume ratio during back-extraction is 2:1~8:1.

[0012] Further, in step (3), the mass ratio of tailings, sulfuric acid and leaching aid is 1:(2.0~3.5):(0.2~1.5); and / or, the holding time for acid roasting is 60~180 min.

[0013] Further, in step (4), the solid-liquid mass ratio of the circulating grass immersion is 1:(3.0~8.0), the temperature is 60~80℃, and the immersion time is 60~180min.

[0014] Furthermore, the magnetic field strength of the magnetic separation in step (2) is 120~300mT.

[0015] Furthermore, the total iron (TFe) content in the iron concentrate is greater than 60 wt.%, and the leaching rate of niobium extracted from the niobium concentrate is greater than 95%.

[0016] Furthermore, the niobium concentrate is a low-grade calcite-type niobium concentrate, wherein the calcite content is 1.0~35 wt.%, the hematite content is 30~70 wt.%, the Nb2O5 content is 1.0~10.0 wt.%, the total iron (TFe) content is 26~50 wt.%, the rare earth oxide (REO) content is 1~10 wt.%, and the Ti content is 1.0~10 wt.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: This invention provides a highly efficient and green comprehensive recovery method for low-grade easily calcified niobium concentrate. The technical route first involves medium-temperature selective reduction roasting to convert the iron minerals into strongly magnetic Fe3O4, followed by efficient separation of the iron concentrate using weak magnetic field separation, achieving priority recovery and removal of iron resources. Subsequently, for niobium-rich tailings, a synergistic process of acid roasting—oxalic acid circulating leaching—resin extraction separation is employed to achieve efficient and selective extraction of niobium. Compared with existing technologies, the core innovation and significant effects of this invention are reflected in: On the one hand, this invention achieves efficient separation and enrichment of iron and niobium from the source through a "stepwise iron-niobium recovery" strategy. Specifically, existing processes often result in low recovery rates due to the mutual interference between iron and niobium. This invention employs a medium-temperature (450-600℃) selective reduction-weak magnetic separation process to pre-separate most of the iron in the form of magnetic minerals. This not only directly produces qualified iron concentrate and improves the iron recovery rate, but more importantly, it removes the main acid-consuming and interfering elements for the subsequent niobium extraction process. The grade of the niobium-rich tailings after iron removal is relatively improved, and the impurity content is significantly reduced, creating optimal material conditions for the efficient and clean extraction of niobium and solving the problem of mutual constraints on the recovery rates of the two elements in iron-niobium symbiotic minerals.

[0018] On the other hand, this invention constructs a new niobium extraction system of "mild transformation - green circular leaching - efficient integrated separation". For niobium-rich materials after iron removal, the subsequent processes of this invention are interconnected, forming a closed technology loop: (a) Acid roasting: Under the action of sulfuric acid and leaching aid, sparingly soluble niobium minerals are transformed into soluble niobium salts. The leaching aid effectively inhibits the dissolution of impurities such as silicon, improving the transformation selectivity and subsequent leaching efficiency.

[0019] (b) Oxalic acid cyclic leaching: Utilizing the stable complex formation between oxalic acid and niobium, highly selective leaching of niobium is achieved under mild conditions. The core advantage of this step is the recycling of the oxalic acid solution: it not only significantly reduces the consumption of fresh reagents and production costs, but more importantly, during the recycling process, niobium in the leachate is continuously accumulated and enriched, resulting in a high-quality leachate with a high niobium concentration, which is beneficial for subsequent treatment. This process reduces wastewater generation and alleviates the load and cost of subsequent separation and enrichment processes.

[0020] (c) Integrated Extraction and Back-Extraction with Extraction Resin: The high-niobium concentration leachate is subjected to integrated extraction and back-extraction using pre-acidified extraction resin. Acidification activates the resin's functional groups, enhancing its selective adsorption capacity and exchange efficiency for niobium, and reducing impurity competition. This method directly separates niobium from the leachate, replacing traditional solvent extraction and overcoming the latter's problems of low efficiency and low leaching rate due to organic phase emulsification and difficult phase separation. This step is simple, requires minimal equipment, and eliminates the risk of organic solvent volatilization, making it crucial for achieving clean and efficient niobium recovery.

[0021] Based on the principles and synergistic effects of each process in this invention, the invention achieves the following results: (1) Improve leaching rate: "reduction-magnetic separation" prioritizes iron extraction to ensure high iron recovery rate; after iron removal, the leaching environment of niobium is optimized, and combined with efficient resin separation, the overall leaching of niobium is significantly improved.

[0022] (2) Simplified process and reduced energy consumption: The entire process does not require high temperature treatment (>1000℃) or high pressure reaction. The reduction roasting temperature is relatively low, the leaching conditions are mild, and the resin separation equipment is compact, which greatly shortens the process flow, reduces the overall energy consumption and equipment investment, and the entire process can be completed under mild atmospheric pressure and medium and low temperature conditions without relying on harsh conditions such as supercritical reactions in existing technologies.

[0023] (3) Reduce production costs: Iron is directly recycled as a by-product, which improves the overall economic benefits of the process; the recycling of oxalic acid and the separation of high-efficiency resin reduce the consumption of chemical reagents; mild conditions reduce equipment maintenance and energy costs.

[0024] (4) Achieving green and environmentally friendly production: Iron is separated from the source, reducing the amount of final tailings and the difficulty of treatment, and avoiding the high-risk pollution problems caused by the use of hydrofluoric acid, concentrated alkali or volatile organic solvents in traditional processes. The oxalic acid system is environmentally friendly, the extraction resin system has no risk of organic phase leakage, and the emissions of waste are low, resulting in good environmental benefits.

[0025] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0026] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0027] Figure 1 This is a schematic flowchart illustrating a method for utilizing low-grade easily calcified niobium concentrate according to an embodiment of the present invention. Detailed Implementation

[0028] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0029] This invention provides a method for utilizing low-grade easily calcified niobium concentrate, comprising the following steps: (1) Niobium concentrate and reducing agent are mixed at a mass ratio of 10: (5.0~3.0), pelletized, and then reduced and roasted at 450~600℃ to obtain roasted ore; (2) The roasted ore is crushed and then subjected to magnetic separation to obtain iron concentrate and tailings; (3) The tailings are mixed with sulfuric acid and leaching aid and then acidified and roasted to obtain re-roasted ore. The acidification and roasting temperature is 300~400℃. (4) The re-roasted ore is mixed with oxalic acid solution for cyclic oxalic leaching, and oxalic leaching solution and oxalic leaching residue are obtained after solid-liquid separation; (5) The herb extract is extracted and back-extracted using a leaching resin, and the leaching resin is acidified before extraction to obtain a niobium-containing back-extract.

[0030] Compared with existing technologies, the core purpose of this invention in controlling the ratio of niobium concentrate to reducing agent is to ensure that iron oxides are fully reduced to strongly magnetic Fe3O4 while preventing excessive carbon. Excess carbon is not only uneconomical, but may also cause Fe3O4 to be further reduced to weakly magnetic FeO, affecting the efficiency of subsequent magnetic separation; at the same time, excessive carbon will create an excessively strong local reducing atmosphere, which may damage the crystal structure of niobium minerals and is not conducive to the subsequent recovery of niobium.

[0031] Furthermore, this invention controls the temperature conditions of the reduction roasting, matching the thermodynamic and kinetic window for the conversion of iron oxides to Fe3O4. While ensuring a high conversion rate, it minimizes side reactions, achieving a balance between high efficiency and energy saving. If the temperature is too low or the time is too short, the reduction reaction cannot be completed, resulting in low iron recovery. If the temperature is too high or the time is too long, it not only increases energy consumption but may also cause Fe3O4 to decompose or be over-reduced, potentially leading to unfavorable phase transformations in niobium minerals.

[0032] For example, in step (1), the reducing agent is a carbonaceous reducing agent.

[0033] For example, the reducing agent is at least one of carbon powder, coke powder, or coal powder. Preferably, it is anthracite with a fixed carbon content ≥76 wt.%, volatile matter ≤7.8 wt.%, ash content ≤15 wt.%, moisture content ≤1 wt.%, and particle size ≤74 μm.

[0034] For example, in step (1), the mass ratio of niobium concentrate to reducing agent is 10:(5.0~3.0), such as 10:5, 10:4.5, 10:4, 10:3.5, 10:3; preferably 10:4.5 to 10:3.5, which achieves an optimized balance between reduction efficiency and selectivity.

[0035] For example, in step (1), the particle size of the pellets obtained after pelletizing is 10~15mm. Controlling the particle size of the pellets is beneficial to ensure sufficient reduction while taking into account a high metal conversion rate and efficiency; if the particle size is too small, it will easily lead to severe pulverization during roasting, increasing the dust collection burden and metal loss; if the particle size is too large, it will be difficult for heat and gas to be transferred to the interior of the pellets, resulting in uneven reduction.

[0036] Specifically, in step (1), the reduction calcination temperature is 450~600℃; for example, the reduction calcination temperature is 450℃, 470℃, 500℃, 520℃, 550℃, 570℃, or 600℃.

[0037] Specifically, in step (1), the holding time for reduction calcination is 60~180min. For example, the holding time for reduction calcination is 60min, 90min, 120min, 150min, or 180min.

[0038] Preferably, in step (1), the reduction calcination temperature is 470~570℃ and the holding time is 60~120min. Such synergistic conditions achieve efficient and selective reduction to Fe3O4 while taking into account the optimal balance between reaction thoroughness, energy consumption economy and phase stability.

[0039] Specifically, in step (1), the reduction roasting is carried out in a muffle furnace. Exemplarily, the muffle furnace is protected by a reducing atmosphere. In step (1), the roasted ore obtained by reduction roasting is cooled by rapid cooling, preferably by water quenching.

[0040] Specifically, the magnetic field strength of the magnetic separation in step (2) is 120~300mT. For example, the magnetic field strength of the magnetic separation is 120mT, 140mT, 160mT, 180mT, 200mT, 220mT, 240mT, 260mT, 280mT, or 300mT; preferably 140~240mT.

[0041] For example, in step (2), the roasted ore is crushed to a particle size of -74μm and a content of 80~95wt.%, and then magnetic separation is performed.

[0042] Specifically, in step (2), the total iron (TFe) content in the iron concentrate is >60 wt.%.

[0043] Specifically, in step (3), the mass ratio of tailings, sulfuric acid and leaching aid is 1:(2.0~3.5):(0.2~1.5).

[0044] For example, the mass ratio of tailings, sulfuric acid and leaching aid is 1:(2.0, 2.2, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.2 or 3.5):(0.2, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.3 or 1.5).

[0045] Preferably, the mass ratio of tailings, sulfuric acid and leaching aid is 1:(2.5~3.0):(0.5~1.1).

[0046] It should be noted that the specific proportion of sulfuric acid ensures sufficient acidolysis and transformation of the tailings, while the appropriate leaching aid selectively destroys the structure of impurities and inhibits their dissolution. This synergistic formulation achieves a high niobium transformation rate while reducing ineffective acid consumption and impurity interference, making the resulting re-roasted ore more suitable for subsequent mild and highly selective oxalic acid leaching systems.

[0047] Specifically, the holding time for the acidification roasting is 60~180 min.

[0048] For example, the acidification and calcination temperature is 300°C, 320°C, 330°C, 340°C, 350°C, 360°C, 380°C, or 400°C.

[0049] For example, the holding time for acidification roasting is 60 min, 80 min, 100 min, 120 min, 130 min, 140 min, 150 min, 160 min, or 180 min.

[0050] Preferably, the acidification calcination temperature is 320~360℃, and the holding time is 120~160min.

[0051] It should be noted that the acid roasting temperature and time window are the key process balance points for achieving efficient and selective transformation. If the temperature is too low or the time is too short, the sulfuric acid decomposition will be insufficient, the niobium mineral transformation will be incomplete, and the subsequent niobium leaching rate will be significantly reduced. If the temperature is too high or the time is too long, it will easily promote the formation of insoluble polymer oxides of niobium and aggravate the dissolution and activation of impurities such as silicon and aluminum, while causing unnecessary increases in energy consumption and equipment load.

[0052] For example, in step (3), the acid roasting process involves directly heating to the target acid roasting temperature at a rate of 5-10°C / min; or heating in stages, specifically including: heating to 200-250°C at a rate of 5-10°C / min and holding for 20-40 minutes, and then continuing to heat to the target acid roasting temperature. The staged heating procedure, through a strategy of gentle dehydration and preliminary activation followed by deep reaction, effectively prevents material splashing, improves sulfuric acid utilization and reaction uniformity, thereby ensuring the safety, efficiency, and product quality stability of the acid roasting process.

[0053] Specifically, in step (3), the acid roasting is carried out in a muffle furnace. Exemplarily, the muffle furnace is protected by a reducing atmosphere.

[0054] In step (3), the re-roasted ore obtained after acid roasting is cooled by rapid cooling, preferably by water quenching.

[0055] Specifically, in step (3), the mass concentration of the sulfuric acid is 60% to 98%, preferably 78% to 92%. For example, the mass concentration of the sulfuric acid is 60%, 70%, 80%, 85%, 90%, 95%, or 98%.

[0056] Specifically, in step (3), the immersion aid is at least one of ammonium sulfate or ammonium bisulfate; preferably ammonium sulfate.

[0057] Specifically, in step (4), the cyclic grass leaching refers to the process where, after the first grass leaching and solid-liquid separation, the leachate continues to leach the next re-roasted ore until the Nb2O5 content in the leachate is greater than 25 g / L.

[0058] Specifically, in step (4), the solid-liquid mass ratio of the circulating grass soaking is 1:(3.0~8.0). For example, the solid-liquid mass ratio of the circulating grass soaking is 1:(3.0, 4.0, 5.0, 6.0, 7.0 or 8.0); preferably 1:(4.0~6.0).

[0059] It should be noted that by controlling the solid-liquid mass ratio of the oxalic acid leaching process, a sufficient liquid volume is ensured in the reaction system. This provides enough oxalic acid to complex niobium, guaranteeing a high leaching rate, while also ensuring good fluidity of the slurry, facilitating stirring and subsequent solid-liquid separation. A too-low solid-liquid ratio (too high liquid volume) will dilute the leachate, hindering subsequent niobium enrichment and increasing oxalic acid consumption; a too-high solid-liquid ratio (too low liquid volume) will result in a viscous slurry, poor mass transfer, and incomplete leaching.

[0060] Preferably, in step (4), the oxalic acid solution is a saturated solution with a mass concentration of 10 wt.% up to the corresponding cyclic oxalic acid immersion temperature.

[0061] It should be noted that the lower limit concentration of oxalic acid solution (10 wt.%) provides the necessary chemical driving force to ensure effective leaching of niobium; the upper limit (saturation concentration at the oxalic acid leaching operating temperature) is the highest concentration allowed to be used under the premise of avoiding oxalic acid crystallization, which is beneficial to improve the leaching rate and the niobium concentration in the final leachate, and achieve efficient enrichment.

[0062] Specifically, in step (4), the temperature of the circulating grass soaking is 60~80℃ and the soaking time is 60~180min.

[0063] For example, the temperature of the circulating grass immersion is 60℃, 65℃, 68℃, 70℃, 72℃, 75℃, and 80℃; the immersion time is 60min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, and 180min.

[0064] Preferably, in step (4), the temperature of the circulating grass soaking is 65~75℃ and the soaking time is 90~150min.

[0065] It should be noted that by controlling the leaching temperature and ensuring sufficient leaching time, the leaching kinetics are effectively accelerated while ensuring a mild reaction system and safe operation, resulting in thorough and complete leaching of niobium. Too low a temperature or too short a time will lead to a decrease in the leaching rate; too high a temperature may cause partial decomposition of oxalic acid, increasing costs and generating unnecessary side reactions.

[0066] It is understood that the "leaching time" refers to the reaction time for completing a single batch of grass leaching operation; after each batch reaches the leaching time, solid-liquid separation is carried out, and the resulting leachate will be recycled as the leachate for the next batch of grass leaching.

[0067] Specifically, in step (4), the grass soaking is carried out under stirring conditions, and the stirring speed is controlled at 200~1200 rpm, preferably 300~800 rpm. For example, the stirring speed is 200 rpm, 400 rpm, 600 rpm, 800 rpm, 1000 rpm, or 1200 rpm.

[0068] It should be noted that in grass leaching, by employing stirring and controlling an appropriate rotation speed, it is possible to prevent solid sedimentation, ensure sufficient and uniform contact between the minerals and the leaching agent, enhance boundary layer diffusion to accelerate reaction transfer, and maintain uniform system temperature. Too low a rotation speed will lead to insufficient mixing, while too high a speed can easily cause excessive shearing, intensified fine mud formation, and increased energy consumption.

[0069] Specifically, the particle size of the extraction resin in step (5) is 60-80 mesh. By controlling the particle size of the extraction resin, an optimized balance is achieved between adsorption efficiency and operational stability, enabling the resin to possess both a large adsorption specific surface area and good bed permeability. This allows for efficient adsorption and rapid mass transfer of niobium, while maintaining a low-resistance, stable flow state within the column and ensuring sufficient mechanical strength to support cyclic use. If the particle size is too fine, the pressure drop will be too high and clogging will be easy; if the particle size is too coarse, the adsorption capacity and rate will decrease.

[0070] For example, the extraction resin is N235 extraction resin. The N235 extraction resin refers to a resin containing trioctyldecyl tertiary amine (molecular formula C...). 27 H 57 N (CAS: 68814-95-9) is the active component, with the general structural formula R3N, where R represents C8-C. 10 Mixed alkyl groups, belonging to the mixed trialkyl tertiary amine class of solid-phase extraction materials. N235 extraction resin is commercially available.

[0071] Specifically, the acidification treatment is carried out using a sulfuric acid solution with a concentration of 0.10~0.50 mol / L, such as sulfuric acid solutions with concentrations of 0.10 mol / L, 0.20 mol / L, 0.25 mol / L, 0.30 mol / L, 0.40 mol / L, and 0.50 mol / L.

[0072] It should be noted that the purpose of acidifying the extraction resin is to convert its functional groups (such as tertiary amine groups) into an active form with the highest selectivity and adsorption capacity for the target ion (niobium oxalate complex anion), and to pre-saturate the resin to reduce competitive adsorption of impurities. Specifically, activation transformation: converting the extractant molecules on the resin into the hydrogen form (H... + (Type) or ammonium salt type, which is its active state for highly efficient adsorption of metal complex anions; pre-saturation and impurity removal: pre-saturating the resin with acid solution can displace impurity ions (such as Na+) introduced during resin synthesis or storage. + Ca² + (etc.), and make its active site H + To occupy and prevent these impurity ions and other cations in the feed solution (such as Fe²⁺) from being absorbed during subsequent adsorption of the feed solution. + Al³ + It competes with the target niobium ions for adsorption sites, thereby improving the adsorption selectivity of niobium.

[0073] Acidification treatment with a suitable concentration of sulfuric acid solution ensures the complete conversion of resin functional groups into high-capacity active groups, while avoiding structural damage such as resin skeleton swelling, hydrolysis, or covalent bond breakage that may be caused by strong acids. This guarantees the mechanical and chemical stability for long-term cyclic use. Furthermore, this moderately low concentration balances economy (low acid consumption) and operational safety (low corrosion risk), and the low residual acidity after treatment facilitates direct transfer to subsequent adsorption operations, achieving a balance between efficient activation and a smooth process.

[0074] For example, acidification treatment typically employs either dynamic column chromatography or static immersion chromatography. No washing of the extraction resin is required after acidification.

[0075] Specifically, in step (5), the solid-liquid volume ratio during extraction is 1:1 to 8:1. The lower limit (1:1) ensures sufficient adsorption capacity of the resin for niobium in the feed solution, guaranteeing a high niobium leaching rate; the upper limit (8:1) avoids excessive scaling up of the resin and equipment, controlling equipment investment and operating costs while ensuring a high leaching rate, and maintaining stable flow within the column. Preferably, the solid-liquid volume ratio during extraction is 2:1 to 6:1.

[0076] Specifically, the back-extraction uses a mixed solution of 0.1~0.5 mol / L nitric acid and 2.0~3.0 mol / L ammonium nitrate as the back-extraction agent, and the solid-liquid volume ratio during back-extraction is 2:1~8:1.

[0077] It should be noted that the efficient desorption and deep enrichment of niobium were achieved through the synergistic design of the composite stripping agent (0.1~0.5 mol / L nitric acid and 2.0~3.0 mol / L ammonium nitrate) and the solid-liquid volume ratio (2:1~8:1). Nitric acid provides a suitable amount of hydrogen ions to disrupt the niobium complex structure, while ammonium nitrate significantly enhances the stripping kinetics and selectivity through competitive displacement by high-concentration ammonium ions and assisted complexation by nitrate ions, while suppressing co-stripping of impurities. Simultaneously, the optimized solid-liquid volume ratio ensures sufficient stripping agent for complete desorption of niobium, yielding a high-concentration stripping solution, while avoiding excessive dilution and increased subsequent processing costs.

[0078] Preferably, the back-extraction uses a mixed solution of 0.2~0.4 mol / L nitric acid and 2.2~2.6 mol / L ammonium nitrate as the back-extraction agent, and the solid-liquid volume ratio during back-extraction is 4:1~6:1.

[0079] In some embodiments, the total iron (TFe) content in the iron concentrate is greater than 60 wt.%, and the leaching rate of niobium extracted from the niobium concentrate is greater than 95%. The Nb2O5 content in the niobium-containing back-extraction solution obtained in step (5) is >70 g / L.

[0080] For example, the niobium concentrate is a low-grade calcite-type niobium concentrate, wherein the calcite content is 1.0~35 wt.%, the hematite content is 30~70 wt.%, the Nb2O5 content is 1.0~10.0 wt.%, the total iron (TFe) content is 26~50 wt.%, the rare earth oxide (REO) content is 1~10 wt.%, and the Ti content is 1.0~10 wt.

[0081] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0082] Example 1: This embodiment provides a method for utilizing low-grade easily calcified niobium concentrate, the specific steps of which are as follows: (1) Reduction roasting: Niobium concentrate and coke powder (reducing agent) are mixed at a mass ratio of 10:4, pelletized, and placed in a muffle furnace (with reducing gas protection) for reduction roasting at 550℃ for 120 min to obtain roasted ore; the particle size of the pellets obtained after pelleting is 10~15mm. (2) Magnetic separation: After the roasted ore is quenched and cooled by water, it is crushed using a sample preparation machine, and then magnetically separated using a magnetic separator under a magnetic field strength of 160 mT to obtain iron concentrate and tailings; the roasted ore is crushed to a particle size of -74 μm with a content of 85 wt.%. (3) Acid roasting: The tailings, sulfuric acid with a mass concentration of 80 wt.% and ammonium sulfate (leaching aid) are mixed at a mass ratio of 1:2.5:0.5 and then acid roasted in a muffle furnace (with reducing gas protection) at 350°C for 120 min to obtain re-roasted ore; the heating process is carried out at a rate of 10°C / min to reach the target temperature of acid roasting of 350°C. (4) Circulating grass leaching: The re-roasted ore and oxalic acid solution with a mass concentration of 30 wt.% are mixed at a solid-liquid mass ratio of 1:4. The mixture is circulated and stirred twice at 70°C and a stirring speed of 450 rpm. Each leaching time is 120 min. After solid-liquid separation, grass leaching solution and grass leaching residue are obtained. After two cycles of grass leaching, the Nb2O5 content in the grass leaching solution is >25 g / L. (5) Extraction and back-extraction: The N235 extraction resin with a particle size of 60-80 mesh was acidified with a sulfuric acid solution of 0.25 mol / L. The grass extract was then extracted with the acidified N235 extraction resin at a solid-liquid volume ratio of 2:1. Then, a mixed solution of 0.2 mol / L nitric acid and 2.5 mol / L ammonium nitrate was used as the back-extraction agent and back-extraction was carried out at a solid-liquid volume ratio of 4:1 to obtain a niobium-containing back-extraction solution.

[0083] The niobium concentrate used in step (1) is the niobium concentrate obtained by flotation in Bayan Obo. It is a low-grade easily calcified niobium concentrate with an easily calcified content of 32.15 wt.%, a hematite content of 37.36 wt.%, a Nb2O5 content of 6.43 wt.%, a total iron (TFe) content of 26.15 wt.%, a rare earth oxide (REO) content of 5.81 wt.%, and a Ti content of 2.58 wt.%.

[0084] The specific process parameters for Examples 1 to 19 are summarized in Tables 1-1 and 1-2. Examples 2 to 19 are based on Example 1, with one or more of the specified process parameters shown in Tables 1-1 and 1-2 adjusted. All other process conditions and operating parameters not listed in Tables 1-1 and 1-2 remain consistent with those of Example 1.

[0085] Table 1-1 Summary of process parameters for the embodiments

[0086] Table 1-2 Summary of process parameters for the embodiments

[0087] Example 20: This embodiment is the same as that in embodiment 1, except that in step (5), a mixed solution of 0.5 mol / L nitric acid and 3.0 mol / L ammonium nitrate is used as the back-extraction agent, and back-extraction is carried out under the condition of a solid-liquid volume ratio of 8:1.

[0088] Comparative Example 1: The difference between this comparative example and Example 1 is that in step (3), the acidification and roasting temperature is 200°C. The remaining steps and conditions are the same as in Example 1.

[0089] Comparative Example 2: The difference between this comparative example and Example 1 is that in step (4), pure water is used instead of oxalic acid solution for cyclic leaching. The remaining steps and conditions are the same as in Example 1.

[0090] Comparative Example 3: The difference between this comparative example and Example 1 is that ammonium sulfate (an leaching aid) is not added during acid roasting in step (3). The remaining steps and conditions are the same as in Example 1.

[0091] Comparative Example 4: The difference between this comparative example and Example 1 is that step (3) is omitted, that is, the tailings obtained in step (2) are directly subjected to the cyclic leaching in step (4). The remaining steps and conditions are the same as in Example 1.

[0092] Comparative Example 5: The difference between this comparative example and Example 1 is that in step (1), the mass ratio of niobium concentrate to reducing agent is 10:6.0. The remaining steps and conditions are the same as in Example 1.

[0093] Comparative Example 6: The difference between this comparative example and Example 1 is that in step (1), the mass ratio of niobium concentrate to reducing agent is 10:2.0. The remaining steps and conditions are the same as in Example 1.

[0094] Comparative Example 7: The difference between this comparative example and Example 1 is that in step (1), the reduction calcination temperature is 400°C. The remaining steps and conditions are the same as in Example 1.

[0095] Comparative Example 8: The difference between this comparative example and Example 1 is that in step (1), the reduction calcination temperature is 650°C. The remaining steps and conditions are the same as in Example 1.

[0096] Comparative Example 9: The difference between this comparative example and Example 1 is that in step (3), the acidification and roasting temperature is 500°C. The remaining steps and conditions are the same as in Example 1.

[0097] Comparative Example 10: The difference between this comparative example and Example 1 is that in step (5), the extraction resin is not subjected to acidification pretreatment. The remaining steps and conditions are the same as in Example 1.

[0098] Comparative Example 11: The difference between this comparative example and Example 1 is that in step (5), a conventional solvent extraction system (e.g., N235 organic phase diluted with kerosene) is used instead of the extraction resin for extraction. The remaining steps and conditions are the same as in Example 1.

[0099] Key indicators of the products in the examples and comparative examples, including the total iron (TFe) content in the iron concentrate, niobium leaching rate, and Nb₂O₅ concentration in the back-extraction solution, were tested and calculated as follows: Element content determination: The content of TFe in iron concentrate, Nb2O5 in various intermediate products and slag, and total rare earth oxides (REO) were determined by X-ray fluorescence spectrometry (XRF).

[0100] The formula for calculating the leaching rate is: Elemental leaching rate (%) = 100% - mass of grass leaching residue × element content in grass leaching residue / (mass of tailings) (Element content in tailings) × 100%.

[0101] For example, niobium leaching rate (%) = 100% The formula is: (Mass of grass leaching residue × Nb2O5 content in grass leaching residue) / (Mass of tailings × Nb2O5 content in tailings) × 100%; where the tailings are obtained by magnetic separation in step (2), and the grass leaching residue is obtained by solid-liquid separation after circulating grass leaching in step (4).

[0102] Table 2 Test results of the embodiments

[0103] Table 3 shows the test results of the comparative examples.

[0104] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for utilizing low-grade easily calcified niobium concentrate, characterized in that, Includes the following steps: (1) Niobium concentrate and reducing agent are mixed at a mass ratio of 10: (5.0~3.0), pelletized, and then reduced and roasted at 450~600℃ to obtain roasted ore; (2) The roasted ore is crushed and then subjected to magnetic separation to obtain iron concentrate and tailings; (3) The tailings are mixed with sulfuric acid and leaching aid and then acidified and roasted to obtain re-roasted ore. The acidification and roasting temperature is 300~400℃. (4) The re-roasted ore is mixed with oxalic acid solution and subjected to cyclic oxalic leaching. After solid-liquid separation, oxalic leaching solution and oxalic leaching residue are obtained. (5) The herb extract is extracted and back-extracted using a leaching resin, and the leaching resin is acidified before extraction to obtain a niobium-containing back-extract.

2. The utilization method according to claim 1, characterized in that, The particle size of the extraction resin in step (5) is 60-80 mesh; and / or, The acidification treatment is carried out using a sulfuric acid solution with a concentration of 0.10~0.50 mol / L.

3. The utilization method according to claim 1, characterized in that, In step (1), the holding time for reduction calcination is 60~180min.

4. The utilization method according to claim 1, characterized in that, In step (4), the cyclic grass leaching refers to the process where, after the first grass leaching and solid-liquid separation, the leachate continues to leach the next re-roasted ore until the Nb2O5 content in the leachate is greater than 25 g / L.

5. The method of utilization according to claim 1, characterized in that, In step (5), the solid-liquid volume ratio during extraction is 1:1 to 8:1; and / or, The back-extraction uses a mixed solution of 0.1~0.5 mol / L nitric acid and 2.0~3.0 mol / L ammonium nitrate as the back-extraction agent, and the solid-liquid volume ratio during back-extraction is 2:1~8:

1.

6. The method of utilization according to claim 1, characterized in that, In step (3), the mass ratio of tailings, sulfuric acid and leaching aid is 1:(2.0~3.5):(0.2~1.5); and / or, the holding time for acid roasting is 60~180 min.

7. The utilization method according to claim 1, characterized in that, In step (4), the solid-liquid mass ratio of the circulating grass immersion is 1:(3.0~8.0), the temperature is 60~80℃, and the immersion time is 60~180min.

8. The utilization method according to claim 1, characterized in that, The magnetic field strength of the magnetic separation in step (2) is 120~300mT.

9. The utilization method according to claim 1, characterized in that, The total iron (TFe) content in the iron concentrate is greater than 60 wt.%, and the niobium leaching rate extracted from the niobium concentrate is greater than 95%.

10. The utilization method according to claim 1, characterized in that, The niobium concentrate is a low-grade calcite-type niobium concentrate, wherein the calcite content is 1.0~35 wt.%, the hematite content is 30~70 wt.%, the Nb2O5 content is 1.0~10.0 wt.%, the total iron (TFe) content is 26~50 wt.%, the rare earth oxide (REO) content is 1~10 wt.%, and the Ti content is 1.0~10 wt.

Images