RU2371492C2 - Extraction method of lithium from spodumene-containing beryllium concentrate - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to processing method of spodumene-containing concentrates of beryllium. Method includes activation of concentrate, its sulfuric acid with receiving of solution of sulphates of beryllium and lithium. After leaching it is implemented chemical processing of sulphate solution with receiving of beryllium hydroxide, primary and secondary crystals of lithium fluoride. Primary crystals of lithium fluoride is treated by 93% sulfuric acid, taken at 1.3÷1.4 ml of acid per 1 g of lithium fluoride, during 1.5+2.0 h at temperature 200÷220°C with receiving of gaseous anhydrous hydrogen fluoride and crystals of lithium fluoride. Received crystals of lithium fluoride are solved at stage of leaching of activated concentrate. Anhydrous hydrogen fluoride is absorbed by water with receiving of hydrofluoric acid, which is used for sedimentation of primary crystals of lithium fluoride.

EFFECT: increasing lithium yield into commercially pure lithium fluoride.

2 cl, 2 dwg, 1 ex

Description

The invention relates to metallurgy, in particular to the processing of spodumene-containing beryl concentrates.

One of the main industrial sources of lithium is the spodumene mineral [LiAl (Si ₂ O ₆ )], the concentrate of which is processed using sulfuric acid technology [Chemistry and technology of rare and trace elements. In 2 t. / Ed. K.A. Bolshakova. - T.2: Technology of rare and trace elements. - M .: Higher school, 1969. - S.12-13, 29-34]. Due to the close association of lithium and beryllium in ores, beryllium flotation concentrates always contain an admixture of lithium [Chemistry and Technology of Rare and Scattered Elements. In 2 t. / Ed. K.A. Bolshakova. - T.2: Technology of rare and trace elements. - M .: Higher school, 1969. - P.16-19, US-116; Moskevich M.M. Mineral resources, production and consumption of beryllium, lithium, niobium and tantalum in capitalist countries. - M .: Nedra, 1966. - S. 22-93, 89, 122-159]. So, the content of spodumene in the flotation concentrate of beryl [Be ₃ Al ₂ (SiO ₃ ) ₆ ] is up to 0.5% of the mass. and more (in terms of lithium) with a beryllium content in the specified concentrate ~ 2% of the mass. Thus, beryl-spodumene concentrates with a high lithium content in them can also be considered as an industrial source of lithium, which is expediently extracted along with the target component (beryllium) during the classical sulfuric acid processing of these concentrates into technical compounds of beryllium [Chemistry and technology of rare and trace elements . In 2 t. / Ed. K.A. Bolshakova. - T.2: Technology of rare and trace elements. - M.: Higher School, 1969. - S.122-126].

A known method of extracting lithium from a beryllium-containing spodumene concentrate with a low beryllium content is 0.13% by mass, with a lithium content of 2.85% by mass. [Samoilov V.I. Hydrometallurgical processing of lithium beryl concentrates with a low beryllium content // Chemical Technology. - M., 2006. - No. 10. - S.32-36], taken as an analogue and including activating the preparation of the concentrate (its melting with soda ash, water granulation of the melt, grinding granules), sulfuric acid leaching of the activated concentrate, separation of the leaching pulp into dump siliceous cake and a solution of lithium, beryllium sulfates, aluminum, sodium and impurities, the subsequent chemical processing of the sulfate solution to produce lithium carbonate, aluminum alum and beryllium-containing cake to clean the solution from impurities. The chemical processing of the sulfate solution by the analogous method includes its evaporation and subsequent cooling with crystallization of aluminum-alum, which are separated from the sulfate solution by filtration. After separation of the alum, the solution is neutralized with sodium hydroxide to pH ~ 7 to remove beryllium, aluminum and iron, which are deposited in the cleaning cake in the form of hydroxides and then filtered off from the sulfate solution. Next, the neutralized solution is additionally treated with sodium hydroxide to precipitate magnesium and beryllium residues in the form of hydroxides at a pH of 12-14, and then treated with a small amount of soda ash to precipitate calcium in the form of carbonate. At the final stage of purification of the sulfate solution, the purification cake deposited from it (a mixture of beryllium, magnesium hydroxides and calcium carbonate) is filtered off. The purified solution is neutralized with sulfuric acid to pH ~ 7, then poorly soluble lithium carbonate is precipitated from it with soda ash, which is filtered off and subjected to filter-repulpative washing with water. Beryllium-containing cakes are processed to produce crude beryllium hydroxide. To this end, cakes are dissolved in a sulfuric acid solution by boiling to obtain a beryllium-containing solution saturated with sulfates of aluminum, iron and magnesium mixed with gypsum. The solution is filtered off from gypsum, then neutralized with sodium hydroxide to pH ~ 1 and cooled, performing crystallization of alumina. Then alum is separated from the sulfate solution by filtration. The filtered solution is neutralized with sodium hydroxide to pH ~ 7, precipitating the crude beryllium hydroxide, which is separated from the magnesium-containing mother liquor by filtration.

The draft beryllium hydroxide obtained by the analogous method is highly contaminated with aluminum and iron hydroxides and therefore contains only ~ 0.5% of the mass. beryllium, which is many times lower than the beryllium content in the crude hydroxide obtained in the hydrometallurgy of beryllium from beryllium concentrate with a beryllium content of ~ 2 wt%. The classical scheme provides for the purification of rough beryllium hydroxide from aluminum with a sodium hydroxide solution and the subsequent washing of the hydroxide from iron with a solution of sulfuric acid [Samoilov VI, Borsuk AN Methods for the joint processing of bertrandite, phenakite and beryl in the hydrometallurgy of beryllium. - Ust-Kamenogorsk: Media - Alliance, 2006. - S.12-17, 25-29] and allows you to get beryllium hydroxide with a beryllium content of at least 18% of the mass. However, the application of the specified technology for purification of crude beryllium hydroxide in the analogue method allows to increase the beryllium content in it from ~ 0.5% by weight. only up to 13% of the mass., i.e. receive low quality hydroxide.

The disadvantage of the analogue method is the low quality of beryllium hydroxide obtained with its use.

The closest set of features to the claimed method is a sulfuric acid method for extracting lithium from spodumene-containing beryllium concentrate with a high content of beryllium - 1.5% of the mass. when the lithium content of 1.7% of the mass. [Samoilov V.I. Processing beryllium lithium ore concentrates with a high content of beryllium // Chemical technology. - M., 2006. - No. 9. - S.27-32], adopted as a prototype and based on the activation of the concentrate by melting the concentrate with soda ash and limestone, water granulation of the melt, grinding granules. Thus activated concentrate (crushed granules) is subjected to sulfuric acid leaching with the extraction of at least 98% of the mass. beryllium and lithium in solution in the form of sulfates. After separation of the obtained sulfate solution from insoluble gypsum and silica cake from the solution, crude beryllium hydroxide is precipitated by the action of sodium hydroxide at pH 7. Then, beryllium hydroxide is separated from the mother liquor. At the stage of beryllium hydroxide precipitation, the direct exit of beryllium from the concentrate to beryllium hydroxide is 80% with the same direct exit of lithium from the concentrate to the mother liquor. Beryllium rough hydroxide is subjected to purification from aluminum impurities with a concentrated sodium hydroxide solution, followed by separation of alkali beryllium hydroxide purified from aluminum from the alkaline mother liquor. Next, alkaline beryllium hydroxide is washed from iron impurities with a solution of sulfuric acid. The beryllium hydroxide purified from iron is separated from the acidic mother liquor and subjected to filter-repulse washing from an impurity of sulfate ion to obtain technical grade beryllium hydroxide.

The lithium-containing mother liquor obtained during the deposition of beryllium crude hydroxide, according to the prototype method, is used for the two-stage deposition of sparingly soluble beryllium fluoride. To this end, ~ 50% of the mass is precipitated from the mother liquor. lithium (from its content in the solution) by the action of the stoichiometrically necessary amount of 40% hydrofluoric acid with the addition of 25% ammonia solution to increase the degree of lithium fluoride precipitation. After separation of the primary lithium fluoride from the solution, the latter is re-treated with hydrofluoric acid to precipitate lithium into secondary lithium fluoride. The primary and secondary lithium fluorides are subjected to filter-repulpation washings with a weakly acidic solution of hydrofluoric acid, then filter-repulpation washings with water. The content of the main substance in the washed primary and secondary lithium fluorides, the mass ratio of which is approximately 1: 1, is respectively ~ 90 and ~ 98.5% of the mass.

Thus, the prototype method is characterized by a low yield of lithium from the concentrate to technically pure lithium fluoride, which is a disadvantage of this method.

The task to be solved by the claimed invention is directed, is the selection of processing conditions for the spodumene-containing beryllium concentrate, which allows increasing the yield of lithium from the concentrate into technically pure lithium fluoride.

The essence of the proposed method for the extraction of lithium from spodumene-containing beryl concentrate is that, in contrast to the known prototype method, which includes activation of the concentrate, sulfuric acid leaching of the activated concentrate to obtain a solution of beryllium and lithium sulfates, chemical processing of a sulfate solution to produce beryllium hydroxide, primary and secondary crystals of lithium fluoride, according to the claimed method, the primary crystals of lithium fluoride are treated with 93% sulfuric acid, taken from the calculation of 1.3 ÷ 1.4 ml of acid per 1 g of lithium fluoride, for 1.5 ÷ 2.0 hours at a temperature of 200 ÷ 220 ° C to obtain gaseous hydrogen fluoride and crystals of lithium sulfate, which are dissolved at the stage of leaching of activated concentrate, and hydrogen fluoride is absorbed by water to produce hydrofluoric acid. In addition, the resulting acid is used to precipitate primary crystals of lithium fluoride.

The solution of the problem and the corresponding technical result are ensured by the fact that in the inventive method, low-grade primary lithium fluoride is not the final, but the circulating product of the technology. In the inventive method, the primary lithium fluoride is sulfatized with sulfuric acid and the obtained lithium sulfate is sent to the sulfuric acid leaching stage of activated spodumene-containing beryllium concentrate. Gaseous hydrogen fluoride formed during the sulfation of primary lithium fluoride is removed from the reaction zone and absorbed in a separate apparatus with water to produce hydrofluoric acid, which is used to precipitate primary lithium fluoride. In the inventive method, the consumption of sulfuric acid for sulfatization of primary lithium fluoride (1.3 ÷ 1.4 ml / g of fluoride), its duration (1.5 ÷ 2.0 hours) and temperature (200 ÷ 220 ° C) are prescribed based on achieving at least 98% conversion of lithium fluoride to lithium sulfate with the formation of gaseous hydrogen fluoride.

An example of the method

The method is carried out on conventional equipment using spodumene-containing beryllium concentrate containing beryllium and lithium, respectively 1.5 and 1.7% by weight, the processing of which is carried out in several cycles. In the first cycle of the implementation of the proposed method, an 11-gram sample of the specified concentrate (in terms of lithium) is processed according to the prototype method to obtain technical beryllium hydroxide, primary and secondary lithium fluorides. Primary lithium fluoride of the first and subsequent cycles is converted to lithium sulfate, for which fluoride is sulfatized with 93% sulfuric acid (in the corresponding cycle) at the rate of 1.3–1.4 ml / g of fluoride, 1.5–2.0 hours at 200 ÷ 220 ° C and absorb the resulting gaseous hydrogen fluoride with water in a separate apparatus with obtaining 40% hydrofluoric acid. In the second, third and subsequent cycles, 11-gram samples of spodumene-containing beryllium concentrate (in terms of lithium) are processed to produce technical beryllium hydroxide, primary and secondary lithium fluorides according to the prototype method, with the difference that sulfate is dissolved in the sulfuric acid leach of the activated concentrate lithium obtained respectively in the first, second and subsequent cycles as a result of sulfatization of primary lithium fluoride precipitated in the first, second and subsequent iklah, and for the primary deposition of lithium fluoride using 40% hydrofluoric acid absorbed in the first, the second and subsequent cycles.

As a result of the circulation of lithium with primary lithium fluoride to the stage of sulfuric acid leaching of the activated concentrate (Fig. 1), there is an increase in the yield of lithium in secondary lithium fluoride from 5 g for lithium (cycle 1) to 10 g for lithium (cycle 10) and in subsequent processing cycles concentrate material balance for lithium in the technological scheme remains unchanged (figure 1). The material balance established in cycle 10 for lithium in the technological scheme is characterized by the following indicators (Fig. 1): of 11 g of concentrate (for lithium) taken for processing, the loss of lithium with cake from the sulfuric acid leach stage of the activated concentrate is 0.5 g, s the mother liquor from the stage of deposition of secondary lithium fluoride (LiF-II in figure 1) - 0.45 g, with technical beryllium hydroxide - 0.05 g, 10 g of lithium are removed from the process with secondary lithium fluoride, and 10 g of lithium continuously turn around with primary flu lithium reed (LiF-I in figure 1). In this case, regardless of the cycle of processing the concentrate, the content of the main substance in the working primary lithium fluoride is 89.5 ÷ 90.0 wt.%, And in the final product - 98.0 ÷ 98.5 wt.%. For comparison with the claimed method, hydrometallurgical processing 11-gram (lithium) weighed portion of the aforementioned spodumene-containing beryllium concentrate according to the prototype method to obtain technical beryllium hydroxide, primary and secondary lithium fluorides (figure 2). When implementing the prototype method, the material balance for lithium in the technological scheme is characterized by the following indicators (FIG. 2): of 11 g of concentrate (for lithium) taken for processing, the loss of lithium with cake from the stage of sulfuric acid leaching of the activated concentrate is 0.5 g, with the mother liquor from the stage of deposition of secondary lithium fluoride (LiF-II in figure 2) - 0.45 g, with technical beryllium hydroxide - 0.05 g, 5 g of lithium are removed from the process with primary and secondary lithium fluorides. The content of the main substance in the primary lithium fluoride is 89.5 ÷ 90.0% by mass, and in the secondary lithium fluoride - 98.0 ÷ 98.5% by mass, so that the final product of the technology (technically pure secondary lithium fluoride) in the prototype method, only 5 g of lithium is obtained, i.e. two times less than in the present method (10 g lithium).

Thus, the claimed method in comparison with the prototype method allows to double the output of lithium from their spodumene-containing beryllium concentrate into technically pure lithium fluoride.

Claims (2)

1. The method of extraction of lithium from spodumene-containing beryllium concentrate, including activation of the concentrate, sulfuric acid leaching of the activated concentrate to obtain a solution of beryllium and lithium sulfates, chemical processing of sulfate solution to obtain beryllium hydroxide, primary and secondary crystals of lithium fluoride, characterized in that the primary lithium crystals are lithium fluoride crystals treated with 93% sulfuric acid, taken at the rate of 1.3-1.4 ml of acid per 1 g of lithium fluoride, for 1.5-2.0 hours at a temperature of 200 ÷ 220 ° C, obtained gaseous hydrogen fluoride and crystals of lithium sulfate, which are dissolved in the leaching stage of the activated concentrate, and hydrogen fluoride is absorbed by water to produce hydrofluoric acid. 2. The method according to claim 1, characterized in that the hydrofluoric acid obtained is used to precipitate primary crystals of lithium fluoride.

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