RU2352659C2 - Extraction method of lithium from mixture of lepidolite and spodumene concentrates - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: lithium extraction method includes batch preparation from the mixture of concentrates and flux, activating batch preparation and water leaching of activated batch. Additionally batch preparation is implemented from the mixture of lepidolite and spodumene concentrates per receiving mass ratio SiO₂/(Na₂O+K₂O+Li₂O) in mixture, equal to 4.5, and flux in the form of lithium carbonate per receiving of mass ratio SiO₂/(Na₂O+K₂O+Li₂O) in batch, equal to 2.3. Activating batch preparation is implemented by means of its melting at the temperature 1350°C, melt granulations by water, granulated melt crushing. Water leaching of activated batch is implemented while sulfuric acid presence.

EFFECT: receiving of relative clean by sodium lithium sulphate solutions, ability of lithium deep extraction from mentioned solutions into lithium carbonate.

3 tbl, 1 ex

Description

The invention relates to metallurgy, in particular to the processing of lepidolite and spodumene concentrates.

Lepidolite (KLi _1,5 Al _1,5 [Si ₃ AlO ₁₀ ] [F, OH] ₂ ) and spodumene (LiAl ₂ [Si ₂ O ₆ ]) are some of the main industrial lithium minerals [Ostroushko Yu.I., Buchihin P.I., Alekseeva V.V. et al. Lithium, its chemistry and technology. M .: Atomizdat, 1960. - S.12-18, 20, 28-31, 90]. In mining and processing industries, lepidolite, spodumene are extracted from ores into the appropriate concentrates.

To extract lithium from its minerals, a large number of known methods can be used: sulfuric acid, sulfate, calcareous and others [Ostroushko Yu.I., Buchihin P.I., Alekseeva V.V. et al. Lithium, its chemistry and technology. M .: Atomizdat, 1960. - P.121-157; Plyushchev V.E., Stepin B.D. Chemistry and technology of compounds of lithium, rubidium and cesium. M .: Chemistry, 1970. - S.226-272]. The main part of these methods for the extraction of lithium from lithium concentrates is designed to process only individual lithium minerals, which significantly narrows the raw material base of lithium industries. The number of known methods for co-processing lithium concentrates is currently limited.

Known sulfuric acid method for the extraction of lithium from spodumene concentrates [Plyushchev V.E., Stepin B.D. Chemistry and technology of compounds of lithium, rubidium and cesium. M .: Chemistry, 1970. S.234-242], adopted for the analogue. In the sulfuric acid process, lithium is selectively extracted by preliminary activating roasting (decryptation) of spodumene (at t = 1100 ° C) and subsequent processing of the activated raw material with sulfuric acid (at t = 250 ÷ 300 ° C). During firing, a change in the crystal lattice of the mineral occurs and it becomes possible to transfer 99 ÷ 100% wt. lithium to water-soluble sulfate by the action of sulfuric acid:

The second reaction product, H ₂ O · Al ₂ O ₃ · 4SiO _2, remains in the insoluble residue during the subsequent aqueous leaching of the sulfated feedstock. Next, the leaching pulp is neutralized with limestone to pH = 6.0–6.5 for purification from aluminum in the form of its hydroxide, which is filtered together with aluminosilicate cake and gypsum from sulfate solution [Ostroushko Yu.I., Buchihin PI, Alekseeva V .AT. et al. Lithium, its chemistry and technology. M .: Atomizdat, 1960. S.144-146]. Loss of water-soluble lithium with an insoluble residue is << 1% wt. from its content in spodumene concentrate. From the ore material to the sulfate solution passes 2 ÷ 4% wt. aluminum [Plyushchev V.E., Stepin B.D. Chemistry and technology of compounds of lithium, rubidium and cesium. M .: Chemistry, 1970. - P.237; Jinheisian L.I. On Sat "Extraction and purification of rare metals." M .: Atomizdat, 1960. - S.99]. The resulting sulfate solution is treated with lime and soda ash to remove magnesium and calcium in the form of magnesium hydroxide and calcium carbonate, which are filtered off from the purified lithium sulfate solution. The purified sulfate solution is evaporated to a lithium sulfate content of 200 g / l, after which it is treated with soda ash while boiling, precipitating lithium carbonate. The latter is filtered off from the stock mother liquor.

The disadvantage of this analogue method is its unsuitability for the joint processing of lepidolite and spodumene concentrates.

A known method of extracting lithium from a mixture of lepidolite and spodumene concentrates [Plyushchev V.E., Stepin B.D. Chemistry and technology of compounds of lithium, rubidium and cesium. M .: Chemistry, 1970. - S.243-249], taken as an analogue and including: 1) mixing spodumene concentrate with limestone (in a mass ratio of 1: 3) and adding to the resulting mixture of lepidolite concentrate in an amount of 10 ÷ 40% wt. .; 2) activating preparation of a mixture composed of concentrates and limestone by sintering it at a temperature of 900 ÷ 950 ° C followed by grinding of cake; 3) water leaching of the activated mixture (ground cake).

As a result of sintering of a mixture of concentrates with alkaline earth flux - limestone, alkaline decomposition of lepidolite and spodumene occurs and water-insoluble lithium aluminate (Li ₂ O · Al ₂ O ₃ ) and calcium silicate (2CaO · SiO ₂ ) are formed. However, due to the excess of limestone supplied to the stage of sintering with concentrates, during the leaching of the crushed cake, water-soluble lithium hydroxide and water-insoluble calcium aluminate are formed:

After separation of the pulp from the stage of leaching the ground cake to a solution of lithium hydroxide and Al-, Ca-, silicon-containing cake and water washing the cake from an alkaline solution, the cake is dumped into a dump. The use in the prototype method of significant amounts of limestone at the stage of its blending with concentrates (115 ÷ 214% of the total mass of concentrates) leads to an extremely poor raw material charge (~ 1% wt. Lithium and less) in lithium content, which leads to high costs the extraction of lithium from this charge, the formation of a large mass of dump cake (washing of which from lithium hydroxide is a difficult task), as a result of which significant amounts of lithium are lost with the cake, so that the extraction of lithium from a mixture of concentrates in solution is it is only 80 ÷ 84% wt.

The disadvantages of the analogue method of processing a mixture of lepidolite and spodumene concentrates are low lithium extraction from a mixture of these concentrates into solution, a large amount of lithium-poor raw material charge and high costs for lithium extraction, the formation of a large amount of dump cake, which requires high processing costs large volumes of cake pulp in the process of washing it from lithium hydroxide and cake burial in special expensive dump fields.

Closest to the claimed invention in terms of similar features is a method for extracting lithium from a mixture of lepidolite and spodumene concentrates, adopted as a prototype [Samoilov V.I., Shipunov N.I. A method for extracting lithium from a mixture of lepidolite and spodumene concentrates: - RF Patent 2299253. - 2007. Bull. No. 14], including the preparation of a mixture from a mixture of concentrates based on the calculation of the mass ratio of SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O) in a mixture of 4.5, and soda ash based on the calculation of the mass ratio of SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O) in a charge of 2.5, activating the preparation of the mixture by melting it at 1350 ° C, granulation of the melt with water, grinding of granular melt and water leaching of the activated mixture in the presence of sulfuric acid. As a result of leaching, a lithium sulfate solution and insoluble silica cake are obtained.

The disadvantage of the prototype method is the high content of sodium sulfate in a solution of lithium sulfate from the stage of sulfuric acid opening of the activated spodumene concentrate, which further reduces the completeness of the deposition of lithium into its carbonate from the sulfate solution by the action of soda ash.

The problem to which the claimed invention is directed, is to develop a method for extracting lithium from a mixture of lepidolite and spodumene concentrates, providing relatively pure sodium solutions of lithium sulfate at the stage of sulfuric acid opening of an activated mixture of lepidolite and spodumene concentrates, which allows deep extraction of lithium from these solutions in lithium carbonate.

The essence of the proposed method for extracting lithium from a mixture of lepidolite and spodumene concentrates is that, in contrast to the known prototype method, which includes preparing a mixture from a mixture of concentrates and flux, activating the preparation of the mixture, water leaching of the activated mixture, according to the claimed invention, the preparation of the mixture is performed from a mixture concentrates based on the mass ratio of SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O) in a mixture of 4.5 and lithium carbonate based on the mass ratio of SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O) in a charge of 2.3, activating the preparation of the charge is carried out by melting it at a temperature of 1350 ° C, granulating it with water, grinding granulated melt, and water leaching of the activated mixture is carried out in the presence of sulfuric acid.

The solution of this problem and the achievement of the corresponding technical results is ensured by the fact that in the known method for extracting lithium from a mixture of lepidolite and spodumene concentrates, including preparing a mixture from a mixture of concentrates and flux, activating the preparation of the mixture and water leaching of the activated mixture, according to the invention, the initial mixture is composed of a mixture of concentrates based on the calculation of the mass ratio of SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O) in a mixture of 4.5 and lithium carbonate based on the calculation of the mass ratio SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O) in a charge of 2.3, activating the preparation of the charge is carried out by melting it at a temperature of 1350 ° C, granulating the melt with water, grinding the granular melt, and water leaching activated the mixture is carried out in the presence of sulfuric acid.

As a result of melting of the alkaline Li-, K-, sodium-containing mixture prepared by the claimed method, and subsequent water granulation of the melt, alkaline decomposition of lepidolite and spodumene occurs with the formation of lithium phases, which are almost completely opened by sulfuric acid. The subsequent interaction of the granulate thus obtained with sulfuric acid ensures the conversion of lithium from the granulate to water-soluble lithium sulfate, due to which, at the stage of sulfuric acid leaching of the granulate, almost complete extraction of lithium from the granulate into the sulfate solution is achieved. In the inventive method, in contrast to the prototype method, high lithium extraction in a sulfate solution is provided at the stage of sulfuric acid leaching of the granulate without contamination of the solution with sodium sulfate, which allows further deep extraction of lithium from these solutions into lithium carbonate.

An example implementation of the method.

The method is carried out on conventional equipment. The chemical composition of the lepidolite and spodumene concentrates used is presented in Table 1.

Table 1
The content of components in lepidolite and spodumene concentrates,% wt. Name of concentrate Li ₂ O K ₂ O Na ₂ O SiO ₂ Lepidolite 4.28 8.19 1.68 58.60 Spodumene 7.92 1.90 1.93 63.15

For the implementation of the proposed method prepare mixtures consisting of lepidolite and spodumene concentrates with a mass ratio

4.5 SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O), to which various amounts of lithium carbonate are added together. The prepared samples of the charge are loaded into graphite crucibles and melted at a temperature of 1350 ° C for 30 minutes. The melt is poured into cold water (water temperature ~ 15 ° C), the resulting granules are crushed. The crushed granulate is pulp in water at a ratio of T: W = 1: 0.8. 93% sulfuric acid is added to the resulting pulp at the rate of 0.7 ml per 1 g of melt. The resulting sulfates are leached with water at T: W = 1: 3 (according to the initial granulate), at a temperature of 95 ° C for 40 minutes. The resulting sulfate pulp is filtered, the filtered cake is subjected to 2-fold filtering with water, acidified with sulfuric acid to a concentration of acid in water of 10 g / l, at T: W = 1: 6 (according to the initial granulate) and a temperature of 90 ° C for 15 minutes . The residual lithium content in the cake determines the completeness of the extraction of lithium from the concentrate into the solution.

Table 2 shows the comparative indicators of the process of extracting lithium from mixtures of lithium concentrates according to the claimed method and the prototype method (obtaining a solution of lithium sulfate from a mixture of concentrates) (symbols used in table 2: LC - lepidolite concentrate, SC - spodumene concentrate) .

table 2 Example No. Implementation Method The mass ratio of SC / LC in their mixture Flux consumption for melting a mixture of concentrates,% wt. to a mixture of concentrates The mass ratio of SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O) in the mixture The Li content in the dump cake, mg The extraction of Li from the concentrate in a sulfate solution (cake),% wt. one The inventive method 1,0 / 2,5 0 4,5 2 80.0 2 1,0 / 2,5 16,2 3.0 0.7 93.0 3 1,0 / 2,5 30,2 2,3 0.1 99.0 four 1,0 / 2,5 52,5 1.7 0.1 99.0 5 Prototype method 1.0 / 1.8 18.0 2.5 0.1 99.0

Note. The initial charge of lithium with a charge in examples 1-5 was 10 g each. The sodium content in sulfate solutions from the stage of sulfuric acid opening of the granules is: in examples 1-4 - 4 ÷ 6 g / l (due to the sodium impurity in the initial mixture of concentrates ), in example 5 - 44 ÷ 47 g / l.

Table 3 shows the comparative indicators of the processing of a mixture of concentrates according to the claimed method and the prototype method (deposition of lithium carbonate from sulfate solutions).

Table 3 Example No. in Table 2 Implementation Method The Li content in the mother liquor after deposition of Li ₂ CO ₃ , g Extraction of Li from a sulfate solution in Li ₂ CO ₃ (according to the mother liquor),% wt. The extraction of Li from the concentrate in Li ₂ CO ₃ ,% wt. 3 The inventive method 1.25 75.0 74,2 5 Prototype method 2.5 50,0 49.5

The initial charge of lithium with a sulfate solution for the deposition of lithium carbonate was 5 g.

From the data presented in table 2, it follows that when implementing the proposed method (example 3), the extraction of lithium is 99% wt. Moreover, in this example, a mixture of lepidolite and spodumene concentrates was calculated to obtain a mass ratio of SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O) in the specified mixture equal to 4.5, and lithium carbonate was added to this mixture of concentrates from calculating the mass ratio of SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O) in the mixture, equal to 2.3. An increase in the addition of flux to the charge (example 4, table 2) does not affect the extraction of lithium and is not economically feasible due to the increase in the consumption of flux, energy consumption for smelting the mixture, consumption of sulfuric acid to neutralize the granulate. With insufficient addition of alkaline flux to the mixture of concentrates (examples 1 and 2, table 2), the extraction of lithium in the sulfate solution is significantly reduced.

In addition, the claimed method (see note to table 2) allows to obtain a sulfate solution with a low sodium content (4 ÷ 6 g / l), while the sulfate solution obtained by the prototype method is highly contaminated with sodium (44 ÷ 47 g / k), which makes it practically impossible to further extract lithium from it in the form of carbonate. As follows from the data of table 3, the inventive method allows to extract lithium from a sulfate solution in lithium carbonate at 75.0% wt. (example 3), and in the prototype method, the specified lithium recovery is only 50.0% wt. (example 5).

Thus, the direct extraction of lithium from a mixture of concentrates in lithium carbonate, calculated according to the tables 2 and 3, is for the prototype method and the proposed method, respectively, 49.5% wt. (0.99 · 0.50 · 100 = 49.5) and 74.2% wt. (0.99 · 0.75 · 100 = 74.2). A higher extraction of lithium from raw materials into lithium carbonate in the inventive method compared to the prototype method is provided by replacing sodium carbonate with lithium carbonate during melting of the raw material, which allows to obtain more pure sodium sulfate solutions at the stage of sulfuric acid opening of the melt.

Claims (1)

A method of extracting lithium from a mixture of lepidolite and spodumene concentrates, comprising preparing a mixture from a mixture of concentrates and flux, activating the preparation of a mixture, water leaching of an activated mixture, characterized in that the preparation of the mixture is performed from a mixture of lepidolite and spodumene concentrates based on the SiO ₂ / ( Na ₂ O + K ₂ O + Li ₂ O) in a mixture of 4.5 and flux in the form of lithium carbonate in the calculation of the mass ratio of SiO ₂ / (Na ₂ O + K ₂ O + Li ₂ O) in the mixture, equal to 2.3, activating the preparation of the mixture carried out by melting it at a temperature of 1350 ° C, granulating the melt with water, grinding granular melt, and the aqueous leaching of the activated charge is carried out in the presence of sulfuric acid.