Method for recovering tantalum resource in potassium fluotantalate mother liquor

Abstract

The invention provides a method for recovering tantalum resources in potassium fluotantalate mother liquor, which comprises the following steps: (1) adding 99% caustic soda flakes into the potassium fluotantalate mother liquor, and stirring to react until the pH value is 10-11 to obtain a turbid solution containing tantalum hydroxide precipitate; (2) adding the turbid solution obtained in the step (1) into a centrifugal machine, carrying out medium-speed centrifugation for 60-120 minutes to obtain a precipitate, washing the precipitate with pure water, and then carrying out high-speed centrifugation for 10-20 minutes to obtain crude tantalum hydroxide; (3) mixing the crude tantalum hydroxide obtained in the step (2), hydrofluoric acid and sulfuric acid, and stirring until the mixture is completely dissolved to obtain a fluorine tantalic acid mixed solution; and (4) extracting the fluorine tantalic acid mixed solution obtained in the step (3) by using sec-octanol, and then performing back extraction by using pure water to obtain fluorine tantalic acid. The tantalum resource in the potassium fluotantalate mother liquor is recovered by adopting 99% caustic soda flakes, and the filtrate after solid-liquid separation does not enter the ammonia distillation stripping tower, so that the treatment efficiency of the ammonia distillation stripping tower is not reduced.

Description

Technical Field

[0001] The present invention relates to a method for recovering tantalum resources from potassium fluotantalate mother liquor. Background Art

[0002] Tantalum-niobium concentrate is dissolved by industrial hydrofluoric acid and industrial sulfuric acid, and then extracted and separated with sec-octanol to obtain a potassium fluotantalate feed solution. The potassium fluotantalate feed solution is successively treated by acid adjustment, steam heating, addition of CP potassium chloride, and after cooling for 48 - 72 hours, needle-shaped potassium fluotantalate will crystallize out in the feed solution. The potassium fluotantalate after being washed with pure water and dried is the raw material for producing tantalum powder. The remaining feed solution after crystallization of potassium fluotantalate is called potassium fluotantalate mother liquor in the present invention. The concentration of tantalum pentoxide equivalent in this mother liquor is 1 - 6 g / L, and the tantalum resources need to be recovered.

[0003] Currently, existing enterprises generally use ammonia to precipitate potassium fluotantalate mother liquor, filter press to obtain tantalum hydroxide, and then dissolve it together with tantalum-niobium concentrate with industrial hydrofluoric acid and industrial sulfuric acid, and then extract and separate with sec-octanol to obtain fluotantalic acid. However, during the process of filter pressing out tantalum hydroxide, the discharged filtrate contains K + , NH4 + , Cl - , F, Sb 3+- plasma and 500 - 2000 ppm of COD. After this filtrate enters the ammonia stripping column, the treatment efficiency will be reduced by 25 - 33%, restricting the sewage discharge volume, and further reducing the output and quality of the product. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for recovering tantalum resources from potassium fluotantalate mother liquor, using 99% caustic soda to recover tantalum resources from potassium fluotantalate mother liquor. The filtrate after solid-liquid separation does not enter the ammonia stripping column, and the treatment efficiency of the ammonia stripping column will not be reduced.

[0005] To solve the above technical problem, the technical solution of the present invention is as follows:

[0006] A method for recovering tantalum resources from potassium fluotantalate mother liquor, comprising the following steps:

[0007] (1) Add 99% caustic soda to the potassium fluotantalate mother liquor, stir and react until the pH value reaches 10 - 11 to obtain a turbid liquid containing tantalum hydroxide precipitate;

[0008] (2) Add the turbid liquid obtained in step (1) to a centrifuge, centrifuge at medium speed for 60 - 120 min to obtain a precipitate, wash the precipitate with pure water, and then centrifuge at high speed for 10 - 20 minutes to obtain crude tantalum hydroxide;

[0009] (3) Mix the crude tantalum hydroxide, hydrofluoric acid, and sulfuric acid obtained in step (2), and stir until completely dissolved to obtain a fluotantalic acid mixture;

[0010] (4) The mixed solution of tantalum fluoride obtained in step (3) is extracted with sec-octanol and then back-extracted with pure water to obtain tantalum fluoride. The mother liquor of potassium tantalum fluoride mainly contains potassium, chlorine, hydrogen, fluorine, and TaF7. 2- , and 99% flake caustic soda needs to be used to precipitate tantalum hydroxide first. The content of tantalum hydroxide converted into tantalum oxide obtained by solid-liquid separation with a centrifuge is about 50-55 wt%. The filtrate is discharged to the sewage treatment plant for treatment with lime; the 99% flake caustic soda used in the present invention is flaky sodium hydroxide with a purity of 99%.

[0011] Further, in step (1) of the present invention, the concentration of tantalum oxide converted in the mother liquor of potassium tantalum fluoride is 1-6 g / L, and the ratio of 99% flake caustic soda to the mother liquor of potassium tantalum fluoride is 1 kg:(17-21) L, ensuring that TaF7 2- is completely converted into Ta(OH)5.

[0012] Further, in step (1) of the present invention, the stirring frequency during the stirring reaction is 40 Hz; the initial feeding speed of 99% flake caustic soda is 80 kg / min. When the feeding ratio of 99% flake caustic soda reaches 80%, the feeding speed of 99% flake caustic soda is adjusted to 40 kg / min. When the feeding ratio of 99% flake caustic soda reaches 90%, the feeding speed of 99% flake caustic soda is adjusted to 20 kg / min.

[0013] Further, in step (2) of the present invention, the centrifugal speed during medium-speed centrifugation is 500-700 r / min, and the centrifugal speed during high-speed centrifugation is 1000-1200 r / min.

[0014] Further, in step (2) of the present invention, the ratio of pure water to the precipitate is (1-10) L:1 kg. This ratio is determined according to whether the potassium, chlorine, and sodium contents in the tantalum fluoride obtained by sec-octanol extraction and separation are all less than 0.001 g / L. The main purpose of washing the precipitate with pure water is to reduce the contents of impurity ions such as K + , Cl - , Na + in tantalum hydroxide.

[0015] Further, in step (3) of the present invention, the concentration of hydrofluoric acid in the mixed solution of tantalum fluoride is 5.5-6.5 mol / L, and the concentration of sulfuric acid in the mixed solution of tantalum fluoride is 2.7-3.2 mol / L, so as to meet the requirements of sec-octanol extraction and separation for the acidity of the raw materials.

[0016] Further, in step (3) of the present invention, the sulfuric acid has a mass concentration of 98%; when the antimony content in the crude tantalum hydroxide obtained in step (2) is < 0.01 wt%, the hydrofluoric acid is AR hydrofluoric acid with a mass concentration of 40%, and after dissolution, it enters the extraction line of high-purity tantalum fluoride acid solution to produce high-purity tantalum fluoride acid solution; when the antimony content in the crude tantalum hydroxide obtained in step (2) is ≥ 0.01 wt%, the hydrofluoric acid is industrial hydrofluoric acid with a mass concentration of 55%, and after dissolution, it enters the ordinary extraction line to produce ordinary tantalum fluoride acid solution.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The impurity ions such as K + , Cl - , Na + , Fe 3+ , W 6+ , Si 4+ in the tantalum fluoride acid finally obtained by the present invention are all less than 0.001 g / L, and it can be used as the raw material solution for producing tantalum oxide or potassium tantalum fluoride, realizing the recycling of tantalum resources.

[0019] 2. Compared with the method of recycling with ammonia, the present invention shortens the process of pressure filtration with slag, and the filtrate after precipitation does not contain ammonium ions. The filtrate does not need to enter the ammonia stripping tower system, which will not affect the treatment efficiency of the ammonia stripping tower and is beneficial to improving the output and quality of the product.

[0020] 3. At the same concentration, sodium hydroxide has a stronger ability to provide hydroxide ions than ammonia water. Therefore, trivalent antimony can react with 99% caustic soda, and finally trivalent antimony and 99% caustic soda form NaSb(OH)4 (the principle is shown below), and it will not be filtered together with tantalum hydroxide in the form of precipitation. Therefore, using 99% caustic soda to precipitate the mother liquor of potassium tantalum fluoride can also effectively reduce the antimony content in the recovered tantalum hydroxide and promote the use of high-antimony tantalum-niobium ore in the production line.

[0021] Sb 3+ + 3OH - = Sb(OH)3

[0022] Sb(OH)3 + OH - = Sb(OH)4 - Specific embodiments

[0023] The present invention will be described in detail below with reference to specific embodiments. Here, the illustrative embodiments of the present invention and the description are used to explain the present invention, but not to limit the present invention.

[0024] Example 1

[0025] The method for recycling tantalum resources from the mother liquor of potassium tantalum fluoride includes the following steps:

[0026] (1) Add 940 kg of 99% caustic soda flakes to 16,000 L of potassium heptafluorotantalate mother liquor. The concentration of tantalum pentoxide equivalent in the potassium heptafluorotantalate mother liquor is 3 g / L. Stir and react at a stirring frequency of 40 Hz until the pH value reaches 10 to obtain a turbid liquid containing tantalum hydroxide precipitate. The initial addition rate of 99% caustic soda flakes is 80 kg / min. When the addition amount of 99% caustic soda flakes reaches 750 kg, adjust the addition rate of 99% caustic soda flakes to 40 kg / min. When the addition amount of 99% caustic soda flakes reaches 850 kg, adjust the addition rate of 99% caustic soda flakes to 20 kg / min. At the same time, it is necessary to detect the pH value of the feed liquid to ensure that tantalum resources can be completely precipitated and no excessive 99% caustic soda flakes are added;

[0027] (2) Add the turbid liquid obtained in step (1) to a centrifuge. Centrifuge at a medium speed of 600 r / min for 80 min to obtain a precipitate. Drain the filtrate for sewage treatment with lime. Wash the precipitate with 200 L of pure water and then centrifuge at a high speed of 1000 r / min for 15 minutes to obtain 93 kg of crude tantalum hydroxide. Take a sample for analysis, containing 51.1% tantalum pentoxide and 0.0076% antimony;

[0028] (3) Mix the crude tantalum hydroxide, hydrofluoric acid, and sulfuric acid obtained in step (2), and stir until completely dissolved to obtain a mixed solution of heptafluorotantalic acid. Calculate the addition amounts based on the target concentrations of 6 mol / L for hydrofluoric acid and 3 mol / L for sulfuric acid in the mixed solution of heptafluorotantalic acid as follows:

[0029] If the crude tantalum hydroxide obtained in step (2) is 93 kg, then it contains Ta2O5: 93×51.1%≈47.5 kg. The total volume V of the mixed solution of heptafluorotantalic acid 总 = 47.5×1000 / 100 = 475 L. The antimony in the crude tantalum hydroxide <0.01%. Dissolve the crude tantalum hydroxide with AR hydrofluoric acid with a mass concentration of 40% + sulfuric acid with a mass concentration of 98%. According to the target concentration of hydrofluoric acid being 6 mol / L, the volume V of 40% mass fraction AR hydrofluoric acid to be added AR氢氟酸 = (475×6 + 93×1000 / 266×7) / 22.83≈232 L. Add 232 L of AR hydrofluoric acid to the tantalum hydroxide acid dissolution tank. According to the target concentration of sulfuric acid being 3 mol / L, the volume V of 98% mass fraction sulfuric acid to be added 硫酸 = 475×3 / 18.36≈77.6 L; The volume V of pure water to be supplemented 纯水 = 475 - 77.6 - 232 = 165.4 L;

[0030] (4) Analyze the mixed solution of tantalum fluoride acid obtained in step (3), which contains 99.6 g / L of tantalum oxide, 5.9 mol / L of hydrofluoric acid, and 2.9 mol / L of sulfuric acid. The mixed solution of tantalum fluoride acid obtained in step (3) enters the extraction line of high-purity tantalum fluoride acid feed liquid. After extraction with sec-octanol and back-extraction with pure water, a high-purity tantalum fluoride acid feed liquid is obtained. The antimony content in the tantalum oxide produced from this high-purity tantalum fluoride acid feed liquid is ≤ 15 ppm.

[0031] Example 2

[0032] The method for recovering tantalum resources from potassium tantalum fluoride mother liquor includes the following steps:

[0033] (1) Add 1294 kg of 99% caustic soda into 22000 L of potassium tantalum fluoride mother liquor. The concentration of tantalum oxide equivalent in the potassium tantalum fluoride mother liquor is 2 g / L. Stir and react at a stirring frequency of 40 Hz until the pH value reaches 11 to obtain a turbid liquid containing tantalum hydroxide precipitate. The initial addition rate of 99% caustic soda is 80 kg / min. When the addition amount of 99% caustic soda reaches 1035 kg, adjust the addition rate of 99% caustic soda to 40 kg / min. When the addition amount of 99% caustic soda reaches 1165 kg, adjust the addition rate of 99% caustic soda to 20 kg / min. At the same time, it is necessary to detect the pH value of the feed liquid to ensure that the tantalum resources can be completely precipitated and no excessive 99% caustic soda is added;

[0034] (2) Add the turbid liquid obtained in step (1) into a centrifuge. Centrifuge at a medium speed of 700 r / min for 110 min to obtain a precipitate. The filtrate is drained and treated with lime for sewage. Wash the precipitate with 300 L of pure water and then centrifuge at a high speed of 1100 r / min for 15 minutes to obtain 83.5 kg of crude tantalum hydroxide. Sampling analysis shows that it contains 52% of tantalum oxide and 0.099% of antimony;

[0035] (3) Mix the crude tantalum hydroxide, hydrofluoric acid, and sulfuric acid obtained in step (2), and stir until completely dissolved to obtain a mixed solution of tantalum fluoride acid. Calculate the addition amount based on the target concentration of 6 mol / L of hydrofluoric acid and 3 mol / L of sulfuric acid in the mixed solution of tantalum fluoride acid. The specific details are as follows:

[0036] If the crude tantalum hydroxide obtained in step (2) is 83.5 kg, then it contains Ta2O5: 83.5 × 52% ≈ 43.4 kg. The total volume V of the mixed solution of tantalum fluoride acid 总 = 43.4 × 1000 / 100 = 434 L. The antimony in the crude tantalum hydroxide > 0.01%. Dissolve the crude tantalum hydroxide with industrial hydrofluoric acid with a mass concentration of 55% + sulfuric acid with a mass concentration of 98%. According to the target concentration of hydrofluoric acid being 6 mol / L, the volume V of industrial hydrofluoric acid with a 55% mass fraction to be added 工业氢氟酸=(434×6 + 83.5×1000 / 266×7) / 31.4 ≈ 153 L. Add 153 L of industrial hydrofluoric acid to the tantalum hydroxide acid dissolution tank. According to the target concentration of sulfuric acid being 3 mol / L, the volume V of 98% by mass sulfuric acid to be added 硫酸 = 434×3 / 18.36 ≈ 71 L; The volume V of pure water to be supplemented 纯水 = 434 - 153 - 71 = 210 L;

[0037] (4) Analyze the mixed tantalum fluoride solution obtained in step (3). It contains 99 g / L of tantalum oxide, 5.7 mol / L of hydrofluoric acid, and 2.85 mol / L of sulfuric acid. The mixed tantalum fluoride solution obtained in step (3) enters the ordinary tantalum fluoride feed liquid extraction line. After extraction with sec-octanol and back-extraction with pure water, an ordinary tantalum fluoride feed liquid is obtained. The antimony content in the tantalum oxide produced from this ordinary tantalum fluoride feed liquid ≤ 500 ppm.

[0038] Example 3

[0039] Use the recovered tantalum hydroxide precipitated by ammonia, numbered PTH1. Analyze the tantalum oxide content to be 54.13% and the antimony content to be 0.488%. The antimony content in terms of tantalum oxide is: 0.488% / 54.13% ≈ 9015 ppm.

[0040] Weigh 40 g of PTH1 and dissolve it with 35 mL of industrial hydrofluoric acid with a mass concentration of 55% and 10 mL of sulfuric acid with a mass concentration of 98% to obtain a 57 mL solution. 22 mL is sent for analysis to obtain Ta solution (test). The analysis results show that it contains 336.3 g / L of tantalum oxide, 3.56 g / L of antimony, and the total acidity is 11.9 N. According to the solution analysis results, the antimony content in terms of tantalum oxide is: 3.56 / 336.3 ≈ 10586 ppm.

[0041] Add 99% sodium hydroxide flakes to the remaining 35 mL of the solution. When the pH value = 11, a white tantalum hydroxide turbid solution is obtained. After filtering with filter paper, place the tantalum hydroxide and the filter paper together on the crucible lid and spread them out. Put them in an oven and keep them warm at 120 °C for 3 hours. Number the dried tantalum hydroxide as PTH2. Send it for analysis. The tantalum oxide content is 90.98% and the antimony content is 0.261%. The antimony content in terms of tantalum oxide is: 0.261% / 90.98% ≈ 2869 ppm.

[0042] In summary, PTH1 is dissolved with hydrofluoric acid and sulfuric acid to obtain Ta solution (test). Add 99% sodium hydroxide flakes to Ta solution (test) to obtain a tantalum hydroxide turbid solution, which is filtered and dried to obtain PTH2. When the antimony content in PTH1, Ta solution (test), and PTH2 is uniformly converted into the antimony content in tantalum oxide, it decreases from 9015 ppm in PTH1 to 2869 ppm in PTH2. The reduction rate of antimony is (9015 - 2869) / 9015 ≈ 68%.

[0043] Example 4

[0044] Take the fluorotantalic acid feed liquid from the 2nd tank of Extraction Line 2. Analysis results (g / L): antimony 0.1, tantalum pentoxide 49.8, niobium pentoxide 0.002, iron, tungsten, and silicon are all <0.001, total acid 1N.

[0045] Prepare a sodium hydroxide solution by mixing 48 mL of 50% sodium hydroxide by mass and 26 mL of pure water. Sampling analysis results show that the mass fraction of the sodium hydroxide solution is 32.26%, the molar concentration is 10.96 mol / L, and the density is 1.359 g / mL, which is used as the 1st precipitant. Use 25% ammonia water by mass as the 2nd precipitant.

[0046] Take 200 mL of the fluorotantalic acid feed liquid from the 2nd tank of Extraction Line 2 and put it into a 500 mL plastic beaker. Add the 1st precipitant to the fluorotantalic acid feed liquid. When 54 mL is added, the pH value of the turbid liquid is measured to be 11. Filter the turbid liquid with a qualitative filter paper with a net weight of 2 g to obtain tantalum hydroxide, numbered PTH3. Pour 150 mL of pure water into the tantalum hydroxide and filter for 16 hours to obtain 325 mL of filtrate, numbered Filtrate 1. Take out PTH3 and the filter paper together from the plastic funnel and place them in a drying oven at 120 °C for drying and heat preservation for 3 hours.

[0047] Take 200 mL of the fluorotantalic acid feed liquid from the 2nd tank of Extraction Line 2 and put it into a 500 mL plastic beaker. Add the 2nd precipitant to the fluorotantalic acid feed liquid. When 52 mL is added, the pH value of the turbid liquid is measured to be 10. Filter the turbid liquid with a qualitative filter paper with a net weight of 2 g to obtain tantalum hydroxide, numbered PTH4. Pour 150 mL of pure water into the tantalum hydroxide and filter for 16 hours to obtain 320 mL of filtrate, numbered Filtrate 2. Take out PTH4 and the filter paper together from the plastic funnel and place them in a drying oven at 120 °C for drying and heat preservation for 3 hours.

[0048] The analysis results of Filtrate 1 and Filtrate 2 are shown in Table 1:

[0049] Filter liquor number Volume mL Sb (mg / L) Na (mg / L) <![CDATA[F - (mg / L)]]> <![CDATA[NH4 +( mg / L)]]> 1 325 ＜1 11612 25000 8.63 2 320 ＜1 962 23000 13213

[0050] Table 1 The analysis results of PTH3 and PTH4 are shown in Table 2:

[0051] Tantalum hydroxide number Weight (g) <![CDATA[Ta2O5(%)]]> Sb (ppm) Na (ppm) <![CDATA[F - (ppm)]]> PTH3 21 55.56 906 43002 13000 PTH4 21.5 48.11 999 10 59000

[0052] Table 2

[0053] According to Tables 1 and 2, the antimony content in the tantalum fluoride solution in Slot 2 of the P2 line, converted to tantalum oxide, is: 0.1 / 49.8 ≈ 2008 ppm; the antimony content in PTH3, converted to tantalum oxide, is: 906 / 55.56% ≈ 1630 ppm; the antimony content in PTH4, converted to tantalum oxide, is: 999 / 48.11% ≈ 2076 ppm. The reduction rate of antimony is (2008 - 1630) / 2008 ≈ 18%.

[0054] Example 5

[0055] Select the potassium tantalum fluoride mother liquor of Batch 2025-2-21. Sampling and analysis show that the potassium tantalum fluoride mother liquor contains 1.52 g / L of tantalum oxide, 0.069 g / L of antimony, and 0.9 N of total acid.

[0056] Add 0.5 L of 25% ammonia water to 2.5 L of potassium tantalum fluoride mother liquor, with pH = 10 and a magnetic stirring speed of 650 r / min to obtain a turbid liquid. Filter the turbid liquid with filter paper to obtain tantalum hydroxide, numbered PTH5. After washing with 75 mL of pure water and then filtering, obtain filtrate 3 with a volume of 4135 mL (because the filter cloth of the Buchner funnel needs to be wetted with pure water before filtration and then a filter paper with a diameter of 180 mm is placed on the filter cloth to prevent the filter paper from being torn. When filtering the tantalum hydroxide turbid liquid, the pure water in the suction flask is not poured out, so the volume of filtrate 3 is larger than that of filtrate 4). Take samples of filtrate 3 for detection: tantalum, antimony, sodium, fluorine, ammonia.

[0057] Dry the tantalum hydroxide PTH5 at 120°C for 30 minutes, with a net weight of 4.7 g. Take samples for detection: tantalum oxide, antimony, sodium, fluorine.

[0058] Add 128.9 g of 99% sodium hydroxide flakes to 2.5 L of potassium tantalum fluoride mother liquor, with pH = 11 and a magnetic stirring speed of 650 r / min to obtain a turbid liquid. Filter the turbid liquid with filter paper to obtain tantalum hydroxide, numbered PTH6. After washing with 75 mL of pure water and then filtering, obtain filtrate 4 with a volume of 2545 mL. Take samples of filtrate 4 for detection: tantalum, antimony, sodium, fluorine, ammonia.

[0059] Dry the tantalum hydroxide PTH6 at 120°C for 30 minutes, with a net weight of 4.8 g. Take samples for detection: tantalum oxide, antimony, sodium, fluorine.

[0060] The analysis results of filtrate 3 and filtrate 4 are shown in Table 3, with the impurity unit being ppm.

[0061] Filter liquor Volume (mL) Ta Sb Na <![CDATA[F - > <![CDATA[NH4 + > 3 4135 ＜1 ＜1 58 10750 23357.2 4 2545 13 ＜1 23637 18250 72

[0062] The analysis results of PTH5 and PTH6 in Table 3 are shown in Table 4, with the impurity unit being ppm.

[0063] Tantalum hydroxide number Weight (g) <![CDATA[Ta2O5(%)]]> Sb Na <![CDATA[F - > PTH5 4.7 78.13 22300 360 90000 PTH6 4.8 76.72 9800 74000 11000

[0064] Table 4

[0065] According to Table 3 and Table 4, the antimony content in the potassium fluotantalate mother liquor converted to tantalum pentoxide is: 0.069 / 1.52 ≈ 45394 ppm, the antimony content in PTH7 converted to tantalum pentoxide is: 22300 / 78.13% ≈ 28542 ppm, and the antimony content in PTH8 converted to tantalum pentoxide is: 9800 / 76.72% ≈ 12774 ppm. In comparison, the antimony precipitated with caustic soda has a reduction of (28542 - 12774) / 28542 ≈ 55% compared to that precipitated with ammonia.

[0066] Comparative example

[0067] Precipitate 30000 L of potassium fluotantalate mother liquor per batch, with a concentration of 2 - 3 g / L and an acidity of 0.9 - 1.1 mol / L. Put it into two potassium fluotantalate mother liquor precipitation tanks, and the maximum volume of a single precipitation tank is 20 m 3 , and the stirring frequency is 40 HZ.

[0068] Add 5500 - 6000 L of 25% ammonia water per batch. Use a wide-range test paper to detect the solution, and the pH value is 9 - 10. The time for adding ammonia water is 20 - 40 minutes. The recovered tantalum hydroxide obtained by precipitating about 6 - 7 batches of potassium fluotantalate mother liquor can be pumped into a filter press of model XAYGM60 / 1000 - UK for solid-liquid separation.

[0069] The turbid tantalum hydroxide solution after each batch of precipitation is subjected to solid-liquid separation using a filter press. The filtrate is drained, and fluorine is removed with lime, then calcium is removed by adding sodium carbonate, and then it enters the ammonia distillation and stripping system. The ammonia nitrogen in the distilled liquid is less than 30 ppm. The tantalum hydroxide in the filter press is pressed with a squeezing water pressure of 0.6 Mpa for 30 minutes, and then unloaded into a ton bag. The tantalum hydroxide is 900 kg, and the sample analysis shows that it contains 49.84% tantalum pentoxide and 0.18% antimony.

[0070] There is 900 kg of tantalum hydroxide. Packed at a rate of 100 kg / barrel, two barrels of tantalum hydroxide are added to every 3.5 tons of tantalum-niobium concentrate. A total of 6300 L of industrial hydrofluoric acid is added in segments, and a total of 2000 L of industrial sulfuric acid is added in segments. The tantalum-niobium containing feed liquid and slag are subjected to pressure filtration separation to obtain a tantalum-niobium containing feed liquid suitable for separation by sec-octanol extraction.

[0071] Sampling analysis results of the tantalum-niobium containing feed liquid: tantalum pentoxide 79.11 g / L, niobium pentoxide 213.94 g / L, HF 6.1 mol / L, H2SO4 2.9 mol / L. The feed liquid enters the ordinary tantalum fluoride feed liquid extraction line, and sec-octanol extraction separation is carried out to obtain an ordinary tantalum fluoride feed liquid. The antimony content in the tantalum pentoxide produced from the ordinary tantalum fluoride feed liquid is ≤ 500 ppm.

[0072] It can be seen from the comparison between Examples 1 - 7 and the comparative example:

[0073] 1) In Example 1, the volume of the potassium fluotantalate mother liquor is close to the volume of the mother liquor corresponding to one batch of potassium fluotantalate on the same day. In Example 2, the volume of the potassium fluotantalate mother liquor is close to the volume of the mother liquor corresponding to two batches of potassium fluotantalate on the same day. In both Example 1 and 2, caustic soda is used for precipitation, and the filtrate after solid-liquid separation does not enter the ammonia distillation and stripping system. In the comparative example, ammonia water is used for precipitation, and the filtrate after solid-liquid separation needs to remove ammonia nitrogen. The chlorine and COD in the filtrate will reduce the efficiency of ammonia distillation and stripping, and the antimony content in tantalum oxide is also higher than that in Example 1 and 2.

[0074] 2) In Example 3, the tantalum hydroxide precipitated by ammonia is dissolved in acid and then precipitated with caustic soda. When the tantalum hydroxide after filtration and drying is uniformly converted into tantalum oxide, the antimony content is reduced by 68%.

[0075] 3) In Example 4, a 32% sodium hydroxide solution and 25% ammonia water are used to precipitate the tantalum fluoride feed liquid in Tank No. 2 of Line 2 of Pu (with a higher tantalum oxide concentration than the potassium fluotantalate mother liquor). When uniformly converted into tantalum oxide, the tantalum hydroxide obtained by precipitating the tantalum liquid with a 32% sodium hydroxide solution is 18% lower than the tantalum fluoride feed liquid in Tank No. 2 of Line 2 of Pu.

[0076] 4) In Example 5, the same potassium fluotantalate mother liquor is used, and caustic soda and 25% ammonia water are respectively added for precipitation. The antimony content in the tantalum hydroxide precipitated by caustic soda, when converted into the antimony content of tantalum oxide, is 55% lower than that precipitated by ammonia water.

[0077] The above examples only illustratively explain the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above examples without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for recovering tantalum resources from potassium fluotantalate mother liquor, characterized in that: It includes the following steps: (1) Add 99% caustic soda flakes to the potassium hexafluorotantalate mother liquor, stir and react until the pH value reaches 10 - 11 to obtain a turbid liquid containing tantalum hydroxide precipitate; (2) Add the turbid liquid obtained in step (1) to a centrifuge, centrifuge at medium speed for 60 - 120 min to obtain a precipitate, wash the precipitate with pure water and then centrifuge at high speed for 10 - 20 minutes to obtain crude tantalum hydroxide; (3) Mix the crude tantalum hydroxide, hydrofluoric acid, and sulfuric acid obtained in step (2), stir until completely dissolved to obtain a mixed solution of fluotantalic acid; (4) Extract the mixed solution of fluotantalic acid obtained in step (3) with sec - octanol and then back - extract with pure water to obtain fluotantalic acid.

2. The recovery method of tantalum resources in potassium heptafluorotantalate mother liquor according to claim 1, characterized in that: In step (1), the concentration of tantalic oxide equivalent in the potassium hexafluorotantalate mother liquor is 1 - 6 g / L, and the ratio of 99% caustic soda flakes to the potassium hexafluorotantalate mother liquor is 1 kg:(17 - 21) L.

3. The recovery method of tantalum resources in potassium fluotantalate mother liquor according to claim 1, characterized in that: In step (1), the stirring frequency during the stirring reaction is 40 Hz; the initial addition rate of 99% caustic soda flakes is 80 kg / min. When the addition ratio of 99% caustic soda flakes reaches 80%, the addition rate of 99% caustic soda flakes is adjusted to 40 kg / min. When the addition ratio of 99% caustic soda flakes reaches 90%, the addition rate of 99% caustic soda flakes is adjusted to 20 kg / min.

4. The recovery method of tantalum resources in potassium fluotantalate mother liquor according to claim 1, characterized in that: In step (2), the centrifugation speed during medium - speed centrifugation is 500 - 700 r / min, and the centrifugation speed during high - speed centrifugation is 1000 - 1200 r / min.

5. A method for recovering tantalum resources from potassium fluotantalate mother liquor according to claim 1, characterized in that: In step (2), the ratio of pure water to the precipitate is (1 - 10) L:1 kg.

6. The method for recovering tantalum resources from potassium heptafluorotantalate mother liquor according to claim 1, wherein: In step (3), the concentration of hydrofluoric acid in the mixed solution of fluotantalic acid is 5.5 - 6.5 mol / L, and the concentration of sulfuric acid in the mixed solution of fluotantalic acid is 2.7 - 3.2 mol / L.

7. The recovery method of tantalum resources in potassium fluotantalate mother liquor according to claim 1, characterized in that: In step (3), the mass concentration of sulfuric acid is 98%; when the antimony content of the crude tantalum hydroxide obtained in step (2) < 0.01 wt%, the hydrofluoric acid is AR hydrofluoric acid with a mass concentration of 40%; when the antimony content of the crude tantalum hydroxide obtained in step (2) ≥ 0.01 wt%, the hydrofluoric acid is industrial hydrofluoric acid with a mass concentration of 55%.