Method for quickly and selectively recovering lithium salts by means of solid-liquid extraction, using technology based on low-molecular-weight organic compounds

Abstract

The present invention discloses a method for quickly and selectively recovering lithium salts by means of solid-liquid extraction, using technology based on low-molecular-weight organic compounds.

Description

[0001] Rapid and selective recovery process for lithium salts by solid-liquid extraction, using technology based on low molecular weight organic compounds.

[0002] DESCRIPTIVE MEMORY

[0003] Technical field

[0004] The present invention teaches a process for rapid and selective recovery of lithium salts from solid waste generated in the solar concentration of brines rich in LiCl and during the conversion of LiCl to Li2CÜ3, by means of solid-liquid extraction with low molecular weight organic extractants.

[0005] Background

[0006] In ion recovery processes from discarded materials in mining operations, the discarded material present in solution is used as a source for extraction, for example, from brines. In the case of extracting ions of interest from brines, there are several problems, such as the fact that this process requires large evaporation ponds and numerous processing steps; the processes have low selectivity, in addition to a low recovery rate of approximately 50%; lithium specificity is lost due to co-precipitation with other salts, as well as due to the impregnation of solids with concentrated LiCl solution. It is difficult to access operating permits (larger volumes of brine extraction for processing) in salt flats, which are currently conditioned by more efficient processes.Current progressive evaporation and concentration processes generate large volumes of solid material (salts) that accumulate in operations. In the case of discarded materials from plant processes for the production of Li2CO3, they are disposed of as liquid industrial waste (LIW). Among the technologies to improve recovery rates, these are designed to replace current processes through solvent extraction (liquid-liquid), nanofiltration, ion exchange, electrochemical processes, etc., but none of them are designed to be carried out on solid accumulated matter, as is the case with the present invention.

[0007] The inventories of discarded salts (precipitated solids) of the companies operating in the Salar de Atacama and containing high lithium contents (1 - 4%) correspond to millions of tons, which have accumulated over more than 30 years of operation.

[0008] This process is also applicable to recover L¡ from waste materials generated in the operations of LÍ2CO3 production plants and whose concentrations are in the order of 0.9% of L¡.

[0009] The following are summaries of various documents relating to the present invention.

[0010] WO2022082324 teaches the selective extraction of lithium salt from the solid mixture of alkaline or alkaline earth salts, suspended in an organic solvent by capturing the cation L¡ + selective with a phosphorus crown ether. Lithium recovery is achieved by simply washing the organic phase containing the metal complex with water, with the exception of any other additives. The organic phase containing the complex is reinjected into the reactor containing the suspended salt mixture for a new extraction cycle.

[0011] Document WO2023054417 teaches an extraction agent capable of selectively extracting lithium salt. Also provided is a composition containing this lithium salt extraction agent and a method for recovering lithium salt using this lithium salt extraction agent.

[0012] Furthermore, in the state-of-the-art, we find the document titled "Extraction of lithium by organic solvents." This document teaches the extraction of lithium using methanol as an organic solvent. It also mentions that n-propanol, isopropanol, n-pentanol, 2-ethylhexanol, acetone, cyclohexane, dioxane, and mixtures of diethyl ether and absolute ethanol have been recommended as extractants for lithium chloride.

[0013] However, there are no technologies for selectively recovering lithium from solids (salts precipitated during the brine concentration process) or waste solids generated in lithium carbonate production plants. This corresponds to an optimization of the technology currently being protected by our group, as shown in the aforementioned document WO2022082324.

[0014] Summary of the invention

[0015] The present invention teaches a process for rapid and selective recovery of lithium salts from solid waste generated in the solar concentration of LiCl-rich brines and during the conversion of LiCl to Li2COs by solid-liquid extraction with low molecular weight organic extractants. The technology allows for the recovery of over 80% in a single extraction and with selectivities greater than 95%. This technology is complementary to current processes and will allow for an increase in the lithium recovery percentage by at least 25%. The present technology seeks to increase the lithium recovery percentages from evaporation processes, brine concentration, and progressive precipitation of unwanted salts.

[0016] 50-60% of the total lithium is not recovered and remains co-precipitated, impregnated and / or occluded in the salts that precipitate in this process.

[0017] This technology is a new, complementary process for extracting lithium from waste materials (solids), which are currently not utilized as raw material for recovering this high-value element.

[0018] The technology is primarily aimed at companies operating in Chile, Argentina, and Bolivia that produce lithium from brines using solar evaporation concentration and coprecipitation of other salts, as well as companies operating in other parts of the world. It is also aimed at companies that recover lithium from spent batteries.

[0019] Some advantages detected with this new technology:

[0020] • There are no technologies to selectively recover lithium from solids.

[0021] • Low-cost formulation, commercially available reagents, used in high-volume industrial processes

[0022] • Extraction yields greater than 40%, reaching 90% in a single stage, depending on the nature of the salt, maximum recovery percentages of chlorides, easy customer access, easy scaling, low energy demand, process at room temperature and atmospheric pressure, technology capable of being reused, loading and unloading time in minutes, minimal carbon footprint. • The implementation of this process requires unit operations known to companies that process brines; no new reactor designs are required.

[0023] Description of the figures

[0024] Figure 1: Process for extracting lithium.

[0025] Figure 2: Extraction from solid SA by varying adsorption times

[0026] Figure 3: Double extraction to a solid SA Tests of two extractions from solid SA with LA (extractant A).

[0027] Figure 4: Tests in a 1-liter reactor.

[0028] Figure 5: Extraction from solid SB (solid B, composition shown in table 2) with different types of drying.

[0029] Figure 5a shows SB Solid previously homogenized with the percolated liquid, with different % humidity.

[0030] Figure 5b shows heterogeneous SB solid slowly dried at 110°C, different layers of the solid without percolated liquid.

[0031] Detailed description of the invention

[0032] In the state of the art, the most widely used method for the extractive separation of lithium from sodium and potassium ions, as well as other alkali metals, is based on the affinity of lithium chloride for oxygen atoms in organic solvents such as aliphatic alcohols, ketones, and ethers, in the presence or absence of dry hydrogen chloride. Under these conditions, the other alkali metals are largely insoluble in these solvents, provided they are present, since the dry chlorides and the solvent used for extraction contain as little water as possible. n-Propanol, isopropanol, n-pentanol, 2-ethylhexanol, acetone, cyclohexane, dioxane, and mixtures of diethyl ether with absolute ethanol have been recommended as extractants for lithium chloride.

[0033] The dry mixture of lithium chlorides and the other alkali metals is equilibrated with the anhydrous extractant, or the separation is carried out using a continuous extraction apparatus.

[0034] Lithium is an element that can be extracted from various sources. In Chile, the largest source of lithium is the Atacama salt flat located in the Antofagasta region. The brine in the salt flat has a vapour composition, containing elements such as potassium, sodium, calcium, magnesium, iron, boron, bromine, chlorine, nitrates, chlorides, sulfates, and carbonates.

[0035] Because many other elements are extracted along with lithium, the extraction method known in the prior art is of very limited applicability. In most cases, it can only be carried out after preliminary separation of lithium and other alkali metals using other procedures. Furthermore, there is always the possibility that some of the sodium ions will pass into the organic phase, especially when they are present in large quantities. Therefore, about one percent of the sodium is co-extracted when lithium chloride is extracted with isopropyl alcohol or in the production of lithium salt using this lithium salt extraction agent.

[0036] In this technological solution, researchers present a novel proposal consisting of the generation of a complementary process to the current lithium extraction process based on low molecular weight organic compounds (100-1000 g / mol), which is capable of selectively separating lithium (LiCl) or other compatible lithium salts from waste materials from mining operations, retaining and leaving the remaining ions present in the waste solid. With this technology, it is possible to recover about 80% of the lithium present (depending on its speciation) and with selectivities greater than 96%.

[0037] For all extraction processes the following procedure is carried out:

[0038] . Choose the container to be used for extraction according to the required scale.

[0039] . Figure 1 shows steps 1 and 2, which are performed to dry the material and proceed with extraction. Step 3 is then shown, where the extractant, solvent, and additives are poured into the container and magnetic or mechanical stirring is initiated according to the required scale. The solid is then added to the stirring organic solution. The mixture is stirred and lithium adsorption occurs (6).

[0040] Step 4 shows vacuum filtration using a filter funnel, frit, or Büchner funnel, depending on the scale required. Step 5 involves transferring the loaded organic phase to a new container and adding an equivalent volume of distilled water to the new container. Shake again to allow lithium desorption (7).

[0041] . Separate phases (8) and (9) using a separatory funnel. Prepare aqueous solutions for quantification by atomic absorption spectroscopy. Dry the discharged organic phase with a drying agent.

[0042] . The entire process is carried out without applying temperature or pressure. In one embodiment of the invention, a process for the selective recovery of lithium salts from solid waste generated in the solar concentration of LiCl-rich brines and during the conversion of LiCl to Li2CÜ3 is described, which comprises: a) Providing salts containing Li, b) Applying temperature to the solid, c) Drying under vacuum, d) Contacting the dried solid with a composition comprising:

[0043] ■ An extractant,

[0044] ■ Low molecular weight organic solvent,

[0045] ■ Additive. e) Apply stirring, f) vacuum filter the resulting mixture, g) Separate the organic phase from the aqueous phase by stirring, h) obtain two streams, one containing water and lithium, and the other containing the extractant.

[0046] In another embodiment of the invention, the process is described where step b) of applying temperature is carried out at 110°C.

[0047] In another embodiment of the invention, the process is described where in step e) stirring at 1200 rpm is applied for 30 min.

[0048] In another embodiment of the invention, the process is described where step e) is carried out by stirring to generate lithium desorption.

[0049] In another embodiment of the invention, the process is described in which stirring is carried out at 1200 rpm for 20 minutes. In another embodiment of the invention, the process is described in which step g) is carried out in less than 2 minutes.

[0050] In yet another embodiment of the invention, a composition is described for the selective recovery of lithium salts from solid waste generated in the solar concentration of brines rich in LiCl and during the conversion of LiCl to Li2CÜ3, comprising:

[0051] • An organic extractant (25 - 35 %v / v),

[0052] • Organic solvent (62 - 73 %v / v),

[0053] • Additive (0.5 - 3.0 %v / v).

[0054] In another embodiment of the invention, the composition is described where the extractant comprises low molecular weight molecules, between 100 and 1000 g / mol.

[0055] In another embodiment of the invention, the composition is described where the boiling point of the extractant is between 70 and 350°C, preferably greater than 100°C.

[0056] In another embodiment of the invention, the composition is described where the extractant comprises an α-octanol where a is 1, 2, 3, 4, (which we will call LA), or a b-ethyl-c-hexanol, where b is 2, 3, and c is 1, 2, (which we will call LB).

[0057] In another embodiment of the invention, the composition is described in which the organic solvent is chosen from heptane, octane, diesel, xylene, toluene, petroleum ether, linear and cyclic alkanes from C7 to C12.

[0058] In another embodiment of the invention, the additive is described in a proportion of 0.5 to 3.0% v / v. In yet another embodiment of the invention, the use of the composition is described because it serves for the selective recovery of lithium salts from solid waste generated in the solar concentration of LiCl-rich brines and during the conversion of LiCl to Li2CO3.

[0059] Examples of implementation

[0060] Extraction is performed from test solids. Extractants obtained using the proposed methodology are then characterized using AAS quantification methodology (quantitative measurements using Atomic Absorption Spectroscopy).

[0061] Solids A and B are used as an example, prepared as follows:

[0062] To synthesize 16.5 g of Solid A, the following methodology is required:

[0063] - Transfer 25 mL of distilled water to a beaker and a magnetic stirrer.

[0064] - Add 5.850 g of NaCl, 3.007 g of LiCl and 0.142 g of KCl gradually to the solution.

[0065] - Stir until solids dissolve (1200 rpm magnetic).

[0066] - Add 6.612 g of Mg(OH)2, 0.858 g of L¡2COs and 0.420 g of CaCOs to the stirring solution.

[0067] - Shake for 30 minutes at 1200 rpm at 110°C on the hot plate.

[0068] - Dry the solid gradually with stirring at 80 - 100°C.

[0069] - Remove the magnetic stirrer.

[0070] - Dry the resulting solid at 110°C in an oven for 24 h.

[0071] - Grind the solid in a quartz mortar.

[0072] - Dry the particulate solid at 110°C. To synthesize 32.6 g of Solid B, the following methodology is required:

[0073] - Transfer 60 ml of distilled water to a beaker and a magnetic stirrer.

[0074] - Add 20.020 g of MgCl2, 10.730 g of LiCl, 1.461 g of NaCl, 0.365 g of KCl and 0.018 g of CaCl2 gradually to the solution.

[0075] - Stir until solids dissolve (1200 rpm magnetic).

[0076] - Shake for 30 minutes at 1200 rpm at 110°C on the hot plate.

[0077] - Dry the solid gradually with stirring at 80 - 100°C.

[0078] - Remove the magnetic stirrer. - Dry the resulting solid at 110°C in an oven for 24 h.

[0079] - Grind the solid in a quartz mortar.

[0080] - Dry the particulate solid at 110°C.

[0081] Table 1 Composition of Solid A Discarded solid production of LÍ2CO3 Table 2 Composition of Solid B Lithium carnallite type solid (LiMqCla-

[0082] Extraction from SA and SB solids with the composition proposed in this technology.

[0083] 1. Select the extraction vessel to be used according to the required scale. 2. Pour the extractant, solvent, and additives into the vessel.

[0084] 3. Start magnetic or mechanical stirring according to the required scale (700 - 1200 rpm).

[0085] 4. Add the solid to the stirring organic solution.

[0086] 5. Shake (700 - 1200 rpm) for 10 - 30 minutes (lithium adsorption).

[0087] 6. Vacuum filter using a filter funnel, frit or Büchner funnel depending on the required scale.

[0088] 7. Transfer the loaded organic phase to a new container.

[0089] 8. Add an equivalent volume of distilled water to the new container.

[0090] 9. Shake (700 - 1200 rpm) for 10 - 30 minutes (lithium desorption).

[0091] 10. Separate the phases with a separating funnel.

[0092] 11. Prepare aqueous solutions to quantify by atomic absorption spectroscopy.

[0093] 12. Drying of the discharged organic phase with some drying agent.

[0094] The results presented in the graphs shown in figures 2, 3 and 4 are obtained, from which the following conclusions are drawn:

[0095] - Figure 2 shows that with 10 min of adsorption it is possible to extract 45.57% of L¡.

[0096] - Figure 3 shows that 52.42-55.25% of L¡ is extracted, i.e., 68-72% of LiCl. - Figure 4 shows that the results when scaling up to 1 L are similar to those on a small scale (10 mL), even in the experiment with 2 extractions from the same solid. It is worth noting that the selectivity increases slightly.

[0097] - Given the information from the tests carried out, it is possible to identify that depending on the type of drying carried out on the SB solid and the respective prior treatment carried out (example: sampling method), different results are obtained (selective to magnesium to selective to lithium).

[0098] - Therefore, it is possible to affirm that the composition derived from the present technology is capable of extracting lithium optimally and selectively, if the sample to be treated is properly dried and is not previously contacted with liquids such as water or others.

[0099] - LA and LB extractants are capable of extracting LiCI efficiently and selectively from solid matrices and contacts in less than 1 hour.

[0100] - Extraction from discarded solids (Solid SA) reaches selectivity values ​​at L¡ greater than 99.5 and with extraction % greater than 50%.

[0101] - Extraction from lithium carnallite type solid (Solid SB) reaches selectivity values ​​at L¡ greater than 95.0 and with % extraction greater than 90%.

[0102] - Mixing LA and LB extractants with apolar organic solvents does not decrease their selectivity and is a solution to reduce costs.

[0103] - When scaling up the extraction to a 1-liter reactor, the results do not vary significantly and maintain their effectiveness in selectively extracting LiCl.

[0104] A number of embodiments of the invention have been described. However, it will be understood that various modifications may be made without departing from the scope and spirit of the invention. Accordingly, other embodiments are within the scope of the following claims.

Claims

CLAIMS 1. A process for selective recovery of lithium salts from solid waste generated in the solar concentration of brines rich in LiCl and during the conversion of LiCl to Li2CO3, CHARACTERIZED in that it comprises: a) Providing solid containing Li to a drying system, b) Applying temperature until removing over 95% of humidity, c) Drying the dry solid under vacuum, d) Contacting the solid with a composition comprising: ■ An extractant, ■ Low molecular weight organic solvent, ■ Additive; e) Adsorption - apply mechanical stirring, f) Vacuum filtration of the resulting organic mixture loaded with lithium, g) Desorption - apply mechanical stirring, h) Separation of the organic phase and the aqueous phase, i) Obtaining two streams, one containing water and lithium, and another with the organic mixture containing the extractant.

2. The process described in the preceding claim, CHARACTERIZED in that step b) the application of temperature is carried out at 100 - 130°C 3. The process described in the previous claim, CHARACTERIZED in that in step e) agitation of 700 - 1500 rpm is applied for 20 - 30 minutes, to generate lithium desorption.

4. The process described in claim 1, CHARACTERIZED in that the desorption is carried out by stirring in a range of 700 - 1500 rpm for 10 - 30 minutes.

5. The process described in claim 1, CHARACTERIZED in that step h) is performed in a time of 30 - 120 seconds.

6. A composition for the selective recovery of lithium salts from solids precipitated during the solar concentration of brines rich in LiCl and during the conversion of LiCl to Li2CO3, CHARACTERIZED in that it comprises - An extractant, - An organic solvent, - Additives.

7. The composition described in claim 6, CHARACTERIZED in that the extractant is present at 25 - 35% v / v.

8. The composition described in claim 6, CHARACTERIZED in that the organic solvent comprises between 62 - 73% v / v.

9. The composition described in claim 7, CHARACTERIZED in that the extractant comprises low molecular weight molecules, between 100 and 1000 g / mol.

10. The composition described in claim 9, CHARACTERIZED in that the boiling point of the extractant is between 70 and 350°C, preferably greater than 100°C.

11. The composition described in claim 10, CHARACTERIZED in that the extractant comprises an a-octanol or a b-ethyl-c-hexanol, where a is 1, 2, 3, 4 and where b is 2, 3, and c is 1, 2.

12. The composition described in claim 8, CHARACTERIZED in that the organic solvent is chosen from heptane, octane, diesel, xylene, toluene, petroleum ether, linear and cyclic alkanes from C7 to C12.

13. The composition described in claim 7, CHARACTERIZED in that the additive is in a proportion of 0.5 - 3.0% v / v.

14. The use of the composition described in claim 7, CHARACTERIZED in that it serves for the selective recovery of lithium salts from solid waste generated in the solar concentration of brines rich in LiCl and during the conversion of LiCl to Li2COs.

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