RU2245305C1 - Method for extractive separation of tantalum and niobium from hydrofluoride-sulfate acidic solutions - Google Patents

Abstract

FIELD: rare and dispersed element metallurgy, in particular extractive separation of tantalum and niobium.

SUBSTANCE: claimed method includes extractive separation tantalum from niobium with organic extractant. separation is carried out by using mixture of 70-85 vol % of tributyl phosphate and 30-15 vol % of aliphatic C1-C7-alkohol as organic extractant. Tantalum is transferred into organic phase, and niobium - into aqueous one. Then organic and aqueous is separated.

EFFECT: increased tantalum recovery degree and improved tantalum and niobium separation degree.

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Description

The invention relates to the field of metallurgy of rare and trace elements. It can be used for extraction extraction and concentration of tantalum from acidic fluoride-sulfate solutions, complex in chemical composition. These solutions can be obtained, for example, by leaching tantalite and columbite concentrates with solutions of hydrofluoric and sulfuric acids. Currently, an extraction method is used to extract tantalum from such technological solutions, which allows concentration of tantalum and its purification from impurities, including niobium.

A known method of extraction extraction and separation of tantalum and niobium from acidic solutions by extraction with methyl isobutyl ketone (MIBK) [Zelikman AN, Korshunov BG Metallurgy of rare metals. - M .: Metallgia, 1991. - 432 p.]. The disadvantage of this method is the relatively high solubility of the extractant in the aqueous phase and the water in it, as well as its high volatility. This leads to significant losses of expensive organic reagent and requires special measures to reduce these losses and purify aqueous solutions from the presence of organic substances. All this causes a significant increase in the cost of the process.

A known method of extracting tantalum and separating it from niobium and acid fluoride-sulfate solutions by extraction with aliphatic alcohols C ₇ -C ₉ [Glubokov Yu.M., Travkin VF, Ilyin EG et al. / Non-ferrous metallurgy. 2001. No. 10, pp. 23-27]. The process includes three stages: extraction of metals, washing of the organic phase with water at a ratio of volumes of organic and aqueous phases O: B≥ 20: 1, re-extraction of tantalum with water. The disadvantage of this method is the need for the extraction process at high acidity of the aqueous phase, a low degree of tantalum extraction and a low separation coefficient of tantalum and niobium.

Closest to the proposed method in terms of technical nature and the achieved result is a method for the extraction separation of tantalum and niobium using tributyl phosphate as an extractant [Korovin SS, Drobot DV, Fedorov PI Rare and scattered elements. Chemistry and technology. - M .: MISIS, 1999. - 464 p.]. The extraction is carried out from strongly acidic solutions (at least 8 M H ₂ SO ₄ ) in the presence of a large excess of fluoride ions. The separation coefficients do not exceed 100. A comparison of all the extraction parameters of the prototype and the proposed method is given in table 1-5. The disadvantages of this method are: high acidity of the aqueous phase (the concentration of free sulfuric acid is at least 300 g / l), a relatively low degree of extraction and separation of tantalum and niobium, a low rate of separation of the organic and aqueous phases and the metal extraction process itself. This leads to the need to use a large number of extraction apparatus and their sizes and, therefore, to increase costs when using the extraction process.

The technical essence of the present invention is to increase the degree of extraction of tantalum into the organic phase, increase the degree of separation of tantalum and niobium, reduce the acidity of the aqueous phase during extraction, as well as increase the rate of metal extraction and the rate of delamination of the organic and aqueous phases.

This goal is achieved by the fact that in the known method of extraction separation of tantalum and niobium, including the extraction of tantalum with tributyl phosphate, extraction is carried out with an organic extractant, which is a mixture of tributyl phosphate (70-85% vol.) And aliphatic alcohol C ₇ -C ₉ (30-15% about.).

The essence of the proposed method is illustrated by the following examples.

Example 1. Tantalum and niobium are extracted from a fluoride-sulfate aqueous solution containing 31.0 g / l of tantalum and 2.3 g / l of niobium. The content of fluoride ions does not exceed the total metal content in a stoichiometric ratio of not more than 7: 1; sulfuric acid content varies between 100-400 g / l. A mixture of 80% vol. Is used as the organic phase. TBP and 20% vol. octanol-1, as well as 100% vol. TBP (prototype). Extraction is carried out at a volume ratio of organic and aqueous phases of O: B = 1: 1 and a temperature of 21 ° C. The contact time of the phases is 3 minutes. Table 1 shows data on the effect of the acidity of the aqueous phase on the extraction of tantalum and niobium in the organic phase.

Table 1
The effect of the acidity of the aqueous phase on the extraction of tantalum and niobium. The concentration of H ₂ SO ₄ , g / l Metal distribution coefficient 100% TBP 80% TBP + 20% octanol-1 D _Ta D _nb D _ta D _nb 100 3,1 0.30 3.6 0.23 150 3.6 0.33 4.2 0.24 200 8.2 0.44 13.0 0.26 250 10,4 0.51 800 0.30 300 90 0.89 870 0.37 350 240 1,6 > 1000 0.46 400 510 3.3 > 1000 0.52

From the data given in Table 1, it can be seen that when using a mixture of TBP and aliphatic alcohol C ₇ -C ₉ as an extractant, the extraction of metals is much higher than for TBP, with a sulfuric acid content of more than 250 g / l.

Example 2. The extraction of tantalum and niobium from a fluoride-sulfate aqueous solution containing 31.0 g / l of tantalum and 2.3 g / l of niobium. The concentration of free sulfuric acid is 300 g / l, and the fluoride ion associated with metals is 23.2 g / l, which corresponds to a metal: fluoride-ion stoichiometric ratio of 1: 7. The organic phase is a mixture of tributyl phosphate and octanol-1 with different ratios. Extraction is carried out at a ratio of organic and aqueous phases O: B = 1: 1 and a temperature of 20.6 ° C. The contact time of the phases is 5 minutes. Table 2 shows data on the effect of the composition of the organic phase on the separation of tantalum and niobium.

table 2
The effect of the composition of the organic phase on the extraction and separation of tantalum and niobium The composition of the organic phase,% vol. Metal distribution coefficient Creep factor, β Ta / Nb Octanol-1 TBF D _Ta D _nb 100 0 7.4 0.18 42 95 5 12.0 0.18 66 90 10 16,0 0.18 91 80 twenty 21.0 0.22 95 60 40 61.5 0.39 157 40 60 92 0.46 198 thirty 70 610 0.92 660 twenty 80 870 0.97 890 fifteen 85 820 1,2 680 10 90 98 1,1 87 0 100 90 1,0 90

The above results indicate that a high extraction of tantalum and its separation from niobium is achieved in the concentration range of TBP and aliphatic alcohol: 70-85% vol. TBP and 30-15% vol. alcohol.

Example 3. The process of extraction separation of tantalum and niobium is carried out at different phase contact times. The composition of the organic phase is shown in Example 2. Extraction is carried out at a ratio of organic and aqueous phases of O: B = 1: 1 and a temperature of 20.9 ° C. Table 3 shows the data on the influence of the phase contact time on the extraction of tantalum and niobium.

Table 3
Effect of phase contact time on tantalum and niobium extraction Phase contact time, min Metal distribution coefficient 100% TBP 80% TBP + 20% octanol-1 D _ta D _nb D _ta D _nb 1 12 0.22 93 0.32 2 28 0.30 320 0.53 3 41 0.43 810 0.96 4 52 0.79 850 0.95 5 90 1,0 870 0.97 10 98 1,1 880 0.96 twenty 101 1,0 860 1,0 thirty 99 1,1 900 0.99 60 106 1,1 880 0.98

From the data given in table 3 it follows that during extraction with an organic solvent containing a mixture of 80% vol. TBP and 20% vol. octanol-1, to achieve the distribution coefficients of tantalum and niobium close to equilibrium, 3-4 minutes of phase contact are sufficient, while when using 100%, at least 10 minutes are necessary.

Example 4. The extraction of tantalum and niobium is carried out in accordance with the conditions of example 3. In the case of using as an organic phase a solution of 80% vol. TBP and 20% vol. octanol-1 maximum productivity by the sum of the flows of the organic and aqueous phases reaches 5.3 m ³ / m ² · hour. At the same time, when undiluted TBP is used as the organic phase, the maximum productivity by the sum of the phases is 2.1 m ³ / m ² · h. Thus, the use of a mixture of TBP and alcohol as an extractant makes it possible to increase the rate of phase separation, and, therefore, the productivity of extraction equipment.

Example 5. The process of extraction separation of tantalum and niobium is carried out in accordance with the conditions of example 1. As the organic phase, tributyl phosphate (80% vol.) With the addition of 20% vol. aliphatic alcohols (ROH, where R: C ₆ is hexanol, C ₇ is heptanol, C ₈ is octanol-2, C ₉ is nonanol and C ₁₀ is decanol). Table 4 shows data on the influence of the nature of alcohol on the separation efficiency of tantalum and niobium.

Table 4
The effect of the nature of alcohol on the separation efficiency of tantalum and niobium The concentration of H ₂ SO ₄ , g / l The separation coefficient, β _{Ta / Nb} Hexanol Heptanol Octanol-2 Nonanol Decanol 100 3 eleven 12 thirteen 4 150 5 fifteen 14 fifteen 7 200 eleven 17 eighteen 17 10 250 100 850 860 850 96 300 130 890 900 910 120 350 107 870 880 870 110 400 83 650 700 710 84

From the data given in table 4, it is seen that the most effective use as an additive is alcohols with a radical length in the aliphatic chain of C ₇ -C ₉ . In addition, the use of hexanol (R - C ₆ ) leads to its large losses due to the sufficiently high solubility in the aqueous phase. When using decanol (R - C ₁₀ ), a sharp deterioration in the process of delamination of the organic and aqueous phases is observed.

Example 6. From a fluoride-sulfate aqueous solution, separation is carried out with an extractant containing 80% vol. TBP and 20% vol. octanol-1. The composition of the initial aqueous phase (g / l): tantalum - 30.5; niobium - 7.8; sulfuric acid - 253; fluoride ion - 39. Extraction is carried out with a volume ratio of organic and aqueous phases O: B = 1.2: 1. Washing the equilibrium organic phase and stripping is carried out with water at different ratios of organic and aqueous phases. Wash water is combined with the initial aqueous phase and sent for extraction. The process conditions and the obtained experimental melon are given in table 5.

Table 5
The main indicators of the process of separation of tantalum and niobium Indicator The proposed method Prototype The composition of the extractant 80% vol. TBP and 20% octanol-1 100% vol. TBF Extraction Number of countercurrent stages 4 4 The ratio of the volume of phases O: In 1.2: 1 1.2: 1 The content of tantalum in the raffinate, g / l 0.004 0.26 The extraction of tantalum in the extract,% 99.9 99.1 Flushing The composition of the wash solution Water 50 g / l H ₂ SO ₄ Number of countercurrent stages 3 3 The ratio of the volume of phases O: In 30: 1 30: 1 Reextraction The composition of the stripping solution Water 10% NH ₄ OH Number of countercurrent stages 4 4 The ratio of the volume of phases O: In 5: 1 5: 1 Tantalum content in reextract 152 141 The extraction of tantalum in re-extract,% 99.5 92.5 The separation coefficient, β _{Ta / Nb} 1790 150

The above example shows that the total extraction of tantalum, as well as the separation coefficient of tantalum and niobium in the claimed method is higher than in the prototype method. At the same time, washing the organic phase and stripping can be carried out with water, while in the case of using undiluted TBP as the organic phase (prototype), aqueous solutions of reagents (sulfuric acid, ammonium fluoride) are used to intensify the process of phase separation.

Thus, the use of the proposed method allows to increase the extraction of tantalum, as well as the degree of extraction separation of tantalum and niobium. In addition, the proposed process allows extraction from less acidic solutions (200-250 g / l sulfuric acid), which leads to lower costs for reagents. Finally, the efficiency of the extraction process is increased by reducing the cost of extraction equipment due to a decrease in the phase contact time and an increase in the rate of delamination of the aqueous and organic phases, which is 5.3 m ³ / m ² · hour for the proposed method and 2.1 m ³ / m ² · Hour for the prototype.

Claims (1)

The method of extraction separation of tantalum and niobium from acid fluoride-sulfate solutions, characterized in that the extraction is carried out with a mixture of tributyl phosphate and aliphatic alcohol C ₇ -C ₉ at a ratio of components, vol.%: Tributyl Phosphate 70-85 Alcohol C ₇ -C ₉ 30-15