RU2157339C2 - Method of production of lithium bromide from brines - Google Patents

Abstract

FIELD: chemical technologies of inorganic substances; preparation of working solutions for refrigerating machines; chemical industry, metallurgy and other industries. SUBSTANCE: lithium bromide is produced from lithium contained in lithium-containing brine after selective extraction on Li-Al-containing sorbent and obtaining aqueous solution of lithium chloride. Aqueous solution of lithium chloride is first subjected to deep cleaning from magnesium and alkaline- earth metals on cations in Li⁺-form, after which it is passed through cationite in H⁺-form and then cationite saturated with lithium ions is washed off remaining chloride ions and treated with solution of hydrobromic acid synthesized beforehand, thus obtaining flow of lithium bromide and cationite in H⁺-form. Bromide solution is evaporated till separation of crystalline hydrate LiBr2H₂O. EFFECT: enhanced economical efficiency of method. 4 cl, 4 dwg, 1 tbl, 8 ex

Description

 The invention relates to the chemical technology of inorganic substances, in particular to methods for producing lithium bromide, which can be used to prepare a working solution of refrigeration machines used in chemical, metallurgical and other industries.

 Known methods for producing lithium bromide by reacting lithium hydroxide [1] or lithium carbonate [2, 3] with liquid bromine in the presence of a reducing agent, which is used as hydrogen peroxide or ammonia water.

 A common drawback of these methods is the need to use expensive materials, lithium and elemental bromine compounds as LiBr raw materials, which ultimately leads to the high cost of the resulting target product.

 A known method of producing bromide salts from chlorides of alkali metals and hydrobromic acid [4]. When lithium chloride is treated with hydrobromic acid, lithium bromide and hydrochloric acid are formed, 94% of which can be distilled off without loss of HBr.

 The disadvantages of the method are the need to use commercial HBr, the industrial production of which is not available, expensive lithium chloride, purification of the resulting LiBr solution from chlorine ions, as well as the use of corrosion-resistant equipment during the distillation of HCl.

Недостатками способа являются: получение разбавленных растворов бромида лития (30-40 г/л) и использование дополнительного реагента, бромида натрия. Кроме того возможно загрязнение раствора бромида лития хлорид - ионами за счет неселективности мембран.A known method of producing lithium bromide from natural brines [5], including selective sorption of lithium from brines on an inorganic aluminum - lithium-containing sorbent, eluting lithium with water to obtain solutions of lithium chloride (eluate) and using the resulting solution to conduct the electrodialysis conversion process using sodium bromide solution by double exchange reaction:
LiCl + NaBr ---> LiBr + NaCl, according to the scheme

The disadvantages of the method are: obtaining dilute solutions of lithium bromide (30-40 g / l) and the use of an additional reagent, sodium bromide. In addition, it is possible that the solution of lithium bromide is contaminated with chloride ions due to the non-selectivity of the membranes.

 This method according to the technical nature and the achieved result is the closest to the claimed and we have taken as a prototype.

 The proposed method is devoid of these disadvantages.

 The technical result of the method is the use of eluates of selective sorption of lithium from natural chloride brines and hydrobromic acid obtained from the same brine by direct contact of the bromide mixture formed after the bromide ion is oxidized to elemental bromine, with a reducing agent and, as a result, increasing the economic parameters of the method.

The technical result is achieved by the fact that to obtain lithium bromide use lithium contained in the starting brine. To do this, the brine after separation of bromine is sent to the selective sorption extraction of lithium using an inorganic aluminum-lithium-containing sorbent to obtain an aqueous solution of lithium chloride. The resulting aqueous solution of lithium chloride after deep purification from magnesium ions and alkaline earth metals on a cation exchange resin in the Li ⁺ form is passed through a cation exchange resin, for example KU-2, in the H ⁺ form to obtain a cation exchange resin saturated with lithium ions and the hydrochloric acid solution stream used in the stage processing the starting brine during the oxidation of bromide ion to elemental bromine. Saturated with lithium ions, cation exchange resin is washed from the residual amount of chloride ions with demineralized water, which is further used in the stage of selective sorption of lithium from brine as a desorbate of lithium chloride from a saturated selective inorganic sorbent. The cation exchange resin saturated with lithium ions, washed from chloride ions, is treated with a solution of hydrobromic acid, previously synthesized by direct contact of the bromine-hydrobromide mixture with a reducing agent, to obtain a stream of a solution of lithium bromide and cation exchange resin in the H ⁺ form. The resulting lithium bromide solution was evaporated to isolate LiBr • 2H ₂ O crystalline hydrate, which was separated from the solution, washed and dried. For the desorption of lithium from cation exchange resin, 2.0 - 2.2 N is used. hydrobromic acid solution, the desorption process is carried out in three stages with a ratio of W: T in each stage of 1: 1, with a decreasing concentration of HBr. As a reducing agent in the synthesis of HBr, substances containing amide or amine groups, for example, hydrazine, hydroxylamine or their derivatives, which form inert gaseous by-products during the course of the redox reaction, are used: nitrogen and carbon dioxide. Hydrobromic acid is synthesized by pre-mixing water and bromine taken in a predetermined ratio, followed by portioned dosing of the reducing agent with constant stirring of the contact mass until it discolors.

 The method is as follows.

According to the flow diagram of the process (Fig. 1), natural bromide-lithium chloride brine or a technological solution of a similar composition is acidified with hydrochloric acid, formed during the saturation of cation exchange resin in the H ⁺ form with lithium, and subjected to oxidizing treatment. As the oxidizing agent can be used balloon chlorine or oxidizing agents (Cl ₂ , OCl ^- ), obtained directly from the brine during its anodic oxidation (membrane electrolysis). In this case, the bromide - ions, being oxidized, turn into elemental Br ₂ by the reaction
2Br ^- + Cl ₂ -> Br ₂ + 2Cl ^- (1)
The oxidation state is 95-97%.

After the bromide ion has been oxidized, the brine is sent to the desorption of bromine. The desorption of bromine from brine is carried out either by direct steam by means of countercurrent supply to the column, or by heated air. Steam is used when the bromine concentration in the brine exceeds 3 kg / m ³ . In this case, bromine vapors in a mixture with water vapors and an excess of chlorine are brought into countercurrent contact with the initial brine, which ensures the most complete interaction of chlorine with bromide ion. A mixture of bromine and water vapors is condensed upon cooling, and the condensed phases are separated into bromine and bromine water by settling. Bromine water is returned to desorption, and bromine is collected in a storage tank. Next, the bromine freed from bromine is fed to the selective sorption of lithium contained in the brine. Selective sorption of lithium is carried out on an inorganic sorbent containing aluminum, for example, a double compound of lithium and aluminum LiCl • 2Al (OH) ₃ • nH ₂ O ((DGAL-Cl). After saturation of the sorbent, lithium chloride is eluted with water, for example, water obtained in the operation sorption separation of Li ⁺ and Cl ^' when washing the cation exchanger from chlorine ion. The eluate obtained in the form of an aqueous solution of LiCl (content of LiCl 5-7 kg / m ³ , the content of impurity chlorides 2-2.5 kg / m ³ ) is sent to clean impurities Ca ^2+, Mg ²⁺ and partly Na ^+, K ^+. Purification was carried out by ion exchange on a cation exchanger, preliminary tionary (during regeneration) in translation Li ⁺ -form by the reaction:
[Me ²⁺ ] _p + R = 2Li ⇄ 2 [Li ⁺ ] _p + R = Me, (2)
where R is cation exchange resin, Me - Ca, Mg.

In the course of the exchange reaction, the solution is enriched in lithium, and the cation exchange resin is saturated with Ca, Mg and, in part, K and Na. In this case, the concentration of lithium chloride in the eluate increases to 8-9 kg / m ³ . The spent cation exchanger is regenerated by a concentrated solution of lithium bromide (LiBr 100-110 kg / m ³ ) prepared from the mother liquor formed at the crystallization stage of LiBr • H ₂ O. In this case, two tasks are solved: cation exchanger regeneration by reaction:
R = Me + 2 [Li ⁺ ] _p ⇄ R = 2Li + Me $\genfrac{}{}{0ex}{}{\text{2+}}{\text{(p)}}$ (3)
and the conclusion with this solution of various impurities that accumulate gradually during the evaporation of the LiBr solution in a closed cycle. The solution obtained after regeneration of the cation exchanger with the conversion of the latter to the Li ⁺ form and containing, along with LiBr (LiBr content ~ 10 kg / m ³ ) halides of impurity cations, is sent to the head of the process, where it is mixed with the initial brine at the stage of Br ^- to Br oxidation ₂ .

The eluate purified from calcium and magnesium, containing mainly LiCl and NaCl with KCl in the form of impurities (total impurity content of 15-20 g / m ³ ), is sent to the sorption separation of Li ⁺ and Cl ^- . Sorption separation is carried out on cation exchange resin in the H ⁺ form according to the exchange reaction:
RH ⁺ + LiCl _(p) ⇄ R-Li ⁺ + HCl _(p) (4)
After the cation exchanger is saturated with lithium, it is deeply washed from chloride ions with demineralized water, which is subsequently used after washing the sorbent at the stage of elution of LiCl from the saturated inorganic sorbent. The resulting HCl solution is used to acidify the starting brine in the oxidation step of Br ^- to Br ₂ .

After washing the cation exchange resin saturated with lithium ions from chloride ions, lithium is desorbed with its simultaneous regeneration with a solution of hydrobromic acid to obtain cation exchange resin in the H ⁺ form and a solution of lithium bromide in accordance with the ion exchange reaction:
R-Li ⁺ + HBr _(p) ⇄ RH ⁺ + LiBr _(p) (5)
There are optimal parameters for conducting the process of desorption of lithium from cation exchanger: the concentration of hydrobromic acid in the regeneration solution should be in the range of 2.0 - 2.2 N. when organizing the desorption process in three stages with a decreasing concentration of HBr at a ratio of W: T in each stage of 1: 1. Only in this case, the maximum concentration of lithium bromide in the final desorbate is achieved while ensuring the complete extraction of lithium from cation exchanger.

Obtaining 2.0-2.2 N. HBr solution for desorption of lily is carried out by the interaction of an aqueous solution of hydrazine with a water-bromine mixture, previously obtained by mixing taken in a given ratio of liquid bromine and water. The interaction is carried out with stirring and portioned dosing of the reducing agent until the contact mass is discolored. The process is described by the following chemical reaction:
N ₂ H ₂ + Br ₂ ⇄ 2HBr ₂ + N ₂ (6)
Thus obtained LiBr solution with a concentration of 160-170 kg / m ³ after neutralizing the residual acidity with lithium hydroxide is sent for evaporation, followed by cooling and crystallization of LiBr • 2H ₂ O. Separation of crystals from the solution phase can be carried out by various methods: filtration, centrifugation, extraction. In this case, the mother liquor is returned to evaporation. Crystals of LiBr • 2H ₂ O are washed with demineralized water, and the washing water is also returned to evaporation. In the process of circulation and evaporation of the mother liquor, impurities accumulate in it. In this regard, part of the mother liquor is constantly removed from the process using this LiBr solution after dilution to regenerate the cation exchange resin at the stage of purification of the selective lithium sorption eluate (LiCl solution) from impurities of cations of alkaline earth elements.

 The one stripped off LiBr solution and the juice vapor condensate are cooled by spent brine. The resulting condensate is mixed with demineralized water and used in the process.

 Thus, the hallmark of the method is the use of a solution of lithium chloride, isolated from brine, after its purification from impurities of calcium and magnesium, followed by sorption separation of lithium and chlorine on cation exchange resin, desorption of lithium from saturated cation exchange resin with a solution of hydrobromic acid, which is obtained by contacting the reducing agent with bromine a mixture obtained from the same brine. This feature allows you to increase the concentration of LiBr in solution, to increase the efficiency of the process by eliminating the imported reagents, which will reduce the cost of the process and increase the economic performance of the method.

 The invention is illustrated by drawings.

 FIG. 1. The technological scheme of the method of producing lithium bromide from brine.

 FIG. 2. Organization diagram of the three-stage desorption of lithium from the resin with HBr solutions with a decreasing concentration of HBr (horizontal arrows indicate the movement of the resin; vertical arrows indicate desorption solutions).

 FIG. 3. Dependence of the degree of completeness of the extraction of lithium from the resin (α,%) on the concentration of the initial stripping solution of HBr (n) during three-stage desorption.

 FIG. 4. The dependence of the height of the working area (Nr.z, m) of the resin on the linear velocity (W, m / h) of transmission of a LiCl solution with a concentration of 12 g / l.

 Information confirming the possibility of implementing the method described in the examples.

Example 1
After bromine extraction, containing brine containing 2.2 g / L LiCl, a brine is passed through a layer of the inorganic sorbent DGAL-Cl selective with respect to LiCl until it is completely saturated.

The sorbent is washed from brine and LiCl is eluted from it with water. After purification on cation exchange resin in the Li ⁺ form, the resulting eluate containing ~ 12 g / L LiCl (residual impurities: NaCl-12 mg / L; KCl - 7 mg / L) is fed to a column with a stationary layer of strongly acidic cation exchanger KU-2 -84C in the H ⁺ form at a speed of 12.3 cm / min (7.4 m / h). The diameter of the column is 1.09 cm, the height is 60 cm, the height of the sorbent layer is 54 cm, the resin volume is 50 ml. During the experiment, the concentration of lithium ions in the solution at the column exit is constantly monitored. After it reaches the initial value, the sorption process is completed, the resin is washed from the residual content of Cl - ion with demineralized water, and lithium is desorbed.

 1.33 L of LiCl solution was passed, 623 mg of lithium adsorbed with the resin, the resin capacity was 1.78 mEq / ml. The estimated height of the working area of the sorbent is 64 cm (0.64 m).

 The desorption of lithium from the resin is carried out in three stages with solutions of hydrobromic acid with decreasing concentrations. For this, a portion of a lithium-saturated resin with a volume of 15 ml is treated for 20 minutes with constant stirring in an equal volume of 0.72 N. HBr solution. After that, the solution is separated from the resin and sent to the second stage of desorption, having previously measured the lithium content in it and, thus, determining the degree of completeness of lithium extraction from the resin and the degree of working out of the desorption solution (decrease in HBr concentration). Next, the process is carried out according to the scheme shown in FIG. 2, while for each stage of desorption, the ratio W: T = 1: 1. The resulting solution contained 62 g / L LiBr, the degree of lithium extraction from the resin was 41%.

Hydrobromic acid is prepared by reacting hydrazine with a bromine mixture. The reaction proceeds in accordance with the stoichiometry of the reacting substances. To get 2 n. A solution of HBr to a mixture prepared from 16 g of liquid bromine and 50 ml of distilled water is added dropwise ~ 50 ml of a 3% solution of hydrazine (H ₂ O: Br ₂ = 6.2). The process is carried out until the complete discoloration of the reaction mass. To obtain 2.2 n. HBr solution use the same mixture with 41 ml of water (H ₂ O: Br ₂ = 5.7). Lower concentration HBr solutions are prepared with an appropriate dilution of 2.0-2.2 N. HBr.

Example 2
The process is carried out as described in example 1, with the difference that for the desorption of lithium from the resin using 1.5 N. HBr solution. The resulting solution of LiBr concentration of 129 g / l, the degree of extraction of lithium from the resin was 71.6%.

Example 3
The same as in example 1, with the difference that the desorption is 2 N. HBr solution. As a result, a 174 g / L LiBr solution was obtained; the degree of lithium extraction from the resin was 98.5%.

Example 4
The same as in example 1, with the difference that the desorption is 2.2 n. HBr solution. As a result, a LiBr solution of a concentration of 174.6 g / L was obtained; the degree of lithium extraction from the resin was 98.8%.

Example 5
The same as in example 1, with the difference that the desorption is 2.5 N. HBr solution. As a result, an HBr solution of 174.6 g / L was obtained; the degree of lithium extraction from the resin was 98.8%.

 Thus, as follows from the relationship shown in FIG. 3, it is inappropriate to maintain the concentration of hydrobromic acid in the stripping solution of less than 2 N. and above 2.2 n.

Example 6
The same as in example 1, with the difference that the initial eluate for sorption served at a speed of 25 cm / min (15 m / h). 1.36 L of the solution was passed, 560 mg of lithium was absorbed by the resin. The sorbent capacity in this case was 1.60 mEq / ml. The estimated height of the working area of the sorbent is 77 cm (0.7751).

Example 7
The same as in example 1, with the difference that the initial eluate for sorption served at a speed of 43 cm / min (26 m / h). 1.38 L of the solution was passed, 552 mg of lithium was absorbed by the resin. The capacity of the sorbent in this case was 1.58 mEq. / ml, the calculated height of the working zone of the sorbent is 89 cm (0.89 m). In FIG. Figure 4 shows the dependence of the height of the working zone on the linear transmission rate of the LiCl solution, from which it follows that with an increase in the linear transmission rate of the solution from 7.4 to 26 m / h, the height of the working zone of cation exchange resin increases by 1.4 times.

Взаимодействие протекает в соответствии со стехиометрией реакции (7) и приблизительно с той же скоростью, что и с гидразином.Example 8
The same as in example 1, with the difference that an HBr solution of a given concentration is obtained by the interaction of an aqueous suspension of bromine with a solution of hydroxylamine according to the equation of the chemical reaction:

The interaction proceeds in accordance with the stoichiometry of reaction (7) and at approximately the same rate as with hydrazine.

 The table shows the main technological indicators of the process of desorption of lithium from a saturated resin with an aqueous solution of HBr, obtained according to the results of the experiments described in examples 1 to 8.

Industrial applicability
The proposed method for producing lithium bromide from brines in comparison with the prototype method allows to increase the efficiency of the process by reducing the cost, achieved by eliminating the need to use a large amount of expensive lithium chloride and commercial hydrobromic acid, as well as transportation costs for their delivery. In addition, the proposed technology allows for a closed production cycle with the rational use of reagents and intermediates: the resulting hydrochloric acid (brine acidification), juice steam condensate (demineralized water), spent brine (refrigerant), and wash water (lithium chloride desorption from an inorganic sorbent), the mother liquor removed after crystallization of LiBr • 2H ₂ O (for the regeneration of cation exchange resin). All this will significantly reduce the cost of the resulting lithium bromide according to rough estimates in 1.5-2.0 times.

The method was tested on a laboratory scale on real highly mineralized brines of the Znamensky deposit in the Irkutsk region, containing 9-11 kg / m ^{3 of} bromine (Br ^- ) and 1.8-2.2 kg / m ³ of lithium chloride.

Sources of information
1. A.S. USSR N 597639, C 01 D 15/04, 1976.

 2. A.S. USSR N 929557, C 01 D 3/10, 1980.

 3. A.c. CCCP N 1038282, C 01 D 15/04, 1980.

 4. Ksenzenko V.I., Stasinevich D.S. Chemistry and technology of bromine, iodine and their compounds. M., "Chemistry", 1995, p. 377-384.

 5. Patent 2090503, C 01 D 15/02, 09/20/97 (prototype).

Claims (4)

1. A method of producing lithium bromide from chloride brines, including selective sorption of lithium on an inorganic lithium-aluminum sorbent, elution of lithium with water to obtain a solution of lithium chloride and its treatment with a bromine-containing compound, characterized in that the eluate is purified from calcium and magnesium on a cation exchange resin in Li ⁺ form , the purified solution is passed through cation exchange resin in the H ⁺ form to obtain lithium-saturated cation exchange resin and hydrochloric acid, the lithium-saturated cation exchange resin is washed from chlorine with water, and lithium is stripped with a bromide solution hydrochloric acid, the resulting lithium bromide solution is evaporated to crystallize LiBr • 2H ₂ O, the crystals are washed and dried, hydrochloric acid obtained in the process is used to acidify the brine in the oxidation step of bromidion in brine to elemental bromine, which is then reduced to give hydrobromic acid, which is directed at the stage of desorption of lithium-saturated cation exchanger.  2. The method according to claim 1, characterized in that for the desorption of lithium from saturated cation exchange resin, a 2.0 - 2.2 N hydrobromic acid solution is used, and the desorption process is carried out in three stages with a decreasing concentration of HBr in desorption solutions at a ratio of W: T at each stage 1: 1.  3. The method according to claims 1 and 2, characterized in that as a reducing agent in the preparation of hydrobromic acid, substances containing amide or amine groups, for example, hydrazine, hydroxylamine or their derivatives, are used.  4. The method according to PP. 1 to 3, characterized in that the bromine is subjected to reduction in the form of a water-bromine mixture at a given ratio of water and bromine, and the reducing agent is dosed portionwise with constant stirring until the mixture becomes discolored.

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