A method for preparing clean tantalum liquid from high-impurity tantalum liquid

Abstract

The application discloses a method for preparing clean tantalum liquid from high-impurity tantalum liquid, and belongs to the technical field of tantalum-niobium hydrometallurgy separation. The method comprises the following steps: adjusting the acidity of antimony-containing reverse tantalum liquid obtained in a tantalum-niobium metallurgy back extraction stage, adding thiourea or thioacetamide, and heating and sulfidizing in a reaction kettle by relying on the self-generated pressure of the system to make antimony and copper and other impurities form sulfide precipitates; after cooling, solid-liquid separation is performed, and the obtained antimony-removed liquid is subjected to multi-stage extraction by methyl isobutyl ketone, optional hydrogen peroxide-sulfuric acid trace niobium washing and multi-stage reverse extraction by pure water to obtain clean tantalum liquid; according to the types of the sulfidizing agent, the acidity, the sulfur-antimony ratio, the reaction temperature and the reaction time are limited respectively, so that the organic sulfidizing agent gradually releases active sulfur-containing species under the condition of acid and closed heating, which is beneficial to deep removal of antimony impurities and reduction of tantalum loss; the obtained sulfidized precipitates are relatively large, and are convenient for subsequent separation; and meanwhile, the multi-stage extraction and multi-stage reverse extraction processes are combined, so that the transfer efficiency of tantalum and the impurity control level of the clean tantalum liquid are improved.

Description

Technical Field

[0001] This invention relates to the field of tantalum-niobium hydrometallurgical separation technology, specifically to a method for preparing clean tantalum solution from tantalum solution with high impurity content. Background Technology

[0002] Tantalum possesses characteristics such as high melting point, excellent corrosion resistance, superior dielectric properties, and high biocompatibility, making it widely used in electronic capacitors, semiconductor devices, high-temperature alloys, chemical corrosion-resistant equipment, and biomedical materials. With the development of the electronics industry, semiconductor manufacturing, and high-end capacitor materials, the purity requirements for tantalum raw material solutions and subsequent products such as tantalum oxide and tantalum powder are constantly increasing, especially requiring strict control of the content of impurity elements such as antimony, niobium, arsenic, copper, iron, and tungsten. For high-purity tantalum materials such as high-purity tantalum oxide and high-specific-capacitance tantalum powder, the depth of impurity removal in the upstream tantalum solution directly affects the purity stability and batch consistency of subsequent products.

[0003] In existing hydrometallurgical processes for tantalum and niobium, tantalum and niobium minerals are typically decomposed using hydrofluoric acid or a hydrofluoric acid-sulfuric acid mixture, followed by extraction and back-extraction separation of tantalum and niobium using organic solvents such as methyl isobutyl ketone. During multi-stage extraction and back-extraction, tantalum and niobium can be separated based on their distribution differences under different acidity conditions. However, antimony exhibits a similar distribution behavior between the organic and aqueous phases to tantalum, easily entering the organic phase along with tantalum and ultimately ending up in the anti-tantalum solution.

[0004] For anti-tantalum solutions with high antimony content, relying solely on increasing the number of extraction, washing, or back-extraction stages for antimony removal typically requires configuring a multi-stage extraction system. This not only prolongs the process flow but also increases the amount of organic extractant used, equipment investment, and operating costs. Furthermore, with increased cycle times, problems such as organic phase entrainment, aqueous phase emulsification, and increased tantalum loss can easily arise, making it difficult to simultaneously achieve both antimony removal depth and tantalum recovery rate. Sulfide precipitation is a common method for removing easily sulfidated metal impurities such as antimony and copper from acidic solutions. Traditional sulfide precipitation processes often use inorganic sulfiding agents such as sodium sulfide, ammonium sulfide, potassium sulfide, or hydrogen sulfide. When added to an acidic medium, inorganic sulfiding agents rapidly release hydrogen sulfide, easily causing excessively high local sulfur ion concentrations. This leads to instantaneous nucleation of antimony sulfide, resulting in fine precipitate particles with low agglomeration and poor filtration performance. Simultaneously, the concentrated release of hydrogen sulfide also poses significant safety and exhaust gas treatment challenges. Furthermore, if the acidity, amount of sulfiding agent, temperature, and time of the sulfidation reaction are not properly controlled, problems such as incomplete antimony sulfidation, tantalum co-precipitation, precipitated particles penetrating the filter material, or insufficient decomposition of the organic sulfiding agent may occur. Therefore, how to provide a method for preparing clean tantalum solution from high-impurity tantalum solution to solve these problems has become an urgent issue for those skilled in the art. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide a method for preparing clean tantalum solution from high-impurity tantalum solution, in order to solve the problems of long multi-stage extraction antimony removal process, rapid release of hydrogen sulfide by inorganic sulfiding agent, small and difficult-to-filter precipitate particles, and difficulty in deep removal of antimony impurities. This invention adds thiourea or thioacetamide to the high-impurity tantalum solution, so that the organic sulfiding agent gradually releases active sulfur species under closed heating and system self-generated pressure, and forms sulfide precipitates with antimony. After antimony removal by sulfidation precipitation, tantalum is recovered by multi-stage extraction with methyl isobutyl ketone and multi-stage reverse tantalum extraction with pure water. As needed, the organic phase loaded with tantalum can be purified by trace niobium washing with a hydrogen peroxide-sulfuric acid mixed solution, thereby achieving stepwise separation of antimony, niobium and tantalum.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a clean tantalum solution from a high-impurity tantalum solution includes the following steps:

[0008] S1. Detect the antimony content in the high impurity tantalum solution, calculate the amount of organic sulfurizing agent to be added based on the antimony content, and adjust the apparent pH of the high impurity tantalum solution to -0.7 to 2.0.

[0009] The high-impurity tantalum solution described in this invention can be the anti-tantalum solution obtained by back-extraction of the organic phase of tantalum-niobium co-extraction in a tantalum-niobium hydrometallurgical production line; the high-impurity tantalum solution is preferably a hydrofluoric acid-sulfuric acid system, wherein, in addition to tantalum, it may also contain one or more of antimony, niobium, arsenic, nickel, tungsten, boron, iron, copper, aluminum, vanadium and tin.

[0010] It should be noted that, since the high-impurity tantalum solution contains hydrofluoric acid, sulfuric acid, and a high concentration of metal fluorine complexes, the pH mentioned in this invention is the apparent pH measured under the same detection conditions, used to represent the relative acidity between the experimental solutions in each group; a negative apparent pH does not indicate the absence of measurable hydrogen ion activity in the solution, but rather indicates that the solution is in a high acidity range.

[0011] S2. Add the adjusted high impurity tantalum solution and organic sulfiding agent to a closed reaction vessel, and carry out a heating sulfidation reaction under the system's self-generated pressure to convert the antimony in the solution into antimony sulfide precipitates.

[0012] The organic vulcanizing agent is thiourea or thioacetamide; the amount of organic vulcanizing agent added is expressed as the ratio of the amount of sulfur in the organic vulcanizing agent to the amount of antimony in the high impurity tantalum solution, n(S) / n(Sb).

[0013] Preferably, when thiourea is used as the organic vulcanizing agent, the apparent pH of the anti-tantalum solution is -0.3 to 2, n(S) / n(Sb) is 25 to 30, the reaction temperature is 150 to 170°C, and the reaction time is 3 to 6 h; when thioacetamide is used as the organic vulcanizing agent, the apparent pH of the anti-tantalum solution is -0.7 to 2, n(S) / n(Sb) is 2.5 to 10, the reaction temperature is 130 to 170°C, and the reaction time is 0.5 to 2 h.

[0014] More preferably, when using thioacetamide, the n(S) / n(Sb) ratio is 2.5-3, the reaction temperature is 150℃, and the reaction time is 60 min, so as to balance the amount of sulfiding agent, the reaction time, and the antimony removal effect.

[0015] The closed reaction vessel is preferably a high-pressure reactor with a polytetrafluoroethylene liner; the liquid volume of the reactants is preferably 3 / 5 of the effective volume of the high-pressure reactor, so as to retain a gas phase space above the reactants; the reactor is sealed before heating, and nitrogen, air or other external pressure media are not introduced during the reaction; the reaction pressure is composed of the vapor pressure generated by the heating of the solution and the reaction products.

[0016] Without being constrained by specific theories, it is believed that thiourea and thioacetamide can gradually hydrolyze or decompose under acidic heating conditions and continuously release sulfur-containing active species. Compared with the instantaneous release of a large amount of hydrogen sulfide after inorganic sulfiding agents are added to acidic solutions, the sulfur release process of organic sulfiding agents is relatively slow, which is conducive to reducing the rapid nucleation caused by excessively high local sulfur concentration, and allows sulfide crystal nuclei to further grow and aggregate.

[0017] Thioacetamide has relatively high reactivity, requiring a lower sulfur-to-antimony ratio and shorter reaction time under the same antimony removal requirements; thiourea has a relatively slow sulfur release rate, usually requiring a higher sulfur-to-antimony ratio and a longer reaction time; therefore, this invention specifies the reaction parameters for the two organic vulcanizing agents separately, rather than using the same reaction conditions for both vulcanizing agents in general.

[0018] S3. After the sulfidation reaction is completed, the sealed reaction vessel is cooled. After the temperature and pressure drop, the pressure is released, and the reaction materials are separated into solid and liquid to obtain sulfide precipitate and antimony-removed liquid.

[0019] Solid-liquid separation can be achieved by vacuum filtration, pressure filtration, centrifugation, or other acid-resistant solid-liquid separation methods. The main antimony-containing crystalline phase of the resulting sulfide precipitate is Sb2S3, and some precipitates may also contain elemental sulfur and sulfides formed by impurities such as copper.

[0020] When thiourea is used, the resulting precipitate can be rod-shaped, needle-shaped, or sheet-shaped crystals; when thioacetamide is used, the resulting precipitate can be sheet-shaped, block-shaped, or micron-sized particles formed by stacking multiple sheet-shaped crystals; compared with the fine precipitate formed by inorganic vulcanizing agents, the precipitate formed by organic vulcanizing agents has a larger particle size and better filtration performance.

[0021] S4. Adjust the concentration of free acid in the antimony-removed solution to 0.5–3.0 mol / L, and perform multi-stage extraction using methyl isobutyl ketone as the extractant to allow tantalum to selectively enter the supported organic phase, thereby obtaining the supported tantalum organic phase and the raffinate aqueous phase.

[0022] The free acid concentration described in this invention is expressed in H+. + The acidity of the sample; the volume ratio of methyl isobutyl ketone to the antimony-removed liquid, i.e., the oil-water ratio O / A, is preferably 0.5 to 2:1, more preferably 1:1; the extraction time per stage is 5 to 15 min, preferably 5 to 10 min; the number of extraction stages is 3 to 5, preferably 4.

[0023] Multistage extraction can employ either cross-flow extraction or counter-flow extraction. In counter-flow extraction, the aqueous phase obtained from the previous stage contacts the fresh or low-loaded methyl isobutyl ketone of the next stage, while the organic phase obtained from the previous stage flows in the opposite direction to the aqueous phase, thereby increasing the cumulative extraction rate of tantalum and reducing the amount of organic phase used.

[0024] After most of the antimony is removed in the sulfide precipitation step, the antimony load entering the extraction process is significantly reduced. Therefore, it is no longer necessary to rely on increasing the number of extraction stages to remove antimony, which helps to shorten the extraction process and reduce the accumulation of antimony in the organic phase.

[0025] S5. The supported tantalum organic phase is subjected to multi-stage back-extraction with pure water to obtain a clean tantalum solution; before the pure water back-extraction, the supported tantalum organic phase is optionally washed and purified with a mixed solution of hydrogen peroxide and sulfuric acid using trace amounts of niobium.

[0026] The mass fraction of hydrogen peroxide in the mixed solution of hydrogen peroxide and sulfuric acid is preferably 0.5% to 2.0%, and the concentration of sulfuric acid is preferably 0.8 to 2.0 mol / L; the O / A ratio of the supported tantalum organic phase to the oil-water ratio of the mixed solution is preferably 0.5 to 2, and the washing contact time is preferably 20 to 40 min.

[0027] It should be noted that the extraction rate of niobium during the methyl isobutyl ketone extraction process is relatively low. The mixed solution of hydrogen peroxide and sulfuric acid is mainly used to wash and purify the small amount of co-extracted or entrained niobium in the tantalum-loaded organic phase, rather than to back-extract a large amount of niobium. This step can reduce the probability that trace amounts of niobium will enter the final anti-tantalum solution along with tantalum.

[0028] The O / A ratio of the supported tantalum organic phase or the supported tantalum organic phase after washing and purification with trace amounts of niobium to the oil-water ratio of pure water is preferably 0.5 to 2. The back-extraction time of each pure water stage is preferably 20 to 40 minutes, and the number of back-extraction stages is preferably 2 to 4. The pure water back-extraction solutions of each stage can be combined to obtain a clean tantalum solution. The methyl isobutyl ketone after back-extraction can be returned to the extraction step for recycling after static phase separation or conventional purification treatment.

[0029] The Sb precipitation rate described in this invention is calculated based on the difference in Sb concentration in the liquid phase before and after the reaction, and the Ta loss rate is calculated based on the difference in Ta content in the liquid phase before and after the reaction. When corrections are needed due to factors such as sampling and volume changes, the calculation is based on the metal mass after material balance.

[0030] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0031] 1. This invention first uses an organic sulfiding agent to sulfide and precipitate antimony from a tantalum solution with high impurity content, followed by multi-stage extraction and back-extraction of tantalum. This reduces the antimony content at the extraction stage, decreases the amount of antimony entering the loaded organic phase with the tantalum, and avoids simply removing antimony by increasing the number of extraction and washing stages. This helps to shorten the tantalum solution purification process and reduce the consumption of extractant. The resulting clean tantalum solution can be used as a front-end feedstock for high-purity tantalum materials such as high-purity tantalum oxide and high-specific-capacity tantalum powder, improving the basis for impurity control in the subsequent preparation of high-purity rare metal materials.

[0032] 2. This invention uses thiourea or thioacetamide as an organic vulcanizing agent, which allows the sulfur source to be gradually released under acidic, closed heating conditions, reducing the violent reaction and fine particle formation caused by a sudden increase in the concentration of the local vulcanizing agent; the resulting precipitate is mainly composed of micron-sized rod-shaped, sheet-shaped, or sheet-shaped stacked structures, and the particle size and filtration performance are superior to those of precipitates formed by traditional inorganic vulcanizing agents, which facilitates subsequent solid-liquid separation.

[0033] 3. This invention sets different apparent pH, sulfur-antimony ratio, reaction temperature and reaction time ranges for thiourea and thioacetamide respectively, which can be matched with the different sulfur release rates of the two organic sulfurizing agents; thioacetamide can remove antimony at a lower sulfur-antimony ratio and a shorter time, while thiourea can form sulfide precipitates with better crystallinity at a higher sulfur-antimony ratio and a longer reaction time.

[0034] 4. In this invention, after tantalum extraction, the supported tantalum organic phase can be further purified by washing with a hydrogen peroxide-sulfuric acid mixed solution to remove trace amounts of niobium. A multi-stage tantalum back-extraction process using pure water is employed, creating a coordinated, graded impurity removal process involving antimony precipitation, tantalum extraction, trace niobium purification, and tantalum back-extraction. When further reduction of niobium content is required, this washing and purification step can reduce the amount of trace niobium entering the final tantalum solution along with the tantalum, thereby improving the impurity control level of the clean tantalum solution and subsequent high-purity tantalum materials such as tantalum oxide and tantalum powder. Attached Figure Description

[0035] Figure 1 This is a process flow diagram of the present invention for preparing clean tantalum solution from high impurity tantalum solution;

[0036] Figure 2 The graph shows the effect of apparent pH of the solution on the sulfide precipitation results using thiourea.

[0037] Figure 3 The graph shows the effect of apparent pH of the solution on the sulfide precipitation results using thioacetamide.

[0038] Figure 4 The graph shows the effect of the molar ratio of sulfur to antimony in thiourea on the sulfide precipitation results.

[0039] Figure 5 The graph shows the effect of the molar ratio of sulfur to antimony in thioacetamide on the sulfidation precipitation results.

[0040] Figure 6 The graph shows the effect of reaction time on the sulfidation precipitation results using thiourea.

[0041] Figure 7 The graph shows the effect of reaction time on the sulfidation precipitation results using thioacetamide.

[0042] Figure 8 The graph shows the effect of reaction temperature on the sulfidation precipitation results using thiourea.

[0043] Figure 9 The graph shows the effect of reaction temperature on the sulfidation precipitation results using thioacetamide.

[0044] Figure 10 The graph shows the effect of hydrogen ion concentration in the solution on the sulfide precipitation results using ammonium sulfide.

[0045] Figure 11 The graph shows the effect of the molar ratio of sulfur to antimony in ammonium sulfide on the sulfide precipitation result.

[0046] Figure 12 The graph shows the effect of reaction temperature on the sulfide precipitation results using ammonium sulfide.

[0047] Figure 13 The graph shows the effect of reaction time on the sulfidation precipitation results using ammonium sulfide.

[0048] Figure 14 X-ray diffraction pattern of the sulfide precipitate obtained using thiourea and thioacetamide;

[0049] Figure 15 Scanning electron microscope and energy dispersive spectroscopy (EDS) images of the sulfurized precipitates obtained using thiourea and thioacetamide.

[0050] Figure 16This is a particle size distribution diagram of the sulfide precipitate obtained using thioacetamide and ammonium sulfide;

[0051] Figure 17 The graph shows the effect of extraction stage number on the extraction rates of Ta, Nb, Sb, and As, and the effect of back-extraction stage number on the tantalum back-extraction rate. Figure 17 Figure (a) shows the effect of extraction stage on the extraction rate of different metal elements. Figure 17 (b) in the figure shows the effect of the number of back-extraction stages on the tantalum back-extraction rate. Detailed Implementation

[0052] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the specific embodiments described below are for illustrative purposes only and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make non-essential improvements and adjustments to this application based on the above description. Unless otherwise specified, detection methods and operating conditions can be performed using conventional methods in the field. All reagents not specifically mentioned are of analytical grade, and the water is deionized water; concentrations are indicated as wt% when expressed as mass concentration.

[0053] In this embodiment, the amount of organic vulcanizing agent is calculated according to the molar ratio of sulfur in the organic vulcanizing agent molecule to antimony in the raw material solution; the oil-water ratio O / A represents the volume ratio of the organic phase to the water phase; the contents of Ta, Sb, Nb, As, Ni, W, B, Fe, Cu, Al, V and Sn in the solution are detected by ICP-MS or ICP-OES; the crystal phase of the precipitate is detected by X-ray diffraction; the morphology and elemental composition of the precipitate are detected by scanning electron microscopy and energy dispersive spectroscopy; and the particle size of the precipitate is detected by laser particle size analyzer.

[0054] raw material liquid

[0055] The high impurity tantalum solution used in the examples was obtained from the back-extraction stage of the tantalum-niobium production line of a tantalum-niobium metallurgical plant in Jiangxi Province. The initial pH was about 2, and the main components are shown in Table 1.

[0056] Table 1. Original composition of high impurity tantalum solution

[0057]

[0058] Example 1

[0059] In this embodiment, thiourea is used as an organic sulfurizing agent.

[0060] Take 60 mL of tantalum solution with high impurity content, calculate the amount of thiourea to be added based on the detected antimony content, and control the molar ratio of sulfur to antimony in thiourea to be n(S) / n(Sb) = 25.

[0061] The apparent pH of the high-impure tantalum solution was adjusted to 2, and then the solution and thiourea were added to a polytetrafluoroethylene-lined high-pressure reactor with an effective volume of 100 mL. The volume of the reactants was about 3 / 5 of the effective volume of the reactor. The reactor was sealed, and no external gas was introduced. The temperature was raised to 150°C, and the reaction was carried out for 3 hours by relying on the self-generated pressure generated by the heating of the system.

[0062] After the reaction is complete, stop heating and allow the reactor to cool naturally. Once the reactor temperature has decreased and the internal pressure has been released to a safe range, open the reactor and perform vacuum filtration on the reactants to obtain sulfide precipitate and antimony-free liquid.

[0063] ICP analysis after the reaction showed that under the above conditions, the antimony precipitation rate was significantly increased, while the tantalum precipitation rate remained at a low level; combined with... Figure 6 The time experiment showed that extending the reaction time of thiourea could further reduce the amount of antimony residue. When the reaction time was extended to 6 hours, the amount of antimony residue could be reduced to 0.24 ppm. XRD analysis of the precipitate showed that the main antimony-containing crystalline phase was Sb2S3. SEM analysis showed that the precipitate was mainly in the form of rod-shaped or plate-shaped micron-sized crystals with a certain degree of overlap and agglomeration between the particles, making it difficult to penetrate the filter material during the filtration process.

[0064] The concentration of free acid in the antimony-removed solution was adjusted to 2 mol / L. Methyl isobutyl ketone was used as the extractant, and four-stage extraction was carried out at O / A = 1:1. Each stage was mixed and extracted for 10 min. After standing and phase separation, the organic phase and aqueous phase were collected separately.

[0065] After extraction, combine Figure 17 The extraction results show that tantalum can effectively enter the MIBK organic phase after four-stage extraction. The loaded organic phase is then purified by trace niobium washing with a mixed solution containing 1 wt% hydrogen peroxide and 0.8–2.0 mol / L sulfuric acid, allowing a small amount of co-extracted or entrained niobium to enter the washing aqueous phase. Subsequently, three-stage back-extraction is performed with pure water at an O / A ratio of 1, with each stage lasting 30 min. The aqueous phases from each back-extraction stage are combined to obtain a clean tantalum solution. Figure 17 The back-extraction results shown indicate that the tantalum back-extraction rate can reach approximately 90% after three-stage pure water back-extraction.

[0066] Example 2

[0067] In this embodiment, thioacetamide is used as an organic vulcanizing agent.

[0068] Take 60 mL of the same high-impurity tantalum solution as in Example 1, and adjust the apparent pH of the solution to 0; add thioacetamide according to the antimony content in the raw material solution, so that the molar ratio of sulfur to antimony in the thioacetamide is n(S) / n(Sb) = 3.

[0069] Add the raw material liquid and thioacetamide to a polytetrafluoroethylene-lined high-pressure reactor, filling the reactor to about 3 / 5 of its effective volume. Seal the reactor, do not introduce any external pressure medium, heat to 150°C, and react for 1 hour under the system's own pressure.

[0070] After the reaction was completed, the solution was cooled, depressurized, and filtered to obtain sulfide precipitate and antimony-removed solution. The test results showed that thioacetamide could achieve deep removal of antimony at a low sulfur-to-antimony ratio and a short reaction time, with an antimony removal rate of about 99.8%, while tantalum was basically retained in the solution.

[0071] The precipitate was mainly observed to be in the form of flakes and lumps by SEM analysis. Some of the flake particles stacked together to form large micron-sized aggregates. EDS analysis showed that the precipitate mainly contained Sb and S elements, and small amounts of Cu, O and F elements, indicating that it could remove some easily sulfidable copper impurities while precipitating antimony.

[0072] The antimony-removed liquid was subjected to four-stage methyl isobutyl ketone extraction, micro-niobium washing purification with hydrogen peroxide-sulfuric acid mixed solution, and three-stage pure water tantalum reaction according to the method in Example 1 to obtain a clean tantalum liquid; the obtained clean tantalum liquid can be further subjected to tantalum precipitation, washing and calcination to obtain a low-impurity tantalum oxide product.

[0073] Compared with Example 1, the sulfur-antimony ratio of the organic vulcanizing agent in this example is significantly reduced, and the vulcanization reaction time is shortened from 3 hours to 1 hour, indicating that thioacetamide has a faster active sulfur release rate at the same temperature.

[0074] Example 3

[0075] Take 90 mL of tantalum solution with high impurity content and add it to a polytetrafluoroethylene-lined high-pressure reactor with an effective volume of 150 mL. Adjust the apparent pH of the raw material solution to 0 and add thioacetamide to make n(S) / n(Sb) = 2.5.

[0076] The sealed high-pressure reactor was heated to 130°C and reacted for 1 hour under the system's own pressure. After the reaction was completed, the reactor was cooled, depressurized, and filtered.

[0077] The free acid concentration of the antimony-removed solution was adjusted to 2 mol / L, and 4-stage countercurrent extraction with methyl isobutyl ketone was performed at O / A=1, with a contact time of 5 min for each stage. The tantalum-loaded organic phase was purified by micro-niobium washing with a hydrogen peroxide-sulfuric acid mixed solution, and then 3-stage reverse tantalum extraction was performed with pure water.

[0078] The obtained clean tantalum solution was processed into tantalum oxide products using conventional tantalum precipitation, washing, and calcination processes, and the results were analyzed by ICP-MS. The results are shown in Table 2.

[0079] Table 2. Test results of tantalum oxide products prepared from clean tantalum solution.

[0080]

[0081] As can be seen from Table 2, the tantalum oxide product obtained after treatment by the method of the present invention has low levels of antimony, niobium, copper, arsenic and nickel, indicating that the sulfide precipitation and subsequent extraction and back-extraction steps can form a synergistic impurity removal effect.

[0082] Comparative Example 1

[0083] This comparative example uses traditional ammonium sulfide as the sulfiding agent.

[0084] Take the same high impurity tantalum solution as in Example 2 and add ammonium sulfide to a normal pressure reaction vessel; after the ammonium sulfide comes into contact with the acidic tantalum solution, it reacts rapidly and produces a distinct pungent odor, requiring the use of a tail gas absorption device to treat the released sulfur-containing gas.

[0085] After the reaction was completed, the precipitate was filtered, and the resulting precipitate particles were relatively fine, which was not conducive to subsequent solid-liquid separation. The test results showed that, under similar conditions of ammonium sulfide dosage and reaction time, the amount of antimony residue was higher than that in the example using thioacetamide.

[0086] Laser particle size analysis showed that the D50 of the precipitate obtained from ammonium sulfide was approximately 2.55 μm, while the D50 of the precipitate obtained from thioacetamide was approximately 40.16 μm. This indicates that the precipitate particles formed by thioacetamide under closed heating conditions are significantly larger than those formed by conventional ammonium sulfide, exhibiting better solid-liquid separation performance.

[0087] Comparative Example 2

[0088] In this comparative example, thioacetamide was used as an organic sulfurizing agent, but the apparent pH of the high impurity tantalum solution was adjusted to 3.

[0089] Except for the apparent pH, the amount of thioacetamide added, the reaction temperature, and the reaction time were the same as in Example 2; after the reaction, the solution was filtered and tested after antimony removal.

[0090] Experimental results show that when the apparent pH increases to 3, the antimony precipitation rate decreases significantly and the amount of residual antimony in the solution increases. This may be because the form of antimony changes under lower acidity conditions, forming some colloidal antimony-containing substances. Colloidal particles are not conducive to a full reaction with active sulfur species and are also easy to pass through the filter material.

[0091] This comparative example illustrates that a higher apparent pH is not necessarily more conducive to sulfide precipitation. When using thioacetamide, controlling the apparent pH within the range of -0.7 to 1 is more beneficial for the deep removal of antimony and the retention of tantalum.

[0092] Comparative Example 3

[0093] This comparative example uses thioacetamide as an organic vulcanizing agent, but the reaction temperature is reduced to 80°C.

[0094] Take the same high impurity tantalum solution as in Example 2, adjust the apparent pH to 0, control n(S) / n(Sb)=3, and react at 80°C for 1 hour.

[0095] After the reaction was completed, solid-liquid separation was performed; the test results showed that the antimony removal rate under this condition was significantly lower than that in Example 2; even if the reaction time was appropriately extended, the improvement in the antimony removal rate was still limited.

[0096] Analysis suggests that the hydrolysis and release of active sulfur in thioacetamide are slow at 80°C, and the active sulfur species formed per unit time are insufficient to fully convert antimony in the solution into antimony sulfide. This comparative example indicates that thioacetamide needs to be used at a temperature not lower than 90°C, preferably 130–150°C.

[0097] Comparative Example 4

[0098] This comparative example uses thioacetamide as an organic vulcanizing agent, but reduces n(S) / n(Sb) to 1.

[0099] Other reaction conditions were the same as in Example 2; after the reaction was completed, the solution was filtered and tested, and the results showed that the antimony removal rate was significantly reduced; after extending the reaction time, the amount of residual antimony was still higher than in Example 2.

[0100] The results indicate that when the amount of organic sulfurizing agent is insufficient, the released active sulfur species are not enough to completely form antimony sulfide precipitates; therefore, when using thioacetamide, n(S) / n(Sb) should be controlled between 2 and 8, preferably between 2 and 3.

[0101] It should be noted that, Figures 2 to 13 The experiments shown are single-factor comparative experiments on apparent pH, organic sulfurizing agent dosage, reaction time, reaction temperature, and sulfurizing agent type. The experimental points in each figure were obtained under corresponding fixed conditions. The optimal experimental points shown in different figures should not be directly combined and regarded as the same batch of experimental conditions. Examples 1 to 3 are used to illustrate the complete sulfur precipitation, extraction, and back-extraction process of the present invention, and Comparative Examples 1 to 4 are used to illustrate the effect of a single reaction factor deviating from the suitable range of the present invention on the antimony removal effect.

[0102] As can be seen from the combined examples and comparative examples, there is a synergistic relationship between apparent pH, type of sulfiding agent, sulfur-antimony ratio, reaction temperature and reaction time.

[0103] Depend on Figure 2It can be seen that when thiourea is used as an organic sulfurizing agent, the antimony precipitation rate increases as the apparent pH of the antitantalum solution gradually increases from -0.7. Within the apparent pH range of -0.3 to 2, the antimony precipitation rate remains at a relatively high level, and the residual amount of antimony is significantly reduced. However, when the apparent pH is further increased to 3, the antimony precipitation rate decreases significantly. The above results indicate that the thiourea system needs to maintain suitable acidic conditions. When the acidity is too high, it is not conducive to the release of effective sulfur-containing species by thiourea. When the acidity is too low, it may change the solution form of antimony, thereby reducing the sulfurization precipitation effect.

[0104] Depend on Figure 3 It can be seen that when thioacetamide is used as an organic sulfurizing agent, a high antimony precipitation rate can be maintained in the apparent pH range of -0.7 to 2, and a high copper precipitation rate is also observed, while the tantalum precipitation rate is generally low. When the apparent pH increases to 3 to 4, the antimony precipitation rate decreases and the residual antimony content increases significantly. Therefore, controlling the apparent pH of the thioacetamide system in the range of -0.7 to 2 is more conducive to the selective precipitation of easily sulfurized impurities such as antimony and copper.

[0105] Depend on Figure 4 It can be seen that when using thiourea, as n(S) / n(Sb) increases, the antimony precipitation rate gradually increases and the antimony residue gradually decreases; when n(S) / n(Sb) is less than 20, the amount of sulfur source is insufficient and the antimony residue is still relatively high; when n(S) / n(Sb) reaches more than 25, the antimony precipitation rate is close to stable, and further increasing the amount of thiourea will have a smaller effect on increasing the antimony precipitation rate; therefore, the suitable n(S) / n(Sb) for thiourea is 25-30.

[0106] Depend on Figure 5 It can be seen that the sulfidation reactivity of thioacetamide is significantly higher than that of thiourea. When n(S) / n(Sb) increases from 1.25 to 2.5, the antimony precipitation rate increases rapidly. When n(S) / n(Sb) is not lower than 2.5, the antimony precipitation rate can be maintained at a high level. When n(S) / n(Sb) is 10, the antimony residue in the figure reaches a minimum of 0.015 ppm. This indicates that n(S) / n(Sb) = 2.5 to 3 is suitable for balancing the consumption of sulfiding agent and the antimony removal efficiency. When it is necessary to further reduce the antimony residue, the dosage of thioacetamide can be appropriately increased.

[0107] Depend on Figure 6 It can be seen that when using thiourea, the antimony precipitation rate is low after 1 hour of reaction, and gradually increases with the extension of reaction time; the antimony precipitation rate tends to stabilize after 4 hours of reaction, and the residual antimony can be reduced to 0.24 ppm after 6 hours of reaction; this result indicates that the release rate of sulfur-containing active species in acidic systems by thiourea is relatively slow, and a longer reaction time is required to achieve deep antimony removal.

[0108] Depend on Figure 7It can be seen that when using thioacetamide, a high antimony precipitation rate can be obtained in a relatively short reaction time. As the reaction time is extended from 10 min to 300 min, the residual antimony content continues to decrease, while the tantalum precipitation rate does not show a significant increase. Considering the treatment efficiency and antimony removal effect, the reaction time is preferably 30 to 120 min, and more preferably 60 min.

[0109] Depend on Figure 8 It can be seen that when using thiourea, the antimony precipitation rate is low at 110℃ and 130℃, indicating that the decomposition or hydrolysis rate of thiourea is slow in this temperature range; when the temperature is increased to 150℃, the antimony precipitation rate increases significantly; at 170℃, the antimony precipitation rate is close to stable, and the residual antimony content decreases to 0.29ppm; therefore, the suitable reaction temperature for the thiourea system is 150~170℃.

[0110] Depend on Figure 9 It can be seen that when using thioacetamide, as the reaction temperature increases from 90℃ to 150℃, the antimony precipitation rate continues to increase and the residual amount of antimony decreases significantly; in the range of 150~170℃, the antimony precipitation rate remains at a high level; thioacetamide has already shown a good sulfidation precipitation effect at 130℃, indicating that the temperature required for it to release sulfur-containing active species is lower than that for thiourea.

[0111] Depend on Figure 10 It can be seen that when using ammonium sulfide, the antimony precipitation effect is quite sensitive to the acidity of the solution; both excessively low and excessively high hydrogen ion concentrations will lead to a decrease in the antimony precipitation rate. Figure 11 It can be seen that when the amount of ammonium sulfide is insufficient, the antimony precipitation is incomplete. Increasing the amount of ammonium sulfide improves the antimony precipitation rate, but continuing to add excessive amounts does not continuously improve the antimony precipitation rate.

[0112] Depend on Figure 12 It can be seen that the antimony precipitation rate of the ammonium sulfide system first increases and then decreases with increasing temperature, and the suitable temperature range is relatively narrow; from Figure 13 It can be seen that extending the reaction time can gradually increase the antimony precipitation rate, but the acidity, dosage and temperature still need to be strictly controlled. The above results indicate that the reaction window of inorganic sulfiding agents is relatively narrow, and they are prone to rapid release of sulfur-containing gases in strong acid systems, which is not conducive to stable control of precipitation nucleation and particle growth.

[0113] Depend on Figures 10-13 It can be seen that the antimony removal effect of the ammonium sulfide system is greatly affected by acidity, sulfiding agent dosage, reaction temperature, and reaction time, and the reaction window is relatively narrow; at the same time, combined with Figure 16 The particle size distribution results show that the D50 of the precipitate particles obtained from ammonium sulfide is 2.55 μm, which is significantly smaller than the D50 of the precipitate particles obtained from thioacetamide, which is not conducive to subsequent solid-liquid separation.

[0114] Depend on Figure 14It can be seen that the X-ray diffraction peaks of the precipitates obtained by using thiourea and thioacetamide correspond to the characteristic peaks of the Sb2S3 standard card PDF#73-0393, and there are also diffraction peaks corresponding to the elemental sulfur S8 standard card PDF#53-1109. This indicates that the antimony in the anti-tantalum solution is mainly converted into Sb2S3 and enters the solid phase, and some of the excess sulfur-containing active species can further form elemental sulfur. This result proves that organic sulfurizing agents can release sulfur-containing active species under acidic and autogenous pressure conditions and promote the transfer of antimony from the liquid phase to the solid phase.

[0115] Depend on Figure 15 As shown in (a) and (b), the precipitate obtained by using thiourea is mainly in the form of slender rod-shaped, needle-shaped, and plate-shaped crystals, with multiple crystals overlapping to form a loose aggregate structure; the corresponding EDS results show that the detection area mainly contains S and Sb elements, with S and Sb atomic percentages of 51.22% and 35.26%, respectively, and contains small amounts of O, Cu, and F elements.

[0116] Depend on Figure 15 As shown in (d) and (e), the precipitate obtained by using thioacetamide mainly exhibits sheet-like, block-like, and sheet-like aggregated structures. The corresponding EDS results show that the atomic percentages of S and Sb in the detection area are 56.51% and 33.99%, respectively, while also containing small amounts of O and Cu elements. The above results indicate that the precipitates obtained by both organic sulfurizing agents are mainly composed of antimony and sulfur components, and can simultaneously carry out some copper impurities.

[0117] Depend on Figure 16 It can be seen that the particle size distribution of the precipitate obtained using thioacetamide generally shifts towards larger particle sizes, with a median particle size D50 of 40.16 μm; the median particle size D50 of the precipitate obtained using ammonium sulfide is 2.55 μm. This indicates that thioacetamide gradually releases sulfur-containing active species under closed heating conditions, which helps to reduce the instantaneous large-scale nucleation, allowing the precipitate crystals to continue to grow and aggregate, resulting in precipitates with larger particle sizes. Larger precipitate particles are less likely to penetrate the filter material, which is more conducive to subsequent filtration and solid-liquid separation.

[0118] Depend on Figure 17 As shown in (a), the cumulative extraction rate of tantalum gradually increases with the increase of the MIBK extraction stage, and the tantalum extraction rate is close to 100% after four stages of extraction; the overall extraction rate of niobium is relatively low, indicating that MIBK has high extraction selectivity for tantalum under the acidity conditions; antimony still has a certain degree of co-extraction, but its extraction rate is significantly lower than that of tantalum. Therefore, using organic sulfide precipitation to reduce the antimony content before extraction can reduce the accumulation of antimony in the supported organic phase.

[0119] Depend on Figure 17As shown in (b), the tantalum extraction rate is about 45% when using pure water for primary extraction, about 78% when using secondary extraction, and about 90% when using tertiary extraction. Therefore, in order to ensure a high tantalum recovery rate, the preferred number of pure water extraction stages is 3 to 4, and it cannot be generally assumed that 2 stages of extraction can achieve more than 90%.

[0120] For thiourea, a relatively high sulfur-to-antimony ratio and a long reaction time are required to ensure that the active sulfur species are fully released. For thioacetamide, a lower sulfur-to-antimony ratio and a shorter reaction time can be used, but the reaction temperature needs to be kept within a range that can promote the hydrolysis of thioacetamide.

[0121] Organic sulfur precipitation pre-reduces the antimony load entering the methyl isobutyl ketone extraction process. Multi-stage extraction is mainly used to bring tantalum into the organic phase. Hydrogen peroxide-sulfuric acid mixed solution is used to remove trace amounts of niobium from the loaded organic phase. Pure water multi-stage back-extraction is used to transfer tantalum into the aqueous phase. Each step separates different impurities or target components, which avoids a single extraction step from undertaking all the impurity removal tasks.

[0122] The embodiments described above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Equivalent substitutions or conventional adjustments made by those skilled in the art to the specifications of the reaction vessel, the solid-liquid separation method, the form of the extraction equipment, and the extraction and back-extraction operation methods without departing from the technical concept of the present invention should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a clean tantalum solution from a high-impurity tantalum solution, characterized in that, Includes the following steps: S1. Detect the antimony content in the high impurity tantalum solution, determine the amount of organic sulfurizing agent to be added based on the antimony content, and adjust the apparent pH of the high impurity tantalum solution to -0.7 to 2.0; S2. The adjusted high-impurity tantalum solution and the organic sulfide agent are added to a sealed reaction vessel, and a heating sulfide reaction is carried out under the system's self-generated pressure to convert the antimony in the solution into antimony sulfide precipitates. The organic sulfide agent is thiourea or thioacetamide, and the amount of organic sulfide agent used is expressed as the molar ratio of sulfur in the organic sulfide agent to antimony in the high-impurity tantalum solution. When thiourea is used, the molar ratio is 20–30, the reaction temperature is 150–170°C, and the reaction time is 3–6 hours. When thioacetamide is used, the molar ratio is 2–8, the reaction temperature is 130–170°C, and the reaction time is 0.5–2 hours. S3. Cool and separate the material after the sulfidation reaction to obtain sulfide precipitate and antimony-removed liquid; S4. Adjust the free acid concentration of the antimony-removed solution to 0.5-3.0 mol / L, and perform multi-stage extraction using methyl isobutyl ketone as the extractant to allow tantalum to enter the supported organic phase, thereby obtaining a supported tantalum organic phase and a raffinate aqueous phase. S5. The supported tantalum organic phase is subjected to multi-stage back-extraction with pure water to obtain a clean tantalum solution; Prior to pure water back-extraction, the supported tantalum organic phase may optionally be purified by trace niobium washing with a mixed solution of hydrogen peroxide and sulfuric acid.

2. The method for preparing clean tantalum solution from high-impurity tantalum solution according to claim 1, characterized in that, The high-impurity tantalum solution is the anti-tantalum solution obtained by back-extraction of the organic phase of tantalum-niobium co-extraction in the tantalum-niobium hydrometallurgical production line. The high-impurity tantalum solution is a hydrofluoric acid-sulfuric acid system and contains one or more impurity elements selected from antimony, niobium, arsenic, nickel, tungsten, boron, iron, copper, aluminum, vanadium and tin.

3. The method for preparing clean tantalum solution from high-impurity tantalum solution according to claim 1, characterized in that, In step S2, the sealed reaction vessel is a high-pressure reactor with a polytetrafluoroethylene liner. The liquid volume of the reaction material formed by the high impurity tantalum liquid and the organic sulfurizing agent is 3 / 5 of the effective volume of the high-pressure reactor. The high-pressure reactor is sealed before heating, and no external pressure medium is introduced during the reaction. The reaction pressure is formed by the vapor pressure generated after the reaction material is heated.

4. The method for preparing clean tantalum solution from high-impurity tantalum solution according to claim 1, characterized in that, When thiourea is used as an organic sulfurizing agent in step S2, the apparent pH of the high impurity tantalum solution is adjusted to 0-2, the molar ratio of sulfur in thiourea to antimony in the high impurity tantalum solution is 25-30, the reaction temperature is 150-170℃, and the reaction time is 5-6h, so that thiourea releases active sulfur species and reacts with antimony under closed heating conditions.

5. The method for preparing clean tantalum solution from high-impurity tantalum solution according to claim 1, characterized in that, When thioacetamide is used as an organic sulfurizing agent in step S2, the apparent pH of the high impurity tantalum solution is adjusted to -0.7 to 1, the molar ratio of sulfur in thioacetamide to antimony in the high impurity tantalum solution is 2 to 3, the reaction temperature is 130 to 150°C, and the reaction time is 0.5 to 1 hour, so that thioacetamide hydrolyzes under closed heating conditions and continuously releases active sulfur species.

6. The method for preparing clean tantalum solution from high-impurity tantalum solution according to claim 1, characterized in that, In step S3, after the sulfidation reaction is completed, the sealed reaction vessel is first cooled to room temperature, and then depressurized and filtered; the resulting sulfide precipitate contains Sb2S3, and the sulfide precipitate is in the form of rod-shaped crystals, plate-shaped crystals, or micron-sized particles formed by stacking plate-shaped crystals.

7. The method for preparing clean tantalum solution from high-impurity tantalum solution according to claim 1, characterized in that, In step S4, the oil-to-water ratio (O / A) of the methyl isobutyl ketone (MEK) and the antimony-removed liquid is 0.5–2, the extraction time for each stage is 5–15 min, and the number of extraction stages is 3–5. Each extraction stage includes the mixing and mass transfer of the organic phase and the aqueous phase, as well as phase separation by settling. The multi-stage extraction is either cross-current extraction or countercurrent extraction. When using countercurrent extraction, the MEK organic phase and the antimony-removed liquid aqueous phase flow sequentially in opposite directions between each extraction stage.

8. The method for preparing clean tantalum solution from high-impurity tantalum solution according to claim 1, characterized in that, In step S5, the mass fraction of hydrogen peroxide in the mixed solution used for washing and purifying trace niobium is 0.5% to 2.0%, and the concentration of sulfuric acid is 0.8 to 2.0 mol / L; the oil-water ratio O / A of the supported tantalum organic phase and the mixed solution is 0.5 to 2, and the washing contact time is 20 to 40 min, so that the trace niobium co-extracted or entrained in the supported tantalum organic phase enters the washing aqueous phase.

9. The method for preparing clean tantalum solution from high-impurity tantalum solution according to claim 1, characterized in that, In step S5, the O / A ratio of the supported tantalum organic phase or the supported tantalum organic phase purified by washing with trace amounts of niobium to pure water is 0.5 to 2, the pure water back-extraction time for each stage is 20 to 40 minutes, and the number of pure water back-extraction stages is 2 to 4. The pure water back-extraction solutions from each stage are combined to obtain the clean tantalum solution, and the methyl isobutyl ketone after back-extraction is returned to step S4 for recycling.

10. The method for preparing clean tantalum solution from high-impurity tantalum solution according to any one of claims 1 to 9, characterized in that, The clean tantalum solution is subjected to tantalum precipitation, washing and calcination to obtain tantalum oxide product. The mass fractions of Sb, Cu, As, Nb and Ni in the tantalum oxide product are not higher than 0.0005%, 0.0003%, 0.0003%, 0.0007% and 0.0003%, respectively.

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