Method of producing granular sorbent for extracting lithium from lithium-containing brine

Abstract

Disclosed a method for the preparation of granular sorbent based on LiCl.2Al(OH).sub.3.nH.sub.2O for lithium recovery from lithium-containing brines, comprising production of a powder of LiCl.2Al(OH).sub.3.nH.sub.2O (DHAL-Cl) from aluminum chloride solution comprising lithium, separation of the powder DHAL-Cl from the obtained solution by centrifugation with further removing the excess LiCl, drying of the powder DHAL-Cl; and, granulation of the powder DHAL-Cl with the addition of chlorinated polyvinylchloride and a organochlorine solvent to obtain the granular sorbent based on LiCl.2Al(OH).sub.3.nH.sub.2O; wherein the aluminum chloride solution comprising lithium is prepared by dissolving crystalline hydrate of hexaaqua aluminum chloride in aqueous solutions comprising lithium in the form of LiCl, Li2CO3, or LiOH.H2O or mixtures thereof, and concentration of aluminum chloride in the solution is 45-220 kg/m.sup.3.

Claims

1. A method for the preparation of a granular sorbent based on LiCl.2Al(OH).sub.3.nH.sub.2O for lithium recovery from lithium-containing brines, the method comprising: preparation of a powder of LiCl.2Al(OH).sub.3.nH.sub.2O (DHAL-Cl) from aluminum chloride solution comprising lithium with addition of an alkaline reagent; separation of the powder DHAL-Cl from the obtained solution by centrifugation with further removing excess LiCl, drying the powder DHAL-Cl; and granulation of the powder DHAL-Cl with the addition of chlorinated polyvinylchloride and an organochlorine solvent to obtain the granular sorbent based on LiCl.2Al(OH).sub.3.nH.sub.2O; wherein the aluminum chloride solution comprising lithium is prepared by dissolving crystalline hydrate of hexaaqua aluminum chloride in an aqueous solution comprising lithium in the form of LiCl, Li.sub.2CO.sub.3 or LiOH.H2O or mixtures thereof, and concentration of aluminum chloride in the solution is from 45 to 220 kg/m.sup.3.

2. The method according to claim 1, wherein the alkaline reagent is sodium hydroxide and sodium hydroxide is added to adjust pH to 6-7.

3. The method according to claim 1, wherein the removing of excess LiCl is carried out by pulping the powder DHAL-Cl in water followed by further centrifugating and recovering the powder DHAL-Cl.

4. The method according to claim 1, wherein the excess LiCl separated from the powder DHAL-Cl is directed to the stage of preparing the aluminum chloride solution comprising lithium.

5. The method according to claim 1, wherein the atomic ratio of Al:Li in the aluminum chloride solution comprising lithium is from 2.0 to 2.3.

6. The method according to claim 1, further comprising grinding the powder DHAL-Cl before granulation.

7. The method according to claim 6, wherein grinding is carried out to a particle size ≤0.10 mm.

8. The method according to claim 1, wherein drying of the powder DHAL-Cl represent two-stage drying.

9. The method according to claim 8, wherein the two-stage drying of the powder DHAL-Cl comprises, at the first stage, heating with air in the fluidized bed mode, maintaining temperature in the drying zone from 70 to 75° C. to residual moisture content in DHAL-Cl from 9.0 to 9.5% by weight; and at the second stage, vacuum drying with stirring and maintaining temperature in the drying zone from 60 to 65° C. to residual moisture content in DHAL-Cl from 1.5 to 2.0% by weight.

10. The method according to claim 1, wherein granulation comprises preparing a paste from powder DHAL-Cl with chlorinated polyvinylchloride with an organochlorine solvent; extruding the prepared paste followed by subjecting the extrudate to countercurrent contact with heated airflow to separate the extrudate from the organochlorine solvent, directing the extrudate to a vacuum degassing stage, followed by subjecting the extrudate to crushing and classification.

11. The method according to claim 10, wherein the organochlorine solvent is selected from methylene chloride, trichlorethylene and tetrachlorethylene or a mixture thereof.

12. The method according to claim 10, wherein the airflow saturated with vapors of the organochlorine solvent or a mixture of organochlorine solvent vapors is directed to compressing stage to recover the organochlorine solvent or a mixture of organochlorine solvent vapors, which are returned to granulation stage.

13. The method according to claim 12, wherein the compressing stage includes: compressing the airflow saturated with vapors of the organochlorine solvent or a mixture of organochlorine solvent vapors to the pressure of 6 atm, while cooling to −3° C., to obtain a liquid phase of the organochlorine solvent or a mixture of organochlorine solvent vapors and water, followed by separation of the condensed phase from gaseous phase by fogging with settling and separation of phases of the organochlorine solvent or a mixture of organochlorine solvents from water; deep cooling to −15° C. of compressed air-vapor stream with deep condensation of the vapors of the organochlorine solvent or a mixture of organochlorine solvent vapors to a liquid phase and condensation of water vapor to ice crystals, followed by separation of the condensed phases from the air stream and separation of the condensed phases into a solid ice phase and liquid organochlorine solvent; decompression of the air flow separated from the condensed phases by heating to 0° C.; heating the air stream to 120-130° C. and directing it to the stage of heated air treatment of the extrudate; recovering the liquid condensed phases of the organochlorine solvent or a mixture of organochlorine solvents.

14. The method according to claim 13, wherein after combining the ice crystals with the liquid condensed water phase, the water phase is directed to the stage of preparing the aluminum chloride solution comprising lithium.

15. A granular sorbent based on compound LiCl.2Al(OH).sub.3.nH.sub.2O with a defective structure, having mechanical strength from 98.9±0.2% to 99.2±0.2% and static exchange capacity for LiCl, mg Li/g, sorbent, from 5.9±0.1 mg to 6.2±0.1 mg.

16. A granular sorbent based on compound LiCl.2Al(OH).sub.3.nH.sub.2O with a defective structure, obtained by the method of claim 1.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a technological scheme for producing a granular sorbent for lithium recovery from lithium-containing brines wherein the present invention is applied as in-line process at a plant for fabrication of commercial lithium products.

(2) FIG. 2 is a table listed the properties of organic solvents used for granulation of DHAL-Cl powder.

(3) FIG. 3 is a vapor pressure-temperature diagram for trichloroethylene (TCE).

(4) FIG. 4 is a table of results obtained when testing the samples of granular DHAL-Cl sorbent, produced by using mixed lithium-containing aqueous solutions of AlCl.sub.3 from various lithium-containing sources.

(5) FIG. 5 is a table used to compare chemical compositions of granular DHAL-Cl sorbent samples with preliminary removal of lithium chloride from the synthesized dispersed phase of DHAL-Cl and without preliminary removal.

(6) FIG. 6 is a table of results obtained when testing the samples of granular DHAL-Cl sorbent after previous removing a free (excessive) lithium chloride, but before drying, grinding and granulation of DHAL-Cl dispersed phase in comparison with the sample passed the step of removing free lithium chloride after granulation and cooling.

DETAILED DESCRIPTION OF THE INVENTION

(7) In accordance with the technological scheme (FIG. 1), the main technological conversion stages of the industrial fabrication of lithium products, for example, the fabrication of lithium products from lithium-containing hydromineral raw materials, are following ones: sorption enrichment of the brine in relation of lithium chloride, followed by removal of the brine residue and obtaining a primary lithium concentrate with LiCl content no more than 10 kg/m.sup.3; concentrating of the primary lithium concentrate to obtain a productive concentrate with LiCl content from 60 kg/m.sup.3 to 480 kg/m.sup.3, according to which lithium product is require; obtaining the commercial lithium products from the productive lithium concentrate as a lithium carbonate of technical grade, lithium carbonate of battery grade, lithium hydroxide monohydrate of brands LGO-3, LGO-2. LGO-1, lithium chloride of technical grade. Each of the commercial products can be used as a starting reagent for the preparation of lithium-containing aqueous solutions of AlCl.sub.3 and synthesis of the dispersed phase of a chlorine-containing species of double aluminum and lithium hydroxide (LiCl.2Al(OH).sub.3.nH2O).

(8) The process of obtaining an aqueous lithium aluminum chloride solution from commercial lithium products is described by the following chemical equations:
H.sub.2O+AlCl.sub.3+Li.sub.2CO.sub.3.fwdarw.AlCl(OH).sub.2+2LiCl+CO.sub.2↑  (1)
H.sub.2O+AlCl.sub.3+LiCl.fwdarw.AlCl.sub.2(OH)+LiCl+HCl  (2)
LiOH.H.sub.2O+AlCl.sub.3.fwdarw.AlCl.sub.2(OH)+LiCl+H.sub.2O  (3)

(9) Since there is no strict requirement to the content of impurities in a mixed lithium aluminum chloride solution, the preparation of that solution can be carried out not only from commercial lithium products, but also from technogenic lithium-containing materials and waste products in the form of a solution or solution mixtures. So, a mixed lithium aluminum water solution can be prepared from a primary lithium concentrate (LiCl solution of concentration 10 kg/m.sup.3 with NaCl and KCl admixture), a productive lithium concentrate (concentrated LiCl solution with NaCl and KCl admixture), which are obtained from the corresponding processing stages in the calculated quantities. In addition, an effective reagent for the preparation of a mixed lithium aluminum chloride solution can be a solution of lithium bicarbonate, which is an industrial intermediate in the production of lithium carbonate of battery grade. In this case, the chemical description of the process is as follows:
LiHCO.sub.3+AlCl.sub.3.fwdarw.AlCl.sub.2(OH)+LiCl+CO.sub.2↑  (4)

(10) The initial reagents for the preparation of a mixed lithium aluminum chloride aqueous solution can be the following ones: a waste product when producing a lithium carbonate of battery grade, namely, the lithium carbonate alkaline solution containing NaCl and KCl as the main impurities; a waste product when producing LiOH.H2O, namely, the LiOH solution containing NaOH and KOH as impurities.

(11) The optimum range of aluminum concentrations in the mixed lithium aluminum chloride aqueous solution is 45 to 220 g/dm.sup.3 in AlCl.sub.3 equivalent. When the content of AlCl.sub.3 below 45 g/dm.sup.3, the precipitated DHAL-Cl begins to be water-saturated and poorly separated from the mother liquor, and when AlCl.sub.3 above 220 g/dm.sup.3 mother liquor is supersaturated in NaCl and the precipitate DHAL-Cl is charged with crystals of sodium chloride.

(12) The mixed lithium aluminum chloride aqueous solution is brought into contact with 1.0-2.5N NaOH solution added portionwise with stirring until the pH of the resulting pulp is adjusted to 6.5-7.0. The resulting pulp is centrifuged, separating the liquid phase (aqueous NaCl solution) from the solid phase of the synthesized compound LiCl.2Al(OH).sub.3.nH.sub.2O. The liquid phase (fugate) is used either as a productive solution for the preparation of crystalline sodium chloride by evaporation and drying, or as a make-up solution to produce a sodium hypochlorite disinfection solution made from NaOH and Cl.sub.2 by membrane electrolysis of aqueous NaCl solution.

(13) The synthesized solid phase of the compound LiCl.2Al(OH).sub.3.nH.sub.2O (DHAL-Cl) is mechanically discharged from the centrifuge by a screw (without grinding of the solid phase) and pulped in a predetermined volume of fresh water and stirred for 20-30 minutes to remove excess LiCl from phase of DHAL-Cl into the liquid phase. The resulting aqueous LiCl solution is separated from DHAL-Cl by centrifugation of the pulp. An aqueous solution of LiCl (fugate) is used to prepare a mixed lithium-aluminum chloride aqueous solution.

(14) Centrifuged DHAL-Cl is dried. The drying of DHAL-Cl should proceed at a temperature in the drying zone that excludes the production of highly crystallized material. In order to achieve maximum performance DHAL-Cl is dried in two stages: at first DHAL-Cl is dried by heated air in fluidized bed at temperature 70 to 75° C. until the residual moisture content is 9.0 to 9.5 wt. %; then DHAL-Cl is dried at 60-65° C. in the vacuum drying mode with stirring until the residual moisture content is 1.5-2.0 wt. %. Dry powder DHAL-Cl is ground to a particle size of <0.1 mm.

(15) The ground powder is mixed with a chlorinated polyvinyl chloride (CPVC plasticizer) powder and organic solvent which is either methylene chloride or trichlorethylene or tetrachlorethylene (perchlorethylene), or mixtures thereof to form a homogeneous paste. The paste is extruded through a drawing nozzle with orifice diameter of 5 mm. The orifice diameter of 5 mm is optimal, it ensures the highest yield of the product of a given size with a sufficiently high degree of degassing of the extrudate. The extrudate is degassed in a countercurrent contact with the air stream. As follows from the table and the vapor pressure-temperature diagram of the solvents shown in FIGS. 2 and 3, the use of tetrachlorethylene is preferable due to the minimization of solvent loss during the production of paste and extrusion, the minimum solubility of water in the solvent, the minimum heat of evaporation, which ultimately minimizes the loss during recovery and the maximizes the recycle to production of the regenerated solvent with high quality.

(16) A more complete removal of the solvent from the extrudate is provided by vacuum treatment under pressure of 0.4 to 0.6 at. The degassed extrudate is crushed and classified. The fine fraction is fed to the mixing operation (preparation of the paste), and the DHAL-Cl granules of size in the range ≥1.0 mm and <2.0 mm are pelletized to give the granules a round shape, the fine fraction is screened and also fed to the mixing operation. Commercial granulated DHAL-Cl is packaged into drums.

(17) The air stream saturated with solvent vapors (P) is fed to compression (under pressure 6 at and temperature −3° C.), to condense partially the solvent and water vapor into the liquid phase and separate the liquid phase from the air-vapor mixture by mist elimination. The water phase is separated from solvent phase by decantating. The compressed air-vapor mixture passed through the mist elimination stage is cooled to a temperature of −15° C. to condense the solvent vapor into the liquid phase, and water vapor into the crystals, and to separate them from the air flow also by mist elimination. The condensed liquid phase of the solvent is separated from the ice crystals, mixed with the solvent condensed in the compression operation and fed to a mixing operation. The ice crystals are mixed with water phase condensed when compressing and used for obtaining a mixed lithium aluminum chloride aqueous solution. This technological process makes it possible to increase the recovery rate of low-boiling solvents up to 97 to 99%.

(18) The cleaned and dried air stream is heated to a temperature of 120 to 130° C. and fed to an air degassing operation of the extrudate.

(19) It is possible to realize the process of solvent recovery in one stage by freezing. In this case a recovery rate of methylene chloride 94 to 95% could be provided when cooling the air-vapor stream to −70° C. If trichlorethylene or tetrachlorethylene is used as a solvent, the recovery rate of 97% or more is achieved when cooling the air-vapor flow to −15° C. The choice of this or that variant of solvent recovery is carried out on the basis of the results of technical and economic calculations performed at the stage of investment justification for the practical implementation of the development.

Example 1

(20) In laboratory conditions, comparative tests of the sorption-desorption properties of batches of the granulated sorbent DHAL-Cl, made from various lithium-containing materials in accordance with the process flow diagram shown in FIG. 1.

(21) Sample No. 1 was produced using a mixed lithium aluminum-containing aqueous chloride solution obtained by dissolving 385.1 g of AlCl.sub.3.6H.sub.2O in a 3.03 liters carbonate-alkaline aqueous solution of the composition (g/dm.sub.3): lithium in terms of Li.sub.2CO.sub.3—10.9000; SO4—0.0531; Ni—0.0016; Pb—0.0075; Cu—0.0060; Na—0.5056; Ca—0.0209; Mg—0.0138; Fe—0.0006; B—0.0938; Cl—0.7502; pH=9.7, which is a real waste of production of lithium carbonate of battery quality, from technical lithium carbonate.

(22) Sample No. 2 was produced using a mixed lithium aluminum-containing aqueous chloride solution obtained by diluting with water to a total volume of up to 1 liter the mixture of 403.5 g of AlCl.sub.3.6H.sub.2O with 0.17 liters of depleted catholyte with composition (g/dm.sub.3): LiOH—120; NaOH—3.5, which is a waste product of LiOH.H.sub.2O from lithium carbonate or lithium chloride.

(23) Sample No. 3 was produced using a mixed lithium aluminum-containing aqueous chloride solution obtained by dissolving 403.4 g of AlCl.sub.3.6H.sub.2O in a 1.0 liter lithium bicarbonate solution (LiHCO.sub.3 content—63.5 g/dm.sub.3).

(24) Sample No. 4 was produced using a mixed lithium aluminum-containing aqueous chloride solution obtained by dissolving 403.2 g of AlCl.sub.3.6H.sub.2O in 3.82 liters of a primary chloride lithium concentrate of composition (g/dm.sub.3): LiCl—10.40; NaCl—0.20; KCl=0.1; MgCl.sub.2=0.02; CaCl.sub.2=0.04; B—0.005; SO.sub.4—0.03, which is a by-product of the production of technical lithium carbonate from natural lithium brine.

(25) Sample No. 5 was produced using a mixed lithium aluminum-containing aqueous chloride solution prepared by mixing 0.39 liters of an aqueous solution of lithium bicarbonate, 1.50 liters of a primary lithium concentrate, 1.25 liters of a lithium carbonate-alkaline solution and 403.2 g of AlCl.sub.3.6H.sub.2O.

(26) Sample No. 6 was prepared using a mixed lithium aluminum-containing aqueous chloride solution prepared by mixing 403.1 g of AlCl.sub.3 with 0.097 liters of a production lithium concentrate of composition (g/dm.sub.3): LiCl—481, KCl+LiCl<4.0 g/dm.sub.3 followed by adding water to bring the total volume of the solution to 1 liter.

(27) Sample No. 7 was produced using a mixed lithium aluminum-containing aqueous chloride solution obtained by mixing 403.3 g of AlCl.sub.3.6H.sub.2O with 40.7 g of technical Li2CO3, produced from lithium natural brine, with the addition of water to bring the total volume of the solution to 1 liter.

(28) As an alkaline reagent, 1.0N NaOH solution was used to prepare all the samples. Trichlorethylene was used as a solvent in the granulation. The obtained samples of granulated DHAL-Cl sorbents were tested for the following parameters: static exchange capacitance for LiCl, mechanical strength, bulk density, swelling according to the methods specified in TU2133-23599583-2002 “Sorbent for selective lithium extraction”. For testing, the lithium natural brine of the Znamensky deposit of the Irkutsk region was used (g/dm.sub.3): LiCl—2.2; NaCl—6.1; KCl=8.2; MgCl.sub.2=115; CaCl2—330; Br is 8.3; SO4=0.6; B=0.3; SrCl.sub.2—3.6 pH—5.1 and distilled water. As follows from the obtained results presented in the table in FIG. 3, all seven samples have almost identical characteristics in terms of exchange capacity and mechanical strength, which confirms the possibility of using a wide spectrum containing lithium in the form of chloride, carbonate, hydroxide, including waste products of commercial lithium products, for the synthesis of granular sorbent as lithium starting reagents.

(29) At the same time, the impurities contained in the lithium-bearing waste do not adversely affect the characteristics of the synthesized granular sorbent.

Example 2

(30) Using as an initial reagent AlCl.sub.3.6H.sub.2O, Li.sub.2CO.sub.3 technical, distilled water, PVC resin, methylene chloride as an organic solvent, two samples of the granular sorbent DHAL-Cl were prepared.

(31) Sample No. 8 was manufactured strictly according to the process schedule provided by the circuit in FIG. 1. Sample No. 9 differed from sample No. 8 in that the operation procedure for removing excess LiCl from the synthesized dispersed phase of DHAL-Cl was excluded from the technological procedure. Samples of 0.2 kg were sampled from each of the samples, which were tested according to the methods presented in Example 1. Before testing, samples of sorbents were analyzed in order to determine their initial quantitative composition. In this case, sample No. 9 was brought into contact with 0.5 dm3 of distilled water prior to testing to remove excess lithium chloride and dried to constant weight in a vacuum drier. The results of the chemical analysis of the quantitative composition of the starting samples are shown in the table in FIG. 5. Test results—in the table in FIG. 6. From the obtained results it follows that the test parameters of the compared samples are identical. However, the removal of excess lithium at the stage of synthesis of the dispersed phase of DHAL-Cl allows, firstly, to return to production the sorbent at the stage of synthesis of 22.5% of expensive lithium chloride from the amount of lithium chloride used, and second, to eliminate the need for a granular sorbent preparation operation for use in direct use.

Example 3

(32) Using as technical reagents AlCl.sub.3.6H.sub.2O, Li.sub.2CO.sub.3 technical, distilled water, PVC resin and various organic solvents (methylene chloride, trichlorethylene and tetrachlorethylene), three samples of the granular sorbent were obtained according to the process flow diagram (FIG. 1). Sample No. 10—solvent methylene chloride, sample No. 11—solvent trichlorethylene, sample No. 12—solvent—tetrachlorethylene. The obtained samples were tested for mechanical strength. The mechanical strength of the tested samples was as follows (%): sample No. 10—99.1±0.1; sample No. 11—99.0±0.1; sample No. 12—99.1±0.1. The difference in the mechanical strength of the tested DHAL-Cl samples of granulated, obtained using various solvents, is within the error of the determination.

Example 4

(33) A sample of the dispersed phase of DHAL-Cl was prepared from the reagents described in Examples 2 and 3, which, after removing free LiCl, was divided into two equal portions. The portions were dried each separately to a residual moisture content of 2% by weight. Sample No. 13 was dried in one step on a vacuum drier. Sample No. 14 was dried in two stages: in the fluidized bed at the first stage to a residual moisture content of 9 wt. %; in the evacuation mode (under pressure 0.6 atm) during torsion. It took 12 hours 40 minutes to dry sample No. 13. The total drying time of sample No. 14 was 3 hours 37 minutes. The transfer of the technological process to two-stage drying allows almost three-fold reduction in the drying time.

Example 5

(34) A batch of granular sorbent DHAL-Cl was prepared according to the technology of FIG. 1. After completion of the technological redistribution and classification, degassed extrudate, the resulting batch of DHAL-Cl of the predetermined granule size was divided into two equal parts. One sample (sample No. 15) was tested for mechanical strength without pelletizing. The second sample (sample No. 16) was pelletized in a rotating drum for 75 minutes and after the screening of the fine fraction was also tested for mechanical strength. Sample No. 15 showed a mechanical strength of 97.7±0.2%. Sample No. 16 showed a mechanical strength of 99.0±0.2%. Tests have shown that pelletizing of crushed DHAL-Cl particles by more than 1% increases its mechanical strength.

Example 6

(35) Two samples of granulated DHAL-Cl sorbent were produced by the process schedule (FIG. One sample (sample No. 17) using commercial tetrachlorethylene as an organic solvent. Another sample (sample No. 18) using reclaimed tetrachlorethylene, which was obtained by freezing (−15° C.) from the vapor-saturated circulating air stream to obtain an aggregate batch of granular DHAL-Cl. Sample No. 17 showed a mechanical strength of 99.1%, sample No. 18 was 99.0%. The difference was within the margin of error, which confirms the suitability of the recovered organic solvent for granulating the DHAL-Cl powder.