Novel atmospheric pressure leaching method of uncalcined lithium concentrate

Abstract

According to the invention, a method is provided for treating a lithium-containing concentrate in uncalcined form by leaching at atmospheric pressure. Generally, the leaching is performed at a temperature lower than the boiling point of the leaching solution, is a mild leaching process, and can be performed without the use of an autoclave.

Description

Technical Field

[0001] The present invention relates to a method for treating lithium-containing concentrates in uncalcined form in an atmospheric pressure leaching step. Background Art

[0002] Lithium is an element that forms compounds with a variety of industrial applications. The lithium used for these purposes is primarily obtained from lithium brines and ores using hydrometallurgical extraction processes. Conventional processes for extracting lithium from ores involve high-temperature calcination or roasting, followed by hydrometallurgical treatments, including pressure leaching.

[0003] For example, US 9255012 B2 and US 11292725 B2 describe leaching of calcined lithium-containing mineral materials by pressure leaching with a leaching solution containing carbonates. In US 9255012 B2, the slurry obtained from the leaching step contains lithium carbonate, which is then converted into lithium bicarbonate and 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 in which pressure leaching using a carbonate-based leaching solution has been used to provide the desired lithium extraction rate.

[0004] One of the problems with existing processes using known leaching conditions is that they require the use of calcination equipment and autoclaves due to the high pressure and temperature conditions used in the calcination and leaching steps. Therefore, new processes are needed in which lithium can be efficiently leached under milder conditions and in simpler equipment. Similarly, leaching in the presence of carbonates is not optimal from an extraction yield perspective. 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, there is provided a method for recovering lithium from a lithium-containing concentrate by leaching at atmospheric pressure.

[0007] According to a second aspect, there is provided a method for leaching a lithium-containing concentrate in the absence of carbonates.

[0008] According to a third aspect, a method is provided which allows the slurry obtained from the leaching step to be further processed to recover lithium therefrom. Optionally, the further processing may include one or more steps for reducing the content of impurities in the slurry or a fraction separated therefrom.

[0009] The present invention therefore relates to a method for treating a lithium-containing concentrate by leaching at a temperature below the boiling point of the leach solution at atmospheric pressure to obtain a slurry containing extractable lithium.

[0010] The present invention is based on the discovery that lithium can be recovered from lithium-containing mineral concentrates without the use of high pressure. In addition, commonly used leaching chemicals, such as carbonate reagents, can be avoided.

[0011] Significant advantages are achieved using the present invention. Among other things, the present invention makes it possible to leach lithium concentrate in atmospheric pressure leaching without an autoclave, thereby achieving significant savings in cost and energy and making it possible to obtain a more sustainable and environmentally friendly lithium product.

[0012] Even the calcination step, which is considered essential for conventional processes, can be avoided. Therefore, the present invention can leach lithium concentrate without calcination pretreatment and the associated expensive equipment, thereby achieving significant savings in cost and energy, reducing gas emissions such as CO2, and obtaining a more sustainable and environmentally friendly lithium product.

[0013] An advantage of the optional impurity removal step in the process is improved recycling options. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A process configuration according to some embodiments of the present invention is shown, wherein box 1 represents the leaching step of the present invention, box 2 represents one or more optional reaction steps for separating impurities or by-products from the leached slurry or solution, and boxes 3 and 4 represent one or more optional steps 3 of converting lithium in the slurry or solid fraction to a readily precipitable form, and / or one or more optional steps 4 of recovering lithium. Dashed arrows represent some possible recycling options.

[0015] Figure 2 A process configuration of an advantageous embodiment is shown, wherein a further block 3a represents a carbonate addition step, preferably carried out on the liquid fraction obtained from the solid / liquid separation step 1 ' and produces a lithium-containing solid fraction which can be further conveyed to steps 3, 4.

[0016] Figure 3A process configuration of an advantageous embodiment is shown, wherein a further block 0 represents an optional slurrying step, block 1' represents an optional solid / liquid separation step, and block 2' represents an optional further solid / liquid separation step after the reaction step of block 2. Thus, in the case of more than one step 2, a single step 2' may be after the last step 2, or preferably each step 2 may be followed by a separate separation step 2'. Furthermore, block 3 here represents a carbonization step, from which the slurry or solution can be conveyed to block 4, which represents a lithium recovery step. The solution obtained from the last separation step 2' can be recycled back to the slurrying step 0 or further conveyed to the carbonization step 3 (as indicated by the dotted arrow).

[0017] Figure 4 Another advantageous embodiment of the process configuration is shown, which includes Figure 2 and Figure 3 An alternative embodiment of the combination of embodiments.

[0018] Figure 5 Another advantageous embodiment of the process configuration is shown, in which block 2 is divided into blocks 2a and 2a', which respectively represent the fluoride reaction and separation from the solution carried over from the solid / liquid separation 1' following the leaching step 1; and blocks 2b and 2b', which respectively represent the silicate reaction and separation. Similarly, further blocks 3' and 4' are shown, representing the optional solid / liquid separation. However, these blocks 3' and 4' are not associated with the impurity separation step of block 2, but rather relate to different embodiments. DETAILED DESCRIPTION

[0019] definition

[0020] Lithium-containing minerals can exist in a variety of different forms, such as those listed in Table 1 below.

[0021] Table 1

[0022]

[0023]

[0024] Spodumene, lepidolite, petalite and lepidolite are of particular interest due to their availability and their favorable structures. Additionally, lithium can be present in clay minerals such as masutomilite, swinefordite, hectorite, cookeite and jadarite.

[0025] Calcination and leaching at high temperatures and pressures are generally considered necessary to provide efficient leaching of the valuable metals of these minerals, but "atmospheric pressure leaching" as used herein refers to a leaching step carried out at atmospheric pressure, thereby avoiding the use of expensive autoclaves.

[0026] 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.

[0027] The present invention relates to a process for treating lithium-containing concentrates in uncalcined form by leaching at a temperature below the boiling point of the leaching solution at atmospheric pressure to obtain a slurry containing extractable lithium (see Figure 1-5 In step 1), the preferred temperature is 20-96° C., more preferably 70-95° C. Similarly, the preferred leaching time is up to 200 hours, more preferably 12-100 hours.

[0028] Typically, leaching 1 is followed by one or more steps to recover the lithium, or to convert the lithium in the slurry or solid fraction into a form that is readily precipitated (see Figure 1-5 3 and 4), and possibly one or more steps of separating impurities or by-products from the leach slurry or leach solution (see Figure 1 and 3 Step 2).

[0029] The lithium-containing concentrate used as starting material is preferably obtained from a lithium-containing mineral such as those mentioned in Table 1 above, or it may be one of the clay minerals listed individually, but preferably selected from spodumene, petalite, lepidolite, jaddarite and lepidolite, or any combination thereof. The starting material for the leaching step contains feeds of varying particle sizes, and since the material has not undergone a grinding step, it does not contain excess chemicals. The calcination step used in conventional processes is omitted, allowing the mineral to enter the leaching step 1 in its raw form. Optionally, a mixture of calcined and uncalcined minerals is used in the concentrate fed to the leaching step.

[0030] In one embodiment, a separate pulping step may be performed before the leaching step (see Figure 3 Step 0) of the leaching step, wherein a mineral concentrate containing lithium is mixed with an aqueous solution for producing a slurry containing lithium. However, the slurry can also be formed as part of the leaching step 1.

[0031] The leaching step 1 is carried out as atmospheric pressure leaching and can be carried out as water leaching, acid leaching or alkaline leaching. Typically, the leaching conditions used are mild, wherein atmospheric pressure is combined with low temperature.

[0032] In one embodiment, the leaching step 1 is performed as alkaline leaching, preferably in a leaching solution containing an alkali metal hydroxide.

[0033] The alkali metal hydroxide can be, for example, selected from sodium hydroxide (NaOH), potassium hydroxide (KOH) and lithium hydroxide (LiOH), or mixtures thereof, preferably sodium hydroxide. It is typically added to the leach solution to 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 results in a particularly high pH value for the solution, which is typically adjusted to 11.5-14, preferably 12-14, using the alkali metal hydroxide. However, at such pH values, the content of the alkaline agent is a more reliable measurement factor than the pH value.

[0034] In another embodiment, the leaching step 1 is carried out in the form of acid leaching, preferably in 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.

[0035] In leaching step 1, the lithium-containing concentrate is mixed with a leach solution to form a slurry. The solids content of this slurry will affect the efficiency of leaching. In the method described herein, the preferred solids content during leaching step 1 is 100-500 g / L, more preferably 150-350 g / L, and particularly preferably 200-300 g / L.

[0036] Pressure leaching processes designed for lithium-containing mineral raw materials are usually carried out at temperatures up to 300°C, in some cases even as low as 150°C, but in the present process even lower temperatures of ≤100°C are sufficient, or even ≤95°C.

[0037] In one embodiment, the temperature during leaching is from 20 to 96° C., preferably from 70 to 95° C. As mentioned above, atmospheric pressure is sufficient for the purposes of the methods described herein.

[0038] Despite the mild leaching conditions described above, it has been found that even uncalcined materials can be leached while achieving reasonable lithium extraction rates, with uncalcined petalite being a particularly advantageous material. For uncalcined raw materials, longer leaching times are preferably used, for example up to 200 hours, preferably 12-100 hours, more preferably 20-50 hours.

[0039] 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 such a carbonate reagent, i.e. without adding carbonate to the leach solution. However, the fresh leach solution can be combined with a recycled solution from a subsequent step of the method before carrying out the leach step 1, whereby some carbonate may be transferred into the solution.

[0040] In some embodiments, the leaching step 1 is carried out with the addition of a carbonate, typically 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 preferably consisting at least in part of sodium carbonate. Typically, the carbonate is added in a stoichiometric amount of >0-3, most preferably >0-2.5, relative to the lithium content of the mineral concentrate of this embodiment.

[0041] After leaching step 1, a leach slurry is obtained, which contains lithium primarily in the form of its silicate salt. Since this intermediate product is only slightly soluble in the leach 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.

[0042] Under the above leaching conditions, the leached slurry obtained after leaching step 1 will still contain lithium in the solids. Therefore, further processing steps with the purpose of recovering lithium can be carried out on the slurry or, preferably, on the solid fraction separated from the slurry, in particular after alkaline leaching. Therefore, the slurry can be subjected to a solid / liquid separation step (see Figures 3 to 5 In another embodiment, the present invention provides a method for separating the lithium ion battery from the lithium ion battery by using a lithium ion battery as the raw material of the lithium ion battery. The method further comprises the steps of: (a) separating the lithium ion battery from the lithium ion battery; (b) separating the lithium ion battery from the lithium ion battery; and (c) separating the lithium ion battery from ... and (b) separating the lithium ion battery from the lithium ion battery. The method further comprises the steps of: (a) separating the lithium ion battery from the lithium ion battery; and (b) separating the lithium ion battery from the lithium ion battery. The method further comprises the steps of: (a) separating the lithium ion battery from the lithium ion battery; and (b) separating the lithium ion battery from the lithium ion battery.

[0043] Since the liquid fraction obtained from the separation step will also contain some lithium, it is preferred to utilize the liquid fraction further in the process. A suitable alternative is to separate the liquid fraction from the leach slurry and recycle it back to the leaching step 1 or the optional slurrying step 0 to be added to the leach solution before the leaching step.

[0044] As mentioned above, the leaching step 1 may be followed by further treatment steps, primarily with the aim of recovering the lithium, but also with the aim of reducing the amount of impurities in the leach slurry or fractions separated therefrom.

[0045] In one embodiment, particularly if the lithium fails to precipitate during the leaching step, the leaching step may be followed by the addition of a carbonate or phosphate salt to the liquid fraction separated from the leach slurry (see Figure 2 and 4 ) to precipitate the lithium therein in the form of lithium carbonate or lithium phosphate. The lithium carbonate or lithium phosphate can then be further processed as described below or combined with the lithium-containing solid fraction previously separated from the leach slurry.

[0046] In another embodiment (not shown) involving an acid leaching option, the leaching step may be followed by a step in which an alkali metal hydroxide, such as sodium hydroxide (NaOH), is added to the liquid fraction separated from the leach slurry to precipitate and remove solid impurities, such as iron (Fe), aluminum (Al), magnesium (Mg), and calcium (Ca) in the form of hydroxides. The remaining purified lithium-rich solution may then be sent to the carbonate addition step described above or to further processing steps, as described below.

[0047] In a further embodiment, the leaching step may be followed by a carbonization step (see Figure 1-5 The present invention also provides a step 3) in which the obtained lithium-containing leached slurry or the solid fraction separated therefrom is reacted with carbon dioxide (CO2) to form lithium bicarbonate. Preferably, the carbon dioxide is used in excess. In this step, the undissolved lithium compounds obtained from the leaching step 1 are converted into soluble lithium bicarbonate and can thus be separated substantially completely from the undesired, undissolved materials.

[0048] The optional carbonization step 3 can be carried out at a temperature of 0 to 50° C., preferably 15 to 40° C., and is typically carried out at a pressure of 1 to 15 bar, more typically 1 to 10 bar, preferably atmospheric pressure. Higher pressures increase the solubility of carbon dioxide in aqueous solutions, but increasing the pressure too much will lead to increased formation of by-products and impurities. Mixing is preferably provided, for example, using any suitable mixer that is very effective in providing mixing for dispersed gases, liquids, and solids.

[0049] The leach slurry or the solid or liquid fractions obtained therefrom may also be further treated to reduce the amount of undesirable components or impurities therein (see Figure 1 and Figure 3 Step 2).

[0050] 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 5The fluoride is reacted in step 2a) to form calcium fluoride, which can be separated from the remaining solution in the solid / liquid separation step 2a'. The reagent dosage is selected to cause only precipitation of fluoride. Therefore, a preferred option is to analyze the fluoride content of the leachate slurry or the liquid fraction separated therefrom before fluoride removal and add approximately the same amount of calcium reagent.

[0051] Another alternative is to provide a silicon removal step, also called a desiliconization step (see Figure 5 Preferably, both fluoride removal and silicon removal are performed, whereby the silicon removal step is performed after the fluoride removal step.

[0052] 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 carbonization step 3), or sent to further impurity removal.

[0053] In the desiliconization step 2b, a calcium reagent, such as 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 to form calcium silicate, which is then removed in the subsequent further solid / liquid separation step 2b'. The calcium reagent is preferably added in a stoichiometric amount of 1-2 relative to the silicon (Si) content in the solution. The temperature during the reaction is preferably 80-100°C, and a duration of 1-10 hours is generally sufficient, for example 1-8 hours. The solution separated from the solids in the further separation step 2b' can be recycled, in particular in the leaching step 1, or reused in the preceding optional pulping step 0, 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 carbonization step 3.

[0054] Thus, in one embodiment, the lithium-containing solution obtained in the present process, such as the solubilized fraction obtained from the carbonization step 3, optionally separated from the residue in the solid / liquid separation step 3', may be subjected to a precipitation or crystallization step (see Figure 1-5 step 4) to recover the lithium in crystalline form, preferably in the form of its carbonate or its hydroxide.

[0055] In addition, before the precipitation step 4, the lithium-containing solution can also be purified (not shown) 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 purification. Ion exchange can be carried out, for example, by using the method disclosed in Finnish Patent 121785. Typically, the purification of ion exchange is carried out by using a cation exchange resin, which can be, for example, iminodiacetic acid (IDA) or aminophosphonic acid (APA). Such resins are, for example, manufactured under the trade names Amberlite IRC 748 (IDA) and Amberlite IRC 7476 (APA). Typically, a cation exchange resin is a resin having a polystyrene matrix cross-linked with divinylbenzene containing aminophosphine groups.

[0056] 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.

[0057] If lithium carbonate is produced, the precipitation step 4 comprises heating the slurry or solution containing lithium bicarbonate, preferably to a temperature of 70-100° C., to decompose the bicarbonate and crystallize out the lithium carbonate.

[0058] During this carbonate precipitation reaction, a slurry containing water and precipitated lithium carbonate is formed. In a solid / liquid separation step, the solid lithium carbonate is separated from the resulting slurry, yielding 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.

[0059] If lithium hydroxide is prepared, the precipitation step 4 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. Also in this reaction, a recycled mother liquor obtained from a subsequent crystallization may be used. The hydroxide precipitation 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 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.

[0060] After the optional solid / liquid separation step 4' (preferably using filtration or by conveying the slurry or solution to a thickener), a relatively high purity lithium hydroxide-containing solution is obtained. However, this lithium hydroxide-containing slurry or solution can also be purified before crystallization, preferably using a purification technology based on dissolved ions and components, more preferably including ion exchange or membrane separation, or both, most preferably by using a cation exchange resin, particularly a selective cation exchange resin. Ion exchange can be carried out, for example, as described above. Membrane separation can be carried out using a semi-permeable membrane that separates ions or other dissolved compounds from an aqueous solution. More precisely, membrane separation can be used to classify the size of dissolved ions and compounds (depending on the pore size of the membrane material) and / or their charge (depending on the surface charge of the membrane material). Positive surface charge repels cations (having a stronger repulsive effect on multivalent cations) and attracts anions, and vice versa. These phenomena will enable purification of, 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 lithium hydroxide solution. Based on the above, it is particularly preferred to combine membrane separation with ion exchange, and it is most appropriate to improve the removal of polyvalent metal cations by first performing membrane separation and then performing ion exchange.

[0061] 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.

[0062] 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.

[0063] In a further embodiment, the crystallization mother liquor or a portion thereof remaining after recovering the crystals in the solid / liquid separation step can be recycled to one or more previous steps, such as the optional carbonization step 3 or the optional precipitation step 4. In an alternative, the mother liquor is recycled to the leaching step 1, or the optional previous pulping step 0, to participate in any pH adjustment therein, thereby reducing the need for further addition of hydroxide reagents. In another alternative, in connection with the hydroxide precipitation route, the mother liquor is recycled to the hydroxide precipitation step for preparing lithium hydroxide. In addition, the carbon dioxide used in the optional carbonization step 3 can be separated from the crystallization mother liquor and recycled back to the carbonization step 3.

[0064] The advantage achieved by recycling to a previous step with lower alkalinity (e.g., lithium precipitation step 4) is that some impurities in the crystallization mother liquor (e.g., aluminum and silicon) have an increasing solubility with increasing alkalinity (e.g., caused by an increase in lithium hydroxide concentration), so that these alkali-soluble impurities can be removed by recycling them in solution to a step with lower alkalinity. For example, in the hydroxide precipitation step, 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 crystallization and contaminate the product.

[0065] It should be understood that the embodiments of the present invention disclosed herein 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.

[0066] 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.

[0067] 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 alternatives to its various parts. It should be understood that such embodiments, embodiments 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] Example

[0072] Example 1 - Leaching of uncalcined petalite

[0073] The uncalcined petalite samples were leached under the conditions shown in Table 1 below.

[0074] Table 1.

[0075] unit Test 1 Leaching temperature ℃ 95 Leaching time h >12h Solid content g / L 250 Add 500g / L NaOH mL / g 2.0

[0076] Test 1:

[0077] The petalite sample from Test 1 was leached as shown in Table 1 above. During the leaching process, multiple samples were extracted from the solution and analyzed. The results showed that the Li concentration as extractable Li increased steadily over time.

[0078] As these results demonstrate, the method of the present invention using an atmospheric pressure leaching step and low temperatures is more versatile than known methods and, surprisingly, provides acceptable leaching rates even for uncalcined samples at the low temperatures disclosed herein.

[0079] Industrial Applicability

[0080] The method of the present invention can be used as part of a hydrometallurgical process for recovering lithium products from lithium-containing minerals and improves the process.

[0081] In particular, the novel leaching process described herein can leach lithium concentrate without the use of expensive autoclaves. Furthermore, the leaching temperature can be kept lower than in prior art processes. Furthermore, conventional calcination equipment can be omitted.

[0082] Reference Signs List

[0083] The method of the present invention comprises a leaching step 1 carried out at atmospheric pressure at a temperature below the boiling point of the leaching solution. Thus, the method of the present invention comprises the following steps:

[0084] 1 atmosphere leaching

[0085] In various embodiments, the method may further include some further steps, such as Figure 1-3 Based on the accompanying drawings, any one of the following optional steps may also be included in the method, or a combination of two or more such additional steps:

[0086] 0Pulping step

[0087] 1' Solid / liquid separation after leaching step 1

[0088] 2. Separation of impurities or by-products from the leach slurry or solution, optionally in the form of:

[0089] 2a Fluoride removal

[0090] 2a'Solid / liquid separation after fluoride removal

[0091] 2b Silicon removal

[0092] 2b' Solid / liquid separation after silicon removal

[0093] 3,4 Convert the lithium in the slurry or solid fraction into a form that is easily precipitated, typically in the following forms:

[0094] 3 Carbonization

[0095] 3' Optional solid / liquid separation after carbonization

[0096] 4 Lithium precipitation / crystallization

[0097] Optional solid / liquid separation after 4'Li precipitation / crystallization

[0098] Reference List

[0099] Patent Literature

[0100] FI 121785B

[0101] US 9255012 B2

[0102] US11292725 B2.

Claims

1. A method for treating a lithium-containing concentrate in an uncalcined form by leaching in a leaching solution at a temperature below the boiling point of the leaching solution and at atmospheric pressure to obtain a lithium-containing slurry.

2. The method of claim 1, wherein the lithium-containing concentrate is obtained from a lithium-containing mineral, preferably selected from spodumene, petalite, lepidolite, jaddarite and ferroleum mica or any combination thereof.

3. A method as claimed in any one of the preceding claims, wherein the leaching step is carried out as water leaching, acid leaching or alkaline leaching.

4. A method according to any one of the preceding claims, wherein the leaching step is carried out as alkaline leaching, preferably in a leaching solution containing an alkali metal hydroxide.

5. The method according to any one of the preceding claims, wherein the leaching step is carried out in a leaching solution containing an alkali metal hydroxide selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2) and lithium hydroxide (LiOH), or mixtures thereof, preferably sodium hydroxide.

6. The process according to claim 4 or 5, wherein the alkali metal hydroxide is added to the leaching 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.

7. The method according to any one of the preceding claims, wherein the pH level of the leach solution is adjusted to 11.5-14, preferably 12-14.

8. The method according to any one of claims 1 to 3, wherein the leaching step is carried out as acid leaching, preferably in a leaching solution containing sulfuric acid.

9. A method as claimed in any one of the preceding claims, wherein the leaching step is carried out in a slurry formed from the lithium-containing concentrate and the leach solution, the slurry having a solids content of 100-500 g / L, preferably 150-350 g / L, more preferably 200-300 g / L.

10. A process as claimed in any one of the preceding claims, wherein the leaching step is carried out at a temperature of from 20°C to below 100°C, preferably from 20°C to 95°C.

11. A method as claimed in any one of the preceding claims, wherein for a concentrate containing uncalcined lithium-containing minerals, the leaching step is carried out for a period of up to 200 hours, preferably 12-200 hours, more preferably 12-100 hours, even more preferably 20-50 hours.

12. A method as claimed in any one of the preceding claims, wherein the leaching step is carried out in the absence of a carbonate reagent in a leach solution to which no carbonate is added.

13. The method of any one of claims 1 to 11, wherein the leaching solution further contains a carbonate reagent, such as sodium carbonate (Na2CO3) or potassium carbonate (K2CO3), preferably in a stoichiometric amount of at most 3, most suitably in a stoichiometric amount of >0-2.5, relative to the lithium content of the concentrate.

14. A method as claimed in 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 leachate slurry.

15. A process as claimed in any one of the preceding claims, wherein a liquid fraction is separated from the leach slurry and recycled back to the leaching step and combined with the leach solution.

16. The method as claimed in any one of the preceding claims, wherein the lithium-containing slurry obtained or the solid fraction separated therefrom is further treated in a carbonization step by reacting it with carbon dioxide (CO2), preferably in excess.

17. A process as claimed in any one of the preceding claims, wherein the lithium-containing slurry obtained or the solid fraction separated therefrom is solubilized in a carbonization step and the solubilized fraction is subsequently subjected to a crystallization step to recover the lithium in crystalline form, preferably in the form of its carbonate or its hydroxide.

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

19. A process as claimed in claim 18, 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.

20. A process as claimed in claim 18 or 19, wherein silicon is removed from the slurry or solid or liquid fraction by reaction with a calcium reagent such as calcium hydroxide or calcium oxide, whereby the silicon is separated as solid calcium silicate.

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