Method and system for separating tantalum powder mixed salt by-product

Abstract

Relates to the technical field of tantalum powder mixed salt byproduct separation, in particular to a tantalum powder mixed salt byproduct separation method and system. The method comprises the steps that tantalum powder mixed salt is leached and separated to obtain a mixed solid containing sodium fluoride and tantalum pentoxide and a mixed salt solution with the main component being potassium chloride; carrying out physical separation on the mixed solid to obtain purified sodium fluoride and tantalum slag; and carrying out defluorination treatment on the mixed salt solution until the concentration of fluorine ions in the mixed salt solution meets a preset condition. Compared with a traditional method, the method for separating the tantalum powder mixed salt byproduct has the advantages that the recovery rate is effectively increased, and meanwhile, the cost is reduced; in addition, less water is used and no waste water is generated, so that the influence on the environment is reduced as much as possible in the whole process.

Description

Technical Field

[0001] This application relates to the technical field of separation of by-products of tantalum powder mixed salts, and particularly relates to a method and system for separating by-products of tantalum powder mixed salts. Background Art

[0002] The method of reducing potassium heptafluorotantalate with metallic sodium, also known as the Hunter method, is a method for preparing tantalum powder using K2TaF7 and metallic sodium as the main raw materials, and adding a halogen salt or a mixture of halogen salts as a diluent during the reaction process. Its chemical reaction equation is: K2TaF7+5Na=Ta+5NaF+2KF The preparation cost of this method is relatively low, and it is the most commonly used tantalum production method. However, during the process, a mixed salt by-product containing a large amount of KF, NaCl, NaF, and KCl and a small amount of Ta2O5 (about 0.4 - 0.7%) will be formed. If this by-product is directly discarded, it will cause great harm to the environment.

[0003] Currently, the traditional treatment methods for this tantalum-containing mixed salt by-product can be divided into three types: The first method is to dissolve all the mixed salts, and then add a large amount of calcium chloride and other fluoride precipitants to remove fluoride in the dissolved solution, so that the fluoride ions in the wastewater meet the discharge standards and are directly discharged, such as CN109399669A. The second method is to dissolve all the mixed salts, and then recover the fluoride ions in the solution in the form of sodium hexafluoroaluminate or potassium fluoroborate and discharge the wastewater, such as CN212102961U. Both methods require dissolving all the mixed salts first and then extracting the ultra-fine tantalum powder and oxides in the filter residue and sending them to the wet process for extracting and recovering the tantalum powder. However, the solubility of sodium fluoride in the tantalum-containing mixed salt by-product is relatively low, and only 4.02 g of sodium fluoride can be dissolved in 100 g of water. Both of these methods will produce a large amount of industrial wastewater, pollute the environment, and have a low recovery rate of valuable elements in the by-product. Moreover, lime is usually used as the defluorination agent, the amount of lime added is large, the defluorination cost is high, and a large amount of lime slag is obtained, increasing the additional stacking and transportation costs. The third method is to directly evaporate the obtained solution to dryness to obtain a composite salt for the preparation of potassium heptafluorotantalate or metallurgical tantalum powder, such as CN102336438A and CN102352444A. Although this method realizes the effective utilization of solid waste, the process differences are relatively large when preparing different types of tantalum powder, resulting in large fluctuations in the mixed salt components in the by-product and being difficult to formulate. Summary of the Invention

[0004] In view of this, it is necessary to provide a method for separating by-products of tantalum powder mixed salts to reduce the recovery cost, reduce wastewater discharge, and avoid environmental pollution, etc.

[0005] A method for separating by-products of tantalum powder mixed salts includes: The tantalum powder mixed salt is leached and separated to obtain a mixed solid containing sodium fluoride solid and tantalum pentoxide solid, and a mixed salt solution mainly composed of potassium chloride; The mixed solid is physically separated to obtain sodium fluoride solid and tantalum pentoxide solid; The mixed salt solution is subjected to defluorination treatment with a defluorinating agent until the fluoride ion concentration in the mixed salt solution meets a preset condition.

[0006] Preferably, the leaching and separation method for obtaining the mixed solid containing sodium fluoride and tantalum pentoxide by leaching the tantalum powder mixed salt includes enhanced leaching, pressure leaching, autoclave leaching, and stirring leaching.

[0007] Preferably, the physical separation method for physically separating the mixed solid to obtain sodium fluoride solid and tantalum pentoxide solid includes density gradient separation method, bubbling method, and air separation method.

[0008] Preferably, the density gradient separation method includes using one or at least two selected from sodium sulfate solution, potassium sulfate solution, and potassium fluorosilicate solution as the heavy density liquid, and the volume ratio of the heavy density liquid to the weight of the tantalum powder mixed salt is 0.1 - 15:1; the reaction temperature is 10 - 100 °C; the contact time is 0.5 - 10 hours.

[0009] Preferably, the volume ratio of the heavy density liquid to the weight of the tantalum powder mixed salt is 0.6 - 7.5:1; the reaction temperature is 35 - 90 °C; the contact time is 0.5 - 8 hours.

[0010] Preferably, it further includes: mechanically stirring after mixing the mixed solid with the test heavy density liquid.

[0011] Preferably, the defluorination treatment of the mixed salt solution includes selecting one or at least two of magnesium chloride, polyaluminum chloride, lanthanum nitrate, calcium chloride, and polyacrylamide as the defluorinating agent.

[0012] Preferably, it further includes: after adding the defluorinating agent for defluorination treatment, performing solid-liquid separation by centrifugal separation method; wherein, the centrifugal speed is 1000 - 8000 rpm; the centrifugal time is 1 - 10 minutes; the centrifugal temperature is 10 - 100 °C.

[0013] Preferably, in the solid-liquid separation by centrifugal separation method, the centrifugal speed is 3000 - 7000 rpm; the centrifugal time is 2 - 8 minutes; the centrifugal temperature is 30 - 90 °C.

[0014] A tantalum powder mixed salt by-product separation system includes: An enhanced leaching device for leaching and separating the tantalum powder mixed salt to obtain a mixed solid containing sodium fluoride and tantalum pentoxide, and a mixed salt solution mainly composed of potassium chloride; A physical separation device for physically separating the mixed solid to obtain sodium fluoride solid and tantalum pentoxide solid; A mixed salt solution treatment device for defluorination treatment of the mixed salt solution until the fluoride ion concentration in the mixed salt solution meets a preset condition.

[0015] Compared with the prior art, the beneficial effects of the present application are as follows: In a new method for separating by-products of tantalum powder mixed salt provided, an enhanced leaching method is adopted, so that a large amount of sodium fluoride still exists in solid form, thereby reducing the fluoride ion content in the solution. In this way, the amount of defluorinating agent used can be reduced, thus reducing the separation cost; further, through physical separation such as density gradient separation method, sodium fluoride and tantalum pentoxide are directly separated without adding a large amount of water to directly dissolve sodium fluoride to obtain tantalum pentoxide, with low separation cost and no wastewater discharge. The solution provided by the present application effectively improves the recovery rate while reducing the cost, and since less water is used and no wastewater is generated, the impact on the environment is minimized throughout the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic flow chart of a method for separating by-products of tantalum powder mixed salt provided by an embodiment of the present application.

[0017] Figure 2 is a schematic plan view of a turning tooling for a conical thin-walled rotating body provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Please refer to Figure 1 , Figure 1 which is a schematic flow chart of a method for separating by-products of tantalum powder mixed salt provided by an embodiment of the present application. The method for separating by-products of tantalum powder mixed salt includes the following steps: S101: Leach and separate the tantalum powder mixed salt to obtain a mixed solid containing sodium fluoride solid and tantalum pentoxide solid, and a mixed salt solution mainly composed of potassium chloride.

[0020] The tantalum powder mixed salt can be intensively leached using a rotating liquid film reactor, which greatly shortens the leaching time compared with the traditional leaching method, enables the full exchange of fluorine, chlorine, sodium, and potassium ions in the tantalum powder mixed salt to be converted into high-value-added KCl and NaF, and sodium fluoride is insoluble in water and is easily separated from the salt solution. Since a large amount of sodium fluoride still exists in solid form after intensive leaching, the fluoride ion content in the solution is less, which can greatly reduce the usage amount of defluorinating agents and thus reduce the separation cost. The reaction equation is: KF + NaCl = NaF + KCl.

[0021] In addition to intensive leaching, methods such as pressure leaching, autoclave leaching, and stirring leaching can also be selected.

[0022] S102: Physically separate the mixed solid to obtain sodium fluoride solid and tantalum pentoxide solid.

[0023] The methods that can be used for physical separation include density gradient separation method, bubbling method, air separation method, etc. Further, the present application preferably adopts the density gradient separation method, uses one or at least two mixtures selected from sodium sulfate solution, potassium sulfate solution, potassium fluorosilicate solution, carbon tribromide monochloride, xylene ether, and carbon tetrabromide as the heavy density liquid, and the volume ratio of the heavy density liquid to the weight of the tantalum powder mixed salt is 0.1 - 15:1; the reaction temperature is 10 - 100 °C; the contact time is 0.5 - 10 hours. To promote full mixing, the mixed solid needs to be mechanically stirred after being mixed with the heavy density liquid, and multiple stirring speeds can be set for multiple differential stirrings during stirring.

[0024] Further, as a preferred embodiment of the present application, the volume ratio of the heavy density liquid to the weight of the tantalum powder mixed salt is 0.6 - 7.5:1; the reaction temperature is 35 - 90 °C; the contact time is 0.5 - 8 hours.

[0025] Using the density gradient separation method can directly separate sodium fluoride and tantalum pentoxide without further treatment, and compared with directly dissolving a large amount of water in sodium fluoride to obtain tantalum pentoxide, the gravity separation method has low operation and separation costs and no wastewater discharge. After separating tantalum pentoxide and sodium fluoride, the density gradient liquid can still be used for the next density gradient separation, which can greatly reduce the usage amount of the density gradient liquid and further reduce the separation cost.

[0026] S103: Treat the mixed salt solution with a defluorinating agent until the fluoride ion concentration in the mixed salt solution meets the preset conditions.

[0027] Fluoride ion removal: The first thing to deal with is the small amount of fluoride ions contained in the solution. According to the present invention, different defluorinating agents can be used to reduce the fluoride ion concentration in the solution, and these defluorinating agents include but are not limited to magnesium chloride, polyaluminum chloride, lanthanum nitrate, calcium chloride, polyacrylamide, etc. Preferably, calcium chloride is used as the defluorinating agent because it reacts with fluoride ions to form calcium fluoride precipitate that is insoluble in water, thereby effectively removing fluoride ions.

[0028] After adding the defluorinating agent for defluorination treatment, solid-liquid separation is carried out by centrifugation; among them, the centrifugal speed is 1000 - 8000 rpm; the centrifugal time is 1 - 10 minutes; the centrifugal temperature is 10 - 100 °C. Preferably, the centrifugal speed is 3000 - 7000 rpm; the centrifugal time is 2 - 8 minutes; the centrifugal temperature is 30 - 90 °C.

[0029] The reaction equation is:

[0030] It should be noted that when using a composite defluorinating agent, the content of calcium ions and the content of fluoride ions in the salt solution should be maintained at a ratio of 1:2 to avoid introducing other unnecessary ions. During the process of fluoride ion removal, the reaction temperature is set within a specific range, usually 10 - 100 °C, preferably 35 - 90 °C. An appropriate temperature helps to improve the chemical reaction efficiency, enabling fluoride ions to be removed more completely.

[0031] After the above treatment of the mixed salt solution, the fluoride ion concentration therein needs to meet the corresponding environmental protection standards or industrial reuse standards. For example, the maximum allowable discharge concentration of fluoride ions in industrial wastewater in China is usually 1 mg / L (i.e., 1 ppm), but in some more stringent regions or for certain specific industries, this value may be lower. If the treated solution is planned to be used in further industrial production processes, such as preparing other chemicals or as process water, it is necessary to ensure that the fluoride ion concentration is lower than the level that affects the performance of subsequent processes (depending on the specific application scenario and process requirements). When the goal of treatment is to convert the solution into a certain salable product, such as high-purity potassium chloride (KCl), the fluoride ion concentration must meet the quality specifications of the corresponding product. Once these standards are met, the solution can be directly sold or further processed by cooling precipitation, evaporation, etc. to obtain a higher-purity potassium chloride (KCl) product.

[0032] The following introduces the separation method of tantalum powder mixed salt by-products in combination with specific embodiments: Taking a certain tantalum by-product as the experimental raw material, after analysis, the weight percentage of its main components is: 26.53% Na, 19.71% F, 27.38% Cl, 25.72% K, and 0.66% Ta2O5.

[0033] The separation process of the tantalum powder mixed salt is as follows: 500 g of the tantalum powder mixed salt is stirred and leached for separation to obtain a mixed solid A containing sodium fluoride and tantalum pentoxide, and a mixed salt solution A; After the obtained solid mixture A is mixed evenly with a saturated sodium sulfate solution under the condition that the solid-liquid ratio is 1:2, density gradient separation is carried out at 80 °C, and mechanical stirring is carried out at 500 rpm, 200 rpm, and 100 rpm for one hour each; The obtained mixed salt solution A is added with a composite defluorinating agent composed of calcium chloride and polyaluminum chloride for defluorination until the fluoride ions in the solution meet the standard. Example 2:

[0034] 500 g of the tantalum powder mixed salt is intensively leached for separation to obtain a mixed solid A containing sodium fluoride and tantalum pentoxide, and a mixed salt solution A; After the obtained solid mixture A is mixed evenly with a saturated sodium sulfate solution under the condition that the solid-liquid ratio is 1:2, density gradient separation is carried out at 80 °C, and mechanical stirring is carried out at 500 rpm, 200 rpm, and 100 rpm for one hour each.

[0035] The obtained mixed salt solution A is added with a composite defluorinating agent composed of calcium chloride and polyaluminum chloride for defluorination until the fluoride ions in the solution meet the standard. Example 3:

[0036] 500 g of the tantalum powder mixed salt is intensively leached for separation to obtain a mixed solid A containing sodium fluoride and tantalum pentoxide, and a mixed salt solution A; After the obtained solid mixture A is mixed evenly with a saturated sodium sulfate solution under the condition that the solid-liquid ratio is 1:2, density gradient separation is carried out at 80 °C, and mechanical stirring is carried out at 500 rpm, 200 rpm, and 100 rpm for one hour each; The obtained mixed salt solution A is added with calcium chloride for defluorination until the fluoride ions in the solution meet the standard. Example 4:

[0037] 500 g of the tantalum powder mixed salt is intensively leached for separation to obtain a mixed solid A containing sodium fluoride and tantalum pentoxide, and a mixed salt solution A; After the obtained solid mixture A is mixed evenly with deionized water under the condition that the solid-liquid ratio is 1:2, density gradient separation is carried out at 80 °C, and mechanical stirring is carried out at 500 rpm, 200 rpm, and 100 rpm for one hour each; The obtained mixed salt solution A is added with a composite defluorinating agent composed of calcium chloride and polyaluminum chloride for defluorination until the fluoride ions in the solution meet the standard. Example 5:

[0038] 500 g of tantalum powder mixed salt was intensively leached and separated to obtain a mixed solid A containing sodium fluoride and tantalum pentoxide, and a mixed salt solution A; The obtained solid mixture A was mixed evenly with saturated sodium sulfate solution under the condition of a solid-liquid ratio of 1:1, and then density gradient separation was carried out at 80 °C with mechanical stirring at 500 rpm, 200 rpm and 100 rpm for one hour each; The obtained mixed salt solution A was added with a composite defluorinating agent composed of calcium chloride and polyaluminum chloride for defluorination until the fluoride ions in the solution met the standard. Example 6:

[0039] 500 g of tantalum powder mixed salt was intensively leached and separated to obtain a mixed solid A containing sodium fluoride and tantalum pentoxide, and a mixed salt solution A; The obtained solid mixture A was mixed evenly with saturated sodium sulfate solution under the condition of a solid-liquid ratio of 1:2, and then density gradient separation was carried out at 20 °C with mechanical stirring at 500 rpm, 200 rpm and 100 rpm for one hour each; The obtained mixed salt solution A was added with a composite defluorinating agent composed of calcium chloride and polyaluminum chloride for defluorination until the fluoride ions in the solution met the standard. Example 7:

[0040] 500 g of tantalum powder mixed salt was intensively leached and separated to obtain a mixed solid A containing sodium fluoride and tantalum pentoxide, and a mixed salt solution A; The obtained solid mixture A was mixed evenly with saturated sodium sulfate solution under the condition of a solid-liquid ratio of 1:2, and then density gradient separation was carried out at 80 °C with mechanical stirring at 500 rpm for one hour; The obtained mixed salt solution A was added with a composite defluorinating agent composed of calcium chloride and polyaluminum chloride for defluorination until the fluoride ions in the solution met the standard.

[0041] Comparative example 500 g of tantalum powder mixed salt was intensively leached and separated to obtain a mixed solid A containing sodium fluoride and tantalum pentoxide, and a mixed salt solution A; The obtained solid mixture A was subjected to air separation; The obtained mixed salt solution A was added with a composite defluorinating agent composed of calcium chloride and polyaluminum chloride for defluorination until the fluoride ions in the solution met the standard.

[0042] Please refer to Table 1. Table 1 is an example of the recovery rates of fluorine, chlorine, sodium, potassium and tantalum pentoxide in the above Examples 1-7 and the comparative example, as well as the fluoride ion concentration in the mixed salt solution after defluorination: Table 1

[0043] It can be seen from Table 1 that: In the embodiments of the present application, the recovery rates of fluorine elements are all relatively high, ranging from approximately 92.17% to 95.91%, indicating that the method of the present application has a significant effect on the effective recovery of fluorine elements.

[0044] In addition to fluorine elements, the three elements of sodium, potassium, and chlorine also show relatively high recovery rates. In particular, potassium and chlorine are close to or exceed 98% in some embodiments, demonstrating the effective separation and recovery ability of the technology of the present invention for multiple elements.

[0045] The recovery rates of tantalum pentoxide vary greatly among the embodiments, ranging from the lowest 11.24% (comparative example) to the highest 46.98% (embodiment 2). This indicates that the selection of the physical separation step has an important impact on the recovery efficiency of tantalum pentoxide. The density gradient separation method used in the present application can significantly improve the recovery efficiency of tantalum pentoxide compared to the air separation method.

[0046] The fluoride ion concentration in the treated mixed salt solution is very low, usually on the order of 10 -5 mol / L, meeting the strict environmental protection emission standards or the requirements of industrial reuse. For example, embodiment 3 reaches the lowest value of 0.01*10 -5 mol / L, while other embodiments remain in a similar low level range.

[0047] Based on the same inventive concept, the present application also provides a tantalum powder mixed salt by-product separation system 200. Please refer to Figure 2 , Figure 2 which is a structural schematic diagram of the tantalum powder mixed salt by-product separation system provided by the embodiments of the present application; the tantalum powder mixed salt by-product separation system 200 includes: A leaching device 201 for leaching and separating the tantalum powder mixed salt to obtain a mixed solid containing sodium fluoride and tantalum pentoxide, and a mixed salt solution mainly composed of potassium chloride; A physical separation device 202 for physically separating the mixed solid to obtain sodium fluoride solid and tantalum pentoxide solid; A mixed salt solution treatment device 203 for defluorinating the mixed salt solution until the fluoride ion concentration in the mixed salt solution meets the preset conditions.

[0048] For the implementation processes of the above tantalum powder mixed salt by-product separation system 200 and its respective devices, please refer to steps S101~S103 and their respective alternative embodiments, which will not be elaborated in the present application.

[0049] In summary, the present application not only realizes the effective recovery of valuable tantalum pentoxide, but also reduces the environmental impact of waste by effectively recovering elements such as fluorine, sodium, potassium, and chlorine. In addition, by optimizing conditions such as temperature, stirring speed and other parameters, the recovery efficiency of various components can be further improved.

Claims

1. A method for separating by-products of tantalum powder mixed salts, characterized in that, Comprising: Leaching and separating tantalum powder mixed salt to obtain a mixed solid containing sodium fluoride solid and tantalum pentoxide solid, and a mixed salt solution mainly composed of potassium chloride; Physically separating the mixed solid to obtain sodium fluoride solid and tantalum pentoxide solid; Subjecting the mixed salt solution to defluorination treatment with a defluorinating agent until the fluoride ion concentration in the mixed salt solution meets a preset condition.

2. The method for separating tantalum powder mixed salt by-products according to claim 1, characterized in that The leaching and separation method for leaching and separating tantalum powder mixed salt to obtain a mixed solid containing sodium fluoride solid and tantalum pentoxide solid includes enhanced leaching, pressure leaching, autoclave leaching, and stirring leaching.

3. The method for separating tantalum powder mixed salt by-products according to claim 1, characterized in that, The physical separation method for physically separating the mixed solid to obtain sodium fluoride solid and tantalum pentoxide solid includes density gradient separation method, bubbling method, and air separation method.

4. The method for separating tantalum powder mixed salt by-products according to claim 3, characterized in that, The density gradient separation method includes using one or at least two selected from sodium sulfate solution, potassium sulfate solution, and potassium fluorosilicate solution as the heavy density liquid, and the volume ratio of the heavy density liquid to the weight of tantalum powder mixed salt is 0.1 - 15:1; the reaction temperature is 10 - 100 °C; the contact time is 0.5 - 10 hours.

5. The method for separating tantalum powder mixed salt by-products according to claim 3, characterized in that, The volume ratio of the heavy density liquid to the weight of tantalum powder mixed salt is 0.6 - 7.5:1; the reaction temperature is 35 - 90 °C; the contact time is 0.5 - 8 hours.

6. The method for separating tantalum powder mixed salt by-products according to any one of claims 1 to 5, characterized in that, Also comprising: Mechanically stirring the mixed solid after mixing it with the test heavy density liquid.

7. The method for separating tantalum powder mixed salt by-products according to claim 1, wherein Subjecting the mixed salt solution to defluorination treatment includes selecting one or at least two of magnesium chloride, polyaluminum chloride, lanthanum nitrate, calcium chloride, and polyacrylamide as the defluorinating agent.

8. The method for separating tantalum powder mixed salt by-products according to claim 7, characterized in that, Also comprising: After adding the defluorinating agent for defluorination treatment, performing solid-liquid separation by centrifugal separation method; wherein, the centrifugal speed is 1000 - 8000 rpm; the centrifugal time is 1 - 10 minutes; the centrifugal temperature is 10 - 100 °C.

9. The method for separating tantalum powder mixed salt by-products according to claim 8, characterized in that, In the solid-liquid separation by centrifugal separation method, the centrifugal speed is 3000 - 7000 rpm; the centrifugal time is 2 - 8 minutes; the centrifugal temperature is 30 - 90 °C.

10. A tantalum powder mixed salt by - product separation system, characterized in that, Comprising: An enhanced leaching device for leaching and separating tantalum powder mixed salt to obtain a mixed solid containing sodium fluoride solid and tantalum pentoxide solid, and a mixed salt solution mainly composed of potassium chloride; A physical separation device for physically separating the mixed solid to obtain sodium fluoride solid and tantalum pentoxide solid; A mixed salt solution treatment device for subjecting the mixed salt solution to defluorination treatment until the fluoride ion concentration in the mixed salt solution meets a preset condition.

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