Method for recovering by-product fluorine-chlorine-sodium-potassium-containing mixed salt in tantalum powder production

Abstract

The invention relates to the field of tantalum powder mixed salt utilization, and discloses a method for recycling a byproduct fluorine-chlorine-sodium-potassium-containing mixed salt in tantalum powder production. The method comprises the following steps: (1) leaching fluorine, chlorine, sodium and potassium-containing mixed salt in the presence of a leaching agent to obtain a solid mixture A and a salt solution B; (2) sorting the solid mixture A obtained in the step (1) to obtain a tantalum pentoxide crude product and a sodium fluoride product; (3) reacting the salt solution B obtained in the step (1) with a composite fluorine removal agent to obtain a fluorine-containing solid and a salt solution C; and (4) crystallizing the salt solution C obtained in the step (3) to obtain a potassium chloride product and a salt solution D. The method can realize separation and recovery of valuable elements to the greatest extent.

Description

Technical Field

[0001] The present invention relates to the field of utilization of tantalum powder mixed salts, and specifically relates to a method for recovering the fluorine, chlorine, sodium, and potassium mixed salts as by-products in tantalum powder production. Background Art

[0002] Sodium thermal reduction of potassium fluotantalate is the most commonly used method for producing metallic tantalum in the world. During the production of tantalum, halogen mixed salts are added as diluents to effectively control the reaction rate, resulting in a large amount of mixed salt by-products. The main components are KF, NaCl, NaF, and KCl, and it also contains 0.4 - 0.7% of Ta2O5.

[0003] Currently, the traditional recovery and treatment methods for tantalum metallurgy by-products in China can be divided into two categories:

[0004] (1) Dissolve it with a large amount of water and then add a defluorinating agent (the common defluorinating agent is lime) to make the wastewater meet the standards and then directly discharge it. This traditional treatment method not only discharges a large amount of industrial wastewater, causing soil salinization, but also wastes a large amount of valuable elements (K, Na, Cl) in the tantalum powder mixed salts.

[0005] For example, in CN212102961U, the fluorine in the tantalum powder mixed salts is recovered in the form of sodium hexafluoroaluminate or potassium fluoroborate, and then the qualified wastewater is directly discharged; in CN109399669A, most of the fluorine is first filtered out in the form of NaF, and then a fluorine precipitant is added to the solution to make the wastewater meet the standards and then directly discharged. Both of these methods will produce a large amount of saline wastewater, pollute the environment, and cannot effectively recover the valuable elements in the tantalum powder mixed salts.

[0006] (2) Another category is to evaporate and concentrate the defluorinated wastewater to obtain a composite salt. This type of recovery method has obvious improvement compared with the previous one, but the evaporation cost of this method is relatively high, and the recovery value of the composite salt is not high.

[0007] For example, in CN102352444A, the defluorinated wastewater is adjusted to pH with hydrogen fluoride and then placed in a concentration crystallizer for vacuum heating and then centrifuged to separate out the composite salt crystals, and the composite salt crystals are dried at 350°C. This type of recovery method not only requires adding a large amount of expensive and toxic hydrogen fluoride, but also requires repeated high-temperature separation, greatly increasing the recovery cost and environmental pressure.

[0008] Based on this, it is urgent to develop a new recovery process. Summary of the Invention

[0009] The purpose of the present invention is to overcome the problems existing in the prior art and provide a method for recovering the fluorine, chlorine, sodium, and potassium mixed salts as by-products in tantalum powder production. This method can maximize the separation and recovery of valuable elements.

[0010] To achieve the above object, on the one hand, the present invention provides a method for recovering a fluorine, chlorine, sodium and potassium mixed salt as a by-product in tantalum powder production, and the method includes the following steps:

[0011] (1) Leaching the fluorine, chlorine, sodium and potassium mixed salt in the presence of a leaching agent to obtain a solid mixture A and a salt solution B;

[0012] (2) Separating the solid mixture A obtained in step (1) to obtain a crude tantalum pentoxide product and a sodium fluoride product;

[0013] (3) Reacting the salt solution B obtained in step (1) with a composite defluorinating agent to obtain a fluorine-containing solid and a salt solution C;

[0014] (4) Crystallizing the salt solution C obtained in step (3) to obtain a potassium chloride product and a salt solution D.

[0015] Preferably, the method further includes: preheating the leaching agent and / or the auxiliary leaching agent first, and then contacting with the fluorine, chlorine, sodium and potassium mixed salt.

[0016] Preferably, the preheating temperature is 50-150 °C, preferably 70-103 °C.

[0017] Preferably, the leaching in step (1) is carried out in a rotating liquid film reactor.

[0018] Preferably, the composite defluorinating agent is at least one of calcium chloride, barium chloride, strontium chloride and lanthanum nitrate, as well as polyaluminum chloride and polyacrylamide.

[0019] Through the above technical solutions, the beneficial effects of the present invention include:

[0020] The method provided by the present invention follows the concept of atom economy law in the process of separating the mixed salt. While minimizing the recovery cost, saving energy and reducing consumption, it maximally realizes the separation of valuable elements and recovers them as products such as potassium chloride and sodium fluoride. In a preferred case, wastewater discharge is maximally avoided, and a nearly zero-emission closed-loop recovery is achieved. Compared with the method of directly recycling in the form of a composite salt, the method of the present invention not only effectively reduces the recovery cost, but also increases the value of the recovered products.

[0021] The process of the present invention is simple and easy to realize large-scale production, and has good development prospects. Brief Description of the Drawings

[0022] Figure 1 is a flowchart of the method of the present invention. Detailed Embodiments

[0023] The endpoints and any values within the ranges disclosed in this document are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this document.

[0024] The present invention provides a method for recovering the by-product fluorine, chlorine, sodium, and potassium mixed salt in tantalum powder production. The method includes the following steps:

[0025] (1) Leaching the fluorine, chlorine, sodium, and potassium mixed salt in the presence of a leaching agent to obtain a solid mixture A and a salt solution B;

[0026] (2) Sorting the solid mixture A obtained in step (1) to obtain crude tantalum pentoxide and sodium fluoride products;

[0027] (3) Reacting the salt solution B obtained in step (1) with a composite defluorination agent to obtain a fluorine-containing solid and a salt solution C;

[0028] (4) Crystallizing the salt solution C obtained in step (3) to obtain potassium chloride products and a salt solution D.

[0029] The present invention has a relatively wide selection range for the type of the leaching agent, and various leaching agents commonly used in the art can be used. Preferably, the leaching agent is water.

[0030] According to the present invention, preferably, the solid-liquid mass ratio of the leaching in step (1) is 1:(0.5 - 20), preferably 1:(1 - 10). Specifically, for example, it can be 1:0.5, 1:1, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, and any value within the ranges formed by any two of these point values. Adopting this preferred embodiment is beneficial to improving the leaching rate.

[0031] It should be noted that when only the leaching agent is added during the leaching process in step (1), the solid-liquid mass ratio refers to the mass ratio of the fluorine, chlorine, sodium, and potassium mixed salt to the leaching agent;

[0032] When a leaching agent and the following co-leaching agent are added during the leaching process in step (1), the solid-liquid mass ratio refers to the ratio of the mass of the fluorine, chlorine, sodium, and potassium mixed salt to the total mass of the leaching agent and the co-leaching agent.

[0033] According to the present invention, preferably, a leaching aid is further added during the leaching process in step (1), and the leaching aid is selected from at least one of ethanol, ethylene glycol, acetone, glucose, and ethylenediamine. Adopting this preferred embodiment is beneficial to further improving the leaching rate.

[0034] According to the present invention, preferably, in step (1), the mass ratio of the leaching agent to the leaching aid is 20:(0.5 - 18), preferably 20:(0.5 - 2). Specifically, for example, it can be 20:0.5, 20:1, 20:1.5, 20:2, 20:3, 20:4, 20:5, 20:6, 20:7, 20:8, 20:9, 20:10, 20:11, 20:12, 20:13, 20:14, 20:15, 20:16, 20:17, 20:18, and any value within the range formed by any two of these point values. Adopting this preferred embodiment can reduce the dosage of the leaching agent while ensuring a high leaching rate, achieving cost reduction and efficiency improvement.

[0035] According to the present invention, preferably, the method further includes: preheating the leaching agent and / or the leaching aid first, and then contacting it with the sodium potassium fluorochloride mixed salt.

[0036] According to the present invention, preferably, the temperature of the preheating is 50 - 150°C, preferably 70 - 103°C.

[0037] Adopting the above preferred embodiment is beneficial for the sodium potassium fluorochloride mixed salt to be leached faster and more, and reach a nearly saturated state.

[0038] The leaching in step (1) of the present invention can be carried out in any common reaction device in the art. To further improve the leaching effect, preferably, the leaching in step (1) is carried out in a rotating liquid film reactor.

[0039] The rotating liquid film reactor of the present invention is a reactor with an enhanced effect on solid-liquid reactions, which has both a narrow reaction space and a high shear rate. By adjusting the slit width, the material passes through the specified slit in a hydraulic state, thereby achieving effective and uniform dispersion and pulverization, and quickly dissolving in the solvent, realizing the rapid exchange of the four elements of fluorine, chlorine, sodium, and potassium at the submicron scale. Most fluoride ions and sodium ions form sodium fluoride solids in seconds, and a saturated solution mainly composed of potassium chloride and sodium fluoride is obtained, achieving simultaneous leaching, exchange, and crystallization. Compared with the traditional reaction kettle dissolution method, the method provided by the present invention ensures a high leaching rate while greatly reducing the reaction time and energy consumption, reducing the usage of deionized water, and increasing the added value of the recovered product.

[0040] According to the present invention, preferably, the slit width of the rotating liquid film reactor is 0.5 - 3.5 μm, preferably 1 - 3 μm. When the slit width is within the above range, it is beneficial to crush and disperse the tantalum powder by-products, increase their contact area with the leaching solution, and improve the leaching efficiency and rate of valuable elements.

[0041] The slit width described in the present invention refers to the width between the rotor and the stator of the rotating liquid film reactor, which is adjusted by moving the rotor.

[0042] When the leaching described in the present invention is carried out in a rotating liquid film reactor, compared with the traditional leaching method, the leaching time is greatly shortened. Preferably, the leaching time is 0.5 - 30 min, preferably 0.5 - 10 min.

[0043] Preferably, the method further includes: subjecting the leaching product in step (1) to solid-liquid separation to obtain a solid mixture A and a salt solution B.

[0044] The present invention does not particularly limit the specific manner of the solid-liquid separation, and conventional technical means in the art can be used, which will not be elaborated herein.

[0045] According to the present invention, preferably, in step (2), the yield of crude tantalum pentoxide is not less than 70%.

[0046] According to the present invention, preferably, the yield of sodium fluoride product is not less than 80%.

[0047] Adopting the above preferred embodiments is conducive to achieving the maximum recovery of tantalum pentoxide and sodium fluoride products.

[0048] The present invention does not particularly limit the specific method of the sorting in step (2), and it can be carried out with reference to the conventional methods in the art, as long as the yields of the crude tantalum pentoxide and / or sodium fluoride products meet the above requirements. The present invention preferably uses the gravity separation method for sorting, which can greatly improve the yield of tantalum pentoxide and the purity of sodium fluoride, and further improve the recovery value. Preferably, the sorting in step (2) is carried out by the gravity separation method. For example, the heavy density liquid separation method, flotation method, air separation method, etc. can be selected. More preferably, the sorting in step (2) is carried out by the heavy density liquid separation method and / or the flotation method.

[0049] The above-mentioned heavy density liquid separation method, flotation method and air separation method are common sorting methods in the gravity separation method, and their method meanings are well known to those skilled in the art.

[0050] Preferably, the method further includes: washing and filtering the crude tantalum pentoxide to obtain a tantalum pentoxide product.

[0051] The present invention has no particular limitation on the specific conditions of the washing, and it can be carried out with reference to the conventional methods in the art until the white sodium fluoride solid in the tantalum pentoxide product is completely dissolved.

[0052] The washing agent used in the present invention is also a conventional choice in the art, and the present invention preferably uses water as the washing agent.

[0053] When the leaching agent in step (1) is water, the washing liquid obtained by the above washing can be returned to step (1) for cyclic leaching of the next batch of materials, realizing zero discharge of the washing liquid while avoiding the loss of fluorine and sodium elements.

[0054] According to the present invention, preferably, the composite defluorinating agent is selected from at least one of calcium chloride, barium chloride, strontium chloride and lanthanum nitrate, and polyaluminum chloride (PAC) and / or polyacrylamide.

[0055] The inventors of the present invention found that when only a single substance (such as calcium chloride) is used as the defluorinating agent, the obtained fluorine-containing particles (such as calcium fluoride) are small, resulting in the fluorine-containing particles being suspended in the salt solution C to form a colloidal solution, which cannot be separated quickly and thoroughly, and the generated fluorine-containing particles are easy to wrap the solid defluorinating agent, resulting in incomplete defluorination. However, using the specific type of composite defluorinating agent of the present invention effectively overcomes the above defects, realizes deep defluorination, effectively reduces the content of fluoride ions in the wastewater, and improves the purity of the subsequent obtained KCl product at the source.

[0056] According to the present invention, preferably, the mass ratio of at least one of calcium chloride, barium chloride, strontium chloride and lanthanum nitrate to polyaluminum chloride and / or acrylamide is 100-200:0.3-10, preferably 100-180:0.3-2, more preferably 100:0.3-2. Specifically, for example, it can be 100:0.3, 100:0.4, 100:0.5, 100:0.6, 100:0.7, 100:0.8, 100:0.9, 100:1, 100:1.1, 100:1.2, 100:1.3, 100:1.4, 100:1.5, 100:1.6, 100:1.7, 100:1.8, 100:1.9, 100:2, and any value within the range formed by any two of these point values.

[0057] According to the present invention, preferably, the composite defluorinating agent is at least one of calcium chloride, barium chloride, strontium chloride and lanthanum nitrate, and polyaluminum chloride and polyacrylamide.

[0058] The inventors of the present invention further found that using the above composite defluorinating agent is more conducive to improving the defluorination effect.

[0059] According to the present invention, preferably, the mass ratio of polyaluminum chloride to polyacrylamide is 5-20:1, preferably 8-20:1. Specifically, for example, it can be 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, and any value within the range formed by any two of these point values. By adopting this preferred embodiment, the defluorination effect can be further improved.

[0060] According to the present invention, preferably, the conditions of the reaction in step (3) include: the temperature is 10-150°C, preferably 60-105°C; the time is 0.5-5 h, preferably 0.5-3 h.

[0061] Preferably, the method further includes: subjecting the reaction product in step (3) to solid-liquid separation to obtain a crude fluorine-containing solid product and a salt solution C.

[0062] The present invention does not particularly limit the specific manner of the solid-liquid separation, and conventional technical means in the art can be used. The present invention preferably adopts the method of centrifugal separation.

[0063] Preferably, the method further includes: washing the crude fluorine-containing solid product to obtain a fluorine-containing solid product.

[0064] The present invention does not particularly limit the specific conditions of the washing, and it can be carried out with reference to the conventional methods in the art, with the purity of the calcium fluoride product being greater than 95% as the criterion.

[0065] Preferably, the conditions of the centrifugal separation include: the rotation speed is 500-8000 rpm, preferably 3000-7000 rpm; the centrifugal temperature is 10-100°C, preferably 30-90°C; the centrifugal time is 1-10 min, preferably 2-8 min.

[0066] The main component of the salt solution C obtained in step (3) of the present invention is potassium chloride, and contains a small amount of sodium chloride and sodium fluoride. According to the differences in solubility and concentration of these substances at different temperatures, gradient crystallization is carried out to obtain potassium chloride with high recovery value. The present invention does not particularly limit the specific crystallization method of the crystallization in step (4), and various common crystallization methods in the art can be used as long as potassium chloride products can be obtained.

[0067] According to the present invention, preferably, the crystallization in step (4) is cooling crystallization. By adopting this preferred embodiment, it is beneficial to obtain high-purity potassium chloride products to the greatest extent. At the same time, compared with evaporation crystallization, the energy consumption is reduced, which is environmentally friendly and conforms to the principle of energy conservation and emission reduction.

[0068] The present invention has no special limitation on the specific conditions of the cooling crystallization described in step (4), and it can be carried out with reference to conventional methods. Preferably, the temperature of the cooling crystallization is 20-70°C, preferably 20-50°C.

[0069] Preferably, the method further includes: first evaporating and concentrating the salt solution C obtained in step (3), and then performing cooling crystallization.

[0070] More preferably, the method further includes: first heating the salt solution C obtained in step (3) to 55-105°C, preferably to 80-105°C for evaporation and concentration, and then cooling to 20-70°C, preferably cooling to 20-50°C for cooling crystallization.

[0071] Preferably, the method further includes: performing solid-liquid separation on the crystallization product described in step (4) to obtain crude potassium chloride and salt solution D.

[0072] The present invention has no special limitation on the specific manner of the solid-liquid separation, and it can be carried out by using conventional technical means in the art. The present invention preferably adopts the method of centrifugal separation.

[0073] Preferably, the method further includes: washing the crude potassium chloride to obtain potassium chloride products.

[0074] The present invention has no special limitation on the specific conditions of the washing, and it can be carried out with reference to conventional methods in the art, with the purity of the potassium chloride product being not less than 90% as the standard.

[0075] The present invention has no special limitation on the washing agent used for the washing, and it can be a conventional choice in the art. For example, saturated potassium chloride solution.

[0076] According to the present invention, preferably, the purity of the potassium chloride product obtained in step (4) is not less than 90%, preferably 93-99%. By adopting this preferred embodiment, the recovery of potassium chloride products can be realized.

[0077] According to the present invention, preferably, the salt solution D obtained in step (4) is returned to the leaching described in step (1). By adopting this preferred embodiment, the salt solution D obtained in step (4) is returned to step (1) for the leaching and separation of the next batch of materials, avoiding the discharge of wastewater from the source and realizing closed-loop recovery.

[0078] The present invention does not particularly limit the specific composition of the mixed salt containing sodium, potassium, fluorine and chlorine, and it can be mixed salts containing sodium, potassium, fluorine and chlorine with various compositions obtained in the method for producing tantalum by sodium thermal reduction of potassium heptafluorotantalate. Preferably, in the mixed salt containing sodium, potassium, fluorine and chlorine, based on the total mass of the mixed salt containing sodium, potassium, fluorine and chlorine, the mass content of sodium element is 24-30%, the mass content of fluorine element is 15-30%, the mass content of chlorine element is 15-30%, and the mass content of potassium element is 12-30%.

[0079] In the mixed salt containing sodium, potassium, fluorine and chlorine of the present invention, the balance is Ta2O5.

[0080] According to a particularly preferred embodiment of the present invention, a method for recovering the mixed salt containing sodium, potassium, fluorine and chlorine as a by-product in the production of tantalum powder, the method comprising the following steps:

[0081] (1) Leaching the mixed salt containing sodium, potassium, fluorine and chlorine in the presence of a leaching agent to obtain a solid mixture A and a salt solution B;

[0082] (2) Sorting the solid mixture A obtained in step (1) to obtain a crude tantalum pentoxide product and a sodium fluoride product;

[0083] (3) Reacting the salt solution B obtained in step (1) with a composite defluorinating agent to obtain a fluorine-containing solid and a salt solution C;

[0084] (4) Crystallizing the salt solution C obtained in step (3) to obtain a potassium chloride product and a salt solution D;

[0085] During the leaching process in step (1), a leaching aid is further added, and the leaching aid is selected from at least one of ethanol, ethylene glycol, acetone, glucose, ethylenediamine and cyclopentane;

[0086] In step (1), the mass ratio of the leaching agent to the leaching aid is 20:(0.5-2);

[0087] The method further comprises: preheating the leaching agent and the leaching aid, and then contacting them with the mixed salt containing sodium, potassium, fluorine and chlorine;

[0088] The temperature of the preheating is 70-103°C;

[0089] The leaching in step (1) is carried out in a rotating liquid film reactor; the slit width of the rotating liquid film reactor is 1-3 μm;

[0090] The composite defluorinating agent is at least one of calcium chloride, barium chloride, strontium chloride and lanthanum nitrate, as well as polyaluminum chloride and polyacrylamide;

[0091] The mass ratio of polyaluminum chloride to polyacrylamide is 8-20:1.

[0092] Adopting the above preferred implementation mode is further conducive to realizing the nearly complete recovery of valuable elements.

[0093] The present invention will be described in detail below through examples.

[0094] The raw materials used in the following examples were analyzed, and the weight percentages of their main components were: 26.53% Na, 19.71% F, 27.38% Cl, 25.72% K, and 0.66% Ta2O5.

[0095] Example 1

[0096] According to Figure 1 the described process.

[0097] (1) 1000 g of the raw material was leached in a rotating liquid film reactor (slit width 1 μm) with 1000 g of a mixed solution of deionized water and ethanol at 80 °C (the mass ratio of deionized water to ethanol was 10:1) for 3 min, and then filtered to obtain about 393 g of a solid mixture A containing sodium fluoride and tantalum pentoxide and a salt solution B.

[0098] (2) The above solid mixture A was mixed with 400 mL of saturated sodium sulfate solution for 30 min, and then rotationally separated to obtain 36 g of crude tantalum pentoxide and 357 g of sodium fluoride product; the crude tantalum pentoxide was washed 3 times with deionized water and then filtered to obtain the tantalum pentoxide product.

[0099] (3) 65 g of anhydrous calcium chloride, 0.4 g of polyaluminum chloride, and 0.04 g of polyacrylamide were added to the salt solution B obtained in step (1), reacted at 90 °C for 1 h, and then the reaction product was centrifuged at 90 °C and 5000 rpm for 6 min to obtain crude calcium fluoride and a salt solution C. The crude calcium fluoride was washed 3 times with deionized water and filtered to obtain the calcium fluoride product with a purity of about 99.2% and a yield of 98%.

[0100] (4) 1000 mL of the salt solution C obtained in step (3) was first heated to 100 °C for evaporation and concentration, and then cooled to 25 °C for cooling crystallization to obtain crude potassium chloride and the remaining 220 mL of salt solution D. The crude potassium chloride was washed with saturated potassium chloride solution to obtain the potassium chloride product. The salt solution D was returned to the leaching described in step (1).

[0101] The purities and yields of the sodium fluoride product, tantalum pentoxide product, and potassium chloride product are shown in Table 1.

[0102] Example 2

[0103] According to Figure 1 the described process.

[0104] (1) 1000 g of raw materials and 1000 g of a mixed solution of deionized water and ethylene glycol at 90 °C (the mass ratio of deionized water to ethylene glycol is 20:1) are leached in a rotating liquid film reactor (slit width 1 μm) for 4 min, and then filtered to obtain about 390 g of a mixture A containing sodium fluoride and tantalum pentoxide solids and a salt solution B.

[0105] (2) The solid mixture A is mixed with 400 mL of saturated sodium sulfate solution for 30 min, and then subjected to rotary separation to obtain 40 g of crude tantalum pentoxide and 350 g of sodium fluoride product; the crude tantalum pentoxide is washed 3 times with deionized water and then filtered to obtain a tantalum pentoxide product.

[0106] (3) 120 g of anhydrous barium chloride, 0.8 g of polyaluminum chloride and 0.08 g of polyacrylamide are added to the salt solution B obtained in step (1), and the reaction is carried out at 70 °C for 1 h. Then the reaction product is centrifuged at 70 °C and 4000 rpm for 4 min to obtain crude barium fluoride and a salt solution C. The crude barium fluoride is washed 3 times with deionized water to obtain a barium fluoride product. The purity of barium fluoride is about 99.1% and the yield is 98.5%.

[0107] (4) 1000 mL of the salt solution C obtained in step (3) is first heated to 102 °C for evaporation and concentration, and then cooled to 30 °C for cooling crystallization to obtain about 210 mL of a salt solution D and crude potassium chloride. The crude potassium chloride is washed with saturated potassium chloride solution to obtain a potassium chloride product. The salt solution D is returned to the leaching described in step (1).

[0108] The purity and yield of the sodium fluoride product, tantalum pentoxide product, and potassium chloride product are shown in Table 1.

[0109] Example 3

[0110] According to Figure 1 the above process.

[0111] (1) 1000 g of raw materials and 1100 g of a mixed solution of deionized water and ethanol at 80 °C (the mass ratio of deionized water to ethanol is 20:1) are leached in a rotating liquid film reactor (slit width 2 μm) for 5 min, and then filtered to obtain about 405 g of a solid mixture A containing sodium fluoride and tantalum pentoxide and a salt solution B.

[0112] (2) The solid mixture A is mixed with 400 mL of saturated sodium sulfate solution for 30 min, and then subjected to rotary separation to obtain 35.4 g of crude tantalum pentoxide and 348 g of sodium fluoride product; the crude tantalum pentoxide is washed 3 times with deionized water and then filtered to obtain a tantalum pentoxide product.

[0113] (3) Add 125 g of anhydrous barium chloride, 0.4 g of polyaluminum chloride, and 0.03 g of polyacrylamide to the salt solution B obtained in step (1), react at 80 °C for 1 h, and then centrifuge the reaction product at 80 °C and 3000 rpm for 6 min to obtain crude barium fluoride and salt solution C. Wash the crude barium fluoride three times with deionized water to obtain a barium fluoride product with a purity of 99.1% and a yield of 98%.

[0114] (4) First, heat 1100 mL of the salt solution C obtained in step (3) to 103 °C for evaporation and concentration, then cool it to 40 °C for cooling crystallization until 200 mL of the solution remains, cool it to 20 °C, and then filter to obtain salt solution D and crude potassium chloride. Wash the crude potassium chloride with saturated potassium chloride solution to obtain potassium chloride product. The obtained salt solution D is returned to the leaching described in step (1).

[0115] The purities and yields of sodium fluoride product, tantalum pentoxide product, and potassium chloride product are shown in Table 1.

[0116] Example 4

[0117] Carry out according to the method of Example 1, except that in step (1), 1000 g of a mixed solution of deionized water and ethanol at 80 °C (the mass ratio of deionized water to ethanol is 10:1) is used for ball milling leaching for 2 h, and then filtered to obtain 433 g of a mixture A of sodium fluoride and tantalum pentoxide solids, and a small amount of potassium chloride, and salt solution B. In step (3), the salt solution B is treated with 65 g of anhydrous calcium chloride, 0.4 g of polyaluminum chloride, and 0.04 g of polyacrylamide as in Example 1 to obtain a calcium fluoride product with a purity of 98.3% and a yield of about 97.1%.

[0118] The purities and yields of sodium fluoride product, tantalum pentoxide product, and potassium chloride product are shown in Table 1.

[0119] Example 5

[0120] Carry out according to the method of Example 1, except that in step (1), 1000 g of raw materials and 1400 g of deionized water at 90 °C are leached in a rotating liquid membrane reactor (slit width 1 μm) for 3 min, and then filtered to obtain 380 g of a mixture A containing sodium fluoride and tantalum pentoxide solids and salt solution B. In step (3), the salt solution B is treated with 65 g of anhydrous calcium chloride, 0.4 g of polyaluminum chloride, and 0.04 g of polyacrylamide as in Example 1 to obtain a calcium fluoride product with a purity of 98.6% and a yield of about 96.5%.

[0121] The purities and yields of sodium fluoride product, tantalum pentoxide product, and potassium chloride product are shown in Table 1.

[0122] Example 6

[0123] It was carried out according to the method of Example 1, except that in step (3), the composite defluorinating agent used was 65 g of anhydrous calcium chloride and 0.4 g of polyaluminum chloride, reacted at 90 °C for 1 h, and then the reaction product was centrifuged at 90 °C and 5000 rpm for 6 min to obtain crude calcium fluoride and salt solution C. The crude calcium fluoride was washed 3 times with deionized water and filtered to obtain a calcium fluoride product with a purity of about 97.9% and a yield of 96.3%.

[0124] The purities and yields of the sodium fluoride product, tantalum pentoxide product, and potassium chloride product are shown in Table 1.

[0125] Comparative Example 1

[0126] It was carried out according to the method of Example 1, except that in step (3), the defluorinating agent used was 65 g of anhydrous calcium chloride, reacted at 90 °C for 1 h, and then the reaction product was centrifuged at 90 °C and 5000 rpm for 6 min to obtain crude calcium fluoride and salt solution C. The crude calcium fluoride was washed 3 times with deionized water and filtered to obtain a calcium fluoride product with a purity of about 97.7% and a yield of 95.5%.

[0127] The purities and yields of the sodium fluoride product, tantalum pentoxide product, and potassium chloride product are shown in Table 1.

[0128] It should be noted that the calcium fluoride solid produced by using single calcium chloride for defluorination is extremely fine and cannot be completely separated, resulting in a relatively high fluoride ion concentration in the salt solution.

[0129] Table 1

[0130]

[0131] It can be seen from the results in Table 1 that the method provided by the present invention can maximize the separation and high-value recovery of valuable elements. Moreover, it can avoid wastewater discharge to the greatest extent, achieve closed-loop recovery, and at the same time, the method provided by the present invention can reduce the recovery cost and save energy and reduce consumption.

[0132] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for recovering a fluorine-containing, chlorine-sodium-potassium mixed salt produced as a by-product in the production of tantalum powder, characterized in that: The method comprises the following steps: (1) leaching a fluorine-containing sodium-chlorine-potassium mixed salt in the presence of a leaching agent to obtain a solid mixture A and a salt solution B; (2) sorting the solid mixture A obtained in step (1) to obtain a crude tantalum pentoxide product and a sodium fluoride product; (3) reacting the salt solution B obtained in step (1) with a composite defluorinating agent to obtain a fluorine-containing solid and a salt solution C; (4) Crystallizing the salt solution C obtained in step (3) to obtain a potassium chloride product and a salt solution D.

2. The method according to claim 1, wherein: The leaching agent is water; Preferably, the solid-liquid mass ratio of the leaching in step (1) is 1:(0.5-20), preferably 1:(1-10); Preferably, a leaching aid is also added during the leaching process in step (1), and the leaching aid is selected from at least one of ethanol, ethylene glycol, acetone, glucose and ethylenediamine; Preferably, in step (1), the mass ratio of the leaching agent to the leaching aid is 20:(0.5-18), preferably 20:(0.5-2).

3. The method according to claim 2, wherein: The method further comprises: preheating the leaching agent and / or the leaching aid and then contacting the leaching agent with the fluorine-containing sodium-chlorine-potassium mixed salt; Preferably, the preheating temperature is 50-150°C, preferably 70-103°C.

4. The method according to any one of claims 1 to 3, wherein: The leaching in step (1) is carried out in a rotating liquid film reactor; Preferably, the slit width of the rotating liquid film reactor is 0.5-3.5 μm, preferably 1-3 μm; Preferably, the leaching time is 0.5-30 min, preferably 0.5-10 min.

5. The method according to any one of claims 1 to 4, wherein: In step (2), the yield of crude tantalum pentoxide is not less than 70%; and / or, the yield of the sodium fluoride product is not less than 80%; Preferably, the separation in step (2) is carried out by gravity separation, preferably by heavy-density liquid separation and / or flotation.

6. The method according to any one of claims 1 to 5, wherein: The composite defluoridating agent is selected from at least one of calcium chloride, barium chloride, strontium chloride and lanthanum nitrate, and polyaluminium chloride and / or polyacrylamide; Preferably, the mass ratio of at least one of calcium chloride, barium chloride, strontium chloride and lanthanum nitrate to polyaluminium chloride and / or acrylamide is 100-200:0.3-10, preferably 100-180:0.3-2, more preferably 100:0.3-2.

7. The method according to claim 6, wherein: The composite defluoridating agent is at least one of calcium chloride, barium chloride, strontium chloride and lanthanum nitrate, as well as polyaluminium chloride and polyacrylamide; Preferably, the mass ratio of polyaluminium chloride to polyacrylamide is 5-20:1, preferably 8-20:

1.

8. The method according to any one of claims 1 to 7, wherein: The reaction conditions of step (3) include: temperature of 10-150°C, preferably 60-105°C; time of 0.5-5h, preferably 0.5-3h.

9. The method according to any one of claims 1 to 8, wherein: The crystallization in step (4) is cooling crystallization; Preferably, the temperature of the cooling crystallization is 20-70°C, preferably 20-50°C.

10. The method according to any one of claims 1 to 9, wherein: The purity of the potassium chloride product obtained in step (4) is not less than 90%; Preferably, the salt solution D obtained in step (4) is returned to the leaching in step (1).

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