Granulated lithium extraction sorbent and method for producing same

Abstract

The present invention relates to granulated sorbents based on a polymeric binder and a lithium-aluminium double hydroxide chloride for use in the selective extraction of lithium from lithium-containing solutions, and further relates to a method for producing such sorbents. The aim of the present invention is to support the recovery of lithium from solutions by means of a durable and effective granulated lithium extraction sorbent based on a lithium-aluminium double hydroxide chloride. The sorbent according to the present invention is a granulated sorbent containing lithium-aluminium double hydroxide chloride particles and, as a binder, a polyvinyl formal. Methods for producing a granulated sorbent according to the present invention are based on a process of mixing lithium-aluminium double hydroxide chloride particles, a polyvinyl formal and dimethylformamide.

Description

[0001] Granular sorbent for lithium extraction and method for its production

[0002] Field of technology.

[0003] The present invention relates to granulated sorbents based on a polymer binder and a chlorine-containing form of double aluminum and lithium hydroxide, which can be used for the selective extraction of lithium from lithium-containing solutions, and a method for their production.

[0004] State of the art.

[0005] In the processes of extracting lithium from hydromineral raw materials and lithium solutions, sorbents based on a chlorine-containing form of double aluminum and lithium hydroxide (Cl-2Al(OH)3 PN2O) have found wide application, which ensures the sorption of lithium due to the intercalation process.

[0006] At the same time, the compound 1лСГ2А1(ОН)з пН2О (hereinafter referred to as DGAL-С1) in its pure form is of little use in industrial methods of lithium extraction, since it is a powder that forms an emulsion during the process of working with solutions, requiring separation, while the loss of sorbent, clogging of pipelines and other technological difficulties are inevitable.

[0007] For this reason, industrial methods for extracting lithium from hydromineral raw materials and solutions are based on the use of DG AL-S1 in the composition of granular sorbents, which ensures the technological efficiency of the process.

[0008] A method for producing a granulated sorbent based on a chlorine-containing variety of double aluminum and lithium hydroxide is known from the prior art according to patent RU2009714C1 (priority date 27.01.1992) “Method for producing a granulated sorbent for extracting lithium from brines”, in which the sorbent granules are obtained by mixing DGAL-C1 with a polymer binder and forming granules, while fluoroplastic is used as a polymer binder.

[0009] A disadvantage of this sorbent is the high cost of the binder, which increases the cost of the pellets and the lithium extraction process. Another drawback of the binder used is its hydrophobicity, which negatively impacts the efficiency of the lithium sorption and desorption process.

[0010] A method for producing a granulated sorbent based on a chlorine-containing variety of double aluminum and lithium hydroxide is known from the prior art according to patent RU2657495C1 (priority date 25.09.2017) "A method for producing a granulated sorbent for extracting lithium from lithium-containing brines under conditions of commercial lithium product production," in which the sorbent granules are obtained by mixing DGAL-C1 with chlorinated polyvinyl chloride in an organochlorine solvent, which is methylene chloride, trichloroethylene, tetrachloroethylene, or mixtures thereof, the prepared paste is extruded through dies with a diameter of 5 mm, the extrudate is brought into counter-current contact with a heated air flow, releasing the extrudate from the chlorine-containing solvent evaporating into the air flow, the extrudate, having passed the air degassing stage, is sent to the vacuum degassing stage under a vacuum of 0.4-0.6 atm, the extrudate after degassing is crushed and classified with the return of the fine fraction of granulated DGAL-C1 to the paste preparation operation, granules with a size of at least 1 ,0 mm and not more than 2.0 mm are subjected to drum rolling.

[0011] The disadvantage of this technical solution is the use of a hydrophobic binder, which negatively affects the sorption capacity of the sorbent.

[0012] A disadvantage of this technical solution is the use of highly volatile organochlorine solvents. The high evaporation rate of these solvents reduces the safety of the work area. Consequently, sealed equipment and expensive ventilation are required, increasing the cost of sorbent production.

[0013] A method for producing a granulated sorbent based on a chlorine-containing variety of double aluminum and lithium hydroxide is known from the prior art according to patent RU2801465C1 (priority date 30.12.2022) "Method for producing granulated sorbent DGAL-S1", in which granules are obtained by mixing DGAL-S1 powder, a binder and a solvent in a granulator-mixer, while chlorinated polyvinyl chloride resin is used as a binder, and methylene chloride as a solvent.

[0014] The disadvantage of this method is the use of methylene chloride as a solvent, which is expensive; to ensure the cost-effectiveness of the process, its recovery is required, which complicates the process of obtaining granules and increases the cost of the equipment.

[0015] Methylene chloride is also toxic and highly volatile, making it difficult to work with.

[0016] The use of hydrophobic chlorinated polyvinyl chloride as a binder negatively affects the sorption capacity of the sorbent.

[0017] A granule for lithium sorption is known from the prior art according to the invention patent RU2805741C1 (priority date 07 / 05 / 2023) "Granule for lithium sorption from an aqueous solution" and according to the patent for utility model RU220087U1 (priority date 07 / 05 / 2023) "Granule for lithium sorption from an aqueous solution", which is a granule based on a chlorine-containing variety of double aluminum and lithium hydroxide, which contains a waterproof spherical core coated with a solution-permeable composite of sorbent particles and a hydrophilic binder, and the hydrophilic binder has an open-pore structure.

[0018] The presence of a water-impermeable spherical core in the sorbent granule is claimed to be an advantage that ensures a reduction in the amount of expensive sorbent (DGAL-C1) in the granule, a reduction in the time of lithium sorption-desorption, due to the fact that a decrease in the thickness of the sorbent layer reduces the internal diffusion resistance to the sorption-desorption process, an expansion of the range of filtration rates of the solution and washing liquid through the granule layer, since it is possible to change the material of the core, its density and other parameters.

[0019] The claimed technical results can indeed be achieved using this granular sorbent; however, this granule configuration also has drawbacks. Reducing the specific amount of DGAL-C1 and the thickness of the DGAL-C1 layer leads to a decrease in the sorbent's sorption capacity. Ensuring a high filtration rate of solutions through the sorbent layer at the expense of sorbent capacity is impractical for systems with large column volumes due to the risk of granule breakage, carryover, localized compaction, uneven movement of the liquid front in the column, and other effects that reduce the efficiency of sorption, washing, and desorption. Therefore, the claimed solution is not universally applicable. The granule characteristics claimed in the invention are also not adapted to ensure a balance between sorption capacity and strength for granules based on coreless polyvinyl chloride.

[0020] A composition for lithium sorption is known from the prior art according to the invention patent RU2734857C1 (Priority date 21.03.2017) “Matrices containing lithium aluminates”, which is a granulated sorbent based on DGAL-C1, wherein the polymer contains from 0.5 to 3 equivalents of side amino groups per liter of the composition in the form of particles, the average pore size of the granules is from 5 to 100 nm, the average harmonic diameter of the granules is 200-1000 μm, the surface area of ​​the granules is from 20 to 150 m 2 / g, and aluminum is present in an amount of 14.5% or more by weight of aluminum atoms based on the total weight of the particulate composition.

[0021] The disadvantages of this granular sorbent include its use of a polymer base containing 0.5 to 3 equivalents of side-chain amino groups per liter of particulate composition. This base is complex and expensive to produce, requiring polymerization of a monomer mixture to produce copolymer granules, functionalization of the copolymer by chloromethylation, followed by amination.

[0022] A method for producing a sorbent is known from the prior art according to patent CN1 06507704B (priority date 30.12.2005) “Technology for preparing a lithium adsorbent”, in which DGAL-C1 is used as a sorbent, and cellulose acetate butyrate, polyethylene, epoxy resin and phenolic resin, polyvinyl acetal, polystyrene or polypropylate can be used as a binder for the granules.

[0023] A disadvantage of this technical solution is the use of binders with low moisture absorption, which significantly reduces the sorption capacity of the sorbent. The use of high temperatures during sorbent synthesis leads to a decrease in sorption characteristics.

[0024] Long synthesis times significantly reduce the volume of output, which is economically inefficient.

[0025] This technical solution, which includes the use of polyvinyl acetal as a binder, is closest to the technical solution claimed in the present invention.

[0026] The essence of the invention.

[0027] Granular sorbents based on a chlorine-containing variety of double aluminum hydroxide are actively used in the lithium mining industry.

[0028] The aim of the present invention is to provide the production of lithium extraction from solutions with a durable and effective granular sorbent for the extraction of lithium based on a chlorine-containing form of double aluminum hydroxide and lithium.

[0029] The technical result to which the invention is directed is the safe production of a durable and effective sorbent based on a chlorine-containing form of double aluminum hydroxide.

[0030] The technical result to which the invention is directed is to ensure an effective sorption capacity of a granular sorbent through the use of a hydrophilic binder.

[0031] The technical result to which the invention is directed is to ensure the strength of a sorbent based on a chlorine-containing form of double aluminum hydroxide while ensuring high sorption properties.

[0032] The technical result of the invention is to reduce the cost of the sorbent by using available raw materials.

[0033] The technical result is achieved in that the granulated sorbent for extracting lithium from a solution based on a chlorine-containing form of double aluminum and lithium hydroxide includes polyvinyl formal as a binder.

[0034] Polyvinyl formal has high strength, which ensures the sorbent's high durability and abrasion resistance. Polyvinyl formal also has high hydrophilicity, compared to other polyvinyl acetals, which ensures good contact of solutions with DGAL-C1 in the sorbent granules, which ensures high sorbent capacity and sorption rate, as well as the efficiency of the lithium sorption and desorption process.

[0035] Polyvinyl formal has higher adhesion to various surfaces compared to other polyvinyl acetals, which also affects the strength of the sorbent due to the strong binding of DGAL-C1 with polyvinyl formal.

[0036] Polyvinyl formal is an accessible and inexpensive raw material for producing sorbent granules.

[0037] The technical result is achieved by producing a granulated sorbent by mixing a powder of a chlorine-containing form of aluminum and lithium double hydroxide with polyvinyl formal in dimethylformamide. The use of dimethylformamide for this purpose ensures effective dissolution of the polyvinyl formal, which ensures a homogeneous mixture, followed by the production of granules with uniformly distributed DGAL-C1 particles, ensuring the effectiveness of the lithium sorption and desorption process. The homogeneity of the mixture ensures a uniform granule structure, which positively affects their strength.

[0038] The technical result is achieved by the fact that dimethylformamide has a lower volatility compared to methylene chloride, and also, compared to phenol derivatives and acetic acid used to dissolve polyvinyl formal, dimethylformamide is less toxic, which makes it possible to increase production safety and simplify the design of the working unit.

[0039] The technical result is achieved by subjecting the resulting mixture to granulation followed by drying, which ensures the production of granules that are convenient for transportation and use in sorption-desorption units for lithium extraction, while drying also allows for the removal of solvent residues from the granules.

[0040] An additional technical advantage is that mixing and granulation of the mixture can occur within the granulator-mixer housing, intensifying the granulation process by creating a vortex field of powdered material particles and a vapor-gas mixture within the granulator-mixer housing. The granulator-mixer ensures mixing of the starting components and granulation of the sorbent in a single process.

[0041] It is possible to carry out the degassing process in a closed circuit of a circulating steam-gas mixture, which reduces the loss of solvent during its recovery in the process.

[0042] Simultaneous mixing, granulation, and degassing of the sorbent reduces the time it takes to produce granulated sorbent. This ensures the production of sorbent granules for lithium extraction from brines.

[0043] An additional technical advantage is that the mixture can be granulated by extruding dropwise through at least one opening into water while stirring. This allows for the production of granules of similar sizes and their use in sorption and desorption processes without additional separation, thereby accelerating the production of granulated sorbent. This ensures the production of sorbent granules for lithium extraction from brines.

[0044] The technical result is achieved by the process of producing granulated sorbent, which involves mixing a powder of a chlorine-containing form of aluminum and lithium double hydroxide with polyvinyl formalin in dimethylformamide. The mixture is then granulated by extruding it through at least one orifice to produce an extrudate, which is then dried and crushed. This provides a simple method for producing sorbent granules, eliminating the need for a separate drying step. This enables the production of sorbent granules for lithium extraction from brines.

[0045] The technical result is achieved in that the obtained granulated sorbent, according to any of the described methods, can be subjected to separation with the selection of a fraction from 0.5 to 3 mm.

[0046] A sorbent granule size of 0.5 to 3 mm is optimal for industrial applications, as the use of smaller fractions increases the risk of granule carryover, while larger fractions require longer sorption, washing, and desorption times due to the difficulty of solution penetration into the granule. Furthermore, larger and smaller granule fractions exhibit greater relative deviations in granule shape compared to the 0.5 to 3 mm fraction, which negatively impacts granule strength and abrasion resistance. Therefore, a granule size of 0.5 to 3 mm maintains the required strength and wear resistance of the sorbent, as well as high lithium sorption and desorption rates.

[0047] In its most general form, the sorbent according to the present invention is a granular sorbent for extracting lithium from lithium chloride solutions, comprising particles of a chlorine-containing variety of double aluminum lithium hydroxide and polyvinyl formal as a binder.

[0048] In the most common method for lithium extraction, the sorbent is placed inside a vertical column and a lithium chloride solution is passed through its bed. The lithium is sorbed through intercalation by the compound DGAL-C1, whose particles are dispersed within the sorbent granules, accessible, among other things, through the pores. After the sorption stage, the remaining lithium chloride solution is drained or displaced from the column with a washing liquid, and the sorbent is washed. The washing liquid can be water or brine, which can be diluted to varying degrees.

[0049] After washing, lithium is desorbed by passing the desorbing liquid through a sorbent layer; water or saline solutions are usually used as the desorbing liquid, with lithium passing into the desorbing liquid to produce an eluate rich in lithium.

[0050] The sorbent washing step increases the purity of the eluate, as the remnants of the original lithium chloride solution, which may contain impurities that can enter the eluate along with the desorbing liquid, are removed from the sorbent layer.

[0051] For industrial use of the sorbent, a high sorption capacity and sorption and desorption rates are important; they directly affect the speed and profitability of the lithium extraction process.

[0052] Pure DGAL-S1 has a sorption capacity of approximately 12 g of lithium per 1 kg. This value is unattainable for granular sorbent. However, the higher the sorption capacity, the more efficient the process. This capacity can be increased, among other things, by increasing the porosity of the sorbent granules and decreasing the granule size. Porosity and small granule size allow for a larger contact area between the lithium chloride solution and the DGAL-S1 particles, which positively impacts sorption and desorption rates and sorption capacity. However, the issue of sorbent strength becomes more pressing, as large pore volumes make the granules brittle, while small granule sizes complicate handling.

[0053] Sorbent granules are prone to wear and tear during operation; for practical use of the sorbent, its strength must be ensured.

[0054] To assess the strength of the sorbent, a method for determining the mechanical strength of granules during abrasion was adopted.

[0055] The essence of the method lies in the mechanical abrasion of a sorbent sample by shaking the granules in a working environment on a reciprocating shaker, separating the resulting fraction smaller than 0.25 mm and determining its percentage (volume) content.

[0056] The strength of the sorbent is calculated using the formula (P, %):

[0057] n = (Vi-V2) / Vi x 100,

[0058] where Vi is the volume of the sorbent sample, cm 3 ; V2 - volume of sorbent with fraction less than 0.25 mm, cm 3 .

[0059] A sample of sorbent with a volume of 100 cm 3 placed in a graduated cylinder with a volume of 250 cm 3 , pour 150 cm 3 water and close the cylinder. The cylinder is secured horizontally on a vibrating apparatus and shaken at a rate of 120 strokes per minute with a stroke length of 60 mm for 10 hours.

[0060] Sufficient strength of the sorbent for its industrial use can be considered to be a strength of at least 95%, calculated in the specified way.

[0061] This strength indicator allows us to reduce sorbent losses associated with mechanical wear to a level of less than 5% per year, under continuous operation conditions with an operating pressure of 1 atm.

[0062] A sample of the claimed granular sorbent with a granule size of 0.5 to 1 mm demonstrated a strength of 95.2%, while a sample of the claimed granular sorbent with a granule size of 1 to 3 mm demonstrated a strength of 96.3%, which can be considered sufficient for the effective use of the sorbent in industrial production. The claimed composition ensures a high working capacity of the sorbent for lithium for its effective extraction, more than 4.0 mg / g.

[0063] The claimed sorbent can be obtained by various methods, including those described in the present invention, but is not limited to them.

[0064] The production of a granulated sorbent is generally carried out by mixing a powder of a chlorine-containing form of double aluminum and lithium hydroxide with polyvinyl formal in dimethylformamide. As a result of mixing, a mixture is obtained that can be subjected to granulation in a granulator-mixer with subsequent drying of the granules, or extrusion with the mixture being fed in the form of drops into water to form granules with their subsequent drying, or extrusion with subsequent drying of the resulting mass and its grinding to obtain granules.

[0065] All the described methods allow to obtain a granulated sorbent with the properties stated above, and the resulting sorbent can be further subjected to separation with the selection of a fraction from 0.5 to 3 mm, as the most effective in use.

[0066] To provide a more detailed disclosure of the essence of the invention, examples of its implementation are provided.

[0067] Example 1.

[0068] Lithium concentrate was obtained from lithium-bearing natural brine.

[0069] The initial brine composition was Na - 91.7 g / dm3 3 , K - 7.7 g / dm 3 , Ca - 2.9 g / dm3 3 , Mg - 3.1 g / dm 3 , Li - 1530 mg / dm 3 , C1 - 164.9 g / dm3 3 , SO4 - 3.2 g / dm 3 , B -0.5 g / dm 3 .

[0070] A granulated sorbent containing particles of a chlorine-containing variety of double aluminum and lithium hydroxide and polyvinyl formal as a binder was used as a sorbent; the sorbent fraction used was from 0.5 to 3 mm.

[0071] The lithium concentrate was obtained as follows: a brine stream was passed through a sorbent layer in a column at a rate of 2 column volumes (hereinafter referred to as VC) / hour for 4 hours, after which the brine was drained from the column and desorption was carried out with distilled water at a rate of 5 VC / hour. The maximum dynamic sorption capacity was determined based on the kinetic curves.

[0072] The sorption capacity of the sample was 4.4 mg / g.

[0073] The strength of the sorbent, determined by the above method, was 95.7%.

[0074] Example 2.

[0075] Lithium concentrate was obtained from a chloride solution.

[0076] The initial brine had a lithium concentration of 1110 mg / dm3. 3 .

[0077] A granulated sorbent containing particles of a chlorine-containing variety of double aluminum and lithium hydroxide and polyvinyl formal as a binder was used as a sorbent; the sorbent fraction used was from 0.5 to 1 mm.

[0078] The lithium concentrate was obtained as follows: a stream of brine was passed through a sorbent layer in a column at a rate of 2 column volumes (hereinafter referred to as VC) / hour for 4 hours, after which the brine was drained from the column and desorption was carried out with distilled water at a rate of 5 VC / hour.

[0079] Based on the kinetic curves, the maximum dynamic sorption capacity was determined.

[0080] The sorption capacity of the sample was 6.13 mg / g.

[0081] The strength of the sorbent, determined by the above method, was 95.2%.

[0082] Example 3.

[0083] Lithium concentrate was obtained from a chloride solution.

[0084] The initial brine had a lithium concentration of 1110 mg / dm3. 3 .

[0085] A granulated sorbent containing particles of a chlorine-containing variety of double aluminum and lithium hydroxide and polyvinyl formal as a binder was used as a sorbent; a sorbent fraction of 2 to 3 mm was used.

[0086] The lithium concentrate was obtained as follows: a stream of brine was passed through a sorbent layer in a column at a rate of 2 column volumes (hereinafter referred to as VC) / h for 4 hours, after which the brine was drained from the column and desorption was carried out with distilled water at a rate of 5 VC / h.

[0087] Based on the kinetic curves, the maximum dynamic sorption capacity was determined.

[0088] The sorption capacity of the sample was 3.04 mg / g.

[0089] The strength of the sorbent, determined by the above method, was 96.4%.

[0090] Example 4.

[0091] In a stirred reactor, powder of a chlorine-containing form of double aluminum and lithium hydroxide, polyvinyl formal and dimethylformamide were mixed, the mixture obtained in the reactor was extruded through calibrated holes to form droplets of controlled size, the drops fell into a container with water, which was continuously stirred, as a result of which the drops formed granules.

[0092] The granules formed from the droplets were separated from the water and dried to obtain sorbent granules, which were used as the sorbent in Example 3.

[0093] The use of this method made it possible to obtain granules of the required size without the need for additional separation with the selection of the target fraction.

[0094] The use of dimethylformamide as a solvent made it possible to easily remove the solvent from the pores of the granules due to the high solubility of dimethylformamide in water during the granulation process.

[0095] Example 5.

[0096] The sorbent was obtained in a manner similar to Example 4, with the difference that the obtained granulated sorbent was subjected to separation with the selection of a fraction from 0.5 to 1 mm, after which the sorbent was used to extract lithium using the method indicated in Example 1.

[0097] Example 6.

[0098] Powder containing a chlorine-containing form of aluminum-lithium double hydroxide and polyvinyl formalin were fed into the granulator-mixer body, mixed, and dimethylformamide was added. Intense turbulent movement of the component flows in the mixer body and the gradual removal of excess solvent ensured the production of granules.

[0099] Dimethylformamide vapors removed from the granulator-mixer housing were condensed, which ensured solvent recovery and savings in the process.

[0100] The granule fraction obtained was from 0.2 to 10 mm.

[0101] The size of the resulting granules depends on the flow rate in the granulator-mixer, the ratio of components, the speed and time of introduction / removal of the solvent, temperature and other parameters; the optimal mode and conditions can be selected empirically for specific requirements for the sorbent granules.

[0102] The use of dimethylformamide as a solvent made it possible to increase the safety of the working area due to the lower evaporation rate of dimethylformamide compared to methylene chloride.

[0103] Example 7.

[0104] The sorbent was obtained in a manner similar to Example 6, with the difference that the obtained granulated sorbent was subjected to separation with the selection of a fraction from 1 to 2 mm, after which the sorbent was used to extract lithium by the method indicated in Example 1.

[0105] The sorption capacity of the sample was 4.1 mg / g.

[0106] The strength of the sorbent, determined by the above method, was 97.1%.

[0107] Example 8.

[0108] In a reactor with a stirrer, powder of a chlorine-containing form of double aluminum and lithium hydroxide, polyvinyl formal and dimethylformamide were mixed, the mixture obtained in the reactor was extruded through holes to obtain cylindrical sausages, the sausages were dried and crushed in a crusher to form a homogeneous fraction of granules.

[0109] The use of dimethylformamide as a solvent made it possible to increase the safety of the working area due to the lower evaporation rate of dimethylformamide compared to methylene chloride. Example 9.

[0110] The sorbent was obtained in a manner similar to Example 8, with the difference that the obtained granulated sorbent was subjected to separation with the selection of a fraction from 0.5 to 2 mm, after which the sorbent was used to extract lithium by the method indicated in Example 1.

[0111] The sorption capacity of the sample was 4.7 mg / g.

[0112] The strength of the sorbent, determined by the above method, was 96.1%.

Claims

CLAUSES OF THE INVENTION 1. A granular sorbent for extracting lithium from a solution based on a chlorine-containing form of double aluminum hydroxide and lithium (DGAL-C1), characterized in that the sorbent granules include polyvinyl formal (PVF) as a binder.

2. A method for producing a granulated sorbent, including mixing a powder of a chlorine-containing form of double aluminum and lithium hydroxide (DGAL-C1) with polyvinyl formalin (PVF) in dimethylformamide (DMF), granulating the mixture and drying.

3. The method according to paragraph 2, characterized in that the mixing and granulation of the mixture is carried out inside the body of the granulator-mixer.

4. The method according to paragraph 2, characterized in that the granulation of the mixture is carried out by extruding it dropwise through at least one hole into water while stirring it.

5. A method for producing a granulated sorbent, which includes mixing a powder of a chlorine-containing form of double aluminum and lithium hydroxide (DGAL-C1) with polyvinyl formalin (PVF) in dimethylformamide (DMF), granulating by extruding the mixture through at least one hole to obtain an extrudate, which is dried and crushed.

6. The method according to any of paragraphs 2-5, characterized in that the obtained granulated sorbent is subjected to separation with the selection of a fraction from 0.5 to 3 mm.