Method for microwave pretreatment of tantalum-niobium concentrate for enhancing acid leaching

Abstract

This invention discloses a method for enhancing the acid leaching of tantalum-niobium concentrate through microwave pretreatment. The method includes: raw material screening: crushing, grinding, and sieving the raw material to obtain tantalum-niobium concentrate powder; microwave pretreatment: feeding the tantalum-niobium concentrate powder into a microwave device preheated to 40-50℃ and spreading it evenly, then microwave treating it at a power of 650-800W, followed by cooling; leaching: adding the microwave-pretreated concentrate powder to a mixed acid solution for leaching, controlling the temperature at 80-90℃ for 4-6 hours, then filtering and separating to obtain the leachate; wherein the hydrogen ion concentration in the mixed acid solution is 28-30 mol / L, obtained by adding hydrofluoric acid and sulfuric acid to water. The technical solution of this invention significantly improves the penetration rate of the leaching agent, enabling the tantalum and niobium leaching rate to stably reach over 99%, shortening the leaching time to less than 6 hours, and significantly reducing hydrofluoric acid volatilization loss and energy consumption, possessing extremely high industrial application value.

Description

Technical Field

[0001] This invention relates to the field of tantalum-niobium concentrate leaching technology, and specifically to a method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate. Background Technology

[0002] Tantalum and niobium, as rare metals with high melting points and high hardness, are widely used in high-end manufacturing fields such as electronics, aerospace, and nuclear industry. Tantalum and niobium concentrate is the core raw material for extracting tantalum and niobium, and its leaching efficiency directly determines the utilization rate and production benefits of tantalum and niobium resources. The existing leaching process for tantalum and niobium concentrate still has the following core problems: (1) Limited leaching kinetics - Tantalum and niobium minerals often exist in a dense embedded form. For example, tantalite forms an intergrowth structure with gangue minerals such as quartz and feldspar. Under traditional conductive heating conditions, the diffusion rate of the leaching agent is low, making it difficult to fully penetrate into the mineral lattice, resulting in a low leaching rate of tantalum and niobium; (2) Low energy utilization efficiency - Traditional water bath or oil bath heating is a non-selective heat transfer method with significant heat loss. The reaction system needs to be heated to 85-95℃, which takes a long time and results in high equipment operating costs; (3) Long leaching heat preservation time - Traditional conductive heating requires a heat preservation period of 45-48 hours to achieve the target leaching rate, which leads to a longer production cycle and low equipment utilization; (4) Low reagent utilization efficiency - Hydrofluoric acid has a high volatilization loss rate when maintained at 85-95℃ for a long time, resulting in high leaching costs. At the same time, the volatilized HF is easy to form acidic waste gas, which not only increases the cost of tail gas treatment but also aggravates environmental pollution.

[0003] The existing related technologies are as follows: Patent CN202510119915 discloses a method for extracting tantalum and niobium from tantalum-niobium ore by alkaline reduction. This process involves multiple steps, including two grinding processes, acid leaching for impurity removal, and solid-liquid separation. It is complex to operate, has a long production cycle, low efficiency, and uses expensive alkali sources, fluxes, and reducing agents, increasing procurement costs. The low solubility of tantalum-niobate leaching in pure water easily leads to insufficient leaching rates. Multiple steps result in potential losses and incomplete reactions, leading to low tantalum and niobium recovery rates. Patent CN119876647A discloses a method for extracting tantalum and niobium from tantalum-niobium concentrate after multiple acid leachings followed by fluoride roasting and melting. This process is cumbersome, involving two acid leachings, multiple filtration and washing processes, drying, two grinding and sieving processes, and roasting. It is complex to operate, easily reducing production efficiency and increasing labor and equipment costs. It also consumes a large amount of acid and faces significant environmental pressure. The use of concentrated acid in the two acid leaching processes increases raw material costs, and improper wastewater treatment can pollute the environment. Furthermore, it carries risks of energy consumption and loss, and multiple operations can easily lead to the loss of the target elements tantalum and niobium, reducing the recovery rate. The literature "Research on Decomposition and Extraction Process of Tantalum-Niobium Concentrate in Sulfuric Acid System" uses Yichun tantalum-niobium concentrate as raw material and adopts a sulfuric acid system with ammonium fluoride introduced for pressure-enhanced conversion to decompose tantalum-niobium ore. Then, tantalum-niobium is separated by MIBK extraction: tantalum-niobium ore decomposition and pressure leaching still have problems such as low leaching efficiency, large energy loss, and environmental unfriendliness.

[0004] Therefore, developing leaching processes for tantalum and niobium concentrates that have high leaching rates, fast leaching efficiency, low energy consumption, and minimal environmental impact is of significant research value and application importance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a microwave pretreatment method for enhanced acid leaching of tantalum-niobium concentrate. This invention aims to solve the following core technical problems: addressing the issues of long leaching time, high reagent consumption, low tantalum-niobium leaching rate, and high energy consumption in traditional conventional heating leaching processes, thereby improving leaching efficiency, reducing production costs, and meeting the needs of large-scale production; providing a complete and feasible industrial technical solution, clearly defining the operating specifications, process parameters, and equipment requirements for each stage, ensuring the technology is scalable and replicable, and providing technical support for upgrading tantalum-niobium concentrate leaching processes.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate includes the following steps:

[0008] (1) Raw material screening: Tantalum and niobium concentrate raw materials are crushed, ground and screened to obtain tantalum and niobium concentrate powder with a particle size of 250-400 mesh;

[0009] (2) Microwave pretreatment: The tantalum-niobium concentrate powder is fed into a microwave device preheated to 40-50°C and spread out, and treated for 12-20 minutes under a power of 650-800W, and then cooled to below 50°C;

[0010] (3) Mixed acid leaching: The microwave pretreated concentrate powder is added to the mixed acid solution for leaching. The liquid-solid ratio is controlled at 3-6:1, the leaching temperature is 80-90℃, and the leaching time is 4-6h. The leached solution is filtered and separated to obtain the leachate. The concentration of hydrogen ions in the mixed acid solution is 28-30mol / L, which is obtained by adding hydrofluoric acid and sulfuric acid in a molar ratio of 3-7:1 to water.

[0011] The technical solution of this invention improves leaching efficiency by using microwave pretreatment with specific power and time before the mixed acid leaching process to rapidly destroy the dense lattice of tantalum-niobium concentrate, significantly increasing the penetration rate of the subsequent leaching agent.

[0012] In the technical solution of this invention, the mixed acid solution undergoes rigorous screening. If the concentration of hydrogen ions in the mixed acid solution is too low, the leaching rate will decrease significantly. If the concentration of hydrogen ions in the mixed acid solution is too high, equipment corrosion will intensify, hydrofluoric acid will volatilize faster, and impurities will dissolve more readily, significantly worsening the leaching effect. Furthermore, if the molar ratio of hydrofluoric acid to sulfuric acid in the mixed acid solution deviates from 3-7:1, and there is too little hydrofluoric acid... Insufficient leaching results in poor soluble tantalum and niobium, leading to a sharp drop in leaching rate; while excessive hydrofluoric acid makes HF highly volatile, worsens subsequent separation, and increases costs.

[0013] Furthermore, in step (1), the total content of Nb2O5 and Ta2O5 in the tantalum-niobium concentrate raw material is >20%, and the moisture content of the tantalum-niobium concentrate powder is controlled to be <1%.

[0014] Furthermore, in step (2), the process parameters for microwave pretreatment are: power of 700-750W and processing time of 14-18min.

[0015] Furthermore, in step (2), the thickness of the tantalum-niobium concentrate powder is 3-5 mm.

[0016] Furthermore, in step (3), the process parameters for mixed acid leaching are: liquid-to-solid ratio of 4-5:1, leaching temperature of 83-87℃, stirring speed of 35-45r / min, and leaching time of 4.5-5.5h.

[0017] Further, in step (3), the concentration of hydrogen ions in the mixed acid solution is 28.5-29.5 mol / L, which is obtained by adding hydrofluoric acid and sulfuric acid in a molar ratio of 4-6:1 to water.

[0018] Further, in step (3), the method for preparing the mixed acid solution is as follows: add hydrofluoric acid to water, then add sulfuric acid and stir evenly.

[0019] Furthermore, the microwave pretreatment enhanced acid leaching method for tantalum-niobium concentrate further includes the following steps: when the total content of Nb2O5 and Ta2O5 in the decomposition residue obtained after filtration and separation in step (3) is ≥1%, the decomposition residue is subjected to secondary mixed acid leaching.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention utilizes microwave pretreatment with specific power and time before mixed acid leaching to rapidly disrupt the dense crystal lattice of tantalum and niobium concentrate, significantly increasing the penetration rate of subsequent leaching agents. This results in a stable leaching rate of over 99% for tantalum and niobium, and a significant improvement in resource utilization.

[0022] This invention employs microwave pretreatment combined with a specific mixed acid system, significantly reducing the traditional 45-48 hour heat preservation leaching time to 4-6 hours, greatly improving equipment turnover and production capacity. The shortened leaching time effectively reduces the high-temperature volatilization loss of hydrofluoric acid, significantly reduces reagent consumption, mitigates environmental pollution risks and exhaust gas treatment costs, and the overall process is efficient, environmentally friendly, and suitable for large-scale production. Attached Figure Description

[0023] Figure 1 A flowchart illustrating the microwave pretreatment method for enhancing acid leaching of tantalum-niobium concentrate, as provided in an embodiment of the present invention.

[0024] Figure 2 This shows the microstructure of the tantalum-niobium concentrate raw ore in Example 1 of the present invention.

[0025] Figure 3 This shows the microstructure of tantalum-niobium concentrate after microwave pretreatment in Example 1 of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] (i) Regarding the selection of raw materials, the present invention uses the following raw materials and standards:

[0028] 1. Tantalum-Niobium Concentrate: The Nb₂O₅ and Ta₂O₅ content must be >20% to ensure the raw material has extraction value and avoid increasing process costs due to low-grade raw materials; there should be no obvious impurities, agglomeration, moisture, or oil contamination; after pretreatment, concentrate powder of 250-400 mesh should be screened out, with a qualified rate of ≥95%. This particle size is the optimal size for microwave penetration and lattice disruption; if too coarse, microwaves will have difficulty penetrating, and if too fine, agglomeration will affect heating. Controlling the qualified rate ensures process stability; moisture content <1%. Excessive moisture will consume microwave energy and reduce heating efficiency, while also avoiding fluctuations in leachate concentration. Only concentrate powder within this particle size range should be microwave-treated; concentrate powder outside this size range should be returned to the pretreatment process for re-grinding and screening to ensure targeted microwave treatment and improve process efficiency.

[0029] 2. Hydrofluoric acid (HF): Industrial grade, molar concentration 28-35 mol / L. This concentration range balances leaching efficiency and operational safety. Too high a concentration can corrode equipment and increase safety risks, while too low a concentration will result in insufficient leaching rate. Purity ≥99% reduces interference from impurities on the leaching reaction and prevents impurities from forming insoluble compounds with tantalum and niobium. There should be no obvious impurities, turbidity, or precipitation. Store in corrosion-resistant polyethylene or polytetrafluoroethylene containers. Do not store with glass, metals, or alkaline substances.

[0030] 3. Sulfuric acid (H2SO4): Industrial grade, molar concentration 17-20 mol / L, used to adjust the acidity of the leachate, promote the leaching of tantalum and niobium minerals by HF, and at the same time reduce the increase in water volume caused by dilution, and avoid the leachate concentration being too low; purity ≥98.5%, reducing the content of impurities, preventing impurities from affecting the leaching effect and subsequent purification, with no obvious turbidity, precipitation and odor; stored in acid-resistant storage tanks, away from flammable and explosive materials.

[0031] 4. High-purity water: conductivity ≤0.1μS / cm. The low conductivity can minimize the interference of impurity ions in the water with the leaching reaction, prevent impurities from co-precipitating with tantalum and niobium, significantly improve the purity of the leachate, and meet the needs of efficient leaching and subsequent purification of tantalum and niobium concentrate. It is free of impurities and ion pollution, and is used for preparing leachate and cleaning equipment. It avoids the introduction of impurities during the cleaning process, extends the service life of equipment, and ensures the stability of subsequent processes.

[0032] (ii) Regarding key equipment, the present invention employs the following equipment:

[0033] Pretreatment equipment: Based on the process requirements for crushing and grinding tantalum-niobium concentrate, the following equipment was selected: PE-150×250 jaw crusher, MQG-1500×3000 grate ball mill, ZS-1000×2000 double-layer vibrating screen, and 5m³ / h ore. 3 The polyethylene silo forms a continuous pretreatment process system of "crushing-grinding-screening-storage". The jaw crusher crushes the raw ore to a particle size ≤5mm, providing qualified feed for the subsequent grinding process. After grinding in the grate ball mill, the material is directly fed into a double-layer vibrating screen for precise screening into 250-400 mesh qualified concentrate powder. Coarse particles on the screen are returned to the ball mill for regrinding, effectively ensuring that the qualified rate of 250-400 mesh concentrate powder after pretreatment is ≥95%, providing raw materials that meet process requirements for subsequent microwave targeted processing. The polyethylene silo is used to separately store qualified 250-400 mesh concentrate powder, avoiding moisture, contamination, and particle size mixing, ensuring a smooth connection between the pretreatment and microwave processing steps.

[0034] Microwave processing equipment: WBF-900 industrial-grade microwave reactor, suitable for continuous industrial production, with a power adjustment range of 600-900W, a frequency of 2450MHz, and a cavity material made of high-temperature ceramic. It has a processing capacity of 1.5-2t / batch and is equipped with ventilation and cooling devices as well as continuous feeding and discharging auxiliary structures to ensure smooth continuous production.

[0035] Leaching equipment: KCF-5000 acid-resistant reactor, lined with polytetrafluoroethylene, which can resist the corrosion of mixed acids such as HF and H2SO4, ensuring long-term stable operation of the equipment; equipped with stirring, temperature and acidity detection devices.

[0036] Example 1

[0037] This embodiment provides a method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate, the flowchart of which is shown below. Figure 1 As shown; the specific steps are as follows.

[0038] (1) Raw material screening: Tantalum-niobium concentrate raw material (Nb2O5+Ta2O5 content is 28%) is crushed, ground and screened to obtain tantalum-niobium concentrate powder with a particle size of 250-400 mesh (accounting for 95.6%) and a moisture content of 0.8%.

[0039] like Figure 2 As shown, the microstructure of the raw tantalum-niobium concentrate is as follows: the mineral particles are mainly large-sized blocky / flaky, with the main particle size being about 40-60μm (estimated using a 10μm scale). The edges are relatively intact and the corners are clear. A small amount of fine powder is attached to the surface, but the overall structure is dense with few cracks, and the mineral lattice remains intact and has not been effectively destroyed.

[0040] (2) Microwave pretreatment: The WBF-900 microwave reactor is preheated at 45°C for 5 minutes. The tantalum-niobium concentrate powder is fed into the microwave equipment and spread to a thickness of 4 mm. It is treated for 16 minutes under a power of 700W, and then cooled to 45°C before being discharged.

[0041] like Figure 3 The image shows the microstructure of tantalum-niobium concentrate after microwave pretreatment. It can be seen that the large mineral particles are significantly broken and refined, with the main particle size reduced to 10-15 μm. A large amount of fine powder and debris <5 μm appears, and the particle size distribution is more uniform. The particle surface becomes rough and uneven, with a large number of microcracks, steps and broken edges, indicating that microwave energy effectively destroys the mineral lattice structure. The increase in fine powder and the loosening of the mineral provide a larger specific surface area for the subsequent leaching reaction.

[0042] (3) Mixed acid leaching: The microwave pretreated concentrate powder is added to the mixed acid solution for leaching. The liquid-solid ratio is controlled at 5:1, the leaching temperature is 85℃, the stirring speed is 40r / min, and the leaching time is 5h. The leached solution is filtered and separated to obtain the leachate. The concentration (acidity) of hydrogen ions in the mixed acid solution is 29mol / L, which is obtained by adding hydrofluoric acid and sulfuric acid in a molar ratio of 5:1 to water.

[0043] Results: Tantalum leaching rate was 99.6%, and niobium leaching rate was 99.4%.

[0044] Example 2

[0045] This embodiment provides a method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate, the specific steps of which are shown below.

[0046] (1) Raw material screening: Tantalum-niobium concentrate raw material (Nb2O5+Ta2O5 content is 22%) is crushed, ground and screened to obtain tantalum-niobium concentrate powder with a particle size of 250-400 mesh (accounting for 95.8%) and a moisture content of 0.59%.

[0047] (2) Microwave pretreatment: The WBF-900 microwave reactor is preheated at 40°C for 5 minutes. The tantalum-niobium concentrate powder is fed into the microwave equipment and spread to a thickness of 3 mm. It is treated for 20 minutes under a power of 650W, and then cooled to 50°C before being discharged.

[0048] (3) Mixed acid leaching: The microwave pretreated concentrate powder is added to the mixed acid solution for leaching. The liquid-solid ratio is controlled at 3:1, the leaching temperature is 80℃, the stirring speed is 35r / min, and the leaching time is 6h. The leached solution is filtered and separated to obtain the leachate. The concentration of hydrogen ions in the mixed acid solution is 28mol / L, which is obtained by adding hydrofluoric acid and sulfuric acid in a molar ratio of 3:1 to water.

[0049] Results: Tantalum leaching rate was 99.3%, and niobium leaching rate was 99.2%.

[0050] Example 3

[0051] This embodiment provides a method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate, the specific steps of which are shown below.

[0052] (1) Raw material screening: Tantalum-niobium concentrate raw material (Nb2O5+Ta2O5 content is 35%) is crushed, ground and screened to obtain tantalum-niobium concentrate powder with a particle size of 250-400 mesh (accounting for 96.4%) and a moisture content of 0.71%.

[0053] (2) Microwave pretreatment: The WBF-900 microwave reactor is preheated at 50°C for 5 minutes. The tantalum-niobium concentrate powder is fed into the microwave equipment and spread to a thickness of 5 mm. It is treated for 12 minutes under a power of 800W, and then cooled to 45°C before being discharged.

[0054] (3) Mixed acid leaching: The microwave pretreated concentrate powder is added to the mixed acid solution for leaching. The liquid-solid ratio is controlled at 6:1, the leaching temperature is 90℃, the stirring speed is 45r / min, and the leaching time is 4h. The leached solution is filtered and separated to obtain the leachate. The concentration of hydrogen ions in the mixed acid solution is 30mol / L, which is obtained by adding hydrofluoric acid and sulfuric acid in a molar ratio of 7:1 to water.

[0055] Results: Tantalum leaching rate was 99.7%, and niobium leaching rate was 99.4%.

[0056] Comparative Example 1

[0057] This comparative example provides a method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate, the specific steps of which are shown below.

[0058] (1) Raw material screening: Same as in Example 1.

[0059] (2) Mixed acid leaching: The concentrate powder is added to the mixed acid solution for leaching. The liquid-solid ratio is controlled at 5:1, the leaching temperature is 85℃, the stirring speed is 40r / min, and the leaching time is 6h. The leached solution is filtered and separated to obtain the leachate. The concentration of hydrogen ions in the mixed acid solution is 29mol / L, which is obtained by adding hydrofluoric acid and sulfuric acid in a molar ratio of 5:1 to water.

[0060] Experimental results show that the leaching rate of tantalum is 85.3% and the leaching rate of niobium is 86.7%.

[0061] Comparative Example 2

[0062] This comparative example provides a method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate, the specific steps of which are shown below.

[0063] (1) Raw material screening: Same as in Example 1.

[0064] (2) Mixed acid leaching: The concentrate powder is added to the mixed acid solution for leaching. The liquid-solid ratio is controlled at 5:1, the leaching temperature is 85℃, the stirring speed is 40r / min, and the leaching time is 48h. The leached solution is filtered and separated to obtain the leachate. The concentration of hydrogen ions in the mixed acid solution is 29mol / L, which is obtained by adding hydrofluoric acid and sulfuric acid in a molar ratio of 5:1 to water.

[0065] Experimental results show that the leaching rate of tantalum is 99.3% and the leaching rate of niobium is 99.2%.

[0066] Comparative Example 3

[0067] This comparative example provides a method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate, the specific steps of which are shown below.

[0068] (1) Raw material screening: Same as in Example 1.

[0069] (2) Microwave pretreatment: The WBF-900 microwave reactor is preheated at 45°C for 5 minutes. The tantalum-niobium concentrate powder is fed into the microwave equipment and spread to a thickness of 4 mm. It is treated for 10 minutes under a power of 500W, and then cooled to 45°C before being discharged.

[0070] (3) Mixed acid leaching: The microwave pretreated concentrate powder is added to the mixed acid solution for leaching. The liquid-solid ratio is controlled at 5:1, the leaching temperature is 85℃, the stirring speed is 40r / min, and the leaching time is 5h. The leached solution is filtered and separated to obtain the leachate. The concentration of hydrogen ions in the mixed acid solution is 29mol / L, which is obtained by adding hydrofluoric acid and sulfuric acid in a molar ratio of 5:1 to water.

[0071] Results: The mineral lattice was not sufficiently disrupted, with tantalum leaching rate at 90.2% and niobium leaching rate at 91.5%, indicating a significant decrease in leaching efficiency.

[0072] Comparative Example 4

[0073] This comparative example provides a method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate, the specific steps of which are shown below.

[0074] (1) Raw material screening: The tantalum-niobium concentrate raw material (Nb2O5+Ta2O5 content is 28%) is crushed, ground and screened to obtain tantalum-niobium concentrate powder with a particle size of 100-200 mesh (accounting for 95.9%) and a moisture content of 0.7%.

[0075] (2) Microwave pretreatment: Same as in Example 1.

[0076] (3) Mixed acid leaching: Same as in Example 1.

[0077] Results: Microwave penetration was insufficient, tantalum leaching rate was 91.6%, niobium leaching rate was 92.8%, and leaching rate was low.

[0078] The detection results in the examples and comparative examples are shown in Table 1.

[0079] Table 1. Detection results in the examples and comparative examples.

[0080]

[0081] As can be seen from the results of the examples and comparative examples, the technical solution of the present invention significantly improves the leaching rate of tantalum and niobium concentrate. Microwave heating rapidly destroys the dense lattice of tantalum and niobium concentrate, greatly increasing the penetration rate of the leaching agent. The leaching rate of tantalum and niobium is more than 10% higher than that of traditional processes (such as Comparative Example 1), and the leaching rate stably reaches over 99%, significantly improving resource utilization. The technical solution of the present invention can significantly shorten the leaching cycle, improve equipment utilization, and reduce production costs. Traditional processes require 45-48 hours of heat preservation leaching (such as Comparative Example 2), while the microwave pretreatment of this solution only takes 12-20 minutes, followed by 4-6 hours of acid leaching heat preservation, shortening the heat preservation leaching time by more than 50%, significantly improving equipment turnover and production capacity. At the same time, the shortened heat preservation time reduces the loss of hydrofluoric acid volatilization, significantly reducing reagent consumption and greatly reducing raw material and equipment operating costs. The technical solution of the present invention can reduce environmental impact and improve production safety; the shorter heat preservation time reduces acidic waste gas generated by HF volatilization, significantly reducing the risk of environmental pollution.

[0082] In addition, Comparative Example 3 used the same batch of raw materials as Example 1, but due to the low microwave power and short time, the mineral lattice was not sufficiently destroyed, resulting in a significant decrease in leaching effect. Comparative Example 4 used the same batch of raw materials as Example 1, but the pretreatment stage was not strictly screened. Coarse tantalum-niobium concentrate powder of 100-200 mesh was used for microwave pretreatment and mixed acid leaching. However, due to the excessive particle size, the microwave penetration was insufficient, and the leaching rate was significantly lower.

[0083] In summary, by limiting the specific particle size of the material and combining it with microwave pretreatment with specific parameters, the present invention can achieve a tantalum and niobium leaching rate of over 99% in approximately 4-6 hours. Compared to the traditional process (Comparative Example 2), which requires 48 hours to achieve a similar leaching rate, the method of the present invention greatly shortens the leaching time and improves production efficiency. At the same time, Comparative Examples 3 and 4 demonstrate the indispensability of the microwave power, time, and material particle size range specified in the present invention for achieving a high leaching rate.

[0084] The foregoing descriptions have outlined some exemplary embodiments of the present invention. It is understood that these embodiments are merely illustrative and do not constitute a limitation on the scope of protection of the present invention. Features in these embodiments can be rearranged in suitable ways, and the resulting solutions remain within the scope of protection claimed by the present invention. All other embodiments obtained by those skilled in the art based on the foregoing embodiments without inventive effort, i.e., all modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate, characterized in that, This includes performing the following steps in sequence: (1) Raw material screening: Tantalum and niobium concentrate raw materials are crushed, ground and screened to obtain tantalum and niobium concentrate powder with a particle size of 250-400 mesh; (2) Microwave pretreatment: The tantalum-niobium concentrate powder is fed into a microwave device preheated to 40-50°C and spread out, and treated for 12-20 minutes under a power of 650-800W, and then cooled to below 50°C; (3) Mixed acid leaching: The microwave pretreated concentrate powder is added to the mixed acid solution for leaching. The liquid-solid ratio is controlled at 3-6:1, the leaching temperature is 80-90℃, and the leaching time is 4-6h. The leached solution is filtered and separated to obtain the leachate. The concentration of hydrogen ions in the mixed acid solution is 28-30mol / L, which is obtained by adding hydrofluoric acid and sulfuric acid in a molar ratio of 3-7:1 to water.

2. The method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate according to claim 1, characterized in that, In step (1), the total content of Nb2O5 and Ta2O5 in the tantalum-niobium concentrate raw material is >20%, and the moisture content of the tantalum-niobium concentrate powder is controlled to be <1%.

3. The method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate according to claim 1, characterized in that, In step (2), the process parameters for microwave pretreatment are: power of 700-750W and processing time of 14-18min.

4. The method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate according to claim 1, characterized in that, In step (2), the thickness of the tantalum-niobium concentrate powder is 3-5 mm.

5. The method for microwave pretreatment-enhanced acid leaching of tantalum-niobium concentrate according to claim 1, characterized in that, In step (3), the process parameters for mixed acid leaching are: liquid-to-solid ratio of 4-5:1, leaching temperature of 83-87℃, stirring speed of 35-45r / min, and leaching time of 4.5-5.5h.

6. The method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate according to claim 1, characterized in that, In step (3), the concentration of hydrogen ions in the mixed acid solution is 28.5-29.5 mol / L, which is obtained by adding hydrofluoric acid and sulfuric acid in a molar ratio of 4-6:1 to water.

7. The method for microwave pretreatment-enhanced acid leaching of tantalum-niobium concentrate according to claim 1, characterized in that, In step (3), the method for preparing the mixed acid solution is as follows: add hydrofluoric acid to water, then add sulfuric acid and stir evenly.

8. The method for microwave pretreatment to enhance acid leaching of tantalum-niobium concentrate according to claim 1, characterized in that, It also includes the following steps: When the total content of Nb2O5 and Ta2O5 in the decomposition residue obtained after filtration and separation in step (3) is ≥1%, the decomposition residue is subjected to secondary mixed acid leaching.

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