RU2330810C2 - Method of lithium chloride purification - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of lithium chloride purification from admixtures involves obtaining processing medium of lithium chloride with lithium oxychloride residues by dissolution of processing lithium hydroxide in water or by preparation of processing lithium carbonate slurry, followed by chlorination of lithium hydroxide solution or lithium carbonate slurry by waste chlorine air mix of electrolytic cells in the presence of a catalyst used for lithium oxychloride reduction. pH of the obtained lithium chloride solution is corrected before continuous sorption purification with lithium hydroxide solution or lithium carbonate till hydroxyl ion (OH^-) content is within 0.0002-0.005 mol/dm³. Lithium chloride solution undergoes sorption purification with cation exchange resin based on cross-linked macroporous polystyrol featuring subacid iminodiacetate groups inserted into the polymer matrix of subacid iminodiacetate groups with linear throughput rate of 3-20 m/h. The method improves purity degree of the processing lithium chloride solution and prolongs performance lifetime of cation exchange resin.

EFFECT: purified lithium chloride solution allows obtaining high-quality metal lithium.

2 ex, 1 tbl, 3 dwg

Description

The invention relates to a method for purifying lithium chloride and obtaining a high-purity lithium chloride salt, which is used to produce high-quality lithium metal. The invention may find use in the chemical, pharmaceutical, metallurgical and other industries.

A known method of purifying a solution of lithium chloride from calcium and magnesium by evaporation, recrystallization and extraction with organic solvents (Lithium, its chemistry and technology. Ostroushko Yu.I. et al. M., Atomizdat, 1960, pp. 164-165). The main disadvantage of this method is the long cleaning cycle, the complexity and insufficient degree of purification of the resulting lithium chloride.

A known method of purification of lithium chloride from impurities of alkali and alkaline earth metals according to patent RU 2092449, IPC С02F 1/58, December 20, 1995. Summary of the invention: lithium salts are contacted in countercurrent with a solution of chlorinated cobalt dicarbolide and polyester in an organic nitro solvent. The optimal concentration of polyester is 0.01-0.6 mol / L, and the concentration of lithium in an aqueous solution does not exceed 5 mol / L. As solvents for the polyester, for example, nitrobenzene, nitrotoluene, nitroethylbenzene are used. As the polyester, polyethylene glycol, crown ether, cryptand or a mixture of substituted polyethylene glycol ethers are used. Upon contact of the lithium salt solution with the extractant, impurities of sodium, potassium, calcium, and magnesium pass into the organic solution. The main disadvantage of the invention is the use of organic compounds, solvents that must be disposed of, which is associated with the need to solve environmental problems, entails additional costs and increases the level of production safety.

Closest to the proposed method according to the technical essence and the achieved result (prototype) is a method for purifying lithium chloride patent RU 2232714, IPC С01D 15/04 of 07/20/2004 Bull.№20, including obtaining lithium chloride by dissolving it in deionized water and continuous sorption cleaning is carried out at a speed of 1.5-6.0 ml / cm ² · min at a temperature of 10 ÷ 40 ° C, where vinyl pyridine ampholyte or chelate type aminophosphonic resins are used as a sorbent.

The disadvantage of this invention is that the chelate aminophosphonic resin contaminates the cleaned technological solution of lithium chloride with phosphate ions, has a low exchange capacity, and vinyl pyridine ampholyte is not available in industrial volumes.

The objective of the invention is to increase the degree of purification of the technological solution of lithium chloride from impurities, increasing the life of the cation exchange resin.

The problem is solved due to the fact that in the method of purification of lithium chloride, including obtaining and continuous sorption purification of a solution of lithium chloride according to the claims, lithium chloride is used as a technological solution of lithium chloride with a residual content of lithium oxychlorides, which is obtained by dissolving lithium hydroxide in water or preparation of pulp of technical lithium carbonate followed by chlorination of a solution of lithium hydroxide or lithium carbonate pulp outgoing from electrolyte Erov hlorvozdushnoy gas mixture in the presence of the catalyst used for decomposing lithium oxychlorides, adjusting pH of the resulting solution of lithium chloride is carried out prior to the continuous sorption cleaning solution of lithium hydroxide or lithium carbonate to a content of hydroxyl ion (OH ^-) within 0,0002-0,005 mol / dm ³ and sorptive purification is carried out on a cation exchange resin based on a crosslinked macroporous polystyrene introduced into the matrix polymer weakly acidic iminodiacetate groups with linear transmission rate of 3-20 / Hour.

The specified set of features is new and has an inventive step, since obtaining a technological solution of lithium chloride involves the use of various technical lithium salts, which can be used as feedstock. The presence of a residual content of lithium oxychlorides imposes certain requirements on the sorbent. The proposed cation exchange resin Lewatit TP 208 based on crosslinked macroporous polystyrene with weakly acidic iminodiacetate groups introduced into the polymer matrix allows avoiding contamination of the solution being purified, has a resistance to a wide pH range, and does not deteriorate. The adjustment of the technological solution of lithium chloride with a solution of lithium hydroxide or lithium carbonate is necessary to neutralize the free acid formed during the chlorination process. The experimentally selected pH of the lithium chloride solution and high-speed modes allow to obtain high-quality lithium chloride salt and increase the life of the used resin.

Figure 1 presents a diagram of a technological solution of lithium chloride, where

I - dissolution in water of technical lithium hydroxide or preparation of pulp of lithium carbonate;

II - chlorination of a solution of lithium hydroxide or pulp of lithium carbonate in the presence of a catalyst;

III - pH adjustment of a technological solution of lithium chloride with a solution of lithium hydroxide or lithium carbonate.

In figure 2. the dependence of the calcium concentration in the purified lithium chloride solution on the volume passed through the resin of the technological solution of lithium chloride is given.

Figure 3 shows graphs of the content of calcium and phosphate ion in a dry lithium chloride salt after purification of a technological solution of lithium chloride on Purolite S 940 and Lewatit TP 208 resin.

The method of cleaning the technological solution is as follows.

Technical lithium hydroxide is loaded into the reactor and dissolved in water with stirring. Instead of lithium hydroxide, technical lithium carbonate can be used, from which an aqueous pulp of lithium carbonate is obtained by dissolving dry technical lithium carbonate in water with stirring in the ratio m: w = 1: (5-10). Then, a solution of lithium hydroxide or lithium carbonate pulp is chlorinated in the presence of a catalyst, a chlorine-air mixture of gases leaving the electrolytic cells. The resulting solution with a residual content of lithium oxychlorides is filtered off and the pH is adjusted with a solution of hydroxide or lithium carbonate. Then control filtration of the technological solution of lithium chloride is carried out and it is passed through an ion-exchange column with a Lewatit TP 208 cation-exchange resin, in the Li-form with a linear transmission velocity of 3-20 m / h. The purification of a solution of lithium chloride is carried out to a breakdown in the content of calcium in the purified solution to 2-3 mg / L. The lithium chloride solution thus obtained is dried to a dry salt and used to produce lithium metal.

Example 1

The technological solution of lithium chloride is obtained according to the scheme shown in figure 1.

Purification of a 4 N technological solution of lithium chloride with a content of LiClO ₃ <5.0 g / dm ³ , LiClO <0.05 g / dm ³ , OH - (0.0002-0.005) mol / dm ³ on Lewatit TP 208 resin to the first regenerations were carried out from June 23, 2005 to October 10, 2005. The volume and flow rate of the solution passed through the ion-exchange column was fixed. During this period, 1,500 m ³ of lithium chloride solution was purified. The calcium content in the crude and purified lithium chloride solutions was determined by atomic absorption (AAS) method. When assessing the exchange capacity of the resin, the average values of calcium content were used for certain periods of time (table 1). The content of phosphate ion in the purified solution was determined by the chemical method. Data on the sorption purification of solutions of lithium chloride from calcium on a cation exchange resin Lewatit TP 208 are presented in table 1.

Table 1. date of The average content of CA before purification, mg / l The content of Ca after purification, mg / l The content of PO ₄ after purification, mg / l Portion of solution, m ³ Total volume, m ³ Sorbir mass. Sa g 06/24/05 14.75 0.27 0.26 12.0 12.0 173.8 06/27/05 14.75 0.11 0.13 47.9 59.9 701.3 07/05/05 14.75 0.23 <1 183.0 242.9 2657,2 07/12/05 14.75 0.1 <1 58.0 300.9 849.7 07/14/05 14.75 0.2 <1 15,5 316.4 225.5 07/15/05 14.75 0.3 <1 17.5 333.9 252.9 07/18/05 14.75 0.09 <1 5.5 339.4 80.6 07/21/05 13.00 0.3 <1 19.5 358.9 247.7 07/26/05 9.90 0.3 <1 74.0 432.9 710.4 08/03/05 12.75 0.3 <1 82.0 514.9 1020.9 08/09/05 10.58 0.1 <1 66.7 581.6 699.0 08/11/05 12.25 0.1 <1 41.0 622.6 498.2 08/18/05 11.13 0.4 <1 66.0 688.6 708.2 08/24/05 14.10 0.4 <1 37.5 726.1 513.8 09/01/05 13.62 0.8 <1 106.0 832.1 1358.9 09/02/05 15.67 0.8 <1 24.5 856.6 364.3 09/08/05 15,99 0.8 <1 104.5 961.1 1587.4 09.09.05 16.63 0.6 <1 25.0 986.1 400.8 09/13/05 21.97 one <1 53.5 1039.6 1121.9 09/16/05 23.50 one <1 22.0 1061.6 495.0 09/19/05 17.50 1,1 <1 35.5 1097.1 582.2 09/20/05 22.00 1,1 <1 14.0 1111.1 292.6 09/21/05 18.00 one <1 8.5 1119.6 144.5 09/26/05 18.69 1.3 <1 101.0 1220.6 1756.4 09/29/05 22.47 1.4 <1 59.5 1,280.1 1253.7 10/04/05 19.89 1,5 <1 69.5 1349.6 1278.1 10/05/05 23,20 1.7 <1 7.0 1356.6 150.5 10/06/05 26.40 2.2 <1 31,0 1387.6 750,2 10/10/05 26,42 2.2 <1 100.5 1488.1 2434.1 amount 23,309.5

The volume of resin in the ion-exchange column is 1 m ³ ; therefore, the capacity of the resin before the breakdown in calcium sorption (C _Ca = 2.2 mg / L) is 23.3 g / L or 1.165 equiv / L. The change in the concentration of calcium from the volume of the purified solution is presented in figure 2. The dependence has an exponential form, extrapolating which, it is possible to obtain the total exchange capacity for sorption of calcium on Lewatit TP 208 resin in Li-form, equal to 1.7 equiv / l. The phosphate ion content in the purified lithium chloride solution was <1 mg / L (table 1).

Example 2

The technological solution of lithium chloride is obtained according to the scheme shown in figure 1

Purification of a 4 N technological solution of lithium chloride with a content of LiClO ₃ <5.0 g / dm ³ , LiClO <0.05 g / dm ³ , OH - (0.0002-0.005) mol / dm ³ from March 29 to June 20, 2005 were conducted on Purolite S 940 resin and from 06.23.05 to 10.10.05 on Lewatit TP 208 resin until the first regeneration. The volume and flow rate of the solution passed through the ion exchange column was fixed. The volume of the resin and the transmission rate of the solution were the same in both the first and second experiments. The content of calcium and phosphate ion impurities in the initial and purified solutions was determined by chemical and AAS methods.

For comparison, a lithium chloride solution was purified during the indicated period and a dry product was obtained after purification with Purolite S 940 resin (based on chelating aminophosphonic acid) and Lewatit TP 208 (based on cross-linked macroporous polystyrene with sloic acid iminodiacetate groups introduced into the polymer matrix) obtaining lithium metal. The higher efficiency of the cation exchange resin Lewatit TP 208 in comparison with Purolite S 940 resin when cleaning lithium chloride solutions can be judged by the content of calcium and phosphate ion in lithium chloride (figure 3). When cleaning solutions of lithium chloride on Purolite S 940 resin, the average content of calcium and phosphate ion was 1.2 · 10 ^-3 and 2.2 · 10 ^-3 %, respectively. When cleaning solutions of lithium chloride on Lewatit TP 208 resin, the average calcium content was 0.87 · 10 ^-3 %, and the phosphate ion was 1.4 · 10 ^-3 %.

During industrial tests, it was found that after two regenerations of Purolite S 940 resin, its total exchange capacity dropped three times, which led to its complete replacement, since its further use was impractical.

Laboratory studies of Lewatit TP 208 resin using a lithium chloride technological solution showed that during the sorption-desorption process 5 times, the total exchange capacity dropped by 10%.

Industrial tests of Lewatit TP 208 resin over a period of five months showed a high exchange capacity before breakthrough (the concentration of calcium impurities in the solution being cleaned was 2.2 mg / L) and a lower content of impurities in the solution being cleaned was lithium chloride.

Claims (1)

The method of purification of lithium chloride, which consists in obtaining and continuous sorption purification of a solution of lithium chloride, characterized in that the lithium chloride is a technological solution of lithium chloride with a residual content of lithium oxychlorides, which is obtained by dissolving lithium hydroxide in water or preparing a pulp of lithium carbonate, followed by chlorination of a solution of lithium hydroxide or pulp of lithium carbonate exhausted from the electrolytic chlorine-gas mixture of gases in the presence of catalysis of the atom used for the decomposition of lithium oxychlorides, the pH of the resulting lithium chloride solution is adjusted before continuous sorption purification with a solution of lithium hydroxide or lithium carbonate to a content of hydroxyl ion (OH ^- ) in the range of 0.0002-0.005 mol / dm ³ , and sorption purification is carried out on a cation exchange resin based on crosslinked macroporous polystyrene with weakly acidic iminodiacetate groups introduced into the polymer matrix with a linear transmission rate of 3-20 m / h.

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