Novel lithium concentrate leaching process

Abstract

According to the invention, there is provided a method for extracting lithium from lithium-containing minerals, preferably in calcined form, in a method using a particularly short leaching step.

Description

Technical Field

[0001] The present invention relates to a method for recovering lithium from lithium-containing ores in a process utilizing a short leaching step. Background Art

[0002] Lithium is an element that forms compounds with a variety of industrial applications. Lithium used for these purposes is primarily obtained from lithium brines and ores using hydrometallurgical extraction processes. Traditional lithium ore extraction involves a high-temperature calcination or roasting process followed by hydrometallurgical treatments such as pressure leaching.

[0003] For example, US 9255012 B2 and US 11292725 B2 describe leaching calcined lithium-containing mineral materials with a carbonate-containing leaching solution under relatively mild leaching conditions. In US 9255012 B2, the solution obtained from the leaching step contains bicarbonate, which is then crystallized into a lithium carbonate product. In US 11292725 B2, the lithium in the leached slurry is further reacted into hydroxide. However, both publications describe methods using long leaching times, which are based on essentially complete dissolution of the lithium.

[0004] One of the main issues with existing methods is that they require harsh leaching conditions to be maintained for extended periods, thus requiring large and expensive equipment. Therefore, new methods are needed in which lithium can be efficiently extracted using simpler procedures. Similarly, leaching in the presence of carbonates is not optimal in terms of extraction yield. Summary of the Invention

[0005] The invention is defined by the features of the independent claims. Particular embodiments are defined in the dependent claims.

[0006] According to a first aspect of the present invention, a method for extracting lithium from a lithium-containing mineral raw material is provided.

[0007] According to a second aspect, there is provided a method for extracting lithium from a lithium-containing mineral feedstock using short leaching times.

[0008] According to a third aspect, a method is provided wherein at least one of the solid and liquid phases of the leach slurry obtained from the leaching step is further treated to reduce the content of by-products and impurities in the process stream.

[0009] Thus, the present invention relates to a method for extracting lithium from a lithium-containing mineral by providing a concentrate of the lithium-containing mineral and pressure leaching the mineral concentrate in a leaching solution for a period of less than 30 minutes to obtain a slurry containing the extracted lithium.

[0010] The present invention is based on the discovery that lithium can be recovered from lithium-bearing minerals in short leaching times without the use of leaching chemicals, particularly carbonate reagents, and without even calcining the minerals, factors that were considered essential in previous methods.

[0011] Significant advantages are achieved using the present invention.

[0012] Since there is no need to cause complete dissolution of all the lithium in the starting material, high extraction yields are achieved within very short leaching times (e.g., a few minutes). In addition to shorter processing times, this has the advantage of requiring smaller and less expensive equipment for the leaching step.

[0013] The surprising finding is that, at least for some lithium-bearing minerals, these improved extraction rates can also be achieved with very short leaching times, thus enabling the use of smaller and cheaper equipment.

[0014] The advantage of the optional impurity removal step in the process is that it improves the recycle options in the process and allows the removal of impurities carried into the process from the mineral and still present in high levels in the leach solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A process configuration according to at least some embodiments of the present invention is shown, wherein box 1 represents the leaching step of the process, and boxes 3 and 4 represent one or more steps for recovering lithium or converting lithium in a slurry or solution to a readily precipitable form. Dashed arrows indicate possible recycling options.

[0016] Figure 2 A process configuration of an advantageous embodiment is shown, wherein the additional block 0 represents an optional slurrying step, block 1' represents an optional solid / liquid separation step, block 2' represents an impurity removal step, and block 2' represents an optional further solid / liquid separation step. Furthermore, block 3 here represents a carbonation step, while block 4 represents a lithium recovery step. The solution obtained from the separation step 2' can be recycled back to the slurrying step 0 or further fed to the carbonation step 3 (as indicated by the dashed arrow).

[0017] Figure 3 Another advantageous embodiment of the process configuration is shown, in which block 0 is divided into different pretreatments, typically including a calcination (0a) and / or a pulping step (0), and block 2 is divided into 2a and 2a' (representing the fluoride reaction and separation, respectively, from the solution carried over from the solid / liquid separation 1' after the leaching step 1) and 2b and 2b' (representing the silicate reaction and separation, respectively). Likewise, further steps 3' and 4' are shown, representing optional solid / liquid separations. Specific implementation plan

[0018] definition

[0019] Lithium-containing minerals can exist in a variety of different forms, such as those listed in Table 1 below, with spodumene being the most commonly used due to its availability.

[0020] Table 1

[0021]

[0022] Additionally, it can occur in the form of clay minerals such as masutomilite, swinefordite, hectorite, cookeite, and jadarite.

[0023] "Calcination" of lithium-bearing minerals is a thermal step that typically alters the crystal structure of the mineral to provide an altered structure that is more easily leached.

[0024] Most of the above-mentioned minerals contain silicon, which is produced as a by-product after the minerals are processed to recover valuable metals therefrom. "Desilication", also known as silicon removal, refers to the removal of silicon from the leach stream obtained from the process.

[0025] The present invention relates to a method for recovering lithium from a lithium-containing mineral, which is provided by providing a concentrate of the lithium-containing mineral and pressure leaching the mineral concentrate in a leaching solution for a period of less than 30 minutes to obtain a slurry containing the extracted lithium.

[0026] The lithium-containing starting material is preferably obtained from a lithium-containing ore, concentrate or recycled material, preferably a concentrate, and is generally in the form of a lithium-containing mineral such as those mentioned in Table 1 above, or may be one of the clay minerals listed individually, but is preferably selected from spodumene, petalite, lepidolite, ferrolithite and a mixture of spodumene and petalite (LiAlSiO 10 ) and spodumene (LiAlSi2O6) with similar structures, such as LiAlSi3O8 and Li2Al2Si3O 10 , more preferably spodumene or petalite. The mineral is preferably used in calcined form, a particularly preferred option being calcined spodumene.

[0027] Since the starting material does not undergo a grinding step, it is typically free of excess chemicals and consists of mineral concentrates of varying particle sizes.

[0028] Typically, the minerals of the starting material fed to the leaching step 1 are used in calcined form, wherein the calcination is preferably carried out at a temperature of 800-1200°C, more preferably 900-1150°C, even more preferably 900-1100°C (see Figure 3 Optionally, a mixture of calcined and uncalcined minerals is used in the concentrate fed to the leaching step. 10 In comparison, the calcined lithium minerals may have different crystal structures.

[0029] In one embodiment, a separate pulping step may be performed before the pressure leaching step (see Figure 2 and Figure 3 The invention relates to a step 0) in which a concentrate of a lithium-containing mineral is mixed into an aqueous solution, optionally in the presence of an alkali metal carbonate and / or hydroxide, to produce a lithium-containing slurry. However, the slurry may also be formed as part of the pressure leaching step 1, and any chemical additions may be made in either the optional slurrying step 0 or the leaching step 1. The preferred alkali metal carbonate is sodium carbonate, and is typically used in excess.

[0030] Leaching step (see Figure 1 Step 1) is preferably carried out by pressure leaching.

[0031] Pressure leaching of lithium-containing mineral feedstock may be carried out at temperatures up to 300°C, although lower temperatures of ≤ 280°C or temperatures of ≤ 240°C may also be sufficient.

[0032] In one embodiment of the present method, the temperature during leaching is therefore preferably 120-300° C., more preferably 120-280° C., such as 120-260° C. or 120-240° C., even more preferably 150-220° C. Thus, in some embodiments, the temperature of the leaching step may be in the range of 120° C. or 150° C. to 220° C., 240° C., 260° C., 280° C. or 300° C.

[0033] The pressure during leaching step 1 is preferably 3-85 bar, more preferably 3-65 bar, even more preferably 3-30 bar, or 5-30 bar, and most preferably 5-25 bar or 10-25 bar. Thus, in some embodiments, the pressure during leaching step 1 may range from 3 bar, 5 bar, or 10 bar to 25 bar, 30 bar, 50 bar, 65 bar, or 85 bar. Pressure may not necessarily need to be adjusted independently, as it will adjust upwards as temperature increases. Thus, pressure is generally higher at higher leaching temperatures.

[0034] In one embodiment, the leach solution used is an alkaline leach solution, preferably a leach solution containing an alkali metal hydroxide.

[0035] The alkali metal hydroxide of this embodiment can be, for example, selected from sodium hydroxide (NaOH), potassium hydroxide (KOH) and lithium hydroxide (LiOH), or mixtures thereof, preferably sodium hydroxide. It is usually added to the leach solution to give a hydroxide ion content of 0.1-250 g / L, preferably 1-200 g / L, more preferably 30-150 g / L, and even more preferably 50-120 g / L. This will give the solution a particularly high pH value, which is usually adjusted to 11.5-14, preferably 12-14, using alkali metal hydroxide. However, at such pH values, the content of the alkaline agent is a more reliable measurement factor than the pH value.

[0036] In one embodiment, the hydroxide ion content is in the range of 0.6-9 mol / L, preferably 1-6 mol / L.

[0037] In another embodiment, the leaching solution is an acid leaching solution, preferably a leaching solution containing sulfuric acid (H2SO4), phosphoric acid (H3PO4) or carbonic acid (H2CO3). The acid is usually added to the leaching solution at a concentration of 1-10 mol / L.

[0038] Under the above conditions, short leaching times are sufficient. It has been found that by carrying out pressure leaching at the temperatures set forth herein, leaching times can be less than 30 minutes, for example, from 1 minute to 25 minutes or from 3 minutes to 15 minutes. Thus, in some embodiments, the leaching time is from 0.5 minutes, 1 minute, or 3 minutes to a maximum of 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.

[0039] Due to the preferred high temperature and pressure, leaching 1 is typically carried out in a suitable autoclave or a series of autoclaves. When leaching times of less than 30 minutes are used, the volume of the equipment can be significantly reduced without reducing the efficiency of the process. The temperature of the leaching step can in turn be slightly increased, for example by using a temperature at the upper end of the temperature range disclosed herein (e.g., a temperature of 220–300° C.), without having a significant negative impact on the equipment (e.g., the autoclave). When selecting the leaching conditions, the type of mineral feedstock may also be considered, for example, lepidolite, ferroleum mica, and lithophore contain fluorine and can therefore be leached at lower temperatures to increase the service life of the equipment.

[0040] While pressure leaching in many common processes is carried out in the presence of a carbonate reagent, the present method can be carried out in the absence of a carbonate reagent, i.e., without adding carbonate to the leach solution. However, in an alternative, the fresh leach solution can be combined with a recycled solution from a subsequent step of the method before the leaching step is carried out, whereby some carbonate may be carried over to the leaching step even without the separate addition of carbonate.

[0041] In a specific embodiment, a calcined lithium-containing mineral selected from the above-mentioned minerals is extracted in an alkaline leach solution to which a carbonate is added. The addition of the carbonate is typically carried out by adding a suitable carbonate reagent, such as an alkali metal carbonate, preferably sodium carbonate (Na2CO3) or potassium carbonate (K2CO3), or a mixture thereof, most suitably consisting at least in part of sodium carbonate. Typically, the carbonate is added in a stoichiometric ratio of >0-3.5 relative to the lithium content of the mineral of this embodiment, preferably in a stoichiometric ratio of >0-2.5 relative to the lithium content of the mineral, and most suitably in a stoichiometric ratio of 1.5-2.5.

[0042] In another embodiment of the process described herein, a separate pulping step is performed before the pressure leaching step (see Figure 2 and 3 ), wherein a concentrate of a lithium-containing mineral is mixed into an aqueous solution to produce a lithium-containing slurry. Optionally, the slurry may also be formed as part of the pressure leaching step 1.

[0043] Thus, in the leaching step 1, lithium from a lithium-containing mineral, such as a lithium oxide or lithium aluminum silicate of the mineral (e.g., LiAlSiO for petalite) is leached. 10 ), converted into a dissolved or partially dissolved form such as lithium metasilicate (Li2SiO3). For example, in the presence of sodium hydroxide, using a petalite-based raw material, in the main reaction, the lithium-containing mineral reacts with OH - Reaction to produce Li2SiO3 and analcime.

[0044] After the leaching step 1, a leaching slurry is obtained, which contains lithium in a converted form (e.g., its silicate form) as an extract. Since the intermediate product is only slightly soluble in the leaching solution, it is obtained in the form of a slurry. The slurry does not contain a large amount of unreacted minerals because it has been converted into, for example, sodium aluminum silicate. In other words, the lithium contained in the mineral has been released. Typically, the yield of lithium released from the leaching step is 90 to 95% by weight, calculated based on the mineral. The slurry obtained can be used as is and is therefore directly subjected to any subsequent reaction, for example, to achieve further dissolution (solubilization). Therefore, in the context of the present disclosure, a lithium extract refers to lithium (i.e., a slurry) that has been converted into such a dissolved or partially dissolved form, wherein the lithium is released from the structure of the initial mineral of the starting material (i.e., the feed).

[0045] In a preferred embodiment, the leachate slurry is therefore subjected to a solid / liquid separation step 1 ' to provide a lithium-containing solid and a liquid containing, inter alia, undesirable compounds such as sodium silicate and other impurities and other lithium compounds in dissolved form.

[0046] The obtained lithium-containing slurry or the solid or liquid fraction separated therefrom may be further processed before or after the carbonation of the lithium in the slurry (see Figure 2 In a further solid / liquid separation step 2', one or more impurities are removed therefrom. This can be done, for example, by adding a calcium reagent such as calcium oxide (CaO) or calcium hydroxide (Ca(OH)2) to the slurry or solution to react with the impurities such as fluoride or silicon, and then removing the impurities in a subsequent further solid / liquid separation step 2'.

[0047] An alternative is to remove fluoride from the leach slurry or the liquid fraction separated therefrom by reaction with a calcium reagent such as calcium hydroxide or calcium oxide (see Figure 3 The fluoride is reacted with calcium fluoride in step 2a) of the present invention to form calcium fluoride, which can be separated from the remaining solution in the solid / liquid separation step 2a'. The dosage of the reagent is selected to cause only the precipitation of fluoride. Therefore, the preferred option is to analyze the fluoride content of the leachate slurry or the liquid fraction separated therefrom before removing the fluoride and add approximately the same amount of calcium reagent.

[0048] Another alternative is to provide a silicon removal step, also called a desiliconization step (see Figure 3 Preferably, both fluoride removal and silicon removal are performed, wherein the silicon removal step is performed after the fluoride removal step.

[0049] Preferably, desilication 2b is performed on the liquid fraction separated from the leach slurry, or on a purified form of the leach slurry (e.g. subjected to fluoride removal), and the desilication solution obtained after this step can be recycled to the leaching step 1, or combined with any stream used in further processing steps (e.g. the slurry or solid fraction sent to the optional carbonation step 3), or sent to further impurity removal.

[0050] In the desiliconization step 2b, a calcium reagent (e.g. calcium oxide (CaO) or calcium hydroxide (Ca(OH)2)) can be added to the silicon-containing solution to be treated, so that the silicon reacts with the calcium and forms calcium silicate, which is then removed in a subsequent further solid / liquid separation step 2b'. The calcium reagent is preferably added in a stoichiometric ratio of 1-2 relative to the silicon (Si) content of the solution. The temperature during the reaction is preferably 80-100°C, and a duration of 1-10 hours is usually sufficient, for example 1-8 hours. The solution separated from the solids in the further separation step 2b' can be recycled, in particular reused in the leaching step 1 or in the preceding optional pulping step 0b, or it can be combined with the leach slurry, or preferably combined with the leach residue (solid fraction) obtained from the solid / liquid separation step 1' after the leaching step 1, and conveyed to a subsequent treatment such as the carbonation step 3. In another embodiment, the recovery steps 3, 4 are carried out after the leaching 1 (directly or via the above-mentioned intermediate separation step 1') (see Figure 1 ), which preferably includes a carbonation step (see Figure 2 Step 3) is also referred to as a bicarbonation step due to the reaction that occurs. In the optional carbonation step 3, the leached slurry obtained or the leached residue separated therefrom (optionally combined with the desiliconized solution obtained from the solid / liquid separation step 2') is reacted with carbon dioxide (CO2), preferably in excess. The undissolved lithium compounds obtained from the leaching step are thus converted into dissolved lithium bicarbonate and can thus be separated substantially completely from the undesired, undissolved materials.

[0051] The optional carbonation step 3 can be carried out at a temperature between 0°C and 50°C, preferably between 15°C and 40°C, and is typically carried out at a pressure of 1-15 bar, more typically 1-10 bar, preferably atmospheric pressure. Higher pressures can increase the solubility of carbon dioxide in aqueous solution, but increasing the pressure too much can lead to increased formation of by-products and impurities. Mixing is preferably provided, for example using any suitable mixer that provides mixing to disperse gases, liquids and solids very effectively.

[0052] The lithium-containing slurry or solution obtained from the previous recovery step 3 can be further conveyed to the subsequent recovery step 4 (see Figure 1 and Figure 2 Step 4) is used to convert the lithium in the slurry or solution into an insoluble compound, i.e., to precipitate or crystallize it. Therefore, this step also forms part of the above-mentioned recovery steps 3 and 4.

[0053] The precipitation or crystallization 4 can be preceded by a solid / liquid separation step 3' (see Figure 3) is subjected to a further step of separating any insoluble reagents from the slurry or solution, typically by filtration, and the liquid fraction is then subjected to a precipitation step 4. The separation step 3' may be carried out, for example, using filtration, or by passing the slurry or solution to a thickener, from which the overflow may be passed to the precipitation step 4, and the underflow may be discarded, recycled, or further filtered to recover any lithium remaining therein.

[0054] Furthermore, before the precipitation step 4, preferably after the solid / liquid separation step (from which the liquid fraction is recovered), a purification 3" (not shown in the figure) may also be carried out to remove impurities, such as trivalent and / or divalent metal ions, such as calcium, magnesium, aluminum and iron ions. Preferably, ion exchange is used for the purification 3". The ion exchange can be carried out, for example, by using the method disclosed in Finnish Patent 121 785. Typically, purification by ion exchange is carried out using a cation exchange resin, which may be, for example, iminodiacetic acid (IDA) or aminophosphonic acid (APA). Such resins are manufactured, for example, under the commercial names Amberlite IRC 748 (IDA) and Amberlite IRC 7476 (APA). Typically, the cation exchange resin is a resin having a polystyrene matrix cross-linked with divinylbenzene containing aminophosphonic groups.

[0055] The above-mentioned precipitation step 4 results in the formation of a solid lithium compound or precipitate, which can be crystallized into pure crystals, preferably pure crystals of lithium carbonate or lithium hydroxide.

[0056] If lithium carbonate is produced, the precipitation step 4a comprises heating the slurry or solution containing lithium bicarbonate, preferably to a temperature in the range of 70-100°C, to decompose the bicarbonate and crystallize out the lithium carbonate.

[0057] In this carbonate precipitation 4a reaction, a slurry containing water and lithium carbonate precipitate is formed. In the solid / liquid separation step 4' (see Figure 3 ), separating solid lithium carbonate from the resulting slurry to produce battery-grade lithium carbonate. Standard battery-grade lithium carbonate contains at least 99.5% lithium carbonate. However, using the methods described herein, it is possible to produce high-quality battery-grade lithium carbonate containing at least 99.99% lithium carbonate.

[0058] If lithium hydroxide is prepared, the precipitation step 4b comprises reacting a slurry or solution containing lithium obtained from the dissolution process or optionally pretreated with a hydroxide reagent, i.e., an alkaline earth metal hydroxide, to produce a slurry containing lithium hydroxide in soluble form. The alkaline earth metal hydroxide used is preferably selected from calcium hydroxide and barium hydroxide, more preferably calcium hydroxide, which is optionally prepared by reacting calcium oxide (CaO) in an aqueous solution. The alkaline earth metal hydroxide may also be mixed with water or an aqueous solution before being used in the reaction. In this reaction, a recycled mother liquor obtained from a subsequent crystallization may also be used. The hydroxide precipitation 4b is typically carried out at a temperature of 10-100°C, preferably 20-60°C, and most preferably 20-40°C. Typically, the hydroxide precipitation 4b is carried out at atmospheric pressure. The presence of the alkaline earth metal hydroxide and the above-mentioned process conditions result in the formation of lithium hydroxide, with carbonates of alkaline earth metals formed as by-products.

[0059] In an optional solid / liquid separation step 4' (preferably performed using filtration or by sending the slurry or solution to a thickener) (see Figure 3 ) after which a solution containing lithium hydroxide of relatively high purity is obtained.

[0060] In one embodiment, the lithium hydroxide-containing slurry or solution may be purified prior to crystallization.

[0061] This optional purification step 4" (not shown in the figures) is preferably based on the purification of dissolved ions and components and more preferably comprises ion exchange or membrane separation or both, most suitably by using a cation exchange resin, in particular a selective cation exchange resin. The ion exchange can be performed, for example, as described above for the preceding optional purification step 3" performed before the precipitation step 4. Membrane separation can be performed using a semipermeable membrane, which separates ions or other dissolved compounds from the aqueous solution. More precisely, membrane separation can be used to fractionate dissolved ions and compounds according to their size (depending on the pore size of the membrane material) and / or their charge (depending on the surface charge of the membrane material). Positive surface charges repel cations (with a stronger repulsion for multivalent cations) and attract anions and vice versa. These phenomena will make it possible to purify, for example, multivalent metal cations, complexed substances (such as aluminum hydroxide complexes), polymeric substances (such as dissolved silica) and larger anions (such as sulfate and carbonate ions) from the lithium hydroxide solution. Based on the above, it is particularly preferred to combine membrane separation with ion exchange, and it is most appropriate to polish the removal of polyvalent metal cations by first performing membrane separation and then performing ion exchange.

[0062] Crystals of lithium hydroxide monohydrate can be recovered from a solution containing lithium hydroxide by crystallization. Crystallization is typically performed by heating the solution to a temperature approximately at the boiling point of the solution to evaporate the liquid, or by recrystallizing the monohydrate from a suitable solvent. The methods described herein enable the production of pure lithium hydroxide monohydrate in excellent yield and purity in a continuous and simple process, typically providing battery-grade lithium hydroxide monohydrate crystals.

[0063] In a preferred embodiment of the process, crystallization, either for the production of carbonate or hydroxide crystals, is typically followed by another solid-liquid separation step, preferably using filtration, or by passing the slurry or solution to a thickener.

[0064] In a further embodiment, the crystallization mother liquor or a portion thereof remaining after the crystals are recovered in the solid / liquid separation step can be recycled to one or more preceding steps of the dissolution process or the preparation of solid lithium compound crystals, thereby allowing any uncrystallized lithium to be recovered. In an alternative, the mother liquor is recycled to the pressure leaching step 1, or the optional preceding pulping step 0, to participate in any pH adjustment therein, thereby reducing the need for further addition of hydroxide reagents. In another alternative, related to the hydroxide approach, the mother liquor is recycled to the hydroxide precipitation step for preparing lithium hydroxide. In another alternative, the mother liquor is recycled back to the crystallization. In addition, the carbon dioxide used in the optional carbonation step 3 of the dissolution process can be separated from the crystallization mother liquor and recycled back to the carbonation step 3.

[0065] An advantage achieved by recycling to a previous step with lower alkalinity (e.g., pressure leaching 1 or lithium precipitation step 4 in certain embodiments) is that some impurities in the crystallization mother liquor (e.g., aluminum and silicon) have increasing solubility with increasing alkalinity (e.g., caused by increasing lithium hydroxide concentration), allowing these alkali-soluble impurities to be removed by recycling them in solution to a step with lower alkalinity. For example, in the hydroxide precipitation step 4b, these impurities form sparingly soluble compounds (e.g., aluminum hydroxide) and can be discarded with the solids after the subsequent separation step. Without these recycling options, impurities would typically concentrate in the crystals and contaminate the product.

[0066] It should be understood that the embodiments of the present invention disclosed are not limited to the specific structures, process steps or materials disclosed herein, but extend to equivalents thereof that will be recognized by those skilled in the relevant art. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments and is not intended to be limiting.

[0067] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.

[0068] As used herein, for convenience, multiple items, structural elements, constituent elements and / or materials can be listed in a general column. However, these lists should be understood as each member in the list being individually identified as a separate and unique member. Therefore, in the absence of an opposite indication, any single member in the list should not be interpreted as being in fact equivalent to any other member in the same list simply based on its presentation in a common group. In addition, various embodiments and examples of the present invention can be mentioned herein together with the alternatives of its various parts. It should be understood that such embodiments, examples and alternatives should not be interpreted as being in fact equivalent to each other, but should be regarded as independent and separate presentations of the present invention.

[0069] In addition, the described features, structures or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, many specific details, such as examples of lengths, widths, shapes, etc., are provided to provide a thorough understanding of the embodiments of the present invention. However, those skilled in the relevant art will recognize that the present invention can be implemented without one or more of the specific details, or using other methods, components, materials, etc. to implement. In other cases, well-known structures, materials or operations are not shown or described in detail to avoid confusing various aspects of the present invention.

[0070] Although the above examples illustrate the principles of the present invention in one or more specific applications, it will be apparent to those skilled in the art that many modifications may be made in form, usage, and implementation details without exercising inventive power and without departing from the principles and concepts of the present invention. Therefore, it is not intended that the present invention be limited except by the following claims.

[0071] As used herein, the verbs "to comprise" and "to include" are open limitations that neither exclude nor require the presence of unrecited features. The features recited in the appended claims are mutually freely combinable unless expressly stated otherwise. Furthermore, it should be understood that the use of "a" or "an" throughout this document, i.e., in the singular, does not exclude a plural reference.

[0072] Example

[0073] Example 1 - Rapid Leaching of Lithium-Containing Materials

[0074] Calcined spodumene concentrate (lithium content of the mineral being 2.66 wt.%) and uncalcined petalite sample (lithium content of the mineral being 1.90 wt.%) were leached in a leach solution containing sodium hydroxide (NaOH). The alkalinity of each leach solution was adjusted by adding a 500 g / L NaOH solution. The dosage of NaOH solution added was 1.25 mL / g of spodumene sample (raw material) and 1.5 mL / g of petalite sample (raw material). The temperature during the leaching process was maintained at approximately 220°C.

[0075] The leach solution was heated to a temperature of 220°C and samples were taken at 0, 3, 5, 10 and 15 minutes (final filter cake). The results for the spodumene sample are shown in Table 2 and the results for the petalite sample are shown in Table 3.

[0076] Table 2

[0077] sample Li Al <![CDATA[OH - ]]> Acid-soluble Li Li extraction rate Calcined spodumene ％ ％ g / L ％ ％ Initial sample 2.66 12.6 58.4 0 minutes 2.40 11.1 48.2 2.54 100 3 minutes 2.47 11.3 51.0 2.67 100 5 minutes 2.47 11.1 51.9 2.63 100 10 minutes 2.48 11.3 51.6 2.62 100 Final filter cake 2.47 11.5 - 2.68 100 Final filtrate - - 41.0 - -

[0078] Table 3

[0079] sample Li Al <![CDATA[OH - ]]> Acid-soluble Li Li extraction rate Uncalcined petalite ％ ％ g / L ％ ％ Initial sample 1.90 7.96 69.3 <0.02 0 0 minutes 2.56 10.7 71.7 2.5 97.7 3 minutes 2.54 10.6 73.1 2.5 98.4 5 minutes 2.59 10.6 72.2 2.6 100 10 minutes 2.43 10.4 72.2 2.6 100 Final filter cake 2.46 10.2 - 2.6 100 Final filtrate - - 56.9 - -

[0080] The results show that the lithium extraction rate is already very high at the beginning of the leaching step and reaches 100% of the theoretical value after five minutes at the latest. For the calcined spodumene sample, the extraction rate reaches 100% at the beginning of the leaching process, that is, when the temperature reaches 220°C.

[0081] To verify the effect of leaching during the heating period in Example 2, a reference test was conducted with a slightly different setup. In the reference test, a second sample of the calcined spodumene concentrate and the uncalcined petalite concentrate were subjected to separate leaching steps, preheated before the addition of the alkaline solution. Leaching was considered to have started when the entire amount of alkaline solution was mixed with the feedstock.

[0082] Leaching was conducted at a temperature of 220°C. In each test, a calcined spodumene feed (560g) and an uncalcined petalite feed (560g) were heated to a leaching temperature of 220°C, at which point a NaOH solution having a concentration of 762g / L was added to each leach solution. The amount of NaOH solution added was 560mL for the spodumene sample and 650mL for the petalite sample.

[0083] The results shown in Tables 4 and 5 below show similar lithium extraction yield results to those in the first experiment (the results of which are shown in Tables 2 and 3).

[0084] Table 4

[0085] sample Li Al <![CDATA[OH - ]]> Acid-soluble Li Li extraction rate Calcined spodumene ％ ％ g / L ％ ％ Initial sample 2.66 12.7 0.059 3 minutes 2.36 11.8 61.9 2.43 100 5 minutes 2.10 10.4 62.2 2.21 100 10 minutes 2.35 11.9 56.2 2.41 100 15 minutes 2.41 12.2 56.2 2.50 100 20 minutes 2.38 12.3 53.8 2.32 100 25 minutes 2.40 12.3 56.9 2.51 100 Final filter cake (30 minutes) 2.33 11.2 - 2.47 100 Final filtrate - - 55.8 - -

[0086] Table 5

[0087] sample Li Al OH- Acid-soluble Li Li extraction rate Uncalcined petalite ％ ％ g / L ％ ％ Initial sample 1.92 7.8 <0.01 3 minutes 2.30 9.9 70.1 2.21 96.3 5 minutes 2.33 9.9 79.2 2.19 94.3 10 minutes 2.39 10.2 76.9 2.40 100 15 minutes 2.35 10.3 77.6 2.44 100 20 minutes 2.45 10.5 79.0 2.50 100 25 minutes 2.45 10.6 77.2 2.57 100 Final filter cake 2.50 10.6 - 2.59 100 Final filtrate - - 64.8 - -

[0088] Industrial Applicability

[0089] The method of the present invention may be used as part of, and improve upon, any hydrometallurgical process for recovering lithium products from lithium-containing minerals.

[0090] In particular, the new leaching steps described herein allow for the leaching of lithium concentrates in shorter processing times and without the need for large, expensive equipment. Despite this, excellent lithium extraction rates can still be achieved.

[0091] Reference List

[0092] Patent Literature

[0093] US 9255012 B2

[0094] US11292725 B2

Claims

1. A method for extracting lithium from lithium-containing minerals, characterized in that: A concentrate containing lithium minerals is provided and the concentrate is pressure leached in a leach solution for a period of less than 30 minutes to obtain a slurry containing extracted lithium.

2. The method according to claim 1, wherein the lithium-containing mineral is selected from calcined spodumene, petalite, lepidolite and ferroleum mica or any combination thereof, preferably at least partially selected from calcined minerals, more preferably at least partially selected from calcined spodumene.

3. The method according to claim 1 or 2, wherein the lithium-containing mineral is selected from a combination of calcined and uncalcined minerals, the mineral being selected from spodumene, petalite, lepidolite and ferroleum mica or any combination thereof, preferably a combination of uncalcined petalite and calcined spodumene.

4. The method according to any one of the preceding claims, wherein the pH is adjusted prior to the leaching step using a hydroxide reagent such as an alkali metal hydroxide, preferably selected from sodium hydroxide (NaOH), potassium hydroxide (KOH) and lithium hydroxide (LiOH) or mixtures thereof, preferably sodium hydroxide.

5. The method according to any one of the preceding claims, wherein the alkali metal hydroxide is added to the leach solution at a hydroxide ion content of 0.1-250 g / L, preferably 1-200 g / L, more preferably 30-150 g / L, even more preferably 50-120 g / L.

6. The method according to any one of claims 1 to 3, wherein the leaching solution is an acid leaching solution, preferably a leaching solution containing sulfuric acid (H2SO4), phosphoric acid (H3PO4) or carbonic acid (H2CO3).

7. The method according to claim 6, wherein the acid is added to the leaching solution at a concentration of 1-10 mol / L.

8. The method according to any one of the preceding claims, wherein the leaching step is carried out at a temperature of 120-300°C, preferably 120-280°C, more preferably 150-220°C.

9. The method according to any one of the preceding claims, wherein the leaching step is carried out at a pressure of 3-85 bar, preferably 3-65 bar, more preferably 5-30 bar, most suitably 10-25 bar.

10. The method according to any one of the preceding claims, wherein the leaching step is carried out for a time of 1 minute to 25 minutes, preferably 3 minutes to 15 minutes.

11. A method according to any one of the preceding claims, wherein the leaching step is carried out in the absence of a carbonate reagent in a leach solution without added carbonate.

12. The method according to any one of claims 1 to 5 or 8 to 10, wherein the leaching solution further comprises a carbonate reagent, such as sodium carbonate (Na2CO3) or potassium carbonate (K2CO3), preferably the carbonate reagent is present in a stoichiometric amount of at most 3.5 relative to the lithium content of the mineral, more preferably in a stoichiometric amount of >0-2.5 relative to the lithium content of the mineral, and most preferably in a stoichiometric amount of 1.5-2.

5.

13. A method according to any one of the preceding claims, wherein a solid / liquid separation step is performed to separate a solid fraction and a liquid fraction from the leach slurry.

14. A method according to any one of the preceding claims, wherein the liquid fraction is separated from the leach slurry and recycled back to the leaching step and combined with the leach solution.

15. The method according to any one of the preceding claims, wherein the lithium-containing slurry obtained or the solid fraction separated therefrom is further treated in a carbonation step by reacting it with carbon dioxide (CO 2 ), preferably in excess.

16. A method according to any one of the preceding claims, wherein the lithium-containing slurry obtained or the solid or liquid fraction separated therefrom is further treated to remove one or more impurities therefrom, before or after carbonation of the lithium in the slurry.

17. A process according to claim 16, wherein fluoride is removed from the slurry or solid fraction by reacting it with a calcium reagent such as calcium hydroxide or calcium oxide, whereby the fluoride is separated as calcium fluoride.

18. A process according to claim 16 or 17, wherein silicon is removed from the slurry or a solid or liquid fraction separated therefrom by reaction with a calcium reagent such as calcium hydroxide or calcium oxide, whereby silicon is isolated as solid calcium silicate.

19. A process according to any one of the preceding claims, comprising a precipitation step to obtain a solid lithium compound.

20. The method of claim 19, wherein the solid lithium compound is lithium carbonate or lithium hydroxide.

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