RU2234367C1 - Method of production of a sorbent for extraction of lithium from saline solutions - Google Patents

Abstract

FIELD: production of a sorbent for extraction of lithium from saline solutions.

SUBSTANCE: the invention is dealt with the methods of production of inorganic sorbents based on aluminum hydroxide and selectively extracting lithium from natural chloride saline solutions and the process saline solutions containing lithium. The method provides for a direct interaction of lithium carbonate with aluminum chloride at the presence of water at L : S = 4.0 - 4.6 with production of LiCl2Al(OH)₃mH₂O sediment and a concentrated solution of LiCl. Then the sediment is filtered off and exposed to water desorption up to achievement of lithium exchange capacity of 6.0-8.0 mg / g (in terms of a dry sorbent). The concentrated solution of LiCl is treated with soda solution, settling lithium carbonate, that is returned in the operation of interaction with aluminum chloride. The technical result of the invention is simplification of the method of the sorbent synthesis and development of a technologically closed cycle of the sorbent production.

EFFECT: simplification of the method of the sorbent synthesis and development of a technologically closed cycle of the sorbent production.

3 cl, 1 dwg, 2 tbl, 7 ex

Description

The invention relates to chemical materials science, in particular to methods for producing inorganic sorbents based on aluminum hydroxide, selectively extracting lithium from natural brines and technological chloride salt solutions containing lithium.

State of the art

A known method of producing a selective sorbent for the extraction of lithium from brines by electrochemical dissolution of aluminum metal in a concentrated solution of lithium chloride with the formation of a compound of the composition LiCl · 2Al (OH) ₃ · mH ₂ O having a sorption capacity of 6-7.5 mg of lithium per 1 g of dry substances [1].

The disadvantages of the method are the high energy consumption for the process and the need to use high-purity metallic aluminum.

A known method of producing microcrystalline hydrated selective sorbent LiCl · 2Al (OH) ₃ suspended in the pores of a macroporous anion-exchange resin [2]. The method includes: a) introducing freshly precipitated aluminum hydroxide into the pores of the resin, for which the resin is soaked in a saturated AlCl ₃ solution, and then treated with aqueous ammonia; b) washing the resin to remove excess reagents; c) treating the resin with Al (OH) ₃ precipitate with a LiOH solution at elevated temperature to transfer the precipitate to the hydrated compound LiOH · 2Al (OH) ₃ ; g) processing the resin with the intermediate compound LiOH · 2Al (OH) ₃ with a solution of hydrochloric acid or lithium chloride to transfer the precipitate to the compound LiCl · 2Al (OH) ₃ · mH ₂ O, which is the sorbent.

The disadvantages of this method are the complexity and multi-stage process, the need for mandatory conversion of aluminum chloride to hydroxide, which is carried out all subsequent operations, as well as the use of expensive anion-exchange resin as a carrier of the sorbent in order to improve its filtering properties.

A known method of obtaining a hydrated composite material based on Al (OH) ₃ composition LiCl / Al (OH) ₃ , designed to extract lithium from brines [3]. The method includes reacting commercial crystalline Al (OH) ₃ (at least + 140 mesh size) in the form of gibbsite, bayerite, or norstrandite with lithium hydroxide in the presence of water at W: T = 0.69 to form a LiOH / Al (OH) composite ) ₃ , in which the molar fraction of LiOH is from 0.2 to 0.33. At 25 ° C, this process takes from 24 to 48 hours. The resulting composite is further treated with a 20% hydrochloric acid solution to convert it to the sorption form LiCl / Al (OH) ₃ . This operation requires caution because LiOH / Al (OH) _{3 is} soluble in hydrochloric acid. The operation is carried out at a pH of 5-7 (preferably in the presence of NaHCO ₃ as a buffer), by slowly adding acid while stirring the pulp for 1-2 hours. Thus obtained sorbent is separated from the mother liquor containing ~ 10 g / l LiCl, and then prepared for the sorption process. For this, it is initially brought into contact with water to remove the necessary amount of LiCl (desorption step). In the subsequent processing of such a sorbent with a lithium-containing brine, the removed amount of LiCl is restored in its structure (sorption stage). Sorption and desorption of lithium is carried out at a temperature of 80 ° C.

According to the technical nature and the achieved result, this method is the closest to the claimed one and is selected as a prototype.

The disadvantages of the method are the two-stage and duration of the sorbent synthesis process, as well as the need to use a concentrated hydrochloric acid solution and the presence of wastewater containing lithium chloride associated with this process. In addition, the sorbent obtained in this way can remove lithium from brines only at a temperature of 80 ° C and higher, due to its crystalline, ordered structure.

SUMMARY OF THE INVENTION

The technical result of the claimed invention is to simplify the method of synthesis of the sorbent and the creation of a closed loop industrial technology for the production of sorbent.

The technical result is achieved by the direct interaction of lithium carbonate with a solution of AlCl ₃ or with its crystalline hexahydrate (AlCl ₃ · 6H ₂ O) in the presence of water at a ratio of liquid and solid phases equal to 4.0-4.6 (in terms of sum of anhydrous reagents), and the concentrated lithium chloride solution obtained during the interaction is treated with a soda solution to precipitate lithium carbonate and return it to the interaction.

The interaction in the system proceeds according to the reaction:

according to which, along with the target product, a concentrated lithium chloride solution is formed with a concentration of 100 - 110 g / l LiCl, depending on the state of aggregation of aluminum chloride and the amount of water introduced into the system. The formation of a background solution of lithium chloride with such a high concentration prevents the formation of Li ₂ CO ₃ · 4Al (OH) ₃ · mH ₂ O, which is not adsorbed with respect to lithium ions in this system.

The precipitate of the compound LiCl · 2Al (OH) ₃ · mH ₂ O obtained by reaction (1) is filtered off and subjected to water treatment to desorb a certain amount of LiCl from it, i.e. provide an indicator of exchange capacity for lithium 6.0-8.0 mg per 1 g of dry matter (or ~ 2.0-2.5 mg of lithium per 1 g of wet product with its moisture content of ~ 70%). Thus prepared sorbent is able to extract lithium from chloride highly mineralized brines at a pH of less than 7.

The mother liquor, which is a pure concentrated lithium chloride solution, is sent for recycling, separating "secondary" lithium carbonate from it by treatment with a soda solution under heating (t ~ 90 ° C). This technique is quite fully described in the literature [4]. The interaction is described by the following reaction:

or in accordance with the amount of LiCl formed by reaction (1), reaction (2) can be represented as follows:

It follows that 2.5 moles of Li ₂ CO ₃ out of 3 moles spent by reaction (1) can be returned to the head of the process, thereby substantially increasing the efficiency of lithium carbonate, resulting in 1 mole of sorbent for reaction (1) will require only 0.5 mol of lithium carbonate.

The interaction according to reaction (1) proceeds at room temperature, but the process proceeds faster at elevated temperatures (up to 40-50 ° C). The resulting sorbent has a defective structure (Fig. 1), which allows sorption of lithium from brines at ambient temperature.

Lithium carbonate can be used only in the solid state due to its low solubility in water (1.26 wt.% At 25 ° C). Aluminum chloride can be used in the form of an aqueous solution or in the form of crystalline hydrate - AlCl ₃ · 6H ₂ O. In the latter case, the hardware design of the sorbent synthesis process is simplified, since there is no need for the preliminary preparation of an AlCl ₃ solution. The upper limit of the amount of added water to the total amount of solid reagents (W: T = 4.6) is limited by the expediency of achieving in the mother liquor a concentration of lithium chloride of at least ~ 100 g / l (Fig. 2) in order to more fully subsequently precipitate lithium carbonate from it at organization of a closed cycle to return Li ₂ CO ₃ to the process. The lower limit of the ratio of liquid and solid phases (L: T = 4.0) is due to the peculiarity of this process, since at lower values of L: T there is a strong thickening of the pulp, it loses fluidity, there are difficulties with its quantitative transfer to the filter and washing the precipitate, although the sorption properties of the sorbent obtained under these conditions do not deteriorate.

Thus, the main distinguishing features of the claimed invention are:

1) the use of lithium carbonate for the synthesis of the sorbent LiCl · 2Al (OH) ₃ · mH ₂ O;

2) increasing the efficiency of lithium carbonate by reducing its consumption due to the return to the head of the process of "secondary" Li ₂ CO ₃ deposited from the mother liquor with soda;

3) the use of aluminum chloride as an aluminum-containing compound as a simultaneous supplier of aluminum and chlorine ions necessary for the formation of the LiCl · 2Al (OH) ₃ · mH ₂ O phase;

4) elimination of the need to use concentrated hydrochloric acid;

5) the implementation of the synthesis of the sorbent in one stage;

6) a decrease in the duration of sorbent synthesis.

These features in combination can significantly simplify the process (Fig. 3) and open up the possibility of creating a waste-free technological process for producing the sorbent, since the lithium chloride solution formed by reaction (1) can be used to precipitate lithium carbonate from it by reaction (3), which returns to the head of the process. The sodium chloride solution formed by reaction (3) can be converted into sodium chloride by evaporation and sold as a commercial product.

The claimed invention is novel, since for the first time a direct interaction of Li ₂ CO ₃ and AlCl _{3 is} proposed for the synthesis of the sorbent LiCl 2Al (OH) ₃ · mH ₂ O, which is not available in available sources of information.

List of drawings and tables

The drawing shows a typical diffractogram of the obtained sorbent, which, in accordance with the data of the ASTM card index (card No. 31-700) and chemical analysis data, corresponds to the compound LiCl · 2Al (OH) ₃ · mH ₂ O.

Table 1 shows the dependence of the composition of sediments and mother liquors on time, temperature, and W: T during the interaction of Li ₂ CO ₃ with AlCl ₃ taken in the form of a solution or crystalline hydrate, as well as the conversion of a LiCl solution to Li ₂ CO ₃ .

Table 2 shows comparative data on the claimed method and the prototype method.

Information confirming the possibility of carrying out the invention is set forth in the examples.

Example 1

To 11.05 g of Li ₂ CO _3, 77 ml of water are added and 34.7 ml of AlCl ₃ solution containing 383 g / l AlCl ₃ (L: T = 4.0) is added with stirring. The synthesis is carried out in a water bath at a temperature of 40 ° C for 1.5 hours. The precipitate is filtered off, washed twice, pulping in water at W: T = 1 with intermediate filtration, and dried in an oven for 4 hours at a temperature of 60 ° C. The compositions of the dried precipitate and mother liquor are shown in table 1 (experiment No. 1).

To determine the sorption capacity of the sorbent, a sample of 8 g is treated with distilled water under heating and W: T ~ 50 to remove ~ 35% lithium chloride bound to Al (OH) ₃ in the structure of the compound LiCl · 2Al (OH) ₃ · mH ₂ O. Thus 6.6 mg of lithium was calculated per 1 g of dry material, which is recorded by analysis of the aqueous extract of lithium using a spectrophotometer. The full static exchange capacity of the sorbent is set on natural chloride brine of the following composition (g / l): LiCl - 5.0; KCl - 2.0; NaCl - 3.7; MgCl ₂ 427.0; CaCl ₂ - 12.0 (total salt ~ 450 g / l); pH 5.30. The sorption capacity of the sorbent was 7.0 mg / g.

Example 2

The same as in example 1, but W: T in the synthesis was 4.1 (added 79 ml of H ₂ O). The composition of the dry sediment is shown in table 1 (experiment No. 2). The total static exchange capacity was 6.0 mg / g. In this example, we used natural chloride brine with a content (g / l): CaCl ₂ - 325.0; MgCl ₂ - 113.5; NaCl - 12.7; KCl - 5.3; LiCl - 2.0; the amount of salts 460 g / l; pH is 4.6.

Example 3

The same as in example 2, but the interaction temperature was 30 ° C. The composition of the dry sediment is shown in table 1 (experiment No. 3). The total static exchange capacity of the sorbent was 6.5 mg / g.

Example 4

410 ml of water are added to 57.1 g of Li ₂ CO ₃ and 173.6 ml of AlCl ₃ solution with a concentration of 383 g / l AlCl ₃ is added with stirring (W: T = 4.2). The synthesis is carried out at a temperature of 40 ° C for 1.5 hours. The precipitate is filtered off, washed and dried in an oven. The composition of the dry sediment is shown in table 1 (experiment No. 4). A portion of the dried sorbent 20 g is treated with distilled water at W: T ~ 50 to remove ~ 35% of structurally bound lithium chloride, which amounted to 8.2 mg / g. After contact with a brine of the same composition as in Example 1, the total exchange capacity of the sorbent was 8.0 mg / g.

Example 5 (the conversion of a solution of LiCl in Li ₂ CO ₃ with the subsequent receipt of sorbent from it).

a) Conversion of a solution of LiCl in Li ₂ CO ₃ . In 330 ml of mother liquor with a concentration of 106.2 g / l LiCl formed in experiment 4 (example 4), heated to a temperature of ~ 90 ° C, 146 ml of a soda solution with a concentration of 300 g / l, also heated to the indicated temperature, are added. The pulp is stirred for 15 minutes and the precipitate formed is filtered off. Received 39.3 g of precipitate Li ₂ CO ₃ with a moisture content of 30%. The composition of the dry sediment is given in table 1 (experiment 5, a).

b) Synthesis of the sorbent from the precipitate Li ₂ CO ₃ obtained according to paragraph 5, a.

207 ml of water are added to the precipitate of the “secondary” Li ₂ CO ₃ obtained according to claim 5, а, heated to 40 ° С and 86 ml of AlCl ₃ solution are added with stirring (W: T = 4.5 in terms of dry reagents ) The resulting sorbent precipitate is filtered off, washed and dried in an oven. The composition of the dry sediment is shown in table 1 (experiment No. 5, b). A portion of the dried sorbent 15 g is treated with distilled water until ~ 7.0 mg of lithium per gram of dry sorbent is removed. After contact with a brine of the same composition as in Example 1, the total exchange capacity was 7.0 mg / g.

Example 6

The same as in example 1, but W: T was 4.6 (added 90 ml of H ₂ O) and the synthesis temperature was 30 ° C (table 1, experiment No. 6). At the end of the interaction, the precipitate is washed and desorbed lithium from the wet cake in an amount of about 2.3 mg per 1 g of wet cake (at a moisture content of ~ 70%), which corresponds to 7.6 mg / g in terms of the dried sorbent. The composition of the dried sorbent is given in table 1 (experiment No. 6). The total exchange capacity after contact with brine was 7.7 mg / g calculated on the dry product.

Example 7

305 ml of water are added to 33.15 g of Li ₂ CO ₃ and 72 g of crystalline aluminum hexahydrate AlCl ₃ · 6H ₂ O are added gradually with stirring. The process is carried out at room temperature. The precipitate is filtered off, washed and dried at a temperature of 60 ° C. The composition of the dried precipitate and the mother liquor is given in table 1 (experiment No. 9). A portion of the sorbent 10 g is treated with distilled water until ~ 7 mg of lithium per gram of sorbent is removed. To establish a full static exchange capacity, a brine was used, the composition of which is given in Example 1. The capacity was 7.5 mg / g.

Examples for W: T <4.0 and W: T> 4.6 (negative) are presented in Table 1 (experiments No. 9, 10, 11).

Industrial applicability

The proposed method in comparison with the prototype method allows you to:

- significantly simplify the process by replacing 2 operations with one and reduce the time of synthesis of the sorbent;

- exclude the use of a concentrated (20%) solution of hydrochloric acid, the flow rate of which is ~ 0.7 kg per 1 kg of sorbent;

- make the process environmentally friendly, eliminating the presence of wastewater generated during the acidification of the reaction mixture with hydrochloric acid;

- reduce the cost of the process and improve sanitary conditions in the production of sorbent, replacing toxic lithium hydroxide with less toxic and cheaper lithium carbonate;

- implement the creation of a closed, waste-free technology for producing sorbent.

Sources of information

1. RF patent No. 2028385 B 01 J 20/00, C 25 V 1/00, application. 05/25/92, publ. 02/09/95. Bull. No. 4 // N.P. Kotsupalo, L.L. Sitnikova, L.T. Menzherez.

2. Pat. US No. 4.347327, C 08 D 5/20, application. 11/19/1979, publ. 08.31.1982 // J.M. Lee, W.C. Bauman.

3. Pat. US No. 6,280.693, C 01 D 15/00, application. 09/20/1996, publ. 08.28.2001 // W.C. Bauman, J.L. Burba (prototype).

4. Pat US No. 5.993.759, C 01 D 15/08, publ. 11/30/1999 // I.Wilkomirsky.

Claims (3)

1. A method of producing a sorbent for the extraction of lithium from brine, including the interaction of aluminum and lithium-containing compounds in the presence of water, obtaining compounds LiCl · 2Al (OH) ₃ · mH ₂ O and a solution of lithium chloride, filtering the precipitate and treating it with water with desorption of a part of lithium from a precipitate, characterized in that aluminum chloride and lithium carbonate are fed into the interaction at a liquid to solid phase ratio of 4.0-4.6, desorption is carried out until a lithium exchange capacity of 6.0-8.0 mg / g is reached, and the resulting concentrated lithium chloride solution treated with a soda solution with precipitation of lithium carbonate and returning it to the reaction. 2. The method according to claim 1, characterized in that the interaction serves aluminum chloride in the form of a solution or solid reagent AlCl ₃ · 6H ₂ O. 3. The method according to claim 1, characterized in that the interaction serves lithium carbonate in the form of a powder.

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