Method of producing inorganic sorbents for extracting lithium from lithium-containing natural and technological brines

Abstract

Disclosed is a method of producing inorganic sorbents for extracting lithium from lithium-containing natural and technological brines. The method is carried by contacting a soluble niobate (V) with an acid in the presence of at least one zirconium (IV) salt to obtain a precipitate of a mixed hydrated niobium and zirconium oxide. Subsequent steps include granulating the precipitate by freezing, converting the product of granulation into a Li-form, calcining the Li-form, and converting the obtained granulated mixed lithium, niobium, and zirconium oxide into an ion-exchanger in an H-form. In the obtained H-form the inorganic sorbent is ready for use in lithium extraction processes.

Claims

1. A method of producing inorganic sorbents for extracting lithium from lithium-containing natural and technological brines, the method comprising the steps of: contacting a soluble niobate (V) with an acid in the presence of at least one zirconium (IV) salt to obtain a precipitate of a mixed hydrated niobium and zirconium oxide, which is a non-stoichiometric compound; granulating the obtained precipitate of a mixed hydrated niobium and zirconium oxide by freezing with subsequent defreezing to obtain a granulated mixed hydrated niobium and zirconium oxide; converting the obtained granulated mixed hydrated niobium and zirconium oxide into a Li-form of the granulated mixed hydrated niobium and zirconium oxide by treating the granulated mixed hydrated niobium and zirconium oxide with a lithium-containing compound selected from the group consisting of a solution of lithium hydroxide LiOH and a solution of Li.sub.2CO.sub.3; calcining the Li-form of the granulated mixed hydrated niobium and zirconium oxide to obtain a granulated mixed lithium, niobium, and zirconium oxide, which comprises a tripled mixed oxide, which is a Li-form of an inorganic ion-exchanger; and converting the obtained granulated mixed lithium, niobium, and zirconium oxide to an ion-exchanger in an H-form by treating the granulated mixed lithium, niobium, and zirconium oxide with an acid solution.

2. The method of claim 1, wherein the step of contacting a soluble niobate (V) with an acid in the presence of at least one zirconium (IV) salt is carried out with an ion ratio of niobium (V) to zirconium (IV) in the soluble niobate and at least one zirconium (IV) salt, respectively, is in the range of (1 to 0.1) to (1 to 0.7).

3. The method according to claim 2, wherein the soluble niobate (V) is an alkali metal orthoniobate.

4. The method according to claim 3, wherein the alkali metal orthoniobate is selected from the group consisting of Li.sub.3NbO.sub.4, Na.sub.3NbO.sub.4, K.sub.3NbO.sub.4, Rb.sub.3NbO.sub.4, and Cs.sub.3NbO.sub.4.

5. The method of claim 4, wherein the at least one zirconium (IV) salt is selected from the group consisting of zirconium (IV) oxychloride ZrOCl.sub.2, zirconium (IV) tetrachloride ZrCl.sub.4, zirconium (IV) oxysulfate ZrOSO.sub.4, and zirconium (IV) sulfate Zr(SO.sub.4).sub.2.

6. The method according to claim 5, wherein the step of converting the obtained granulated mixed hydrated niobium and zirconium oxide into a is carried out with concentration of the lithium-containing compound in the rage of 0.05 M to 0.2 M.

7. The method according to claim 5, wherein the step of calcining the Li-form of the granulated mixed hydrated niobium and zirconium oxide to obtain a granulated mixed lithium, niobium, and zirconium oxide, which comprises a tripled mixed oxide and is a Li-form of an inorganic ion-exchanger, is carried out at a temperature in the range of 450 C. to 600 C.

8. The method according to claim 4, wherein the step of freezing is carried out at a temperature in the range of 3 C. to 10 C. during time from 20 hours to 40 hours.

9. The method according to claim 3, wherein the at least one zirconium (IV) salt is selected from the group consisting of zirconium (IV) oxychloride ZrOCl.sub.2, zirconium (IV) tetrachloride ZrCl.sub.4, zirconium (IV) oxysulfate ZrOSO.sub.4, and zirconium (IV) sulfate Zr(SO.sub.4).sub.2.

10. The method according to claim 9, wherein the step of freezing is carried out at a temperature in the range of 3 C. to 10 C. during time from 20 hours to 40 hours.

11. The method according to claim 2, wherein the step of converting the obtained granulated mixed hydrated niobium and zirconium oxide into a is carried out with concentration of the lithium-containing compound in the rage of 0.05 M to 0.2 M.

12. The method according to claim 2, wherein the step of calcining the Li-form of the granulated mixed hydrated niobium and zirconium oxide to obtain a granulated mixed lithium, niobium, and zirconium oxide, which comprises a tripled mixed oxide and is a Li-form of an inorganic ion-exchanger, is carried out at a temperature in the range of 450 C. to 600 C.

13. The method according to claim 1, wherein the soluble niobate (V) is an alkali metal orthoniobate.

14. The method according to claim 13, wherein the alkali metal orthoniobate is selected from the group consisting of Li.sub.3NbO.sub.4, Na.sub.3NbO.sub.4, K.sub.3NbO.sub.4, Rb.sub.3NbO.sub.4, and Cs.sub.3NbO.sub.4.

15. The method according to claim 1, wherein the at least one zirconium (IV) salt is selected from the group consisting of zirconium (IV) oxychloride ZrOCl.sub.2, zirconium (IV) tetrachloride ZrCl.sub.4, zirconium (IV) oxysulfate ZrOSO.sub.4, and zirconium (IV) sulfate Zr(SO.sub.4).sub.2.

16. The method according to claim 1, wherein the step of freezing is carried out at a temperature in the range of 3 C. to 10 C. during time from 20 hours to 40 hours.

17. The method according to claim 1, wherein the step of converting the obtained granulated mixed hydrated niobium and zirconium oxide into a is carried out with concentration of the lithium-containing compound in the rage of 0.05 M to 0.2 M.

18. The method according to claim 1, wherein the step of calcining the Li-form of the granulated mixed hydrated niobium and zirconium oxide to obtain a granulated mixed lithium, niobium, and zirconium oxide, which comprises a tripled mixed oxide and is a Li-form of an inorganic ion-exchanger, is carried out at a temperature in the range of 450 C. to 600 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph that shows dependence of the capacitance on lithium (E.sub.Li) and an effect of the ion separation factor in lithium and sodium (P.sub.Li,Na) on the content in the sorbent of zirconium ions.

(2) FIG. 2 is a graph illustrating the influence of the heat treatment temperature in the synthesis of the material, on the sorption-selective properties and the chemical stability of the sorption materials obtained.

DETAILED DESCRIPTION OF THE INVENTION

(3) The invention relates to the field of chemical technology, namely, to the production of selective inorganic sorbents for the extraction of lithium from natural and technological brines. The invention may be used in the extraction of lithium from alkaline and slightly alkaline solutions with a high content of sodium ions and ions of other metals. In particular, the invention relates to the aforementioned method, which is carried out in the presence of oxidizing or reducing agents and by using ion sieves.

(4) The term brines used in the context of the present patent specification covers any natural or technological solutions that contain lithium.

(5) Ionic sieves are inorganic ion-exchange sorbents that exhibit the so-called ion-sieve effect, which is the effect of separation of ions in a solution in accordance with the difference in their ionic radii. Dimension positions in crystal structure of the material corresponds to certain ions, and ions of a larger size cannot enter unspecified positions. Thus, the ion-sieve effect provides high selectivity in the sieve-effect sorbents. A unique feature of the method of the present invention is that the method makes it possible to obtain inorganic ion-exchange sorbents with a specific structure that provides high selectivity especially to lithium ions.

(6) It is also important to note that in the context of the present specification the term mixed hydrated niobium and zirconium oxide does not mean a mechanical mixture of the hydrated niobium oxide with a hydrated zirconium oxide but rather means a chemical compound of a non-stoichiometric composition.

(7) The objective of the invention is to increase the exchange capacity of the sorbent and its selectivity with respect to lithium ions.

(8) The objective is achieved by a method of obtaining an inorganic sorbent for extracting lithium from lithium-containing natural and technological brines. The method consists of contacting soluble niobates (V) with an acid in the presence of zirconium (IV) salts at an atomic niobium/zirconium ratio in the range of 1:(0.1 to 0.7) to obtain a mixed hydrated niobium and zirconium oxide, which is then granulated and subsequently converted into a lithium-form sorbent (hereinafter referred to as a sorbent). The granulation is carried out by freezing the obtained precipitate at a temperature of 5 to 7 C. for 24 to 30 hours with subsequent defreezing.

(9) This conversion is carried out by treating the obtained product with a lithium-containing compound selected from the group consisting of a solution of lithium hydroxide LiOH and a solution of lithium carbonate Li.sub.2CO.sub.3. As a result, a Li-form of a granulated mixed hydrated niobium and zirconium oxide is obtained.

(10) The obtained Li-form is calcined at an elevated temperature, specifically at 450600 C., the finished product is then treated with an acid solution, e.g., a nitric acid solution, to obtain a target product, i.e., a hydrogen-form sorbent (hereinafter referred to as an H-form sorbent).

(11) Soluble niobates suitable for use in the method of the invention are represented by alkali metal orthoniobates, such as Li.sub.3NbO.sub.4, Na.sub.3NbO.sub.4, K.sub.3NbO.sub.4, Rb.sub.3NbO.sub.4, Cs.sub.3NbO.sub.4.

(12) Zirconium salts suitable for the method of the invention can be exemplified by ZrCl.sub.4, ZrBr.sub.4, ZrI.sub.4, ZrOCl.sub.2, ZrOI.sub.2, Zr(SO.sub.4).sub.2, Zr(NO.sub.3).sub.4.

(13) Examples of H-form sorbents are given below in Table 1 (the Li-forms are similar and therefore are not included).

(14) Uniqueness of the proposed method lies in the fact that the step of contacting a soluble niobate (V) with an acid is carried out in the presence of zirconium (IV) salts and in that the ionic ratio of niobium (V) to zirconium (IV) in their interaction ranges from 1 to (0.10.7). Another feature is that calcination of the precipitate in the Li form is carried out at a temperature in the range of 450 to 600 C.

(15) The method is carried out as follows:

(16) In the first step, a mixed hydrated niobium (V) and zirconium (IV) oxide is produced by contacting a soluble niobate (V) with an acid solution that contains zirconium salts. To obtain a mixed hydrated niobium (V) and zirconium (IV) oxide, a process of coprecipitation is used. This process is carried out by pouring an acid solution of zirconium salts into a solution of a soluble niobate. For this purpose, solutions of hydrochloric acid, nitric acid or sulfuric acid can be used. To carry out this process, acids may have concentration in the range of 0.5 to 1.0 N. Zirconium compounds may be represented by aforementioned zirconium salts.

(17) The step of pouring is accompanied by stirring. The content of the components in the miscible solutions is taken at a level providing a ratio of zirconium (IV) to niobium (V) in the range of (0.1 to 0.7) to 1 and obtaining suspensions with pH=5 to 6.

(18) An excess of the resulting electrolyte is washed out from the obtained precipitate of a mixed hydrated niobium and zirconium oxide by successive decantation. The obtained precipitate of the mixed hydrated niobium and zirconium oxide is granulated by freezing, and then the granulated product is defrosted. The step of freezing is carried out for 24 to 30 hours at a temperature of 5 to 7 C. After defreezing, a granular material with a particle size of 0.3 to 1.0 mm is obtained.

(19) The resulting granular material is placed in an ion-exchange column and treated with a solution of lithium carbonate or lithium hydroxide at a concentration of 0.05 to 0.1 M until no traces of potassium are found in the filtrate. As a result, a product saturated with lithium ions is obtained. The obtained product is comprised of a lithium-saturated granulate, which is discharged from the column, dried in air, and calcined at a temperature in the range of 450 to 600 C. for 2 to 3 hours. After cooling and transferring to the H-form (by treating with 0.10.2 M HNO.sub.3), the obtained ion exchanger is ready for sorption of lithium ions.

(20) The above conditions for obtaining the sorbent allow to synthesize an ion exchanger, which has increased chemical stability, high exchange capacity, and efficient selectivity to lithium ions.

(21) An optimal ratio between niobium and zirconium in the material is chosen on the basis of the experimental data obtained in studying the dependence of the exchange capacitance of the sorbent on lithium and the separation coefficient for lithium and sodium ions on the content of zirconium ions in the sorbent (FIG. 1).

(22) FIG. 1 shows dependence of the capacitance on lithium (E.sub.Li) and the separation factor for the ion in lithium and sodium (P.sub.Li,Na) on the content in the sorbent of zirconium ions, where n=Zr (IV):Nb (V) is the ionic ratio in the sorbent. In this drawing, curve 1 corresponds to E.sub.Li obtained with the use of 0.1 N LiOH. Curve 2 corresponds to E.sub.Li obtained with the use of a solution of lithium and sodium salts at ionic ratio Li.sup.+:Na.sup.+=1:10, pH=12. Curve 3 corresponds to P.sub.Li,Na obtained with the use of a solution of lithium and sodium salts at ionic ratio Li.sup.+:Na.sup.+=1:10, pH=12. The calcination temperature of the samples is 520 C.

(23) The obtained data shown in FIG. 1 indicate that the maximum value of the exchange capacity and selectivity to lithium ions is exhibited by materials whose composition corresponds to the ratio of niobium to zirconium in the range of 1 to (0.1 to 0.7).

(24) To obtain such a composition, it is necessary to keep the ratio of the hydrated niobium oxide to the hydrated zirconium oxide in the solution the same as prior to mixing. In other words, the entire contents of the niobium and zirconium should transfer to a solid state contained in the precipitate.

(25) The optimal conditions needed for heat treatment of the obtained granular material saturated with lithium ions were determined from the experimental data relating to sorption properties of sorbent samples prepared with a Zr (IV) to Nb (V) ratio equal in the solid phase to 0.30:1. The samples were calcined at different temperatures. The results are shown in FIG. 2, which illustrates the influence of the heat treatment temperature in the synthesis of the material on the sorption-selective properties and the chemical stability of the sorption materials obtained.

(26) In the drawing, curve 1 corresponds to E.sub.Li obtained with the use of 0.1 N LiOH; curve 2 corresponds to E.sub.Li obtained with the use of a solution of lithium and sodium salts at ionic ratio Li.sup.+:Na.sup.+=1:10, pH=12; curve 3 corresponds to P.sub.Li,Na obtained with the use of a solution of lithium and sodium salts at ionic ratio Li.sup.+:Na.sup.+=1:10, pH=12; and curve 4 shows sorbent losses (m) per 1 work cycle in a solution of lithium and sodium salts at the ionic ratio Li.sup.+:Na.sup.+=1:10, pH=12.

(27) The results of the experiments show that the optimum temperature for calcining the Li-form of the granulated mixed hydrated niobium and zirconium oxide to obtain a granulated mixed lithium, niobium, and zirconium oxide (i.e., a tripled mixed oxide, which is a Li-form of an inorganic ion exchanger) is in the range of 450 C. to 600 C. A time needed to keep the material at this temperature for the formation of the sorbent structure should be in the range of 2 to 3 hours. If heat treatment is carried out under these conditions, the obtained sorbent, which in this case possesses the ion-sieve effect, acquires a maximum exchange capacity and selectivity to lithium ions and is characterized by minimal losses in alternating sorption-desorption cycles.

(28) The remaining operations of the proposed method for obtaining the granulated sorbent on the basis of precipitate of a mixed hydrated niobium and zirconium oxide and saturating the granulated material with lithium were carried out under the same conditions as in the method disclosed in the aforementioned article of P. Kudryavtsev, et al. More specifically, the cation exchanger ISN-1 was prepared by precipitation of hydrated niobium pentoxide (GPN) by mixing 0.1 M solutions of potassium niobate and hydrochloric acid, granulating the GPN, saturating the granular product with lithium ions from 0.050.1 M solution of lithium carbonate, and then calcinating the product at 40025 C. for 23 hours. After calcination and conversion to the H-form (treatment with 0.1-0.2 M nitric acid solution), the sorbent was ready for lithium sorption. The obtained sorbent was suitable for extracting lithium from slightly alkaline solutions in the presence of both oxidizing agents and reducing agents.

(29) The effectiveness of the proposed method is illustrated by the examples given below. It is understood, however, that these examples should not be construed as limiting the scope of the invention and that they are given only for illustrative purposes.

(30) The following methods and instruments were used for processing the materials and measuring properties of the obtained products mentioned in the subsequent examples.

(31) Equipment and Procedures Used in the Method of the Invention

(32) Ion-Exchange Column

(33) As ion-exchange column used in the method of the invention was a standard chromatographic column with a diameter of up to 10 mm. The height of the sorbent layer was maintained in the range of 10 to 15 column diameters. The solution was fed through the column at a constant linear speed, in the range of 1 to 10 mm/s. The feed rate of the solution was maintained by means of a peristaltic pump. During sorption experiments, special measures were taken to prevent air from entering the sorbent layer and to partially dry the sorbent granules.

(34) Determination of the Content of Lithium

(35) Determination of lithium in solutions was carried out by the method of emission photometry of a flame. The most intense resonance line in the spectrum of lithium, 670.8 nm, was used for the analysis. This line corresponds to the transition between the energy levels 2.sup.2S.sub.1/2 and 2.sup.2P.sup.0.sub.3/2 at the excitation energy of 1.85 eV. The sensitivity of the method, in determining lithium (with the use of the FLAME PHOTOMETER, FP8000 series device; A. KRSS Optronic), was 0.001-0.0005 g Li/ml. The content of lithium was determined from the calibration based on reference solutions prepared based on pure metal salts and their mixtures present in the solutions under study, which were close in proportion to the test solutions. Determination of sodium content was carried out in a similar way.

(36) Determination of the Content of Zirconium

(37) Determination of the content of zirconium and niobium in the composition of the investigated sorbent samples was carried out by X-ray fluorescence spectroscopy. The experiments were performed on a VRA-30 spectrometer. The source of excitation was a tube with a tungsten anode, operating at U=30 kV, I=15 mA. A LiF single crystal was used as the analyzer crystal. The registration was carried out using a proportional counter.

(38) The Determination of the Content of Niobium

(39) The determination of the content of niobium was carried out along the line K.sub..sub.1,2, the sensitivity of the method was 0.05%. Determination of the zirconium content was carried out along the line K.sub..sub.1, the sensitivity of the method was 0.003%. The background in the analysis was taken into account by the method of linear interpolation and by using a blank sample. Samples of materials for X-ray fluorescence analysis were prepared by compressing them in the form of tablets with NaCl (S7653 SIGMA-ALDRICH 99.5% (AT)) at a pressure of 4000 kg/cm.sup.2. The instrument was calibrated using samples containing fixed amounts of niobium pentoxide (203920 ALDRICH 99.99% trace metals basis) and zirconium dioxide (230693 ALDRICH 99% trace metals basis).

(40) Sorption-Selective Parameters

(41) The following characteristics are taken as parameters describing sorption-selective properties: a total exchange capacitance E.sub.Li0, obtained by using 0.1 N LiOH solution as a sorbent; a selective lithium capacitance El.sub.i1 used for sorption from a solution of lithium and sodium salts at an ionic ratio Li.sup.+:Na.sup.+ in the range of 1 to 10 at pH=12; and a coefficient P.sub.Li,Na of selectivity of the sorbent with respect to lithium, which is a direct parameter that characterizes separation of lithium from sodium and which is represented by the following formula:
P.sub.Li,Na=E.sub.Li1.Math.C.sub.Na/E.sub.Na1.Math.C.sub.Li,
where

(42) E.sub.Li1 is a selective lithium capacity at sorption from a solution of lithium and sodium salts at ionic ratio Li.sup.+/Na.sup.+ of 1/10 at pH=12 (mg-eqv/g sorb.);

(43) E.sub.Na1 is a sodium capacity at sorption from a solution of lithium and sodium salts at ionic ratio Li.sup.+/Na.sup.+ of 1/10 at pH=12 (mg-eqv/g sorb.);

(44) C.sub.Li is a molar concentration of Li.sup.+ in a solution of lithium and sodium salts at ionic ratio Li.sup.+/Na.sup.+ of 1/10 at pH=12 (mol/l);

(45) C.sub.Namolar concentration of Na.sup.+ in a solution of lithium and sodium salts at ionic ratio Li.sup.+/Na.sup.+ of 1/10, pH=12 (mol/l).

EXAMPLES

Example 1

(46) A predetermined amount of 0.05 M solution ZrOCl.sub.2 in 1.0 M HCl is poured to 2.0 l of a 0.05 M solution of K.sub.3NbO.sub.4 (pH=12.7) with a vigorous stirring. The pH of the precipitation process is 5 to 6 (correction with HCl). The resulting precipitate of a mixed hydrated niobium and zirconium oxide is washed by successive decantations to a residual concentration of potassium ions equal to 0.08-0.09 g/l and then frozen at t=6 C for about 30 hours. The freezing produces a granulated material. After thawing, the granulate is placed in an ion-exchange column, and about 4 l of a 0.1 M solution of Li.sub.2CO.sub.3 is passed. Next, the precipitate of the mixed hydrated niobium and zirconium oxide is discharged from the column, air-dried, then heated to the desired temperature (with a temperature increasing rate of 10 deg/min; specific temperatures are given below in Tables 1 and 2), and held at this temperature for 3 hours. As a result, a sorbent is obtained, the main fraction of which is a granule with a granule size of 0.20.7 mm.

(47) The effect of synthesis conditions in obtaining ion exchanger on its sorption properties is summarized in Table 1. This table presents results of tests of sorbents obtained at various conditions of synthesis but within the scope of the present invention. In the ion-exchange test, a solution of the following composition (g/l) is used: Li.sub.2CO.sub.35.5; NaCl: 53.0; NaOH3.0 (pH=12.1).

(48) TABLE-US-00001 TABLE 1 Influence of synthesis conditions on compositions and properties of sorbents (synthesis under conditions within the scope of the present invention) The sorbent obtaining conditions Test results Zr(IV): Total Nb(V) ion Selective Output of the ration in exchange capacity LiNa working solution Treatment capacity by separation fraction during temperature E.sub.Li0, Li, E.sub.Li1, coefficient, (0.2 0.7 mm), synthesis T, C. Sorbent composition* mg-eqv/g mg-eqv/g P.sub.Li,Na mass % 0.191 520 H.sub.0.98NbO.sub.2.990.191ZrO.sub.2 3.39 2.52 48.2 96 0.010 520 H.sub.0.19NbO.sub.2.590.191ZrO.sub.2 0.70 0.60 37.3 96 0.053 500 H.sub.0.38NbO.sub.2.990.053ZrO.sub.2 1.41 1.14 27.7 94 0.069 400 H.sub.0.94NbO.sub.2.970.069ZrO.sub.2 3.41 1.57 20.0 91 0.069 550 H.sub.0.39NbO.sub.2.690.069ZrO.sub.2 1.41 1.06 25.0 96 0.103 600 H.sub.0.35NbO.sub.2.670.103ZrO.sub.2 1.25 0.89 23.4 97 0.136 470 H.sub.0.80NbO.sub.2.900.136ZrO.sub.2 2.85 2.24 28.6 92 0.191 440 H.sub.1.04NbO.sub.3.020.191ZrO.sub.2 3.61 2.43 24.0 92 0.191 580 H.sub.0.75NbO.sub.2.880.191ZrO.sub.2 2.60 1.67 31.0 97 0.300 470 H.sub.1.05NbO.sub.3.030.300ZrO.sub.2 3.48 2.31 29.4 91 0.366 550 H.sub.0.91NbO.sub.2.960.366ZrO.sub.2 2.93 1.80 34.1 97 0.450 500 H.sub.1.05NbO.sub.3.020.450ZrO.sub.2 3.26 1.90 34.6 94 0.660 470 H.sub.1.10NbO.sub.3.050.660ZrO.sub.2 3.17 1.40 21.2 92 0.660 520 H.sub.0.91NbO.sub.2.960.660ZrO.sub.2 2.62 1.11 30.8 96 *The composition of the sorbent prepared for sorption of lithium (H-form)

(49) Table 2 shows results of tests of sorbents obtained at various conditions of synthesis but beyond the scope of the present invention.

(50) TABLE-US-00002 TABLE 2 Influence of synthesis conditions on the composition and properties of sorbents (synthesis under conditions beyond the scope of the present invention) The sorbent obtaining conditions Test results Zr(IV): Total Nb(V) ion Selective Output of the ration in exchange capacity LiNa working solution Treatment capacity by separation fraction during temperature E.sub.Li0, Li, E.sub.Li1, coefficient, (0.2 0.7 mm), synthesis T, C. Sorbent composition* mg-eqv/g mg-eqv/g P.sub.Li,Na mass % 0.269 355 H.sub.1.09NbO.sub.3.050.269ZrO.sub.2 3.65 2.22 6.1 85 0.660 625 H.sub.0.40NbO.sub.2.700.660ZrO.sub.2 1.15 0.66 7.5 96 0.995 400 H.sub.1.20NbO.sub.3.100.995ZrO.sub.2 3.09 1.40 6.9 88 0.995 440 H.sub.1.16NbO.sub.3.080.995ZrO.sub.2 2.98 1.20 11.5 90 0.995 580 H.sub.0.73NbO.sub.2.870.995ZrO.sub.2 1.89 0.60 14.8 94 *The composition of the sorbent prepared for sorption of lithium (H-form)

(51) It can be seen from the presented data that the total exchange capacity of the samples of the sorbents E.sub.Li0 synthesized under conditions is 2.580.56 mg-eqv/g; the selective lithium capacitance is E.sub.Li1 is 1.620.35 mg-eqv/g; the coefficient P.sub.Li,Na of selectivity of the sorbent with respect to lithium reaches values of PLi, Na=304, and its value for the optimum composition (i.e., for the conditions within the scope of the present invention) is P.sub.Li,Na=48. For samples obtained outside the range of optimal conditions, these values are E.sub.Li0=2.51.2 mg-eqv/g, E.sub.Li1=1.20.8 mg-eqv/g, and P.sub.Li,Na=9.44.6. These data show that obtaining of the sorbents under optimal conditions produce great results, over both the total exchange capacity and the selective capacity of lithium. The differences between optimal and non-optimal synthesis conditions are reflected especially noticeably on coefficient P.sub.Li,Na of selectivity of the sorbent with respect to lithium.

(52) The advantages of the sorbent produced by the proposed method over the prototype are given in Table 3. Lithium sorption is carried out from the solution with the above composition. The elution of lithium from the sorbent is carried out with 0.1 N HNO.sub.3 solution. The table shows average results for 5 cycles of sorbent operation.

Example 2

(53) To compare the properties of the sorbents prepared by the method of the invention and conventional methods, weights of sorbents (50 g each) are placed in ion exchange columns with parameters of 3.2 cm.sup.230 cm. Sorption is conducted from a solution containing (g/l): Li.sub.2SO.sub.45.5; NaCl56.0; NaOH3.0; pH=12.1.

(54) Tests of sorbents are carried out in the following sequence. The sorbents are loaded into columns and treated with solutions of HNO.sub.3 at concentration of 0.2 mol/l. The columns are then washed with water until the reaction of media became neutral, and lithium is sorbed from the solutions of the above compositions (filtration rate: 40-60 ml/h, flowing volume: 1500-1600 ml). After sorption of lithium, the columns are washed with water (300-400 ml), and ion exchangers are regenerated under the action of 0.1-0.2 mol/l of HNO.sub.3. At the regeneration stage, the filtration rate is maintained at about 100 ml/h, and 800-900 ml of the solution is passed. After completion of regeneration, the columns are washed with water until the media become neutral, and a new lithium sorption cycle is started. In total, during the tests, five sorption/desorption's cycles are conducted. The averaged test results are shown in Table 3.

(55) TABLE-US-00003 TABLE 3 Sorbent Test Results with Model Solutions Exchange capacity, LiNa Losses per Column mg-eqv/g separation one working Treated Sorbent E.sub.Li1 E.sub.Na1 coefficient, P.sub.Li, Na cycle, % Volumes According to 2.45 0.20 0.35 0.03 49 5 1.8 95 8 the invention Conventional 1.42 0.20 0.36 0.04 38 6 2.1 51 7

(56) As can be seen from Table 3, the sorbent obtained according to the proposed method has sorption-selective characteristics and chemical stability more than two times higher than the sorbent obtained by the known methods.

(57) In the second series of tests, experiments are conducted for testing a synthesized sorbent by sorption from a natural underground brine of high mineralization. The brine has the following composition (g/l): Li.sup.+0.013; Na.sup.+76.0; K.sup.+2.7; Mg.sup.2+3.8; Ca.sup.2+19.5; NH.sub.4.sup.+0.13; Cl.sup.154; Br.sup.0.7; I.sup.0.01; SO.sub.4.sup.20.12; HCO.sub.3.sup.0.07; pH=8.7. Prior to desorption, the sorbent is washed with a 0.1M NH.sub.4Cl solution to remove salting-out alkaline earth ions. The desorption is conducted with a solution of 0.1N HNO.sub.3.

(58) Comparative data on the characteristics of sorbents obtained by the known and proposed methods are presented in Table 4.

(59) TABLE-US-00004 TA 4 Sorbent Test Results on Real Natural Brines Exchange capacity, LiNa Losses per Column mg-eqv/g separation one working Treated Sorbent E.sub.Li1 E.sub.Na1 coefficient, P.sub.Li, Na cycle, % Volumes According to 2.55 0.15 0.33 0.08 (1.4 0.2) .Math. 10.sup.4 1.1 4200 200 the invention Conventional 0.87 0.11 0.18 0.02 (0.9 0.1) .Math. 10.sup.4 1.3 1800 200

(60) The technical and economic advantages of this method in comparison with the base object (the prototype method) are the following: increase in the sorption capacity for lithium and the selectivity of the sorbent to this metal in 1.82.0 times; and 20-25% improvement in the operating properties of the sorbent by reducing its losses in repeated cycles of sorption and desorption.

(61) Thus, it has be shown that the sorbent obtained by the method of the invention is suitable for industrial production of lithium by extraction from complex natural and technological brines.

(62) The method of the invention for obtaining inorganic sorbents for extracting lithium from natural and technological brines was described with reference to specific examples of compositions and technological steps. It is understood, however, that these compositions and process steps were give only as examples and that any changes and modifications are possible within the scope of the attached patent claims. For examples, the units of the synthesis equipment may vary, depending on specific conditions. The brines may be taken from different sources. The sorbents obtained by the method of the invention may find different applications, and the synthesis of the sorbents can be conducted at different temperatures selected according to specific conditions. Various acids can be used in the method.