RU2611869C1 - Method of producing highly pure tantalum oxide from tantalum-containing solutions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method for producing highly pure tantalum oxide from the tantalum-containing solutions comprises tantalum hydroxide preparation for the cleansing extraction. Precipitating of tantalum hydroxide, ageing and filtration of pulp, washing of precipitate are carried out consecutively. Then, tantalum hydroxide is dissolved in a mixture of sulfuric and hydrofluoric acids to obtain the base solution for the cleansing extraction. The mentioned base solution has the following composition: tantalum oxide 140-160 g/l, total fluoride-ion is 80-97 g/l, sulfuric acid 200-300 g/l. The cleansing extraction of the resulting solution by an extracting agent, followed by washing of saturated extract andre-extraction are carried out. Octanol-1 is used as an extracting agent. Washing of the saturated extract is carried out in two steps: The resulting tantalum re-extract is diluted, tantalum hydroxide is precipitated. Filtration and washing of the precipitate, followed by its repulping are carried out. Then, tantalum hydroxide is dried and calcined to obtain tantalum oxide.

EFFECT: invention reduces costs during production of tantalum oxide, increases its purity.

4 cl, 3 dwg, 9 tbl

Description

The invention relates to the field of chemical technologies, in particular, to methods for producing high-purity oxides from acid solutions containing tantalum, which can be obtained, for example, by leaching columbite and tantalite concentrates with solutions of hydrofluoric and / or other mineral acids, as well as in other methods for producing oxides tantalum from tantalum-containing raw materials.

High-purity tantalum metal and its oxide are becoming increasingly important in the electronics industry to produce advanced electronic materials used in the manufacture of devices such as surface acoustic wave filters, pyroelectric infrared sensors, and optoelectric devices.

Tantalum capacitors are widely used in aerospace instrumentation, automotive electronics, cell phones, computers, and other electronic devices. They are indispensable in special-purpose electronic equipment where special reliability is required. Tantalum capacitors, in comparison with other types of capacitors, have a larger capacity per unit volume, a wide range of operating temperatures (-60 ° С to 200 ° С), a high degree of reliability and a long shelf life (up to 25 years) and operation (up to 150,000 hours) ) One of the most significant applications of tantalum is the production of heat-resistant alloys, which are used in the production of gas turbines and various parts of jet engines. In addition, high purity tantalum oxide is required to obtain tantalum x-ray phosphors, which are necessary in the manufacture of screens for x-ray amplifiers. Tantalum oxide and hydroxide are the starting material for producing tantalum metal.

The purity of the metal tantalum and its oxide used in the manufacture of these materials should exceed 99.99% and preferably be 99.9999%.

There are three main methods for purifying tantalum-containing materials: distillation (or chlorination), liquid extraction, and ion exchange. In the distillation method, a mixture of contaminated tantalum-containing material and carbon interacts with gaseous chlorine at a temperature of 600-800 ° C. Although distillation is a well-studied and operating industrial process for the purification of tantalum-containing materials, they are faced with the problem of separation of tantalum and niobium due to the close boiling points of tantalum chloride (239 ° C) and niobium chloride (249 ° C). Since niobium is a ubiquitous impurity of tantalum-containing materials, solvent extraction methods and ion exchange are preferred over distillation in those cases where it is desirable to obtain tantalum and its high purity oxide.

In ion exchange methods, the contaminated tantalum-containing material is dissolved in hydrofluoric acid and then passed through an anion-exchange column that selectively holds tantalum metal. Impurities remain in solution and are removed with wastewater. The retained tantalum compounds are then eluted from the column and precipitated as tantalum hydroxide as described above. An example of such a method is described in US patent No. 4446115. However, due to the relatively low exchange capacity of the anion exchange resin, this method is expensive for use on an industrial scale.

A known method of producing tantalum oxide by liquid-phase physico-chemical interaction of chlorine-containing compounds of tantalum with oxygen-containing chemicals, moreover, as the initial chlorine-containing chemical compounds of tantalum and / or niobium use a polymer organometallic compound of tantalum, which is subjected to physico-chemical interaction with concentrated hydrogen peroxide and concentrated sulfuric acid under normal conditions; The resulting solution of the tantalum chloride-sulfate-peroxide complex compound is diluted with distilled water and heated until a suspension of tantalum hydroxide is separated, which is concentrated, filtered off, mixed with concentrated sulfuric acid and evaporated to remove white sulfuric anhydride vapor, the resulting solid residue is leached out with hot distilled water and calcined to for producing crystalline tantalum oxide (RF Patent No. 2092441, publ. 10.10.1997).

The method of producing tantalum oxide is as follows. A measured amount of concentrated hydrogen peroxide (33% H ₂ O ₂ ) with the addition of concentrated sulfuric acid (density 1.84 g / cm ³ ) H ₂ SO _{4 is} poured into the reactor with a stirring and heat exchange device. The tantalum (niobium) solid polymeric organometallic metal compound is loaded into the resulting solution in small portions (to maintain room temperature in the reactor, since the reaction of the tantalum polymeric organometallic compound with hydrogen peroxide takes place with the release of thermal energy, and with a large load, boiling and rapid decomposition of hydrogen peroxide is possible ) The suspension is effectively mixed and cooled using a heat exchanger device of the reactor to room temperature. The solution of the tantalum chloride-sulfate-peroxide complex compound obtained as a result of physicochemical interaction (the initial product with the reagents) is diluted with distilled water and heated until the complex chemical compound of tantalum decomposes, and hydrolysis takes place with the release of a suspension of tantalum hydroxide, which becomes coarse-grained when heated. A suspension of tantalum (niobium) hydroxide is concentrated and filtered off, the precipitate is transferred to an evaporation bowl, mixed with concentrated sulfuric acid and evaporated in a sand bath to remove dense white vapor of sulfuric anhydride (SO ₃ ). The solid residue is washed into the reactor and leached with hot distilled water until all water-soluble impurities are completely removed. The suspension is filtered off, the precipitate is dried at a temperature of 105 ° C to constant weight and then calcined in a muffle furnace at a temperature of 830-900 ° C in order to obtain a stable modification of crystalline tantalum oxide.

The disadvantages of the liquid-phase hydrolysis method are: difficulties in filtering and high sorption ability of the resulting hydroxide precipitates, leading to contamination of the product; the use of bulky equipment for hydrolysis, filtration, drying and calcination.

A known method of producing tantalum oxide (RF patent No. 2259321, published October 10, 2004) in which, as the initial tantalum-containing compound is used potassium fluorotantalate (FTK) with a particle size of -100 + 40 μm more than 85%, which is achieved by 1-3 times heating coarse crystalline FTK to a temperature of 220-250 ° C with intermediate cooling to 70-80 ° C. As a result of multiple polymorphic transformations, the crystals self-grind to the required sizes. Treatment with FTK with ammonia water leads to the formation of (NH ₄ ) KTa (OH) ₅ F ₂ while maintaining the size and shape of the initial particles. The precipitate quickly (1-2 minutes) and completely, with the formation of a dense layer, settles. This allows us to further eliminate filtering during intermediate operations. Ammonia treatment is carried out at room temperature, which allows to reduce the consumption of ammonia water by a factor of 2.0-2.5, and after the first ammonia treatment, water washing of the precipitate is carried out, which eliminates the loss of tantalum during acid treatment. Acid treatment is introduced by hydrochloric acid. Depending on the desired purity of the final product, cycles of ammonia-hydrochloric acid treatment are carried out (2-4 cycles).

In FTK decomposition operations, it is allowed to use household drinking or artesian water and reagents of the “technical” grade, without mechanical impurities. And only at the last acid treatment is it necessary to use distilled water and hydrochloric acid of the brand “analytical grade”, “chemical grade”.

After completion of all cycles of ammonia-hydrochloric acid treatment, the pulp is stirred for 0.5 hours and filtered. The filtered precipitate is washed on the filter twice with 50 ml of water and dried at a temperature of 120 ° C. The content in the precipitate of fluorine <0.1%, potassium 0.009% in terms of Ta ₂ O ₅ . Calcination of the precipitate is carried out at a temperature of 300-550 ° C.

The disadvantage of this method is the duration of the process (at least 4 cycles of FTK decomposition), as well as the questionable degree of purification from impurities, since tantalum is required, in addition to other impurities, to niobium and the main difficulty in obtaining pure tantalum compounds is to separate them. However, when evaluating the obtained tantalum oxide, niobium is not indicated as an impurity.

Currently, the most widely used in industry are methods for producing high-purity tantalum oxide using separation of tantalum and niobium by liquid extraction.

During liquid extraction, the contaminated tantalum-containing material is dissolved in a medium of hydrofluoric acid and brought into contact with an organic solvent. Tantalum compounds are selectively extracted into the organic phase, then back extracted into an aqueous solution, and precipitated as tantalum hydroxide by hydrolysis with aqueous ammonia. Precipitated hydroxide can be converted to tantalum oxide by calcination in air. However, to obtain a high-purity product, a multi-stage cyclic extraction-re-extraction process is required. Examples of the use of liquid extraction are given in US patents No. 31117833, 3712939 and 4673554, as well as RF patents No. 2245305, 2269582.

The most complete studies of the extraction method for the separation of tantalum and niobium are given in the dissertation of EA Koval “Extraction of tantalum and niobium from fluoride-sulfate solutions with alcohols” (abstract of the dissertation for the degree of candidate of chemical sciences, Moscow, 2006), which was adopted as a prototype of the proposed technical solution.

The conditions for the extraction of tantalum were chosen so that they ensured the possibility of achieving in the organic phase the necessary concentration of tantalum and the minimum permissible concentration of interfering impurities, as well as the corresponding completeness of their extraction.

The parameters of the extraction process were selected depending on the nature of the initial tantalum-containing solution, the method of its preparation (dissolution) for extraction, and the extractant used.

Testing of the conditions for the extraction separation of tantalum from niobium was carried out on a laboratory extraction plant of the mixer-settler type using an aqueous solution obtained after dissolution of tantalum hydroxide. OKL-2 was used as an extractant, as well as a 60% (vol.) Mixture of MIBK with OKL-1 and 80% (vol.) A mixture of TBP with OKL-1.

The effect of the concentration of sulfuric acid in the initial aqueous solution on the extraction of tantalum and niobium during extraction with octanol isomers was studied.

The extraction separation of tantalum and niobium was carried out from a fluoride-sulfate solution. The fluoride ion content did not exceed the total metal content in a stoichiometric ratio of not more than 7: 1, the sulfuric acid content varied in the range of 100-400 g / l, the ratio of the volumes of organic and aqueous phases was O: B = 1: 1.

As a result, the following were considered optimal: as an extractant, the use of a mixture of MIBK (60 vol.%) And octanol-1 - the rest, when the content of sulfuric acid in the solution is more than 250 g / l.

The almost complete extraction of tantalum, in comparison with niobium, is achieved from less acidic solutions. In the case of tantalum, it is sufficient to have 23 M acid in the solution, while for niobium it should be higher than 7 M. This character of the dependence of the extraction on the acid concentration makes it possible to separate the metals by maintaining it at a certain concentration level. The nature of the change in the extractability of metals correlates with their form of existence and the nature of its change with increasing acid concentration.

After extraction, washing with water at O: B = (15-7): 1 was accepted. The specific value of this ratio, as well as the number of washing steps, is determined by the requirements for the quality and completeness of tantalum separation in the final product. The smaller this ratio and the greater the number of washing steps, the more tantalum is washed out of the organic phase. The resulting wash solution is combined with the original solution and, after adjusting the composition, is sent to the extraction. Such an organization of the extraction process minimizes the loss of tantalum in this operation.

The obtained re-extract is subjected to processing according to the traditional scheme: dilution of the obtained tantalum re-extract, precipitation of tantalum hydroxide, filtration and washing of the precipitate, followed by its repulpation; drying and calcining tantalum hydroxide at a temperature above 550 ° C at which tantalum hydroxide is dehydrated to produce tantalum oxide.

The physicochemical characteristics of the obtained materials from tantalum oxide strongly depend on its purity. For this reason, when producing tantalum oxide, effective methods are needed to isolate and control the content of a large group of interfering elements at a trace level, therefore, the calcination temperature depends on the method of further use of tantalum oxide.

In the process of applying the known technology for the production of tantalum oxide, it was revealed that the parameters of individual operations are not optimal, which affects the quality of the finished product, therefore it is necessary to optimize them, as well as to increase the reliability of the equipment at certain stages of the technological process.

The present invention is the implementation of the production of pure tantalum oxides with a high yield of the final product in the least expensive way.

The technical result is achieved due to the fact that in the known method for producing high-purity tantalum oxide from tantalum-containing solutions, which includes preparing tantalum hydroxide for purification extraction by sequentially performing tantalum hydroxide precipitation, soaking and filtering the pulp, washing the precipitate, then dissolving the tantalum hydroxide in a mixture of sulfur and hydrofluoric acid, purification extraction of the resulting solution with an extractant containing octanol-1, washing the saturated extract and reextraction, further ra bavlenie obtained reextract tantalum, tantalum hydroxide precipitation, filtration and washing of the precipitate, followed by repulping it, and then drying and calcination of tantalum hydroxide to afford, amended and changed tantalum oxide, namely:

- dissolution of tantalum hydroxide with a mixture of sulfuric and hydrofluoric acid is carried out to obtain the initial solution for the purification extraction of a composition having the following concentrations of components: tantalum oxide - 140-160 g / l; total ion fluoride - 80-97 g / l and sulfuric acid 200-300 g / l;

- as an extractant use only octanol-1;

- washing of the saturated extract is carried out sequentially in two stages, with the first stage being sulfuric acid with a concentration of 250-300 g / l, and the second with denounced water at a ratio of O: B = (20-15): 1 in both stages;

- dilution of the tantalum reextract is completed when the tantalum oxide content is in the range of 60-80 g / l;

- drying of tantalum hydroxide is carried out in two stages, at different temperatures, and calcination at high temperature (about 1000 ° C) and time from 6-8 hours.

The choice of industrial extractant is determined by a compromise between numerous, often conflicting requirements. Among them, the most important are extraction and reactivity, selectivity, interfacial tension, density, toxicity and cost. Methylisobutylketone (MIBK), octanol (OKL), tributyl phosphate (TBP) and cyclohexanone (CCN) proved to be substantially satisfying this set of requirements, which confirms the practice of using them in the production of niobium and tantalum compounds. OKL is close in extraction ability, but somewhat inferior to MIBK and TsGN. However, these extractants have several disadvantages: high solubility in aqueous solutions, fire and explosion hazard (especially MIBK), high volatility, therefore, octanol-1 was chosen as the extractant. In addition, CCN in an acidic environment is easily subjected to deep chemical transformations. Due to the fact that OKL is a less basic extractant than TBP, the extraction of tantalum and niobium must be carried out at higher values of the ratio of the volumes of the organic and aqueous phases. Along with the disadvantages noted above, OKL has several advantages over TBP. An important characteristic of the extractant is its stability during prolonged contact with technological solutions, so OKL remains suitable for reuse.

Selective extraction of tantalum is preferable to carry out from fluoride-sulfate solutions. Introduction to the extraction system of sulfuric acid allows several times to reduce the ratio of V _O : V _B.

According to the prototype, we can also conclude that the best separation of tantalum and niobium is realized when the content of sulfuric acid is more than 200 g / l. At a lower concentration of H ₂ SO _{4, the} co-extraction of niobium is much lower, however, the degree of tantalum extraction is reduced, which does not allow its complete extraction to be achieved or requires the implementation of too many equilibrium steps on the extraction cascade.

The components of the initial extraction extraction solution were determined based on numerous studies of the extraction process of solutions containing tantalum oxide.

Below are the results of experiments on the selection of optimal parameters for the continuous extraction process, washing the extract and re-extraction of tantalum.

Extraction purification of fluorotantalic acid, which was formed upon dissolution of tantalum hydroxide, from impurities was organized as follows.

The continuous countercurrent extraction cascade involved 24 working and 4 sedimentary stages of countercurrent mixing-sedimentary extractors. In the process of continuous testing of the extraction purification of fluorotantalic acid, a search was carried out for optimal extraction redistribution modes.

A series of studies in this phase was aimed at finding the optimal modes for obtaining a tantalum reextract of the required quality.

The number of steps in the contours of the cascade:

- the total number of working steps in the cascade n = 28

- the number of steps in the extraction part n = 8

- the number of steps in the washing part n = 8 (6 + 2)

- the number of steps on the re-extraction of niobium n = 8

- the number of sludge chambers of the organic and aqueous phases n = 4.

Parameters of working solutions

1. The initial tantalum-containing solution is in accordance with table. one;

2. Wash solution No. 1: H ₂ SO ₄ - variable composition in accordance with table. 3;

3. Wash solution No. 2: deionized water;

4. Reextracting solution: deionized water;

5. The extractant is circulating octanol-1 (ρ = 0.825 g / l).

The efficiency of the extraction cascade was judged by the content of impurity elements in tantalum oxide obtained from a tantalum reextract diluted to a concentration of 60-80 g / l using Ta ₂ O ₅ .

Table 1 below presents data on the chemical composition of the initial tantalum-containing solutions entering the extraction cascade. Table 2 presents the results of determining the content of impurities in the obtained samples of tantalum oxide.

Data analysis table. 1 and 2 shows that the optimal starting solution for the process of extraction purification of fluorotantalic acid is a solution of the composition, g / l: H ₂ SO ₄ - 300; Ta ₂ O ₅ - 150; F ^- - 90. A decrease in the concentration of sulfuric acid below 200 g / l leads to an increase in the content of impurities (primarily niobium) in the finished product — high-purity tantalum oxide; It should also be noted that the degree of extraction of Ta ₂ O ₅ into the organic phase is reduced. With an increase in sulfuric acid content above 300 g / l, the extractability of Nb ₂ O ₅ and its content in tantalum oxide increase, and the amount of expensive sulfuric acid required to prepare the initial solution increases.

An increase in the concentration of F ^- above 100 g / l in the initial solution leads to an increase in the content of Nb ₂ O ₅ in tantalum oxide due to the increasing extractability of Nb ₂ O ₅ , while with the content of F ^- - 80 g / l and less extractability of Ta ₂ About ₅ to the organic phase and the effectiveness of the subsequent washing of the saturated extract is reduced. Also, losses of Ta ₂ O ₅ with raffinate may be observed.

The concentration of Ta ₂ O ₅ equal to 140-160 g / l ensures optimal density and viscosity of the aqueous and organic phases and prevents the possibility of phase inversion in the chambers of the extraction cascade.

Table 3 below presents data on the washing conditions of the saturated extract at the washing stage No. 1. Table 4 presents the results of determining the content of impurities in samples of tantalum oxide obtained under various washing conditions No. 1.

Data analysis table. 3 and 4 shows that the optimal washing solution for the washing stage No. 1 is a solution of the composition H ₂ SO ₄ - 280-300 g / l and the ratio O: B = (20 ÷ 15): 1. With an increase in the concentration of H ₂ SO ₄ to 320, there is no significant decrease in the content of impurities in the finished product — highly pure oxy-de tantalum. With a decrease in the concentration of H ₂ SO ₄ to 250 g / l, an increase in the content of "vulgar" impurities in the finished product is observed.

With a decrease in the O: B ratio to 10: 1, there is no significant increase in the content of "vulgar" impurities in the finished product, while the consumption of expensive sulfuric acid increases. With an increase in the O: B ratio to 25: 1, there is an increase in the content of “vulgar” impurities in the finished product — high-purity tantalum oxide.

Table 5 below presents data on the washing conditions of the saturated extract at the washing stage No. 2. Table 6 presents the results of determining the content of impurities in samples of tantalum oxide obtained under various washing conditions No. 2.

Data analysis table. 5 and 6 shows that the optimal ratio for flushing No. 2 is O: B = (20 ÷ 15): 1. With a decrease in the O: B ratio to 10: 1, there is no significant increase in the content of "vulgar" impurities in the finished product, while the consumption of expensive sulfuric acid increases. With an increase in the O: B ratio to 25: 1, there is an increase in the content of “vulgar” impurities in the finished product — high-purity tantalum oxide.

Table 7 below shows the deposition conditions and the F ^- content in the tantalum hydroxide precipitate, depending on the tantalum oxide content in the solution.

Data analysis table. 7 shows that when the concentration of Ta ₂ O ₅ in the solution for precipitation in the range of 60-80 g / l provides the content of F ^- in the precipitate of tantalum hydroxide at a level of 3.5-4.8%. With an increase in the concentration of Ta ₂ O ₅ in the solution, the content of F ^- in the precipitate of tantalum hydroxide increases to 5.5–5.8%. A decrease in the concentration of Ta ₂ O ₅ in the solution by sedimentation to 40 g / l does not significantly affect the F ^- content of the tantalum hydroxide precipitate and leads to an increase in dilution water consumption and, as a consequence, an increase in the volume of the generated wash water.

The analysis of the prior art by the applicant did not reveal sources of information that disclosed a technical solution characterized by a combination of features or equivalent to all the essential features of the proposed solution, so we can conclude that the latter meets the requirements of “novelty” and “inventive step”.

The claimed invention is illustrated by figures 1-3. In FIG. 1. The flow chart is presented, which is presented as a set of sequential operations at the individual stages of the corresponding process for producing high-purity tantalum oxide, which is a flow diagram of the process.

The whole process of obtaining high-purity tantalum oxide consists of three stages: preparatory, purification extraction and processing of the tantalum reextract to the finished product.

In FIG. 2 schematically shows the equipment on which the first two stages of the process are implemented, and in FIG. 3 equipment of the third stage of the process.

In each block shown in FIG. 1, there is information about the name of the operation and the parameters of each operation, which facilitates the understanding of the description of the operation of the technological scheme, therefore, does not require special explanations. The arrows indicate the direction of subsequent operations and the introduced or reverse flows for the corresponding operation, for example, the dissolution of tantalum hydroxide, including the supply (indicated by arrows) of concentrated sulfuric acid, hydrofluoric acid and water, and the parameters of the end of the process are given in the block itself.

A tantalum-containing solution (tantalum hydroxide) obtained by extraction separation of niobium and tantalum during the processing of columbite concentrate is used as the initial product for the production of high-purity tantalum oxide.

In FIG. 2 shows: reactors R-1 and R-3, designed to precipitate tantalum hydroxide and dissolve it, respectively; F-2 and F-4 nutsche filters designed to filter the tantalum hydroxide precipitate; containers E-5 and E-7 - for collecting and storing the initial solution for treatment extraction; 28 extractors of the mixer-settler type EK-6, which are designed for extraction, washing of the extractant and re-extraction; containers E-8, E-11 for storage and preparation of the extractant, washing solution No. 1 and No. 2, reextraction solution, as well as containers E-17, E-18 for raffinate and re-extract of tantalum. Capacities E-7 - E-11 are respectively connected to the drive of peristaltic pumps N-12-H-16. In FIG. 2 also shows pipe fittings (mainly valves) that are not numbered. Symbol FTI - indicates the flowmeter of the corresponding reagent. The inscriptions shown in FIG. 2, contribute to a better understanding of equipment operation.

In FIG. 3 shows equipment for implementing the third stage of the process for producing high-purity tantalum oxide (the right side of the technological scheme in accordance with Fig. 1).

It includes: R-20 and R-22 reactors equipped with M20 and M22 mixers with PR20 and PR21 drives; Nutsche filters F-21, F-22; tanks for collecting and transporting sludge; a P-24 furnace for drying and a P-26 furnace for calcining tantalum oxide, and a K-25 screen is located between them to screen a certain fraction of tantalum oxide after drying. The TE symbol indicates temperature meters.

The invention is illustrated by the technological scheme (Fig. 1).

The tantalum-containing solution enters the reactor and is mixed in it with aqueous ammonia at a temperature of 40-50 ° C to a pH value of 9.0-9.5.

The reaction mass in the form of pulp enters the next reactor where it is aged for an hour. Then filtered. The precipitate is washed on the filter with water at a ratio of T: W = 1 (1.5-2.0). Wet tantalum hydroxide enters the dissolution reactor, where an initial solution is prepared for purification extraction. This reactor receives the calculated amount of concentrated sulfuric and hydrofluoric acids, as well as water to bring the solution to a specific composition, which is a solution containing the following concentrations of the main components: C _HF = 80-97 g / l, C _H2SO4 = 200-300 g / l, C _Ta2O5 = 140-160 g / l. At this stage, the preparatory stage ends and the initial solution enters countercurrent extraction, which is carried out on 8 mixing-settling extractors with a ratio of O: B = 1.2: 1.

The raffinate is sent for disposal, and the extract is washed in the first stage with sulfuric acid (C _H2SO4 = 250-300 g / l), and in the second stage with deionized water at a ratio of O: B = (20-15): 1 in both washes. From the washed extract, tantalum is extracted with deionized water at a ratio of O: B = 1.5: 1. Saturated Ta ₂ O ₅ reextracting solution (re-extract), having passed nine chambers towards the extractant, is collected in a collection from which it is periodically taken to the operation of deposition of tantalum hydroxide.

The reverse extractant is sent for extraction, the tantalum re-extract is subjected to further processing.

The precipitation of tantalum hydroxide to obtain further oxide is carried out from high-purity fluorotantalum reextracts with a concentration of 120-250 g / l (according to Ta ₂ O ₅ ). Reextracts before precipitation are diluted with deionized water to a concentration of 60-80 g / l according to Ta ₂ About ₅ . The calculated volume of aqueous ammonia is supplied to the precipitation operation.

The end of the hydroxide precipitation process is controlled by the approximate pH value and by the volume of ammonia added. The final pH should be 9.0-9.5. Freshly precipitated tantalum hydroxide is deposited in the precipitation reactor, then the clarified part is decanted, and the condensed part is filtered on a suction filter under vacuum. Next, the precipitate is washed on the same nutsche filter with 1% ammonia solution, then the precipitate is well wrung out on the filter and transferred to the repulpator, where it is pulp for an hour at a ratio of T: G = 1: (5-7).

The wet precipitate of tantalum hydroxide is fed to the drying, which is carried out in two stages, so that the hydroxide does not sinter and does not lose the developed specific surface formed during the deposition. In the first stage, tantalum hydroxide is dried at a temperature of 75-90 ° C, and in the second - 170-190 ° C. The drying time at each stage is 3.0-3.5 hours

Further, tantalum hydroxide is calcined at a temperature of 950-1000 ° C for 6-8 hours. After cooling, tantalum oxide with tantalum scoops after cooling is loaded into a plastic container filled with dried argon.

The following is a specific example of the implementation of the method for producing high-purity tantalum oxide on the equipment shown in FIG. 2 and 3.

The operation of the equipment is as follows.

The tantalum-containing solution for the precipitation of tantalum hydroxide enters the reactor R-1. As the reextract accumulates, the tantalum hydroxide precipitation process is carried out. The initial solution for precipitation is heated with the help of heating elements (T1) to a temperature of 50-55 ° C. For the precipitation process, ammonia water is poured with constant stirring of the pulp by means of a mixer (M1) equipped with a drive (PR1) until the final pulp pH is 9.0-9.5. After this, the pulp is still stirred for 1 hour to mature the precipitate and after that gravity is directed to filtration on a F-2 nutsche filter. After the filtration process is completed, the precipitate is washed with water and pulled on a suction filter.

The filtrate and wash water are sent to the disposal of fluoride-sulfate solutions.

The obtained tantalum hydroxide (for example, in the processing of columbite concentrate) contains up to 99.0-99.7% (in terms of tantalum oxide) of the main substance and can be used as the final product.

However, to obtain high-purity tantalum oxide, it is necessary to perform additional purification of fluorotantalic acid by liquid extraction.

After washing the precipitate, the precipitate is removed from the F-2 suction filter and sent to the P-3 reactor to dissolve the tantalum hydroxide in order to obtain an initial solution for the extraction cascade of fluorotantalic acid purification.

The preparation of the initial solution for purification extraction is carried out in the reactor R-3 as follows. The calculation of the number of reagents for the preparation of the initial solution is based on the following values: concentration of Ta ₂ O ₅ ~ 150 g / l; the concentration of sulfuric acid (brand "o.s.ch") in solution - 300 g / l; concentration F ^- - 90 g / l. For the preparation of the initial solution and working solutions on the extraction cascade, sulfuric acid of the s.h. grade is used, and hydrofluoric acid also of the s.h. grade and deionized water are used.

The calculated amount of water, hydrofluoric acid is successively poured into the R-3 reactor, then the tantalum hydroxide precipitate is fed after filtration. The pulp is mixed for 1 hour by means of a mixer (M3) equipped with a drive (PR3), after which the calculated amount of concentrated sulfuric acid is poured into the solution. After this, the solution is mixed for ~ 15 min., And gravity is sent to the control filtration.

Filtration is carried out on a F-4 nutsche filter. The obtained filtrate is fed into the tank E-5, from where it enters the tank E-7 for storage of the initial solution for the extraction cascade.

The extraction cascade consists of 28 EK-6 mixer-settler extractors with mechanical stirring.

The extraction cascade for the purification of fluorotantalic acid extraction consists of the following circuits with the following number of stages (extractors):

- extraction part: 8 chambers EK-6 / 1-8;

- EK-6/9 - sludge chamber of the organic phase from mechanically captured particles of the aqueous phase;

- washing part 1: 6 chambers - EK-6 / 10-15;

- washing part 2: 2 chambers - EK-6 / 16-17;

- EK-6/18 - a chamber of sedimentation of the organic phase from mechanically captured particles of the aqueous phase;

- EK-6/19 - a chamber of sedimentation of the aqueous phase from mechanically captured particles of the organic phase;

- Tantalum re-extraction: 8 cameras EK-6 / 20-27;

- EK-6/28 - a chamber of sedimentation of the organic phase from mechanically captured particles of the aqueous phase.

The process of extraction purification of tantalum from niobium and vulgar impurities on the extraction cascade EK-6 / 1-28 includes the following operations:

- receiving the initial solution and feeding it to the extraction - capacity E-7;

- reception and supply to the cascade of extractant (100% octanol-1) - capacity E-8;

- preparation and supply to the cascade of washing solution No. 1 - capacity - 9;

- supply to the cascade of washing solution No. 2 - capacity 10;

- supply to the cascade reextracting tantalum solution - capacity 11;

- extraction of tantalum, washing the saturated extract from niobium and other impurities sequentially with washing solution No. 1 and No. 2, tantalum re-extraction.

The following solutions are used for the extraction cascade:

- extractant - 100% octanol-1;

- stock solution for the extraction cascade (capacity E-7;

- washing solution No. 1 - 300 g / l H ₂ SO ₄ ;

- wash solution No. 2 - deionized water;

- reextracting tantalum solution - deionized water.

Thus, consumable containers E-8, E-7, E-9, E-10, E-11 are designed to supply working solutions to the extraction cascade, respectively: reverse extractant, stock solution, wash solution No. 1, wash solution No. 2 reextracting tantalum solution.

The extraction cascade works as follows.

The initial sulfate-fluoride solution containing ~ 140-160 g / l Ta ₂ O ₅ is supplied from the E-7 tank by the N-12 peristaltic pump to the head chamber of the EK-6/8 extraction circuit.

The extractant (100% octanol-1 reverse) from the E-8 tank is fed by a N-13 peristaltic pump countercurrent to the initial solution into the chamber EK-6/1 of the extraction circuit.

The initial solution moving along the extraction circuit of the cascade from the EK-6/8 chamber to the EK-6/1 chamber is depleted in Ta ₂ O ₅ , because Ta ₂ O ₅ passes into the organic phase, and from the last chamber EK-6/1 is drained by gravity into the E-17 container in the form of a raffinate with Ta ₂ O ₅ content less than 0.05 g / l and then sent for disposal. Impurities that were in the initial solution (mainly Nb ₂ O ₅ , Fe, Si, etc.) are removed with the raffinate.

Wash solution No. 1 (sulfuric acid) from the E-9 tank is supplied by an N-14 peristaltic pump countercurrent to the organic phase into the chamber EK-6/15 of the wash circuit No. 1.

Wash solution No. 2 (deionized water) from the E-10 tank is supplied by an N-15 peristaltic pump countercurrent to the organic phase into the chamber EK-6/17 of the wash circuit No. 2.

Saturated Ta ₂ O ₅ extractant enters from the chamber EK-6/9 into the chamber of the washing circuit EK-6/10. In addition to Ta ₂ O ₅ , impurities also pass to the organic phase to various degrees (primarily the vast majority of Nb ₂ O ₅ ), therefore, upon contact with washing solution No. 1 entering the chamber EK-6/15, these impurities are displaced from the organic phase to the aqueous. As a result, at the exit from the washing circuit No. 1, the extractant will be saturated with Ta ₂ O ₅ , and the washing solution No. 1, passing through the washing circuit No. 1 and simultaneously removing a certain amount of Ta ₂ O ₅ , is connected in the chamber EK-6/8 to the initial solution on extraction.

The extractant washed in the washing circuit No. 1 enters from the chamber EK-6/15 into the chamber EK-6/16. The organic phase, in addition to Ta ₂ O ₅ , contains Nb ₂ O ₅ , therefore, upon contact with the washing solution No. 2 entering the chamber EK-6/17, the final displacement of Nb ₂ O ₅ from the organic phase to the aqueous phase occurs, in fact with a solution of fluorotantalic acid . Wash solution No. 2, having passed the washing circuit No. 2, is attached in the chamber EK-6/15 to the washing solution No. 1 and then attached in the chamber EK-6/8 to the initial solution for extraction.

The washed extractant enters from the chamber EK-6/18 into the chamber EK-6/20 of the tantalum re-extraction circuit. In this case, a reextracting solution is supplied to the chamber EK-6/27 with an N-16 peristaltic pump from the E-11 tank in countercurrent to the extractant. Having passed 8 chambers countercurrently, the stripping solution “removes” Ta ₂ O ₅ from the organic phase, and from the last chamber EK-6/19, the stripping circuit is gravity drained into the E-18 tank in the form of a tantalum stripping.

The tantalum re-extract, as it accumulates, is fed to the precipitation of tantalum hydroxide into the P-20 reactor (Fig. 3).

As the reextract accumulates, the tantalum hydroxide precipitation process is carried out. To do this, in the R-20 reactor, the tantalum reextract is diluted to a concentration of 70 g / l (no more than 60-80 g / l is allowed) Ta ₂ O ₅ . In this case, the initial diluted re-extract is preheated to 50-55 ° C using TENs (T20). Next, ammonia water is poured (brand “s.p.h.") with constant stirring with a mixer (M20) with a drive (PR20) until the final pulp pH is 9.0-9.5. After that, the pulp is still stirred for 1 hour to mature the sediment and then gravity is sent to the F-21 nutsche filter for filtration. The filtrate is sent to the disposal of fluoride-sulfate solutions. After completion of the filtration process, the precipitate is washed with 0.5-1% ammonia water and pulled on a suction filter.

After washing and drying the precipitate on the filter, the precipitate is sent to the reactor R-22 for repulping with a solution of 0.5-1% ammonia water. The solution for repulse is heated with the help of a heater (T22) to 50 ° C, the mixing time is 1 hour. Thus, repulpation is carried out from 4 to 6 times. After this, the pulp is sent for filtration to a nutsche filter F-23. After filtration, the filtrate is sent to the disposal of fluoride-sulfate solutions. After completion of the filtration process, the precipitate is washed and pulled on a suction filter. From the F-23 filter, the squeezed sediment is unloaded into a transport container and sent to drying and calcination.

Tantalum hydroxide is dried in two stages in a P-24 furnace so that the hydroxide does not sinter and does not lose the developed specific surface formed during precipitation.

In the first stage of drying I, tantalum hydroxide is dried at a temperature of 80 ° C (soft drying). The wet sediment of washed tantalum hydroxide with a moisture content of 54% is laid out by a tantalum scoop on pallets protected by a layer of fluoroplastic. At the first stage of drying, the main moisture is removed (up to 85%), the pieces of sediment begin to crumble when pressed.

Then, the drying stage of II dried tantalum hydroxide is carried out, which is carried out in a P-24 furnace at 180 ° C. The finally dried precipitate of tantalum hydroxide is sieved on a K-25 screen on a 0.250 mm sieve. The lower fraction (-0.250 mm) is sent for calcination in P-26, and the upper +0.250 mm is crushed by hand and sieved again on a +0.250 mm sieve. The dried and sieved tantalum hydroxide is sent to the calcination operation.

Tantalum hydroxide is calcined at a temperature of 980 ° C for 6-8 hours. The heating of the working space of the calcining furnace is carried out due to electric energy, while the material is subjected to calcination of the final dehydration. The efficiency of obtaining high-purity tantalum oxide is judged by the chemical composition of the impurities in tantalum oxide and the amount of loss during calcination of calcined tantalum oxide.

The calcined tantalum oxide after cooling is loaded into the prepared container and sent to the consumer.

As a result of the implementation of the method for producing high-purity tantalum oxide, a product is obtained having the following impurity composition:

According to the technology of the prototype, the impurity composition in tantalum oxide was as follows.

Thus, the technical result of the invention is achieved by optimizing the parameters of the main operations of the process for producing high-purity tantalum oxide.

Currently, according to the results of research, the preparation of technical documentation for the industrial use of the proposed technical solution is being carried out, in accordance with the economic contract.

Claims (4)

1. A method of producing high-purity tantalum oxide from tantalum-containing solutions, including preparing tantalum hydroxide for purification by sequentially performing the operations of precipitating tantalum hydroxide, holding and filtering the pulp, washing the precipitate, then dissolving the tantalum hydroxide in a mixture of sulfuric and hydrofluoric acids, and purifying the resulting solution with an extractant containing octanol-1, subsequent washing of the saturated extract and stripping, dilution of the obtained tantalum stripping, precipitation of hydroxide tantalum ide, filtering and washing the precipitate, followed by its repulpation, and then drying and calcining tantalum hydroxide to obtain tantalum oxide, characterized in that the dissolution of tantalum hydroxide with a mixture of sulfuric and hydrofluoric acids is carried out to obtain the initial solution for the purification extraction of a composition having the following concentrations of components : tantalum oxide 140-160 g / l; total fluoride ion 80-97 g / l and sulfuric acid 200-300 g / l, only octanol-1 is used as an extractant, washing of the saturated extract is carried out sequentially in two stages. 2. The method according to p. 1, characterized in that the washing of the extract in the first stage is carried out with sulfuric acid with a concentration of 250-300 g / l, and in the second with deionized water at a ratio of O: B = (20 ÷ 15): 1 on both stages. 3. The method according to p. 1, characterized in that the dilution of the tantalum reextract is completed when the tantalum oxide content is in the range of 60-80 g / l. 4. The method according to p. 1, characterized in that the drying of tantalum hydroxide is carried out in two stages at different temperatures at each stage.

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